Fuel cell system

Abstract

To improve operation efficiency.SOLUTION: A fuel cell system 100 comprises: a fuel cell body 120, provided inside a closed container 110, which has a fuel electrode 122, an air electrode 126, a fuel gas supply port 124a, and an anode off-gas exhaust port 124b facing an inner space of the closed container; an ammonia decomposer 150 provided inside the closed container; a fuel pipe 152, provided inside the closed container, which brings the fuel gas supply port into communication with the ammonia decomposer; a fuel supply part 130 which supplies the ammonia decomposer with material gas containing ammonia; a heat exchanger 180, provided inside the closed container, which exchanges heat between gas after the reaction and the oxygen-containing gas; an oxygen-containing gas supply pipe 190, provided inside the closed container, which is connected to an outlet of the oxygen-containing gas on the heat exchanger, and which has an opening facing the air electrode; an oxygen-containing gas supply part 160 which supplies the oxygen-containing gas to the heat exchanger; and a water supply part 204 which supplies water to the oxygen-containing gas passing through the heat exchanger.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a fuel cell system.

Background Art

[0002] Fuel cell systems that use hydrocarbons such as natural gas, city gas, and LP gas as fuel are becoming widespread. As such a fuel cell system, an open-type fuel cell system has been developed in which anode off-gas and cathode off-gas exhausted from a fuel cell are burned in a storage container.

[0003] As an open-type fuel cell system, for example, Patent Document 1 proposes a configuration in which a fuel cell, a vaporization unit for vaporizing water, and a reformer for steam reforming fuel are provided in a storage container. In the technology of Patent Document 1, the vaporization unit and the reformer are provided above the fuel cell, and the vaporization unit and the reformer are heated by the combustion heat of the anode off-gas and the cathode off-gas exhausted from the upper end of the fuel cell.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in recent years, ammonia has attracted attention as a fuel that does not emit CO2. For this reason, using ammonia instead of hydrocarbons as the fuel of the above open-type fuel cell system has been studied. When ammonia is used as fuel, a reformer is unnecessary in the fuel cell system. In addition, ammonia has a smaller heat absorption amount per unit hydrogen generation amount than hydrocarbons. For this reason, there is a problem that heat surplus occurs in the storage container and the operating efficiency of the fuel cell system decreases.

[0006] In view of these challenges, this disclosure aims to provide a fuel cell system capable of improving operating efficiency. [Means for solving the problem]

[0007] To solve the above problems, a fuel cell system according to one aspect of the present disclosure comprises a sealed container, a fuel cell body provided inside the sealed container having at least a fuel electrode, an air electrode, a fuel gas supply port, and an anode off gas exhaust port facing the internal space of the sealed container, an ammonia decomposer provided inside the sealed container and equipped with a catalyst that promotes the decomposition of ammonia, a fuel pipe provided inside the sealed container and connecting the fuel gas supply port and the ammonia decomposer, a fuel supply unit that supplies a raw material gas containing at least ammonia to the ammonia decomposer, a heat exchanger provided inside the sealed container and heat-exchanges a post-reaction gas produced by the reaction of an oxygen-containing gas containing at least oxygen and a cathode off gas, as well as an anode off gas, with an oxygen-containing gas, an oxygen-containing gas supply pipe provided inside the sealed container and connected to the outlet of the oxygen-containing gas in the heat exchanger, with its opening facing the air electrode, an oxygen-containing gas supply unit that supplies oxygen-containing gas to the heat exchanger, and a water supply unit that supplies water to the oxygen-containing gas passing through the heat exchanger.

[0008] Furthermore, the fuel cell system may include a condenser that cools the post-reaction gas exhausted from the heat exchanger to produce water, and the water supply unit may supply the water produced in the condenser.

[0009] Furthermore, the fuel cell system may include a steam generation unit that converts water into steam, and the water supply unit may supply the steam generated by the steam generation unit.

[0010] Furthermore, the ammonia decomposer may face the anode off-gas exhaust port.

[0011] Furthermore, the ammonia decomposer may recover the heat contained in the gas after the reaction. [Effects of the Invention]

[0012] According to this disclosure, it will be possible to improve driving efficiency. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a diagram illustrating the fuel cell system of this embodiment. [Figure 2] Figure 2 illustrates the sensors provided in the fuel cell system according to this embodiment. [Figure 3] Figure 3 is a flowchart showing the processing flow of the fuel cell system startup method according to this embodiment. [Figure 4] Figure 4 is a flowchart showing the processing flow of the normal operation method of the fuel cell system according to this embodiment. [Figure 5] Figure 5 is a flowchart showing the processing flow of the method for stopping the fuel cell system according to this embodiment. [Modes for carrying out the invention]

[0014] Embodiments of this disclosure will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples for the purpose of facilitating understanding and do not limit this disclosure unless otherwise specified. In this specification and in the drawings, elements having substantially the same function or configuration are denoted by the same reference numerals to avoid redundant explanations. Elements not directly related to this disclosure are omitted from the illustrations.

[0015] Figure 1 is a diagram illustrating the fuel cell system 100 according to this embodiment. Figure 2 is a diagram illustrating the sensors provided in the fuel cell system 100 according to this embodiment.

