JP2015179582A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery system that can stably supply reformed gas to a hydrodesulfurizer through a recycle path even when the power generation of a fuel battery power generator is low output power generation.SOLUTION: A fuel battery system has a fuel battery power generator 2 for generating power by using fuel and air, a raw material pressure increasing unit 5 for supplying raw material, a hydrodesulfurizer 4 for removing sulfur components contained in the raw material, a reformer 3 for generating reformed gas as fuel from the raw material from which the sulfur components are removed by the hydrodesulfurizer 4, a gas path 21 as a passage through which the generated reformed gas is supplied to the fuel battery power generator 2 and exhaust gas discharged from the fuel battery power generator 2 is led to the outside, a recycle path 7 as a passage which is branched from the gas path 21 and leads a part of the reformed gas to the upstream side of the hydrodesulfurizer 4, and a pressure loss control unit for controlling to vary the pressure loss occurring at a downstream portion of the gas path more greatly than that at a branch portion R1 at which the recycle path 7 is branched from the gas path 21.

Description

  The present invention relates to a fuel cell system including a hydrodesulfurizer that removes a sulfur component from a raw material containing hydrocarbons.

  In a fuel cell system in which hydrocarbons are supplied as a raw material, power is generated using hydrogen-containing gas (reformed gas) obtained by reforming hydrocarbons as fuel. For reforming the raw material, for example, steam reforming using steam can be used. Moreover, although a steam reforming catalyst is used for promoting steam reforming, the steam reforming catalyst may be deteriorated by a sulfur component such as an odorant or a sulfur compound contained in the raw material. Therefore, in order to suppress degradation of the steam reforming catalyst, it is common to supply the raw material from which the sulfur component has been removed to the steam reforming catalyst.

  As a method for removing the sulfur component, two types of adsorption desulfurization and hydrodesulfurization are mainly used. When hydrodesulfurization is used, it is necessary to add hydrogen to the raw material upstream of the hydrodesulfurizer in order to advance a hydrogenation reaction that hydrogenates sulfur components. Therefore, a configuration has been proposed in which a part of hydrogen generated in the reforming reaction (a part of the reformed gas) is returned to the upstream side of the hydrodesulfurizer in order to add hydrogen to the raw material. As the configuration for returning the reformed gas from the outlet portion of the reformer filled with the steam reforming catalyst to the upstream side of the hydrodesulfurizer, for example, a configuration is provided in which a feed pump is provided in the recycling path, and hydrogen is pumped by this feed pump. There is. Moreover, the structure which can return hydrogen by self-pressure, without providing a feed pump etc. in a recycle path | route is proposed (for example, patent document 1, 2).

  In Patent Document 1, as shown in FIG. 8, a part of the reformed gas is supplied from the circulation flow path branching section G1 between the reformer 103 and the cell stack 104 to the hydrogen through the circulation flow path (recycling path) 105. A fuel cell system that joins the upstream side of the feed pump P in the contained material supply path 101 has been proposed. Here, by providing the first pressure reduction unit 108 on the upstream side of the circulation channel merging portion G2 in the hydrogen-containing raw material supply path 101, the pressure of the circulation channel branching portion G1 becomes higher than that of the circulation channel merging portion G2. It is configured as follows.

  In the case of the configuration disclosed in Patent Document 1, it is not necessary to provide a pump for pumping the reformed gas in the path of the circulation channel 105, and the reformed gas is supplied upstream of the feed pump P while realizing cost reduction. It becomes possible to return to the side.

  In Patent Document 2, as shown in FIG. 9, a part of the reformed gas generated by the reformer 205 is added to the raw material introduced from the gas pipe 201 through the recycle gas channel (recycle channel) 208. A fuel cell power generation system is disclosed. The raw material to which the reformed gas is added is configured to be introduced into the hydrodesulfurizer 204 through the fuel blower 203. In the fuel cell power generation system according to Patent Document 2, a pressure adjustment orifice 214 is provided on the upstream side of the fuel blower 203. For this reason, the pressure of the gas supplied to the fuel blower 203 can be adjusted by the pressure adjusting orifice 214, and the reformed gas is pumped to the recycle gas flow path 208 as in the fuel cell system according to Patent Document 1. Therefore, the reformed gas can be returned to the upstream side of the fuel blower 203 without providing a pump for the purpose.

International Publication No. 2012/128369 JP 2013-225411 A

  By the way, in order to effectively perform hydrodesulfurization, it is necessary to stably supply hydrogen at a flow rate necessary for the hydrodesulfurization reaction to the hydrodesulfurizer. However, in the conventional fuel cell systems disclosed in Patent Document 1 and Patent Document 2, when the power generation of the fuel cell power generation unit is low power generation, the flow rate of the reformed gas flowing through the recycling path does not vary, and the modified There is a problem that it is difficult to stably supply the quality gas to the upstream side of the hydrodesulfurizer.

  The present invention has been made in view of such circumstances, and stably supplies the reformed gas to the hydrodesulfurizer through the recycling path even when the power generation of the fuel cell power generation unit is low power generation. A fuel cell system is provided.

  In order to solve the above-described problem, a fuel cell system according to the present invention uses a supplied fuel and air to generate power by a power generation reaction, a fuel cell power generation unit that supplies raw materials, A hydrodesulfurizer that removes the sulfur component contained in the raw material supplied from the raw material supply unit, and a reformer that generates a reformed gas that serves as the fuel from the raw material from which the sulfur component has been removed by the hydrodesulfurizer And a gas path that is a path for supplying the reformed gas generated by the reformer to the fuel cell power generation unit and leading the exhaust gas exhausted from the fuel cell power generation unit to the outside, and the gas path A part of the reformed gas generated by the reformer branching from the gas path and leading to the upstream side of the hydrodesulfurizer, and from the gas path The recycling route is The branch unit to and a pressure loss control unit performs control so as to change the pressure loss produced in a downstream portion of the gas path.

  The fuel cell system according to the present invention is configured as described above, and stably supplies the reformed gas to the hydrodesulfurizer through the recycling path even when the power generation of the fuel cell power generation unit is low power generation. There is an effect that can be done.

It is the schematic diagram which showed an example of the structure of the fuel cell system which concerns on embodiment of this invention. It is the schematic diagram which showed an example of the structure of the fuel cell system which concerns on the modification 1 of embodiment of this invention. It is the schematic diagram which showed an example of the structure of the fuel cell system which concerns on the modification 2 of embodiment of this invention. It is the schematic diagram which showed an example of the structure of the fuel cell system which concerns on the modification 3 of embodiment of this invention. It is the schematic diagram which showed an example of the structure of the fuel cell system which concerns on the modification 4 of embodiment of this invention. It is the schematic diagram which showed an example of the structure of the fuel cell system which concerns on the modification 4 of embodiment of this invention. It is the schematic diagram which showed an example of the structure of the fuel cell system which concerns on the modification 5 of embodiment of this invention. It is a schematic diagram which shows a prior art and shows an example of a structure of a fuel cell system. It is a schematic diagram which shows a prior art and shows an example of a structure of a fuel cell system.

(Background to obtaining one embodiment of the present invention)
The present inventor conducted intensive research on the conventional fuel cell system disclosed in Patent Documents 1 and 2 described in “Background Art”. In the conventional fuel cell system, a low-power generation of the fuel cell is distributed through a recycling path. It has been found that there may be a problem that the reformed gas cannot be stably supplied to the hydrodesulfurizer without the flow rate of the reformed gas being varied. And as a result of repeated investigations on this problem, the present inventor has obtained the following knowledge.

