Method and apparatus for preparing syngas by staged biomass gasification

Abstract

The present disclosure belongs to the technical field of biomass gasification, and provides a method and apparatus for preparing syngas by staged biomass gasification. The method for preparing syngas by staged biomass gasification comprises: introducing a biomass fuel and a first gasification agent or carrier gas into a first fluidized bed reactor, and extracting volatiles from the biomass fuel via a pyrolysis reaction or partial gasification reaction, to produce a tar-containing gas-solid mixture and semi-coke particles; after separating the tar-containing gas-solid mixture with a first gas-solid separator, obtaining a tar-containing mixed gas and solid particulates of first particle size; transporting the tar-containing mixed gas and a third gasification agent into a downer reactor, and thermally cracking the tar in the tar-containing mixed gas via a thermal cracking reaction, to produce a tar-free syngas.

Description

Method and device for preparing synthesis gas by biomass staged gasification TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of biomass gasification, and particularly relates to a method and device for preparing synthesis gas by biomass staged gasification. BACKGROUND

[0002] Under the background of "double carbon", biomass as a zero-carbon renewable energy has attracted widespread attention for its clean and efficient use. Biomass gasification is an important way for clean and efficient use of biomass. Through gasification, biomass can be efficiently and cleanly converted into synthesis gas, which can then be used to produce green hydrogen and bulk chemicals such as methanol, fuel ethanol, and bio-kerosene. These chemicals can be used as fuels in the transportation sector, replacing fossil fuels while achieving carbon dioxide emission reduction.

[0003] The mainstream technologies for biomass gasification include fixed-bed gasification and fluidized-bed gasification. Neither fixed-bed gasification nor fluidized-bed gasification has been widely used in the field of biomass gasification for green chemicals. There are also some key problems, such as: 1) high tar content in synthesis gas, affecting the stable operation of the device; 2) poor raw material adaptability and operation stability; 3) complex process and high cost.

[0004] Therefore, there is an urgent need to develop a clean and efficient, low-cost, wide fuel adaptability, and long-term stable operation biomass gasification technology. SUMMARY

[0005] To address the above technical problems, the present disclosure provides a method and device for preparing synthesis gas by biomass staged gasification, in order to at least partially solve the above technical problems. In this regard, the specific technical solutions provided by the present disclosure are as follows.

[0006] As a first aspect of the present disclosure, a method for preparing synthesis gas by biomass staged gasification is provided, comprising:

[0007] Introducing biomass fuel and a first gasification agent or carrier gas into a first fluidized-bed reactor to extract volatile components in the biomass fuel through pyrolysis or partial gasification, producing a tar-containing gas-solid mixture and semi-coke particles;

[0008] After the tar-containing gas-solid mixture is separated by a first gas-solid separator, a tar-containing mixed gas and first-particle-size solid particulate matter are obtained;

[0009] Introducing the tar-containing mixed gas and a third gasification agent into a down-flow bed reactor to pyrolyze the tar in the tar-containing mixed gas through thermal cracking, producing tar-free synthesis gas.

[0010] As a second aspect of the present disclosure, a device for preparing synthesis gas by biomass staged gasification is provided, comprising: a first fluidized bed reactor, a first gas-solid separator and a down-flow bed reactor connected in sequence;

[0011] The first fluidized bed reactor is provided with a biomass fuel inlet, an inlet of a first gasification agent or carrier gas, a first gasification product outlet for discharging a tar-containing gas-solid mixture, and a semi-coke outlet for discharging semi-coke particles;

[0012] The first gas-solid separator is provided with a first gas-solid mixture inlet connected with the first gasification product outlet, and a first gas outlet and a first solid outlet for discharging a tar-containing mixed gas and first particle size solid particles obtained after gas-solid separation, respectively; and

[0013] The down-flow bed reactor is provided with a down-flow bed reactor gas inlet connected with the first gas outlet of the first gas-solid separator, a third gasification agent inlet, and a synthesis gas outlet for discharging tar-free synthesis gas generated by thermal cracking reaction of tar in the tar-containing mixed gas.

[0014] Based on the above technical solution, the method and device for preparing synthesis gas by biomass staged gasification provided by the present disclosure at least have one of the following beneficial effects:

[0015] (1) In the embodiment of the present disclosure, the biomass fuel is passed into the first fluidized bed reactor to generate tar, a gas with a high content of methane, i.e., a tar-containing gas-solid mixture, through pyrolysis reaction or partial gasification reaction. After the tar-containing gas-solid mixture is separated by the first gas-solid separator, it is then passed into the down-flow bed reactor to crack the tar and methane in the tar-containing mixed gas to obtain tar-free synthesis gas, thereby solving the problem that the device cannot be stably operated due to a high content of tar in the traditional process. Meanwhile, through the synergistic effect of the pyrolysis reaction or partial gasification reaction in the first fluidized bed reactor and the thermal cracking reaction in the down-flow bed reactor, the tar in the synthesis gas is removed, the quality of the synthesis gas is improved, the gasification system can be normally operated, and the cost of preparing high-quality synthesis gas is reduced.

[0016] (2) In the embodiment of the present disclosure, by combining the first fluidized bed reactor and the down-flow bed reactor, the size of the cracking reactor (i.e., the down-flow bed reactor) is reduced through staged gasification, the investment of the device for preparing synthesis gas by gasification is greatly reduced, and the economic efficiency of operation is increased. BRIEF DESCRIPTION OF DRAWINGS

[0017] FIG. 1 is a flow diagram of the preparation of synthesis gas by biomass staged gasification in the first embodiment of the present disclosure;

[0018] Figure 2 is a flow diagram of a process for preparing synthesis gas from biomass by staged gasification according to a second embodiment of the present disclosure;

[0019] Figure 3 is a schematic diagram of a down-flow bed reactor in a process for preparing synthesis gas from biomass by staged gasification according to a third embodiment of the present disclosure.

[0020] BRIEF DESCRIPTION OF DRAWINGS A-biomass fuel, B0-carrier gas, B1-first gasification agent, B2-second gasification agent, B3-third gasification agent, C-tar-containing gas-solid mixture, D-solid particles of a first size, E-tar-containing mixed gas, F-tar-free gas-solid mixture, G-tar-free synthesis gas, H-solid particles of a second size, I-bottom ash, J-char particles, K-ash; 1-first fluidized bed reactor, 2-second fluidized bed reactor, 3-down-flow bed reactor, 4-first gas-solid separator, 5-second gas-solid separator; 1a-biomass fuel inlet, 1b-inlet for first gasification agent or carrier gas, 1c-first gasification product outlet, 1d-char outlet; 2a-first solid particle inlet, 2b-second gasification agent inlet, 2c-second gasification product outlet, 2d-bottom ash outlet, 2e-second solid particle inlet, 2f-gasification agent injection port; 3a-cracking gas passage, 3b-gasification agent injection nozzle, 3c-synthesis gas outlet, 3d-gas-solid burner unit, 3e-ash outlet, 3f-material inlet of down-flow bed reactor, 3a1-gas inlet of down-flow bed reactor, 3b1-third gasification agent inlet, 3d1-first passage, 3d2-second passage. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present disclosure clearer, the technical solutions of the present disclosure will be further described in detail below with reference to specific embodiments and the accompanying drawings.

