Technical Field

In general, the present disclosure relates to apparatus, system and methods for production of hydrogen gas with water purified by thermal membrane distillation in a water electrolysis system. More specifically, the present disclosure relates to an integrated purified water and hydrogen production system.

Background

Hydrogen gas is an important part of the industrialized world as hydrogen is vital for many chemical processes. With the emerging shift from fossil fuel, the interest and importance of hydrogen gas has increased. Hydrogen can for example be used for production of electricity, heating or in a fuel cell in hydrogen gas driven cars.

Today, hydrogen is mainly produced from fossil fuel. In view of the current urge to address climate effects of human activities it is becoming increasingly important to manufacture hydrogen in an environmentally sustainable manner. One method of producing hydrogen is by electrolysis of water, i.e. by using electricity to decompose water into oxygen and hydrogen gas. The raw material required for water electrolysis is water and electrical energy. Electrolysis of water can be made by any source of electricity and thus also by environmentally friendly electricity production methods. The residual product of water electrolysis is oxygen and there is nothing in the process per se that adds to green gas pollution or other pollution.

A major concern in hydrogen production with water electrolysis is the energy costs. A large amount of energy goes into the process with a conversion loss in the range of 20 - 30 %, a great part of which is released as waste heat. Solar power is an attractive energy source for hydrogen production. However, there is also a conversion loss of energy in solar power generators. For example, a solar powered steam turbine to produce electricity needs to be cooled and with a photovoltaic solar power collector a part of the sun light influx is transformed to electricity and a remaining part of the influx becomes heat. Another concern is the consumption of water. For example, it takes about 9.1 ton of water to produce 1.1 ton of hydrogen. Generally, hydrogen production by water electrolysis requires high-quality water. In order to increase hydrogen production in the amounts that will be required, it is a general concern how to supply water with sufficient quality for hydrogen production in a sustainable manner. For example, in many parts of the world there is already a shortage of water with a quality suitable for drinking and it would not be feasible to take water for hydrogen production from such scarce water resources. Using for example sea water or recirculated wastewater is therefore a possible solution, provided it can be efficiently cleaned to the required quality.

The minimum water quality that is recommended to use in hydrogen production with water electrolysis is generally process water or boiler feeder water dependent on electrolyser technology. One major effect of good water quality is to reduce wear in electrolyser equipment, especially the electrodes, and thereby reduce costs for maintenance and renewal of the equipment.

Related Art

An example of a solar powered hydrogen production apparatus based on water electrolysis is found in the utility model publication CN205099761 to ZHANG WANJUN. This piece of related art discloses a water electrolysis hydrogen system including a solar cell panel, a solar control ware, a solar battery and a water electrolysis arrangement for hydrogen production powered by the solar cell panel. Another example of related art is shown in the patent publication FR2927907 to AREVA H2GEN/ORFAGEN. This publication shows a hydrogen production apparatus based on water electrolysis with a water purification arrangement to supply clean water to an electrolyser.

An example of related art where waste heat from water electrolysis is used in a water treatment system is found in EP2791062B1. In this piece of related art, thermal energy is supplied from an electrolysis facility to a water processing facility and is used to produce deionized water by membrane distillation. In EP2791062B1 it is emphasized that the water produced using membrane distillation is deionized water. Deionized distilled water is provided as cleaning water for a solar power facility and as fresh water for the electrolysis process in the electrolysis plant.

Another example of related art where waste heat from water electrolysis is used in a water treatment facility is found in EP2623640A1. In the publication EP2623640A1, waste heat occurring in a water electrolysis facility is used for production of deionized water. As described in EP2623640A1, waste heat is stored and carried by a heat transfer medium to a heat exchanger integrated in the water treatment facility. Raw water is conducted into the heat exchanger that is integrated in the water treatment facility and is desalinated and deionized in the context of a thermal treatment process. As stated in paragraph [0012] of EP2623640A1, the waste heat is used in the thermal water treatment to produce deionized water. In paragraph [0020] of the same publication it is referred to another related art document DE102008051731A1 as an example of a description of low temperature distillation where vaporization and condensation are used in a process to produce deionized water.

