JP4453211B2 - Waste heat treatment method and apparatus for fuel cell power generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust heat treatment method and an exhaust heat treatment apparatus for a fuel cell power generator, and more particularly to a method and an apparatus using an air-cooled cooler.
[0002]
[Prior art]
As is well known, a phosphoric acid fuel cell, a solid polymer electrolyte fuel cell, a molten carbonate fuel cell, and the like are provided with a fuel electrode and an oxidant electrode having an electrode catalyst layer for a fuel gas and an oxidant gas as reaction gases. The energy of the fuel is electrochemically converted into electrical energy.
[0003]
In these fuel cells, it is possible to use a fuel gas or oxidant gas containing carbon dioxide due to the nature of the electrolyte. Therefore, in these fuel cells, hydrogen-rich reformed gas obtained by steam reforming a hydrocarbon-based raw fuel such as methanol or natural gas with a fuel reformer is usually used as fuel gas. It is used as.
[0004]
FIG. 4 shows an example of a schematic system configuration of a conventional phosphoric acid fuel cell power generator.
[0005]
In FIG. 4, a fuel cell 1 is schematically shown, and is provided with a fuel electrode 2 and an air electrode 3 that sandwich a phosphoric acid electrolyte layer (not shown) and a cooling unit that is disposed each time a plurality of unit cells composed of these are stacked. And a cooling plate 4 having a tube.
[0006]
On the other hand, the fuel reformer 7 separates the raw fuel such as natural gas supplied through the raw fuel supply system 9 together with the steam separated by the steam separator 21 and supplied through the steam supply system 22 together with the reforming catalyst. Below, it heats by the combustion heat by the combustion of the off gas mentioned later in a burner, and reforms to gas rich in hydrogen, and produces | generates reformed gas.
[0007]
The reformed gas generated in the fuel reformer 7 is supplied to the fuel electrode 2 of the fuel cell 1 via the reformed gas supply system 11 having the CO converter 8, while the cell reaction is performed from the fuel electrode 2. Off-gas containing hydrogen that does not contribute to the fuel is supplied as fuel to the burner of the fuel reformer 7 via the off-gas supply system 12.
[0008]
Further, a blower 13 for supplying combustion air is connected to the burner of the fuel reformer 7, and the combustion exhaust gas emitted from the fuel reformer 7 is sent to the water recovery condenser 41 by the combustion exhaust gas system 15. It is sent and discharged after water recovery.
[0009]
The fuel cell 1 includes an air supply system 17 including a reaction air blower 16 that supplies air to the air electrode 3, and an air discharge system 18 that supplies the air after the battery reaction to the water recovery condenser 41. Is connected.
[0010]
The cooling pipe of the cooling plate 4 of the fuel cell 1 includes a water vapor separator 21, a cooling water circulation pump 24, and a heat exchanger 23 for recovering waste heat from the fuel cell cooling water in order to circulate cooling water when the fuel cell 1 generates power. A cooling water circulation system 20 is connected. The cooling water circulation system 20 includes a cooling water adjustment valve 25 so that the circulation of the cooling water to the waste heat recovery heat exchanger 23 can be adjusted as necessary.
[0011]
In the water vapor separator 21, the cooling water that is a two-phase flow of water and steam discharged from the cooling pipe of the fuel cell 1 is separated into water vapor and cooling water. The separated water vapor is sent out through the water vapor supply system 22 so as to be mixed with the raw fuel going to 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.
[0012]
As described above, the flue gas exhaust system 15 and the air exhaust system 18 are connected to the water recovery condenser 41, and the water recovery condenser 41 has a condensed water recovery system having a recovery tank 44 for product water and the like. 42 is connected.
[0013]
The recovered water is brought into contact with air in the decarbonation tower 43 and decarboxylated, and then introduced into the ion-exchange water treatment device 47 by the make-up water pump 46 to be purified, and then the water is pumped by the feed water pump 49. Reflux is supplied to the separator 21 and used as water necessary for steam reforming of the raw fuel.
