JP5197944B2 - Indirect internal reforming solid oxide fuel cell system - Google Patents

Description

  The present invention relates to an indirect internal reforming solid oxide fuel cell having an indirect internal reforming solid oxide fuel cell in which a reformer for reforming liquid fuel such as kerosene is arranged in the vicinity of the solid oxide fuel cell. The present invention relates to a fuel cell system.

  Solid oxide fuel cells (Solid Oxide Fuel Cell, sometimes referred to as SOFC) are usually generated by reforming hydrocarbon fuels (raw fuel) such as kerosene and city gas in a reformer. A hydrogen-containing gas (reformed gas) is supplied. In the SOFC, the reformed gas and air are reacted electrochemically to generate electricity. The SOFC is usually operated at a high temperature of about 550 ° C to 1000 ° C.

  The steam reforming reaction used for reforming is a reaction with a very large endotherm, and the reaction temperature is relatively high, requiring a high-temperature heat source. Therefore, an indirect internal reforming SOFC is known in which a reformer is installed in the vicinity of the SOFC (a position that receives heat radiation from the SOFC) and the reformer is heated by radiant heat from the SOFC. An indirect internal reforming SOFC is described in Patent Document 1.

In addition, in an indirect internal reforming SOFC, combustible anode off-gas (gas discharged from the SOFC anode) is combusted in an indirect internal reforming SOFC container (module container), and this combustion heat is used as a heat source. As mentioned above, the reformer is also heated. Such an indirect internal reforming SOFC and its starting method are described in Patent Document 2.
JP 2002-358997 A JP 2004-319420 A

  In the indirect internal reforming SOFC system, the following points are different between the case where liquid fuel such as kerosene is used as raw fuel and the case where city gas or liquefied petroleum gas (LPG) is used as raw fuel.

  Since liquid fuel such as kerosene is a high-order hydrocarbon, when it is used as raw fuel, if raw fuel that has not undergone reforming is discharged from the reformer (called slip) and flows into the SOFC, even in a short time In some cases, the stability of operation may be impaired by carbon deposition in the SOFC. Therefore, it is desirable that liquid fuel such as kerosene be reliably converted to lower hydrocarbons before being supplied to the SOFC.

  On the other hand, when city gas or LPG is used as raw fuel, the raw fuel can be reformed inside the SOFC even if the raw fuel flows into the SOFC without being reformed. That is, raw material slip is allowed.

  In particular, in an indirect internal reforming SOFC of the type in which anode off gas is burned in a module container and the combustion heat is used to heat a reformer or SOFC, when the raw fuel is a liquid fuel, the slip of the raw fuel is reduced. Under possible circumstances, it is desirable not to supply raw fuel to the SOFC upon startup. For this reason, it is conceivable to use a separate start-up device such as an external reformer, but this can be a cost-up factor.

  Also, not only at startup, but also during normal operation (rated operation or partial load operation), if there is an abnormality in the liquid fuel supply system due to disturbance or the like, even if it is a short time, slip In order to avoid the problems caused by the operation, the operation may be stopped.

The purpose of the present invention, a system with a type of indirect internal reforming SOFC to heat the combustion heat reformer and SOFC utilizing the combustion of the anode off-gas in the module container, additional equipment for Atsushi Nobori It is an object of the present invention to provide a method for starting an indirect internal reforming SOFC system that can be easily started while preventing slipping.