DE102008051731A1 shows an arrangement for separation of substances solved in a liquid by means of vaporization and condensation. The arrangement described in this publication shows a first closed circuit that conducts the liquid in a first direction, in which first closed circuit there is at least one unit having an evaporator and a condenser, and a heat exchanger. Further, the described arrangement has a second closed circuit that conducts a heat carrier fluid in an opposite direction, in which second closed circuit the condenser and the heat exchanger are situated. A carrier gas is circulated through the evaporator taking up heat and moist, and through the condenser releasing heat and moist, thereby releasing the condensate. The arrangement has means for drawing off substances that are deposed in the evaporator, means for introducing an amount of liquid corresponding to the amount of drawn off substances and of the drawn off condensate in which liquid substances are dissolved, and means for drawing off the condensate that has been formed in the condenser of one or more units.

The patent publication US 4,391,676 to Finn Torberger shows an example of a membrane purification apparatus based on thermal differences between a supply water flow and a cooling water flow.

There is a fundamental difference between deionization of water as in the mentioned related art EP2791062B1 and EP2623640A1 compared to membrane distillation of water as in the mentioned related art US 4,391,676. Deionized water is water that has been treated to remove all ions, i.e. typically all dissolved mineral salts that appear in water are removed.

Distilled water on the other hand is water that has been heated into steam and then condensed into water phase again leaving impurities behind but still having a content of ions. Water purified by thermal membrane distillation is not per se deionized. Consequently, the water treatment described in EP2791062B1 and EP2623640A1) that uses thermal membrane distillation to produce deionized water is different from thermal membrane distillation to produce pure but not deionized water.

Object of Disclosed Embodiments The object of embodiments disclosed herein is to provide a hydrogen production system that improves the cost efficiency in the production of hydrogen gas.

Summary

The object is achieved by embodiments of a hydrogen gas production system 100, comprising a water electrolysis apparatus 102 configured to generate hydrogen gas 221 from purified water 104 and electricity 106 from an electric energy source 108, said water electrolysis apparatus further generating waste heat 110; a membrane purification apparatus 112 configured to produce purified water 104 from water heated by waste heat recovered from the hydrogen gas production system; a water supply system 114 configured to supply water from a water source 116 to the water electrolysis apparatus 102 via the membrane purification apparatus 112. The hydrogen gas production system is configured to conduct supply water from the water supply system 114 first through a cold water side of the heat exchanger 120,160 to receive waste heat from the water electrolysis apparatus 102 and then to a hot water circuit 122 of the membrane purification apparatus 112 to produce purified water 104 by condensing steam having passed a semipermeable membrane 125, and is configured o input the purified water (104) to the water electrolysis apparatus 112.

Method embodiments of producing hydrogen gas in a hydrogen gas production system 100, comprises generating hydrogen gas 221 and waste heat 110 in a water electrolysis apparatus 102 configured to generate hydrogen gas from input purified water 104 and from electricity 106 from an electric energy source 108; producing purified water 104 in a membrane purification apparatus 112 configured to produce purified water 104 from water heated by waste heat recovered from the hydrogen gas production system and inputting said purified water to the water electrolysis apparatus 112; supplying water, in a water supply system 114, from a water source 116 to the water electrolysis apparatus 102 via the membrane purification apparatus 112 to produce purified water 104 and inputting the purified water 104 to the water electrolysis apparatus 112 to generate said hydrogen gas 221. The method further comprises conducting water from the water supply system 114 first through a cold water side of the heat exchanger 120,160 to receive waste heat from the water electrolysis apparatus 102 and then to a hot water circuit 122 of the membrane purification apparatus 112 to produce purified water 104 by condensing steam having passed a semipermeable membrane 125; and inputting the purified water 104 to the water electrolysis apparatus 112.

Brief description of drawing

Embodiments disclosed herein will be further explained with reference to the accompanying drawing, in which:

FIG 1 schematically illustrates a hydrogen production system in accordance with embodiments.

Detailed description of embodiments

General embodiments comprise a hydrogen production system wherein waste heat from one or more water electrolysis apparatus is recovered and used for water purification in a membrane purification apparatus.

