JP2005289704A - System for producing fuel gas and method for stopping the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent the excess temperature rise in a combustion unit by a simple constitution and control without using an off-gas tank. <P>SOLUTION: When a PSA (pressure swing adsorption) unit 42 is stopped, the off-gas discharged from the PSA unit 42 is charged into a combustor 20 and burnt. Then, after the discharge operation of the off-gas has satisfied a prescribed conditions, the residual gas remaining at the upstream side of the PSA unit 42, that is to say, in a reformed gas feeding passage 40 is purged to the combustor 20 from an air feeding passage 36 for discharging the off-gas through a first a branch flow passage 46a and a second branch flow passage 46b, and burnt. Accordingly, the off-gas discharged from the PSA unit 42 and the purge gas purged from the reformed gas feeding passage 40 are controlled by shifting timing being charged to the combustor 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel gas production system that generates hydrogen-rich fuel gas by reforming a hydrogen-containing fuel and a method for stopping the fuel gas production system.

  For example, a hydrocarbon fuel such as natural gas or a hydrogen-containing fuel containing alcohol such as methanol is reformed to generate a hydrogen-containing gas (reformed gas), and this hydrogen-containing gas is supplied as a fuel gas to a fuel cell or the like. Hydrogen production equipment (fuel gas production system) is adopted.

  For example, as shown in FIG. 8, a hydrogen production apparatus disclosed in Patent Document 1 is a hydrodesulfurization unit 2 in which a fuel such as city gas is supplied from a compressor 1, and steam reforms the fuel after desulfurization. A steam reforming unit 3 that produces a high-concentration hydrogen-containing gas (hydrogen-rich gas), a catalyst combustion unit 4 that is externally mounted around the steam reforming unit 3 and that catalytically burns hydrogen and oxygen in the air, the hydrogen A gas shift unit 5 that converts carbon monoxide in the contained gas into carbon dioxide and hydrogen, and a PSA (Pressure Swing Adsorption) unit 6 that separates high-purity hydrogen from the hydrogen-containing gas after gas shift by pressure adsorption are provided. .

  The PSA unit 6 includes a hydrogen storage tank 8 that temporarily stores high-purity hydrogen before being supplied to the polymer electrolyte fuel cell (PEFC) 7, and off-gas (exhaust gas) adsorbed and removed by the PSA unit 6. An off-gas holder 9 for temporary storage is connected. The off-gas holder 9 supplies off-gas to the catalytic combustion unit 4 as fuel for heating the steam reforming unit 3.

  In this case, the PSA unit 6 is provided with a plurality of adsorption towers filled with an adsorbent that selectively adsorbs components other than hydrogen under high pressure and desorbs under reduced pressure. Then, by causing each adsorption tower to perform a cyclic operation consisting of adsorption-desorption-substitution-pressure increase, high-purity hydrogen is taken out while other components are discharged as off-gas.

JP 2002-20102 A (FIG. 1)

  In the above hydrogen production apparatus, the off gas holder 9 needs to be several times larger than the PSA unit 6 in order to effectively exhibit its function, and the entire hydrogen production apparatus is considerably enlarged. In particular, in a domestic hydrogen production apparatus, the installation space is small and it is difficult to employ a hydrogen production apparatus equipped with an offgas holder 9, so a hydrogen production apparatus that does not use a large tank such as the offgas holder 9 is desired. ing.

  By the way, in the PSA unit 6, the stop state of each tower is unknown. For example, off gas may be released after the PSA unit 6 is stopped, while in the steam reforming unit 3 or from the steam reforming unit 3. Hydrogen rich gas remains in the path of the PSA unit 6. Normally, when the hydrogen production apparatus is stopped, the residual combustible gas in the path, for example, the above-described hydrogen rich gas is supplied to the catalyst combustion unit 4 by purge and burned.

  However, particularly in a configuration that does not use a large tank, when the PSA unit 6 is stopped, purging in the path and release of off-gas from the PSA unit 6 are performed simultaneously, and the catalytic combustion unit 4 has a purge gas ( There is a risk that an excessive amount of combustion gas including hydrogen-rich gas) and off-gas may be input. For this reason, there is a problem that the calorie content tends to be excessive with respect to the capacity of the catalyst combustion unit 4 and the catalyst combustion unit 4 is easily damaged.

