JP2003272689A - Fuel cell system - Google Patents

Abstract

(57) [Summary] An efficient output is obtained by avoiding condensation of water in a CO remover. A CO remover (5) for removing carbon monoxide in a reformed gas generated by a reforming reactor (4) by a selective oxidation catalyst, and a moisture in the reformed gas installed upstream of the CO remover (5). Remover 6 for condensing and removing water, and moisture remover 6 and C
A pressure regulating valve 40 installed between the O remover 5, a reforming cooling system 35 for cooling the moisture remover 6 and the CO remover 5 with a refrigerant, and a moisture remover using the pressure regulator 40. Control means for controlling the pressure inside the water remover 6 and controlling the amount of water condensed in the water remover 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system, and more particularly to means for preventing water condensation in a CO remover.

[0002]

2. Description of the Related Art As a fuel cell system having a conventional reformer, Japanese Patent Laid-Open No. 8-106913 has been proposed. The fuel cell system according to the present invention includes a water remover upstream of a CO remover for removing carbon monoxide that causes deterioration of a platinum catalyst or the like filled in the fuel cell,
After removing excess water in the reformed gas discharged from the reforming means installed in the reforming reactor with a moisture remover, carbon monoxide is removed with a CO remover, and the reformed gas is humidified again. Supply to the fuel cell.

Here, in order to remove the excess moisture in the reformed gas in the moisture remover, a method of cooling the reformed gas and condensing the excess moisture is adopted. In addition, heat exchange type CO
Even when carbon monoxide in the reformed gas is removed by the selective oxidation catalyst in the remover, the reformed gas is cooled at the same time because the catalyst is cooled to maintain the activation temperature. JP-A-8-1
In 06913, cooling of the reformed gas supplied to the moisture remover and the catalyst filled in the CO remover is performed using a single cooling water circulation system.

The reformed gas discharged from the shift conversion means flowing into the moisture remover contains a large amount of surplus steam, but CO
Before being introduced into the eliminator, excess water vapor is condensed and recovered by passing through the moisture eliminator, which wets the surface of the selective oxidation catalyst used in the CO eliminator to cause clogging and gas on the active surface. Prevents from blocking contact.

[0005]

[Problems to be solved by the invention] However,
In such a fuel cell system, since the pressure adjustment of the reformed gas in the moisture remover and the CO remover is performed by adjusting the operating pressure of the fuel cell, there are the following problems.

First, since the reforming gas pressures in the moisture remover and the CO remover are almost the same, the moisture remover and the heat exchange type
When the CO remover is cooled by one system of cooling medium, there is a problem that water condensation occurs in the CO remover. If the moisture eliminator has sufficient capacity and the temperature of the reformed gas is not lowered to reduce the amount of water vapor until the temperature difference between the cooling medium and the reformed gas is almost eliminated, the temperature of the reformed gas is further reduced in the CO eliminator. As a result, the selective oxidation catalyst is clogged in the CO remover due to the condensation of water vapor, and the selective oxidation reaction of carbon monoxide is hindered.

Further, since the amount of water flowing into the CO remover is controlled by the flow rate of the cooling water flowing into the water remover, there is a response time corresponding to the time required for circulating the cooling water and the heat capacity of the water remover itself. On the other hand, when the fuel cell system is used as a power source for a system such as a vehicle in which the load changes frequently, the pressure in the fuel cell system changes rapidly.
Therefore, there is a problem in that the response time of the conventional water removing device causes a response delay and the water is condensed in the CO remover.

Further, in the polymer electrolyte fuel cell, since the fuel cell is operated at a lower temperature than each reforming element including the CO remover, in order to obtain a sufficient cooling amount of the fuel cell, There is a problem that it is necessary to increase the size of the cooling device for the cooling medium for cooling the fuel cell to secure a sufficient amount of heat radiation.

Therefore, an object of the present invention is to provide a fuel cell system capable of avoiding the condensation of water in a CO remover, sufficiently cooling the fuel cell, and obtaining an output efficiently.

