JP4413646B2 - Circulating fluidized bed gasification system - Google Patents

Description

  The present invention relates to a circulating fluidized bed gasification system that gasifies solid fuel.

  Conventionally, gasification of solid fuels involves burning fuel and using the heat to pyrolyze (reduction reaction) the fuel in the presence of water vapor to produce gasified gases such as hydrogen and carbon monoxide. Done. In this gasification process, if the fuel is burned with air and a gasification reaction is performed at the same time, a large amount of nitrogen is contained in the gasification gas. Therefore, when this gasified gas is supplied to a gas engine, a gas turbine, a fuel cell, or the like and used for power generation, a sufficient amount of heat cannot be obtained and power generation efficiency deteriorates. Therefore, as shown in Patent Document 1, a combustion part that fluidizes and burns fuel with air and a gasification part that thermally decomposes fuel are formed separately, and heated by unburned fuel and the combustion part. It has been proposed to perform a gasification reaction by introducing a bed material into the gasification section, using the heated bed material as a heat source for the gasification section, and supplying water vapor to the gasification section to cause fluidization. ing.

  In the gas generator described in this patent document 1, since the combustion part and the gasification part have isolate | separated, the gasification gas with a high density | concentration which does not contain nitrogen can be obtained.

JP 2003-171673 A

  However, in the gas generator described in Patent Document 1, in order to prevent the inflow of air, a path when the bed material moves from the combustion section to the gasification section is configured in a complicated manner, and the bed material is burned. It is not possible to easily move from the section to the gasification section, it is difficult to control the circulation amount of the bed material, and the efficiency is low. Moreover, since a combustion part and a gasification part are arranged side by side, a large installation area is required.

  Then, an external circulation type fluidized bed gasification system as shown in Japanese Patent Application No. 2003-201826 (Title of Invention: Fluidized Bed Gasification System) has been proposed. In this external circulation type fluidized bed gasification system, the combustion section is a high-speed fluidized bed, and is configured separately from the gasification section. In the combustion section, the bed material is raised together with the fuel and discharged from the combustion section. It is shown that the bed material is recovered by the cyclone provided in the above and moved to the gasification section. In this external circulation fluidized bed gasification system, the bed material is recovered by the cyclone, so the bed material can be separated from the exhaust gas and reliably moved by gravity from the combustion section to the gasification section. Control amount is easy. However, since the combustion section is a high-speed fluidized bed, in order to give a sufficient amount of heat to the bed material by combustion, the height of the combustion section has to be taken high enough, and the apparatus becomes large, and for small facilities Not suitable. Further, when the bed material moves from the combustion section through the cyclone to the gasification section, there is a concern that heat loss occurs and efficiency is lowered.

  Accordingly, an object of the present invention is to provide a gasification system that solves the above-described problems, can easily control the circulation of the bed material, and can be miniaturized with high efficiency.

In order to achieve the above object, the present invention according to claim 1 is configured such that the fuel and the bed material to be circulated are input from the upper part, and the moving layer of the fuel and the bed material is partitioned at the lower part. A cylindrical gasification furnace in which a fluidized bed of fuel and bed material is defined, and extends from the upper part of the combustion furnace to the bottom of the combustion furnace and has an open lower end in the combustion furnace And an air supply air diffuser for supplying air into the combustion furnace in order to form the fluidized bed by fluidizing the fuel and the bed material introduced into the middle stage in the vertical direction in the combustion furnace with air. The bed material and the unburned fuel moved to the opening of the gasification furnace while forming the moving bed by gravity flowing from the fluidized bed to the bottom of the combustion furnace, and the gasification furnace. Move up in the meantime while the above unburned fuel or as needed To perform the gasification of the fuel is introduced into the gasifier, the steam supply for the injection nozzle for injecting upward steam to said gasification furnace through the opening portion of the gasifier is provided, further the gasification Connect the upper part of the furnace to the cyclone for separating the bed material, separate the gasification gas generated by the cyclone and the bed material, and connect the bed material return path to return the bed material separated from the cyclone to the combustion furnace one in which the.

According to a second aspect of the present invention for achieving the above object, the moving bed blocks air supplied from the air supply diffuser tube from flowing into the gasifier, and the gasifier A material seal is formed to block the gasification gas generated in step 1 from flowing into the combustion furnace.

According to a third aspect of the present invention for achieving the above object, the water vapor supplied from the water vapor supply injection nozzle is produced by heat recovery from exhaust gas extracted from the combustion furnace or the like.

    According to the present invention, the following excellent effects are exhibited.

  (1) By providing the opening of the gasification furnace below the fluidized bed that heats the bed material, the bed material can be naturally moved by gravity.

  (2) By letting the bed material flow down from the fluidized bed, a material seal is formed between the fluidized bed and the gasifier opening, and the gas flow between the combustion furnace and the gasifier is blocked. it can.

