JPH0765848A - Cooling water exhaust heat recovery method and its device for fuel cell thermoelectric supply facility - Google Patents

Abstract

PURPOSE:To provide a means to recover the exhaust heat of cooling water effectively in addition to means to separate the cooling water from which heat produced at generation of fuel cell is removed into steam and cooling water and feed the steam other than that fed to a fuel reforming device to an exhaust gas turbine generator. CONSTITUTION:The steam in a steam separator 12 is fed to a fuel reforming device 6 after controlling the required amount of flow by a flow control valve 27, and the remaining excess steam is fed to an exhaust gas turbine 22 after controlling the pressure in the steam separator 12 by a pressure control valve 31 to obtain power by a generator 21. In addition, an absorbing type refrigerator 40 is provided. The steam flow-controlled by a flow control valve 44 is fed to the absorption refrigerator 40 to obtain cool water of a specified temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to combined heat and power supply for a fuel cell, in which exhaust heat of cooling water for removing reaction heat generated during power generation of a fuel cell is recovered to obtain power by an exhaust gas turbine and cold water by an absorption refrigerator. The present invention relates to a method for recovering waste heat of cooling water of equipment and an apparatus thereof.

[0002]

2. Description of the Related Art Cooling water from which heat of reaction generated during power generation of a fuel cell is removed is introduced into a steam separator and separated into steam and cooling water, which is used again to remove heat of reaction. ,
The steam is added to the hydrocarbon-based or alcohol-based raw fuel such as natural gas, LPG, and methanol supplied for steam reforming in the fuel reformer, and the remaining excess steam is generated by the generator. The exhaust heat of the cooling water is recovered by being supplied to the exhaust gas turbine that drives the exhaust gas turbine that drives and the compressor that supplies the reaction gas air to the fuel cell.

The prior art will be described below with reference to the drawings. FIG. 4 is a system diagram of a fuel cell combined heat and power supply facility for recovering exhaust heat of cooling water. In FIG. 4, the fuel cell 1 includes an electrolyte layer (not shown), a fuel electrode 2 and an air electrode 3 that sandwich the electrolyte layer, and a cooling plate 5 having a heat transfer tube 4.
The fuel reformer 6 includes a reaction part 7 filled with a catalyst for steam reforming raw fuel, and a burner 8 for generating combustion gas for heating the reaction part 7.

The steam separator 12 separates the cooling water from which the reaction heat generated during power generation of the fuel cell 1 is removed into steam and cooling water, and the cooling water circulation system 10 has a circulation pump 11 and a heat transfer tube of the fuel cell 1. 4 and the water vapor separator 12 are connected and provided. The reformed gas supply system 13 is connected to the reaction section 7 of the fuel reformer 6 and the fuel electrode 2 of the fuel cell 1, and the fuel off-gas discharge system 14 is connected to the fuel electrode 2 and the burner 8 of the fuel reformer 6. It is provided by connecting.

The air supply system 15 is connected to the compressor 17 driven by the electric motor 16 and the air electrode 3 of the fuel cell 1.
Further branching from this, a combustion air supply system 18 is connected to the burner 8 of the fuel reformer 6. The air off-gas discharge system 20 is connected to the air electrode 3 of the fuel cell 1, and is connected to the outlet of the combustion exhaust gas of the combustion gas generated by the combustion in the burner 8 of the fuel reformer 6 and the exhaust gas turbine 22 that drives the generator 21. It is joined to the connected combustion exhaust gas discharge system 23.

The raw fuel supply system 25 is provided so as to be connected to the reaction section 7 of the fuel reformer 6, and a reforming steam supply system 28 which joins this system is connected to the steam section of the steam separator 12. It is provided with a flow rate detector 26 and a flow rate control valve 27. The steam supply system 30 is connected to the steam part of the steam separator 12 with a pressure control valve 31 and joined to the combustion exhaust gas discharge system 23. The pressure detector 32 detects the pressure inside the water vapor separator 12.

With this structure, the raw fuel is supplied to the reaction section 7 of the fuel reformer 6 through the raw fuel supply system 25. At this time, the flow rate of the steam separated by the steam separator 12 is controlled and added to the raw fuel through the reforming steam supply system 28. In the flow rate control in this case, the flow rate detector 26 detects the flow rate of the steam flowing through the reforming steam supply system 28, and the controller 33 determines the deviation between the detected flow rate and the target value of the predetermined flow rate corresponding to the raw fuel flow rate. This is performed by controlling the flow rate control valve 27.

