CN106753567B - Updraft type water vapor gasification device for mixture of biomass and tar - Google Patents

Abstract

The invention discloses an updraft type water vapor gasification device and method for a mixture of biomass and tar.A biomass material and an emulsified tar are fully mixed at the upper part of an updraft type fixed bed biomass gasification furnace, the temperature of a gasified fuel gas is reduced by utilizing the mixture of the biomass material and the tar, and the content of heavy tar in the fuel gas is reduced; meanwhile, the middle height of the updraft type fixed bed biomass gasifier is utilized to uniformly dry the mixture of the biomass and the tar at a low speed, and the moisture of the mixture of the biomass and the tar is dried to be below 10%, so that the working conditions of a pyrolysis reduction area and an oxidation combustion area at the lower part of the updraft type fixed bed biomass gasifier are not influenced by the moisture of the tar, and the mixed gasification of the biomass materials and the tar in the gasifier is realized, and the problem that the gasification effect is poor due to the fact that the tar with high water content is sent back to a high-temperature oxidation area to cause the change of the working conditions of the oxidation combustion area of gasification equipment (such as temperature reduction, air ratio increase and the like) in the prior art is solved.

Description

Updraft type water vapor gasification device for mixture of biomass and tar

The technical field is as follows:

the invention relates to the technical field of biomass energy, in particular to an updraft water vapor gasification device for a mixture of biomass and tar.

Background art:

common biomass gasification devices include fluidized beds, downdraft fixed beds, updraft and mixed flow fixed beds, and the like. Compared with a fluidized bed gasification furnace, the fixed bed gasification furnace is not easy to amplify, has lower gasification strength, but also has the obvious advantages of simple structure, low cost, easy operation, capability of being used for blocky materials, low fly ash content and the like, thereby still being a better choice in the field of medium and small-scale biomass gas production.

The fixed bed gasification furnace comprises an updraft type and a downdraft type, and is mainly characterized in that the operation directions of air flow and fuel are different, the air flow in the updraft type gasification furnace flows from bottom to top, the air flow in the downdraft type gasification furnace flows from top to bottom, and the fuel falls freely by means of gravity. Because of the difference of the reaction characteristics in the furnace, the hearth structures of the two furnace types are also different. Compared with a downdraft fixed bed gasifier, the updraft gasifier has the main advantages that: the heat utilization is more sufficient, the heat value of the fuel gas is higher, the running resistance is low, and the fly ash is less to carry. However, the updraft fixed bed gasifier also has a significant disadvantage that is difficult to overcome, i.e. the tar content in the fuel gas is high, generally about 30-150 g/Nm3(s.heidenreich, et al, Prog Energy Combust Sci, 2015).

The existence of tar reduces the gasification efficiency and is easy to block gas pipelines, dust removing equipment and gas equipment. Some applications require the gas to be reduced to extremely low levels: gas turbines, synthetic fuels, etc. require gas tar contents below the magnitude of several mg/Nm3 (n.abdoulumumosine et al.appl.energy, 2015); the national standard GB/T13612 and 2006 Artificial gas stipulates that the total content of tar and dust is lower than 10mg/m 3; the national standard GB 50494-2009 town gas technical Specification states that town gas should not contain solid, liquid or colloidal substances from any source. Therefore, in order to meet the requirements of special application, the operation load of a subsequent deep purification system can be greatly reduced by reducing the tar content of the fuel gas at the outlet of the gasification furnace.

