JPH04355060A - Fused carbonate fuel cell generating device - Google Patents

Abstract

PURPOSE:To facilitate change operation by eliminating a differential pressure adjusting valve for controlling a differential pressure between a fuel call vessel and a fuel cell. CONSTITUTION:A fuel cell I is stored in a vessel 4. After an unconverted component in anode outlet gas in the fuel cell I is burned by oxygen in cathode outlet gas, the gas is cooled through a heat exchanger to decrease a temperature, boosted by a low temperature recycle blower 31 to join with air A and supplied to a cathode 2. Gas of low temperature, boosted by this blower 31, is partly supplied into the vessel 4 of the fuel cell I so as to balance a pressure of the vessel 4 with a pressure of the cathode 2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fuel cells used in the energy sector for directly converting the chemical energy of fuel into electrical energy, and particularly to a power generation device using a molten carbonate fuel cell.

0002

2. Description of the Related Art Among conventional molten carbonate fuel cells, for example, a power generation device using a natural gas reformed molten carbonate fuel cell has an electrolyte plate 1 as a cathode 2 as schematically shown in FIG. A fuel cell I having a structure in which cells sandwiched between both electrodes of an anode 3 are laminated via a separator to form a stack is housed in a container 4, and the cathode 2 is connected to a turbine shaft 7 by a turbine 6 of a supercharger 5. Air A compressed by a compressor 8 rotated through the air supply line 9 is supplied through an air supply line 9, and cathode outlet gas discharged from the cathode 2 is introduced into a catalytic combustor 12 through a cathode outlet gas line 11. At the same time, a part of the cathode outlet gas is transferred to a high temperature recycle blower 14 from a recycle line 13 branched from the cathode outlet gas line 11.
The pressure is increased by the air supply line 9 on the cathode inlet side, and some of the cathode outlet gas is recycled to the air supply line 9 on the cathode inlet side.
The gas is introduced into the combustor 16 through a branch line 15 branched from the cathode outlet gas line 11. A fuel supply line 17 and an air branch line 18 branched from the air supply line 9 are connected to the combustion chamber 16, and part of the air supplied to the cathode 2, fuel, and cathode outlet gas are combusted. The gas discharged from the turbine 6 is guided to a turbine 6 of the supercharger 5 to drive the turbine 6, and the gas discharged from the turbine 6 is passed through an exhaust gas line 1.
9, the steam is discharged through a steam superheater 20 and a steam generator 21. On the other hand, natural gas NG as a raw material gas for reforming is desulfurized by a desulfurizer (not shown) and then passed through a natural gas preheater 23 from a natural gas supply line 22 to a reformer 2.
The reformed gas that is supplied to the reforming chamber 24a of No. 4 and reformed in the reforming chamber 24a is supplied to the anode 3 through the fuel gas supply line 25, the natural gas preheater 23, and the anode 3. The anode outlet gas discharged from the anode 3 is
The unreacted portion ( combustible components) (H2, CO, CH
4, etc.) with oxygen in the cathode outlet gas,
The exhaust gas from the catalytic combustor 12 is transferred to the combustion chamber 2 of the reformer 24.
4b, and is further connected to the air supply line 9 from the exhaust gas line 27. In addition, water that is pressurized by a water supply pump (not shown) and led to the steam generator 21 is evaporated here and becomes steam, and this steam is superheated in the steam superheater 20 and then released from the steam line 32 into natural water. It is designed to lead to the gas supply line 22.

In such a molten carbonate fuel cell power generation device, the pressure difference between the container 4 and the fuel cell I, and the
It is necessary to control the differential pressure between the cathode 2 and the anode 3. Conventionally, differential pressure control valves 33 and 34 are provided midway between the cathode outlet gas line 11 and the anode outlet gas line 26, and the pressure difference between the container 4 and the anode 3 is controlled. A differential pressure controller 35 provided between the container 4 and the air supply line 9 adjusts the differential pressure regulating valve 33 to control the differential pressure between the container 4 and the cathode 2,
Further, the differential pressure control valve 34 is adjusted by a differential pressure controller 36 provided between the cathode outlet gas line 11 and the anode outlet gas line 26 to control the differential pressure between the cathode 2 and the anode 3. In addition, in order to control the pressure inside the container 4, the N2 supply line 37 and the exhaust line 38 are connected to the container 4, and both lines 37 and 3 are connected to the container 4.
Flow control valves 39 and 40 provided at 8 are controlled by a pressure controller 41.

