Method for preparing green fuel through biomass gasification and combustion coupling

Abstract

The invention relates to the technical field of green fuel preparation, and discloses a method for preparing green fuel by coupling biomass gasification and combustion, which comprises the following steps: (1) separating N2 from air, taking a part of residual gas as a gasification agent, and taking the other part as combustion gas; (2) carrying out chemical chain gasification on the biomass through steam under the condition of a gasifying agent to obtain H2 and CO2; (3) carrying out chemical looping combustion on the biomass under the conditions of an oxygen carrier and combustion gas to obtain CO2; (4) electrolyzing a part of obtained CO2 by using electric energy obtained by biomass chemical looping combustion to obtain CO; (5) synthesizing N2 and H2 to prepare a green NH3 product; and synthesizing H2, CO2 and CO to prepare a green methanol product. According to the method, a biomass fuel chemical looping power generation and biomass chemical looping gasification coupling technology is applied, a carbon source in biomass is fully utilized, meanwhile, green NH3 and methanol products are prepared, and efficient utilization of resources is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of green fuel preparation, and in particular to a method for preparing green fuel by coupling biomass gasification and combustion. Background Art

[0002] The rapid development of modern economy and society has brought about a large consumption of fossil energy, resulting in an increase in the concentration of carbon dioxide in the atmosphere year by year. CO2 emission reduction has become a major scientific issue of global concern, and the development of renewable electricity is an important way to replace fossil energy.

[0003] At present, the large-scale development of renewable energy is facing two major challenges. The primary problem is the volatility and imbalance of renewable electricity production, which has continuously aggravated the difficulty of grid balance and absorption. Although electrochemical energy storage technology provides the possibility of balancing the capacity of the system, the system cost it brings has also risen accordingly. Secondly, the development of renewable electricity is deeply restricted by the power load. There is a significant inverse contradiction between the geographical distribution of renewable resources and electricity demand. Remote areas are usually rich in renewable resources, which makes the transmission of renewable energy particularly difficult. Although large-scale ultra-high voltage transmission technology provides a possible solution to this problem, its high cost and the pressure caused by the volatility of renewable energy on the power transmission and receiving grids are issues that cannot be ignored.

[0004] Carbon dioxide can be used as a rich carbon source. Using different technologies to convert captured carbon dioxide into green fuels and chemicals can not only achieve efficient conversion and utilization of carbon resources, but also is an important way to achieve a closed carbon cycle. Combining CO2 catalytic conversion technology with renewable energy-driven green hydrogen production technology to synthesize green fuels can effectively achieve the recycling of carbon resources.

[0005] Methanol is a clean and efficient alcohol fuel. At present, methanol is mainly produced from coal, natural gas, coke oven gas, industrial by-product hydrogen-rich tail gas and other raw materials to produce synthesis gas CO and H2. The synthesis gas reacts to produce methanol under certain temperature and pressure conditions. Coupling the CO2 conversion process with the green hydrogen production process driven by renewable energy to produce green methanol not only stores the energy of renewable energy in methanol fuel, which is convenient for storage and transportation, but also achieves near-zero or even negative carbon dioxide emissions. At the same time, replacing traditional fossil fuel oil with green alcohol can also reduce sulfur oxides SO x 、Nitrogen oxides NO x , particulate matter PM and other pollutant emissions, provides a new way for the strategic adjustment of the energy structure, has a very broad development prospect, and is of great practical significance for solving the increasingly serious environmental and energy problems.

[0006] The invention patent with application number 202111286319.1 discloses a method for producing methanol by gasifying pulverized coal waste boilers and coupling green electricity and green hydrogen to achieve near-zero carbon emissions. This method eliminates the boiler in the traditional coal-to-methanol route through the gasification process, and basically all the carbon elements enter the methanol product, achieving near-zero carbon production of methanol products. However, this process uses fossil fuels as the carbon source and is equipped with a high-energy-consuming air separation device, while all the electricity used in the process comes from the new energy power generation system, so this method still has the problem of volatility and imbalance in the production of renewable electricity. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a method for preparing green fuel by coupling biomass gasification and combustion. By using the coupling technology of biomass fuel chemical chain power generation and biomass chemical chain gasification, green NH3 products and green methanol products are synthesized and prepared at the same time, thereby realizing efficient utilization of resources.

