JP2013101822A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system which is capable of hydrodesulfurization to a desired sulfur content by a desulfurizer stably at low cost.SOLUTION: A fuel cell system according to the present invention comprises: a first desulfurizer 2 which removes sulfur contents from a hydrogen-containing raw material gas by hydrodesulfurization; a first reformer 3 which receives desulfurized raw material gas having its sulfur contents removed by the first desulfurizer 2 and reforms the desulfurized raw material gas to generate fuel gas; a fuel cell 4 which receives fuel gas generated by the first reformer 3 and generates electricity by power generation reaction of the fuel gas with air supplied from the outside; and a second reformer 1 which partially reforms the raw material gas by partial oxidation reaction to generate hydrogen-containing partially reformed raw material gas and supplies the generated partially reformed raw material gas to the desulfurizer 2 as the hydrogen-containing raw material gas.

Description

  The present invention relates to a fuel cell system provided with a hydrodesulfurization device that removes sulfur-containing components of raw fuel gas (raw gas) containing hydrogen.

  In a fuel cell system using hydrocarbons as a raw fuel gas, for example, steam reforming using steam is used to reform the raw fuel gas. A steam reforming catalyst is used to promote the steam reforming. However, the raw fuel gas contains an odorant or a sulfur compound, which may deteriorate the steam reforming catalyst. There is. Therefore, in order to prevent deterioration of the steam reforming catalyst, a desulfurization apparatus that reduces the odorant or sulfur compound contained in the raw fuel gas is used.

  As such a desulfurization apparatus, 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 desulfurization is performed by the hydrodesulfurization method, but the raw fuel gas usually does not contain hydrogen. For this reason, a mechanism for supplying hydrogen from somewhere to the hydrodesulfurization apparatus is required.

  For example, in Patent Document 1, as shown in FIG. 7, a part of the raw fuel gas desulfurized by the desulfurizer 104 is passed upstream of the desulfurizer 104 via a branch return passage 142 in which a hydrocarbon reforming catalyst is installed. A solid oxide fuel cell system returned to the side is disclosed. FIG. 7 is a diagram showing a configuration of a fuel cell according to the prior art.

  As shown in FIG. 7, in the solid oxide fuel cell system of Patent Document 1, a part of the water and raw fuel gas mixed in the mixer 120 is introduced into the branch return flow path 142. Then, the hydrogen-containing gas obtained by reforming the hydrocarbon is returned to the upstream side of the booster 117 by the hydrocarbon reforming catalyst in the double pipe 144 of the branch return channel 142. As a result, hydrogen is supplied to the desulfurizer 104 to hydrodesulfurize the raw fuel gas.

JP 2006-54171 A JP-A-5-221602 JP 2007-098250 A Japanese Patent Laid-Open No. 2001-200288 Japanese Patent No. 2999307

  However, the conventional fuel cell system as described above has a problem that it cannot be desulfurized to a desired sulfur concentration stably at low cost.

  More specifically, in the configuration of the prior art, when steam reforming is performed in the branch return flow path 142, dew condensation may occur in the branch return flow path 142. For this reason, in the branch return flow path 142, pressure loss occurs due to water clogging due to condensation, and the gas does not easily flow through the branch return flow path 142. Therefore, the flow rate of the hydrogen-containing gas returned to the upstream side of the booster 117 decreases, and there arises a problem that the desulfurizer 104 cannot desulfurize to a desired sulfur concentration. In addition, there is a problem that condensation occurs in the desulfurizer 104 or the booster 117 while the operation is stopped.

  In addition, in order to prevent dew condensation, it can respond by installing a water condensation heat exchanger in the branch return flow path 142, and making it the structure which collects water compulsorily. Alternatively, this can be dealt with by heating the branch return channel 142 with a heater. However, in the case of the former configuration, in the configuration of the prior art, it is necessary to further include a water condensing heat exchanger and a flow channel pipe for guiding the recovered water to a desired location. For this reason, the configuration of the fuel cell system becomes complicated and expensive. Further, in the case of the latter configuration, the cost for installing the heater and the cost of electric power necessary for the operation of the heater are increased, resulting in an increase in cost.

  When partial oxidation reforming is performed in the branch return flow path 142, the nitrogen concentration in the branch return flow path 142 gradually increases, and the hydrogen gas flow rate in the hydrogen-containing gas returned upstream of the booster 117 decreases. End up. For this reason, there is a problem that the desulfurizer 104 cannot desulfurize to a desired sulfur concentration.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to realize a fuel cell system that can be stably hydrogenated and desulfurized by a desulfurizer to a desired sulfur concentration at a low cost. is there.