  In the fuel cell system, the power load is not always constant, and the power load is low at night when the power consumption is small. When the power load is low and the power generation output of the fuel cell power generation unit is low power generation lower than the normal output, the flow rate of the supplied raw material is smaller than that during normal operation. For this reason, at the time of low power generation, the pressure of the reformed gas flowing through the branch part (for example, the circulation flow path branch part G1 in Patent Document 1) where the recycle path branches from the gas path becomes smaller than that during normal operation.

  Therefore, in the conventional fuel cell systems disclosed in Patent Document 1 and Patent Document 2, a portion where the reformed gas returned through the recycling path merges with the raw material (for example, the circulation flow path merge portion G2 in Patent Document 1). ) Must be further reduced than during normal operation by controlling the first pressure reducing unit 108 or the pressure adjusting orifice 214 or the like. However, when the amount of decompression increases, it becomes difficult to control the first pressure reducing unit 108 or the pressure adjusting orifice 214. For this reason, the flow rate of the reformed gas flowing through the recycling path varies, and there arises a problem that the reformed gas cannot be stably supplied to the hydrodesulfurizer.

  Based on these findings, the present inventors have determined the pressure of the branch part (circulation flow path branch part G1 in Patent Document 1) where the recycle path branches from the gas path part between the reformer and the fuel cell power generation part. As a result, it has been found that the reformed gas can be stably supplied to the hydrodesulfurizer through the recycling path even in the case of low power generation. And in this invention, the aspect shown below is provided.

  A fuel cell system according to a first aspect of the present invention includes a fuel cell power generation unit that generates power by a power generation reaction using supplied fuel and air, a raw material supply unit that supplies a raw material, and the raw material supply A hydrodesulfurizer that removes a sulfur component contained in the raw material supplied from the section, and a reformer that generates a reformed gas serving as the fuel from the raw material from which the sulfur component has been removed by the hydrodesulfurizer , Supplying a reformed gas generated by the reformer to the fuel cell power generation unit, and a gas path that is a path for guiding exhaust gas exhausted from the fuel cell power generation unit to the outside, and a branch from the gas path A part of the reformed gas generated in the reformer that circulates in the gas path, a recycle path that is a path for guiding the reformed gas upstream to the hydrodesulfurizer, and the recycle from the gas path. Branch part where the route branches And a pressure loss control unit performs control so as to change the pressure loss produced in the downstream portion in Rimo該 gas path.

  According to the above configuration, since the pressure loss control unit is provided, the pressure loss generated in the downstream portion of the gas path can be changed. Here, when the pressure loss is increased in the downstream portion of the gas path from the branch portion, the pressure in the upstream side, that is, the branch portion can be increased from the portion where the pressure loss is increased. In this way, the pressure at the branch portion can be increased. For this reason, the difference between the pressure at the branching portion in the recycling path and the pressure at the upstream side of the hydrodesulfurizer and where the reformed gas is guided through the recycling path and merges with the gas path (merging portion) is increased. be able to.

  For this reason, even if it is a case where the pressure in a branch part becomes low like the time of low output electric power generation, the above-mentioned pressure difference in a recycling route is securable.

  Therefore, the combustion cell system according to the present invention has an effect that the reformed gas can be stably supplied to the hydrodesulfurizer through the recycling path even when the power generation of the fuel cell power generation unit is low power generation. Play.

  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 pressure loss control unit is configured by the branch portion in the gas path according to a change in pressure in the branch portion. Alternatively, the pressure loss generated in the downstream portion may be controlled to change.

  According to the said structure, the pressure loss control unit can change the pressure loss which arises in a downstream part rather than this branch part according to the change of the pressure in a branch part. For this reason, for example, even in the case where the pressure of the branch portion decreases during low-power power generation, the pressure loss control unit increases the pressure loss generated in the downstream portion of the branch portion in the gas path, It is possible to keep the difference between the pressure at the branch portion in the recycle path and the pressure at the upstream side of the hydrodesulfurizer, where the reformed gas is guided through this recycle path and merges with the raw material path (merging section).

  In the fuel cell system according to the third aspect of the present invention, in the first or second aspect described above, the raw material supply unit is a raw material pressure increase unit that pressurizes the raw material and supplies the raw material to the hydrodesulfurizer. There may be.

  According to the above configuration, the raw material supply unit is the raw material boosting unit. For this reason, it is possible to easily generate a difference between the pressure at the branching portion and the pressure at the portion where the reformed gas is guided through the recycling path and merges with the raw material path by using the power of the raw material boosting section.

  The fuel cell system according to a fourth aspect of the present invention is the fuel cell system according to the third aspect described above, wherein the recycling path is supplied to the raw material booster and is sent from the raw material booster to the hydrodesulfurizer. In the raw material path | route through which a raw material distribute | circulates, it may be comprised so that the said reformed gas may be distribute | circulated to the inlet side of this raw material pressure | voltage rise part.

  According to the above configuration, since the pressure on the inlet side of the raw material boosting portion is reduced, a difference between the pressure in the branch portion and the pressure in the upstream portion of the hydrodesulfurizer where the reformed gas is guided through the recycling path is likely to occur. can do.

  In the fuel cell system according to the fifth aspect of the present invention, in the third aspect described above, the raw material that is supplied to the raw material pressurizer and from which the raw material sent from the raw material pressurizer to the hydrodesulfurizer circulates is provided. In the path, an ejector for sucking the reformed gas may be provided on the outlet side of the raw material booster, and the recycling path may be configured to be connected to the ejector.

  According to the above configuration, since the pressure of the suction portion of the ejector is low by adopting a configuration in which the reformed gas flowing through the recycling path is sucked by the ejector, a differential pressure from the pressure at the branch portion can be easily generated.

  The fuel cell system according to a sixth aspect of the present invention is the above-described fourth or fifth aspect, wherein the reforming that circulates the raw material that flows through the raw material path and the recycling path in the raw material path. It may be configured to include a first pressure reduction unit that is provided on the upstream side of the merge part where the gas merges and that reduces the pressure in the merge part.

  According to the said structure, since the 1st pressure reduction part is provided, the pressure of a confluence | merging part can be reduced. Thus, since the pressure of the confluence portion can be lowered by the first pressure reduction portion, the magnitude of the pressure to be increased at the branch portion can be suppressed. For this reason, the difference of the pressure in a branch part and the pressure in a confluence | merging part can be ensured appropriately, suppressing the increase in the pressure loss in the gas path | route by a pressure loss control unit in the appropriate range.

  The fuel cell system according to a seventh aspect of the present invention is the fuel cell system according to any one of the first to sixth aspects, wherein the unused fuel is burned in the fuel cell power generation unit. The pressure loss control unit may be configured to change the pressure loss of the exhaust gas path, which is the path part through which the combustion exhaust gas generated by the combustion part flows, in the gas path. Good.

  According to the above configuration, the pressure loss control unit is configured to change the pressure loss of the exhaust gas path.

  Here, the exhaust gas path is a path in the downstream (downstream side) portion of the gas path from the fuel cell power generation unit and the combustion unit. Therefore, for example, even when the pressure loss control unit is configured to supply a fluid such as air to the exhaust gas path and change the pressure loss generated in the exhaust gas path, The influence on performance and combustion characteristics in the combustion section can be suppressed.

  The fuel cell system according to an eighth aspect of the present invention is the fuel cell system according to the seventh aspect described above, further comprising an air supply path for supplying air to the exhaust gas path, and the pressure loss control unit includes the air supply The configuration may be such that the pressure loss generated in the exhaust gas path is changed by adjusting the flow rate of the air flowing through the path.