[0010]

[Means for Solving the Problems] The first invention is a reforming fuel cell system for generating electric power by using the reformed gas produced by a reforming reaction in a fuel cell to produce reformed gas. CO for removing carbon monoxide in the reformer gas produced by the reactor and the reforming reactor by a selective oxidation catalyst
A remover and a water remover installed upstream of the CO remover for removing water by condensing the water in the reformed gas;
A pressure adjusting valve installed between the water removing device and the CO removing device, a reforming cooling system for cooling the water removing device and the CO removing device with a refrigerant, and the water content using the pressure adjusting valve. And a control means for controlling the amount of water condensed in the water remover by adjusting the pressure in the water remover.

In a second aspect based on the first aspect, the pressure inside the moisture remover is controlled based on the pressure and temperature of the CO remover.

In a third aspect based on the first aspect, the pressure and temperature in the moisture remover are controlled based on the pressure and temperature in the CO remover.

A fourth invention is the fuel cell system according to any one of the first to third inventions, wherein:
The amount of water in the reformed gas flowing into the CO remover is estimated from the amount of water supplied to the upstream side of the CO remover and the amount of air supplied to the reforming reactor according to the operating load. And a pressure in the water remover is controlled based on the estimation result by the model.

A fifth aspect of the invention is the fuel cell system according to any one of the first to fourth aspects of the invention, in which a detector for detecting water condensation is provided upstream of the CO remover, and the pressure of the water remover is detected by the detector. Control based on the result.

A sixth aspect of the present invention is the air supply device for power generation for supplying air to the fuel cell, and the reforming air for supplying air to the reforming reactor according to any one of the first to fifth aspects. And a supply device, and the reforming air supply device is of a small capacity and high pressure type with respect to the power generation air supply device.

A seventh aspect of the present invention is the fuel cell system according to any one of the first to sixth aspects, wherein water is supplied to the reformed gas after being discharged from the CO remover and before being used for power generation in the fuel cell. A water supply unit for cooling the fuel cell, and under operating conditions in which the heat release amount of the power generation cooling system is insufficient, the pressure of the water remover is increased to increase the amount of the reformed gas. By increasing the amount of condensed water, the amount of heat radiation of the reforming cooling system is increased to compensate for the insufficient amount of heat radiation in the power generation cooling system.

An eighth invention is the fuel cell system according to any one of the first to seventh inventions, wherein the pressure of the reforming gas in the fuel cell is controlled and then the pressure of the water remover is controlled.

[0018]

According to the first aspect of the invention, since the control means for controlling the amount of condensed water in the moisture remover by the pressure is provided, the amount of condensed water can be controlled with good response even when the operating conditions of the fuel cell are changed. By increasing and avoiding water condensation in the CO remover, clogging of the selective oxidation catalyst can be prevented.

According to the second aspect of the present invention, by adjusting the pressure inside the moisture remover based on the pressure and temperature of the CO remover, the pressure increase in the moisture remover is suppressed within the range where water does not condense in the CO remover. be able to.

According to the third aspect of the present invention, by adjusting the pressure and temperature of the water remover, it is possible to avoid the water condensation in the CO remover with good response by the pressure and adjust the temperature to adjust the temperature of the water remover. Since the pressure increase can be suppressed, it is possible to prevent the system efficiency from being lowered due to the pressure increase.

According to the fourth aspect of the present invention, since the pressure is adjusted according to the operating conditions of the fuel cell, the pressure adjustment is omitted under the condition that the amount of water contained in the reformed gas is small and water condensation does not originally occur. The efficiency can be improved.

According to the fifth aspect of the present invention, the provision of the means for detecting the condensation of water makes it possible to surely adjust the pressure of the water remover.

According to the sixth invention, since the reforming air supply device is of a small capacity and high pressure type with respect to the power generation air supply device, an increase in power of the air supply device can be suppressed small.

According to the seventh aspect of the present invention, by increasing the pressure of the moisture remover to increase the condensation amount of the moisture in the reformed gas, the heat radiation amount of the reforming cooling system is increased.
It is possible to compensate for the lack of heat radiation in the power generation cooling system.

According to the eighth aspect of the present invention, the pressure of the reformed gas in the fuel cell is first adjusted before controlling the pressure in the moisture remover, so that the fuel cell required for obtaining the required output is modified. The controllability is improved because it is possible to reliably realize the high gas operation pressure.