  (3) By blocking the inflow of exhaust gas or the like into the gasification furnace, a product gas having a low nitrogen concentration and a high calorific value can be obtained, and utilization efficiency can be enhanced at the product gas application destination.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  Drawing 1 shows the lineblock diagram of the circulation type fluidized-bed gasification system of an embodiment.

  The circulating fluidized bed gasification system of the present embodiment uses biomass such as coffee grounds, coal, and the like as fuel, and separates a combustion furnace 1 for burning fuel and a gasification furnace 2 for gasifying fuel. Formed. Further, a bed material such as dredged sand is used as a medium for transferring the heat of the combustion furnace 1 to the gasification furnace 2, and this is circulated.

  As shown in FIG. 1, the circulating fluidized bed gasification system of this embodiment includes a combustion furnace 1 and a gasification furnace 2.

  The combustion furnace 1 includes a body portion 4 having a substantially square cross section, and a collecting portion 5 that is formed below the body portion 4 and narrows downward.

  The gasification furnace 2 is formed in a cylindrical shape having an opening 6 that extends downward at the lower end, and is disposed in the combustion furnace 1.

  The opening 6 at the lower end of the gasification furnace 2 is disposed so as to face the bottom 8 of the combustion furnace 1, and the upper part is provided so as to extend beyond the top of the combustion furnace 1.

  A combustion fuel supply line 9 for supplying fuel is provided at the top of the combustion furnace 1 and an exhaust passage 10 for discharging combustion exhaust gas is connected. A char separation cyclone 11 is connected to the exhaust passage 10 to separate the char (solid content) from the exhaust gas and then return the char to the combustion furnace 1 again. The char separation cyclone 11 is connected to the char separation cyclone 11 from the exhaust gas. A fine powder separation cyclone 12 for separating fine powder (ash) is connected.

  The middle stage of the combustion furnace 1 is provided with an air supply air diffuser 15 for fluidizing the injected fuel and the bed material to form a fluidized bed 14 (combustion part). The air supply diffusing pipe 15 is connected to an external air supply device (not shown) and penetrates the wall surface of the combustion furnace 1, and is connected to the air supply pipe 16. The diffuser pipe 18 is disposed throughout the horizontal section of the gas diffuser, and a plurality of nozzles 19 connected to the upper part of the diffuser pipe 18 and formed with a plurality of minute air supply ports (not shown). The

  At the center of the bottom 8 of the combustion furnace 1, there is provided a water vapor supply injection nozzle 20 that is located in the opening 6 of the gasification furnace 2 and injects water vapor upward into the gasification furnace 2. A water vapor supply air diffuser 21 is provided around the injection nozzle 20. The steam supply diffuser pipe 21 includes a steam supply pipe 22 connected to an external steam supply device (not shown), an annular steam diffuser pipe 24 connected to the upper portion of the steam supply pipe 22, The plurality of nozzles 25 are connected to the water vapor diffusion pipe 24.

  The water vapor injected from the water supply nozzle 20 is supplied so that the fuel and the bed material can be fluidized at a high speed while being raised in the gasification furnace 2, and supplied from the water supply pipe 21. The steam to be supplied is supplied so that the bed material and the fuel can be floated and guided to the opening 6 of the gasification furnace 2.

  A gasification fuel supply path 30 for dropping fuel into the gasification furnace 2 as necessary is provided in the middle stage of the gasification furnace 2.

  Connected to the downstream end of the gasification furnace 2 is a bed material separation cyclone 31 for separating the bed material from the generated gasification gas. The bed material separation cyclone 31 includes a bed material return path 32 communicating with the upper portion of the combustion furnace 1 and a fine powder separation cyclone 34 for separating fine powder (ash) from the gasified gas from which the bed material is separated. Is connected.

  Next, the operation of the circulating fluidized bed gasification system according to this embodiment will be described.

  The combustion furnace 1 is preliminarily filled with the bed material above the air supply diffuser tube 15, and then fuel such as biomass is introduced from the combustion fuel supply passage 9 at the top of the combustion furnace 1. The fuel and the bed material are fluidized by the air supplied from the air supply air diffusion pipe 15 to form the fluidized bed 14 and the fuel is combusted. The combustion exhaust gas is discharged from the exhaust passage 10, the solid content (char) contained in the exhaust gas is separated by the char separation cyclone 11, returned to the combustion furnace 1, and the combustion exhaust gas from which the solid content is separated is the fine powder in the latter stage Fine powder (ash) is separated and discharged by the separation cyclone 12.

  In the fluidized bed 14, the fuel is combusted at about 800 ° C. and the bed material is heated. The bed material and unburned fuel flow down below the air supply diffuser 15 and form a moving bed 35 over the collection unit 5 and the bottom 8 of the combustion furnace 1.

  The bed material and unburned fuel collected at the bottom 8 are floated by the steam supply diffuser pipe 21 and introduced to the gasification furnace 2 by the steam (about 400 ° C.) jetted from the steam supply injection nozzle 20. It is burned.