According to the present invention, a reformer having a reforming catalyst layer capable of partial oxidation reforming and steam reforming of vaporized liquid fuel, and a solid oxide fuel that generates power using the reformed gas obtained by the reformer A battery and a container for containing the reformer and the solid oxide fuel cell, wherein the reformer is disposed at a position to receive heat radiation from the solid oxide fuel cell, and the solid oxide fuel An indirect internal reforming solid oxide fuel cell capable of combusting anode off-gas discharged from the anode of the cell in the vessel; liquid fuel vaporization supply means for supplying the reformer after vaporizing the liquid fuel; and A method for starting an indirect internal reforming solid oxide fuel cell system having a gaseous fuel supply means for supplying gaseous fuel to the reformer,
a) Gas fuel is introduced into the solid oxide fuel cell through the reformer, the anode off gas is combusted in the vessel, and the reformer and the solid oxide fuel cell are burned using the combustion heat of the anode off gas. Heating the step,
b) When the temperature of the reforming catalyst layer becomes equal to or higher than the partial oxidation reforming reaction start temperature of the gaseous fuel, the gaseous fuel is partially oxidized and reformed in the reformer and then introduced into the solid oxide fuel cell. Combusting offgas in the vessel and heating the reformer and the solid oxide fuel cell using partial oxidation reforming reaction heat and anode offgas combustion heat;
c) When the temperature of the reforming catalyst layer reaches 550 ° C. or higher, the fuel supplied to the reformer is switched from the gaseous fuel to the vaporized liquid fuel, and the vaporized liquid fuel is partially oxidized and reformed before solid oxidation. The step of introducing the fuel into the physical fuel cell, combusting the anode off gas in the vessel, and heating the reformer and the solid oxide fuel cell using the heat of partial oxidation reforming reaction and the combustion heat of the anode off gas. A starting method for an indirect internal reforming solid oxide fuel cell system is provided.

The start-up method further includes after step c)
d) The liquid fuel vaporized in the reformer is steam reformed without partial oxidation reforming and then introduced into the solid oxide fuel cell, the anode off gas is burned in the vessel, and the combustion heat of the anode off gas And heating the reformer and the solid oxide fuel cell.

According to the present invention, a system having an indirect internal reforming SOFC of a type in which anode off gas is combusted in a module vessel and the combustion heat is used to heat the SOFC, and a separate heating device is required. Thus, there is provided a method for starting an indirect internal reforming SOFC system that can be easily started while preventing slipping.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

〔System configuration〕
FIG. 1 shows an outline of an example of the indirect internal reforming SOFC system of the present invention. Here, kerosene is used as the liquid fuel, and city gas (methane is the main component) is used as the gaseous fuel. In addition, an oxygen-containing gas is used for any of the electrochemical reaction in the SOFC, the combustion reaction of the anode off gas, and the partial oxidation reforming reaction in the reformer. Here, air is used for all of these.

  This system has an indirect internal reforming SOFC1. The indirect internal reforming SOFC has a reformer 2 and a SOFC 3 (in FIG. 1, A represents the anode of the SOFC, and C represents the cathode of the SOFC). The reformer 2 includes a reforming catalyst layer 2a capable of partially oxidizing and steam reforming vaporized liquid fuel. The SOFC 3 can generate power using the reformed gas obtained from the reformer 2. The reformer and the SOFC are accommodated in a container (module container) 4 and modularized. The reformer is disposed at a position where it receives heat radiation from the solid oxide fuel cell. The module container 4 is airtight so that the inside and the outside (atmosphere) do not communicate with each other.

  Further, a gas (anode off gas) discharged from the anode of the SOFC can be burned in the module container 4. For example, the SOFC anode and cathode have cell outlets that open in the module container, and anode off-gas discharged from the anode-side cell outlet and cathode off-gas discharged from the cathode-side cell outlet are discharged into the module container. Can be adopted. An ignition means such as an igniter is appropriately provided at the cell outlet, and the anode off gas can be burned at the cell outlet.

  The SOFC system also includes liquid fuel vaporization supply means for supplying the reformer 2 after vaporizing the liquid fuel. The liquid fuel vaporization supply means has a kerosene tank 11 for storing liquid fuel, a kerosene pump 12 for boosting kerosene, and a kerosene vaporizer 13 for vaporizing kerosene, and a pipe for appropriately connecting the kerosene tank to the reformer inlet. It has a member. Moreover, it can have valves, such as a flow control valve and a stop valve. In the kerosene vaporizer, gas discharged from the module container 4 can be used as a heat source for vaporizing kerosene.

  Furthermore, this SOFC system has a gaseous fuel supply means for supplying gaseous fuel to the reformer 2. The gaseous fuel supply means has a blower 21 that boosts the city gas, and has a piping member that appropriately connects the city gas line outside the system to the reformer inlet. Moreover, it can have valves, such as a flow control valve and a stop valve.

