JPH07302605A - Cooling water circulation system control device of fuel cell power generating system - Google Patents

Abstract

PURPOSE:To control the supply amount of exhaust heat recovery steam to a steam flow rate instruction value by installing a steam flow rate control means which controls the supply amount of the exhaust heat recovery steam and a cooling water amount control means which controls the cooling water amount of a cooling heat exchanger. CONSTITUTION:An opening of a control valve 27 which controls the supply amount of an exhaust heat steam 26 supplied to an outside system heat load is controlled according to a steam flow rate instruction value required by an outside system load with a steam flow rate control means 41. The cooling amount of a cooling heat exchanger 29 is controlled by controlling the water flow rate of secondary cooling water by operating a control valve 31 with a cooling water amount control means 42. A valve opening of the control valve 31 is controlled according to the difference between a measured temperature signal of a temperature sensor 40 and a setting temperature signal previously set according to a load level of a fuel cell 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling water circulation system control device for a fuel cell power generation system, and more particularly to a cooling water circulation system control device for a fuel cell power generation system with improved exhaust heat recovery steam supply performance to an external heat load. It is about.

[0002]

2. Description of the Related Art Generally, a fuel cell power generation system electrochemically reacts a hydrogen-rich gas obtained by reforming a raw fuel such as natural gas with an oxidant gas such as air,
It directly converts the chemical energy of raw fuel into electrical energy. Such a fuel cell power generation system is a highly efficient and low-pollution system, and has the advantage that exhaust heat can be easily recovered in the form of steam or hot water. Therefore, it is an excellent system that can supply both electricity and heat. Recently, it has attracted widespread attention as a cogeneration system.

FIG. 3 shows a conventional example of such a fuel cell power generation system. In this conventional example, the fuel reformer 1 is used as one of the methods usually performed to obtain a hydrogen-rich gas. The fuel reformer 1 introduces a raw material gas composed of a hydrocarbon such as natural gas or coal gas, and converts this into a hydrogen-rich reformed gas by steam reforming.

The fuel reformer 1 is equipped with a reforming reaction tube 2 having a catalyst layer therein and a reformer burner 3. The reforming reaction tube 2 is fed to the raw material gas 4 and reforming steam. Are introduced through the control valves 7 and 8 by the raw material gas supply pipe and the steam supply pipes 5 and 6, respectively. In the reforming reaction tube 2 supplied with the raw material gas 4 and the reforming steam, the reforming burner 3 heats the reforming reaction heat to give the reforming reaction heat.
The raw material gas 4 is converted into a hydrogen-rich reformed gas.

Further, after the reformed gas is cooled in the cooler 9, the carbon monoxide in the reformed gas reacts with the steam in the CO shift converter 10 to be further transformed into a gas rich in hydrogen. . Then, the fuel electrode 11 of the fuel cell 11
is supplied to a. The cooler 9 is provided to cool the hot reformed gas at the outlet of the fuel reformer 1 to the reaction temperature level of the CO shift converter 10.

An air supply system 12 is connected to the air electrode 11b of the fuel cell 11 so that air as an oxidant is controlled by the control valve 1.
DC power is generated by an electrochemical reaction with hydrogen on the fuel electrode 11a side. In the air supply system 12, a blower 14 is used to insert an amount of air required for the system from the atmosphere.

On the other hand, from the outlet of the fuel electrode 11a of the fuel cell 11, the exhaust heat gas containing unreacted hydrogen gas is exhausted through the gas exhaust pipe 15. This exhaust fuel gas is discharged from the fuel reformer 1. The fuel is supplied to the reformer burner 3 as fuel, and is mixed with fuel air supplied from the air supply pipe 16 through the control valve 17 and burned.

The combustion gas of the exhausted fuel gas and the combustion air heats the reforming reaction tube 2 in the fuel reformer 1, and then is discharged as combustion exhaust gas from the gas exhaust tube 18a to the outlet of the air electrode 11b of the fuel cell 11. Is discharged from the gas exhaust system 18 to the outside of the system together with the exhaust air passing through the gas exhaust pipe 18b.

The power generation output of the fuel cell 11 is taken out as DC power to the outside, but if necessary, it is converted to an AC output via an orthogonal converter (not shown) and then supplied to an electric load or a power system. To be done.

Fuel electrode 1 accompanying power generation in fuel cell 11
The reaction heat generated between 1a and the air electrode 11b is the cooling device 1
A cooling water circulation system 20 is provided for this purpose, though the cooling water is removed by circulating it through 1c.

