JP4612322B2 - Fuel gas production system and operation method thereof - Google Patents

Description

  The present invention relates to a fuel gas production system that generates hydrogen-rich fuel gas by reforming a hydrogen-containing fuel, and an operation method thereof.

  For example, a hydrogen-containing gas (reformed gas) is obtained by reforming a hydrocarbon fuel such as natural gas or an alcohol such as methanol to obtain a hydrogen-containing gas (reformed gas), and this hydrogen-containing gas is supplied to a fuel cell or the like as a fuel gas A production apparatus (fuel gas production system) is employed.

  In this type of hydrogen production apparatus, a hydrocarbon fuel such as natural gas or city gas is steam reformed to produce a hydrogen-containing gas that is a high-concentration hydrogen-rich gas, and through the PSA (Pressure Swing Adsorption) apparatus, High purity hydrogen is separated from the hydrogen-containing gas by pressure adsorption.

Specifically, the steam-reformed hydrogen-containing gas contains unnecessary substances such as CO, CO ₂ , H ₂ O, and CH ₄ in addition to the main component hydrogen gas. Therefore, the PSA apparatus is equipped with, for example, three adsorption towers, and high purity hydrogen is produced by causing each adsorption tower to perform a cyclic operation including adsorption, decompression, pressure equalization, brokedown, and purge steps. On the other hand, other components are discharged as off-gas (exhaust gas).

  The off-gas released from the PSA device is usually temporarily stored in an off-gas tank and supplied as a combustion fuel to a burner (combustion device) of a reformer for hydrogen production. At that time, off gas is intermittently supplied from the respective adsorption towers to the off gas tank, which causes pressure fluctuations in the off gas tank. However, the pressure fluctuation in the off-gas tank affects the operation of the reformer, the PSA device, and the like and also changes the combustion state of the burner. Therefore, it is necessary to suppress the pressure fluctuation.

  Therefore, for example, a method for controlling the off-gas pressure disclosed in Patent Document 1 is known. In this control method, as shown in FIG. 6, an offgas tank 2 is arranged in the middle of an offgas passage 1 communicating from the PSA device to the reformer combustion section. A pressure gauge 3 is arranged at the outlet side conduit of the off gas tank 2, and an off gas flow rate adjusting valve 4 whose opening degree can be changed by the actual pressure measured by the pressure gauge 3 is downstream of the pressure gauge 3. Is provided. A flow meter 5 is disposed downstream of the off gas flow rate adjusting valve 4.

  Therefore, with the minimum pressure of the offgas tank 2 as a reference, the opening degree of the offgas flow rate adjusting valve 4 disposed in the outlet side conduit of the offgas tank 2 is increased or decreased with respect to its full opening in a predetermined minute increment. Thereby, the pressure fluctuation of the off gas from the off gas tank 2 is suppressed, and the off gas can be stably supplied to the burner of the reformer combustion section.

Japanese Patent Laid-Open No. 2001-10806 (FIG. 2)

  However, the offgas tank 2 needs to be several times larger than the PSA apparatus in order to effectively exhibit its function, and the entire hydrogen production apparatus is considerably increased in size. In particular, in a domestic hydrogen production apparatus, there is a problem that the installation space is small and it is difficult to adopt a hydrogen production apparatus provided with the large off-gas tank 2.

  The present invention solves this type of problem, and eliminates the need for an offgas tank, and with a simple configuration, a fuel gas production system capable of well responding to fluctuations in the amount of offgas supplied to the combustion device And an operation method thereof.

  The present invention relates to a reformer that reforms hydrogen-containing fuel to obtain a reformed gas, a PSA device that purifies hydrogen-rich fuel gas by removing unnecessary substances from the reformed gas, and a PSA device. A combustion apparatus that combusts exhaust gas; an air supply apparatus that includes at least a compressor that supplies air to the combustion apparatus; and an air amount adjustment mechanism downstream of the compressor; and at least an air amount that is necessary for the combustion apparatus For controlling the compressor so as to supply air, and controlling the air amount adjusting mechanism so that the amount of air supplied to the combustion device varies in synchronization with fluctuations in the amount of exhaust gas from the PSA device Device.

  The air supply device includes a combustion air flow path for supplying combustion air to the combustion device, and a reforming air flow channel for supplying reforming air to the reforming device, and the control device includes the combustion air flow path. Controlling the compressor so as to supply more air than necessary for the apparatus and the reformer, and maintaining a constant flow rate or supply pressure of the reforming air supplied to the reformer, It is preferable to control the air amount adjusting mechanism so that the amount of combustion air supplied to the combustion device fluctuates in synchronization with the fluctuation of the exhaust gas amount from the PSA device.

