fuel cell system

Abstract

A technology is provided that can improve the efficiency of an entire system including a fuel cell system and other systems. [Solution] A fuel cell system 1 according to one embodiment comprises a fuel cell 10 that generates electricity by chemically reacting hydrogen and oxygen, a water supply unit 30 that supplies water produced by the fuel cell 10 to a caustic soda production process, an exhaust path 15 that discharges exhaust gas from the fuel cell 10 to the outside, a refrigerant circuit RC2 through which a refrigerant flows, a refrigerant supply unit 20 that supplies refrigerant to the refrigerant circuit RC2, and a heat exchanger 12 that absorbs the exhaust heat from the fuel cell 10 into the refrigerant in the refrigerant circuit RC2. The water supply unit 30 supplies condensed water CW obtained by condensing water vapor contained in the exhaust gas through heat exchange between the refrigerant in the low-temperature path of the refrigerant circuit RC2 that runs from the refrigerant supply unit 20 to the heat exchanger 12 and the exhaust gas in the exhaust path 15 to the caustic soda production process.

Description

[Technical Field]

[0001] The present disclosure relates to fuel cell systems. [Background technology]

[0002] For example, a technique is known for operating a fuel cell system in cooperation with other systems (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-208420 Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is room for improvement in the cooperation between the fuel cell system and other systems in terms of improving the efficiency of the entire system.

[0005] In view of the above-mentioned problems, an object of the present invention is to provide a technology that can improve the efficiency of the entire system including the fuel cell system and other systems. [Means for solving the problem]

[0006] In order to achieve the above object, in one embodiment of the present disclosure, A fuel cell that generates electricity through a chemical reaction between hydrogen and oxygen; a water supply unit that supplies water produced by the fuel cell to a caustic soda production process; A fuel cell system is provided. [Effects of the Invention]

[0007] According to the above-described embodiment, it is possible to improve the efficiency of the entire system including the fuel cell system and other systems. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the configuration of a first example of a fuel cell system. [Figure 2] FIG. 10 is a diagram showing the configuration of a second example of a fuel cell system. [Figure 3] FIG. 10 is a diagram showing the configuration of a third example of a fuel cell system. [Figure 4] FIG. 10 is a diagram showing the configuration of a fourth example of a fuel cell system. [Figure 5] FIG. 10 is a diagram showing the configuration of a fifth example of a fuel cell system. [Figure 6] FIG. 10 is a diagram showing the configuration of a sixth example of a fuel cell system. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment will be described with reference to the drawings.

[0010] [First example of a fuel cell system] A first example of a fuel cell system 1 according to this embodiment will be described with reference to FIG.

[0011] FIG. 1 is a diagram showing the configuration of a first example of a fuel cell system 1. As shown in FIG.

[0012] In this example, the fuel cell system 1 functions as a power source for the caustic soda production system 100 .

[0013] The caustic soda production system 100 does not necessarily have to use the fuel cell system 1 as a power source.

[0014] The caustic soda production system 100 is installed, for example, in a predetermined plant (factory), and produces caustic soda using salt water (specifically, an aqueous sodium chloride solution) as a raw material by an ion exchange membrane method.

[0015] <Caustic soda manufacturing system> As shown in FIG. 1, the caustic soda production system 100 includes a brine purification processing unit 110, an electrolytic cell 120, a concentration processing unit 130, a chlorine gas processing unit 140, and a hydrogen gas processing unit 150.

[0016] The brine purification unit 110 performs a brine purification process for purifying impurities contained in raw salt from brine. The brine purification unit 110 includes a dissolution tank 111 and an impurity removal unit 112.

[0017] Industrial water and the return brine from the electrolytic cell 120 are supplied to the dissolution tank 111, and the raw salt is dissolved therein until the concentration is close to saturation. The brine produced in the dissolution tank 111 is sent to the impurity removal section 112.

[0018] The impurity removal unit 112 removes impurities from the saltwater. For example, the impurity removal unit 112 includes a thickener, various filters, a chelating resin tower, and the like.

[0019] The purified brine that has passed through the impurity removal section 112 is supplied to the anode chamber 121 of the electrolytic cell 120 .

[0020] The electrolytic cell 120 produces caustic soda by an ion exchange membrane method. The electrolytic cell 120 includes an anode chamber 121 in which an anode 121T is provided, a cathode chamber 122 in which a cathode 122T is provided, and an ion exchange membrane 123 that separates the anode chamber 121 from the cathode chamber 122.

[0021] Purified brine is supplied to the anode chamber 121 of the electrolytic cell 120, and pure water is supplied to the cathode chamber 122 of the electrolytic cell 120, and a DC voltage is applied between the anode 121T and the cathode 122T. As a result, cations are attracted to the cathode chamber 122 via the ion exchange membrane 123, and anions are attracted to the anode chamber 121.

[0022] In the anode chamber 121, sodium chloride (NaCl) is dissolved and the resulting chloride ions (Cl -) by an anode reaction, chlorine gas (Cl2) is generated from the water, and in the cathode chamber 122, hydrogen gas (H2) is generated from the water by a cathode reaction, and hydroxide ions (OH - ) is generated.

[0023] The ion exchange membrane 123 is a cation exchange membrane, and has the property of blocking anions and allowing only cations to pass through. Therefore, sodium ions generated in the anode chamber 121 can pass through the ion exchange membrane 123 and move to the cathode chamber 122. As a result, sodium ions and hydroxide ions combine in the cathode chamber 122 to produce sodium hydroxide (NaOH), i.e., caustic soda.

[0024] The caustic soda produced in the cathode chamber 122 is sent to the concentration treatment unit 130. The caustic soda discharged from the cathode chamber 122 contains a relatively large amount of water, and the concentration is, for example, 32 weight percent (32 wt%).

[0025] The chlorine gas and hydrogen gas produced as by-products in the anode chamber 121 and the cathode chamber 122 are sent to a chlorine gas treatment section 140 and a hydrogen gas treatment section 150, respectively.

[0026] The concentration treatment unit 130 performs a concentration step of concentrating the caustic soda produced in the cathode chamber 122 of the electrolytic cell 120. The concentration treatment unit 130 includes an evaporator 131 and a boiler 132.

[0027] In the evaporator 131, the water contained in the caustic soda supplied from the cathode chamber 122 of the electrolytic cell 120 is evaporated by steam, and the caustic soda is concentrated to a concentration required for the product (for example, 48 weight percent (48 wt%)).

[0028] The boiler 132 generates high-temperature steam by heating water supplied from the outside, and supplies the high-temperature steam to the evaporator 131 .

[0029] The chlorine gas treatment unit 140 performs a pretreatment process (chlorine gas treatment process) for supplying the chlorine gas by-produced in the anode chamber 121 of the electrolytic cell 120 to a user. The chlorine gas treatment unit 140 includes a water washing tower 141 and a drying tower 142.