In this cooling water circulation system 20, the fuel cell 1
The battery outlet cooling water 21 that has undergone heat exchange by the cooler 11c of No. 1 and has risen in temperature and has boiled is used as two-phase running water in the steam separator 2
It is introduced into the steam generator 2 and separated into steam 23 and high-temperature water 24. Some of the separated steam is steam for reforming 25
Is supplied to the fuel reformer 1 via the steam supply pipe 6, and the other part of the separated steam is used as the exhaust heat recovery steam 26 from the fuel cell power generation system, which is the control valve 2
It is supplied to the heat load outside the system via 7.

On the other hand, the high-temperature water 24 separated by the steam separator 22 is circulated again to the cooler 11c of the fuel cell 11 via the pump 28 and the cooling heat exchanger 29. Further, a water supply system 30 is provided to compensate for the reduction of the circulating cooling water due to steam separation in the steam separator 22. Further, a coolant such as secondary cooling water is supplied to the cooling heat exchanger 29 via a control valve 31, and the control valve 31 controls the cooling amount of the cooling heat exchanger 29.

In such a cooling water circulation system, the temperature inside the fuel cell 11 that generates heat and the cooler 1 are set so that the cooler 11c of the fuel cell has sufficient heat removal performance.
There must be a sufficient temperature difference with the temperature of the cooling water flowing in 1c. For this reason, it has been conventionally practiced to adjust the temperature of the inlet and outlet of the fuel cell cooling water to a predetermined temperature level according to the load to operate the cooling water circulation system. Since the two-phase running water at the fuel cell outlet is saturated, the temperature at the fuel cell cooling water outlet side can also be adjusted by adjusting the pressure of the steam separator 22.

Specifically, as shown in FIG. 3, a temperature sensor 32 is provided in the downstream side line of the cooling heat exchanger 29, and the temperature of the cooling water at the inlet side of the fuel cell measured here is the load level of the fuel cell in advance. The cooling amount of the cooling heat exchanger 29 is adjusted by the control valve 31 so as to approach the set temperature determined according to the above. Further, the pressure sensor 33 is provided in the steam separator 22, and the pressure measured here is set in advance in the fuel cell 11
To approach the set pressure determined according to the load level of
The supply amount of the exhaust heat recovery steam 26 supplied to the heat load outside the system is adjusted by the control valve 27.

[0015]

However, when considering use as a cogeneration system for recovering exhaust heat from a fuel cell power generation system as steam,
It is desirable to adjust the amount of exhaust heat recovery steam supplied according to the demand for heat load outside the system.

In the structure of the conventional fuel cell power generation system as shown in FIG. 3, as described above, the pressure measured by the pressure sensor 33 provided in the steam separator 22 is the fuel cell in advance. The supply amount of the exhaust heat recovery steam 26 supplied to the heat load outside the system is adjusted by the adjustment valve 27 so that the set pressure determined according to the load level of 11 is approached. Therefore, the supply amount of the exhaust heat recovery steam 26 to the external heat load is determined by the load level of the fuel cell 11,
It cannot be adjusted according to the demand of heat load outside the system.

Further, the temperature of the fuel cell cooling water outlet line or the steam / water separator 22 is measured, not the pressure of the steam / water separator 22, and the measured temperature is determined in advance according to the load level of the fuel cell 11. Even when the supply amount of the exhaust heat recovery steam 26 supplied to the heat load outside the system is adjusted by the control valve 27 so as to approach the set temperature, the supply amount of the exhaust heat recovery steam 26 depends on the load level of the fuel cell 11. It is the same in that it cannot be adjusted according to the demand of the heat load outside the system. Therefore, the conventional fuel cell power generation system has a problem that it is difficult to adjust the amount of exhaust heat recovery steam supplied to the external heat load according to the demand of the external heat load.

An object of the present invention is to control the cooling water circulation system of a fuel cell power generation system such that the supply amount of exhaust heat recovery steam to the external heat load can be adjusted according to the demand of the external heat load. To provide a device.

[0019]

A cooling water circulation system controller for a fuel cell power generation system according to the present invention is configured so that the supply amount of exhaust heat recovery steam supplied to a heat load outside the system becomes a steam flow rate command value. Steam flow control means for controlling,
And a cooling water amount control means for controlling the cooling water amount of the cooling heat exchanger so that the process amount corresponding to the outlet cooling water temperature of the fuel cell becomes a set value corresponding to the load level of the fuel cell.