  The present invention solves this type of problem, and a fuel gas production system that can reliably prevent an excessive temperature rise of a combustion apparatus with a simple configuration and control without using an off-gas tank, and It aims at providing the stop method.

  A fuel gas production system according to the present invention includes a reformer provided with a combustor while reforming a hydrogen-containing fuel to obtain a reformed gas, and a hydrogen-rich fuel gas by removing unnecessary substances from the reformed gas. A PSA apparatus for purifying the gas, an off-gas flow path connecting the exhaust gas outlet of the PSA apparatus and the combustor, a reformed gas supply path connected from the reformer to the reformed gas inlet of the PSA apparatus, and the combustion A purge gas flow path connecting the combustor, a timing at which exhaust gas is discharged from the PSA device to the combustor when the PSA device is stopped, and a gas remaining upstream of the PSA device is purged by the combustor. And a control device that performs control for shifting the timing.

  In addition, a reformed gas pressure feeding device for feeding the reformed gas obtained by the reforming device to the PSA device is provided, and one end of the purge gas flow path is connected between the reforming device and the reformed gas pressure feeding device. And a second branch channel whose other end is connected to the off-gas channel, one end connected between the reformed gas pumping device and the PSA device, and the other end connected to the off-gas channel. Preferably, the first and second branch flow paths are provided with first and second valves that can be opened and closed, respectively.

  Furthermore, the present invention provides a reformer provided with a combustor while reforming a hydrogen-containing fuel to obtain a reformed gas, and a PSA for purifying a hydrogen-rich fuel gas by removing unnecessary substances from the reformed gas. A combustor, an off-gas passage connecting the exhaust gas outlet of the PSA device and the combustor, and a reformed gas supply path connecting from the reformer to the reformed gas inlet of the PSA device And a purge method for stopping the fuel gas production system.

  Therefore, first, with the operation stop of the PSA apparatus, exhaust gas is discharged from the PSA apparatus to the combustor through the off-gas flow path. Next, after the exhaust gas release process satisfies a predetermined condition, the gas remaining on the upstream side of the PSA device is purged to the combustor through the purge gas flow path.

  In the present invention, the combustion gas including the exhaust gas and the purge gas released after the PSA device is stopped is not charged in a large amount at a time into the combustor. For this reason, the combustor does not have excessive calories, and the temperature of the combustor does not exceed the upper limit of the normal operation temperature. This eliminates the need for an off-gas tank and can effectively prevent damage to the combustor with a simple configuration and control.

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

  The home fuel gas production system 10 is modified to obtain hydrogen-rich gas (hereinafter referred to as reformed gas) by reforming a hydrogen-containing fuel, for example, hydrocarbon fuel such as methane or propane (hereinafter referred to as reformed fuel). And a refining unit 14 for purifying high-purity hydrogen gas (hereinafter referred to as fuel gas) from the hydrogen-rich gas, and a storage unit 16 for storing the fuel gas.

  The reforming unit 12 includes an evaporator 18 that evaporates the reforming fuel. A combustor (combustion catalyst) 20 is attached to the evaporator 18, and a reactor 22 that reforms reforming fuel to obtain a reformed gas is disposed downstream of the evaporator 18. . A cooler 24 that cools the reformed gas is disposed downstream of the reactor 22, and a gas that separates the cooled reformed gas into a gas component and moisture is disposed downstream of the cooler 24. A liquid separator 26 is provided.

  The reforming unit 12 is provided with an air supply mechanism 28. The air supply mechanism 28 includes an air compressor 30, and a reforming air supply path 32 and an off-gas discharge air supply path 36 are connected to the air compressor 30. The reforming air supply path 32 is connected to the evaporator 18, and the offgas discharge air supply path 36 is connected to the combustor 20 via a PSA device 42 described later. The reforming air supply path 32 and the off-gas discharge air supply path 36 can be connected to the air compressor 30 via valves 38a and 38b.

