JP2009096895A - Gasification method and gasification apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gasification method and a gasification apparatus, for gasifying a biomass in an entrained bed gasification furnace to produce a gas used as a fuel or a chemical raw material, which each does not cause a piping trouble due to tars, uses a part of the produced gas as a carrying gas, and thereby totally increases the calorific power of the produced gas in the gasification apparatus. <P>SOLUTION: This gasification apparatus 100 for gasifying the biomass supplied to the entrained bed gasification furnace 130 by a gas flow carrying method, to produce a gas is characterized by cooling the produced gas used as the carrying gas, removing tars from the cooled produced gas, and supplying the tar-removed gas to a carried gas supply device 120, the carried gas supply device 120 uses a part or all of the produced gas as the carrying gas, and the gasification method using the apparatus 100. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gasification method and a gasification device, and more particularly to a gasification method and a gasification device that gasify biomass in a spouted bed gasification furnace to obtain a product gas used as a fuel or a chemical raw material.

  In recent years, with the background of soaring fossil resource fuels (for example, coal, oil, natural gas, kerosene, light oil, heavy oil, etc.) and global warming problems, development aimed at using biomass as energy has become active. Yes.

  Since biomass contains abundant carbon and hydrogen, biomass is used in place of fossil resource fuel to reduce the amount of fossil resource fuel used. However, because biomass contains a lot of oxygen and has a high water content, it is an inferior fuel with a low calorific value per unit mass compared to fossil fuels, and also has a pretreatment (drying and crushing) load. Is high (high equipment costs, high operating costs). Therefore, the driving force of social significance (corporate attitude, carbon dioxide reduction pressure, etc.) and subsidies (equipment assistance, RPS merit) is presupposed for the introduction of biomass. On top of that, since technology that uses biomass in place of fossil fuels is economically established, development of technology that can achieve high efficiency and low cost (low equipment cost, low operation cost) is being promoted.

  Technologies for converting biomass into gas energy (pyrolysis, partial combustion) include fixed bed processes, moving bed processes, fluidized bed processes, spouted bed processes, and combinations of these processes. However, in order to achieve the above-mentioned high efficiency, it is necessary to be a process that has a low overall heat loss or a process that can recover heat, so that the reaction proceeds sufficiently at low temperatures or the heat dissipated at high temperatures is kept low. Is the key to technology. Although the decomposition reaction itself tends to have better conversion efficiency at lower temperatures, the reaction rate decreases at lower temperatures, the reaction takes longer (the reactor becomes larger), and the number of unreacted substances increases. Efficiency does not necessarily improve. Moreover, in order to gasify the pyrolysis residue, it is necessary to perform combustion, partial combustion, etc., and a high temperature field will be generated.

  For example, Patent Document 1 proposes a process for producing methanol by converting biomass into spouted bed gas. Spouted bed gasification is a technology that has been developed using coal as a raw material, but gasification reactions up to carbon monoxide and hydrogen are possible in a short time (reaction time is several seconds, moving bed is several hours, fluidized bed is (Several tens of minutes) In addition, since the effect of reducing the volume due to pressurization is great, it is possible to expect a significant reduction in the heat dissipated by reducing the surface area by making compact. In particular, when coal is used, a reaction temperature of 1500 to 1600 ° C. is required, whereas when biomass is used, a reaction temperature of 1000 to 1200 ° C. may be sufficient, and this is a representative technology that can be expected to achieve high-efficiency gas conversion. It is a case.

JP-A-8-296975 JP 2004-34534 A

  As described above, when using a biomass raw material, which is an inferior fuel with a low calorific value per unit weight as compared to fossil fuels, high efficiency and low cost are essential. However, most of the raw materials for which pretreatment such as drying and pulverization is an important factor occupy the majority, and the equipment cost increases compared to coal and the like, so it is almost difficult to reduce the cost. Therefore, in order to use biomass raw materials, it is necessary to develop a technology for improving the efficiency. Therefore, the present inventors have selected a spouted bed gasification technology and sought to improve the efficiency further.

  Spouted bed gasification is a technology that produces raw materials such as carbon monoxide, hydrogen, and methane by partially burning and reacting raw materials with oxygen in a reaction vessel (gasification furnace). In order to improve efficiency, it is necessary to have a process with a low overall heat loss. For that purpose, the key to the technology is to proceed the reaction sufficiently at a low temperature or to keep the heat dissipated low at a high temperature. Here, the gasification reaction itself has more hydrocarbons at lower temperatures, and the generated gas heat generation increases, while at low temperatures the reaction rate decreases and the reaction takes longer (the reactor becomes larger) or unreacted. There is a problem that the amount of generated gas decreases due to an increase in the number of objects, and the efficiency is not necessarily improved as a whole.