[0014]
The water treatment device 47 requires a certain amount of water flow rate due to the adsorption rate. For this reason, a closed circuit in which water circulates is provided in the water treatment device, and a constant flow rate is always passed through the water treatment device. It is common to maintain a predetermined SV value (space velocity 1 / h) as possible. In this case, as shown in FIG. 4, the water treatment apparatus 47 includes a pipe for recirculation of treated water, and a part of the water treated water is supplied to the water vapor separator 21 by the feed water pump 49 and the rest The pure water is returned to the water treatment device 47 again via the recirculation pipe 48.
[0015]
In the case of a solid polymer electrolyte fuel cell power generator, the reformed gas derived from the CO converter is usually introduced into a CO remover provided at the subsequent stage of the CO converter, and the CO is oxidized. The CO concentration in the reformed gas is reduced to about 10 ppm.
[0016]
FIG. 4 shows an example of a standard system configuration, but the system configuration has various forms according to needs, and various forms exist even when the exhaust heat treatment method of the fuel cell power generation apparatus is limited. For example, Figure 5, by effectively utilizing the exhaust heat of the fuel cell, and in order to prevent white smoke of exhaust gas discharged from the water recovery device, proposed by the same applicant, Japanese Patent Application No. 2000-285796 An example of the configuration described in is shown.
[0017]
In FIG. 5, some components such as the water treatment apparatus in FIG. 4 are omitted, and the same components as those in FIG.
[0018]
In FIG. 5, the water recovery device 52 includes an exhaust gas heating heat exchanger 52 for heating the exhaust air and combustion exhaust gas recovered from the water above the exhaust gas cooler 53 for water recovery. Further, the cooling water led out from the water vapor separator 21 is passed through the exhaust heat utilization heat exchanger 54 to be cooled, and then passed through the exhaust gas heating heat exchanger 52 to be further cooled. A cooling water circulation circuit 55 that joins the water derived from the water vapor separator 21 is provided.
[0019]
The water vapor separator 21 includes a pressure gauge 32, and the cooling water circulation circuit 55 includes a flow rate adjustment valve 33 that controls the pressure in the water vapor 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 31 denotes a makeup water pump.
[0020]
In the above configuration, a part of the battery cooling water is branched, passed through the exhaust heat utilization heat exchange device 54 and cooled, and then passed through the exhaust gas heating heat exchanger 52 for further cooling, whereby the fuel cell The amount of heat generated and the amount of heat removed can be balanced. Incidentally, the temperature of each part shown by T1-T10 in FIG. 5 is as follows. At the following temperatures, the numerical values shown in parentheses are representative temperatures.
[0021]
T1: 160-170 ° C (160 ° C), T2: 140-170 ° C (145 ° C)
T3: 85-95 ° C. (95 ° C.), T4: 50-90 ° 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: 40-45 ° C (45 ° C), T10: 45-55 ° 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 this exhaust gas is heated by the excess heat of the cooling water by the exhaust gas heating heat exchanger 52. However, by setting the temperature T10 to 45 to 55 ° 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 generated immediately, and the white smoke of the exhaust gas can be prevented.
[0022]
Incidentally, as shown in FIGS. 4 and 5, in general, in a fuel cell power generator, a fuel cell and a fuel reformer that generates a hydrogen-rich reformed gas by a reforming reaction of hydrocarbon and steam A low-temperature water heat exchanger and a high-temperature water heat exchanger for exchanging heat discharged from the fuel cell and the fuel reformer by cooling water having different temperature levels, and an air-cooled cooler Thus, the final exhaust heat treatment is performed.
[0023]
In the system shown in FIG. 5, the exhaust gas cooler 53 corresponds to a heat exchanger for low-temperature water, and the exhaust heat utilization heat exchanger 54 corresponds to a heat exchanger for high-temperature water. In the system shown in FIG. 4, 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. Also in FIG. 4, the representative temperature is the same level as the low temperature water heat exchanger and the high temperature water heat exchanger in FIG. 5.