  In order to solve the above problems, a fuel cell system according to the present invention removes a sulfur component of a raw material gas containing hydrogen by hydrodesulfurization, and the sulfur component is removed by the first desulfurizer. Receiving the desulfurized raw material gas, reforming the desulfurized raw material gas to generate a fuel gas, receiving the fuel gas generated by the first reformer, the fuel gas and the outside A fuel cell that generates electricity by causing a power generation reaction with air supplied from the fuel, and a partial reforming raw material gas containing hydrogen by partially reforming the raw material gas by a partial oxidation reaction, and the generated partial reforming raw material A second reformer that supplies gas to the first desulfurizer as a raw material gas containing hydrogen.

  According to the above configuration, since the first desulfurizer is provided, the raw material gas from which the sulfur component has been removed can be supplied to the first reformer. For this reason, it is possible to prevent the activity of the reforming catalyst charged in the first reformer from being lowered by the sulfur component. Therefore, the raw material gas reformed by the first reformer can be stably provided to the fuel electrode of the fuel cell stack.

  In addition, since the second reformer is provided, the raw material gas is partially reformed by a partial oxidation reaction to generate a partially reformed raw material gas containing hydrogen and provided to the first desulfurizer as a raw material gas containing hydrogen. can do. For this reason, the first desulfurizer can remove the sulfur component from the raw material gas by hydrodesulfurization so that the desired sulfur concentration is stably obtained.

  By the way, the second reformer partially reforms the raw material gas. That is, the second reformer only needs to reform only the raw material gas having a flow rate necessary for obtaining hydrogen used for hydrodesulfurization of the sulfur component of the raw material gas.

  Here, the sulfur component of the raw material gas is generally several ppm, and the hydrogen necessary for hydrodesulfurization is theoretically as small as several tens of ppm. For this reason, since the second reformer can be realized with a reformer having a remarkably small capacity as compared with the first reformer that reforms the entire raw material gas, it does not cost much to install the second reformer. .

  Therefore, the fuel cell according to the present invention has an effect that it can be hydrodesulfurized by a desulfurizer (first desulfurizer) to a desired sulfur concentration stably at low cost.

  The fuel cell system according to the present invention is configured as described above, and has an effect that it can be hydrodesulfurized with a desulfurizer to a desired sulfur concentration at low cost and stably.

It is a block diagram which shows an example of a structure of the fuel cell which concerns on embodiment of this invention. It is the figure which showed typically an example of the structure of the 2nd reformer with which the fuel cell shown in FIG. 1 is provided. It is a block diagram which shows an example of a structure of the fuel cell which concerns on embodiment of this invention. It is a block diagram which shows an example of a structure of the fuel cell which concerns on the modification 1 of embodiment of this invention. It is a block diagram which shows an example of a structure of the fuel cell which concerns on the modification 2 of embodiment of this invention. It is a block diagram which shows an example of a structure of the fuel cell which concerns on the modification 3 of embodiment of this invention. It is a figure which shows the structure of the fuel cell which concerns on a prior art.

  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 fuel cell system according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing an example of the configuration of a fuel cell system according to an embodiment of the present invention.

  As shown in FIG. 1, the fuel cell system includes a second reformer 1, a desulfurizer (first desulfurizer) 2, a reformer (first reformer) 3, and a fuel cell 4. It is.

  The second reformer 1 reforms the hydrocarbons contained in the raw fuel gas from the input raw fuel gas (raw gas) and reformed air to generate hydrogen, which is a modification for partial oxidation reforming. It is a quality device. The second reformer 1 does not reform all the hydrocarbons of the input raw fuel gas to generate hydrogen, but generates a necessary amount of hydrogen by hydrodesulfurization in the subsequent desulfurizer 2. As described above, the raw fuel gas is partially reformed to generate a partially reformed raw fuel gas (partial reforming raw material gas).

  As shown in FIG. 2, the second reformer 1 has a cylindrical shape in which the direction in which the raw fuel gas flows is longer, and the reforming catalyst impregnated with Ni in the alumina carrier is clogged therein. ing. FIG. 2 is a diagram schematically showing an example of the configuration of the second reformer 1 provided in the fuel cell system shown in FIG.

  The reforming catalyst charged in the second reformer 1 is not limited to the above-described reforming catalyst as long as partial oxidation reforming can be performed. For example, Ru or Rh supported on zirconia or stabilized zirconia (for example, Patent Document 2), rhodium, and at least one metal selected from Group VIII metals of the periodic table other than rhodium, alumina and zirconia (For example, Patent Document 3) may be used which is supported on a carrier containing

  The second reformer 1 is supplied with raw fuel gas such as city gas and reformed air (oxidant gas) through the raw fuel gas supply path 11 and the reformed air supply path 12, respectively. As the raw fuel gas, other gas mainly composed of hydrocarbon such as propane gas may be used instead of the above-described city gas. The reformed air may be air in the atmosphere as long as it contains oxygen at a required flow rate, or pure oxygen.

  Although not particularly shown in the fuel cell system according to the present embodiment, a member for supplying raw fuel gas and reformed air to the second reformer 1 is provided with, for example, a booster or a blower. Also good.

