DECARBONATION PROCESS OF CARBONATED MATERIALS IN A MULTI-SHAFT

VERTICAL KILN

Technical Field [0001] The present invention relates to a decarbonation process of carbonated materials and to a multi-shaft vertical kiln for carrying said process.

Background Art

[0002] The increasing concentration of carbon dioxide in the atmosphere is recognized as one of the causes of global warming, which is one of the greatest concern of present days. This increase is largely owed to human actions and particularly to the combustion of carbon-containing fossil fuel, for instance for transportation, household heating, power generation and in energy-intensive industries such as steel, cement and lime manufacturing.

[0003] Within the lime production process, natural limestone (mainly composed of calcium carbonate) is heated to a temperature above 900°C in order to cause its calcination into quicklime (calcium oxide) and carbon dioxide according to the following reversible reaction :

CaCCh < CaO + CO2 DH = 178 kJ/mol : Equation 1

[0004] Calcium oxide is considered as one of the most important raw materials and is used in a multitude of applications such as steel manufacturing, construction, agriculture, flue gas and water treatment as well as in glass, paper and food industry. The global annual production is estimated to be above 250 million tons.

[0005] As indicated in equation 1 , CO2 is a co-product of the lime production process meaning that approximately 760 to 790 kg of CO2 is unavoidably generated when producing 1 ton of lime. Moreover, the heat required for heating limestone and for conducting the reaction is usually provided by the combustion of a carbonaceous fuel, which results in additional production of CO2 (ranging between 200 and more than 700 kg per ton of lime depending on the nature of the fuel and efficiency of the kiln).

[0006] The use of vertical shaft kiln prevails in the lime industry as they are particularly suitable for the production of lumpy quicklime compared to other types of furnaces, such as rotary kiln, and because they have the advantage of lower specific 2 energy input.

[0007] In a single shaft vertical kiln, limestone or dolomitic limestone is fed through the top of the shaft and the produced lime is discharged at its bottom. In the pre-heating zone, the limestone is heated by hot gases flowing upward from the combustion zone. In the combustion zone, heat is produced through the direct firing of a fuel to reach a temperature above 900°C and consequently causing the decomposition of the limestone into quicklime and CO2. The lime then enters the cooling zone where it is cooled by air fed from the bottom of the shaft. The produced lime is finally discharged, ground and sieved into the desired particle size. Flue gas leaves the shaft at the top of the pre-heating zone and is fed to a filter system before it is vented to the atmosphere. Specific energy consumption for such single-shaft vertical kilns ranges between 4 and 5 GJ per ton of lime.

[0008] Parallel flow regenerative kilns (PFRK) are a variant of vertical shafts that are considered as the best available technology for lime production with design capacity up to 800 tons per day. They consist in several vertical shafts (usually 2 or 3) connected by a cross-over channel. Each shaft operates alternately according to a defined sequence. Initially, fuel is burnt in one of the shaft (“in combustion”) with combustion air flowing downwards (“parallel flow” with the limestone). Hot gases are then transferred to the other shafts (“in regeneration”) through the cross-over channel in order to pre-heat limestone in said other shafts. A reversal between combustion and regeneration shafts occurs typically every 15 minutes.

[0009] This operational mode enables optimal recovery of the heat contained in product and hot gases bringing the specific energy consumption down to 3.6 GJ per ton of lime. The combustion of the fuels required to bring this heat results in the production of approximately 200 kg of CO2 per ton of lime when natural gas is used.

[0010] The lime industry is making efforts for reducing its CO2 emissions by improving energy efficiency (including investment in more efficient kilns), using lower-carbon energy sources (e.g. replacing coal by natural gas or biomass) or supplying lime plants with renewable electricity. The CO2 related to energy can thus be reduced to some extent. Nevertheless, none of these actions impacts the CO2 which is inherently produced during decarbonation of limestone.

[0011] A route for further reducing emission consists in capturing CO2 from the lime kiln flue gas for permanent sequestration (typically in underground geological formation) or recycling for further usage (e.g. for the production of synthetic fuels). Those processes 3 are known under the generic term CCUS (Carbon Capture, Utilization and Storage).

[0012] Combustion air used in conventional lime kilns contains approximately 79 vol% nitrogen resulting in CO2 concentration in flue gas not higher than 15-25 vol%. Additional measures are thus required to obtain a CO2 stream sufficiently concentrated to be compatible with transportation, sequestration and/or utilization.

[0013] Several technologies have been investigated for concentrating CO2 in particular for the power, steel and cement industry.

[0014] The reference technology for CO2 capture is a post-combustion technology based on absorption with aqueous amine solvents. A typical process includes an absorption unit, a regeneration unit and additional accessory equipment. In the absorption unit, CC>2-containing flue gas is contacted with amine solution to produce a CC>2-free gas stream and an amine solution rich in CO2. The rich solution is then pumped to the regeneration unit where it is heated with steam to produce a concentrated stream of CO2 and a lean amine that can be recycled to the absorber. The CO2 stream is then cleaned and liquefied for storage and transportation.

[0015] The energy requirements for regenerating an amine solvent (e.g. mono- ethanolamin (MEA)) is substantial (approx. 3.5 GJ per ton of CO2 for MEA). While recovering waste heat to produce low temperature steam is often possible in other industrial processes, almost no waste heat is available from a PFRK (as a consequence of the high energy efficiency of PFRK). Fuel must thus be burnt for the purpose of generating steam, resulting in additional CO2 production.

[0016] As described above, limestone calcination in a PFRK is an intermittent process in terms of gas flow rate (e.g. absence of flow during reversal) and in term of flue gas composition (CO2 concentration varies during a cycle). However, amine scrubbers optimally operate with continuous and relatively steady flue gas. In other words, adapting the process to PFR kilns could only be achieved at the expense of a negative impact on the overall efficiency and a complex control of the process.

[0017] It is estimated that amine-based CO2 capture would approximately more than double the production cost of lime or dolime. Those costs are mostly owed to fuel consumption for generating steam, electrical consumption for amine scrubbing and compression, and capital cost for equipment.

[0018] Other post-combustion technologies have been proposed for capturing CO2 from flue gas (e.g. chilled ammonia, adsorption, cryogenic distillation, membranes). All these options show with varying degrees identical drawbacks to those of amines regarding 4 capital cost, energy penalty and adaptability to intermittent processes.

[0019] Oxy-combustion is an alternative to post-combustion capture which consists in burning fuel with technical oxygen instead of conventional combustion air in order to increase CO2 concentration in the flue gas. Within this process, downstream purification is eased at the expense of requiring a source of substantially pure oxygen. For instance, patent CN 105000811 B discloses the use of oxy-combustion for PFRK.

[0020] Oxygen is industrially produced using an air separation unit (based on cryogenic distillation of air) or by pressure swing adsorption. An amount of 200-230 kWh of electricity is required to produce one ton of oxygen with an air separation unit.

Aims of the Invention

[0021] The invention aims to provide a solution to overcome at least one drawback of the teaching provided by the prior art.

[0022] More specifically, the invention aims to provide a process for simultaneously allowing a decarbonation with a high production throughput of a product (e.g. quicklime, dolime) with a high decarbonation grade while producing a CC>2-rich stream that is suitable for sequestration or use.

Summary of the Invention [0023] For the above purpose, the invention is directed to a process of carbonated materials, in particular limestone and dolomitic limestone, preferably with CO2 recovery, in a multi-shaft vertical kiln comprising a first, a second, and optionally a third shaft with preheating, heating and cooling zones and a cross-over channel between each shaft, the process alternately heating carbonated materials by a combustion of at least one fuel with at least one comburent, preferably said comburent comprising less than 70% N2 (dry volume), more preferably less than 50% of N2 (dry volume), in particular said comburent being oxygen-enriched air or substantially pure oxygen, up to a temperature range in which carbon dioxide of the carbonated materials is released, the combustion of the fuel and the decarbonatation generating an exhaust gas, wherein decarbonated materials are cooled in the cooling zones with one or more cooling streams, wherein a mixing between the exhaust gas and the one or more cooling streams is minimized, by providing the cross over channel arranged between the first and the second shaft with a closure means, said means preventing a gas transfer between the first and the second shaft and operating 5 said kiln in a mode, in which the first and second shaft are alternately cooled with the one or more cooling streams or heated in a phase shift manner.

[0024] Preferred embodiments of the process disclose one or more of the following features: - the closure means divides the cross-over channel into a first and a second portion, opening respectively in the first and the second shaft, said process further providing an exhaust passage in each portion, said closure means comprising at least one valve for allowing or preventing a gas transfer between the first and the second shaft, or a plug arranged in a form-fitting manner in the cross-over channel for preventing a gas transfer between the first and the second shaft.

- at least two of the following cycles, preferably two or three of sequential cycles are carried out by:

C1) heating the carbonated materials in the heating zone of the first shaft, while cooling the decarbonated materials in the second and/or third shafts with the one or more streams, preferably feeding the first shaft with the fuel and the at least one comburent and optionally with the recycled exhaust gas from said shaft, while feeding either - the second shaft with the one or more cooling streams supplied at the lower portion of the cooling zone and extracted at the upper portion of the preheating zone and/or the cooling zone and/or from the second cross-over channel portion or - the second shaft with the one or more cooling streams at its cooling zone lower portion while reinjecting the one or more heated cooling streams extracted at least: at the cooling zone upper portion of the second shaft and/or from the cross over channel between the first and second shaft, in a lower portion of the preheating zone of the second shaft, in particular by means of a collecting ring; C2) heating the carbonated materials in the heating zone of the second shaft, while cooling the decarbonated materials in the first and/or third shafts with said stream, preferably feeding the second shaft with the fuel and the at least one comburent, optionally with recycled exhaust gas from said shaft, while feeding either - the first shaft with the one or more cooling streams supplied at the lower portion of the cooling zone and extracted at the upper portion of the preheating zone and/or the cooling zone and/or from the first cross-over channel portion or - the first shaft with the one or more cooling streams at its cooling zone lower portion while reinjecting the one or more heated cooling streams extracted at least: at the cooling zone upper portion of the first shaft and/or from the cross-over channel between the first and second shaft, in a lower portion of the preheating zone of the first shaft, in particular 6 by means of a collecting ring;

C3) heating the carbonated materials in the heating zone of the third shaft, while cooling the decarbonated materials in the first and/or second shafts with said stream, preferably feeding the third shaft with the fuel and the at least on comburent;

- providing two closure means, said closure means comprising at least one valve for allowing or preventing a gas transfer between the two corresponding shafts, respectively, in the cross-over channel between the first and the third shaft and in the cross-over channel between the second and the third shaft, operating said kiln in a mode, in which, during one cycle, at least one of the shafts is heated with one of its two closure means open allowing a fluid connection with another shaft, while the other shaft is cooled by the one or more cooling streams with its two closure means being closed.

