[0001] BACKGROUND INFORMATION

[0002] Technical Field

[0003] The present disclosure relates in general to systems and methods useful in the production of biocrude from biomass, where biocrude is a liquid fuel like petroleum crude that can be upgraded to the whole distillate range of petroleum derived fuel products. In particular, the present disclosure relates to systems and methods for production of biocrude using hydrothermal liquefaction (HTL).

[0004] Background Art

[0005] HTL requires very high pressures and temperatures, about 3,000 psi and 300 °C. These temperatures and pressures are a very challenging operating conditions particularly under continuous processing conditions, typically requiring specialized pumps, depressurizing valves and pressure recovery, heat exchangers that are not commercially available, exotic metallurgy and atypical wall thicknesses. In addition, there are numerous issues related to excessive wear and tear, safety, redundancy requirements and very high costs. In particular, the high thermal energy required to heat feed biomass slurry to the desired temperature must be recovered for economic viability, thereby requiring heat exchangers capable of operating at the target temperatures and pressures which are not commercially available for the relatively high processing rates.

[0006] At this time, globally, there are no commercial scale HTL operations for converting biomass to biocrude, largely due to these challenges. While use of HTL systems and methods to produce biocrude have increased, there remains a need for improved HTL systems and methods for production of biocrude from biomass.

[0007] SUMMARY

[0008] In accordance with the present disclosure, systems, and methods of using same are described which reduce or overcome many of the faults of previously known HTL systems and methods. Systems and methods of the present disclosure comprise converting biomass at high volumetric flow rates into biocrude using HTL while minimizing hydrothermal carbonization. The biomass is prepared to generate a biomass slurry for HTL processing.

[0009] A first aspect of the disclosure is a system comprising (or consisting essentially of, or consisting of): a well having a well depth, a top positioned at a surface location, and a bottom portion positioned at a subterranean location, the well comprising a casing and one or more tubing (in certain embodiments, coiled tubing) positioned therein, forming an annulus there between, the casing and the one or more tubing defining a hydrothermal liquefaction (HTL) reaction zone in the bottom portion of the well and a heat transfer and separation zone above the HTL reaction zone; the well further comprising a cable comprising an electric heating element positioned in one or more of the one or more the tubing in the HTL reaction zone and configured to transfer energy endothermically to a biomass slurry flowing downward through at least one of the one or more tubing, and convert at least a portion of the biomass slurry into biocrude oil by HTL, the biomass slurry entering into the tubing at the top of the well at a first temperature and a first pressure, the well depth and the electrical heating element sufficient to produce a second temperature and a second pressure in the reaction zone sufficient to form sub-critical water but insufficient to form supercritical water, and produce a product fluid comprising the biocrude oil.

[0010] A second aspect of the disclosure is a system comprising (or consisting essentially of, or consisting of): a well having a well depth, a top positioned at a surface location, and a bottom portion positioned at a subterranean location, the well comprising a casing and a single tubing positioned therein, forming an annulus there between, the casing and the tubing defining a hydrothermal liquefaction (HTL) reaction zone in a first section of the bottom portion, a return fluid plenum in a second section of the bottom portion, the second section located below the first portion, and a heat transfer and separation zone above the HTL reaction zone; the well further comprising a cable comprising an electric heating element positioned in the tubing in the HTL reaction zone and configured to transfer energy endothermically to a biomass slurry flowing downward through the one or more tubing, and convert at least a portion of the biomass slurry into biocrude oil by HTL, the biomass slurry entering into the tubing at the top of the well at a first temperature and a first pressure, the well depth and the electrical heating element sufficient to produce a second temperature and a second pressure in the reaction zone sufficient to form sub-critical water but insufficient to form supercritical water, and produce a product fluid comprising the biocrude oil.

[0011] A third aspect of this disclosure is a method comprising (or consisting essentially of, or consisting of): flowing a biomass slurry into a top of one or more tubing positioned inside a casing of a well, the well having a well depth, a top positioned at a surface location, and a bottom portion positioned at a subterranean location, the well comprising a casing and one or more tubing positioned therein, forming an annulus there between, the casing and the one or more tubing defining a hydrothermal liquefaction (HTL) reaction zone in the bottom portion of the well and a heat transfer and separation zone above the HTL reaction zone; heating the biomass slurry flowing downward through the HTL reaction zone employing a cable comprising an electric heating element positioned in one or more of the one or more tubing in the HTL reaction zone; converting at least a portion of the biomass slurry into biocrude oil by HTL in the HTL reaction zone, the biomass slurry entering into the tubing at the top of the well at a first temperature and a first pressure, the well depth and the electrical heating element sufficient to produce a second temperature and a second pressure in the HTL reaction zone sufficient to form sub-critical water but insufficient to form supercritical water, and produce a product fluid comprising the biocrude oil; flowing the product fluid comprising the biocrude oil upward through the annulus between the casing and the one or more tubing; and transferring heat between the product fluid and the biomass slurry in the heat transfer and separation zone.

[0012] A fourth aspect of this disclosure is a method comprising (or consisting essentially of, or consisting of): flowing a biomass slurry into a top of a single tubing positioned inside a casing of a well, the well having a well depth, a top positioned at a surface location, and a bottom portion positioned at a subterranean location, the well comprising a casing and a tubing positioned therein, forming an annulus there between, the casing and the tubing defining a hydrothermal liquefaction (HTL) reaction zone in a first section of the bottom portion, a return fluid plenum in a second section of the bottom portion, the second section located below the first portion, and a heat transfer and separation zone above the HTL reaction zone; heating the biomass slurry flowing downward through the HTL reaction zone employing a cable comprising an electric heating element positioned in the tubing in the HTL reaction zone; converting at least a portion of the biomass slurry into biocrude oil by HTL in the HTL reaction zone, the biomass slurry entering into the tubing at the top of the well at a first temperature and a first pressure, the well depth and the electrical heating element sufficient to produce a second temperature and a second pressure in the HTL reaction zone sufficient to form sub-critical water but insufficient to form supercritical water, and produce a product fluid comprising the biocrude oil; flowing the product fluid comprising the biocrude oil upward through the annulus between the casing and the tubing; and transferring heat between the product fluid and the biomass slurry in the heat transfer and separation zone. The third and fourth aspects appear to be the same.

[0013] The annual global biomass volume is estimated to be 5 billion tons/yr. that could be converted to potentially generate 12.6 billion bbl. of biocrude. In accordance with the present disclosure, systems and methods with a single well reactor having a single inner tubing and surface separation facility could process 46,000 tons of wet biomass annually while generating 45,000 bbl. (7,150 m ³ ) of biocrude. In addition, preventing 20,000 tons/yr. of CO ₂ emissions which is the equivalent of the emissions from 4,200 vehicles. This excludes the use of char sludge which encapsulates the carbon preventing further CO ₂ emissions. Certain systems and methods of the present disclosure generate greater than 10X more energy than they consume, and in certain embodiments greater than 20X more energy than they consume. Certain systems and methods of the present disclosure can use renewable sources of power to operate the process.

[0014] The systems and methods of the present disclosure utilize hydrothermal liquefaction for the conversion of biomass to biocrude. In certain embodiments the biomass is made into a slurry of approximately 20 percent biomass, 75 percent water and 5 percent inert solids; and pumped into a deep well with an inner and outer tube which could be a non-producing oil and gas well with a typical production casing (outer tube) and production tubing (inner tube). Certain embodiments may comprise pumping the biomass slurry at a flow rate of approximately 10 m ³ /hr. into the inner tube at about 100 psi to a depth of about 2,380 m (length of the inner tube) and product fluid returned to the surface in the annulus. An electrically heated cable is located at the bottom of the inner tube and operated to preheat the incoming fluid, in certain embodiments up to 300 °C. Preheating comes from the countercurrent flow of hot product fluid in the annulus, the inner and outer tubes essentially forming a tube in tube heat exchanger. In certain embodiments at the bottom of the well, the hydrostatic pressure may range from about 2,500 to about 3,000 psi where the biomass conversion reactions take place. The product fluid comprising biocrude then moves up the annulus along with water and some gases (CO ₂ mostly with some CH4). Technical and safety challenges associated with high pressure slurry pumping, high pressure and high temperature heat exchanger and depressurizing in a continuous process are alleviated. In certain embodiments, heat losses to the environment are minimized through the selection and placement of thermally resistant and high insulating drilling fluids and cement during well construction. High solids in the feed material are prone to settling and plugging the wellbore when circulation is temporarily stopped. To avoid this risk, in certain embodiments a non-thermally sensitive inorganic additive is used to create a shear thinning feed biomass slurry. In certain embodiments, heat transfer and reaction kinetics are enhanced through the selection of static mixers, pipe geometry and flow regimes in the inner and outer tube. As the biomass is heated to 300 °C, hydrothermal carbonization of biomass occurs between temperatures ranging from about 180 to about 250 °C which reduces the biocrude yield. In certain embodiments of the present disclosure, carbonization is reduced through pipe geometry design, velocity and residence time control.

[0015] These and other features of the systems and methods of the disclosure will become more apparent upon review of the brief description of the drawings, the detailed description, and the claims that follow. Wherever the term “comprising” is used herein, other embodiments where the term “comprising” is substituted with “consisting essentially of” are explicitly disclosed herein. Wherever the term “comprising” is used herein, other embodiments where the term “comprising” is substituted with “consisting of” are explicitly disclosed herein. Moreover, the use of negative limitations is specifically contemplated; for example, certain systems and methods may comprise several physical components and features but may be devoid of certain optional hardware and/or other features. For example, certain systems may be devoid of auxiliary tanks, pumps, and other equipment. As another example, systems of this disclosure may be devoid of heat exchangers employing inert metals, or other expensive equipment. In yet another example, systems of the present disclosure may be devoid of any unit or component that would introduce an oxidizing chemical into the biomass slurry. [0016] BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The manner in which the objectives of this disclosure and other desirable characteristics can be obtained is explained in the following description and attached drawings in which:

[0018] FIG. 1 schematically illustrates generic HTL systems and methods for producing biocrude oil, which may then be separated into renewable chemicals, hydrocarbon biofuels for transportation uses, and renewable fuels for heating;

[0019] FIG. 2 is a graphical representation of change of oxygen content of lignocellulose as molecular weight is lowered by processing the lignocellulose into biocrude and the processing the biocrude into fuel;

[0020] FIGS. 3A, 3B, 5, 6, 8, 9, 11, 11A, 11B, 11C, 12, 13A, 13B, 15, 17, 18, 18A, 22, and 23, schematically illustrate various system and method embodiments in accordance with the present disclosure;

[0021] FIG. 4 is a schematic representation of a material balance for one system with one feed tube and method embodiment of the present disclosure;

[0022] FIGS. 7 and 10 are graphical representation of pressure and temperatures in HTL systems and methods in accordance with the present disclosure, specifically pressure and temperature combinations to avoid hydrothermal carbonization and promote HTL;

[0023] FIGS. 14A and 14B are graphical representation of pressure vs. residence time and temperature vs. residence time, respectively, in HTL systems and methods in accordance with the present disclosure, specifically pressure, temperature, and residence time combinations to avoid hydrothermal carbonization and promote HTL;

[0024] FIG. 16A is a schematic illustration of a mixing collar sleeve producing turbulent flow conditions, and FIG. 16B is a schematic illustration of laminar flow conditions when the mixing collar is not present in well reactors in accordance with the present disclosure; [0025] FIGS. 19, 20, 21A, and 21B are schematic illustrations of electrical heating elements, electrical power supply systems, and how the electrical heating elements may be introduced into the well reactors in certain embodiments of the present disclosure;

[0026] FIGS. 24 and 25 illustrate schematically the effect that formation temperature has on system heat loss in embodiments of the present disclosure;

[0027] FIG. 26 illustrates graphically, and FIG. 27 schematically illustrates days to reach steady state temperature at certain distances from the wellbore wall in certain embodiments of the present disclosure;

[0028] FIGS. 28A and 28B illustrate graphically heat loss to formation from start up to day 5, and to day 50, respectively, at a distance 0.37 meter from the wellbore center in certain embodiments of the present disclosure;

[0029] FIG. 29 illustrates graphically heat loss vs. depth at various time intervals in certain embodiments of the present disclosure;

[0030] FIGS. 30A and 30B illustrate heat loss to formation by day, and FIG. 30C illustrates heat transfer and distribution between fluid and formation for first 100 days, in certain embodiments of the present disclosure;

[0031] FIGS. 31, 31A, 31B, and 31C illustrate schematically the use of insulating cement in well reactors in certain embodiments of the present disclosure;

[0032] FIGS. 32 and 32 A illustrate schematically the use of insulating cement and insulating drilling fluid in well reactors in certain embodiments of the present disclosure;

[0033] FIGS. 33A, 33B, and 33C illustrate typical well construction, HTL well construction using drilling fluid and non-insulating cement (“NIC”), and well construction using drilling fluid, insulating cement (“IC”), and NIC;

[0034] FIGS. 34A and 34B is a schematic process flow diagram of one embodiment of an overall system and method of the present disclosure; and [0035] FIGS. 35A and 35B are schematic illustrations of various phases of flow in the annulus in certain systems and methods of the present disclosure, and FIG. 35C is a graphical representation of the flow regimes illustrated schematically in FIG. 35B.

[0036] It is to be noted, however, that the appended drawings are not to scale and illustrate only typical embodiments of this disclosure, and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. Identical reference numerals are used throughout the several views for like or similar elements.

[0037] DETAILED DESCRIPTION

[0038] In the following description, numerous details are set forth to provide an understanding of the disclosed methods, systems, and apparatus. However, it will be understood by those skilled in the art that the methods, systems, and apparatus may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. All U.S. published patent applications, U.S. Patents, and non-patent literature referenced herein are hereby explicitly incorporated herein by reference. In the event definitions of terms in the referenced patents and applications conflict with how those terms are defined in the present application, the definitions for those terms that are provided in the present application shall be deemed controlling. Where a range of values describes a parameter, all sub-ranges, point values and endpoints within that range are explicitly disclosed herein. This document follows the well-established principle that the words “a” and “an” mean “one or more” unless we evince a clear intent to limit “a” or “an” to “one.” For example, when we state “flowing a biomass slurry into a top of a tubing positioned inside a casing of a well”, we mean that the specification supports a legal construction of “a tubing” that encompasses structure distributed among multiple physical structures, and a legal construction of “a well” that encompasses structure distributed among multiple physical structures.

