JPH0652880A - Phosphoric acid type fuel cell power generating unit - Google Patents

Abstract

PURPOSE:To cool a CO converter at good efficiency of heat exchange and to miniaturize the CO converter by using in the cooling system of the CO converter both water from a steam separator and condensed water of a low temperature level obtained from the exhaust gas of a fuel cell. CONSTITUTION:The cooling water of the cooling system 13 of a CO converter 4 is a mixture of pressurized water from a steam separator 6 and water supplied from water treatment equipment 11. The water supplied from the equipment 11 consists of water 51, 52 condensed from the exhaust gas of a fuel cell 5 and city water 14, and there is almost no need for the city water 14 to be supplied only if a sufficient amount of condensed water is recycled by lowering the temperature of the exhaust gas. If the amount of the condensed water flow from the separator 6 is constant, then the higher the load and the larger the amount of water supply, the lower the cooling water temperature of the converter 4. Therefore, the rate of heat exchange in the converter 4 is improved and a catalyst is held at appropriate temperature so as to reduce the concentration of CO in reformed gas at the outlet of the converter 4 and then the converter 4 can be miniaturized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphoric acid fuel cell power generator.

[0002]

2. Description of the Related Art FIG. 5 is a system diagram showing a conventional phosphoric acid fuel cell power generator disclosed in, for example, Japanese Patent Laid-Open No. 1-265461. In the figure, 1 is a reformer for reacting fuel and steam to obtain hydrogen, and 2 and 3 are heat exchanges between the gas reformed by the reformer 1 (hereinafter referred to as reformed gas) and the fuel. A heat exchanger 4 for carrying out and preheating the fuel is a CO modifier for converting carbon monoxide contained in the reformed gas reformed by the reformer 1 into hydrogen. It is water-cooled for the removal of. Reference numeral 5 is a phosphoric acid type fuel cell that obtains a direct current from hydrogen in the reformed gas and air as an oxidizing gas. Reference numeral 6 supplies a steam to the reformer 1, and at the same time, the fuel cell 5 and the CO shift converter 4 are provided. A steam separator for obtaining pressurized water for cooling the fuel cell, a pump 7 for circulating cooling water for cooling the fuel cell 5 and the CO shifter 4, a desulfurizer for removing sulfur contained in the fuel, and a fuel cell 9 It is a quadrature conversion device that converts the direct current generated by No. 5 into alternating current power.
Reference numeral 10 is a high-level heat recovery device for recovering heat from the steam taken out from the steam separator, and the condensed water is returned to the system. Reference numeral 11 is a water treatment device for city water and condensed water.

Next, the operation will be described. The reformer 1 is
A reformed gas, which is a hydrogen-rich gas, is produced by using hydrocarbons such as LNG and steam supplied from the steam separator 6 as raw materials. This reformed gas contains a considerable amount of CO, and this CO becomes a catalyst poison to the fuel cell 5. Therefore, it is necessary to lower the CO concentration (for example, about 1% or less),
The CO transformer 4 is used. The reaction in the CO converter 4

CO + H ₂ O → CO ₂ + H ₂ --- Equation 1

It is an exothermic reaction represented by, and has the effect of lowering the CO concentration and simultaneously producing hydrogen. The reformed gas is the low temperature CO shift catalyst in the CO shift converter 4 by the heat exchangers 2 and 3.
After the temperature is lowered to an operating temperature (not shown) (170 ° C. to 280 ° C.), the CO converter 4 is introduced. The reformed gas inlet of the CO shifter 4 is connected to the outlet of the fuel gas preheater 3, and the reformed gas outlet of the CO shifter 4 is connected to the inlet of the fuel electrode 5a of the fuel cell 5. The inlet of the cooling water of the CO shift converter 4 is connected to the pump 7, and the outlet thereof is connected to the steam part (upper part) of the steam separator 6. The pressurized water circulated by the pump 7 from the pressurized water portion 6a of the steam separator 6 is introduced into the CO shift converter 4, the heat generated by the catalyst is removed, and then introduced into the steam separator 6. The reaction on the low-temperature CO shift catalyst hardly occurs when the temperature is too low (160 ° C. or lower), and when the temperature is too high, the equilibrium of Formula 1 is biased to the left, so the CO concentration is lowered too much. Absent. Therefore C
In order to reduce the O concentration to about 1% or less, the catalyst temperature near the outlet of the CO shift converter 4 should be set to about 200 ° C. or less.