- at least one of the following cycles, preferably the following sequential cycles, are carried out by:

T1) heating the carbonated materials in the heating zone of the first shaft while transferring the generated exhaust gas to the second shaft via the corresponding cross-over channel, while cooling with the one or more cooling streams the decarbonated materials in the third shaft, preferably feeding the first shaft with the fuel and the at least one comburent, optionally with the recycled exhaust gas from the second shaft, while feeding either - the third shaft with the one or more cooling streams at the lower portion of the cooling zone, while extracting the one or more heated cooling streams at the upper portion of the preheating zone and/or the cooling zone and/or from at least one of the corresponding cross-over channel portions or - the third shaft with the one or more cooling streams at the lower portion while reinjecting the one or more heated cooling streams extracted at least: at the cooling zone upper portion of the third shaft and/or from the cross-over channel between the second and third shaft and/or the cross-over channel between the third and first shaft, in a lower portion of the preheating zone of the third shaft, in particular by means of a collecting ring;

T2) heating the carbonated materials in the heating zone of the second shaft while transferring the generated exhaust gas to the third shaft via the corresponding cross over channel, while cooling with the one or more cooling streams the decarbonated materials in the first shaft, preferably feeding the second shaft with the fuel and the at least one comburent, optionally with the recycled exhaust gas from the third shaft, while feeding either - the first shaft with the one or more cooling streams at the lower 7 portion of the cooling zone, while extracting the one or more heated cooling streams at the upper portion of the preheating zone and/or the cooling zone, and/or from at least one of the corresponding cross-over channel portions or - the first shaft with the one or more cooling streams at the lower portion while reinjecting the one or more heated cooling streams extracted at least: at the cooling zone upper portion of the first shaft and/or from the cross-over channel between the first and second shaft and/or the cross-over channel between the third and first shaft, in a lower portion of the preheating zone of the first shaft, in particular by means of a collecting ring;

T3) heating the carbonated materials in the heating zone of the third shaft while transferring the generated exhaust gas to the first shaft via the corresponding cross over channel, while cooling with the one or more cooling streams the decarbonated materials in the second shaft, preferably feeding the third shaft with the fuel and the at least one comburent, optionally with the recycled exhaust gas from the first shaft, while feeding either - the second shaft with the one or more cooling streams at the lower portion of the cooling zone, while extracting the one or more heated cooling streams at the upper portion of the preheating zone and/or the cooling zone, and/or from at least one of the corresponding cross-over channel portions or - the second shaft with the one or more cooling streams at the lower portion while reinjecting the one or more heated cooling streams extracted at least at the cooling zone upper portion of the second shaft and/or from the cross-over channel between the first and second shaft and/or the cross-over channel between the second and third shaft, in a lower portion of the preheating zone of the second shaft, in particular by means of a collecting ring.

- providing at least one combustion chamber, in particular a pair of combustion chambers supplied with the fuel, the at least one comburent and the recycled exhaust gas from at least the first shaft, the second shaft, the third shaft, a buffer and/or a storage tank, wherein the at least one combustion chamber is in fluid communication with the first and the second shaft, preferably the at least one combustion chamber being arranged between the first and the second shaft, in particular said chamber being arranged in the corresponding cross-over channel;

- feeding the first shaft with a gas mixture resulting from the combustion of the fuel and the at least one comburent, and the recycled exhaust gas from the first shaft, said mixture being generated in the combustion chamber fluidly connected to the first shaft, while the exhaust gas is extracted at the upper portion of the first shaft, and while the second shaft is cooled with the one or more cooling streams, in one cycle; 8

- feeding the second shaft with the gas mixture resulting from the combustion of the fuel and the at least on comburent, and the recycled exhaust gas from the second shaft, said mixture being generated in the combustion chamber fluidly connected to the second shaft, while the exhaust gas is extracted at the upper portion of the second shaft preheating or cooling zone, and while the first shaft is cooled with the one or more cooling streams, in a subsequent cycle;

- providing an auxiliary combustion chamber supplied with at least a part of the fuel to be injected in the first shaft and the at least one comburent, and optionally with the recycled exhaust gas that is alternately extracted from the first or second shaft, and at least one mixing chamber, in particular a pair of mixing chambers, the at least one mixing chamber being supplied with the at least one comburent and the exhaust gas generated in the auxiliary combustion chamber, the at least one mixing chamber being interposed between the first and the second shaft, in particular said chamber being arranged in the corresponding cross-over channel;

- the multi-shaft vertical kiln comprises fuel injection means provided in each shaft, further comprising;

- feeding the first shaft with an exhaust gas mixture generated in the mixing chamber fluidly connected to the first shaft, while supplying the remaining part of fuel to be injected in the first shaft via the fuel injection means disposed in the first shaft, while the exhaust gas is extracted at the upper portion of the first shaft, and while the second shaft is cooled with the one or more cooling streams, in one cycle;

- feeding the second shaft with the gas mixture generated in the mixing chamber connected to the second shaft, while the complementary supply of the fuel is carried out in the second shaft via the fuel injection means disposed in the second shaft, while the exhaust gas is extracted at the upper portion of the second shaft preheating zone, and while the first shaft is cooled with the one or more cooling streams, in a subsequent cycle.

- during a transition phase between one cycle and the subsequent cycle, the following steps:

- stopping the cooling of the second shaft;

- filling the second shaft with an gas mixture comprising a part of the generated exhaust gas in the auxiliary combustion chamber, while pursuing the feeding of the first shaft with both:

- a gas mixture comprising the other part of the exhaust gas generated in the 9 auxiliary combustion chamber and - the fuel through the fuel injection means, before the second shaft is heated.

- providing at least a first and second hoppers for conditioning the carbonated materials before they are fed to at least one of the first and/or the second shaft, and supplying the first hopper with the exhaust gas extracted from one of the cross-over channel portions while supplying the second hopper with the one or more the heated cooling streams extracted from either the other cross-over channel portion, or the upper portion of the preheating or cooling zone of the shaft connected to the other cross over channel portion.

- providing one or more additional kilns to the multi-shaft vertical kiln forming a plurality of kilns generating an aggregated exhaust gas stream, so as to minimize flow variation of the aggregated exhaust gas stream entering a CO ₂ purification unit, in particular coordinating the plurality of kilns by selecting appropriate cycles phasing and duration of said kilns.

- the CO ₂ purification unit is continuously fed with either the exhaust gas from the buffer, the exhaust gas from the storage tank, the exhaust gas from the multi-shaft vertical kiln, the one or more additional kilns or a combination of them.

- feeding the carbonated materials into at least one of the first, second or third shaft, via a feeding system, each system comprising a lock chamber delimited by an upstream valve assembly and a downstream valve assembly, said feeding system being configured to collect the carbonated materials in the lock chamber, while the upstream valve assembly is open and the downstream valve assembly is closed, to store in a substantially gas tight manner the carbonated materials, while both the upstream and downstream valve assemblies are closed, and to release the carbonated materials, while the upstream valve assembly is closed and the downstream valve assembly is open.

- discharging the decarbonated materials from at least one of the first, second or third shaft, via a discharging system, each system comprising a lock chamber delimited by an upstream valve assembly and a downstream valve assembly, said discharging being configured to collect the decarbonated materials, while the upstream valve assembly is open and the downstream valve assembly is closed, to store in a substantially gas tight manner the decarbonated materials, while both the upstream and downstream valve assemblies are closed, and to release the decarbonated materials, while the upstream valve assembly is closed and the downstream valve 10 assembly is open.

- the upstream or downstream valve assembly comprising a single or multiple flap valve, a table feeder, a rotary valve, a cone valve, a J valve, a L valve, a trickle valve, preferably a single or multiple flap valve.

Brief Description of Drawings

[0025] Aspects of the invention will now be described in more detail with reference to the appended drawings, wherein same reference numerals illustrate same features. [0026] Figures 1 to 22 show the first to the twenty-second embodiments according to the invention.

[0027] Figures 23 and 24 show further embodiments according to the invention.

[0028] List of reference symbols 11

Detailed description

[0029] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may however be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness.

[0030] Figure 1 shows the first embodiment according to the invention. The first embodiment comprises a multi-shaft vertical kiln MSVK comprising a first 100 and a second 200 shaft with preheating 110, 210, heating 120, 220 and cooling 130, 230 zones, as well as a cross-over channel 412 arranged between the first 100 and second 200 shafts. In use, the carbonated materials 10 are introduced at an upper portion 111, 211 of each shaft 100, 200. The carbonated materials 10 slowly move to the bottom. In the preheating zones 110, 210, the carbonated materials 10 are essentially preheated with the alternating regenerative exhaust gas 40. In the combustion zones 210, 220, the carbonated materials 10 are alternately heated by a combustion of fuel 20 with at least one comburent 30, 31, 32, namely air, up to a temperature range in which carbon dioxide of the carbonated materials 10 is released. Both the combustion of the fuel 20 with the at least one comburent 30, 31, 32 and the decarbonatation generate the exhaust gas 40. The decarbonated materials 50 formed after the release of the CO2 from the carbonated materials 10 are directly cooled in the cooling zones 130, 230 by an air stream 91 that is 12 burnt with the fuel. Contrary to a traditional parallel flow regenerative kiln, the exhaust gas 40 is extracted in the cross-over channel 412. A closure means 512 divides the cross over channel 412 into a first 170 and a second portion 270, opening respectively in the first 100 and the second 200 shaft. Exhaust passages are provided in each portion 170, 270 allowing the extraction of the exhaust gas 40. A portion of the exhaust gas can be alternately recycled to the shafts 100, 200.

[0031] The closure means 512 can comprise:

- one or more valves that can be controlled in an open or close position during the operation of the kiln or

- a plug arranged in a form-fitting manner in an inner wall section of the cross-over channel, in particular a refractory brick wall preventing a gas transfer between the shafts 100, 200.