In view of operation cost and practicability, the existing updraft type gasification furnace is generally matched with a wet type purification system for use, but as the operation time is prolonged, the coke washing wastewater is gradually saturated, and how to consume the coke washing wastewater becomes a technical problem which troubles the development of the industry. Chinese patent 200910025366.3 discloses an updraft or downdraft fixed bed straw gasifier with a tar backflash device, the gasified crude fuel gas is firstly dedusted by a filter deduster, and then tar is trapped by a tar trap combining inertia and cooling, the trapped tar is refluxed to the combustion area of the gasifier under the action of gravity and gas injection, and the tar is cracked and burned under the high temperature condition of the area. Similarly, chinese patent publication 201510532462.2 discloses a method for self-treatment of dust-containing tar by introducing it back into the oxygen-rich zone of a gasifier for combustion. The common feature of these patents is that the biomass tar is returned to the gasifier combustion zone, and the high temperature environment of the gasifier oxidation zone is utilized to combust or crack the tar components. Due to the high water content of the tar, the return of the tar can cause the working condition change (such as temperature reduction, air ratio increase and the like) of the combustion area of the gasification equipment, and the gasification effect is poor, so the implementation is difficult.

The invention content is as follows:

the invention aims to provide an updraft type water vapor gasification device and method for a mixture of biomass and tar.A characteristic that the updraft type fixed bed biomass gasification furnace is low in upper temperature and long in retention time is utilized, emulsified tar is fully mixed with biomass materials at the upper part of the updraft type fixed bed biomass gasification furnace, the temperature of gasified fuel gas is reduced by utilizing the mixture of the biomass materials and the tar, and the content of heavy tar in the fuel gas is reduced; meanwhile, the middle height of the updraft type fixed bed biomass gasifier is utilized to uniformly dry the mixture of the biomass and the tar at a low speed, and the moisture of the mixture of the biomass and the tar is dried to be below 10%, so that the working conditions of a pyrolysis layer, a reduction layer and an oxidation layer at the lower part of the updraft type fixed bed biomass gasifier are not influenced by the moisture of the tar, and the mixed gasification of the biomass material and the tar in the gasifier is realized, and the problem that the gasification effect is poor due to the fact that the tar with high water content is sent back to a high-temperature oxidation zone to cause the change of the working condition of the oxidation layer of the gasification equipment (such as temperature reduction, air ratio increase and the like) in the prior art is solved.

The invention is realized by the following technical scheme:

an updraft type water vapor gasification device for a mixture of biomass and tar comprises an updraft type gasification furnace, wherein the updraft type gasification furnace is sequentially divided into an oxidation layer, a reduction layer, a pyrolysis layer, a drying layer and a mixing zone from bottom to top; the upper part of the updraft gasifier is provided with a gas outlet and a feed inlet, the top of the updraft gasifier is provided with an emulsified tar water spraying inlet, and the bottom of the oxidation layer is provided with an air interface; the gas outlet is connected with an indirect cooler for separating tar from gas to obtain upper-layer tar-containing water and lower-layer tar-containing water; a common nozzle interface is arranged at the junction of the oxidation layer and the reduction layer in the circumferential direction and is communicated with a pressurized steam interface, and pressurized steam is uniformly sprayed into the hearth from the common nozzle interface at the junction of the oxidation layer and the reduction layer; the emulsified tar water injection inlet is used for inputting heavy tar-containing water or light tar-containing water.

Particularly, the common nozzle interface is also communicated with the light tar-containing water interface, and the light tar-containing atomized water is mixed with pressurized steam and then is uniformly sprayed into the hearth from the common nozzle interface of the pressurized steam and the light tar-containing atomized water at the junction of the oxidation layer and the reduction layer.

The height of the mixing zone is not less than 2.0m, the heights of the drying layer and the pyrolysis layer are not less than 4.0m, and the heights of the oxidation layer and the reduction layer are not less than 1.0 m.

Particularly, the number of the emulsified tar water spraying inlets is 1-4; and 4-6 common nozzle interfaces for pressurizing water vapor and light tar-containing water are circumferentially arranged at the junction of the oxidation layer and the reduction layer.