[0016] As shown in FIGS. 1 and 2, the fuel cell system 100 includes a sealed container 110, one or more fuel cell bodies 120, a fuel supply unit 130, an ammonia decomposer 150, a fuel pipe 152, an oxygen-containing gas supply unit 160, a heat exchanger 180, an oxygen-containing gas supply pipe 190, an exhaust pipe 192, a condenser 200, a drain tank 202, a water supply unit 204, a water supply pipe 206, a water vapor generator 208, a nitrogen supply unit 210, an inverter 220, an operation unit 230, a central control unit 240, a housing 250, a ventilation unit 260, a battery temperature sensor 270, a decomposer temperature sensor 272, a water level sensor 274, and an exhaust gas sensor 276.

[0017] In FIG. 1, the dashed arrows indicate the flow of water. Also, in FIG. 1, the solid arrows indicate the flow of fluids other than water. In FIG. 2, the solid arrows indicate the flow of signals.

[0018] The fuel cell system 100 according to the present embodiment is an open-type fuel cell system 100 in which anode off-gas and cathode off-gas react inside the sealed container 110.

[0019] The sealed container 110 houses at least the fuel cell body 120, ammonia decomposer 150, fuel pipe 152, heat exchanger 180, oxygen-containing gas supply pipe 190, and water vapor generator 208, which will be described later. The sealed container 110 suppresses heat transfer from the fuel cell body 120 to the outside. The sealed container 110 is a container made of a heat insulating material or a vacuum container.

[0020] The fuel cell body 120 is composed of a cell stack. The fuel cell body 120 includes a fuel electrode 122, a manifold 124, an air electrode 126, and an electrolyte 128.

[0021] The fuel electrode 122, that is, the anode, contains either or both of nickel (Ni) and nickel compounds (for example, nickel oxide (NiO)). The manifold 124 is connected to the fuel electrode 122.

[0022] The manifold 124 is provided with a fuel gas supply port 124a and an anode off-gas exhaust port 124b. A fuel pipe 152 is connected to the fuel gas supply port 124a. The anode off-gas exhaust port 124b faces the internal space of the sealed container 110. In other words, the anode off-gas exhaust port 124b is an opening facing into the sealed container 110. The fuel electrode 122 is exposed to the internal space of the manifold 124. The manifold 124 is heated by the heat generated by the fuel cell body 120.

[0023] The air electrode 126, or cathode, contains an oxide that exhibits electron conductivity. Examples of electron-conductive oxides include LSM ((La,Sr)MnO3), LSC ((La,Sr)CoO3), or LSCF ((La,Sr)(Co,Fe)O3). The air electrode 126 is exposed to the internal space of the sealed container 110.

[0024] The electrolyte 128 is provided between the fuel electrode 122 and the air electrode 126. The electrolyte 128 contains a solid oxide having oxide ion conductivity. An example of a solid oxide having oxide ion conductivity is YSZ (yttria-stabilized zirconia).

[0025] The fuel supply unit 130 supplies a raw material gas containing at least ammonia to the ammonia decomposer 150. In this embodiment, the fuel supply unit 130 includes a raw material supply pipe 132, a pressure reducing valve 134, a shut-off valve 136, a flow rate adjustment mechanism 138, and a hydrogen generator 140.

[0026] The raw material supply pipe 132 connects the ammonia supply source 102 to the ammonia decomposer 150. The ammonia supply source 102 is, for example, a high-pressure container (cylinder) for storing ammonia. The pressure reducing valve 134 is located downstream of the ammonia supply source 102 in the raw material supply pipe 132. The pressure reducing valve 134 reduces the pressure of the ammonia supplied from the ammonia supply source 102. The shut-off valve 136 is located downstream of the pressure reducing valve 134 in the raw material supply pipe 132. The shut-off valve 136 opens and closes the flow path formed in the raw material supply pipe 132. The flow rate adjustment mechanism 138 is located downstream of the shut-off valve 136 in the raw material supply pipe 132. The flow rate adjustment mechanism 138 is, for example, a mass flow controller or a pump (for example, a diaphragm pump or a rotary impeller pump). The flow rate adjustment mechanism 138 adjusts the flow rate of ammonia flowing through the raw material supply pipe 132.

[0027] The hydrogen generator 140 is located downstream of the flow rate adjustment mechanism 138 in the raw material supply pipe 132. The hydrogen generator 140 includes a housing containing a catalyst that promotes the decomposition of ammonia, and an electric heater for heating the catalyst. The catalyst is, for example, either one or both of a nickel-based catalyst and a ruthenium (Ru)-based catalyst. The hydrogen generator 140 (electric heater) operates when the fuel cell system 100 is started. In this embodiment, the amount of catalyst in the hydrogen generator 140 is less than the amount of catalyst in the ammonia decomposer 150.

[0028] The ammonia decomposer 150 is equipped with a catalyst that promotes the decomposition of ammonia. In this embodiment, the ammonia decomposer 150 is directly opposite the anode off-gas exhaust port 124b. In other words, there is no shielding between the ammonia decomposer 150 and the anode off-gas exhaust port 124b. As will be described in detail later, the anode off-gas exhausted from the fuel gas supply port 124a reacts (oxidation reaction, combustion reaction) with either or both of the ambient gases in the sealed container 110, namely the cathode off-gas and air, near the fuel gas supply port 124a (fuel cell body 120) to produce a post-reaction gas. Therefore, this reaction heat (combustion heat) is directly transferred to the ammonia decomposer 150. Furthermore, the generated post-reaction gas collides with the ammonia decomposer 150 along with the flow of anode off-gas exhausted from the anode off-gas exhaust port 124b. Therefore, the ammonia decomposer 150 is heated to, for example, 400°C to 800°C by the heat of the reaction and the sensible heat of the reaction gas.

