System and method for producing synthesis gas by coupling biomass double-fluidized-bed chemical looping gasification and oxygen-enriched combustion

Abstract

The invention discloses a system and a method for producing synthesis gas by coupling biomass double-fluidized-bed chemical looping gasification and oxygen-enriched combustion, and belongs to the technical field of energy, environmental protection and chemical engineering. The system comprises a stock bin, a feeder, a fluidized bed gasifier, a return feeder, a fluidized bed oxygen-enriched combustion furnace, a cyclone separator, a heat exchanger and a purifier. Biomass and an oxygen carrier are subjected to a chemical chain gasification reaction in the fluidized bed gasification furnace to generate high-quality synthesis gas, residual carbon and the oxygen carrier after the reaction enter the fluidized bed oxygen-enriched combustion furnace to be subjected to an oxygen-enriched combustion reaction to generate high-concentration carbon dioxide, and the oxygen carrier returns to the fluidized bed gasification furnace after being regenerated. By coupling the double-fluidized-bed chemical-looping gasification and oxygen-enriched combustion technologies, the problems of low carbon conversion rate and the like of the existing biomass chemical-looping gasification are solved, the co-production of high-quality synthesis gas and high-concentration carbon dioxide is realized, the flexibility of a process organization for producing green liquid fuel by taking biomass as a raw material is improved, and the production cost is reduced. The requirements on follow-up synthesis process parameters are reduced, and the material and energy utilization efficiency of the whole system is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical fields of energy, environmental protection and chemical engineering, and particularly relates to a system and method for coupling chemical-looping gasification and oxy-fuel combustion of biomass to produce syngas. Background Art

[0002] Developing the preparation technologies of green liquid fuels (such as methanol and aviation kerosene, etc.) is one of the important ways to ensure China's energy security and optimize the energy structure, and is of great significance for promoting China's industrial upgrading and realizing the sustainable development in fields such as transportation and chemical engineering. Taking methanol as an example, the global methanol production in 2022 was 110 million tons, but the production of green methanol was only about 500,000 tons, less than 1%, indicating a broad market demand.

[0003] Biomass is the only renewable resource that can be directly converted into carbon-containing liquid fuels and plays an irreplaceable role in the field of preparing green liquid fuels. Gasification synthesis is one of the efficient routes for producing green liquid fuels from biomass. In this route, biomass is first converted into syngas (CO + H2) through gasification, and then the syngas is prepared into liquid fuels through catalytic synthesis. For example, Patent CN119020073A proposes a fuel generation system for coupling chemical-looping gasification of biomass and electrolytic water hydrogen production. Using steam as the gasifying agent, a high-quality syngas is produced by using a dual-fluidized bed gasifier, and at the same time, it is combined with the hydrogen obtained from the electrolytic water system for producing liquid fuels, which can effectively reduce the energy consumption and cost in the production process.

[0004] Different from traditional gasification technologies, the biomass dual-fluidized bed chemical-looping gasification technology uses an oxygen carrier instead of a traditional gasifying agent. By circulating the oxygen carrier in the combustion reactor and the gasification reactor, the oxygen in the air is transferred to the biomass, realizing the production of high-quality syngas without air separation and at low cost. In recent years, the related technologies have developed very rapidly. For example, Patent CN114574250A proposes a method and device for producing clean syngas by chemical-looping gasification of biomass. Using a dual-cycle oxygen carrier and a tar carbon dioxide reforming catalyst, the in-situ and efficient conversion of biomass gasification and tar and carbon dioxide in its gaseous products is realized, improving the yield and quality of syngas, and significantly increasing the atomic and energy utilization rates.

[0005] In addition to using gasification technologies, biomass can also first generate carbon dioxide through oxy-fuel combustion, and then the carbon dioxide is combined with green hydrogen to produce green liquid fuels. For example, Patent CN113944544A proposes an energy system based on renewable energy and hydrogen methanolization. Using the carbon dioxide generated by biomass oxy-fuel combustion and the hydrogen generated by electrolyzing water to synthesize methanol can effectively consume renewable energy electricity and achieve zero-carbon or negative carbon emissions.

