JP2015133201A - fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of controlling entire desulfurization catalyst to an appropriate temperature with a simple constitution at a low cost.SOLUTION: A fuel cell system 100 includes: a desulfurizer 2 that removes sulfur compounds from raw materials; a fuel cell 1 that generates electric power by means of electrochemical reaction using a fuel which is obtained by modifying the raw materials from which the sulfur compounds are removed by the desulfurizer 2 and an air supplied for generating electric power; a desulfurizer heating section 3 that heats up the desulfurizer 2 by utilizing heat carried by an exhaust gas flowing through the fuel cell system; an exhaust gas guide path 6 for guiding the exhaust gas to the desulfurizer heating section 3; and a preheating section 4 that preheats the raw material which is supplied to the desulfurizer 2 by utilizing the heat of the exhaust gas flowing through the exhaust gas guide path 6.

Description

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

  In a solid oxide fuel cell system using a raw material containing a hydrocarbon such as city gas or propane gas, for example, steam reforming using steam is used to reform the raw material. A steam reforming catalyst is used to promote the steam reforming, but the raw material contains an odorant or a sulfur compound, which may cause the steam reforming catalyst to deteriorate. . Therefore, in order to prevent deterioration of the steam reforming catalyst, a desulfurizer that reduces the odorant or sulfur compound contained in the raw material is used.

  As such a desulfurizer, for example, a sulfur compound is reacted with hydrogen on a desulfurization catalyst to be converted into hydrogen sulfide, and this hydrogen sulfide is taken into zinc oxide and removed to remove water by so-called hydrodesulfurization. Examples thereof include an addition desulfurization apparatus.

  The hydrodesulfurization apparatus requires hydrogen when desulfurization is performed by the hydrodesulfurization method, but the raw material 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).

  By the way, since the performance of the desulfurization catalyst enclosed in the desulfurizer varies depending on the ambient temperature, it is necessary to heat the desulfurizer when using a desulfurization catalyst that has a higher sulfur component removal performance at a temperature higher than normal temperature. . Therefore, in order to control the catalyst of the desulfurizer to have an appropriate temperature, a fuel cell system that heats the raw material (raw fuel) supplied to the desulfurizer has been proposed (for example, Patent Document 3).

  The fuel cell system according to Patent Document 3 has the configuration shown in FIG. 7 and performs temperature control of the raw material. FIG. 7 shows the prior art and is a system diagram around the desulfurizer 238 and the fuel reformer 237.

  That is, in the fuel cell system according to Patent Document 3, the raw fuel preheater 234 that preheats the raw material by heat exchange with the reformed gas, and the desulfurized raw material desulfurized by the desulfurizer 238 is preheated by heat exchange with the reformed gas. The desulfurized raw fuel preheater 239 is integrally formed. The reformed gas is sent from the reforming pipe 236 of the fuel reformer 237 to the raw fuel preheater 234 and the desulfurized raw fuel preheater 239.

  In such a configuration, in the fuel cell system according to Patent Document 3, a path (raw fuel supply system 230) in which a raw material containing a sulfur component is sent to the raw fuel preheater 234 together with hydrogen and flows into the desulfurizer 238 after preheating. In addition, a path (bypass raw fuel supply system 231) that bypasses the raw fuel preheater 234 and mixes with the preheated raw material and flows into the desulfurizer 238 is provided. And according to the detection result of the temperature of the desulfurization catalyst by the temperature detector 235, the control means 233 controls the flow rate adjusting valve 232 to control the flow rate of the raw material circulated by the bypass raw fuel supply system 231. .

  With such a configuration, the fuel cell system according to Patent Document 3 can be controlled to have a predetermined temperature suitable for the desulfurization reaction in the desulfurization catalyst of the desulfurizer 238.

JP 2011-216308 A JP 2006-54171 A Japanese Patent Laid-Open No. 9-7617

  However, the conventional fuel cell system described in Patent Document 3 has a problem that the entire desulfurization catalyst cannot be brought to an appropriate temperature with an inexpensive and simple configuration. That is, in this prior art fuel cell system, it is necessary to provide a temperature detector, a flow rate adjusting valve, and the like in order to preheat the raw material to an appropriate temperature, which makes the structure complicated and requires manufacturing costs.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell system that can bring the entire desulfurization catalyst to an appropriate temperature with an inexpensive and simple configuration.