[0024]
For convenience of explanation of the present invention, a simplified system diagram relating to the configuration of the conventional waste heat treatment system is shown in FIG.
[0025]
In FIG. 3, 61 is a heat exchanger for low temperature water for taking out the heat generated in the fuel cell power generator as low temperature water, and 62 is the heat generated in the fuel cell power generator. It is a heat exchanger for high-temperature water for taking out as outside. 63 is a low temperature water pump for circulating low temperature water, and 64 is a high temperature water pump for circulating high temperature water. Reference numeral 65 denotes a cooler for cooling the low-temperature water by the 67 air cooling fan, and reference numeral 66 is a cooler for cooling the high-temperature water by the 67 air cooling fan. Reference numeral 69 denotes a temperature sensor for controlling low-temperature water, and reference numeral 70 denotes a temperature sensor for controlling high-temperature water. In FIG. 3, reference numerals 81 and 82 denote a low-temperature cooling water circulation path and a high-temperature cooling water circulation path, respectively. 101 and 102 denote air-cooled coolers for low-temperature water and high-temperature water, respectively.
[0026]
The low-temperature water in the low-temperature heat exchanger 61 is sent to the cooler 5 by the circulation pump 63, and is controlled by the temperature sensor 69 and a control device (not shown) to control the air volume of the air-cooling fan 67 to reach the set temperature. The Similarly, the high-temperature water in the high-temperature heat exchanger 62 is sent to the cooler 66 by the circulation pump 64, and the air volume of the air-cooling fan 67 is controlled by the temperature sensor 70 and a control device (not shown) so as to reach the set temperature. Controlled.
[0027]
[Problems to be solved by the invention]
By the way, the above-described conventional heat treatment method and apparatus for a fuel cell power generator have the following problems.
[0028]
When an air-cooled cooler is used to cool the exhaust heat of the fuel cell power generation device, as shown in FIG. 3, cooling of the low-temperature water and high-temperature water is performed using separate air-cooling fans and coolers, respectively. The temperature was controlled. Therefore, the number of parts, dimensions, weight, and the like of the air-cooled cooler are increased, and the power consumption is also increased, resulting in an increase in equipment cost and operation cost.
[0029]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for exhaust heat treatment of a fuel cell power generation device, which can achieve compactness, power saving, and cost reduction of an air-cooled cooler, and To provide an apparatus.
[0030]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a fuel cell, a fuel reformer that generates a hydrogen-rich reformed gas by a reforming reaction between a hydrocarbon and steam, and the fuel cell and the fuel reformer. In the exhaust heat treatment method for a fuel cell power generation apparatus comprising a low-temperature water heat exchanger and a high-temperature water heat exchanger for exchanging heat discharged from cooling water having different temperature levels and discharging it,
Cooling water having different temperature levels in the heat exchanger for low-temperature water and the heat exchanger for high-temperature water is circulated to a cooler for low-temperature water and a cooler for high-temperature water respectively in an air-cooled cooler that collectively cools with an air-cooling fan. Cool,
The cooling air in the air-cooled cooler is cooled by flowing from the low-temperature water cooler side to the high-temperature water cooler side ,
Measure the cooling water temperature at the inlet of the heat exchanger for low-temperature water and the heat exchanger for high-temperature water, respectively, determine whether or not the air cooling needs to be increased compared to each predetermined set temperature, and at least one of them needs the air cooling enhancement When it is determined that the air volume of the air cooling fan is increased,
In order to prevent overcooling of cooling water in heat exchangers (other heat exchangers) other than those determined to require enhancement of air cooling, at least part of the cooling water in the other heat exchangers The low-temperature water cooler or the high-temperature water cooler corresponding to this heat exchanger is bypassed and circulated and cooled (invention of claim 1).
[0031]
According to the first aspect of the present invention, the number of air-cooling fans is reduced as compared with the prior art, and the air-cooled cooler can be made compact as a whole. Thereby, power saving and cost reduction are possible. Moreover, by bypassing and circulatingly cooling, the cooling water can be prevented from being overcooled and rational cooling water temperature control can be realized.