[0006] In the existing biomass dual-fluidized bed chemical-looping gasification process, there will be some residual carbon remaining in the gasification reactor, which will enter the combustion reactor with the oxygen carrier and burn to become carbon dioxide. Since the main component of the flue gas after the combustion reaction is nitrogen and the cost of carbon dioxide capture is relatively high, this flue gas is generally directly discharged after waste heat recovery and purification, resulting in a low carbon utilization rate of biomass in the chemical-looping gasification process. Although the carbon utilization rate of the biomass direct oxy-fuel combustion technology is relatively high, since its product is mainly carbon dioxide and the degree of oxidation is relatively high, additional hydrogen is required for deoxygenation in subsequent processes such as hydrogenation to produce methanol and aviation kerosene, and the reaction conditions are relatively demanding, and the atom utilization rate and energy efficiency are relatively low.

[0007] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0008] In view of the above deficiencies of the existing technology, the purpose of the present invention is to provide a system and method for coupling biomass dual-fluidized bed chemical-looping gasification and oxy-fuel combustion to produce syngas, aiming to solve the problem of low carbon conversion rate in current biomass chemical-looping gasification, and to realize the co-production of high-quality syngas from biomass and high-concentration carbon dioxide for subsequent synthesis of green liquid fuels such as methanol and aviation kerosene, and to improve the material and energy utilization efficiency and process flexibility of the production process.

[0009] The technical solution of the present invention is as follows:

[0010] Combined Figure 1 As shown, a system for coupling biomass dual-fluidized bed chemical-looping gasification and oxy-fuel combustion to produce syngas provided by the present invention includes a silo (1), a feeder (2), a fluidized bed gasification furnace (3), a downcomer (4), a fluidized bed oxy-fuel combustion furnace (5), a gasification furnace cyclone separator (6), a syngas heat exchanger (7), a syngas purifier (8), a combustion furnace cyclone separator (9), an upcomer (10), a flue gas heat exchanger (11), and a flue gas purifier (12).

[0011] The silo (1) is connected to the feeder (2), and the feeder (2) is connected to the fluidized bed gasifier (3) to input biomass (101) into the fluidized bed gasifier (3). The fluidized bed gasifier (3) is respectively connected to the downcomer (4) and the gasifier cyclone separator (6) to input biomass residual carbon and reduced oxygen carriers (301) into the downcomer (4) and syngas (302) into the gasifier cyclone separator (6). The gasifier cyclone separator (6) is connected to the syngas heat exchanger (7) to input high-temperature syngas (601) into the syngas heat exchanger (7). The syngas heat exchanger (7) is connected to the syngas purifier (8) to input low-temperature syngas (701) into the syngas purifier (8). The syngas purifier (8) is respectively connected to the fluidized bed gasifier (3) and the subsequent chemical synthesis unit. A part of the purified syngas is transported as recycled syngas (801) to the fluidized bed gasifier (3), and the rest is input as product syngas (802) into the subsequent chemical synthesis unit. The downcomer (4) is connected to the fluidized bed oxy-fuel combustion furnace (5) to transport biomass residual carbon and reduced oxygen carriers to the fluidized bed oxy-fuel combustion furnace (5). The fluidized bed oxy-fuel combustion furnace (5) is connected to the combustion furnace cyclone separator (9) to input flue gas and oxygen carriers (501) into the combustion furnace cyclone separator (9), and the ash slag (502) is discharged from the bottom of the fluidized bed oxy-fuel combustion furnace (5). The combustion furnace cyclone separator (9) is respectively connected to the upcomer (10) and the flue gas heat exchanger (11) to input oxidized oxygen carriers (901) into the upcomer (10) and high-temperature flue gas (902) into the flue gas heat exchanger (11). The upcomer (10) is connected to the fluidized bed gasifier (3) to transport the oxidized oxygen carriers back to the fluidized bed gasifier (3). The flue gas heat exchanger (11) is connected to the flue gas purifier (12) to input low-temperature flue gas (1101) into the flue gas purifier (12). The flue gas purifier (12) is respectively connected to the fluidized bed oxy-fuel combustion furnace (5) and the subsequent chemical synthesis unit. A part of the purified flue gas is transported as recycled carbon dioxide (1201) to the fluidized bed combustion furnace (5), and the rest is input as product carbon dioxide (1202) into the subsequent chemical synthesis unit.

