JP4196249B2 - Hydrogen generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
[0002]
The present invention, methanol or natural gas, LNG, because the raw fuel gas mainly composed of any hydrocarbon that LP G and water vapor (steam), relates to a hydrogen generating apparatus for producing hydrogen.
[Prior art]
[0003]
In an industrial device or a fuel cell power plant that uses hydrogen as an atmospheric gas, a hydrogen generator is required. Conventionally, as one of hydrogen generators, a reformer that generates a hydrogen-rich reformed gas by passing a raw material gas such as natural gas, LNG, LPG, or methanol together with water vapor through a catalyst layer, and a reformed gas A hydrogen generator composed of a pressure swing adsorption device (PSA) that separates and purifies hydrogen is employed.
[0004]
With regard to this type of hydrogen generator, the applicant of the present application has proposed a device that aims to improve the controllability of steam supply control accompanying fluctuations in hydrogen load and to improve overall energy efficiency (specialty). Application 2000-242281).
[0005]
FIG. 3 shows a schematic system diagram of the hydrogen generator described in Japanese Patent Application No. 2000-242281. The hydrogen generator shown in FIG. 3 first includes a reformer 1 having a reforming pipe 1a having a catalyst layer and a burner 1b, a PSA 5 that separates and purifies hydrogen from the reformed gas, and a hydrogen separation and removal process in the PSA 5. The residual gas supply pipe 6 for supplying the residual gas still containing hydrogen to the burner 1b of the reformer is provided.
[0006]
The reforming raw material gas is introduced into the catalyst layer of the reformer 1 from the reforming raw material gas introduction pipe 9 together with water vapor, reformed to a hydrogen-rich gas by a reforming reaction by the catalyst, and necessary through the CO converter 10. In accordance with the above, after being compressed by a compressor (not shown), it is purified by PSA 5 to increase the hydrogen concentration. 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.
[0007]
As the combustion fuel of this burner, the residual gas that still contains hydrogen after the separation and removal treatment of hydrogen in the aforementioned PSA 5 is used, and the residual gas is supplied from the PSA 5 to the burner 1b via the flow control valve 8. Is done. If the amount of heat is insufficient with only the residual gas, auxiliary fuel is supplied from the auxiliary fuel pipe 7 for burner and burned. Moreover, a part of reformed gas may be used as combustion gas as needed. Combustion air is supplied from the air supply pipe 11 to the burner 1b.
[0008]
Next, the steam and raw fuel supply system will be described. The vapor separated from the gas and liquid by the water vapor separator 2 is introduced into the ejector 4 through a steam flow control valve 13 and a steam flow meter (or pressure gauge) 23 provided in the steam supply line 12, and the raw fuel gas supply line 14. Then, a raw fuel (gas) such as natural gas is sucked by the ejector suction force of the water vapor flow, and a mixture of the raw fuel gas and water vapor is introduced into the reformer 1. The raw fuel is reformed into a hydrogen-rich gas by a reforming reaction in the reformer.
[0009]
The combustion exhaust gas line of the reformer 1 is provided with a heat exchanger 40 for recovering the reformer exhaust heat, and the water in the water vapor separator 2 is sent to the heat exchanger 40 by the pump 32 and steam generated by heating. Is supplied to the water vapor separator 2, the auxiliary electric heater 50 is provided on the water circulation circuit, and the electric power adjustment device 51 for controlling the pressure in the water vapor separator 2 to be substantially constant is provided. 50 outputs are controlled. The pressure in the water vapor separator 2 is adjusted to approximately 6.1 kg / cm @ 2 (temperature is about 160 DEG C.), for example, by gauge pressure. It should be noted that an amount corresponding to the steam consumed in the reformer 1 is supplied from the water supply source 35 to the circulating water system pipe below the steam separator 2 or, for example, to the circulating water system pipe between the steam separator 2 and the pump 32. Water is supplied.
