Biomass gasifier system based on decoupling partition and tar in-situ cracking

Abstract

The utility model belongs to the technical field of biomass energy, and particularly relates to a biomass gasification furnace system based on decoupling partition and tar in-situ cracking, which comprises a furnace body, a feeding mechanism and a preheating mechanism, the furnace body is of a vertical multi-section cavity structure, and the furnace body is internally divided into a cracking area, an oxidation area and a reduction area from top to bottom. The areas are separated by at least one group of partition plates with holes; a gas distributor is fixed at the side part of the furnace body and is communicated with the oxidation zone; a rotating blade loaded with a catalyst is arranged in the reduction area; the feeding mechanism is arranged above the furnace body and used for providing biomass raw materials for the furnace body. The biomass gasification system has the advantages that the tar content is reduced through decoupling partition design and catalytic cracking cooperative control, the output rate and the low calorific value of combustible gas are improved, and the biomass gasification system has an obvious cooperative upgrading effect on obtained mixed gas.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of biomass energy, especially relates to a biomass gasification furnace system based on decoupling partition and tar in-situ cracking. BACKGROUND

[0002] Biomass gasification is to carry out pyrolysis and gasification reaction of agricultural and forestry wastes (such as straw, branches, sawdust, etc.) under high temperature and anaerobic conditions, and combustible gas mainly composed of carbon monoxide (CO), hydrogen (H2) and methane (CH4) is generated. The gasification process is usually divided into: (1) drying and pyrolysis: the water in the biomass is evaporated, and macromolecular organic matter is decomposed into small molecular gas and solid residue. (2) gasification and combustion: under high temperature and anaerobic conditions, the biomass is further cracked to generate combustible gas. The gasification furnace is the key equipment to realize biomass gasification, which has the advantages of wide raw material adaptability, high efficiency, energy saving, environmental protection, etc., but the existing biomass gasification furnace also has many drawbacks. For example, the fixed bed gasification furnace:

[0003] 1. High tar content: the tar product of the traditional fixed bed gasification furnace is 20-50 g / Nm 3 , which needs to rely on water washing, electric capture and other post-processing processes, and the process is long and the cost is high;

[0004] 2. Insufficient temperature gradient between oxidation zone and reduction zone, large fluctuation range of CO and H2 composition concentration, low volume fraction of combustible gas (CO, H2), only 20%-35%;

[0005] 3. Tar and ash coking at high temperature, shortening the service life of the equipment, difficult to handle and high cost.

[0006] The coke removal methods mainly include water washing method, electric capture method and catalytic cracking method. The water washing method and the electric capture method have long process and high cost, and are easy to cause secondary pollution after failure; the catalytic cracking method converts the tar into small molecules at high temperature, but it has problems such as catalyst deactivation, reduction of surface carbon catalytic efficiency, short contact time and rapid escape of tar.

[0007] In the prior art, patent publication number CN107418629A discloses a biomass gasification device, which optimizes gas production through a multi-stage separator, but still does not solve the problem of in-situ cracking of tar, and the economic efficiency is poor. SUMMARY

[0008] In order to overcome the shortcomings of the prior art, the utility model aims at providing a biomass gasification furnace system based on decoupling partition and tar in-situ cracking, which reduces the tar content of the gasification furnace, improves the gasification efficiency and solves the problem of easy blockage of the equipment.

[0009] In order to achieve the above-mentioned purpose, the utility model realizes the following technical scheme:

[0010] The utility model provides a kind of biomass gasifier system based on decoupling partition and tar in-situ cracking, including furnace body, feeding mechanism, preheating mechanism, furnace body is vertical multistage cavity structure, furnace body is divided into cracking zone, oxidation zone, reduction zone from top to bottom in it, and at least one group of perforated partition is separated between each zone;Gas distributor is fixed on the side of furnace body, and gas distributor is communicated with oxidation zone;Rotary vane with catalyst is arranged in reduction zone;Feeding mechanism is arranged above furnace body, for providing biomass raw material to furnace body.

[0011] The oxidation zone and the reduction zone are of an inner-outer double-layer structure, the inner-layer cavity is gradually increased from the middle to both ends, and the inner-layer cavity serves as a heat exchange and transfer channel to transfer heat from the oxidation zone to the reduction zone.

