JP2002373683A - Exhaust heat utilization method and device for fuel cell power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust heat utilization method and a device for a fuel cell power generation system, that save energy in a heat source for preventing freeze up of makeup water and/or a heat source for heating cooling water for a hot-water-fired absorption chiller/heater. SOLUTION: The exhaust heat utilization method, which is for a fuel cell power generation system, comprising a fuel cell 1, a fuel reformer for generating hydrogen-rich reformate gas by a reforming reaction of hydrocarbon and steam, exhaust heat processing equipment 65 for subjecting exhaust heat from the fuel cell and the fuel reformer to heat exchange, with the cooling water of different temperature levels and delivering the exhaust, and makeup water supply piping 69 for water for the reforming reaction and water for the cooling water, utilizes lower temperature level cooling water in the cooling water of the different temperature levels in heating the makeup water supply piping 69 in a cold environment, in order to prevent freezing of the makeup water. The lower temperature level cooling water is utilized in heating the cooling water 63 for the hot-water fired absorption chiller/heater 66.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for utilizing exhaust heat of a fuel cell power generator.

[0002]

2. Description of the Related Art As is well known, phosphoric acid type fuel cells, solid polymer electrolyte type fuel cells, molten carbonate type fuel cells, and the like use a fuel gas as a reaction gas and an oxidizing gas as a fuel provided with an electrode catalyst layer. The energy is continuously supplied to the electrode and the oxidant electrode, and the energy of the fuel is electrochemically converted into electric energy.

[0003] In these fuel cells, it is possible to use fuel gas or oxidizing gas containing carbon dioxide due to the nature of the electrolyte. Therefore, in these fuel cells, usually, air is used as an oxidizing gas, and a hydrogen-rich reformed gas obtained by steam reforming a hydrocarbon raw fuel such as methanol or natural gas by a fuel reformer is used as a fuel gas. Used as

FIG. 6 shows an example of a schematic system configuration of a conventional phosphoric acid fuel cell power generator.

[0006] In FIG. 6, a fuel cell 1 is schematically shown, and is provided with a fuel electrode 2 and an air electrode 3 sandwiching a phosphoric acid electrolyte layer (not shown), and each time a plurality of unit cells composed of these are stacked. And a cooling plate 4 having cooling pipes.

On the other hand, the fuel reformer 7 converts a raw fuel such as natural gas supplied through a raw fuel supply system 9 into a steam separator 2.
Along with the steam separated in step 1 and supplied through the steam supply system 22, it is heated under the reforming catalyst by the combustion heat of the below-described off-gas combustion in the burner, reformed into a hydrogen-rich gas, and reformed. Generates quality gas.

[0007] The reformed gas generated by the fuel reformer 7 is supplied to the fuel electrode 2 of the fuel cell 1 via a reformed gas supply system 11 having a CO converter 8, while the fuel electrode 2 The off gas containing hydrogen that does not contribute to the cell reaction is supplied to the burner of the fuel reformer 7 through the off gas supply system 12 as fuel.

A blower 13 for supplying combustion air is connected to the burner of the fuel reformer 7.
Is discharged to the water recovery condenser 41 by the flue gas system 15 and discharged after water recovery.

The fuel cell 1 has an air supply system 17 having a reaction air blower 16 for supplying air to the air electrode 3.
And an air discharge system 18 that supplies air after the battery reaction to the water recovery condenser 41.

A steam separator 21, a cooling water circulation pump 24, and a heat exchanger for recovering fuel cell cooling water waste heat are provided in the cooling pipe of the cooling plate 4 of the fuel cell 1 in order to circulate the cooling water during power generation of the fuel cell 1. A cooling water circulation system 20 provided with 23 is connected. The cooling water circulation system 20 includes a cooling water control valve 25 so that the flow of the cooling water to the waste heat recovery heat exchanger 23 can be adjusted as needed.