Reference numeral 42 indicates an air flow rate controller, 43 indicates a steam flow rate controller, 44 indicates a fuel (natural gas) flow rate controller, and 45 indicates an air flow rate, a steam flow rate, and a fuel flow rate according to the output of the fuel cell I, respectively. ,4
This is the master controller that instructs the controller.

[0005]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional molten carbonate fuel cell power generation device, two Differential pressure regulating valves 33 and 34 are required, but since both the outlets of the cathode 2 and anode 3 are at high temperatures, the differential pressure regulating valves are not only expensive, but also the gas flow rate is particularly low on the cathode 2 side. Because of the large number of pipes, there are problems such as large pipe diameters, poor control response, and a considerable amount of space required for arrangement. In addition, in the case of variable pressure operation, the pressure inside the container 4 of the fuel cell I needs to be changed according to pressure fluctuations during partial load operation of the fuel cell I, and in particular,
During low-load operation, as the gas flow rate discharged from the fuel cell I decreases, the gas flow rate entering the turbine 6 decreases, resulting in a decrease in turbine output, which also decreases the ability of the compressor 8 to pressurize air, reducing the air pressure to the cathode. The pressure of the air entering the container 4 becomes lower, and the pressure of the cathode outlet gas also becomes lower, so control is required to lower the pressure in the container 4. In this case, the pressure can be controlled by removing the N2 in the container 4. Also, when the load is high, the output of the fuel cell I increases, so N2 is injected to increase the pressure inside the container 4. In addition, when lowering the pressure inside the container 4, there is a problem that there is a lot of waste because the N2 gas, which has become hot due to heat radiation from the battery, is thrown out of the container.

Therefore, the present invention eliminates the need for the differential pressure regulating valve used in conventional molten carbonate fuel cell power generation devices, and controls the differential pressure between the fuel cell and the container.
Another object of the present invention is to provide a molten carbonate fuel cell power generation device that can eliminate the need for N2 to maintain the pressure inside the fuel cell container and can recover the heat released by the fuel cell inside the container. .

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a fuel cell in which a cell in which an electrolyte plate is sandwiched between cathode and anode electrodes is stacked with a separator in between, and is housed in a container. Then, the cathode outlet gas discharged from the cathode of the fuel cell and the anode outlet gas discharged from the anode are introduced into a catalytic combustor to burn unreacted components in the anode outlet gas, and then passed through a heat exchanger. In a molten carbonate fuel cell power generation device having a configuration in which the low-temperature gas is cooled, dehumidified, pressurized by a low-temperature recycle blower, and supplied to the cathode together with air, a recycle line on the discharge side of the low-temperature recycle blower is provided. A check valve is provided, and a low-temperature gas branch line is connected to the recycle line between the check valve and the low-temperature recycling blower, and the other end of the low-temperature gas branch line is connected to the container of the fuel cell to recycle to the cathode. A portion of the low-temperature gas to be supplied to the container can be supplied to the container. Further, a part of the cathode outlet gas discharged from the cathode of the fuel cell is pressurized by a high-temperature recycle blower and supplied to the cathode, so that a part of the cathode outlet gas discharged from the cathode of the fuel cell is provided between the suction side of the high-temperature recycle blower and the container of the fuel cell. are connected by an exhaust line for discharging the gas in the container, and a check valve is provided on the upstream side of the exhaust line, and a flow rate adjustment valve is provided on the downstream side, and the flow rate adjustment valve is connected to a temperature controller on the exhaust line. The configuration is such that it can be adjusted by. Furthermore, an exhaust branch line is connected between the check valve and the flow control valve of the exhaust line via a directional valve, and the other end of the exhaust branch line is connected to a catalytic combustor, and further, the exhaust branch line is connected to a catalytic combustor. The directional control valve may be configured to be switched by a combustible gas detection switch provided on the container or exhaust line.