[0012] The gas distributor includes a shell, a gasification agent inlet and a gas distribution plate, a preheating pipe passes through the shell and is fixedly connected with the shell, an air inlet is arranged above the shell, an air outlet is arranged below the shell, a gasification agent inlet is arranged on the shell, the gas distribution plate is arranged in the shell and is fixed to the inner wall of the furnace body, and the gasification agent in the shell enters the gasification agent inlet through the gas distribution plate and then enters the inner-layer cavity through the gasification agent inlet.

[0013] The biomass gasification furnace system further comprises a spraying pipe arranged in the reduction zone, and the spraying pipe is connected with the furnace body and can spray water vapor into the reduction zone.

[0014] The partition plate is provided with a plurality of through holes, and the through holes arranged on the partition plate between the cracking zone and the oxidation zone have a larger diameter than the through holes arranged on the partition plate between the oxidation zone and the reduction zone.

[0015] The cracking zone is connected with an ignition flange.

[0016] Compared with the prior art, the biomass gasification furnace system has the following beneficial effects:

[0017] The biomass gasification furnace system solves the problems of high tar content, low gas yield and easy blockage of equipment in the traditional gasification furnace system gasification technology. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a structural schematic view of the biomass gasification furnace system.

[0019] Figure 2 is a tar content curve of the traditional gasification furnace and the biomass gasification furnace system.

[0020] In the figure: 1-driving motor; 2-feeding inlet; 3-ignition flange; 4-distributing device; 5-cracking zone; 6-oxidation zone; 7-reduction zone; 8-plate one; 9-plate two; 10-air distributor; 11-gasification agent feeding inlet; 12-gas inlet of preheating pipe; 13-gas outlet of preheating pipe; 14-gasification agent inlet; 15-spraying pipe; 16-rotary blade; 18-outer cavity. DETAILED DESCRIPTION

[0021] The utility model will be described in detail below in combination with the drawings of the specification, but it should be pointed out that the implementation of the utility model is not limited to the following embodiments.

[0022] See Figure 1 A biomass gasification furnace system based on decoupling partition and tar in-situ cracking, comprising a furnace body, a feeding mechanism and a preheating mechanism, the furnace body is a vertical multi-section cavity structure, the furnace body is divided into a cracking zone 5, an oxidation zone 6 and a reduction zone 7 from top to bottom, and each zone is separated by at least one group of hole plate; an air distributor 10 is fixed on the side of the furnace body, and the air distributor 10 is communicated with the oxidation zone 6; a rotary blade 16 loaded with catalyst is arranged in the reduction zone 7; the feeding mechanism is arranged at the top of the furnace body and is used for providing biomass raw materials to the furnace body. The oxidation zone 6 and the reduction zone 7 are double-layer structures, the inner cavity is gradually increased from the middle to both ends, and the inner cavity is used as a heat exchange transmission channel to transmit the heat of the oxidation zone 6 to the reduction zone 7.

[0023] The air distributor 10 comprises a shell, a preheating pipe, a gasification agent inlet 14, a spraying pipe 15 and an air distribution plate, the preheating pipe penetrates through the shell and is fixedly connected with the shell, the gas inlet 12 of the preheating pipe is arranged above the shell, the gas outlet 13 of the preheating pipe is arranged below the shell, the spraying pipe 15 is connected with the furnace body and can spray water vapor to the reduction zone 7; the gasification agent feeding inlet 11 is arranged on the shell, and the air distribution plate is arranged in the shell and is fixed to the outer wall of the furnace body, the gasification agent in the shell enters the gasification agent inlet 14 through the air distribution plate and then enters the inner cavity through the gasification agent inlet 14. A plurality of through holes with a diameter of 0.5-2 mm are formed in the air distribution plate, and the opening rate is 30%-45%.

[0024] The air distribution plate is made of refractory material, and the risk of increasing the content of generated tar is avoided. The air distribution plate comprises the following raw materials in percentage by mass: aluminum magnesium spinel 85%-90%, aluminum oxide powder 5%-8%, magnesium oxide powder 3%-5% and polyvinyl alcohol or carboxymethyl cellulose 2%-3%. The above raw materials are uniformly mixed and stirred at room temperature, are pressed into a shape, are dried at 110-130 DEG C to remove water, and a dry rough blank is obtained; the rough blank is sintered at 1600-1650 DEG C for 6-8 hours, is cooled, and the air distribution plate is obtained.