[0008] The purpose of the present invention is achieved through the following technical solutions: The present invention provides a method for preparing green fuel by coupling biomass gasification and combustion, comprising the following steps: (1) Separate N2 from air, and use part of the remaining gas as a gasifier, with the gasifier accounting for 70-80% of the volume of the remaining gas, and the other part as a combustion gas; (2) chemical chain gasification of biomass by steam under gasification agent conditions to obtain H2 and CO2; (3) Chemically combusting biomass in the presence of an oxygen carrier and combustion gas to produce CO2; (4) Using the electricity obtained from biomass chemical chain combustion to electrolyze part of the CO2 obtained to obtain CO; (5) N2 and H2 are synthesized in a volume ratio of 1:3 to prepare green NH3 products; H2, CO2 and CO are synthesized in a volume ratio of 27:7:3 to prepare green methanol products.

[0009] Chemical looping combustion power generation and chemical looping hydrogen production are currently advanced energy conversion methods. The basic principle of chemical looping combustion (CLC) is to decompose the traditional combustion reaction of direct contact between fuel and air into two gas-solid reactions with the help of oxygen carriers (OC). The fuel and air do not need to contact, and the oxygen carrier transfers oxygen in the air to the fuel. The use of chemical looping technology for thermochemical conversion of solid fuel coal / biomass has natural technical advantages and is a promising way to convert and utilize clean energy.

[0010] Biomass chemical chain hydrogen production can directly obtain ultra-pure hydrogen from biomass and simultaneously capture high-concentration CO2 without producing greenhouse gases. This method of hydrogen production can effectively overcome the practical disadvantage that the cost of hydrogen production by electrolysis of water is relatively high and cannot be applied on a large scale in industry for the time being. It also overcomes the non-green characteristics of CO2 produced by coal and natural gas hydrogen production.

[0011] Preferably, in step (2), the operating temperature of the chemical chain gasification is 800-1000°C, the pressure is atmospheric pressure; the mass ratio of water vapor to biomass introduced per unit time is 1:1.05-1.15; Preferably, in step (2), the mass ratio of biomass to gasifying agent per unit time is 1.45:1.30-1.40.

[0012] Preferably, in step (3), the operating temperature of the chemical looping combustion is 900-1200°C and the pressure is normal pressure.

[0013] Preferably, in step (3), the mass ratio of biomass to combustion gas per unit time is 1:1.25-1.35; the mass ratio of biomass to oxygen carrier per unit time is 1:4.1-4.2; and the oxygen carrier is Fe2O3.

[0014] Preferably, in step (4), the catalyst used for electrolysis is Cu-In2O3; the operating temperature of electrolysis is 600-800°C, and the current density is 1-5A / cm².

[0015] Preferably, in step (4), the volume percentage of CO2 used for electrolysis is 25-30% of the total volume of CO2 obtained in steps (2) and (3).

[0016] Preferably, in step (5), during the synthesis of N2 and H2 to prepare the green NH3 product, the synthesis conditions are 400-500°C and 10-30MPa.

[0017] Preferably, in step (5), during the synthesis of H2, CO2 and CO to prepare the green methanol product, the synthesis conditions are 200-300°C and 5-10MPa.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention, by ingeniously using the coupling technology of biomass fuel chemical chain power generation and biomass chemical chain gasification, not only completely eliminates the generation of nitrogen oxide impurities, but also avoids direct pollution of the atmosphere by flue gas, thereby greatly saving the investment in denitrification or desulfurization purification equipment and simplifying the entire process. At the same time, in the process of the present invention, the carbon source in the biomass is fully utilized without any waste, which greatly improves the utilization rate of the raw materials. Compared with the traditional pure CO2-rich methanol production process, the present invention significantly increases the proportion of CO in the raw gas, so that the single-pass conversion rate of methanol synthesis can be as high as 60% or more, truly realizing the efficient utilization of resources.

[0019] (2) The present invention not only avoids the generation of nitrogen oxides, but also directly synthesizes NH3 from the N2 separated by the chemical chain and the H2 produced by the chemical chain, thereby converting N2 into high-quality green chemicals.

[0020] (3) The present invention effectively solves the problem of producing green hydrogen from traditional energy sources. It can directly use the hydrogen produced by the biomass chemical chain as the raw material of green methanol, and can effectively avoid the problem of producing green hydrogen from renewable energy power generation under the influence of unstable factors such as weather and climate. This innovative design enhances the stability and reliability of electricity consumption in the process flow, allowing the process and system of the present invention to operate continuously and stably, thereby increasing production and laying a solid foundation for improving economic benefits.