  As one of the measures for solving such a problem, for example, in Patent Document 2, in a process of producing methanol by using a waste plastic as a raw material to produce spouted bed gas, a part of the generated gas is replaced with a carrier gas and generated as a whole. A method for increasing the calorific value of gas has been proposed.

  However, when a part of the product gas is used as the carrier gas, there is a problem that the amount and quality of tar in the product gas are greatly affected. That is, when the tar in the generated gas condenses, piping troubles such as a differential pressure increase and piping blockage may occur. In particular, tar produced by gasification of biomass is very poor in properties during condensation and is likely to cause piping troubles as compared to tar produced by gasification of plastic as in Patent Document 2. Therefore, when using biomass, it is difficult to use a part of the generated gas as a carrier gas, and there is no practical example.

  Therefore, the present invention has been made in view of such a problem, and in a gasification method and a gasification apparatus for gasifying biomass in a spouted bed gasification furnace to obtain a product gas used as a fuel or a chemical raw material. An object of the present invention is to increase the calorific value of the product gas as a whole gasifier by using a part of the product gas as a carrier gas without causing piping trouble due to tar.

  As a result of intensive studies in order to solve the above problems, the present inventors have actively removed a small amount of tar remaining in the product gas after the cooling step for fractionating tar from the product gas. By using the product gas from which tar has been removed as a carrier gas, a part of the product gas can be used as a carrier gas without causing piping troubles due to tar condensation. Based on this finding, the present inventors have completed the present invention.

  In this way, by positively removing a small amount of tar remaining in the product gas after the cooling step for fractionating tar from the product gas, the product gas from which the tar has been removed is used as a carrier gas. Since the tar concentration in the product gas used as the carrier gas can be reduced, even if the tar is condensed, the amount of condensation is so small that a situation that causes piping trouble can be prevented.

That is, the gist of the present invention is as follows.
(1) A transporting process for transporting biomass to an entrained bed gasification furnace, a gasification process for generating a product gas by gasifying the biomass transported by the air stream in the spouted bed gasification furnace, and the product gas And a tar removal step for removing tar from the product gas cooled in the cooling step. In the transfer step, one of the product gases from which tar has been removed in the tar removal step. A gasification method characterized by using a part or all as a carrier gas at the time of carrying the air current.
(2) The gasification method according to (1), wherein a tar concentration of the product gas used as the carrier gas is less than 100 mg / Nm ³ .
(3) In a gasification apparatus that supplies biomass to an entrained bed gasification furnace by airflow conveyance and gasifies the biomass in the entrained bed gasification furnace to generate a generated gas, biomass as a raw material is converted into the entrained bed gasification Tar is removed from the product gas cooled by the raw material supply device supplied to the furnace, the carrier gas supply device for supplying the carrier gas in the air current conveyance, the cooling device for cooling the product gas, and the cooling device A part or all of the product gas from which the tar has been removed by the tar removal device is supplied to the carrier gas supply device, and the carrier gas supply device is a part of the product gas. Part or all of the gasifier is used as the carrier gas.
(4) The gasifier according to (3), wherein the tar removal device has a tar concentration of the product gas of less than 100 mg / Nm ³ .
(5) The gasifier according to (3), wherein the tar removing device is a filter using a nonwoven fabric or a packed bed filled with alumina.

  According to the present invention, in a gasification method and a gasification apparatus for gasifying biomass in a spouted bed gasification furnace to obtain a product gas used as a fuel or a chemical raw material, without generating piping trouble due to tar By using a part of the gas as the carrier gas, the calorific value of the product gas can be increased as a whole gasifier.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[Configuration and operation of general gasifier]
Prior to describing a gasifier according to an embodiment of the present invention, first, the configuration and operation of a general gasifier will be described with reference to FIG. FIG. 3 is an explanatory diagram showing a configuration of a general gasifier 10.

