JP2809561B2 - Phosphoric acid fuel cell power generator - Google Patents

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 type fuel cell power generator disclosed in Japanese Patent Application Laid-Open No. 1-265461, for example. In FIG. 1, reference numeral 1 denotes a reformer for reacting fuel with steam to obtain hydrogen, and reference numerals 2 and 3 denote heat exchange between the fuel reformed by the reformer 1 (hereinafter referred to as reformed gas) and the fuel. And a heat exchanger 4 for preheating the fuel, a CO converter 4 for converting carbon monoxide contained in the reformed gas reformed by the reformer 1 into hydrogen, and the CO reformer 4 It is water-cooled to remove water. Reference numeral 5 denotes a phosphoric acid type fuel cell that obtains a direct current from hydrogen in the reformed gas and air as an oxidizing gas, and 6 supplies a steam to the reformer 1 and a fuel cell 5 and a CO converter 4. , A pump for circulating cooling water for cooling the fuel cell 5 and the CO converter 4, 8 a desulfurizer for removing sulfur contained in the fuel, 9 a fuel cell 5 is a quadrature conversion device that converts the direct current generated by 5 into AC power.
Reference numeral 10 denotes a high-level heat recovery device for recovering heat from the steam taken out of the steam separator, and condensed water is returned to the system. 11 is a water treatment device for city water and condensed water.

Next, the operation will be described. The reformer 1
A reformed gas, which is a hydrogen-rich gas, is produced 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),
A CO transformer 4 is used. The reaction in the CO converter 4

[0004] CO + H ₂ O → CO ₂ + H ₂

This is an exothermic reaction represented by the following formula, and has the effect of producing hydrogen at the same time as lowering the CO concentration. The reformed gas is converted into a low-temperature CO conversion catalyst in the CO converter 4 by the heat exchangers 2 and 3.
After the temperature is lowered to the operating temperature (170 ° C. to 280 ° C.) (not shown), it is introduced into the CO transformer 4. The reformed gas inlet of the CO converter 4 is connected to the outlet of the fuel gas preheater 3, and the reformed gas outlet of the CO converter 4 is connected to the fuel electrode 5 a of the fuel cell 5. The inlet of the cooling water of the CO converter 4 is connected to the pump 7, and the outlet is connected to the steam (upper) of the steam separator 6. The pressurized water circulated by the pump 7 from the pressurized water section 6a of the steam separator 6 is introduced into the CO converter 4, where the heat generated by the catalyst is removed and introduced into the steam separator 6. In the reaction on the low-temperature CO conversion catalyst, if the temperature is too low (160 ° C. or less), almost no reaction occurs, and if the temperature is too high, the equilibrium of the formula 1 is biased to the left, so that the CO concentration decreases too much. Absent. Therefore C
In order to reduce the O concentration to about 1% or less, it is preferable to set the catalyst temperature near the outlet of the CO converter 4 to about 200 ° C. or less.

The heat of reaction of the fuel cell 5 is removed by pressurized water from the steam separator 6 and is introduced into the steam separator 6. Some of this heat is used to generate steam to be supplied to the reformer from the pressurized water. The remaining heat is taken out as steam and recovered by the high-order 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 steam supply source to the cooling water for the fuel cell and the reformer,
The temperature is maintained at about 165 to 180 ° C. The city water and the condensed water are supplied to the steam separator as pure water from which impurities are removed by the water treatment device 11.

[0007]

Since the conventional phosphoric acid type fuel cell power generator is configured as described above, the supply temperature of the cooling water for the CO converter is equal to the temperature of the saturated water of the steam separator. Since they are the same, they are always constant, usually 16
It is in the range of 5-180 ° C. The catalyst near the inlet of the CO converter 4 generates a large amount of heat due to the reaction, and has a temperature of 200 ° C to 2 ° C.
Since the temperature is about 80 ° C., the temperature difference from the cooling water is large and the cooling water is sufficiently cooled.
If 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. There is a problem that the capacity is small and the CO concentration in the reformed gas at the outlet of the CO converter does not become low, or the size of the CO converter 4 becomes large in order to take a sufficient heat transfer area to make up for it. .

The present invention has been made in order to solve the above problems, and has as its object to obtain a fuel cell power generator in which a CO transformer is downsized.

[0009]

According to a first aspect of the present invention, there is provided a phosphoric acid-type fuel cell power generation apparatus which converts water obtained by a steam separator and condensed water obtained from gas discharged from a fuel cell. The cooling system of the CO transformer which cools the CO transformer by using is provided.

[0010] A phosphoric acid type fuel cell power generator according to claim 2 of the present invention is a CO transformer that cools a CO transformer using water obtained by a steam separator and water recovered from a high-level heat recovery device. It has.