[0021] (4) The present invention also introduces the saturated steam generated in the biomass chemical chain gasification and methanol synthesis process into the biomass fuel chemical chain power generation process to generate electricity through flue gas superheating. At the same time, the steam condensed by the extraction condensing steam turbine generator set is used in the methanol synthesis process and the methanol distillation process respectively. This design not only realizes the cascade utilization of energy, but also avoids the setting of additional steam production systems, which not only reduces equipment investment and floor space, but also improves energy utilization efficiency, injecting new vitality into the sustainable development of the process. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is described below with specific embodiments, but the protection scope of the present invention is not limited thereto: The present invention provides a biomass chemical chain gasification and combustion system, which includes an air separation unit, a biomass chemical chain gasification unit, a biomass chemical chain combustion unit, an electrolysis unit, and a green fuel synthesis unit. Through this system, efficient conversion of biomass can be achieved, and green NH3 and methanol products can be produced at the same time.

[0023] Lignin, cellulose or agricultural waste are selected as biomass raw materials. The biomass raw materials are crushed to a suitable particle size (<5mm) and dried to remove moisture. The biomass raw materials are simultaneously introduced into the biomass chemical chain gasification unit and the biomass chemical chain combustion unit for biomass chemical chain gasification and combustion. The electrolysis unit is connected to the biomass chemical chain gasification unit and the biomass chemical chain combustion unit respectively to transmit electricity and CO2 to the electrolysis unit.

[0024] The air separation unit includes an air separator, in which N2 is separated from the air and transported to an N2 buffer tank for storage, and then transported to a green NH3 synthesis unit for synthesis. A portion of the remaining gas is used as a gasifying agent and transported to a biomass chemical chain gasification unit, and the other portion is used as a combustion gas and transported to a biomass chemical chain combustion unit.

[0025] The biomass chemical chain gasification unit includes a gasification reactor, in which a steam gasification hydrogen production reaction is carried out. The gasification reactor uses a fluidized bed gasification reactor, and the operating temperature is 800-1000°C, the pressure is normal pressure or micro pressure, and the flow rate of the gasifier and water vapor is adjusted according to the water content of the biomass raw material and the gasification demand. Through steam gasification, a gasification product rich in H2 and CO2 is obtained, wherein the H2 content is about 30-50%, and the CO2 content is about 40-60%. H2 and CO2 are separated by condensation and gas separation technology, and H2 and CO2 are further purified to remove impurities and moisture. H2 is transported to the H2 buffer tank for storage, and CO2 is transported to the CO2 buffer tank for storage.

[0026] The biomass chemical chain combustion unit includes a combustion reactor and a power generation device. A fixed bed or fluidized bed combustion reactor is selected. The operating temperature is 900-1200°C and the pressure is normal pressure. The oxygen concentration during the combustion process is controlled by adjusting the air flow. Fe2O3 is selected as an oxygen carrier. During the combustion process, the oxygen carrier is reduced to metal Fe or low-valent oxide FeO, and then regenerated in air or oxygen. After FeO / Fe enters SR, it is oxidized to Fe3O4 by water vapor. After Fe3O4 enters AR, it is further oxidized to Fe2O3, thus completing the entire cycle. The combustion produces high-temperature flue gas, which contains CO2 and incompletely burned residual gas. CO2 is obtained by separation and purification, and the CO2 is transported to the CO2 buffer tank for storage. Part of the heat energy is converted into electrical energy through thermochemical conversion. The power generation device is a steam turbine or a gas turbine, which converts the heat energy of the high-temperature flue gas into electrical energy. According to the thermal efficiency of the combustion reactor and the conversion efficiency of the power generation system, the power output is calculated and transported to the electrolysis unit.

[0027] The electrolysis unit includes an electrolysis device, which uses a solid oxide electrolysis cell or a molten salt electrolysis cell. The electricity source comes from the biomass chemical chain combustion unit (when the electricity is insufficient, wind, light and other new energy sources can be used to generate electricity at the same time). The operating temperature is 600-800°C and the current density is 1-5A / cm². CO and O2 are obtained by electrolyzing part of the CO2 stored in the CO2 buffer tank, where the CO production is calculated based on the electrolysis efficiency and the purity of CO2. CO is obtained by separation and purification, and transported to the CO buffer tank for storage.