  Furthermore, the present invention provides a reformer that reforms a hydrogen-containing fuel to obtain a reformed gas, a PSA device that purifies hydrogen-rich fuel gas by removing unnecessary substances from the reformed gas, and the PSA device A method for operating a fuel gas production system, comprising: a combustion device that combusts exhaust gas from a fuel; and an air supply device that includes at least a compressor that supplies air to the combustion device and that has an air amount adjustment mechanism downstream of the compressor It is.

  Therefore, by controlling the compressor, at least air exceeding the amount of air necessary for the combustion device is supplied, and by controlling the air amount adjustment mechanism, it is synchronized with fluctuations in the exhaust gas amount from the PSA device. Thus, the amount of air supplied to the combustion device is varied.

  Furthermore, the air for reforming supplied to the reforming device under the action of the air amount adjusting mechanism while supplying air exceeding the air amount necessary for the combustion device and the reforming device under the action of the compressor. It is preferable to vary the amount of combustion air supplied to the combustion device in synchronism with the variation in the amount of exhaust gas from the PSA device while maintaining the supply pressure at a constant.

  In the present invention, the amount of air supplied to the combustion device is changed in synchronization with the change in the amount of exhaust gas from the PSA device. Therefore, when the supply amount of exhaust gas decreases due to the pulsation of the PSA device, the supply of air The amount is also reduced. For this reason, it is possible to prevent a decrease in the temperature of the combustion device due to a relative increase in the supply amount of combustion air with respect to the supply amount of exhaust gas, and it is favorable that unburned components are generated in this combustion device. It can be avoided. Thereby, unburned components are not directly discharged to the outside, and clean exhaust gas can be obtained reliably.

  Furthermore, it is possible not to change the output of the compressor in response to the fluctuation of the exhaust gas amount. According to this, the endurance load of the compressor, for example, the compressor does not increase, and it is possible to prevent excessive power consumption when the output increases, which is economical.

  FIG. 1 is a schematic configuration diagram of a household fuel gas production system (fuel gas production system) 10 for carrying out an operation method according to a first embodiment of the present invention.

  The household fuel gas production system 10 includes an evaporation device 16 that has a combustion catalyst (combustion device) 14 and evaporates the reforming fuel. A reformer 18 for reforming reforming fuel to obtain a reformed gas is disposed downstream of the evaporator 16, and between the evaporator 16 and the reformer 18, the reformer 18 is disposed between the evaporator 16 and the reformer 18. A heat exchanging device 20 that heats the evaporated reforming fuel by exchanging heat with the reformed gas is interposed. A cooling device 22 that cools the heat-exchanged reformed gas is disposed downstream of the heat exchange device 20, and the cooled reformed gas is mixed with gas components and moisture downstream of the cooling device 22. A gas-liquid separation device 24 that separates the two is disposed.

  A PSA compressor 28 that compresses the reformed gas from which water has been separated and supplies the reformed gas to the PSA device 26 is disposed downstream of the gas-liquid separator 24. As shown in FIG. 2, the PSA device 26 constitutes, for example, a three-column pressure swing adsorption device that can be connected to the PSA compressor 28, and includes adsorption columns 30, 32, and 34. Valves 36 a to 36 c are provided at one ends of the entrances and exits of the adsorption towers 30 to 34, and the adsorption towers 30 to 34 are connected to the off-gas flow path 38 via the valves 36 a to 36 c. The off gas passage 38 is connected to the combustion catalyst 14, and a valve 40 is disposed in the middle of the off gas passage 38.

  Valves 42 a to 42 c are provided at the other ends of the entrances and exits of the adsorption towers 30 to 34, and the adsorption towers 30 to 34 can communicate with the tank 46 via the valve 44. As shown in FIG. 1, the tank 46 communicates with an off gas passage 38 through a pipe 48, and an air supply device 50 is connected to the off gas passage 38.

  The air supply device 50 includes a compressor, for example, an air compressor 52, which serves as both a combustion air supply mechanism and a reforming air supply mechanism. A combustion air passage 54 and a reforming air passage 56 are connected to the air compressor 52. The combustion air flow path 54 communicates with the off gas flow path 38 to supply combustion air to the combustion catalyst 14, and a pressure regulating valve (air amount adjusting mechanism) 57 is connected to the combustion air flow path 54. Is disposed. A pressure adjusting valve (air amount adjusting mechanism) 58 and an injector 60 are disposed in the reforming air flow path 56, and the reforming air is supplied to the evaporator 16 together with the reforming fuel and water.