When raw fuel gas and reformed air are supplied to the second reformer 1, a part of the raw fuel gas and oxygen in the reformed air are expressed by the following formula in a temperature range of 800 to 1000 ° C. The partial oxidation reforming reaction represented by (1) is performed to generate hydrogen gas and carbon monoxide.
C _n H _m + (n / 2) O ₂ → n · CO + (m / 2) H ₂ (n and m are arbitrary natural numbers) (1)
Here, the density | concentration of the sulfur compound contained in normal city gas is about several ppm (parts per million). For this reason, the hydrogen flow rate required for hydrodesulfurization performed in the desulfurizer 2 is theoretically about several tens of ppm relative to the raw fuel gas flowing through the desulfurizer 2. However, for example, as disclosed in Patent Document 4, it is preferable that the raw fuel gas is desulfurized while adding more hydrogen in consideration of dispersibility. Also, the oxygen flow rate in the reformed air supplied to the second reformer 1 is theoretically about several ppm with respect to the raw fuel gas, but more in consideration of dispersibility. It is preferable that the raw fuel gas is desulfurized while adding air.

  The second reformer 1 is attached to the fuel cell system so as to be detachable. When the reforming catalyst (for example, Ni catalyst) deteriorates due to the sulfur component contained in the input raw fuel gas, it becomes impossible to obtain hydrogen at a flow rate necessary for hydrodesulfurization of the desulfurizer 2. The second reformer 1 can be exchanged.

  When the raw fuel gas is supplied, in the second reformer 1, the reaction rate between the reforming catalyst and the sulfur component in the raw fuel gas, the passing rate of the raw fuel gas passing through the second reformer 1, and From this relationship, the activity of a certain amount of the reforming catalyst decreases. The amount of the reforming catalyst whose activity decreases as the raw fuel gas circulates through the second reformer 1 is determined in what period and how much the reforming catalyst is charged. Depends on the type of catalyst.

  For example, in the example of the second reformer 1 shown in FIG. 2, the activity of the reforming catalyst group (first group; first Gr.) From the side to which the raw fuel gas is supplied to the third stage is reduced in one year. . And the activity of all the reforming catalysts will fall in four years.

  More specifically, as shown in FIG. 2, most of the reforming catalysts belonging to the first Gr. Reforming catalyst group deteriorate after one year of operation of the fuel cell system. In addition, in reality, a part of the raw fuel gas passes through the first Gr. With the sulfur component, so even the reforming catalyst groups of the second Gr. And the third Gr. Any difference will cause partial deterioration. In addition, two years after the operation of the fuel cell system, the first Gr. Is completely deteriorated and the second Gr. Is also substantially deteriorated. The third Gr. And the fourth Gr. Are also partially degraded. After three years, the first and second Gr. Are completely degraded, and the third Gr. Is almost degraded. Furthermore, the 4th Gr. In the subsequent stage is partially degraded.

  As described above, in the example shown in FIG. 2, when the second reformer 1 is used for four years, almost all of the reforming catalyst deteriorates and is replaced with a new second reformer 1.

  When the second reformer 1 is replaced, the first valve 41 and the second valve 42 provided on the upstream side and the downstream side of the second reformer 1 are closed as shown in FIG. Prevent gas from leaking outside. Then, the second reformer 1 is removed and replaced with a new second reformer 1. That is, the second reformer 1 is detachable in the fuel cell system and can be easily replaced.

  When the raw fuel gas and the reformed air are thus supplied to the second reformer 1 and hydrogen gas is generated by the partial oxidation reforming reaction, the second reformer 1 A raw material gas containing carbon and nitrogen is supplied to the desulfurizer 2 through the upstream reformed raw fuel gas supply path 13.

  The desulfurizer 2 is for removing sulfur components contained in the raw fuel gas by a desulfurization method of hydrodesulfurization. As a desulfurization agent with which it fills in the desulfurizer 2, the desulfurization agent containing copper and zinc is mentioned, for example (for example, patent document 5). 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 2 hydrocrackes organic sulfur in the raw fuel gas in a temperature range of 350 to 400 ° C. And the desulfurizer 2 adsorb | sucks and removes produced | generated H2S in the temperature range of 350-400 degreeC.

For example, when the raw fuel 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 in the desulfurizer 2 in the form of ZnS by the following reaction formulas (formulas (2) and (3)) or in the form of physical adsorption.
C ₂ H ₆ S + 2H ₂ → 2CH ₄ + H ₂ S (2)
H ₂ S + ZnO → H ₂ O + ZnS (3)
The odorant that can be desulfurized is not limited to the above-described DMS, and may be other sulfur compounds such as TBM (C ₄ H ₁₀ S) or THT (C ₄ H ₈ S).

