JP2008069017A - Method for producing hydrogen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique to efficiently produce hydrogen in low temperature gasification advantageous to small-scale gasification device. <P>SOLUTION: A method for producing hydrogen comprises a first heat exchanging means 105 using a gas product 104 generated by reacting an organic material 101 with steam 103 in a reaction medium 102 as a high-temperature heat source, a second heat exchanging means 107 using a gas product 106 after heat exchanging in the first heat exchanging means 105 as a high-temperature heat source, and a hydrogen separation means 110 to separate hydrogen from a gas product 109, wherein the gas product 109 which moves to the hydrogen separation means 110 from the second heat exchanging means 107 is used as a low-temperature heat source of the first heat exchanging means 105. Tar and the like are removed by condensation in the second heat exchanging means 107, and the cooled gas product 109 is reheated in the first heat exchanging means 105 and supplied to the hydrogen separation means 110, thereby capable of suppressing the temperature reduction of the hydrogen separation means 110 and efficiently separating hydrogen to produce high concentration hydrogen. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for efficiently producing hydrogen using organic materials such as coal and biomass as raw materials.

  Rapid pyrolysis has been developed as a new utilization technology that can convert organic matter such as coal and biomass into gases, liquids and solids with high utility value. For example, when coal is used, the coal can be used in a non-oxidizing atmosphere of 873 to 1273K. It is known that when pyrolyzing is produced, a combustible gas composed of hydrocarbon, carbon monoxide, hydrogen and the like, and tar and char as chemical raw materials are produced.

  A method in which char among these pyrolysis products is separated from high-temperature combustible gas with a cyclone, etc., recycled, gasified with oxygen and steam in a gasification furnace, coal is blown into the high-temperature gas, and pyrolysis is performed Is described in Patent Document 1.

  On the other hand, in high-temperature flammable gas after passing through the cyclone, there are solid powders such as tar vapor, residual char and fly ash, and these are partially mixed with solid powder by orifice and water spray dust removal such as Venturi scrubber. It is recovered as a condensed tar mixture. Further, the remaining tar vapor is condensed by direct cooling by water spray or by indirect cooling by a water-cooled tube or a water-cooled wall as described in Patent Document 2, Patent Document 3, Patent Document 4, etc., for example, as a liquid mixture Collected.

  In this way, among the rapidly pyrolyzed products, the solid component char is separated by a cyclone or the like and recycled to the gasification furnace, where it is gasified and used as a heat source for the coal pyrolysis reaction. By using the product efficiently, high thermal efficiency can be obtained. However, usually 40-60% of pyrolysis coal is char, but the amount of char required for gasification is only a part of the generated char, and the rest is used for other purposes such as solid fuel. The

  On the other hand, the gas after separating the char contains fine powders such as tar char and cyclone unrecovered, and solid powders such as fly ash, which are partially condensed with the solid powders by a venturi scrubber or the like. A mixture with tar, ie tar sludge, is recovered. This mixture can be used as a fuel because of its high combustible component, but it must be treated with ash because of its high ash component, and it is easy to solidify because it is a mixture with heavy tar. Since there are problems such as difficulty in handling, conventionally, its use has been limited to low value-added uses such as industrial waste treatment fuel.

  Also, the tar recovered after the venturi scrubber does not sufficiently dissociate the high-molecular-weight substances in the coal when rapid coal pyrolysis of young coal with a high oxygen content. In addition, many fine solids were also mixed. Therefore, conventionally, the remainder obtained by separating the active ingredient from the tar mixture by distillation cannot be a chemical raw material, and has been limited to the same usage as described above.

  As described above, the conventional method does not always effectively utilize the thermal decomposition product, and some improvement measures are required.

  Therefore, recently, as a method for efficiently utilizing the distillation residue of char, sludge and tar generated in rapid pyrolysis of coal, there is a technique disclosed in Patent Document 5.

  However, as a gasification method for distributed gasification power generation that uses waste biomass as a raw material and uses gas as a fuel for power generation at the source of the biomass, it is not purified tar or char but external use It is required to discharge as possible gas.

  However, in order to make a substance containing hydrocarbons that have once been energized and reduced in molecular weight, such as tar and solid powder obtained by condensing the product gas, to be a gas that can be used externally, Since energy is applied, low energy may be used to further reduce the molecular weight of the gas, but it is not always efficient when obtaining usable exhaust gas.