[0030] In the water washing tower 141, mist-like salt (sodium chloride) contained in the chlorine gas supplied from the electrolytic cell 120 is removed by countercurrent contact with water, and the relatively high-temperature chlorine gas is cooled. The chlorine gas that has passed through the water washing tower 141 is sent to the drying tower 142.

[0031] In the drying tower 142, for example, moisture contained in the chlorine gas is removed by countercurrent contact with sulfuric acid (H2SO4). As a result, chlorine gas (dry chlorine) with a relatively low moisture content can be provided to the user.

[0032] The hydrogen gas processing unit 150 performs a pretreatment process (hydrogen gas processing process) for supplying the hydrogen gas by-produced in the cathode chamber 122 of the electrolytic cell 120 to a user. The hydrogen gas processing unit 150 includes a water washing tower 151, a compressor 152, an adsorption tower 153, a deoxidation tower 154, and a dehumidification tower 155.

[0033] In the water washing tower 151, mist-like salt contained in the hydrogen gas supplied from the electrolytic cell 120 is removed by countercurrent contact with water, and the relatively high-temperature hydrogen gas is cooled.

[0034] A portion of the hydrogen gas that has passed through the water washing tower 151 (hereinafter, for convenience, referred to as “electrolytic hydrogen”) is sent to the fuel supply line FL1, and the remaining portion is sent to the compressor 152.

[0035] All of the electrolytic hydrogen may be sent to the fuel supply line FL1, in which case the compressor 152, the adsorption tower 153, the deoxidation tower 154, and the dehumidification tower 155 are omitted.

[0036] The compressor 152 compresses the hydrogen gas that has passed through the water washing tower 151. The hydrogen gas pressurized by the compressor 152 is sent to the adsorption tower 153.

[0037] In the adsorption tower 153, impurities contained in the pressurized hydrogen gas are adsorbed and removed by an adsorbent. The hydrogen gas that has passed through the adsorption tower 153 is sent to the deoxidation tower 154.

[0038] In the deoxidizing tower 154, oxygen contained in the hydrogen gas is removed by, for example, a predetermined catalyst. The hydrogen gas that has passed through the deoxidizing tower 154 is sent to the dehumidifying tower 155.

[0039] In the dehumidifying tower 155, moisture contained in the hydrogen gas is removed, for example, by an adsorbent. The hydrogen gas that has passed through the dehumidifying tower 155 is provided to users as purified hydrogen in which the content of impurities has been reduced to an acceptable range. For example, some or all of the purified hydrogen is sent to the fuel supply line FL1 (see the dashed arrow in FIG. 1).

[0040] The group of components included in the hydrogen gas processing unit 150 and the order of the group of processes performed by the group of components are not limited to this example. For example, some of the water washing tower 151, compressor 152, adsorption tower 153, deoxidation tower 154, and dehumidification tower 155 may be omitted, or other components for performing other processes may be added instead of or in addition to some of these components. Furthermore, for example, the water washing tower 151, compressor 152, adsorption tower 153, deoxidation tower 154, and dehumidification tower 155 may be replaced with other components capable of performing similar processes.

[0041] <Fuel cell system> As shown in FIG. 1, the fuel cell system 1 includes a fuel cell 10, a fuel supply path FL1, an air supply path AL1, an exhaust path 15, a refrigerant circuit RC2, a refrigerant supply unit 20, a water supply unit 30, and an exhaust heat recovery unit 40.

[0042] The fuel cell 10 generates electricity by chemically reacting hydrogen and oxygen, and includes a fuel cell stack 11, a heat exchanger 12, a pump 13, and a refrigerant circuit RC1.

[0043] The fuel cell stack 11 includes a plurality of unit cells (fuel cell units) each consisting of an air electrode, a fuel electrode, and an electrolyte, and the plurality of fuel cell units are connected in series inside the fuel cell stack 11. The fuel cell stack 11 generates electricity by causing a chemical reaction between hydrogen SH supplied to the fuel electrode and oxygen contained in air SA supplied to the air electrode.

[0044] The power generated by the fuel cell stack 11 is boosted by, for example, a booster device (not shown) and then output to the outside of the fuel cell system 1. The power output from the fuel cell system 1 is then supplied to the caustic soda production system 100. The power output from the fuel cell system 1 may also be supplied to a power company's system via grid interconnection. In this case, the power generated by the fuel cell stack 11 is converted from direct current to three-phase alternating current by, for example, a power conversion device (not shown), then output to the outside of the fuel cell system 1 and electrically connected to the power company's distribution system via a grid interconnection panel. The grid interconnection panel and a transformer rectifier may also be electrically connected, and the three-phase alternating current output to the outside of the fuel cell system 1 may be supplied to the transformer rectifier via the grid interconnection panel. The voltage converted from the three-phase alternating current to a direct current of a predetermined voltage by the transformer rectifier may then be applied between the anode 121T and the cathode 122T of the electrolytic cell 120. This allows the fuel cell system 1 to supply direct current to the electrolytic cell 120 via the grid interconnection panel and the transformer rectifier.

[0045] The fuel cell stack 11 is, for example, a polymer electrolyte fuel cell (PEFC), and has a stack structure in which a large number of unit cells (fuel cell cells) of the polymer electrolyte fuel cell are stacked.

[0046] In the fuel cell stack 11, which is a polymer electrolyte fuel cell, each fuel cell comprises a membrane electrode assembly (MEA) including a polymer electrolyte membrane and a pair of electrodes provided on both sides of the polymer electrolyte membrane. The polymer electrolyte membrane selectively transports hydrogen ions. Each of the pair of electrodes is formed from a porous material. Each of the pair of electrodes has a catalyst layer primarily composed of carbon powder that supports a platinum-based metal catalyst (electrode catalyst), for example, and a gas diffusion layer that is both breathable and electronically conductive. Furthermore, the fuel cell has a pair of separators that sandwich the membrane electrode assembly (MEA) from both sides.

[0047] The fuel cell stack 11 may be composed of unit cells of other types of fuel cells, such as phosphoric acid fuel cells (PAFCs), solid oxide fuel cells (SOFCs), and molten carbonate fuel cells (MCFCs).

[0048] The fuel cell stack 11 discharges exhaust EH, which contains hydrogen that did not undergo chemical reaction, from the fuel electrode of the fuel cell to exhaust path 15A. The fuel cell stack 11 also discharges exhaust EA, which is air SA from which oxygen has been consumed, from the air electrode of the fuel cell to exhaust path 15B.

[0049] The refrigerant circuit RC1 is provided so that a predetermined refrigerant (also referred to as "coolant") can circulate between the flow path inside the fuel cell stack 11 and the heat exchanger 12. The refrigerant is, for example, cooling water in which a main component such as ethylene glycol or propylene glycol is added to pure water.