When a desulfurizing agent containing copper and zinc is used, the desulfurizer 2 performs desulfurization in a temperature range of about 10 to 400 ° C, preferably about 200 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 at high temperatures (H ₂ S + ZnO → H ₂ O + ZnS). In this case, the sulfur content contained in the raw fuel gas after desulfurization is 1 vol ppb (parts per billion) or less, usually 0.1 vol ppb or less.

  As described above, when the desulfurizer 2 is filled with a desulfurization agent containing either a Ni-Mo-based or Co-Mo-based catalyst or copper or zinc, the sulfur component removal amount per unit volume is increased. For this reason, the required amount of the desulfurizing agent for removing sulfur to a desired sulfur concentration can be reduced.

  The raw fuel gas desulfurized by the desulfurizer 2 as described above flows through the gas supply path 14 and is mixed with the air introduced from the reformed air supply path 21 in the mixing unit 22. The mixed air and the raw fuel gas after desulfurization are supplied to the first reformer 3.

  The first reformer 3 is a reformer that partially reforms hydrocarbons in raw fuel gas into hydrogen and carbon monoxide. As the reforming catalyst filled in the first reformer 3, an alumina carrier impregnated with Ni is used. The reforming catalyst to be filled is not limited to the above-described one, and any reforming catalyst that can perform partial oxidation reforming may be used as in the second reformer 1. For example, Ru or Rh supported on zirconia or stabilized zirconia (for example, Patent Document 2), rhodium, and at least one metal selected from Group VIII metals of the periodic table other than rhodium, alumina and zirconia (For example, Patent Document 3) may be used which is supported on a carrier containing

  The mixed gas obtained by mixing the raw fuel gas and the reformed air supplied to the first reformer 3 is a partial oxidation reforming reaction represented by the above chemical formula (1) in the temperature range of 800 to 1000 ° C. To produce hydrogen gas and carbon monoxide. Then, a gas containing the generated hydrogen gas is supplied as fuel gas to the fuel cell 4 through the anode gas supply path 15.

  The fuel cell 4 generates power by a reaction between the fuel gas supplied from the anode gas supply path 15 and the air (air for power generation) supplied from the cathode gas supply path 16. That is, the fuel cell 4 has a fuel electrode to which the raw fuel gas reformed by the first reformer 3 is supplied, and an air electrode to which power generation air is supplied. The fuel electrode, the air electrode, A plurality of fuel cell single cells that generate electricity by performing a power generation reaction between them are connected in series. The fuel cell 4 has a configuration in which a plurality of fuel cell single cells are connected in series as described above, but this directly connected configuration may be further connected in parallel.

  As a single fuel cell constituting the fuel cell 4, zirconia doped with yttria (YSZ) is used. The fuel cell unit cell is not limited to the above-described cell as long as it can perform a power generation reaction. For example, a fuel cell unit cell made of zirconia doped with yttrium or scandium, or a lanthanum gallate solid electrolyte It may be used. When the fuel cell unit cell is YSZ, the power generation reaction is performed in a temperature range of about 600 to 1000 ° C., depending on the thickness.

  The anode off-gas and cathode off-gas discharged from the fuel cell 4 are supplied to the anode off-gas passage 17 and the cathode off-gas passage 18, respectively.

  The electricity generated by the fuel cell 4 is supplied to an external circuit via a current collecting terminal member (not shown).

  As described above, the fuel cell system according to the present embodiment has a configuration in which the second reformer 1 is replaced with a new second reformer 1 at a predetermined cycle. That is, as described above, the fuel cell system is provided with the second reformer 1 so as to be detachable from the fuel cell. The second reformer 1 is, for example, after a certain period of operation of the fuel cell system. It becomes exchangeable. For this reason, in the fuel cell system, the desulfurizer 2 can be operated only for a long period of time at the replacement cost of the second reformer 1.

  Here, the hydrogen flow rate required for hydrodesulfurization performed in the desulfurizer 2 disposed on the downstream side of the second reformer 1 is theoretically about several tens of ppm, which is very small. For this reason, the 2nd reformer 1 should just be able to produce | generate this hydrogen of about several dozen ppm, and it is realizable with a small reformer. Since the second reformer 1 can be realized with a small reformer as described above, even if the second reformer 1 is replaced with a new second reformer 1 at a predetermined cycle, the cost required for the replacement. Is small.

  Moreover, as long as it is replaced with a new second reformer 1 at a predetermined cycle, the problem that it cannot be desulfurized to a desired sulfur concentration as in the prior art shown in Patent Document 1 described above can occur stably. Hydrodesulfurization can be performed. In other words, it is not necessary to recycle the hydrogen gas necessary for hydrodesulfurization as in the prior art, so that the hydrogen-containing gas supplied to the hydrodesulfurizer does not condense or the nitrogen concentration increases, Hydrodesulfurization can be performed stably.

  The fuel cell 4 described above may be a solid oxide fuel cell (SOFC) or a polymer electrolyte fuel cell (PEFC). Alternatively, it may be a phosphoric acid fuel cell (PAFC) or a molten carbonate fuel cell (MCFC).