[0032]
In addition, as a preferred exhaust heat treatment apparatus for a fuel cell power generator for carrying out the exhaust heat treatment method according to claim 1 , a fuel cell, a fuel reformer, a heat exchanger for low temperature water, and a heat exchange for high temperature water A low-temperature cooling system provided between the low-temperature water heat exchanger and the low-temperature water cooler, an air-cooled cooler having a cooler for low-temperature water and a cooler for high-temperature water collectively cooled by an air-cooling fan A water circulation path, and a high-temperature cooling water circulation path provided between the high-temperature water heat exchanger and the high-temperature water cooler, and the low-temperature cooling water circulation path and the high-temperature cooling water circulation path are respectively bypassed. A bypass pipe and a three-way valve for circulating cooling, a temperature sensor for measuring the temperature of each heat exchanger inlet cooling water, and a control device for preventing the cooling water from being overcooled (invoice) Item 2 ).
[0033]
In order to further save power, in the exhaust heat treatment apparatus according to claim 4, the air cooling fan includes a VVVF inverter for adjusting the air volume (invention of claim 3 ).
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below based on the drawings.
[0035]
FIG. 2 is a diagram showing an embodiment of the present invention, and FIG. 1 is a diagram showing a system configuration having no bypass system for preventing overcooling in FIG. 1 and 2, the same functional members as those in FIG.
[0036]
The basic difference in system configuration between FIG. 1 and FIG. 3 is that in FIG. 1, the cooling water having different temperature levels in the low-temperature water heat exchanger 61 and the high-temperature water heat exchanger 62 is replaced with an air-cooled cooler. 100 is configured to be circulated and cooled to the low-temperature water cooler 65 and the high-temperature water cooler 66 in FIG. 100 and collectively cooled by a single air-cooling fan 67, and the cooling air in the air-cooled cooler 100 is This is a configuration in which cooling is performed by flowing from the water cooler 65 side to the high temperature water cooler 66 side.
[0037]
In the above configuration, the inlet cooling water temperatures 69 and 70 of the low-temperature water heat exchanger 65 and the high-temperature water heat exchanger 66 are respectively measured, and whether or not it is necessary to enhance air cooling compared to each predetermined set temperature, When it is determined by a control device (not shown) and it is determined that at least one of the air cooling needs to be increased, control for increasing the air volume of the air cooling fan 67 is performed. The air cooling fan 67 adjusts the air volume by performing ON / OFF operation or performing rotation speed control using the VVVF inverter 68 to control the temperature of the cooling water.
[0038]
Next, the embodiment of FIG. 2 will be described. The difference between the embodiment of FIG. 1 and FIG. 2 is that, in FIG. 2, the low-temperature cooling water circulation path 81 and the high-temperature cooling water circulation path 82 are bypass bypass lines 83 and 84 and a three-way valve 91 for circulating cooling. , 92 and a control device (not shown) that inputs the measured values of the temperature sensors 69 and 70 for measuring the temperature of the cooling water at the inlet of each heat exchanger and controls the three-way valve in order to prevent the cooling water from being overcooled. It is a point to prepare.
[0039]
According to the above-described embodiment, as described above, it is possible to prevent the cooling water from being overcooled and to perform reasonable cooling water temperature control.
[0040]
【The invention's effect】
As described above, according to the present invention, the fuel cell, the fuel reformer that generates the hydrogen-rich reformed gas by the reforming reaction of hydrocarbon and steam, and the fuel cell and the fuel reformer are discharged. When performing heat treatment of a fuel cell power generator equipped with a heat exchanger for low-temperature water and a heat exchanger for high-temperature water that exchanges heat with cooling water having different temperature levels and discharges the heat, Cooling water having different temperature levels in the heat exchanger and the high-temperature water heat exchanger is circulated and cooled to the low-temperature water cooler and the high-temperature water cooler in the air-cooled cooler that collectively cools with an air-cooling fan, The cooling air in the air-cooled cooler is cooled by flowing from the low-temperature water cooler side to the high-temperature water cooler side , and the inlet cooling water temperature of the low-temperature water heat exchanger and the high-temperature water heat exchanger is set. Measure each one When it is determined whether or not the air cooling needs to be increased compared to the constant temperature, and when at least one of the air cooling is determined to be required, the air volume of the air cooling fan is increased, In order to prevent overcooling of the cooling water in the heat exchanger (other heat exchanger), at least a part of the cooling water in the other heat exchanger is cooled for low-temperature water corresponding to the other heat exchanger. Since it is configured to circulate and cool by bypassing the cooler or high-temperature water cooler ,
The air-cooled cooler can be made compact, save power and reduce costs.