[0008]

[Effect] By making it possible to supply a portion of the low-temperature gas that is pressurized by the low-temperature recycle blower and supplied to the cathode into the fuel cell container, the gas pressure of the system, which fluctuates in response to load fluctuations, acts on the inside of the container. Therefore, the cathode pressure and the pressure inside the container can always be balanced, and variable pressure operation can be performed, and this method eliminates the need for N2 for maintaining the pressure inside the container. In addition, if the gas in the container is led from the exhaust line to the suction side of a high-temperature recycle blower, and the high-temperature recycle blower increases the pressure together with the cathode outlet gas and supplies it to the cathode, the heat radiated from the fuel cell is recovered by the gas and the gas is transferred to the cathode. It is possible to reduce heat escaping to the outside. Furthermore, by guiding the exhaust gas from inside the container to the catalytic combustor, when flammable gas leaks from the fuel cell, it becomes possible to combust the flammable gas.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which a cathode outlet gas from a cathode 2 and an anode outlet gas from an anode 3 of a fuel cell I are introduced into a catalytic combustor 12.
After burning the unreacted content (combustible components) in the anode outlet gas with oxygen in the cathode outlet gas, the gas is transferred to the reformer 2.
The gas, which has been cooled through the combustion chamber 24b of No. 4, the air preheater 10, and the gas cooler 28, and from which moisture has been removed by the gas-liquid separator 29, is pressurized by the low-temperature recycle blower 31, and the low-temperature gas is combined with the air to form the cathode 2. In a configuration configured to supply low-temperature gas to the cathode 2, a low-temperature gas branch line 4 is provided between a check valve 46 provided in the middle of a recycle line 30 that recycles low-temperature gas to the cathode 2, and a low-temperature recycle blower 31.
7 and the other end of the low-temperature gas branch line 47 is connected to the container 4 of the fuel cell I, so that a part of the low-temperature recycle gas supplied to the cathode 2 is directly supplied into the container 4, and the other end of the low-temperature gas branch line 47 is connected to the container 4. 4 and the cathode 2 are balanced, the conventional mechanism for controlling the differential pressure regulating valve 33 by the differential pressure controller 35 can be omitted, and the N2 supply line 38 for maintaining the pressure inside the container 4 can be omitted. do it like this. 48 is a valve.

In addition, in place of the exhaust line 38 connected to the container 4 in FIG. 3, an exhaust line 49 connecting the container 4 and the suction side of the high-temperature recycle blower 14 is provided, and a check valve is provided on the upstream side of the exhaust line 49. A valve 50 and a flow rate control valve 51 are provided on the downstream side, and a temperature controller 52 for detecting the exhaust temperature is installed between the check valve 50 and the flow rate control valve 51 on the exhaust line 49. A flow control valve 51 can be adjusted by a temperature controller 52 so that when the temperature of the gas discharged from the blower 4 is higher than a set value, the gas is sent to the suction side of a high temperature recycle blower 14.

The pressure within the container 4 of the fuel cell I must be changed in response to pressure fluctuations in the fuel cell I, but in the present invention, the pressure within the container 4 can be automatically balanced to the pressure of the cathode 2. That is, when the pressure of fuel cell I decreases,
The pressure of the cathode outlet gas decreases. If a part of the cathode outlet gas is introduced into the turbine 6 of the supercharger 5 without combusting the combustor 16, the output of the turbine 6 will decrease, so the compressor 8 will not be able to compress the air to the required pressure. Gas pressure in the system decreases. Since this reduced gas enters the container 4 from the low temperature gas branch line 47, the pressure inside the container 4 is automatically lowered, resulting in variable pressure operation. On the other hand, when the output of the fuel cell I is high, the system operates at high pressure, so the high pressure gas entering the container 4 from the low-temperature gas branch line 47 automatically causes the interior of the container 4 to operate at high pressure. be able to. As a result, conventionally, the container 4
The differential pressure regulating valve 33 provided to balance the pressure inside the cathode 2 and the pressure inside the cathode 2 and the N2 for maintaining pressure inside the container 4 can be eliminated. Since the low-temperature gas is introduced into the container 4, the fuel cell I can be cooled from the outside, and the flow rate of the cooling gas flowing to the cathode 2 can be reduced. This makes it possible to improve the power transmission end efficiency. Note that since the cathode outlet gas and the anode outlet gas are introduced into the catalytic combustor 12, there is no pressure difference between the two.