The steam separator 21 separates the cooling water discharged from the cooling pipe of the fuel cell 1 into a two-phase flow of water and steam into steam and cooling water. The steam separated here is sent out through the steam supply system 22 so as to be mixed with the raw fuel toward the fuel reformer 7. At that time, the ejector 6 is used for mixing with the raw fuel having a low original pressure. The ejector 6 uses steam as a driving fluid and raw fuel as a driven fluid. The raw fuel supply system 9 generally includes a desulfurizer 5.

As described above, the flue gas system 15 and the air discharge system 18 are connected to the water recovery condenser 41, and the water recovery condenser 41 has a coagulation tank 44 having a recovery tank 44 such as generated water. A water recovery system 42 is connected.

The recovered water is brought into contact with air in a decarbonation tower 43 to perform decarbonation treatment, and then introduced into an ion-exchange type water treatment device 47 by a makeup water pump 46 to be purified and purified. The steam is fed back to the steam separator 21 by 49 and is used as water required for steam reforming of the raw fuel.

The water treatment device 47 requires a constant amount of water flow rate because of the adsorption speed. Therefore, a closed circuit in which water circulates is provided in the water treatment device, and the water treatment device 47 constantly supplies a constant flow rate. To a predetermined SV value (space velocity 1
/ H) is generally maintained. In this case, as shown in FIG. 6, the water treatment device 47
8, and a part of the treated water is partially supplied with a water supply pump 49.
Is supplied to the steam separator 21, and the remaining pure water is
The water is returned to the water treatment device 47 again via the recirculation pipe 48.

In the case of a solid polymer electrolyte fuel cell power generator, normally, the reformed gas derived from the CO converter is introduced into a CO remover provided at the subsequent stage of the CO converter, and CO is removed. Oxidizes to reduce the CO concentration in the reformed gas to 10 pp
m.

FIG. 6 shows an example of a standard system configuration. The system configuration has various forms according to needs.
Even when the method is limited to the method of using exhaust heat of the fuel cell power generator, various modes exist. For example, FIG. 7 is proposed by the same applicant in order to effectively use the exhaust heat of the fuel cell and to prevent the exhaust gas discharged from the water recovery device from becoming white smoke, and Japanese Patent Application No. 2000-285796. 2 shows a configuration example described in FIG.

In FIG. 7, some components such as the water treatment apparatus in FIG. 6 are omitted, and the same components as those in FIG.

In FIG. 7, the water recovery device 52 is provided with an exhaust gas heating heat exchanger 52 for heating the exhaust air and the combustion exhaust gas whose water has been recovered, above an exhaust gas cooler 53 for water recovery. Further, the cooling water derived from the steam separator 21 flows through the exhaust heat utilizing heat exchange device 54 to be cooled, and then flows through the exhaust gas heating heat exchanger 52 for further cooling. , A cooling water circulation circuit 55 that merges with water derived from the steam separator 21.

The steam separator 21 has a pressure gauge 32, and the cooling water circulation circuit 55 has a flow rate control valve 33 for controlling the pressure in the steam separator 21 to be constant based on the measurement value of the pressure gauge 32. . Reference numeral 30 denotes a battery cooling water circulation pump, and reference numeral 31 denotes a makeup water pump.

In the above configuration, a part of the battery cooling water is branched, flows through the exhaust heat utilizing heat exchange device 54 to be cooled, and then flows through the exhaust gas heating heat exchanger 52 for further cooling. In addition, the amount of heat generated and the amount of heat removed in the fuel cell can be balanced. Incidentally, FIG. 7 shows T
The temperature of each part shown by 1 to T10 is exemplified as follows. At the following temperatures, numerical values shown in parentheses are representative temperatures.