[0039] The challenge to decrease the world’s reliance on fossil fuels requires the implementation of cost-effective, large-scale, renewable energy-based transport fuel projects. Ong et al., “A Kraft Mill-Integrated Hydrothermal Liquefaction Process for Liquid Fuel Co-Production” , pp. 1-23, Processes 2020, 8, 1216 (2020), MDPI, Basel, Switzerland (hereafter Ong et al.). [0040] Bioenergy is a renewable energy that uses biomass to produce energy. Biomass can be sewage sludge, manure, municipal solid waste, agriculture, forest residues, energy crops and others. The major concerns of bioenergy are biomass availability, sustainability issues and competition between the alternative uses of biomass (for instance, competition for feed and food). Hence, the use of waste streams may contribute to an improvement of bioenergy production. Moreover, the use of waste for production of energy contributes to a circular economy that, in turn, is a global plan for reduction of waste generation and reduction of the use of resources. Moura, T. C. P., “Modelling of Wet Air Oxidation in a Deep Well Reactor for Biomass Treatment" , Master dissertation (October 2021), available from A Faculdade De Engenharia Da Universidade Do Porto Em Chemical Engineering (hereafter “Moura”).

[0041] The estimated annual global volume of biomass (as of 2020) is as presented in Table 1, where biocrude volumes are based on 40% conversion of biomass (dry wt.%):

[0042] Hydrothermal Liquefaction Technology

[0043] Presently, there are three main methods to produce renewable fuels: saccharification and fermentation (producing fuel ethanol); transesterification (producing biodiesel); and thermolytic decomposition (i.e., pyrolysis, gasification, and hydrothermal liquefaction). Hydrothermal liquefaction uses a combination of heat, pressure and water/solvent immersion to decompose organic material into a combination of solid char, liquid biocrude, and off-gases. Hydrothermal processing is divided into three separate processes, depending on the severity of the operating conditions. At temperatures below about 247 °C, it is known as hydrothermal carbonization. The main product is a hydrochar which has a similar property to that of a low rank coal. At intermediate temperature ranges between about 247 °C and about 374 °C, the process is defined as hydrothermal liquefaction resulting in the production of a liquid fuel known as biocrude. Biocrude is similar to petroleum crude and can be upgraded to the whole distillate range of petroleum derived fuel products. A discussion of biocrude properties is presented herein. At higher temperatures above about 374 °C gasification processes start to dominate and the process is defined as hydrothermal gasification, resulting in the production of a synthetic fuel gas. Elliott, et al., “Hydrothermal liquefaction of biomass: Developments from batch to continuous process". Bioresource Technology 178. 147 - 156 (2015) ISSN 0960-8524, Published by Elsevier Ltd. (hereafter Elliott).

[0044] Referring to FIG. 1 , a schematic generic flow diagram of hydrothermal liquefaction is presented. Hydrothermal liquefaction (HTL) is a thermochemical process that depolymerizes biomass present in a pretreated wet biomass slurry 5 into liquid fuels 21 in a HTL reactor 6 operating at high temperature and pressure and sufficient time to decompose the solid natural polymeric structure to mostly liquid compounds. It is a flexible conversion process due to the variability of bio-based or waste feedstock 2 that have been successfully tested. Biomass wet waste 3 is pretreated in a pretreater 4. An HTL product fluid 7 is routed to a phase separator 8 where the product fluid 7 is separated into a water stream 9 that is separated and recycled to pretreater 4, a biochar and sludge stream 11, and a stream 13 comprising primarily biocrude oil. Biocrude stream 13 is further separated into a hydrocarbon light ends stream 15 that may be further processed into renewable chemicals, a middle distillates stream 19, and a hydrocarbon heavy ends stream that may be used as renewable fuels stream 17 for heating purposes. Middle distillate stream 19 may be further processed by one or more catalytic processes in one or more process units 10, for example catalytic hydrotreating (where hydrogen is added in stream 23, promoting breakdown of large molecules into smaller molecules), and/or catalytic reforming in a catalytic reforming unit (CRU to enhance cyclic hydrocarbons such as benzene, toluene, and xylenes and hydrogen) to form hydrocarbon biofuels for transportation uses. The key advantage of why the HTL process is successful is because the feedstock 2 of the HTL process does not have to undergo a separate drying process but undergoes pretreatment 4 to provide the pretreated biomass slurry 5. Water 9 in the HTL process serves as a reactant and catalyst in the subcritical region as the properties of the water change in the extreme. (Water has a critical point of 374 °C and 221 bar (22.1 MPa).) In the subcritical region, the dielectric constant of water decreases significantly, as compared to ambient water. For example, the dielectric constant of water changes from about 80 at 20 °C and decreases below 20 at 300 °C. [0045] The water in the hydrothermal liquefaction process acts as a solvent and a reactant. When water is heated close to its critical temperature in a pressurized system, it begins to behave as a non-polar liquid and dissociates much easier. The non-polar behavior of the liquid helps to solvate the organics in the biomass, and the H ₃ O+ and OH- ions aid in the conversion of biomass molecules into more desirable compounds.

[0046] Prior to the systems and methods of the present disclosure, the HTL process has been shown to be difficult to scale up. Most of the research into HTL has been done in the laboratory setting in small scale reactors. This means that the process conditions and costs are estimated but not implicitly known. The pressures and temperatures needed will greatly increase the cost of large-scale equipment Bailey, et al., “Hydrothermal Liquefaction of Food Waste, A Major Qualifying Project Report” , submitted to the faculty of Worcester Polytechnic Institute, April 26, 2018 (hereinafter Bailey et al.).

[0047] Referring again to FIG. 1, approximately 16 percent (dry ash free wt. percent) of the feedstock 2 is converted into HTL off-gas stream 25 consisting of CO ₂ , CH4, CO and H ₂ , primarily composed of 92 percent CO ₂ and 8 percent C ₁ -C5 gases. “Conceptual Biorefinery Design and Research Targeted for 2022: Hydrothermal Liquefaction Processing of Wet Waste to Fuels”, December 2017, Prepared for the U.S. Department of Energy under Contract DE-AC05- 76RL01830 by Pacific Northwest National Laboratory. CO ₂ and hydrocarbon gases in stream 25 can be separated using well established methods such as amine solution extraction and pressure swing adsorption allowing for the recovery of hydrocarbon gases to supplement fuel consumption in the general process or electricity production.

[0048] Some feedstock is converted into solid elemental carbon char from hydrothermal carbonization (HTC) which is a thermochemical conversion process that uses heat to convert wet biomass feedstocks to hydrochar. HTC occurs at temperatures ranging from about 180 °C to about 250 °C, under autogenous (automatically generated) pressure, with feedstock residence time ranging from about 0.5 to 8 hours. Ahmad, F., et al., “Hydrothermal processing of biomass for anaerobic digestion - A review”, Renewable and Sustainable Energy Reviews, 98, 108-124 (2018).; Khan, T. A., et al., “Hydrothermal carbonization of lignocellulosic biomass for carbon rich material preparation: A review, Biomass and Bioenergy, 130, 105384 (2019). This solid carbon cannot revert to carbon dioxide or methane and subsequently be released to the atmosphere. When used as a soil amendment, the carbon is permanently removed from the atmosphere. The use of hydrochar can improve soil quality by enhancing its water and nutrient retention properties. Zhang, Z., et al., “Insights into biochar and hydrochar production and applications: a review”, Energy, 171, 581-598 (2019). However, the char may contain toxic compounds which could limit its use as soil amendment. Sivaprasad, S. et al., “Hydrothermal Carbonization: Upgrading Waste Biomass to Char”, Department of Food, Agricultural and Biological Engineering, The Ohio State University, downloaded from url: Hence the converted biomass into liquid and solid products is carbon negative or in other words, carbon is removed from the atmosphere. While there are benefits of HTC, it reduces HTL biocrude yields. If the objective is to maximize biocrude yields as is the case for the systems and methods of the present disclosure, then the feed slurry should remain in the temperature range of about 180 °C to about 250 °C environment for as short a time as possible.

[0049] HTL Physical Chemistry - Properties of sub and supercritical water. (See Kambo, H. S., et al., “A comparative review of biochar and hydrochar in terms of production, physico-chemical properties and applications”, Renewable and Sustainable Energy Reviews, pp. 359-378, May 2015, Elsevier.) From the phase diagram of water, the critical point is at 374 °C and 22.1 MPa (221 bar). Liquid water, below the critical point, is referred to as subcritical water and above as supercritical water. According to the systems and methods of the present disclosure, the treatment of biomass is carried out in subcritical water, at which water is still in a liquid phase and acts as a non-polar solvent enhancing the solubility of organic compounds of biomass. Water at high temperature and high pressure has a high degree of ionization and starts dissociating into acidic hydronium ions ( H ₃ O+) and basic hydroxide ions (OH-), therefore, shows both acidic and basic characteristics. At 24 MPa, the dielectric behavior of 200 °C water is similar to that of ambient methanol, 300 °C water is similar to ambient acetone, 370 °C water is similar to methylene chloride, and 500 °C water is similar to ambient hexane.

[0050] Water at subcritical conditions has a much lower dielectric constant and higher ion product than water at normal conditions and therefore provides a reaction medium with improved solvent and catalytic properties. While HTL chemistry is complicated, the general reaction pathways can be put into three basic categories: depolymerization of the biomass components; decomposition of biomass monomers by cleavage, dehydration, decarboxylation, and deamination; and recombination of reactive fragments. The biocrude from sludge is similar to biocrude from algae HTL and comprises a mixture of fatty acids, amides, ketones, hydrocarbons, phenols, alcohols and other components. Furthermore, long residence times have shown a decrease in the viscosity of the biocrude. A generalized reaction pathway of HTL processes is illustrated in Rudra, et al., “Hydrothermal liquefaction of biomass for biofuel production" . Department of Engineering Science, Faculty of Engineering and Sciences, University of Agder, Norway, April 2021.

[0051] Biomass to Biocrude

[0052] Liquid biocrude is the key product of HTL systems and methods of the present disclosure. With an upgrading process, this biocrude can be transformed to the whole distillate range of petroleum-derived equivalent fuel products. When compared to gasification, pyrolysis and HTL have a simpler technical conversion of biomass to a liquid fuel . However, when compared to pyrolysis oils, the lower oxygen content in HTL biocrude makes it less corrosive and provides it with higher heating value. Conventional (fossil fuel-derived) petroleum that has a calorific content of 43-46 MJ/kg compared with 30-36 MJ/kg for HTL bio-crude, and 15-22 MJ/kg for pyrolysis oils.

[0053] HTL processes have been shown to produce bio-oils with energy densities between 35-37 MJ/kg and bio-char with an energy density around 28 MJ/kg which is similar to that of coal. The hydrothermal liquefaction of biomass has been previously shown to produce more energy than it consumes (Gollakota, 2017). This means that systems and methods of the present disclosure could be run by burning part of the oil/ char they produce and have a percentage left over. The percentage remaining can even be chemically upgraded to produce transportation fuels.

[0054] Referring to FIG. 2, the main pathway that produces biocrude in systems and methods of the present disclosure is through the reduction of oxygen and other oxidizing compositions in the biomass feed. Oxygen accounts for about 40-60 percent of the dry weight of biomass. This is done in systems and methods of the present disclosure by reducing the number of oxygen molecules bound to the organics and increasing the organic molecules size. The reduction of bound oxygen reduces the solubility of the organic compound by making it less polar and more hydrophobic. This reduction in oxygen increases the energy density of the resulting biocrude. Two major chemical reactions (Lange, J-P., “Lignocellulose Liquefaction to Biocrude: A Tutorial Review", ChemSusChem (2018), 11, 997 - 1014) taking place are alkylation of phenolic compounds and the ketonization of carboxylic acids. Removing oxygen in these ways is ideal for systems and methods of the present disclosure as it either removes it as water, increasing the total carbon yield, or as carbon dioxide which increases the hydrogen to carbon ratio of the final products. Biocrude products of the HTL systems and methods of the present disclosure on average are less than 1 percent oxygen. The addition of catalysts have been shown to improve the percent conversion from the aqueous to oil phase.

[0055] Wet biomass feedstocks — properties and preparation for processing (Elliott et al.)

[0056] Most biomass can be processed in HTL systems and methods of the present disclosure because of the hydrophilic nature of biomass and the reasonable ease in forming water slurries of biomass particles at pumpable concentrations, typically from about 5 to about 35 percent dry solids. In embodiments using lignocellulosic biomass, which is lower in moisture content, recovery and reuse of the water for slurry preparation is a key feature. For high-moisture biomass, like algae, some dewatering is desired prior to processing in order to lessen the processing costs of excessive water. Table 2 presents some common feedstock utilized in HTL systems and methods of the present disclosure. Wet feedstocks are particularly suited for the HTL systems and methods of the present disclosure and especially algae biomass. This means additional energy spent to achieve a dry feedstock required for most thermochemical biofuel pathways is not required and nor is additional water added as required for a dry biomass feedstock for HTL systems and methods of the present disclosure. Their pumpability has been demonstrated on a large scale. The particle size is in direct correlation to pumpability and pressure control in continuous reactors. In certain embodiments using woody biomass, grinding prior to processing as is discussed herein is employed. Microalgae, some strains of macroalgae and certain manures and sludges are of suitable small size for direct processing. Table 2 also presents a summary of the HTL results published on the respective feedstock to date. It can be seen that the wet manure and sewage sludge feedstock have not been processed in continuous systems, although results from batch systems are promising for their application in continuous systems. A further advantage of using hydrothermal processing for sludges and manures is the effect of sterilizing bioactive contaminants. Table 2. Summary of HTL feedstock and continuous-flow reactor results (Elliott et al.)