  Although the first reformer 3 provided in the fuel cell system is a reformer that performs a partial oxidation reforming reaction, it may be a reformer that performs a steam reformer.

  More specifically, as shown in FIG. 3, reformed water (water or steam) is introduced into the mixing unit 22 instead of the reformed air. The first reformer 3 is configured to steam reform the mixed gas of the reformed water and the raw material gas. FIG. 3 is a block diagram showing an example of the configuration of the fuel cell system according to the embodiment of the present invention.

  The steam reforming is an endothermic reaction, and the thermal energy of the cathode offgas discharged from the air electrode side and the anode offgas discharged from the fuel electrode side is supplied to the power generation reaction in the fuel cell 4 for this steam reforming. It is suitable that it is configured to be used. When the fuel cell system is configured in this way, the first reformer 3 performs steam reforming of hydrocarbons in the raw fuel gas into hydrogen and carbon monoxide. As the reforming catalyst filled in the first reformer 3, an alumina carrier impregnated with Ni is used. The reforming catalyst charged in the first reformer 3 is not limited to the alumina carrier impregnated with Ni, but may be any catalyst that can perform steam reforming. For example, the reforming catalyst may be a reforming catalyst containing at least one of ruthenium, palladium, rhodium and nickel.

The mixed gas of raw fuel gas and reformed water supplied to the first reformer 3 performs a steam reforming reaction represented by the following formula (4) in a temperature range of 400 to 800 ° C., Produces hydrogen gas and carbon monoxide.
_{C n H m + n · H} 2 O → n · CO + (m / 2 + n) H 2 (n, m is an arbitrary natural number) (4)
Then, the first reformer 3 supplies a gas containing the generated hydrogen gas as a fuel gas to the fuel cell 4 through the anode gas supply path 15.

  Although not shown, the heat exchanger further includes a heat exchanger for supplying exhaust heat of off-gas (anode off-gas and cathode off-gas) discharged from the fuel cell 4 to the first reformer 3, and the first reformer is provided. The heat necessary for steam reforming in the vessel 3 may be provided by this exhaust heat.

  Alternatively, a heat exchanger for supplying off-gas exhaust heat to the second reformer 1 or the desulfurizer 2 is further provided, and heat for maintaining the temperature at a predetermined high temperature in the second reformer 1 or the desulfurizer 2. It may be configured to cover this by this exhaust heat.

  As described above, when the second reformer 1 and the desulfurizer 2 are maintained at a predetermined high temperature by exhaust heat of the off gas, the thermal energy of the off gas discharged from the fuel cell 4 can be effectively used. For this reason, the power generation efficiency in the fuel cell system can be improved.

  The operating temperature of the second reformer 1 that performs partial oxidation reforming is, for example, about 800 to 1000 ° C. The operating temperature of the desulfurizer 2 is, for example, about 350 to 400 ° C. Therefore, a startup heater for heating the second reformer 1 and the desulfurizer 2 to an appropriate operating temperature at the startup of the fuel cell system may be provided.

  The fuel cell system according to the present embodiment further includes an adsorptive desulfurizer as an auxiliary desulfurizer. When the fuel cell system is started, the raw fuel gas is supplied to the auxiliary desulfurizer and desulfurized to be desulfurized. You may comprise so that it may guide | induced to the downstream of this. The auxiliary desulfurizer is a desulfurizer that removes sulfur components by adsorbing them on an adsorbent such as zeolite at room temperature.

  Even if the second reformer 1 and the desulfurizer 2 are provided with startup heaters, and these heaters are operated and heated at the time of startup of the fuel cell system, the second reformer 1 and the desulfurizer 2 can be operated at appropriate temperatures. Does not rise up quickly. For this reason, at the time of starting the fuel cell system, the second reformer 1 and the desulfurizer 2 cannot sufficiently reform and desulfurize.

  Therefore, an auxiliary desulfurizer that can be desulfurized at room temperature is further provided, and this auxiliary desulfurizer allows the raw fuel to be supplied from the start of the fuel cell system until the second reformer 1 and desulfurizer 2 are heated to an appropriate operating temperature. It may be configured to perform gas desulfurization.

  In addition, by providing the auxiliary desulfurizer in this way, when the second reformer 1 and the desulfurizer 2 are maintained and inspected or replaced, the auxiliary fuel can be desulfurized in the raw fuel gas by the auxiliary desulfurizer. There is no need to stop driving.

  The auxiliary desulfurizer is not suitable for a long-time operation because only the sulfur component (sulfur compound) is adsorbed on the surface of the desulfurizing agent, but the second reformer 1 and the desulfurizer 2 are appropriately operated. There is no problem as long as it is a short time, such as until it is heated to the temperature, or during these replacement operations.

(Modification 1)
Next, Modification 1 of the fuel cell system according to the present embodiment will be described below with reference to FIG.