[0022] The main stream technologies of biomass gasification include fixed bed gasification technology and fluidized bed gasification technology. The fixed bed gasification has high tar content in the synthesis gas, and is mainly used for producing hot fuel gas, and is mostly used in the field of biomass gasification power generation. The fluidized bed gasification has better mass transfer and heat transfer, and the temperature in the hearth is uniform, and the circulation of the semi-coke in the gasification process can promote the cracking of tar to some extent, but because the ash melting point of biomass is generally low, the operating temperature of the gasification furnace is generally controlled between 700-850℃, while the effective cracking temperature of tar is above 1000℃, so the traditional fluidized bed gasification technology cannot effectively solve the problem of tar. In addition, whether it is fixed bed gasification or fluidized bed gasification technology, there is a problem that the tar content in the synthesis gas is high, which blocks the conveying pipeline and equipment, so that the gasification system cannot operate normally, and also affects the quality of the synthesis gas synthesized by the synthesis process. In order to pursue a higher carbon conversion rate, a relatively high gasification temperature is required, and the high alkali content of biomass can easily lead to hearth slagging at high temperature (above 1000℃), which restricts the long-term stable operation of the device, and leads to poor adaptability of raw materials. In addition, the high methane content in the synthesis gas needs to be separated to meet the downstream synthesis demand, which increases the separation device, leading to complex process and high cost.

[0023] In view of the above problems, the present disclosure provides a method and device for preparing synthesis gas by biomass staged gasification, which reduces the content of tar and methane in the synthesis gas by means of staged gasification, solves the problem of high tar and methane content in biomass gasification, and obtains synthesis gas without tar by staged gasification of semi-coke particles after extracting volatile matter, while avoiding the influence of semi-coke particles on the stability of long-term operation of the device due to hearth slagging, and widening the adaptability of biomass raw materials.

[0024] Figure 1 is a flow diagram of the preparation of synthesis gas by biomass staged gasification in the first embodiment of the present disclosure.

[0025] In combination with Figure 1, a method for preparing synthesis gas by biomass staged gasification in the embodiment of the present disclosure is described in detail.

[0026] As a first embodiment of the first aspect of the present disclosure, the present disclosure provides a method for preparing synthesis gas by biomass staged gasification, comprising: introducing biomass fuel A and first gasification agent B1 or carrier gas B0 into a first fluidized bed reactor 1, extracting volatile matter in the biomass fuel A through pyrolysis reaction or partial gasification reaction, to produce tar-containing gas-solid mixture C and semi-coke particles J; after the tar-containing gas-solid mixture C is separated by a first gas-solid separator 4, tar-containing mixed gas E and first particle size solid particulate D are obtained; the tar-containing mixed gas E and the third gasification agent B3 are transported into a down-flow bed reactor 3, and the tar in the tar-containing mixed gas E is cracked through thermal cracking reaction to produce tar-free synthesis gas G.

[0027] In the embodiment of the present disclosure, the biomass fuel A is introduced into the first fluidized bed reactor 1 to perform pyrolysis reaction or partial gasification reaction, so as to extract the volatile components in the biomass, to generate tar, gas with high content of methane, i.e. the tar-containing gas-solid mixture C. After the tar-containing gas-solid mixture C is separated by the first gas-solid separator 4, it is introduced into the down-flow bed reactor 3 to perform thermal cracking reaction, so as to crack and remove the tar and methane, to obtain the tar-free synthesis gas G, thereby solving the problem that the device cannot be stably operated due to high content of tar in the traditional process.

[0028] In the first embodiment of the present disclosure, the biomass fuel A includes forestry biomass or agricultural biomass, the forestry biomass includes any one of tree branches, tree bark, and waste wood, the agricultural biomass includes any one of corn stalks, wheat stalks, rice stalks, and cotton stalks, and other biomass fuels can also be used, which are only used as examples and are not further limited. In the case of partial gasification reaction in the first fluidized bed reactor 1, the first gasification agent B1 is introduced into the first fluidized bed reactor 1, and the first gasification agent B1 is a mixed gas of oxygen and steam or carbon dioxide. In the first gasification agent B1, the molar ratio of oxygen to steam or carbon dioxide is 0.3-0.5, and a too low molar ratio of oxygen to steam or carbon dioxide will lead to a decrease in the effective gas (CO+H2) component, and a too high molar ratio will easily lead to the slagging of semi-coke particles J and affect the stability of the operation of the first fluidized bed reactor 1. In the case of pyrolysis reaction in the first fluidized bed reactor 1, the carrier gas B0 is introduced into the first fluidized bed reactor 1, and the carrier gas B0 includes any one of nitrogen and carbon dioxide, and at this time, an external heating type heating mode is used as the reaction heat source of the first fluidized bed reactor 1, for example, green electricity or hot flue gas can be used to heat the first fluidized bed reactor 1. When the input amount of the biomass fuel A is constant, the reaction temperature in the first fluidized bed reactor 1 and the reaction degree of the gasification reaction or the pyrolysis reaction are controlled by controlling the amount of the first gasification agent B1 or the carrier gas B0 introduced. Similarly, the gasification reaction degree and the reaction temperature in the down-flow bed reactor 3 are controlled by controlling the amount of the third gasification agent B3 introduced. According to the different types of biomass fuel A, the design principles of the operating temperatures of the first fluidized bed reactor 1 and the down-flow bed reactor 3 are as follows: the first fluidized bed reactor 1 can achieve an ash removal rate of greater than 90% in the biomass fuel A, and if the volatilization removal rate in the first fluidized bed reactor 1 is too low, it will lead to a high content of tar and methane in the synthesis gas gas produced after the gasification reaction in the down-flow bed reactor 3 and the second fluidized bed reactor 2 arranged in the subsequent part of the embodiment, which will cause the synthesis gas (i.e., product gas) to be unable to meet the chemical requirements. If the gasification reaction share in the first fluidized bed reactor 1 is too high, it will lead to an increase in the gas amount entering the down-flow bed reactor 3, which will increase the size of the down-flow bed reactor 3 and increase the equipment investment. Therefore, in the first embodiment of the present disclosure, the temperature in the first fluidized bed reactor 1 is controlled by controlling the amount of the first gasification agent B1 or the carrier gas B0, and then the extraction amount of the volatilization in the biomass fuel A and the treatment load of the tar-containing mixed gas E in the down-flow bed reactor 3 are controlled. The reaction in the first fluidized bed reactor 1 is 450-650℃, which can fully extract the volatilization in the biomass fuel A in this temperature range, while avoiding the slagging of the biomass fuel A due to a too high reaction temperature, and avoiding the increase in the gas amount in the down-flow bed reactor 3 and the increase in the load.The third gasifying agent B3 is selected from oxygen or a mixed gas of oxygen and steam, and the molar ratio of oxygen to steam is 0.6-0.9. By controlling the amount of the third gasifying agent B3 introduced into the down-flow bed reactor 3, the reaction temperature of the down-flow bed reactor 3 is controlled to be 900-1400°C, so that the tar and methane in the tar-containing mixed gas E introduced into the down-flow bed reactor 3 are fully cracked, and meanwhile the yield of the synthesis gas (CO+H2) is not lost.