[0028] The biomass chemical chain gasification unit, the biomass chemical chain combustion unit, and the electrolysis unit are respectively connected to the green fuel synthesis unit, and the green fuel synthesis unit includes a green NH3 synthesis unit and a green methanol synthesis unit. The air separation unit transports N2 to the green NH3 synthesis unit, and the biomass chemical chain gasification unit transports H2 to the green NH3 synthesis unit. The N2 in the N2 buffer tank and the H2 in the H2 buffer tank are transported to the green NH3 synthesis unit through a compressor, and a synthesis reaction is carried out under the action of a catalyst. The reaction conditions are 400-500°C and 10-30MPa. The catalyst is a ruthenium-based catalyst to obtain NH3. The biomass chemical chain gasification unit delivers H2 to the green methanol synthesis unit, the biomass chemical chain combustion unit delivers CO2 to the green methanol synthesis unit, and the electrolysis unit delivers CO to the green methanol synthesis unit. The H2 in the H2 buffer tank, the CO2 in the CO2 buffer tank, and the CO in the CO buffer tank are delivered to the green methanol synthesis unit through a compressor, and a synthesis reaction is carried out under the action of a catalyst. The reaction conditions are 200-300°C, 5-10MPa, and the catalyst is a copper-zinc-based catalyst to obtain methanol. NH3 and methanol are separated and purified to obtain green fuel that meets market demand.

[0029] A method for preparing green fuel by coupling biomass gasification and combustion, comprising the following steps: (1) In the air separator, N2 is separated from air, and part of the remaining gas is used as a gasifying agent and the other part is used as a combustion gas. The volume percentage of the gasifying agent and the combustion gas is 70-80%: 20-30%.

[0030] (2) Biomass chemical chain gasification: Biomass, gasifying agent and water vapor are introduced into the gasification reactor together. The mass ratio of biomass to gasifying agent per unit time is 1.45:1.30-1.40, and the mass ratio of water vapor to biomass per unit time is 1:1.05-1.15. Biomass is steam-gasified to produce hydrogen under the condition of gasifying agent. The operating temperature of steam gasification hydrogen production is 800-1000℃, and the pressure is normal pressure. H2 and CO2 are separated.

[0031] (3) Biomass chemical chain combustion: Biomass, oxygen carrier (Fe2O3) and combustion gas are transported to a combustion reactor, with the mass ratio of biomass to oxygen carrier per unit time being 1:4.1-4.2, and the mass ratio of biomass to combustion gas per unit time being 1:1.25-1.35; biomass is converted into electricity through thermochemical conversion in the presence of oxygen carrier and combustion gas, with the operating temperature of thermochemical conversion power generation being 900-1200°C and the pressure being normal pressure, to obtain CO2.

[0032] (4) Using the electricity obtained from the chemical chain combustion of biomass to electrolyze CO2, the volume percentage of CO2 used for electrolysis is 25-30% of the total volume of CO2 obtained in steps (2) and (3), the catalyst used for electrolysis is Cu-In2O3, the operating temperature is 600-800°C, the current density is 1-5A / cm², and CO is produced.

[0033] (5) N2 and H2 are synthesized to prepare green NH3 products, the volume ratio of N2 and H2 is 1:3, the catalyst is a ruthenium-based catalyst, and the synthesis conditions are 400-500°C, 10-30MPa; H2, CO2 and CO are synthesized to prepare green methanol products, the volume ratio of H2, CO2 and CO is 27:7:3, the catalyst is a copper-zinc-based catalyst, and the synthesis conditions are 200-300°C, 5-10MPa.

[0034] Example 1 The biomass chemical chaining gasification and combustion system includes an air separation unit, a biomass chemical chaining gasification unit, a biomass chemical chaining combustion unit, an electrolysis unit, and a green fuel synthesis unit.

[0035] Lignin, cellulose or agricultural waste are selected as biomass raw materials. The biomass raw materials are crushed to a suitable particle size (<5mm) and dried to remove moisture. The biomass raw materials are simultaneously introduced into the biomass chemical chain gasification unit and the biomass chemical chain combustion unit for biomass chemical chain gasification and combustion. The electrolysis unit is connected to the biomass chemical chain gasification unit and the biomass chemical chain combustion unit respectively to transmit electricity and CO2 to the electrolysis unit.

[0036] The air separation unit includes an air separator, in which N2 is separated from the air and transported to an N2 buffer tank for storage, and then transported to a green NH3 synthesis unit for synthesis. A portion of the remaining gas is used as a gasifying agent and transported to a biomass chemical chain gasification unit, and the other portion is used as a combustion gas and transported to a biomass chemical chain combustion unit.