  The air supply device 50 includes a supply pressure control regulator (air amount adjustment mechanism) 59 disposed downstream of the air compressor 52, and a pressure detection sensor 61 is disposed in the vicinity of the supply pressure control regulator 59.

  The tank 46 can communicate with a fuel gas flow path (not shown) in the polymer electrolyte fuel cell stack (PEFC) 64 via a valve 62 that performs flow rate adjustment or pressure adjustment, and a flow rate control valve 66 and The high pressure tank 70 can communicate with the high pressure tank 70. The high-pressure tank 70 can supply hydrogen to a fuel cell vehicle (FC vehicle) (not shown) via the hydrogen dispenser 72 by supplying hydrogen to the hydrogen dispenser 72. The fuel cell stack 64 is stationary and includes a hydrogen (fuel) circulation system.

  The home fuel gas production system 10 communicates and controls with each auxiliary machine, and in the first embodiment, in particular, the amount of air required for the combustion catalyst 14 and the reforming device 18 (at least the combustion catalyst 14) exceeds the amount of air. While controlling the air compressor 52 to supply air and maintaining a constant supply pressure of the reforming air supplied to the reforming device 18, in synchronism with fluctuations in the amount of exhaust gas from the PSA device 26, For example, a control ECU (Electronic Control Unit) 74 is provided as a control unit that controls the pressure regulating valves 57 and 58 so that the amount of combustion air supplied to the combustion catalyst 14 varies. When using a pressure regulating valve (not shown) instead of the supply pressure control regulator 59, the control ECU 74 controls the pressure regulating valve.

  The operation of the domestic fuel gas production system 10 configured as described above will be described below in relation to the fuel gas generation method.

  In the household fuel gas production system 10, the start signal of the control ECU 74 is turned on, and the air compressor 52 is started to operate at a predetermined rotational speed. For this reason, the combustion air and the reforming air are supplied to the combustion catalyst 14 and the evaporator 16 via the combustion air passage 54 and the reforming air passage 56, respectively.

  In the reforming air flow path 56, the pressure difference of the reforming air sent from the air compressor 52 is reduced (amplitude reduced) by the pressure adjusting valve 58, and further adjusted to a substantially constant pressure via the injector 60. After that, it is sent to the evaporator 16.

  In addition to the above reforming air, reforming fuel and water are supplied to the evaporator 16, while the combustion catalyst 14 is supplied with combustion air and hydrogen from a tank 46 as necessary to perform combustion. And the reforming fuel evaporates. The evaporated reforming fuel is supplied to the reforming device 18 through the heat exchange device 20, and is heated by exchanging heat with the reformed gas discharged from the reforming device 18. .

In the reformer 18, for example, CH ₄ + 2O ₂ → CO ₂ + 2H ₂ O (exothermic reaction), which is an oxidation reaction, and fuel reforming reaction by reforming fuel, for example, methane, oxygen in the air, and water vapor. A certain CH ₄ + 2H ₂ O → CO ₂ + 4H ₂ (endothermic reaction) is performed simultaneously (autothermal method).

  The reformed gas supplied from the reformer 18 to the heat exchange device 20 is heat-exchanged with the reforming fuel, then cooled by the cooling device 22 and supplied to the gas-liquid separator 24. . The reformed gas from which moisture has been separated by the gas-liquid separation device 24 is compressed by the PSA compressor 28 and supplied to the PSA device 26.

  In the PSA device 26, the reformed gas is selectively supplied to the adsorption towers 30, 32 and 34 as shown in FIG. At that time, in the PSA device 26, for example, an adsorption process is performed in the adsorption tower 30, a decompression process in the adsorption tower 32, and a purge process in the adsorption tower 34. For this reason, components other than hydrogen are adsorbed in the adsorption tower 30, and fuel gas containing high-concentration hydrogen (hydrogen-rich) is supplied to the tank 46.

  Further, after the adsorption process in the adsorption tower 30, the pressure equalization process in the adsorption tower 32, and the pressure equalization process in the adsorption tower 34, the adsorption process in the adsorption tower 30, the blow-down process in the adsorption tower 32, and the adsorption tower 34 are performed. A boosting step is performed. Therefore, off-gas generated by the blow-down process in the adsorption tower 30 is supplied to the off-gas flow path 38 under the opening action of the valve 36 a and is supplied to the combustion catalyst 14 through the valve 40.