[0029] In the first embodiment of the present disclosure, as shown in Fig. 1, the method for preparing synthesis gas by biomass staged gasification further comprises: the first particle size solid particulate D and the semi-coke particles J are respectively transported into the second fluidized bed reactor 2, and are subjected to a gasification reaction with the second gasifying agent B2 introduced into the second fluidized bed reactor 2, to produce the bottom ash I and the tar-free gas-solid mixture F; after the tar-free gas-solid mixture F is separated by the second gas-solid separator 5, the second particle size solid particulate H and the tar-free synthesis gas G are obtained.

[0030] In the first embodiment of the present disclosure, by transporting the semi-coke particles J produced by the pyrolysis reaction or the partial gasification reaction in the first fluidized bed reactor 1 and the first particle size solid particulate D separated by the first gas-solid separator 4 into the second fluidized bed reactor 2 respectively, and subjecting them to a gasification reaction with the second gasifying agent B2 introduced into the second fluidized bed reactor 2, the tar and the methane contained in the semi-coke particles J and the first particle size solid particulate D are further gasified, and meanwhile the carbon in the semi-coke particles J and the first particle size solid particulate D is further converted, so that the utilization rate and the carbon conversion rate of the semi-coke particles J and the first particle size solid particulate D are improved, and the tar-free gas-solid mixture F and the bottom ash I are produced.

[0031] Further, by means of the external return pipe, the second particle size solid particulate H separated by the second gas-solid separator 5 is returned to the second fluidized bed reactor 2 through the return pipe for secondary reaction, so that the quality of the synthesis gas and the carbon conversion efficiency can be further improved.

[0032] In the first embodiment of the present disclosure, as shown in Fig. 1, the second gasifying agent B2 is introduced into the dense phase zone of the second fluidized bed reactor 2, so that the semi-coke particles J and / or the first particle size solid particulate D are subjected to a gasification reaction with the second gasifying agent B2 to produce the bottom ash I and the tar-free gas-solid mixture F. Further, the second gasifying agent B2 is optionally introduced into the dilute phase zone of the second fluidized bed reactor 2, so as to improve the carbon conversion efficiency of the first particle size solid particulate D and / or the second particle size solid particulate H in the second fluidized bed reactor 2, wherein the particle size (d 50 ) of the first particle size solid particulate D is 60-80 μm, and the particle size (d 50) is 30-40 pm. The second gasification agent B2 is a mixed gas of oxygen and steam or carbon dioxide, and the molar ratio of oxygen to steam or carbon dioxide is 0.3-0.5. By controlling the molar ratio of oxygen to steam or carbon dioxide in the second gasification agent B2, the reaction degree and reaction temperature in the second fluidized bed reactor 2 are controlled. When the molar ratio of oxygen to steam or carbon dioxide in the second gasification agent B2 is too low, the quality of the synthetic gas prepared by the gasification reaction in the second fluidized bed reactor 2 will be reduced; if the molar ratio of oxygen to steam or carbon dioxide is too high, it is easy to cause the semi-coke particles J to be slagged in the second fluidized bed reactor 2, thereby affecting the stability of the operation of the second fluidized bed reactor 2. The reaction temperature in the second fluidized bed reactor 2 is determined according to the ash melting point and ash composition of the biomass fuel A, and under the condition of no slagging, the operating temperature in the second fluidized bed reactor 2 is as high as possible. A higher operating temperature is conducive to improving the carbon conversion efficiency, reducing the content of tar and methane in the synthetic gas, and improving the quality of the synthetic gas. Therefore, the reaction temperature in the second fluidized bed reactor 2 in the present disclosure is set to 650-900°C.

[0033] Figure 2 is a flow diagram of a method for preparing synthetic gas by biomass staged gasification according to a second embodiment of the present disclosure.

[0034] As shown in Figure 2, in the method for preparing synthetic gas by biomass gasification according to the second embodiment, the biomass fuel A and the first gasification agent B1 or the carrier gas B0 are introduced into the first fluidized bed reactor 1 to extract the volatile matter in the biomass fuel A through pyrolysis reaction or partial gasification reaction, thereby producing a tar-containing gas-solid mixture C and semi-coke particles J. After the tar-containing gas-solid mixture C is separated by the first gas-solid separator 4, a tar-containing mixed gas E and first particle size solid particles D are obtained. The tar-containing mixed gas E and the third gasification agent B3 are transported into the downer reactor 3 to pyrolyze the tar in the tar-containing mixed gas E through thermal cracking reaction, thereby producing tar-free synthetic gas G.

[0035] In the second embodiment of the present disclosure, the method for preparing synthetic gas further comprises: transporting the first particle size solid particles D and the semi-coke particles J into the second fluidized bed reactor 2, respectively, and performing gasification reaction with the second gasification agent B2 introduced into the second fluidized bed reactor 2, thereby producing bottom ash I and tar-free gas-solid mixture F. After the tar-free gas-solid mixture F is separated by the second gas-solid separator 5, second particle size solid particles H and tar-free synthetic gas G are obtained.