  In order to solve the above-described problems, a solid oxide fuel cell system according to the present invention includes a desulfurizer that removes sulfur compounds in a raw material and a raw material from which sulfur compounds are removed by the desulfurizer. A fuel cell that generates electricity by an electrochemical reaction using the obtained fuel and supplied power generation air, and a desulfurizer that heats the desulfurizer using heat of exhaust gas flowing in the fuel cell system Preheating for preheating the raw material supplied to the desulfurizer using the heating unit, the exhaust gas introduction path for guiding the exhaust gas to the desulfurizer heating unit, and the heat of the exhaust gas flowing through the exhaust gas introduction path A section.

  The fuel cell system according to the present invention is configured as described above, and has an effect that the temperature of the desulfurization catalyst and the raw fuel gas can be controlled with a simple and inexpensive structure.

It is the block diagram which showed an example of the structure of the fuel cell system which concerns on embodiment. It is the schematic diagram which showed an example of the structure of the fuel cell system which concerns on embodiment. It is the schematic diagram which showed an example of the structure of the fuel cell system which concerns on embodiment. It is a figure which shows typically the structural example of the fuel cell system which concerns on an Example. It is the end elevation which looked at the desulfurizer heating part of the fuel cell system concerning an example from the top side of the case. It is a table | surface which shows the experimental result of the preheating effect in the desulfurizer of the fuel cell system which concerns on an Example. It is a system diagram showing the prior art and around the desulfurizer and the fuel reformer.

  The present invention provides the following aspects.

  A fuel cell system according to a first aspect of the present invention is supplied with a desulfurizer that removes sulfur compounds in a raw material, and a fuel obtained by reforming a raw material from which sulfur compounds have been removed by the desulfurizer. A fuel cell that generates electricity by an electrochemical reaction using the generated air, a desulfurizer heating unit that heats the desulfurizer using the heat of the exhaust gas circulating in the fuel cell system, and the exhaust gas An exhaust gas introduction path for leading to the desulfurizer heating section, and a preheating section for preheating the raw material to be supplied to the desulfurizer using heat of the exhaust gas flowing through the exhaust gas introduction path.

  According to the above configuration, the desulfurizer can be heated to a desired temperature by the desulfurizer heating section using the heat of the exhaust gas flowing through the exhaust gas introduction path. For this reason, when the optimal reaction temperature of the desulfurization catalyst of a desulfurizer becomes higher than normal temperature, a desulfurization catalyst can be heated so that it may become this optimal reaction temperature. Moreover, since a preheating part is provided, it can prevent that a raw material flows into a desulfurizer with normal temperature. Therefore, in the desulfurizer, the temperature of the desulfurization catalyst in the vicinity of the raw material inlet can be prevented from becoming low, and the entire desulfurization catalyst can be heated to an appropriate temperature without temperature unevenness.

  In addition, the preheating unit is configured to preheat the raw material using exhaust gas that is a heat source for heating the desulfurizer by the desulfurizer heating unit. For this reason, the raw material heated to the temperature substantially the same as the temperature at which a desulfurizer is heated can be guide | induced to this desulfurizer. Therefore, when the raw material is preheated to an appropriate temperature, it is not necessary to provide a temperature detector, a flow rate adjusting valve, or the like as in the prior art, and an inexpensive and simple configuration can be achieved.

  Therefore, the fuel cell system according to the first aspect of the present invention has an effect that the entire desulfurization catalyst can be brought to an appropriate temperature with an inexpensive and simple configuration.

  The fuel cell system according to a second aspect of the present invention is the fuel cell system according to the first aspect, further comprising a raw material supply path for supplying the raw material to the desulfurizer, and the preheating. The part may be formed by inserting a part of the raw material supply path into the exhaust gas introduction path.

  According to the above configuration, the preheating portion can be formed with a simple configuration in which a part of the raw material supply path is inserted into the exhaust gas introduction path.

  The fuel cell system according to a third aspect of the present invention is the fuel cell system according to the second aspect described above, wherein the power generation air is provided in the middle of the exhaust gas introduction path and supplied to the fuel cell. An air heat exchanger that heats the exhaust gas using the heat of the exhaust gas, and the preheating unit is disposed in the exhaust gas introduction path that is downstream of the air heat exchanger in the flow direction of the exhaust gas. The inserted raw material supply path portion may be used.

  According to the above configuration, since the preheating unit is provided on the downstream side of the air heat exchanger, heat is taken away by the air heat exchanger, and the raw material can be heated using the temperature-adjusted exhaust gas. . For this reason, a raw material can be heated with the exhaust gas adjusted to appropriate temperature.

  The fuel cell system according to a fourth aspect of the present invention is the fuel cell system according to the first aspect described above, wherein the preheating part is the raw material supply path part inserted into the desulfurizer heating part. Also good.

