JP2014107186A - Solid oxide fuel cell system - Google Patents

Abstract

A solid oxide fuel cell system capable of preventing an excessive temperature rise in a desulfurizer is provided.
[Solution]
The solid oxide fuel cell system includes a solid oxide fuel cell 6 that generates power by a power generation reaction using fuel and air, a combustion unit 23 that burns unused fuel and air, and a raw material. A desulfurizer 3 for removing sulfur components by hydrodesulfurization, an exhaust gas generated by combustion of unused fuel, and an exhaust gas path 20 having the desulfurizer 3 in the path, and a raw material desulfurized by the desulfurizer 3 The reformer 4 for generating reformed gas to be fuel from the fuel, the evaporator 9 for vaporizing the reformed water supplied to the reformer 4, and the heat insulating portion 22 on the inner wall are provided, and at least a solid oxide fuel cell 6, a combustion section 23, a desulfurizer 3, an exhaust gas path 20, a reformer 4, and a casing 7 that accommodates the evaporator 9. The exhaust gas path 20 is disposed in the heat insulating section 22. And the exhaust gas path portion 20a Vessel 9 and are arranged to face through a heat insulating portion 22.
[Selection] Figure 1

Description

  The present invention relates to a solid oxide fuel cell system including a desulfurizer that removes a sulfur component from a raw material gas (raw fuel gas, raw material) containing hydrocarbons.

  In a solid oxide fuel cell system using hydrocarbons as a raw material gas, for example, steam reforming using steam is used to reform the raw material gas. A steam reforming catalyst is used to promote this steam reforming, but the raw material gas contains, for example, a sulfur compound as an odorant, which may deteriorate the steam reforming catalyst. There is. Therefore, in order to prevent the steam reforming catalyst from deteriorating, a desulfurization apparatus (desulfurizer) that reduces sulfur compounds contained in the raw material gas is used.

  As such a desulfurizer, for example, a sulfur compound is reacted with hydrogen on a catalyst (Ni-Mo system, Co-Mo system) to convert it into hydrogen sulfide, and the hydrogen sulfide is taken into zinc oxide and removed. Examples thereof include a hydrodesulfurization apparatus that performs desulfurization by a so-called hydrodesulfurization method.

  The hydrodesulfurization apparatus requires hydrogen when performing desulfurization by the hydrodesulfurization method, but the source gas usually does not contain hydrogen. Therefore, a solid oxide fuel cell system having a configuration for supplying hydrogen to a hydrodesulfurization apparatus has been proposed (for example, Patent Documents 1 and 2).

  More specifically, in Patent Document 1, as shown in FIG. 4, a part of the reformed gas flowing through the reformer 110 is returned to the upstream side of the booster 111 through the recycle gas supply path 113. A solid oxide fuel cell system configured as described above is disclosed. The returned reformed gas is boosted by the booster 111 and supplied to the desulfurizer 102.

  Moreover, in patent document 2, as shown in FIG. 5, the solid oxide fuel cell system which has the structure shown below is proposed. That is, in the solid oxide fuel cell system of Patent Document 2, the water mixed by the mixer 220 and the raw fuel gas after desulfurization are supplied to the evaporator 226. And the structure by which a part of raw fuel gas after desulfurization containing water vapor | steam supplied from the evaporator 226 to the reformer 206 is returned to the fuel gas supply path 216 via the branch return flow path 242 is disclosed. . In addition, a hydrocarbon reforming catalyst is provided in the double pipe 244 of the branch return flow path 242, and thereby the hydrogen-containing gas obtained by reforming the hydrocarbon is returned to the upstream side of the booster 217. be able to. The returned hydrogen-containing gas is boosted by the booster 217 and supplied to the desulfurizer 204.

JP 2011-216308 A Japanese Patent No. 4911927 Japanese Patent No. 2999307

  However, the solid oxide fuel cell systems disclosed in Patent Documents 1 and 2 have a problem that it is not possible to appropriately prevent an excessive temperature rise in the desulfurizer.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a solid oxide fuel cell system capable of preventing an excessive temperature rise in a desulfurizer.

  In order to solve the above-described problems, a solid oxide fuel cell system according to the present invention includes a solid oxide fuel cell that generates power by a power generation reaction using supplied fuel and air, and the solid oxide. A combustion unit that burns unused fuel and air in a fuel cell, a desulfurizer that removes sulfur components contained in the supplied raw material by hydrodesulfurization, and combustion of unused fuel by the combustion unit An exhaust gas path having the desulfurizer in the path, a reformer for generating a reformed gas as the fuel from the raw material from which sulfur components have been removed by the desulfurizer, and the reformer A first evaporator for vaporizing the reforming water to be supplied to the inside, and a heat insulating part is provided on the inner wall, and at least the solid oxide fuel cell, the combustion part, the desulfurizer, the exhaust gas path, Reformer, And a housing portion that houses the first evaporator, wherein the exhaust gas path is disposed in the heat insulating portion, and the exhaust gas path portion in which the desulfurizer is disposed and the first evaporator are It arrange | positions in the position which opposes via a heat insulation part.