[0037] The biomass chemical chain gasification unit includes a gasification reactor, in which a steam gasification hydrogen production reaction is carried out. The gasification reactor uses a fluidized bed gasification reactor, and obtains a gasification product rich in H2 and CO2 through steam gasification. H2 and CO2 are separated by condensation and gas separation technology, and further purified to remove impurities and moisture. H2 is transported to an H2 buffer tank for storage, and CO2 is transported to a CO2 buffer tank for storage.

[0038] The biomass chemical chain combustion unit includes a combustion reactor and a power generation device, and a fluidized bed combustion reactor is selected. Fe2O3 is selected as the oxygen carrier. During the combustion process, the oxygen carrier is reduced to metallic Fe or low-valent oxide FeO, and then regenerated in air or oxygen. After FeO / Fe enters the SR, it is oxidized to Fe3O4 by water vapor. After Fe3O4 enters the AR, it is further oxidized to Fe2O3, thus completing the entire cycle. Combustion produces high-temperature flue gas, which contains CO2 and incompletely burned residual gas. CO2 is obtained through separation and purification, and the CO2 is transported to the CO2 buffer tank for storage. The power generation device is a steam turbine, which converts the thermal energy of the high-temperature flue gas into electrical energy and transports it to the electrolysis unit.

[0039] The electrolysis unit includes an electrolysis device, which uses a solid oxide electrolysis cell and uses electricity from a biomass chemical chain combustion unit. CO and O2 are obtained by electrolyzing part of the CO2 stored in the CO2 buffer tank. CO is obtained through separation and purification, and transported to the CO buffer tank for storage.

[0040] The biomass chemical chain gasification unit, the biomass chemical chain combustion unit, and the electrolysis unit are respectively connected to the green fuel synthesis unit, and the green fuel synthesis unit includes a green NH3 synthesis unit and a green methanol synthesis unit. The air separation unit transports N2 to the green NH3 synthesis unit, and the biomass chemical chain gasification unit transports H2 to the green NH3 synthesis unit. The N2 in the N2 buffer tank and the H2 in the H2 buffer tank are transported to the green NH3 synthesis unit through a compressor, and a synthesis reaction is carried out under the action of a catalyst to obtain NH3. The biomass chemical chain gasification unit transports H2 to the green methanol synthesis unit, the biomass chemical chain combustion unit transports CO2 to the green methanol synthesis unit, and the electrolysis unit transports CO to the green methanol synthesis unit. The H2 in the H2 buffer tank, the CO2 in the CO2 buffer tank, and the CO in the CO buffer tank are transported to the green methanol synthesis unit through a compressor, and a synthesis reaction is carried out under the action of a catalyst to obtain methanol. NH3 and methanol are separated and purified to obtain green fuels that meet market demand.

[0041] The method for preparing green fuel by coupling biomass gasification and combustion using the above system comprises the following steps: (1) In the air separator, N2 is separated from air, and part of the remaining gas is used as a gasifier and the other part is used as a combustion gas. The volume percentage of the gasifier and the combustion gas is 70%:30%.

[0042] (2) Biomass chemical chain gasification: Biomass, gasifying agent and water vapor are introduced into the gasification reactor together. The biomass input amount is 14569 kg / hr, the gasifying agent input amount is 13564.24 kg / hr, and the water vapor input amount is 13506.16 kg / hr. Biomass is steam-gasified to produce hydrogen under the condition of gasifying agent. The operating temperature of steam gasification hydrogen production is 850°C and the pressure is normal pressure. H2 and CO2 are separated.

[0043] (3) Biomass chemical chaining combustion: Biomass and oxygen carrier (Fe2O3) are transported to a combustion reactor. The biomass input is 7569 kg / hr, the oxygen carrier input is 31262.64 kg / hr, and the combustion gas input is 5813.25 kg / hr. The biomass is converted into electricity through thermochemical conversion under the conditions of oxygen carrier and combustion gas. The operating temperature of the thermochemical conversion power generation is 1100°C and the pressure is normal pressure to obtain CO2.

[0044] (4) The electric energy obtained from the chemical chain combustion of biomass is used to electrolyze CO2, wherein the volume percentage of CO2 used for electrolysis is 30% of the total volume of CO2 obtained in steps (2) and (3), the catalyst used for electrolysis is Cu-In2O3, the operating temperature is 750°C, the current density is 3A / cm2, and CO is produced.

