JP4147446B2 - Hydrogen generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydrogen generator equipped with a pressure swing adsorption device (PSA) for separating and purifying hydrogen from reformed gas.
[0002]
[Prior art]
In an industrial device or a fuel cell power plant that uses hydrogen as an atmospheric gas, a hydrogen generator is required.
[0003]
Conventionally, as one of the hydrogen generators, a catalyst layer for producing a hydrogen-rich reformed gas by reacting a hydrocarbon-based raw fuel such as natural gas, LNG, LPG, and methanol with water vapor in the presence of a catalyst. A reformer provided with a burner for using combustion exhaust gas as a heating medium for the reforming reaction, a steam separator provided for supplying the steam to the reformer, and the inside of the steam separator An exhaust gas cooler for heating water with the combustion exhaust gas of the burner to generate water vapor, a compressor for pressurizing the reformed gas or reformed raw fuel, and hydrogen from the pressurized reformed gas There are known a pressure swing adsorption device (PSA) for separation and purification, and a hydrogen generator configured to burn the residual gas after hydrogen is separated and removed in the PSA by supplying it to the reformer burner.
[0004]
With regard to this type of hydrogen generator, the present applicant has proposed a device intended to enable safe and rational energy recovery without wasteful release of PSA residual gas after hydrogen purification. (See Japanese Patent Application No. 2000-266966). 3 and 4 are schematic system diagrams of the hydrogen generator described in Japanese Patent Application No. 2000-266966.
[0005]
The hydrogen generator shown in FIG. 3 includes a reformer 1 including a burner 1a and a catalyst layer 1b, a compressor 2 for pressurizing the reformed gas, and a PSA 3 that separates and purifies hydrogen from the reformed gas. A residual gas supply pipe 10 for supplying residual gas still containing hydrogen after separation and removal of hydrogen in the PSA to the burner 1a of the reformer, and for supplying steam to the reformer 1 A water vapor separator 4, an exhaust gas cooler 7 for heating the water in the water vapor separator 4 with the combustion exhaust gas of the burner to generate water vapor, and a water circulation pump 5.
[0006]
Further, in FIG. 3, a combustor 6 is provided, and after the surplus residual PSA gas with respect to the amount of heat necessary for the reforming reaction is combusted in the combustor 6, the combustion exhaust gas is exhausted together with the burner combustion exhaust gas. A combustor exhaust gas supply line 12 for introduction into the cooler 7 is provided. Combustion air is introduced into the combustor 6 and the reformer burner 1a by a blower (not shown) or the like. Conventionally, the combustion exhaust gas burned by the combustor 6 was released to the atmosphere, but with the configuration of FIG. 3, both the combustion exhaust gas of the reformer burner and the combustion exhaust gas in the combustor are introduced into the exhaust gas cooler. Since energy can be recovered, energy efficiency is greatly improved compared to conventional devices.
[0007]
In FIG. 3, the reforming raw fuel is introduced into the catalyst layer 1b of the reformer 1 from its introduction pipe together with water vapor, and is converted into a hydrogen-rich gas containing hydrogen, carbon dioxide, and carbon monoxide by the reforming reaction by the catalyst. Reformed. Carbon monoxide in the reformed gas is converted into carbon dioxide and hydrogen by a carbon monoxide converter (not shown). The composition of the reformed gas after the transformation is about 70% hydrogen concentration and about 20% carbon dioxide, and the remainder is water vapor, methane and some carbon monoxide.
[0008]
The reformed gas is compressed to about 0.6 to 0.9 MPa (G) by the compressor 2 and then purified by PSA to increase the hydrogen concentration. FIG. 3 shows a system in which the reformer 1 is operated at substantially atmospheric pressure, and the reformed gas charged into the PSA 3 is pressurized by the compressor 2, but the raw fuel is pressurized and reformed together with high-pressure steam. The reformer 1 can also be operated in a pressurized state by supplying to the reactor 1. In this case, the reformed gas compressor 2 is not necessary, but means for pressurizing the raw fuel is required.