Further, the gas in the container 4 is introduced from the exhaust line 49 into the suction side of the high temperature recycle blower 14, and the flow rate control valve 51 is opened as long as the gas temperature is above the set value. High temperature recycling blower 1
If the heat is returned to the cathode 2 after increasing the pressure in step 4, the heat released from the fuel cell I in the container 4 will be recovered as gas and returned to the inlet side of the cathode 2, so the flow rate of gas passing through the air preheater 10 will be reduced. This makes it possible to downsize the air preheater 10.

Next, as another embodiment, between the check valve 50 and the flow control valve 51 of the exhaust line 49 shown in FIG.
An exhaust branch line 54 is connected via a directional switching valve 53,
The other end of the exhaust branch line 54 is connected to the catalytic combustor 12, and a flammable gas detection switch 55 for switching the directional control valve 53 is connected to the exhaust gas line 49 or the container 4.
(Exhaust gas line 49 in the figure).

According to this embodiment, when the flammable gas detection switch 55 detects that flammable gas is leaking from the fuel cell I, the flow of gas in the container 4 is switched to the directional control valve 53. switch to the exhaust branch line 54,
Gas from container 4 is led directly to catalytic combustor 12 for combustion. As a result, even if flammable gas leaks from the fuel cell I, safety can be improved by introducing it into the catalytic combustor 12 and burning it.

Next, FIG. 2 shows still another embodiment of the present invention, in which the low-temperature gas discharged from the low-temperature recycle blower 31 is recycled into the container 4 of the fuel cell I in the same system configuration as shown in FIG. Instead of a configuration that allows direct input to
An air branch line 56 is connected to the air supply line 9, and a portion of the air pressurized by the compressor 8 is actively introduced into the container 4.

According to this embodiment, there is an advantage that oxygen can be introduced into the container 4 and corrosion of the fuel cell I can be prevented.

In the embodiment shown in FIGS. 1 and 2 described above,
Similar to the conventional example shown in FIG. 3, the master controller 45
There is a control system configured to instruct each flow rate controller 42, 43, 44 of the required flow rate of air, steam, and fuel according to the output of the fuel cell I, but in such a system, the plant is completely preheated. In addition, when the start button is pressed when entering output operation from a state where the fuel cell output is zero, a control program that inputs a small amount of simulated load is started, which causes the anode 3 and cathode 2 of the fuel cell to generate electricity respectively. By flowing the necessary gas and actually applying a load to the fuel cell after a certain delay, it will be possible to start up the fuel cell without supplying a special gas such as H2 from the outside.

[0019]