When the at least one valve is closed, the gas transfer between the first 100 and the second 200 shafts is interrupted. In such a situation, the kiln MVSK could be operated in theory in a mode where the shafts 100, 200 are operated in independent manner. However, in the first embodiment, the control of the shafts 100, 200 is coordinated so as to generate synergies in the uses of the cooling stream 91 and exhaust gas 40 stream, in terms of heat recovery and capacity utilization. In particular, the first 100 and second shafts 200 are alternately cooled with the cooling stream 91 or heated in a phase-shift manner as shown in Figure 1. This way of operating the kiln MVSK is named “split use”.

[0032] In the first embodiment, the control of the MVSK can comprise the following sequential cycles:

[0033] Cycle 1 comprises feeding the first shaft 100 with the fuel 20, the comburent 30 and the recycled exhaust gas 40 from the same shaft 100, while feeding the second shaft 200 with the cooling stream 91 supplied at the lower portion 232 of the cooling zone 230 and extracted from the second cross-over channel portion 170: H1C2 (heating shaft 1 , cooling shaft 2)

[0034] Cycle 2 comprises feeding the second shaft 200 with the fuel 20, the comburent 30 and the recycled exhaust gas 40 from the same shaft 200, while feeding the first shaft with the cooling stream 91 supplied at the lower portion 132 of the cooling zone 130 and extracted from the first cross-over channel portion 170: C1C2 (cooling shaft 1 , heating shaft 2)

[0035] The above-mentioned sequence can be described as H1C2, C1H2, ..., H1C2, C1 H2. The invention is not limited to this sequence and can follow various patterns that 13 can be adjusted depending on the circumstances such as H1C2, C1 (cooling of shaft 1 only), H2 (heating of shaft 2 only), ...

[0036] In Figure 1 , the three following separate supply passages per shaft are shown:

- a first passage arranged at an upper portion of the multi-shaft vertical kiln (e.g. PFRK) traditionally supplying a (first) comburent 30, 31 (e.g. primary air supply). Even if Figure 1 shows one first supply passage, the multi-shaft vertical kiln MSVK may comprise more than one first supply passage per shaft 100, 200. The one or more first passage outlet openings are arranged in the corresponding shaft 100, 200. In the present disclosure, the comburent 30 or the first comburent 31 is preferably oxygen- enriched air or substantially pure oxygen.

- a second passage (e.g. fuel lance) traditionally supplying fuel 20 (e.g. natural gas, oil) and optionally the second comburent 32 (e.g. air). Even if Figure 1 shows only one second supply passage, the multi-shaft vertical kiln comprises one or more second supply passages per shaft 100, 200 generally under the form of fuel/air lances. For instance, a mixture of fuel 20 and the second comburent 32 (e.g. coke with the conveying second comburent such as air) can be supplied through at least a part of the lances. Alternatively, a group of lances supplies the second comburent 32 (e.g. air), while another group of lances supplying the fuel 20 (natural gas or oil). In the present disclosure, the second comburent 32 is preferably oxygen-enriched air or substantially pure oxygen.

- a third passage is shown in Figure 1. Such a passage is traditionally not present on a multi-shaft vertical kiln MSVK, in particular a parallel flow regenerative kiln PFRK. Said third passage is dedicated to the supply of the recycled exhaust gas 40. The present disclosure is not limited to a single third passage. Indeed, it can be foreseen that one or more third passages are in fluid connection with the corresponding shaft 100, 200.

In an alternative preferred form (not shown), a downstream end of the third passage is connected to the first passage. The present disclosure is not limited to a single third passage connected to a single first passage. Indeed, it can be foreseen that one or more downstream ends of the third passage(s) are connected to one or more first passages. The one or more first passages can feed the corresponding shaft 100, 200 with:

- a gas mixture comprising the recycled exhaust gas 40 and the first comburent 31 (e.g. oxygen-enriched air or substantially pure oxygen) according to the first preferred alternative, or 14

- the recycled exhaust gas 40 according to the second preferred alternative.

In the above-mentioned first preferred alternative, the fuel 20 (e.g. natural gas or oil, dihydrogen) is supplied via the one or more second passages.

In the above mentioned second preferred alternative, the one or more second passages supply both the second comburent 32 (e.g. oxygen-enriched air or substantially pure oxygen) and the fuel 20 (e.g. natural gas, oil, coke or dihydrogen). For instance, a group of lances supply the second comburent 32 (e.g. oxygen-enriched air or substantially pure oxygen) while another group supplies the fuel 20 (e.g. natural gas, oil or dihydrogen).

The first, second and third passages can be found in other embodiments of the present invention.

[0037] Figure 2 represents the closure means 512 according to the second embodiment according to the invention. The second embodiment differs from the first in that the closure means 512 comprises a plug, in particular a double refractory brick wall. The plug, in particular the double refractory brick wall, can be assembled or dismantled by stopping the kiln MSVK.

[0038] Figure 3 shows the closure means 512 according to the third embodiment according to the invention. The third embodiment differs from the first in that the closure means 512 comprise a valve, in particular a gate valve. The blade of the valve blade can be covered with refractory bricks (not shown). In an alternative, the blade can be made out of heat-resistant material such as inconel (shown), ceramic, another material, or any combination of them. The valve in Figure 3 has a surface comparable to the size of the cross-over channel 412 inner section.

[0039] In an first alternative to the third embodiment, the cross-over channel 412 can be sealed with a plug in the form of refractory bricks. In this alternative, the multi-shaft vertical kiln comprises at least one passage, preferably two, whose respective ends connect the first and second shafts, is arranged adjacent to the cross-over channel 412. A smaller gate valve as that shown in Figure 3 can be provided in the or each passages. In a further alternative, at least one smaller gate valve as that shown in Figure 3 can be provided in a wall formed inside the cross-over channel 412, said wall being covered with refractory bricks.

[0040] Figure 4 shows the fourth embodiment according to the invention. The fourth embodiment differs from the first embodiment in that it comprises means 151, 152, 160, 251, 252, 260 to condition, in particular preheat the carbonated materials 50 with recycled heat before they are fed into the shafts 100, 200. For instance, during Cycle 1 , two 15 hoppers 251, 252 arranged in series in the downstream(lower) section of a carbonated material supply row connected to the second shaft 200. The term “downstream” is related to the carbonated material 10 supply flow wherein gravity can be used as a moving force. These two hoppers 251 , 252 are heated with the exhaust gas 40 from the first shaft 100, while another hopper 260 arranged in an upstream section of the same carbonated material supply row as that of the two previous hoppers 252, 251, is heated with a heated cooling stream 91 extracted from the second shaft 100. In Cycle 2, the operations can be reversed, wherein two hoppers 152, 151 arranged in series in the downstream (lower) section of the other carbonated material supply row connected to the first shaft 100 are heated with the exhaust gas 40 from the second shaft 200, while a further hopper 160 in the upstream section of the same row is heated with the heated cooling stream 91 extracted from the first shaft 100. Instead of using pairs of hoppers 151, 152, 251, 252 arranged in series in the lower section of each carbonated material supply row, a larger hopper in each supply row can be foreseen. In order to efficiently operate the kiln in the split use according to Figure 19, at least a first and a second hoppers 151, 152, 160, 251 , 252, 260 for conditioning the carbonated materials 10 per shaft 100, 200 are needed, wherein the first hopper 151, 152, 251, 252 in the downstream section is supplied with the exhaust gas 40 from one of the cross-over channel portions 170, 270 while the second hopper 160, 260 in the upstream section is supplied with the heated cooling stream 91 extracted from the upper portion 111, 211 of the preheating zone 110, 210 of the corresponding shaft 100, 200.

[0041] Figure 5 shows the fifth embodiment according to the invention. The fifth embodiment differs from the fourth embodiment in that the flows of exhaust gas 40 alternately generated in the first or second shaft are distributed “continuously” to the hoppers 151, 152, 251, 252 of the downstream(lower) sections of the carbonated material supply rows. Equally, the heated cooling gas 91 extracted from the preheating zone 110, 210 is also distributed “continuously” to a pair of hoppers 160, 260 of the upstream(upper) sections of the carbonated material supply rows .

[0042] Figure 6 shows the sixth embodiment according to the invention. The sixth embodiment differs from the fourth embodiment in that :

- the extraction of the heated cooling stream 91 takes place in the cross-over channel portions 170, 270 instead of in the upper portion of the preheating zone 110, 210 and

- each hopper 151 , 152, 160, 252, 262, 260 is alternatively heated by the exhaust gas 40 or the heated cooling stream 91.

[0043] Figure 7 shows the seventh embodiment according to the invention. The 16 seventh embodiment at least differs from the sixth embodiment in that each hopper arranged in the upstream(upper) sections of the carbonated material supply rows is alternatively heated by the exhaust gas 40 or the heated cooling stream 91 and optionally a complementary venting passage are provided in the preheating upper portion 111, 211.

[0044] Figure 8 shows the eight embodiment according to the invention. The eight embodiment differs from the seventh embodiment in that only one hopper per shaft is alternatively heated by the exhaust gas 40 or the heated cooling stream 91 coming either from the portions 170, 270 of the cross-over channel 412 or the upper portions 111 , 211 of preheating zone 110, 210. This embodiment shows that only two hoppers for a two shaft vertical kiln can be advantageously used.

[0045] Figures 9A and 9B show the ninth embodiment according to the invention. The ninth embodiment differs from the first embodiment in that the kiln MVSK comprises a third shaft 300. This embodiment is a generalization of the “split” use to a three-shaft kiln. As for the first embodiment, the operation sequences, in the ninth embodiment, follow the “split” use in which one and another shaft are alternately cooled with the one or more cooling streams 91 or heated in a phase shift manner. Figure 9A shows a top view of a kiln MVSK according to the ninth embodiment. Figure 9B presents a lateral view of an “unrolled” kiln MVSK, where all the shafts are arranged in a plane. Figure 9B schematically shows the fluid flows during a given operating cycle. In this cycle, the first shaft 100 is fed with fuel 20, the comburent 30 and the recycled exhaust gas 40. At the same time, the exhaust gas 40 generated during the combustion and decarbonation is transferred to the second shaft 200, and the third shaft 300 is cooled with the cooling stream 91. In this cycle, the closure means 512 in the cross-over channel 412 is open while the closure means 523, 531 in the cross-over channel 412, 431 are closed.

[0046] A typical sequence for a three-shaft vertical kiln according to the ninth embodiment is described as follow:

[0047] Cycle 1 (shown in Fig. 9B) comprises feeding the first shaft 100 with the fuel 20, at least one comburent 30, 31, 32 in particular oxygen-enriched air with and the recycled exhaust gas 40 from said shaft 100, while transferring the generated exhaust gas 40 to the second shaft 200 and feeding the third shaft 300 with the cooling streams 91 supplied at the lower portion 332 of the cooling zone 330 and extracted at the upper portion 331 of the preheating zone 310: H1 R2C3 (heating shaft 1 , regenerating shaft 2, cooling shaft 3).