  In addition, a line for supplying air to the cathode, a line for supplying air to the reformer, a line for supplying water vapor to the reformer, and the like are appropriately provided.

Further, as a thermometer for detecting the temperature of the reforming catalyst layer, provided with thermometer 103 for detecting the inlet temperature T _in of the reforming catalyst layer, and a thermometer 104 for detecting the outlet temperature T _out of the reforming catalyst layer It is done.

The control means 100 is configured to supply the gaseous fuel from the gaseous fuel supply means to the reformer according to the temperature detected by the thermometer (for example, T _in or T _out ), from the liquid fuel vaporization supply means. It has a function of switching to supply of liquid fuel to the reformer. A signal corresponding to the temperature detected by the thermometer is input to the control means, and the control means determines whether or not this temperature is equal to or higher than a predetermined temperature. When it is determined that the temperature is equal to or higher than the predetermined temperature, the control unit outputs a stop signal to the city gas blower 21 and outputs a start signal to the kerosene pump 12, for example.

  A kerosene flow meter 101 is provided downstream of the kerosene pump and upstream of the kerosene vaporizer. The kerosene flow meter only needs to be able to detect the flow rate of kerosene supplied to the reformer. Here, the kerosene flow meter detects the flow rate of kerosene in a liquid state, but is not limited thereto, and may detect the flow rate of gaseous kerosene. In that case, the kerosene flow meter can be provided downstream of the kerosene vaporizer.

  A pressure gauge 102 is provided to detect the pressure of the reformer. The pressure outlet of the pressure gauge may be provided in the reformer (for example, upstream of the reforming catalyst layer of the reformer), but is not limited thereto. Since it is sufficient if the pressure inside the reformer can be detected substantially, the pressure outlet may be provided on the upstream side of the reformer, particularly outside the module container, as shown.

  In addition to the above-described function, the control means 100 determines whether the flow rate detected by the kerosene flow meter 101 and the pressure detected by the pressure gauge 102 are abnormal. The amount of gaseous fuel supplied to the reformer is increased (including the case where the gaseous fuel is increased from zero, that is, the supply of gaseous fuel is started), and the liquid fuel is supplied from the liquid fuel vaporization supply means to the reformer. Has the function to stop supply. For this reason, a signal corresponding to the kerosene flow rate and a signal corresponding to the reformer pressure are input to this control means. Further, for example, a stop signal is output from the control means to the kerosene pump 12 and an activation signal is output to the city gas blower 21.

  As the control means, known control means can be used in process control such as a sequencer or a computer.

  An automatic flow control valve can be used to adjust the supply amount of liquid fuel or gaseous fuel. If the pump or blower has a flow rate adjustment function, it may be used. For this purpose, a signal can be sent from the control means to the automatic flow control valve, and a signal can be sent to the control device provided in the pump or blower. In order to start or stop the supply of liquid fuel or gaseous fuel, a stop valve (automatic valve) can be controlled from the control means, and on / off control of the pump and blower can be performed.

[System startup method]
The SOFC system can be started from room temperature by performing the following steps a) to c) in this order.
a) introducing gaseous fuel into the SOFC via the reformer, burning the anode off-gas in the module container, and heating the reformer and the SOFC using the combustion heat of the anode off-gas;
b) When the temperature of the reforming catalyst layer becomes equal to or higher than the partial oxidation reforming reaction start temperature of the gaseous fuel, the gaseous fuel is partially oxidized and reformed in the reformer and then introduced into the SOFC, and the anode off-gas is introduced into the module container. Combusting and heating the reformer and the SOFC using the partial oxidation reforming reaction heat and the combustion heat of the anode off gas.
c) When the temperature of the reforming catalyst layer reaches 550 ° C or higher, the fuel supplied to the reformer is switched from gaseous fuel to vaporized liquid fuel, and the vaporized liquid fuel is partially oxidized and reformed before being introduced into the SOFC. And heating the reformer and the SOFC using the partial oxidation reforming reaction heat and the combustion heat of the anode off gas by burning the anode off gas in the module container.

  First, step a) is performed. Specifically, with the kerosene pump 12 stopped, the city gas blower 21 is started and the flow rate is adjusted as appropriate. In addition, air is supplied to the SOFC cathode. In this step, air may not be supplied to the reformer.