[0029] The fuel pipe 152 connects the fuel gas supply port 124a and the ammonia decomposer 150.

[0030] The oxygen-containing gas supply unit 160 supplies oxygen-containing gas to the heat exchanger 180. The oxygen-containing gas contains at least oxygen. Examples of oxygen-containing gas include air and oxygen-enriched air. Here, we will use the case where the oxygen-containing gas is air as an example.

[0031] In this embodiment, the oxygen-containing gas supply unit 160 includes an air supply device 162, an air supply pipe 164, a flow control valve 166, a bypass pipe 168, a flow control valve 170, and an air heater 172.

[0032] The air supply device 162 pressurizes the air that has been filtered by the filter 252a, which will be described later. The air supply device 162 pressurizes the air to a pressure of, for example, 10 kPaG or more. The air supply device 162 is, for example, a blower, a diaphragm pump, or a fan. The intake side of the air supply device 162 is connected to the filter. The discharge side of the air supply device 162 is connected to the air supply pipe 164. The air supply pipe 164 connects the discharge side of the air supply device 162 to the air inlet 182a of the heat exchanger 180. A flow control valve 166 is provided in the air supply pipe 164. The flow control valve 166 adjusts the flow rate of the air flowing through the air supply pipe 164.

[0033] The bypass pipe 168 connects the air supply device 162 and the flow control valve 166 in the air supply pipe 164 to the oxygen-containing gas supply pipe 190. The bypass pipe 168 is equipped with a flow control valve 170 and an air heater 172. The flow control valve 170 adjusts the flow rate of air flowing through the bypass pipe 168. The air heater 172 is located downstream of the flow control valve 170 in the bypass pipe 168. The air heater 172 heats the air flowing through the bypass pipe 168 to, for example, about 900°C. The air heater 172 is, for example, an electric heater. The air heater 172 operates when the fuel cell system 100 is started up.

[0034] The heat exchanger 180 exchanges heat between air and the post-reaction gas. As a result, the air is heated by the sensible heat of the post-reaction gas. On the other hand, the post-reaction gas is cooled by the air. The heat exchanger 180 includes an air channel 182 and a post-reaction gas channel 184.

[0035] The air passage 182 has an air inlet 182a and an air outlet 182b. An air supply pipe 164 is connected to the air inlet 182a. An oxygen-containing gas supply pipe 190 is connected to the air outlet 182b (outlet for oxygen-containing gas). Air supplied from the air supply device 162 flows through the air inlet 182a into the air passage 182 and is exhausted from the air outlet 182b.

[0036] The post-reaction gas flow path 184 has a post-reaction gas inlet 184a and a post-reaction gas outlet 184b. The post-reaction gas inlet 184a communicates with the internal space of the sealed container 110. In other words, the post-reaction gas inlet 184a is an opening facing into the sealed container 110. An exhaust pipe 192 is connected to the post-reaction gas outlet 184b. Post-reaction gas generated in the sealed container 110 flows through the post-reaction gas flow path 184a and is exhausted from the post-reaction gas outlet 184b.

[0037] In this embodiment, the airflow in the air channel 182 and the post-reaction gas flow in the post-reaction gas channel 184 are opposite each other.

[0038] The oxygen-containing gas supply pipe 190 is connected to the air outlet 182b of the heat exchanger 180, with its opening facing the air electrode 126. In this embodiment, the tip of the oxygen-containing gas supply pipe 190 is branched into a plurality of branch pipes 190a. Openings are formed at the tips of the plurality of branch pipes 190a. These openings face the air electrode 126.

[0039] As described above, when fuel gas containing ammonia is supplied to the raw material supply pipe 132 by the fuel supply unit 130, at least a portion of the ammonia is decomposed in the process of passing through the ammonia decomposer 150 to produce hydrogen (reaction equation (1) below). In addition, ammonia is also decomposed on the fuel electrode 122 to produce hydrogen as shown in reaction equation (1) below. NH3 → 3 / 2H2 + 1 / 2N2…Reaction equation (1) Therefore, hydrogen is supplied to the fuel electrode 122, and the oxidation reaction shown in the following reaction equation (2) proceeds at the fuel electrode 122. H2+ O 2- → 2H2O + 2e - ...Reaction equation (2)

[0040] Furthermore, as described above, air is supplied to the air electrode 126 through the oxygen-containing gas supply unit 160, the heat exchanger 180, and the oxygen-containing gas supply pipe 190. As a result, the reduction reaction shown in the following reaction equation (3) proceeds at the air electrode 126. Then, oxide ions (O 2- The fuel cell body 120 generates electricity as the electrolyte 128 is conducted (moved). When the fuel cell body 120 reaches a predetermined temperature of, for example, 200°C or higher, it starts generating electricity, and the temperature of the fuel cell body 120 itself rises due to the Joule heat generated during this power generation. 1 / 2O2+ 2e - → O 2- ...Reaction equation (3)

[0041] Then, the anode-off gas (containing water (water vapor), hydrogen, and ammonia) produced as a result of the oxidation reaction shown in reaction equation (2) is exhausted into the sealed container 110 through the fuel gas supply port 124a. In addition, the cathode-off gas (containing oxygen and nitrogen) produced as a result of the reaction shown in reaction equation (3) is also exhausted into the sealed container 110. Then, within the sealed container 110, either or both of the cathode-off gas and air, along with the anode-off gas, react to produce a post-reaction gas. The post-reaction gas thus produced is guided to the post-reaction gas flow path 184 through the post-reaction gas inlet 184a of the heat exchanger 180.