[0048] Cycle 2 comprises feeding the second shaft 200 with the fuel 20 and at least one comburent 30, 31 , 32 in particular oxygen-enriched air with and the recycled exhaust 17 gas 40 from said shaft 200, while transferring the generated exhaust gas 40 to the third shaft 300 and feeding the first shaft 100 with the cooling stream 91 supplied at the lower portion 132 of the cooling zone 130 and extracted at the upper portion 111 of the preheating zone 110: C1 H2R3 (cooling shaft 1, heating shaft 2, regenerating shaft 3).

[0049] Cycle 3 comprises feeding the third shaft 300 with the fuel 20 and at least one comburent 30, 31 , 32, in particular oxygen-enriched air with and the recycled exhaust gas 40 from said shaft 300, while transferring the generated exhaust gas 40 to the first shaft 100 and feeding the second shaft 200 with the cooling streams 91 supplied at the lower portion 232 of the cooling zone 230 and extracted at the upper portion 211, 231 of the preheating zone 210: R1C2H3 (regeneration shaft 1 , cooling shaft 2, heating shaft 3).

[0050] The above-mentioned sequence can be described as H1R2C3, C1H2R3, R1C2H3. The invention is not limited to this sequence and can follow various patterns that can be adjusted depending on the circumstances such as H1 R2C3, R1C2H3, C1 H2R3, H1 R2 (shaft 330 is not cooled with a cooling steam), C1-3 (cooling of the three shafts 100,200, 300 with a cooling stream), ...

[0051] Figure 10 shows the tenth embodiment. The tenth embodiment differs from the ninth embodiment in that a water steam stream 92 is used for the extraction of the CO2 from decarbonation during cooling phase. The water steam stream 92 conveys the CO2 outside of the shafts 100, 200, where a condenser separates the water from the cooling stream 92, thereby obtaining a stream enriched in CO2.

[0052] We understand by water steam stream a stream comprising at least 50% by weight water, preferably at least 80% by weight water, more preferably at least 90% by weight water.

[0053] The eleventh embodiment of the present invention according to Figure 11 differs from the ninth embodiment in that the heated cooling stream 91 is extracted at the upper portion 131 , 231 , 331 of the cooling zone instead of the upper portion 111 , 211, 311 of the preheating zone. Figure 11 shows that the heated cooling stream 91 is extracted via one or more apertures formed in wall sections of the upper portions of the cooling zones 130, 230, 330. Alternatively, or in combination to the one or more apertures, suction pipes extending vertically in a central portion of the cooling zones 130, 230, 330 according to the twelfth embodiment of the present invention (Fig. 12) can be provided. Indeed, Figure 12 shows a multi-shaft vertical kiln MSVK. In particular, one or more apertures (in Fig. 12, only one aperture is shown per shaft), through which the heated cooling stream 91 is extracted, are formed in a pipe assembly preferably centrally arranged in each shaft 100, 200. The one or more apertures are covered by a screen assembly preventing the 18 intrusion of solid materials into the cooling extraction system.

[0054] The thirteenth embodiment of the present invention according to Figure 1 differs from the ninth embodiment in the provision of heat exchangers in the cooling zone 130, 230, 330. As shown in Figure 13, the heats exchanger 130, 230, 330 reduce the direct cooling of the decarbonated materials 50 with the cooling stream 91, thereby reducing that CO2 from decarbonation during cooling phase conveyed with the cooling streams. Furthermore, the decarbonated materials 50 in the cooling zones 130, 230, 330 can be indirectly cooled during the heating cycle.

[0055] Figure 14 shows a multi-shaft vertical kiln MSVK according to the fourteenth embodiment of the present invention. The fourteenth embodiment differs from the thirteenth embodiment in a specific design of heat exchanger 133, 233, 333 namely a plurality of passages is provided in the cooling zones of the first 100, the second 200 and third 300 shafts. The passages extending preferably vertically are delimited by walls, in which the cooling stream, in particular air stream circulates. Air is presented as a preferred cooling medium because of its accessibility but other fluid can be used depending on the circumstances.

[0056] Figure 15 shows a multi-shaft vertical kiln MSVK according to a fifteenth embodiment of the present invention. The fifteenth embodiment differs from any of the previous embodiments in that a selective separation means 141 , 241 , 341 is provided in each shaft 100, 200, 300. Each selective separation means 141 , 241 , 341 is arranged in an upper portion of the cooling zone 130, 230, 330 and arranged so as to allow the transfer of the decarbonated materials 50 downwards while substantially preventing the passage of the one or more cooling streams comprising air 91 and/or the exhaust gas 40. Each separation means 141, 241 can be suspended by a partition wall extending from the corresponding inner shaft wall to the center of said shaft. Typically, the wall can present a funnel shape. Alternatively, a plurality of selective separation means 141 , 241 , 341 can be provided. In comparison to the solutions presented in Figure 11 or 12, the presence of selective separation means 141, 241, 341 substantially prevents any mixing of the cooling medium and the exhaust gas 40. As shown in Figure 15, the heated cooling stream 91 can be extracted at an upper portion of the cooling zones 130, 230, 330 though one or more apertures formed in a wall section of the corresponding shaft. In such a case, the one or more apertures are positioned below the partition wall outer circumferential end that connects the inner wall of the corresponding shaft. The lock assembly can comprise a rotary valve, a double flap sluice or any other suitable means.

[0057] Figure 16 shows the sixteenth embodiment according to the invention. The 19 sixteenth embodiment differs from the first embodiment in that:

- a pair of combustion chambers 180, 280 are positioned in the cross-over channel 412 and arranged between the first 100 and the second 200 shaft;

- the exhaust passages connected to the first 170 and second 270 portion are used to supply the chambers 180, 280 with recycled exhaust gas 40 extracted at an upper portion 111, 211 of the preheating zone 110, 210 instead of transferring the recycled exhaust gas 40 from the cross-over channel 412 to the first and second preheating zone upper portions 111, 211. In other words, the flows of recycled exhaust gas 40 is inverted requiring adaptations such as the provision of reversible exhaust gas pumps or changes in the pump designs and/or positioning in the exhaust passages. Furthermore, these chambers 180, 280 are supplied with the fuel 20, the comburent 30 and the recycled exhaust gas 40 form the first shaft 100 or the second shaft 200. Said chambers 180, 280 are in fluid communication with the first 100 and the second 200 shaft respectively. Preferably, the closure means 512 is a plug, in particular a refractory brick wall, because of the limited space in the cross-over channel 412 that already contains the combustion chambers 180, 280.

[0058] Typically, the kiln according to sixteenth embodiment can be operated in the following manner (see Fig. 16):

[0059] Cycle 1 comprises feeding the first shaft 100 with a gas mixture 42 resulting from the combustion of the fuel 20 and the comburent 30, in particular oxygen-enriched air or substantially pure oxygen, as well as the recycled exhaust gas 40 from the first shaft 100, while the exhaust gas 40 resulting from the gas mixture 42 and the decarbonation, is extracted at the upper portion 111 (preheating zone 120) of the first shaft 100, and the second shaft 200 is cooled with the cooling stream 91.

[0060] Cycle 2 comprises feeding the second shaft 200 with the gas mixture 42 resulting from the combustion of the fuel 20 and the comburent, in particular air enriched in oxygen or substantially pure oxygen 30 as well as the recycled exhaust gas 40 from the second shaft 200, while the exhaust gas 40 resulting from the gas mixture 42 and the decarbonation is extracted at the upper portion 211 of the second shaft preheating 210, and the first shaft 100 is cooled with the cooling stream 91.

[0061] Combustion chambers and their combustion means are common in the field of lime/ calcination as shown in JP S5553685 (in particular Fig. 6 and 7). The skilled person knows how to adapt them to one’s particular needs.

[0062] Preferably, the fuel 20 injected in the combustion chamber 180, 280 is the sole fuel source foreseen to generate the heat in the first 100 and second shaft 100, to the 20 extent that fuel lances are not required in the shafts 100, 200, thereby simplifying the design with a reduction of the number of pipes and valves.

[0063] Figure 17 shows the seventeenth embodiment. The seventeenth embodiment differs from the sixteenth embodiment in :

- an auxiliary combustion chamber 600, and

- a pair of mixing chambers 190, 290 instead of a pair of combustion chambers 180, 280.

Furthermore, the pair of mixing chambers 190, 290 are arranged in the corresponding cross-over channel portions 170, 270. These chambers 190, 290 are positioned downstream from the auxiliary combustion chamber 600. The mixing chambers 190, 290 are supplied with the comburent 30 and the exhaust gas 41 generated by the auxiliary combustion chamber 600. Preferably, fuel injection means 126, 226 are provided in each shaft 100, 200 for supplying the fuel 20.

[0064] Mixing chambers 190, 290 can be in a simpler form a cavity with inlets for feeding the fluid to be mixed and one or more outlets for releasing the mixed fluids. Optionally, the chambers 190,290 can comprise multiple cavities and/or deflecting means to increase the turbulence and therefore enhancing the mixing of the fluids to be mixed. The inner surface of the mixing chambers advantageously comprise a refractory material.

[0065] Typically, the kiln according to the seventeenth embodiment can be operated in the following manner (see Fig. 11):

[0066] Cycle 1 comprises feeding the first shaft 100 with an exhaust gas mixture 42 generated in the mixing chamber 190 fluidly connected to the first shaft 100, while the remaining part of fuel 20 to be injected is supplied in the first shaft 100 via the fuel injection means 126 disposed in the first shaft 100, the exhaust gas 40 resulting from the post combustion of the gas mixture 42 and the decarbonation is extracted at the upper portion 111 of the first shaft 100, and the second shaft 200 is cooled with the cooling stream 91.

[0067] Cycle 2 comprises feeding the second shaft 200 with the gas mixture 42 generated in the mixing chamber 290 connected to the second shaft 200, while the remaining part of supply of fuel 20 to be injected is supplied in the second shaft 200 via the fuel injection means 226 disposed in the second shaft 200, the exhaust gas 40 resulting from the post combustion of the gas mixture 42 and the decarbonation is extracted at the upper portion 211 of the second shaft preheating 210 zone, and the first shaft 100 is cooled with the cooling stream 91.

[0068] Figure 17 also shows how the flows are controlled during a transition phase 21 between Cycle 1 and Cycle 2.