  The gasifier 10 is an apparatus that gasifies biomass as a raw material to produce a gas that becomes a fuel or a chemical raw material, and a product gas obtained by gasifying the biomass includes, for example, a combustion burner, chemical synthesis (acetic acid synthesis, Alcohol synthesis, etc.) It is used for general use of gas mainly composed of carbon monoxide and hydrogen, such as an apparatus and a hydrogen separator. Specifically, as shown in FIG. 3, the gasifier 10 mainly includes a raw material supply device 11, a carrier gas supply device 12, a spouted bed gasification furnace 13, a cooling device 14, and a booster device. 15 and.

  The raw material supply device 11 supplies biomass as a raw material to the spouted bed gasifier 13.

  The carrier gas supply device 12 supplies a carrier gas carrying biomass to the spouted bed gasifier 13. In the gasifier 10, a gas such as nitrogen or steam is used as the carrier gas when the apparatus is started up, and part or all of the generated gas is used after the biomass is gasified and the generated gas is generated. The biomass raw material supplied from the raw material supply device 11 is air-flowed by the carrier gas supplied from the carrier gas supply device 12 and supplied to the spouted bed gasifier 13.

  The spouted bed gasifier 13 combusts biomass therein and generates a product gas mainly composed of hydrogen and carbon monoxide by a partial oxidation reaction. Inside the spouted bed gasifier 13, a partial oxidation reaction (exothermic reaction) occurs due to the biomass raw material supplied from the raw material supply device 11 and the oxidant supplied from the outside, and the spouted bed gasifier 13 is generated by the reaction heat. The internal temperature can be maintained at 1000 to 1200 ° C. In addition, by controlling the partial oxidation reaction uniformly, it is possible to properly control the complete combustion of the raw material biomass.

  The product gas generated from the spouted bed gasifier 13 is a gas mainly generated by hydrocarbons such as carbon monoxide, hydrogen, carbon dioxide, water vapor, nitrogen, methane, etc., generated by a partial oxidation reaction. It is a combustible gas having a calorific value calculated by multiplying the composition ratio (volume ratio) of hydrocarbons such as carbon, hydrogen, methane and the like with each calorific value.

  The cooling device 14 cools the high-temperature product gas generated from the spouted bed gasification furnace 13 in order to remove components such as tar and light oil contained in the product gas. The temperature of the product gas after being cooled by the cooling device 14 varies depending on the purpose of use of the product gas, but is usually set to a temperature of about 200 ° C. from around normal temperature. The cooling capacity and equipment scale of the cooling device 14 become excessive as the temperature of the product gas after cooling is lower. In particular, a cooling device that uses a lot of energy, such as a chiller, is required to bring the temperature to around room temperature. On the other hand, the higher the temperature of the product gas after cooling, the more tar and light oil remaining in the product gas. However, even if the temperature of the product gas is lowered to near normal temperature, some tar remains and the tar is not completely removed.

  In order to supply the product gas cooled by the cooling device 14 to the spouted bed gasifier 13, the booster 15 is boosted to a pressure higher than that of the spouted bed gasifier 13. A part of the product gas boosted by the pressure booster 15 is supplied to the carrier gas supply device 12, and the remaining product gas is used as a product gas in equipment installed in the subsequent stage. The equipment installed in the latter stage is equipment that uses a gas mainly composed of carbon monoxide and hydrogen, such as a combustion burner, a chemical synthesis (acetic acid synthesis, alcohol synthesis, etc.) apparatus, a hydrogen separator, and the like. Note that the booster 15 is not necessarily provided as long as the product gas cooled by the cooling device 14 can be supplied to the spouted bed gasification furnace 13.

  By the way, in the general gasifier 10 described above, when a part of the generated gas generated in the spouted bed gasifier 13 is used as a carrier gas, the amount and quality of tar in the generated gas have a great influence. There was a problem that. That is, when the tar in the generated gas condenses, piping troubles such as a differential pressure increase and piping blockage may occur. Specifically, for example, tar (mainly mist-like tar) that cannot be removed by detoxification (removing water-soluble gas such as hydrochloric acid and ammonia with water spray etc.) decreases the temperature of the product gas. There is a case where condensation occurs and accumulates at a portion (temperature lowering portion) or a narrowed portion of the flow path (for example, in the vicinity of the flow control valve, in the vicinity of the gas merging portion).