[0012] A method for coupling chemical-looping gasification and oxy-fuel combustion of biomass in a dual fluidized bed to produce syngas, wherein the syngas is produced by using the system for coupling chemical-looping gasification and oxy-fuel combustion of biomass in a dual fluidized bed according to the present invention. The method for producing syngas includes the steps:

[0013] The biomass (101) in the silo (1) is conveyed to the fluidized bed gasifier (3) by a feeder (2). In the fluidized bed gasifier (3), the biomass (101) contacts with the high-temperature oxygen-carrying oxidant (901) and undergoes a chemical looping gasification reaction to obtain syngas (302) mainly composed of CO and H2. The syngas (302) leaves the fluidized bed gasifier (3) from the top, enters the gasifier cyclone separator (6), and after the fly ash (602) is separated by the cyclone action, it enters the syngas heat exchanger (7). The remaining solid biomass carbon residue and reduced oxygen-carrying agent (301) after the reaction leave the fluidized bed gasifier (3) from the bottom under the action of gravity and enter the downcomer (4). In the downcomer (4), the biomass carbon residue and the reduced oxygen-carrying agent (301) enter the bottom of the fluidized bed oxy-fuel combustion furnace (5) under the action of the downcomer air (401).

[0014] In the fluidized bed oxy-fuel combustion furnace (5), the biomass carbon residue and the reduced oxygen-carrying agent (301) contact with the oxygen (503) in the fluidizing gas. Among them, the biomass carbon residue undergoes an oxy-fuel combustion reaction to generate flue gas mainly composed of CO2 and H2O. The reduced oxygen-carrying agent undergoes an oxidation reaction and is re-transformed into an oxygen-carrying oxidant. The flue gas and the oxygen-carrying agent (501) after the reaction leave the fluidized bed oxy-fuel combustion furnace (5) from the top and enter the combustion furnace cyclone separator (9). The ash residue (502) generated after the combustion of the biomass carbon residue is discharged from the bottom of the fluidized bed oxy-fuel combustion furnace (5). In the combustion furnace cyclone separator (9), the high-temperature flue gas is separated from the oxygen-carrying oxidant by the cyclone action. Among them, the oxygen-carrying oxidant (901) enters the upcomer (10) and returns to the fluidized bed gasifier (3) under the action of the upcomer air (1001) to repeat the chemical looping gasification reaction with the biomass (101). The high-temperature flue gas (902) enters the flue gas heat exchanger (11).

[0015] In the syngas heat exchanger (7), waste heat recovery is carried out by exchanging heat between the high-temperature syngas (601) and water or recycled syngas. The cooled low-temperature syngas (701) enters the syngas purifier (8) for purification treatment to further remove impurities such as dust and tar contained in the syngas. A part of the purified syngas is used as recycled syngas (801), which is preheated and then input into the fluidized bed gasifier (3), and the remaining is used as product syngas (802) and input into the subsequent chemical synthesis system.

[0016] In the flue gas heat exchanger (11), waste heat recovery is carried out by heat exchange between high-temperature flue gas (902) and water or recycled carbon dioxide. The cooled low-temperature flue gas (1101) enters the flue gas purifier (12) for purification treatment to remove pollutant components such as dust in the flue gas, and a gas mainly composed of carbon dioxide is obtained. Among them, part of the carbon dioxide is used as recycled carbon dioxide (1201), which is preheated and then mixed with oxygen (503) in a certain proportion and input into the fluidized bed oxy-fuel combustion furnace (5), and the remaining is input into the subsequent chemical synthesis system as product carbon dioxide (1202).

[0017] Preferably, the temperature of the fluidized bed gasifier (3) is 700 - 950 °C, and the temperature of the fluidized bed oxy-fuel combustion furnace (5) is 750 - 1000 °C.

[0018] Preferably, the fluidizing gas of the fluidized bed gasifier (3) is recycled syngas or steam or a mixture of recycled syngas and steam; the fluidizing gas of the fluidized bed oxy-fuel combustion furnace (5) is a mixture of recycled carbon dioxide (1201) and the oxygen (503), and the oxygen (503) is by-product oxygen from electrolytic water hydrogen production or oxygen obtained by air separation, and the volume concentration of the oxygen (503) in the mixture is 21% - 50%.

