JP6218591B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system including a heat exchanger that exchanges heat between an oxidizing gas supplied to a fuel cell and an exhaust gas flowing through the fuel cell system.

  In recent years, a fuel cell system in which a stack of fuel cells is housed in a housing has been proposed (for example, Patent Document 1). As shown in FIG. 4, the fuel cell system (power generation device) disclosed in Patent Literature 1 performs heat exchange in which heat is exchanged between a plurality of fuel cells in a housing 101 and exhaust gas and air supplied to the fuel cells. And a device 107. In addition, a purification device 151 is provided in the upper region of the reformer in the housing 101 so as to remove and purify harmful components of the exhaust gas discharged from the discharge port to the outside air. Further, the exhaust gas released from the housing 101 is introduced into the waste heat recovery device 122, used for producing hot water, etc., and discharged from the discharge port to the outside air.

  However, the fuel cell system disclosed in Patent Document 1 cannot appropriately control the temperature of the purification device 151, and the purification catalyst of the purification device 151 may not sufficiently react. That is, the temperature control of the purification device 151 of Patent Document 1 depends on the temperature of the exhaust gas recovered by the heat exchanger 107 and having a low temperature. For this reason, when the heat utilization of the exhaust gas is promoted in order to improve the power generation efficiency in the fuel cell system, the temperature of the exhaust gas may fall below an appropriate temperature range where the purification catalyst reacts sufficiently. is there.

  Therefore, a system that enables temperature management of the purification device 151 has also been proposed (for example, Patent Document 2).

  The combustion exhaust gas purification processing system disclosed in Patent Document 2 includes a temperature sensor for detecting the internal temperature of the purification device as shown in FIG. 5, and the temperature detected by this temperature sensor is less than a predetermined temperature. The air is sent to the purification device via the air pump. Thereby, the oxygen shortage in the purification apparatus can be eliminated, and the temperature of the purification apparatus can be raised.

JP 2011-146397 A JP 2002-79058 A

  However, the conventional combustion exhaust gas purification processing system described in Patent Document 2 has a problem in that an air pump or the like is separately required for controlling the temperature of the purification device, and costs are increased.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell system capable of heating a heated portion to a predetermined temperature range with an inexpensive configuration while improving power generation efficiency. There is to do.

  In order to solve the above-described problem, a fuel cell system according to the present invention includes a fuel cell that generates power by an electrochemical reaction using fuel generated from supplied raw materials and supplied power generation air. A battery system, a heated part heated to a predetermined temperature range by heat of exhaust gas flowing in the fuel cell system, and guiding the exhaust gas to the heated part and circulating in the fuel cell system And an auxiliary air that is disposed in the exhaust gas path and preheats the power generation air supplied to the fuel cell by using heat of the exhaust gas flowing through the exhaust gas path A heat exchanger and an air heat exchanger for further preheating the power generation air preheated by the auxiliary air heat exchanger by using heat of exhaust gas flowing through the exhaust gas path , Wherein the air heat exchanger from the upstream side of the exhaust gas path, is arranged the heated portion, and the order of the auxiliary air heat exchanger.

  The fuel cell system according to the present invention is configured as described above, and has an effect that the heated portion can be heated to a predetermined temperature range with an inexpensive configuration while improving the power generation efficiency.

It is the block diagram which showed an example of the principal part structure of the fuel cell system which concerns on embodiment. It is a schematic diagram which shows the structure of the fuel cell system which concerns on Example 1 of embodiment. It is a schematic diagram which shows the structure of the fuel cell system which concerns on Example 2 of embodiment. It is a figure which shows the prior art and showed the structure of the electric power generating apparatus. It is a figure which shows the prior art and showed the structure of the combustion exhaust gas purification processing system.

  The present invention provides the following aspects.

  A fuel cell system according to a first aspect of the present invention is a fuel cell system including a fuel cell that generates electricity by an electrochemical reaction using fuel generated from supplied raw materials and supplied power generation air. And a heated part heated to a predetermined temperature range by heat of exhaust gas flowing in the fuel cell system, and an exhaust for guiding the exhaust gas to the heated part and circulating in the fuel cell system A gas path; and an auxiliary air heat exchanger that is disposed in the exhaust gas path and preheats the power generation air supplied to the fuel cell using heat of exhaust gas flowing through the exhaust gas path. An air heat exchanger for further preheating the power generation air preheated by the auxiliary air heat exchanger using heat of the exhaust gas flowing through the exhaust gas path. Wherein the upstream side of the gas path air heat exchanger, the heated portion, and are arranged in order of the auxiliary air heat exchanger.

  According to the above-described configuration, the air heat exchanger, the heated portion, and the auxiliary air heat exchanger are arranged in this order from the upstream side of the exhaust gas path, so that the heat covered by the exhaust gas used by the air heat exchanger is used. The heating part can be heated.

  Here, since the auxiliary air heat exchanger is provided, before the air for power generation is preheated by the air heat exchanger using the heat of the exhaust gas flowing through the exhaust gas path in the fuel cell system, Can be preheated. Thus, since the air heat exchanger is configured to further preheat the power generation air preheated by the auxiliary air heat exchanger, the amount of heat of the exhaust gas flowing through the exhaust gas path used in the air heat exchanger Can be suppressed.