  According to the above configuration, since the preheating part is a raw material supply path portion inserted into the desulfurizer heating part, the raw material can also be heated by the exhaust gas serving as a heat source of the desulfurizer heating part. That is, the raw material can be heated at the same temperature as the temperature at which the desulfurizer is heated. Furthermore, since the preheating unit is configured to insert the raw material supply path portion into the desulfurizer heating unit, it is not necessary to prepare a space for forming the preheating unit, and the configuration of the fuel cell system is prevented from becoming large. Can do.

  The fuel cell system according to a fifth aspect of the present invention is the fuel cell system according to the fourth aspect described above, wherein the raw material supply path serves as the preheating part, and is horizontal in the desulfurizer heating part. You may have the pipe-shaped part bent in the direction.

  According to the above configuration, the preheating portion can be formed as a portion where a part of the raw material supply path is bent, and thus can be easily formed without requiring particularly complicated processing. In addition, since the raw material supply path that functions as the preheating section has a bent pipe shape, it is possible to provide a pipe length that allows the raw material flowing through the raw material supply path to be sufficiently preheated in the desulfurization section heating section.

(Embodiment)
A fuel cell system 100 according to an embodiment will be described with reference to FIG. In the present embodiment, a fuel cell system including a solid oxide fuel cell as the fuel cell 1 will be described as an example. However, the fuel cell 1 is not limited to a solid oxide fuel cell. FIG. 1 is a block diagram showing an example of the configuration of a fuel cell system 100 according to an embodiment.

  As shown in FIG. 1, the fuel cell system 100 includes a fuel cell 1 (solid oxide fuel cell), a desulfurizer 2, a desulfurizer heating unit 3, and a preheating unit 4. . Further, the fuel cell system 100 includes an exhaust gas introduction path 6 for guiding the exhaust gas discharged from the fuel cell 1 to the desulfurizer heating unit 3 and an exhaust gas for discharging the exhaust gas from the desulfurizer heating unit 3 to the outside. An exhaust gas discharge path 7, a raw material supply path 8 for supplying the raw material to the fuel cell 1, and an air path 10 for supplying power generation air are provided.

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

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

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

  The fuel cell system 100 according to this embodiment includes a combustion unit that generates combustion exhaust gas by burning unused fuel and power generation air in the fuel cell 1, and introduces exhaust gas using the combustion exhaust gas as exhaust gas. The structure which guide | induced to the desulfurizer heating part 3 through the path | route 6 may be sufficient. Alternatively, when the fuel cell 1 is a flat plate fuel cell, the cathode off-gas exhausted from the cathode may be used as exhaust gas and led to the desulfurizer heating unit 3 through the exhaust gas introduction path 6. The cathode offgas is heated by the high operating temperature of the fuel cell 1 and has a sufficient amount of heat to function as a heat source in the desulfurizer heating unit 3.

  Although not particularly shown in FIG. 1, a raw material supply path 8 is provided with a reformer (not shown) between the desulfurizer 2 and the fuel cell 1, and the raw material from which the sulfur compound is removed by the desulfurizer 2, The reformer may be configured to reform. Alternatively, since the operating temperature of the solid oxide fuel cell is as high as about 600 to 900 ° C., the steam reforming (internal reforming) is performed in the fuel cell 1 by the catalytic action of nickel which is the main component of the fuel electrode. It is good.

  The desulfurizer 2 removes sulfur compounds in the raw material using hydrogen. That is, the desulfurizer 2 is a hydrodesulfurizer that removes sulfur components contained in the raw material by a so-called hydrodesulfurization method. A raw material supply path 8 is connected to the desulfurizer 2, and the raw material supplied from the outside through the raw material supply path 8 flows into the desulfurizer 2. Although not particularly shown in FIG. 1, the raw material flowing into the desulfurizer 2 contains hydrogen. The hydrogen contained in the raw material may be hydrogen supplied from the outside, or may be a part of the reformed gas generated by reforming in the reformer, for example. Alternatively, when the fuel cell 1 is a flat plate fuel cell, it may be a part of the anode off gas discharged from the anode.