The membrane purification apparatus is preferably of the type as described in above mentioned patent publication US 4,391,676 to Finn Torberger, i.e. a membrane purification apparatus based on thermal differences between a supply water flow and a cooling water flow. This technology is also known as thermal membrane distillation and is a separation technology by means of transfer of vaporized fluid through a hydrophobic semi-permeable membrane. In thermal membrane distillation of water, water is heated and conducted in a hot water circuit past a hydrophobic semi-permeable membrane. Vaporized water thus in the form of steam appearing at the membrane passes through the membrane leaving impurities behind in the hot water circuit and is condensed into liquid phase purified water at the other side of the membrane where it meets a cool surface.

In this kind of purification apparatus, a heated supply water flow conducted in a hot water circuit is separated by a membrane and a gap from a cooling surface confining the cooling water flow. The membrane is configured to allow water vapor to pass from the supply water flow into the gap between the membrane and the cooling surface. Vapor having entered the gap is condensed against the cooling surface and the condensed water is conducted into a purified water flow to an outlet for purified water. The structure and functionality of a membrane purification apparatus used jn embodiments described herein is thus per se known and details are found inter alia in the mentioned publication and in other publications as well as existing products.

Other general embodiments are configured independently of the membrane purification apparatus, i.e. configured with or without a membrane purification apparatus, and are configured to drive water electrolysis for example by means of recovered waste heat from the hydrogen production process or from renewable energy sources.

FIG 1 schematically illustrates a hydrogen gas production system 100 in accordance with embodiments. Embodiments of such a hydrogen gas production system comprises a water electrolysis apparatus 102 configured to generate hydrogen gas from input purified water 104 and electricity 106 from an electric energy source 108, said water electrolysis apparatus further generating waste heat 110. A membrane purification apparatus 112 is configured to produce purified water 104 from water heated by waste heat recovered from the hydrogen gas production system. A water supply system 114 is configured to supply water from a water source 116 to the water electrolysis apparatus 102 via the membrane purification apparatus 112.

Method embodiments for producing hydrogen gas in such a hydrogen gas production system 100, comprises generating hydrogen gas 221 and waste heat 110 in a water electrolysis apparatus 102 configured to generate hydrogen gas from input purified water 104 and from electricity 106 from an electric energy source 108. With the water electrolysis apparatus in operation, these embodiments comprise producing purified water 104 in a membrane purification apparatus 112 configured to produce purified water 104 from water heated by waste heat recovered from the hydrogen gas production system and inputting said purified water to the water electrolysis apparatus 112. To cater for the water consumption in the process, such embodiments comprise supplying water, in a water supply system 114, from a water source 116 to the water electrolysis apparatus 102 via the membrane purification apparatus 112 to produce purified water 104 and inputting the purified water 104 to the water electrolysis apparatus 112 to generate said hydrogen gas 221.

In order to recover waste heat from the water electrolysis process, system embodiments comprise a heat exchanger 120 configured to transfer waste heat 110 from the hydrogen gas production system to a hot water circuit 122 of the membrane purification apparatus 112. Method embodiments thus comprises transferring waste heat 110 via a heat exchanger 160 from the water electrolysis apparatus 102 to a hot water circuit 122 of the membrane purification apparatus 112.

In embodiments illustrated in Fig 1, the system is configured to conduct supply water from the water supply system 114 first through a cold water side of the heat exchanger 120,160 to receive waste heat from the water electrolysis apparatus 102 and then to a hot water circuit 122 of the membrane purification apparatus 112 to produce purified water 104 by condensing steam having passed a semipermeable membrane 125, and to input the purified water 104 to the water electrolysis apparatus 112. Supply water is conducted from a water supply system 114 from a water storage 118 being provided with water from a water source 116, into a cold water side of a heat exchanger 120,160. Waste heat 110 is transferred from the water electrolysis apparatus 102 to the supply water via a hot water side of the heat exchanger 120,160. The heated supply water is conducted into the hot water circuit 122 of the water purification apparatus where it passes a membrane 125, preferably a hydrophobic semi-permeable membrane. Steam appearing at the membrane passes from the hot water circuit 122 through the membrane to a gap 129 and is condensed into liquid phase water when facing a cool surface 127 that is cooled by a cool water circuit 124. Impurities in the supply water are left behind in the hot water circuit and the condensed water is pure and supplied as purified water 104 to the water electrolysis apparatus in a purified water line 105.