  According to the above configuration, the pressure loss control unit can control a change in pressure loss that occurs in the exhaust gas path with a simple configuration in which the air flowing through the air supply path is supplied to the exhaust gas path.

  A fuel cell system according to a ninth aspect of the present invention, in the eighth aspect described above, collects condensed water that is provided in the exhaust gas path and that is obtained by condensing the combustion exhaust gas generated in the combustion section. A condensed water recovery part may be provided, and the air supply path may be configured to be connected to the downstream side of the condensed water recovery part in the exhaust gas path.

  According to the above configuration, since the air supply path is connected to the downstream side of the condensed water recovery unit in the exhaust gas path, air can be supplied without lowering the dew point of the combustion exhaust gas. Further, since the condensed water recovery unit recovers the condensed water while the dew point of the combustion exhaust gas is kept high, it is easy to recover the water in the combustion exhaust gas, and water self-sustained operation in the fuel cell system can be realized.

  The fuel cell system according to a tenth aspect of the present invention is the fuel cell system according to the seventh aspect described above, further comprising an adjustment valve for adjusting the magnitude of the pressure loss generated in the downstream portion of the gas path from the branch portion. The pressure loss control unit may be configured to control so as to change the magnitude of the generated pressure loss by opening and closing the regulating valve.

  In addition, when it is set as the structure which provides such an adjustment valve in an exhaust gas path, it becomes possible to arrange | position an adjustment valve avoiding the position which becomes high temperature with the combustion heat of a combustion part, and can improve durability of an adjustment valve. .

  The fuel cell system according to an eleventh aspect of the present invention is the fuel cell system according to any one of the first to tenth aspects described above, in order to adjust the flow rate of the reformed gas flowing through the recycle path. It may be constituted so that the 2nd pressure reduction part which lowers may be provided.

  According to the above configuration, since the second pressure reduction unit is provided, the recycling path is made to circulate even when the differential pressure fluctuation between the branching part and the joining part in the recycling path becomes large due to fluctuations in the power load or the like. The flow rate of the reformed gas can be stabilized.

  A fuel cell system according to a twelfth aspect of the present invention includes the condensing unit for condensing moisture in the reformed gas flowing through the recycling path in the first to eleventh aspects. May be.

  According to the said structure, since a condensation part is provided, the pressure loss fluctuation | variation which arises in the recycle path | route resulting from the water in a recycle path | route, ie, condensed water, can be suppressed. For this reason, it is possible to stabilize the flow rate of the reformed gas flowing through the recycle path and prevent the water from being mixed into each part of the reformed gas supply destination, such as the raw material supply unit, and failing.

  Hereinafter, specific examples of the embodiments will be described with reference to the drawings. In the following description, the same or corresponding components are denoted by the same reference symbols throughout the drawings, and the description thereof may be omitted.

(Configuration of fuel cell system)
A configuration of a fuel cell system 100 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram showing an example of the configuration of a fuel cell system 100 according to an embodiment of the present invention.

  As shown in FIG. 1, a fuel cell system 100 includes a fuel cell power generation unit 2, a reformer 3, a hydrodesulfurizer 4, a raw material boosting unit 5 that functions as a raw material supply unit of the present invention, and a combustion unit. 6, a reforming air pump 16, and a control unit 90. Further, the fuel cell system 100 includes a raw material path 1, a gas path 21, a reforming water path 20, a reforming air path 17, a recycling path 7, and an air supply path 9.

  The raw material path 1 is a path from the outside of the system to the reformer 3 via the raw material booster 5. As the raw material, for example, a gas mainly composed of hydrocarbons such as city gas, natural gas, and LPG is used. The gas path 21 is a path from the reformer 3 to the outside of the system via the fuel cell power generation unit 2 and the combustion unit 6. The reformed air path 17 is a path from which reforming air supplied from outside the system reaches the raw material path 1 via the reformed air pump 16. The reformed water path 20 is a path from the supplied reformed water to the raw material path 1. The air supply path 9 is a path that branches from the reformed air path 17 and reaches the gas path 21 (exhaust gas path 8). Details of these routes will be described later.

  The hydrodesulfurizer 4 desulfurizes sulfur components contained in the raw material supplied to the reformer 3. The hydrodesulfurizer 4 is filled with a desulfurization catalyst (not shown) for removing sulfur components. In the present embodiment, a hydrodesulfurization method in which a sulfur component is removed by reacting with hydrogen is adopted as the desulfurization method. In order to carry out the hydrodesulfurization method, the raw material is supplied to the hydrodesulfurizer 4 with the reformed gas added as a gas containing hydrogen. In addition to the hydrodesulfurization method, another desulfurization method such as an adsorptive desulfurization method may be used in combination.

  The reformer 3 is filled with a reforming catalyst, and generates a hydrogen-rich reformed gas using the raw material after passing through the hydrodesulfurizer 4. The reformer 3 is supplied with reforming water through the reforming water path 20 in order to perform a reforming reaction. When the reforming water is supplied in a liquid state, the reforming water is evaporated. The evaporator is provided in the front stage of the reformer 3. The reforming method in the reformer 3 is not particularly limited, and for example, a steam reforming reaction, a partial reforming reaction, an autothermal reaction, and other methods can be adopted. In the present embodiment, a configuration in which steam reforming and partial oxidation reforming are used in combination is taken as an example. That is, when the fuel cell system 100 is started, the heat energy is insufficient to perform the steam reforming reaction that is an endothermic reaction in the reformer 3. Therefore, when the fuel cell system 100 is started up, reforming water is not supplied, but reforming air is introduced into the reformer 3 through the reforming air path 17, and this air is used to reform the fuel. The vessel 3 performs partial oxidation reforming.

  Further, as the fuel cell system 100 is activated and power generation proceeds, the temperature of the reformer 3 rises, and when the temperature rises above a predetermined temperature, the steam reforming reaction is switched. The reformed gas generated by the reformer 3 is supplied to the fuel cell power generation unit 2.

  The reformer 3 may have a different configuration depending on the type of the fuel cell power generation unit 2. For example, in the case of a polymer electrolyte fuel cell or a phosphoric acid fuel cell, since it is necessary to remove carbon monoxide in the reformed gas in the reformer 3, the structure of a shift reaction unit, a selective oxidation reaction unit, etc. It is comprised so that carbon monoxide may be removed. Since the reformer 3 has the same configuration as that used in a known fuel cell system, further detailed description is omitted.

  The fuel cell power generation unit 2 performs a power generation reaction using the reformed gas generated in the reformer 3 and oxygen in the air. The fuel cell power generation unit 2 includes a fuel electrode to which the reformed gas is supplied, and an air electrode to which power generation air is supplied from outside the system through a path (not shown), between the fuel electrode and the air electrode. A cell stack is formed by connecting a plurality of fuel cell single cells that generate electricity in series. The fuel cell power generation unit 2 may further have a configuration in which cell stacks connected in series are connected in parallel. The reformed gas that is not used in the fuel cell power generation unit 2 is used for the combustion reaction. The fuel cell power generation unit 2 includes, for example, a solid oxide fuel cell (SOFC), a polymer electrolyte fuel cell (PEFC), a molten polymer fuel cell (MCFC), and a molten carbonate fuel cell (MCFC; Molten Carbonate Fuel). Cell), a phosphoric acid fuel cell (PAFC; Phosphor Acid Fuel Cell) and the like can be employed.