T1: 160 to 170 ° C. (160 ° C.), T2: 140 to 170 ° C. (145 ° C.) T3: 85 to 95 ° C. (95 ° C.), T4: 50 to 90 ° C. (60 ° C.) T5: 70 to 85 ° C (85 ° C), T6: 80 to 95 ° C (90 ° C) T7: 30 to 40 ° C (40 ° C), T8: 40 to 60 ° C (50 ° C) T9: 40 to 45 ° C (45 ° C), T10: 45 to 55 ° C. (50 ° C.) As described above, the temperature T9 of the exhaust gas cooled and recovered in the water recovery device 51 is 40 to 45 ° C., and the exhaust gas is supplied to the exhaust gas heating heat exchanger 52. And the temperature T10 is increased by 45-55.
By setting the temperature to ° C., even if the water vapor in the exhaust gas is exposed to the outside air, the white smoke of the water vapor is not immediately generated, and the white smoke of the exhaust gas can be prevented.

By the way, as shown in FIGS. 6 and 7, in general, in a fuel cell power generation apparatus, a fuel cell and a fuel reformer that generates a hydrogen-rich reformed gas by a reforming reaction between hydrocarbons and steam. Heat from the fuel cell and the fuel reformer, and heat is exchanged with cooling water having different temperature levels to be discharged, or the heat exchanger for low-temperature water and the heat for high-temperature water are used to effectively use the exhaust heat. And an air-cooled cooler for final exhaust heat treatment.

In the system shown in FIG. 7, the exhaust gas cooler 53 corresponds to a low-temperature water heat exchanger, and the exhaust heat utilizing heat exchanger 54 corresponds to a high-temperature water heat exchanger. In the system shown in FIG. 6, the water recovery condenser 41 and the fuel cell cooling water waste heat recovery heat exchanger 23 correspond to a low-temperature water heat exchanger and a high-temperature water heat exchanger, respectively. In FIG. 6 as well, the representative temperature is the same temperature as the low-temperature water heat exchanger and the high-temperature water heat exchanger in FIG. 7. Is about 50 ° C., and high-temperature water is about 90 ° C.

The high-temperature wastewater at a temperature of 90 ° C. is generally effectively used as a heating source for hot water supply equipment and a hot water absorption absorption chiller / heater, and is used for cooling in summer and for heating in winter. On the other hand, the low-temperature drainage at the 50 ° C. level has a low temperature, and therefore has few targets for its effective use.
It is released by an exhaust heat treatment facility consisting of an air-cooled cooler.

On the other hand, in the fuel cell power generator and the exhaust heat treatment equipment, it is necessary to supply replenishing water from the outside depending on the operation state during the operation, in addition to the water filling before the operation of the apparatus.
The fuel cell generates water by reaction, but generates a large amount of water during high-load operation, and it is not necessary to supply water from the outside. However, when the load is reduced or when water is discharged out of the system for some reason, replenishment is required. Even in the high-temperature water system of the waste heat treatment facility, replenishment is required when water is discharged out of the system for some reason in addition to water filling before operation of the device due to a closed loop.

For this reason, it is necessary to connect a supply water supply pipe so that replenishment can always be performed. However, as described above, the replenishing water does not always flow, but only when replenishment is required.Therefore, the water in the replenishing water system hardly flows, and when installed outdoors, it may freeze in cold weather. There is. Conventionally, therefore, an electric heater is wound around the supply water supply pipe or hot water is passed through a hot water flow pipe (so-called trace pipe) to prevent freezing.

FIG. 5 shows a simplified system diagram of the configuration of the conventional exhaust heat utilization system having the hot water absorption absorption chiller / heater and make-up water supply pipe for convenience of the description of the present invention. In FIG. 5, members having the same functions as those of the components of the system shown in FIG. 6 or FIG.

The main differences between FIG. 5 and FIG. 6 or FIG.
In FIG. 5, a system such as a hot water-fired absorption chiller / heater or makeup water supply pipe indicated by reference numerals 61 to 70 and its related members are provided. In FIG. 5, reference numeral 61 denotes a low-temperature level cooling water line of the exhaust heat cooling water, 62 denotes a high-temperature level cooling water line, and the cooling water exhaustion in 61 is air-cooled exhaust water in 65. Released by heat treatment equipment.

