JP2011093719A - Method for producing and utilizing hydrogen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new method for producing and utilizing hydrogen, which efficiently generates high purity hydrogen from biomass as raw material and reduces the amount of carbon dioxide discharged from the whole system. <P>SOLUTION: The method for producing and utilizing hydrogen includes: a thermal decomposition gasification step of generating hydrogen-containing biogas by thermally decomposing biomass as raw material; a membrane shift reaction step in which the biogas is modified to hydrogen-rich gas in a membrane shift reactor and the hydrogen is separated; and a separation step of separating carbon dioxide from concentrated carbon dioxide-containing gas obtained by hydrogen separation. The method can achieve so-called carbon-negative. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing and using hydrogen from biomass as a raw material.

  As a result of mass consumption of fossil fuels after the industrial revolution, the concentration of carbon dioxide in the atmosphere continues to rise, causing a global warming phenomenon, which has become a major social problem. Therefore, hydrogen is attracting attention as an energy substance to replace fossil fuel, and a hydrogen production method aimed at mass production is being studied at a low cost.

  Hydrogen is used as a reaction gas for fuel cells and is a clean energy substance because the only substance produced during power generation is water, but there is a problem that a large amount of carbon dioxide is emitted in the hydrogen production process. . Thus, recently, hydrogen production technology using biomass or waste as a raw material has been proposed in place of conventional fossil fuel-derived hydrogen, thereby achieving so-called carbon neutral.

  For example, (Patent Document 1) is a method for producing hydrogen from biomass, and (i) a first step of gasifying biomass to produce a mixed gas containing hydrocarbon, hydrogen and carbon monoxide, (Ii) a second step for purifying the gas mixture obtained in the first step, (iii) a third step for converting hydrocarbons contained in the gas mixture obtained in the second step into hydrogen and carbon monoxide; (Iv) A method including a fourth step of recovering hydrogen from the gas mixture obtained in the third step is disclosed.

  Further, (Patent Document 2) discloses a biomass pyrolysis method characterized in that biomass is heat-treated at a temperature of 600 to 1200 ° C. and a pressure of 5 atm or less in the presence of water.

  As described above, it is possible to generate hydrogen from biomass by pyrolysis gasification. However, since the hydrogen partial pressure is generally low, it is necessary to perform an aqueous shift reaction to increase the hydrogen partial pressure. In order to obtain it, hydrogen purification by means such as PSA (Pressure Swing Adsorption) (Patent Document 3) or membrane separation was required. Furthermore, although the hydrogen energy extracted from the biomass raw material is regarded as carbon neutral, carbon dioxide is still discharged and there is room for improvement.

JP 2004-182501 A Japanese Patent Laid-Open No. 07-041767 JP 2005-177716 A

  Therefore, in view of the above-described conventional situation, the present invention provides a novel method for producing and using hydrogen that efficiently generates high-purity hydrogen using biomass as a raw material and reduces carbon dioxide discharged from the entire system. The purpose is to provide.

  The present inventors can desorb the biogas obtained by pyrolyzing biomass with a membrane shift reactor, so that hydrogen can be taken out in one step, and further, the carbon dioxide produced is separated and recovered as described above. The present inventors have found that the problems can be solved and completed the present invention.

That is, the gist of the present invention is as follows.
(1) Pyrolysis gasification process using biomass as a raw material to produce hydrogen-containing biogas by pyrolysis, and membrane shift reaction process for separating the biogas into hydrogen-rich gas and separating hydrogen using a membrane shift reactor And a separation step of separating carbon dioxide from a gas containing concentrated carbon dioxide obtained by separating hydrogen.
(2) The method for producing and utilizing hydrogen according to (1), further comprising a fuel cell power generation step using hydrogen separated in the membrane shift reaction step as a reaction gas.
(3) Between the membrane shift reaction step and the separation step, a combustion step of burning a gas containing concentrated carbon dioxide using a burner and / or a combustion catalyst, and cooling and / or adsorption from the burned gas The method for producing and using hydrogen according to (1) or (2), further comprising a moisture removing step for removing moisture.
(4) The method for producing and using hydrogen according to (3) above, wherein the gasifying agent in the pyrolysis gasification step and the oxidizing agent in the combustion step are oxygen, and the water removal step also serves as a separation step for separating carbon dioxide. .
(5) Using the exhaust heat obtained in the pyrolysis gasification process, preheating the gasifying agent in the pyrolysis gasification process, preheating the oxidizing agent in the combustion process, and / or dehydration when removing moisture by adsorption The method for producing and utilizing hydrogen according to (3) or (4) above, wherein heating for regeneration of the adsorbent is performed.
(6) Using the exhaust heat obtained in the combustion step, preheating the gasifying agent in the pyrolysis gasification step, preheating the oxidant in the combustion step, and / or dehydrating adsorbent when removing moisture by adsorption The method for producing and utilizing hydrogen according to any one of (3) to (5), wherein heating for regeneration is performed.

