JP2008226602A - Temperature control system of reformer in fuel cell device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lower CO concentration in a reformed gas to a value below a predetermined value without degrading desulfurization efficiency even when temperature variation of an ambient environment due to season or temporal change due to an individual difference of operation of a system occurs, to prevent voltage drop of a fuel cell from being caused, to improve reliability of the system, to improve durability of a catalyst of a low-temperature reactor, and to improve durability of the system. <P>SOLUTION: The fuel cell device is provided with: a fuel reform part 5 having a desulfurizer 1, a reformer 2, a CO converter 3, and a CO remover 4 on this order from the upstream side to produce hydrogen from a fuel gas; and a fuel cell part 6 generating power by reacting the hydrogen produced by the fuel reform part 5 with oxygen; and is structured to exchange heat between the fuel gas before being supplied to the desulfurizer 1 and the reformed gas on the downstream side of the reformer 2. By detecting the temperature of the desulfurizer 1 or/and the temperature of the CO converter 3, the temperature of the reformer 2 is controlled based on the detected temperature(s). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a temperature control system for a reformer in a fuel cell device.

  Conventionally, a fuel reformer that has a desulfurizer, a reformer, a CO converter, and a CO remover in order from the upstream side to produce hydrogen from fuel gas, and oxygen to the hydrogen produced by the fuel reformer Patent application title: FUEL CELL DEVICE, comprising a fuel cell unit that reacts to generate electricity, and configured to exchange heat between the fuel gas supplied to the desulfurizer and the reformed gas sent from the CO remover to the anode of the fuel cell unit It is known from Document 1 and the like.

In the conventional fuel cell apparatus as described above, the temperature of the reformer is generally set to a certain value. However, the temperature of other low-temperature reactors (desulfurizers and CO converters) changes due to changes in the temperature of the surrounding environment due to the season, changes in the system due to differences in the system, and changes over time, and the original performance cannot be achieved. If the temperature of the low-temperature reactor deviates from the optimum temperature, the desulfurization efficiency is reduced, the CO concentration in the reformed gas is increased, the voltage of the fuel cell is lowered, and the reliability of the system is lowered. is there. Moreover, when the catalyst temperature of a low temperature reactor is high, there exists a problem that durability of a catalyst itself is impaired and durability of a system is reduced.
JP 2002-25588 A

  The present invention has been invented in view of the above-mentioned conventional problems, and even if there is a change in the temperature of the surrounding environment due to the season, a difference in system solids or a change over time due to operation, the desulfurization efficiency does not decrease, and the improvement is made. The CO concentration in the gaseous gas can be lowered to a predetermined value or less, so that the fuel cell voltage is not lowered, the system reliability is improved, and the durability of the catalyst in the low temperature reactor is improved. It is an object of the present invention to provide a temperature control system for a reformer in a fuel cell device that can improve the durability of the system.

  In order to solve the above problems, a reformer temperature control system in a fuel cell apparatus according to the present invention includes a desulfurizer 1, a reformer 2, a CO converter 3, and a CO remover 4 in order from the upstream side. The fuel before being supplied to the desulfurizer 1 is provided with a fuel reforming section 5 that produces hydrogen from the fuel gas, and a fuel cell section 6 that generates electricity by reacting oxygen with the hydrogen produced by the fuel reforming section 5. In the fuel cell device configured to exchange heat between the gas and the reformed gas downstream of the reformer 2, the temperature of the desulfurizer 1 and / or the CO converter 3 is detected and detected. The temperature of the reformer 2 is controlled based on the temperature.

  By adopting such a configuration, when the temperature of the desulfurizer 1 or / and the temperature of the CO converter 3 deviates from the preset optimum temperature range, the temperature of the reformer 2 is lowered or raised. The temperature of the low-temperature reactor (desulfurizer 1 or CO converter 3) can be adjusted to the optimum temperature range, the desulfurization efficiency does not decrease, and the CO concentration in the reformed gas is reduced to a predetermined concentration or less. In addition, the durability of the catalyst itself can be improved by preventing the catalyst temperature of the low temperature reactor from becoming higher than a predetermined temperature.

  In the present invention, the temperature of the reformer is controlled based on the detected temperature by detecting the desulfurizer temperature or / and the CO converter temperature. Even if there is a change over time, the desulfurizer and CO converter can be brought to the original optimum temperature, the desulfurization efficiency is not lowered, and the CO concentration in the reformed gas can be lowered to a predetermined value or less. In addition, the fuel cell voltage is not reduced, the system reliability is improved, and the catalyst temperature of the low temperature reactor is prevented from becoming higher than a predetermined temperature, thereby improving the durability of the catalyst. And the durability of the system can be improved.

  Hereinafter, the present invention will be described based on embodiments shown in the accompanying drawings.

  The fuel cell device of the present invention comprises a fuel reforming unit 5 and a fuel cell unit 6 as shown in the schematic configuration diagram of FIG.