The invention also provides an updraft water vapor gasification method for a biomass and tar mixture, which comprises the following steps when the common nozzle interface is only communicated with the pressurized water vapor interface: emulsified heavy tar water obtained by condensing and emulsifying tar-containing gas prepared by pyrolyzing and gasifying a biomass raw material in an updraft type gasification furnace is mixed with the biomass raw material in a mixing zone at the upper part of the updraft type gasification furnace, and part of tar in a gas flow is cooled and trapped while the drying layer meets a hot gas flow rising below the drying layer to remove water; the raw material with the moisture removed moves downwards to a pyrolysis layer to be further heated to be pyrolyzed and decomposed into volatile components and solid coke, and the volatile components are carried upwards by the airflow; the solid coke enters a reduction layer and an oxidation layer below the solid coke in sequence; meanwhile, air enters an oxidation layer from the bottom of the updraft gasifier and is subjected to oxidation reaction with solid coke to release a large amount of heat; the oxidation product and coke are subjected to reduction reaction in a reduction layer to generate carbon monoxide, hydrogen and methane, and the carbon monoxide, the hydrogen and the methane are upwards mixed with the volatile components decomposed by pyrolysis; pressurized steam is uniformly sprayed from the junction of the oxidation layer and the reduction layer; the gas generated by the reduction layer and the gas obtained by the oxidative cracking and reforming of the light tar upwards enter the pyrolysis layer, enter the mixing zone together with the volatile components decomposed by pyrolysis, and are discharged from the gas outlet.

When the common nozzle interface is also communicated with the light tar-containing water interface, the updraught water vapor gasification method for the mixed mixture of the biomass and the tar comprises the following steps: emulsified tar oil obtained by condensing and emulsifying tar-containing gas prepared by pyrolyzing and gasifying biomass raw materials in an up-draft gasifier is mixed with the biomass raw materials in a mixing zone at the upper part of the up-draft gasifier, and part of tar in air flow is cooled and intercepted while the drying layer meets hot air flow rising below the drying layer to remove water; the raw material with the moisture removed moves downwards to a pyrolysis layer to be further heated to be pyrolyzed and decomposed into volatile components and solid coke, and the volatile components are carried upwards by the airflow; the solid coke enters a reduction layer and an oxidation layer below the solid coke in sequence; meanwhile, air enters an oxidation layer from the bottom of the updraft gasifier and is subjected to oxidation reaction with solid coke to release a large amount of heat; the oxidation product and coke are subjected to reduction reaction in a reduction layer to generate carbon monoxide, hydrogen and methane, and the carbon monoxide, the hydrogen and the methane are upwards mixed with pyrolysis volatile components; the light tar water is mixed with pressurized water vapor and then is uniformly sprayed from the junction of an oxidation layer and a reduction layer, on one hand, the light tar is subjected to oxidative cracking in a high-temperature environment, and on the other hand, the water vapor simultaneously participates in the reforming reaction of the tar; the gas generated by the reduction layer and the gas obtained by cracking and reforming the light tar upwards enter the pyrolysis layer, enter the mixing zone together with the volatile components decomposed by pyrolysis, and are discharged from the gas outlet.

The tar-containing gas prepared by pyrolyzing and gasifying the biomass raw material in the updraft gasifier is condensed to separate tar from the gas, and the obtained tar-containing wastewater is divided into light tar-containing wastewater at the upper layer and heavy tar-containing wastewater at the lower layer.

The invention has the following beneficial effects:

1) the invention utilizes the free space at the upper part of the updraft type gasification furnace and the feeding device to mix the emulsified condensed tar with the biomass raw material, thereby realizing the purpose of sending the tar back to the gasification furnace for secondary gasification and avoiding the loss of energy carried by the tar;

2) the characteristics of high water content and low temperature after the biomass raw material and the emulsified tar are mixed are utilized, the temperature of the crude fuel gas at the fuel gas outlet of the gasification furnace is reduced, so that heavy tar components in the fuel gas are condensed and adsorbed to the surface of the raw material, and the content of heavy tar carried by the fuel gas and the sensible heat loss are greatly reduced;