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

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

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

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

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

  The raw material desulfurized by the desulfurizer 2 as described above is supplied to the fuel cell 1 when reformed by internal reforming and to the reformer when reformed by the reformer. The reformer may be used for partial oxidation reforming, but in order to realize more efficient operation, the specification can perform not only partial oxidation reforming reaction but also steam reforming reaction. It is advantageous to keep

  The desulfurizer heating unit 3 heats the desulfurizer 2 using the heat of the exhaust gas discharged from the fuel cell 1. Specifically, the exhaust gas discharged from the fuel cell 1 is guided to the desulfurizer heating unit 3 through the exhaust gas introduction path 6 and circulates inside the desulfurizer to thereby remove a part of the heat of the exhaust gas. The temperature is raised to the desired temperature. That is, inside the desulfurizer heating unit 3, a circulation path for circulating the exhaust gas is formed, and the exhaust gas flows through this circulation path and is then discharged to the outside through the exhaust gas discharge path 7. .

  The desulfurizer 2 and the desulfurizer heating unit 3 described above are disposed on the desulfurizer heating unit 3 and are in surface contact with each other on one or more surfaces. Moreover, the exterior (housing | casing) of the desulfurizer 2 and the desulfurizer heating part 3 is comprised from metals, such as stainless steel. And if exhaust gas distribute | circulates the distribution path formed in the inside of the desulfurizer heating part 3, the heat | fever which exhaust gas has will be transferred from the desulfurizer heating part 3 to the desulfurizer 2 through this contact surface. As a result, the temperature of the desulfurization catalyst inside the desulfurizer 2 is maintained at an appropriate temperature.

  The preheating unit 4 preheats the raw material supplied to the desulfurizer 2 by using the heat of the exhaust gas guided to the desulfurizer heating unit 3 through the exhaust gas introduction path 6. Thus, the fuel cell system 100 according to the present embodiment has a configuration in which the raw material can be preheated before the raw material is supplied to the desulfurizer 2. Further, since the raw material is preheated by the exhaust gas flowing into the desulfurizer heating unit 3, the desulfurizer 2 heated by the desulfurizer heating unit 3 using the temperature of the preheated raw material and the heat of the exhaust gas. The temperature is almost the same. For this reason, since the temperature of the raw material is lower than the operation temperature desired in the desulfurizer 2, the catalytic action of the desulfurization catalyst is small in the vicinity of the raw material inlet in the desulfurizer 2, and the sulfur component cannot be sufficiently removed. Can be prevented.

  As shown in FIGS. 2 and 3, the fuel cell system 100 according to the present embodiment further includes an air heat exchanger 5. 2 and 3 are schematic views showing an example of the configuration of the fuel cell system 100 according to the embodiment. 2 and 3 further show the configuration of the fuel cell system 100 including the air heat exchanger 5.

  The air heat exchanger 5 heats (preheats) the power generation air supplied to the fuel cell 1 using the heat of the exhaust gas discharged from the fuel cell 1. That is, the air heat exchanger 5 heats the power generation air supplied from the outside to a predetermined temperature by heat exchange with the exhaust gas. For example, the power generation air after flowing through the air heat exchanger 5 is heated to 400 to 800 ° C. by heat exchange with the exhaust gas. The heated power generation air is supplied to the fuel cell 1. Thus, in the case of the configuration further including the air heat exchanger 5, in the fuel cell system 100, the exhaust gas from which part of the heat held by the air heat exchanger 5 by exchanging heat with the power generation air is taken. Is guided to the desulfurizer heating unit 3. For this reason, in the fuel cell system 100, exhaust gas having a high temperature of 400 to 800 ° C. is lowered to a temperature suitable for heating the desulfurizer 2 by the air heat exchanger 5 and guided to the desulfurizer heating unit 3. it can.

  Here, with reference to above-mentioned FIG. 2 and FIG. 3, the structure of the preheating part 4 and the position in which this preheating part 4 is provided are demonstrated. As shown in FIG. 2, the preheating unit 4 may be a raw material supply path 8 portion that is inserted into the exhaust gas introduction path 6 on the rear side of the air heat exchanger 5. That is, as shown in FIG. 2, a part of the raw material supply path 8 is inserted into the exhaust gas introduction path 6 through which the exhaust gas using a part of the retained heat is circulated by the air heat exchanger 5. Thus, the preheating unit 4 is configured. And the raw material which distribute | circulates the raw material supply path 8 is heated by the heat of the exhaust gas which distribute | circulates the exhaust gas introduction path 6 in this preheating part 4, and is supplied to the desulfurizer 2. FIG.

  Or the preheating part 4 may be the raw material supply path | route 8 part penetrated in the desulfurizer heating part 3, as shown in FIG. That is, as shown in FIG. 3, a part of the raw material supply path 8 is inserted into the desulfurizer heating unit 3 through which the exhaust gas using a part of the retained heat is circulated by the air heat exchanger 5. Thus, the preheating unit 4 is configured. And the raw material which distribute | circulates the raw material supply path 8 is heated with the heat | fever of the exhaust gas led in the desulfurizer heating part 3 in this preheating part 4, and is supplied to the desulfurizer 2. FIG.