[0010]
The raw fuel gas supply line 14 includes a raw fuel gas flow meter 26, a raw fuel gas flow control valve 16, and a desulfurizer 17 between the raw fuel supply source 15 and the ejector 4. Thus, the fuel gas supply amount is adjusted according to the hydrogen load. Since raw fuel such as city gas contains a sulfur component as a odorant, a desulfurizer 17 is provided to remove this.
[0011]
A portion of the raw fuel gas branches from the raw fuel gas supply line 14 and is supplied from the burner auxiliary fuel pipe 7 to the reformer burner 1b as described above.
[0012]
As described above, the fuel gas supply amount is adjusted according to the hydrogen load by the raw fuel gas flow control valve 16, but when the raw fuel gas is increased or decreased, the steam flow rate must also be increased or decreased. The steam flow rate is determined so as to be preset S / C (ratio of moles of steam to carbon atoms in the raw fuel gas) according to the raw fuel gas composition. 3 has a function of adjusting the opening degree of the raw fuel gas flow rate control valve 16 and the steam flow rate control valve 13 in accordance with the required hydrogen load so as to obtain a preset S / C. The S / C is usually set in the range of 2.5 to 4.0 for city gas and LPG, and about 1.3 to 2.0 for methanol.
[0013]
That is, the hydrogen generator shown in FIG. 3 basically includes a reformer 1, a pressure swing adsorption device (PSA) 5, a steam generator 2 having a steam separator 2 and a water heater, and a reformer. The raw fuel gas flow rate control valve 16 and the steam flow rate control valve 13 provided in each line for supplying the fuel gas and the water vapor, and the flow rate control valve of each of the flow rate control valves according to the hydrogen load so as to have a preset S / C. And an adjuster 20 for adjusting the opening, and the water heater is a heat exchanger for recovering the reformer exhaust heat provided to heat the water in the steam separator with the combustion exhaust gas of the reformer. 40 and the auxiliary electric heater 50, and the auxiliary electric heater 50 includes a power adjusting device 51 for controlling the pressure in the water vapor separator to be substantially constant.
[0014]
According to the said structure, the steam for a heating conventionally supplied as a heat source for water heating becomes unnecessary, and becomes energy saving by that much. Also, since the raw fuel gas flow rate is increased or decreased according to the increase or decrease of the hydrogen load and the reformed gas amount is also increased or decreased accordingly, the amount of heat necessary for reforming inevitably increases or decreases, and the reformer exhaust heat amount also increases or decreases. To do. Therefore, since the amount of steam generated in the heat exchanger 40 for recovering exhaust heat from the reformer as a water heater also increases and decreases, matching between the increase and decrease in the hydrogen load and the increase and decrease in the amount of steam generated in the variable steam separator The pressure fluctuation is smaller than that of the conventional apparatus. Furthermore, the heating energy that is insufficient with the reformer exhaust heat amount is compensated by the auxiliary electric heater 50 to finely adjust the pressure fluctuation, thereby improving controllability and improving the energy efficiency as a whole.
[Problems to be solved by the invention]
[0015]
The hydrogen generator as described above also has the following problems from the viewpoint of energy efficiency.
[0016]
In the hydrogen generator, as described above, the amount of make-up water corresponding to the steam for reforming consumed in the reformer is supplied to the lower part of the steam separator or the circulating water system piping of the steam separator. . In this case, since supplementary water at normal temperature is supplied, it is necessary to raise the temperature to the circulating water temperature of the high-temperature steam separator, and energy for that is required. Furthermore, the generation of thermal stress accompanying the temperature difference at the confluence of makeup water and circulating water is also undesirable from the viewpoint of facility reliability.
[0017]
The present invention has been made in view of the above, and the object of the present invention is to reduce the temperature rise energy of make-up water and to generate thermal stress accompanying the temperature difference at the confluence of make-up water and circulating water. An object of the present invention is to provide a hydrogen generator that is suppressed.