[0019] Preferably, the lower solids return valve (4) is a U-shaped valve or a V-shaped valve or an L-shaped valve or a mechanical solids return valve, the upper solids return valve (10) is a U-shaped valve or a V-shaped valve or an L-shaped valve or a mechanical solids return valve, the lower solids return air (401) is steam or recycled carbon dioxide, and the upper solids return air (1001) is steam or recycled syngas.

[0020] Preferably, after heat exchange, the syngas heat exchanger (7) is used to produce steam or preheat the recycled syngas (801), and after heat exchange, the flue gas heat exchanger (11) is used to produce steam or preheat the recycled carbon dioxide (1201).

[0021] Preferably, the biomass in the present invention includes but is not limited to one or more of crop straws, forestry wastes, municipal solid wastes, and sludge, etc. For raw biomass, it should be pretreated such as crushed and then input into the system of the present invention.

[0022] The present invention has the following beneficial effects: (1) By coupling biomass dual-fluidized bed chemical-looping gasification with oxy-fuel combustion technology, the co-production of high-quality syngas and high-concentration carbon dioxide is realized, effectively improving the flexibility of the process organization for producing green liquid fuels from biomass; (2) By changing the air combustion furnace in the traditional biomass dual-fluidized bed chemical-looping gasification technology to an oxy-fuel combustion furnace, the residual carbon in the traditional biomass chemical-looping gasification process is further converted into high-concentration carbon dioxide through oxy-fuel combustion. The flue gas (with carbon dioxide as the effective component) that could not be recycled at low cost in the original air combustion furnace can be efficiently recycled and used as a raw material for chemical synthesis, thereby increasing the carbon conversion rate of biomass and solving the problem of low raw material carbon conversion rate in the current biomass chemical-looping gasification process; (3) Through chemical-looping gasification technology, most of the carbon in biomass is converted into carbon monoxide, and only a small part is converted into carbon dioxide by oxy-fuel combustion. While ensuring a high carbon conversion rate of biomass, the requirements for the process parameters of the subsequent synthesis of green liquid fuels are effectively reduced, and the energy efficiency of the system is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FIG. is a schematic diagram of a system for co-producing syngas by coupling biomass dual-fluidized bed chemical-looping gasification with oxy-fuel combustion according to the present invention.

[0024] Figure 2 FIG. is a schematic diagram of a system for co-producing syngas by coupling biomass dual-fluidized bed chemical-looping gasification with oxy-fuel combustion in a specific embodiment.

[0025] In the figure: 1 - feed bin; 2 - feeder; 3 - fluidized bed gasifier; 4 - downcomer; 5 - fluidized bed oxy-fuel combustion furnace; 6 - gasifier cyclone separator; 7 - syngas heat exchanger; 8 - syngas purifier; 9 - combustion furnace cyclone separator; 10 - upcomer; 11 - flue gas heat exchanger; 12 - flue gas purifier; 13 - electrolyzed water unit; 14 - methanol synthesis unit; 101 - biomass; 301 - biomass residual carbon and reduced oxygen carrier; 302 - syngas; 401 - downcomer air; 501 - flue gas and oxygen carrier; 502 - ash; 503 - oxygen; 601 - high-temperature syngas; 602 - fly ash; 701 - low-temperature syngas; 702 - syngas waste heat; 801 - recycled syngas or steam; 802 - product syngas; 803 - syngas impurities such as dust and tar; 901 - oxidized oxygen carrier; 902 - high-temperature flue gas; 1001 - upcomer air; 1101 - low-temperature flue gas; 1102 - flue gas waste heat; 1201 - recycled carbon dioxide; 1202 - product carbon dioxide; 1203 - flue gas impurities such as dust; 1301 - wind power; 1302 - water; 1303 - hydrogen; 1401 - green methanol. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The present invention provides a system and method for coupling biomass dual-fluidized bed chemical-looping gasification and oxy-fuel combustion to produce syngas. To make the objectives, technical solutions and effects of the present invention clearer and more definite, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] Combined Figure 2 As shown, an embodiment of the present invention provides a system and method for coupling biomass dual-fluidized bed chemical-looping gasification and oxy-fuel combustion to produce syngas. The biomass is made into compressed pellets from the waste in the wood processing process (its raw material characteristics are shown in Table 1), the oxygen is produced by wind power electrolyzing water, and the syngas is used to produce green methanol. The annual biomass processing capacity of the system is 50,000 tons (dry basis), specifically as follows:

[0028] (1) The system for processing the above biomass includes a silo 1, a feeder 2, a fluidized bed gasifier 3, a downcomer 4, a fluidized bed oxy-fuel combustion furnace 5, a gasifier cyclone separator 6, a syngas heat exchanger 7, a syngas purifier 8, a combustion furnace cyclone separator 9, an upcomer 10, a flue gas heat exchanger 11, a flue gas purifier 12, an electrolytic water unit 13, and a methanol synthesis unit 14.

[0029] (2) The feeder 2 is used to convey the biomass 101 in the silo 1 to the fluidized bed gasifier 3. In the fluidized bed gasifier 3, the biomass 101 contacts with the high-temperature oxidized oxygen carrier 901 returned from the fluidized bed oxy-fuel combustion furnace 5 and undergoes a chemical-looping gasification reaction. The gasification reaction temperature is 900 °C, and syngas 302 mainly composed of CO and H2 is obtained. The generated syngas 302 leaves the fluidized bed gasifier 3 from the top, enters the gasifier cyclone separator 6, and after being separated by the cyclone action to remove the fly ash 602, enters the syngas heat exchanger 7. The remaining solid biomass carbon residue and reduced oxygen carrier 301 after the reaction leave the fluidized bed gasifier 3 from the bottom under the action of gravity and enter the U-shaped downcomer 4. In the downcomer 4, with recycled carbon dioxide as the fluidizing gas, the biomass carbon residue and the reduced oxygen carrier 301 are input into the bottom of the fluidized bed oxy-fuel combustion furnace 5.

[0030] (3) In the fluidized bed oxy-fuel combustion furnace 5, the biomass char and the reduced oxygen carrier 301 come into contact with the oxygen 503 generated by electrolyzing water (the volume concentration of oxygen in the fluidizing gas of the fluidized bed combustion furnace is 30%), and oxy-fuel combustion and oxidation reactions occur, with the reaction temperature being 950 °C. Among them, the flue gas mainly composed of CO2 and H2O is generated after the biomass char burns. The reduced oxygen carrier undergoes an oxidation reaction and is transformed back into the oxidized oxygen carrier. The flue gas and the oxygen carrier 501 after the reaction leave the fluidized bed oxy-fuel combustion furnace 5 from the top and enter the combustion furnace cyclone separator 9. The ash residue 502 generated during the combustion process of the biomass char is discharged from the bottom of the fluidized bed oxy-fuel combustion furnace 5. In the combustion furnace cyclone separator 9, the high-temperature flue gas 902 is separated from the oxidized oxygen carrier 901 through the cyclone effect. Among them, the oxidized oxygen carrier 901 enters the U-shaped upper return feeder 10 and returns to the fluidized bed gasifier 3 under the action of the upper return air 1001 (the upper return air uses recycled syngas), repeating the chemical looping gasification reaction with the biomass 101, and the high-temperature flue gas 902 enters the flue gas heat exchanger 11.

[0031] (4) In the syngas heat exchanger 7, the recycled syngas 801 is first preheated by the high-temperature syngas 601 to increase the temperature of the recycled syngas 801 entering the fluidized bed gasifier 3, and then the high-temperature syngas 601 is used to produce low-pressure steam for external supply to further recover waste heat. The cooled low-temperature syngas 701 enters the syngas purifier 8 for purification treatment to further remove syngas impurities 803 such as dust and tar contained in the syngas. Part of the purified syngas is used as the recycled syngas 801, which is preheated and then input into the fluidized bed gasifier 3, and the rest is used as the product syngas 802 and input into the methanol synthesis unit 14.