  The solid oxide fuel cell system according to the present invention includes a solid oxide fuel cell that generates power by a power generation reaction using supplied fuel and air, and the solid Combustion unit that burns unused fuel and air in an oxide fuel cell, a desulfurizer that removes sulfur components contained in the supplied raw material by hydrodesulfurization, and combustion of unused fuel by the combustion unit An exhaust gas path having the desulfurizer in the path, a reformer for generating a reformed gas as the fuel from the raw material from which sulfur components have been removed by the desulfurizer, and the modified A heater for heating the reforming water supplied to the mass device, an evaporator for vaporizing the reforming water heated by the heater, a heat insulating part is provided on the inner wall, and at least the solid Oxide form A fuel cell, the combustion section, the desulfurizer, the exhaust gas path, the reformer, the heater, and a housing that houses the evaporator, and the exhaust gas path is disposed in the heat insulating section. In addition, the exhaust gas path portion where the desulfurizer is disposed and the heater are disposed at positions facing each other through the heat insulating portion.

  The solid oxide fuel cell system according to the present invention is configured as described above, and has an effect that it is possible to appropriately prevent an excessive temperature rise in the desulfurizer.

It is the schematic diagram which showed an example of the structure of the solid oxide fuel cell system which concerns on embodiment of this invention. It is the schematic diagram which showed an example of the structure of the solid oxide fuel cell system which concerns on embodiment of this invention. It is the schematic diagram which showed an example of the structure of the solid oxide fuel cell system which concerns on the modification of embodiment of this invention. It is a schematic diagram which shows a prior art and showed an example of the structure of the solid oxide fuel cell system. It is a schematic diagram which shows a prior art and showed an example of the structure of the solid oxide fuel cell system.

(Background to obtaining one embodiment of the present invention)
As a result of intensive research on the conventional solid oxide fuel cell system described in “Background Art”, the present inventor has found that, for example, an abnormality occurs in a combustion part and the like, In the oxide fuel cell system, it has been found that there is a possibility that an excessive temperature rise in the desulfurizer cannot be prevented appropriately when the temperature inside the casing becomes higher than necessary. It was. And as a result of repeated investigations on this problem, the present inventor has obtained the following knowledge.

  That is, in the solid oxide fuel cell systems according to Patent Documents 1 and 2, the desulfurizer is disposed outside the inner casing in the heat insulating layer, and the combustion heat of the combustion section in the inner casing is propagated. Thus, the desulfurizer was heated. For this reason, when the temperature in an internal housing | casing becomes higher than desired temperature, the temperature which heats a desulfurizer also becomes proportionally high, and there exists a problem that a desulfurizer will be overheated.

  Based on these findings, the present inventors have found that an excessive temperature rise in the desulfurizer can be appropriately prevented by devising the arrangement of the evaporator, and have reached the present invention. And in this invention, the aspect shown below is provided.

  A solid oxide fuel cell system according to a first aspect of the present invention includes a solid oxide fuel cell that generates electric power by a power generation reaction using supplied fuel and air, and the solid oxide fuel cell. A combustion section that burns unused fuel and air, a desulfurizer that removes sulfur components contained in the supplied raw material by hydrodesulfurization, and an exhaust gas generated by the combustion of unused fuel by the combustion section In addition, an exhaust gas path having the desulfurizer in the path, a reformer that generates a reformed gas as the fuel from a raw material from which sulfur components have been removed by the desulfurizer, and a reformer that supplies the reformer A first evaporator for vaporizing the quality water, a heat insulating part is provided on the inner wall, and at least the solid oxide fuel cell, the combustion part, the desulfurizer, the exhaust gas path, the reformer, And the first evaporation And the exhaust gas path is disposed in the heat insulating part, and the exhaust gas path part in which the desulfurizer is disposed and the first evaporator are opposed to each other through the heat insulating part. It is arranged at the position to do.

  According to the above configuration, since the combustion section and the exhaust gas path are provided, the exhaust gas generated in the combustion section can be circulated in the exhaust gas path. Further, since the desulfurizer is provided in the exhaust gas path, the desulfurizer can be heated by the heat held by the exhaust gas flowing through the exhaust gas path. In particular, since the exhaust gas path is provided in the heat insulating portion, it is possible to reduce the loss of heat retained by the exhaust gas due to heat dissipation.

  Moreover, the exhaust gas path part in which the desulfurizer is arrange | positioned and the 1st evaporator are arrange | positioned in the position which opposes via a heat insulation part. For this reason, it is possible to prevent the first evaporator from transmitting high-temperature radiant heat or the like from the combustion section or the like provided in the casing section from the inside of the casing to the desulfurizer through the heat insulating section.