  In other words, it is required to gasify a material suitable for gasification and burn a material suitable for combustion to obtain an exhaust gas that can be used as a heat source with high efficiency. There is a HYCOL (entrained bed coal gasification technology) process that is being developed by NEDO (New Energy Industrial Technology Development Organization) with a pulverized coal air current carrying one-chamber two-stage swirl flow system.

  However, since this process is operated at a high temperature of 1773 to 2073 K and a high pressure of 10 to 30 atm, there are many problems to be solved in view of safety in continuous operation over a long period of time. Is expected to be extremely difficult.

  Patent Document 6 describes that char can be pyrolyzed, char separated from tar and the like as a gasification raw material, and heated with a relatively low temperature (1023 to 1073 K) and normal pressure for a long period of time. A spouted bed type gasifier with a draft tube using heat storage ceramic particles as a supply medium is disclosed.

  However, in such a gasifier, it is possible to obtain hydrogen as a main component of the gas. However, since this mixed gas contains carbon monoxide at a high concentration, it is difficult to use it in a fuel cell. It is preferable to reduce the carbon monoxide concentration to about 10 ppm.

  In view of this, water and oxygen are allowed to act on coal to produce a mixed gas mainly composed of hydrogen and carbon monoxide, and hydrogen is separated from the mixed gas with high purity by a reformer having a hydrogen separation and permeable membrane. The invention is disclosed (for example, see Patent Document 7).

  FIG. 3 is a schematic explanatory view showing a conventional hydrogen production system, which is shown in Patent Document 7 described above.

In FIG. 3, coal gasification is performed by supplying coal, steam, and oxygen to the gasification furnace 1. In the gasification furnace 1, as an example, steam and oxygen are allowed to act on coal in a high temperature and high pressure state of a temperature of 1300 to 1400 ° C. and a pressure of 50 to 60 kg / cm ² to obtain a gasified combustible gas. This combustible gas maintains a high pressure and a high temperature at a temperature of 1350 ° C. and a pressure of about 65 kg / cm ² , and is transferred to the reformer 3 by the line 2.

  In the reformer 3, the high-temperature and high-pressure combustible gas is used as a heat source for reforming the natural gas 4. That is, in the reformer 3, hydrogen gas is generated from natural gas using the hydrogen separation / permeation membrane described above, and this reaction is an endothermic reaction.

  The combustible gas used as the heating source of the reformer 3 is cooled to about 450 ° C. and then transferred to the desulfurizer 6 via the line 5 to remove hydrogen sulfide, SOX, and the like.

  The combustible gas that has been subjected to the desulfurization treatment is led to a combustor 8 that constitutes a gas turbine power generation device via a line 7.

The remaining off-gas 9 from which hydrogen has been separated from the reformer 3 includes CO ₂ , unreacted natural gas, hydrogen, CO, steam, and the like. This off-gas is directly passed from the reformer 3 via the line 9. It can be transferred to the combustor 8 and used as fuel. In such a case, it is also useful for improving fuel efficiency.

  The combustor 8 generates high-temperature and high-pressure combustion gas by burning combustible gas. The combustion gas is guided to the gas turbine 11 through the line 10 and rotates the gas turbine 11. This rotational force is partially used by an air compressor 12 that supplies compressed air to the combustor 8, and the rest is converted into electric power by a generator 13.

  The combustion waste gas discharged from the gas turbine 11 after rotating the gas turbine 11 is maintained at a high temperature of 450 to 650 ° C. even after the gas turbine 11 is rotated, and the waste heat recovery boiler passes through the line 14. 15 is sent. Then, it is emitted from the chimney 16 to the atmosphere.

  A reformer 17 is installed in the waste heat recovery boiler 15 and is heated by high-temperature combustion waste gas. In the reformer 17, the natural gas 4 is reformed as in the reformer 3, and high-purity hydrogen is generated by the action of the hydrogen separation and permeable membrane.

  The natural gas 4 is transferred to the reformers 3 and 17 through the lines 19 and 20 together with the water 18 preheated in the waste heat recovery boiler 15. Hydrogen produced by the reformers 3 and 17 is supplied to the fuel cell 23 via the lines 21 and 22 and used for power generation.