On the other hand, the fuel off-gas discharged from the fuel electrode 2 during power generation of the fuel cell 1 is supplied to the burner 8 of the fuel reformer 6 through the fuel off-gas discharge system 14, while the electric motor 16
Air discharged from the compressor 17 driven by is supplied to the burner 8 via the combustion air supply system 18, and the fuel off gas is combusted by this air. The combustion heat from this combustion heats the reaction section 7, and the raw fuel added with steam flowing through the reaction section 7 is steam-reformed into a reformed gas rich in hydrogen.

The above reformed gas is supplied to the fuel electrode 2 of the fuel cell 1 via the reformed gas supply system 13, and the air discharged from the compressor 17 is supplied to the air electrode 3 via the air supply system 15 to supply the fuel cell. 1 generates a power by causing a cell reaction with the supplied reformed gas and air. During power generation, the cooling water in the steam separator 12 is supplied from the circulation pump 11 to the cooling water circulation system 1.
Flowing through the heat transfer tube 4 of the fuel cell 1 and the reaction heat generated during power generation is removed by this cooling water to maintain the operating temperature.

The cooling water discharged from the heat transfer tube 4 of the fuel cell 1 and having steam generated by the reaction heat flows into the steam separator 12 and is separated into steam and cooling water. While being added, the remaining steam is supplied to the exhaust gas turbine 22 that drives the generator 21.
At this time, the air off gas exhaust system 20
Air off-gas and fuel reformer 6 exhausted,
The combustion exhaust gas passing through the combustion exhaust gas discharge system 23 is also supplied to the exhaust gas turbine 22 together with the remaining steam, and the generator 2
Drive 1 to get power.

The pressure inside the water vapor separator 12 is controlled to a predetermined pressure by controlling the pressure control valve 31 by the controller 34 from the deviation between the detected pressure detected by the pressure detector 32 and the target value of the predetermined pressure. At the same time, the flow rate of steam flowing during this control flows through the steam supply system 30 and is supplied to the exhaust gas turbine 22. At this time, the amount of generated steam is controlled so that the pressure in the steam separator 12 is maintained at a predetermined pressure, the cooling water in the steam separator 12 is maintained at a constant saturation temperature corresponding to the predetermined pressure, and this cooling is performed. The reaction heat of the fuel cell is removed by water to maintain the operating temperature.

FIG. 5 is a system diagram of a conventional fuel cell combined heat and power supply facility of a different example. In FIG. 5, the exhaust gas turbine 22 shown in FIG. 4 and the generator 21 connected thereto are removed, and the electric motor 16 that drives the compressor 17 is replaced by the exhaust gas turbine 35, and the air off gas exhaust system 20 and the steam supply system 30 are provided.
And the flue gas exhaust system 23 that joins the exhaust gas turbine 3
5 is the same as FIG. 4 except that it is connected to FIG.

With this structure, the air supplied to the air electrode 3 of the fuel cell 1 and the burner 8 of the fuel reformer 6 is
The steam from the steam separator 12, the combustion exhaust gas from the fuel reformer 6, and the air off gas from the air electrode 3 of the fuel cell 1 are supplied by a compressor 17 driven by an exhaust gas turbine 35. FIG. 6 is a system diagram of another conventional fuel cell combined heat and power supply facility of the conventional example. In FIG. 6, a cooling medium circulating through the heat transfer tube 4 of the fuel cell 1 is used as cooling air, and a cooling air circulation system 38 including a circulation blower 36 and a heat exchanger 37 and a cooling water circulation system passing through the steam separator 12 are provided. It is the same as FIG. 4 except that 10 is provided in the heat exchanger 37 so that the cooling water flowing through the cooling water circulation system 10 exchanges heat with the cooling air.

With such a configuration, the reaction heat generated during power generation of the fuel cell 1 is circulated through the cooling air circulation system 38 and the blower 3
Heat is removed by the cooling air circulated by 6 and heat is removed by the heat exchanger 37 to remove heat from the cooling air and the cooling water circulating in the cooling water circulation system 10 is heated and supplied to the steam separator 12. Thereby, the exhaust heat of the cooling water is recovered as described above.

[0015]

As described above, the pressure inside the steam separator 12 for storing the cooling water from which the reaction heat generated during power generation of the fuel cell 1 is removed is set to a predetermined pressure to separate the steam from the cooling water. Driving the exhaust gas turbines 22 and 35 by means of converting the energy of water vapor into rotational energy, further converting into electric energy by the generator 21 and air energy by the compressor 17 is not so high in energy conversion efficiency. There are drawbacks.