* daf = dry, ash free

N/A - no reference available on the subject

[0057] Overall carbon yield, including hydrotreatment of the biocrude product, was nearly 50 percent, with the resulting product exhibiting a large fraction in the distillate range. These results are based on lignocellulosic feedstock, and the results could be significantly different for other biomasses, such as algae, with high nitrogen contents. [0058] Systems and Methods of the Present Disclosure

[0059] The systems and methods of the present disclosure continuously convert biomass at high volumetric flow rates into biocrude using hydrothermal liquefaction while minimizing hydrothermal carbonization. Biomass is prepared to generate a biomass slurry for HTL processing. As discussed herein, HTL requires very high pressures and temperatures, for example from about 2,500 psi to about 3,500 psi and from about 250 °C to about 350 °C, or from about 2,700 psi to about 3,300 psi and from about 275 °C to about 325 °C, or about 3,000 psi and about 300 °C. These temperatures and pressures are very challenging operating conditions particularly under continuous processing conditions. In previously known systems and processes, specialized pumps, depressurizing valves and pressure recovery, heat exchangers not commercially available, exotic metallurgy and atypical wall thicknesses were required. In addition, there are numerous issues related to excessive wear and tear, safety, redundancy requirements and very high costs. In particular, at least some of the high thermal energy required to heat the feed biomass slurry to the desired HTL temperatures should be recovered for economic viability. Ordinarily this would require heat exchangers capable of operating at the target HTL temperatures and pressures which are not commercially available for the relatively high processing rates.

[0060] At this time, globally, there are no commercial scale operations, largely due to these challenges. To overcome many of these challenges, systems and methods of the present disclosure utilize a deep well, in certain embodiments deep wells commonly drilled and constructed for oil and gas production. These deep wells can safely and inexpensively generate the high pressures required via hydrostatic pressure by using commonly available metallurgy, dimensions and geometry. The depth of the well determines the pressure. In certain embodiments, as in embodiment 100 illustrated schematically in FIGS. 3A and 3B, the well includes an inner tubing 32 and an outer tubing (casing) 30 where the feed slurry enters inner tubing 32 at the top 44 of the well at the surface 46 and flows to the bottom portion 42 of the well, and product fluid 7 returns to the surface in an annulus 38 formed between inner tubing 32 and casing 30. No high-pressure pumping is required as the systems and methods take advantage of the hydraulic U tube effect and hydrostatic pressure simultaneously. Biomass slurry 5 is heated at the bottom of the well to the target temperature by a heating element 36 of an electric cable 34 but prior to reaching bottom portion 42 of the well, while product fluid 7 returning in annulus 38 preheats the incoming biomass slurry 5. The majority of the heat in product fluid 7 is recovered via the transfer of thermal energy from the hot product fluid 7 flowing upward in annulus 38 to the incoming cold feed biomass slurry 5 in a heat transfer and separation zone 40. In systems and methods of the present disclosure, the temperature of the preheated feed slurry in inner tubing 32 is boosted at bottom portion 42 (HTL reaction zone) of the well under pressure to ensure the biomass slurry fluid remains as a liquid for the hydrothermal liquefaction reactions to occur. The deep well will essentially be our reactor. The heat source comes from the submersed electrical resistance heater cable (34, 36 powered by a power source 48, which may employ grid power or other power) which is commonly used in oil and gas production to reduce viscosity of heavy oils and waxes, flow assurance and to increase production or other methods of heating inner tubing 32. Also illustrated in FIG. 3A are pressure chart 52, depth chart 54, and a schematic scale model of the well reactor at 1 : 12.222 scale ratio.

[0061] To perform the efficient operation of an HTL plant in terms of total operating costs and optimal physio-chemical performance, certain systems and methods of the present disclosure may employ: (a) energy recovery; (b) feed slurry preheating; c) boost heating to reach HTL temperature; and d) drilling fluid and/or cements having insulating properties to minimize heat losses. Some or all of these may be satisfied by the design of specific thermal components, as well as configuration design of the processing systems. In certain embodiments, thermal management in systems and embodiments of the present disclosure may include one or more of the following components: (1) a heat exchanger which is designed to ensure the thermal energy recovery with primary functions of feed biomass slurry preheating and product fluid cooling; (2) the electrical heater, which serves to boost the temperature after pre-heating; and (3) the well reactor where the majority of chemical HTL reactions occur.

[0062] In certain embodiments, the well can be a non-producing oil and gas well which is an operational liability to the owner of the well requiring an expensive plug and abandonment procedure. In addition, a non-producing well can be an environmental liability that can leak fluids and methane into the environment. Methane is more than 25 times as potent as carbon dioxide at trapping heat in the atmosphere. The systems and methods of the present disclosure turn these liabilities into valuable assets. The technology reverses these negative environmental impacts while simultaneously generating a biocrude vs. extraction of crude thereby significantly reducing GHG emissions.

[0063] FIG. 8 illustrates a high-level process flow diagram and material balance of one system and method embodiment of the present disclosure which will be described in more detail herein in various embodiments. All streams are expressed in metric tons/day. Feed biomass slurry stream 5 includes 215 metric tons/day biomass slurry, which includes 44 metric tons/day biomass, 168 metric tons/day water, and 9 metric tons/day solids, as depicted in chart 60. A recovered gas stream 15 includes 6.4 metric tons CCh and 0.6 metric tons/day CH ₄ , as depicted in chart 62. An HTL products fluid stream 7 includes 17.1 metric tons/day biochar, 20 metric tons/day biocrude, 163 metric tons/day water, and 9 metric tons/day solids, as depicted in chart 64. Recovered water stream 9 is 147 metric tons/day, while an HTL sludge stream 11 includes 17.1 metric tons/day biochar, 25.8 metric tons/day water, and 6.8 metric tons/day solids, as depicted in chart 66. Finally, recovered biocrude stream 13 is 15.7 metric tons/day.

[0064] Environmental Advantages

[0065] The systems and methods of the present disclosure hold a number of very significant environmental advantages over systems and methods that generate a fuel such as methane from biosolids using current aerobic and anaerobic digestion processes that require a large area, weeks long digestion periods, generate large liquid wastes, require sensitive biochemistry and temperatures, and significant resources to operate treatment facilities. When biosolids are treated such as in a municipal wastewater treatment plant the biosolids are biodegraded, applied to the surface or placed in landfills, where biodegradation releases 180 kg of CO ₂ equivalent of methane and carbon dioxide per ton of biomass. Daniel-Gromke et al., “Digestion of bio-waste - GHG emissions and mitigation potential". Energy, Sustainability and Society (2015) 5:3 DOI 10.1186/sl3705-014-0032-6. The methane in particular is a potent greenhouse gas with potential contribution to global warming. This is estimated to be 0.8 and 10.3 million tons annually of CO ₂ equivalent methane and CO ₂ respectively. In the United States alone, livestock manure accounts for about 250 million tons of dry solids annually and land application of these wastes has been linked to the spread of hormones, pathogens, and nutrient runoff. See Vardon, D. R., “Hydrothermal Liquefaction for Energy Recovery from High-Moisture Waste Biomass”, Thesis for the degree of Master of Science in Environmental Engineering in Civil Engineering, University of Illinois at Urbana-Champaign, 2012.

[0066] A facility utilizing one or more of the systems and methods of the present disclosure provides the following advantages:

• [0067] Greater protection for surface and groundwater; • [0068] Reduced truck traffic and associated emissions;

• [0069] Reduced greenhouse gas (CH4 and CO ₂ ) release to atmosphere;

• [0070] Recovery and beneficial use of near carbon neutral generated biocrude and methane as a clean fuel; and

• [0071] Recovery of solids residue which is a soil amendment that is carbon negative due to the sequestration of carbon. The solids residue is also free of pathogens common to agricultural and human bio-solids.

[0072] While one main objective of the systems and methods of the present disclosure is to minimize solids residue in the form of sludge, some production of sludge is inevitable. The solid residue (mostly made up of biochar) produced from hydrothermal liquefaction systems and methods of the present disclosure can be used for soil amendment to earn GHG credits. According to some estimates, about 75 percent of the organic compounds in the biochar would break down into the soil while the remaining carbon would be released into the atmosphere as GHG emissions.

[0073] Based on one example used for calculations described further herein, one ton of biomass (wet as received) can generate 158 L of biocrude. Certain embodiments of systems and methods of the present disclosure generate greater than about 10-times more energy than they consume, and in some embodiments more than about 20-times. The systems and methods of the present disclosure can be completely operated on electrical power which can be generated from renewable sources such as wind and solar. Certain systems and methods of the present disclosure made up of a single well reactor and a single inner tube and surface separation facility can process about 46,000 tons/yr. of wet biomass while generating about 45,000 bbl. (7,150 m ³ ) of biocrude. In addition, certain embodiments prevent about 20,000 tons/yr. of CO ₂ emissions which is the equivalent of the emissions from about 4,200 vehicles. This excludes the use of char sludge which encapsulates carbon preventing further CO ₂ emissions.

[0074] Biocrude Properties

[0075] HTL biocrudes are semi-liquid, viscous, dark-colored and have a smoke-like smell. The typical viscosity of bio-crudes is about 10 to about 10,000 times higher than that of diesel and biodiesel. Moreover, heating values are not comparable with conventional fossil fuels and biodiesel. These properties make HTL biocrude difficult to use as transportation fuels, apart from marine applications. While it is feasible to directly use HTL biocrudes by blending with fossil fuel diesel, the blends to date have been predominantly fossil fuel diesel. Therefore, there is an opportunity in certain system and method embodiments of the present disclosure to maximize the benefits of using a totally renewable fuel by improving the properties of the HTL biocrude through upgrading using one or more of the catalytic processes previously mentioned, such as hydrotreating and reforming.

[0076] Generating Hydrothermal Reactions in Systems and Methods of the Present Disclosure

[0077] Feed Biomass Slurry Characteristics and Processing Rates

[0078] In certain systems and methods of the present disclosure the biomass is prepared to achieve consistent physical and chemical properties such that it can be easily pumped using simple centrifugal pumps at low pressures. One example of typical properties includes those shown in Table 3:

Table 3. Typical Biomass Properties

The prepared biomass slurry is pumped at low pressures (for example, less than 100 psi, or less than 75 psi, or less than 50 psi) into a deep well to generate hydrostatic pressure to depths of about 2,380 m (7,800 ft). At these depths, the hydrostatic pressure of the slurry reaches about 3,000 psi which is the target pressure for HTL. In practice, the depths could range from about 1,566 m (4,921 ft) to about 2,600 m (8,530 ft) which would generate a hydrostatic pressure of ranging from about 134 bar (1,961 psi) to about 224 bar (3,257 psi) depending upon the density of the slurry, as shown in Table 4:

Table 4. Typical Flow Rate and Density of Feed Biomass Slurries

Referring again to embodiment 100 as illustrated in FIG. 3, biomass slurry 5 enters inner tubing 32 at the top of the well 44 at the surface 46 and flows to the bottom 42 of inner tubing 32 and product fluid 7 returns to the surface 46 in annulus 38. Inner tubing 32 contains an electric resistance heating cable (34, 36) to raise feed biomass slurry 5 temperature to the target HTL temperature.

[0079] Slurry Preparation

[0080] Biomass has a wide range of liquid and solid material types, content and particle size. In certain embodiments, before the biomass can be processed, it must be mechanically and chemically prepared to make a homogenous slurry suitable for pumping into a wellbore.

[0081] Mechanical Preparation of Feed Slurry

[0082] In certain systems and methods of the present disclosure, biomass having a wide particle size distribution is processed to increase surface area to promote HTL chemical reactions, allow it to pass through narrow piping and pump’s rotor/stator housing, and reduce settling in the biomass slurry. In certain systems and methods of the present disclosure, this may be accomplished using a series of equipment reducing biomass size as follows, referring to embodiment 1100 illustrated schematically in FIGS. 34A and 34B: • [0083] Chipper - can handle larger biomass such as branches and pieces of wood and break them down into smaller chips. This is typically done on location at the source of the biomass (as indicated by the dashed line box in FIG. 34A);

• [0084] Shredder - similar to a chipper but can handle wet biomass also breaking down into smaller pieces. For model example: WEIMA WLK 1000, 125 rpm, 37 kW;

• [0085] Re-shredder - material is then processed through a re-shredder to achieve < 10 mm granulate which is then followed by a hammermill;

• [0086] Hammermill - also known as a pulverizer, works on the principle of impact grinding. A hammermill consists of a rotor with impact hammers and external housing where material passes through the housing. For example: Scanhugger EU 4000 Hammermill with the main motor: 45 - 75 kW and capacity of 3000 - 4200 kg/h.

[0087] Multiple passes may be required to achieve the target particle size. Wet material may also be passed through a hammermill. Alternatively, a hardened pump erosion resistant impeller and housing referred to as a grinding pump, may be used depending upon the feed material size and type. A grinding pump is suitable when the particle size is <5 mm in a slurry. A hammermill and a grinding pump can be used in combination.

[0088] One embodiment is illustrated in FIGS. 34A and 34B, where one or more tank trucks 70 may deliver biomass to a receiving pit 71 (about 500 m ³ ), from which a tractor 72 or other equipment may be employed to load the biomass onto a particle sizer and metal screener 73. Any metal is rejected into a trash bin 74. The main biomass stream is then routed to an agitated preparation tank 75 (about 10 ³ m) to which make up water is added via tanks 76A and 76B (about 50 m ³ each). A grinder pump 82 is used to achieve the target particle size, a slurry loop is used with a circulating pump 77 feeding a hammermill 79 to pass the slurry over a vibrating shaker 80 with the target particle screen of 1 mm which rejects the oversize particles and directs the oversized material to further grinding through hammer mill 79 and/or grinder pump 82. The regrind slurry is passed over the vibrating shaker in a loop. The material passing through the screen on vibrating shaker 80 is ready for further feed slurry preparation and fed to staging tank 78 (about 10 m ³ ). In practice, the particle size of the biomass slurry to be fed into the well reactors may range from about 0.1 mm to about 20 mm, or from about 0.25 mm to about 10 mm. [0089] Chemical Preparation Feed Slurry

[0090] In certain embodiments, the staging tank 78 (or feed prep tank) can also receive various chemicals to assist with the process such as corrosion inhibitors, cleaning chemicals such as surfactants, pH adjustment chemicals, heterogeneous and non-heterogeneous catalysts, and temperature resistant rheological additives such as bentonite.