  In particular, an evaporator is a member that consumes the most heat per unit volume in a solid oxide fuel cell system. For this reason, the propagation of heat to the desulfurizer can be effectively blocked by disposing the first evaporator at a position facing the exhaust gas passage portion where the desulfurizer is disposed via the heat insulating portion. Therefore, the effect that the excessive temperature rise of a desulfurizer can be prevented appropriately is produced.

  Further, in the solid oxide fuel cell system according to the second aspect of the present invention, in the first aspect described above, the reformed water that is provided in the casing and has not been vaporized by the first evaporator. You may be comprised so that the 2nd evaporator for making it vaporize may be further provided.

  The solid oxide fuel cell system according to the third aspect of the present invention is the solid oxide fuel cell system according to the first or second aspect described above, wherein the area where the first evaporator is in contact with the heat insulating portion is disposed by the desulfurizer. The exhaust gas path portion that is provided may be configured to have an area larger than the area in contact with the heat insulating portion.

  According to the configuration described above, the area where the first evaporator is in contact with the heat insulating portion is equal to or larger than the area where the exhaust gas passage portion where the desulfurizer is disposed is in contact with the heat insulating portion. For this reason, it is possible to prevent heat from being propagated to the exhaust gas passage portion where the desulfurizer is disposed by the first evaporator.

  In the solid oxide fuel cell system according to the fourth aspect of the present invention, a solid oxide fuel cell that generates electric power by a power generation reaction using supplied fuel and air, and the solid oxide fuel Combustion section for burning unused fuel and air in the battery, desulfurizer for removing sulfur components contained in the supplied raw material by hydrodesulfurization, and exhaust gas generated by combustion of unused fuel by the combustion section An exhaust gas path having the desulfurizer in the path, a reformer for generating a reformed gas as the fuel from a raw material from which sulfur components have been removed by the desulfurizer, and a supply to the reformer A heater for heating the reformed water to be heated, an evaporator for vaporizing the reformed water heated by the heater, a heat insulating part is provided on the inner wall, and at least the solid oxide fuel Battery, the fuel A housing part that accommodates a part, the desulfurizer, the exhaust gas path, the reformer, the heater, and the evaporator, and the exhaust gas path is disposed in the heat insulating part, and the desulfurizer Is disposed at a position where the exhaust gas passage portion and the heater face each other with the heat insulating portion interposed therebetween.

  According to the above configuration, since the combustion section and the exhaust gas path are provided, the exhaust gas generated in the combustion section can be circulated in the exhaust gas path. Further, since the desulfurizer is provided in the exhaust gas path, the desulfurizer can be heated by the heat held by the exhaust gas flowing through the exhaust gas path. In particular, since the exhaust gas path is provided in the heat insulating portion, it is possible to reduce the loss of heat retained by the exhaust gas due to heat dissipation.

  Further, the exhaust gas passage portion where the desulfurizer is disposed and the heater are disposed at positions facing each other through the heat insulating portion. For this reason, it can prevent with a heater that high temperature radiant heat from the combustion part etc. which were provided in the housing | casing part propagate to a desulfurizer via the heat insulation part from the inside of a housing | casing.

  In addition, the reformed water heated by the heater is vaporized by the evaporator. For this reason, the heat recovered by the heater can also be contributed as the heat for vaporizing the reforming water, and a highly efficient system without heat loss can be realized.

  Further, in the solid oxide fuel cell system according to the fifth aspect of the present invention, in the above-described fourth aspect, the area where the heater is in contact with the heat insulating portion is an exhaust gas path in which the desulfurizer is disposed. You may be comprised so that a part may become more than the area which contact | connects the said heat insulation part.

  According to the configuration described above, the area where the heater is in contact with the heat insulating portion is equal to or larger than the area where the exhaust gas passage portion where the desulfurizer is disposed is in contact with the heat insulating portion. For this reason, this heater can prevent heat from propagating to the exhaust gas passage portion where the desulfurizer is disposed.

  The solid oxide fuel cell system according to the sixth aspect of the present invention is the reformed material reformed by the reformer in any one of the first to fifth aspects. A recycle path for returning a part of the gas to the raw material supply path may be further provided.

  According to the configuration described above, since the recycling path is further provided, it is possible to return part of the reformed gas to the raw material supply path and add hydrogen to the raw material gas supplied to the desulfurizer. For this reason, the desulfurizer can perform hydrodesulfurization using this hydrogen.

  In the solid oxide fuel cell system according to the seventh aspect of the present invention, in the sixth aspect described above, the solid oxide fuel cell system further includes a condenser for condensing the moisture of the reformed gas flowing through the recycling path. May be.

  According to the above configuration, since the condenser is provided, when the reformed gas flowing through the recycling path is cooled, moisture can be recovered by the condenser. For this reason, problems such as water clogging in the path due to condensed water can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following, the same or corresponding components are denoted by the same reference numerals throughout all the drawings, and the description thereof is omitted.