  As described above, in the adsorption towers 30, 32, and 34, the adsorption process, the pressure reduction process, the purge process, the pressure equalization process, and the blow-down process are selectively performed, so that the hydrogen-rich fuel gas is supplied to the tank 46. The On the other hand, off-gas which is exhaust gas is continuously supplied to the combustion catalyst 14 via the off-gas flow path 38 under the opening and closing action of the valves 36a to 36c.

  In this case, in the first embodiment, as shown in FIG. 3, the flow rate of the reforming air necessary for the reformer 18 is substantially constant, whereas the combustion supplied to the combustion catalyst 14 is performed. The flow rate of the working air fluctuates corresponding to the amount of offgas release that increases or decreases due to the pressure pulsation of the PSA device 26 (see the required flow rate 80).

  Therefore, the control ECU 74 controls the air compressor 52 that constitutes the air supply device 50, and supplies air having a required flow rate of 80 or more for reforming air and combustion air by output fluctuation (or constant output) control ( Air compressor discharge flow rate 82).

  Further, the control ECU 74 keeps the pressure adjustment valve 58 at a constant opening and maintains the supply pressure of the reforming air supplied from the evaporation device 16 to the reforming device 18 while maintaining a constant pressure from the PSA device 26. The pressure regulating valve 57 is adjusted in synchronization with the fluctuation of the offgas release amount. At this time, if surplus pressure is generated with fluctuations in the supply pressure of the combustion air, the supply pressure control regulator 59 releases air for the surplus pressure to the outside. Note that excess air released from the supply pressure control regulator 59 is released to the atmosphere or used effectively in the system.

  As described above, in the first embodiment, the pressure adjustment valve 57 is controlled in synchronization with the amount of off-gas released that increases or decreases due to the pressure pulsation of the PSA device 26 to increase or decrease the supply amount of combustion air. Therefore, when the amount of off-gas supplied to the combustion catalyst 14 decreases, the supply amount of combustion air decreases, and the temperature of the combustion catalyst 14 can be prevented from decreasing.

  This effectively prevents off-gas unburned components from being generated in the combustion catalyst 14, and this unburned portion is not directly disposed outside, making it possible to reliably obtain clean exhaust gas. Become.

  Furthermore, in the first embodiment, the air compressor 52 is always operated at an output exceeding the required air flow rate, and the output does not fluctuate in response to the increase / decrease in the amount of offgas emission from the PSA device 26. Is possible. In this case, the endurance load of the air compressor 52 does not increase, and it is possible to prevent excessive power consumption when the output is increased, thereby obtaining an economical effect.

  Furthermore, when the pressure adjustment valve 57 is controlled to increase or decrease the supply amount of combustion air in response to fluctuations in the offgas release amount from the PSA device 26, excess air is externally supplied by the supply pressure control regulator 59. Is not released into the reforming air flow path 56.

  Thereby, the supply pressure of the reforming air detected by the pressure detection sensor 61 is always maintained at a constant pressure, and the flow rate of the reforming air supplied to the reforming device 18 does not fluctuate. That is, as shown in FIG. 4, the supply pressure of the reforming air is maintained at a substantially constant pressure, and the catalyst temperature of the reformer 18 does not fluctuate, so that a stable reformed gas can be obtained reliably. There is an advantage that you can.

  FIG. 5 is a schematic configuration diagram of a household fuel gas production system (fuel gas production system) 90 for carrying out the operating method according to the second embodiment of the present invention. In addition, the same referential mark is attached | subjected to the component same as the household fuel gas manufacturing system 10 which concerns on 1st Embodiment, and the detailed description is abbreviate | omitted.

  The domestic fuel gas production system 90 includes an air supply device 92, and a three-way control valve 94 is disposed in the combustion air flow path 54 constituting the air supply device 92. The air supply device 92 does not use the supply pressure control regulator 59 that constitutes the air supply device 50 of the first embodiment.

  In the second embodiment configured as described above, by controlling the three-way control valve 94, the flow rate of the combustion air supplied to the combustion catalyst 14 is increased or decreased. The excess oxygen can be increased or decreased in response to the above, and excess oxygen can be released to the outside.