[0032] (5) In the flue gas heat exchanger 11, the recycled carbon dioxide 1201 is first preheated by the high-temperature flue gas 902, and then the high-temperature flue gas 902 is used to produce low-pressure steam for external supply to further recover waste heat. The cooled low-temperature flue gas 1101 enters the flue gas purifier 12 for purification treatment to remove pollutants 1203 such as dust in the flue gas, and a gas mainly composed of carbon dioxide is obtained. Among them, part of it is used as the recycled carbon dioxide 1201, which is preheated and then mixed with the oxygen 503 generated by the electrolysis water unit 13 in a certain proportion (oxygen: carbon dioxide = 3:7, volume ratio) and input into the fluidized bed oxy-fuel combustion furnace 5, and the rest is used as the product carbon dioxide 1202 and input into the methanol synthesis unit 14.

[0033] (6) In the electrolysis water unit 13, renewable wind power 1301 is used for electrolyzing water. Part of the generated oxygen is used as the oxygen 503 required for oxy-fuel combustion and input into the fluidized bed oxy-fuel combustion furnace 5, and the rest is supplied as a product. The generated hydrogen 1303 is used as a raw material gas and input into the methanol synthesis unit 14, where it is mixed and blended with the product syngas 802 and the product carbon dioxide 1202, and green methanol 1401 is synthesized under the action of a catalyst.

[0034] Table 1. Analysis of Biomass Raw Materials, Elements, and Calorific Value

[0035]

[0036]

[0037] When the system described in this embodiment operates stably, the main performance parameters are shown in Table 2, and the main components of the product syngas are shown in Table 3.

[0038] Table 2. System Performance Parameters

[0039]

[0040] Table 3. Analysis of the Main Components of the Product Syngas

[0041] Component CO <![CDATA[H2]]> <![CDATA[CO2]]> <![CDATA[CH4]]> ％ 50.91 45.50 1.75 1.76

[0042] In summary, the present invention provides a system and method for coupling biomass dual-fluidized bed chemical looping gasification and oxy-fuel combustion to produce syngas. Specifically, biomass is fed into the fluidized bed gasifier by a feeder, contacts with the oxygen carrier returned from the fluidized bed combustor, and undergoes chemical looping gasification reaction to generate syngas. After heat exchange and purification treatment, a part of the syngas is returned to the fluidized bed gasifier as recycle gas, and the rest is output as product. The oxygen carrier after the reaction in the fluidized bed gasifier and the remaining biomass char are sent back to the fluidized bed oxy-fuel combustor, contact with oxygen for oxidation and combustion reactions. The oxidized oxygen carrier is sent back to the fluidized bed gasifier to react with biomass for gasification. The flue gas is subjected to heat exchange and purification treatment, and a part of it is returned to the fluidized bed oxy-fuel combustor as recycle gas, and the rest is output as product. Through the coupling of biomass dual-fluidized bed chemical looping gasification and oxy-fuel combustion technologies, the present invention realizes the co-production of high-quality syngas and high-concentration carbon dioxide, effectively improving the flexibility of the process organization for producing green liquid fuels from biomass as raw materials; by applying oxy-fuel combustion technology in the fluidized bed combustor, the residual char in the biomass chemical looping gasification process is further converted into high-concentration carbon dioxide and recycled, solving the problem of low raw material carbon conversion rate in the current biomass chemical looping gasification process and effectively improving the material utilization efficiency; through chemical looping gasification technology, most of the carbon in biomass is converted into carbon monoxide, and only a small part is converted into carbon dioxide by oxy-fuel combustion. While ensuring a high carbon conversion rate of biomass, the requirements for the process parameters of the subsequent synthesis of green liquid fuels are effectively reduced, and the energy efficiency of the system is improved.

[0043] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or changes can be made according to the above description, and all such improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims

1. A system for producing synthesis gas by coupling biomass dual fluidized bed chemical chaining gasification and oxygen-enriched combustion, characterized in that: The system comprises a silo (1), a feeder (2), a fluidized bed gasifier (3), a lower returner (4), a fluidized bed oxygen-enriched combustion furnace (5), a gasifier cyclone separator (6), a synthesis gas heat exchanger (7), a synthesis gas purifier (8), a combustion furnace cyclone separator (9), an upper returner (10), a flue gas heat exchanger (11) and a flue gas purifier (12); The silo (1) is connected to the feeder (2) and the fluidized bed gasifier (3) in sequence, and the feeder (2) is used to feed the biomass (101) in the silo (1) into the fluidized bed gasifier (3); the fluidized bed gasifier (3) is connected to the lower returner (4) and the gasifier cyclone separator (6) respectively, and the biomass carbon residue and the reduced oxygen carrier (301) are fed into the lower returner (4), and the synthesis gas (302) is fed into the gasifier cyclone separator (6); the gasifier cyclone separator (6) is connected to the synthesis gas heat exchanger (7) The high-temperature synthesis gas (601) is input into the synthesis gas heat exchanger (7); the synthesis gas heat exchanger (7) is connected to the synthesis gas purifier (8), and the low-temperature synthesis gas (701) is input into the synthesis gas purifier (8); the synthesis gas purifier (8) is respectively connected to the fluidized bed gasifier (3) and the subsequent chemical synthesis unit, and the circulating synthesis gas (801) is transported to the fluidized bed gasifier (3), and the product synthesis gas (802) is input into the subsequent chemical synthesis unit; the lower return device (4) is connected to the fluidized bed oxygen-enriched combustion furnace (5), and the biomass (801) is transported to the subsequent chemical synthesis unit. The residual carbon and the reducing oxygen carrier are transported to the fluidized bed oxygen-enriched combustion furnace (5); the fluidized bed oxygen-enriched combustion furnace (5) is connected to the combustion furnace cyclone separator (9), the flue gas and the oxygen carrier (501) are input into the combustion furnace cyclone separator (9), and the ash (502) is discharged from the bottom of the fluidized bed oxygen-enriched combustion furnace (5); the combustion furnace cyclone separator (9) is respectively connected to the upper return material (10) and the flue gas heat exchanger (11), the oxidizing oxygen carrier (901) is input into the upper return material (10), and the high-temperature flue gas (902) is input into the flue gas heat exchanger ( 11); the upper return device (10) is connected to the fluidized bed gasification furnace (3) to input the oxidized oxygen carrier into the fluidized bed gasification furnace (3); the flue gas heat exchanger (11) is connected to the flue gas purifier (12) to input the low-temperature flue gas (1101) into the flue gas purifier (12); the flue gas purifier (12) is respectively connected to the fluidized bed oxygen-enriched combustion furnace (5) and the subsequent chemical synthesis unit to transport the circulating carbon dioxide (1201) to the fluidized bed oxygen-enriched combustion furnace (5) and input the product carbon dioxide (1202) into the subsequent chemical synthesis unit.