[0025] The feeding mechanism is a screw conveyor, the feeding port 2 of the screw conveyor is arranged at the top of the furnace body, a valve is connected at the feeding port 2, and a material level meter is arranged in the furnace to control the feeding amount of the gasification furnace. The raw material is fed into the feeding port 2 and is sent into the cracking zone in the furnace body under the action of the driving motor 1. The through hole diameter of the partition plate arranged between the cracking zone 5 and the oxidation zone 6 is larger than the through hole diameter of the partition plate arranged between the oxidation zone 6 and the reduction zone 7, that is, the through hole of the partition plate one 8 is larger than the through hole of the partition plate two 9. The cracking zone 5 is connected with the ignition flange 3.

[0026] The partition plate arranged between the cracking zone 5 and the oxidation zone 6 is provided with a plurality of through holes; similarly, the partition plate two 9 arranged between the oxidation zone 6 and the reduction zone 7 is also provided with a plurality of through holes. According to the needs, there is at least one or more partition plates. The cracking zone 5 is connected with the ignition flange 3.

[0027] The supported catalyst includes, by mass percentage:

[0028] Ni: 20% to 25%; rare earth elements: 2% to 5%; Al2O3: 65% to 70%; MgO: 3% to 5%; SiO2: 2% to 4%; the rare earth elements include, by mass percentage, Ce: 80% to 95%, and the rest is La.

[0029] Preparation of the supported catalyst: Al2O3, MgO and SiO2 are ball-milled and mixed, then a mixed solution of a nickel nitrate solution and a lanthanum nitrate solution is mixed, and after stirring uniformly, spray drying is performed; then calcination is performed at a temperature of 500 to 800 DEG C, and the calcination time is 3 to 5 h; then the rare earth elements are mixed, and the temperature is continued to be calcined at 700 to 750 DEG C for 1 to 3 h; then reduction treatment is performed in a hydrogen atmosphere, the reduction temperature is 400 to 600 DEG C, and the reduction time is 2 to 4 h, and after cooling, the supported catalyst is obtained.

[0030] The supported catalyst has high activity, controllable cost and is suitable for high-temperature reaction (700 to 900 DEG C). The supported catalyst is loaded on the rotating blade 16, the mixed fuel gas stays for 5 to 10 s, and the supported catalyst is used to treat the gaseous tar contained in the mixed fuel gas; the reduction zone 7 is longitudinally provided with at least one group of supported catalyst rotating blades 16, the contact area and time of the tar and the catalyst are expanded, the tar cracking and reforming is accelerated, and the problems of catalyst carbon deposition are better solved through gravity and centrifugal force of rotation.

[0031] A tar control method, comprising:

[0032] 1) Raw material pretreatment: after the biomass raw material is crushed, dried and sieved, impurities are removed; the biomass raw material is cotton stalks and wood chips and other agricultural and forestry wastes.

[0033] 2) Biomass raw materials are fed into the furnace body from the feed inlet 2, and after entering the furnace body, the biomass raw materials pass through the pyrolysis zone 5, the oxidation zone 6 and the reduction zone 7 in sequence to generate products and be discharged from the furnace body; cotton stalks and wood chips and other agricultural and forestry wastes can be gasified in the furnace body by high-temperature gasification reaction with a gasification agent, and after high-temperature pyrolysis, oxidation and reduction reactions, are converted into mixed fuel gas CO, CO2, H2, CH4 and the like, while generating by-products in the form of solid carbon powder; the gasification agent can be selected from air, pure oxygen, steam or a composite gasification agent.

[0034] In this process, the temperature of the pyrolysis zone 5 is controlled at 400-600℃, and the biomass raw materials release volatile matter at low temperature pyrolysis; the temperature of the oxidation zone 6 is controlled at above 1000℃, the input amount of the gasification agent is controlled by the gas distributor 10, and the air-fuel ratio of the oxidation zone 6 is controlled at 0.2-0.4, preferably close to 0.3, to release pyrolysis heat energy in the oxygen zone; due to the lack of nitrogen dilution, the heat value of the generated mixed fuel gas is greatly improved compared with pure air gasification, the gas production efficiency is improved by 20%, and the volume fraction of combustible gas is increased to more than 50%. When the temperature of the oxidation zone 6 is higher than 1100℃, water vapor is sprayed through the gas distributor 10 to reduce the temperature, and the water vapor is decomposed into H2 and CO in the reduction zone 7; the gasification agent and the high-temperature water vapor sprayed in different proportions can adjust the proportion of CO and H2 in the combustible gas, and the addition of water vapor helps to adjust the temperature in the furnace.