  In particular, tar produced by gasification of biomass is very poor in properties during condensation and is likely to cause piping troubles as compared to tar produced by gasification of plastic as in Patent Document 2. This is because tar generated from biomass is mainly composed of aromatic tars due to the raw material structure and thermal decomposition characteristics of biomass. That is, tars mainly composed of aliphatic tar generated from waste plastics are generated with a wide variety of tar distributions, whereas tars mainly composed of aromatic tar generated from biomass are Since the product is cut at a position where it can be easily cut, a certain amount of product bias and the characteristics of the product cause adverse effects. Among such aromatic tars, naphthalenes are sensitive to temperature because they have sublimation properties, and are likely to precipitate (solidify) at a stretch in the temperature-decreasing portion. Also, since aromatics other than naphthalene often have a viscosity that suddenly increases upon condensation, it is difficult to use part of the product gas as a carrier gas when using biomass. No.

  In addition, there is an operation measure as one method for avoiding the generation of tar. Specifically, during the gasification reaction in biomass, the temperature is high (for example, in wood, the reaction temperature range during a normal gasification reaction is 1000 to 1200 ° C., and the high temperature indicates around 1200 ° C. or higher). There is a method of performing a gasification reaction in order to reduce tar generated by a thermal decomposition reaction. However, as a result of performing the gasification reaction at a high temperature, the heat dissipation becomes high, resulting in a decrease in efficiency, and the efficiency improvement effect by replacing the carrier gas with the product gas is negated. For this reason, the above operational measures are usually not adopted for the purpose of improving efficiency.

  Therefore, in one embodiment of the present invention described below, after the generated gas generated from the entrained bed gasification furnace is cooled by a cooling device, the tar remaining in a trace amount in the cooled generated gas is actively added. By providing a removing device (tar removing device), it is possible to prevent the occurrence of piping troubles due to tar condensation.

  Since the tar concentration in the product gas used as the carrier gas can be reduced by the above method, even if the tar is condensed, the amount of condensation is so small that it prevents a situation that causes piping trouble. be able to.

  Therefore, a part of the generated gas can be used as the carrier gas without causing a piping trouble due to the condensation of tar, so that the heat generation amount of the generated gas can be increased as a whole gasifier. Hereinafter, in one embodiment of the present invention, the above method will be described in detail.

[One Embodiment of the Present Invention]
(Configuration of gasifier 100)
Based on FIG. 1, the structure of the gasifier which concerns on one Embodiment of this invention is demonstrated. In addition, FIG. 1 is explanatory drawing which shows the structure of the gasifier 100 which concerns on this embodiment.

  The gasifier 100 is an apparatus that gasifies biomass as a raw material to produce a gas that becomes a fuel or a chemical raw material, and a product gas obtained by gasifying the biomass may be, for example, a combustion burner, chemical synthesis (acetic acid synthesis, Alcohol synthesis, etc.) It is used for general use of gas mainly composed of carbon monoxide and hydrogen, such as an apparatus and a hydrogen separator. Specifically, as shown in FIG. 1, the gasifier 100 mainly includes a raw material supply device 110, a carrier gas supply device 120, a spouted bed gasification furnace 130, a cooling device 140, and a booster. 150 and a tar removing device 160.

  The raw material supply device 110 supplies biomass as a raw material to the spouted bed gasifier 13. In addition, the biomass in this embodiment specifically includes, for example, agricultural biomass (straw, sugarcane, rice straw, vegetation, etc.), forestry biomass (paper waste, sawn timber, thinned wood, wood firewood, etc.) , Livestock biomass (livestock waste), aquaculture biomass (fishery processing residue), waste biomass (raw garbage, refuse solidified fuel (RDF), garden trees, construction waste, sewage sludge, etc.) Point to.

  The carrier gas supply device 120 supplies a carrier gas carrying biomass to the spouted bed gasifier 130. In the gasifier 100, a gas such as nitrogen or steam is used as a carrier gas when the apparatus is started up, and a part or all of the generated gas is used after the biomass is gasified and the generated gas is generated. The biomass raw material supplied from the raw material supply device 110 is air-flowed by the carrier gas supplied from the carrier gas supply device 120 and supplied to the spouted bed gasifier 130.

  Here, as will be described in detail later, in the gasifier 100 according to the present embodiment, in order to prevent piping trouble due to tar condensation that may occur when using part or all of the generated gas as a carrier gas. Further, a tar removing device 160 is provided.