[0026]

FIG. 1 shows the configuration of a fuel cell system according to the first embodiment.

An appropriate amount of air is supplied to the oxygen electrode of the internal humidification type polymer electrolyte fuel cell 2 (hereinafter referred to as fuel cell 2) from a blower 7 which is an air supply device for power generation, while the fuel electrode is described later. A hydrogen-containing gas is supplied by the fuel reforming system, and hydrogen ions move between the electrodes to convert chemical energy into electric energy. At this time, the temperature of the fuel cell 2 is raised as thermal energy for the portion that cannot be converted into electric energy. Therefore, in order to perform efficient power generation, the fuel cell 2 is cooled by the refrigerant circulating in the fuel cell refrigerant passage 31. The flow rate and temperature of the refrigerant are adjusted by the fuel cell refrigerant pump 32 and the fuel cell cooling device 30 installed on the fuel cell refrigerant passage 31.

Exhaust gas from the fuel cell 2 is discharged into the exhaust air flow path 2
It is supplied to the combustor 1 through 0 and the exhaust hydrogen gas passage 21. On the exhaust air flow passage 20 and the exhaust hydrogen gas flow passage 21, pressure adjusting valves 41 and 42 for adjusting the pressure of each electrode of the fuel cell 2 and capacitors 22 and 23 are installed. The condensers 22 and 23 are connected to a water tank 10 that supplies water to a fuel reforming system, which will be described later, and collect water in the exhaust gas from the fuel cell 2 in the water tank 10 for use again in the fuel cell system. .

The exhaust gas supplied to the combustor 1 is
The combustion catalyst filled in the inside generates heat necessary for the fuel reforming system described later, and then is discharged to the outside of the fuel cell system.

Next, a fuel reforming system for producing a reformed gas containing hydrogen used in such a fuel cell system will be described.

The hydrocarbon fuel, such as methanol, held in the fuel tank 11 and the water held in the water tank 10 are respectively shifted by the fuel pump 12 and the water pump 13 to perform a reforming reaction and shift. It is supplied to the reforming reactor 4 equipped with a shift section for carrying out the reaction. In the reforming reactor 4, a reforming reaction and a shift reaction occur under the pressure applied by the compressor 8 which is a reforming air supply device, and a hydrogen-rich reformed gas is generated. The reformed gas thus generated contains carbon monoxide which causes deterioration of the platinum catalyst filled in the fuel cell 2. Therefore, in order to remove this, a CO remover 5 is installed downstream of the reforming reactor 4.

The CO remover 5 is composed of a selective oxidation catalyst layer and a heat exchanger for removing the heat of oxidation generated in the selective catalyst layer and maintaining the activation temperature of the catalyst. CO remover 5
The temperature inside is adjusted by the refrigerant circulating in the refrigerant passage 33 described later, and the reformed gas in the CO remover 5 is pressurized by the compressor 8.

Here, the reformed gas generated in the reforming reactor 4 contains a large amount of water vapor, and if this is directly supplied to the CO remover 5, the selective oxidation catalyst layer filled in the CO remover 5 will be described. May cause clogging due to excess steam.
If clogging due to condensation occurs, the area of the catalyst in contact with the reformed gas decreases, and the reaction may not be performed sufficiently.
In order to prevent this clogging, a water remover 6 is installed between the reforming reactor 4 and the CO remover 5.

The moisture remover 6 is composed of a heat exchanger for cooling the reformed gas with a refrigerant circulating in a refrigerant passage 33, which will be described later, and a steam separator for separating excess moisture in the reformed gas. The condensation amount of water in the reformed gas can be adjusted by the temperature and flow rate of the refrigerant flowing in the water remover 6.

The refrigerant for cooling the CO remover 5 and the water remover 6 is supplied through the one-system refrigerant flow path 33. A cooling device 35 and a pump 34 are provided on the coolant channel 33.
Is installed, and the refrigerant whose temperature and flow rate are adjusted is supplied to the water remover 6. The refrigerant condenses excess water in the water remover 6, cools the selective oxidation catalyst layer and the reformed gas in the CO remover 5, and is supplied to the cooling device 35 again.