[0009]
PSA is a device that adsorbs and separates specific gas species by filling a plurality of containers with adsorbents such as activated carbon and zeolite, and changing the pressure. Depending on the operating conditions and performance, On the other hand, approximately 65 to 75% is separated and purified. The remaining hydrogen and other components are discharged downstream. The residual gas of this PSA released downstream contains a large amount of combustible components of hydrogen, methane, and carbon monoxide. On the other hand, since the reforming reaction is an endothermic reaction, it is necessary to supply heat from the outside. For this reason, the combustion exhaust gas of the burner is used as a heating medium, and the combustion gas of the burner is mainly used in the PSA 3 described above. The residual gas that still contains hydrogen after separation and removal of hydrogen is used, and the residual gas is supplied from the PSA 3 to the burner 1a via a flow control valve (not shown).
[0010]
Note that the amount of water vapor necessary for the reforming reaction in the reformer 1 is insufficient with only the amount of water vapor generated in the exhaust gas cooler 7. Therefore, in order to secure a necessary amount of water vapor, the water vapor separator 4 includes an additional heat source (not shown) such as an electric heater or a boiler, detects the pressure in the water vapor separator 4, and this pressure is a predetermined pressure. The amount of heat generated by the additional heat source is controlled so as to maintain the above. The steam separator 4 is connected to a supply water supply pipe (not shown) so that water corresponding to the amount of steam used is supplied.
[0011]
FIG. 4 is a schematic system diagram of a hydrogen generator different from FIG. 3 described in Japanese Patent Application 2000-266966. On the line 13 for supplying the combustion exhaust gas of the reformer burner 1a to the exhaust gas cooler 7, An air preheater 8 for preheating the combustion air supplied to the burner 1a with the combustion exhaust gas of the burner is provided, and further, a catalytic combustor 6a is provided downstream of the air preheater 8a. 3 differs from FIG. 3 in that the residual gas of the PSA is combusted by residual oxygen contained in the discharged combustion exhaust gas and this combustion exhaust gas is supplied to the exhaust gas cooler 7.
[0012]
Since the amount of air supplied from the preheated air supply line 14 to the reformer burner 1a is usually 1.2 to 1.5 times the stoichiometric air-fuel ratio, Excess oxygen remains and can be used for combustion in the catalytic combustor 6a. Moreover, in the example of FIG. 4, the cooling air supply piping 15 which supplies air to the catalyst combustor 6a for cooling is provided. This cooling air always prevents the catalytic combustor 6a from being heated. With the above configuration, stable combustion can be performed regardless of changes in the composition and flow rate of the PSA residual gas and the degree of excess residual gas.
[0013]
[Problems to be solved by the invention]
The above hydrogen generator also has the following problems from the viewpoint of safety.
[0014]
The hydrogen separation function of PSA changes depending on the outside air temperature, the reformed gas composition change, the characteristic change over time, and the like, and the composition and flow rate of the PSA residual gas change. For this reason, when a large amount of residual PSA gas (hydrogen-rich gas) is introduced into the above-described combustor, the temperature of the combustor, particularly the catalytic combustor, may rapidly increase, for example, to 800 ° C. In this case, not only is it not preferable from the viewpoint of the life of the catalytic combustor, but there is a risk of damaging the subsequent equipment.
[0015]
Further, in the combustor, unreacted gas, that is, unburned gas, may be generated. If this gas is released to the atmosphere via a subsequent device, it is a fire hazard and also in the environment. It is not preferable.
[0016]
The present invention has been made to solve the above-described problems, and an object of the present invention is to prevent hydrogen emission from the unburned gas in the combustor and to prevent abnormal temperatures, and to enable safe operation of the hydrogen generator. Is to provide.