  A solid oxide fuel cell system according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. 1 and 2 are schematic views showing an example of a configuration of a solid oxide fuel cell system according to an embodiment of the present invention. In FIG. 1, the structure when the solid oxide fuel cell system which concerns on embodiment is seen from the side part is shown typically. In FIG. 2, the structure when the inside of the housing | casing 7 of the solid oxide fuel cell system which concerns on embodiment is seen from the top is shown typically.

  As shown in FIGS. 1 and 2, the solid oxide fuel cell system includes a raw material gas path 1, a desulfurizer 3, a reformer 4, an air heat exchanger 5, a solid oxide fuel cell 6, an evaporator ( (First evaporator) 9, air path 10, reformed water path 11, reformed air path 12, post-desulfurization source gas path 14, fuel gas supply path 16, air supply path 17, decompression unit 18, recycle path 19, exhaust gas The path 20 and the heat insulating part (heat insulating member) 22 are arranged inside the housing (housing part) 7. In addition, a combustion unit 23 is provided on the solid oxide fuel cell 6 so as to face the reformer 4. In addition, in FIG. 1, in order to show the state in which the desulfurizer 3 is disposed in the exhaust gas path 20, the width of the path is expressed only in the portion of the exhaust gas path 20 in which the desulfurizer 3 is disposed.

  In the solid oxide fuel cell system, the raw material gas (raw fuel gas) supplied from the outside of the casing 7 is reformed by the reformer 4, and the reformed reformed gas and the air supplied from the outside The solid oxide fuel cell 6 is configured to generate power by a power generation reaction using the above.

  In this specification, the gas supplied from the outside through the raw material gas path 1 is referred to as a raw material gas (raw material), the sulfur component is removed from the raw material gas, and the reformer reformed by the reforming reaction in the reformer 4. The quality gas is referred to as fuel gas (fuel).

  In the solid oxide fuel cell system, during operation of the solid oxide fuel cell 6 (during power generation), the combustion unit 23 burns the reformed gas and air that have not been used for the power generation reaction, thereby increasing the temperature. The exhaust gas is generated and the thermal energy is used effectively to realize highly efficient operation. Further, in the solid oxide fuel cell system, a heat insulating portion (heat insulating member) 22 made of a heat insulating material is provided inside the housing 7 to block heat radiation from the inside of the housing 7 to the outside as much as possible. It is configured as follows.

  In the solid oxide fuel cell system, the booster 2 is arranged outside the housing 7. The pressurizing unit 2 is configured to pressurize the source gas supplied through the source gas path 1 and introduce it into the desulfurizer 3 disposed in the casing 7. In addition, as the source gas supplied through the source gas path 1, city gas or gas mainly composed of hydrocarbons such as propane gas can be used.

  The desulfurizer 3 is for removing sulfur components contained in the raw material gas by the hydrodesulfurization method, and is provided in the exhaust gas path 20. In the first embodiment, as shown in FIG. 1, the exhaust gas path 20 communicates with the inside of the housing 7 in the vicinity of the approximate center on the upper surface side of the housing 7, and the housing on the upper side (the right side in FIG. 1). It arrange | positions in the heat insulation part 22 so that it may communicate with the exterior of the body 7. FIG.

  More specifically, the desulfurizer 3 is disposed in the heat insulating portion 22 that is located above and opposite to the combustion portion 23 (that is, the upper surface side of the housing 7). Then, the desulfurizer 3 provided in the exhaust gas path 20 is heated by the high-temperature exhaust gas flowing through the exhaust gas path 20. A detailed description of the flow of the exhaust gas for heating the desulfurizer 3 and the temperature adjustment of the exhaust gas will be described later.

Examples of the desulfurizing agent filled in the desulfurizer 3 include a desulfurizing agent containing copper and zinc (for example, Patent Document 3). The desulfurizing agent is not limited to this desulfurizing agent as long as it can perform hydrodesulfurization, and may be a combination of a Ni—Mo based or Co—Mo based catalyst and zinc oxide. In the case of a desulfurization agent in which a Ni—Mo or Co—Mo catalyst and zinc oxide are combined, the desulfurizer 3 hydrocrackes organic sulfur in the raw material gas in a temperature range of 350 to 400 ° C. Then, the desulfurizer 3 removes the generated H ₂ S by adsorbing it to ZnO in a temperature range of 350 to 400 ° C.

For example, when the source gas 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 desulfurizer 3 in the desulfurizer 3 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 desulfurizing agent to be filled contains copper and zinc, the desulfurizer 3 performs desulfurization in a temperature range of about 10 to 400 ° C, preferably about 150 to 300 ° C. This copper zinc-based desulfurization agent 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 raw material gas after desulfurization is 1 vol ppb (parts per billion) or less, usually 0.1 vol ppb or less.

  Thus, when the desulfurizer 3 is filled with a Ni-Mo-based or Co-Mo-based catalyst, or a desulfurizing agent containing either copper and zinc, the sulfur component removal amount per unit volume is increased. Therefore, when the above-described desulfurizing agent is used, the amount of the desulfurizing agent necessary for removing sulfur to a desired sulfur concentration can be reduced.