In the fuel reforming system as described above, the temperature of the refrigerant supplied to the water remover 6 and the temperature of the CO remover 5 are almost the same, so that the reformed gas in the water remover 6 reaches the refrigerant temperature. If it has not decreased, the reformed gas is further cooled in the selective oxidation catalyst layer of the CO remover 5 to condense steam, and as a result, the catalyst may be clogged. Therefore, in the present embodiment, the pressure adjusting valve 40 is installed between the water remover 6 and the CO remover 5. This pressure regulating valve 4
By setting 0 to make the pressure of the water remover 6 higher than the pressure of the CO remover 5, condensation of water vapor in the CO remover 5 is avoided.

When adjusting the pressure of the reformed gas in the water remover 6, first, by the pressure adjusting valve 42 installed on the exhaust hydrogen gas passage 21 which is the exhaust gas passage from the fuel electrode of the fuel cell 2, The reformed gas pressure in the fuel cell 2 is adjusted to the reformed gas pressure required to obtain the required output. At the same time, the pressure adjusting valve 41 installed on the exhaust air flow path 20 is adjusted so that the air electrode of the fuel cell 2 has a pressure according to the operating conditions. After the reformed gas pressure in the fuel cell 2 reaches a predetermined pressure, the pressure of the reformed gas in the moisture remover 6 is adjusted by the pressure adjusting valve 40 installed downstream of the moisture remover 6 to reduce the amount of condensed water. adjust. In this way, the reformed gas pressure in the fuel cell 2 is controlled before controlling the pressure in the water remover 6, so that the reformed gas operating pressure of the fuel cell 2 required to obtain the required output can be ensured. It can be realized and the controllability can be improved.

Next, referring to FIGS. 2 and 3, by making the pressure of the moisture remover 6 higher than the pressure of the CO remover 5, C
The point that the condensation of water vapor in the O 2 remover can be avoided will be described. FIG. 2 and FIG. 3 show changes in pressure (total pressure and steam partial pressure) with respect to gas temperature in the conventional example and the present invention together with a saturated steam partial pressure curve.
2 and 3, the pressure of the CO remover 5 is Pco, the gas temperature flowing into the moisture remover 6 is Th, and the gas temperature after being cooled by the moisture remover 6, that is, CO
Let the temperature of the gas flowing into the remover 5 be Tr and the temperature of the gas in the CO remover be Tco. On the other hand, in FIG. 3, the pressure of the water remover 6 is set to Pr higher than Pco. Where Tr
The Tco is lower than that in the case where the temperature of the reformed gas does not drop to the refrigerant temperature inside the water remover, so that the refrigerant having the temperature Tr or less flows into the CO remover,
This is because the temperature of the reformed gas drops in a region where the reaction is not particularly active in the remover.

In FIG. 2, when a gas having a temperature Th and a steam partial pressure Pa flows into the moisture remover 6, it is cooled to a temperature Tr and the steam partial pressure is reduced to a saturated steam partial pressure Psr.
However, when the temperature further reaches the CO remover and becomes Tco due to the reason described above, the steam partial pressure becomes Psco, and the steam corresponding to the differential pressure between Psr and Psco is condensed in the CO remover.

On the other hand, in FIG. 3, the pressure P of the water remover 6
Since r is higher than the pressure Pco of the CO remover 5, the gas flowing into the moisture remover 6 has a temperature Th and a water vapor partial pressure Pb. At this time, in FIGS. 2 and 3, the partial pressure ratios of the water vapor and the gas components other than the water vapor contained in the gas flowing into the water remover 6 are the same, and the symbols in the figures show the relationship of A: B = C: D. It is made up. When the gas having the temperature Th and the steam partial pressure Pb flows into the moisture remover 6, the temperature is cooled to Tr and the steam partial pressure is reduced to the saturated steam partial pressure Psr. After this, in the present invention, before flowing into the CO remover, the pressure regulating valve 4
0 is provided, and by passing through the pressure regulating valve 40, the pressure is reduced to Pco which is the same as the pressure of the CO remover 5, and the steam partial pressure is also reduced from Psr to Pc. Since the partial pressure ratios of water vapor and gas components other than water vapor contained in the gas before passing through the pressure regulating valve 40 and the gas after passing through the pressure regulating valve 40 are the same, the relationship of E: F = G: H is established in the symbols in the figure. There is. The gas having the temperature Tr and the water vapor partial pressure Pc in this manner flows into the CO remover 5 and the temperature becomes T.
Even if it becomes co, the steam partial pressure Pc is the saturated steam partial pressure Ps.
Since it is less than or equal to co, condensation of water does not occur.