[Means for Solving the Problems]
[0018]
To attain the above object, in the present invention, the raw fuel gas mainly composed of methanol or a hydrocarbon reformer for reforming the hydrogen-rich gas by steam (steam) from the reformed gas A pressure swing adsorption device (PSA) for separating and purifying hydrogen, a water vapor separator, and a water heater for heating the water in the water vapor separator to generate the steam, and the water heater further comprises: In a hydrogen generator comprising a heat exchanger for recovering exhaust heat from a reformer and an auxiliary electric heater provided to heat water in a steam separator with combustion exhaust gas from the reformer,
A feed water preheater that preheats make-up water to the steam separator with combustion exhaust gas from the reformer discharged from the reformer exhaust heat recovery heat exchanger is provided (invention of claim 1).
[0019]
As an embodiment of the invention of claim 1, the following is preferable. That is, in the hydrogen generator according to claim 1, the auxiliary electric heater is provided with a power adjusting device for controlling the pressure in the water vapor separator substantially constant (invention of claim 2). Furthermore, in the hydrogen generator according to claim 1 or 2, the residual gas after separation and purification of hydrogen in the PSA is supplied to a burner provided in the reformer and burned. (Invention of claim 3).
[0020]
According to the first aspect of the invention, since the reformer exhaust heat is effectively used for water heating of the steam separator and preheating of make-up water, running cost can be reduced. Further, according to the inventions of claims 2 and 3, it is possible to improve controllability and further improve energy efficiency.
[0021]
Further, in the hydrogen generator according to claim 3, the combustion air supplied to the burner is provided on a line for supplying the combustion exhaust gas of the reformer to the heat exchanger for recovering the reformer exhaust heat. An air preheater for preheating with the combustion exhaust gas of the reformer and a catalyst combustor for burning a part of the PSA residual gas are provided, and included in the combustion exhaust gas discharged from the air preheater in this catalyst combustor A part of the residual PSA gas is combusted by the residual oxygen, and the combustion exhaust gas is supplied to the heat exchanger for recovering the reformer exhaust heat (invention of claim 4).
[0022]
According to the fourth aspect of the present invention, both the combustion exhaust gas of the reformer burner and the combustion exhaust gas in the catalytic combustor are introduced into the reformer exhaust heat recovery heat exchanger, and energy recovery is possible. Further improve. The amount of air supplied to the reformer burner is normally 1.2 to 1.5 times the stoichiometric air-fuel ratio, so excess oxygen is present in the burner flue gas. It remains and is available for combustion in the catalytic combustor.
DETAILED DESCRIPTION OF THE INVENTION
[0023]
Embodiments of the present invention will be described below based on the drawings.
[0024]
FIG. 1 is a schematic system diagram of a hydrogen generator showing an embodiment according to the present invention. The same components as those in the system diagram shown in FIG.
[0025]
The main difference between FIG. 1 and FIG. 3 is that in FIG. 1, makeup water to the steam separator 2 is preheated by the combustion exhaust gas of the reformer discharged from the heat exchanger 40 for recovering the reformer exhaust heat. It is a point provided with the feed water preheater 64.
[0026]
In FIG. 1, makeup water is supplied from a makeup water line 60 through a feed water preheater 64 to a circulating water system pipe between the steam separator 2 and the pump 32 by a feed water pump 62. The makeup water line 60 includes a water treatment device 61 and a check valve 63 for purifying water.
[0027]
According to the above configuration, the energy efficiency is improved by preheating the makeup water.
[0028]
FIG. 2 shows a schematic system diagram of a hydrogen generator according to an embodiment different from FIG. The main difference between FIG. 1 and FIG. 2 is that a catalytic combustor 70 and an air preheater 72 are provided in FIG.