The process quantity corresponding to the outlet cooling water temperature of the fuel cell uses the temperature in the cooling water circulation system, specifically, the high temperature water temperature of the steam separator.

As the process amount corresponding to the outlet cooling water temperature of the fuel cell, the pressure of the cooling water circulation system is used, specifically, the pressure in the steam separator.

[0022]

In this fuel cell power generation system, the steam flow control means is provided so that the supply amount of the exhaust heat recovery steam supplied to the heat load outside the system becomes the steam flow command value required by the heat load outside the system. The cooling water amount control means controls the cooling water amount of the cooling heat exchanger so that the process amount corresponding to the outlet cooling water temperature of the fuel cell becomes a set value corresponding to the load level of the fuel cell. Therefore, while maintaining the temperature or pressure of the two-phase flow cooling water at the fuel cell outlet at a value close to the set temperature or set pressure, the operation of adjusting the supply amount of the exhaust heat recovery steam according to the demand of the external heat load Is possible.

[0023]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a block diagram showing a first embodiment of the present invention. The same members as those in the conventional example shown in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted.

In the first embodiment, the steam flow rate control means 41 for controlling the supply amount of the exhaust heat recovery steam supplied to the heat load outside the system to the steam flow rate command value, and the outlet of the fuel cell 11. A cooling water amount control means 42 for controlling the cooling water amount of the cooling heat exchanger 29 is provided so that the process amount corresponding to the cooling water temperature becomes a set value corresponding to the load level of the fuel cell 11, and the steam separator. A temperature sensor 40 is provided to measure the temperature of the hot water line from 22.

That is, in this first embodiment,
The supply amount of the exhaust heat recovery steam supplied to the heat load outside the system is controlled by the steam flow control unit 41 so that the steam flow command value required by the heat load outside the system is obtained, and the steam-water separator 22 The temperature of the high temperature water line of the fuel cell 11
The cooling water amount control means 42 is configured to adjust the cooling amount of the cooling heat exchanger 29 so as to approach the set temperature determined according to the load level.

That is, the temperature in the cooling water circulation system is used as the process amount corresponding to the outlet cooling water temperature of the fuel cell, specifically, the high temperature water temperature of the steam separator is used.

Specifically, the opening degree of the control valve 27 for adjusting the supply amount of the exhaust heat recovery steam 26 supplied to the heat load outside the system is determined by the steam flow rate control means 41 for the steam flow rate required by the outside load. It is controlled according to the command value. This flow rate command value can be set as a function of temperature, pressure, flow rate, etc. according to, for example, the steam demand of the external heat load, and a field flow control by the steam flow rate measurement value is provided by providing a flow rate sensor (not shown). It is also possible to combine them.

On the other hand, the cooling amount of the cooling heat exchanger 29 is adjusted by adjusting the flow rate of the secondary cooling water by the control valve 31 in the cooling water amount control means 42. The valve opening degree of the control valve 31 is adjusted by, for example, PID control or the like according to the difference between the measured temperature signal of the temperature sensor 40 and the set temperature signal determined in advance according to the load level of the fuel cell 11. As a result, the cooling amount of the cooling heat exchanger 29 is adjusted via the adjustment valve 31 so that the temperature of the high temperature water measured by the temperature sensor 40 approaches the preset temperature determined in advance according to the load level of the fuel cell. can do.

Thus, the supply amount of the exhaust heat recovery steam 26 supplied to the heat load outside the system is controlled by the control valve 27 according to the steam flow rate command value.

On the other hand, a temperature sensor 40 is provided in the hot water line of the steam separator 22 and a control valve 31 for adjusting the flow rate of the secondary cooling water that cools the cooling heat exchanger 29 using this measured temperature signal. The cooling heat exchanger 29 is configured to adjust the valve opening so that the temperature of the high-temperature water measured by the temperature sensor 40 approaches a preset temperature determined in advance according to the load level of the fuel cell 11. The amount of cooling can be adjusted. Since the temperature of the high-temperature water separated by the steam separator 22 is quite close to the temperature of the fuel cell outlet cooling water, the fuel cell outlet cooling water 21 of the cooling water circulation system 20 is configured by the configuration of the fuel cell power generation system shown in FIG. Can be operated with a temperature close to the set temperature determined according to the load level of the fuel cell 11, and the temperature of the fuel cell inlet cooling water must be cooled by the cooling heat exchanger 29 so that the fuel cell must be operated. It can be kept below the temperature of the outlet cooling water.