  The spouted bed gasifier 130 burns biomass therein and generates a product gas mainly composed of hydrogen and carbon monoxide by a partial oxidation reaction. Inside the spouted bed gasifier 130, a partial oxidation reaction (exothermic reaction) occurs by the biomass raw material supplied from the raw material supply device 110 and the oxidant supplied from the outside, and the spouted bed gasifier 130 is generated by the reaction heat. The internal temperature can be maintained at 1000 to 1200 ° C. In an ordinary gasification reaction, for example, an oxygen-containing gas, a mixed gas of oxygen-containing gas and water vapor, or the like can be used as an oxidant. In addition, by controlling the partial oxidation reaction uniformly, it is possible to appropriately control the complete combustion of the raw material biomass.

  The product gas generated from the spouted bed gasifier 130 is a gas mainly generated by hydrocarbons such as carbon monoxide, hydrogen, carbon dioxide, water vapor, nitrogen, methane, etc., generated by partial oxidation reaction. It is a combustible gas having a calorific value calculated by multiplying the composition ratio (volume ratio) of hydrocarbons such as carbon, hydrogen, methane and the like with each calorific value.

  The cooling device 140 cools the high-temperature product gas generated from the spouted bed gasification furnace 130 in order to remove components such as tar and light oil contained in the product gas. The temperature of the product gas after being cooled by the cooling device 140 varies depending on the purpose of use of the product gas, but is usually set to a temperature of about 200 ° C. from around normal temperature. As the temperature of the product gas after cooling is lower, the cooling capacity and facility scale of the cooling device 140 become excessive. In particular, a cooling device that uses a lot of energy, such as a chiller, is required to bring the temperature to around room temperature. On the other hand, the higher the temperature of the product gas after cooling, the more tar and light oil remaining in the product gas. However, even if the temperature of the product gas is lowered to near normal temperature, some tar remains and the tar is not completely removed.

  In order to supply the product gas cooled by the cooling device 140 to the spouted bed gasifier 130, the booster 150 is boosted to a pressure higher than that of the spouted bed gasifier 130. A part of the product gas boosted by the pressure booster 150 is supplied to the carrier gas supply device 120, and the remaining product gas is used as a product gas in equipment installed in the subsequent stage. The equipment installed in the latter stage is equipment that uses a gas mainly composed of carbon monoxide and hydrogen, such as a combustion burner, a chemical synthesis (acetic acid synthesis, alcohol synthesis, etc.) apparatus, a hydrogen separator, and the like. Note that the booster 150 is not necessarily provided as long as the product gas cooled by the cooling device 140 can be supplied to the spouted bed gasification furnace 130.

By the way, in this embodiment, a part or all of the generated gas cooled by the cooling device 140 is supplied to the carrier gas supply device 120 and used as a substitute for part or all of the carrier gas. Here, in the generated gas, there are carbon dioxide, water vapor, and nitrogen as gases that affect the direction of decreasing the calorific value. However, for carbon dioxide and water vapor, since the composition in accordance with the equilibrium constant of the shift reaction is settled when the temperature in the spouted bed gasifier 130 is determined, it is not an operating factor that intentionally changes the calorific value. . That is, in the equilibrium reaction of “CO ₂ + H ₂ ⇔CO + H ₂ O”, when each concentration is [CO ₂ ], [H ₂ ], [CO], [H ₂ O], K = ([CO ₂ ] · [H ₂ ]) / ([CO] · [H ₂ O]), the value of K is constant, so the amount of heat generated depends on the reaction temperature. Further, since water vapor condenses in the course of cooling by the cooling device 140, in the cooling device 140 and later, basically, a portion corresponding to the saturated vapor pressure at the temperature at that time remains in the product gas. Become.

Therefore, attention is paid to the remaining nitrogen excluding carbon dioxide and water vapor among the gases affecting the direction of decreasing the calorific value. Nitrogen sources include nitrogen used as a carrier gas, nitrogen contained in air when air is used as an oxidant, nitrogen contained in biomass, nitrogen for purging, etc. And oxidizers account for the majority. In particular, when oxygen is used as the oxidizing agent, nitrogen used as the carrier gas becomes most of the nitrogen source. Since nitrogen hardly participates in the gasification reaction, the efficiency of the entire gasification process is lowered by going through the process of being heated in the spouted bed gasification furnace 130 and cooled in the cooling device 140. That is, as the energy required to raise the temperature of nitrogen increases, it is necessary to increase the oxygen ratio to increase the temperature to the same gasification temperature (increase the calorific value in an operation close to complete combustion), resulting in combustible components. That is, CO and H ₂ are reduced. Further, even if heat recovery is performed during cooling by the cooling device 140 (for example, heat recovery is performed using a boiler), the recovery efficiency does not reach 100%, and thus heat loss occurs.