  When the temperature of the pipe or device reaches a temperature at which the problem due to steam condensation can be avoided, steam can be supplied to the reformer for the purpose of preventing carbon deposition in the reforming catalyst layer.

  The city gas passes through the reformer 2 and the SOFC 3 in this order, and the city gas is discharged from the anode as an anode off gas. In the vicinity of the cell outlet, the anode off gas is burned by the air discharged from the cathode cell outlet. In the vicinity of the cell outlet, ignition can be appropriately performed using ignition means such as an igniter. With this combustion heat, the reformer is heated together with the SOFC, and these are heated. The combustion heat can be transferred to the SOFC and further to the reformer by radiation. Further, the SOFC or the reformer may be heated by contacting the combustion gas with the SOFC or the reformer.

  When the temperature of the reforming catalyst layer 2a becomes equal to or higher than the partial oxidation reforming reaction start temperature of city gas, the preheated air is appropriately supplied to the reformer 2 as necessary, and the gaseous fuel is partially oxidized in the reformer. Reform. The reformed gas obtained from the reformer is introduced into the SOFC 3 and the anode off-gas combustion at the cell outlet is continued. The partial oxidation reforming reaction is an exothermic reaction, which generates heat in the reforming catalyst layer. Therefore, it is possible to heat the inside of the reformer directly. Moreover, since the reformed gas passes through the inside of the SOFC, the SOFC can be heated from the inside by the reformed gas. Therefore, performing partial oxidation reforming is effective in raising the temperature of the reformer and also the SOFC.

The partial oxidation reforming reaction start temperature (represented as T _{gas, pox} ) of gaseous fuel is the temperature at which partial oxidation reforming can be performed under the conditions used (type of reforming catalyst and type of gaseous fuel). Means the lower limit. T _{gas, pox} can be known in advance by a preliminary test or the like. T _{gas, pox} is generally about 400 ° C. to 500 ° C. when city gas is used as fuel, and about 300 ° C. to 400 ° C. when LPG is used as fuel.

As described above, when the reforming catalyst layer temperature (denoted as T _{cat, 1} ) is lower than T _{gas, pox} , the operation of step a) is performed, and the reforming catalyst layer temperature becomes equal to or higher than T _{gas, pox.} Then, the operation proceeds to step b). T _{cat, 1} can be measured, for example, at the inlet end of the reforming catalyst layer. If the temperature at the inlet side end of the reforming catalyst layer is equal to or higher than T _{gas, pox} , heat is generated at the inlet side end of the reforming catalyst layer, and the entire reforming catalyst layer is heated by heat generated by the partial oxidation reaction. This is preferable. However, the position for measuring T _{cat, 1} is not limited to this, and may be a position where it can be determined that partial oxidation reforming can be performed in at least a part of the reforming catalyst layer.

For example, the reforming catalyst layer temperature T _{cat, 1} the inlet side end portion temperature T _in the reforming catalyst layer measured in the thermometer 103 is adopted as if T _{gas, pox} is 400 ° C., a temperature gauge 103 The operation of step a) is performed while monitoring T _in, and the operation of step b) may be performed when a value of 400 ° C. or higher is detected as T _in . However, it is not necessary to immediately proceed to step b) when T _in is 400 ° C. or higher. For example, when T _in reaches 450 ° C. or higher, such as 450 ° C. or higher, a desired temperature of 400 ° C. or higher. You can also.

  Step b) is performed, and when the temperature of the reforming catalyst layer 2a becomes 550 ° C. or higher, the fuel supplied to the reformer 2 is switched from gaseous fuel to liquid fuel (previously vaporized) (step c)). Specifically, the kerosene pump 12 is started, kerosene is vaporized in the kerosene vaporizer 13, and vaporized kerosene is supplied to the reformer 2. Also, the city gas blower 21 is stopped, and the supply of city gas is stopped.

  As a result, the liquid fuel is partially oxidized and reformed, the reformed gas is supplied to the SOFC, and the anode off gas burns in the vicinity of the cell outlet. Although the type of fuel is changed, the reformer and the SOFC are heated by the heat generated by partial oxidation reforming and the combustion heat of the anode off gas, as in step b).