Further, the present applicant has studied how to effectively use the water vapor in the water vapor separator by other means, and also studied how to sufficiently recover the exhaust heat of the cooling water. The object of the present invention is not only to use the steam in the steam separator for the exhaust gas turbine, but also to use it by other means to increase the overall energy efficiency of the plant. A recovery method and an apparatus therefor are provided.

[0017]

In order to solve the above problems, according to the present invention, cooling water from which heat generated during power generation of a fuel cell is removed or cooling water that has exchanged heat with cooling air is used in a steam separator. The steam is separated into steam and cooling water, the flow rate of the steam is controlled, and the steam is supplied to the fuel reformer to be added to the raw fuel to be steam-reformed. Further, the steam has a predetermined pressure in the steam separator. Of the fuel cell cogeneration system that recovers the exhaust heat of the cooling water by supplying it to the exhaust gas turbine that drives the generator by pressure control as described above or the exhaust gas turbine that drives the compressor that supplies the reaction gas air to the fuel cell. In the cooling water exhaust heat recovery method, the flow rate of water vapor in the water vapor separation gas is controlled and supplied to an absorption refrigerator, and the water supplied to this refrigerator is cooled to be cold water at a predetermined temperature.

Further, a fuel cell as an apparatus adopting the above-mentioned cooling water exhaust heat recovery method, cooling water from which heat generated during power generation of this fuel cell is removed, or cooling by heat exchange with cooling air in a heat exchanger A steam separator for separating water into steam and cooling water, a fuel reformer for steam reforming by supplying the added raw fuel by controlling the flow rate of steam from the steam separator, and steam from the steam separator And an exhaust gas turbine connected to a generator that supplies pressure-controlled so that the pressure in the separator becomes a predetermined pressure, or an exhaust gas turbine connected to a compressor that supplies reaction gas air to a fuel cell. In a cooling water exhaust heat recovery device of a fuel cell combined heat and power supply facility that recovers the cooling water exhaust heat of a fuel cell, an absorption type that supplies steam from a steam separator and cools the supplied water to cold water With refrigerator Temperature flow of cold water in the steam supplied to the absorption chiller is assumed to provide a flow control means for controlling to a predetermined temperature.

The above flow rate control means comprises a flow rate control valve for controlling the flow rate of steam supplied from the steam separator to the absorption refrigerator, a temperature detector for detecting the temperature of cold water obtained from the absorption refrigerator, Control means for controlling the flow control valve based on the deviation between the temperature detected by this detector and the target value of the predetermined temperature of the cold water is provided.

[0020]

The heat generated during the power generation of the fuel cell is removed by the cooling water or the cooling air and kept at the operating temperature. By the way, the heat-removed cooling water or the cooling water that has exchanged heat with the cooling air generates steam by heat removal, and the cooling water containing this steam is guided to a steam separator to be separated into steam and cooling water. It At this time, the steam in the steam separator is added to the raw fuel to be supplied to the fuel reformer as in the conventional case, and the remaining steam is supplied to the exhaust gas turbine connected to the generator and the compressor. It is supplied to a refrigerator and the water supplied to this refrigerator is cooled to chilled water. At this time, the flow rate control valve is controlled by the control means from the deviation between the detected temperature of the cold water detected by the temperature detector and the target value of the predetermined temperature of the cold water to control the flow rate of the steam supplied to the absorption refrigerator, thereby controlling the cold water. To the specified temperature.