  In the combustion unit 6, the fuel cell power generation unit 2 burns unused fuel (reformed gas) to generate a heat source. As the oxygen-containing gas used for the combustion reaction, unutilized air (cathode off-gas) in the fuel cell power generation unit 2 can be used. Or the structure which supplies the air for combustion from another path | route and performs a combustion reaction may be sufficient. The combustion heat generated in the combustion unit 6 is used for the reforming reaction in the reformer 3 and the like. In particular, in the case of a solid oxide fuel cell or the like that operates at a high temperature, the reformer 3, the fuel cell power generation unit 2, and the combustion unit 6 are housed in one casing, and the fuel cell power generation unit 2 is kept at a predetermined operating temperature. This combustion heat can be used as a heat source for maintaining the range.

  The raw material path 1 is a path for supplying a raw material supplied from outside the system to the reformer 3 via the hydrodesulfurizer 4, and is disposed downstream of the hydrodesulfurizer 4. Connected to the inlet of the reformer 3. Moreover, in the raw material path | route 1, the raw material pressure | voltage rise part 5 is provided in the upstream of the hydrodesulfurizer 4 as a raw material supply part which sends a raw material to the hydrodesulfurizer 4 side. The raw material booster 5 is, for example, a constant displacement pump such as a diaphragm, but is not limited thereto. Under the control instruction from the control unit 90, the raw material booster 5 adjusts the output of the raw material supplied to the fuel cell power generation unit 2 so that the flow rate of the raw material becomes a target value corresponding to the power load. That is, in the raw material path 1, the raw material boosting unit 5 boosts the raw material supplied from the outside and sends it to the hydrodesulfurizer 4. The raw material sent from the raw material pressure raising unit 5 is guided to the hydrodesulfurizer 4, and the sulfur component is removed by the hydrodesulfurizer 4. The raw material from which the sulfur component has been removed is supplied to the reformer 3 through the raw material path 1.

  The gas path 21 is a path provided on the downstream side of the reformer 3, and the reformed gas generated by the reformer 3 and the exhaust gas (anode off gas and cathode off gas) discharged from the fuel cell power generation unit 2. ), An exhaust gas (combustion exhaust gas) discharged from the combustion unit 6 and the like. The gas path 21 goes from the outlet of the reformer 3 to the outside of the system via the fuel cell power generation unit 2 and the combustion unit 6. Of the gas path 21, the part through which the combustion exhaust gas generated in the combustion unit 6 circulates is particularly referred to as the exhaust gas path 8 in this specification.

  That is, in the gas path 21, the reformed gas generated by the reformer 3 is supplied to the fuel cell power generation unit 2. The fuel cell power generation unit 2 generates power using the reformed gas (fuel) and air (not shown) supplied from the outside. Unmodified reformed gas (anode off gas) in power generation flows through the gas path 21 and is supplied to the combustion unit 6 provided on the downstream side of the fuel cell power generation unit 2. The combustion unit 6 discharges combustion exhaust gas generated by burning the supplied anode off gas. The combustion exhaust gas discharged from the combustion unit 6 flows through the gas path 21 (exhaust gas path 8) and is led out of the system.

  In addition, it can be set as the structure which provided the heat exchanger (not shown) for producing | generating hot-water supply water on the waste gas path 8. FIG. Moreover, it is good also as a structure which further provided the heat exchange part (not shown) for performing heat exchange with the air for generation | occurrence | production or a raw material on the waste gas path 8. FIG. In the case of the configuration in which the heat exchanger and the heat exchange unit are provided in this manner, the exhaust heat can be recovered by performing heat exchange with the combustion exhaust gas.

  The reforming water path 20 is a path for supplying water necessary for performing the steam reforming reaction in the reformer 3, and is upstream of the reformer 3 in the raw material path 1 and hydrodesulfurization. It is connected to a position on the downstream side of the vessel 4. Further, if necessary, the reformed water path 20 is set so that the reformed water returned to the upstream side of the hydrodesulfurizer 4 or the combustion exhaust gas generated in the combustion unit 6 and the reformed water exchange heat. The structure to arrange | position may be sufficient.

  The reformed air path 17 is a path for supplying air necessary for performing partial oxidation reforming in the reformer 3, and is upstream of the reformer 3 in the raw material path 1 and hydrodesulfurized. It is connected to a position on the downstream side of the vessel 4. A reforming air pump 16 is provided in the reforming air path 17, and the reforming air is pressurized by the reforming air pump 16 and sent to the raw material path 1.

  The air supply path 9 is a path that branches from the reformed air path 17 and supplies a part of the air flowing through the reformed air path 17 into the exhaust gas path 8. One end of the air supply path 9 is connected to the downstream side of the reformed air pump 16 in the reformed air path 17, and the other end is connected to the exhaust gas path 8 portion. Then, the air sent from the reformed air pump 16 is configured to be guided to the exhaust gas path 8. Further, a reforming air valve 15 is provided in the reforming air path 17 on the downstream side of the reforming air pump 16, and an air supply valve 12 is provided in the air supply path 9. Under the control instruction from the control unit 90, By opening and closing the reformed air valve 15 and the air supply valve 12, the flow rate of air flowing through the reformed air path 17 and the air supply path 9 can be adjusted. For example, when the fuel cell system 100 in which the reformer 3 performs partial oxidation reforming is started, the air supply valve 12 is closed and the reforming air valve 15 is opened in accordance with an instruction from the control unit 90. As a result, air can be supplied to the reformer 3. On the other hand, when the temperature of the reformer 3 rises and is switched from partial oxidation reforming to steam reforming, the reforming air valve 15 is closed according to an instruction from the control unit 90. Further, when the pressure of the branch portion R1 decreases, the air supply valve 12 is opened in accordance with an instruction from the control unit 90, and air is supplied to the exhaust gas path 8 to increase the pressure loss generated in the exhaust gas path 8.

  The recycle path 7 is a path for branching from the gas path 21 and returning a part of the reformed gas generated in the reformer 3 to the upstream side of the hydrodesulfurizer 4. One end of the recycle path 7 is connected to the gas path 21 at the branch portion R1, and the other end is connected to the raw material path 1 at the junction R2. Further, the pressure of the branching portion R1 is maintained to be higher than the pressure of the merging portion R2, and the reformed gas is supplied by the self-pressure to the upstream side of the hydrodesulfurizer 4 (in the example shown in FIG. (Upstream).

  Further, in the fuel cell system 100 according to the present embodiment, the pressure of the reformed gas flowing through the branch portion R1 is higher than the pressure of the raw material gas flowing through the junction R2 even when the fuel cell power generation unit 2 is generating low power. In order to maintain the differential pressure so as to increase, a pressure loss control unit is provided for controlling the pressure loss of the gas flowing through the gas path 21 to increase as described above.

  More specifically, the pressure loss control unit of the present invention is realized by the control unit 90, the reforming air pump 16, the air supply path 9, and the air supply valve 12. That is, when the pressure of the reformed gas flowing through the branch portion R1 decreases by a predetermined amount, the control unit 90 activates the reformed air pump 16 and controls the air supply valve to be in an open state. Thereby, air is sent to the exhaust gas path 8 through the air supply path 9. By supplying air to the exhaust gas path 8 in this way, the pressure loss of the exhaust gas path 8 can be increased, and as a result, the pressure in the branch portion R1 can be increased. By maintaining the pressure difference between the branch portion R1 and the merge portion R2 in this way, a part of the reformed gas can be returned to the upstream side of the hydrodesulfurizer 4 through the recycle path 7 by the self-pressure. .

  In the present embodiment, the supply of air to the exhaust gas path 8 is performed by the reformed air pump 16. This is because, as described above, when the fuel cell system 100 is started, the reformer 3 performs partial oxidation reforming, so that reforming air is supplied to the reformer 3, but thereafter it is switched to steam reforming. It is not necessary to supply air for reforming. On the other hand, the pressure drop in the branch portion R1 occurs not during the startup of the fuel cell system 100 but during the operation. For this reason, the reformed air pump 16 can be used as a pump for sending air to the exhaust gas path 8.