(7) Between the membrane shift reaction step and the separation step, a combustion step of burning a gas containing concentrated carbon dioxide using a burner and / or a combustion catalyst, and cooling and / or adsorption from the burned gas A water removal step for removing water, and further a fuel cell power generation step using hydrogen separated in the membrane shift reaction step as a reaction gas, and using the exhaust heat obtained in the fuel cell power generation step, a pyrolysis gas Production of hydrogen as described in (1) above, wherein preheating of the gasifying agent in the conversion step, preheating of the oxidizing agent in the combustion step, and / or heating for regeneration of the adsorbent for dehydration when removing moisture by adsorption ·How to Use.
(8) Pyrolysis gasification step of producing biogas containing hydrogen by pyrolysis using biomass as a raw material, and membrane shift reaction step of separating the biogas into hydrogen-rich gas in a membrane shift reactor and separating hydrogen And a water removal step for removing water from the gas containing concentrated carbon dioxide obtained by separating hydrogen by cooling and / or adsorption, and a separation step for separating carbon dioxide from the gas from which water has been removed. A hydrogen production / utilization method comprising recycling a gas containing hydrogen obtained through the separation step to a pyrolysis gasification step and / or a membrane shift reaction step.
(9) Use of the exhaust heat obtained in the pyrolysis gasification step to preheat the gasifying agent in the pyrolysis gasification step and / or to regenerate the adsorbent for dehydration when moisture is removed by adsorption. The method for producing and utilizing hydrogen according to (8), wherein the temperature is increased.
(10) The method for producing and utilizing hydrogen according to (8) or (9), further comprising a fuel cell power generation step using hydrogen separated in the membrane shift reaction step as a reaction gas.
(11) Using the exhaust heat obtained in the fuel cell power generation process, preheating the gasifying agent in the pyrolysis gasification process and / or heating for regeneration of the adsorbent for dehydration when removing moisture by adsorption The method for producing and using hydrogen according to (10) above.
(12) The method for producing and utilizing hydrogen according to any one of the above (1) to (11), wherein the temperature of the membrane shift reactor is increased using exhaust heat obtained in the pyrolysis gasification step.

  According to the present invention, hydrogen that can be used for a fuel cell or the like can be efficiently obtained by performing a membrane shift reaction step after pyrolyzing biomass. Further, by separating and recovering carbon dioxide from a gas containing concentrated carbon dioxide remaining after separating hydrogen, a so-called carbon negative superior to carbon neutral can be achieved as a whole system.

It is a block diagram which shows 1st embodiment of this invention. It is a block diagram which shows 2nd embodiment of this invention.

Hereinafter, the present invention will be described in detail.
First, a first embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, the hydrogen production / utilization method of the present invention includes a pyrolysis gasification step of generating biogas containing hydrogen by pyrolysis using biomass as a raw material.

  The biomass to be subjected to pyrolysis is applicable as long as it is an organic resource derived from a living organism. Preferably, an organic substance such as an organic waste, a resource crop, or its waste is used. Examples include, but are not limited to, organic waste in the food industry, paper industry, agricultural and livestock industry (wheat straw, rice straw, sugar cane juice residue, etc.), forestry, etc. (wood chips, sawdust, etc.). It is not a thing. The raw material biomass is preferably used after being cut into small pieces. Moreover, in order to increase the efficiency of thermal decomposition, the biomass may be dried before being supplied to the thermal decomposition gasification step. The degree of drying is not particularly limited, but drying is preferably performed so that the moisture content is about 15 to 20% by weight.

  Thermal decomposition can be performed by a conventionally known method. Specifically, air or oxygen is supplied as a gasifying agent, and biomass is gasified by heat treatment at a temperature of 700 to 900 ° C. It is not limited. Biogas containing hydrogen, carbon dioxide, carbon monoxide, water and the like is generated by pyrolysis of biomass. When air is used as the gasifying agent, nitrogen is also included.