  FIG. 4 is a block diagram showing an example of the configuration of the fuel cell system according to Modification 1 of the embodiment of the present invention. In FIG. 4, the same components as those of the fuel cell system according to the embodiment of the present invention described above are denoted by the same reference numerals, and the description thereof is omitted.

  The fuel cell system according to Modification 1 is different from the above-described fuel cell system according to the embodiment of the present invention in the following points.

  That is, the fuel cell system according to Modification 1 further includes a second reformer bypass path 23 in the configuration of the fuel cell system according to the embodiment of the present invention shown in FIG. 1 or FIG. The difference is that the part is circulated through the second reformer bypass path 23. More specifically, in the fuel cell system according to Modification 1, not all of the supplied raw fuel gas and reformed air are supplied to the second reformer 1, but only a part of the raw fuel gas is supplied to the second reformer 1. 2 Supply to the reformer 1. Then, the remaining raw material gas is circulated through the second reformer bypass path 23 and introduced into the desulfurizer 2.

  Here, as described above, the concentration of the sulfur compound contained in the raw fuel gas is about several ppm. For this reason, the theoretical hydrogen flow rate required for the hydrodesulfurization performed in the desulfurizer 2 is theoretically about several tens of ppm relative to the raw fuel gas. Theoretically, if several ppm of the total raw fuel gas flow rate is supplied to the second reformer 1 and subjected to partial oxidation reforming, a necessary hydrogen flow rate can be obtained. However, in consideration of dispersibility, it is preferable that the raw fuel gas is flowed to the second reformer 1 more than this several ppm.

  As described above, the fuel cell system according to Modification 1 further includes the second reformer bypass path 23 that supplies the raw fuel gas to the desulfurizer 2 without passing through the second reformer 1. The desulfurizer 2 then converts the sulfur components of the partially reformed gas supplied from the second reformer 1 and the raw fuel gas supplied from the second reformer bypass path 23 into the second reformer 1. It is configured to be removed by hydrodesulfurization using the hydrogen generated in 1. Further, in the fuel cell system according to the modified example 1, a raw fuel gas having a flow rate capable of obtaining a hydrogen flow rate necessary for hydrodesulfurization by the desulfurizer 2 is supplied to the second reformer 1, and the remaining raw fuel gas is supplied. It can be said that it is configured to be supplied to the first desulfurizer via the second reformer bypass path 23.

  According to the configuration described above, since the second reformer bypass path 23 is further provided, the flow rate of the raw material gas flowing through the second reformer can be reduced. Therefore, the pressure loss in the second reformer can be reduced. In addition, the deterioration of the reforming catalyst in the second reformer can be reduced.

  The operating temperature of the second reformer 1 is as high as about 800 to 1000 ° C., but the operating temperature of the desulfurizer 2 is about 200 to 300 ° C. and is lower than that of the second reformer 1. For this reason, when all the raw fuel gas is circulated through the second reformer 1 as in the fuel cell system according to the embodiment of the present invention, the raw material reformed and discharged by the second reformer 1. The fuel gas becomes hot and exceeds the operating temperature of the desulfurizer 2. For this reason, in the fuel cell system according to the embodiment of the present invention, the discharged raw fuel gas needs to be lowered to an appropriate temperature and supplied to the desulfurizer 2.

  However, in the fuel cell system according to Modification 1, as shown in FIG. 4, a large amount of raw fuel gas is led to the desulfurizer 2 at room temperature, and only a small amount of raw fuel gas is supplied to the second reformer 1. . For this reason, the high temperature raw fuel gas discharged from the second reformer 1 and the room temperature raw fuel gas can be easily adjusted so as to have an appropriate temperature by mixing in the desulfurizer 2.

(Modification 2)
Next, Modification 2 of the fuel cell system according to the present embodiment will be described below with reference to FIG.

  FIG. 5 is a block diagram showing an example of the configuration of a fuel cell system according to Modification 2 of the embodiment of the present invention. In FIG. 5, the same components as those of the fuel cell system according to the embodiment of the present invention are denoted by the same reference numerals, and the description thereof is omitted.

  The fuel cell system according to Modification 2 is different from the fuel cell system according to the embodiment of the present invention in the following points. That is, the fuel cell system according to the modified example 2 includes the second reformer bypass path 23 in the configuration of the fuel cell system according to the embodiment of the present invention shown in FIG. 1 or FIG. Is different in that it flows through the second reformer bypass path 23. Further, the fuel cell system according to the embodiment of the present invention is configured to supply, for example, air in the atmosphere as reformed air to the second reformer 1. On the other hand, the fuel cell system according to the modified example 2 further includes a cathode offgas recycling path 26, and a part of the high temperature cathode offgas is used as the reformed air of the second reformer 1, and the cathode offgas recycling path 26. It is different in that it is introduced through.

  That is, the fuel cell system according to Modification 2 is configured such that an orifice mechanism is provided in the middle of the cathode offgas passage 18 so that a predetermined amount of cathode offgas flows through the cathode offgas recycling passage 26.

