JP3359146B2 - Fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell installed in a demand area for supplying electric power and heat to facilities such as factories, hotels, hospitals and the like.

[0002]

2. Description of the Related Art FIG. 1 is a schematic system diagram of a fuel cell of this type, in which a natural gas and steam sucked by an ejector 7 are supplied to a fuel reformer 1, and these are fed to a catalyst. The hydrogen obtained by the reaction is converted into the fuel cell body 3
The heat of the exhaust gas is supplied to the exhaust gas condenser 2
Collected at. In the fuel cell body 3, hydrogen reacts with oxygen in the air to generate electricity and heat. Since this electricity is DC, it is converted into AC for general use by the inverter 4,
The heat generated in the fuel cell body 3 is recovered by the exhaust heat recovery device 5. The water collected by the exhaust gas condenser 2 is converted into steam by the exhaust heat from the fuel cell body 3 by the steam generator 6 and sent to the ejector 7. As described above, the energy use efficiency of the entire fuel cell is extremely high, and the power generation efficiency is about 4%.
0%, waste heat recovery efficiency is about 40%, and heat wasted by exhaust gas is about 20%.

FIG. 2 specifically shows the configuration of FIG. 1. An exhaust heat recovery device 5 in FIG. 1 includes a steam-water separator 6 as a steam generator, a separator of the fuel cell body 3, and a high-temperature heat load. It is composed of a heat exchanger and the like interposed in the path to 10 . The pressure in the steam separator 6 is maintained at 6 to 7 atm.
° C hot water is sent out, and the exhaust heat is recovered as high temperature steam of about 170 ° C. The fuel cell body 3 is formed by stacking a large number of cells (cells) each having an electrolyte matrix sandwiched between a fuel electrode using a platinum catalyst and an air electrode with a separator interposed therebetween, and is provided in the separator. Cooling water is passed through a number of pores to make the cell about 175 to 190 ° C suitable for the reaction.
The high-temperature steam coming out of the fuel cell main body 3 undergoes heat exchange with the high-temperature heat load 10 and returns to the steam separator 6.

[0004] The steam evaporated in the steam separator 6 is mixed with natural gas (main component: CH4) by an ejector 7 provided at a natural gas supply port of the fuel reformer 1 to become a raw material for generating hydrogen. In a steady state, the heat required for the reaction in the fuel reformer 1 is supplied by combustion of excess hydrogen returning from the fuel electrode of the fuel cell body 3. Therefore, the combustion exhaust gas from the fuel reformer 1 contains a large amount of water vapor, and this water vapor is condensed in the exhaust gas condenser 2, purified by the pure water device 8, and returned to the steam separator 6. It is. The heat of condensation at this time is taken out of the exhaust gas condenser 2 as hot water of about 55 ° C., and is circulated and supplied to the low-temperature heat load 11 by the pump 9.

[0005]

In the conventional fuel cell, the heat recovery efficiency is about 40% as described above, and about half of the recovered heat is high in the form of high-temperature steam at 160 ° C. to 170 ° C. Although the utility value is high because it is supplied to the thermal load 10, the other half is low utility value because it is supplied to the low-temperature heat load 11 as hot water having a relatively low temperature of about 55 ° C. May not be found,
There is a problem that the actual heat recovery efficiency is not so high. Therefore, an object of the present invention is to improve the exhaust heat recovery device of a fuel cell to increase the ratio of high-quality heat that can be used in high-temperature heat utilization equipment.

[0006]

As shown in FIGS. 3 and 4, the fuel cell according to the present invention is characterized in that the amount of heat generated during power generation is extracted as high-temperature saturated steam and low-temperature hot water. The steam in the evaporator is sucked by an ejector that is guided to the evaporator and inserted in the path of the high-temperature saturated steam, the output steam of the ejector is supplied to a high-temperature heat load, and the low-temperature hot water remaining in the evaporator is supplied. Is supplied to a low-temperature heat load.

[0007]

In the evaporator 13, hot water of about 55 ° C. is vaporized by the sprayer 14, and the vapor is sucked into the ejector 12, so that the pressure in the evaporator 13 is reduced to about 0.1 atm. Then, the heat of vaporization is lost, and the temperature drops to about 45 ° C. On the high temperature side, a large amount of saturated steam of 45 ° C. is sucked together with latent heat from the low temperature side into steam of about 170 ° C. and 6 to 7 atm. Although the flow rate is reduced, the flow rate is greatly increased, and as a result, about 1.5 times the amount of heat is supplied to the high-temperature heat load 10 having a high effective energy utilization rate.