[0042] One end of the exhaust pipe 192 is connected to the post-reaction gas outlet 184b of the heat exchanger 180. The other end of the exhaust pipe 192 is open to the atmosphere. The other end of the exhaust pipe 192 is located outside the housing 250.

[0043] The condenser 200 exchanges heat between the post-reaction gas, which is exhausted from the heat exchanger 180 and passes through the exhaust pipe 192, and water (e.g., feedwater), which is at a temperature of, for example, 200°C or higher. This cools the post-reaction gas, and the water vapor in the post-reaction gas condenses to produce liquid water. Meanwhile, the water heated by the sensible heat of the post-reaction gas is supplied as hot water to a hot water utilization facility (not shown) or air-cooled by a heat exchanger (not shown). The condenser 200 is composed of, for example, a radiator. The feedwater used by the condenser 200 is 50% to 100% of the water produced from the post-reaction gas.

[0044] The drain tank 202 stores the water (drain) produced by the condenser 200. Before the fuel cell system 100 is started up, the drain tank 202 stores a predetermined amount of water. The drain tank 202 is equipped with a drain valve (not shown). When the drain valve is opened, water is discharged from the drain tank 202.

[0045] The water supply unit 204 supplies water to the air passing through the heat exchanger 180. The water supply unit 204 is, for example, a pump. The suction side of the water supply unit 204 is connected to the drain tank 202. The discharge side of the water supply unit 204 is connected to the water supply pipe 206.

[0046] The water supply pipe 206 connects the discharge side of the water supply unit 204 to the air passage 182 of the heat exchanger 180.

[0047] The steam generation unit 208 is located in the middle of the water supply pipe 206. In this embodiment, the steam generation unit 208 is located near the post-reaction gas inlet 184a inside the sealed container 110. The steam generation unit 208 is a pipe having a plurality of straight pipe sections 208a and a plurality of connecting sections 208b. The straight pipe sections 208a are located opposite the post-reaction gas inlet 184a. The connecting sections 208b connect adjacent straight pipe sections 208a. Water passing through the steam generation unit 208 undergoes heat exchange with the post-reaction gas inside the sealed container 110. This heats the water and generates steam. The steam generated by the steam generation unit 208 is supplied to the air passage 182 of the heat exchanger 180.

[0048] The nitrogen supply unit 210 supplies nitrogen to the raw material supply pipe 132. The nitrogen supply unit 210 operates when the fuel cell system 100 is started up. In this embodiment, the nitrogen supply unit 210 includes a nitrogen supply pipe 212, a pressure reducing valve 214, a shut-off valve 216, and a flow control valve 218.

[0049] The nitrogen supply pipe 212 connects the nitrogen supply source 104, the flow rate adjustment mechanism 138 in the raw material supply pipe 132, and the hydrogen generator 140. The nitrogen supply source 104 is, for example, a high-pressure container (cylinder) for storing nitrogen, or utility piping. The supply pressure of the nitrogen supply source 104 is, for example, 10 kPaG or higher. The pressure reducing valve 214 is provided downstream of the nitrogen supply source 104 in the nitrogen supply pipe 212. The pressure reducing valve 214 reduces the pressure of the nitrogen supplied from the nitrogen supply source 104. The shut-off valve 216 is provided downstream of the pressure reducing valve 214 in the nitrogen supply pipe 212. The shut-off valve 216 opens and closes the flow path formed in the nitrogen supply pipe 212. The flow rate adjustment valve 218 is provided downstream of the shut-off valve 216 in the nitrogen supply pipe 212. The flow control valve 218 maintains the flow rate of nitrogen flowing through the nitrogen supply pipe 212 at a predetermined value. The flow control valve 218 is, for example, a needle valve or an orifice.

[0050] The inverter 220 is connected to the fuel electrode 122 and air electrode 126 of the fuel cell body 120. The inverter 220 converts the DC current output from the fuel cell body 120 into AC current and supplies it to the load. The inverter 220 is designed based on the number of cell stacks in the fuel cell body 120, the number of fuel cell bodies 120, the load connection method (series or parallel), and the load voltage (100V, 200V, etc.). If the voltage output from the fuel cell body 120 is lower than the load voltage, a boost converter (DC-DC converter) is provided before the inverter 220.

[0051] The control unit 230 consists of a touch panel or hard switches. When the control unit 230 receives an operation input from the user, it outputs a signal to the central control unit 240 according to the type of operation input received. Examples of operation inputs include starting up, starting normal operation (power generation), stopping, etc.