  However, an air pump may be provided separately from the reforming air pump 16 and air may be supplied to the exhaust gas path 8 using this air pump. However, the configuration that can supply air to the reformed air path 17 or the exhaust gas path 8 in combination with the reformed air pump 16 that sends out reforming air as in the present embodiment has a smaller number of parts. This is advantageous in that it can be reduced and the cost can be suppressed.

(Operation of fuel cell system)
Next, the operation of the fuel cell system 100 of the first embodiment having the above-described configuration will be described. In the fuel cell system 100, the raw material is pressurized by the raw material boosting unit 5 and supplied to the hydrodesulfurizer 4. Thereafter, the raw material is desulfurized in the hydrodesulfurizer 4 and becomes a hydrogen-rich reformed gas by the reforming reaction of the reformer 3. As described above, the branch portion R1 is provided between the reformer 3 and the fuel cell power generation unit 2 in the gas path 21, and through the recycle path 7 branched from the gas path 21 at the branch section R1. A part of the reformed gas can be returned to the upstream side of the hydrodesulfurizer 4.

  Here, the pressure in the branch portion R1 correlates with the flowing gas flow rate (reformed gas flow rate), and the pressure in the branch portion R1 increases as the flow rate increases. That is, since a larger amount of raw material and air are required at the time of high output power generation than at the time of low output power generation, the flow rate of the reformed gas flowing through the gas path 21 is increased. For this reason, the pressure of the branch portion R1 increases as the power output increases. On the other hand, the flow rate of the reformed gas flowing during the low-output power generation decreases, and as a result, the pressure level at the branch portion R1 may be equal to or lower than the pressure level at the junction portion R2.

  Further, the magnitude of the pressure in the branch portion R1 is affected by the magnitude of the pressure loss that occurs in the gas path 21 on the downstream side of the branch portion R1. That is, the pressure in the branch portion R1 can be increased by increasing the pressure loss generated in the gas path 21 on the downstream side of the branch portion R1.

  Therefore, the fuel cell system 100 according to the present embodiment has a configuration including a pressure loss control unit that changes the pressure loss of the gas path 21 at the downstream side of the branch portion R1, for example, the exhaust gas path 8. Specifically, the pressure loss control unit can be realized by the control unit 90, the reformed air pump 16, the air supply path 9, and the air supply valve 12, as described above. The pressure loss control unit supplies air to the exhaust gas path 8 so that the pressure of the gas flowing through the branch portion R1 is higher than the pressure of the raw material flowing through the junction portion R2 even during low power generation.

  As described above, by operating the pressure loss control unit so as to change the pressure loss generated on the downstream side of the branch portion R1 in the gas path 21, in particular, the pressure difference between the branch portion R1 and the junction portion R2 is increased. Even in the case of a small SOFC, the reformed gas can be returned to the upstream side of the hydrodesulfurizer 4 through the recycle path 7 by its own pressure, and the hydrodesulfurizer 4 can be stably operated.

  Note that the flow rate of the raw material delivered from the raw material booster 5 is different during normal output power generation, high output power generation, and low output power generation. For this reason, the reformed gas may be returned to the upstream side of the hydrodesulfurizer 4 via the recycle path 7 so as to always have a constant ratio with respect to the flow rate change of the delivered raw material. In this way, in the case of a configuration in which the reformed gas having a constant ratio according to the change in the raw material flow rate is returned via the recycle path 7, the control unit 90 controls the reformed air pump 16 and the air supply valve 12 as follows. To do.

  That is, the flow rate of the reformed gas returned to the upstream side of the hydrodesulfurizer 4 is set to a constant ratio with respect to the flow rate of the raw material, and the differential pressure between the branching portion R1 and the merging portion R2 is increased as the power output is increased. Control to increase gradually. More specifically, the target flow rate of the reformed gas flowing through the recycle path 7 corresponding to the raw material flow rate flowing through the raw material path 1 or the power generation output by the fuel cell power generation unit 2 or the current value of electricity obtained by power generation is previously set. Set it. Further, a target differential pressure in the recycling path 7 corresponding to the raw material flow rate, the power generation output or the current value is set in advance. A pressure detection sensor and a flow rate sensor (not shown) are provided in the recycle path 7, and a flow rate sensor (not shown) is also provided in the raw material path 1. In such a configuration, the control unit 90 opens the air supply valve 12 from the detection results of the pressure detection sensor and the flow rate sensor in the recycle path 7, the detection result of the flow rate sensor in the raw material path 1, the power generation output or the current value. The output of the reforming air pump 16 is controlled so that the recycling path 7 has a target differential pressure and a target flow rate corresponding to the power generation output.

  In addition, when the flow rate of the raw material delivered from the raw material booster 5 during low power generation decreases and the differential pressure between the branch R1 and the merger R2 decreases, the pressure in the branch R1 is increased and the branch R1 It controls so that the differential pressure | voltage between merging part R2 increases. Specifically, the control unit 90 opens the air supply valve 12 and adjusts the flow rate of air supplied to the exhaust gas path 8 by the reformed air pump 16 so as to increase the branching unit R1 and the merging unit. Control can be performed to ensure a differential pressure with R2.

  As described above, when the reformed air pump 16 is used to supply air to the exhaust gas path 8, the control unit 90 opens and closes the air supply valve 12 and turns on / off the reformed air pump 16. By controlling, a constant flow of air can be supplied to the exhaust gas path 8. Here, in order to ensure the differential pressure so that the pressure at the branching portion R1 is always greater than the pressure at the merging portion R2, the control unit 90 sets the timing of supplying air to the exhaust gas path 8. It is necessary to decide.

  For example, the control unit 90 may be configured to always supply the air flow rate corresponding to the power load to the exhaust gas path 8 while the fuel cell system 100 is moving, or air is supplied only during low power generation. Thus, the configuration controlled by the control unit 90 may be used.

  Further, as described above, in the case of the configuration in which the flow rate of air supplied to the exhaust gas path 8 is controlled to ensure the differential pressure between the branch portion R1 and the junction portion R2, the fuel cell system 100 detects the change in the power load. A sensor (not shown), a pressure measuring sensor (not shown) for measuring the pressure at the branching portion R1, or a sensor (not shown) for detecting a change in the flow rate of the material sent from the material boosting unit 5 determined according to the power load At least one sensor is provided, and the control unit 90 controls the timing for switching ON / OFF of the reforming air pump 16 and the timing for switching opening / closing of the air supply valve 12 based on the detection result from this sensor. For example, the control unit 90 determines whether or not the pressure in the branch portion R1 has decreased by a predetermined amount in the recycle path 7 based on a measurement result from a pressure measurement sensor (not shown). When it is determined that the pressure has decreased by a predetermined amount, the reformed air pump 16, the air supply valve 12, and the like are controlled so as to increase the pressure loss generated in the exhaust gas path 8.

  Moreover, the flow rate adjustment of the air flow rate supplied to the exhaust gas path 8 can be performed as follows, for example. In the case where the supply amount of air to the exhaust gas passage 8 is variable by turning on / off the reforming air pump 16, a flow meter (not shown) for measuring the air flow rate on the air supply passage 9 or the pressure of the air A pressure gauge for measuring And the control part 90 is comprised so that the output of the reforming air pump 16 may be controlled according to the air flow measured by the flow meter or the air pressure measured by the pressure gauge.