  The fuel reforming unit 5 is for producing hydrogen from a fuel gas (process gas) such as city gas. The desulfurizer 1, the reformer 2, the CO converter 3, and the CO remover 4 are sequentially installed from the upstream side. It has.

  The desulfurizer 1 is for desulfurizing fuel gas such as city gas. The fuel gas desulfurized by the desulfurizer 1 is mixed with water vapor generated by the reforming steam generator 8, and the fuel gas desulfurized and mixed with water vapor is sent to the reformer 2.

  The reformer 2 has a reformer burner 9, and by burning the reformer burner 9, the fuel gas in which the city gas is mixed with steam as described above is steam-modified while the reforming catalyst is heated. The gas reformed by the reformer 2 is CO-converted by the CO converter 3, and the CO-converted gas that has been CO-converted by the CO converter 3 is the CO remover. 4, CO selective oxidation is performed by the CO remover 4 to remove carbon monoxide, and a hydrogen-rich reformed gas having a low CO concentration is produced.

  The fuel cell unit 6 is formed by stacking a large number of cells each having a layer of an anode (fuel electrode) 12, an electrolyte 13, and a cathode (air electrode) 14 via separators (not shown). It is. Here, the anode 12 and the cathode 14 have a structure that allows gas to pass through, and as shown in FIG. 2, the hydrogen-rich reformed gas produced by the fuel reforming unit 5, that is, hydrogen is supplied to the anode 12, and the cathode By supplying air from the blower to the hydrogen 14, hydrogen is separated into electrons by the action of the catalyst in the anode 12 to become hydrogen ions, and the electrolyte 13 has a property that only ions pass through. The hydrogen ions that have gone out and moved in the electrolyte react with oxygen sent to the cathode 14 on the opposite side and electrons returned from the outside through an electric wire (external circuit) to become water. Since the electricity generated in this way is direct current, it is converted to alternating current by the direct current alternating current converter 10.

  Since the anode off-gas exhausted from the anode 12 of the fuel cell unit 6 contains residual hydrogen, it is sent to the reformer burner 9 of the reformer 2 via the anode off-gas line 16 and used as fuel gas. The reformer burner 9 is also supplied with the city gas and air, and the anode off-gas containing residual hydrogen, city gas and air are mixed and burned in the reformer burner 9. As described above, the fuel gas obtained by mixing the city gas with water vapor is reformed while heating the reforming catalyst. The combustion exhaust gas from the reformer burner 9 is discharged via the combustion exhaust gas exhaust line 17.

  Cathode off-gas discharged from the cathode 14 of the fuel cell unit 6 is discharged via a cathode off-gas conduit 18.

  The fuel cell unit 6 is cooled by battery cooling water circulating through the battery cooling water circulation pipe 19.

  Here, in the present invention, heat is exchanged between the fuel gas before being supplied to the desulfurizer 1 and the reformed gas on the downstream side of the reformer 2 in the heat exchanging unit 21. In the desulfurizer 1, the supplied fuel gas is set to a temperature suitable for a desulfurization reaction for removing sulfur compounds in the odorant by a desulfurization catalyst.

  In the embodiment shown in the figure, heat exchange is performed between the reformed gas sent from the CO remover 4 downstream of the reformer 2 to the anode 12 of the fuel cell unit 6 and the fuel gas before being supplied to the desulfurizer 1. Heat is exchanged in the section 21 to heat the fuel gas.

  The desulfurizer 1 and the CO converter 3 are low-temperature reactors that react at a lower temperature than the reformer 2, and the desulfurizer 1 and the CO converter 3 that are the low-temperature reactors are provided with a temperature sensor 23. As the temperature sensor 23, there are a temperature sensor 23a for detecting the temperature in the desulfurizer 1, and a temperature sensor 23b for detecting the temperature in the CO converter 3 (for example, the outlet temperature of the CO converter 3), which are shown in FIG. In the embodiment, the temperature sensors 23a and 23b are provided in the desulfurizer 1 and the CO converter 3, respectively. However, when the temperature sensor 23a is provided only in the desulfurizer 1, or only in the CO converter 3 is a temperature. The case where the sensor 23b is provided may be sufficient.

  Based on the detected temperature in the desulfurizer 1 and / or the detected temperature in the CO converter 3 by the temperature sensor 23, the controller 24 controls the reformer burner 9 to control the temperature of the reformer 2. It is supposed to be.

  That is, the temperature range suitable for the desulfurization reaction by the desulfurization catalyst in the desulfurizer 1 and the temperature range suitable for the shift reaction for the CO conversion in the CO converter 3 are registered in the controller 24 in advance, and the temperature sensor The temperature in the desulfurizer 1 or / and the temperature in the CO converter 3 detected by 23 is a temperature range suitable for the previously registered desulfurization reaction or / and a temperature range suitable for a shift reaction for CO conversion. This is done by adjusting the flow rate of the city gas supplied to the reformer burner 9 so that it does not come off. In the embodiment, the flow rate of the city gas is adjusted by adjusting the adjustment valve 27 provided in the gas supply pipe 26 that supplies the city gas to the reformer burner 9, and the temperature of the reformer 2 is controlled. Yes.