  The raw material gas desulfurized by the desulfurizer 3 as described above is supplied to the reformer 4 after desulfurization.

  Next, the reformer 4 will be described. The reformer 4 may be used for partial oxidation reforming. However, in order to realize more efficient operation, the reformer 4 is designed to perform not only partial oxidation reforming reaction but also steam reforming reaction. It is advantageous to keep it. As shown in FIG. 1, in the present embodiment, an evaporator 9 is disposed upstream of the reformer 4 (on the side where the post-desulfurization source gas path 14 is disposed), and the reformed water path is routed to the desulfurized source gas. The water (reformed water) supplied through 11 can be mixed and supplied to the reformer 4.

As the reforming catalyst filled in the reformer 4, 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, at the time of starting the solid oxide fuel cell system, heat energy is insufficient to perform the steam reforming reaction which is an endothermic reaction in the reformer 4. Therefore, at the time of starting the solid oxide fuel cell system, the air introduced into the reformer 4 through the reformed air path 12 is used without supplying water from the reformed water path 11 to the evaporator 9. The reformer 4 performs a partial oxidation reforming reaction represented by the following formula (3) to generate hydrogen gas and carbon monoxide.
_{C n H m + (n /} 2) O 2 → n · CO + (m / 2) H 2 (n, m is an arbitrary natural number) (3)
Then, these hydrogen gas and carbon monoxide are supplied to the solid oxide fuel cell 6 through the fuel gas supply path 16 and are combined with the air supplied through the air supply path 17 to perform a power generation reaction.

As the solid oxide fuel cell system starts up and power generation proceeds, the temperature of the reformer 4 rises. That is, the partial oxidation reforming reaction represented by the above formula (3) is an exothermic reaction, and the temperature of the reformer 4 is raised by the exhaust gas and the radiant heat from the combustion unit 23. And if the temperature of the reformer 4 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.
_{C n H m + 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 has a larger amount of hydrogen that can be generated from the same amount of hydrocarbon (C _n H _m ). As a result, the amount of reformed gas that can be used for the power generation reaction in the solid oxide fuel cell 6 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), the heat held in the exhaust gas discharged from the combustion unit 23, and the combustion unit 23 The steam reforming reaction is allowed to proceed while supplementing the necessary amount of heat using the radiant heat from. And, if the temperature of the reformer 4 becomes 600 ° C. or more, for example, the amount of heat necessary for the steam reforming reaction of the formula (4) can be supplemented only by the heat of the exhaust gas and the radiant heat from the combustion section 23 Therefore, it is possible to switch to the operation of only the steam reforming reaction.

  The evaporator 9 is installed to perform a steam reforming reaction in the reformer 4. In the evaporator 9, the water (reformed water) supplied from the reforming water path 11 is vaporized using the heat of the exhaust gas discharged from the combustion unit 23 and the radiant heat from the combustion unit 23. Mix with the supplied raw material gas after desulfurization. Then, the evaporator 9 introduces the mixed raw material gas into the reformer 4. Note that the solid oxide fuel cell system according to the embodiment is characterized in the position where the evaporator 9 is disposed. Details of the arrangement of the evaporator 9 will be described later.

  The air heat exchanger 5 is for heating air (power generation air) used for a power generation reaction in the solid oxide fuel cell 6 and is provided at a position facing the combustion unit 23. The air heat exchanger 5 heats air (power generation air) supplied from the outside through the air path 10 by heat exchange between exhaust gas generated by combustion in the combustion unit 23 and radiant heat of the combustion unit 23. For example, the air after flowing through the air heat exchanger 5 is heated to 400 to 800 ° C. The heated air is supplied to the solid oxide fuel cell 6. Although details will be described later, the exhaust gas from which part of the heat held by the heat exchange with the air is removed by the air heat exchanger 5 is guided to the desulfurizer 3 through the exhaust gas path 20. Yes.

  As described above, the solid oxide fuel cell 6 generates power by a power generation reaction using the reformed gas supplied through the fuel gas supply path 16 and the air (power generation air) supplied through the air supply path 17. Is to do. That is, the solid oxide fuel cell 6 has a fuel electrode to which the reformed gas is supplied and an air electrode to which power generation air is supplied, and performs a power generation reaction between the fuel electrode and the air electrode to generate power. A plurality of fuel cell single cells to be connected are connected in series to form a cell stack. Note that the solid oxide fuel cell 6 may further have a configuration in which cell stacks connected in series are connected in parallel.

  As the single unit cell constituting the solid oxide fuel cell 6, for example, a single unit cell made of zirconia doped with yttria (YSZ), zirconia doped with yttrium or scandium, or a lanthanum gallate solid electrolyte is used. be able to. For example, when the single fuel cell is YSZ, the power generation reaction is performed in a temperature range of about 600 to 900 ° C., depending on the thickness.