  A reformed gas pressure feeding device 41 is disposed downstream of the gas-liquid separator 26 via a reformed gas supply path 40, and the reformed gas pressure feeding device 41 modifies the PSA device 42 constituting the purification unit 14. A reformed gas from which moisture is separated is supplied to the PSA device 42 connected to the gas source. Connected to the reformed gas supply path 40 is a first branch flow path 46a that is a purge gas flow path that can be connected to the off-gas discharge air supply path 36 via a three-way valve (first valve) 44. A compressor 48 is provided downstream of the three-way valve 44.

  The reformed gas supply passage 40 is connected to a second branch passage 46 b that is a purge gas passage that can be connected to the off-gas discharge air supply passage 36 via a valve (second valve) 54.

  The PSA device 42 is, for example, a three-column pressure swing adsorption device that can be connected to the compressor 48 constituting the reformed gas pressure feeding device 41, and includes adsorption columns 60a, 60b, and 60c as shown in FIG. . Each adsorption tower 60a-60c is provided with pressure gauges 62a-62c for detecting the pressure in the tower. Valves 66a to 66c are disposed at one ends of the entrances and exits of the adsorption towers 60a to 60c, and the exhaust gas outlets of the adsorption towers 60a to 60c are connected to the off-gas flow path 68 via the valves 66a to 66c. . The off gas passage 68 is connected to the off gas discharge air supply passage 36, and a valve 70 is disposed in the off gas passage 68.

  Valves 72 a to 72 c are provided at the other ends of the entrances and exits of the adsorption towers 60 a to 60 c, and the adsorption towers 60 a to 60 c can communicate with the fuel gas path 76 via the valve 74. A compressor 78 is disposed in the fuel gas path 76, and the fuel gas path 76 is connected to a filling tank 82 constituting the storage unit 16 via a valve 80. A branch fuel gas path 84 is provided in the middle of the fuel gas path 76, and a power generation tank 88 is connected to the branch fuel gas path 84 via a valve 86.

  The filling tank 82 supplies fuel gas to a fuel cell vehicle (not shown), while the power generation tank 88 supplies fuel gas to the stationary fuel cell in order to generate electricity in the home fuel cell (not shown). Supply.

  The home fuel gas production system 10 communicates with and controls each auxiliary machine. In particular, in this embodiment, off-gas (exhaust gas) is released from the PSA device 42 to the combustor 20 when the PSA device 42 is stopped. For example, a control ECU (Electronic Control Unit) 90 is used as a control device that performs control to shift the timing at which the residual gas remaining on the upstream side of the PSA device 42 (purge gas) is purged by the combustor 20. Prepare.

  The operation of the household fuel gas production system 10 configured as described above will be described below.

  In the domestic fuel gas production system 10, the air compressor 30 is operated via the control ECU 90, and the reforming air and the offgas exhaust air are supplied to the reforming air supply path 32 and the offgas exhaust air supply path 36, respectively. Sent to.

  The reforming air supplied to the reforming air supply path 32 is supplied to the evaporator 18, and the evaporator 18 is supplied with reforming fuel such as natural gas and water, for example. . On the other hand, the combustor 20 is supplied with combustion air and, if necessary, hydrogen or the like and burned, and the evaporator 18 evaporates the reforming fuel and water.

The evaporated reforming fuel is sent to the reactor 22. In this reactor 22, for example, CH ₄ + 2O ₂ → CO ₂ + 2H ₂ O (exothermic reaction) and fuel reforming reaction are performed 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).

  As described above, the reformed gas reformed by the reactor 22 is cooled by the cooler 24 and then supplied to the gas-liquid separator 26. The reformed gas from which moisture has been separated by the gas-liquid separator 26 is compressed by the compressor 48 and selectively supplied to the adsorption towers 60a to 60c constituting the PSA device 42 (see FIG. 2).

  At that time, as shown in FIG. 3, in the PSA apparatus 42, for example, an adsorption process is performed in the adsorption tower 60a, a purge process in the adsorption tower 60b, and a pressure reduction (washing) process in the adsorption tower 60c. Therefore, in the adsorption tower 60 a, components other than hydrogen are adsorbed to purify the fuel gas containing high-concentration hydrogen (hydrogen rich), and this fuel gas is supplied to the fuel gas path 76. As shown in FIG. 1, the fuel gas is selectively stored in a filling tank 82 and a power generation tank 88.