[0036] The second embodiment differs from the first embodiment in that the second particle size solid particulate H is transported into the down-flow bed reactor 3 for secondary reaction to completely convert the carbon in the second particle size solid particulate H, to produce the ash K and the tar-free synthesis gas G. Specifically, the second particle size solid particulate H is directly transported into the down-flow bed reactor 3 through a pipeline, and is subjected to gasification reaction with the third gasification agent B3 introduced into the down-flow bed reactor 3, to completely convert the carbon in the second particle size solid particulate H into the ash K and the tar-free synthesis gas G, to achieve complete conversion of the biomass fuel A, and the heat released during the gasification reaction will promote sufficient thermal cracking of the tar and the methane in the tar-containing mixed gas E entering the down-flow bed reactor 3, to improve the quality of the synthesis gas. The reaction parameters and conditions in the first gasification agent B1 or the carrier gas B0, the second gasification agent B2, the third gasification agent B3, the first fluidized bed reactor 1, the second fluidized bed reactor 2, and the down-flow bed reactor 3 in the second embodiment are the same as those in the first embodiment, and will not be described in detail here.

[0037] In the second embodiment of the present disclosure, by using the two-stage fluidized bed reactor and the down-flow bed reactor, the gasification process of the biomass fuel A is controlled in stages, the advantages of the fluidized bed reactor are utilized to effectively broaden the adaptability of the biomass fuel, to reduce the tar content in the synthesis gas, and the high-temperature gasification advantage of the down-flow bed reactor 3 is utilized to achieve sufficient cracking of the tar and the methane and efficient complete conversion of the biomass fuel A. By adjusting the operating parameters of the fluidized bed reactor and the down-flow bed reactor 3 and controlling the gasification share of the biomass fuel A in each reactor, the composition of the synthesis gas can be regulated to meet the gas component requirements of different chemical synthesis gases. In addition, by the staged gasification of the biomass fuel A, the tar content in the synthesis gas is reduced, the cost of separating the methane and other gases from the synthesis gas is reduced, the carbon conversion efficiency of the biomass fuel A is improved, and the stability of the long-term operation of the synthesis gas preparation device is ensured by avoiding slagging in the furnace and tar blocking the pipeline.

[0038] FIG. 3 is a schematic diagram of the down-flow bed reactor in the third embodiment of the present disclosure for preparing synthesis gas by biomass staged gasification.

[0039] As shown in Fig. 3, the third embodiment of the present disclosure for preparing synthesis gas is the same as the second embodiment, except that the second particle size solid particles H are transported into the down-flow bed reactor 3 for secondary reaction, which comprises: transporting the second particle size solid particles H into the gas-solid burner unit 3d, mixing with the part of the tar-containing mixed gas E in the form of jet to form jet gas-solid mixture, and carrying the second particle size solid particles H into the down-flow bed reactor 3 by the tar-containing mixed gas E; the third gasification agent B3 is introduced into the down-flow bed reactor 3 through the gasification agent nozzle 3b, and reacts with the jet gas-solid mixture, and the released heat promotes the other part of the tar-containing mixed gas E introduced into the down-flow bed reactor 3 through the pyrolysis gas passage 3a to perform thermal cracking reaction, so that the tar in the tar-containing mixed gas E is fully thermally cracked to form tar-free synthesis gas G. In the jet gas-solid mixture, the mass ratio of the tar-containing mixed gas E to the second particle size solid particles H is 1:20-1:30 kg / kg, the jet velocity of the jet gas-solid mixture is 20-50 m / s, and the part of the tar-containing mixed gas E introduced into the gas-solid burner unit 3d accounts for 1 / 3-1 / 5 of the total volume of the tar-containing mixed gas E.

[0040] In the third embodiment of the present disclosure, the tar-containing mixed gas E enters the down-flow bed reactor 3 from two different positions for thermal cracking reaction, wherein a part of the tar-containing mixed gas E enters the gas-solid burner unit 3d in the form of jet to mix with the second particle size solid particles H to form jet gas-solid mixture, and the tar-containing mixed gas E carries the second particle size solid particles H into the down-flow bed reactor 3 as the blowing gas of the second particle size solid particles H. At the same time, around the gas-solid burner unit 3d, the third gasification agent B3 introduced into the down-flow bed reactor 3 in the form of jet performs gasification reaction to form a local high-temperature area, so as to maximize the complete conversion of carbon in the second particle size solid particles H to form ash K. At the same time, the heat released during the gasification reaction of the third gasification agent B3 and the second particle size solid particles H provides a high-temperature cracking environment (900-1400℃) for the tar cracking of the other part of the tar-containing mixed gas E introduced into the down-flow bed reactor 3 through the pyrolysis gas passage 3a, so that the tar and methane in the tar-containing mixed gas E are thermally cracked to form tar-free synthesis gas G.

[0041] As the first embodiment of the second aspect of the present disclosure, a device for preparing synthesis gas by biomass pyrolysis gasification is provided, which is shown in Fig. 1, and comprises: a first fluidized bed reactor 1, a first gas-solid separator 4 and a down-flow bed reactor 3 connected in sequence.

[0042] The first fluidized bed reactor 1 is provided with a biomass fuel inlet 1a, an inlet 1b for the first gasification agent B1 or carrier gas B0, a first gasification product outlet 1c for discharging tar-containing gas-solid mixture C, and a semi-coke outlet 1d for discharging semi-coke particles J.

[0043] The first gas-solid separator 4 is provided with a first gas-solid mixture inlet connected with the first gasification product outlet 1c, and a first gas outlet and a first solid outlet for discharging the first particle size solid particles D and the tar-containing mixed gas E obtained after gas-solid separation, respectively.

[0044] The down-flow bed reactor 3 is provided with a down-flow bed reactor gas inlet 3a1 connected with the first gas outlet of the first gas-solid separator 4, a third gasification agent inlet 3b1, and a synthesis gas outlet 3c for discharging the tar-free synthesis gas G generated by thermal cracking reaction of the tar in the tar-containing mixed gas E.

[0045] In the first embodiment of the present disclosure, the biomass fuel A enters the first fluidized bed reactor 1 through the biomass fuel inlet 1a, the first gasification agent B1 or the carrier gas B0 enters the first fluidized bed reactor 1 through the inlet 1b of the first gasification agent B1 or the carrier gas B0 to perform pyrolysis reaction or partial gasification reaction, and the generated tar-containing gas-solid mixture C is discharged through the first gasification product outlet 1c. The semi-coke particles J are discharged through the semi-coke outlet 1d. The first gasification product outlet 1c is connected with the first gas-solid mixture inlet of the first gas-solid separator 4, so that the tar-containing gas-solid mixture C enters the first gas-solid separator 4 to perform gas-solid separation. The first particle size solid particles D generated after separation are discharged through the first solid outlet, and the generated tar-containing mixed gas E is discharged through the first gas outlet. Further, the first gas outlet of the first gas-solid separator 4 is connected with the down-flow bed reactor 3 gas inlet 3a1 through a pipeline, so that the tar-containing mixed gas E is transported to the down-flow bed reactor 3 through the pipeline, and performs thermal cracking reaction with the third gasification agent B3 entering the down-flow bed reactor 3 through the third gasification agent inlet 3b1. The tar in the tar-containing mixed gas E is fully cracked to generate the tar-free synthesis gas G, which is discharged through the synthesis gas outlet 3c.