[0091] The relatively high solids content in the feed slurry material are prone to settling and high risk of plugging the wellbore with solids when circulation is temporarily stopped. To avoid this risk, from about 0.1 to about 5 wt. percent (based on weight of feed biomass slurry) of a thermally resistant viscosifier capable of operating at 300 °C may be used to reduce the settling rate of solids. In certain embodiments, the viscosifier generates a non-Newtonian slurry that is thixotropic, exhibiting a stable form at rest but becoming fluid when agitated to reduce solids settling rate; this is called “shear thinning.” This fluid flow behavior also reduces high friction losses when flowing thus resulting in lower pump pressures and low Reynolds numbers which negatively impact heat transfer coefficients. High heat transfer coefficients are important to reduce the requirement for high tube surface area for heat exchange between the inner tubing 32 and product fluid flowing in annulus 38. One such viscosifier is bentonite which after hydration, the bentonite particles expand 10 - 20 times their original volume. Bentonite is a mixture of various clay minerals that consists of from about 60 to about 80 percent montmorillonite. Further accompanying minerals can include quartz, mica, feldspar, pyrite or also calcite.

[0092] Fluids containing clays such as bentonite exhibit a pronounced thixotropic behavior. Thixotropic materials are fluids containing some form of structure as a result of formation of flocs or aggregates between suspended particles or moieties. In clay suspensions the formation of structure is promoted by increased encounter between suspended particles, which can result from Brownian motion of the particles or from the velocity gradient when the bulk of the material is sheared. Tehrani, A., “Thixotropy in Water-Based Drilling Fluids", M-I SWACO Research and Technology Centre, Aberdeen, United Kingdom. Annual Transactions of the Nordic Rheology Society, Vol. 16, 2008. Fluids may be characterized as non-Newtonian plastic; Bingham plastic; non-Newtonian pseudoplastic (shear-thinning, n < 1); Newtonian material, n = 1; and nonNewtonian, dilatant (shear-thickening, n > 1), where “n” is a parameter known as the “flow index” in the three-parameter rheological model for fluids known as Herschel- Bulkley fluids. [0093] In certain embodiments, bentonite can be prehydrated with fresh water into a fluid and mixed with the feed biomass slurry. Alternatively, bentonite can be added directly to the feed biomass slurry while ensuring that the water phase in the feed biomass slurry is within pH and hardness range to fully hydrate. In addition to modifying the rheological properties, bentonite has distinctive features such as a versatile metal free catalyst that can be used to promote various chemical reactions. Bentonite clays have a variable net negative charge, which is balanced by Na, Ca, Mg and, or H adsorbed externally on the interlamellar surfaces. The structure, chemical composition, exchangeable ion type and small crystal size of the clay are responsible for several unique properties, including a large chemically active surface area, a high cation exchange capacity and interlamellar surfaces having unusual hydration characteristics as previously mentioned. Odom, I. E., “Smectite clay minerals: properties and uses”, American Colloid Company, Phil Trans. R. Soc. Land. A311, 391- 409 (1984). Catalysts can potentially reduce reaction temperatures and increase biocrude yields.

[0094] Water and Sludge Recycling

[0095] Referring to FIG. 5 and embodiment 200, the HTL product fluid 7 exiting the annulus of the wellbore of the deepwell reactor 86 contains gas and liquid phases. Gases are separated from the liquids in a gas/liquid separator, 8A, while an oil/water/solids separator 8B separates the mostly liquid phase comprising water, biocrude, and small amount of solids into three primary streams: biocrude oil 13, water 9, and solids 11, each containing varying degrees of the other stream. In certain embodiments, one or more of these streams may be polished via centrifuge 88 to generate relatively contaminant free streams, such as dewatered, polished biocrude stream 13A.

[0096] The water 9 separated from the process can be recycled and mixed directly with the feed material 2 as part of the feed biomass slurry 5 preparation. The separated solids 11 are the sludge from the settled solids layer that contains unreacted biomass solids, carbonized biomass and other inert feed solids residuals from oil water solids separator 8B. The solids separated from the process can be used for land application or sold as a beneficial reuse as an inert carbon rich product. Similar to the separated water, this sludge 11 may be returned and mixed with the feed biomass slurry to further process the unreacted or partially reacted biomass to increase the biocrude yield. Other benefits of returning the sludge to the feed is that the stream does not require any dewatering and all heat energy in the sludge is conserved. The fate of the chemical additives will depend upon numerous factors, some of which are not known at this time. However, it is expected that some of the dissolved inorganic chemicals will oxidize and precipitate, be removed with the sludge or stay in the circulating loop. For organic chemicals, it is likely that at the operating temperatures, they will be decomposed or removed with the sludge or stay in the circulating loop.

[0097] Deep Well Reactor Construction Examples

[0098] FIG. 6 schematically illustrates another system and method embodiment 300 in accordance with the present disclosure. In embodiment 300, the well is constructed using an existing oil and gas production well, so that terminology is used. The well includes of production tubing 104 serving as the inner tubing, and a production casing 102 serving as an outer tubing that is bonded to the subsurface formation using cement 90, forming a well annulus 106. Multiple inner tubes could be used but for simplicity, only one is described in this embodiment. “Casing” in this embodiment includes a conductor casing 92, surface casing 94, intermediate casing 96, and production casing 102. Drilling mud (also referred to herein as drilling fluid) is used between the upper portions of production casing 102 and the formation 28, and between casings 94, 96, and 102, as illustrated in FIG. 6. The inner tubing length is selectively sized (or modified as described in other embodiments to achieve the selected length) to achieve the desired hydrostatic pressure. In embodiment 300 the inner tubing length is typically about 2,380 m. This type of well construction is commonly used in the production of oil and gas.

[0099] The graph of FIG. 7 illustrates schematically the temperature and pressure of the feed biomass slurry (upper dotted line) of embodiment 300 as it travels down the inner pipe of the wellbore while increasing temperature and depth/pressure. The return HTL product fluid (lower dotted line) exits the inner tube and travels to the surface as it decreases in temperature and pressure. Depth and pressure are directly correlated with hydrostatic pressure. The graph also shows the general pressure and temperature environments where HTL and HTC physical chemical reactions occur. As previously indicated, HTC reduces the biocrude yield so the time spent in the HTC favorable environments should be minimized as further explained herein.

[0100] Referring to FIGS. 8 and 9, another deep well HTL reactor embodiment 400 of the present disclosure is presented, comprising two primary zones and a third zone:

• [0101] Heat Transfer & Sub-surface Separation Zone (110);

• [0102] HTL Reaction Zone (112); and

• [0103] Return (product) fluid plenum (114). [0104] In the Heat Transfer & Sub-surface Separation Zone 110, hot reacted HTL fluid that is heated at the bottom of the well travels to the surface in annulus 38. The HTL fluid in zone 110 preheats incoming feed slurry stream 5 in inner tubing 32 from ambient to approximately 280 °C. Most of the heat is recovered via the transfer of thermal energy from the hot fluid in annulus 38 to incoming cold feed slurry 5 in inner tubing 32 while the remaining heat is lost to formation 28. In addition, the biocrude generated from the HTL reactions coalesce and separate from water in annulus 38 in zone 110. There is sufficient hydrostatic pressure to ensure that the water does not boil to steam.

[0105] In HTL Reaction Zone 112, the temperature of preheated feed slurry 5 flowing downward in inner tubing 32 is boosted from about 280 °C to about 300 °C at the bottom portion of the well, 112. At this depth and in zones 112, 114, the feed biomass slurry is under sufficient pressure to ensure the fluid remains as a liquid and not turn to steam which is critical for HTL reactions to occur. The heat source comes from a submersed electrical resistance heater cable 36 inside inner tubing 32. A cement plug 1 16 is used to create the plenum zone 1 14. FIG. 9 illustrates schematically with arrows the heat loss to formation (118), heat transfer from hot HTL product fluid 7 to cold feed biomass slurry 5 (120), and heat transferred to feed biomass slurry 5 from electrical resistance heating cable 36 (122). The arrows show the direction of the heat transfer. Cable 36 heats the fluid in inner tubing 32 which then transfers the heat to the fluid in the annulus which then transfers some heat to the formation which is lost. This cross-section illustration in FIG. 9 changes with depth. It will essentially be the same if the cross-section is taken higher up the reactor but with no heating cable (only the power cable) and the heat source arrows will be in the opposite direction as identified in FIG. 9.

[0106] As the temperature of the feed biomass slurry 5 increases, sufficient pressure must be applied to ensure that feed biomass slurry 5 remains substantially (at least 95 percent, or at least 99 percent) in the liquid phase and above the liquid- gas saturation curve (FIG. 10) as the feed slurry is heated and cooled in the deep well reactor system for two reasons:

• [0107] To ensure that steam is not generated that can impact fluid flow and heat transfer coefficient; and

• [0108] To ensure energy is not wasted for the energy intensive step of water vaporization. The pressure in the system is generated by the hydrostatic pressure, as illustrated in the graph in FIG. 10 which illustrates the feed biomass slurry (upper straight dotted line) and return HTL fluid (lower straight dotted line) are not in proximity to the saturation line (curved dotted line) thereby eliminating the risk of steam generation.

[0109] Deep Well HTL Reactor Design With Sensor Cable

[0110] While there is no standard well design given the numerous possible combinations of tubing lengths, tubing diameters, metallurgy, thickness, connectors, and the like, the following example provides insight into the process equipment and methods, operating parameters, features and limitations that determine deep well HTL reactor design. (Refer to Table 5.)

Table 5. Well Construction Mechanics

[0111] Since there is no advantage in higher pressures to promote HTL reactions, the length of inner tubing 32 should be kept to the minimum length to minimize heat losses to the environment, cost of power and heater cable (34, 36), reduce repairs/maintenance and well intervention costs. If greater residence time is required, the length of inner tubing 32 could be increased and/or increase the diameter of outer tubing (casing) 30. As illustrated schematically in FIGS. 11 and 12, a sensor cable 130 may be provided, having connections to one or more temperature sensors 132 (260 °C sensor), 134 (300 °C sensor), and secured to collars 138 using coupling cable clamps/protectors 136. Cross-sections A-A, B-B, and C-C in FIG. 11 are illustrated schematically in FIGS. 11A, 11B, and 11C, and cross- sections A-A and B-B in FIG. 12 are illustrated schematically in FIGS. 12A and 12B.

[0112] Most existing oil and gas production wells exceed the typical depth required for HTL reactions. Therefore, in certain embodiments using such wells, the well is sealed from the unused bottom portion of the well. There are two primary methods of sealing a well at the bottom of the outer tubing that are commonly used in oil and gas well construction: cement plug and packer. A plug of cement or similar material placed as a slurry in a specific location within the wellbore and which has been set to provide a means of pressure and flow isolation. An inner cement plug (such as 116 from FIG. 8) and an outer cement plug positioned between outer tubing 30 and formation 28 may be employed. Cement plugs are preferred due to simplicity and ability to withstand high temperatures. A packer can be run into a wellbore with a smaller initial outside diameter that then expands externally to seal the wellbore. An inflatable packer employs flexible, elastomeric elements that expand. The well can be sealed at depths ranging from about 10 to about 20 m below a bottom or distal end of the inner tubing to create an upper plenum above the inner cement plug 116 and a lower plenum below the inner cement plug 116 to ensure:

• [0113] sufficient space in the upper plenum for the fluid 5 to reverse flow towards the surface,

• [0114] allow for the thermal expansion of inner tubing 32 (calculations indicate that the inner tube 32 will expand and grow in length approximately 2.7 - 4.0 m depending upon steel type)

• [0115] provide separation that cools the wellbore fluid 5 between inner tubing 32 bottom and the seal if a non-cement plug or seal 116 is used, and

• [0116] prevent the flow of fluids or gases via lower plenum from the original oil and gas bearing formation. [0117] Inner and Outer Tubes Design Examples

[0118] Tubing suitable for use as inner tubing 32 useful in the systems and methods of the present disclosure are made of corrosion resistant material, high thermal conductivity and low wall thickness. The wall thickness is determined primarily by structural requirements due to weight of pipe and joint connections and primarily for pressure differential across the pipe wall as the pressure is essentially the same. Inner tubing 32 is affixed to the wellhead at the surface which forces the thermal expansion of inner tubing 32 axially in the downward direction where a sufficient gap exists in the upper plenum between the bottom of inner tubing and plug 116.

[0119] Inner tubing 32 diameter is designed to provide relatively high velocity and turbulent flow regime to:

• [0120] Increase heat transfer coefficient for the heat transfer from the hot product fluid 7 traveling up to the surface in annulus 38 to the cold biomass slurry 5 traveling to the bottom of inner tubing 32;

• [0121] Minimize deposition and fouling of the inside wall of inner tubing 32;

• [0122] Increase rate of depolymerization and decomposition of the wet slurry biomass into smaller compounds;

• [0123] Minimize residence time of the feed biomass slurry 5 in inner tubing 32 until HTL reaction zone (112) is reached to less than about 45 min. This is important to minimize the time the feed slurry spends in the carbonization environment (temperatures ranging from about 180 to about 250 °C) which the feed biomass slurry must pass through to reach HTL temperature and pressure environments. Carbonization negatively impacts biocrude yields. The length of inner tubing 32 section where the carbonization environment is present is approximately 450 m, therefore at velocity of about 0.84 m/s the time spent is 8.9 minutes of the total 48 min or 20 percent.

[0124] Conversely, in annulus 38, outer tube 30 (casing) diameter is designed to provide low velocity and laminar flow regime to:

• [0125] Increase residence time for HTL reactions to occur in HTL reaction zone 112;

• [0126] Promote repolymerization of small compounds formed from the decomposition and depolymerization in inner tubing 32;

• [0127] Increasing residence times decreases viscosity of the biocrude; • [0128] Promotes the coalescence of the hydrocarbons generated by HTL reactions.

• [0129] Increases the separation of the hydrocarbons from water. (Refer to Tables 6 and 7 below)

Table 6. Flow in Tubing and Annulus

Table 7. Residence Time

[0130] The two graphs presented in FIGS. 14A and 14B illustrate the length of the time the feed biomass slurry (dotted line) and HTL product fluid (x line) remain in their respective temperatures and pressures while flowing through inner tubing 32 and annulus 38, respectively in certain embodiments of the systems and methods of the present disclosure. In addition, the HTC and HTL temperature and pressure environments are overlaid to show the amount of time spent in those environments in certain embodiments. As previously indicated, to maximize biocrude yields, the time spent in the HTC environment should be minimized. This is reflected in the relatively short period in the HTC environment for these embodiments (less than about 10 min vs. HTL about 30 min).