  The biogas generated from the pyrolysis gasification step is recovered as exhaust heat by a heat recovery device including a heat exchanger and supplied to the membrane shift reactor. Membrane shift reactors consist of Cu-based (for low-temperature shift reaction at about 300 ° C.), Fe—Cr and Pt-based (for high-temperature shift reaction at about 500 ° C.), pellets, porous, molded ( (Honeycomb), fluidized bed, etc. are filled in the reactor, and a hydrogen separation membrane made of Pd, Pd alloy, non-Pd-based material (V, Nb, Ta) or the like is embedded in the reactor. . Specifically, for example, a flat layer made of a CO conversion catalyst is formed, and a plurality of cylindrical hydrogen separation membranes (hydrogen separation pipes) are arranged in parallel in the layer, or made of a CO conversion catalyst. A membrane shift reactor can be constructed by forming a cylindrical layer and arranging a plurality of cylindrical hydrogen separation membranes along the axis of the cylinder in the layer. It is preferable to control the temperature of the aqueous shift reaction to be optimal depending on the flow rate and temperature, for example, by circulating cooling water inside or outside the CO conversion catalyst layer. When biogas is supplied into the reactor, an aqueous shift reaction occurs, and carbon dioxide and hydrogen are generated from carbon monoxide and water, which are converted into a hydrogen-rich gas having a high hydrogen concentration. The reaction temperature at this time is about 320 to 450 ° C. Only hydrogen in the hydrogen-rich gas selectively permeates into the inside of the cylindrical hydrogen separation membrane, and high purity hydrogen is separated and collected. Further, from the membrane shift reactor, a gas containing concentrated carbon dioxide (consisting of a small amount of hydrogen, carbon dioxide, carbon monoxide, water, nitrogen, etc.) remaining after separation of hydrogen is separately provided off-gas. It is discharged from the exit. The configuration of the membrane shift reactor as described above is described in detail in JP-A Nos. 2000-143208 and 2000-143210, and these configurations can be appropriately employed in the present invention.

  In the first embodiment, hydrogen separated in the membrane shift reaction step is directly supplied to the fuel cell as a reaction gas to generate power (fuel cell power generation step). Thereby, the electric power which uses biomass as a raw material can be obtained. Alternatively, the produced hydrogen may be supplied to a hydrogen gas station or the like.

  As shown in FIG. 1, the first embodiment of the present invention further includes a combustion step of burning a gas containing concentrated carbon dioxide discharged from a membrane shift reactor using a burner or a combustion catalyst. Yes. Combustion with a burner or a combustion catalyst may be performed in combination. Further, when burning, an oxidant such as air or oxygen is supplied.

  A method using a combustion catalyst is a method of oxidizing a gas at a low temperature by a catalytic action of a noble metal or the like. As the catalyst, noble metals such as platinum, palladium, ruthenium, rhodium and silver, and nitrates and chlorides thereof can be applied. Usually, they are supported by being supported on a structure such as a metal honeycomb, a ceramic honeycomb or a ball pellet.

  In the combustion process, combustible components such as hydrogen and carbon monoxide are burned to convert the gas composition into water and carbon dioxide. When air is supplied as an oxidant in the combustion process, nitrogen is also included in the gas after combustion.

  Subsequently, in the moisture removal step, the gas that has passed through the combustion step is cooled or brought into contact with an adsorbent such as silica gel to remove moisture. The cooling and adsorption operations may be performed in combination.

  When air is used as the oxidant in the combustion process, the gas that has undergone the water removal process contains nitrogen as well as carbon dioxide, so that carbon dioxide is separated and recovered in the separation process. As a carbon dioxide separation method, various methods can be applied, specifically, a method of compressing, cooling and liquefying, a purification by PSA (pressure swing adsorption), a method of absorbing in an amine solution, and the like. There is no particular limitation. By recovering the carbon dioxide generated together with the production of hydrogen in this way, the raw material is biomass, so that the system as a whole can achieve a carbon negative, which is very advantageous in industry.

  In addition, when oxygen is used instead of air as the gasifying agent in the pyrolysis gasification step and the oxidant in the combustion step, nitrogen is not included in the gas that has passed through the fuel step. In this case, the water removal step can also serve as the separation step without separately providing a step for separating carbon dioxide. That is, carbon dioxide can be separated and recovered as a remaining component simultaneously with the removal of moisture in the moisture removal step.

  As shown in FIG. 1, the exhaust heat obtained in the pyrolysis gasification process or the combustion process is used to preheat the gasification agent in the pyrolysis gasification process, preheat the oxidant in the combustion process, and / or adsorb moisture. Heating may be performed for regeneration of the adsorbent for dehydration when removing water. Thereby, the efficiency of a system can be raised more. The recovery of the exhaust heat can be appropriately performed using a heat exchanger or the like.

  Similarly, in order to increase the efficiency of the system, the exhaust heat obtained in the fuel cell power generation process is used to remove moisture by preheating the gasifying agent in the pyrolysis gasification process, preheating the oxidant in the combustion process, and / or adsorption. You may perform the heating for reproduction | regeneration of the adsorbent for dehydration at the time of removing.