In embodiments, the water purification apparatus 112 comprises one or more units having a described membrane 125, gap 129, cooling surface 127, hot water circuit 122 and purified water line 105. The hot water circuits of the respective units are in embodiments coupled in parallel or in series, whereas the purified water lines 105 from the respective unit are joined to feed one or more lines of purified water to the electrolysis apparatus.

The impurities are carried away from the water purification apparatus with supply water in the hot water circuit. The hot water circuit is in embodiments an open circuit connected to the supply water lines to receive supply water heated by waste heat and to recirculate non-purified water exiting from the water purification apparatus 112 to the supply water lines.

In embodiments the temperature of the supply water in the hot water circuit 122 of the water purification apparatus 112 is controlled by mixing the supply water that has been heated by waste heat from the electrolysis apparatus 102 with cooler supply water for example entered via connection point B or via a connection point at the line joint 131. Embodiments comprise one or more valves and oner or more temperature sensors configured for controlling the temperature of the heated supply water entering the hot water circuit 122 of the water purification apparatus 112Embodiments of the hydrogen gas production system 100 are further being configured to produce electricity 134 from waste heat 110 from the water electrolysis apparatus 102 and to supply said electricity to said water electrolysis apparatus for generation of hydrogen gas. Method embodiments of producing hydrogen gas, in such embodiments thus comprises producing electricity 134 from waste heat 110 from the water electrolysis apparatus 102 and supplying electricity to said water electrolysis apparatus 102 for generation of hydrogen gas 221. Variants of such embodiments comprises a hot water turbine 130 with a hot water input 132 coupled to a waste heat water circuit 128 of the hydrogen gas production system and being configured to produce electricity 134 from waste heat 110 from the water electrolysis apparatus 102 and output electricity to an electric power supply system 140 of the hydrogen gas production system. Method embodiments of producing hydrogen gas in such system embodiment variants comprises inputting hot water recovered from waste heat of the water electrolysis apparatus 102 to a hot water circuit 128. Further supplying hot water from the hot water circuit 128 to a hot water turbine 130 to produce electricity 134 and providing said electricity 134 to an electric power supply system 140 of the hydrogen gas production system 100. Such embodiments would make use of the waste heat of the water electrolysis to supply the water electrolysis process with electricity. Such embodiments may be configured independently of the membrane purification apparatus, i.e. be configured with or without a membrane purification apparatus.

Other embodiments make use of solar power. Such embodiments of the hydrogen gas production system 100 comprise a solar power generator 150 configured to generate electricity 152 from incident sun light 154, said solar power generator further generating waste heat 156. A method embodiment of producing hydrogen gas comprises generating electrical power and waste heat from incident sun light in a solar power generator 102 and supplying said electric power to the water electrolysis apparatus to generate the hydrogen gas.

In order to recover waste heat, embodiments comprises a selection of one or more heat exchangers. In one embodiment the hydrogen gas production system 100 comprises a first heat exchanger 160 configured to transfer waste heat 110 from the water electrolysis apparatus 102 to a hot water circuit 122 of the membrane purification apparatus 112. A method embodiment of producing hydrogen gas in such a variant of a hydrogen gas production system comprises transferring waste heat 110 via a first heat exchanger 160 from the water electrolysis apparatus 102 to a hot water circuit 122 of the membrane purification apparatus 112.

Another embodiment of the hydrogen gas production system 100 comprises a second heat exchanger 170 configured to transfer waste heat 156 from the solar power generator 150 to a hot water circuit 122 of the membrane purification apparatus 112. A method embodiment of producing hydrogen gas in such a variant of a hydrogen gas production system comprises transferring waste heat 156 via a second heat exchanger 170 from the solar power generator 150 to a hot water circuit 122 of the membrane purification apparatus 112.

The membrane purification apparatus 112 also produces waste heat when keeping a cold side of the apparatus cool. An embodiment of the hydrogen gas production system 100 comprises a third heat exchanger 180 configured to transfer heat from a cooling water circuit 124 of the membrane purification apparatus 112 to a waste heat circuit, for example the waste heat water circuit 128 of the water supply system 114. A method embodiment of producing hydrogen gas in such an embodiment of a hydrogen gas production system comprises transferring heat via a third heat exchanger 180 from a cooling water circuit 124 of the membrane purification apparatus 112 to a waste heat circuit, for example the waste heat water circuit 128 of the water supply system 114.