[0017]
[Means for Solving the Problems]
In order to solve the above-described problems, in the present invention, a catalyst layer for reacting a hydrocarbon-based raw fuel and steam in the presence of a catalyst to generate a hydrogen-rich reformed gas, and a combustion exhaust gas are modified. A reformer provided with a burner for use as a heating medium for quality reaction, a steam separator provided for supplying the steam to the reformer, and combustion of the water in the steam separator into the burner An exhaust gas cooler for generating steam by heating with exhaust gas, a compressor for pressurizing the reformed gas or reformed raw fuel, and a pressure swing adsorption device for separating and purifying hydrogen from the pressurized reformed gas (PSA), the residual gas after separation and removal of hydrogen in this PSA is supplied to the reformer burner and burned, and a part of the residual gas is provided separately from the burner. Supply to the vessel Is burnt, the hydrogen generating apparatus comprising introducing into the exhaust gas cooler flue gas together with the combustion exhaust gas of the burner in the combustor,
The residual gas supply line to the combustor has a gas flow rate control valve and a gas switching valve, and introduces into the flare stack a part of the residual gas supplied from the gas switching valve to the combustor. A combustor exhaust gas supply line for connecting the combustor and the exhaust gas cooler, a temperature detector for detecting an outlet gas temperature of the combustor, and an outlet gas in the outlet gas. A gas analyzer for detecting unburned gas, and further, based on the measured values of the temperature detector and the gas analyzer, for preventing atmospheric discharge of the unburned gas and temperature abnormality in the combustor. A control device that outputs a control signal to the gas flow rate control valve and the gas switching valve is provided (invention of claim 1).
[0018]
According to the first aspect of the present invention, when unburned gas is detected based on the measured values of the temperature detector and the gas analyzer, the flare stack can burn and detoxify it and release it to the atmosphere. Moreover, temperature abnormality in the combustor can be prevented by adjusting the residual gas supply amount to the combustor based on temperature detection. Furthermore, by adjusting the residual gas supply amount based on both detection of unburned gas and temperature detection, the probability of occurrence of unburned gas and temperature abnormality can be complementarily reduced. Details will be described later.
[0019]
As an embodiment of the invention of claim 1, the inventions of claims 2 to 4 below are preferable. That is, in the hydrogen generator according to claim 1, the combustor is a catalytic combustor (invention of claim 2).
[0020]
3. The hydrogen generator according to claim 2, wherein the combustion air supplied to the burner is preheated by the combustion exhaust gas of the burner on a line for supplying the combustion exhaust gas of the reformer burner to the exhaust gas cooler. An air preheater and the catalytic combustor are provided, and the residual gas of the PSA is burned by residual oxygen contained in the combustion exhaust gas discharged from the air preheater in the catalyst combustor, and the combustion exhaust gas is cooled by the exhaust gas. It is supposed to be supplied to a container (Invention of Claim 3).
[0021]
Further, in the hydrogen generator according to claim 3, the catalytic combustor includes an air introduction line for cooling (invention of claim 4).
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below based on the drawings.
[0023]
FIGS. 1 and 2 are schematic configuration diagrams showing different embodiments of the present invention which are improved from FIGS. 1 and 2, the same members as those of the conventional apparatus of FIGS. 3 and 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0024]
The difference between FIG. 1 and FIG. 3 is the configuration of the lines before and after the combustor 6. In FIG. 1, the residual gas supply line to the combustor 6 includes a gas flow rate adjustment valve 22 and a gas switching valve 24, and a part of the residual gas supplied from the gas switching valve 24 to the combustor 6. Is provided with an unburned gas discharge line 20 that is introduced into the flare stack 21. Part number 23 is a check valve.
[0025]
The combustor exhaust gas supply line 12 connecting the combustor 6 and the exhaust gas cooler 7 includes a temperature detector 32 (for example, a thermocouple) that detects the outlet gas temperature of the combustor, and unburned gas in the outlet gas. And a control signal for preventing the combustion of the unburned gas in the combustor 6 from being released into the atmosphere and temperature abnormalities based on the measured values of the temperature detector 32 and the gas analyzer 34. Is provided to the gas flow rate adjusting valve 22 and the gas switching valve 24.