Further, the remaining off-gas from which hydrogen is separated from the reformer 17 includes CO ₂ , unreacted natural gas, hydrogen, CO, steam, and the like, and is used as fuel for the combustor 8 via the line 24. is there.
Japanese Patent Laid-Open No. 4-122897 JP 7-82564 A JP-A-7-82565 JP 7-268355 A JP 2000-239671 A JP-A-2-286788 Japanese Patent No. 3453218

However, the system operating conditions the gasifier 1, a temperature 1300-1400 ° C., a high-temperature high-pressure state of the pressure 50~60kg / cm ^2, the combustible gases generated even if the temperature 1350 ° C., a pressure 65 kg / cm ² High pressure and high temperature.

  For this reason, the gasification furnace 1 needs a sufficient heat and pressure resistant design and safety device. In a relatively large plant with a daily coal consumption of several tens of tons, these measures can be taken to ensure safety, but a small-scale power generation system that generates power at a place where electricity is consumed is assumed. For a scale gasifier, a design that can withstand the above-mentioned severe operating conditions results in a large outer dimension with respect to the internal volume of the gasification furnace 1, and it is difficult to reduce the size.

  For these reasons, low-temperature and low-pressure operating conditions are preferable for small-scale gasifiers. However, in general, chemical reactions are temperature-dependent, and by reducing the temperature of the gasification furnace 1, the reactivity becomes slow and unmodified. Since the quality tar is increased, there is a problem that the tar is attached to the surface of the hydrogen separation membrane in the reformer 3 and the separation performance is deteriorated in addition to the reduction in the recovery rate of the combustible gas.

  For this reason, a technique for efficiently producing hydrogen has been demanded even in low-temperature gasification advantageous for a small-scale gasification apparatus.

  In order to solve the above problem, the present invention uses a gas product generated by thermochemical reaction of an organic substance and water vapor as a high-temperature heat source of the first heat exchange means, and the first heat exchange means. Hydrogen gas separation means for separating the hydrogen from the gas product after the heat exchange by the second heat exchange means, using the gas product after the heat exchange by the second heat exchange means as the high temperature heat source of the second heat exchange means And the low-temperature heat source of the first heat exchange means is the gas product that moves from the second heat exchange means to the hydrogen separation means.

  As a result, the undecomposed tar contained in the gas product generated from the reaction means operated at a relatively low temperature is condensed and removed by the second heat exchange means, and the low-temperature gas product is converted into the first product. The heat product is heated again to a high temperature, and the gas product at the high temperature can be supplied to the hydrogen separation means, so that the temperature drop of the hydrogen separation means can be suppressed and the separation performance can be maintained. it can.

  According to the present invention, compared with the prior art described in Patent Document 7, the steam gasification reaction of organic matter such as coal and biomass is performed at a low temperature, and even if tar and the like contained in the gas product increase, This gas flow is once cooled and condensed and removed. Furthermore, the gas product whose temperature has been lowered by this cooling operation is heated again using the heat that it had before cooling, and is supplied to the hydrogen separator without reducing the separation performance. A gas rich in hydrogen can be recovered.

  The invention according to claim 1 is a reaction means for thermochemically reacting an organic substance and water vapor, a first heat exchange means using a gas product generated from the reaction means as a high-temperature heat source, and the first heat. A second heat exchanging means using the gas product after exchanging heat by the exchanging means as a high-temperature heat source; and a hydrogen separating means for separating hydrogen from the gas product after exchanging heat by the second heat exchanging means. The low-temperature heat source of the first heat exchange means is the gas product that moves from the second heat exchange means to the hydrogen separation means.

  Thus, undecomposed tar contained in the gas product generated from the reaction means operated at a relatively low temperature is condensed and removed by the second heat exchange means.

  And the gas product which became low temperature is again heated by the heat which self had before cooling by the said 1st heat exchange means, and becomes high temperature. Thus, since the gas product which became high temperature can be supplied to the said hydrogen separation means, the temperature fall of the said hydrogen separation means can be suppressed, and separation performance can be maintained. For this reason, hydrogen can be efficiently separated from the gas product, and high-concentration hydrogen can be produced.

  In the invention according to claim 2, the temperature of the reaction means is in the range of 700 ° C to 1000 ° C.

  As a result, tar contained in the gas product can be suppressed as much as possible while the temperature is relatively low. For this reason, since the yield of a gas product increases and the amount of hydrogen generation increases accordingly, more highly concentrated hydrogen can be produced.