[0046] Continuing as shown in FIG. 1, the device for preparing synthesis gas by biomass staged gasification in the first embodiment of the present disclosure further comprises a second fluidized bed reactor 2 and a second gas-solid separator 5.

[0047] The first solid outlet of the first gas-solid separator 4 is connected with the first solid particle inlet 2a of the second fluidized bed reactor 2, the semicoke outlet 1d of the first fluidized bed reactor 1 is connected with the second solid particle inlet 2e of the second fluidized bed reactor 2, the second gasification agent inlet 2b is arranged in the dense phase zone of the second fluidized bed reactor 2, the second fluidized bed reactor 2 is further provided with a bottom ash outlet 2d and a second gasification product outlet 2c for discharging the bottom ash I and the tar-free gas-solid mixture F produced by the gasification reaction in the second fluidized bed reactor 2 respectively; and the second gasification product outlet 2c of the second fluidized bed reactor 2 is connected with the second gas-solid mixture inlet of the second gas-solid separator 5, the second gas-solid separator 5 is further provided with a second solid outlet and a second gas outlet for discharging the second particle size solid particle H and the tar-free synthesis gas G obtained by the gas-solid separation respectively. The first solid particle inlet 2a can be one or more, and the multiple first solid particle inlets 2a are circumferentially distributed at the upper part of the second fluidized bed reactor 2, at least one first solid particle inlet 2a is connected with the first solid outlet of the first gas-solid separator 4. Further optionally, the second solid outlet of the second gas-solid separator 5 is connected with the at least one first solid particle inlet 2a. Specifically, the second solid outlet of the second gas-solid separator 5 is connected with the at least one first solid particle inlet 2a through a return pipeline to return the second particle size solid particle H to the second fluidized bed reactor 2 for secondary reaction. It should be noted that the first solid particle inlets 2a connected with the first solid outlet of the first gas-solid separator 4 and the second solid outlet of the second gas-solid separator 5 can be the same or different. The optional meaning indicates that the second solid outlet of the second gas-solid separator 5 is connected with or not connected with the first solid particle inlet 2a.

[0048] In the first embodiment of the present disclosure, the coupling matching between the first fluidized bed reactor 1, the second fluidized bed reactor 2, the down-flow bed reactor 3, and the first gas-solid separator 4 and the second gas-solid separator 5 is the basis for stable and efficient operation of the system, and the material transportation between the reactors is the key. According to the particle size of the product after the reaction of the biomass fuel A, the semi-coke particles J produced by the first fluidized bed reactor 1 can be transported into the second fluidized bed reactor 2 in a hot or cold manner. For example, if the semi-coke particles J are small, they can be directly hot transported into the second fluidized bed reactor 2 by pneumatic conveying; if the semi-coke particles J are large, they need to be cooled first, and then transported into the second fluidized bed reactor 2 by mechanical conveying. The first particle size solid particles D separated by the first gas-solid separator 4 are transported into the second fluidized bed reactor 2 in a natural falling manner. In order to facilitate the smooth transportation of the first particle size solid particles D, blowing gas can be provided on the transportation pipeline. In order to improve the carbon conversion rate in the second fluidized bed reactor 2, the first solid particle inlet 2a and the second solid particle inlet 2e in the second fluidized bed reactor 2 should be located as far as possible in the lower part of the second fluidized bed reactor 2, but from the comprehensive consideration of the stable operation of the second fluidized bed reactor 2 and the smooth return of the material, the first solid particle inlet 2a and the second solid particle inlet 2e should not be arranged in the dense phase zone of the second fluidized bed reactor 2. Therefore, the first solid particle inlet 2a and the second solid particle inlet 2e should be arranged between the dense phase zone and the dilute phase zone in consideration of the stable return of the material and the improvement of the carbon conversion rate. Specifically, according to the height (h) of the second fluidized bed reactor 2, the second solid particle inlet 2e and the first solid particle inlet 2a are arranged at 0.1h-0.3h from the bottom of the second fluidized bed reactor 2, and h is the height of the second fluidized bed reactor 2.

[0049] According to the first embodiment of the present disclosure, as shown in FIG. 1, in order to improve the carbon conversion rate of the second fluidized bed reactor 2, one or more gasification agent nozzles 2f are arranged in the dilute phase zone of the second fluidized bed reactor 2, and the second gasification agent B2 is introduced into the dilute phase zone of the second fluidized bed reactor 2 through the gasification agent nozzles 2f, so that the first particle size solid particles D and / or the second particle size solid particles H are subjected to gasification reaction with the second gasification agent B2, and the gasification agent nozzles 2f are arranged at different heights of the second fluidized bed reactor 2.

[0050] In the second embodiment of the present disclosure, the second gasifying agent B2 enters the second fluidized bed reactor 2 by dispersion feeding through one or more gasifying agent nozzles 2f arranged in the dilute phase zone of the second fluidized bed reactor 2 (i.e. the upper part of the second fluidized bed reactor 2), which increases the temperature of the dilute phase zone of the second fluidized bed reactor 2, so that the first particle size solid particulate D and / or the second particle size solid particulate H is completely converted in the dilute phase zone, thereby improving the carbon conversion rate of the second fluidized bed reactor 2. In order to make the temperature of the dilute phase zone more uniform, a plurality of gasifying agent nozzles 2f can be arranged at different heights along the second fluidized bed reactor 2, so that the second gasifying agent B2 fully contacts the first particle size solid particulate D and / or the second particle size solid particulate H.

[0051] According to the second embodiment of the present disclosure, as shown in FIG. 2, the device for preparing synthesis gas by biomass decomposition and gasification has the same first fluidized bed reactor 1, first gas-solid separator 4, second fluidized bed reactor 2, second gas-solid separator 5 and down-flow bed reactor 3 as shown in FIG. 1, and the corresponding connection relationship, and the difference between the device shown in FIG. 2 and the device shown in FIG. 1 is that the second solid outlet of the second gas-solid separator 5 is connected with the down-flow bed reactor 3 to transport the second particle size solid particulate H into the down-flow bed reactor 3 for secondary reaction, and the down-flow bed reactor 3 is further provided with an ash outlet 3e for discharging the ash K generated by the secondary reaction of the second particle size solid particulate H. Specifically, connecting the second solid outlet of the second gas-solid separator 5 with the down-flow bed reactor 3 includes: connecting the second solid outlet of the second gas-solid separator 5 with the material inlet 3f of the down-flow bed reactor 3 through a pipeline to directly transport the second particle size solid particulate H into the down-flow bed reactor 3 to be subjected to secondary reaction with the third gasifying agent B3 to generate the tar-free synthesis gas G and the ash K. It should be noted that the device shown in FIG. 2 does not have one or more gasifying agent nozzles 2f arranged in the dilute phase zone of the second fluidized bed reactor 2, but this does not mean that the gasifying agent nozzles 2f cannot be arranged in the dilute phase zone of the second fluidized bed reactor 2, and FIG. 2 in the second embodiment of the present disclosure is only an example to illustrate that the gasifying agent nozzles 2f can not be arranged in the dilute phase zone of the second fluidized bed reactor 2.