The high-temperature cooling water 62 flows through a hot-water-absorbing absorption-type hot / cold water heater 66 and then flows through the waste heat treatment facility 65 to release heat. Reference numeral 67 denotes an air conditioner through which cold water or hot water generated in the hot water-fired absorption type cold / hot water machine 66 flows. 63 is a cooling water in the hot water-fired absorption chiller / heater 66, and 68 is a cooling tower for cooling the cooling water.

Reference numeral 69 denotes a makeup water supply pipe, and reference numeral 70 denotes
Fig. 4 shows a heater laying portion or a trace pipe for preventing freezing provided in a makeup water supply pipe.

[0031]

The above-mentioned FIG.
However, the conventional method and apparatus for utilizing exhaust heat of a fuel cell power generation apparatus as described above have the following problems.

When the heater is energized to prevent the make-up water from freezing, the amount of power consumption substantially reduces the power generation efficiency of the fuel cell, and there is basically a problem from the viewpoint of energy saving. The same applies to the case where hot water for preventing freezing flows through the trace pipe.

In recent years, in computer rooms and offices with a high density of OA equipment, the need for cooling operation has been increasing even in winter, and when performing cooling operation using the hot-water-absorption absorption chiller / heater, It is necessary to constantly heat the cooling water in the hot water-fired absorption chiller / heater. The reason for this is that in the case of a hot water-fired absorption chiller / heater, it is necessary to maintain the cooling water chiller / heater inlet temperature at about 24 ° C. during the operation for efficient operation.
At the start of the cooling operation of the hot water-fired absorption chiller / heater, it is required that the temperature be at least 20 ° C.

Therefore, it is necessary to constantly heat the cooling water not only in winter but also in some areas in cold weather, and it is desired to procure this heating source and save energy.

The present invention has been made in view of the above points, and an object of the present invention is to reduce the energy consumption of a heat source for preventing make-up water from freezing and a heating heat source for cooling water in a hot water absorption absorption chiller / heater. It is an object of the present invention to provide a method and an apparatus for utilizing exhaust heat of a fuel cell power generator.

[0036]

In order to solve the above-mentioned problems, the present invention provides a fuel cell and a fuel reformer for producing a hydrogen-rich reformed gas by a reforming reaction between hydrocarbon and steam. A waste heat treatment facility for exchanging heat discharged from the fuel cell and the fuel reformer with cooling water having different temperature levels and discharging the same, and a makeup water for the reforming reaction water and a cooling water. In the method of utilizing exhaust heat of a fuel cell power generator including a supply pipe, the cooling water having a low temperature level among the cooling water having the different temperature levels may be cooled, in order to prevent the makeup water from freezing, It is used for heating the makeup water supply pipe (the invention of claim 1).

In the method for utilizing exhaust heat according to claim 1, the water used for heating the makeup water supply pipe is
Instead of the low-temperature-level cooling water, high-temperature-level cooling water of the different-temperature-level cooling water is used (the invention of claim 2). Furthermore, in the method of utilizing exhaust heat according to claim 2, instead of using the high-temperature level cooling water for heating the makeup water supply pipe, a part of the high-temperature level cooling water is used, It is introduced into the makeup water supply pipe (the invention of claim 3).

According to the first to third aspects of the present invention, the exhaust heat of the fuel cell power generation device is effectively used to prevent the make-up water from freezing, and energy saving can be achieved as compared with the related art.

Further, a fuel cell, a fuel reformer for producing a hydrogen-rich reformed gas by a reforming reaction of hydrocarbons and steam, and a heat exhausted from the fuel cell and the fuel reformer, A fuel comprising: a waste heat treatment facility for exchanging heat with cooling water having different levels to discharge the same; and a hot water-fired absorption chiller / heater using a high-temperature cooling water as a heating source among the cooling water having different temperature levels. In the method for utilizing exhaust heat of a battery power generator, cooling water having a low temperature level among the cooling waters having different temperature levels is used for heating cooling water in the hot water-fired absorption chiller / heater. invention).