[0131] Referring to FIG. 15, in another embodiment referred to as embodiment 600, to further decrease the time in the HTC environment 150, a section 152 of inner tubing 32 operating at between about 180 °C to about 250 °C can be reduced in diameter from the reference 73 mm to 44 mm at depths of about 1300 to about 1800 m, or for a total length of about 500 m, as illustrated schematically in FIG. 15. The diameter reduction has the benefit of reducing the residence time of feed slurry 5 in HTC environment 150 from about 10 to about 6 min, a reduction of about 40 percent. Methods to reduce inner tubing 32 effective diameter can be accomplished with smaller diameter section of inner tubing 32 such as smaller ID production tubing sections commonly found in 9.1 m sections and screwed together with a threaded collar or a metal insert with the selected ID which could be placed in sections or the entire length represented in 150, about 500 m in inner tubing 32.

[0132] Mixing Device in Annulus

[0133] To improve mixing in the laminar flow regime in annulus 38, an apparatus and method to increase turbulence is proposed for use in one or more embodiments of the present disclosure. Generic static inline mixers are available in various geometries; however, these geometries are unsuitable for very long lengths and can be prone to fouling when solids are present. As such, an apparatus and that is less prone to solids build up and bridging may be used in certain embodiments. Referring to FIGS. 16A (turbulent flow indicated by non-straight arrows and “T”) and 16B (laminar flow indicated by straight arrow and “L”), this may be accomplished by modifying an interconnect tube collar with a mixing collar sleeve 154 attachment that is clamped to an existing collar 156 to reduce annulus 38 diameter, embodiment 600 or a modified collar design with a similar outer diameter, collectively referred to as a mixing collar. The reduced annular distance increases velocity and at the downstream end of mixing collar 154, flow is disrupted and eddy currents are generated, thereby enhancing mass and energy transfer. Mixing collar 154 can be made of any material that is resistant to corrosion and temperature with the lowest density so as not to increase weight on inner tubing 32. Mixer collar 154 can also be made of hollow material. In certain embodiments an upper end of mixer collar sleeve 154 has a flat face to promote the disruption of flow, rather than a sloped face. Mixing collar 154 can be secured with a latch or strapping or two halves screwed together. In certain embodiments, mixing collar sleeve 154 covers the top and bottom sections of collar 156 so that mixing collar sleeve 154 can rest on collar 156 to prevent sliding of mixing collar sleeve 154 in normal contraction/expansion and flow of fluids. All materials used for securing should be of similar properties as mixing collar sleeve 156. The number of mixing collar sleeves 154 is dependent upon the flow regime and distance where the flow returns from turbulent to laminar flow. In certain embodiments, mixing collars sleeves 154 are positioned apart a distance ranging from about 3 to about 15 m (from about 10 to about 50 feet). If oil field production tubing is used as inner tubing 32, then interconnecting tube collars 156 are typically utilized every 9.15 m (30 ft), therefore in those embodiments each mixing collar sleeve is positioned at each tube collar 156.

[0134] Embodiments Using Coiled Tubing as Inner Tubing

[0135] In certain embodiments, such as embodiment 700 illustrated schematically in FIG. 17, inner tubing 32 can be a coiled tubing string 164 supplied by Halliburton, Schlumberger, Weatherford, and the like, typically on a truck 160. Referring to FIG. 17, coiled tubing (CT) is a long, continuous length of pipe 164 wound on a reel or spool 162. The pipe is straightened prior to pushing into a wellbore and rewound to coil the pipe back onto the transport and storage spool 162. Depending on the pipe diameter (1 in. to 4-1/2 in.) and the spool size, coiled tubing can range from 2,000 ft to 15,000 ft (610 to 4,570 m) or greater length. To deploy CT downhole (solid arrows indicate direction moving into the wellbore reactor, not illustrated in FIG. 17), the CT operator spools CT 164 off reel 162, usually assisted by a crane 172, and leads it through a gooseneck 166, which directs the CT downward to an injector head 168, where the CT is straightened just before it enters the borehole at wellhead 174. A stripper blowout preventer (BOP) 170 is also provided. The portability of a coiled tubing unit allows the removal of the tubing from the well for inspection and maintenance, clean any deposition on the tubing wall and repairs and maintenance that can be spooled back onto the reel. A CT unit could be installed permanently and fully integrated with the wellhead. In certain embodiments, as explained herein with reference to FIG. 21A, a lower pressure-rated wellhead could be employed.

[0136] Material build up on the exterior wall of inner tubing 32 is expected. Less material is expected on the interior wall of the inner tubing 32 due to high velocity and low residence time. A cleaning system 176 enclosed in a box with high pressure water sprayer nozzles 184 around inner tubing 32 with fluid collection, separation and return to high pressure pump loop can be utilized (pump 180, solids separator 182). Surfactants, acids and caustic chemicals may also aid in the removal of any deposition. The tube continuously moves through cleaning system 176 in these embodiments. (Dashed arrows in FIG. 17 indicate movement of CT out of the wellbore reactor.) The nozzle design, number of nozzles, nozzle flow rates, nozzle exit pressure, and nozzle positioning will vary from system to system, but certain embodiments may featuretwo sets of four flat fan nozzles with fan angle ranging from about 25 to about 36 degrees spray positioned in a spiral staircase manner essentially covering the pipe twice (available from Lechler or the like), flow rates ranging from about 20 to about 40 L/min (about 5 to about 10 gpm) per nozzle, at nozzle exit pressures ranging form aboutlO to about 20 bar (from about 145 to about 290 psi), the nozzles set back about 1 to about 1.5 times the pipe diameter, and positioned in a spiral around the pipe offset 90 degrees from each other and the same in the axial direction. Flow rates, exit pressures, and angle of attack from nozzle to nozzle may be the same or different.

[0137] In certain embodiments, the heater cable, sensor cable and sensors can be integrated into the coiled tubing where the coiled tubing is preassembled with the heater cable placed inside the coiled tubing prior to mobilizing on location. These embodiments would provide for greater assurance of proper heater cable placement and reduces risk of potential blockages in the inner tubing when on location.

[0138] Multiple Feed Biomass Slurry Tubes

[0139] For maximum capital, footprint, startup and heat loss efficiency, in certain embodiments, such as embodiment 800 illustrated schematically in FIGS. 18 and 18A, multiple feed biomass slurry inner tubings 32 may be utilized within a single wellbore, each having its own heater cable 36. The wellbore geometry should be such that the fluid velocities, residence times and flow regimes remain in the same range as outlined herein. Generally, this would involve a larger diameter outer tubing 30 to accommodate a larger flow through annulus 38. In these embodiments the flow to each inner tubing 32 would be controlled to be independent and monitored so as not to have reverse flow. It will be understood that other embodiments are possible than those illustrated in FIGS. 18 and 18A. For example, the number of inner tubing 32 and heater cables 34, 36, may be lower or higher than illustrated. FIG. 18A illustrates seven inner tubing 32 and seven heater cables 36. [0140] Heat Source Method

[0141] Referring to FIG. 19, heating in HTL reaction zone (42, 112) is provided by heater cable 34 placed inside inner tubing 32. The downhole power and heating cable 34 consists of two sections: power transmission and heating. FIG. 19 illustrates schematically a portion of the power transmission cable, with some parts cut away, including the heating element 34, magnesium oxide insulation 190, and a stainless steel sheath 192. In certain embodiments, the power transmission and heating sections are bonded together in series and wound on a single spool at the surface. The coiled power cable 208a & 208b provides the required voltage from the power control cabinet 201 to the coiled heating cable 209. The downhole heating cable provides the heating density required for maintaining wellbore temperature. This designed cable will produce heat via resistance and the skin effect principle for safe and effective heating downhole of the feed biomass slurry.

[0142] Heating Cable Specifications

• [0143] Power Cables (208 a & 208 b):

• [0144] Cable Size: OD ∅30mm (01.181in), Three

• [0145] Core Conductor

• [0146] Rated Voltage: 1,500 V

• [0147] Working Temperature Range: 250°C @ 1560 m (208 a)

• [0148] Working Temperature Range: 600°C @ 500 m (208 b)

• [0149] Tensile Strength: 630MPa (91.4ksi)

• [0150] Cable Weight: 3.0kg/m (2.021bs/ft)

• [0151] Heater Cable 209:

• [0152] Rated Power: 350kW

• [0153] Insulation Resistance: > 300MΩ·km (Temperature at 20°C, Humidity 80%)

• [0154] Sheath Outer Tubular Material: 316L Stainless Steel (eq. to US ASTM Gr. 240)

• [0155] Heater Cable Length: 220m at 600°C (1,112°F).

[0156] The length of the heater cable is determined by the watt density of the heater cable, typically ranging from about 0.8 to about 2.0 W/m, and the heating requirement. Higher heating power watt density is desirable as it will reduce the time to heat the formation resulting in a faster startup of feed biomass slurry.

[0157] Power Distribution Design for Heater Cable

[0158] In certain embodiments, and referring to Table 8 and FIG. 20, the control cabinet power (201) is 470 kilowatts with a three phase AC input voltage of 480V or 600V, depending on main grid voltage. The medium voltage fuse cabinet (203) is rated 1,600V at 135 A from the transformer to protect the heater cable.

Table 8. Wellbore Electrical Heating Design, Component Descriptions

[0159] Heater cable and Wellhead Adapter

[0160] The wellbore containing the inner and outer tubes along with the plug seal completely isolates the formation therefore influx of fluids into the wellbore is not possible which eliminates any unwanted high-pressure event. Since the wellbore is never in communication with the producing formation when the cable is in the well, a lower specification well head adapter design, as illustrated schematically in FIGS. 21A-B, can be adopted compared to a traditional well head requiring high pressure specifications. The pressure at the well head adapter is expected to be less than 100 psi to accommodate pressure line losses in the inner/outer tubes and any back pressure required for the surface downstream separation equipment. The heating cable is run on the inner diameter of the tubing and therefore the cable weight will be hung off at the wellhead. FIGS 21A- B illustrate schematically a neutral cable 214 and a soft power cable 216 connected to explosion proof junction box 206, which in turn is connected to power and electrical heating cable 34, 36 (also 208a & 208b & 209). The cable is routed through wellhead stuffing box 207 and a pumping tee 218, then through an adapter bonnet 220 and tubing head 222. A tubing hanger 224 is used, along with a tubing nipple and collar 228. Tubing head 222 is welded at 230 to outer tubing 30. Bull plugs 226 are provided for maintenance. As detailed in FIG. 28B, wellhead stuffing box 207 is sealed using cable suspension sealer 232, typically rubber resistant to the temperatures and pressures of the HTL environment.

10161 J Heat Transfer

[0162] One of the biggest advantages of systems and methods of the present disclosure is the ability to transfer heat without the addition of a high-pressure heat exchanger to the overall process, high pressure safety systems and instrumentation. The heat from the HTL product fluid moving to the surface in the annulus is efficiently and safely transferred to the cold feed biomass slurry moving through the inner tube via the inner tube wall. Efficient heat transfer between the inner and outer tubes is critical to minimize energy consumption and controlling high returning product fluid 7 temperatures.

[0163] As illustrated in FIGS. 22 and 23, feed biomass slurry enters the well in most embodiments at ambient temperature and low pressure, about 50 psi for example. The feed biomass slurry rapidly increases in temperature in inner tubing 32 at 18.1 and 18.7 °C/min in heat transfer and sub-surface separation zone 110 and HTL reaction zone 112, respectively. This high rate of heat transfer is due to the high velocity in inner tubing 32. The temperature gradient in inner tubing is positive 0.08 °C/m (as illustrated at 242) vs. negative gradient of 0.12 °C/m in the annulus (as illustrated at 240) as heat is transferred to the feed biomass slurry in inner tubing 32. The difference in inner tubing and annulus is due to the temperature differential which is required for the heat transfer. The thermal energy from the exiting fluid can be further recovered by preheating the feed biomass slurry with commonly available high surface area plate frame heat exchangers or heat exchanger designs that can operate in the relatively low temperature and pressure environments at the surface. Alternatively, the separated water in the HTL product fluid 7 can be mixed directly with the feed biomass slurry as part of the makeup water to harness all the energy in the HTL product fluid 7. Separation equipment at surface will need to withstand the operating temperature of the outbound HTL product fluid 7. As illustrated schematically in FIG. 23, arrows 246 illustrate heat loss to formation 28, and arrows 244 illustrate temperature increase in the HTL reaction zone. And arrows 242 illustrate the heat transfer to the HTL project fluid 7 resulting in temperature increase.

[0164] Modeling transient heat loss to the formation is a geomechanical, thermal and fluid flow problem which can be conducted with finite and discrete elemental methods as typically used for modeling heat and steam transfer to the heavy oil or bitumen formation such as steam assisted gravity drainage production. Heat transfer and thermodynamic equations can be used to calculate the heat losses over time. Fundamentally, the thermal energy is transferred to the formation via the outer tube wall and cement bond interface between the outer tube and formation from the heated fluid with the heater cable as the source.

[0165] Heat Loss to Formation

[0166] In order to model heat loss to the formation, several characteristics and parameter assumptions must be made including geological properties, wellbore construction, thickness and length of wellbore materials, thermal conductivity and specific heat of steel, concrete, drilling fluids and formation, surface areas and impacted formation volume, operating and formation temperature. Calculated results based on the assumptions described herein are illustrated schematically in FIG. 27. Calculations were conducted in equally spaced segments in the vertical direction. In systems and methods of the present disclosure the temperature inside the wellbore is assumed to be equal to the temperature of the outer tubing. This generates a temperature gradient with the reservoir temperature at a particular distance from the interface. It is generally understood that formation temperatures increase with depth at approximately 0.025 °C/m but is location specific and dependent upon many geological factors and can be as high as 0.04 °C/m. (SINTEF. “Drilling the world's hottest geothermal well", ScienceDaily, 23 October 2015).

[0167] Overtime, as illustrated in FIG. 26, as heat is lost radially to the formation, the formation temperature will rise and exceed the natural formation temperature eventually reaching a steady state temperature at a particular distance. The time taken to reach the outer edge temperature at a particular distance was modeled and the results depicted in FIG. 27. This can be generally referred to as “soak time”. Line 250 in FIGS. 24 and 25 shows heat loss to formation 28 in kW, and line 252 in FIGS. 24 and 25 shows temperature of formation 28 of 110 °C and 75 °C respectively. FIGS 24 and 25 illustrate the impact of higher formation temperatures resulting in lower heat losses to the formation.