In order to perform such control, the pressure sensor 5 for measuring the pressure upstream and downstream of the pressure regulating valve 40.
0, 51, a temperature sensor 70 that measures the temperature of the refrigerant supplied to the CO remover 5, and a temperature sensor 71 that measures the temperature of the moisture remover 6 are installed. Further, the control means 60 for controlling the opening degree of the pressure regulating valve 40 based on these measurement results is installed.

Next, FIG. 4 shows a control method of the fuel cell system in the pressure control means 60. The flow shown in FIG. 4 is repeatedly executed at regular intervals. First, in step S1, the CO remover pressure is measured by the pressure sensor 51. Since the CO remover is located downstream of the pressure adjusting valve 40, the CO remover pressure is almost equal to the operating pressure of the fuel cell 2 controlled by the pressure adjusting valve 42, and the pressure of the fuel cell 2 or its target value is removed by CO. It can also be the pressure of the vessel. In step S2, the temperature of the CO remover is measured. In the present embodiment, the temperature of the refrigerant flowing into the CO remover is measured by the temperature sensor 70 and used as the lowest temperature that the CO remover can take, thereby reducing the chance of water condensation. Then, in step S3, the amount of water that does not cause water condensation even when flowing into the CO removal, that is, the allowable amount of inflow water is calculated. As for this water content, the maximum value of the inflowing water content (= inflowing water content per unit flow rate) that does not cause water condensation in the CO remover is shown in FIG. 5, which shows the relationship between the temperature and pressure of the CO remover. Can be obtained from the pressure and temperature obtained in steps S1 and S2.

Next, in step S4, the temperature inside the moisture remover is measured by the temperature sensor 71. Alternatively, the temperature of the gas discharged from the moisture remover 6 can be measured and regarded as the temperature of the moisture remover. In step S5, the pressure of the water remover is calculated such that the amount of water passing through the water remover becomes the allowable inflow water amount of the CO remover obtained in step S3. This pressure is shown in FIG. 6, which shows the maximum value of the ratio of the amount of water contained in the gas discharged from the water remover (= the amount of water passing per unit flow rate) in relation to the pressure of the water remover and the temperature. Can be obtained from the allowable inflow water amount of the CO remover obtained in step S3 and the water remover temperature measured in step S4. In step S6, the opening degree of the pressure control valve 40 is adjusted such that the pressure measured by the pressure sensor 50 becomes the pressure obtained in step S5. As the pressure control valve 40, it is desirable to use a highly reactive valve having a high operation speed in order to enhance controllability.

By controlling the pressure in the water remover in this way, it is possible to avoid water condensation in the CO remover and maintain a high CO removal performance.

Further, since air is supplied from the blower 7 to the fuel cell 2 and air is supplied to the reforming reactor 4 from the compressor 8, the pressures of the fuel cell 2 and the reforming reactor 4 are set independently. be able to. Here, the reforming reactor 4 is supplied with high pressure and small flow rate air, and the fuel cell 2 is supplied with lower pressure and larger flow rate air. As a result, it is not necessary to increase the pressure of the air supplied to the fuel cell 2 in accordance with the increase in the reformed gas pressure in the moisture remover 6, and it is possible to suppress the increase in power of the air supply device (blower 7, compressor 8). it can.

Further, since the water remover 6 and the cooling system of the fuel cell 2 are independently installed, the refrigerant of the water remover 6 has a higher temperature than that of the fuel cell 2 (for example, 100 ° C. to 100 ° C.).
For example, when heat is radiated to the atmosphere, the temperature difference between the atmosphere and the refrigerant becomes larger than that of the refrigerant (for example, 60 to 80 ° C.) of the fuel cell 2 and the cooling device 35 is cooled. Can be small. Further, the heat radiation in the cooling device 35 can be increased, and the shortage of the heat radiation amount of the refrigerant of the fuel cell 2 from the cooling device 30 can be compensated.