  As described above, the branch portion R1 and the merging portion are configured so that the ratio of the reformed gas to the raw material becomes constant by changing the flow rate of air sent from the reformed air pump 16 according to the pressure change in the branch portion R1. It is advantageous to adjust the differential pressure with R2. However, in order to simplify the overall configuration of the fuel cell system 100, the reforming air pump 16 is turned on at a predetermined timing when the pressure of the branching portion R1 decreases (for example, when the output power generation is lower than normal). It is good also as a structure which switches / OFF and supplies the air of fixed flow volume to the waste gas path 8.

  As described above, in the fuel cell system 100 according to Embodiment 1, the pressure loss control unit is operated, and the operation is controlled so that the pressure difference from the junction R2 is ensured by increasing the pressure of the branch R1. . In addition, since the differential pressure between the branch portion R1 and the junction portion R2 in the recycling path 7 can be ensured even during low power generation, the reformed gas is surely returned to the upstream side of the hydrodesulfurizer 4. Can do. In particular, during low power generation, it is possible to reduce the variation in the flow rate of the reformed gas that flows through the recycle path 7 and returns to the upstream side of the hydrodesulfurizer 4 as compared with the configuration in which the pressure at the junction R2 is reduced. . For this reason, the hydrodesulfurizer 4 can be operated stably.

(Modification 1)
Modification 1 in the embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic diagram showing an example of the configuration of the fuel cell system 100 according to Modification 1 of the embodiment of the present invention. As shown in FIG. 2, the fuel cell system 100 according to the first modification differs from the fuel cell system 100 according to the embodiment of the present invention described above in the following points.

  That is, in the fuel cell system 100 according to the modified example 1, the joining portion R2 of the recycle path 7 is provided on the downstream side of the raw material boosting section 5 in the raw material path 1 and on the upstream side of the hydrodesulfurizer 4. It is different in point. Further, it is also different in that it further includes an ejector 19 that is connected to the recycle path 7 to the merging section R2 and sucks the reformed gas flowing through the recycle path 7 in accordance with a control instruction from the control section 90. . Regarding the other members, the fuel cell system 100 according to Modification 1 has the same configuration as the fuel cell system 100 according to the embodiment shown in FIG.

  In the configuration in which the ejector 19 is further provided as in the fuel cell system 100 according to the first modification, when the raw material is sent from the raw material boosting unit 5 to the hydrodesulfurizer 4, the reformed gas flowing through the recycle path 7 is ejected. 19 sucks and joins the raw material. In this way, by adopting a configuration in which the reformer gas flowing through the recycling path 7 is sucked by the ejector 19, since the pressure of the suction portion of the ejector 19 is low, a differential pressure from the pressure at the branch portion can be easily generated. .

  Here, in order to ensure a differential pressure between the branching portion R1 and the joining portion R2 in the recycling path 7, it is necessary to make the pressure of the suction portion of the ejector 19 negative. However, since the pressure of the branching portion R1 becomes small as described above at the time of low output power generation, the ejector 19 provided in the merging portion R2 needs to increase the amount of pressure reduction compared to the normal time, and the pressure to be reduced is large. Variations are likely to occur. That is, it is difficult to accurately control the amount of decompression at the suction portion of the ejector 19 during low-power power generation.

  However, since the fuel cell system 100 according to the modified example 1 is configured to include the pressure loss control unit in the same manner as the fuel cell system 100 according to the embodiment shown in FIG. 1, it is possible to increase the pressure at the branch portion R1. it can. For this reason, for example, when the pressure of the branch portion R1 is reduced as in low power generation, air is supplied to the exhaust gas path 8 by the pressure loss control unit, and the pressure loss generated in the exhaust gas path 8 is increased. As a result, the pressure at the branch portion R1 is increased. Thereby, the pressure reduction amount by the suction part of the ejector 19 can be suppressed. As a result, it is possible to reduce the pressure variation that is reduced in the suction portion of the ejector 19 and stabilize the flow rate of the reformed gas that is returned to the upstream side of the hydrodesulfurizer 4 through the recycle path 7.

(Modification 2)
Next, Modification 2 of the embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic diagram showing an example of the configuration of the fuel cell system 100 according to Modification 2 of the embodiment of the present invention. As shown in FIG. 3, the fuel cell system 100 according to the modified example 2 differs from the fuel cell system 100 according to the embodiment of the present invention described above in the following points.

  That is, the fuel cell system 100 according to Modification 2 is different in that the first pressure reduction unit 10 is provided on the upstream side of the merging unit R2 in the raw material path 1. The first pressure reduction unit 10 reduces the pressure of the junction R2 in the raw material path 1, and for example, an orifice, a capillary, a governor, a pressure reducing valve, or a proportional valve can be used. In addition, the 1st pressure fall part 10 is not limited to these, What is necessary is just to make the pressure loss characteristic of merge part R2 variable.

  Here, in order to ensure the differential pressure between the branch portion R1 and the junction portion R2 of the recycling path 7, a method of increasing the pressure of the branch portion R1 as in the fuel cell system 100 according to the present embodiment, On the contrary, there is a method of reducing the pressure of the merging portion R2. The fuel cell system 100 according to Modification 2 has a configuration in which these two methods are combined.

  That is, air is supplied to the exhaust gas path 8 by the pressure loss control unit to increase the pressure in the branch portion R1, and the first pressure reduction unit 10 depressurizes the merge portion R2, thereby causing the branch portion R1 and the merge portion R2 to The differential pressure between the two can be ensured.

  Further, in the configuration in which the pressure difference between the branch portion R1 and the junction portion R2 is ensured only by reducing the pressure of the junction portion R2 by the first pressure reduction portion 10, as described above, the amount of pressure reduction is reduced at the time of low output power generation. Variation will increase. However, as in the fuel cell system 100 according to the modified example 2, when the pressure loss control unit increases the pressure at the branch portion R1 and the first pressure reduction portion 10 reduces the pressure at the junction R2, the low output Even during power generation, the amount of pressure reduction at the junction R2 by the first pressure drop unit 10 can be suppressed. For this reason, the 1st pressure fall part 10 can control the pressure reduction amount in the junction part R2 accurately, and can ensure the differential pressure | voltage between the branch part R1 and the junction part R2 uniformly.

  In addition, regarding the pressure loss control unit that increases the pressure loss by supplying air to the exhaust gas path 8, there is an upper limit for the amount of increase in the pressure loss. This is because if the amount of increase in pressure loss is large, the stability of the combustion section 6 and the power generation performance of the fuel cell power generation section 2 may be adversely affected. However, when the range in which the pressure loss can be increased is small, it is difficult to always ensure the differential pressure between the branch portion R1 and the junction portion R2 in a wide power generation output range.

  Therefore, in order to always ensure the differential pressure between the branch portion R1 and the junction portion R2, the pressure reduction and pressure of the junction portion R2 by the first pressure reduction portion 10 as in the fuel cell system 100 according to the second modification example. A configuration may be combined with boosting of the branching section R1 by the loss control unit.

(Modification 3)
Next, a third modification of the embodiment of the present invention will be described with reference to FIG. FIG. 4 is a schematic diagram showing an example of the configuration of the fuel cell system 100 according to Modification 3 of the embodiment of the present invention. As shown in FIG. 4, the fuel cell system 100 according to the modified example 3 differs from the fuel cell system 100 according to the embodiment of the present invention described above in the following points.

  That is, the fuel cell system 100 according to the modified example 3 includes a pressure regulating valve in the exhaust gas path 8 instead of including the reformed air pump 16, the air supply path 9, and the air supply valve 12 as the above-described pressure loss control unit. 22 is different.