  In the configuration shown in FIG. 3, since the preheating unit 4 is formed in the desulfurizer heating unit 3, it is not necessary to prepare a separate space for forming the preheating unit 4, and there is a space necessary for installing the fuel cell system 100. Further increase in size can be prevented.

  Incidentally, although not particularly shown in FIGS. 1 to 3, the fuel cell 1 described above is accommodated in a housing 30 (see FIG. 4 described later) in which a heat insulating portion 31 is arranged on the wall surface, and the desulfurizer 2 and the desulfurizer. It can be set as the structure which provided the heating part 3 in the heat insulation part 31 (refer FIG. 4 mentioned later). When configured in this way, the fuel cell 1, the desulfurizer 2, and the desulfurizer heating unit 3 can be accommodated in the same housing 30, respectively, and therefore the efficiency of heat utilization of the exhaust gas is reduced due to heat radiation. Can be prevented. Hereinafter, an embodiment of the fuel cell system 100 having the configuration in which the fuel cell 1 described above is accommodated in the housing 30 and the desulfurizer 2 and the desulfurizer heating unit 3 are provided in the heat insulating unit 31 will be described with reference to FIG. I will explain.

(Example)
Specifically, the fuel cell system 100 according to the present embodiment can be configured as in the example shown in FIG. FIG. 4 is a diagram schematically illustrating a configuration example of the fuel cell system 100 according to the embodiment. In FIG. 4, the fuel exhaust gas generated by burning unused fuel and unused air in the fuel cell 1 is used as exhaust gas, and the preheating unit 4 is provided in the desulfurizer heating unit 3. An example will be described.

  In the example illustrated in FIG. 4, the fuel cell system 100 includes an auxiliary air heat exchanger 11, in addition to the fuel cell 1, the desulfurizer 2, the desulfurizer heating unit 3, the preheating unit 4, and the air heat exchanger 5. A reformer 14, an evaporator 15, a combustion unit 16, a decompression unit 17, and a booster unit 33 are further provided, and the fuel cell 1, the reformer 14, and the evaporator 15 are surrounded by a heat insulation unit 31. The desulfurizer 2, the desulfurizer heating unit 3, the air heat exchanger 5, and the auxiliary air heat exchanger 11 are arranged in the heat insulating unit 31.

  In the fuel cell system 100 shown in the embodiment, the raw material boosted by the booster 33 is supplied through the raw material supply path 8. The supplied raw material is mixed with a reformed gas containing about 70% of hydrogen gas (about 10% with respect to the raw material) necessary for the hydrodesulfurization reaction. A raw material containing hydrogen at a required flow rate is introduced into the housing 30.

  Here, when the raw material is supplied as it is from the pressure raising unit 33 to the desulfurizer 2, the raw material flowing into the desulfurizer 2 becomes normal temperature (about 20 ° C.). For this reason, the temperature of the raw material in this case is considerably lower than the optimum reaction temperature (about 250 ° C. to 300 ° C.) of the desulfurization catalyst containing copper and zinc, for example. When the raw material flows into the desulfurizer 2 at this low temperature, the optimum reaction temperature of the desulfurization catalyst is not reached near the inlet and sufficient desulfurization cannot be performed.

  Therefore, in the fuel cell system 100 according to the embodiment, before the raw material is allowed to flow into the desulfurizer 2, the inside of the desulfurizer heating unit 3 provided at the lower portion of the desulfurizer 2 is used in order to set the desulfurization catalyst to an optimum reaction temperature. It is configured to pass through and preheat. That is, an exhaust gas of about 300 ° C. is circulated in the desulfurizer heating unit 3 as a heat source for heating the desulfurizer 2, and one of the raw material supply paths 8 is in the distribution path through which the exhaust gas circulates. The part is inserted and the raw material is preheated. Thus, the preheating part 4 for preheating a raw material in the desulfurizer heating part 3 is formed.

  In the present embodiment, the preheating portion 4 can be formed as shown in FIG. 5, for example. FIG. 5 is an end view of the desulfurizer heating unit 3 of the fuel cell system 100 according to the embodiment as viewed from the top side of the casing.