  Further, as shown in FIG. 3, after the adsorption process at the adsorption tower 60a, the pressure equalization process at the adsorption tower 60b and the pressure equalization process at the adsorption tower 60c, the adsorption process at the adsorption tower 60a, and the pressure increase process at the adsorption tower 60b. And the desorption process is carried out in the adsorption tower 60c. Accordingly, off-gas generated by the desorption process in the adsorption tower 60c is discharged to the off-gas flow path 68 under the opening action of the valve 66c (purge process).

  As shown in FIG. 1, the off-gas flow path 68 is connected to the off-gas discharge air supply path 36, and the off-gas flow path 68 passes through the off-gas discharge air flowing along the off-gas discharge air supply path 36. The off gas discharged to 68 is sent to the combustor 20. This off gas is used as a combustion fuel for the combustor 20.

  As described above, in the adsorption towers 60a to 60c, the adsorption process, the pressure reduction process, the pressure equalization process, the desorption process, and the purge process are sequentially performed, so that the fuel gas is continuously purified by the PSA device 42. This fuel gas is supplied from the fuel gas path 76 to the storage unit 16 and is selectively filled into the filling tank 82 and the power generation tank 88.

  Next, a method for stopping the home fuel gas production system 10 will be described below.

  In the PSA device 42, when each of the adsorption towers 60a to 60c is stopped in the state shown in FIG. 4, for example, the adsorption tower 60b is in the course of the desorption process and the off-gas is continuously released. For this reason, when the residual gas (reformed gas) remaining in the reformed gas supply path 40 is purged into the combustor 20 simultaneously with the stop of the PSA device 42, the residual gas and the off-gas released from the PSA device 42 are Are introduced into the combustor 20 at a time. Therefore, the temperature of the combustor 20 becomes an abnormally high temperature far exceeding the maximum temperature during steady operation, and the heat load of the combustor 20 becomes considerably high (see the abnormally high temperature in FIG. 4).

  Therefore, in the present embodiment, when the PSA device 42 is stopped, as shown in FIG. 5, the three-way valve 44 is operated to the PSA device 42 side, the valve 54 is closed, and the valve 70 is opened. Only the off gas from the PSA device 42 is discharged to the combustor 20. Next, after the off-gas release process satisfies a predetermined condition, the combustor 20 purges the residual gas remaining on the upstream side of the PSA device 42, that is, in the reformed gas supply path 40.

  Here, the predetermined condition is a timing condition that several seconds to several tens of minutes have elapsed after the PSA device 42 is stopped, or a flow rate that the off-gas flow rate introduced into the combustor 20 reaches a predetermined flow rate. A temperature condition that the combustor 20 has reached a predetermined temperature due to combustion of offgas, or a concentration condition that the concentration of combustibles in the offgas flowing downstream of the offgas discharge air supply path 36 has reached a predetermined concentration. Say.

  Then, after the predetermined condition is satisfied, the three-way valve 44 is switched to connect the reformed gas supply path 40 to the first branch path 46a. Therefore, residual gas remaining in the supply path including the reformed gas supply path 40 and the first branch flow path 46a from the reforming air supply path 32 is supplied to the reforming air supply under the opening action of the valve 38a. The combustor 20 is purged through the passage 32, the reformed gas supply passage 40, and the first branch passage 46a (see FIG. 6).

  Further, under the switching action of the three-way valve 44, the reformed gas supply path 40 and the second branch flow path 46b are communicated and the valve 54 is opened. Accordingly, the residual gas remaining in the second branch flow path 46b from the reformed gas supply path 40 is subjected to the reforming air supply path 32, the reformed gas supply path 40, and the second branch under the opening action of the valve 38a. The residual gas is combusted through the flow path 46b and combusted (see FIG. 6).

  As described above, in the present embodiment, after the PSA device 42 is stopped, at least a part of the off-gas (exhaust gas) discharged from the PSA device 42 is supplied to the combustor 20 and burned, and then the reformed gas supply path. Residual gas (reformed gas) remaining in 40 is purged by the combustor 20 and burned.

  For this reason, the off gas from the PSA device 42 and the purge gas from the reformed gas supply path 40 are not input to the combustor 20 at a time, and this combustor 20 can be prevented from becoming excessive in calories. it can. Thereby, as shown in FIG. 7, the temperature of the combustor 20 does not exceed the upper limit of the normal operation temperature, and the effect that it is possible to effectively prevent the combustor 20 from being damaged or the like can be obtained. .