3) the retention time of the biomass raw material and tar mixture in the gasification furnace is prolonged, the biomass and tar mixture is uniformly dried and pyrolyzed by using high-temperature fuel gas of the reduction layer of the gasification furnace, and the working conditions of the pyrolysis layer, the reduction layer and the oxidation layer at the lower part of the gasification furnace are not influenced by high moisture content of heavy tar-containing wastewater, so that the mixed gasification of the biomass material and tar in the gasification furnace is realized;

4) high-pressure water vapor is used for atomizing condensed wastewater containing light tar, the generation of the slag bonding phenomenon in the furnace is inhibited by the steam and the atomized wastewater, the reduction reaction effect is improved, and the fuel gas components are regulated and controlled.

In a word, the emulsified tar is fully mixed with the biomass material at the upper part of the updraft type fixed bed biomass gasification furnace by utilizing the characteristics of low temperature and long retention time at the upper part of the updraft type fixed bed biomass gasification furnace, the temperature of gasified fuel gas is reduced by utilizing the mixture of the biomass material and the tar, and the content of heavy tar in the fuel gas is reduced; meanwhile, the middle height of the updraft type fixed bed biomass gasifier is utilized to uniformly dry the mixture of the biomass and the tar at a low speed, the moisture of the mixture of the biomass and the tar is dried to be below 10%, and the working conditions of a pyrolysis layer, a reduction layer and an oxidation layer of the updraft type fixed bed biomass gasifier are not influenced by the moisture of the tar, so that the mixed gasification of the biomass materials and the tar in the gasifier is realized. The invention has simple process, clean gas production, low energy consumption and high gasification efficiency, greatly reduces gas fly ash and slag bonding in the gasifier, prolongs the overhaul period, and more stably and reliably operates the gasifier, thereby solving the problem that the gasification effect is poor due to the change of the working condition of the oxidation layer of the gasification equipment (such as temperature reduction, air ratio increase and the like) caused by the return of tar with high water content to the high-temperature oxidation layer in the prior art.

Description of the drawings:

FIG. 1 is a schematic structural view of the present invention;

fig. 2 is a sectional view a-a of fig. 1.

Wherein, 1, an oxide layer; 2. a reduction layer; 3. a pyrolytic layer; 4. drying the layer; 5. a mixing zone; 6. a feed inlet; 7. the emulsified tar is sprayed into the inlet; 8. an air interface; 9. a pressurized water vapor interface; 10. an atomized water interface containing light tar; 11. a gas outlet; 12. a nozzle interface; 13. and (4) a hearth.

The specific implementation mode is as follows:

the following is a further description of the invention and is not intended to be limiting.

Example 1:

as shown in figure 1, the updraft type water vapor gasification device for the mixture of biomass and tar has the biomass treatment capacity of 1.5t/h, and comprises an updraft type gasification furnace, wherein the main body of the updraft type gasification furnace is a cylindrical refractory material masonry hearth 13 and a steel furnace shell, a rotary grate connected through dynamic sealing is arranged at the lower part of the furnace shell, and the rotary grate has the functions of air inlet and distribution; the updraft gasifier is sequentially divided into an oxidation layer 1, a reduction layer 2, a pyrolysis layer 3, a drying layer 4 and a mixing zone 5 from bottom to top; the upper part of the updraft gasifier is provided with a gas outlet 11 and a feed inlet 6, the top of the updraft gasifier is provided with 1-3 emulsified tar water injection inlets 7, and the bottom of an oxidation layer is provided with an air interface 8; the gas outlet 11 is connected with an indirect cooler for separating tar from gas to obtain upper-layer light tar-containing water and lower-layer heavy tar-containing water; 5 common nozzle interfaces 12 are arranged at the junction of the oxidation layer 1 and the reduction layer 2 in the circumferential direction, the common nozzle interfaces 12 are respectively communicated with a pressurized steam interface 9 and a light-tar-containing atomized water interface 10, and light-tar-containing atomized water obtained by atomizing light-tar-containing water through an atomizer is mixed with pressurized steam and then is uniformly sprayed into a hearth 13 from the pressurized steam at the junction of the oxidation layer 1 and the reduction layer 2 and the common nozzle interfaces 12 containing the light-tar atomized water; the emulsified tar water injection inlet 7 is used for inputting heavy tar-containing water or light tar-containing water;

the height of the mixing zone 5 is not less than 2.0m, the heights of the drying layer and the pyrolysis layer 3 are not less than 4.0m, and the heights of the oxidation layer 1 and the reduction layer 2 are not less than 1.0 m.