According to the fourth aspect of the present invention, the exhaust heat of the fuel cell power generation device is effectively used for heating the cooling water in the hot water absorption type chiller / heater. Can be achieved.

Further, as a preferred exhaust heat utilization device of the fuel cell power generator for carrying out the invention of claim 1 or 4, the following invention of claim 5 is preferable. That is, an apparatus for performing the exhaust heat utilization method according to claim 1 or 4, wherein the fuel cell and a reforming reaction between hydrocarbon and steam generate a hydrogen-rich reformed gas. A heat treatment facility for exchanging heat discharged from the fuel cell and the fuel reformer with cooling water having different temperature levels and discharging the same, and water for the reforming reaction and water for cooling water. A makeup water supply pipe, and a hot-water-absorption absorption chiller / heater using a high-temperature cooling water as a heating source among the cooling waters having different temperature levels, and further, A means for heating the makeup water supply pipe with low-temperature cooling water and / or a means for heating cooling water in the hot-water-absorption absorption chiller / heater with the low-temperature cooling water; Shall be.

[0042]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing an embodiment of the present invention. The same functional members as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

The basic difference in the system configuration between FIG. 1 and FIG. 5 is that in FIG. 1, a cooling water branch line 80 and a make-up water heating line 81 at a low temperature level are provided.

The branch line 80 branches from the cooling water line 61 at a low temperature level.
Connected to. The makeup water heating line 81 is provided instead of the heater laying portion or the trace pipe 70 in FIG. The water after heating the make-up water is returned to the low temperature level cooling water line 61 via a return line (not shown). In practicing the second aspect of the present invention, in FIG. 1, the branch line 80 branches from a high temperature level cooling water line 62 instead of the low temperature level cooling water line 61.

Next, the embodiment shown in FIGS. 2 and 3 will be described. The embodiments of FIGS. 2 and 3 are both embodiments according to the third aspect of the present invention.
For convenience of explanation, attention is focused on a cooling water line and a makeup water supply line at a high temperature level, and the others are shown in a simplified manner. 2 and 3, the same functional members as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. 2 and 3 are substantially the same from the viewpoint of utilization of exhaust heat. The difference is that FIG. 2 shows a closed system having an expansion tank 90, and FIG.
The only difference is that an open system having 4a is configured. Therefore, this embodiment will be described below with reference to FIG.

In FIG. 2, the fuel cell power generator main body 10
0 has a low temperature level heat exchanger 100a and a high temperature level heat exchanger 100b, and the high temperature level cooling water line 62 is expanded with the exhaust heat utilization equipment 90, the high temperature water pump 91, the exhaust heat treatment equipment 65, And a tank 94. Further, the cooling water branch line 92 of the high temperature level is connected to the makeup water supply pipe 69 to prevent freezing. Reference numeral 7a denotes a supply water supply line to the high temperature level cooling water line 62. The supply water is supplied after being purified in the resin cylinder 93.

Next, the embodiment shown in FIG. 4 will be described. The basic difference in the system configuration between FIG. 4 and FIG. 5 is that, in FIG. 4, the system for heating cooling water in the hot-water-absorption absorption chiller / heater branched from the low-temperature-level cooling water line 61. The point is that a heating line 85 for cooling water is provided.

According to the above embodiment, as described above, the exhaust heat of the fuel cell power generation device is effectively used, and energy saving can be achieved as compared with the related art. FIGS. 1 and 4 show embodiments corresponding to the first and fourth aspects of the present invention. However, FIG. 1 is different from FIG. 5 in that both of the systems added to FIGS. 1 and 4 are provided. You can also.