The reaction heat of the fuel cell 5 is removed by the pressurized water from the steam separator 6 and introduced into the steam separator 6. A part of these heats is used to generate the steam supplied to the reformer from the pressurized water. The remaining heat is taken out as a steam and is recovered by the high-level heat recovery device 10.
Here, the steam is condensed and water is returned to the system at about 90 ° C. Since the pressurized water of the steam separator 6 has a role as a cooling water for the fuel cell and a steam supply source to the reformer,
The temperature is kept at about 165 to 180 ° C. The city water and the condensed water are supplied to the water vapor separator as pure water from which impurities have been removed by the water treatment device 11.

[0007]

Since the conventional phosphoric acid fuel cell power generator is constructed as described above, as a CO shifter, the supply temperature of the cooling water is the same as the saturated water temperature of the steam separator. Since it is the same, it is always constant, usually 16
It is in the range of 5 to 180 ° C. The catalyst near the inlet of the CO shift converter 4 has a large amount of heat generated by the reaction, and the temperature is 200 ° C to 2 ° C.
Since the temperature is about 80 ° C., the temperature difference with the cooling water is large and the cooling is sufficiently performed, but the catalyst near the outlet of the CO shift converter 4 is
When it is desired to lower the CO concentration at the outlet of the O-transformer 4, it is necessary to lower the reaction temperature to about 160 to 200 ° C. as described above. At this cooling water temperature, the temperature difference between the cooling water and the catalyst is small, so cooling There is a problem that the capacity is small and the CO concentration in the reformed gas at the outlet of the CO transformer does not become low, or the size of the CO transformer 4 becomes large in order to take a sufficient heat transfer area to compensate for it. .

The present invention has been made to solve the above problems, and an object thereof is to obtain a fuel cell power generator in which the CO transformer is miniaturized.

[0009]

A phosphoric acid fuel cell power generator according to a first aspect of the present invention is provided with water obtained by a steam separator and condensed water obtained from gas discharged from a fuel cell. It is configured so as to have a cooling system for the CO transformer used.

The fuel cell power generator according to the second aspect of the present invention is configured to have a cooling system for the CO shifter by the water obtained by the steam separator and the water recovered from the high-level heat recovery device.

A fuel cell power generator according to a third invention is C
The control device controls the temperature of the cooling system in the vicinity of the outlet of the O-transformer or in the CO-transformer depending on the catalyst temperature.

A fuel cell power generator according to a fourth invention is C
A CO sensor is provided near the outlet of the O-transformer, and a control device for controlling the temperature of the cooling system according to the output of the CO sensor is provided.

[0013]

In the cooling system of the first aspect of the present invention, the water introduced from the steam separator and the condensed water of a desired low temperature level obtained from the exhaust gas of the fuel cell are used in combination to reduce CO
Cool the transformer efficiently with heat exchange.

In the cooling system in the second aspect of the present invention, the water introduced from the steam separator and the condensed water introduced from the high-order heat recovery device whose temperature has been lowered to a desired level are used together to reduce CO Cool the transformer efficiently with heat exchange.

The control device according to the third aspect of the present invention controls the temperature of the cooling water of the CO shifter according to the temperature of the reformed gas near the CO shifter outlet or the temperature of the catalyst in the CO shifter. The CO concentration in the reformed gas at the CO shifter outlet is reduced.

The control device in the fourth aspect of the present invention controls the temperature of the cooling water of the CO shifter according to the concentration of CO in the reformed gas at the CO shifter outlet, whereby the reformed gas at the CO shifter outlet is controlled. Reduce the CO concentration in the inside.

[0017]

【Example】

Example 1. FIG. 1 is a system diagram schematically showing a fuel cell power generator according to an embodiment of the first invention. In the figure, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 are
The description is omitted because it is the same as the above-mentioned conventional device. 1
Reference numeral 2 denotes a cooling system of the CO transformer 4, and a pipe line 12 connected to an inlet 4a of cooling water of the CO transformer 4 and an outlet 7a of the pump 7.
a, a pipeline 12b connecting the water treatment device 11 and the inlet 4a
Condensed water 5 of the exhaust gas of the fuel cell 5
1, 52, and low temperature water such as city water 14 are introduced.