The operation load of the gasification furnace is 1t/h, the spraying amount of the water solution containing light tar at the top is 300kg/h, the tar concentration of the water solution containing light tar is 15 wt.% (namely the mass ratio of tar to water is 15:85), and the air quantity is about 1000Nm at the bottom through an air interface 8³And h, introducing saturated steam through a pressurized steam interface 9, wherein the saturated steam has the parameters of 0.25-0.4 MPa and 127-143 ℃, and closing the light tar-containing water atomization interface 10. Under the operation condition, emulsified heavy tar water obtained by condensing and emulsifying tar-containing gas prepared by a biomass raw material in an updraught gasifier is mixed with the biomass raw material in a mixing zone 5 at the upper part of the gasifier, the retention time is 1-2 h, the drying layer 4 meets hot air flow rising from the lower part, and partial tar in the air flow is cooled and intercepted while moisture is removed; the raw material with the moisture removed moves downwards to the pyrolysis layer 3 to be further heated to be pyrolyzed and decomposed into volatile components and solid coke, and the volatile components are brought upwards by the airflow; the solid coke enters a reduction layer 2 and an oxidation layer 1 below in sequence; the retention time in the reduction layer 2 is 2-3 hours, the retention time in the combustion zone of the oxidation layer 1 is about 0.5 hour, and meanwhile, air enters the oxidation layer 1 from the bottom of the updraft type gasification furnace and is subjected to oxidation reaction with solid coke to release a large amount of heat; the oxidation products and coke are subjected to reduction reaction in the reduction layer 2 to generate carbon monoxide, hydrogen and methane, and the carbon monoxide, the hydrogen and the methane are upwards mixed with volatile components decomposed by pyrolysis; pressurized steam is uniformly sprayed from the junction of the oxidation layer 1 and the reduction layer 2; the gas that the reduction layer produced upwards gets into the pyrolysis layer, gets into the mixing area with the volatile that the pyrolysis decomposed together, discharges from the gas export. The outlet temperature of the fuel gas is 80-100 ℃, the composition and the heat value of the fuel gas are analyzed and shown in table 1, and the tar content of the outlet fuel gas is lower than 30mg/Nm³The gasification cold gas efficiency is about 79%.

TABLE 1 analysis of gas composition and calorific value

Example 2:

the apparatus according to example 1 was operated at a load of 1t/h and an air input of 1000Nm³And h, spraying the heavy tar-containing aqueous solution at the top of the water tank for 200kg/h, wherein the concentration of the heavy tar-containing aqueous solution is 50 wt.%, the input of saturated water vapor at the bottom of the water tank is about 50-80 kg/h, the light tar-containing water atomization interface 10 is opened, and the input of light tar-containing atomized water at the bottom of the water tank is 20kg/h, wherein the concentration of tar is 15 wt.%. Under the condition, the emulsified heavy tar water is mixed with the biomass raw material in the upper mixing area of the updraft gasifier, and part of tar in the airflow is cooled and trapped while the drying layer meets the hot airflow rising below the updraft gasifier to remove water; the raw material with the moisture removed moves downwards to a pyrolysis layer to be further pyrolyzed into volatile components and solid coke, and the volatile components are carried upwards by the airflow; the solid coke enters a reduction layer and an oxidation layer below the solid coke in sequence; meanwhile, air enters an oxidation layer from the bottom of the updraft gasifier and is subjected to oxidation reaction with solid coke to release a large amount of heat; the oxidation product and coke are subjected to reduction reaction in a reduction layer to generate carbon monoxide, hydrogen and methane, and the carbon monoxide, the hydrogen and the methane are upwards mixed with the volatile components decomposed by pyrolysis; after being mixed with pressurized water vapor, the water containing light tar is atomized from the junction of an oxidation layer and a reduction layer and then is uniformly sprayed, on one hand, the light tar is subjected to oxidative cracking in a high-temperature environment, and on the other hand, the water vapor simultaneously participates in the reforming reaction of the tar; the gas generated by the reduction layer and the gas obtained by the oxidative cracking and reforming of the light tar upwards enter the pyrolysis layer, enter the mixing zone together with pyrolysis volatile components, and are discharged from the gas outlet. The resulting gas properties are shown in table 1. The tar content of the outlet fuel gas is lower than 30mg/Nm³The gasification cold gas efficiency is about 82%.