  As shown in FIG. 5, the desulfurizer heating unit 3 has a configuration in which a flow path 50 for flowing exhaust gas is formed in a rectangular parallelepiped housing. Exhaust gas that has flowed into the desulfurizer heating unit 3 from the exhaust gas inlet 51 flows through a flow path 50 provided to be bent in the casing of the desulfurizer heater 3 and is discharged from the exhaust gas outlet 52. It is like that. In addition, a pipe that is part of the raw material supply path 8 and is formed in a U-shape is inserted into the distribution path 50 as the preheating unit 4. For example, a stainless steel pipe having a total length of about 200 mm can be adopted as the U-shaped pipe (preheating portion 4). However, the length and material of the pipe are not limited thereto. Absent. The length of the piping is appropriately set in consideration of the housing dimensions of the desulfurizer heating unit 3 and the flow rate of the raw material flowing through the raw material supply path 8.

  Thus, since the preheating unit 4 is provided in the flow path 50 in the desulfurizer heating unit 3, the raw material flowing through the raw material supply path 8 is desulfurized by this U-shaped pipe (preheating unit 4). It can be preheated to about 250 ° C. by the heat of the exhaust gas of about 300 ° C. flowing through the heating unit 3. In this way, since the raw material is preheated so as to have substantially the same temperature as the desulfurizer 2 and then flows into the desulfurizer 2, the catalyst temperature near the inlet of the desulfurizer 2 is lowered as described above, and the catalytic reaction Can prevent the problem of not functioning sufficiently.

  Further, the U-shaped pipe functioning as the preheating unit 4 can be installed simply by welding and fixing at two locations in the desulfurizer heating unit 3, and can be manufactured at low cost. Moreover, since it is the structure which accommodates piping inside the housing | casing of the desulfurizer heating part 3, it is not necessary to ensure the new space for accommodating this piping, and it can be set as a simple structure.

  In addition, when the preheating unit 4 is preheated so as to raise the temperature of the raw material to an appropriate temperature, for example, it is not necessary to use an electric valve or the like, so that the control design of such a valve becomes unnecessary and power consumption can be suppressed. Furthermore, since the heat source used for preheating the raw material is the exhaust gas discharged from the fuel cell 1, no new heat source is required for preheating the raw material.

  As described above, when the preheated raw material flows into the desulfurizer 2, the desulfurizer 2 includes hydrogen in the raw material by hydrodesulfurization reaction using hydrogen while the raw material passes through the desulfurization catalyst. Remove sulfur components.

  Since the desulfurizer 2 is covered with the heat insulating portion 31, the desulfurizer 2 is configured so as to avoid heat dissipation and heat transfer as much as possible. For this reason, the temperature of the desulfurization catalyst heated by the desulfurizer heating unit 3 can be stabilized in a temperature range (about 250 to 300 ° C.) appropriate for the desulfurization reaction. The raw material after the desulfurization is led from the desulfurizer 2 to an evaporator 15 provided in front of the reformer 14.

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

  For example, an evaporator 15 is provided in front of the reformer 14, and water (reformed water) supplied through a reformed water path (not shown) is mixed with the raw material desulfurized by the desulfurizer 2. It is set as the structure supplied. Here, the evaporator 15 is installed to perform the steam reforming reaction in the reformer 14, and uses the heat of the exhaust gas discharged from the combustion unit 16 and the radiant heat from the combustion unit 16. Then, water (reformed water) supplied from the reforming water path is vaporized and mixed with the raw material after desulfurization supplied from the desulfurizer 2. Then, the evaporator 15 introduces the mixed raw material into the reformer 14.

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

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

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

  Further, in the configuration of the fuel cell system 100 shown in FIG. 4, the reformed gas generated by the reformer 14 is branched in the middle of the reformed gas path 9 (branch portion) from the reformer 14 to the fuel cell 1. A recycling path 19 is provided for returning a part of the material to the raw material supply path 8. For this reason, it becomes possible to add hydrogen to the raw material supplied to the desulfurizer 2, and the desulfurizer 2 can perform the above-mentioned hydrodesulfurization using this hydrogen.

  In the configuration of the fuel cell system 100 shown in FIG. 4, the decompression unit 17 is provided in the middle of the recycling path 19. The decompression unit 17 adjusts the flow rate of the reformed gas flowing through the recycle path 19 and can be realized by, for example, a capillary tube or an orifice. That is, the decompression unit 17 is configured such that the reformed gas flows through the recycle path 19 by a desired flow rate by narrowing the flow path with a capillary tube or an orifice to increase the pressure loss. The position of the decompression unit 17 is disposed outside the housing 30 in FIG. 4, but may be inside the housing 30. When arranged outside the housing 30, there is an advantage that direct exposure to high-temperature exhaust gas or the like can be prevented. On the other hand, when the decompression unit 17 is disposed in the housing 30, the interior of the housing 30 is at a high temperature, so that there is an advantage that moisture is hardly condensed in the decompression unit 17.