  If the temperature of the reforming catalyst layer is 550 ° C. or higher, preferably 600 ° C. or higher, either the partial oxidation reforming and the steam reforming of the liquid fuel or more reliably preventing the liquid fuel from slipping or You can do both.

  From the viewpoint of preventing coking, the temperature of the reforming catalyst layer is preferably 850 ° C. or lower even at the highest temperature.

The temperature of the reforming catalyst layer (denoted as T _{cat, 2} ) used for the determination to move from step b) to step c) may be measured at the same position as T _{cat, 1} described above. That is, T _{cat, 1} and T _{cat, 2} may be the same. Alternatively, T _{cat, 2} may be measured at a position different from T _{cat, 1} . If at least a part of the reforming catalyst layer is 550 ° C. or higher, more preferably 600 ° C. or higher, the liquid fuel can be prevented from slipping. Therefore, T _{cat, 2} is the highest in the reforming catalyst layer. The temperature may be measured at a location where the temperature is generated. From this viewpoint, the temperature at the outlet side end of the reforming catalyst layer can be adopted as T _{cat, 2} .

For example, when adopting the T _cat, the _second reforming catalyst layer measured in the thermometer 104 as an outlet side end portion temperature T _out, do the step b) while monitoring the T _out, 550 ° C. as T _out When the above values are detected, the operation of step c) may be performed. However, it is not necessary to immediately go to step c) when T _out becomes 550 ° C. or higher. For example, after T _out becomes 600 ° C. or 650 ° C. or higher, a desired temperature of 550 ° C. or higher, then go to step c). You can also.

  The fuel switching may be performed at once or may be performed gradually.

  In step b), when steam is supplied to the reformer, steam reforming may proceed in addition to partial oxidation reforming in the reforming catalyst layer. The steam reforming reaction start temperature of the gaseous fuel is generally about 400 ° C to 450 ° C. Further, in step c), when steam is supplied to the reformer, steam reforming may proceed in addition to partial oxidation reforming in the reforming catalyst layer. Alternatively, in step b) or step c), the reformed gas composition can be adjusted using steam reforming as desired.

  Power generation in the SOFC may be performed as appropriate as long as power generation is possible.

  Through the steps a) to c), the reformer and the SOFC can be heated to a temperature at which normal operation (rated operation and partial load operation) is possible. At this time, the rate of temperature rise and the reached temperature can be adjusted by appropriately adjusting the flow rate of the fluid, particularly the fuel, supplied to the indirect internal reforming SOFC.

  In addition, the amount of reaction of partial oxidation reforming and steam reforming can be adjusted as appropriate by appropriately adjusting the amount of air and steam to be added, and the heat generated by partial oxidation reforming reaction and anode off-gas combustion, steam It is possible to adjust the temperature increase rate and the ultimate temperature by adjusting the endotherm due to reforming.

From the viewpoint of SOFC power generation efficiency, it is preferable to perform only steam reforming as reforming. Therefore, it is preferable to perform only steam reforming of the liquid fuel as reforming in normal operation, and after step c), partial oxidation reforming can be stopped and only steam reforming of the liquid fuel can be performed. That is, after step c)
d) The liquid fuel vaporized in the reformer is steam reformed without partial oxidation reforming and then introduced into the SOFC, the anode off gas is burned in the module vessel, and the reformer is used by using the combustion heat of the anode off gas. And a step of heating the SOFC.

  Thereby, before normal operation, the process can be stabilized under conditions for performing steam reforming of the liquid fuel. That is, the heat balance can be stabilized and the reformed gas composition can be adjusted. In this case, the SOFC and the reformer are heated by the combustion heat of the anode off gas. When power generation is performed, the heat generated by SOFC accompanying power generation also becomes a heat source.

  In order to heat the reformer and the SOFC, combustion may be performed in the module container using a separate burner.