  According to a third aspect of the present invention, the low temperature heat source temperature of the second heat exchanging means is not higher than the condensation temperature of water vapor.

  As a result, not only the tar contained in the gas product but also water vapor can be condensed and removed. For this reason, since the water vapor | steam density | concentration which is not valuable as a fuel can be reduced, the hydrogen density | concentration in a gas product can be improved relatively. As a result, the hydrogen separation means can separate hydrogen more efficiently and produce high-concentration hydrogen.

  Invention of Claim 4 makes the low-temperature heat source of the said 2nd heat exchange means water, and the steam generation means to generate | occur | produce the water vapor | steam supplied to the said reaction means from the said water heated by the said 2nd heat exchange means It is equipped with.

  As a result, the gas product that is the high-temperature heat source and the heat of the water vapor move to the water of the low-temperature heat source in the second heat exchange means, and based on this, water vapor is generated by the steam generation means, and the reaction Since it is supplied to the means, a lot of heat can be effectively used in the system. For this reason, the input energy from the outside can be reduced, and high-concentration hydrogen can be produced more efficiently.

  According to a fifth aspect of the present invention, the combustible component of the residue of the gas product from which hydrogen has been separated by the hydrogen separation means is burned, the combustion heat is used as the high-temperature heat source, and the first heat exchange means A third heat exchange means using the gas product moving to the hydrogen separation means as a low-temperature heat source is provided.

  Thus, the combustion heat contained in the gas product after hydrogen separation can be effectively used, and the gas product supplied to the hydrogen separation means can be heated to a high temperature. Thus, since the gas product which became high temperature can be supplied to the said hydrogen separation means, the temperature fall of a hydrogen separation means can be suppressed and separation performance can be maintained. For this reason, hydrogen can be more efficiently separated from the gas product, and high-concentration hydrogen can be produced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Further, the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a flowchart for explaining the steps of the hydrogen production method according to the first embodiment.

  As shown in FIG. 1, the organic substance 101 is so-called biomass such as coal, firewood, wood chips, and sludge. In the reaction means 102, the organic substance 101 reacts with the water vapor 103, and as a result, a gas product 104 mainly composed of hydrogen, methane, carbon monoxide, carbon dioxide, ethylene, etc. is generated.

  In addition, condensable tar is also produced as a byproduct from the reaction. Therefore, it is preferable to operate the reaction means 102 in the range of 700 ° C. to 1000 ° C. so that the tar reacts with the water vapor 103 to increase the yield of the gas product 104 as much as possible.

  The temperature of the gas product 104 immediately after being discharged from the reaction means 102 is equal to that of the reaction means 102 and is used as a high-temperature heat source for the first heat exchange means 105.

  The gas product 106 after passing through the first heat exchange means 105 is supplied to the second heat exchange means 107. In the second heat exchanging means 107, the tar and surplus steam 103 flowing together with the gas product 106 are the high-temperature heat source, and the condensable tar and the steam 103 are condensed by exchanging the heat with the low-temperature heat source. These are then separated from the gas product 106 and removed.

  Here, the condensing temperature of the water vapor 103 depends on the system pressure, but when assuming a small-scale gasifier, it is preferable to use a normal pressure, so that a refrigerant (cooling water) 108 of 100 ° C. or lower is used as a low-temperature heat source. Use it.

  The gas product 106 is cooled by the cooling water 108 in the second heat exchange means 107, where condensable impurities are reduced and the gas product 106 is purified. At this time, the gas product 109 becomes a mixed gas containing hydrogen and is supplied to the hydrogen separation means 110. Then, only hydrogen is separated by the hydrogen separation means 110, whereby high purity hydrogen 111 is produced as a fuel gas.

  The hydrogen separation means 110 is preferably a metal film having excellent hydrogen permeation performance such as palladium. In addition, since the hydrogen permeation performance of such a metal membrane is generally temperature-dependent, it is not possible to supply the gas product 109 cooled by the second heat exchange means 107 to the hydrogen separation means 110 as it is. There is a risk of deteriorating hydrogen separation performance.

  However, in the first embodiment, the gas product 109 is cooled by the cooling water 108 in the second heat exchange means 107 while the gas product 109 is supplied from the second heat exchange means 107 to the hydrogen separation means 110. Since it is heated by the first heat exchange means 105 and reaches a temperature of about 500 ° C., the hydrogen separation performance of the hydrogen separation means 110 is maintained by this temperature rise. As a result, high-purity hydrogen 111 can be produced, and power can be generated by supplying the high-purity hydrogen 111 to the fuel cell 112.