[0069] Preferably, the cooling of the second shaft 200 is interrupted at the beginning of the transition phase. The valves and blowers are configured to allow a smooth transition from the first cycle to the second cycle. In order to do so, a progressive partition of the exhaust gas 41 generated in the auxiliary combustion chamber 600 between the first 100 shaft and the second shaft 200 is ensured. In particular, the second shaft 200 is filled with a gas mixture 42 (essentially resulting from a first part of the exhaust gas 41), while the first shaft 100 is supplied with a gas mixture 42 (comprising the other part of the exhaust gas 41 generated in the auxiliary combustion chamber 600 and the comburent 30). During the transition, the fuel 20 is still injected by the fuel injection means 126 so as to pursue a post combustion a the residual oxygen in the first shaft 100. This measure allows that the second shaft is progressively filled with the exhaust gas 40 enriched in CO2 before combustion starts in the second shaft 200.

[0070] Figure 18 shows the eighteenth embodiment according to the invention. The eighteenth embodiment differs from any of the previous embodiment in that a buffer 910 and a CO2 purification unit CPU are provided in the exhaust line connected to the kiln MSVK. The buffer 910 ensures that the CO2 purification unit CPU can be fed at any time with the exhaust gas 40. The CO2 purification unit CPU is configured to remove at least one of the following elements: acid gases, 02, Ar, CO, H2O, NOx, sulfur compounds, heavy metals, in particular Hg, Cd, and/or organic compounds, in particular CFU, benzene, hydrocarbons. Preferably, the CO2 purification unit CPU is adapted to adjust the composition of the exhaust gas 40 to the specification required by a carbon capture and utilization or carbon capture and storage application, preferably with a CO2 content above 80% (dry volume) and more preferably above 95% (dry volume).

[0071] Figure 19 shows the nineteenth embodiment according to the invention. The nineteenth embodiment differs from the eighteenth embodiment in the provision of a condensation unit 700 arranged in the exhaust line. The condensation unit 700 allows to increase the concentration of CO2 by removing water. The water separated could be recycled for the cooling of the cooling zones 130, 230, 230 of the kiln MSVK.

[0072] Figure 20 shows the twentieth embodiment according to the invention. The twentieth embodiment differs from the eighteenth embodiment in a recycling passage connecting the buffer 910 to the kiln MSVK. The buffer 910 allows to supply the kiln MSVK with exhaust gas 40 enriched with CO2.

[0073] Figure 21 shows the twenty-first embodiment according to the invention. The twenty-first embodiment differs from the eighteenth embodiment in the provision of a 22 storage tank 920 positioned downstream from the CO2 purification unit CPU. The storage tank 920 is filled with purified CO2, in particular in liquid form for the carbon capture and utilization or carbon capture and storage application. Furthermore, a recycling passage is provided for connecting the storage tank 920 to the kiln MSVK. The storage tank 920 allows to supply the kiln MSVK with exhaust gas 40 enriched with CO2. The storage tank 920 can comprise a blow-off valve for cooling liquid CO2 stored in said tank 920. The boiled CO2 can be recycled to the kiln MVSK or any kiln of any type. The cooled CO2 extracted from the storage tank can be used a cooling stream 91 before it is fed to the shafts of the kiln MSVK to enrich the exhaust gas in CO2.

[0074] Figure 22 shows the twenty-second embodiment of the present invention. The twenty-second embodiment differs from the twenty-first embodiment in that one or more multi-shaft vertical kilns according to any previous embodiments MSVK _1, MSVK _2, MSVK_N or either one or more traditional limestone kilns K_1, K_N are connected to the C0 ₂ purification unit CPU. These kilns MSVK, MSVK_1, MSVK_2, MSVK_N, K_1, K_N generate an aggregated exhaust gas stream, thereby minimizing flow variation of the aggregated exhaust gas stream entering the CO2 purification unit CPU. In particular, the kilns MSVK, MSVK _1 , MSVK _2, MSVK _N, K_1 , K_N can be coordinated by selecting appropriate cycles phasing and duration of said kilns MSVK, MSVK _1, MSVK_2, MSVK _N, K_1, K_N. Advantageously, the purification unit CPU is continuously fed with either the exhaust gas 40 from one or more of the buffers 910, the exhaust gas 40 from the storage tank 920, the exhaust gas 40 from the kiln MSVK, the one or more additional kilns MSVK _1 , MSVK_2, MSVK_N, K_1, K_N or a combination of them.

[0075] The control of the closure means 512, 523, 531 offers the possibility to change the nature of the operation of the kiln MSVK. For instance, starting from a traditional MSVK with three shaft, it is possible to operate said kiln in different modes such as :

- a regular use mode, namely traditional MSVK operation, with the three closure means 512, 523, 531 in an open position;

- an “intermittent flush” use (shown in Fig. 23A, 23B) with the closure means 512, 523, 531 in an open position; and/or

- a “split use”, requiring a suitable control of the closure means. Owing to this measure, the kiln MSVK can be tuned to meet different types of fuel and/or produce a lime or dolime according to certain specifications (e.g. CO2 residual concentration, reactivity).

[0076] Figure 23 shows a further embodiment according to the invention, which differs from the first embodiment in that the MSVK comprises feeding and discharging systems 1100, 1200, respectively, for the feeding of carbonated materials 10 and the 23 discharge of the decarbonated material 50, in order to minimize the idle time between cycles (reversal time) to reduce or even eliminate the need for exhaust gas buffering before the C02 purification unit (CPU). The feeding and discharge systems 1100, 1200, with for instance an upstream gas-tight flap valve and a downstream gas-tight flap valve can be integrated to anyone of the previously mentioned embodiments. The lock chamber delimited by the gas-tight flap valve and a downstream gas-tight flap valve presents a working volume adapted to store the material batches to be fed into or discharged from the corresponding shaft 100, 200. By gas tight, is meant a valve assembly that substantially limits the gas exchanges to as to ensure an efficient usage of the kiln and minimize combustion gas leakage into the atmosphere.

[0077] Figure 24 presents another advantageous embodiment according to the invention, which differs from the first embodiment in that the heated cooling streams 91 by-pass the combustion zones 120, 220 and are used to heat the carbonated material 10 in the preheating zones 110, 210. This measure reduces the extraction of CO2 present (the concentration of CO2 increases with the temperature) in combustion zones 120, 220 by the heated cooling streams 91. Thus, the concentration of CO2 contained in the heated cooling streams 91 can be reduced. This solution can be extended to a kiln with more than two shafts MSVK, in particular a three shaft kiln MSVK.

[0078] Advantageously, the at least one fuel 20 used in a kiln MSVK according to the invention, in particular in any of the previous embodiments is either carbon-containing fuel or dihydrogen-containing fuel or a mixture of them. A typical fuel can be either wood, coal, peat, dung, coke, charcoal, petroleum, diesel, gasoline, kerosene, LPG, coal tar, naphtha, ethanol, natural gas, hydrogen, propane, methane, coal gas, water gas, blastfurnace gas, coke oven gas, CNG or any combination of them. Furthermore, the kiln MVSK can use, for instance, two sources of fuel with different compositions.

[0079] Advantageously, the decarbonated materials 50 produced in a kiln MSVK according to the invention, in particular in any of the previous embodiments have a residual CO2 <5%, preferably <2%, resulting from the rapid cooling of the decarbonated materials 50.

[0080] Preferably, measures are undertaken to recover heat from the one or more of the cooling streams 91, 92, and/or the recirculated exhaust gas 40.

[0081] Advantageously, the combustion of at least one fuel 20 with the at least one comburent 30 is under an oxygen-to-fuel equivalence ratio greater or equal to 0.9.

[0082] The comburent comprises less than 70% N2 (dry volume), in particular less than 50% of N2 (dry volume), in particular oxygen-enriched air. In particular, the comburent 24 used in the invention, is a mixture of air with a substantially pure oxygen, the comburent comprising at least 50% 02 (dry volume), preferably more that 80% 02 (dry volume).

[0083] The meaning of “substantially pure oxygen” in the present disclosure is an oxygen gas comprising at least 90 % (dry volume) dioxygen (i.e. O2), preferably at least 95% (dry volume) dioxygen(i.e. O2).

[0084] The use of valves as closure means 512, 523, 531 in the cross-over channels 412, 423, 531 of a three-shaft vertical kiln or alternatively the “bypass” passages provided with “smaller valves” between each shafts, allows to advantageously switch the operation between any of the following a “split use” to a “intermittent flush” and a “regular use” (traditional way to operate PFRK) rendering the kiln flexible in terms of production outputs and fuels. Furthermore, it offers an additional levy, namely the selection of type of mode, to control the specification of the decarbonated materials 50.

[0085] The meaning of “multi vertical-shaft kiln” in the present disclosure is a kiln comprising at least two shafts 100, 200, 300. The shafts 100, 200, 300 are not coaxial and are disposed side by side to the extent that any shaft of a group consisting of the first and second, and optimally the third shaft 100, 200, 300 is not encircled by the other or another shaft 100, 200, 300 of said group. In other words, the cross-over channel(s) 412, 423, 431 are arranged outside the shafts 100, 200, 300. This definition excludes a annular- shaft kiln in case it were interpreted as being a multi vertical-shaft kiln. A parallel-flow regenerative kiln is a specific form of a multi vertical-shaft kiln in the present definition. According to the invention, the term “vertical” in “multi vertical-shaft kiln” does not necessarily require that the longitudinal axes of the shafts 100, 200, 300 have an exact vertical orientation. Rather, an exact vertical directional component of the alignment should be sufficient, with regard to an advantageous gravity-related transport of the material in the shafts, an angle between the actual alignment and the exact vertical alignment amounts to at most 30°, preferably at most 15° and particularly preferably of 0° (exact vertical alignment).

[0086] Each shaft 100, 200, 300 of the multi-shaft vertical kiln comprises a preheating zone 110, 210, 310, a heating zone 120, 220, 320 and a cooling zone 130, 230, 330. A cross-over channel 412, 423, 431 is disposed between each shaft 100, 200, 200. According to the present disclosure, the junction between the heating zones 120, 220, 320 and the cooling zones 130, 230, 330 is substantially aligned with the lower end of the cross-over channel(s) 412, 423, 431.