[0052] In the second embodiment of the present disclosure, the second solid outlet of the second gas-solid separator 5 is directly connected with the material inlet 3f of the down-flow bed reactor 3 through a pipeline to deliver the second particle size solid particles H into the down-flow bed reactor 3, and the second particle size solid particles H are subjected to a gasification reaction with the third gasification agent B3 introduced into the down-flow bed reactor 3 through the pipeline, so that the second particle size solid particles H are completely converted to form the ash K, and the heat released in the gasification reaction provides a high-temperature environment for the thermal cracking reaction of the tar-containing mixed gas E, which helps the tar and methane in the tar-containing mixed gas E to be fully cracked to form the tar-free synthesis gas G. Meanwhile, the staged gasification of the biomass fuel A through the first fluidized bed reactor 1, the second fluidized bed reactor 2 and the down-flow bed reactor 3 achieves complete carbon conversion, and the carbon conversion efficiency is improved.

[0053] According to the third embodiment of the present disclosure, the device for preparing synthesis gas by gasification of biomass has the same first fluidized bed reactor 1, first gas-solid separator 4, second fluidized bed reactor 2, second gas-solid separator 5 and down-flow bed reactor 3 as those in FIGS. 1 and 2, and the corresponding connection relationship. The difference between the device for preparing synthesis gas shown in FIG. 3 and the device shown in FIG. 1 lies in that the second solid outlet of the second gas-solid separator 5 is connected with the down-flow bed reactor 3. The difference between the device shown in FIG. 3 and the device shown in FIG. 2 lies in that the second solid outlet of the second gas-solid separator 5 is connected with the material inlet 3f of the down-flow bed reactor 3 through a gas-solid burner unit 3d, and the down-flow bed reactor 3 is provided with a plurality of gasification agent nozzles 3b and a plurality of cracking gas passages 3a. The gas-solid burner unit 3d is arranged on the central axis of the down-flow bed reactor 3, the plurality of gasification agent nozzles 3b are arranged in a symmetrical manner around the gas-solid burner unit 3d, the plurality of cracking gas passages 3a are arranged in a symmetrical manner around the gasification agent nozzles 3b, and the included angle β between the gasification agent nozzles 3b and the cracking gas passages 3a and the central axis of the down-flow bed reactor 3 is 135°-175°. Further, the gas-solid burner unit 3d is provided with a first passage 3d1 connected with the second solid outlet of the second gas-solid separator 5 and a plurality of second passages 3d2 obliquely arranged through the first passage 3d1. The first passage 3d1 is used to deliver the second particle size solid particles H, and the second passages 3d2 are used to deliver part of the tar-containing mixed gas E. The second particle size solid particles H and the tar-containing mixed gas E are mixed in the gas-solid burner unit 3d to form a jet gas-solid mixture, the jet gas-solid mixture enters the down-flow bed reactor 3 through the material inlet 3f of the down-flow bed reactor 3, and the included angle α between the second passages 3d2 and the first passage 3d1 is 5°-30°. The gasification agent nozzle 3b has a gasification agent passage connected with a third gasification agent inlet 3b1, and the gasification agent passage is configured to deliver the third gasification agent B3 to the down-flow bed reactor 3. The cracking gas passage 3a is connected with a gas inlet 3a1 of the down-flow bed reactor 3 to introduce another part of the tar-containing mixed gas E into the down-flow bed reactor 3.

[0054] In the third embodiment of the present disclosure, the tar-containing gas E enters the down-flow bed reactor 3 from two different positions, one part of the tar-containing gas E enters the second passage 3d2 of the gas-solid burner unit 3d in the form of jet, mixes with the second particle size solid particles H in the first passage 3d1 of the gas-solid burner unit 3d to form a high-speed jet gas-solid mixture, the part of the tar-containing gas E as the blowing gas transports the second particle size solid particles H into the down-flow bed reactor 3, the jet speed of the formed high-speed jet gas-solid mixture is 20-50 m / s, the mass ratio of the part of the tar-containing gas E to the second particle size solid particles H is 1:20-1:30 kg / kg, and the formed jet gas-solid mixture is sprayed into the down-flow bed reactor 3 in the form of dense phase transport. From the material transport point of view, the included angle α between the part of the tar-containing gas E and the second particle size solid particles H is 5°-30°, that is, the included angle α between the second passage 3d2 and the first passage 3d1 is 5°-30°.

[0055] Another part of the tar-containing gas E enters the down-flow bed reactor 3 through the cracking gas passage 3a to perform cracking reaction, wherein the tar-containing gas E used as the blowing gas accounts for 1 / 3-1 / 5 of the total volume of the tar-containing gas E. In order to maximize the conversion of carbon in the second particle size solid particles H in the down-flow bed reactor 3 and at the same time reduce the consumption of the effective gas (CO+H2) in the tar-containing gas E as much as possible, the structure and angle of the cracking gas passage 3a through which the third gasification agent B3 is introduced and the gas-solid burner unit 3d through which the second particle size solid particles H are introduced are optimized, which involves that the heat required for the thermal cracking reaction of the tar-containing gas E in the down-flow bed reactor 3 is provided by the combustion of carbon in the second particle size solid particles H as much as possible, so as to reduce the consumption of the effective gas (CO+H2) in the tar-containing gas E. Therefore, a plurality of gasification agent nozzles 3b are arranged around the gas-solid burner unit 3d, the plurality of gasification agent nozzles 3b are arranged in a symmetrical manner and the gasification agent nozzles 3b are arranged near the material inlet 3f of the down-flow bed reactor 3, so that the third gasification agent B3 introduced in the form of high-speed jet reacts with the second particle size solid particles H in the jet gas-solid mixture to form a local high-temperature zone (900-1400℃), thereby realizing high-efficiency conversion of the second particle size solid particles H. A plurality of cracking gas passages 3a are arranged around the gasification agent nozzles 3b in a symmetrical manner, and the high-temperature zone formed by the gasification reaction promotes the thermal cracking of tar and methane in another part of the tar-containing gas E entering the down-flow bed reactor 3 through the cracking gas passage 3a, thereby forming tar-free synthesis gas G. From the point of view of effective contact of the third gasification agent B3 with the jet gas-solid mixture and another part of the tar-containing gas E, the included angle β between the gasification agent nozzles 3b and the cracking gas passages 3a and the central axis of the down-flow bed reactor 3 is 135°-175°.