Therefore, the cooler 11c of the fuel cell 11
It is possible to operate such that the supply amount of the exhaust heat recovery steam is adjusted according to the demand of the external heat load while having sufficient heat removal performance.

Although the cooling heat exchanger 29 is cooled by the secondary cooling water in the first embodiment shown in FIG. 1, the coolant is not limited to this, and other water or gas may be used. Alternatively, air or the like may be used. In addition, the cooling heat exchanger 2
9 may be a steam generator for generating steam on the secondary side.

Further, in the first embodiment shown in FIG. 1, the cooling heat exchanger 29 is constructed as one heat exchanger, but a combination of a plurality of heat exchangers or a cooler such as a steam generator is used. It may be configured. Even in this case, the temperature sensor 40
If the cooling amount of one of the heat exchangers is adjusted so that the temperature of the high-temperature water measured in step 1 approaches the set temperature, the same effect can be obtained.

Further, in the first embodiment of FIG. 1, the temperature sensor 40 is provided at a position for measuring the high temperature water temperature, but another temperature sensor which can measure a temperature close to the temperature of the two-phase cooling water at the fuel cell outlet is used. It may be provided at any position. For example, it may be provided in a two-phase cooling water line at the outlet of the fuel cell, or a steam separator, or a steam supply line separated by the steam separator.

Therefore, in this first embodiment, the temperature of the two-phase flow cooling water at the fuel cell outlet or the steam separator 22
A temperature sensor 40 for measuring the temperature of the steam or high-temperature water separated by is provided, and the cooling amount of the cooling heat exchanger 29 is adjusted so that the measured temperature approaches a preset temperature determined in advance according to the load level of the fuel cell 11. With this configuration, the amount of exhaust heat recovery steam supplied to the external heat load can be adjusted according to the demand of the external heat load, and the exhaust heat recovery steam of the external heat load can be adjusted. The supply performance can be improved.

Next, FIG. 2 is a block diagram showing a second embodiment of the present invention. In the second embodiment, as in the first embodiment, the steam flow control means 41 for controlling the supply amount of the exhaust heat recovery steam supplied to the heat load outside the system to the steam flow command value. And a cooling water amount control means 42 for controlling the cooling water amount of the cooling heat exchanger 29 so that the process amount corresponding to the outlet cooling water temperature of the fuel cell 11 becomes a set value corresponding to the load level of the fuel cell 11. Therefore, the pressure of the cooling water circulation system, specifically, the pressure in the steam separator 29 is used as the process amount corresponding to the outlet cooling water temperature of the fuel cell 11.

That is, in this second embodiment,
The control valve 27 is adjusted by the steam flow control means 41 so that the supply amount of the exhaust heat recovery steam 26 supplied to the heat load outside the system becomes the steam flow command value. On the other hand, the cooling amount of the cooling heat exchanger 29 is adjusted so that the measured pressure measured by the pressure sensor 33 provided in the steam separator 22 approaches the set pressure determined in advance according to the load level of the fuel cell 11. Is configured. That is, the pressure sensor 33
The valve opening degree of the control valve 31 is adjusted by, for example, PID control or the like based on the difference between the measured pressure signal and the set pressure signal that is predetermined according to the load level of the fuel cell 11.

Thus, the supply amount of the exhaust heat recovery steam 26 supplied to the heat load outside the system is controlled so as to be the steam flow rate command value, and the steam separator 22 measured by the pressure sensor 33. The cooling amount of the cooling heat exchanger 29 can be adjusted via the adjustment valve 31 so that the pressure of 1 is brought close to the set pressure that is previously determined according to the load level of the fuel cell 11.

Since the fuel cell outlet cooling water is in a two-phase flow saturated state, the pressure of the steam separator 22 has a relationship corresponding to the temperature of the fuel cell outlet cooling water. Therefore, by setting the set pressure of the steam separator 22 in advance so as to correspond to the required fuel cell outlet temperature level according to the load level of the fuel cell 11, the fuel cell outlet cooling water 21 of the cooling water circulation system 20 is set. Can be maintained at a desired temperature according to the load level of the fuel cell 11, and the temperature of the fuel cell inlet cooling water is cooled by the cooling heat exchanger 29 so that the temperature of the fuel cell outlet cooling water must be the same. Can be kept lower.

Therefore, it is possible to make a necessary temperature difference between the temperature inside the fuel cell 11 and the temperature of the cooling water flowing in the cooler 11c. It can have performance.