[0008]

FIG. 3 shows an embodiment of the present invention, in which high-temperature hot water sent from a steam separator 6 is supplied to cooling pores provided in a separator between cells in the fuel cell body 3. The high-temperature steam that has passed through is subjected to heat exchange at the high-temperature heat load 10 to condense, and returns to the steam separator 6. On the other hand, low-temperature hot water for cooling is circulated through an exhaust gas condenser 2 for recovering water from the combustion exhaust gas of the fuel reformer 1 that supplies hydrogen to the fuel cell body 3, and exits from the exhaust gas condenser 2. Low-temperature hot water is supplied to the low-temperature heat load 11. The present invention
A part of the heat supplied to the low-temperature heat load 11 is directed to the high-temperature heat load 10. The ejector 12 is interposed in the path from the steam separator 6 to the high-temperature heat load 10. Sucking saturated steam from an evaporator 13 provided in a path of low-temperature hot water downstream of the exhaust gas condenser ,
The output steam of the ejector 12 is supplied to the high-temperature heat load 7, and the low-temperature hot water remaining in the evaporator 13 is supplied to the low-temperature heat load 11. A heat pump A for pumping heat to a high temperature side is formed.

In FIG. 3, the fuel cell body 3 is cooled by high-temperature hot water sent from a steam-water separator 6 at a pressure of 6 to 7 atm 160 ° C., and high-temperature steam coming out of the fuel cell body 3 is sent to a high-temperature heat load 7. An ejector 12 is provided in a pipe for feeding, and an evaporator 13 having a sprayer 14 is provided in a pipe in which low-temperature hot water of about 55 ° C. is circulated from a waste gas condenser 2 to a low-temperature heat load 11 by a pump 9. The saturated steam of about 45 ° C. evaporated from the evaporator 13 is sucked by the ejector 12 and
Is supplied to the high-temperature heat load 7 and the evaporator 1
3 is supplied to the low-temperature heat load 11 by the heat pump A formed by the ejector 12 and the evaporator 13. It is possible to pump half to the hot side. In the figure, reference numeral 15 denotes a steam trap which shuts off steam and allows only condensed water to pass therethrough. Reference numeral 16 denotes an electromagnetic valve controlled by a liquid level switch 17 and condensed water corresponding to the amount of steam sucked into the ejector 12 is supplied to the evaporator 13. It is for returning inside. With this configuration, the high-temperature heat load 10 having a high effective utilization rate of heat is about 30 times that of the conventional natural gas input, which is 1.5 times that of the conventional case.
%, The low-temperature heat load 11 having a low effective utilization rate is supplied with a heat amount of 10% which is half of the conventional heat load, and the quality of the recovered heat can be improved.

FIG. 4 shows another embodiment of the present invention, in which the high-temperature cooling water circulated from the steam separator 6 to the fuel cell main body 3 is not sent to the load 10 but is temporarily stopped. The high-temperature steam of about 160 ° C. is sent from the steam separator 6 to the high-temperature heat load 10. The high-temperature steam pipe is provided with the ejector 12 of the heat pump A. Is the same.

[0011]

According to the present invention, as described above, of the waste heat recovered from the conventional fuel cell, the ratio of the high-temperature heat that can be effectively used can be increased from 50% to 75%.
Thereby, there is an advantage that the substantial heat recovery efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram of a conventional fuel cell.

FIG. 2 is a specific system diagram of the above.

FIG. 3 is a system diagram of one embodiment of the present invention.

FIG. 4 is a system diagram of another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel reformer 2 Exhaust gas condenser 3 Fuel cell main body 4 Inverter 5 Exhaust heat recovery device 6 Steam separator 7 Ejector 8 Pure water device 9 Pump 10 High temperature heat load 11 Low temperature heat load 12 Ejector 13 Evaporator A Heat pump

Claims (3)

(57) [Claims] 1. A fuel cell in which the amount of heat generated during power generation is taken out as high-temperature saturated steam and low-temperature hot water,
The low-temperature hot water is led to an evaporator, and the steam in the evaporator is sucked by an ejector interposed in a path of the high-temperature saturated steam, and the output steam of the ejector is supplied to a high-temperature heat load, and the evaporator is A low-temperature hot water remaining in the fuel cell is supplied to a low-temperature heat load. 2. The high-temperature hot water sent from the steam-water separator is passed through cooling pores provided in the separator between the cells in the fuel cell body, and the high-temperature steam that has come out is subjected to heat exchange with a high-temperature heat load. After being condensed, return to the steam-water separator, and circulate low-temperature hot water for cooling to an exhaust gas condenser that collects water from the combustion exhaust gas of the fuel reformer that supplies hydrogen to the fuel cell main body. In a fuel cell adapted to supply to a low-temperature heat load, an ejector interposed in the path of the high-temperature steam causes steam to be sucked from an evaporator provided in a path of low-temperature hot water downstream of the exhaust gas condenser. Fuel cell. 3. A high-temperature steam for cooling is circulated from the steam separator to the fuel cell main body, and the high-temperature steam sent from the steam separator to the high-temperature heat load is condensed by the load and returned to the steam separator. A low-temperature hot water for cooling is circulated through an exhaust gas condenser for collecting water from a combustion exhaust gas of a fuel reformer for supplying hydrogen to the fuel cell body, and the low-temperature hot water is supplied to a low-temperature heat load. A fuel cell comprising a battery, wherein an ejector interposed in a path from the steam-water separator to a high-temperature heat load sucks steam from an evaporator provided in a path of low-temperature hot water downstream of the exhaust gas condenser .