  Furthermore, by changing the ratio of the heat exchange capacity of each of the auxiliary air heat exchanger and the air heat exchanger, the amount of heat of the exhaust gas used in the subsequent air heat exchanger can be adjusted. The heat exchange capacity can be adjusted by changing the conditions defining the heat exchange efficiency such as the area of the heat exchange surface in the auxiliary air heat exchanger 4 and the air heat exchanger 5. For this reason, in the fuel cell system according to the first aspect of the present invention, exhaust gas in an appropriate temperature range can be guided to the heated portion. Therefore, the heated part can be stably heated to have an appropriate temperature. Therefore, only by providing an inexpensive auxiliary air heat exchanger, it is possible to heat the heated portion so as to be within a predetermined temperature range without the need of separately providing an expensive air pump or the like as in the prior art.

  Further, since the auxiliary air heat exchanger preheats the power generation air using a part of the heat of the exhaust gas, heat can be efficiently recovered from the exhaust gas circulating in the fuel cell system. For this reason, the fuel cell system according to the first aspect of the present invention can increase the power generation efficiency.

  Therefore, the fuel cell system according to the first aspect of the present invention has an effect that the heated part can be heated to be in the predetermined temperature range with an inexpensive configuration while improving the power generation efficiency.

  The fuel cell system according to a second aspect of the present invention is the fuel cell system according to the first aspect described above, wherein the fuel cell, the heated portion, the air heat exchanger, and the auxiliary air heat exchanger are arranged. The auxiliary air heat exchanger includes a housing for housing, and the auxiliary air heat exchanger includes exhaust gas flowing through the exhaust gas path inside and outside the double pipe, and power generation air before being preheated by the air heat exchanger. It may be configured to be arranged so as to extend in the vertical direction along the side wall of the casing.

  According to the above configuration, the auxiliary air heat exchanger 4 can be a double-pipe heat exchanger that can be configured at low cost. In addition, the double-pipe heat exchanger is disposed so as to extend in the vertical direction along the side wall of the housing. For this reason, when installing an auxiliary air heat exchanger in a housing | casing, a big space becomes unnecessary and the size reduction of a housing | casing can be achieved. Therefore, it is possible to reduce the size of the fuel cell system while reducing the cost.

  The fuel cell system according to a third aspect of the present invention is the above-described fuel cell system according to the first or second aspect, wherein the heated portion is a purification catalyst for removing harmful components contained in the exhaust gas. Part.

  According to the above configuration, the purification catalyst unit can be heated using the heat of the exhaust gas, so that heat can be efficiently recovered from the exhaust gas circulating in the fuel cell system, and the power generation efficiency can be increased. .

  The fuel cell system according to a fourth aspect of the present invention is the fuel cell system according to the first or second aspect described above, wherein the heated portion reforms the raw material by a reforming reaction and supplies the fuel. The reformer to produce | generate may be sufficient.

  According to the above configuration, since the reformer can be heated using the heat of the exhaust gas, the heat can be efficiently recovered from the exhaust gas circulating in the fuel cell system, and the power generation efficiency can be increased. .

  A fuel cell system according to a fifth aspect of the present invention is the fuel cell system according to the first or second aspect, wherein a reformer that reforms the raw material by a reforming reaction to generate the fuel is provided. The heated part may be an evaporator that vaporizes water supplied to the reformer.

  According to the above configuration, since the evaporator can be heated using the heat of the exhaust gas, heat can be efficiently recovered from the exhaust gas circulating in the fuel cell system, and the power generation efficiency can be increased.

(Embodiment)
A fuel cell system 100 according to an embodiment will be described with reference to FIG. In the embodiment, a fuel cell system including a solid oxide fuel cell (SOFC) will be described as an example of the fuel cell 1, but the fuel cell 1 is limited to a solid oxide fuel cell. is not. Any fuel cell that can be installed in a fuel cell system having a configuration that exhausts high-temperature exhaust gas may be used, for example, a molten carbonate fuel cell (MCFC) or a polymer electrolyte fuel cell (PEFC). Good. FIG. 1 is a block diagram showing an example of a main configuration of a fuel cell system 100 according to an embodiment.

  As shown in FIG. 1, the fuel cell system 100 includes a fuel cell 1 (solid oxide fuel cell), a heated portion 3, an auxiliary air heat exchanger 4, and an air heat exchanger 5. It is a configuration. Further, in the fuel cell system 100, for example, an exhaust gas path 6 for distributing exhaust gas discharged from the fuel cell 1 through the fuel cell system 100, and a raw material supply path 8 for supplying the raw material to the fuel cell 1. And an air path 10 for supplying power generation air.

  The fuel cell 1 generates power by an electrochemical reaction using fuel obtained by reforming a raw material from which sulfur compounds have been removed and power generation air supplied through an air path 10. The fuel cell system 100 is configured to be able to supply the raw material to the desulfurizer 2 through the raw material supply path 8 as will be described later. As the raw material, city gas or gas mainly composed of hydrocarbon such as propane gas can be used. In the present specification, the reformed gas obtained by removing sulfur components from the raw material in the desulfurizer 2 and reformed by the reforming reaction is referred to as fuel.

  The fuel cell 1 includes a fuel electrode (anode) to which fuel is supplied and an air electrode (cathode) to which power generation air is supplied, and performs an electrochemical reaction between the fuel electrode and the air electrode to generate power. A plurality of single cells to be connected may be connected in series to form a cell stack. Further, the fuel cell 1 may have a configuration in which cell stacks connected in series are further connected in parallel. Alternatively, a cell including two layers of electrodes (anode and cathode) may be configured in a cylindrical shape, and fuel may be supplied to the inside of the cylindrical cell and power generation air may be supplied to the outside.