[0087] The present disclosure presents a multi-shaft vertical kiln with two or three shafts. The present teaching applies to multi-shaft vertical kiln with four and more shafts. 25

[0088] Embodiments as discussed above are defined by the following numbered clauses:

1. Decarbonation process of carbonated materials (10), in particular limestone and dolomitic limestone, with CO2 recovery in a multi-shaft vertical kiln (MSVK) comprising a first (100), a second (200), and optionally a third (300) shaft with preheating (110, 210, 310), heating (120, 220, 320) and cooling (130, 230, 330) zones and a cross-over (412, 423, 431) channel between each shaft (100, 200, 300), alternately heating carbonated materials (10) by a combustion of at least one fuel (20) with at least one comburent (30, 31 , 32), (preferably said comburent comprising less than 70% N2 (dry volume), in particular less than 50% of N2 (dry volume), in particular said comburent being oxygen- enriched air or substantially pure oxygen) up to a temperature range in which carbon dioxide of the carbonated materials (10) is released, the combustion of the fuel (20) and the decarbonatation generating an exhaust gas (40) (preferably exiting said kiln containing at least 45 %, on an average value during said combustion, preferably 60% of CO2 (dry volume)), the decarbonated materials (50) being cooled in the cooling zones (130, 230, 330) with one or more cooling streams (91, 92), wherein a mixing between the exhaust gas (40) and the one or more cooling streams (91, 92) is minimized in the case where said cooling streams contain air, by one or more of the following steps: a) providing a heat exchanger (133, 233, 333) in the cooling zone (130, 230, 330) of at least the first, the second and/or the third shaft (100, 200, 300) for the cooling of the decarbonated materials (50), said heat exchangers (133, 233, 333) being fed by the one or more cooling streams (91, 92); b) feeding the cooling zone (130, 230, 330) of at least the first, the second and/or the third shaft with the one or more cooling streams (91) and extracting at least one of the one or more heated cooling streams (91 , 92) at an upper portion (131, 231 , 331) of said cooling zone (130, 230, 330); c) separating each shaft (100, 200, 300) with a selective separation means (141, 241) arranged in an upper portion of the corresponding cooling zone (130, 230, 330), said selective separation means (141 , 241) dividing the inner space of the corresponding shaft (100, 200, 300) into an upper and lower space, said selective separation means (141, 241) being arranged so as to allow the transfer of the decarbonated materials (50) between the upper and the lower space while substantially preventing the passage of the one or more cooling streams (91 , 92) and/or the exhaust gas (40); d) providing the cross-over channel (412) arranged between the first (100) and the second (200) shaft with a closure mean (512), said mean (512) preventing a gas transfer 26 between the first (100) and the second (200) shaft (preferably in a split use, or allowing the gas transfer between the first (100) and the second shaft (200) in the intermittent flush use or a regular use of said kiln, subsequently closing the closure mean (512)) and operating said kiln in a mode wherein the first (100) and second shafts (200) are alternately cooled with the one or more cooling streams (91 or heated in a phase shift manner; e) cooling the decarbonated materials (50) with the one or more cooling streams (92) comprising a water steam stream, said stream being fed in the cooling zone (130, 230, 330) of at least the first (100), the second (200) and/or the third (300) shaft; f) recirculating at least a portion of the exhaust gas alternately exiting the second or the first shaft, injecting the recirculated exhaust gas in a lower portion of the preheating zone of the second shaft or the first shaft, respectively, in particular by means of a collecting ring encircling said shaft, feeding the cooling zone (130, 230) of at least one of the first (100) and/or the second (200) shaft with the one or more cooling streams (91), heating the recirculated exhaust gas (40) with the one or more heated cooling streams (91) extracted from the upper portion (131, 231) of the cooling zone (130, 230) of the at least one of the first (100) and/or the second (200) shaft.

2. Process according to clause 1 , further comprising recirculating the exhaust gas (40) exiting alternately the second (200) or first (100) shaft, to the first (100) or second (200) shaft, respectively, preferably by means of a positive displacement fan or blower,

3. Process according to clause 1 or 2, further comprising the recirculated exhaust gas (40) is mixed with the at least one comburent (30) before the resulting mixture is fed to the correspond shaft (100, 200, 300).

4. Process according to any of the preceding clauses, wherein the first (100) and second shafts (200) in step (a), comprise a plurality of passages arranged in the cooling zones of the first (100) and the second (200) shaft, said passages being delimited by walls, in which the one or more cooling streams (91) circulates.

5. Process preferably according to any of the preceding clauses, comprising feeding a buffer (910) or a storage tank (920) with the exhaust gas (40) extracted from a/the multi shaft vertical kiln (MSVK), said buffer or storage tank (920) being adapted so that a CO2 purification unit (CPU) connectable to said storage or buffer can be fed at any time with the exhaust gas (40), preferably boiling liquid CO2 stored in said tank (920) to form recycled exhaust gas (40) and transferring said gas (40) to the kiln (MSVK).

6. Process according to any of the preceding clauses, wherein the closure means (512) in step d) divides the cross-over channel (412) into a first (170) and a second portion 27

(270), opening respectively in the first (100) and the second (200) shaft, said process further providing an exhaust passage in each portion, preferably said closure means (512) comprising:

- at least one valve for allowing or preventing a gas transfer between the first (100) and the second (200) shaft, or

- a plug arranged in a form-fitting manner in an inner wall section of the cross-over channel (412) for preventing a gas transfer between the first (100) and the second (200) shaft.

7. Process according to any of the preceding clauses, wherein in step 1d) the following sequential cycles are carried out: d1) heating the carbonated materials (10) in the heating zone (120) of the first shaft (100), while cooling the decarbonated materials (50) in the second (200) and/or third (300) shafts with the one or more streams (91); d2) heating the carbonated materials (10) in the heating zone (220) of the second shaft (200), while cooling the decarbonated materials (50) in the first (100) and/or third (300) shafts with said stream (91); optionally further comprising : d3) heating the carbonated materials (10) in the heating zone (320) of the third shaft (300), while cooling the decarbonated materials (50) in the first (100) and/or second (200) shafts with said stream (91);

8. Process according to the preceding clause, further comprising:

- feeding the first shaft (100) with the fuel (20) and the at least one comburent (30, 31) and optionally with the recycled exhaust gas (40) from said shaft (100), while feeding either the second shaft (200) with the one or more cooling streams (91) supplied at the lower portion (232) of the cooling zone (230) and extracted: at the upper portion (211, 231) of the preheating zone (210) and/or the cooling zone (230); and/or from the second cross-over channel portion (270), or the second (200) shaft with the one or more cooling streams (91) at its cooling zone lower portion (232) while reinjecting the one or more heated cooling streams (91) extracted at least: 28 at the cooling zone upper portion (231) of the second shaft (200) and/or from the cross-over channel (412) between the first (100) and second shaft (200), in a lower portion (212) of the preheating zone (210) of the second shaft (200) by means of a collecting ring, during the first cycle d1), and

- feeding the second shaft (200) with the fuel (20) and the at least on comburent (30, 31), optionally with recycled exhaust gas (40) from said shaft (100), while feeding either the first shaft with the one or more cooling streams (91) supplied at the lower portion (132) of the cooling zone (130) and extracted:

- at the upper portion (111 , 131) of the preheating zone (110) and/or the cooling zone (130); and/or

- from the first cross-over channel portion (170), or the first (100) shaft with the one or more cooling streams (91) at its cooling zone lower portion (132) while reinjecting the one or more heated cooling streams (91) extracted at least:

- at the cooling zone upper portion (131) of the first shaft (100) and/or

- from the cross-over channel (412) between the first (100) and second shaft (200), in a lower portion (112) of the preheating zone (110) of the first shaft (100) by means of a collecting ring, during the second cycle d2).

9. Process according to any of the preceding clauses, further providing two closure means (523, 531), at least one of the two closure means (523, 531) comprising at least one valve for allowing or preventing a gas transfer between the two corresponding shafts, respectively, in the cross-over (431) channel between the first (100) and the third (300) shaft and in the cross-over channel (423) between the second (200) and the third (100) shaft, operating said kiln in the split use of step d) in a mode, in which, during one cycle, at least one of the shafts (100, 200, 300) is heated with one of its two closure means (512, 523, 531) open allowing a fluid connection with another shaft (100, 200, 300), while the 29 other shaft (100, 200, 300) is cooled by the one or more cooling streams (91) with its two closure means (512, 523, 531) being closed.

10. Process according to any of the preceding clauses 1 to 8, wherein the closure means (512) is a first plug, said process further providing at least one first further passage being arranged between and in fluid communication with the first shaft (100) and the second shaft ( 200), said passage comprising at least one valve that is open to allow the gas transfer between said shafts (100, 200) or closed to prevent gas transfer between said shafts (100, 200), said passage being positioned adjacent to the cross-over channel (412) arranged between said shafts (100, 200), preferably said passage presenting a section of between 10 to 50% of the minimal section of said cross-over channel (412), and optionally said process comprising providing :

- a second plug (523) arranged in the cross-over (423) channel between the first (200) and the third (300) shaft, said plug preventing gas transfer between said shafts (200, 300);

- a third plug (531) arranged in the cross-over (431) channel between the first (100) and the third (300) shaft, said plug preventing gas transfer between said shafts (100, 300);

- at least one second further passage arranged between and in fluid communication with the second (200) and the third (300) shaft, said passage comprising at least one valve that is open to allow the gas transfer between said shafts (200, 300) or closed to prevent gas transfer between said shafts (200, 300);

- at least one third further passage arranged between and in fluid communication with the first (100) and the third (300) shaft, said passage comprising at least one valve that is open to allow the gas transfer between said shafts (100, 300) or closed to prevent gas transfer between said shafts (100, 300);

- operating said kiln in a mode, in which, during one cycle, at least one of the shafts (100, 200, 300) is heated with one of its further passages open allowing a fluid connection with another shaft (100, 200, 300), while the other shaft (100, 200, 300) is cooled by the one or more cooling streams (91) with its further passages (512, 523, 531) being closed.

11. Process according to clause 9 or 10, wherein at least one of the following cycles, preferably the following sequential cycles, are carried out:

T1) heating the carbonated materials (10) in the heating zone (120) of the first shaft (100) while transferring the generated exhaust gas (40) to the second shaft (200) via the 30 corresponding cross-over channel (412), while cooling with the one or more cooling streams (91) the decarbonated materials (50) in the third shaft (300);

T2) heating the carbonated materials (10) in the heating zone (220) of the second shaft (200) while transferring the generated exhaust gas (40) to the third shaft (300) via the corresponding cross-over channel (423), while cooling with the one or more cooling streams (91) the decarbonated materials (50) in the first shaft (100);

T3) heating the carbonated materials (10) in the heating zone (320) of the third shaft (300) while transferring the generated exhaust gas (40) to the first shaft (100) via the corresponding cross-over channel (431), while cooling with the one or more cooling streams (91) the decarbonated materials (50) in the second shaft (200).