2. A method for producing synthesis gas by coupling biomass dual fluidized bed chemical chain gasification and oxygen-enriched combustion, characterized in that: The system for producing synthesis gas by coupling biomass dual fluidized bed chemical chaining gasification and oxygen-enriched combustion as claimed in claim 1 is used to produce synthesis gas, and the method for producing synthesis gas comprises the steps of: The biomass (101) in the silo (1) is transported to the fluidized bed gasifier (3) by means of a feeder (2). In the fluidized bed gasifier (3), the biomass (101) contacts with a high-temperature oxidizing oxygen carrier and undergoes a chemical chain gasification reaction to obtain a synthesis gas (302) mainly composed of CO and H2. The synthesis gas (302) leaves the fluidized bed gasifier (3) from the top and enters the gasifier cyclone separator (6). After the fly ash (602) is separated by the cyclone, the high-temperature synthesis gas (601) enters the synthesis gas heat exchanger (7). The solid biomass carbon residue and the reduced oxygen carrier (301) remaining after the reaction leave the fluidized bed gasifier (3) from the bottom under the action of gravity and enter the lower return feeder (4). In the lower return feeder (4), the biomass carbon residue and the reduced oxygen carrier (301) enter the bottom of the fluidized bed oxygen-enriched combustion furnace (5) under the action of the lower return air (401). In the fluidized bed oxygen-enriched combustion furnace (5), the biomass carbon residue and the reduced oxygen carrier (301) are in contact with the oxygen (503) in the fluidized gas; wherein the biomass carbon residue undergoes an oxygen-enriched combustion reaction to generate flue gas mainly composed of CO2 and H2O, and the reduced oxygen carrier undergoes an oxidation reaction to be converted back into an oxidized oxygen carrier. The flue gas and the oxygen carrier (501) after the reaction leave the fluidized bed oxygen-enriched combustion furnace (5) from the top and enter the combustion furnace cyclone separator (9); the biomass carbon residue is burned The ash (502) generated later is discharged from the bottom of the fluidized bed oxygen-enriched combustion furnace (5); in the combustion furnace cyclone separator (9), the high-temperature flue gas and the oxidizing oxygen carrier are separated by the cyclone action, wherein the oxidizing oxygen carrier (901) enters the upper return material device (10) and returns to the fluidized bed gasification furnace (3) under the action of the upper return material wind (1001), repeating the chemical chain gasification reaction with the biomass (101), while the high-temperature flue gas (902) enters the flue gas heat exchanger (11); In the synthesis gas heat exchanger (7), waste heat is recovered by heat exchange between the high-temperature synthesis gas (601) and water or circulating synthesis gas. The low-temperature synthesis gas (701) after cooling enters the synthesis gas purifier (8) for purification treatment to remove impurities contained in the synthesis gas. A part of the purified synthesis gas is used as circulating synthesis gas (801) and is input into the fluidized bed gasifier (3) after preheating. The rest is used as product synthesis gas (802) and is input into the subsequent chemical synthesis unit. In the flue gas heat exchanger (11), waste heat is recovered by heat exchange between the high-temperature flue gas (902) and water or circulating carbon dioxide, and the low-temperature flue gas (1101) after cooling enters the flue gas purifier (12) for purification treatment to remove pollutants in the flue gas and obtain a gas mainly composed of carbon dioxide; among them, part of the carbon dioxide is used as circulating carbon dioxide (1201), which is mixed with oxygen (503) after preheating and input into the fluidized bed oxygen-enriched combustion furnace (5), and the rest is used as product carbon dioxide (1202) and input into the subsequent chemical synthesis unit.

3. The method for producing synthesis gas by coupling biomass dual fluidized bed chemical chaining gasification and oxygen-enriched combustion according to claim 2, characterized in that: The temperature of the fluidized bed gasification furnace (3) is 700-950°C, and the temperature of the fluidized bed oxygen-enriched combustion furnace (5) is 750-1000°C.

4. The method for producing synthesis gas by coupling biomass dual fluidized bed chemical chaining gasification and oxygen-enriched combustion according to claim 2, characterized in that: The fluidizing gas of the fluidized bed gasifier (3) is circulating synthesis gas or water vapor or a mixed gas of circulating synthesis gas and water vapor.

5. The method for producing synthesis gas by coupling biomass dual fluidized bed chemical chaining gasification and oxygen-enriched combustion according to claim 2, characterized in that: The fluidizing gas of the fluidized bed oxygen-enriched combustion furnace (5) is a mixed gas of circulating carbon dioxide (1201) and oxygen (503), wherein the oxygen (503) is derived from oxygen produced as a byproduct of hydrogen production by electrolysis of water or oxygen produced by air separation, and the volume concentration of the oxygen (503) in the mixed gas is 21%-50%.

6. The method for producing synthesis gas by coupling biomass dual fluidized bed chemical chaining gasification and oxygen-enriched combustion according to claim 2, characterized in that: The lower return device (4) is a U-shaped valve, a V-shaped valve, an L-shaped valve, or a mechanical return valve, the upper return device (10) is a U-shaped valve, a V-shaped valve, an L-shaped valve, or a mechanical return valve, the lower return air (401) is water vapor or recycled carbon dioxide, and the upper return air (1001) is water vapor or recycled synthesis gas.

7. The method for producing synthesis gas by coupling biomass dual fluidized bed chemical chaining gasification and oxygen-enriched combustion according to claim 2, characterized in that: The synthesis gas heat exchanger (7) is used to produce steam or preheat the circulating synthesis gas (801) after heat exchange, and the flue gas heat exchanger (11) is used to produce steam or preheat the circulating carbon dioxide (1201) after heat exchange.

8. The method for producing synthesis gas by coupling biomass dual fluidized bed chemical chaining gasification and oxygen-enriched combustion according to claim 2, characterized in that: The biomass includes one or more of crop straw, forestry waste, urban domestic garbage and sludge, and the biomass is input into the silo (1) after being pretreated.

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