[0050] The fuel cell stack 11 generates heat when generating electricity through a chemical reaction between hydrogen and oxygen. Therefore, the fuel cell stack 11 is cooled by heat exchange with the refrigerant flowing through the refrigerant circuit RC1, and the exhaust heat of the fuel cell stack 11 is absorbed by the refrigerant in the refrigerant circuit RC1.

[0051] The heat exchanger 12 exchanges heat between the refrigerant in the refrigerant circuit RC1 and the refrigerant in the refrigerant circuit RC2 outside the fuel cell stack 11. Specifically, the thermal energy of the refrigerant in the refrigerant circuit RC1, which has absorbed the waste heat from the fuel cell stack 11 and is at a relatively high temperature, is absorbed by the refrigerant in the refrigerant circuit RC2. As a result, the waste heat from the fuel cell stack 11 is absorbed by the refrigerant in the refrigerant circuit RC2 via the refrigerant circuit RC1.

[0052] The pump 13 circulates the refrigerant in the refrigerant circuit RC1. In this example, the pump 13 sends the refrigerant on the heat exchanger 12 side to the fuel cell stack 11 side.

[0053] The fuel cell stack 11 may be configured to be directly cooled by the refrigerant circuit RC2, in which case the refrigerant circuit RC1, the heat exchanger 12, and the pump 13 are omitted.

[0054] The fuel supply path FL1 supplies hydrogen SH to the anode of the fuel cell stack 11 (specifically, each fuel cell therein). In this example, as described above, electrolytic hydrogen is introduced into the fuel supply path FL1, and the fuel supply path FL1 can supply electrolytic hydrogen to the fuel cell stack 11 as hydrogen SH. This allows the fuel cell system 1 to prevent the fuel cells from drying out, thereby extending the life of the fuel cells. This is because the electrolytic hydrogen does not pass through the compressor 152 or the dehumidifying tower 155 and therefore contains more moisture than purified hydrogen. The fuel supply path FL1 may also mix the electrolytic hydrogen and purified hydrogen and supply the resulting mixture to the anode of the fuel cell stack 11. The fuel supply path FL1 may also be provided with a component (e.g., a switching valve) that can switch between a state in which only the electrolytic hydrogen out of the electrolytic hydrogen and purified hydrogen is supplied to the anode and a state in which only the purified hydrogen is supplied to the anode. Furthermore, hydrogen gas at any stage of the process group performed by the component elements of the hydrogen gas processing unit 150 may be supplied to the fuel supply path FL1. For example, instead of the purified hydrogen described above, hydrogen gas flowing out from either the adsorption tower 153 or the deoxidation tower 154 may be supplied to the fuel supply path FL1.

[0055] The air supply path AL1 supplies air to the air electrodes of the fuel cell stack 11 (specifically, each fuel cell therein).

[0056] The exhaust path 15 is a path for discharging exhaust gases EH and EA discharged from the fuel electrode and the air electrode of the fuel cell stack 11 (specifically, each fuel cell therein) to the outside. The exhaust path 15 is mainly configured as a pipe, for example. The exhaust path 15 includes exhaust paths 15A, 15B, 15D, 15E, and 15G and mixing sections 15C and 15F.

[0057] Exhaust EH flows into the exhaust path 15A from the fuel electrode of the fuel cell stack 11. Exhaust EA flows into the exhaust path 15B from the air electrode of the fuel cell stack 11.

[0058] The mixer 15C mixes the exhausts EH and EA from the exhaust paths 15A and 15B.

[0059] The exhaust path 15D connects the mixer 15C and the water supply unit 30, and sends the exhaust gas EX, which is the exhaust gases EH and EA mixed in the mixer 15C, to the water supply unit 30.

[0060] The exhaust path 15E connects the water supply unit 30 and the mixer 15F, and sends the exhaust gas EX (exhaust gas EXa) that has passed through the water supply unit 30 to the mixer 15F.

[0061] The mixer 15F mixes and dilutes the exhaust gas EXa with the air RA in the space in which the fuel cell 10 is installed. The air RA is, for example, air ventilated between the housing that houses the fuel cell 10 and the outside.

[0062] The exhaust gas EXa (exhaust gas EXb) diluted by the mixer 15F is discharged to the outside of the fuel cell system 1 through the exhaust path 15G.

[0063] The refrigerant circuit RC2 is provided so that a predetermined refrigerant (cooling liquid) can circulate between the heat exchanger 12 of the fuel cell 10 and the refrigerant supply unit 20.

[0064] The refrigerant supply unit 20 cools the refrigerant in the refrigerant circuit RC2 and sends it to the refrigerant circuit RC2, thereby supplying the refrigerant to the refrigerant circuit RC2 for cooling the fuel cell 10. The refrigerant supply unit 20 is, for example, a chiller (also referred to as a "coolant circulation device" or "coolant circulator") or a cooling tower. Hereinafter, in the refrigerant circuit RC2, the path along which the refrigerant flows from the refrigerant supply unit 20 to the heat source (heat exchanger 12 of the fuel cell 10) may be referred to as the "low-temperature side path," and the path along which the refrigerant flows from the heat source (heat exchanger 12 of the fuel cell 10) to the refrigerant supply unit 20 may be referred to as the "high-temperature side path," to distinguish them from each other.

[0065] In this example, the refrigerant in the refrigerant circuit RC2 is circulated by the refrigerant supply unit 20, but the refrigerant supply unit 20 only has the function of cooling the refrigerant, and a separate pump may be provided to circulate the refrigerant in the refrigerant circuit RC2.

[0066] The water supply unit 30 supplies water (produced water) produced by the fuel cell 10 to the caustic soda production process in the caustic soda production system 100. In this example, the water supply unit 30 cools the exhaust gas EX by heat exchange between the exhaust gas EX and the refrigerant in the low-temperature path of the refrigerant circuit RC1, thereby condensing the water vapor contained in the exhaust gas EX and producing condensed water CW. This reduces the water vapor contained in the exhaust gas from the fuel cell 10 and makes it possible to suppress the generation of white smoke that occurs when the exhaust gas EXb is cooled by outside air.

[0067] Since the condensed water CW is substantially pure water, the water supply unit 30 supplies the condensed water CW to the cathode chamber 122 of the electrolytic cell 120 in the caustic soda production system 100 through the water supply path WL1. This allows the caustic soda production system 100 to effectively utilize the condensed water CW, which is produced by the fuel cell 10, in the electrolytic cell 120. Therefore, the caustic soda production system 100 can reduce the cost of producing or procuring pure water. The condensed water CW may be supplied to the electrolytic cell 120 after carbon dioxide and other substances in the exhaust gas EA that may be dissolved in the condensed water CW have been removed. For example, the water supply path WL1 may be provided with a component that removes carbon dioxide and other substances. The caustic soda production system 100 may also be provided with a component that removes carbon dioxide and other substances from the condensed water CW. The condensed water CW may also be used as raw water for a pure water production system provided in the caustic soda production system 100.