Next, the operation will be described. CO transformer 4
The cooling water of the cooling system 12 is a mixed fluid of the pressurized water from the steam separator 6 and the feed water from the water treatment device 11.
The water supplied from the water treatment device 11 consists of condensed water 51, 52 and city water 14, and if the temperature of the exhaust gas from the plant is cooled to about 50 ° C. and the condensed water 51, 52 is sufficiently recovered, Supply is almost unnecessary. The city water and the condensed water are preheated up to about 90 ° C. in the water treatment device 11 in order to perform deaeration (mainly carbon dioxide). Since the pressurized water from the steam separator 6 is 165 to 180 ° C., if the flow rate of the pressurized water from the steam separator 6 is constant, the CO shifter 4 increases as the amount of the city water 14 and the condensed water 51, 52 to be mixed increases. The temperature of the cooling water becomes low. Since the amounts of city water and condensed water supplied are almost proportional to the load, the higher the load, the lower the temperature of the CO transformer cooling water. In addition, the amount of heat generated by the reaction in the CO converter is almost proportional to the load,
Although the catalyst temperature and the like increase, the higher the load, the lower the temperature of the cooling water supplied to the CO shift converter 4, which is effective for cooling.

By thus improving the heat exchange in the CO shift converter 4, the catalyst temperature can be kept at an appropriate temperature to reduce the CO concentration in the reformed gas at the outlet of the CO shift converter, and at the same time, the CO shift can be performed. It is possible to downsize the container 4. In addition, using city water and condensed water necessary for continuous operation of the plant, CO
Since the temperature of the transformer cooling water is lowered, there is no decrease in thermal efficiency, unlike when supplying new water for cooling.

Example 2. FIG. 2 is a system diagram showing a fuel cell power generator according to an embodiment of the second invention. In FIG. 2, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
Is the same as the conventional device described above. Reference numeral 12 denotes a cooling system, which is composed of a conduit 12a connected to the inlet 4a of the cooling water of the CO shift converter 4 and an outlet 7a of the pump 7, a conduit 12c connected to the high-level heat recovery device 10, and the like. .

Next, the operation will be described. CO transformer 4
The cooling water of the cooling system 12 is a mixed fluid of the pressurized water from the steam separator 6 and the feed water from the high-level heat recovery device 10. The water supplied from the high-level heat recovery device 10 is composed of water obtained by condensing the excess steam of the steam separator 6, and is usually about 90 ° C. On the other hand, the pressurized water from the steam separator 6 is 165
Since the temperature is up to 180 ° C., if the flow rate of the pressurized water from the steam separator 6 is constant, the temperature of the cooling water for the CO shift converter 6 becomes lower as the amount of the recovered water from the high-order heat recovery device 10 to be mixed increases. . Since the water recovered from the high-order heat recovery device 10 is almost proportional to the load, the higher the load, the lower the temperature of the CO shift converter 4. Also, the amount of heat generated by the reaction in the CO shift converter 4 is almost proportional to the load, so that the catalyst temperature and the like increase, but the higher the load, the lower the temperature of the cooling water supplied to the CO shift converter 4 is, which is effective for cooling. Target.

As described above, by improving the heat exchange in the CO shift converter 4 to keep the catalyst temperature at an appropriate temperature, the CO concentration in the reformed gas at the outlet of the CO shift converter 4 can be reduced, and The CO transformer 4 can be miniaturized. Further, since the temperature of the CO shifter 4 cooling water is lowered by using the water recovered from the high-level heat recovery device 10, there is no decrease in thermal efficiency, unlike the case where new water is supplied for cooling.

Example 3. FIG. 3 is a system diagram showing a fuel cell power generator according to an embodiment of the third invention. In FIG. 3, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 are the same as the above-described conventional device. Reference numeral 13 is a temperature sensor provided in the vicinity of the outlet of the CO shift converter 4, 14 is a flow rate control valve provided in the line of the water supplied from the water treatment device 11 to the CO shift converter 4, and 15 is a high-level heat recovery device. 10 to CO
It is a flow rate control valve provided in the middle of the line of the supply water to the transformer 4. The inlet 4a of the cooling water of the CO shift converter 4 is connected not only to the outlet of the pump 7, but also to the high-level heat recovery device 10 and the water treatment device 11. Reference numeral 16 is a control device that controls the opening degrees of the control valves 14 and 15 according to the output of the temperature sensor 13.