[0056] In the first to third embodiments of the present disclosure, the first fluidized bed reactor 1 and the second fluidized bed reactor 2 are bubbling fluidized bed reactors or circulating fluidized bed reactors.

[0057] In summary, the main function of the first fluidized bed reactor 1 in the embodiments of the present disclosure is to extract the volatile components in the biomass fuel, to generate a gas-solid mixture with high tar and methane (i.e., the tar-containing gas-solid mixture C) and semi-coke particles J. The main function of the second fluidized bed reactor 2 is to gasify the semi-coke particles J generated in the first fluidized bed reactor 1 to generate tar-free syngas G. The main function of the downer reactor 3 is to crack the tar-containing gas-solid mixture C generated in the first fluidized bed reactor 1 to generate tar-free syngas G, and to further convert the residual carbon in the semi-coke particles J to improve the carbon conversion rate. By combining the fluidized bed reactor and the downer reactor, the gasification process of the biomass is controlled in stages, the advantages of the fluidized bed reactor are utilized to broaden the adaptability of the biomass fuel and reduce the tar content in the syngas, and the advantages of the high-temperature gasification of the downer are utilized to achieve the thermal cracking of tar and methane and the efficient conversion of biomass. By adjusting the operating parameters of the fluidized bed reactor and the downer reactor and controlling the gasification share of the biomass in each reactor, the composition of the syngas can be precisely controlled to meet the gas component requirements of different chemical syntheses.

[0058] The specific embodiments described above further illustrate the purposes, technical solutions, and beneficial effects of the present disclosure. It should be understood that the above description is only for specific embodiments of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A method for producing synthesis gas from biomass by staged gasification, characterized in that, The method comprises: feeding the biomass fuel (A) and a first gasification agent (B1) or a carrier gas (B0) into a first fluidized bed reactor (1) to extract volatile components in the biomass fuel (A) through a pyrolysis reaction or a partial gasification reaction, to produce a tar-containing gas-solid mixture (C) and semi-coke particles (J); after the tar-containing gas-solid mixture (C) is separated by a first gas-solid separator (4), a tar-containing mixed gas (E) and first-particle-size solid particles (D) are obtained; feeding the tar-containing mixed gas (E) and a third gasification agent (B3) into a downward-flowing bed reactor (3) to pyrolyze tar in the tar-containing mixed gas (E) through a thermal cracking reaction, to produce tar-free synthesis gas (G).

2. The method of claim 1, wherein, The method further comprises: feeding the first-particle-size solid particles (D) and the semi-coke particles (J) into a second fluidized bed reactor (2) respectively, and performing a gasification reaction with a second gasification agent (B2) fed into the second fluidized bed reactor (2), to produce a bottom slag (I) and a tar-free gas-solid mixture (F); after the tar-free gas-solid mixture (F) is separated by a second gas-solid separator (5), second-particle-size solid particles (H) and tar-free synthesis gas (G) are obtained.

3. The method of claim 2, wherein, the second-particle-size solid particles (H) are returned to the second fluidized bed reactor (2) through a return pipeline for secondary reaction; or the second-particle-size solid particles (H) are fed into the downward-flowing bed reactor (3) for secondary reaction to completely convert carbon in the second-particle-size solid particles (H), to produce an ash slag (K) and tar-free synthesis gas (G).

4. The method of claim 3, wherein, feeding the second-particle-size solid particles (H) into the downward-flowing bed reactor (3) for secondary reaction comprises: the second-particle-size solid particles (H) are directly fed into the downward-flowing bed reactor (3) through a pipeline for secondary reaction; or the second-particle-size solid particles (H) are fed into a gas-solid burner unit (3d) to mix with a part of the tar-containing mixed gas (E) fed into the gas-solid burner unit (3d) in the form of a jet to form a jet gas-solid mixture, and the second-particle-size solid particles (H) are carried into the downward-flowing bed reactor (3) by the tar-containing mixed gas (E); the third gasification agent (B3) fed into the downward-flowing bed reactor (3) through a gasification agent nozzle (3b) reacts with the jet gas-solid mixture, and the released heat promotes another part of the tar-containing mixed gas (E) fed into the downward-flowing bed reactor (3) through a cracked gas passage (3a) to perform a thermal cracking reaction to form tar-free synthesis gas (G).

5. The method of claim 4, wherein, The mass ratio of the tar-containing mixed gas (E) to the second-particle-size solid particles (H) in the jet gas-solid mixture is 1:20-1:30 kg / kg, the jet velocity of the jet gas-solid mixture is 20-50 m / s, and the part of the tar-containing mixed gas (E) fed into the gas-solid burner unit (3d) accounts for 1 / 3-1 / 5 of the total volume of the tar-containing mixed gas (E).

6. The method of claim 1, wherein, In the case that partial gasification reaction occurs in the first fluidized bed reactor (1), a first gasification agent (B1) is introduced into the first fluidized bed reactor (1), wherein the first gasification agent (B1) is a mixed gas of oxygen and steam or carbon dioxide; In the case that pyrolysis reaction occurs in the first fluidized bed reactor (1), a carrier gas (B0) is introduced into the first fluidized bed reactor (1), wherein the carrier gas (B0) includes any one of nitrogen, carbon dioxide.

7. The method of claim 6, wherein, In the first gasification agent (B1), the molar ratio of oxygen to steam or carbon dioxide is 0.3-0.5, and the reaction temperature in the first fluidized bed reactor (1) is 450-650℃.

8. The method of claim 1 or 4, wherein, The third gasification agent (B3) is selected from oxygen or a mixed gas of oxygen and steam, the molar ratio of oxygen to steam is 0.6-0.9, and the reaction temperature in the down-flow bed reactor (3) is 900-1400℃.

9. The method of claim 3, wherein, In the dense phase zone of the second fluidized bed reactor (2), a second gasification agent (B2) is introduced so that the semi-coke particles (J) and / or the first particle size solid particles (D) are subjected to gasification reaction with the second gasification agent (B2), wherein the second gasification agent (B2) is a mixed gas of oxygen and steam or carbon dioxide; and Optionally, the second gasification agent (B2) is also introduced into the dilute phase zone of the second fluidized bed reactor (2) to improve the carbon conversion efficiency of the first particle size solid particles (D) and / or the second particle size solid particles (H) in the second fluidized bed reactor (2).