[0050]

As described above, according to the present invention, the low-temperature water in the cooling water for exhaust heat, which has conventionally been difficult to use effectively in the fuel cell power generator, is used to prevent the freezing water from freezing and / or to absorb hot water. By effectively utilizing the cooling water of the chiller / heater for heating the cooling water, the electric power for the anti-freezing electric heater and the energy for the heating heat source for the cooling water are not required, and the energy can be saved. In addition, by effectively utilizing a part of the high-temperature water in the cooling water for exhaust heat as described above to prevent the make-up water from freezing, energy can be saved similarly.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an exhaust heat treatment apparatus for a fuel cell power generator according to the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention which is different from FIG. 1;

FIG. 3 is a diagram showing an embodiment different from FIG. 2 of the present invention;

FIG. 4 is a diagram showing an embodiment of the present invention which is further different from FIG. 1;

FIG. 5 is a diagram showing an example of a schematic configuration of a conventional exhaust heat utilization device of a fuel cell power generator.

FIG. 6 is a diagram showing an example of a schematic system configuration of a conventional phosphoric acid fuel cell power generator.

FIG. 7 is a diagram showing a schematic system configuration of a conventional fuel cell power generator different from FIG. 6;

[Explanation of symbols]

1: fuel cell, 23: heat exchanger for waste heat recovery, 41: condenser for water recovery, 53: exhaust gas cooler for water recovery, 61: cooling water line at low temperature level, 62: cooling at high temperature level Water line, 63: cooling water, 65: waste heat treatment equipment, 6
6: hot water-fired absorption chiller / heater, 67: air conditioner, 68: cooling tower, 69: makeup water supply pipe, 81: makeup water heating line, 80: low temperature cooling water branch line, 85: cooling water Heating line, 92: high temperature level cooling water branch line.

Claims (5)

[Claims] 1. A fuel cell, a fuel reformer that generates a hydrogen-rich reformed gas by a reforming reaction between hydrocarbons and steam, and heat discharged from the fuel cell and the fuel reformer, In a method for utilizing exhaust heat of a fuel cell power generator, comprising: a waste heat treatment facility for exchanging heat with different levels of cooling water and discharging the same; and a supply water supply pipe for the reforming reaction water and cooling water. A fuel cell characterized in that low-temperature-level cooling water among the cooling waters having different temperature levels is used for heating the makeup water supply pipe in order to prevent the makeup water from freezing in cold weather. How to use the waste heat of the power generator. 2. The method according to claim 1, wherein the water used for heating the makeup water supply pipe is replaced with the low-temperature cooling water, and the cooling water having the different temperature level is used. A method for utilizing exhaust heat of a fuel cell power generator, wherein the cooling water is at a high temperature level in the inside. 3. The method according to claim 2, wherein the high-temperature level cooling water is partially used instead of using the high-temperature level cooling water for heating the makeup water supply pipe. Is introduced into the make-up water supply pipe. 4. A fuel cell, a fuel reformer that generates a hydrogen-rich reformed gas by a reforming reaction between hydrocarbons and steam, and heat discharged from the fuel cell and the fuel reformer is converted into a temperature. A fuel comprising: a waste heat treatment facility for exchanging heat with cooling water having different levels to discharge the same; and a hot water-fired absorption chiller / heater using a high-temperature cooling water as a heating source among the cooling water having different temperature levels. In the method of using exhaust heat of a battery power generation device, the method further comprises using low-temperature-level cooling water in the cooling water having different temperature levels for heating cooling water in the hot-water-fired absorption-type chiller / heater. A method for utilizing exhaust heat of a fuel cell power generator. 5. An apparatus for carrying out the method of utilizing exhaust heat according to claim 1, wherein a hydrogen-rich reformed gas is produced by a reforming reaction between a fuel cell and hydrocarbons and steam. A fuel reformer, a waste heat treatment facility for exchanging heat discharged from the fuel cell and the fuel reformer with cooling water having different temperature levels and discharging the same, and a water and a cooling water for the reforming reaction. Supply water supply pipe, and a hot water-fired absorption chiller / heater using a high-temperature level cooling water among the cooling waters having different temperature levels as a heating source. Means for heating the makeup water supply pipe with low-temperature cooling water, and / or heating the cooling water in the hot-water-absorption absorption chiller / heater with the low-temperature cooling water. Characterized by having means Waste heat utilization device of a fuel cell power generator.