By providing the absorption refrigerator for producing cold water in this way, the amount of water vapor added to the raw fuel supplied to the fuel reformer is determined by the composition and flow rate of the raw fuel. In addition to the conventional exhaust gas turbine, it can be supplied to an absorption chiller as a driving heat source.Therefore, when the summer cold water is needed, cold water is produced by the absorption chiller, and when the winter cold water is unnecessary, excess steam is generated. Can be supplied to the exhaust gas turbine to obtain electric power. Therefore, the exhaust heat of the cooling water can be effectively used, and the overall energy efficiency is improved.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a fuel cell combined heat and power supply facility adopting a method for recovering cooling water exhaust heat of a fuel cell according to an embodiment of the present invention. 1 differs from the conventional example of FIG. 4 in that an absorption refrigerator 40 and an absorption liquid that branches from the steam supply system 30 and absorbs the refrigerant of the absorption refrigerator 40 are heated to generate refrigerant vapor. Flow meter 4 connected to the heat transfer tube 41
2, which is connected to a refrigerator steam supply system 43, a flow control valve 44 that controls the flow rate of steam, and a heat transfer tube 45 of an evaporator that evaporates the condensed refrigerant, so that water supplied from a cold water customer can pass through. The flowing pipe 46, the cold water pipe 47 through which the cold water supplied to the cold water demand flows, the temperature detector 48 for detecting the temperature of the cold water, the detected temperature of the cold water at the temperature detector 48 and the predetermined temperature of the cold water. It is the same as FIG. 4 except that a controller 49 for controlling the flow control valve 44 based on the deviation from the target value is provided.

With such a structure, the water vapor separator 12
Through the steam supply system 43 for the refrigerator, flows into the heat transfer tube 41 of the generator of the absorption refrigerator 40, heats the absorbing liquid in the generator by sensible heat and latent heat of the steam, and generates refrigerant vapor. . Since this refrigerant vapor is condensed in the condenser and then evaporated in the evaporator, the water supplied from the demand destination flowing through the heat transfer tube 45 is cooled to be cold water and supplied to the demand destination.

At this time, the flow rate control valve 44 is controlled by the controller 49 from the deviation between the detected temperature of the cold water detected by the temperature detector 48 and the target value of the predetermined temperature of the cold water required by the customer, and the absorption refrigeration is performed. By controlling the flow rate of steam supplied to the machine 40, the temperature of the cold water is controlled to a predetermined temperature. Next, the effect of the above embodiment will be specifically described. The amount of steam generated in the steam separator when the power generation output of the fuel cell is 5000 kW in the fuel cell combined heat and power supply facility is 4370 kg / h. Among them, the amount of steam supplied to the fuel reformer is 2910 kg / h, and therefore the amount of surplus steam is 1460 kg / h = (4370-2910) kg / h.

When the surplus steam is used as follows, that is, when the entire amount of the surplus steam is supplied to the exhaust gas turbine, by supplying the surplus steam of 1460 kg / h to the exhaust gas turbine, power generation driven by the exhaust gas turbine The electric output of the machine is 1190kW. As a result, the power generation efficiency evaluated by the total electric output of the generator driven by the fuel cell and the exhaust gas turbine is 42.1%.

When surplus steam is also supplied to the absorption refrigerator, 1170 kg / h of the surplus steam of 1460 kg / h is used as a driving heat source of the absorption refrigerator, and the remaining 290 kg / h is the pressure in the steam separator. Is supplied to the exhaust gas turbine while being controlled to a predetermined pressure, 1050 kW is obtained as the electric output of the generator driven by the exhaust gas turbine. on the other hand,
The amount of cold heat obtained from the absorption refrigerator is 730 Mcal / h. Here, the power generation efficiency evaluated by the total electric output of the fuel cell and the generator is 40.9%, but the cold heat recovery efficiency is 7.8%, so the total power generation efficiency and the cold heat recovery efficiency are The total is 48.7%, which is higher than the above case.

When water vapor is introduced into the absorption refrigerator in the summer, the load on the fuel cell is small, so that a sufficient amount of steam to operate the absorption refrigerator cannot be secured, or the demand for cold water is small. When the generated excess steam cannot be introduced into the absorption refrigerator, the entire amount of the steam is introduced into the exhaust gas turbine. Further, when the amount of excess steam is excessive with respect to the demand for cold water, the excess steam can be introduced into the exhaust gas turbine and the absorption chiller can be operated. Since the pressure in the separator is controlled to a predetermined pressure, the cooling water temperature of the fuel cell is maintained at a constant saturation temperature, and the operability of the fuel cell combined heat and power facility is greatly improved.

FIG. 2 is a system diagram of a fuel cell combined heat and power supply facility equipped with a cooling water exhaust heat recovery device for a fuel cell according to another embodiment of the present invention. 2, the absorption type refrigerator 40, the steam supply system 43 for the refrigerator, and the flow control valve 4 are added to the conventional example of FIG.
4, a temperature detector 48, a controller 49, etc. are provided, and the operation and effect thereof are the same as those in FIG. FIG. 3 is a system diagram of a fuel cell combined heat and power supply facility including a fuel cell cooling water exhaust heat recovery device according to another embodiment of the present invention. Figure 3
In the conventional example shown in FIG. 6, an absorption refrigerator 40, a steam supply system 43 for the refrigerator, a flow control valve 44, a temperature detector 48,
An adjuster 49 and the like are provided, and the operation and effect thereof are the same as those in FIG.