12. Process according to the preceding clause, further comprising:

- feeding the first shaft (100) with the fuel (20) and the at least one comburent (30, 31), optionally with the recycled exhaust gas (40) from the second shaft (200), while feeding either the third shaft (300) with the one or more cooling streams (91) at the lower portion (332) of the cooling zone (330), while extracting the one or more heated cooling streams (91) at :

- the upper portion (311, 331) of the preheating zone (310) and/or the cooling zone (330); and/or

- from at least one of the corresponding cross-over channel portions (370, 371), or the third (300) shaft with the one or more cooling streams (91) at the lower portion (332) while reinjecting the one or more heated cooling streams (91) extracted at least:

- at the cooling zone upper portion (331) of the third shaft (300) and/or

- from the cross-over channel (423) between the second (200) and third shaft (300) and/or the cross-over channel (431) between the third (300) and first shaft (100), in a lower portion (312) of the preheating zone (310) of the third shaft (300), in particular by means of a collecting ring, during the first cycle (T1),

- feeding the second shaft (200) with the fuel (20) and the at least one comburent (30, 31

31), optionally with the recycled exhaust gas (40) from the third shaft (300), while feeding either the first shaft (100) with the one or more cooling streams (91) at the lower portion (132) of the cooling zone (130), while extracting the one or more heated cooling streams (91) at:

- the upper portion (111, 131) of the preheating zone (110) and/or the cooling zone (130), and/or

- from at least one of the corresponding cross-over channel portions (170, 171), or the first (100) shaft with the one or more cooling streams (91) at the lower portion (132) while reinjecting the one or more heated cooling streams (91) extracted at least:

- at the cooling zone upper portion (131) of the first shaft (100) and/or

- from the cross-over channel (412) between the first (100) and second shaft (200) and/or the cross-over channel (431 ) between the third (300) and first shaft (100), in a lower portion (112) of the preheating zone (110) of the first shaft (100), in particular by means of a collecting ring, during the second cycle (T2);

- feeding the third shaft (300) with the fuel (20) and the at least one comburent (30, 31), optionally with the recycled exhaust gas (40) from the first shaft (100), while feeding either the second shaft (200) with the one or more cooling streams (91) at the lower portion (232) of the cooling zone (230), while extracting the one or more heated cooling streams (91) at:

- the upper portion (211; 231) of the preheating zone (210) and/or the cooling zone (230), and/or

- from at least one of the corresponding cross-over channel portions (270, 271), or the second (200) shaft with the one or more cooling streams (91) at the lower portion (232) while reinjecting the one or more heated cooling streams (91) 32 extracted at least: at the cooling zone upper portion (231) of the second shaft (200) and/or from the cross-over channel (412) between the first (100) and second shaft (200) and/or the cross-over channel (423) between the second (200) and third shaft (300), in a lower portion (212) of the preheating zone (210) of the second shaft (200), in particular by means of a collecting ring, during the third cycle (T3).

13. Process according to clause 6, further comprising:

- providing at least one combustion chamber (180, 280), in particular a pair of combustion chambers supplied with the fuel (20), the at least one comburent (30, 31) and the recycled exhaust gas (40) from at least the first shaft (100), the second shaft (200), the third shaft (300), the buffer (910) and/or the storage tank, wherein the at least one combustion chamber (180, 280) is in fluid communication with the first (100) and the second (200) shaft, preferably the at least one combustion chamber (180, 280) being arranged between the first (100) and the second (200) shaft, in particular said chamber (180, 280) being arranged in the corresponding cross-over channel (412).

14. Process according to the preceding clause, further comprising:

- feeding the first shaft (100) with a gas mixture (42) resulting from the combustion of the fuel (20) and the at least one comburent (30, 31), and the recycled exhaust gas (40) from the first shaft (100), said mixture (42) being generated in the combustion chamber (180) fluidly connected to the first shaft (100), while the exhaust gas (40) is extracted at the upper portion (111) of the first shaft (100), and while the second shaft (200) is cooled with the one or more cooling streams (91), in one cycle;

- feeding the second shaft (200) with the gas mixture (42) resulting from the combustion of the fuel (20) and the at least on comburent (30, 31), and the recycled exhaust gas (40) from the second shaft (200), said mixture (42) being generated in the combustion chamber (280) fluidly connected to the second shaft (200), while the exhaust gas is extracted at the upper portion (211) of the second shaft preheating (210) or cooling (230) zone, and while the first shaft (100) is cooled with the one or more cooling streams (91), in a subsequent cycle.

15. Process according to the previous clause, wherein the fuel (20) injected in the at least one chamber (180, 280) is the sole fuel source foreseen to generate the heat in the 33 first (100) and/or second shaft (100).

16. Process according to clause 6, further comprising providing:

- an auxiliary combustion chamber (600) supplied with at least a part of the fuel (20) to be injected in the first shaft (100) and the at least one comburent (30, 31), and optionally with the recycled exhaust gas (40) that is alternately extracted from the first (100) or second (200) shaft, and optionally

- at least one mixing chamber (190, 290), in particular a pair of mixing chambers, the at least one mixing chamber (190, 290) being supplied with the at least one comburent (30, 31) and the exhaust gas (41) generated in the auxiliary combustion chamber (600), the at least one mixing chamber (190, 290) being interposed between the first (100) and the second (200) shaft, in particular said chamber (190, 290) being arranged in the corresponding cross-over channel (412).

17. Process according to the preceding clause, wherein multi-shaft vertical kiln (MSVK) comprises fuel injection means (126, 226) provided in each shaft (100, 200), further comprising:

- feeding the first shaft (100) with an exhaust gas mixture (42) generated in the mixing chamber (190) fluidly connected to the first shaft (100), while supplying the remaining part of fuel (20) to be injected in the first shaft (100) via the fuel injection means (126) disposed in the first shaft (100), while the exhaust gas (40) is extracted at the upper portion (111) of the first shaft (100), and while the second shaft (200) is cooled with the one or more cooling streams (91), in one cycle;

- feeding the second shaft (200) with the gas mixture (42) generated in the mixing chamber (290) connected to the second shaft (200), while the complementary supply of the fuel (20) is carried out in the second shaft (200) via the fuel injection means (226) disposed in the second shaft (200), while the exhaust gas (40) is extracted at the upper portion (211) of the second shaft preheating (210) zone, and while the first shaft (100) is cooled with the one or more cooling streams (91), in a subsequent cycle.

18. Process according to the preceding clause, comprising, during a transition phase between one cycle and the subsequent cycle, the following steps:

- stopping the cooling of the second shaft (200);

- filling the second shaft (200) with an gas mixture (42) comprising a part of the generated exhaust gas (41) in the auxiliary combustion chamber (600), while pursuing the feeding of the first shaft (100) with both:

- an gas mixture (42) comprising the other part of the exhaust gas (41) generated in 34 the auxiliary combustion chamber (600) and

- the fuel (20) through the fuel injection means, before the second shaft (200) is heated.

19. Process according to any of the preceding clauses, further providing at least a first and second hoppers (151, 152, 160, 251, 252, 260) for conditioning the carbonated materials (10) before they are fed to at least one of the first (100) and/or the second shaft (200), and supplying the first hopper (151 , 152, 160, 251 , 252, 260) with the exhaust gas (40) extracted from one of the cross-over channel portions (170, 270) while supplying the second hopper (151, 152, 160, 251 , 252, 260) with the one or more the heated cooling streams (91) extracted from either:

- the other cross-over channel portion (270, 170), or

- the upper portion (111 , 211) of the preheating (110, 210) or cooling zone (130, 230) of the shaft (100, 200) connected to the other cross-over channel portion (270, 170).

20. Process according to any of the preceding clauses, wherein further comprising:

- providing water for the water steam stream (92) in step 1e) via :

- cooling the exhaust gas (40) extracted from at least the first (100), the second (200) and/or the third (300) shaft in a separate condensation (700) unit ; and/or

- an external water source;

- boiling the water in :

- at least one boiler (800); and/or

- at least one of the heat exchangers (133, 233, 333), into the water steam stream (92) that is fed in at least the first (100), second (200) and/or third (300) shaft.

21. Process according to any preceding clauses, wherein the one or more cooling streams (91, 92) comprise:

- the water steam stream in step 1e) (92), and;

- an additional cooling stream (91) comprising at least 90% air CO2 (dry volume) and optionally less than or equal to 5 % of CO2 (dry volume), said process further comprising feeding the additional cooling stream (91) in the cooling zone (130, 230, 330) of at least the first (100), the second (200) and/or the third (300) shaft, and extracting the heated additional cooling stream (91) from said shafts (100, 200, 300), wherein an inlet opening in the first, the second or the third shaft cooling zone (130,230,330), through which the water steam stream (92) is fed, is positioned above an 35 outlet opening in the same shaft (100, 200, 300), through which the heated additional cooling (91) is extracted, preferably the additional cooling stream (91) being supplied at the lower portion (132, 232, 332) of least the first (100), the second (200) and/or the third (300) shaft, and optionally extracted at the corresponding upper portion (131, 231 , 331) of said cooling zones (130, 230, 330).

22. Process according to any of the preceding clauses, further purifying the exhaust gas (40) extracted from the multi-shaft vertical kiln (MSVK), preferably by removing at least one of the following elements: acid gases, 02, Ar, CO, H20, NOx, sulfur compounds, heavy metals, in particular Hg, Cd, and/or organic compounds, in particular CH4, benzene, hydrocarbons, in a CO2 purification unit (CPU) adapted to adjust the composition of the exhaust gas (40) to the specification required by a carbon capture and utilization or carbon capture and storage application, preferably with a CO2 content above 80% (dry volume) and more preferably above 95% (dry volume).

23. Process according to any of the preceding clauses, wherein the recirculation of the exhaust gas (40) to the multi-shaft vertical kiln (MSVK) is achieved by extracting the exhaust gas (40) from the buffer (910) or the storage tank (920).

24. Process in particular according to any of the preceding clauses, further providing one or more additional kilns (MSVK _1 , MSVK _2, MSVK _N, K_1, K_N) to a/the multi shaft vertical kiln (MSVK) forming a plurality of kilns generating an aggregated exhaust gas stream, so as to minimize flow variation of the aggregated exhaust gas stream entering the CO2 purification unit (CPU), in particular coordinating the plurality of kilns by selecting appropriate cycles phasing and duration of said kilns.