[0045] (5) N2 and H2 were synthesized to prepare green NH3 products. The volume ratio of N2 and H2 was 1:3. The catalyst was a ruthenium-based catalyst. The synthesis conditions were 500°C and 15 MPa. H2, CO2 and CO were synthesized to prepare green methanol products. The volume ratio of H2, CO2 and CO was 27:7:3. The catalyst was a copper-zinc-based catalyst. The synthesis conditions were 250°C and 8 MPa.

[0046] During the biomass chemical chain gasification process, the volume content of CO and H2 in argon atmosphere reached 85% and the gas production rate was 1.13 m 3 / kg, gasification efficiency can reach 77.8%, carbon conversion rate can reach 96%. In the biomass chemical chain combustion process, the carbon conversion rate reaches 94%, and the methanol synthesis single-pass conversion rate reaches 61.2%.

[0047] Example 2 The method for preparing green fuel by coupling biomass gasification and combustion using the above system comprises the following steps: (1) In the air separator, N2 is separated from air, and part of the remaining gas is used as a gasifier and the other part is used as a combustion gas. The volume percentage of the gasifier and the combustion gas is 80%:20%.

[0048] (2) Biomass chemical chain gasification: Biomass, gasifying agent and water vapor are introduced into the gasification reactor together. The biomass input amount is 14569 kg / hr, the gasifying agent input amount is 15501.99 kg / hr, and the water vapor input amount is 14066.62 kg / hr. Biomass is steam-gasified to produce hydrogen under the condition of gasifying agent. The operating temperature of steam gasification hydrogen production is 950℃ and the pressure is normal pressure. H2 and CO2 are separated.

[0049] (3) Biomass chemical chaining combustion: Biomass and oxygen carrier (Fe2O3) are transported to a combustion reactor. The biomass input is 5231 kg / hr, the oxygen carrier input is 21605.88 kg / hr, and the combustion gas input is 3875.50 kg / hr. The biomass is converted into electricity through thermochemical conversion in the presence of oxygen carrier and combustion gas. The operating temperature of the thermochemical conversion power generation is 1100°C and the pressure is normal pressure to obtain CO2.

[0050] (4) The electric energy obtained from the chemical chain combustion of biomass is used to electrolyze CO2, wherein the volume percentage of CO2 used for electrolysis is 30% of the total volume of CO2 obtained in steps (2) and (3), the catalyst used for electrolysis is Cu-In2O3, the operating temperature is 750°C, the current density is 3A / cm2, and CO is produced.

[0051] (5) N2 and H2 were synthesized to prepare green NH3 products. The volume ratio of N2 and H2 was 1:3. The catalyst was a ruthenium-based catalyst. The synthesis conditions were 550°C and 25 MPa. H2, CO2 and CO were synthesized to prepare green methanol products. The volume ratio of H2, CO2 and CO was 27:7:3. The catalyst was a copper-zinc-based catalyst. The synthesis conditions were 300°C and 10 MPa.

[0052] During the biomass chemical chain gasification process, the volume content of CO and H2 in argon atmosphere reached 94% and the gas production rate was 1.53 m 3 / kg, gasification efficiency can reach 79.5%, carbon conversion rate can reach 98%. In the biomass chemical chain combustion process, the carbon conversion rate reaches 91%, and the methanol synthesis single-pass conversion rate reaches 60.5%.

[0053] Example 3 The method for preparing green fuel by coupling biomass gasification and combustion using the above system comprises the following steps: (1) In the air separator, N2 is separated from air, and part of the remaining gas is used as a gasifier and the other part is used as a combustion gas. The volume percentage of the gasifier and the combustion gas is 70%:30%.

[0054] (2) Biomass chemical chain gasification: Biomass, gasifying agent and water vapor are introduced into the gasification reactor together. The biomass input amount is 14569 kg / hr, the gasifying agent input amount is 13564.24 kg / hr, and the water vapor input amount is 13506.16 kg / hr. Biomass is steam-gasified to produce hydrogen under the condition of gasifying agent. The operating temperature of steam gasification hydrogen production is 850°C and the pressure is normal pressure. H2 and CO2 are separated.