  Moreover, it is good also as a structure which provided the condenser (not shown) in the middle of this recycle path | route 19. FIG. In the case of a configuration including a condenser, when the reformed gas flowing through the recycling path 19 is cooled, moisture can be recovered by the condenser. For this reason, it is possible to suppress problems such as water in the path due to condensed water and corrosion or breakage of the booster 33. This condenser can use a double-pipe heat exchanger that uses raw fuel gas, air, or water as a cooling source. The condensed water produced | generated by the condenser may be discharge | released outside, for example, the structure reused for the reformed water etc. of the fuel cell system 100 may be sufficient.

  Further, the fuel cell system 100 according to the embodiment is configured such that the power generation air supplied to the fuel cell 1 is preheated by the two heat exchangers (the air heat exchanger 5 and the auxiliary air heat exchanger 11). ing. Specifically, as shown in FIG. 4, the power generation air supplied from the outside is heat-exchanged and preheated by the exhaust gas after passing through the desulfurizer heating unit 3 and the auxiliary air heat exchanger 11. Further, the power generation air preheated by the auxiliary air heat exchanger 11 is heat-exchanged by the air heat exchanger 5 with the exhaust gas burned and generated by the combustion unit 16, and is heated to about the operating temperature of the fuel cell 1. , Supplied to the fuel cell 1. The exhaust gas from which heat has been removed by heat exchange with the power generation air in the auxiliary air heat exchanger 11 is released to the outside.

(Exhaust gas flow, exhaust gas temperature adjustment, and desulfurizer temperature rise)
Taking the configuration of the fuel cell system 100 shown in FIG. 5 as an example, the flow of exhaust gas, temperature adjustment of the exhaust gas, and temperature rise of the desulfurizer will be described. Specifically, the desulfurizer 2 is heated by circulating the exhaust gas as follows. In the case of the fuel cell system 100 shown in FIG. 5, the exhaust gas used for heating the desulfurizer 2 is combustion exhaust gas generated by burning unused fuel and air in the combustion unit 16.

  Regarding the flow rate of exhaust gas (combustion exhaust gas) generated in the combustion section 16 and its temperature, the fuel utilization rate of the fuel and power generation air in the fuel cell 1 (the ratio of the fuel cell 1 consumed as fuel during power generation) is adjusted. By doing so, it is possible to control. In the fuel cell system 100 shown in FIG. 5, for example, the fuel utilization rate of the fuel and power generation air in the fuel cell 1 is set so that the temperature range of the combustion unit 16 is about 600 to 900 ° C.

  The exhaust gas generated by burning unused fuel and power generation air in the combustion section 16 set to have a desired temperature range in this way first passes through the reformer 14 and the evaporator 15. Heat. Thereby, a part of the heat of the exhaust gas is consumed. Further, the exhaust gas that has consumed part of the heat flows into the air heat exchanger 5, and heat exchange between the power generation air and the exhaust gas by the air heat exchanger 5 further deprives the heat of the exhaust gas. The temperature is lowered to a temperature suitable for heating the desulfurizer 2. The exhaust gas whose temperature has been further lowered in this manner flows through the exhaust gas introduction path 6 and is supplied to the desulfurizer heating unit 3.

  That is, the temperature of the exhaust gas generated in the combustion unit 16 is as high as about 600 ° C. to 900 ° C., for example. However, if the reformer 14 and the evaporator 15 are heated by this exhaust gas and further heat exchange with the power generation air is performed by the air heat exchanger 5, the exhaust gas is exhausted before reaching the exhaust gas introduction path 6. The temperature drops.

  As described above, the temperature of the exhaust gas flowing through the exhaust gas introduction path 6 and flowing into the desulfurizer heating unit 3 is the flow rate and temperature of the exhaust gas generated in the combustion unit 16, the reformer 14 and the evaporation. The amount of heat absorbed by the heat exchanger 15 and the amount of heat absorbed by the air heat exchanger 5 are taken into consideration and controlled to a desired value.

  Thus, by installing the desulfurizer heating unit 3 in the exhaust gas introduction path 6, the desulfurizer 2 can be set to a desired temperature suitable for hydrodesulfurization. At the same time, the temperature of the raw material supplied to the desulfurizer 2 can be preheated to this desired temperature.