  As a single cell constituting the fuel cell 1, for example, a single cell made of zirconia doped with yttria (YSZ), zirconia doped with yttrium or scandium, or a lanthanum gallate solid electrolyte can be used. For example, when the single cell is YSZ, power generation is performed in a temperature range of about 600 to 900 ° C., depending on the thickness.

  The fuel cell system 100 according to the embodiment includes a combustion unit that generates combustion exhaust gas by burning unused fuel and power generation air in the fuel cell 1, and distributes the combustion exhaust gas through the fuel cell system 100. Exhaust gas may be used. Alternatively, in the case where the fuel cell 1 is a flat plate fuel cell, unused power generation air (cathode off-gas) discharged from the cathode may be used as exhaust gas flowing through the fuel cell system 100. The cathode off gas is heated by the high operating temperature of the fuel cell 1 and has a sufficient amount of heat to preheat the power generation air.

  The heated portion 3 is heated by utilizing a part of the heat held by the exhaust gas flowing in the fuel cell system 100. In this Embodiment, the to-be-heated part 3 is heated with the exhaust gas using a part of heat | fever which the air heat exchanger 5 holds. For example, as the heated part 3, when the exhaust gas is a combustion exhaust gas, a purification catalyst part 31 that removes harmful components such as carbon monoxide contained in the combustion exhaust gas is exemplified. Further, the heated portion 3 is not limited to the purification catalyst portion 31 and may be an evaporator that vaporizes reforming water supplied to the reformer or the reformer. The exhaust gas in which a part of the heat held by the heated part 3 is used is guided to the auxiliary air heat exchanger 4.

  The air heat exchanger 5 heats (preheats) the power generation air supplied to the fuel cell 1 using the heat of the exhaust gas flowing in the fuel cell system 100. That is, the air heat exchanger 5 heats the power generation air supplied from the outside to a predetermined temperature by heat exchange with the exhaust gas. For example, the power generation air after flowing through the air heat exchanger 5 is heated to 400 to 800 ° C. by heat exchange with the exhaust gas. The heated power generation air is supplied to the fuel cell 1. As described above, in the fuel cell system 100, the exhaust gas from which part of the retained heat is removed is guided to the heated portion 3 by performing heat exchange with the power generation air in the air heat exchanger 5.

  The auxiliary air heat exchanger 4 preheats the power generation air before being preheated by the air heat exchanger 5 using the heat of the exhaust gas that has lost part of the heat held in the heated portion 3. Is. Here, sufficient heat remains in the exhaust gas after heating the heated portion 3. Therefore, the auxiliary air heat exchanger 4 can suppress the amount of heat of the exhaust gas used in the air heat exchanger 5 by preheating the power generation air in advance using the heat of the exhaust gas. it can. Furthermore, the heat quantity of the exhaust gas utilized in the subsequent air heat exchanger 5 can be adjusted by changing the ratio of the heat exchange capabilities of the auxiliary air heat exchanger 4 and the air heat exchanger 5. For this reason, exhaust gas in an appropriate temperature range can be guided to the heated portion 3.

  As described above, in the fuel cell system 100 according to the present embodiment, before the power generation air is preheated using the heat of the exhaust gas in the air heat exchanger 5, the auxiliary air heat exchanger 4 performs the power generation air. Is configured to preheat.

  Further, when the flow rate of the power generation air increases due to a change in the power generation load, the exhaust gas is deprived of a larger amount of heat than before the change of the power generation load due to heat exchange between the power generation air and the air heat exchanger 5. . For this reason, the exhaust gas may not have a sufficient amount of heat to function as a heat source for the heated portion 3. Therefore, in the fuel cell system 100 according to the present embodiment, the auxiliary air heat exchanger 4 is provided in the front stage of the air heat exchanger 5 so that the air heat exchanger 5 can be used for heat exchange with power generation air. The amount of heat of the exhaust gas can be suppressed.

  Furthermore, as compared with a configuration in which the exhaust gas after flowing through the heated portion 3 is directly discharged to the outside of the housing 30, the heat of the exhaust gas is recovered by the auxiliary air heat exchanger 4 to generate power from the fuel cell 1. Therefore, the power generation efficiency in the fuel cell system 100 can be increased.

  Next, a case where the fuel cell 1 of the fuel cell system shown in FIG. 1 is configured as a cylindrical fuel cell and a case where the fuel cell 1 is configured as a flat plate fuel cell will be described as Examples 1 and 2, respectively.

Example 1
First, Example 1 of the fuel cell system 100 according to the embodiment will be described with reference to FIG. FIG. 2 is a schematic diagram showing the configuration of the fuel cell system 100 according to Example 1 of the embodiment.

  When the fuel cell 1 is a cylindrical fuel cell, the fuel cell system 100 according to the embodiment shown in FIG. 1 can be configured as in Example 1 shown in FIG. 2, for example. The fuel cell system 100 includes the purification catalyst unit 31 as the heated part 3, but the heated part 3 is not limited to the purification catalyst part 31.