[0052] The central control unit 240 consists of a semiconductor integrated circuit (control board, or PLC (programmable logic controller)) including a CPU (central processing unit). The central control unit 240 reads programs and parameters for operating the CPU from ROM. The central control unit 240 works in cooperation with RAM and other electronic circuits as a work area to manage and control the entire fuel cell system 100.

[0053] In this embodiment, the central control unit 240 controls the shut-off valve 136, the flow rate adjustment mechanism 138, the hydrogen generator 140, the air supply device 162, the flow rate adjustment valves 166 and 170, the air heater 172, the water supply unit 204, the shut-off valve 216, and the inverter 220 based on signals output from the operation unit 230. The control by the central control unit 240 will be described in detail later.

[0054] The housing 250 houses the sealed container 110, part of the fuel supply unit 130, the oxygen-containing gas supply unit 160, the condenser 200, the drain tank 202, the water supply unit 204, part of the nitrogen supply unit 210, the inverter 220, the central control unit 240, and the ventilation unit 260. In other words, the ammonia supply source 102, the pressure reducing valve 134, the nitrogen supply source 104, the pressure reducing valve 214, and the operating unit 230 are located outside the housing 250.

[0055] The housing 250 has an air intake port 252 and an exhaust port 254. A filter 252a is provided in the air intake port 252. The filter 252a removes dust from the atmosphere.

[0056] The ventilation unit 260 is composed of, for example, a fan. The ventilation unit 260 exhausts the air inside the housing 250 to the outside through the exhaust port 254. As a result, atmospheric air is introduced into the housing 250 from the outside through the intake port 252. In other words, the ventilation unit 260 ventilates the inside of the housing 250. The ventilation unit 260 ventilates the inside of the housing 250 so that the temperature inside the housing 250 reaches a predetermined temperature (for example, around 50°C).

[0057] The battery temperature sensor 270 measures the temperature of the fuel cell body 120. The decomposer temperature sensor 272 measures the temperature of the ammonia decomposer 150. The water level sensor 274 measures the water level of the drain tank 202. The exhaust gas sensor 276 measures the concentration of ammonia and hydrogen contained in the post-reaction gas exhausted from the condenser 200.

[0058] During operation, the central control unit 240 controls one or more of the output of the water supply unit 204, the power generation load, and the air supply device 162 so that the temperature of the fuel cell body 120, as measured by the battery temperature sensor 270, reaches the temperature at which the power generation efficiency of the fuel cell body 120 is maximized. The temperature at which the power generation efficiency of the fuel cell body 120 is maximized is, for example, 600°C to 800°C.

[0059] Furthermore, during operation, the central control unit 240 controls one or more of the following: the output of the flow rate adjustment mechanism 138, the air supply device 162, the water supply unit 204, and the power generation output of the fuel cell body 120, so that the temperature of the ammonia decomposition unit 150, as measured by the decomposition unit temperature sensor 272, is at the temperature at which the ammonia decomposition efficiency is maximized. The temperature at which the ammonia decomposition efficiency is maximized is, for example, 700°C to 800°C.

[0060] During operation, the central control unit 240 controls the opening and closing of the drain valve provided in the drain tank 202 so that the water level in the drain tank 202, as measured by the water level sensor 274, is within a predetermined range. If the water level in the drain tank 202, as measured by the water level sensor 274, is below the lower limit of the predetermined range, the central control unit 240 stops the operation of the water supply unit 204.

[0061] Furthermore, the central control unit 240 controls the flow rate adjustment mechanism 138 so that the ammonia concentration measured by the exhaust gas sensor 276 remains below the regulated value during operation. If the hydrogen concentration measured by the exhaust gas sensor 276 exceeds a predetermined value during operation, the central control unit 240 controls the inverter 220 to stop power generation by the fuel cell unit 120. The predetermined value is determined based on the explosion range, for example, 25% LEL (lower explosive limit).

[0062] Furthermore, the central control unit 240 operates the hydrogen generator 140 and the air heater 172 during startup.

[0063] [How to start up the fuel cell system 100] Next, the method for starting the fuel cell system 100 will be described. Figure 3 is a flowchart showing the processing flow of the fuel cell system 100 startup method according to this embodiment. As shown in Figure 3, the startup method for the fuel cell system 100 includes a nitrogen purge start process S110, a temperature rise process S112, a decomposition temperature determination process S114, a nitrogen purge end process S116, an ammonia supply start process S118, an OCV determination process S120, an ammonia increase process S122, a first fuel cell temperature determination process S124, a switching process S126, a second fuel cell temperature determination process S128, and a power generation load determination process S130. Each process will be described below. Before startup, the shut-off valves 136 and 216 and the flow control valves 166 and 170 are closed, and the air supply device 162 and the water supply unit 204 are stopped.

[0064] [Nitrogen purging start process S110] The central control unit 240 opens the flow control valve 170 and starts the air supply device 162. The central control unit 240 also opens the shut-off valve 216 and starts nitrogen purging.

[0065] [Temperature increase treatment S112] The central control unit 240 operates the hydrogen generator 140 and the air heater 172.