As described above, according to the molten carbonate fuel cell power generation device of the present invention, the fuel cell is housed in a container, and the cathode outlet gas discharged from the cathode and anode of the fuel cell and the anode outlet are separated. After the gas is combusted in a catalytic combustor, the gas is cooled by heat exchange, dehumidified and pressurized by a low-temperature recycle blower, and combined with air to be supplied to the cathode. Since a part of the low-temperature gas discharged from the fuel cell is directly introduced into the container of the fuel cell, the gas in the system that is supplied to the cathode is introduced into the container, so that the pressure between the container and the cathode can always be balanced. and automatic variable voltage operation in which the inside of the fuel cell container can be operated at high pressure when the output of the fuel cell is high, and the inside of the container can be operated at low pressure when the output of the fuel cell is low; It eliminates the need for the differential pressure control valve that was previously required, which is advantageous in terms of installation space and economy, and because low-temperature gas flows into the fuel cell container, the fuel cell can be cooled from the outside. It is possible to reduce the flow rate of the cooling gas flowing to the cathode, and as a result, the power of the recycle blower is reduced, improving the transmission end efficiency, and eliminating the need for N2 to maintain the pressure inside the fuel cell container. Excellent effects can be achieved, such as the fact that the cathode outlet gas and the anode outlet gas are directly guided to the catalytic combustor, thereby eliminating the need for differential pressure control between the cathode and the anode. Further, an exhaust line is provided that connects the suction side of a high temperature recycling blower that recycles the cathode outlet gas of the fuel cell to the cathode at a high temperature and the container of the fuel cell, and a check valve is provided on the upstream side of the exhaust line, and By installing flow control valves on the downstream side and allowing the gas in the container to enter the suction side of the high temperature recycle blower,
The advantage is that the heat radiated from the fuel cell can be recovered as gas and returned to the cathode inlet side, reducing the gas flow rate supplied to the cathode through the air preheater, and making the air preheater more compact. Furthermore, an exhaust branch line is connected in the middle of the exhaust line via a directional valve, and the other end of the exhaust branch line is connected to a catalytic combustor, and the fuel cell container or If the directional control valve is switched by a flammable gas detection switch installed in the exhaust line, even if flammable gas leaks from the fuel cell, it can be introduced directly into the catalytic combustor, making it safer. This effect can also be achieved.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram showing an embodiment of a molten carbonate fuel cell power generation device of the present invention.

FIG. 2 is a system configuration diagram showing another embodiment of the molten carbonate fuel cell power generation device of the present invention.

FIG. 3 is a system configuration diagram schematically showing a conventional molten carbonate fuel cell power generation device.

[Explanation of symbols]

I Fuel cell 1　Electrolyte plate 2 Cathode 3 Anode 4 Container 9 Air supply line 10 Air preheater 11 Cathode outlet gas line 12 Catalytic combustor 13 Recycling line 14 High temperature recycling blower 26 Anode outlet gas line 28 Cooler 29 Gas-liquid separator 30 Recycling line 31 Low temperature recycling blower 47 Low temperature gas branch line 49 Exhaust line 50 Check valve 51 Flow control valve 53 Directional switching valve 54 Exhaust branch line 55 Flammable gas detection switch A Air

Claims (4)

[Claims] Claim 1: A fuel cell in which cells each having an electrolyte plate sandwiched between cathode and anode electrodes are stacked with a separator in between is housed in a container, and cathode outlet gas discharged from the cathode of the fuel cell and the anode are housed in a container. The anode outlet gas discharged from the anode outlet gas is introduced into the catalytic combustor to burn the unreacted content in the anode outlet gas, and the gas is dehumidified after being cooled by heat exchange, and the low temperature gas is pressurized by a low temperature recycle blower. In the molten carbonate fuel cell power generation device, the low temperature gas branch line connects the discharge side of the low temperature recycle blower and the inside of the fuel cell container, and the low temperature gas is supplied to the cathode together with air. A molten carbonate fuel cell power generation device characterized in that a portion of gas enters a container. 2. The molten carbonate fuel cell power generation device according to claim 1, wherein the anode outlet gas and the cathode outlet gas are directly introduced into the catalytic combustor. 3. An exhaust line is provided that connects the suction side of the high temperature recycle blower and the fuel cell container to pressurize the cathode outlet gas and return it to the cathode inlet side, and a check valve is provided on the upstream side of the exhaust line. 2. The molten carbonate fuel cell power generation device according to claim 1, further comprising a flow rate regulating valve on the downstream side. 4. An exhaust branch line is connected in the middle of the exhaust line via a directional valve, the other end of the exhaust branch line is connected to a catalytic combustor, and the exhaust branch line is connected to the container of the fuel cell or the exhaust line. 4. The molten carbonate fuel cell power generating apparatus according to claim 3, wherein said directional control valve is switched by a combustible gas detection switch.