  Therefore, in the gasification apparatus 100 according to the present embodiment, a part or all of the carrier gas is replaced with the product gas, thereby reducing the amount of nitrogen used as the entire gasification apparatus 100 and increasing the wasteful temperature of the nitrogen gas. And heat loss in cooling can be reduced. In addition, since the generated gas, which is a flammable gas, is blown into the spouted bed gasification furnace 130 instead of nitrogen as the carrier gas, the input heat amount per unit raw material can be increased. As a result, the fossil resource fuel The same effect as using a raw material with such a high calorific value can be obtained. Thus, by using part or all of the generated gas as the carrier gas, it is possible to reduce the heat loss in wasteful temperature rise and cooling of the nitrogen gas and increase the input heat amount per unit raw material. Therefore, the oxygen ratio for raising the temperature to the same gasification temperature can be reduced, and the heat generation amount of the product gas can be increased.

  However, in order to replace part or all of the carrier gas with the product gas in this way, as described above, it is necessary to prevent piping troubles due to tar condensation. In order to positively remove tar from the product gas after cooling by the apparatus 140, a tar removing apparatus 160 is provided.

  The tar removing device 160 is installed in the subsequent stage of the cooling device 140, and actively removes tar in order to prevent piping troubles due to tar condensation. The gas cleaned up by the tar removing device 160 is boosted by the booster 150 and supplied to the carrier gas supply unit 120 and then used as a carrier gas.

  Examples of the tar removing device 160 include a mist removing device using a filter, a mist separator in which a baffle plate is effectively arranged, a packed bed filled with an adsorbent, a simple alumina ball, and the like. These examples were given because the tar content (mainly mist tar) that could not be completely condensed by the cooling device 140 is to be removed by the tar removing device 160, so that the tar is physically captured. It depends on the method being effective. In particular, tar contained in biomass has a large trapping effect due to a method of physically trapping tar, and if it is a two-column exchange type with a filter, a packed bed or the like, it is excellent in continuous operability and maintainability.

Furthermore, the tar removing device 160 preferably reduces the tar concentration in the product gas after cooling by the cooling device 140 to less than 100 mg / Nm ³ . As shown in the examples to be described later, this is because the troubles caused by the remaining amount of tar in the generated gas conducted by the present inventors have been confirmed to cause trouble in piping at a tar concentration of less than 100 mg / Nm ^3. Although it was not seen, it was because a case that led to blockage of piping was seen at a tar concentration of 100 mg / Nm ³ or more. In the above test, it has been confirmed that a tar concentration of less than 100 mg / Nm ³ can be achieved in the nonwoven fabric filter and the alumina packed layer as the tar removing device 160.

  As described above, according to the gasifier 100 according to the present embodiment, the calorific value of the generated gas can be increased without changing the specifications of the gasifier and without any trouble in piping due to tar. Is possible. That is, when the same amount of the same raw material is used, the amount of heat generated from the product gas that can be taken out increases, improving the overall efficiency of the gasifier as a whole, reducing the amount of oxygen used, and the like.

(Gasification method)
Although the configuration of the gasifier 100 according to the present embodiment has been described above, the gasification method according to the present embodiment using the gasifier 100 having such a configuration will be described below.

  The gasification method according to the present embodiment generates a product gas by gasifying the biomass transported by airflow in the spouted bed gasification furnace 130 and transporting the raw material biomass to the spouted bed gasification furnace 130. A gasification step, a cooling step for cooling the product gas generated from the spouted bed gasification furnace 130, and a tar removal step for removing tar from the product gas cooled in the cooling step.

  In the gasification method according to the present embodiment, part or all of the product gas from which tar has been removed in the tar removal step is used as the carrier gas for airflow conveyance in the conveyance step. In this way, by using the product gas from which tar has been positively removed as the carrier gas, most of the tar remaining in the product gas in a trace amount can be removed after the cooling step, so piping troubles due to condensation of tar. Can be effectively prevented.

  Since the method for removing tar from the product gas after the cooling step has been described in detail in the description of the gasifier 100 described above, detailed description thereof is omitted here.

In the gasification method according to the present embodiment, the tar concentration of the product gas used as the carrier gas is preferably less than 100 mg / Nm ³ . This is also the knowledge obtained by the test conducted by the present inventors as described above, and details will be described in the following examples.