[0055] (3) Biomass chemical chaining combustion: Biomass and oxygen carrier (Fe2O3) are transported to the combustion reactor. The biomass input is 4310 kg / hr, the oxygen carrier input is 18100.59 kg / hr, and the combustion gas input is 5813.25 kg / hr. The biomass is converted into electricity through thermochemical conversion under the conditions of oxygen carrier and combustion gas. The operating temperature of thermochemical conversion power generation is 1200°C and the pressure is normal pressure to obtain CO2.

[0056] (4) The electric energy obtained from the chemical chain combustion of biomass is used to electrolyze CO2, wherein the volume percentage of CO2 used for electrolysis is 30% of the total volume of CO2 obtained in steps (2) and (3), the catalyst used for electrolysis is Cu-In2O3, the operating temperature is 800°C, the current density is 4A / cm2, and CO is produced.

[0057] (5) N2 and H2 were synthesized to prepare green NH3 products. The volume ratio of N2 and H2 was 1:3. The catalyst was a ruthenium-based catalyst. The synthesis conditions were 500°C and 15 MPa. H2, CO2 and CO were synthesized to prepare green methanol products. The volume ratio of H2, CO2 and CO was 27:7:3. The catalyst was a copper-zinc-based catalyst. The synthesis conditions were 250°C and 8 MPa.

[0058] During the biomass chemical chain gasification process, the volume content of CO and H2 in argon atmosphere reached 85% and the gas production rate was 1.13 m 3 / kg, gasification efficiency can reach 77.8%, carbon conversion rate can reach 96%. In the biomass chemical chain combustion process, the carbon conversion rate reaches 97%, and the methanol synthesis single-pass conversion rate reaches 62.0%.

[0059] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing green fuel by coupling biomass gasification and combustion, characterized in that: The steps include: (1) Separate N2 from air, and use part of the remaining gas as a gasifier, with the gasifier accounting for 70-80% of the volume of the remaining gas, and the other part as a combustion gas; (2) chemical chain gasification of biomass by steam under gasification agent conditions to obtain H2 and CO2; (3) Chemically combusting biomass in the presence of an oxygen carrier and combustion gas to produce CO2; (4) Using the electricity obtained from biomass chemical chain combustion to electrolyze part of the CO2 obtained to obtain CO; (5) N2 and H2 are synthesized in a volume ratio of 1:3 to prepare green NH3 products; H2, CO2 and CO are synthesized in a volume ratio of 27:7:3 to prepare green methanol products.

2. The method for preparing green fuel by coupling biomass gasification and combustion according to claim 1, characterized in that: In step (2), the operating temperature of the chemical chaining gasification is 800-1000°C and the pressure is atmospheric pressure.

3. The method for preparing green fuel by coupling biomass gasification and combustion according to claim 1, characterized in that: In step (2), the mass ratio of water vapor to biomass introduced per unit time is 1:1.05-1.

15.

4. The method for preparing green fuel by coupling biomass gasification and combustion according to any one of claims 1 to 3, characterized in that: In step (2), the mass ratio of biomass to gasifying agent per unit time is 1.45:1.30-1.

40.

5. The method for preparing green fuel by coupling biomass gasification and combustion according to claim 1, characterized in that: In step (3), the operating temperature of the chemical looping combustion is 900-1200°C and the pressure is atmospheric pressure.

6. The method for preparing green fuel by coupling biomass gasification and combustion according to claim 1 or 5, characterized in that: In step (3), the mass ratio of biomass to combustion gas per unit time is 1:1.25-1.35; the mass ratio of biomass to oxygen carrier per unit time is 1:4.1-4.

2.

7. The method for preparing green fuel by coupling biomass gasification and combustion according to claim 1, characterized in that: In step (4), the operating temperature of electrolysis is 600-800°C and the current density is 1-5A / cm².

8. The method for preparing green fuel by coupling biomass gasification and combustion according to claim 1 or 7, characterized in that: In step (4), the volume percentage of CO2 used for electrolysis is 25-30% of the total volume of CO2 obtained in steps (2) and (3).

9. The method for preparing green fuel by coupling biomass gasification and combustion according to claim 1, characterized in that: In step (5), during the process of synthesizing N2 and H2 to prepare the green NH3 product, the synthesis conditions are 400-500°C and 10-30MPa.

10. The method for preparing green fuel by coupling biomass gasification and combustion according to claim 1 or 9, characterized in that: In step (5), during the process of synthesizing H2, CO2 and CO to prepare the green methanol product, the synthesis conditions are 200-300°C and 5-10MPa.