[0011]

The cooling system according to the first aspect of the present invention uses water guided from the steam separator and condensed water at a desired low temperature level obtained from the exhaust gas of the fuel cell in combination.
The CO transformer is cooled with good heat exchange efficiency.

[0012] The cooling system according to the second aspect of the present invention uses the water guided from the steam separator and the condensed water whose temperature guided from the high-order heat recovery unit is reduced to a desired level. The CO transformer is cooled with good heat exchange efficiency.

[0013]

[Embodiment 1] FIG. 1 is a system diagram schematically showing a fuel cell power generator according to one embodiment of the present invention. In the figure, 1, 2,
3, 4, 5, 6, 7, 8, 9, 10, and 11 are the same as those of the above-described conventional device, and thus description thereof is omitted. 12 is CO
It is a cooling system of the transformer 4 and includes a pipe 12a connected to the cooling water inlet 4a of the CO transformer 4 and the outlet 7a of the pump 7, a pipe 12b connecting the water treatment device 11 to the inlet 4a, and the like. The condensed water 51 and 52 of the condenser obtained from the exhaust gas of the fuel cell 5 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 supply water from the water treatment device 11.
The water supplied from the water treatment device 11 is composed of the condensed waters 51 and 52 and the city water 14. If the temperature of the exhaust gas from the plant is cooled to about 50 ° C. and the condensed waters 51 and 52 are sufficiently collected, the city water 14 Supply is almost unnecessary. The city water and the condensed water are preliminarily heated to about 90 ° C. in the water treatment device 11 in order to perform degassing (mainly carbon dioxide). Since the pressure of 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 larger the amount of the city water 14 and the condensed water 51 and 52 to be mixed, the larger the CO converter 4 The temperature of the cooling water decreases. Since the amount of supplied city water and condensed water is almost proportional to the load, the higher the load, the lower the temperature of the CO transformer cooling water. Also, since the calorific value of the reaction in the CO converter is almost proportional to the load,
Although the catalyst temperature and the like increase, it is effective for cooling that the temperature of the cooling water supplied to the CO converter 4 decreases as the load increases.

By improving the heat exchange in the CO converter 4 in this manner, the catalyst temperature can be maintained at an appropriate temperature, so that the CO concentration in the reformed gas at the outlet of the CO converter can be reduced. The size of the vessel 4 can be reduced. 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 the case where new water is supplied for cooling.

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

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 supply water from the high-order heat recovery device 10. The supply water from the high-order 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
If the flow rate of the pressurized water from the steam separator 6 is constant, the temperature of the cooling water of the CO converter 6 decreases as the amount of the recovered water from the high-level heat recovery device 10 increases, since the temperature is about 180 ° C. . Since the recovered water from the high-level heat recovery device 10 is almost proportional to the load, the higher the load, the lower the temperature of the CO converter 4. The amount of heat generated by the reaction in the CO converter 4 is almost proportional to the load, so that the catalyst temperature and the like increase. However, the higher the load, the lower the temperature of the cooling water supplied to the CO converter 4 is. It is a target.

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

Reference Example 1 FIG. 3 is a system diagram showing a fuel cell power generator according to Embodiment 1 of the present invention. In FIG. 3, 1, 2, 3, 4, 5,
Reference numerals 6, 7, 8, 9, 10, and 11 are the same as those of the conventional device described above. 13 is a temperature sensor provided near the outlet of the CO converter 4, 14 is a flow control valve provided in the middle of a line of water supplied from the water treatment device 11 to the CO converter 4, 15
Is a flow control valve provided in the middle of the line of the supply water from the high-order heat recovery device 10 to the CO converter 4. The inlet 4a of the cooling water of the CO converter 4 is not only connected to the outlet of the pump 7, but also the high-order heat recovery unit 10 and the water treatment unit 1.
1 is also connected. Reference numeral 16 denotes a control device that controls the opening 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-order heat recovery device 10 are used as the cooling water. 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.
Adjustment is possible by 4 and 15. The portion not used as cooling water for the CO converter 4 is sent directly to the steam separator 6. Water supplied from water treatment device 11 and high-level heat recovery device 10
Is about 90 ° C., but the pressure of 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 apparatus 11
The temperature of the CO converter 4 decreases as the amount of water supplied from the high-temperature heat recovery device 10 increases. CO transformer 4
The operating temperature of the catalyst is 160 to 280 ° C., and if the reaction temperature is high, the CO concentration cannot be too low. Conversely, if the reaction temperature is too low, the reaction does not proceed unless the catalyst operation temperature is reached. Therefore, it is important to set the catalyst temperature at least in the vicinity of the outlet of the CO converter 4 to 160 to 200 ° C. in order to lower 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 first and second embodiments of the present invention, the cooling water temperature can be lowered by increasing the low-temperature supply water amount as the load becomes higher, When the load fluctuates, there is a case where the temperature of the cooling water of the CO transformer 4 does not match the load due to a delay of water from the water treatment device 11 or the high-level heat recovery device 10, and the like. The temperature sensor 13 detects the temperature of the reformed gas near the outlet of the vessel 4, and when the temperature of the reformed gas is higher than a predetermined level, the control valve 14 and / or the control valve 1
The control unit 16 controls the opening degree of the CO 5 to be large and the opening degree to be small when the opening degree is low.
Heat exchange in the transformer was enabled.