  According to the gasification method according to the present embodiment as described above, there is no piping trouble due to tar, and it is possible to increase the heat generation amount of the generated gas. That is, when the same amount of the same raw material is used, the amount of heat generated from the product gas that can be taken out increases, and the overall efficiency of the gasification reaction process as a whole can be improved and the amount of oxygen used can be reduced. .

  Next, the present invention will be described more specifically with reference to examples.

(Example)
In this example, as raw material biomass, a wood chip containing moisture: 14% by mass, carbon: 48% by mass-dry, hydrogen: 6% by mass-dry, oxygen: 44% by mass-dry is used as the raw material biomass. used. Moreover, it crushed until it became a particle size of 5 mm or less as a pre-process of the raw material biomass for airflow conveyance, and sifted and dried. The test conditions were such that the average biomass supply was 175 kg / hr. Further, in the initial stage of starting the gasifier, nitrogen gas is used as a carrier gas, and the condition is that the flow rate of nitrogen as the carrier gas is 110 Nm ³ / h. Oxygen was used as the oxidizing agent, and the flow rate was 61 Nm ³ / h. The temperature of the spouted bed gasifier was 1095 ° C. The composition of the product gas generated at this time is H ₂ : 17% by volume, CO: 26% by volume, CO ₂ : 19% by volume, CH ₄ : 0.7% by volume, and the calorific value of the product gas is 5.3MJ. / Nm ³ -dry. When the carrier gas (flow rate: 50 Nm ³ / h) is replaced with a part of the product gas under the above conditions, the flow rate of nitrogen as the carrier gas under the condition that the temperature of the spouted bed gasifier is almost the same as 1099 ° C. There 67Nm ³ / h, the flow rate of the product gas as a carrier gas 50 Nm ³ / h, the oxygen flow rate as an oxidizing agent was a 56 Nm ³ / h. The composition of the product gas generated at this time is H ₂ : 19 vol%, CO: 32 vol%, CO ₂ : 20 vol%, CH ₄ : 0.9 vol%, and the calorific value of the produced gas is 6.4 MJ / Nm ³ -dry and had the same effect as in Example 1. That is, the heat generation amount of the product gas increased by 1.1 MJ / Nm ³ -dry, and the oxygen amount decreased by 5 Nm ³ / h.

Further, the tar concentration in the product gas after the tar removal by the tar removal device was measured, and the test results regarding the trouble occurrence state due to the remaining amount of tar in the product gas are shown in Table 1. As shown in Table 1, pipe trouble did not occur when the tar concentration in the product gas was less than 100 mg / Nm ³ , but when the tar concentration was 100 mg / Nm ³ or more, there was a case that led to blockage of the pipe. It was.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

It is explanatory drawing which shows the structure of the gasification apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which shows the structure of a common gasifier.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Gasifier 110 Raw material supply apparatus 120 Carrier gas supply apparatus 130 Spouted bed gasification furnace 140 Cooling apparatus 150 Booster apparatus 160 Tar removal apparatus

Claims (5)

A conveying step of conveying biomass to the spouted bed gasifier,
A gasification step of gasifying the biomass conveyed by the air current in the spouted bed gasification furnace to generate a product gas;
A cooling step for cooling the product gas;
A tar removal step of removing tar from the product gas cooled in the cooling step;
Including
In the conveying step, a part or all of the generated gas from which tar has been removed in the tar removing step is used as a conveying gas in the air current conveying. The gasification method according to claim 1, wherein a tar concentration of the product gas used as the carrier gas is less than 100 mg / Nm ³ . In a gasifier for supplying biomass to an entrained bed gasification furnace by airflow conveyance and gasifying the biomass in the entrained bed gasification furnace to generate a product gas,
A raw material supply device for supplying biomass as a raw material to the spouted bed gasifier,
A carrier gas supply device for supplying a carrier gas during the air current conveyance;
A cooling device for cooling the generated gas;
A tar removal device for removing tar from the product gas cooled by the cooling device;
With
Part or all of the product gas from which tar has been removed by the tar removal device is supplied to the carrier gas supply device,
The carrier gas supply device uses a part or all of the generated gas as the carrier gas. The gasifier according to claim 3, wherein the tar removing device makes the tar concentration of the product gas less than 100 mg / Nm ³ .   The gasifier according to claim 3, wherein the tar removing device is a filter using a nonwoven fabric or a packed bed filled with alumina.

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