Next, a second embodiment will be described. The second embodiment has a configuration as shown in FIG. 7 and is different from the first embodiment in that the cooling system of the water remover 6 and the cooling system of the CO remover 5 are independent. That is, the cooling system of the water remover includes the refrigerant passage 33, the pump 34, and the cooling device 3.
5, and the cooling system of the CO remover includes the refrigerant flow path 3
6, a pump 37, and a cooling device 38.
With such a configuration, the temperature of the water remover can be controlled without affecting the temperature of the CO remover suitable for the reaction.

As described above, the amount of water passing through the water remover depends on the pressure and temperature of the water remover. In the first embodiment, since the flow rate and temperature of the cooling water are determined in order to maintain the CO remover temperature at a temperature suitable for the reaction, the temperature of the water remover cannot be controlled and only the pressure can be controlled. Controlled. In some cases, the operating pressure of the compressor 8 located upstream of the reformer must be increased in order to increase the pressure. However, in general, a compressor that sends out gaseous air consumes more power than a liquid pump, especially on the high pressure side. Is big. Therefore, when the operating pressure is increased, the total power consumption of the entire system becomes large, and the increased pressure reduces the system efficiency. Therefore, in the second embodiment, the cooling system of the water remover 6 is made independent of the cooling system of the CO remover 5 so that the amount of passing water can be reduced by lowering the temperature of the water remover. Therefore, it is not necessary to continue the operation while keeping the compressor pressure high, and the efficiency is improved, and while the cooling water temperature does not reach the target, as in the first embodiment, by controlling the pressure, water with high responsiveness is obtained. Condensation can be prevented.

FIG. 8 shows a control method according to the second embodiment. The flow shown in FIG. 8 is repeatedly executed at regular intervals. Steps S1 to S6 are the same as those in the first embodiment, and steps S7 and S8 are newly added. Since the description from step S1 to step S6 is the same as the first embodiment, step S7, step S6
8 will be described.

In step S7, the target temperature of the water remover 6 is calculated from the target pressure of the water remover 6 and the allowable amount of water flowing into the CO remover. If the pressure control valve 40 is opened as much as possible, the output of the compressor 8 can be small.
The pressure when the pressure control valve 40 is opened, that is, the pressure of the CO remover 5 is set as the target pressure of the moisture remover 6. Therefore, the target temperature of the water remover can be obtained from the CO remover pressure obtained in step S1 and the CO remover allowable inflow water amount obtained in step S3 using the relationship of FIG. In step S8, in order to bring the temperature of the water remover 6 to the target temperature, the flow rate or temperature of the refrigerant is reduced by controlling the pump 34 or the cooling device 35 based on a predetermined control amount.

By controlling in this manner, it is not necessary to continue the operation while keeping the compressor pressure high, and therefore it is possible to improve efficiency and prevent water condensation with high response.

Next, a third embodiment will be described. The configuration of the third embodiment is the same as that of the first embodiment (FIG. 1) or the second embodiment (FIG. 7). In the third embodiment, the amount of water contained in the gas is estimated by the reforming reaction model, and when the estimated amount of water is less than or equal to the allowable amount of water of the CO remover, the water condensation prevention control of the CO remover is performed. It is characterized by not having it. By controlling in this manner, when the amount of water originally flowing into the CO remover is smaller than the allowable amount of inflow water and the water condensation prevention control is unnecessary, it is possible to reduce the compressor and temperature required for increasing the pressure of the water condenser. Efficiency can be improved by preventing unnecessary cooling water pumps or cooling devices from operating in vain.

FIG. 9 shows a control flow chart of this embodiment.
This flow is repeatedly executed at regular intervals. Step S1
The steps from step S8 to step S8 are the same as those in the second embodiment (FIG. 8), and step S9 and step S10 are newly added. The explanation from step S1 to step S8 is the second
Since it is the same as the embodiment described above, step S9 and step S10 will be described.