  In addition to the bed material and unburned fuel introduced into the gasification furnace 2, fuel is further fed into the gasification furnace 2 from the gasification fuel supply path 30. The fuel and the bed material rise while being fluidized at high speed in the gasification furnace 2 by a steam jet ejected from the steam supply injection nozzle 20, and during that time, a thermal decomposition (reduction) reaction (about 800). ° C) and steam gasification (reduction) (about 800 ° C). By these reactions, gasified gas (combustible gas) composed of water, such as hydrogen, carbon monoxide, and methane is generated from the fuel. The pyrolysis reaction and the steam gasification reaction (water gas reaction) are endothermic reactions, and the reaction is performed by the amount of heat of the bed material introduced into the gasification furnace 2 and the fluidized bed 14 surrounding the gasification furnace 2. The reaction is also performed with the amount of heat transmitted from the moving bed 35.

  The gasified gas generated by the thermal decomposition reaction and the steam gasification reaction flows into the bed material separation cyclone 31 to separate the bed material, and the fine powder (ash) is removed by the fine powder separation cyclone 34. Although not shown, after the water vapor content is removed, it is supplied to a gas turbine and used for power generation, and the active components (carbon monoxide, hydrogen, methane) are extracted and used as synthesis gas.

  The bed material separated by the bed material separation cyclone 31 passes through the bed material return path 32 and is returned to the combustion furnace 1 again.

As described above, the gasification furnace 2 is provided in the combustion furnace 1, the fluidized bed 14 is formed above the middle stage of the combustion furnace 1, and the moving bed 35 made of a bed material (including partially unburned fuel) is provided below the fluidized bed 14. Since the bed material heated in the fluidized bed 15 can be naturally introduced from the moving bed 35 to the gasification furnace 2 only by the force of gravity, the heat can be reliably transferred and the moving circulation amount can be reduced. It can be controlled easily. Further, since the bed material can be directly flowed into the gasification furnace 2 from the fluidized bed 15, the heat loss is small and the efficiency is high. Moreover, since the moving bed 35 serves as a material seal, the inflow of the exhaust gas from the combustion furnace 1 to the gasification furnace 2 can be blocked, and the gasification gas and water vapor generated in the gasification furnace 2 can move to the fluidized bed 14 side. Can be suppressed.
Therefore, by shutting off the inflow of air into the gasification furnace 2, a gasification gas having a low nitrogen concentration and a high calorific value and calories can be obtained. There is an effect that it is possible to improve the utilization efficiency in the use of generated gas such as utilization and synthesis gas.

  In addition, by arranging the gasification furnace 2 in the combustion furnace 1, there is an effect that the gasification furnace 2 can be efficiently cooled and an installation area is reduced.

  Note that the steam for gasification supplied from the steam supply spray nozzle 20 and the steam supply diffuser pipe 21 may be produced by heat recovery of the exhaust gas extracted from the combustion furnace 1 or the like. The thermal efficiency of the mold fluidized bed gasification system can be further increased.

The block diagram of the circulation type fluidized-bed gasification system of this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Combustion furnace 2 Gasification furnace 6 Opening part 14 Fluidized bed 15 Air supply diffuser pipe 20 Steam supply spray nozzle 31 Bed material separation cyclone 35 Moving bed

Claims (3)

A combustion furnace in which fuel and a bed material to be circulated are introduced from above, a moving bed of fuel and bed material is defined in the lower part, and a fluidized bed of fuel and bed material is defined on the moving layer. Forming,
In the combustion furnace, a cylindrical gasification furnace extending from the upper part of the combustion furnace to the bottom of the combustion furnace and having an open lower end is provided.
An air supply air diffuser for supplying air into the combustion furnace is provided in the middle of the combustion furnace in the vertical direction so as to form the fluidized bed by fluidizing the injected fuel and the bed material with air.
The bed material and unburned fuel moved up to the opening of the gasification furnace while flowing down from the fluidized bed to the bottom of the combustion furnace by gravity to form the moving bed, and rise in the gasification furnace. In order to gasify the unburned fuel or the fuel to be introduced into the gasifier as needed, water vapor is jetted upward into the gasifier from the opening of the gasifier. Providing a water vapor supply spray nozzle ,
Further, the upper part of the gasification furnace is connected to a bed material separation cyclone, the gasification gas generated by the cyclone and the bed material are separated, and the bed material separated from the cyclone is put into the combustion furnace and returned to the bed material. A circulating fluidized bed gasification system characterized by connecting a return path . The moving bed blocks air supplied from the air supply air diffuser from flowing into the gasification furnace, and blocks gasification gas generated in the gasification furnace from flowing into the combustion furnace. The circulating fluidized bed gasification system according to claim 1, wherein a material seal is formed . The circulating fluidized bed gasification system according to claim 1 or 2, wherein water vapor supplied from the water vapor supply injection nozzle is produced by heat recovery from exhaust gas extracted from the combustion furnace or the like .

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