  Further, in the solid oxide fuel cell system according to the first embodiment, a part of the reformed gas supplied from the reformer 4 by branching the fuel gas supply path 16 toward the solid oxide fuel cell 6 in the middle. A recycling path 19 for returning the gas to the source gas path 1 is provided. For this reason, it becomes possible to add hydrogen to the raw material gas which distribute | circulates the raw material gas path | route 1 and is supplied to the desulfurizer 3, and the desulfurizer 3 performs the above-mentioned hydrodesulfurization using this hydrogen. It is configured to be able to.

  A decompression unit 18 is provided in the vicinity of the branch point between the fuel gas supply path 16 and the recycle path 19 and in the recycle path 19. The decompression unit 18 adjusts the flow rate of the reformed gas flowing through the recycle path 19 and can be realized by, for example, a capillary tube. That is, the decompression unit 18 is configured so 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 the like and increasing the pressure loss.

(Evaporator arrangement)
Next, the arrangement of the evaporator 9 which is a characteristic configuration of the solid oxide fuel cell system according to the embodiment will be described. As described above, the solid oxide fuel cell system according to the embodiment can be heated to a temperature suitable for hydrodesulfurization with high-temperature exhaust gas by installing the desulfurizer 3 in the exhaust gas path 20. It is. Therefore, before explaining the arrangement of the evaporator 9 in detail, the flow of the exhaust gas generated in the combustion unit 23 will be explained. Specifically, the desulfurizer 3 is heated by circulating the exhaust gas as follows.

  Regarding the flow rate and temperature of the exhaust gas generated in the combustion unit 23, the fuel utilization rate of reformed gas and air (power generation air) in the solid oxide fuel cell 6 (the solid oxide fuel cell 6 as fuel by the power generation reaction) It is possible to control by adjusting the ratio of consumption at (1). In the embodiment, for example, the fuel utilization rate of the reformed gas and air in the solid oxide fuel cell 6 is set so that the temperature range of the combustion unit 23 is approximately 600 to 900 ° C.

  In the combustion section 23 in which the temperature range is set in this way, the exhaust gas generated by burning unused reformed gas and air heats the reformer 4 and the evaporator 9. Thereby, a part of the heat of the exhaust gas is consumed. Further, the air heat exchanger 5 is heated by the exhaust gas in which a part of the heat is consumed. Due to the heat exchange between the air and the exhaust gas by the air heat exchanger 5, the heat of the exhaust gas is further removed, and the temperature is lowered to an appropriate temperature for heating the desulfurizer 3. The exhaust gas whose temperature has been further lowered in this way flows through the exhaust gas passage 20 and is supplied to the desulfurizer 3.

  That is, the temperature of the exhaust gas generated in the combustion unit 23 is as high as about 600 ° C. to 900 ° C., for example. However, if the reformer 4 and the evaporator 9 are heated by the exhaust gas, and further, heat is exchanged with the air by the air heat exchanger 5 and the air is heated, the temperature of the exhaust gas is reached before reaching the exhaust gas path 20. Will decline.

  In particular, when generating power of 1 kW using the solid oxide fuel cell 6, for example, it is necessary to heat air of 50 L / min or more from the outside temperature to about 400 to 800 ° C. 5 requires a large amount of heat. Therefore, this necessary amount of heat is covered by the amount of heat of the exhaust gas.

  As described above, the temperature of the exhaust gas flowing through the exhaust gas path 20 is determined based on the flow rate and temperature of the exhaust gas generated in the combustion unit 23, the amount of heat absorbed by the reformer 4 and the evaporator 9, and the heat absorbed by the air heat exchanger 5. It is controlled so as to have a desired value in consideration of the amount of heat generated. Then, the exhaust gas that has reached the exhaust gas path 20 circulates in the path and flows to the desulfurizer 3.

  Next, the exhaust gas temperature desired when reaching the desulfurizer 3 will be described. When the desulfurizer 3 is filled with a desulfurizing agent containing copper and zinc, the flow rate and temperature of the exhaust gas generated in the combustion unit 23 so that the exhaust gas temperature when reaching the desulfurizer 3 is about 150 to 350 ° C. The amount of heat absorbed by the reformer 4 and the amount of heat absorbed by the air heat exchanger 5 are adjusted.

  On the other hand, when the desulfurizer 3 is filled with a desulfurization agent that is a combination of a Ni—Mo or Co—Mo catalyst and zinc oxide, the exhaust gas temperature when reaching the desulfurizer 3 is about 350 to 450 ° C. As described above, the flow rate and temperature of the exhaust gas generated in the combustion unit 23, the amount of heat absorbed by the reformer 4, and the amount of heat absorbed by the air heat exchanger 5 are adjusted.