  That is, the fuel cell system 100 according to the first embodiment includes the desulfurizer 2 in addition to the fuel cell 1, the heated portion 3 (purification catalyst portion 31), the auxiliary air heat exchanger 4, and the air heat exchanger 5. , The reformer 14, the evaporator 15, the combustion unit 16, the decompression unit 17, the boosting unit 33, the water pump 34, and the air pump 35. Of these members, members other than the decompression unit 17, the boosting unit 33, the water pump 34, and the air pump 35 are accommodated in the housing 30. The casing 30 is provided with a heat insulating member (not shown) on its inner wall surface, and the fuel cell 1, the reformer 14, and the evaporator 15 are disposed in a space formed by the heat insulating member. The desulfurizer 2, the purification catalyst unit 31, the air heat exchanger 5, and the auxiliary air heat exchanger 4 are arranged in a heat insulating member.

  Further, the fuel cell system 100 according to the first embodiment has a configuration in which combustion exhaust gas generated by burning unused fuel and unused power generation air in the fuel cell 1 in the combustion unit 16 is used as exhaust gas. ing. And the structure which provided the purification | cleaning catalyst part 31 as the to-be-heated part 3 as mentioned above is mentioned as an example.

  The purification catalyst unit 31 is for removing harmful components contained in the exhaust gas. For example, harmful components such as carbon monoxide contained in the combustion exhaust gas are removed. The exhaust gas passage 6 is supplied with the combustion exhaust gas after a part of the heat held in the air heat exchanger 5 is used to the purification catalyst unit 31. The purification catalyst unit 31 is configured such that the supplied combustion exhaust gas passes through the purification catalyst filled in the purification catalyst unit 31. As the purification catalyst, for example, a Pt-based noble metal catalyst supported on a honeycomb carrier is used. However, the purification catalyst is not limited to this.

  In the fuel cell system 100 shown in the first embodiment, the raw material boosted by the booster 33 is supplied into the housing 30 through the raw material supply path 8. Further, the power generation air pressurized by the air pump 35 is supplied into the housing 30 through the air path 10. Further, the reforming water is supplied into the housing 30 through the reforming water path 11 by the water pump 34.

  The raw material supplied into the housing 30 is mixed with a reformed gas containing about 70% hydrogen gas (about 10% with respect to the raw material) necessary for the hydrodesulfurization reaction. A raw material containing hydrogen at a necessary flow rate is guided to the desulfurizer 2 in the housing 30. The desulfurizer 2 is configured to be covered with a heat insulating member as described above. For this reason, it can comprise so that there may be no heat dissipation and heat transfer from the desulfurizer 2 as much as possible. Further, when the desulfurization catalyst charged in the desulfurizer 2 has temperature dependency, the desulfurizer 2 is placed at a position where the radiant heat of the combustion section 16 or the heat of the combustion exhaust gas is transferred and heated in a predetermined temperature range. Deploy. The raw material that has been desulfurized by the desulfurizer 2 is guided to an evaporator 15 provided in a stage preceding the reformer 14.

  Here, first, the desulfurizer 2 provided in the fuel cell system 100 shown in the first embodiment will be described in more detail. The desulfurizer 2 removes sulfur compounds in the raw material using hydrogen. That is, the desulfurizer 2 is a hydrodesulfurizer that removes sulfur components contained in the raw material by a so-called hydrodesulfurization method. A raw material supply path 8 is connected to the desulfurizer 2, and the raw material supplied from the outside through the raw material supply path 8 flows into the desulfurizer 2. The raw material flowing into the desulfurizer 2 contains hydrogen as described above.

The desulfurizer 2 is filled with a desulfurization catalyst, and examples of the desulfurization catalyst include a desulfurization catalyst containing copper and zinc. The desulfurization catalyst is not limited to this desulfurization catalyst as long as hydrodesulfurization can be performed, and may be a combination of a Ni—Mo-based or Co—Mo-based catalyst and zinc oxide. In the case of a desulfurization catalyst in which a Ni—Mo or Co—Mo catalyst and zinc oxide are combined, the desulfurizer 2 hydrocrackes organic sulfur in the fuel gas in a temperature range of 350 to 400 ° C. Then, the desulfurizer 2 removes the generated H ₂ S by adsorbing it to ZnO in a temperature range of 350 to 400 ° C.

For example, when the raw material is city gas, dimethyl sulfide (C ₂ H ₆ S, DMS), which is a sulfur compound, is contained as an odorant. This DMS is removed by the desulfurization catalyst 2 in the desulfurizer 2 in the form of ZnS according to the following reaction formulas (formulas (1) and (2)) or in the form of physical adsorption.
C ₂ H ₆ S + 2H ₂ → 2CH ₄ + H ₂ S (1)
H ₂ S + ZnO → H ₂ O + ZnS (2)
The odorant is not limited to the above-described DMS, and may be another sulfur compound such as TBM (C ₄ H ₁₀ S) or THT (C ₄ H ₈ S).

When the desulfurization catalyst to be filled contains copper and zinc, the desulfurizer 2 performs desulfurization in a temperature range of about 10 to 400 ° C, preferably about 250 to 300 ° C. This copper zinc-based desulfurization catalyst has a physical adsorption capability in addition to a hydrodesulfurization capability, and can mainly perform physical adsorption at low temperatures and chemical adsorption (H ₂ S + ZnO → H ₂ O + ZnS) at high temperatures. In this case, the sulfur content contained in the fuel gas after desulfurization is 1 vol ppb (parts per billion) or less, and usually 0.1 vol ppb or less.

  Thus, when the desulfurizer 2 is filled with a Ni—Mo or Co—Mo catalyst or a desulfurization catalyst containing either copper and zinc, the sulfur component removal amount per unit volume is increased. Therefore, when the above-described desulfurization catalyst is used, the amount of the desulfurization catalyst necessary for removing sulfur to a desired sulfur concentration can be reduced.