Example 3:

the device is as in example 1, except that the biomass treatment capacity is 2t/h, 4 emulsified tar water injection inlets 7 are installed at the top of the device, and 4 common nozzle ports 12 are circumferentially arranged at the junction of the oxidation layer 1 and the reduction layer 2.

The operation load is 2t/h, the spraying amount of the water solution containing heavy tar at the top is 300-500 kg/h, and the air introducing amount of the bottom through an air interface 8 is 2000Nm³And/h, the input amount of saturated steam at the bottom through a pressurized steam interface 9 is 650kg/h, the parameters of the saturated steam are 0.25-0.4 MPa and 127-143 ℃, the input amount of light tar-containing atomized water at the bottom through a light tar-containing atomized water interface 10 is 100kg/h, and the tar content is 50-100 g/L. Under the operating condition, the retention time of the heavy tar-containing water solution and the biomass raw material in the upper mixing zone 5 of the updraft type gasification furnace is 1.0-1.5 h, the retention time in the drying layer 4 is 1.0-1.5 h, the retention time in the pyrolysis layer 3 is 1.0h, the retention time in the reduction layer 2 is 1.0h, the retention time in the oxidation layer 1 is about 0.5h, and the temperature of a fuel gas outlet is equal to<The tar content of the outlet fuel gas is 30mg/Nm at the temperature of 120 DEG C³The tar content of the fuel gas after indirect condensation and electric tar-capturing separation is 20mg/Nm³And the gasification efficiency is 83.5 percent.

The gas outlet temperature of the general updraft fixed bed gasification furnace which does not adopt the invention is generally higher than 200 ℃, and the gasification efficiency is hardly higher than 75%. Compared with the traditional updraft type gasification furnace, the invention can obviously reduce the tar content of the outlet gas, improve the gasification efficiency, effectively consume the coke washing wastewater, improve the heat value of the gas, greatly reduce the gas fly ash and the slag bonding in the furnace, prolong the maintenance period and ensure that the gasification furnace is more stable and reliable.

Claims (6)

1. An updraft type water vapor gasification device for a mixture of biomass and tar is characterized by comprising an updraft type gasification furnace, wherein the updraft type gasification furnace is sequentially divided into an oxidation layer, a reduction layer, a pyrolysis layer, a drying layer and a mixing zone from bottom to top; the upper part of the updraft gasifier is provided with a gas outlet and a feed inlet, the top of the updraft gasifier is provided with an emulsified tar water spraying inlet, and the bottom of the oxidation layer is provided with an air interface; the gas outlet is connected with an indirect cooler; a common nozzle interface is arranged at the junction of the oxidation layer and the reduction layer in the circumferential direction and is communicated with a pressurized water vapor interface, and pressurized water vapor is uniformly sprayed into the hearth from the common nozzle interface at the junction of the oxidation layer and the reduction layer; the emulsified tar water injection inlet is used for inputting heavy tar-containing water or light tar-containing water.