[0066] [Decomposition temperature determination process S114] The central control unit 240 determines whether the temperature of the hydrogen generator 140 has reached the ammonia decomposition temperature. If the temperature of the hydrogen generator 140 is below the ammonia decomposition temperature (NO in S114), the central control unit 240 repeats the decomposition temperature determination process S114 until the temperature reaches the ammonia decomposition temperature. Once the temperature of the hydrogen generator 140 reaches the ammonia decomposition temperature (YES in S114), the central control unit 240 moves on to the nitrogen purge completion process S116.

[0067] [Nitrogen purging completion process S116] The central control unit 240 closes the shut-off valve 216 to terminate the nitrogen purge.

[0068] [Ammonia supply start process S118] The central control unit 240 opens the shut-off valve 136 to start supplying ammonia.

[0069] [OCV detection process S120] The central control unit 240 determines whether the OCV (open-circuit voltage) of the fuel cell body 120 has stabilized. If the OCV of the fuel cell body 120 is not yet stable (NO in S120), the central control unit 240 repeats the OCV determination process S120 until the OCV stabilizes. Once the OCV of the fuel cell body 120 stabilizes (YES in S120), the central control unit 240 moves on to the ammonia increase process S122.

[0070] [Ammonia increase treatment S122] The central control unit 240 adjusts the flow rate adjustment mechanism 138 to increase the ammonia supply. The central control unit 240 also controls the inverter 220 to increase the power generation load.

[0071] [First fuel cell temperature determination process S124] The central control unit 240 refers to the measurement value of the battery temperature sensor 270 and determines whether the temperature of the fuel cell body 120 has reached 400°C. If the temperature of the fuel cell body 120 is less than 400°C (NO in S124), the central control unit 240 repeats the first fuel cell temperature determination process S124 until it reaches 400°C. Once the temperature of the fuel cell body 120 reaches 400°C (YES in S124), the central control unit 240 moves on to the switching process S126.

[0072] [Switching process S126] The central control unit 240 opens the flow control valve 166 and closes the flow control valve 170. The central control unit 240 also stops the operation of the air heater 172.

[0073] [Second fuel cell temperature determination process S128] The central control unit 240 refers to the measurement value of the battery temperature sensor 270 and determines whether the temperature of the fuel cell body 120 has reached 600°C. If the temperature of the fuel cell body 120 is less than 600°C (NO in S128), the central control unit 240 repeats the second fuel cell temperature determination process S128 until it reaches 600°C. Once the temperature of the fuel cell body 120 reaches 600°C (YES in S128), the central control unit 240 moves on to the power generation load determination process S130.

[0074] [Power generation load determination process S130] The central control unit 240 determines whether the power generation load has reached the power generation load command. If the power generation load has not reached the power generation load command (NO in S130), the central control unit 240 repeats the power generation load determination process S130 until the power generation load command is reached. Once the power generation load has reached the power generation load command (YES in S130), the central control unit 240 stops the operation of the hydrogen generator 140 and switches to normal operation.

[0075] [Normal operation method for fuel cell system 100] Next, the normal operation method of the fuel cell system 100 will be described. Figure 4 is a flowchart showing the processing flow of the normal operation method of the fuel cell system 100 according to this embodiment. As shown in Figure 4, the normal operation method of the fuel cell system 100 includes load control processing S210 and temperature control processing S212.

[0076] [Load control processing S210] The central control unit 240 controls the inverter 220 to control the power generation load based on the power generation load command. The central control unit 240 also controls the flow rate adjustment mechanism 138 and the flow rate adjustment valve 166 according to the power generation load.

[0077] [Temperature control process S212] Furthermore, the central control unit 240 refers to the measurement value of the battery temperature sensor 270 and controls the flow control valve 166 and the water supply unit 204 so that the fuel cell body 120 is maintained at a temperature between 600°C and 800°C.

[0078] [How to shut down the fuel cell system 100] Next, the method for stopping the fuel cell system 100 will be described. Figure 5 is a flowchart showing the processing flow of the fuel cell system 100 stopping method according to this embodiment. As shown in Figure 5, the method for stopping the fuel cell system 100 includes a cooling process S310, a power generation stop process S312, a fuel cell temperature determination process S314, an ammonia supply stop process S316, a nitrogen purge start process S318, a hydrogen generator stop process S320, and a nitrogen purge end process S322. Each process will be described below.

[0079] [Temperature cooling process S310] The central control unit 240 controls the flow control valve 166 to change the air supply rate to a predetermined flow rate. The central control unit 240 also stops the water supply unit 204. The central control unit 240 operates the hydrogen generator 140. The central control unit 240 also reduces the power generation load at a predetermined speed and controls the flow control mechanism 138 based on the power generation load to reduce the ammonia supply flow rate.

[0080] [Power generation shutdown process S312] The central control unit 240 stops the power generation load command and stops the power generation output from the inverter 220.

[0081] [Fuel cell temperature determination process S314] The central control unit 240 refers to the measurement value of the battery temperature sensor 270 and determines whether the temperature of the fuel cell body 120 has reached 200°C or below. If the temperature of the fuel cell body 120 is above 200°C (NO in S314), the central control unit 240 repeats the fuel cell temperature determination process S314 until it reaches 200°C or below. Once the temperature of the fuel cell body 120 reaches 200°C or below (YES in S314), the central control unit 240 moves on to the ammonia supply stop process S316.

[0082] [Ammonia supply shutdown procedure S316] The central control unit 240 closes the shut-off valve 136 to stop the supply of ammonia.