  By the way, when the fuel cell device is operated in summer or in a place where the atmospheric temperature is high, the temperature of the desulfurizer 1 and the CO converter 3 which are low-temperature reactors is used to bring out the performance of the original desulfurizer 1 and the CO converter 3. It becomes higher than the temperature (that is, outside the temperature range suitable for the desulfurization reaction registered in advance and the temperature range suitable for the shift reaction for CO conversion). In such a case, the temperature of the reformer 2 is lowered by adjusting the regulating valve 27 so as to reduce the flow rate of the city gas, thereby preliminarily registering the temperatures of the desulfurizer 1 and the CO converter 3. Therefore, the temperature range is suitable for the desulfurization reaction and the temperature range suitable for the shift reaction for CO conversion. Conversely, when the fuel cell device is operated in winter or in a place where the ambient temperature is low, the temperature of the desulfurizer 1 and the CO converter 3 that are low-temperature reactors brings out the performance of the original desulfurizer 1 and the CO converter 3. (That is, out of the temperature range suitable for the desulfurization reaction registered in advance and the temperature range suitable for the shift reaction for CO conversion). In such a case, the temperature of the reformer 2 is raised by adjusting the regulating valve 27 so as to increase the flow rate of the city gas, thereby preliminarily registering the temperatures of the desulfurizer 1 and the CO converter 3. Therefore, the temperature range is suitable for the desulfurization reaction and the temperature range suitable for the shift reaction for CO conversion.

  In this way, the temperature of the desulfurizer 1 and the CO converter 3 that are low-temperature reactors is kept at an appropriate temperature by a simple method, and the desulfurizer 1 that is a reactor is maintained regardless of the atmospheric temperature and seasonal variations at the installation site. The original performance of the CO transformer 3 can be reliably extracted, and the reliability and durability of the system can be improved.

  In the above example, the temperature of the reformer 2 is controlled by controlling the amount of city gas supplied to the reformer burner 9, but the temperature control of the reformer 2 can be controlled by controlling the amount of process gas. Alternatively, the temperature of the reformer 2 may be controlled by controlling both the amount of city gas supplied to the reformer burner 9 and the amount of process gas.

  Hereinafter, an example of the present invention will be specifically described.

  Conventionally, in the fuel cell device, the temperature of the desulfurizer 1 and the CO converter 3 is designed so as to become a temperature that depends on the outlet temperature of the reformer 2 (the temperature of the reformed gas at the outlet). In the conventional control, when the outside air temperature of the system changes by 40 ° C., the temperature of the desulfurizer 1 and the CO converter 3 which are low temperature reactors changes by about 30 ° C. For example, the outlet temperature of the reformer 2 is normally set to around 650 ° C. Below this set temperature of the reformer 2, the temperature of the desulfurizer 1 in winter is 280 ° C., and the outlet temperature of the CO converter 3 is 180 ° C. It is possible to operate the system with a good temperature distribution.

  However, if summer operation is carried out with the outlet temperature of the reformer 2, the temperature of the desulfurizer 1 becomes 310 ° C, the outlet temperature of the CO converter 3 becomes about 210 ° C, and the catalyst of the desulfurizer 1 ensures durability. As a result, the CO converter 3 exceeds the temperature (200 ° C.) for ensuring the CO concentration of 0.5% or less at the outlet of the CO converter 3.

  Therefore, in the present invention, when the temperature of the desulfurizer 1 is 300 ° C. or the outlet temperature of the CO converter 3 exceeds 200 ° C., the outlet temperature setting of the reformer 2 is controlled to be lowered by 10 ° C. .

  Conversely, when the temperature of the desulfurizer 1 is 260 ° C. or the outlet temperature of the CO converter 3 is lower than 160 ° C., the outlet temperature setting of the reformer 2 is controlled to be raised by 10 ° C.

It is a schematic block diagram of the fuel cell apparatus of this invention. It is a schematic explanatory drawing same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Desulfurizer 2 Reformer 3 CO converter 4 CO remover 5 Fuel reforming part 6 Fuel cell part

Claims (1)

In order from the upstream side, there are a desulfurizer, a reformer, a CO converter, and a CO remover. A fuel reformer that produces hydrogen from fuel gas, and oxygen reacted with the hydrogen produced in the fuel reformer A fuel cell device comprising a fuel cell unit for generating electricity and configured to exchange heat between a fuel gas before being supplied to a desulfurizer and a reformed gas downstream from the reformer. A temperature control system for a reformer in a fuel cell device, wherein the temperature of the reformer is detected based on the detected temperature or / and the CO transformer temperature.

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