[0026]
With the above configuration, control for preventing unburned gas from being released into the atmosphere and temperature abnormality is performed, for example, as follows. When the temperature detection value of the temperature detector 32 reaches, for example, 500 ° C., the gas switching valve 24 is switched so that a part of the remaining gas is bypassed and introduced into the flare stack 21. At the same time, the residual gas supply amount of PSA to the combustor 6 is decreased by the gas flow rate control valve 22. Thereafter, when the temperature detection value of the temperature detector 32 reaches, for example, 450 ° C., the gas switching valve 24 is switched to stop the bypass. The gas flow rate adjustment valve 22 adjusts to a predetermined opening according to the detected temperature value.
[0027]
When the gas analyzer 34 detects unburned gas, the gas switching valve 24 is immediately switched to stop the remaining gas from being introduced into the combustor 6 and introduced into the flare stack 21 for natural It is diffused and burned, detoxified, and released to the atmosphere. At the same time, an operation of decreasing the PSA residual gas supply amount to the combustor 6 by the gas flow rate control valve 22 by a predetermined ratio is performed. Thereafter, the gas switching valve 24 is switched again to stop the bypass. Even after the remaining gas supply amount is reduced, if unburned gas is detected, the same operation as described above is performed.
[0028]
As described above, it is possible to prevent unburned gas from being released into the atmosphere and abnormal temperature rise.
[0029]
FIG. 2 shows an embodiment different from FIG. 1 relating to the improvement of FIG. Similar to the difference between FIG. 1 and FIG. 3, the difference between FIG. 2 and FIG. 4 is that the residual gas supply line to the combustor 6 a has a gas flow rate adjustment valve 22 and a gas switching valve 24. And the point provided with the unburned gas discharge line 20 which bypasses a part of residual gas supplied to the combustor from the gas switching valve 24 and introduces it into the flare stack 21, and the combustor 6a and the exhaust gas cooler 7 The combustor exhaust gas supply line to be connected has a temperature detector 32 for detecting the outlet gas temperature of the combustor, and a gas analyzer 34 for detecting unburned gas in the outlet gas, and further includes a temperature detector. And a control device 40 for outputting a control signal for preventing unburned gas from being released into the atmosphere and temperature abnormalities in the combustor 6a to the gas flow control valve and the gas switching valve based on the measured values of the gas analyzer 32 and the gas analyzer 34. It differs in the point to prepare.
[0030]
In FIG. 2, unlike FIG. 1, the combustion air supplied to the burner 1a is preheated by the combustion exhaust gas of the burner on the line 13 for supplying the combustion exhaust gas of the reformer burner 1a to the exhaust gas cooler 7. The air preheater 8 is provided, and further, a catalytic combustor 6 is provided downstream thereof, in which the residual gas of the PSA is burned by residual oxygen contained in the combustion exhaust gas discharged from the air preheater 8. Since the combustion exhaust gas is supplied to the exhaust gas cooler 7, stable combustion can be performed regardless of changes in the composition and flow rate of PSA residual gas and the degree of excess residual gas (for details, see (See Japanese Patent Application No. 2000-266966).