[0068] The exhaust heat recovery unit 40 recovers exhaust heat from the fuel cell stack 11 from the refrigerant in the high-temperature path of the refrigerant circuit RC2. The exhaust heat recovery unit 40 is, for example, a water heater, a space heater, a boiler feedwater heater, an absorption chiller, or a binary power generation system. The exhaust heat recovered by the exhaust heat recovery unit 40 is the exhaust heat from the fuel cell stack 11 discharged into the refrigerant in the refrigerant circuit RC2 through the refrigerant circuit RC1 and the heat exchanger 12, and the exhaust heat from the fuel cell stack 11 discharged into the refrigerant in the refrigerant circuit RC2 through the water supply unit 30.

[0069] Furthermore, the exhaust heat recovery unit 40 recovers the exhaust heat from the fuel cell stack 11 and the heat of the exhaust gas from the fuel cell stack 11, and supplies the energy to the caustic soda production process in the caustic soda production system 100. In this example, the exhaust heat recovery unit 40 supplies the energy of the recovered exhaust heat as a heat source to the caustic soda concentration process. For example, as shown in FIG. 1 , the exhaust heat recovery unit 40 supplies the energy of the recovered exhaust heat as a heat source to the boiler 132. In this case, the exhaust heat recovery unit 40 is, for example, a heater that heats the feedwater of the boiler 132. Furthermore, the exhaust heat recovered by the exhaust heat recovery unit 40 may be supplied to a heat pump to generate high-temperature water or steam, and the high-temperature water or steam may be used as a heat source for the evaporator 131. For example, the exhaust heat recovered by the exhaust heat recovery unit 40 is absorbed by the refrigerant passing through the evaporator of the compression heat pump through heat exchange, and high-temperature water or steam is generated by heat exchange between the compressed high-temperature, high-pressure refrigerant passing through the condenser of the compression heat pump and water. As a result, the caustic soda production system 100 can effectively utilize the exhaust heat of the fuel cell stack 11 and the exhaust gas EX in the caustic soda concentration process. Therefore, the fuel cell system 1 can reduce the operating costs of the caustic soda concentration process. Furthermore, the exhaust heat obtained by the exhaust heat recovery unit 40 of the fuel cell system 1 may be used for heating or keeping the electrolytic cell 120 of the caustic soda production system 100 warm, heating pure water, etc.

[0070] As described above, in this example, the fuel cell system 1 can supply energy corresponding to the water produced and the exhaust heat of the fuel cell 10 to the caustic soda production process in the caustic soda production system 100. Furthermore, the fuel cell system 1 can operate the fuel cell 10 using electrolytic hydrogen, which is by-produced in the caustic soda production system 100, as fuel. Therefore, the fuel cell system 1 can improve the efficiency of the entire system including the caustic soda production system 100.

[0071] [Second example of a fuel cell system] A second example of the fuel cell system 1 according to this embodiment will be described with reference to FIG.

[0072] Hereinafter, in this example, the same symbols are used for configurations that are the same as or correspond to those in the first example (FIG. 1) described above, and the explanation will focus on the parts that are different from the first example described above, and explanations of the parts that are the same as or correspond to those in the first example described above may be omitted.

[0073] FIG. 2 is a diagram showing the configuration of a second example of the fuel cell system 1. As shown in FIG.

[0074] As shown in Figure 2, the fuel cell system 1 of this example differs from the first example described above in that condensed water CW is supplied to the concentration process of the caustic soda production process in the caustic soda production system 100 through a water supply path WL2, but may be the same as the first example described above in other respects.

[0075] The water supply unit 30 supplies the condensed water CW to the boiler 132 through the water supply path WL2. This allows the caustic soda production system 100 to effectively utilize the condensed water CW as water produced by the fuel cell 10 in the boiler 132. Therefore, the fuel cell system 1 can suppress the deposition of scale inside the evaporator 131, and as a result, can reduce the maintenance costs of the boiler 132 for suppressing the deposition of scale. Furthermore, as in the first example described above, the condensed water CW may be utilized in the caustic soda production system 100 after carbon dioxide and the like have been removed therefrom.

[0076] [Third example of fuel cell system] A third example of the fuel cell system 1 according to this embodiment will be described with reference to FIG.

[0077] Hereinafter, in this example, the same symbols are used for configurations that are the same as or correspond to those in the first example (FIG. 1) and second example (FIG. 2) described above, and the explanation will focus on parts that are different from the first and second examples described above, and explanations of parts that are the same as or correspond to those in the first and second examples described above may be omitted.

[0078] FIG. 3 is a diagram showing the configuration of a third example of the fuel cell system 1. In FIG.

[0079] As shown in FIG. 3, the fuel cell system 1 of this example differs from the first and second examples described above in that condensed water CW is supplied to the chlorine gas treatment process of the caustic soda production process in the caustic soda production system 100 through a water supply path WL3, but may be the same as the first and second examples described above in other respects.

[0080] The water supply unit 30 supplies the condensed water CW to the water wash tower 141 through the water supply path WL3. This allows the caustic soda production system 100 to effectively utilize the condensed water CW as water produced by the fuel cell 10 in the water wash tower 141. As in the first and second examples described above, the condensed water CW may be used in the caustic soda production system 100 after carbon dioxide and the like have been removed.

[0081] The water supply unit 30 may supply the condensed water CW to the water washing tower 151 instead of or in addition to the water washing tower 141. That is, the water supply unit 30 may supply the condensed water CW to at least one of the chlorine gas treatment step and the hydrogen gas treatment step.

[0082] [Fourth example of fuel cell system] A fourth example of the fuel cell system 1 according to this embodiment will be described with reference to FIG.

[0083] Hereinafter, in this example, the same symbols are used for the same or corresponding configurations as the first example (FIG. 1) to the third example (FIG. 3) described above, and the explanation will focus on the parts that are different from the first to third examples described above, and explanations of the parts that are the same or corresponding to the first to third examples described above may be omitted.

[0084] As shown in FIG. 4, the fuel cell system 1 according to this embodiment differs from the first to third embodiments in that it includes a pre-treatment unit 60, but may be the same as the first embodiment in other respects.

[0085] The pretreatment unit 60 is provided in the fuel supply path FL1 and removes impurities contained in the electrolytic hydrogen supplied through the water washing tower 151. The impurities are substances that may degrade the performance of the fuel cell 10 when supplied to the anode of the fuel cell stack 11. The impurities may also be impurities contained in the raw salt of the brine and consequently contaminate the hydrogen by-produced in the electrolysis process. The impurity may be, for example, ammonia. The raw salt (sodium chloride) used in the caustic soda production process may be derived from seawater. In this case, ammonia generated by the metabolism of marine organisms may be contained in the brine. The pretreatment unit 60 removes ammonia using, for example, an activated carbon filter or a chemical filter containing zeolite, ion exchange resin, or Prussian blue. The pretreatment unit 60 can further improve ammonia removal performance by using an acid-treated activated carbon filter. The pretreatment unit 60 may also include a water washing tower that removes impurity particles and water-soluble components contained in the electrolytic hydrogen by countercurrent contact with water.