  For example, a pressure reducing valve or a proportional valve that opens and closes the valve body under a control instruction from the control unit 90 can be used as the pressure adjusting valve 22. The pressure regulating valve 22 is not limited to these, and may be any one that makes the pressure loss characteristics of the combustion exhaust gas flowing through the exhaust gas path 8 variable according to a control instruction from the control unit 90. In addition, in the example shown in FIG. 4, there is one exhaust gas path 8, but this exhaust gas path 8 is composed of a plurality of paths, and a pressure regulating valve 22 is provided in each path, and by opening and closing these pressure regulating valves 22 The pressure loss in the exhaust gas path 8 may be adjusted.

  Note that, in the fuel cell system 100 according to the modified example 3, as in the pressure loss control unit of the fuel cell system 100 according to the above-described embodiment, for example, the pressure loss generated in the exhaust gas path 8 in response to a change in the power load is large. The valve opening degree of the pressure regulating valve 22 may be adjusted under the control instruction of the control unit 90 so that the height is variable. Alternatively, the valve opening degree of the pressure regulating valve 22 may be fixed under the control instruction of the control unit 90 so that a certain pressure loss occurs in the exhaust gas path 8. Furthermore, the valve opening degree of the pressure regulating valve 22 may be adjusted so as to generate a pressure loss in the exhaust gas path 8 under a control instruction from the control unit 90 only during low power generation.

(Modification 4)
Next, Modification 4 of the embodiment of the present invention will be described with reference to FIG. FIG. 5 is a schematic diagram showing an example of the configuration of the fuel cell system 100 according to Modification 4 of the embodiment of the present invention. As shown in FIG. 5, the fuel cell system 100 according to the modified example 4 is different from the fuel cell system 100 according to the embodiment of the present invention described above in the following points.

  That is, the fuel cell system 100 according to the modified example 4 includes the first pressure reduction unit 10 on the upstream side of the joining portion R2 in the raw material path 1, and the second pressure reduction unit 11 in the recycling path 7. It differs in that it has.

  Since the first pressure reduction unit 10 has been described in the fuel cell system 100 according to the second modification, the description thereof is omitted here. The second pressure lowering unit 11 decompresses the recycle gas so that the flow rate of the reformed gas flowing through the recycle path 7 becomes a predetermined flow rate. As the 2nd pressure fall part 11, a capillary, an orifice, a check valve, a proportional valve, a governor etc. can be used, for example. Moreover, you may use the 2nd pressure fall part 11 from which a pressure loss characteristic becomes variable.

  Here, the flow rate of the reformed gas that flows through the recycle path 7 is determined by the differential pressure between the branch portion R1 and the junction R2, and the magnitude of the pressure loss that occurs when the reformed gas flows through the recycle path 7. When the pressure loss that occurs in the recycle path 7 is small and the differential pressure between the branch portion R1 and the junction R2 changes, the change in the flow rate of the reformed gas flowing through the recycle path 7 increases. Therefore, even if the above-described differential pressure fluctuates so as to slightly vary, the flow rate of the reformed gas flowing through the recycle path 7 may vary greatly.

  In addition, when the pressure loss generated in the recycle path 7 is small and the differential pressure between the branch portion R1 and the junction R2 becomes excessively large during high-output power generation, the reformed gas flow rate flowing through the recycle path 7 is increased. May be excessive.

  Therefore, in the fuel cell system 100 according to Modification 4 of the embodiment of the present invention, the second pressure reduction unit 11 is provided in the recycle path 7. By providing the second pressure reduction unit 11 in this way, even if the above-described differential pressure fluctuates, it is possible to reduce the influence of the flow rate variation of the reformed gas flowing through the recycle path 7. . As a result, the flow rate of the reformed gas supplied to the hydrodesulfurizer 4 can be stabilized.

  Further, even when the differential pressure between the branch portion R1 and the junction portion R2 is greatly different during high-output power generation, the flow rate of the reformed gas flowing through the recycle path 7 is controlled to be an appropriate flow rate. Can do.

  Therefore, the fuel cell system 100 according to the modified example 4 can easily control the flow rate of the reformed gas flowing through the recycling path in the range of all power generation outputs. In addition, even if the differential pressure between the branch portion R1 and the junction portion R2 fluctuates transiently due to fluctuations in the magnitude of the power generation output, the second pressure drop portion 11 circulates the recycle path 7. It is possible to reduce the influence of fluctuations in the reformed gas flow rate.

  Further, the pressure loss changed by each of the first pressure reduction unit 10 and the second pressure reduction unit 11 may be constant, or at least one of them may be variable.

  For example, when the magnitude of the pressure loss caused by the first pressure drop unit 10 is variable, the flow rate of the raw material flowing through the raw material route 1 is changed, or the pressure of the branch portion R1 is changed, whereby the recycling route is changed. 7, even if the differential pressure between the branch portion R1 and the junction portion R2 changes, it is possible to easily obtain an appropriate differential pressure by adjusting the magnitude of the pressure loss caused by the first pressure drop portion 10. Can do.

  Further, when the second pressure drop unit 11 is variable, there is an upper limit to the pressure loss that can be increased by the pressure loss control unit, and when the range that can be increased is small, or the magnitude of the pressure loss caused by the first pressure drop unit 10 Even when it is not variable, the flow rate of the reformed gas returned to the upstream side of the hydrodesulfurizer 4 via the recycle path 7 can be appropriately controlled.

  Since the reformed gas flowing through the recycle path 7 contains moisture, when the pressure of the reformed gas is reduced by the second pressure reducing unit 11, the moisture may be condensed. For this reason, in particular, in SOFC or the like, it is preferable to provide the second pressure drop unit 11 in a high temperature region inside the hot module so that the reformed gas does not fall below the dew point.

  Furthermore, as shown in FIG. 6, the fuel cell system 100 according to Modification 4 may further include a condensing unit 13 in the recycle path 7. FIG. 6 is a schematic diagram showing an example of the configuration of the fuel cell system 100 according to Modification 4 of the embodiment of the present invention.

  As described above, when the reformed gas flows through the recycle path 7, moisture may condense, which may cause pressure loss fluctuations and water clogging in the recycle path 7. Therefore, by providing the condensing unit 13 in the recycle path 7 and recovering condensed water from the reformed gas, fluctuations in pressure loss and water clogging in the recycle path 7 can be suppressed. Thereby, in the fuel cell system 100 according to the modification 4, the flow rate of the reformed gas flowing through the recycle path 7 can be stabilized. Further, it is possible to prevent moisture from being mixed into the raw material boosting unit 5 and the like to cause the raw material boosting unit 5 to fail.

  In the fuel cell system according to the modified example 4, a heat exchange unit (not shown) is provided in the recycle path 7, and heat is exchanged between the reformed gas and the reformed water or the raw material that are circulated in the heat exchange unit. It is good also as a structure which preheats quality water or a raw material. When configured in this way, the condensing unit 13 is desirably configured to be provided on the downstream side of the heat exchanging unit in the recycling path 7.

  In the configuration of the fuel cell system according to Modification 4 shown in FIG. 6, the condensing unit 13 is disposed downstream of the second pressure reducing unit 11 in the recycling path 7 (the pressure of the reformed gas is reduced by the second pressure reducing unit 11). Is arranged on the side). However, the arrangement of the condenser 13 is not limited to this. For example, the condensing unit 13 may be provided on the upstream side of the second pressure reducing unit 11 (the side where the pressure of the reformed gas is not reduced by the second pressure reducing unit 11).