[0168] By way of two examples, FIGS. 28A and 28B illustrate the heat loss profile at two different times and at a fixed radial distance from center of the wellbore. The heat loss is significantly more at Day 5 vs Day 50 at all depths. The graph in FIG. 29 shows an alternate depiction of the heat loss over time and depth. Mathematically integrating the heat loss profile, the heat loss over time can be calculated as shown in FIGS 30A and 30B.

[0169] Heat loss to the formation is greatest at the cold start of the process where the temperature gradient between the fluid 7 in the annulus and the formation 28 is the greatest. As illustrated in FIG 30B, the heat loss to the formation 28 reduces over time as the formation around the wellbore increases in temperature, specifically the delta T associated at that depth which is variable with depth, i.e. heat loss is greater at the bottom of the wellbore vs surface. Initially, the majority of the heat is transferred to the formation as the starting fluid 5 (feed biomass slurry or a simple water starting fluid) is circulated through the wellbore. The starting fluid is circulated in and out of the wellbore until the formation reaches target temperature after which the feed biomass slurry can be fed into the deep well reactor. When the heat loss to the formation equals the heat output of the heaters (350 kW), then the net heat to the feed biomass slurry is initiated. As time passes, an increasing amount of heat is transferred to the feed biomass slurry while heat loss to the formation is decreasing. Practically, this means the feed biomass slurry processing rate increases and cost of energy decreases over time.

[0170] Heat loss to the formation is the greatest source of energy requirement for the systems and methods of the present disclosure. The graph in FIG. 30C shows the accumulated thermal energy and the distribution to the fluid 5 and formation. Once the formation is heated sufficiently, i.e. at about Day 15, a greater portion of the heat added to the system is distributed to the fluid. For example, at Day 20 only 16 percent of the energy is transferred to the fluid versus 64 percent at Day 100. This trend continues slowly but indefinitely, i.e. 91 percent after four years. [0171] Wellbore Heat Loss Reduction Methods

[0172] In certain embodiments, steps can be taken to minimize wellbore heat losses through wellbore design but cannot be eliminated. The following list summarizes methods to minimize losses:

• [0173] insulating cement,

• [0174] drilling fluid selection, and

• [0175] placement of cement.

[0176] Insulating Cement

[0177] FIGS. 31, 31A, 31B, and 31C illustrate schematically use of thermal resistant insulating cement at the time of well construction to reduce heat losses. FIG. 31 illustrates schematically a typical wellbore and drilling rig 260, with well bore 262 depicted in FIG. 31 A. A cement float collar 264 and cement guide shoe 266 may be used with a cementing head 268 and cementing manifold 268 to inject insulating cement 272 (for example comprising perlite). FIGS. 32 and 32A illustrate schematically at 280 bonding of insulating cement 227 to casing 30, and bonding at 282 of insulating cement 272 to formation 28. Drilling fluid is allowed to permeate at regions 284 and flow between formation 28 and insulting cement 272.

[0178] Cement has a wide range of thermal conductivity 0.62 - 3.3 W/mK depending upon temperature, moisture condition and types of coarse aggregate. For the purposes of modeling, 1.7 W/mK was used. Significant improvements in insulating properties can be made with the addition of fly ash (Shahedan, et al., “Thermal Insulation Properties of Insulated Concrete”, Revista de Chimie. 70. 10.37358/RC.19.8.7480 (2019)); use of foamed thermal resistant cement; or the addition of perlite to the cement. Perlite is an amorphous volcanic glass and thermal conductivity as low as 0.15 W/mK is possible. In particular, foamed thermal resistant cement may withstand stresses and loads that occur in well construction during the curing, pressure test, completion, production, and injection phases of its life and provide zonal isolation during the life of the well. Petty et al., “Life Cycle Modeling of Wellbore Cement Systems Used for Enhanced Geothermal System Development”, Proceedings 28th Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, January 27-29, 2003. The density of cement is 1.96 kg/L and was reduced to 1.08 kg/L with 20% foam cement, a 45 percent reduction. In addition, the thermal conductivity of the 20 percent foam cement was reduced by 65 percent. Maddi, “Smart Foam Cement Characterization for Real Time Monitoring of Ultra-Deepwater Oil Well Cementing Applications” (2016). The overall impact of a 65 percent reduction in thermal conductivity of cement on the entire wellbore results in an initial reduction of 4 percent in heat loss based on the example wellbore.

[0179] Drilling Fluid Selection

[0180] Referring to FIGS. 33A-C, well reactor embodiments 900 and 1000 are described. During drilling and well construction, some drilling fluid 98 permeates into formation 28 between cement 90 and formation 28, and some drilling fluid 98 remains behind the most outer casing 92 and formation 28 by design, typically between 1 mm - 50 mm respectively. Intuitively using a lower thermal conductivity drilling fluid when drilling makes good sense because the thermal conductivity of generic water-based fluid is around 0.575 Wm.k (Hong et al., “Influence of M0S2 Nanosheet Size on Performance of Drilling Mud”) and that of generic oil-based fluid is around 0.275 Wm.k (Fazelabdolabadi et al., "Thermal and rheological properties improvement of drilling fluids using functionalized carbon nanotubes”). Alternatively, a well can be drilled using air drilling methods in formations where there is no influx of water or hydrocarbon liquids. Compressed air at high flow rates and moderate pressures are used to circulate through the well bore. Air drilling eliminates the use of liquids entirely thereby inherently generating a porous and insulating layer between the outer casing 92 and formation 28 and the cement 90 and formation 28. Mist and foam drilling can also provide similar benefits as they use limited amounts of water.

[0181] Placement of Cement

[0182] The placement of cement between the casing (outer tube 92) and borehole is to ensure wellbore security, support casing, corrosion protection, isolating formation fluids and pressure containment. At intermediate depths, typical placement of cement is not taken to the surface as illustrated in FIG. 33 A, which illustrates the top of cement (TOC) 290 at 6,000 ft or 1,500 ft (292) of cement placement. Where possible, as illustrated in FIG. 33B and embodiment 900, the depth of cement should be kept to a minimum due to the thermal conductivity of cement at 1.7 W/mK vs drilling fluid at 0.572 W/mK. Drilling fluid provides better insulating properties than cement. In addition, as mentioned herein and illustrated in FIG. 33B, water based drilling fluid will evaporate overtime (294, 296) at lower depths where temperatures exceed 100 °C thereby leaving more void space and improving thermal insulating properties. In alternative embodiments, such as embodiment 1000, drilling fluid 98 behind the casing can be displaced entirely with insulating cement (IC) 272 along with non-insulating cement (NIC) 90 used for securing the casing as illustrated in FIG. 33C. This provides the benefit of structural integrity of cement and improved reduction in heat losses to the formation based on 0.572 W/mK for drilling fluid vs 0.15 W/mK for insulating cement as previously described.

[0183] Geothermal

[0184] One might believe that geothermal energy could be applied as a CO ₂ - free and natural source of heat, however there is a practical limitation to the access to geothermal energy. The temperatures at which the HTL well reactors operate in accordance with the present disclosure are well beyond any current geothermal wells which are typically less than 150 °C. At deeper levels, drilling operations and materials integrity are faced with major challenges. Steel becomes brittle, and materials such as plastics and electronics either fail or start to melt. Normally, wellbore tool electronics only function for a short time at temperatures greater than 200 °C. These problems must be resolved if the extraction of high-temperature geothermal heat is to become a going concern. However, geothermal energy can still play an important role in certain embodiments in minimize energy requirements by reducing heat loss to the formation by reducing the delta T between the fluid in the annulus and the formation. Smaller the delta T, lower the heat loss as previously discussed.

[0185] Process Flow Diagram & Operations

[0186] Process Flow Diagram

[0187] Referring to FIGS. 34A and 34B, systems and methods of the present disclosure can be broken out into four modules:

• [0188] Feed Receiving, Storage and Preparation Module

• [0189] Feed Slurry, Mix and Pump Module

• [0190] Deep Well Reactor Module

• [0191] Gas-Liquid-Sludge Separation & Storage Module [0192] While not required in all embodiments, embodiment 1100 includes equipment at both surface and subsurface that are fully integrated. The process takes in biomass materials and outputs four products: biocrude, process water, process gas and sludge.

[0193] Module 1 Feed Receiving, Storage and Preparation Module Process description

[0194] The purpose of this module is to receive, screen, store the feed biomass material as it is received. Feed materials are sampled, homogenized, and adjusted for viscosity and solids content with water. The module also grinds the feed solids for the target particle size. Various wet biomass materials collected from sources are dumped or pumped into the receiving pit 71. Material is typically received in vacuum trucks 70, tankers, sealed roll off bins and other containers. A gantry crane (not illustrated) equipped with a clam shell bucket homogenizes the material into a homogenous mixture/slurry in pit 71. Recovered and separated water 9 from the downstream separation process is routed to makeup water tank(s) 76A and 76B and mixed with the biomass mixture in one or more feed tanks 304 to make the biomass slurry 5. One or more additives may be mixed into the biomass slurry from tanks 302, such as catalysts, pH adjustment chemicals such as sodium hydroxide or sulfuric acid, chlorine, and the like. The biomass slurry passes over a vibrating screen 73 to remove debris, oversize material, and metal. The reject material is collected in a roll off bin 74 and transferred to a landfill. The material passing through the screen enters the grinding system. The grinding system prepares the biomass slurry so that particles are reduced to less than 1 mm. The grinding system in embodiment 1100 includes feed prep tank 75, grinder pump 82 having a hardened impeller and pump housing for attrition, classifying vibrating screen 80, and an oversize particle return and feed prep tank 75. The biomass slurry is received in the grinding system receiving tank(s) 71 from one or more trucks 70 (or via railroad or other transport mechanism) and pumped to the classifying vibrating screen 73. The grinder pump 82 includes a hardened impeller and pump housing designed for attrition of the biomass materials while pumping the biomass slurry to the classifying vibrating screen 73. The classifying vibrating screen 73 utilizes 1 mm screens to separate >1 mm for further attrition. The >1 mm reject material is returned to the grinding system receiving tank 71 and passes through grinding pump 82 in a continuous loop, while the <lmm slurry is transferred by gravity to feed prep tank 75. In certain embodiments, the screen size could range from about 0.5 mm to about 10 mm. [0195] Module 2: Feed Slurry, Mix and Pump Module

[0196] The purpose of this module is to add and mix chemicals from tanks 302 to the biomass slurry precursor to prepare HTL feed biomass slurry before pumping to a feed preheater heat exchanger 310 to recover thermal energy from an HTL product fluid 7A from which light ends have been removed exiting from Module 3. This module also pumps (via one or more feed pumps 306A, 306B) the HTL feed biomass slurry to deep well reactor 100 in Module 3. Recovered water 9 from Module 4 can be added to the ground feed slurry in feed tanks 304. The feed biomass slurry 5 is prepared to meet flow and viscosity characteristics suitable for pumping as described in Table 3. The feed tanks 304 are equipped with agitators which could include circulating pumps with jets or standard shaft/impeller agitators to ensure solids remain suspended in the slurry. Feed tanks 304 can also receive various chemicals 302 to assist with the process such as corrosion inhibitors, cleaning chemicals such as surfactants, pH adjustment chemicals such as sodium hydroxide, sulfuric acid, chlorine, and the like, heterogeneous and non-heterogeneous catalysts, and thermal resistant rheological additives such as bentonite. The biomass slurry feed pump 306A, 306B may be a vertical multistage centrifugal slurry pump capable of pumping up to 10,000 L/hr., 100 cP, 1.5 SG and 7 bar such as a Gol Pump model SBI 10 - 16. Biomass slurry 5 from feed tanks 304 is pumped at <100 psi pressure and ambient temperature into the feed preheater heat exchanger 310, which may be a plate frame heat exchanger or other design, where feed biomass slurry 5 is heated with return HTL product fluid 7 A (from which light ends have been removed in two-phase separator 308) from annulus 38 of well reactor 100. HTL product fluid 7 comprises products from the hydrothermal liquefaction reactions of the biomass, typically biocrude, biochar, water, gasses, and inert materials at temperature less than about 70 °C and less than about 100 psi. The feed biomass slurry 5 is heated from ambient to about 20 °C less than the HTL product fluid temperature or approximately 50 °C in feed preheater heat exchanger 310. Optionally, in certain embodiments, a coiled tubing unit 311 and high-pressure cleanout unit 312 may be employed, as indicated by dashed lined arrows downstream of preheater heat exchanger 310 and as discussed previously herein.

[0197] Module 3: Deep Well Reactor Module

[0198] The purpose of the Deep Well Reactor Module is to take the feed biomass slurry 5 and apply sufficient pressure, temperature and residence time for HTL reactions to occur while minimizing hydrothermal carbonization reactions. After the conversion of the biomass slurry, the HTL product fluid and gas byproducts are returned to the surface for separation and recovery. The preheated feed biomass slurry 5 enters the deep well biomass conversion reactor 100 through the inner tubing 32 of the reactor about 2380 m (about 7800 ft.) in length that comprises two zones. As the feed biomass slurry 5 travels to the bottom of inner tubing 32, it gathers heat from HTL product fluid 7 in annulus 38 to about 280 °C to 2160 m, referred to herein as Zone 1, Heat Transfer

6 Sub-surface Separation (110). HTL product fluid 7 travels to the surface counter-currently to feed biomass slurry 5. Feed biomass slurry 5 is further subjected to heat from the heater cable 36, raising the temperature from about 280 °C to the target of 300 °C, referred to as Zone 2 HTL Reaction (112). In this example, the residence time of feed biomass slurry 5 in inner tubing 32 in Zone 1 and 2 are about 48 minutes and about 5 minutes, respectively, which times may vary depending on the feed biomass slurry characteristics, well reactor structure, and efficiency of the heater cable. The residence time in Zone 1 should preferably be as low as practical, ranging from about 20 to about 60 minutes. The residence time in Zone 2 should be such that the fluid temperature is raised to the target temperature in as short as time as possible which ranges from about 2 to about 8 minutes. The velocity of feed biomass slurry 5 in inner tubing 32 may range from about 0.6 to about 1.5 m/s, and velocity of HTL product fluid 7 in annulus 38 may range from about 0.10 to about 0.2 m/s. Feed biomass slurry 5 exits inner tubing 32 at about 2,380 m and enters return plenum 114 where the flow is thereafter channeled to annulus 38 where HTL product fluid 7 travels to the surface. HTL reactions occur in Zone 2 (112), both in inner tubing 32 and in annulus 38 at temperatures ranging from about 280 °C to about 300 °C and pressures ranging from about 180 to about 205 bar. In this example, the residence time of HTL product fluid

7 in annulus 38 in Zone 1 (110) and Zone 2 (112) are about 333 minutes and about 48 minutes, respectively, in embodiment 1100.