[0086] This makes it possible for the fuel cell system 1 to prevent a situation in which the performance of the fuel cell 10 is reduced due to impurities contained in the electrolytic hydrogen.

[0087] [Fifth example of fuel cell system] A fifth example of the fuel cell system 1 according to this embodiment will be described with reference to FIG.

[0088] Hereinafter, in this example, the same symbols are used for configurations that are the same as or correspond to those in the first example (FIG. 1) to fourth example (FIG. 4) described above, and the explanation will focus on the parts that are different from the first to fourth examples described above, and explanations of the parts that are the same as or correspond to those in the first to fourth examples described above may be omitted.

[0089] FIG. 5 is a diagram showing the configuration of a fifth example of the fuel cell system 1. In FIG.

[0090] As shown in Figure 5, the fuel cell system 1 of this example differs from the first to fourth examples described above in that the exhaust heat recovery section 40 recovers the exhaust heat of the auxiliary section 70 through the refrigerant circuit RC2, but may be the same as the first example described above in other respects.

[0091] The fuel cell system 1 includes an auxiliary unit 70.

[0092] The auxiliary section 70 includes an auxiliary 71 for operating the fuel cell 10, a refrigerant circuit RC3, and a heat exchanger 72.

[0093] The auxiliary device 71 is, for example, a compressor provided in the air supply path AL1, a control device (controller) that controls the fuel cell 10, and the like.

[0094] The refrigerant circuit RC3 is provided so that a predetermined refrigerant can circulate between the auxiliary device 71 and the heat exchanger 72.

[0095] The auxiliary device 71 generates heat during its operation. Therefore, the auxiliary device 71 is cooled by heat exchange with the refrigerant flowing through the refrigerant circuit RC3, and the exhaust heat of the auxiliary device 71 is absorbed by the refrigerant in the refrigerant circuit RC3.

[0096] The heat exchanger 72 exchanges heat between the refrigerant in the refrigerant circuit RC3 and the refrigerant in the refrigerant circuit RC2 outside the fuel cell stack 11. Specifically, the thermal energy of the refrigerant in the refrigerant circuit RC1, which absorbs the waste heat from the auxiliary equipment 71 and has a relatively high temperature, is absorbed by the refrigerant in the low-temperature path in the refrigerant circuit RC2. As a result, the waste heat from the auxiliary equipment 71 is absorbed by the refrigerant in the refrigerant circuit RC2 via the refrigerant circuit RC3. Therefore, the waste heat recovery unit 40 can recover the waste heat from the auxiliary equipment 71 in addition to the waste heat from the fuel cell 10 and the heat of the exhaust gas from the fuel cell 10.

[0097] The refrigerant circuit RC3 may be provided with a pump for circulating the refrigerant, similar to the refrigerant circuit RC1. The auxiliary equipment 71 may be directly cooled by the refrigerant circuit RC2. In this case, the refrigerant circuit RC3 and the heat exchanger 72 are omitted.

[0098] As described above, in this example, the fuel cell system 1 can recover not only the exhaust heat of the fuel cell 10 and the heat of the exhaust gas from the fuel cell 10, but also the exhaust heat of the auxiliary equipment 71. Therefore, the caustic soda production system 100 can effectively utilize energy corresponding to the exhaust heat of the auxiliary equipment 71 in the caustic soda production process. Therefore, the fuel cell system 1 can further improve the efficiency of the entire system including the caustic soda production system 100.

[0099] [Fuel cell system example 6] A sixth example of the fuel cell system 1 according to this embodiment will be described with reference to FIG.

[0100] Hereinafter, in this example, the same symbols are used for the same or corresponding configurations as the first example (FIG. 1) to the fifth example (FIG. 5) described above, and the explanation will focus on the differences from the first to fifth examples described above, and explanations of the same or corresponding parts as the first to fifth examples described above may be omitted.

[0101] FIG. 6 is a diagram showing the configuration of a sixth example of the fuel cell system 1. In FIG.

[0102] As shown in FIG. 6, the fuel cell system 1 of this example differs from the fifth example described above in that the configurations of the refrigerant circuit RC2 and the exhaust heat recovery section 40 are different, but in other respects it may be the same as the fifth example described above.

[0103] Unlike the first to fifth examples described above, the refrigerant circuit RC2 is provided so as to be able to circulate refrigerant in parallel with the heat exchanger 12, the water supply unit 30, and the heat exchanger 72, with the refrigerant supply unit 20 as the reference. Specifically, the refrigerant circuit RC2 includes a refrigerant circuit RC21, a refrigerant circuit RC22, and a refrigerant circuit RC23 that allow refrigerant to circulate between the refrigerant supply unit 20 and the heat exchanger 12, the water supply unit 30, and the heat exchanger 72, respectively.

[0104] The exhaust heat recovery unit 40 is provided so as to be able to recover heat from the refrigerant in the high-temperature side path of each of the refrigerant circuits RC21 to RC23, thereby enabling the exhaust heat recovery unit 40 to more efficiently recover the exhaust heat from the fuel cell 10, the heat of the exhaust gas from the fuel cell 10, and the exhaust heat from the auxiliary equipment 71.

[0105] [Another example of a fuel cell system] Another example of the fuel cell system according to this embodiment will be described.

[0106] Appropriate modifications and changes may be made to the first example (FIG. 1) to the sixth example (FIG. 6) of the fuel cell system 1. Hereinafter, examples in which modifications and changes are made to the above-described embodiments will be referred to as "modified examples" for convenience.

[0107] For example, in the fourth to sixth examples of the fuel cell system 1 described above, the condensed water CW may be supplied to the boiler 132 instead of the electrolytic cell 120, as in the second example of the fuel cell system 1 described above, or may be supplied to at least one of the water washing tower 141 and the water washing tower 151, as in the third example of the fuel cell system 1 described above.

[0108] Furthermore, in the first to fifth examples of the fuel cell system described above, the refrigerant circuit RC2 exchanges heat in series between the heat exchanger 12 and the water supply unit 30, but the refrigerant may be configured to exchange heat in parallel between the heat exchanger 12 and the water supply unit 30. For example, the refrigerant circuit RC2 is configured by the refrigerant circuits RC21 and RC22 in the sixth example of the fuel cell system 1 described above. In this case, for example, the exhaust heat recovery unit 40 is configured to recover heat from the high-temperature side paths of the refrigerant circuits RC21 and RC22.