(Modification 5)
Next, a fifth modification of the embodiment of the present invention will be described with reference to FIG. FIG. 7 is a schematic diagram showing an example of the configuration of the fuel cell system 100 according to Modification 5 of the embodiment of the present invention. As shown in FIG. 7, the fuel cell system 100 according to the modified example 5 differs from the fuel cell system 100 according to the above-described embodiment of the present invention in the following points.

  That is, the fuel cell system 100 according to the modified example 5 further includes a condensed water recovery unit 14 for recovering condensed water obtained by condensing the combustion exhaust gas in the exhaust gas path 8, and this condensed water recovery unit 14 in that the air supply path 9 is connected to the downstream side.

  Thus, the fuel cell system 100 according to the modified example 5 has a configuration in which the air supply path 9 is connected to the downstream side of the condensed water recovery unit 14 in the exhaust gas path 8 so that air is supplied. For this reason, air can be supplied without lowering the dew point of the exhaust gas. In addition, the condensed water recovery unit 14 condenses the exhaust gas and recovers the condensed water while maintaining the dew point of the exhaust gas high, so that the water can be easily recovered from the exhaust gas, and the modification required in the fuel cell system 100 is required. Can provide quality water.

  That is, in the fuel cell system 100 according to the modified example 5, the fuel cell system 100 supplies water from the outside by adopting a configuration in which the water (condensed water) recovered by the condensed water recovery unit 14 is returned to the reformed water path 20. It becomes possible to operate without receiving (water self-sustained operation). Moreover, in order to implement | achieve water self-sustained operation, it is necessary to condense and collect | recover more water | moisture content contained in combustion exhaust gas. Therefore, the condensed water recovery unit 14 is provided in the subsequent stage of various heat exchange units (not shown) in the exhaust gas path 8.

  In the fuel cell system 100 according to the above-described embodiment of the present invention and Modifications 1 to 5, the pressure loss control unit is provided so as to increase the pressure loss in the exhaust gas path 8 in the gas path 21. Met. However, the portion where the pressure loss is increased by the pressure loss control unit is not limited to the exhaust gas path 8, but may be a gas path 21 portion on the downstream side of the branch portion R1.

  Further, as an operation method of the fuel cell system 100, when the temperature of the fuel cell power generation unit 2 is lower than a predetermined value, the flow rate of air supplied to the fuel cell power generation unit 2 is decreased, and conversely, when the temperature is high. Can be configured to cool by increasing the air flow rate. As described above, in the configuration in which the flow rate of the generated air is changed, the magnitude of the pressure loss generated in the gas path 21 (in the exhaust gas path 8) is changed, or the pressure of the branch portion R1 is changed with the change of the pressure loss. Or change. Therefore, the pressure loss control unit may be configured to change the magnitude of the pressure loss generated in the gas path 21 (exhaust gas path 8) according to the flow rate of the generated air supplied to the fuel cell power generation unit 2. . For example, the flow rate of the air supplied to the exhaust gas path 8, the opening / closing of the pressure regulating valve 22, or the valve opening degree may be controlled according to the flow rate of the generated air supplied to the fuel cell power generation unit 2.

  From the above invention, many modifications and other embodiments of the present invention are obvious to one 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.

  The present invention can return part of the reformed gas generated in the reformer 3 through the recycle path 7 to the upstream side of the hydrodesulfurizer 4 by self-pressure even during low load operation. Therefore, a part of the reformed gas generated in the reformer 3 can be widely used in a fuel cell having a configuration in which the reformed gas is returned to the upstream side of the hydrodesulfurizer 4 through the recycle path 7.

DESCRIPTION OF SYMBOLS 1 Raw material path | route 2 Fuel cell electric power generation part 3 Reformer 4 Hydrodesulfurizer 5 Raw material pressurization part 6 Combustion part 7 Recycling path 8 Exhaust gas path 9 Air supply path 10 1st pressure reduction part 11 2nd pressure reduction part 12 Air supply valve DESCRIPTION OF SYMBOLS 13 Condensing part 14 Condensed water collection | recovery part 15 Reformed air valve 16 Reformed air pump 17 Reformed air path 19 Ejector 20 Reformed water path 21 Gas path 22 Pressure control valve 90 Control part 100 Fuel cell system R1 Branch part R2 Merge part

Claims (12)

A fuel cell power generation unit that generates electricity by a power generation reaction using the supplied fuel and air;
A raw material supply section for supplying raw materials;
A hydrodesulfurizer for removing sulfur components contained in the raw material supplied from the raw material supply unit;
A reformer that generates a reformed gas serving as the fuel from the raw material from which sulfur components have been removed by the hydrodesulfurizer;
A gas path which is a path for supplying the reformed gas generated by the reformer to the fuel cell power generation unit and leading the exhaust gas exhausted from the fuel cell power generation unit to the outside;
A recycle path which is a path for branching from the gas path and leading a part of the reformed gas generated in the reformer flowing in the gas path to the upstream side of the hydrodesulfurizer;
And a pressure loss control unit that performs control so as to change a pressure loss generated in a downstream portion of the gas path rather than a branching part where the recycling path branches from the gas path.   2. The fuel cell system according to claim 1, wherein the pressure loss control unit performs control so as to change a pressure loss generated in a portion downstream of the branch portion in the gas path in accordance with a change in pressure in the branch portion.   The fuel cell system according to claim 1 or 2, wherein the raw material supply unit is a raw material pressurization unit that pressurizes the raw material and supplies the raw material to the hydrodesulfurizer.   The recycling path is configured to distribute the reformed gas to the inlet side of the raw material boosting section in the raw material path through which the raw material supplied to the raw material boosting section and sent from the raw material boosting section to the hydrodesulfurizer flows. Item 4. The fuel cell system according to Item 3. In the raw material path through which the raw material supplied to the raw material pressurization unit and sent from the raw material pressurization unit to the hydrodesulfurizer flows, an ejector for sucking the reformed gas is provided on the outlet side of the raw material pressurization unit,
The fuel cell system according to claim 3, wherein the recycling path is connected to the ejector.   In the raw material path, a first pressure is provided on the upstream side of a merging section where the raw material flowing through the raw material path and the reformed gas flowing through the recycling path merge to reduce the pressure at the merging section. The fuel cell system according to claim 4 or 5, comprising a lowering portion. A combustion unit for generating combustion exhaust gas by burning the unused fuel in the fuel cell power generation unit;
The fuel cell according to any one of claims 1 to 6, wherein the pressure loss control unit changes a pressure loss of an exhaust gas path which is a path part through which the combustion exhaust gas generated by the combustion unit flows in the gas path. system. An air supply path for supplying air to the exhaust gas path;
The fuel cell system according to claim 7, wherein the pressure loss control unit controls the pressure loss generated in the exhaust gas path by changing a flow rate of air flowing through the air supply path. A condensate recovery unit that is provided in the exhaust gas path and recovers condensed water obtained by condensing the combustion exhaust gas generated in the combustion unit;
The fuel cell system according to claim 8, wherein the air supply path is connected to a downstream side of the condensed water recovery unit in the exhaust gas path. An adjustment valve for adjusting the magnitude of the pressure loss generated in the downstream portion of the gas path from the branch portion;
The fuel cell system according to claim 7, wherein the pressure loss control unit performs control so as to change the magnitude of the generated pressure loss by opening and closing the adjustment valve.   The fuel cell system according to any one of claims 1 to 10, further comprising a second pressure reduction unit that reduces a pressure of the recycle path in order to adjust a flow rate of the reformed gas flowing through the recycle path.   The fuel cell system according to any one of claims 1 to 11, further comprising a condensing unit that condenses moisture in the reformed gas flowing through the recycling path.

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