[0083] [Nitrogen purge initiation process S318] The central control unit 240 opens the shut-off valve 216 and starts the nitrogen purge.

[0084] [Hydrogen generator shutdown process S320] The central control unit 240 stops the operation of the hydrogen generator 140 and the air supply device 162.

[0085] [Nitrogen purging completion process S322] The central control unit 240 closes the shut-off valve 216 and terminates the nitrogen purging after a predetermined time has elapsed since executing the hydrogen generator shutdown process S320.

[0086] As described above, the fuel cell system 100 of this embodiment is an open-system fuel cell system 100 and includes an ammonia decomposer 150 inside a sealed container 110. The ammonia decomposer 150 is directly heated by the heat of reaction and the sensible heat of the reaction gas. Therefore, the fuel cell system 100 can decompose ammonia into hydrogen using the heat of reaction and the sensible heat of the reaction gas without requiring a separate heater for ammonia decomposition. This enables the ammonia decomposer 150 to efficiently decompose ammonia. In addition, the ammonia decomposer 150 recovers the heat of reaction and the sensible heat of the reaction gas. Therefore, the ammonia decomposer 150 can reduce the excess heat inside the sealed container 110.

[0087] Furthermore, the fuel cell system 100 includes a water supply unit 204 that supplies water vapor to the air passing through the heat exchanger 180. This ensures that water vapor is supplied into the sealed container 110. Consequently, the water supply unit 204 can increase the heat capacity of the atmospheric gas in the sealed container 110. Therefore, the water supply unit 204 can lower the temperature inside the sealed container 110 on average. In addition, the water supply unit 204 can increase the amount of gas (a mixture of air and water vapor) passing through the air passage 182 of the heat exchanger 180 compared to the case where only air is passed through. This allows the heat exchanger 180 to efficiently cool the post-reaction gas. Consequently, the water supply unit 204 can further lower the temperature inside the sealed container 110.

[0088] Furthermore, as described above, the ammonia decomposer 150 faces the anode off gas exhaust port 124b. The reactions of the anode off gas (oxidation reaction, combustion reaction) proceed in the vicinity of the anode off gas exhaust port 124b. Therefore, by facing the anode off gas exhaust port 124b, the ammonia decomposer 150 is directly heated by the heat of reaction and the sensible heat of the reaction gas. As a result, the ammonia decomposer 150 can decompose ammonia even more efficiently.

[0089] Furthermore, as described above, the fuel cell system 100 includes a condenser 200. This allows the fuel cell system 100 to circulate the water supplied by the water supply unit 204 to lower the temperature inside the sealed container 110. Therefore, the fuel cell system 100 can omit a mechanism for supplying water from an external source.

[0090] Furthermore, as described above, the fuel cell system 100 is equipped with a steam generation unit 208, and the water supply unit 204 supplies the steam generated by the steam generation unit 208 to the heat exchanger 180. This makes it possible to suppress pressure fluctuations in the water supply unit 204.

[0091] Furthermore, as described above, the steam generation unit 208 is located near the post-reaction gas inlet 184a within the sealed container 110. The ambient temperature near the post-reaction gas inlet 184a is relatively high. Therefore, the steam generation unit 208 can efficiently generate steam.

[0092] Furthermore, the fuel cell system 100 is equipped with a hydrogen generator 140 in addition to the ammonia decomposer 150. This makes it possible for the fuel cell system 100 to avoid the generation of nitrogen oxides (NOx) during startup, normal operation, or shutdown.

[0093] Furthermore, the fuel cell system 100 is equipped with an air heater 172. This makes it possible to raise the temperature of the fuel cell body 120 from the inside. Therefore, the fuel cell body 120 can be started up in a short time.

[0094] Furthermore, the fuel cell system 100 is equipped with a sealed container 110. This suppresses the outflow of heat generated in the fuel cell body 120 to the outside due to radiation. In addition, the raw material supply pipe 132, ammonia decomposer 150, fuel pipe 152, bypass pipe 168, oxygen-containing gas supply pipe 190, and steam generation unit 208, which receive radiant heat, can recover radiant heat from the fuel cell body 120 in addition to the sensible heat of the post-reaction gas.

[0095] Furthermore, the fuel cell system 100 is equipped with a housing 250. This protects the fuel cell body 120 and other components from wind, rain, dust, and other elements.

[0096] While embodiments have been described above with reference to the attached drawings, it goes without saying that this disclosure is not limited to the embodiments described above. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of this disclosure.

[0097] For example, in the above embodiment, we have given an example where the condenser 200 uses water to cool the reaction gas. However, there are no limitations on the refrigerant used by the condenser 200. For example, the condenser 200 may use air to cool the reaction gas. Also, when the condenser 200 uses water as the refrigerant, the heated water may be cooled by another radiator.

[0098] Furthermore, in the above embodiment, an example was given in which the fuel cell system 100 is equipped with a condenser 200. However, the condenser 200 is not an essential component.