[0109] Furthermore, in the second, third, fifth and sixth examples of the fuel cell system 1 described above and their modifications, the pre-treatment unit 60 of the fourth example of the fuel cell system 1 described above may be employed.

[0110] In the first to sixth examples and their modifications of the fuel cell system 1 described above, the condensed water CW may be supplied to two or more supply destinations. For example, the condensed water CW may be supplied to at least two of the cathode chamber 122 of the electrolytic cell 120, the boiler 132, the water washing tower 141, and the water washing tower 151.

[0111] In the first to sixth examples of the fuel cell system 1 and their modified examples, the heat recovered from the refrigerant in the refrigerant circuit RC2 by the exhaust heat recovery unit 40 may be supplied as another form of energy to the caustic soda production system 100. For example, the exhaust heat recovery unit 40 may recover heat from the refrigerant on the high-temperature side in the refrigerant circuit RC2 as electric energy, and supply the electric energy to the caustic soda production system 100 as a power source.

[0112] Furthermore, in the first to fourth examples of the fuel cell system 1 described above and their modified examples, the refrigerant circuit RC2 may be replaced by two separate refrigerant circuits corresponding to the heat exchanger 12 of the fuel cell 10 and the water supply unit 30, respectively. In this case, the exhaust heat recovery unit 40 may be replaced by two exhaust heat recovery units corresponding to the two refrigerant circuits, respectively.

[0113] Furthermore, in the fifth and sixth examples of the fuel cell system 1 and their modifications, the refrigerant circuit RC2 may be replaced by three separate refrigerant circuits corresponding to the heat exchanger 12 of the fuel cell 10, the water supply unit 30, and the heat exchanger 72 of the auxiliary equipment 71, respectively. In this case, the exhaust heat recovery unit 40 may be replaced by three separate exhaust heat recovery units corresponding to the three refrigerant circuits, respectively. Furthermore, the exhaust heat recovery unit 40 may be replaced by an exhaust heat recovery unit corresponding to any two of the three refrigerant circuits and an exhaust heat recovery unit corresponding to the remaining one. Furthermore, the refrigerant circuit RC2 may be replaced by a refrigerant circuit corresponding to any two of the heat exchanger 12 of the fuel cell 10, the water supply unit 30, and the heat exchanger 72 of the auxiliary equipment 70, and a refrigerant circuit corresponding to the remaining one. In this case, the exhaust heat recovery unit 40 may be replaced by two separate exhaust heat recovery units corresponding to the two refrigerant circuits, respectively.

[0114] Furthermore, in the first to sixth examples of the fuel cell system 1 described above and their modified examples, the fuel cell system 1 may supply the water produced by the fuel cell 10 or the energy recovered by the exhaust heat recovery unit 40 to another plant system instead of the caustic soda production system 100. In this case, the other plant system may or may not use the fuel cell system 1 as a power source.

[0115] [Effect] Next, the operation of the fuel cell system according to this embodiment will be described.

[0116] In a first aspect of this embodiment, a fuel cell system includes a fuel cell and a water supply unit. The fuel cell system is, for example, the fuel cell system 1 described above. The fuel cell is, for example, the fuel cell 10 described above. The water supply unit is, for example, the water supply unit 30 described above. Specifically, the fuel cell generates electricity by chemically reacting hydrogen and oxygen. The water supply unit supplies water produced by the fuel cell to a caustic soda manufacturing process.

[0117] This allows the water produced by the fuel cell to be effectively used in the caustic soda production process, thereby improving the efficiency of the entire fuel cell system, including the caustic soda production system.

[0118] In a second aspect of this embodiment, based on the first aspect described above, the fuel cell system may include an exhaust path. The exhaust path is, for example, the exhaust path 15 described above. Specifically, the exhaust path is provided to discharge exhaust from the fuel cell to the outside. The water supply unit may supply condensed water obtained by cooling the exhaust gas passing through the exhaust path and condensing water vapor contained in the exhaust gas to the manufacturing process. The condensed water is, for example, the condensed water CW described above.

[0119] This allows the fuel cell system to supply condensed water, which is obtained by condensing water vapor contained in the exhaust gas from the fuel cell, as nearly pure water to the caustic soda manufacturing process.

[0120] In a third aspect of this embodiment, based on the second aspect described above, the fuel cell system may include a refrigerant circuit, a refrigerant supply unit, and a first heat exchange unit. The refrigerant circuit may be, for example, the refrigerant circuit RC2 described above. The refrigerant supply unit may be, for example, the refrigerant supply unit 20 described above. The first heat exchange unit may be, for example, the heat exchanger 12 described above. Specifically, a refrigerant may flow through the refrigerant circuit. The refrigerant supply unit may supply a refrigerant to the refrigerant circuit. The first heat exchange unit may absorb exhaust heat from the fuel cell into the refrigerant of the refrigerant circuit. The water supply unit may condense water vapor contained in the exhaust gas through heat exchange between the refrigerant of a low-temperature path of the refrigerant circuit that runs from the refrigerant supply unit to the first heat exchange unit and the exhaust gas of the exhaust path.

[0121] This allows the fuel cell system to condense water vapor in the exhaust gas from the fuel cell using the refrigerant at a relatively low temperature before heat is absorbed by the first heat exchanger, thereby enabling the fuel cell system to obtain more condensed water and, as a result, supply more water to the caustic soda production process.

[0122] In a fourth aspect of this embodiment, based on the first to third aspects described above, the manufacturing process may include an electrolysis step of producing caustic soda by electrolyzing brine supplied to an electrolytic cell. The electrolytic cell may be, for example, the electrolytic cell 120 described above. The water supply unit may supply water produced by the fuel cell to a cathode chamber of the electrolytic cell. The cathode chamber of the electrolytic cell may be, for example, the cathode chamber 122 described above.

[0123] This allows the water produced by the fuel cell to be effectively utilized in the electrolysis step of the caustic soda manufacturing process.

[0124] In a fifth aspect of the present embodiment, based on any one of the first to fourth aspects described above, the manufacturing process may include an electrolysis process for producing caustic soda by electrolyzing brine supplied to an electrolytic cell, and a concentration process for concentrating the caustic soda by evaporating water from the caustic soda produced in the electrolysis process using steam supplied from a boiler. The boiler may be, for example, the boiler 132 described above. The water supply unit may supply water produced by the fuel cell to the boiler.

[0125] This allows the water produced by the fuel cell to be effectively used as a water supply source for the boiler in the concentration step of the caustic soda manufacturing process.