[0035] 3) The heat exchange transfer channel is formed under the action of the inner and outer double-layer structures, the residence time of the biomass raw materials in the oxidation zone 6 is prolonged, and the temperature of the reduction zone 7 is maintained by the residual heat of the oxidation zone 6;

[0036] 4) The temperature of the reduction zone 7 is controlled at 700-900℃: the mixed fuel gas stays in this zone for 5-10s, and the mixed fuel gas is subjected to secondary pyrolysis and reforming by the secondary action of the catalyst in the reduction zone 7 to complete the reduction of the gas and the catalytic pyrolysis of the tar into CO and H2.

[0037] 5) The gasification products discharged from the furnace body are subjected to heat recovery through a heat exchanger, enter a cyclone dust collector (to remove more than 80% of the carbon powder) and a bag filter for purification to obtain pure mixed fuel gas, and the carbon powder is sent to a collection box through a screw conveyor for collection and can be used for activated carbon preparation.

[0038] The utility model solves the problems of high tar content, low gas yield and easy blockage of equipment in the traditional gasification furnace system. The utility model realizes the reduction of tar content, improves the output rate and low calorific value of combustible gas, and has obvious synergistic upgrading effect on the obtained mixed fuel gas through the biomass gasification furnace system. Figure 2 , the gasification furnace adopts a decoupling partition structure, and the gasification efficiency is significantly improved with air as the gasification agent, and the volume fraction of combustible gas is increased to more than 50%. The tar content is reduced to 10 mg / Nm 3The following.

Claims

1. A biomass gasifier system based on decoupled zoning and in-situ tar cracking, characterized by, The device comprises a furnace body, a feeding mechanism and a preheating mechanism, the furnace body is a vertical multi-section cavity structure, the furnace body is divided into a cracking zone, an oxidation zone and a reduction zone from top to bottom, and each zone is separated by at least one set of hole-separation plates; a gas distributor is fixed to the side of the furnace body and is connected with the oxidation zone; a rotating blade loaded with catalyst is arranged in the reduction zone; the feeding mechanism is arranged above the furnace body and is used for providing biomass raw materials to the furnace body.

2. The biomass gasification furnace system based on decoupling zoning and tar in-situ cracking according to claim 1, characterized in that, The oxidation zone and the reduction zone are double-layer structures, the inner layer cavity is gradually increased from the middle to the two ends, and the inner layer cavity is used as a heat exchange transmission channel to transmit the heat of the oxidation zone to the reduction zone.

3. The biomass gasification furnace system based on decoupled zoning and tar in-situ cracking of claim 1, wherein, The gas distributor comprises a shell, a gasification agent inlet and a gas distribution plate, a preheating pipe penetrates through the shell and is fixedly connected with the shell, an air inlet is arranged above the shell, an air outlet is arranged below the shell, a gasification agent inlet is arranged on the shell, the shell is provided with a gas distribution plate, the gas distribution plate is fixed to the inner wall of the furnace body, the gasification agent in the shell enters the gasification agent inlet through the gas distribution plate, and then enters the inner layer cavity through the gasification agent inlet; a plurality of through holes with a diameter of 0.5-2 mm are formed in the gas distribution plate.

4. The biomass gasification furnace system based on decoupled zoning and tar in-situ cracking of claim 1, wherein, The device further comprises a spraying pipe, the spraying pipe is arranged in the reduction zone, the spraying pipe is connected with the furnace body and can spray water vapor to the reduction zone.

5. The biomass gasification furnace system based on decoupled zoning and tar in-situ cracking of claim 1, wherein, A plurality of through holes are arranged on the separation plate; the through holes arranged on the separation plate between the cracking zone and the oxidation zone have a larger diameter than the through holes arranged on the separation plate between the oxidation zone and the reduction zone.

6. The biomass gasification furnace system based on decoupled zoning and tar in-situ cracking of claim 1, wherein, The cracking zone is connected with a fire ignition flange.

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