In step S9, the water content W contained in the reformed gas is calculated using the reforming reaction model. A method for calculating the water content W contained in the reformed gas will be described with reference to FIG.

First, the amount of water consumed by the reforming reaction is calculated. The oxygen amount W _O2 contained in the air supplied to the reforming reactor 4 and the carbon amount W _C contained in the fuel supplied to the reforming reactor 4 are calculated from the operating conditions required for the fuel cell system. From this result, the amount of water W ₂ consumed in the reforming reaction is estimated using the reforming reaction model as shown in FIG.

Next, the amount of water consumed by the shift reaction is calculated. In FIG. 11, the carbon monoxide amount W _CO produced in the reforming reaction is determined from the oxygen amount W _O2 and the carbon amount W _C. Using this and the reforming reactor operation load, the amount of water W required for the shift reaction from the shift reaction model as shown in FIG.
Estimate ₃ .

The amount of water supplied to the reforming reactor 4 W ₁
In addition, the amount W ₄ of water supplied until it is supplied to the water remover 6 is calculated from the operating conditions required for the fuel cell system, and included in the reformed gas supplied to the water remover 6 from these. The water content W is calculated by the following formula.

[0058]

[Formula 1] Then, in step S10, the water contents W and C contained in the gas are
Compare the allowable inflow water amount of O 2 remover. If the water content W contained in the gas exceeds the CO removal device allowable inflow water content, the process proceeds to step S4 and subsequent steps to continue the water condensation prevention control. On the other hand, when the water content W contained in the gas is equal to or less than the CO inflow allowable water content of the CO remover, the water condensation prevention control is not performed. In this way, it is possible to improve efficiency by preliminarily determining the case where the water condensation prevention control is unnecessary and preventing unnecessary operation.

The structure of the fuel cell system according to the fourth embodiment is shown in FIG.

Between the pressure adjusting valve 40 and the CO remover 5, C
A moisture condensation sensor 80 that starts detecting water condensation from a concentration lower than the moisture concentration of the reformed gas that causes water condensation in the O remover 5 is provided. As the sensor 80, for example, in the bypass passage of the reformed gas controlled at a temperature lower than that of the CO remover 5, when condensed water adheres, the resistance of the heat ray changes to detect water condensation, etc. The method of can be considered.

As a result, the case where water is condensed can be detected by the water condensation sensor 80. Therefore, even when the performance of the catalyst for carrying out the reforming reaction or shift reaction in the reforming reactor 4 is deteriorated, the CO remover 5 is used. Condensation of water can be surely avoided.

FIG. 14 shows the configuration of the fuel cell system according to the fifth embodiment.

In the fuel cell system of the first embodiment, a temperature sensor 72 for detecting the temperature of the refrigerant for cooling the fuel cell 2 is provided, and whether the operating temperature of the fuel cell 2 exceeds the upper limit setting based on the detected refrigerant temperature. Determine whether
When it is determined that the upper limit setting is exceeded, the pressure adjusting valve 40 is adjusted to increase the reforming gas pressure of the water remover 6 and reduce the amount of water flowing into the CO remover 5 and the fuel cell 2. . Although the power generation efficiency is reduced due to the decrease in water content of the reformed gas supplied to the fuel cell 2, a means for supplying water to the reformed gas downstream of the CO remover 5, for example, in the present embodiment, the fuel cell 2 is internally humidified. By using a mold, it is possible to suppress a decrease in power generation efficiency.

By reducing the amount of water flowing into the fuel cell 2 in this way, the heat capacity of the reformed gas is reduced, and the fuel cell 2
Since the amount of heat flowing into the fuel cell 2 decreases, it is possible to lower the temperature of the fuel cell 2 and prevent the performance from deteriorating. At this time, although the heat radiation by the fuel cell cooling device 30 is reduced,
Since the heat radiation amount of the moisture remover 6 with respect to the refrigerant circulating through 3 increases, and the heat radiation amount of the cooling device 35 also increases accordingly, the decrease of the heat radiation amount of the cooling device 30 can be compensated. Further, although the amount of water collected in the condensers 22 and 23 is also reduced, it can be similarly compensated by the water condensed in the water remover 6.