[0031]
【The invention's effect】
As described above, according to the present invention, a catalyst layer for reacting a hydrocarbon-based raw fuel and water vapor in the presence of a catalyst to generate a hydrogen-rich reformed gas, and a combustion exhaust gas are converted into the reforming reaction. A reformer provided with a burner for use as a heating medium for the above, a steam separator provided for supplying the steam to the reformer, and water in the steam separator by combustion exhaust gas of the burner An exhaust gas cooler for heating and generating steam, a compressor for pressurizing the reformed gas or reformed raw fuel, and a pressure swing adsorption device (PSA) for separating and purifying hydrogen from the pressurized reformed gas In the PSA, a residual gas after separating and removing hydrogen in the PSA is supplied to the reformer burner for combustion, and a part of the residual gas is provided in a combustor provided separately from the burner. Supply and burn this In the hydrogen generating apparatus comprising introducing into the exhaust gas cooler with the combustion exhaust gas of the burner flue gas in baked device,
The residual gas supply line to the combustor has a gas flow rate control valve and a gas switching valve, and introduces into the flare stack a part of the residual gas supplied from the gas switching valve to the combustor. A combustor exhaust gas supply line for connecting the combustor and the exhaust gas cooler, a temperature detector for detecting an outlet gas temperature of the combustor, and an outlet gas in the outlet gas. A gas analyzer for detecting unburned gas, and further, based on the measured values of the temperature detector and the gas analyzer, for preventing atmospheric discharge of the unburned gas and temperature abnormality in the combustor. By comprising a control device that outputs a control signal to the gas flow rate control valve and the gas switching valve,
It is possible to provide a hydrogen generator capable of safe operation by preventing unburned gas from being released into the combustor into the atmosphere and temperature abnormalities.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a hydrogen generator showing an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a hydrogen generator showing an embodiment different from FIG. 1 of the present invention. Schematic configuration diagram of hydrogen generator [Fig. 4] Schematic configuration diagram of hydrogen generator different from conventional Fig. 3 [Explanation of symbols]
1: reformer, 1a: burner, 1b: catalyst layer, 2: compressor, 3: pressure swing adsorption device (PSA), 4: steam separator, 6, 6a: combustor, 7: exhaust gas cooler, 8 : Air preheater, 20: Unburned gas discharge line, 21: Flare stack, 22: Gas flow control valve, 24: Gas switching valve, 32: Temperature detector, 34: Gas analyzer, 40: Control device.

Claims (4)

A catalyst layer for producing a hydrogen-rich reformed gas by reacting a hydrocarbon raw fuel and steam in the presence of a catalyst, and a burner for using combustion exhaust gas as a heating medium for the reforming reaction. A reformer provided, a steam separator provided for supplying the steam to the reformer, and an exhaust gas cooler for generating water vapor by heating water in the steam separator with combustion exhaust gas of the burner And a compressor for pressurizing the reformed gas or reformed raw fuel, and a pressure swing adsorption device (PSA) for separating and purifying hydrogen from the pressurized reformed gas, and hydrogen is separated in this PSA The residual gas after the removal treatment is supplied to the burner for the reformer and burned, and a part of the residual gas is supplied to the burner provided separately from the burner and burned. The exhaust gas is In the hydrogen generating apparatus comprising introducing into the exhaust gas cooler with flue gas burner,
The residual gas supply line to the combustor has a gas flow rate control valve and a gas switching valve, and introduces into the flare stack a part of the residual gas supplied from the gas switching valve to the combustor. With an unburned gas discharge line that
The combustor exhaust gas supply line connecting the combustor and the exhaust gas cooler includes a temperature detector for detecting an outlet gas temperature of the combustor, and a gas analyzer for detecting unburned gas in the outlet gas. And
Further, based on the measured values of the temperature detector and the gas analyzer, a control signal for preventing the unburned gas from being discharged into the atmosphere and temperature abnormality in the combustor is output to the gas flow rate control valve and the gas switching valve. A hydrogen generator comprising a control device. 2. The hydrogen generator according to claim 1, wherein the combustor is a catalytic combustor. 3. The hydrogen generator according to claim 2, wherein air for preheating the combustion air supplied to the burner with the combustion exhaust gas of the burner is provided on a line for supplying the combustion exhaust gas of the reformer burner to the exhaust gas cooler. And a catalytic combustor, the residual gas of the PSA is burned by residual oxygen contained in the flue gas discharged from the air preheater in the catalytic combustor, and the flue gas is sent to the flue gas cooler. A hydrogen generator characterized by being supplied. 4. The hydrogen generator according to claim 3, wherein the catalytic combustor includes an air introduction line for cooling.

Images