[Brief description of the drawings]
[1] relates to exhaust the heat treatment device of a fuel cell power generator of the present invention, FIG. [2] showing the no system configuration bypass system for preventing supercooling embodiment of the exhaust treatment apparatus of a fuel cell power generator of the present invention FIG. 3 is a diagram showing an example of a schematic configuration of a conventional exhaust heat treatment apparatus for a fuel cell power generator. FIG. 4 is a diagram showing an example of a schematic system configuration of a conventional phosphoric acid fuel cell power generator. FIG. 5 is a diagram showing a schematic system configuration of a conventional fuel cell power generator different from FIG.
61: Heat exchanger for low-temperature water, 62: Heat exchanger for high-temperature water, 65: Cooler for low-temperature water, 66: Cooler for high-temperature water, 67: Air cooling fan, 68: VVVF inverter, 69, 70: Temperature sensor 81: Low-temperature cooling water circuit, 82: High-temperature cooling water circuit, 83, 84: Bypass pipe, 91, 92: Three-way valve, 100: Air-cooled cooler.

Claims (3)

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 are cooled at different temperature levels. In the exhaust heat treatment method for a fuel cell power generation apparatus comprising a low-temperature water heat exchanger and a high-temperature water heat exchanger that exchange heat with
Cooling water having different temperature levels in the heat exchanger for low-temperature water and the heat exchanger for high-temperature water is circulated to a cooler for low-temperature water and a cooler for high-temperature water respectively in an air-cooled cooler that collectively cools with an air-cooling fan Cool down
The cooling air in the air-cooled cooler is cooled by flowing from the low-temperature water cooler side to the high-temperature water cooler side ,
Measure the cooling water temperature at the inlet of the heat exchanger for low-temperature water and the heat exchanger for high-temperature water, respectively, determine whether or not the air cooling needs to be increased compared to each predetermined set temperature, and at least one of them needs the air cooling enhancement When it is determined that the air volume of the air cooling fan is increased,
In order to prevent overcooling of cooling water in heat exchangers (other heat exchangers) other than those determined to require enhancement of air cooling, at least part of the cooling water in the other heat exchangers A waste heat treatment method for a fuel cell power generation apparatus, characterized in that the low temperature water cooler or the high temperature water cooler corresponding to the heat exchanger is bypassed and circulated and cooled . The exhaust heat treatment apparatus for a fuel cell power generator for carrying out the exhaust heat treatment method according to claim 1 , wherein the fuel cell, a fuel reformer, a low temperature water heat exchanger and a high temperature water heat exchanger, and a low temperature An air-cooled cooler having a cooler for water and a cooler for high-temperature water that is collectively cooled by an air-cooling fan; a low-temperature cooling water circulation path provided between the heat exchanger for low-temperature water and the cooler for low-temperature water; A high-temperature cooling water circuit provided between the high-temperature water heat exchanger and the high-temperature water cooler, and the low-temperature cooling water circuit and the high-temperature cooling water circuit are circulated and cooled by the bypass respectively. And a three-way valve, a temperature sensor for measuring the temperature of each heat exchanger inlet cooling water, and a control device for preventing overcooling of the cooling water. Waste heat treatment equipment. 3. The exhaust heat treatment apparatus according to claim 2 , wherein the air cooling fan includes a VVVF inverter for adjusting the air volume.

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