Next, the operation will be described. CO transformer 4
In addition to the pressurized water from the steam separator 6, the supply water from the water treatment device 11 and the supply water from the high-level heat recovery device 10 are mixed and used as the cooling water for the above. The amount of water supplied from the water treatment device 11 and the amount of water supplied from the high-level heat recovery device 10 are controlled by the control valve 1
It can be adjusted by 4, 15. The portion not used as cooling water for the CO shift converter 4 is directly sent to the steam separator 6. Supply water from the water treatment device 11 and the high-level heat recovery device 10
The supplied water from the steam separator 6 is about 90 ° C., but the pressurized water from the steam separator 6 is 165 to 180 ° C. Therefore, if the flow rate of the pressurized water from the steam separator 6 is constant, the water treatment device 11
As the amount of water supplied from the CO 2 and the amount of water supplied from the high-level heat recovery device 10 increase, the temperature of the CO shift converter 4 decreases. CO transformer 4
The operating temperature of the catalyst is 160 to 280 ° C. When the reaction temperature is high, the CO concentration cannot be lowered so much. On the contrary, if the reaction temperature is too low, the reaction does not proceed unless the catalyst operating temperature is reached. Therefore, it is important to set the catalyst temperature at least near the outlet of the CO shift converter 4 to 160 to 200 ° C. in order to reduce the CO concentration. The cooling water temperature must not be too low or too high to keep the catalyst temperature in a certain range.

As described in the operation of the embodiments of the first and second aspects of the invention, the cooling water temperature can be lowered by increasing the amount of low-temperature supply water as the load increases, but the load changes rapidly. At times such as water treatment equipment 11 and high-level heat recovery equipment 1
Although there is a case where the temperature of the cooling water of the CO shifter 4 does not match the load due to a delay of water from 0, etc., in this embodiment, the temperature sensor 13 indicates the temperature of the reformed gas near the outlet of the CO shifter 4. When the reformed gas temperature is detected and the reformed gas temperature is higher than a predetermined level, the control device 16 controls so that the opening of the control valve 14 and / or the control valve 15 is large, and when the temperature is low, the opening is small. Adjust the amount of low-temperature water supply to C
The temperature of the cooling water of the O-transformer 4 was changed so that optimum heat exchange in the CO-transformer could be performed.

By thus improving the heat exchange in the CO shift converter 4 and keeping the catalyst temperature at an appropriate temperature, the CO concentration in the reformed gas at the outlet of the CO shift converter can be reduced and the CO shift ratio of the CO shift converter can be reduced. Miniaturization is possible. In this embodiment, the control valve is attached to both the water supply line from the water treatment device 11 and the water supply line from the high-level heat recovery device 10, but only one of the control valves may be installed. Of course. Further, in this embodiment, the mixed water amount is changed depending on the reformed gas temperature near the outlet of the CO shift converter 4, but the same effect can be obtained by using the catalyst temperature in the CO shift converter 4 instead of the reformed gas temperature. .

Example 4. FIG. 4 is a system diagram showing a fuel cell power generator according to an embodiment of the fourth invention. In FIG. 4, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 are the same as the above-described conventional device. Reference numeral 17 denotes a CO sensor provided near the outlet of the CO shift converter 4, and reference numeral 18 denotes a control device that adjusts the opening degree of the flow rate adjusting valve 14 or 15 according to the output of the CO sensor 17. The inlet 4a of the cooling water of the CO shifter is connected not only to the outlet of the pump 7, but also to the high-level heat recovery device 10 and the water treatment device 11.

Next, the operation will be described. CO sensor 1
Numeral 7 monitors the CO concentration in the reformed gas at the outlet 4a of the CO shift converter 4, and according to the degree of deviation from the set level,
Flow control valve 14 and / or 1 in the direction of decreasing CO concentration
By adjusting 5, the amount of low temperature water supply can be adjusted to
O Change the temperature of the transformer cooling water. By changing the cooling water temperature, the heat exchange in the CO shift converter 4 is optimized, and by keeping the catalyst temperature at an appropriate temperature, the CO concentration in the reformed gas at the CO shift outlet can be reduced and the CO concentration can be reduced. The transformer can be miniaturized. Other operations are the same as those of the third invention. In this embodiment, the control valve is provided on both the feed water line from the water treatment device and the feed water line from the high-level heat recovery device, but it is the same as the third invention that the control valve may be installed on only one side. Is. The CO sensor 17 is C
It is not limited to the one that detects the O concentration, but may be one that detects the CO partial pressure, for example. Further, the flow rate adjusting valves 14 and 15 can be controlled by the sensor for detecting the catalyst temperature or the gas temperature in the CO shift converter 4 and the gas temperature at the outlet and the output of the CO sensor 17.