  Further, as described above, these desulfurizers 2 are installed so as to be covered with the heat insulating member. Thus, by comprising the desulfurizer 2 so that it may be covered with a heat insulating member, heat release from the desulfurizer 2 can be prevented, and for example, combustion generated by radiant heat of the combustion unit 16 or combustion in the combustion unit 16 Direct exposure to high-temperature heat such as exhaust gas heat can be prevented. Moreover, since heat dissipation from the desulfurizer 2 can be prevented, the temperature distribution in the desulfurizer 2 can be made substantially uniform, and temperature unevenness can be suppressed. Thereby, temperature control of the desulfurization catalyst in the desulfurizer 2 can be facilitated.

  Further, when the desulfurization catalyst of the desulfurizer 2 is deteriorated after the fuel cell system 100 is operated for a long time, the performance of the fuel cell system 100 is deteriorated. Therefore, the desulfurizer 2 may be detachably provided in the fuel cell system 100 so that the desulfurizer 2 having a deteriorated desulfurization catalyst can be replaced with a new desulfurizer.

  The raw material desulfurized by the desulfurizer 2 as described above is supplied to the reformer 14.

  Next, the reformer 14 will be described. In the fuel cell system 100 according to the first embodiment, the reformer 14 can be configured as follows. That is, the reformer 14 may be used for partial oxidation reforming, but in order to realize more efficient operation, not only partial oxidation reforming reaction but also steam reforming reaction can be performed. Keep to specifications.

  For example, the raw material desulfurized by the desulfurizer 2 is mixed with water (reformed water) sent from the water pump 34 through the reformed water path 11 and supplied to the reformer 14. In addition, the evaporator 15 is provided in front of the reformer 14.

  The evaporator 15 vaporizes the water (reformed water) supplied through the reforming water path 11 using the heat of the combustion exhaust gas generated by the combustion unit 16 and the radiant heat from the combustion unit 16, and the desulfurizer 2. And mixed with the raw material after desulfurization supplied from. Then, the evaporator 15 introduces the mixed raw material into the reformer 14.

In addition, as the reforming catalyst filled in the reformer 14, the Al ₂ O ₃ (alumina) sphere surface is impregnated with Ni and supported, or the Al ₂ O ₃ sphere surface is provided with ruthenium. Can be used as appropriate.

By the way, when the fuel cell system 100 is started, the heat energy is insufficient to perform the steam reforming reaction which is an endothermic reaction in the reformer 14. Therefore, when the fuel cell system 100 is started, the reforming air is introduced into the reformer 14 through the reforming air path (not shown) without supplying water from the reforming water path 11 to the evaporator 15, Using this reforming air, the reformer 14 performs a partial oxidation reforming reaction represented by the following formula (3) to generate hydrogen gas and carbon monoxide.
CnHm + (n / 2) O ₂ → n · CO + (m / 2) H ₂ (n and m are arbitrary natural numbers)
... (3)
Then, these hydrogen gas and carbon monoxide are supplied to the fuel cell 1 through the reformed gas path 9 and are generated together with the power generation air.

Further, as the fuel cell system 100 starts up and power generation proceeds, the temperature of the reformer 14 increases. That is, the partial oxidation reforming reaction represented by the above formula (3) is an exothermic reaction, and the temperature of the reformer 14 is increased by the combustion exhaust gas. And if the temperature of the reformer 14 becomes 400 degreeC or more, for example, it will become possible to perform the steam reforming reaction represented by the following formula | equation (4) in parallel.
_{CnHm + n · H 2 O →} n · CO + (m / 2 + n) H 2 (n, m is an arbitrary natural number)
... (4)
Compared with the partial oxidation reforming reaction represented by the formula (3), the steam reforming reaction represented by the formula (4) described above increases the amount of hydrogen that can be generated from the same amount of hydrocarbon (CnHm). As a result, the amount of reformed gas that can be used for the power generation reaction in the fuel cell 1 increases. That is, the reforming gas can be generated more efficiently by the steam reforming reaction. Further, since the steam reforming reaction shown in the formula (4) is an endothermic reaction, the heat generated by the partial oxidation reforming reaction shown in the formula (3) and the heat held by the combustion exhaust gas discharged from the fuel cell 1 are used. The steam reforming reaction is allowed to proceed while supplementing the necessary amount of heat. If the temperature of the reformer 14 is, for example, 600 ° C. or higher, the amount of heat necessary for the steam reforming reaction of the formula (4) can be supplemented only by the heat of the combustion exhaust gas, etc. It is possible to switch to a quality-only operation.

  Further, in the configuration of the fuel cell system 100 shown in FIG. 2, the reformed gas generated by the reformer 14 is branched in the middle of the reformed gas path 9 from the reformer 14 toward the fuel cell 1 (branch portion). A recycling path 19 is provided for returning a part of the material to the raw material supply path 8. For this reason, it becomes possible to add hydrogen to the raw material supplied to the desulfurizer 2, and the desulfurizer 2 can perform the above-mentioned hydrodesulfurization using this hydrogen.