  Further, although not shown, the temperature of the membrane shift reactor may be increased at the time of starting the system using the exhaust heat obtained in the pyrolysis gasification step.

  Next, a second embodiment of the present invention will be described with reference to FIG. In the example of FIG. 2, the gas containing the concentrated carbon dioxide obtained from the membrane shift reaction process is directly supplied to the moisture removal process without going through the combustion process. In this embodiment, since the gas containing hydrogen, carbon monoxide, and the like is discharged after the separation step, this gas is supplied to the pyrolysis gasification step and recycled. Although not shown, the membrane shift reaction step may be recycled instead of or in addition to the pyrolysis gasification step.

  The present invention is not limited to the first and second embodiments, and can be implemented by appropriately combining them.

Claims (12)

  A pyrolysis gasification step in which biogas containing hydrogen is generated by pyrolysis using biomass as a raw material; a membrane shift reaction step in which the biogas is denatured into a hydrogen-rich gas in a membrane shift reactor and hydrogen is separated; and hydrogen And a separation step of separating carbon dioxide from a gas containing concentrated carbon dioxide obtained by separating the gas.   The method for producing and using hydrogen according to claim 1, further comprising a fuel cell power generation step using hydrogen separated in the membrane shift reaction step as a reaction gas.   Between the membrane shift reaction process and the separation process, a combustion process in which a gas containing concentrated carbon dioxide is burned using a burner and / or a combustion catalyst, and moisture is removed from the burned gas by cooling and / or adsorption. The hydrogen production / utilization method according to claim 1, further comprising: a moisture removing step.   The method for producing and using hydrogen according to claim 3, wherein the gasifying agent in the pyrolysis gasification step and the oxidant in the combustion step are oxygen, and the water removal step also serves as a separation step for separating carbon dioxide.   Using the exhaust heat obtained in the pyrolysis gasification process, preheating the gasifying agent in the pyrolysis gasification process, preheating the oxidant in the combustion process, and / or desorbing adsorbent when removing moisture by adsorption The method for producing and utilizing hydrogen according to claim 3 or 4, wherein heating for regeneration is performed.   Use of exhaust heat obtained in the combustion process to preheat the gasifying agent in the pyrolysis gasification process, preheat the oxidant in the combustion process, and / or regenerate the adsorbent for dehydration when removing moisture by adsorption The method for producing and utilizing hydrogen according to claim 3, wherein the heating is performed.   Between the membrane shift reaction process and the separation process, a combustion process in which a gas containing concentrated carbon dioxide is burned using a burner and / or a combustion catalyst, and moisture is removed from the burned gas by cooling and / or adsorption. A fuel cell power generation process using hydrogen separated in the membrane shift reaction process as a reaction gas, and using exhaust heat obtained in the fuel cell power generation process, The method for producing and utilizing hydrogen according to claim 1, wherein preheating of the gasifying agent, preheating of the oxidant in the combustion process, and / or heating for regeneration of the adsorbent for dehydration when moisture is removed by adsorption.   A pyrolysis gasification step in which biogas containing hydrogen is generated by pyrolysis using biomass as a raw material; a membrane shift reaction step in which the biogas is denatured into a hydrogen-rich gas in a membrane shift reactor and hydrogen is separated; and hydrogen A water removal step for removing water by cooling and / or adsorption from a gas containing concentrated carbon dioxide obtained by separating the carbon dioxide, and a separation step for separating carbon dioxide from the gas from which water has been removed, A hydrogen production / utilization method in which a gas containing hydrogen obtained through a separation step is recycled to a pyrolysis gasification step and / or a membrane shift reaction step.   Using the exhaust heat obtained in the pyrolysis gasification process, preheating the gasifying agent in the pyrolysis gasification process and / or heating for regeneration of the adsorbent for dehydration when moisture is removed by adsorption. The method for producing and utilizing hydrogen according to claim 8.   The method for producing and using hydrogen according to claim 8 or 9, further comprising a fuel cell power generation step using hydrogen separated in the membrane shift reaction step as a reaction gas.   Claims for preheating the gasifying agent in the pyrolysis gasification process and / or heating for regeneration of the adsorbent for dehydration when removing moisture by adsorption using the exhaust heat obtained in the fuel cell power generation process Item 11. The method for producing and utilizing hydrogen according to Item 10.   The hydrogen production / utilization method according to any one of claims 1 to 11, wherein the temperature of the membrane shift reactor is increased using exhaust heat obtained in the pyrolysis gasification step.

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