[0029]

As is apparent from the above description, according to the present invention, by the method and configuration described above, the excess steam remaining in the steam separator in the required amount is supplied to the fuel reformer. In addition to supplying electric power from the generator to the exhaust gas turbine or air of the reaction gas from the compressor, it can be supplied to the absorption refrigerator to obtain cold water, which has the effect of increasing the total energy efficiency. is there.

Further, depending on the amount of excess steam other than the amount of steam required for the fuel reformer and the presence / absence of demand for cold water in summer and winter, the entire amount of excess steam may be supplied to the exhaust gas turbine or a part thereof. Can also be supplied to the absorption chiller, which has the effect of greatly improving the operability of the plant.

[Brief description of drawings]

FIG. 1 is a system diagram of a fuel cell combined heat and power supply facility including a cooling water exhaust heat recovery device for a fuel cell according to an embodiment of the present invention.

FIG. 2 is a system diagram of a fuel cell combined heat and power supply facility including a cooling water exhaust heat recovery device for a fuel cell according to a different embodiment of the present invention.

FIG. 3 is a system diagram of a fuel cell combined heat and power supply facility including a cooling water exhaust heat recovery device for a fuel cell according to another embodiment of the present invention.

FIG. 4 is a system diagram of a conventional fuel cell combined heat and power supply facility.

FIG. 5: System diagram of different conventional fuel cell combined heat and power equipment

FIG. 6 is a system diagram of another conventional fuel cell combined heat and power facility.

[Explanation of symbols]

 1 Fuel Cell 6 Fuel Reforming Device 12 Steam Separator 17 Compressor 21 Generator 22 Exhaust Gas Turbine 35 Exhaust Gas Turbine 40 Absorption Refrigerator 44 Flow Control Valve 48 Temperature Detector 49 Regulator

Claims (3)

[Claims] 1. A fuel for which cooling water from which heat generated during power generation of a fuel cell is removed or cooling water that has exchanged heat with cooling air is separated into steam and cooling water by a steam separator and the flow rate of the steam is controlled. An exhaust gas turbine that feeds a reformer and adds the raw fuel to be steam-reformed, and further controls the pressure of the steam so that the pressure in the steam separator is a predetermined pressure to drive a generator, or a fuel cell In the cooling water exhaust heat recovery method of the fuel cell combined heat and power supply facility that supplies the exhaust gas turbine that drives the compressor that sends the reaction gas air to the exhaust gas turbine to recover the exhaust heat of the cooling water, the flow rate of the steam in the steam separator is controlled. A cooling water exhaust heat recovery method for a fuel cell combined heat and power supply facility, characterized in that the water supplied to the absorption chiller is cooled and the water supplied to the chiller is cooled to chilled water of a predetermined temperature. 2. A fuel cell and a steam separator for separating cooling water from which heat generated during power generation of the fuel cell is removed, or cooling water which has undergone heat exchange with cooling air in a heat exchanger into steam and cooling water. A fuel reformer for steam reforming by supplying the added raw fuel by controlling the flow rate of steam from the steam separator, and the steam from the steam separator, the pressure inside this separator becomes a predetermined pressure Exhaust gas turbine connected to a generator that supplies pressure-controlled gas or an exhaust gas turbine connected to a compressor that supplies reaction gas air to the fuel cell, and recovers exhaust heat of the cooling water of the fuel cell In a cooling water exhaust heat recovery device of a fuel cell combined heat and power supply facility, an absorption chiller that supplies steam from a steam separator and cools the supplied water into chilled water, and supplies this absorption chiller The flow rate of steam is cold water Degrees cooling water exhaust heat recovery apparatus of a fuel cell cogeneration facility which is characterized in that a flow control means for controlling to a predetermined temperature. 3. The flow rate control means according to claim 2, wherein the flow rate control means controls a flow rate of steam supplied from the steam separator to the absorption refrigerator, and the temperature of cold water obtained from the absorption refrigerator. Cooling water exhaust heat recovery of a fuel cell combined heat and power supply facility characterized by comprising a detector and control means for controlling the flow control valve based on a deviation between a temperature detected by the detector and a target value of a predetermined temperature of cold water apparatus.