  In the configuration of the fuel cell system 100 shown in FIG. 2, the decompression unit 17 is provided in the middle of the recycling path 19. The decompression unit 17 adjusts the flow rate of the reformed gas flowing through the recycle path 19 and can be realized by, for example, a capillary tube or an orifice. That is, the decompression unit 17 is configured such that the reformed gas flows through the recycle path 19 by a desired flow rate by narrowing the flow path with a capillary tube or an orifice to increase the pressure loss. The position of the decompression unit 17 is disposed outside the housing 30 in FIG. 2, but may be inside the housing 30. When arranged outside the housing 30, there is an advantage that it can be prevented from being directly exposed to high-temperature combustion exhaust gas or the like. On the other hand, when the decompression unit 17 is disposed in the housing 30, the interior of the housing 30 is at a high temperature, so that there is an advantage that moisture is hardly condensed in the decompression unit 17.

  Moreover, it is good also as a structure which provided the condenser (not shown) in the middle of this recycle path | route 19. FIG. In the case of a configuration including a condenser, when the reformed gas flowing through the recycling path 19 is cooled, moisture can be recovered by the condenser. For this reason, it is possible to suppress problems such as water in the path due to condensed water and corrosion or breakage of the booster 33. This condenser can use a double-pipe heat exchanger that uses raw fuel gas, air, or water as a cooling source. The condensed water produced | generated by the condenser may be discharge | released outside, for example, the structure reused for reforming water etc. may be sufficient.

  In the fuel cell system 100 according to the first embodiment, as described above, the power generation air supplied to the fuel cell 1 is preheated by the two heat exchangers (the air heat exchanger 5 and the auxiliary air heat exchanger 4). It is configured to be. Specifically, as shown in FIG. 2, the power generation air supplied from the outside is first heat-exchanged and preheated with the combustion exhaust gas after passing through the purification catalyst unit 31 in the auxiliary air heat exchanger 4. The Further, the power generation air preheated by the auxiliary air heat exchanger 4 is heat-exchanged with the combustion exhaust gas generated by the combustion unit 16 in the air heat exchanger 5. By this heat exchange, the power generation air is heated to about the operating temperature of the fuel cell 1 and supplied to the fuel cell 1.

  On the other hand, the combustion exhaust gas generated by burning unused fuel (anode offgas) and air (cathode offgas) in the combustion section 16 is used by heat in each section and discharged outside as follows. That is, the combustion exhaust gas heats the reformer 14 and the evaporator 15 in the housing 30 and then is guided to the air heat exchanger 5. In the air heat exchanger 5, the combustion exhaust gas loses a part of the heat held by heat exchange with the power generation air preheated by the auxiliary air heat exchanger 4 and is led to the purification catalyst unit 31.

  The combustion exhaust gas passes through the purification catalyst unit 31 to remove harmful components such as carbon monoxide. Further, when the combustion exhaust gas passes through the purification catalyst part 31, the purification catalyst part 31 is heated and a part of the heat held by itself is lost. Thus, the combustion exhaust gas that has lost part of the heat held in the purification catalyst unit 31 is guided to the auxiliary air heat exchanger 4. In the auxiliary air heat exchanger 4, heat exchange is performed between the combustion exhaust gas that has lost some of the heat held in the purification catalyst unit 31 and the power generation air supplied from the outside. By this heat exchange, the combustion exhaust gas is further deprived of the retained heat and discharged outside.

  As described above, in the fuel cell system 100 according to Example 1 of the present embodiment, the combustion exhaust gas uses the heat retained by heat exchange with the power generation air in the air heat exchanger 5 and the auxiliary air heat exchanger 4. Further, it is also used for heating the purification catalyst unit 31. For this reason, the heat which combustion exhaust gas holds can be recovered efficiently.

(Example 2)
In the fuel cell system 100 according to the embodiment, the fuel cell 1 may be configured as a flat plate fuel cell. In the case of such a configuration, the fuel cell system 100 has a configuration shown in FIG. 3, for example. FIG. 3 is a schematic diagram showing a configuration of the fuel cell system 100 according to Example 2 of the embodiment. In the second embodiment shown in FIG. 3, the evaporator 15 is described as an example of the heated part 3, but the heated part 3 is not limited to the evaporator 15, for example, the reformer 14. It may be.

  As shown in FIG. 3, the fuel cell system 100 according to Example 2 of the embodiment includes the same components as those of Example 1, but differs from Example 1 in the following points.

  That is, the fuel cell system 100 according to the second embodiment is different from the fuel cell 1 in that unused power generation air (cathode offgas) and unused fuel (anode offgas) are discharged through separate paths. Different from 1. For this reason, the fuel cell system 100 according to the second embodiment has a configuration further including the anode offgas passage 13 through which the anode offgas flows.

  Further, the exhaust gas for heating the heated portion 3 and preheating the power generation air in the air heat exchanger 5 and the auxiliary air heat exchanger 4 was combustion exhaust gas in the first embodiment, whereas 2 also differs in that it is a cathode off-gas. Further, the combustion exhaust gas generated by burning the anode off-gas is used for heating the reformer 14 and the evaporator 15, but thereafter, the combustion exhaust gas is discharged to the outside of the housing 30 through the combustion exhaust gas path 12. Is different. Further, it is different from the first embodiment in that not only the heat of the combustion exhaust gas is used for heating the evaporator 15 but also the heat of the cathode off gas is used.

  In the fuel cell system 100 according to the first embodiment, a part of the reformed gas (fuel) reformed by the reformer 14 is supplied to the upstream side of the booster 33 through the recycle path 19. . On the other hand, the fuel cell system 100 according to the second embodiment is different in that a part of the anode off-gas discharged from the fuel cell 1 is supplied to the upstream side of the booster 33 through the recycle path 19.