  As described above, water vapor can be supplied to the reformer at a stage where the temperature of the pipes and equipment reaches a temperature at which problems due to water vapor condensation can be avoided. For example, when gaseous fuel is supplied to the reformer, steam is prevented so that the S / C is 2.0 to 4.0 at 400 ° C. or higher in order to prevent carbon deposition in the reforming catalyst layer. Is preferably supplied. Further, when liquid fuel is supplied to the reformer, it is preferable to supply water vapor so that the S / C is 2.5 to 5.0 at 550 ° C. or higher.

Therefore, when switching from gaseous fuel to liquid fuel, it is preferable to increase the amount of water vapor supplied. At this time, the water vapor supply amount can be increased simultaneously with the fuel switching, but it is preferable to increase the water vapor supply amount prior to the fuel switching. For example, when T _{cat, 2} exceeds 550 ° C., the steam supply amount is first increased, and the fuel switching operation is started after waiting for the steam supply amount supplied to the reformer to reach a desired amount. be able to. In actuality, taking into account the piping capacity, etc., calculate the time sufficient for the amount of steam supplied to the reformer to reach the desired amount, and delay the start of fuel switching operation from the start of steam supply by that amount of time. Can do.

  The generation of water vapor and the vaporization of kerosene use the heat in the system, such as the heat held by the gas discharged from the module container, or in some cases separately burn liquid fuel or gaseous fuel prepared as a reforming raw fuel It is possible to appropriately carry out by using the generated combustion heat. The steam generator and the kerosene vaporizer may be outside the module container or may be accommodated in the module container.

[System stop method]
When the SOFC system is stopped, in order to prevent the liquid fuel from slipping, when the temperature T _{cat, 2} of the reforming catalyst layer is less than 550 ° C., the liquid fuel may not be supplied to the reformer. it can. The SOFC system can be stopped by adopting an appropriate method such as a method of stopping all the fuel supply to the reformer at the time of stop and a method of lowering the temperature while continuing the fuel supply to the reformer. From the viewpoint of protecting the equipment, it is preferable to lower the temperature while continuing to supply the fuel to the reformer.

(Abnormality response)
When there is an abnormality in the supply of liquid fuel to the reformer while supplying the vaporized liquid fuel to the reformer 2, the supply of the liquid fuel to the reformer is stopped and the reformer is supplied. It is possible to increase the supply amount of the gaseous fuel (including the case of starting the gaseous fuel supply).

  Abnormality in the supply of liquid fuel to the reformer can be determined by determining that at least one of the flow rate of liquid fuel supplied to the reformer and the pressure of the reformer is outside the allowable range. For example, the flow rate of the liquid fuel and the reformer pressure (actually the pressure in the upstream line of the reformer) are monitored by the flow meter 101 and the pressure gauge 102, and the liquid fuel is supplied when these values are out of a predetermined range. The kerosene pump 12 is stopped to stop the supply of liquid fuel to the reformer, and the amount of city gas supplied from the city gas blower is increased.

  This operation can be performed when liquid fuel is supplied to the reformer, regardless of whether the operation is a start operation, a normal operation, or a stop operation.

  As a result, even when there is an abnormality in the supply of liquid fuel, it is possible to continue operation using gaseous fuel.

[Internal reforming SOFC]
In the internal reforming SOFC, the reformer is preferably disposed at a position where radiation heat can be directly transferred from the SOFC to the outer surface of the device. Accordingly, it is preferable that no shielding material is disposed between the internal reformer and the SOFC, that is, a gap is provided between the reformer and the SOFC. Further, it is preferable to shorten the distance between the reformer and the SOFC as much as possible.

  Each supply gas is appropriately preheated as necessary and then supplied to the reformer or SOFC.

  As the module container, an appropriate container capable of accommodating the SOFC and the internal reformer can be used. As the material, for example, an appropriate material having resistance to the environment to be used, such as stainless steel, can be used. The container is appropriately provided with a connection port for gas exchange and the like.

[SOFC]
As the SOFC, known SOFCs of various shapes such as a flat plate type and a cylindrical type can be appropriately selected and employed. In the SOFC, oxygen ion conductive ceramics or proton ion conductive ceramics are generally used as an electrolyte.

  The SOFC may be a single cell, but in practice, a stack in which a plurality of single cells are arranged (in the case of a cylindrical type, sometimes referred to as a bundle, but the stack in this specification includes a bundle) is preferable. Used. In this case, one or more stacks may be used.