The city water used in each of the above-mentioned embodiments is preferably a public water supply, but it is not limited to this, and it goes without saying that a private water supply or the like may be used.

[0030]

As described above, according to the first aspect of the present invention, the CO transformer using the water obtained by the steam separator and the condensed water obtained from the gas discharged from the fuel cell is used. Since the cooling system is provided, the concentration of CO in the reformed gas at the outlet of the CO shifter is reduced, and the phosphoric acid fuel cell power generation device having a smaller CO shifter can be obtained.

According to the second aspect of the invention, the water obtained by the steam separator and the water recovered from the high-level heat recovery device are used to remove C
By being configured to have a cooling system for the O-transformer,
It has the same effect as the first invention.

According to the third aspect of the invention, the control device for controlling the temperature of the cooling system in the vicinity of the outlet of the CO shifter or the temperature of the catalyst in the CO shifter is provided. Has the same effect as.

Further, according to the fourth aspect of the invention, the CO sensor is provided in the vicinity of the outlet of the CO transformer, and the control device for controlling the temperature of the cooling system according to the output thereof is provided. The same effect as the invention of.

[Brief description of drawings]

FIG. 1 is a system diagram of a phosphoric acid fuel cell power generator according to an embodiment of the first invention.

FIG. 2 is a system diagram of a phosphoric acid fuel cell power generator according to an embodiment of the second invention.

FIG. 3 is a system diagram of a phosphoric acid fuel cell power generator according to an embodiment of the third invention.

FIG. 4 is a system diagram of a phosphoric acid fuel cell power generator according to an embodiment of the fourth invention.

FIG. 5 is a system diagram of a conventional phosphoric acid fuel cell power generator.

[Explanation of symbols]

 1 reformer 4 CO shifter 5 phosphoric acid type fuel cell 6 steam separator 10 high-level heat recovery device 12 cooling system 13 temperature sensor 16 controller 17 CO sensor 18 controller

Claims (4)

[Claims] 1. A CO shifter for reacting carbon monoxide in the reformed gas obtained by the reformer with H ₂ O, and the reformed gas and the oxidizing gas that have passed through the CO shifter are caused to act to generate electric power. Fuel cell to be obtained, steam separator for obtaining pressurized water for cooling the fuel cell and steam required for the reformer, condenser for obtaining condensed water from gas discharged from the fuel cell, steam separator A phosphoric acid fuel cell power generator comprising a cooling system for cooling the CO shifter using the water obtained by the above and the condensed water obtained by the condenser. 2. A CO shifter for reacting carbon monoxide in the reformed gas obtained by the reformer with H ₂ O, and the reformed gas and the oxidizing gas that have passed through the CO shifter are caused to act to generate electric power. A fuel cell to be obtained, a steam separator for obtaining pressurized water for cooling the fuel cell and for obtaining steam necessary for the reformer, a high-level heat recovery device connected to the steam separator to obtain condensed water from excess steam, A phosphoric acid fuel cell power generator comprising a cooling system for cooling the CO shifter by using the pressurized water obtained by the steam separator and the condensed water recovered by the high-level heat recovery device. 3. A CO shifter for reacting carbon monoxide in the reformed gas obtained by the reformer with H ₂ O, and the reformed gas and the oxidizing gas that have passed through the CO shifter act to generate electric power. A fuel cell to be obtained, a steam separator for obtaining pressurized water for cooling the fuel cell and steam required for the reformer, and the CO shift converter is cooled by the pressurized water and low temperature water obtained from the steam separator. A phosphoric acid fuel cell power generator comprising a cooling system, a control device for changing the temperature of the reforming gas near the outlet of the CO shift converter, or the temperature of the cooling system used in the cooling system according to the CO shift catalyst temperature. 4. A CO shifter for reacting carbon monoxide in the reformed gas obtained by the reformer with H ₂ O, and the reformed gas and the oxidizing gas that have passed through the CO shifter are caused to act to generate electric power. A fuel cell to be obtained, a steam separator for obtaining pressurized water for cooling the fuel cell and steam required for the reformer, and the CO shift converter is cooled by the pressurized water and low temperature water obtained from the steam separator. A cooling system, a CO sensor provided in the flow path of the reformed gas passing through the CO converter,
A phosphoric acid fuel cell power generator including a control device that changes the temperature of the cooling system according to the output of a sensor.