[0126] Furthermore, in a sixth aspect of this embodiment, based on any one of the first to fifth aspects described above, the production process may include an electrolysis process for producing caustic soda by electrolyzing brine supplied to an electrolytic cell, and a chlorine gas treatment process for treating chlorine gas by-produced in the electrolysis process. The chlorine gas treatment process may include a process for removing sodium chloride contained in chlorine gas by-produced in the electrolysis process using a first water wash tower. The first water wash tower is, for example, the above-described water wash tower 141. The hydrogen gas treatment process may include a process for removing sodium chloride contained in hydrogen gas by-produced in the electrolysis process using a second water wash tower. The second water wash tower is, for example, the above-described water wash tower 151. The water supply unit may supply water produced by the fuel cell to at least one of the first water wash tower and the second water wash tower.

[0127] This allows the water produced by the fuel cell to be effectively utilized in the chlorine gas treatment process and the hydrogen gas treatment process in the caustic soda manufacturing process.

[0128] In addition, in a seventh aspect of the present embodiment, based on any one of the first to sixth aspects described above, the fuel cell system may include a fuel supply path that supplies hydrogen to the fuel cell. The fuel supply path is, for example, the fuel supply path FL1 described above. The manufacturing process may include an electrolysis process that produces caustic soda by electrolyzing brine supplied to an electrolytic cell. The fuel supply path may supply hydrogen by-produced in the electrolysis process to the fuel cell.

[0129] This allows the fuel cell system to effectively utilize hydrogen (by-product hydrogen) produced as a by-product in the caustic soda production process as fuel for the fuel cell, thereby improving the efficiency of the entire system, including the caustic soda production system.

[0130] In addition, in an eighth aspect of this embodiment, based on the seventh aspect described above, the fuel supply path may supply hydrogen, which is a by-product of the electrolysis step, to the fuel cell without pre-treatment primarily aimed at reducing the water vapor contained therein.

[0131] This allows the fuel cell system to use hydrogen, which has a relatively high water vapor content, as fuel for the fuel cell, which prevents the fuel cell cells that make up the fuel cell from drying out, thereby extending the life of the fuel cell cells.

[0132] In addition, in a ninth aspect of this embodiment, based on the seventh or eighth aspect described above, the fuel supply path may be provided with a pre-treatment unit for reducing impurities contained in hydrogen by-produced in the electrolysis step. The impurities may be, for example, the ammonia described above. The pre-treatment unit may be, for example, the pre-treatment unit 60 described above.

[0133] This allows the fuel cell system to suppress performance degradation of the fuel cell units that make up the fuel cell due to impurities such as ammonia, for example.

[0134] In a tenth aspect of the present embodiment, based on any one of the first to ninth aspects, the fuel cell system may further include a first exhaust heat recovery unit that recovers exhaust heat from the fuel cell and supplies the energy to the manufacturing process. The first exhaust heat recovery unit is, for example, the exhaust heat recovery unit 40 described above.

[0135] This allows the energy recovered from the exhaust heat of the fuel cell to be effectively utilized in the caustic soda production process, thereby improving the efficiency of the entire fuel cell system, including the caustic soda production system.

[0136] In an eleventh aspect of the present embodiment, based on any one of the first to tenth aspects described above, the manufacturing process may include an electrolysis process for producing caustic soda by electrolyzing brine supplied to an electrolytic cell, and a concentration process for concentrating the caustic soda by evaporating water from the caustic soda produced in the electrolysis process. The first exhaust heat recovery unit may recover exhaust heat from the fuel cell and supply the energy to the concentration process as a heat source.

[0137] This makes it possible to effectively utilize the energy recovered from the exhaust heat of the fuel cell in the concentration step of the caustic soda manufacturing process.

[0138] In a twelfth aspect of the present embodiment, based on the eleventh aspect described above, the concentrating step may concentrate the caustic soda by evaporating water from the caustic soda produced in the electrolysis step using steam supplied from a boiler. The first exhaust heat recovery unit may recover exhaust heat from the fuel cell and supply the recovered energy to the boiler as a heat source for heating feedwater.

[0139] As a result, in the concentration step of the caustic soda manufacturing process, the energy recovered from the exhaust heat of the fuel cell can be effectively used as a heat source for heating the boiler feedwater.

[0140] In a thirteenth aspect of this embodiment, based on the eleventh aspect described above, in the concentration step, water may be evaporated from the caustic soda produced in the electrolysis step by using, as a heat source, high-temperature water or steam produced by heating water through heat exchange with a refrigerant passing through a condenser of a heat pump. The first exhaust heat recovery unit may supply the recovered exhaust heat to the heat pump, and cause the refrigerant passing through an evaporator to absorb the heat.

[0141] As a result, in the concentration step of the caustic soda production process, the energy recovered from the exhaust heat of the fuel cell can be effectively used as a heat source for evaporating the water content of the caustic soda via a heat pump.

[0142] In addition, in a fourteenth aspect of the present embodiment, on the premise of any one of the tenth to thirteenth aspects described above, the fuel cell system may include an exhaust path, a refrigerant circuit, a refrigerant supply unit, a first heat exchange unit, and a second heat exchange unit. The exhaust path is, for example, the exhaust path 15 described above. The refrigerant circuit is, for example, the refrigerant circuit RC2 described above. The refrigerant supply unit is, for example, the refrigerant supply unit 20 described above. The first heat exchange unit is, for example, the heat exchanger 12 described above. The second heat exchange unit is, for example, the water supply unit 30 described above. Specifically, the exhaust path may exhaust exhaust from the fuel cell to the outside. A refrigerant may flow through the refrigerant circuit. The refrigerant supply unit may supply the refrigerant to the refrigerant circuit. The first heat exchange unit may absorb exhaust heat from the fuel cell into the refrigerant of the refrigerant circuit. The second heat exchange unit may exchange heat between the refrigerant in a low-temperature path of the refrigerant circuit that runs from the refrigerant supply unit to the fuel cell and the exhaust gas in the exhaust path, and the first exhaust heat recovery unit may recover heat from the refrigerant in a high-temperature path of the refrigerant circuit through which the refrigerant flowing out of the first heat exchange unit flows.

[0143] This allows the fuel cell system to recover the exhaust heat of the fuel cell from the heated refrigerant through both the first heat exchange unit and the second heat exchange unit, thereby enabling the fuel cell system to recover more energy and, as a result, improving the efficiency of the entire system, including the caustic soda manufacturing system.

[0144] In addition, in a fifteenth aspect of this embodiment, based on any one of the first to fourteenth aspects described above, the fuel cell system may include a second exhaust heat recovery unit that recovers exhaust heat from an auxiliary device for operating the fuel cell and supplies the heat to the manufacturing process. The auxiliary device is, for example, the above-mentioned auxiliary device 71. The second exhaust heat recovery unit is, for example, the above-mentioned exhaust heat recovery unit 40.

[0145] This allows the efficient use of energy recovered from the exhaust heat of the auxiliary equipment used to operate the fuel cell in the caustic soda production process, thereby improving the efficiency of the entire fuel cell system, including the caustic soda production system.