[Raw fuel]
In the present invention, both liquid fuel and gaseous fuel are used as the raw fuel to be reformed by the reformer.

  The liquid fuel is a fuel that is liquid at normal temperature and normal pressure (25 ° C., 0.10 MPa). As the liquid fuel, a known liquid fuel can be used as a raw fuel in the field of the SOFC system. For example, a compound containing carbon and hydrogen (may contain other elements such as oxygen) in the molecule or a mixture thereof can be used as appropriate, and hydrocarbons (for example, having 6 or more carbon atoms), alcohols, or the like can be used. it can. For example, hydrocarbon fuels such as gasoline, naphtha, kerosene, and light oil, alcohols such as methanol and ethanol, ethers such as dimethyl ether, and the like. Of these, kerosene is preferable because it is easily available for industrial use and consumer use, and is easy to handle.

  The gaseous fuel is a fuel that is gaseous at normal temperature and normal pressure (25 ° C., 0.10 MPa). As the liquid fuel, a known gaseous fuel can be used as a raw fuel in the field of the SOFC system. For example, hydrocarbons having 4 or less carbon atoms such as methane, ethane, propane, and butane can be used, and industrially, natural gas, city gas, liquefied petroleum gas (LPG), and the like can be used.

[Reformer]
The reformer produces a reformed gas containing hydrogen from a hydrocarbon fuel using a partial oxidation reforming reaction and / or a steam reforming reaction. In the reformer, a partial oxidation reforming reaction or a steam reforming reaction can be performed, and autothermal reforming accompanied by a partial oxidation reaction in the steam reforming reaction may be performed. In particular, in normal operation, it is preferable that the partial oxidation reaction does not occur from the viewpoint of power generation efficiency of SOFC. In autothermal reforming, steam reforming is dominant, and therefore the reforming reaction becomes endothermic in overall. Then, heat necessary for the reforming reaction is supplied from the SOFC.

  The reforming catalyst layer can include a reforming catalyst having partial oxidation reforming ability and a reforming catalyst having steam reforming ability. An autothermal reforming catalyst having both partial oxidation reforming ability and steam reforming ability may be used for the reforming catalyst layer.

[Reforming catalyst]
A known catalyst can be used for each of the steam reforming catalyst, the partial oxidation reforming catalyst, and the autothermal reforming catalyst. Examples of the partial oxidation reforming catalyst include platinum-based catalysts, examples of the steam reforming catalyst include ruthenium-based and nickel-based catalysts, and examples of the autothermal reforming catalyst include rhodium-based catalysts.

[Operating conditions during normal operation]
Hereinafter, rated operation conditions when liquid fuel is used as raw fuel for each of steam reforming and autothermal reforming will be described.

The reaction temperature of the steam reforming can be performed, for example, in the range of 450 ° C to 900 ° C, preferably 500 ° C to 850 ° C, and more preferably 550 ° C to 800 ° C. The amount of steam introduced into the reaction system is defined as the ratio of the number of moles of water molecules to the number of moles of carbon atoms contained in the raw fuel (steam / carbon ratio), and this value is preferably 1 to 10, more preferably 1. 5 to 7, more preferably 2 to 5. The space velocity (LHSV) at this time can be expressed by A / B when the flow rate in the liquid state of the raw fuel is A (L / h) reforming and the catalyst layer volume is B (L). Preferably, it is set in the range of 0.05 to 20 h ⁻¹ , more preferably 0.1 to 10 h ⁻¹ , and still more preferably 0.2 to 5 h ⁻¹ .