[0099] Furthermore, in the above embodiment, an example was given in which the steam generation unit 208 is provided near the post-reaction gas inlet 184a inside the sealed container 110. However, the steam generation unit 208 is not limited to its installation location as long as it can convert water into steam. The steam generation unit 208 may, for example, be provided in the post-reaction gas flow path 184 of the heat exchanger 180. In this case, the steam generation unit 208 exchanges heat between the sensible heat of the post-reaction gas passing through the post-reaction gas flow path 184 and water. Alternatively, the steam generation unit 208 may, for example, be provided upstream of the condenser 200 in the exhaust pipe 192 outside the sealed container 110. In this case, the steam generation unit 208 exchanges heat between the sensible heat of the post-reaction gas passing through the exhaust pipe 192 and water.

[0100] Furthermore, in the above embodiment, a configuration in which the fuel cell system 100 includes a steam generation unit 208 was given as an example. However, the steam generation unit 208 is not an essential component. In this case, water (liquid) is supplied to the air passage 182 of the heat exchanger 180.

[0101] Furthermore, in the above embodiment, the case in which the ammonia decomposer 150 faces the anode off-gas exhaust port 124b was given as an example. However, the ammonia decomposer 150 is not limited in its installation location as long as it is provided inside the sealed container 110.

[0102] Furthermore, in the above embodiment, a configuration in which the fuel cell system 100 includes a hydrogen generator 140 was given as an example. However, the hydrogen generator 140 is not an essential component. In this case, an electric heater is provided in the ammonia decomposer 150. The electric heater is operated when starting up and stopping the fuel cell system 100.

[0103] Furthermore, in the above embodiment, an example was given in which the fuel cell system 100 is equipped with a nitrogen supply unit 210. However, if the fuel cell body 120 does not deteriorate even in an oxidizing atmosphere, the nitrogen supply unit 210 can be omitted. In this case, air purging is performed instead of nitrogen purging.

[0104] Furthermore, in the method for starting the fuel cell system 100, the fuel cell body 120 may be heated (heated up) from the outside. Also, a heat transfer resistor (sheath heater) may be provided inside the sealed container 110.

[0105] Alternatively, instead of the battery temperature sensor 270, an inlet temperature sensor that measures the temperature near the post-reaction gas inlet 184a may be provided. However, if the water vapor generation unit 208 is located near the post-reaction gas inlet 184a, the inlet temperature sensor should measure the temperature of the post-reaction gas before heat exchange occurs by the water vapor generation unit 208.

[0106] Furthermore, in the above embodiment, the inverter 220 was described as being provided inside the housing 250 as an example. However, the inverter 220 may be provided outside the housing 250.

[0107] Furthermore, if the fuel cell system 100 is installed in a location exposed to direct sunlight, a light-shielding plate may be installed in the area of ​​the housing 250 that is exposed to direct sunlight. This makes it possible to suppress the temperature inside the housing 250.

[0108] This disclosure can contribute, for example, to Sustainable Development Goal (SDG) 7, "Ensure access to affordable, reliable, sustainable and modern energy," Goal 8, "Promote inclusive and sustainable economic growth, employment and decent work for all," Goal 9, "Build resilient infrastructure, promote sustainable industrialization and foster innovation," and Goal 13, "Take urgent action to combat climate change and its impacts." [Explanation of symbols]

[0109] 100 Fuel Cell Systems 110 airtight container 120 Fuel cell body 122 Fuel electrode 124a Fuel gas supply port 124b Anode Off Gas Exhaust Port 126 Air pole 128 Electrolytes 130 Fuel supply section 150 Ammonia Decomposer 152 Fuel pipe 160 Oxygen-containing gas supply unit 180 Heat exchanger 182 Airflow channel 182b Air outlet 184b Reaction gas outlet 190 Oxygen-containing gas supply pipe 200 condenser 204 Water supply section 208 Steam generation unit

Claims

1. A sealed container, A fuel cell body provided within the sealed container, having at least a fuel electrode, an air electrode, a fuel gas supply port, and an anode off-gas exhaust port facing the internal space of the sealed container, An ammonia decomposer is provided inside the aforementioned sealed container and contains a catalyst that promotes the decomposition of ammonia, A fuel pipe is provided inside the sealed container and connects the fuel gas supply port and the ammonia decomposer, A fuel supply unit that supplies a raw material gas containing at least ammonia to the ammonia decomposer, A heat exchanger is provided inside the sealed container to exchange heat between the oxygen-containing gas, which contains at least oxygen, and a cathode off gas, or either one or both of them, and an anode off gas, and the post-reaction gas produced by the reaction of the oxygen-containing gas. An oxygen-containing gas supply pipe is provided inside the sealed container, connected to the outlet of the oxygen-containing gas in the heat exchanger, with its opening facing the air electrode, An oxygen-containing gas supply unit that supplies the oxygen-containing gas to the heat exchanger, A water supply unit that supplies water to the oxygen-containing gas passing through the heat exchanger, A fuel cell system equipped with the following features.

2. The system includes a condenser that cools the post-reaction gas exhausted from the heat exchanger to produce water. The fuel cell system according to claim 1, wherein the water supply unit supplies water generated in the condenser.

3. It is equipped with a water vapor generation unit that converts water into water vapor, The fuel cell system according to claim 1 or 2, wherein the water supply unit supplies steam generated by the steam generation unit.

4. The fuel cell system according to claim 1 or 2, wherein the ammonia decomposer faces the anode off-gas exhaust port.

5. The fuel cell system according to claim 1 or 2, wherein the ammonia decomposer recovers the heat contained in the reaction gas.

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