25. Process according to any of the preceding clauses, wherein the CO2 purification unit (CPU) is continuously fed with either the exhaust gas (40) from the buffer (910), the exhaust gas (40) from the storage tank (920), the exhaust gas (40) from the MSVK, the one or more additional kilns or a combination of them.

26. Process according to any of the preceding clauses, wherein the fuel (20) used is either carbon-containing fuel or dihydrogen-containing fuel or a mixture of them.

27. Process according to any of the preceding clauses, wherein the decarbonated materials (50) produced have a residual CO2 <5%, preferably <2%.

28. Process according to any of the preceding clauses, further comprising recovering heat from the one or more of the cooling streams (91 , 92), and/or the recirculated exhaust gas (40).

29. Process according to any of the preceding clauses, wherein the combustion of at 36 least one fuel (20) with at least one comburent (30, 31) is under an oxygen-to-fuel equivalence ratio greater or equal to 0.9.

30. Process according to any of the preceding clauses, wherein any shaft of a group consisting of the first, second and optionally the third shaft (100, 200, 300) is not encircled by the other or another shaft (100, 200, 300) of said group.

31. Process according to any of the preceding claims, wherein in step 1a), 1b), 1c) 1e), or 1f), further providing at least one hopper (900) for conditioning the carbonated materials (10) before they are fed to at least one of the first (100) and/or the second shaft (200), and supplying the at least one hopper (900) with the one or more of the heated cooling streams (91) extracted from the upper portion (111, 211) and/or the heat exchanger (133, 233) of the cooling zone (130, 230) of the first and/or second shafts (100, 200).

32. Process according to any of the preceding claims, comprising feeding the carbonated materials (10) into and/or discharging the decarbonated materials (50) form at least one of the first, second and/or third shaft (100, 200, 300), via a feeding and/or discharging system (1100, 1200), respectively, each system (1100, 200) comprising a lock chamber delimited by an upstream valve assembly and a downstream valve assembly, said feeding or discharging system (1100, 1200) being configured to collect the carbonated (10) or decarbonated materials (50), respectively, while the upstream valve assembly is open and the downstream valve assembly is closed, to store in a substantially gas tight manner the carbonated (10) or decarbonated materials (50), respectively, while both the upstream and downstream valve assemblies are closed, and to release the carbonated (10) or decarbonated materials (50), respectively, while the upstream valve assembly is closed and the downstream valve assembly is open.

33. Process according to any of the preceding claims wherein the upstream or downstream valve assembly comprising a single or multiple flap valve, a table feeder, a rotary valve, a cone valve, a J valve, a L valve, a trickle valve, preferably a single or multiple flap valve.

34. Multi-shaft vertical kiln (MSVK) comprising a first (100), a second (200), and optionally a third (300) shaft with preheating (110, 210, 310), heating (120, 220, 320) and cooling (130, 230, 330) zones and a cross-over (412, 423, 431) channel between each shaft (100, 200, 300), said kiln (MSVK) being arranged for being cooled with one or more cooling streams (91, 92), said kiln (MSVK) being adapted for carrying out the process according to any of the preceding clauses 1 to 33, said kiln (MSVK) comprising at least one of the following elements: 37

- a heat exchanger (133, 233, 333) arranged in each cooling zone(130, 230, 330);

- at least one first aperture for extracting the one or more cooling streams (91), said aperture being arranged in a wall section of at least the first, the second and/or the third shaft (100, 200, 300) at an upper portion (131, 231, 331) of the corresponding cooling zone (130, 230; 330);

- at least one second aperture for extracting the one or more cooling streams (91), said first aperture being arranged in a pipe assembly centrally arranged in at least the first, the second and/or the third shaft (100, 200, 300), said aperture being vertically positioned in an upper portion (131, 231, 331) the corresponding cooling zone (130, 230; 330);

- a selective separation means (141 , 241) arranged in an upper portion of the cooling zone (130, 230, 330), said selective separation means comprising:

- a wall separating the inner space of corresponding shaft (100, 200, 300) into an upper and lower space, and

- at least one passage arranged in said wall, said passage being arranged so as to allow the transfer of the decarbonated materials (50) between the upper and the lower space while substantially preventing the passage of the one or more cooling streams (91, 92) and/or the exhaust gas (40).

- a closure means (512) arranged the cross-over channel (412) between the first (100) and the second (200) shaft, said means (512) being arranged to prevent a gas transfer between the first (100) and the second (200), preferably the closure means (512) comprising at least one valve or a plug; and/or

- at least one injection means for supplying the one or more cooling streams (92) comprising a water steam stream, said injection means being arranged in the cooling zone (130, 230, 330) of at least the first (100), the second (200) and/or the third (300) shaft.

35. Multi-shaft vertical kiln (MSVK) according to the previous clause, wherein each heat exchanger (133, 233, 333) comprises a plurality of passages arranged in the corresponding cooling zone (130, 230, 330), said passages being delimited by walls, in which the one or more cooling streams (91) circulates.

36. Multi-shaft vertical kiln (MSVK) according to clause 34 or 35, comprising two closure means (523, 531), respectively in the cross-over (431) channel between the first (100) and the third (300) shaft and in the cross-over channel (423) between the second (200) 38 and the third (100) shaft, preferably the two closure means (523, 531) being each at least one valve or a plug.

37. Multi-shaft vertical kiln (MSVK) according to any of the clauses 34 to 36, wherein the or each of the closure means (512, 523, 531) is configured to allow the gas transfer between the first (100) and the second shaft (200);

38. Multi-shaft vertical kiln (MSVK) according to clause 36, wherein at least one further passage is arranged between and in fluid communication with at least one of the shafts (100, 200, 300) and the other or another shafts (100, 200, 300), said passage comprising at least one valve that is open to allow the gas transfer between said shafts (100, 200, 300), said passage being positioned adjacent to the cross-over channel (412, 423, 431) arranged between said shafts (100, 200, 300), preferably said passage presenting a section of between 10 to 50% of the minimal section of said cross-over channel (412, 423, 431).

39. Multi-shaft vertical kiln (MSVK) according to any of the clauses 34 to 38, comprising at least one hopper (151, 152, 160, 251 , 252, 260) for conditioning the carbonated materials (10) before they are fed to the first shaft (100) or the second shaft (200), and optionally the third shaft (300), said hopper (151, 152, 160, 251, 252, 260) being in fluid communication with at least one the following elements : one or both of the cross-over channel portions (170, 270), the first shaft preheating zone upper portion (111) and/or the second shaft preheating zone upper portion (211).

40. A kiln for a decarbonation of carbonated materials (10), in particular limestone and dolomitic limestone, preferably a multi-shaft vertical kiln (MSVK) preferably according to any of the clauses 34 to 39, said kiln comprising a buffer (910) and/or the storage tank (920) arranged downstream form said kiln (MSVK) for storing the exhaust gas (40) generated in said kiln in a gasified or liquid form, respectively, preferably said storage tank comprising a blow-off valve for cooling liquid CO2 stored in said tank (920), in particular an outlet of said blow-off valve being fluidly connected to said kiln (MSVK) via a recirculation passage for transferring boiled exhaust gas (40) to said kiln (MSVK).

41. Multi-shaft vertical kiln (MSVK) according to any of the clauses 34 to 40, wherein the closure means (512) divides the cross-over channel (412) into a first (170) and a second portion (270), said first (170) and second (270) portions each comprising an exhaust passage for extracting at least the one or more heated cooling flow (91, 92) or the exhaust gas (34), said passage being formed in a wall section of said cross-over channel (412).

42. Multi-shaft vertical kiln (MSVK) according to any of the clauses 34 to 41 , comprising 39 at least one combustion chamber (180, 280), in particular a pair of combustion chambers supplied with the fuel (20), the at least one comburent (30, 31) and the recycled exhaust gas (40) form at least the first shaft (100), the second shaft (200), the third shaft (300), a buffer (910) and/or a storage tank (920), wherein the at least one combustion chamber (180, 280) is in fluid communication with the first (100) and the second (200) shaft, preferably the at least one combustion chamber (180, 280) being arranged between the first (100) and the second (200) shaft, in particular said chamber (180, 280) being arranged in the corresponding cross-over channel (412).

43. Multi-shaft vertical kiln (MSVK) according to any of the clauses 34 to 42, comprising an auxiliary combustion chamber (600) supplied with at least a part of the fuel (20) to be injected in the first shaft (100) and the at least one comburent (30, 31), and optionally with the recycled exhaust gas (40) that is alternately extracted from the first (100) or second (200) shaft.

44. Multi-shaft vertical kiln (MSVK) according to the preceding clause, comprising at least one mixing chamber (190, 290), in particular a pair of mixing chambers positioned downstream from the auxiliary combustion chamber (600), the at least one mixing chamber (190, 290) being supplied with the at least one comburent (30, 31) and the exhaust gas (41) generated in the auxiliary combustion chamber (600), the at least one mixing chamber (190, 290) being in fluid communication with the first (100) and the second (200) shaft, preferably said chamber (190, 290) being interposed between the first (100) and the second (200) shaft, in particular said chamber (190, 290) being arranged in the corresponding cross-over channel (412).

45. Multi-shaft vertical kiln (MSVK) according to any of the clauses 34 to 40, wherein the or each cross-over channel (412, 423, 431) comprise at least one cooling passage for extracting the one or more heated cooling flow (91 , 92), said passage being formed in a wall section of the corresponding cross-over channel (412, 423, 431).

46. Multi-shaft vertical kiln (MSVK) according to any of the clauses 34 to 45, wherein any shaft of a group comprising the first, second and optimally third shaft (100, 200, 300) is not encircled by the other or another shaft (100, 200, 300) of said group.

47. A system for carbon capture and utilization or carbon capture and storage application comprising preferably a multi-shaft vertical kiln (MSVK) according to any of the clauses 34 to 46, said system comprising a CO2 purification unit (CPU) for purifying the exhaust gas (40) exiting said kiln (MSVK).

48. A system for carbon capture and utilization or carbon capture and storage application according to the previous clause, comprising one or more additional kilns (K_1 , 40

K_N, MSVK_1, MSVK_N) generating an exhaust gas stream, the CO2 purification unit (CPU) being selectively connected to the one or more additional kilns (K_1, K_N, MSVK_1, MSVK_N) and/or to said kiln (MSVK).