  In Example 2 shown in FIG. 3, power generation air is supplied to the cathode of the fuel cell 1 through the air path 10, and fuel is supplied from the reformer 14 to the anode of the fuel cell 1 through the reformed gas path 9. The fuel cell 1 can be configured, for example, by connecting in series a plurality of single cells that generate electricity by performing an electrochemical reaction between an anode and a cathode. For such a single cell, for example, a known configuration in which yttria-stabilized zirconia, which is zirconia added with yttrium oxide, is used as an electrolyte can be adopted.

  First, the power generation air sent out by the air pump 35 is preheated by exchanging heat with the cathode off gas used in the evaporator 15 in the auxiliary air heat exchanger 4. Before the preheated power generation air is supplied to the cathode of the fuel cell 1, heat is exchanged with the cathode offgas discharged from the fuel cell 1 by the air heat exchanger 5 and preheated again. The power generation air heated to near the operating temperature of the fuel cell 1 by the preheating twice is supplied to the cathode of the fuel cell 1. The cathode off-gas discharged from the fuel cell 1 loses a part of the heat held by the heat exchange with the power generation air supplied to the fuel cell 1 as described above and is led to the evaporator 15.

  The evaporator 15 is heated using the heat of the cathode offgas in addition to the heat of the combustion exhaust gas. The evaporator 15 vaporizes the water (reformed water) supplied from the water pump 34 through the reformed water path 11 and mixes it with the raw material after desulfurization supplied from the desulfurizer 2. Then, the evaporator 15 introduces the mixed raw material into the reformer 14. The heating of the evaporator 15 by the cathode off gas may be performed via a heat exchange unit (not shown) that performs heat exchange between the evaporator 15 and the cathode off gas, for example. Or it is good also as a structure which equips the housing | casing which encloses an evaporator, distribute | circulates cathode offgas in this housing | casing, and heats the outer periphery of the evaporator 15 whole.

  On the other hand, the cathode offgas discharged from the evaporator 15 is heat-exchanged with the power generation air in the auxiliary air heat exchanger 4 as described above. That is, since the cathode off-gas discharged from the evaporator 15 contains a heat amount that has not been used yet, the auxiliary air heat exchanger 4 is arranged so that the necessary heat amount can be recovered in the fuel cell system 100. It is configured. Then, the cathode off gas that has lost a part of heat due to the heat exchange is discharged to the outside of the housing 30.

(Exhaust gas temperature adjustment)
Next, the temperature adjustment of the exhaust gas will be described by taking the configuration of the fuel cell system 100 according to the first embodiment shown in FIG. 2 as an example. In the case of the fuel cell system 100 shown in FIG. 2, the exhaust gas used for heating the heated part 3 (purification catalyst part 31) is combustion generated by burning the unused fuel and air by the combustion unit 16. It becomes exhaust gas.

  The flow rate and temperature of the combustion exhaust gas generated in the combustion unit 16 are controlled by adjusting the fuel utilization rate of the fuel and power generation air in the fuel cell 1 (the ratio of the fuel cell 1 consumed as fuel during power generation). It is possible. In the fuel cell system 100 according to the first embodiment illustrated in FIG. 2, for example, the fuel utilization rate of the fuel and power generation air in the fuel cell 1 is set so that the temperature range of the combustion unit 16 is about 600 to 900 ° C. To do.

  In this way, exhaust gas (combustion exhaust gas) generated by burning unused fuel and power generation air in the combustion section 16 set to have a desired temperature range is first converted into the reformer 14 and The evaporator 15 is heated. Thereby, a part of the heat of the exhaust gas is consumed. Further, the exhaust gas that has consumed a part of the heat flows into the air heat exchanger 5, and heat exchange between the power generation air and the exhaust gas in the air heat exchanger 5 further deprives the heat of the exhaust gas. The temperature of the purification catalyst unit 31 is lowered to an appropriate temperature. Specifically, in the purification catalyst unit 31, in order to efficiently reduce harmful components such as carbon monoxide and hydrocarbons contained in the combustion exhaust gas by oxidative decomposition, an optimum temperature range (for example, 250 ° C.). Before and after). Therefore, the temperature of the exhaust gas is lowered to this optimum temperature range.

  The exhaust gas whose temperature has been further lowered in this way flows through the exhaust gas path 6 and is supplied to the purification catalyst unit 31. Then, the exhaust gas that has heated the purification catalyst unit 31 and has lost a part of the heat held therein is led to the auxiliary air heat exchanger 4 through the exhaust gas path 6. In the auxiliary air heat exchanger 4, the exhaust gas is further deprived of heat by heat exchange with the power generation air before being preheated by the air heat exchanger 5 as described above.

  As described above, the temperature of the exhaust gas flowing through the exhaust gas path 6 and flowing into the heated part 3 (for example, the purification catalyst part 31) is the flow rate and temperature of the exhaust gas generated in the combustion part 16, The amount of heat absorbed by the reformer 14 and the evaporator 15 and the amount of heat absorbed by the air heat exchanger 5 are taken into consideration and controlled to a desired value.

  Further, by providing the auxiliary air heat exchanger 4, it is possible to adjust the amount of heat of exhaust gas taken away by heat exchange with the air heat exchanger 5. For this reason, the exhaust gas having an appropriate amount of heat can be guided to the heated portion 3.