It is needless to say that the present invention is not limited to the above embodiment, and various changes can be made within the scope of the technical idea described in the claims.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a fuel cell system according to a first embodiment.

FIG. 2 is a diagram showing changes in temperature and pressure of reformed gas in a conventional example.

FIG. 3 is a diagram showing changes in the temperature and pressure of the reformed gas in the first embodiment.

FIG. 4 is a flowchart showing a control method of the fuel cell system in the first embodiment.

FIG. 5 is a diagram showing the ratio of the allowable inflowing water amount of the CO remover as a relationship between the pressure and temperature of the CO remover.

FIG. 6 is a diagram showing the ratio of the amount of water passing through the water remover in relation to the pressure and temperature of the water remover.

FIG. 7 is a configuration diagram of a fuel cell system according to a second embodiment.

FIG. 8 is a flowchart showing a control method of the fuel cell system in the second embodiment.

FIG. 9 is a flowchart showing a control method of the fuel cell system in the third embodiment.

FIG. 10 shows a method for calculating the amount of water in the reformed gas according to the third embodiment.

FIG. 11 is a reaction model of a reforming reaction in the third embodiment.

FIG. 12 is a reaction model of a shift reaction in the third embodiment.

FIG. 13 is a configuration diagram of a fuel cell system according to a fourth invention.

FIG. 14 is a configuration diagram of a fuel cell system according to a fifth invention.

[Explanation of symbols]

2 Fuel cell 4 reforming reactor 5 CO remover 6 Moisture eliminator 7 Blair (Air supply device for power generation) 8 Compressor (reforming air supply device) 30 Fuel cell cooling device (cooling system for power generation) 35 Cooling device (reforming cooling system) 40 Pressure control valve 60 control means 80 Water condensation sensor (detection means) 70-72 Temperature sensor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 8/04 H01M 8/04 P // H01M 8/10 8/10

Claims (8)

[Claims] 1. A reforming fuel cell system for generating power using a reformed gas produced by a reforming reaction in a fuel cell, the reforming reactor producing reformed gas, and the reforming reactor produced. A CO remover for removing carbon monoxide in the reformed gas by a selective oxidation catalyst; a moisture remover installed upstream of the CO remover by condensing moisture in the reformed gas; A pressure adjusting valve installed between the water remover and the CO remover, a reforming cooling system for cooling the water remover and the CO remover with a refrigerant, and the water content using the pressure adjusting valve. A fuel cell system comprising: a controller for controlling the amount of condensation of water in the water remover by adjusting the pressure in the water remover. 2. The fuel cell system according to claim 1, wherein the pressure in the moisture remover is controlled based on the pressure and temperature of the CO remover. 3. The fuel cell system according to claim 1, wherein the pressure and temperature in the moisture remover are controlled based on the pressure and temperature in the CO remover. 4. The CO based on the operating load of the fuel cell system, the amount of water supplied upstream of the CO remover according to the operating load, and the amount of air supplied to the reforming reactor. The model which estimates the water content in the reformed gas which flows into a removal device is provided, and the pressure in the said water removal device is controlled based on the estimation result by the said model. Fuel cell system. 5. A detection means for detecting water condensation is provided upstream of the CO remover, and the pressure of the water remover is controlled based on the detection result of the detection means. The fuel cell system according to 1. 6. A power generation air supply device for supplying air to the fuel cell, and a reforming air supply device for supplying air to the reforming reactor. The fuel cell system according to any one of claims 1 to 5, wherein the reforming air supply device is of a small capacity and high pressure type. 7. A water supply unit for supplying moisture to the reformed gas between the time when the fuel cell is discharged from the CO remover and the time when the fuel cell is used for power generation, and a power generation cooling system for cooling the fuel cell. In an operating condition in which the amount of heat released from the cooling system for power generation is insufficient, the pressure of the water remover is increased to increase the amount of water condensed in the reformed gas. The fuel cell system according to any one of claims 1 to 6, wherein a heat radiation amount of the system is increased to compensate for a shortage of the heat radiation amount in the power generation cooling system. 8. The fuel cell system according to claim 1, wherein the pressure of the reforming gas in the fuel cell is controlled and then the pressure of the water remover is controlled.