  Here, the oxygen utilization rate in the fuel cell 4 is about 30%. For this reason, assuming that the amount of oxygen supplied to the fuel cell 4 is 100%, about 70% of oxygen remains in the cathode off-gas and contains sufficient oxygen to be supplied to the second reformer 1. For this reason, in the fuel cell system according to Modification 2, the cathode offgas can be supplied instead of the reformed air.

  For example, when the single fuel cell of the fuel cell 4 is YSZ, a cathode off gas of about 600 to 1000 ° C. is exhausted from the fuel cell 4. For this reason, by supplying the cathode off gas to the second reformer 1, the second reformer 1 and the desulfurizer 2 disposed downstream of the second reformer 1 can be heated.

  That is, the fuel cell system according to Modification 2 includes the mixing unit 22 that mixes reformed water with the raw fuel gas (desulfurized raw material gas) from which the sulfur component has been removed by the desulfurizer 2 as described above. In addition, the first modification is performed by using exhaust heat (thermal energy) of the cathode offgas, which is the air discharged from the fuel cell 4 without being consumed by the power generation reaction in the fuel cell 4, and the anode offgas, which is the fuel gas. The mass device 3 is configured to steam reform the desulfurization raw material gas mixed with reforming water in the mixing unit 22.

  For this reason, in the fuel cell system according to Modification 2, the energy of the anode off-gas and the cathode off-gas discharged from the fuel cell 4 can be effectively used for steam reforming of the first reformer, which is an endothermic reaction. For this reason, the fuel cell system can improve the power generation efficiency of the fuel cell.

(Modification 3)
Next, Modification 3 of the fuel cell system according to the present embodiment will be described below with reference to FIG.

  FIG. 6 is a block diagram showing an example of the configuration of a fuel cell system according to Modification 3 of the embodiment of the present invention. In FIG. 6, the same components as those of the fuel cell system according to the embodiment of the present invention described above are denoted by the same reference numerals, and the description thereof is omitted.

  The fuel cell system according to Modification 3 differs from the fuel cell system according to the embodiment of the present invention in the following points. That is, the fuel cell system according to Modification 3 includes the second reformer bypass path 23 in the configuration of the fuel cell system shown in FIG. 1 or FIG. 3, and part of the raw fuel gas is supplied to the second reformer bypass path. 23 in that it is distributed. The fuel cell system according to Modification 3 is different in that it further includes an adsorptive desulfurizer (second deflower) 6 that is an adsorption-type desulfurizer at the upstream side (upstream side) of the second reformer 1. .

  By the way, an adsorption-type desulfurizer such as the adsorptive desulfurizer 6 has a configuration in which a sulfur component (sulfur compound) is adsorbed on the surface of the desulfurizing agent as described above, and therefore usually has a large capacity. If this is not prepared, the raw fuel gas cannot be desulfurized for a long time. However, in the fuel cell system according to the modified example 3, only a small amount of raw fuel gas necessary to generate hydrogen gas of several tens of ppm with respect to the total raw fuel gas flow rate flows through the adsorptive desulfurizer 6. It is. For this reason, the amount of sulfur component adsorbed on the surface of the desulfurizing agent is very small, and it is not necessary to prepare a large-capacity desulfurizer.

  However, although the amount of adsorbed sulfur component is very small, if this adsorbing desulfurizer 6 is used during the long-time operation of the fuel cell system, the sulfur component is adsorbed on the entire surface of the desulfurizing agent. In some cases, further sulfur components cannot be adsorbed. Therefore, the adsorptive desulfurizer 6 can be attached and detached in the fuel cell system, and can be replaced with a new adsorptive desulfurizer 6 at an appropriate timing.

  In the fuel cell system according to Modification 3, when raw fuel gas is supplied, a small amount of raw fuel gas necessary to generate hydrogen gas of about several tens of ppm is absorbed and desulfurized with respect to the total raw fuel gas flow rate. Most of the remaining raw fuel gas is introduced into the vessel 6 and flows into the desulfurizer 2 through the second reformer bypass passage 23.

  The adsorptive desulfurizer 6 removes the sulfur component contained in the supplied raw fuel gas and supplies it to the second reformer 1. In the second reformer 1, partial oxidation reforming is performed by the raw fuel gas from which the sulfur component supplied from the adsorptive desulfurizer 6 is removed and the reformed air to generate hydrogen. Then, the generated hydrogen is supplied to the desulfurizer 2.

  In the desulfurizer 2, the sulfur component is removed from the raw fuel gas supplied via the second reformer bypass path 23 by hydrodesulfurization using hydrogen added from the second reformer 1, and the mixing unit 22 is removed. To the first reformer 3. Since the subsequent processing is the same as that of the fuel cell system according to the embodiment of the present invention described above, the description thereof is omitted.