[0199] In most embodiments, while not absolutely necessary, before the feed slurry flow to the well reactor can be initiated the wellbore is heated to ensure that feed biomass slurry 5 will reach the target temperature. In these embodiments, initially, the temperature of the steel tubing/casing, concrete and adjacent drilling fluid is heated followed by the formation to a certain distance as described previously herein. This is generally referred to as the soak period which has been calculated to be approximately 15 days based on assumptions of well construction and formation characteristics used in the modeling. The heat is provided by circulating a heat soak fluid, for example, but not limited to inorganic fluids such as water, steam, nitrogen, air, synthetic air, and organic fluids, such as natural gas, light hydrocarbons, glycol solutions, and the like through inner tubing 32 and heated with the 350 kW heater cable 36. The heat soak fluid, if not already at temperature (such as when steam is used), is heated to about the same temperature as the feed biomass slurry. The heat soak fluid in annulus 38 heats outer steel tubing/casing 92, cement 90 and/or 272, drilling fluid 98, and formation 28. In the case of water used as the heat soak fluid, the same water is returned to inner tubing 32 inlet 44 and recirculated. After 15 days of recirculating and heating, the feed biomass slurry can be initiated at a rate that matches the heat energy available which equals the heat generation from the heater cable less the heat loss to the formation as previously discussed. Heat loss to the formation is continuously decreasing over time and therefore the feed biomass slurry feed rate can be increased accordingly.

[0200] The heat soak period can be accelerated by adding heat at the surface to the water or other heat soak fluid exiting annulus before returning to the inner tubing. The heating at the surface can be performed by a traditional water heater, raising the temperature to below boiling point of approximately 90 °C while ensuring that the annulus water temperature does not exceed boiling temperature. This accelerated heat soak configuration is not illustrated in FIGS. 34A and 34B.

[0201] Referring to FIGS. 35A-C, CO ₂ and some hydrocarbon gasses are formed in the practice of the systems and methods of the present disclosure, as described earlier. These gasses are in the liquid phase due to the hydrostatic pressure in the well bore, however as the flow of liquids travels to the surface, gaseous products separate from the liquid phase. The gas flow pattern is dependent upon volume, density, temperature, pressure, pipe geometry that determines the relative velocities of gas and liquid. The flow pattern starts as a single liquid phase flow transitioning to bubble flow somewhere in the wellbore annulus and eventually reaching annular flow regime as fluid nears the surface while gas velocities increase significantly. It is desirable to minimize gas velocity to improve heat transfer in the well bore between the counter fluid flows in the inner tubing(s) and annulus along with the external feed preheater 310 because gas is a poor conductor of heat. Also, relatively high volumes of gas require larger volume two phase separator (gas/liquid) vessels (308 in embodiment 1100, FIG. 34B). To minimize gas flow and velocity, back pressure on wellbore annulus exit is applied (via backpressure valve 341 in embodiment 1100, FIG. 34B) to minimize the specific density of the gas phase by adjusting backpressure valve (BPV) 341 downstream of two-phase separator 308. This is discussed further herein.

[0202] Module 4 Gas-Liquid-Sludge Separation & Storage Module [0203] The purpose of this module is to separate the gas/liquid/solids phases from Module 3. The phases are further separated and/or treated for maximum recovery of valuable products and to minimize waste. The valuable products are stored with non-biocrude products either recycled internally or sold externally. The gas and liquid in annulus 38 exit the wellbore and are routed into one or more two phase separators (308). The liquid phase is allowed to settle (via gravity?) under velocity and pumped via transfer pump Pl to preheater heat exchanger 310, and then to oil/water separator 314, while the gas phase from two phase separator 308 is transferred to a knock-out vessel 342. The liquid level in two phase separator 308 is determined by regulating BPV 341 which also controls the flow of liquid to the oil/water/sludge separator (OWS), 314. The flow to OWS 314 can be accomplished with a knock-out vessel transfer pump P2 or the pressure in two- phase separator 308 via a valve (not illustrated in FIG. 41) working in concert with BPV 341.

[0204] Referring again to FIGS. 34A and 34B, OWS 314 separates the incoming fluid into three streams via gravity. One stream is a “raw” biocrude stream 7B, essentially floating oil in OWS 314 which is skimmed and transferred via recovered raw biocrude pump P3 to a recovered raw biocrude tank 320 and a polishing step to remove solids and water contaminants via biocrude polishing centrifuge including a disc stack 322 which further separates the recovered raw biocrude into (A) a saleable, in-spec biocrude (13) that is routed to tank 324, routed to sales tanks 326 via storage pump P10, and to offloading to trucks or other transport 330 via biocrude sale pump P9; (B) process water (9) which is routed from polishing centrifuge including a disc stack 322 to recovered water tank 332 for recycling via recovered water pump P7, and (C) sludge (11) which is routed to sludge receiver 334, sludge auger 336, and sludge storage bins 338 for disposal or sale (in certain embodiments sludge receiver 334, sludge processor 336, and sludge storage bins 338 may be in an off-site sludge management facility, 340). Polished biocrude tank 324, sales tanks 326, biocrude sales pump P9, and biocrude storage pump P10 may reside in an insulated facility, designed by the dashed area 328 in FIG. 34B. The recovered and polished biocrude may be stored in sales tanks 326 at moderate temperatures (>50 °C) to ensure low viscosity for pumping and handling. The second stream produced by OWS 314 is a process water stream 9, pumped by recovered water pump P5 to recovered water tank 332.

[0205] A second stream produced by OWS 314 is an emulsion (9a) - a floating middle layer composed of oil/water and fine solids emulsion which may build up overtime in OWS 314; in certain embodiments this emulsion layer is intermittently processed with an OWS centrifuge or tricanter 318 via an emulsion pump P4, tricanter feed pump P6, and tricanter feed tank 316. Tricanter 318 recovers more biocrude 7B, returns separated process water 9 to recovered water tank 332, and routs recovered sludge 11 to sludge receiver 334 for disposal or sale. Demulsifier chemicals may also be used in OWS 314 to aid in the separation process. A third stream produced by the OWS 314 is sludge (9). Sludge is a settled solids layer that contains unreacted biomass solids, carbonized biomass and other inert feed solids residuals and water slurry. This sludge is removed from OWS 314 via pump P5 and continuously processed with tricanter 318 or a separate decanter (not shown) for dewatering. The dewatered solids 11 are collected in sludge receiver 334 and managed as previously described. The separated water from Tricanter or decanter 318 is collected in recovered water tank 332 which is subsequently returned to Module 1, 76A and 76B. The sludge consisting mostly of biochar is analyzed and stored to determine value as a soil amendment for further reuse or disposal.

[0206] Referring again to FIGS. 34A and 34B, embodiment 1100, the gas phase separated in two- phase separator 308 from the raw biocrude stream 7 is processed to remove fine droplets of water and/or biocrude contaminants that are entrained in the gas phase. These contaminants are removed using one or more knock out vessels 342, 346, which in certain embodiments may include coalescing media, along with a heat exchanger (condenser) 344 that chills the gas stream using a chiller 352 and chiller circulation pump P8 to further remove any contaminants in the vapor phase. Any recovered liquid is returned to OWS 314 for recovery. The polished gas phase which contains mostly CO ₂ but also some non-condensable gasses such as light hydrocarbons (C ₁ - C ₄ ), and small quantities of H ₂ and CO, is processed to separate CO ₂ via commonly available methods such as membrane or pressure swing adsorption or amine solution (348). The CO ₂ free gas phase can then be used as fuel for internal processes as natural gas (NG), used in a natural gas generator 350, or sold as renewable natural gas (RNG). A rupture disc 354 allows venting to a vent line 356. In certain embodiments several rupture discs of various pressure ratings may be employed, and/or one or more pressure relief valves.

[0207] Wellbore Flow Pattern in the Annulus

[0208] FIGS. 35A and 35B are schematic illustrations of various phases of flow in the annulus in certain systems and methods of the present disclosure, and FIG. 35C is a graphical representation of the flow regimes illustrated schematically in FIG. 35B. Approximately 16 percent (dry ash free wt%) of the feedstock is converted into HTL off-gas comprising CO ₂ , CH ₄ , CO and H ₂ , primarily composed of 92 percent CO ₂ and 8 percent C ₁ -C ₅ gasses. “Conceptual Biorefinery Design and Research Targeted for 2022: Hydrothermal Liquefaction Processing of Wet Waste to Fuels", December 2017, Prepared for the U.S. Department of Energy under Contract DE-AC05- 76RL01830 Pacific Northwest National Laboratory. These gasses are in the liquid phase due to the hydrostatic pressure in the well bore, however as the flow of liquids travels to the surface, gaseous products separate from the liquid phase. The gas flow pattern is dependent upon volume, density, temperature, pressure, pipe geometry that determines the relative velocities of gas and liquid. Two-phase flow in vertical pipelines may be categorized into five different flow patterns, as illustrated in FIGS. 35A-C and listed here: Bubble flow, Slug flow, Churn flow, Froth flow and Annular flow. h

[0209] Modeling of the flow pattern in the wellbore was based on the reference feed biomass slurry flow rate and the gas generation as previously discussed. Table 9 shows the velocity of the gas and liquid phases. The flow pattern starts as a single liquid phase flow transitioning to bubble flow in the wellbore annulus and eventually reaching churn and froth flow in the last approximately 50 m before the gas and liquid exits the annulus.

Table 9. Modeling flow pattern in a wellbore reactor

[0210] Process Control Methods

[0211] To ensure efficient and safe transfer and separation of fluids, systems and methods of the present disclosure are controlled by one or more programmable logic controllers.

[0212] Subsurface

[0213] Two methods are described to control the heater cable which in turn provides the desired set temperature and subsequently the heat transfer required for the HTL reactions. With reference to Table 8 and FIG. 20, a first method is to use a thermocouple (TC) 210 with a cable 212 to measure the temperature of the inner tubing wall. The temperature delta between target and measured will trigger the power controls 201 to turn on/off the power to the heater cable 209 to maintain temperature. In certain embodiments, three TCs 210 will be used: TCI is the primary TC to control the heater cable and is placed at the bottom of the inner tubing which will be used to ensure that the temperature of the feed biomass slurry has reached a set point of 300 °C. A second thermocouple, TC2 is used to confirm the expected target temperature of 280 °C at the start of the heater section. Both TCI and TC2 can be used jointly in certain embodiments to minimize response time and troubleshooting. A third thermocouple, TC3, is placed midway of the 600 °C rated power supply cable 208 (lower portion, at greater depth) and is used to protect the 250 °C rated power supply cable 205 (upper portion, extending from the 600 °C rated power supply cable 208 to surface). If the TC3 temperature exceeds 250 °C, essentially a High High trigger, then power to the heater cable can be stopped until high temperature subsides.

[0214] In other system and methods embodiments of the present disclosure, Distributed Temperature Sensing (DTS) systems may be employed to measure downhole temperatures, where a single fiber optic cable can be run to the bottom of a well and the temperature can be monitored at several points along the wellbore, such as that supplied by Yokogawa (yokogawa.com). Yokogawa’s DTSX200 is an integrated optical fiber sensing system designed to provide the most accurate distributed temperature measurements over long distances while reducing operating costs and increasing production. Measuring temperature across the entire wellbore can provide greater insight into the temperature profile of the fluid temperature thereby providing greater process control and troubleshooting. Distributed temperature sensing systems (DTS) are optoelectronic devices which measure temperatures by means of optical fibers functioning as linear sensors. Temperatures are recorded along the optical sensor cable, thus not at points, but as a continuous profile. A high accuracy of temperature determination is achieved over great distances. Typically the DTS systems can locate the temperature to a spatial resolution of 1 m with accuracy to within ±1°C at a resolution of 0.01°C. Measurement distances of greater than 30 km can be monitored and some specialized systems can provide even tighter spatial resolutions.

[0215] The systems and methods of the present disclosure are continuous and subsequent challenges are significantly reduced.

[0216] Pumping

[0217] Pumping of wet biomass slurries is known in the pulp and paper industry, where slurries move through their facilities, but only at lower pressures. The use of higher-pressure systems at high temperatures has limited commercial experience, and thus remains a technological challenge. Matsumara, Y. et al., “Biomass gasification in near- and super-critical water: status and prospects”, Biomass Bioenergy 29 (4), 269-292. Relevant industrial scale pumping systems have been identified but have not been demonstrated for this application. Berglin et al., “Review and Assessment of Commercial Vendors/Options for Feeding and Pumping Biomass Slurries for Hydrothermal Liquefaction”, (2012) PNNL-21981, Pacific Northwest National Laboratory, Richland, Washington, USA. When considering capital costs for such systems, more concentrated feed stock slurries should require smaller processing systems for equivalent throughput and resulting lower capital costs. Similarly, higher temperature will lead to higher reaction rates also resulting in reduced reactor size and cost. However, higher temperature will require higher pressure to maintain a liquid water phase for slurry transport in HTL systems. Therefore, the economic drivers for capital cost reduction in hydrothermal processes are higher slurry concentrations and higher operating pressures both of which lead to increasing difficulties for pumping.