  Further, at least the desulfurizer 2, the desulfurizer heating unit 3, and the exhaust gas introduction path 6 are installed so as to be covered with the heat insulating unit 31 as much as possible. In this way, heat dissipation from these members can be prevented, and these members can be prevented from being directly exposed to the high-temperature heat in the housing 30. In particular, since the desulfurizer 2 and the desulfurizer heating unit 3 are configured to be covered by the heat insulating unit 31, the temperature distribution in the desulfurizer 2 and the desulfurizer heating unit 3 can be made as uniform as possible to suppress variations. Thereby, the temperature control of the desulfurization catalyst in the desulfurizer 2 can be facilitated.

(Experimental example)
Finally, in the configuration of the fuel cell system 100 of the embodiment shown in FIG. 4 described above, a comparative experiment was performed on the temperature of the desulfurizer 2 in the configuration in which the preheating unit 4 was provided and the configuration in which the preheating unit 4 was not provided. The result shown in FIG. 6 was obtained. FIG. 6 is a table showing experimental results of the preheating effect in the desulfurizer 2 of the fuel cell system 100 according to the example.

  As shown in FIG. 6, in the configuration of the fuel cell system provided with the preheating unit 4 (with a preheating unit), the raw material inlet in the desulfurizer 2 was 256 ° C., whereas the preheating unit 4 was In the case of the configuration of the fuel cell system not provided (no preheating part), the temperature is only 185 ° C., and the temperature is such that the desulfurization catalyst cannot act effectively.

  Further, in the case of the configuration of the fuel cell system provided with the preheating unit 4, the temperature of the raw material outlet in the desulfurizer 2 is 245 ° C, the minimum temperature on the upper surface of the desulfurizer 2 is 252 ° C, and the maximum temperature is 256 ° C. . Further, the average temperature in the entire desulfurizer 2 is 254 ° C., and the temperature distribution in the desulfurizer 2 is less uneven.

  On the other hand, in the case of the configuration of the fuel cell system in which the preheating unit 4 is not provided, the temperature of the raw material outlet in the desulfurizer 2 is 253 ° C., the minimum temperature on the upper surface of the desulfurizer 2 is 231 ° C., and the maximum temperature is 260. It is ℃. Furthermore, the average temperature in the desulfurizer 2 as a whole is 255 ° C., and it can be seen that the uneven temperature distribution in the desulfurizer 2 is clearly larger than that in the configuration in which the preheating unit 4 is provided.

  The present invention provides a fuel cell system that is provided in a preceding stage of a reformer that reforms a hydrocarbon-based raw material into a hydrogen-rich gas and that needs to optimize the temperature of the desulfurizer that desulfurizes sulfur contained in the raw material. Useful for.

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Desulfurizer 3 Desulfurizer heating part 4 Preheating part 5 Air heat exchanger 6 Exhaust gas introduction path 7 Exhaust gas discharge path 8 Raw material supply path 9 Reformed gas path 10 Air path 11 Auxiliary air heat exchanger 14 Reformation Ventilator 15 Evaporator 16 Combustion part 17 Decompression part 19 Recycling path 30 Housing 31 Heat insulation part 33 Booster part 50 Distribution path 51 Exhaust gas inlet 52 Exhaust gas outlet

Claims (5)

A desulfurizer that removes sulfur compounds in the raw material;
A fuel cell that generates electricity by an electrochemical reaction using a fuel obtained by reforming a raw material from which sulfur compounds have been removed by the desulfurizer, and supplied power generation air;
A desulfurizer heating section that heats the desulfurizer using heat of exhaust gas flowing through the fuel cell system;
An exhaust gas introduction path for guiding the exhaust gas to the desulfurizer heating section;
A fuel cell system comprising: a preheating unit that preheats a raw material supplied to the desulfurizer using heat of exhaust gas flowing through the exhaust gas introduction path. A raw material supply path for supplying the raw material to the desulfurizer;
The fuel cell system according to claim 1, wherein the preheating unit is formed by inserting a part of the raw material supply path into the exhaust gas introduction path. An air heat exchanger that is provided in the middle of the exhaust gas introduction path and heats the power generation air supplied to the fuel cell using heat of the exhaust gas;
3. The fuel cell system according to claim 2, wherein the preheating portion is the raw material supply path portion that is inserted into the exhaust gas introduction path that is downstream of the air heat exchanger in the flow direction of the exhaust gas.   2. The fuel cell system according to claim 1, wherein the preheating unit is the raw material supply path portion inserted into the desulfurizer heating unit.   The fuel cell system according to claim 4, wherein the raw material supply path has a pipe-shaped portion bent in a horizontal direction in the desulfurizer heating section as the preheating section.