  As described above, the fuel cell system according to Modification 3 has a configuration in which the adsorptive desulfurizer 6 is further provided in the previous stage of the second reformer 1. That is, the fuel cell system according to Modification 3 is detachably provided in the fuel cell system, adsorbs and desulfurizes the sulfur component of the raw fuel gas, and supplies the desulfurized raw fuel gas to the second reformer 1. The adsorbing desulfurizer 6 is further provided.

  For this reason, this adsorption desulfurizer 6 can prevent the sulfur component from entering the second reformer 1, and the activity of the second reformer 1 can be prevented from being lowered. For this reason, it is not necessary to replace the second reformer 1 at a predetermined cycle.

  That is, in the fuel cell system according to the modified example 3, in order to operate the desulfurizer 2 for a long period of time as described above, it is not necessary to replace the second reformer 1 at a predetermined cycle. Instead, the adsorptive desulfurizer 6 Need to be exchanged at predetermined intervals.

  Therefore, although it depends on the composition of the raw fuel gas to be distributed, the operation cost of the fuel cell system is lower when the adsorption desulfurizer 6 is replaced at a predetermined period than the second reformer 1. It is preferable to adopt the configuration of the fuel cell system.

  On the contrary, when the operating cost of the fuel cell system is lower when the second reformer 1 is replaced at a predetermined cycle than the adsorptive desulfurizer 6, the fuel cell system according to the present embodiment or Modification 1 Alternatively, the fuel cell system according to 2 is preferably employed.

  From the foregoing 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.

  Since the fuel cell system according to the present invention can perform hydrodesulfurization inexpensively and stably, it is useful in a fuel cell system including a hydrodesulfurization device. It can also be applied to other uses that require desulfurization of source gas such as diesel generators.

DESCRIPTION OF SYMBOLS 1 2nd reformer 2 Desulfurizer 3 1st reformer 4 Fuel cell 6 Adsorption desulfurizer 11 Raw fuel gas supply path 12 Reformed air supply path 13 Original reformed raw fuel gas supply path 14 Gas supply path 15 Anode gas supply path 16 Cathode gas supply path 17 Anode off gas path 18 Cathode off gas path 21 Reformed air supply path 22 Mixing unit 23 Second reformer bypass path 26 Cathode off gas recycle path 41 First valve 42 Second valve 104 Desulfurizer 117 Booster 120 Mixer 142 Branch return flow path

Claims (8)

A first desulfurizer for removing the sulfur component of the raw material gas containing hydrogen by hydrodesulfurization;
A first reformer for receiving a desulfurization raw material gas from which sulfur components have been removed by the first desulfurizer, and reforming the desulfurization raw material gas to generate a fuel gas;
A fuel cell that receives the fuel gas generated by the first reformer and generates electricity by causing a power generation reaction between the fuel gas and air supplied from the outside; and
A partial reforming raw material gas containing hydrogen is generated by partially reforming the raw material gas by a partial oxidation reaction, and the generated partial reforming raw material gas is supplied to the first desulfurizer as the raw material gas containing hydrogen. And a second reformer. A bypass path for supplying the raw material gas to the first desulfurizer without passing through the second reformer;
The first desulfurizer uses hydrogen generated by the second reformer for the sulfur component of the partially reformed gas supplied from the second reformer and the raw material gas supplied from the bypass path. The fuel cell system according to claim 1, wherein the fuel cell system is configured to be removed by hydrodesulfurization.   A raw material gas having a flow rate capable of obtaining a hydrogen flow rate required for hydrodesulfurization by the first desulfurizer is supplied to the second reformer, and the remaining raw material gas is supplied to the first desulfurizer via the bypass path. The fuel cell system according to claim 2, configured to be supplied. A cathode offgas recycling path for guiding cathode offgas, which is air discharged from the fuel cell without being consumed by a power generation reaction in the fuel cell, to the second reformer;
The fuel cell system according to any one of claims 1 to 3, wherein the cathode offgas is configured to be used by a second reformer for a partial oxidation reaction.   The fuel cell system according to any one of claims 1 to 4, wherein the second reformer is detachably provided to the fuel cell.   The fuel cell system further includes a second desulfurizer that is detachably provided, adsorbs and desulfurizes a sulfur component of the raw material gas, and supplies the desulfurized raw material gas to the second reformer. 6. The fuel cell system according to any one of items 1 to 5. A mixing unit that mixes reformed water with the desulfurization source gas from which the sulfur component has been removed by the first desulfurizer;
The first reformer uses the thermal energy of the cathode offgas, which is the air discharged from the fuel cell without being consumed by the power generation reaction in the fuel cell, and the anode offgas, which is the fuel gas, to mix the first reformer. The fuel cell system according to any one of claims 1 to 6, wherein the desulfurization raw material gas mixed with reforming water is steam reformed in the section.   The fuel cell system according to any one of claims 1 to 7, wherein the fuel cell is a solid oxide fuel cell.