On the other hand, the supply amount of the exhaust heat recovery steam 26 supplied to the heat load outside the system is controlled by the control valve 27 according to the steam flow rate command value. That is, the fuel cell 11
It is possible to perform an operation in which the supply amount of the exhaust heat recovery steam is adjusted according to the demand of the external heat load while the cooling device 11c of FIG.

Although the pressure sensor 33 is installed in the steam / water separator in FIG. 2, the pressure in the cooling water circulation system does not have a large pressure difference over the pressure in the steam / water separator 22. Pressure sensor 33 at any point in the system
May be installed. That is, a pressure sensor for measuring a representative pressure of the cooling water circulation system is provided at an appropriate location, and the measured pressure signal is used to adjust the cooling amount of the cooling heat exchanger 29 by the control valve 31. It is possible to operate so as to bring the system pressure close to a set pressure that is determined in advance according to the load level of the fuel cell 11. By setting this set pressure in correspondence with the required fuel cell outlet temperature level according to the load level of the fuel cell 11,
It is possible to operate while maintaining the temperature of the fuel cell outlet cooling water 21 at a desired temperature according to the load level of the fuel cell 11.

The cooling heat exchanger 29 is not limited to the secondary cooling water, but may be cooled by using other water, gas, air or the like. Further, the cooling heat exchanger 29 may be configured by a combination of a plurality of heat exchangers or coolers such as a steam generator, instead of a single heat exchanger.

[0044]

As described above, according to the present invention, the steam flow control means for controlling the supply amount of the exhaust heat recovery steam supplied to the heat load outside the system to the steam flow command value, Cooling water quantity control means for controlling the cooling water quantity of the cooling heat exchanger so that the process quantity corresponding to the outlet cooling water temperature of the fuel cell becomes a set value corresponding to the load level of the fuel cell, and cooling the outlet of the fuel cell Since the process amount corresponding to the water temperature uses the temperature in the cooling water circulation system, it is possible to adjust the supply amount of exhaust heat recovery steam to the external heat load according to the demand of the external heat load. And again,
The temperature of the fuel cell outlet cooling water can be maintained at a desired temperature depending on the load level of the fuel cell. That is, it is possible to improve the supply performance of the exhaust heat recovery steam to the external heat load.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a conventional example.

[Explanation of symbols]

 1 Fuel Reformer 11 Fuel Cell 11a Fuel Electrode 11b Air Electrode 11c Cooler 20 Cooling Water Circulation System 21 Battery Outlet Cooling Water 22 Steam Separator 26 Exhaust Heat Recovery Steam 27 Control Valve 29 Cooling Heat Exchanger 31 Control Valve 33 Pressure Sensor 40 Temperature Sensor 41 Steam Flow Rate Control Means 42 Cooling Water Amount Control Means

Claims (5)

[Claims] 1. A fuel cell for causing an electrochemical reaction,
A cooling water circulation system for removing heat of electrochemical reaction of the fuel cell; a steam separator for separating cooling water discharged from the fuel cell into steam and high-temperature water, the cooling water circulation system; A cooling heat exchanger arranged in a water circulation system to cool the hot water from the steam separator.
In a cooling water circulation system control device of a fuel cell power generation system configured to supply at least a part of the steam to a heat load outside the system, a supply amount of exhaust heat recovery steam supplied to the heat load outside the system is Steam flow rate control means for controlling to a steam flow rate command value, and the cooling heat exchanger so that the process amount corresponding to the outlet cooling water temperature of the fuel cell becomes a set value corresponding to the load level of the fuel cell. And a cooling water amount control means for controlling the cooling water amount of the cooling water circulation system control device for the fuel cell power generation system. 2. The cooling water circulation system controller for a fuel cell power generation system according to claim 1, wherein the process amount corresponding to the outlet cooling water temperature of the front fuel cell is the temperature in the cooling water circulation system. . 3. The cooling water circulation system controller for a fuel cell power generation system according to claim 2, wherein the temperature in the cooling water circulation system is the high temperature water temperature of the steam separator. 4. The cooling water circulation system controller for a fuel cell power generation system according to claim 1, wherein the process amount corresponding to the outlet cooling water temperature of the fuel cell is the pressure of the cooling water circulation system. 5. The cooling water circulation system controller of the fuel cell power generation system according to claim 4, wherein the pressure of the cooling water circulation system is a pressure in the steam separator.