[0146] Although the embodiments have been described in detail above, the present disclosure is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist described in the claims. [Explanation of symbols]

[0147] 1. Fuel cell system 10 fuel cell 11 Fuel Cell Stack 12 Heat exchanger 13 Pump 15 Exhaust route 15A Exhaust route 15B Exhaust route 15C Mixing section 15D Exhaust route 15E Exhaust route 15F Mixing section 15G exhaust route 20 Refrigerant supply section 30 Water supply section 40 Exhaust heat recovery section 60 Pretreatment section 70 Auxiliary Machinery 71 Auxiliary Machine 72 Heat exchanger 100 Caustic soda production system 110 Brine purification processing section 111 Dissolution tank 112 Impurity removal section 120 Electrolytic cell 121 Anode chamber 121T anode 122 Cathode Chamber 122T cathode 123 Ion exchange membrane 130 Concentration processing section 131 Evaporator 132 Boiler 140 Chlorine gas treatment unit 141 Water washing tower 142 Drying tower 150 Hydrogen gas processing unit 151 Water washing tower 152 Compressor 153 Adsorption tower 154 Deoxygenation Tower 155 Dehumidifying tower AL1 Air supply path CW Condensed water EA Exhaust EH exhaust EX exhaust EXa exhaust EXb Exhaust FL1 fuel supply line RA Air RC1 refrigerant circuit RC2 refrigerant circuit RC3 refrigerant circuit RC21 refrigerant circuit RC22 refrigerant circuit RC23 refrigerant circuit SA Air SH Hydrogen WL1 Water supply route WL2 Water supply route WL3 Water supply route

Claims

1. A fuel cell that generates electricity through a chemical reaction between hydrogen and oxygen; a water supply unit that supplies water produced by the fuel cell to a caustic soda production process; Fuel cell system.

2. an exhaust path for discharging exhaust gas from the fuel cell to the outside; the water supply unit cools the exhaust gas passing through the exhaust path and condenses water vapor contained in the exhaust gas to obtain condensed water, and supplies the condensed water to the manufacturing process. The fuel cell system according to claim 1 .

3. a refrigerant circuit through which a refrigerant flows; a refrigerant supply unit that supplies a refrigerant to the refrigerant circuit; a first heat exchange unit that absorbs exhaust heat from the fuel cell into a refrigerant in the refrigerant circuit; the water supply unit condenses water vapor contained in the exhaust gas through heat exchange between the refrigerant in a low-temperature path of the refrigerant circuit that runs from the refrigerant supply unit to the first heat exchange unit and the exhaust gas in the exhaust path. The fuel cell system according to claim 2 .

4. The manufacturing process includes an electrolysis step of producing caustic soda by electrolysis of brine supplied to an electrolytic cell; the water supply unit supplies water produced by the fuel cell to the electrolytic cell; 4. The fuel cell system according to claim 1.

5. The manufacturing process includes an electrolysis process of producing caustic soda by electrolyzing brine supplied to an electrolytic cell, and a concentration process of concentrating the caustic soda by evaporating water from the caustic soda produced in the electrolysis process using steam supplied from a boiler, the water supply unit supplies water generated by the fuel cell to the boiler; 4. The fuel cell system according to claim 1.

6. the production process includes an electrolysis step of producing caustic soda by electrolyzing brine supplied to an electrolytic cell, a chlorine gas treatment step of treating chlorine gas by-produced in the electrolysis step, and a hydrogen gas treatment step of treating hydrogen gas by-produced in the electrolysis step; the chlorine gas treatment step includes a step of removing sodium chloride contained in the chlorine gas by-produced in the electrolysis step by a first water washing tower, the hydrogen gas treatment step includes a step of removing sodium chloride contained in the hydrogen gas by-produced in the electrolysis step by a second water washing tower; the water supply unit supplies water produced by the fuel cell to at least one of the first water wash tower and the second water wash tower; 4. The fuel cell system according to claim 1.

7. a fuel supply path for supplying hydrogen to the fuel cell; The manufacturing process includes an electrolysis step of producing caustic soda by electrolysis of brine supplied to an electrolytic cell; the fuel supply path supplies hydrogen, which is a by-product of the electrolysis process, to the fuel cell; 4. The fuel cell system according to claim 1.

8. the fuel supply path supplies hydrogen, which is a by-product of the electrolysis process, to the fuel cell without pre-treatment, the main purpose of which is to reduce water vapor contained therein; The fuel cell system according to claim 7 .

9. a pre-treatment unit for reducing impurities contained in hydrogen produced as a by-product in the electrolysis step is provided in the fuel supply path; The fuel cell system according to claim 7 .

10. a first exhaust heat recovery unit that recovers exhaust heat from the fuel cell and supplies the energy to the manufacturing process; 4. The fuel cell system according to claim 1.

11. The manufacturing process includes an electrolysis process of producing caustic soda by electrolyzing brine supplied to an electrolytic cell, and a concentration process of concentrating the caustic soda by evaporating water from the caustic soda produced in the electrolysis process, the first exhaust heat recovery unit recovers exhaust heat from the fuel cell and supplies the energy to the concentration step as a heat source; The fuel cell system according to claim 10.

12. In the concentrating step, water is evaporated from the caustic soda produced in the electrolysis step by steam supplied from a boiler, thereby concentrating the caustic soda; the first exhaust heat recovery unit recovers exhaust heat from the fuel cell and supplies the recovered energy to the boiler as a heat source for heating feedwater; The fuel cell system of claim 11.

13. In the concentration step, water is evaporated from the caustic soda produced in the electrolysis step by utilizing, as a heat source, high-temperature water or steam produced by heating water through heat exchange with a refrigerant passing through a condenser of a heat pump; The first exhaust heat recovery unit supplies the recovered exhaust heat to the heat pump, and causes the refrigerant passing through an evaporator to absorb the heat. The fuel cell system of claim 11.

14. an exhaust path for discharging exhaust gas from the fuel cell to the outside; a refrigerant circuit through which a refrigerant flows; a refrigerant supply unit that supplies a refrigerant to the refrigerant circuit; a first heat exchange unit that absorbs exhaust heat from the fuel cell into a refrigerant in the refrigerant circuit; a second heat exchange unit that exchanges heat between a refrigerant in a low-temperature side path of the refrigerant circuit that runs from the refrigerant supply unit to the fuel cell and exhaust gas in the exhaust path, the first exhaust heat recovery unit recovers heat from a refrigerant in a high-temperature path of the refrigerant circuit through which the refrigerant flowing out of the first heat exchange unit flows; The fuel cell system according to claim 10.

15. a second exhaust heat recovery unit that recovers exhaust heat from an auxiliary device for operating the fuel cell and supplies the exhaust heat to the manufacturing process; 4. The fuel cell system according to claim 1.

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