  In autothermal reforming, an oxygen-containing gas is added to the raw material in addition to steam. The oxygen-containing gas may be pure oxygen, but air is preferred because of its availability. An oxygen-containing gas can be added so that the endothermic reaction accompanying the steam reforming reaction is balanced, and a heat generation amount capable of maintaining the temperature of the reforming catalyst layer and SOFC or raising the temperature thereof can be obtained. The addition amount of the oxygen-containing gas is preferably 0.005 to 1, more preferably 0.01 to 0.75 as the ratio of the number of moles of oxygen molecules to the number of moles of carbon atoms contained in the raw fuel (oxygen / carbon ratio). More preferably, it is 0.02 to 0.6. The reaction temperature of the autothermal reforming reaction is set, for example, in the range of 400 ° C to 900 ° C, preferably 450 ° C to 850 ° C, and more preferably 500 ° C to 800 ° C. The space velocity (LHSV) at this time is preferably selected in the range of 0.05 to 20, more preferably 0.1 to 10, and still more preferably 0.2 to 5. The amount of steam introduced into the reaction system is preferably 1 to 10, more preferably 1.5 to 7, and still more preferably 2 to 5 as a steam / carbon ratio.

[Other equipment]
Known components of the SOFC system can be appropriately provided as necessary. Specific examples include desulfurizers for desulfurizing liquid fuels and / or gaseous fuels, vaporizers for vaporizing liquids (including steam generators), pumps for pressurizing various fluids, compressors, blowers, etc. Pressure increasing means, flow rate adjusting means such as a valve for adjusting the flow rate of fluid or shutting off / switching the flow of fluid, flow path shutting / switching means, heat exchanger for heat exchange / heat recovery, gas Condensing condenser, heating / heat-retaining means for externally heating various devices with steam, storage means for gaseous fuel and liquid fuel, instrumentation air and electrical system, control signal system, control device, output and power The electrical system.

  The indirect internal reforming SOFC of the present invention can be used for, for example, a stationary or moving power generation system and a cogeneration system.

It is a flowchart which shows the outline of an example of the indirect internal reforming type | mold SOFC system of this invention.

Explanation of symbols

1: Indirect internal reforming SOFC
2: Reformer 3: SOFC
4: Module container 11: Kerosene tank 12: Kerosene pump 13: Kerosene vaporizer 21: City gas blower 100: Control means 101: Flow meter 102: Pressure gauge 103: Thermometer 104: Thermometer A: SOFC anode C: SOFC Cathode

Claims (2)

A reformer comprising a reforming catalyst layer capable of partially oxidizing and steam reforming the vaporized liquid fuel, a solid oxide fuel cell for generating electric power using the reformed gas obtained from the reformer, and A reformer and a container containing the solid oxide fuel cell, and the reformer is disposed at a position where the reformer receives heat radiation from the solid oxide fuel cell, from the anode of the solid oxide fuel cell An indirect internal reforming solid oxide fuel cell capable of combusting discharged anode off-gas in the vessel; liquid fuel vaporization supply means for supplying the reformer after vaporizing the liquid fuel; and gaseous fuel A method for starting an indirect internal reforming solid oxide fuel cell system having a gaseous fuel supply means for supplying to the reformer,
a) Gas fuel is introduced into the solid oxide fuel cell through the reformer, the anode off gas is combusted in the vessel, and the reformer and the solid oxide fuel cell are burned using the combustion heat of the anode off gas. Heating the step,
b) When the temperature of the reforming catalyst layer becomes equal to or higher than the partial oxidation reforming reaction start temperature of the gaseous fuel, the gaseous fuel is partially oxidized and reformed in the reformer and then introduced into the solid oxide fuel cell. Combusting offgas in the vessel and heating the reformer and the solid oxide fuel cell using partial oxidation reforming reaction heat and anode offgas combustion heat;
c) When the temperature of the reforming catalyst layer reaches 550 ° C. or higher, the fuel supplied to the reformer is switched from the gaseous fuel to the vaporized liquid fuel, and the vaporized liquid fuel is partially oxidized and reformed before solid oxidation. The step of introducing the fuel into the physical fuel cell, combusting the anode off gas in the vessel, and heating the reformer and the solid oxide fuel cell using the heat of partial oxidation reforming reaction and the combustion heat of the anode off gas. A method for starting up an indirect internal reforming solid oxide fuel cell system in order. Furthermore, after said step c)
d) The liquid fuel vaporized in the reformer is steam reformed without partial oxidation reforming and then introduced into the solid oxide fuel cell, the anode off gas is burned in the vessel, and the combustion heat of the anode off gas reformer and method of claim 1, further comprising the step of heating the solid oxide fuel cell using the.

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