The cooling water circuit 124 is in embodiments a closed circuit carrying cooling water via a heat exchanger 180 where it transfers heat for example to a supply water line via connection points A.

For the purpose of supplying the water electrolysis process with electricity, embodiments of the hydrogen gas production system 100 comprise an electric power supply system 140 configured to energize one or more of water electrolysis apparatus 102, the membrane purification apparatus 112 and the water supply system 114. A method embodiment of producing hydrogen gas in such a hydrogen gas production system comprises energizing via an electric power supply system 140 one or more of the water electrolysis apparatus 102, the membrane purification apparatus 112 and the water supply system 114.

Embodiments of an electric power supply system 140 comprises one or more of an electric energy source 108 and a set of components configured to supply apparatuses and subsystems of the hydrogen gas production system with electric energy.

The electric energy source comprises, in various embodiments, one or more of a hot water turbine 130, a general mains electricity source 190, a battery pool 200 and a solar power generator 150, being configured to feed electricity to a main electric supply line 300.

The solar power generator 150 is in embodiments based on photovoltaic cells generating electric power and waste heat, and in other embodiments based on solar thermal collectors generating electric power by means of a steam turbine. In order to drive the water electrolysis apparatus, embodiments of the hydrogen gas production system 100 comprise a first electric power transformer 141 configured to adapt and transfer electric power from one or more of a hot water turbine 130, a general mains electricity source 190, a battery pool 200 and a solar power generator 150 to one or more electrolysers of the water electrolysis apparatus 102. A method embodiment of producing hydrogen gas in such a hydrogen gas production system comprises adapting and transferring, via a first electric power transformer 141, electric power from one or more of a hot water turbine 130, a general mains electricity source 190, electric power storage 200 and a solar power generator 150 to one or more electrolysers of the water electrolysis apparatus 102.

In embodiments of the hydrogen gas production system 100 there is comprised a second electric power transformer 143 configured to adapt and transfer electric power from one or more of the hot water turbines 130, a general mains electricity source 190, an electric power storage 200 or a solar power generator 150 to components of one more of the water electrolysis apparatus 02, the membrane purification apparatus 112, the water supply system 114 and the electric power supply system 140. Method embodiments of producing hydrogen gas in a hydrogen gas production system, further comprising: adapting and transferring, via a second electric power transformer 142, electric power from one or more of a hot water turbine 130, a general mains electricity source 190, electric power storage 200 and a solar power generator 150 to components of one more of the water electrolysis apparatus 02, the membrane purification apparatus 112, the water supply system 114 and the electric power supply system 140. In embodiments of the hydrogen gas production system 100, the components comprise one or more of control electronics, sensor devices, pumps, valves, heaters, coolers, batteries and communication devices.

The water supply system 114, in embodiments, takes water from a water source 116 to a water storage 118. The water storage 118 is, as illustrated in FIG 1., coupled in a waste heat water circuit 128 that circulates waste heat water collecting waste heat from the water electrolysis apparatus and back to the water storage 118. In embodiments, the waste heat water circuit 128 is connected to a hot water circuit 122 of a membrane purification apparatus 112. The waste heat water circuit 128 may further be coupled to a water processing unit 119 for example configured to separate sludge or concentrated pollution from the waste heat water. The pollution is in this context impurities left behind in the waste heat water supply water in the hot water circuit of the water purification apparatus 112. The waste heat water circuit comprises cool connection points A for circulating cool water to heat exchangers comprised in the system, as well as hot connection points B for circulating hot water heated by recovered heat from different apparatuses in the system to the waste heat water circuit.

Waste heat water output from the water processing apparatus 119 is in embodiments conducted to the water storage 118 to be recirculated in the supply water system. In embodiments, the water storage 118 comprises one or more compartments, with a separate compartment for water that has passed the water purification apparatus 112 and in applicable embodiments the water processing apparatus 119 in order to separate it from water entering the water supply system 114 from the water source 116.

Exemplifying embodiments are described herein, further embodiments and configurations based on the described concepts are also conceivable.