[0029]
As described above, the combustion air supplied to the reformer burner 1b is supplied to the reformer combustion exhaust gas on the line that supplies the reformer combustion exhaust gas to the reformer exhaust heat recovery heat exchanger 40. An air preheater 72 for preheating is provided, and the combustion exhaust gas of the reformer discharged from the air preheater 72 and a part of the PSA residual gas are passed through the branch line 74 to the catalyst combustor 70 and burned. By supplying the combustion exhaust gas to the heat exchanger 40 for recovering the reformer exhaust heat, energy efficiency is further improved.
[0030]
Note that an air supply line 76 to the catalytic combustor 70 is provided as necessary.
【The invention's effect】
[0031]
As described above, according to the present invention, the separation a reformer for reforming the hydrogen-rich gas raw fuel gas mainly composed of methanol or hydrocarbons with steam (steam), the hydrogen from the reformed gas A pressure swing adsorption device (PSA) to be purified; a water vapor separator; and a water heater that heats water in the water vapor separator to generate the steam, and the water heater further includes the reformer. A hydrogen generator comprising a reformer exhaust heat recovery heat exchanger and an auxiliary electric heater provided to heat the water in the steam separator with the combustion exhaust gas of
Since the reformer exhaust gas recovered from the reformer exhaust heat recovery heat exchanger includes a feed water preheater that preheats makeup water to the steam separator,
By reducing the temperature rise energy of the make-up water, the energy efficiency can be further improved as compared with the improved conventional hydrogen generator. Moreover, generation | occurrence | production of the thermal stress accompanying the temperature difference of the confluence | merging point of makeup water and circulating water can also be aimed at.
[Brief description of the drawings]
[0032]
1 is a schematic system diagram of a hydrogen generator according to an embodiment of the present invention. FIG. 2 is a schematic system diagram of a hydrogen generator according to an embodiment different from FIG. 1. FIG. 3 is an improved conventional hydrogen. General system diagram of the generator [Explanation of symbols]
[0033]
1: reformer, 2: steam separator, 4: ejector, 5: pressure swing adsorption device (PSA), 6: residual gas supply pipe, 12: steam supply line, 13: steam flow control valve, 14: raw fuel Gas supply line 16: Raw fuel gas flow control valve 32: Pump 40: Reformer exhaust heat recovery heat exchanger 50: Auxiliary electric heater 51: Power regulator 60: Makeup water line 64: Feed water preheater, 70: catalytic combustor, 72: air preheater.

Claims (4)

A reformer for reforming the hydrogen-rich gas methanol or raw fuel gas to a hydrocarbon as a main component with steam (steam), the pressure swing adsorption system from the reformed gas separating and purifying hydrogen and (PSA) A water vapor separator and a water heater that heats the water in the water vapor separator to generate the steam, and the water heater uses the combustion exhaust gas of the reformer to produce water in the water vapor separator. In a hydrogen generator comprising a reformer exhaust heat recovery heat exchanger and an auxiliary electric heater provided to heat the reformer, the reformer combustion exhaust gas discharged from the reformer exhaust heat recovery heat exchanger A hydrogen generator comprising a feed water preheater for preheating the makeup water to the steam separator.   The hydrogen generator according to claim 1, wherein the auxiliary electric heater includes a power adjusting device for controlling the pressure in the water vapor separator to be substantially constant.   3. The hydrogen generator according to claim 1, wherein the residual gas after separation and purification of hydrogen in the PSA is supplied to a burner provided in the reformer and burned. Characteristic hydrogen generator.   4. The hydrogen generator according to claim 3, wherein combustion air supplied to the burner is supplied to the reformer on a line for supplying combustion exhaust gas of the reformer to the heat exchanger for recovering heat of exhaust heat from the reformer. Provided with an air preheater for preheating with the combustion exhaust gas and a catalytic combustor for burning part of the PSA residual gas, and residual oxygen contained in the combustion exhaust gas discharged from the air preheater in the catalyst combustor A part of the PSA residual gas is combusted by the above, and the combustion exhaust gas is supplied to the reformer exhaust heat recovery heat exchanger.

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