  Thus, in a relatively low temperature range such as 700 ° C. to 1000 ° C., an organic substance 101 such as coal or biomass reacts with the water vapor 103 to generate the gas product 104, and impurities such as tar and water vapor are contained. After removing and purifying, high purity hydrogen 111 can be produced. In addition, since the system pressure is almost normal pressure, hydrogen can be efficiently produced even in a small-scale gasifier without a heavy structure and safety design.

  In addition, as organic substance 101, not only solid substances, such as coal and biomass, but city gas, propane gas, alcohols, etc. may be used.

  Further, in order to improve the recovery rate of the gas product 104, a catalyst having a hydrocarbon decomposition function such as nickel or activated alumina may be added to the reaction means 102.

(Embodiment 2)
FIG. 2 is a flowchart for explaining the steps of the hydrogen production method according to the second embodiment. Components similar to those in FIG. 1 are denoted by the same reference numerals, and here, different from those in the first embodiment. The contents will be mainly described.

  In FIG. 2, water 201 is supplied as a low-temperature heat source for the second heat exchange means 107 in order to condense and remove tar and excess water vapor 103 as impurities of the gas product 104. The water 201 whose enthalpy has increased by the heat exchange in the second heat exchange means 107 is heated by the steam generator 202 to become the water vapor 103.

  On the other hand, the gas product 109 cooled by the second heat exchange means 107 is heated by the first heat exchange means 105 and then reheated by the third heat exchange means 203. The heat source at this time is the combustion heat of combustible components such as methane contained in the gas product 204 after the hydrogen is separated by the hydrogen separation means 110, and is mixed with the air 205 to be mixed by the third heat exchange means 203. It occurs when burned.

  As described above, in a series of hydrogen production processes, by effectively utilizing a part of the latent heat of condensation of the excess steam 103 and the amount of heat of the gas product 204, it is advantageous for a small-scale gasifier and a low-temperature reaction. Hydrogen can be efficiently produced even at a temperature.

  As described above, the hydrogen production method according to the present invention makes it possible to produce hydrogen, which is fuel for fuel cells, from coal or biomass with high efficiency even on a small scale, and to generate power. For this reason, hydrogen can be produced in power consuming areas such as hotels, restaurants, and houses, which can contribute to the spread of distributed power sources with less loss due to power transmission.

Flow chart illustrating the steps of the hydrogen production method in Embodiment 1 of the present invention Flow chart illustrating the steps of the hydrogen production method according to Embodiment 2 of the present invention Schematic illustration of a hydrogen production system showing conventional technology

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Organic substance 102 Reaction means 103 Water vapor 104 Gas product 105 1st heat exchange means 106 Gas product 107 2nd heat exchange means 108 Cooling water 109 Gas product 110 Hydrogen separation means 201 Water 202 Steam generation means 203 3rd Heat exchange means 204 Gas product

Claims (5)

  Reaction means for thermochemical reaction of organic matter and water vapor, first heat exchange means using a gas product generated from the reaction means as a high-temperature heat source, and the heat exchange after the first heat exchange means A second heat exchange means using a gas product as a high-temperature heat source; and a hydrogen separation means for separating hydrogen from the gas product after heat exchange by the second heat exchange means. A hydrogen production method in which the low temperature heat source of the means is the gas product that moves from the second heat exchange means to the hydrogen separation means.   The method for producing hydrogen according to claim 1, wherein the temperature of the reaction means is in the range of 700 ° C to 1000 ° C.   The hydrogen production method according to claim 1 or 2, wherein a low temperature heat source temperature of the second heat exchange means is set to be equal to or lower than a condensation temperature of water vapor.   The low-temperature heat source of the second heat exchange means is water, and steam generation means for generating water vapor to be supplied to the reaction means from the water heated by the second heat exchange means is provided. The method for producing hydrogen according to any one of the above.   Combusting the combustible component of the residue of the gas product from which hydrogen has been separated by the hydrogen separation means, using the combustion heat as the high-temperature heat source, and further moving from the first heat exchange means to the hydrogen separation means The hydrogen production method according to any one of claims 1 to 4, further comprising third heat exchange means using the gas product as a low-temperature heat source.

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