  Thus, by installing the desulfurizer 3 in the exhaust gas path 20, the desulfurizer 3 can be set to a desired temperature suitable for hydrodesulfurization. Further, the desulfurizer 3 is installed so that at least a part of the exhaust gas path 20 provided in the path is covered with the heat insulating portion 22. If it does in this way, while releasing heat from desulfurizer 3, it can prevent that desulfurizer 3 is directly exposed to the heat of 500-600 ° C in case 7.

  However, even when the exhaust gas path 20 is provided in the heat insulating portion 22 as described above, for example, high-temperature radiant heat is transmitted from the combustion portion 23 through the heat insulating portion 22 to heat the desulfurizer 3. End up. For this reason, the desulfurizer 3 may be overheated.

  Therefore, in the solid oxide fuel cell system according to the embodiment, as shown in FIGS. 1 and 2, the exhaust gas passage portion 20 a provided with the desulfurizer 3 and the evaporator 9 form the heat insulating portion (heat insulating member) 22. It arrange | positions in the position which opposes via.

  That is, the evaporator 9 is a member that consumes the most heat per unit volume in the solid oxide fuel cell system. For this reason, by disposing the evaporator 9 at a position facing the exhaust gas path portion 20a where the desulfurizer 3 is disposed via the heat insulating portion 22, the propagation of heat to the desulfurizer 3 can be effectively blocked. Can do. Thereby, the excessive temperature rise of the desulfurizer 3 can be prevented appropriately. Furthermore, since heat can be prevented from propagating from the inside of the housing 7 to the desulfurizer 3 via the heat insulating portion 22, the desulfurizer 3 is heated only by the heat that the exhaust gas holds.

  For this reason, the temperature at which the desulfurizer 3 is heated needs to consider only the temperature of the exhaust gas, and management of the temperature at which the desulfurizer 3 is heated becomes easy.

  In addition, it is advantageous that the area of the evaporator 9 in contact with the heat insulating portion 22 is equal to or larger than the area in which the exhaust gas passage portion 20 a where the desulfurizer 3 is disposed contacts the heat insulating portion 22. The larger the area in contact with the heat insulating part 22 of the evaporator 9, the more the influence of radiant heat from the combustion part 23 can be prevented in a wider range. Or the arrangement of other members may be hindered. Therefore, the evaporator 9 is set to an appropriate size in consideration of the size of the casing 7, the size of the desulfurizer 3, and the like.

(Modification)
Next, a modification of the solid oxide fuel cell system according to the embodiment will be described with reference to FIG. FIG. 3 is a schematic diagram showing an example of the configuration of a solid oxide fuel cell system according to a modification of the embodiment. FIG. 3 schematically shows a configuration when the solid oxide fuel cell system according to the modification of the embodiment is viewed from the side.

  The solid oxide fuel cell system according to the modification of the embodiment has a configuration further including an auxiliary evaporator (second evaporator) 21 in the configuration of the solid oxide fuel cell system described above.

  The auxiliary evaporator 21 is provided auxiliary to vaporize the reformed water that has not been vaporized in the evaporator 9. That is, since the evaporator 9 is disposed so as to be in contact with the heat insulating portion 22, the evaporator 9 is disposed at a position farther from the combustion portion 23 than the reformer 4 and the air heat exchanger 5. For this reason, the amount of heat obtained from exhaust gas or the like during normal operation may not be enough to sufficiently vaporize the reforming water. In such a case, the reformed water that has not been vaporized is vaporized by the auxiliary evaporator 21.

  As shown in FIG. 3, the auxiliary evaporator 21 is located upstream of the reformer 4 (on the side where the desulfurized raw material gas flow path 14 is disposed) and between the reformer 4 and the evaporator 9. Arranged between. In the example of FIG. 3, the auxiliary evaporator 21 is disposed adjacent to the upstream side of the reformer 4.

  As described above, in the solid oxide fuel cell system according to the modified example, even if the reforming water cannot be sufficiently vaporized by the evaporator 9, the auxiliary evaporator 21 can reliably reform. Water can be vaporized.

  Note that, in the solid oxide fuel cell system according to the above-described modified example, the reforming water is not vaporized instead of the evaporator 9, for example, provided with a heater that is heated to about 60 ° C., and is heated by the heater. The reformed water may be vaporized by the auxiliary evaporator (evaporator) 21. When configured in this way, it is assumed that high-temperature radiant heat from the combustion section 23 and the like provided in the casing 7 propagates from the casing 7 to the desulfurizer 3 through the heat insulating section 22. Can be prevented.

  Further, since the reformed water heated by the heater can be vaporized by the auxiliary evaporator (evaporator) 21, the heat recovered by the heater also contributes as heat for vaporizing the reformed water. And an efficient system without heat loss can be realized.