  As described above, the desulfurizer 2 is heated to a desired temperature range in the heat insulating member of the housing 30 by the radiant heat of the combustion unit 16 that transfers heat to the heat insulating member and the heat of the combustion exhaust gas. Placed in position. For example, when the desulfurizer 2 is filled with a desulfurization catalyst that is a combination of a Ni—Mo-based or Co—Mo-based catalyst and zinc oxide, the desulfurizer 2 is heated and disposed in a temperature range of about 250 to 300 ° C. The

  In the fuel cell system 100 according to the present embodiment, the exhaust gas whose temperature has been adjusted as described above can be caused to flow into the heated part 3 (for example, the purification catalyst part 31) through the exhaust gas path 6. For this reason, in the fuel cell system 100, the heated portion 3 can be heated to a desired temperature by the heat of the exhaust gas.

  In addition, since the exhaust gas after flowing through the heated portion 3 has a heat quantity that can be used sufficiently, if this exhaust gas is discharged to the outside as it is, the heat balance in the fuel cell system 100 deteriorates and power generation Efficiency may be reduced. In the fuel cell system 100 according to the embodiment, the auxiliary air heat exchanger 4 is provided, and further heat recovery is performed from the exhaust gas discharged from the heated portion 3, so that the amount of heat discharged from the housing 30 to the outside can be suppressed. As a result, the efficiency of the entire system can be improved.

  Further, the heat exchange amount between the exhaust gas and the power generation air in the auxiliary air heat exchanger 4 may be smaller than the heat exchange amount in the air heat exchanger 5. For this reason, the auxiliary air heat exchanger 4 can be a heat exchanger that is smaller than the air heat exchanger 5. Further, the temperature of the exhaust gas flowing into the auxiliary air heat exchanger 4 is about 200 to 300 ° C., which is considerably lower than the temperature at the time when the fuel cell 1 is discharged. For this reason, the heat-resistant temperature requested | required with the auxiliary air heat exchanger 4 becomes lower than the member arrange | positioned around the fuel cell 1. FIG.

  Therefore, the auxiliary air heat exchanger 4 does not need to be entirely formed of a high-temperature heat-resistant material such as stainless steel. Further, the brazing process is sufficient for the joining portion in the auxiliary air heat exchanger 4 and the like. For this reason, the auxiliary air heat exchanger 4 employs the most simple and inexpensive tubular counter-flow double-tube heat exchanger, and this counter-flow double-tube heat exchanger is For example, as shown in FIG. 2, it can be arranged so as to extend in the vertical direction along the side wall of the housing 30. For this reason, when installing the auxiliary air heat exchanger 4 in the housing | casing 30, a big space becomes unnecessary and size reduction of the housing | casing 30 can be achieved. Therefore, the fuel cell system 100 can be reduced in size. In particular, the auxiliary air heat exchanger 4 is preferably disposed at a corner position on the bottom surface of the housing 30.

  Furthermore, when the auxiliary air heat exchanger 4 is constituted by a double tube heat exchanger, it is easy to replace it with another double tube heat exchanger having a different length. Also, there is an advantage that the amount of heat exchange between the exhaust gas and the power generation air can be adjusted.

  From the above description, many modifications and other embodiments of the present invention are apparent to persons skilled in the art. Accordingly, the foregoing description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and / or function may be substantially changed without departing from the spirit of the invention.

  In the fuel cell system of the present invention, the heated portion can be heated with exhaust gas in an appropriate temperature range, and the efficiency as a fuel cell is not impaired. For this reason, it can be widely applied to a fuel cell system including a heated portion that needs to be heated to increase the operating temperature.

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Desulfurizer 3 Heated part 4 Auxiliary air heat exchanger 5 Air heat exchanger 6 Exhaust gas path 8 Raw material supply path 9 Reformed gas path 10 Air path 11 Reformed water path 12 Combustion exhaust gas path 13 Anode off gas path DESCRIPTION OF SYMBOLS 14 Reformer 15 Evaporator 16 Combustion part 17 Decompression part 19 Recycling path 30 Case 31 Purification catalyst part 33 Booster part 34 Water pump 35 Air pump 100 Fuel cell system

Claims (1)

A fuel cell system including a fuel cell that generates electricity by an electrochemical reaction using fuel generated from a supplied raw material and supplied power generation air,
A heated portion that is heated to a predetermined temperature range by heat of exhaust gas flowing in the fuel cell system;
An exhaust gas path for guiding the exhaust gas to the heated part and circulating in the fuel cell system;
An auxiliary air heat exchanger that is arranged in the exhaust gas path and preheats the power generation air supplied to the fuel cell by using heat of exhaust gas flowing through the exhaust gas path;
An air heat exchanger for further preheating the power generation air preheated by the auxiliary air heat exchanger using heat of the exhaust gas flowing through the exhaust gas path;
A reformer that reforms the raw material by a reforming reaction to produce the fuel;
A housing for housing the fuel cell, the heated portion, the air heat exchanger, the auxiliary air heat exchanger, and the reformer;
With
Arranged in the order of the air heat exchanger, the heated part, and the auxiliary air heat exchanger from the upstream side of the exhaust gas path ,
The heated portion is a purification catalyst portion that removes harmful components contained in the exhaust gas, or an evaporator that vaporizes water supplied to the reformer,
The auxiliary air heat exchanger performs heat exchange between exhaust gas flowing through the exhaust gas path and power generation air before being preheated by the air heat exchanger inside and outside the double pipe. A fuel cell system which is a tubular heat exchanger and is arranged to extend in a vertical direction along a side wall of the casing .

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