2. The updraft water vapor gasification apparatus for biomass and tar mixtures of claim 1, wherein said common nozzle port is further in communication with a light tar-containing water port.

3. The updraft water vapor gasification apparatus for biomass and tar mixture according to claim 1 or 2, wherein the height of the mixing zone is not less than 2.0m, the height of the drying layer and the height of the pyrolysis layer are not less than 4.0m, and the height of the oxidation layer and the height of the reduction layer are not less than 1.0 m.

4. The updraft water vapor gasification apparatus for biomass and tar mixture according to claim 1 or 2, wherein the number of emulsified tar water injection inlets is 1-4; and 4-6 common nozzle interfaces for pressurizing steam and atomized water containing light tar are arranged at the junction of the oxidation layer and the reduction layer in the circumferential direction.

5. An updraft steam gasification method for a mixture of biomass and tar, which is characterized in that the updraft steam gasification device for the mixture of biomass and tar, which is disclosed in claim 1, is used, and the method comprises the following steps: the biomass raw material is condensed and emulsified to obtain emulsified heavy tar-containing water, which is mixed with the biomass raw material in a mixing zone at the upper part of the updraught gasifier, and the biomass raw material is cooled and trapped when meeting hot air flow rising below a drying layer to remove water; the raw material with the moisture removed moves downwards to a pyrolysis layer to be further heated to be pyrolyzed and decomposed into volatile components and solid coke, and the volatile components are carried upwards by the airflow; the solid coke enters a reduction layer and an oxidation layer below the solid coke in sequence; meanwhile, air enters an oxidation layer from the bottom of the updraft gasifier and is subjected to oxidation reaction with solid coke to release a large amount of heat; the oxidation product and coke are subjected to reduction reaction in a reduction layer to generate carbon monoxide, hydrogen and methane, and the carbon monoxide, the hydrogen and the methane are upwards mixed with pyrolysis volatile components; pressurized steam is uniformly sprayed from the junction of the oxidation layer and the reduction layer; the gas generated by the reduction layer and the gas obtained by cracking and reforming the light tar upwards enter the pyrolysis layer, enter the mixing zone together with pyrolysis volatile components, and are discharged from the gas outlet.

6. An updraft steam gasification method for a mixture of biomass and tar, which is characterized in that the updraft steam gasification device for the mixture of biomass and tar according to any one of claims 2 to 4 is used, and comprises the following steps: the method comprises the following steps that (1) emulsified tar oil obtained by condensing and emulsifying tar-containing gas prepared by a biomass raw material in an up-draft gasifier is mixed with the biomass raw material in a mixing zone at the upper part of the up-draft gasifier, and when a drying layer meets hot air flow rising below, part of tar in the air flow is cooled and trapped while moisture is removed; the raw material with the moisture removed moves downwards to a pyrolysis layer to be further heated to be pyrolyzed and decomposed into volatile components and solid coke, and the volatile components are carried upwards by the airflow; the solid coke enters a reduction layer and an oxidation layer below the solid coke in sequence; meanwhile, air enters an oxidation layer from the bottom of the updraft gasifier and is subjected to oxidation reaction with solid coke to release a large amount of heat; the oxidation product and coke are subjected to reduction reaction in a reduction layer to generate carbon monoxide, hydrogen and methane, and the carbon monoxide, the hydrogen and the methane are upwards mixed with the volatile components decomposed by pyrolysis; after being mixed with pressurized water vapor, the water containing light tar is atomized from the junction of an oxidation layer and a reduction layer and then is uniformly sprayed, on one hand, the light tar is subjected to oxidative cracking in a high-temperature environment, and on the other hand, the water vapor simultaneously participates in the reforming reaction of the tar; the gas generated by the reduction layer and the gas obtained by the oxidative cracking and reforming of the light tar upwards enter the pyrolysis layer, enter the mixing zone together with pyrolysis volatile components, and are discharged from the gas outlet.

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