As described above, by improving the heat exchange in the CO converter 4 to maintain the catalyst temperature at an appropriate temperature, the CO concentration in the reformed gas at the outlet of the CO converter can be reduced, and the CO converter The size can be reduced. Note that, in this reference example, an example is shown in which both the supply water line from the water treatment device 11 and the supply water line from the high-level heat recovery device 10 are provided with control valves, but the control valve may be installed on only one side. Of course. Further, in this reference example, the mixed water amount was changed depending on the reformed gas temperature near the outlet of the CO converter 4, but the same effect can be obtained by using the catalyst temperature in the CO converter 4 instead of the reformed gas temperature. .

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

Next, the operation will be described. CO sensor 1
7 monitors the CO concentration in the reformed gas at the outlet 4a of the CO converter 4 and, depending on the degree of deviation from the set level,
The flow control valve 14 and / or 1
5 to adjust the amount of low-temperature supply water,
Change the temperature of the O transformer cooling water. By changing the temperature of the cooling water, the heat exchange in the CO converter 4 is optimized, and by keeping the catalyst temperature at an appropriate temperature, the CO concentration in the reformed gas at the outlet of the CO converter can be reduced, and the CO The transformer can be downsized. Other operations are the same as in the first embodiment. In this reference example, the control valve is provided on both the supply water line from the water treatment device and the supply water line from the high-level heat recovery device. However, it is the same as in reference example 2 that only one of the control valves may be installed. is there. Note that the CO sensor 17
It is not limited to the one that detects the concentration, but may be one that detects the partial pressure of CO, for example. In addition, a sensor for detecting the catalyst temperature or the gas temperature in the CO converter 4 and the gas temperature at the outlet portion, and the output of the CO sensor 17 allow the flow control valve 1
4 and 15 can also be controlled.

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

[0026]

As described above, according to the first aspect of the present invention, C is obtained by using water obtained by the steam separator and condensed water obtained from gas discharged from the fuel cell.
By providing a cooling system for cooling the O-transformer, the concentration of CO in the reformed gas at the outlet of the CO-transformer is reduced, and a phosphoric acid-type fuel cell power generation device with a reduced size of the CO-transformer is obtained. Unlike supplying fresh water for
There is no decrease in thermal efficiency.

According to the second aspect of the present invention, the cooling system for cooling the CO converter by using the water obtained by the steam separator and the recovered water from the high-level heat recovery device is provided.
There is an effect similar to that of the first aspect.

[Brief description of the drawings]

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

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

FIG. 3 is a system diagram of a phosphoric acid fuel cell power generator according to Reference Example 1.

FIG. 4 is a system diagram of a phosphoric acid fuel cell power generator according to Reference Example 2.

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

[Explanation of symbols]

1 reformer, 4 CO shift converter, 5 phosphoric acid type fuel cell, 6 steam separator, 10 high-order heat recovery unit, 12
Cooling system, 13 temperature sensor, 16 controller, 17 C
O sensor, 18 control unit.

Claims (2)

(57) [Claims] 1. A CO converter for reacting carbon monoxide in a reformed gas obtained by a reformer with H ₂ O. An electric power is generated by allowing the reformed gas and the oxidizing gas passing through the CO converter to act. Fuel cell, water separator for obtaining water for cooling the fuel cell, and water vapor required for the reformer, condenser for obtaining condensed water from gas discharged from the fuel cell, and water vapor separator A phosphoric acid fuel cell power generator comprising a cooling system that cools the CO converter using the water obtained by the method and the condensed water obtained by the condenser. 2. A CO converter for reacting carbon monoxide in the reformed gas obtained by the reformer with H ₂ O, and reacting the reformed gas and the oxidizing gas passed through the CO converter to generate electric power. A fuel cell to obtain, a steam separator to obtain pressurized water for cooling the fuel cell and obtain steam required 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 converter using the water obtained by the steam separator and the condensed water recovered by a high-level heat recovery device.