[0218] High-pressure feeding systems for biomass slurries have been recognized as a process development issue but scaled-up systems have not been demonstrated. Pumping biomass slurries was accomplished at the laboratory scale at several sites, but in all cases the slurry concentration was limited. Early work at the Pittsburgh Energy Research Center (PERC) suggests, “Perhaps the areas (sic) of greatest operational difficulty in the bench-scale plant involves the pumping of the waste slurry.” (Wender et al., “Clean liquid and gaseous fuels from organic solid wastes”, in Henstock, M.E. (Ed.), “recycling and Disposal of Solid Waste”, Pergamon Press, New Elmsford, New York, pp. 43-99.) As a result, PERC could only process at up to 15 percent dry solids of municipal solid waste (MSW) in water slurry. Yet, “This pumping problem is not anticipated in large-scale operation.” But, “It is doubtful, however, because of the low bulk density of dried organic refuse, that slurries containing greater than 30 weight percent solids can be pumped (even in commercial installations).” Similar results were reported in the larger scale plant operated for the Department of Energy at Albany, Oregon, for the production of oil from wood flour. In the final report of a contract (Thigpen, P.L., Final Report: An Investigation of Liquefaction of Wood at the Biomass Liquefaction Facility, Albany, Oregon, Battelle Pacific Northwest Laboratories, Department of Energy, Wheelabrator Cleanfuel Corporation, Technical Information Center, Office of Scientific and Technical Information, U.S. Department of Energy, 1982), it was disclosed that wood flour (60 mesh) could be pumped at up to 10 percent in water. Attempts to pre-hydrolyze the wood at concentrations up to 23 percent were accomplished (with either flour or chips) but the prehydrolyzed feed needed to be diluted back to 18 percent in water (12 percent suspended solids) for high-pressure pumping in order to avoid plugging. Both of these cases used progressing cavity pumps for low-pressure pumping and reciprocating plunger pumps with ball check valves for high-pressure pumping. Subsequent evaluation of other pumping methods that were tested at the bench-scale in laboratories around the world were reviewed by (Elliott, D. G., “Hydrothermal Processing”, in “Thermochemical Processing of Biomass ” , John Wiley & Sons Ltd., Chichester, U.K., pp. 200-231.)

[0219] Systems and methods of the present disclosure advantageously reduce or eliminate high pressure pumping as the pressure is generated using hydrostatic pressure.

[0220] High Pressure Let Down Challenges

[0221] In known laboratory and pilot plant processing of biomass using HTL, the reacted fluid is produced at high pressure and high temperature that is later cooled using a high pressure heat exchanger and let down to a low pressure of only a few bars. The typical approach used in these applications has been to use slurry pressure letdown valves to accomplish this pressure letdown. These valves usually control the level in the upstream pressure vessel, which receives direct effluent from the product reactor and allows low pressure liquid separation. In conjunction with the pressure letdown valves, slurry block valves upstream and downstream of the pressure letdown valves have been used to isolate the letdown valves for maintenance/repair and by-pass of the process stream. Block valves and pressure bleed valves are used throughout the plants to isolate process equipment such as pumps, pressure letdown valves, sampling lines, instrumentation, bypass lines, and the like from the flow medium when these equipment components need repair or replacement. Because of the combination of temperatures to 300°C, pressures to 3000 psig, and the abrasiveness of the solid particles in the biomass slurry, these valves require special considerations in the design, selection of materials, and fabrication.

[0222] While reducing high pressures and / or velocities, these valves can be subject to not only turbulence, vibration and noise, but abrasion, corrosion and viscous sludge. Because these applications endure rough wear, routine maintenance and inspection have traditionally been a major concern with linear control and isolation valves. In known HTL demonstration and pioneer commercial plants, availability is heavily dependent on the reliability and successful operation of these critical valves. Krishnan, R. P., “Assessment of Slurry Pressure Letdown Valve and Slurry Block Valve Technology for Direct Coal Liquefaction Demonstration and Pioneer Commercial Plants”, October 1984, Prepared by the Oak Ridge National Laboratory, Oak Ridge, TN. Overcoming the short service life of high-pressure letdown valves has been a major engineering problem in the HTL environments. In contrast to known systems and methods, high pressure is let down in systems and methods of the present disclosure in the wellbore column over a long distance.

[0223] Energy recovery

[0224] HTL is an energy-intensive process that operates at high temperature and pressure. With these high operating conditions, heat and energy recovery during cooling and depressurization of the product flow greatly affects the economic competitiveness of the process. (Ong et al.) Therefore, the pre-heating of the feed biomass slurry with the hot HTL product fluid is critical to the systems and methods of the present disclosure. This is accomplished through the use of heat exchangers, however these heat exchangers are not commercially available. It is possible to custom design such a heat exchanger but it will be very expensive with exotic metallurgy and thickness, and requires a very large footprint. The 2019 State of Technology (Snowden-Swan et al.) showed that approximately 50 percent of the capital cost for a commercial HTL plant is from the heat exchangers used to preheat process slurry to the reactor temperature (350°C). The high cost of the exchangers stems from the high viscosity of the biomass slurry feedstock, which leads to low Reynolds numbers and a large effective area requirement. The high operating pressure of the HTL process also leads to thick tube and shell walls. Snowden-Swan et al., “VVc/ Waste Hydrothermal Liquefaction and Biocrude Upgrading to Hydrocarbon Fuels: 2020 State of Technology", March 2021, Pacific Northwest National Laboratory Richland, Washington. Overcoming the size, exotic metallurgy, construction of large wall thickness heat exchanger is required before HTL can be commercially successful. Systems and methods of the present disclosure solve this issue by use of wellbore inner tubing and outer tubing/casing along with insulating well construction design, whereby the heat is transferred from the annulus to the feed biomass slurry which recovers a majority of the heat with the remaining going to heat losses to the formation. The interesting thing about utilizing a deep well reactor is that the pressure differential across the production (“inner”) tubing(s) is minimal, thereby allowing a relatively thin wall thickness and metallurgy that is high in thermal conductivity, even aluminum could be used with adequate corrosion protection. The current calculations herein used a standard production tubing made of carbon steel with moderate thermal conductivity but using metals such aluminum, which would normally not be applied in oil and gas production due to the corrosive nature of the produced water/brines, has merit due to the unique aspects of the deep well HTL reactor and feed biomass slurries. The feed biomass slurries are generally fresh water based, low chlorides, low oxygen (also no oxidizers are added) and contain minimal dissolved solids and are near neutral pH (or can be made to a neutral pH without impacting the HTL reactions). Using aluminum and aluminum alloys provides the advantage of light weight, high strength is not required, low cost, can be extruded for unique surface geometries (such as axial fins for increased heat transfer surface) and made in long sections. Corrosion protection is important and can detrimental. For example, cannot touch the steel (carbon or stainless steel) as it will promote galvanic reaction and lead to corrosion which of course is the principle of anodic protection. The use of aluminum or aluminum alloys carries some risk that requires further investigation but has potential and plenty benefits.

[0225] In general, the production or inner tubing 32 may have an outer diameter (OD) ranging from about 1 inch up to about 50 inches (2.5 cm to 127cm), or from about 2 inches up to about 40 inches (5cm to 102cm), or from about 4 inches up to about 30 inches (10cm to 76cm), or from about 6 inches up to about 20 inches (15cm to 51cm).

[0226] Biocrude Properties (from Ramirez et al., “A Review of Hydrothermal Liquefaction Bio¬

Crude Properties and Prospects for Upgrading to Transportation Fuels'") [0227] Physical Properties

[0228] Viscosity - Viscosity is a measure of flow behavior of a fluid and an important quantity in many fluid flow calculations. For an organic compound its viscosity is related to its chemical structure. Boelhouwer, J.W.M., et al., “Viscosity data of organic liquids”, Appl. Sci. Res. 1951, 2, 249-268 concluded that straight chain hydrocarbons have higher viscosities than branched hydrocarbons, and alcohol or acid groups have more effect on viscosity compared to esters and ketones. Kinematic viscosity is more commonly used for fuels. High-viscosity fuel will not be well-atomized, leading to poor combustion, increased engine deposits, and higher energy requirements for fuel pumping. Moreover, higher fuel viscosity has been observed to increase carbon monoxide (CO) and UHC. In contrast, very low fuel viscosity leads to poor lubrication of fuel injection pumps, causing leaks and increased wear. This results in biodiesel standards having upper and lower limits in kinematic viscosity.

[0229] Density - In fuels, density is related to the energy content for a given volume. Since the engine injection system measures the fuel by volume, a higher density fuel will have a greater power output from combustion of a larger fuel mass. Density has also been correlated with increases in nitrogen oxides (NOx), particulate matter (PM), CO, and unbumt hydrocarbon (UHC) in emissions. The heating value and cetane number are also both related to density. In literature and in legislated standards, specific gravity is sometimes reported instead of density.

[0230] Heating Value - The fuel heating value is a common criterion for evaluating a liquefaction process. The heating value is a quantitative representation of the biocrude’s energy content, which can be used to evaluate efficiency of converting feedstock to fuel. This quantity also gives the energy density of the fuel, which dictates how much energy is released with each volume of fuel injected into the combustion chamber. Heating value can be presented as a higher heating value (HHV) or a lower heating value (LHV). The HHV takes into account the heat of vaporization of water during combustion, while the LHV does not. In fuels, HHV has been correlated with chemical composition given by ultimate and proximate analyses. Recently, this approach has been applied for HTL biocrudes. Correlations state that heating value is directly proportional with the elemental composition, with carbon and hydrogen increasing heating value and oxygen and nitrogen having a negative effect. However, Ramirez notes that traditional correlations do not closely match experimental data for HTL biocrudes and so existing correlations should be modified. While HHV quantity is not regulated, it is prudent to produce biofuels with heating values similar to conventional fuels to ensure minimal modifications to engines, particularly in injection technology.

[0231] Chemical Properties

[0232] Oxygen Content - Liquefaction biocrudes have significant oxygen content resulting from the depolymerization of biomass components (i.e., cellulose, hemicellulose and lignin). These oxygenated compounds take the form of organic acids, alcohols, ketones, aldehydes, sugars, furans, phenols, guaiacols, syringols, and other oxygenates. In crude oil refining, oxygen is removed to prevent poisoning of catalysts in the reforming process. Studies correlating oxygen content to fuel properties, engine operation and performance have been done on biodiesel. Lower CO emissions and PM have been observed for relatively highly oxygenated fuels such as biodiesel.

[0233] Nitrogen Content - Nitrogen in fuel may interact with degradation products and form solid deposits. Nitrogen content is not regulated by diesel or biodiesel standards, although in crude oil refining, nitrogen content is reduced through hydrotreatment to minimize catalyst deactivation and improve diesel stability. Biocrude from HTL of lignocellulosic materials usually has low levels of nitrogen with a maximum of 2 percent. Higher levels of nitrogen have been reported for biocrudes produced from garbage, wastewater sludge, and algae (up to 10 percent) due to the protein content of the feedstock.

[0234] Sulfur Content - The sulfur content of fuel is a regulated quantity as burning sulfur in fuel produces sulfur oxides and sulfate particles that contribute to PM emissions. Moreover, sulfur can cause increased cylinder wear and deposit formation. ASTM D975 and D6751 limits sulfur content in diesel and biodiesel, respectively, to 15 ppm. Lignocellulosic materials and algae have very minimal sulfur content. Biocrude has been produced with only 0.1-1.3 wt % sulfur. Biochar, on the other hand, has a higher sulfur content, which may mean reactions in liquefaction favor sulfur binding into compounds in the solid fraction.

[0235] Chemical Composition - Diesel is mainly composed of alkanes, alkenes and aromatics, while biodiesel is more oxygenated, comprised of fatty acid methyl/ethyl esters. HTL biocrude, on the other hand, is a complex mixture of oxygenated organic chemicals, aliphatics, sugars, oligomers, nitrogenous aliphatics, and nitrogenous aromatics. Table 10 shows the main chemical groups for biocrude. The chemical composition of biocrudes is usually determined through gas chromatography-mass spectrometry (GC-MS). However, the vast number of components and high complexity of the biocrude prevent effective chromatographic separation, resulting in broad background signals. More recent studies have used nuclear magnetic resonance (NMR) spectroscopy and Fourier transform ion cyclotron resonance-mass spectrometry (FTICR-MS) to perform analyses with higher resolution and accuracy.

Table 10. Groups of chemicals of hydrothermal liquefaction bio-crude

Note * Area % from gas chromatography-mass spectrometry results

1 - Rudra, et al.

2 - Ong et al.

3 - Petty et al.

4 - Thigpen

5 - Snowden-Swan et al.

6 - Moura

[0236] The effects of varying compositions on the physical properties of diesel and biodiesel have been studied, while for HTL bio-crudes these relationships have not been elucidated. Table 11 shows the properties of various groups in diesel and their effect on fuel properties. In biodiesels, chain length and unsaturation of fatty acids are usually correlated to properties. Increasing chain length increases cetane number (an indication of ignition quality), heating value and viscosity, while increasing unsaturation in fatty acids decreases viscosity and cetane number, but increases density and volumetric heating value. Although these relationships are for diesel and biodiesel, they provide an idea of the potential effects chemical composition may have on the physical properties of HTL biocrude.

Table 11. Properties of various chemical groups and their effect on diesel properties

[0237] Key Fuel Properties

[0238] These final fuel properties may not be directly influenced by upgrading processes; however, some consideration should also be given to improving them when processing biocrude. Brief discussions of some key fuel properties to be considered are provided here.

[0239] Cetane Number - The Cetane Number (CN) is related to the fuel ignition delay time. Dorn et al. determined the relationship between fuel components and CN. Normal alkanes increase cetane number the most, followed by branched alkanes, normal alkenes, branched alkenes, cycloalkanes, and aromatics. A high CN signifies good ignition quality, good cold start properties, minimal white smoke in exhaust , and low UHC and CO emissions. On the other hand, a low CN is related to a longer ignition delay time, which leads to higher amounts of injected fuel mixed prior to combustion. This then causes high rates of combustion and pressure rise that manifests as diesel knock. This also brings about premixed burning that leads to high combustion temperatures and increased NOx.

[0240] Vapor Pressure - Total vapor pressure of the fuel is dependent on the interactions of components within the mixture. Vapor pressure of a mixture can be estimated through the use of activity coefficients and thermodynamic models. These models demonstrate the dependence of vapor pressure on fuel chemical composition. As a fuel property, vapor pressure affects performance of fuels, especially during cold start conditions. However, a high vapor pressure is a concern due to higher fuel evaporation that contributes to increased hydrocarbon emissions. [0241] From the foregoing detailed description of specific embodiments, it should be apparent that patentable systems, methods, and computer-readable media have been described. Although specific embodiments of the disclosure have been described herein in some detail, this has been done solely for the purposes of describing various features and aspects of the systems, methods and media, and is not intended to be limiting with respect to the scope of the systems, methods and media. It is contemplated that various substitutions, alterations, and/or modifications, including but not limited to those implementation variations which may have been suggested herein, may be made to the described embodiments without departing from the scope of the appended claims.