10. The method of claim 9, wherein, In the second gasification agent (B2), the molar ratio of oxygen to steam or carbon dioxide is 0.3-0.5, and the reaction temperature in the second fluidized bed reactor (2) is 650-900℃.

11. An apparatus for producing synthesis gas from biomass by staged gasification, characterized in that The device comprises a first fluidized bed reactor (1), a first gas-solid separator (4) and a down-flow bed reactor (3) connected in sequence; The first fluidized bed reactor (1) is provided with a biomass fuel inlet (1a), an inlet (1b) for the first gasification agent (B1) or the carrier gas (B0), a first gasification product outlet (1c) for discharging a tar-containing gas-solid mixture (C), and a semi-coke outlet (1d) for discharging semi-coke particles (J); The first gas-solid separator (4) is provided with a first gas-solid mixture inlet connected with the first gasification product outlet (1c), and a first gas outlet and a first solid outlet for discharging a tar-containing mixed gas (E) and first particle size solid particles (D) obtained after gas-solid separation, respectively; and The down-flow bed reactor (3) is provided with a down-flow bed reactor gas inlet (3a1) connected with the first gas outlet of the first gas-solid separator (4), a third gasification agent inlet (3b1), and a synthesis gas outlet (3c) for discharging tar-free synthesis gas (G) generated by thermal cracking reaction of tar in the tar-containing mixed gas (E).

12. The apparatus of claim 11, wherein, The device further comprises a second fluidized bed reactor (2) and a second gas-solid separator (5); wherein the first solids outlet of the first gas-solid separator (4) is connected to the first solids inlet (2a) of the second fluidized bed reactor (2), the semi-coke outlet (1d) of the first fluidized bed reactor (1) is connected to the second solids inlet (2e) of the second fluidized bed reactor (2), a second gasifying agent inlet (2b) is arranged in the dense phase zone of the second fluidized bed reactor (2), and the second fluidized bed reactor (2) is further provided with a bottom ash outlet (2d) and a second gasification product outlet (2c) for discharging the bottom ash (I) and the tar-free gas-solid mixture (F) produced by the gasification reaction in the second fluidized bed reactor (2), respectively; and the second gasification product outlet (2c) of the second fluidized bed reactor (2) is connected to the second gas-solid mixture inlet of the second gas-solid separator (5), and the second gas-solid separator (5) is further provided with a second solids outlet and a second gas outlet for discharging the second particle size solids (H) and the tar-free synthesis gas (G) obtained by the gas-solid separation, respectively; wherein the first solids inlet (2a) is one or more, and a plurality of the first solids inlets (2a) are circumferentially distributed on the upper portion of the second fluidized bed reactor (2), at least one first solids inlet (2a) is connected to the first solids outlet of the first gas-solid separator (4), and optionally the second solids outlet of the second gas-solid separator (5) is connected to at least one first solids inlet (2a).

13. The apparatus of claim 12, wherein, the second solids outlet of the second gas-solid separator (5) is connected to at least one first solids inlet (2a) through a return pipe to return the second particle size solids (H) to the second fluidized bed reactor (2) for secondary reaction; or the second solids outlet of the second gas-solid separator (5) is connected to a down-flow bed reactor (3) to deliver the second particle size solids (H) to the down-flow bed reactor (3) for secondary reaction, and the down-flow bed reactor (3) is further provided with an ash outlet (3e) for discharging the ash (K) produced by the reaction of the second particle size solids (H).

14. The apparatus of claim 13, wherein, The second solids inlet (2e) and the first solids inlet (2a) are arranged at a distance of 0.1h-0.3h from the bottom of the second fluidized bed reactor (2), and h is the height of the second fluidized bed reactor (2); Optionally, one or more gasifying agent nozzles (2f) are arranged in the dilute phase zone of the second fluidized bed reactor (2) to introduce the second gasifying agent (B2) into the dilute phase zone of the second fluidized bed reactor (2) through the gasifying agent nozzles (2f) so that the first particle size solids (D) and / or the second particle size solids (H) are subjected to gasification reaction with the second gasifying agent (B2), wherein a plurality of the gasifying agent nozzles (2f) are arranged at different heights of the second fluidized bed reactor (2).

15. The apparatus of claim 13, wherein, connecting the second solids outlet of the second gas-solid separator (5) to a down-flow bed reactor (3) includes: The second solid outlet of the second gas-solid separator (5) is connected to the material inlet (3f) of the down-flow bed reactor (3) through a pipeline; or The second solid outlet of the second gas-solid separator (5) is connected to the material inlet (3f) of the down-flow bed reactor (3) through a gas-solid burner unit (3d), and a plurality of gasification agent nozzles (3b) and a plurality of cracking gas passages (3a) are arranged on the down-flow bed reactor (3), the gas-solid burner unit (3d) is arranged on the central axis of the down-flow bed reactor (3), a plurality of the gasification agent nozzles (3b) are arranged around the gas-solid burner unit (3d) in a symmetrical manner, a plurality of cracking gas passages (3a) are arranged around the gasification agent nozzles (3b) in a symmetrical manner, and the included angle β between the gasification agent nozzles (3b) and the cracking gas passages (3a) and the central axis of the down-flow bed reactor (3) is 135°-175°; The gas-solid burner unit (3d) is provided with a first passage (3d1) connected to the second solid outlet of the second gas-solid separator (5) and a plurality of second passages (3d2) obliquely arranged through the first passage (3d1), the first passage (3d1) is used for conveying the second particle size solid particulate matter (H), the second passage (3d2) is used for conveying the tar-containing mixed gas (E), the second particle size solid particulate matter (H) and the tar-containing mixed gas (E) are mixed in the gas-solid burner unit (3d) to form a jet gas-solid mixture, the jet gas-solid mixture enters the down-flow bed reactor (3) through the material inlet (3f) of the down-flow bed reactor, and the included angle α between the second passage (3d2) and the first passage (3d1) is 5°-30°.

16. The apparatus of claim 15, wherein, The tar-containing mixed gas (E) is conveyed into the down-flow bed reactor (3) through a pipeline; or The gasification agent nozzle (3b) has a gasification agent passage connected to the third gasification agent inlet (3b1), and the gasification agent passage is configured to convey the third gasification agent (B3) to the down-flow bed reactor (3); the cracking gas passage (3a) is connected to the down-flow bed reactor gas inlet (3a1) to pass the tar-containing mixed gas (E) into the down-flow bed reactor (3).

17. The apparatus of claim 12, wherein, The first fluidized bed reactor (1) and the second fluidized bed reactor (2) are bubbling fluidized bed reactors or circulating fluidized bed reactors.

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