  For this reason, when the amount of off-gas supplied to the combustion catalyst 14 decreases, the supply amount of combustion air can be reduced, and the supply amount of reforming air supplied to the reformer 18 can be reduced. The same effect as the first embodiment can be obtained, for example, it can be maintained constant.

  In the second embodiment, the three-way control valve 94 is disposed in the combustion air flow path 54, but the three-way control valve is substituted for the reforming air flow path 56 in place of the pressure adjustment valve 58. 94 may be provided.

  In the first and second embodiments, the combustion catalyst 14 is used as the combustion device. However, the present invention is not limited to this, and various heating means such as a burner may be used.

It is a schematic block diagram of the domestic fuel gas manufacturing system for enforcing the operating method concerning a 1st embodiment of the present invention. It is schematic structure explanatory drawing of the PSA apparatus which comprises the said household fuel gas manufacturing system. It is explanatory drawing of the required flow volume of reforming air and combustion air, and the discharge flow volume of an air compressor. FIG. 6 is a relationship diagram of the supply pressure of reforming air, the catalyst temperature of the reformer, the supply gas temperature of the reformer, and the reformer internal pressure. It is a schematic block diagram of the household fuel gas manufacturing system for enforcing the operating method which concerns on the 2nd Embodiment of this invention. It is explanatory drawing of the control method of the off-gas pressure of patent document 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 90 ... Domestic fuel gas production system 14 ... Combustion catalyst 16 ... Evaporator 18 ... Reformer 20 ... Heat exchanger 22 ... Cooling device 24 ... Gas-liquid separator 26 ... PSA device 28 ... PSA compressor 30, 32, 34 ... Adsorption towers 36a to 36c, 42a to 42c, 44, 62 ... Valve 38 ... Off gas flow path 40, 57, 58 ... Pressure regulating valve 46 ... Tank 50, 92 ... Air supply device 52 ... Air compressor 54 ... Combustion air Flow path 56 ... Reforming air flow path 59 ... Supply pressure control regulator 60 ... Injector 61 ... Pressure detection sensor 64 ... Fuel cell stack 70 ... High pressure tank 74 ... Control ECU 94 ... Three-way control valve

Claims (4)

A reformer for reforming hydrogen-containing fuel to obtain reformed gas;
A PSA device for purifying hydrogen-rich fuel gas by removing unnecessary substances from the reformed gas;
A combustion device for combusting exhaust gas from the PSA device;
An air supply device having at least a compressor for supplying air to the combustion device, and an air amount adjusting mechanism downstream of the compressor;
The compressor is controlled so as to supply at least air necessary for the combustion device, and the amount of air supplied to the combustion device fluctuates in synchronization with fluctuations in the amount of exhaust gas from the PSA device. A control device for controlling the air amount adjusting mechanism;
A fuel gas production system comprising: The fuel gas production system according to claim 1, wherein the air supply device includes a combustion air flow path for supplying combustion air to the combustion device;
A reforming air flow path for supplying reforming air to the reforming device;
With
The control device controls the compressor so as to supply air exceeding the amount of air necessary for the combustion device and the reforming device, and the flow rate or supply pressure of the reforming air supplied to the reforming device. The air amount adjusting mechanism is controlled so that the amount of combustion air supplied to the combustion device fluctuates in synchronism with fluctuations in the amount of exhaust gas from the PSA device while maintaining the fuel pressure constant. Gas production system. A reformer that reforms a hydrogen-containing fuel to obtain a reformed gas, a PSA device that removes unnecessary substances from the reformed gas to purify a hydrogen-rich fuel gas, and burns exhaust gas from the PSA device An operating method of a fuel gas production system, comprising: a combustion device; and an air supply device that includes a compressor that supplies air to at least the combustion device, and an air amount adjusting mechanism downstream of the compressor,
Supplying at least air more than the amount of air necessary for the combustion device by controlling the compressor; and
Varying the amount of air supplied to the combustion device in synchronism with fluctuations in the amount of exhaust gas from the PSA device by controlling the air amount adjustment mechanism;
A method for operating a fuel gas production system, comprising: 4. The operation method according to claim 3, wherein air exceeding the amount of air necessary for the combustion device and the reforming device is supplied under the action of the compressor, and the reforming is performed under the action of the air amount adjustment mechanism. The amount of combustion air supplied to the combustion device is changed in synchronization with the change in the amount of exhaust gas from the PSA device while maintaining the flow rate or supply pressure of the reforming air supplied to the quality device constant. A method for operating a fuel gas production system.

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