  In the present embodiment, when purging the residual gas remaining in the reformed gas supply path 40, first, the three-way valve 44 is operated to purge from the first branch flow path 46a, and then the valve 54 Is purged from the second branch flow path 46b, but is not limited to this. For example, first, the residual gas may be purged from the second branch flow path 46b and then purged from the first branch flow path 46a under the switching action of the three-way valve 44. Alternatively, the three-way valve 44 may be replaced with a PSA device. It may be connected to the side 42 and the valve 54 may be opened to purge the residual gas in the reformed gas supply path 40 at once.

It is a schematic block diagram of the domestic fuel gas manufacturing system for enforcing the stop method concerning the embodiment of the present invention. It is principal part explanatory drawing of the PSA apparatus which comprises the said household fuel gas manufacturing system. It is a time chart explaining operation | movement of the said PSA apparatus. It is explanatory drawing of the stop state of the said PSA apparatus, and a combustor temperature. It is explanatory drawing at the time of discharge | releasing offgas from the said PSA apparatus. It is explanatory drawing at the time of purging residual gas from a reformed gas supply path. It is explanatory drawing of the stop state of the said PSA apparatus at the time of implementing the said stop method, and the said combustor temperature. 1 is a schematic system diagram of Patent Document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Domestic fuel gas production system 12 ... Reforming part 14 ... Purification part 16 ... Storage part 18 ... Evaporator 20 ... Combustor 22 ... Reactor 24 ... Cooler 26 ... Gas-liquid separator 28 ... Air supply mechanism 30 ... Air compressor 36 ... Air supply passages 38a, 38b, 52, 54, 66a to 66c, 70, 72a to 72c, 74, 80, 86 ... Valve 40 ... Reformed gas supply passage 41 ... Reformed gas pressure feeding device 42 ... PSA device 44 ... Three-way valves 46a, 46b ... Branch channel 50 ... Reformed gas branch channel 60a-60c ... Adsorption tower 62a-62c ... Pressure gauge 68 ... Off gas channel 76 ... Fuel gas channel 82 ... Filling tank 88 ... Power generation Tank 90 ... control ECU

Claims (3)

A reforming device for reforming the hydrogen-containing fuel to obtain a reformed gas and providing a combustor;
A PSA device for purifying hydrogen-rich fuel gas by removing unnecessary substances from the reformed gas;
An off-gas passage connecting the exhaust gas outlet of the PSA device and the combustor;
A purge gas flow path connecting the reformer with a reformed gas supply path connected to the reformed gas inlet of the PSA apparatus and the combustor;
A control device that controls to shift the timing at which exhaust gas is released from the PSA device to the combustor and the timing at which the gas remaining upstream of the PSA device is purged by the combustor when the PSA device is stopped When,
A fuel gas production system comprising: The fuel gas production system according to claim 1, further comprising a reformed gas pumping device that pumps the reformed gas obtained by the reformer to the PSA device,
The purge gas flow path has a first branch flow path having one end connected between the reformer and the reformed gas pressure feed device and the other end connected to the off-gas flow path;
A second branch flow path having one end connected between the reformed gas pressure feeding apparatus and the PSA apparatus and the other end connected to the off-gas flow path;
With
The first and second branch flow paths are provided with first and second valves that can be opened and closed, respectively. A reformer that reforms a hydrogen-containing fuel to obtain a reformed gas and that includes a combustor, a PSA device that purifies hydrogen-rich fuel gas by removing unnecessary substances from the reformed gas, and the PSA device An off-gas passage for connecting the exhaust gas outlet of the exhaust gas to the combustor, and a purge gas passage for connecting the reformer to the reformed gas inlet of the PSA device from the reformer and the combustor. A method for stopping a fuel gas production system, comprising:
Discharging the exhaust gas from the PSA device to the combustor through the off-gas flow path when the PSA device is shut down;
Purging gas remaining on the upstream side of the PSA device to the combustor via the purge gas flow path after the exhaust gas release process satisfies a predetermined condition;
A method for stopping a fuel gas production system, comprising:

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