  Further, in the solid oxide fuel cell system according to the above-described embodiment, the desulfurizer 3 is disposed in the heat insulating portion 22 that is located above the combustion portion 23 and that is opposed (that is, on the upper surface side of the housing 7). Was configured. However, the position at which the desulfurizer 3 is disposed is not limited to this position, and may be disposed in the heat insulating portion 22 below the side surface of the housing 7, for example. In addition, when the desulfurizer 3 is arrange | positioned in the heat insulation part 22 below the side surface of the housing | casing 7, arrangement | positioning of the evaporator 9 is also changed according to this position.

  Further, when the reforming catalyst of the desulfurizing agent charged in the desulfurizer 3 deteriorates after a long operation, there is a concern that the performance of the entire solid oxide fuel cell system is remarkably lowered. Therefore, the desulfurizer 3 is detachable from the housing 7. For this reason, it is possible to operate for a longer time simply by replacing the desulfurizer 3 with the deteriorated reforming catalyst with a new desulfurizer 3.

  In the solid oxide fuel cell system, the fuel gas supply path 16 toward the solid oxide fuel cell 6 is branched in the middle, and a part of the reformed gas supplied from the reformer 4 is supplied to the raw material gas path 1. In order to return to the above, a recycling path 19 is provided. 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 the configuration including the condenser as described above, when the reformed gas flowing through the recycle path 19 is lowered in temperature, moisture can be recovered by the condenser. For this reason, the malfunction of the water in the path | route by condensed water, or the corrosion or damage of the pressure | voltage rise part 2 can be suppressed.

From the above description, 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.

  In the solid oxide fuel cell system of the present invention, the desulfurizer that performs hydrodesulfurization can be heated by exhaust gas that has been lowered to an appropriate temperature. Therefore, it can be widely applied to fuel cell systems that remove sulfur components from raw material gas by hydrodesulfurization.

DESCRIPTION OF SYMBOLS 1 Raw material gas path 2 Booster part 3 Desulfurizer 4 Reformer 5 Air heat exchanger 6 Solid oxide fuel cell 7 Case 9 Evaporator 10 Air path 11 Reformed water path 12 Reformed air path 14 Desulfurized raw material gas Path 16 Fuel gas supply path 17 Air supply path 18 Decompression section 19 Recycling path 20 Exhaust gas path 21 Auxiliary evaporator 22 Heat insulation section 23 Combustion section

Claims (7)

A solid oxide fuel cell that generates electricity by a power generation reaction using the supplied fuel and air; and
A combustion section for burning unused fuel and air in the solid oxide fuel cell;
A desulfurizer for removing sulfur components contained in the supplied raw material by hydrodesulfurization;
An exhaust gas path having the desulfurizer in the path, while circulating the exhaust gas generated by the combustion of unused fuel by the combustion section,
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 desulfurizer;
A first evaporator for vaporizing the reforming water supplied to the reformer;
A heat insulating portion is provided on the inner wall, and a housing portion that houses at least the solid oxide fuel cell, the combustion portion, the desulfurizer, the exhaust gas path, the reformer, and the first evaporator; With
The exhaust gas path is disposed in the heat insulating portion;
A solid oxide fuel cell system in which an exhaust gas path portion in which the desulfurizer is disposed and the first evaporator are disposed at positions facing each other through the heat insulating portion.   2. The solid oxide fuel cell system according to claim 1, further comprising a second evaporator that is provided in the housing portion and vaporizes the reformed water that has not been vaporized by the first evaporator.   3. The solid oxide fuel cell system according to claim 1, wherein an area in which the first evaporator is in contact with the heat insulating portion is equal to or larger than an area in which an exhaust gas passage portion in which the desulfurizer is disposed is in contact with the heat insulating portion. . A solid oxide fuel cell that generates electricity by a power generation reaction using the supplied fuel and air; and
A combustion section for burning unused fuel and air in the solid oxide fuel cell;
A desulfurizer for removing sulfur components contained in the supplied raw material by hydrodesulfurization;
An exhaust gas path having the desulfurizer in the path, while circulating the exhaust gas generated by the combustion of unused fuel by the combustion section,
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 desulfurizer;
A heater for heating the reforming water supplied to the reformer;
An evaporator for vaporizing the reformed water heated by the heater;
A housing having an inner wall provided with a heat insulating portion and containing at least the solid oxide fuel cell, the combustion portion, the desulfurizer, the exhaust gas path, the reformer, the heater, and the evaporator And comprising
The exhaust gas path is disposed in the heat insulating portion;
A solid oxide fuel cell system in which an exhaust gas path portion in which the desulfurizer is disposed and the heater are disposed at positions facing each other via the heat insulating portion.   5. The solid oxide fuel cell system according to claim 4, wherein an area in which the heater is in contact with the heat insulating portion is equal to or larger than an area in which an exhaust gas passage portion where the desulfurizer is disposed is in contact with the heat insulating portion.   6. The solid oxide fuel cell system according to claim 1, further comprising a recycle path for returning a part of the reformed gas reformed by the reformer to a raw material supply path. The solid oxide fuel cell system according to claim 6, further comprising a condenser for condensing moisture of the reformed gas flowing through the recycling path.