Method for producing ethanol by thermochemical conversion of biomass

Abstract

The invention discloses a method for producing ethanol by thermochemical conversion of biomass, and relates to the technical field of ethanol production. The method comprises the following steps: carrying out pyrolysis, deoxidation and carbonization on a pretreated non-grain biomass raw material to generate biochar and biological combustible gas, and carrying out split-flow conveying on the biochar and the biological combustible gas; the shunted biological combustible gas is subjected to combustion treatment to supply energy to each unit of the whole process; the method comprises the following steps: carrying out gasification treatment on separated biochar, carrying out dust removal purification on generated crude synthesis gas containing H2 and CO, carrying out shift reaction on the crude synthesis gas and water, carrying out CO2 removal treatment, separating out part of CO and H2, carrying out synthesis reaction on the residual hydrogen-rich gas, carrying out rectification, reacting with CO, refining, and carrying out esterification reaction in a rectification mode, and after purification, carrying out hydrogenation reaction under the action of a hydrogenation catalyst, and finally carrying out refining treatment to obtain ethanol. According to the method, all-component high-value utilization of the biomass is realized, and the process is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of ethanol production technology, and more specifically to a method for producing ethanol through the thermochemical conversion of biomass. Background Technology

[0002] Ethanol, as an important basic chemical raw material, is widely used in pharmaceuticals, food, energy, materials, and other fields. Currently, industrial ethanol production mainly relies on grain fermentation and ethylene hydration. Grain fermentation has the limitation of competing with humans for grain resources, while ethylene hydration is highly dependent on petroleum fossil resources, resulting in insufficient sustainable development. Furthermore, the cost of producing cellulosic ethanol from pretreated biomass through enzymatic hydrolysis of saccharified cellulose and hemicellulose to obtain fermentable sugars is too high. Currently, there is no mature technology for producing ethanol using biomass gasification. This technology converts low-value biomass such as agricultural and forestry waste into syngas, which is then used for multi-step catalytic synthesis to produce ethanol, offering advantages such as wide raw material adaptability and large-scale potential.

[0003] However, direct biomass gasification to ethanol still suffers from the following key performance shortcomings: First, biomass contains approximately 45% oxygen, resulting in low gasification efficiency and low carbon conversion rate. The process also generates large amounts of tar and moisture, easily causing pipeline blockage and equipment corrosion, leading to process instability and frequent malfunctions. Second, the ability to regulate and utilize syngas components is insufficient, making it difficult to simultaneously match the differentiated feedstock requirements of downstream multi-reaction units. Atom utilization is low, and process byproducts cannot be utilized in a closed-loop, high-value manner, resulting in insufficient system economics. Therefore, the feedstock utilization rate, energy efficiency, and industrial adaptability of existing biomass-to-ethanol processes still need improvement. Summary of the Invention

[0004] The purpose of this invention is to provide a method for producing ethanol through the thermochemical conversion of biomass, thereby solving the following technical problems:

[0005] Existing biomass direct gasification to ethanol production processes still suffer from problems such as low gasification efficiency, low carbon conversion rate, unstable process flow, low raw material utilization rate, and high energy consumption.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for producing ethanol from biomass through thermochemical conversion includes the following steps:

[0008] S1: Non-grain biomass raw materials are dehydrated and impurity removed before being sent to the biomass thermal fractionation unit for thermal deoxygenation and carbonization reaction to generate biochar and biocombustible gas, which are then diverted and transported.

[0009] S2: The diverted biogas is introduced into the green steam / electricity production unit for combustion treatment, and the heat generated by combustion powers all units in the process.

[0010] S3: The diverted biochar is sent to the biochar gasification unit for gasification to obtain crude syngas;

[0011] S4: After dust removal and purification, the crude syngas is sent to the water-gas shift reaction unit to react with water to obtain syngas;

[0012] S5: After CO2 removal treatment of the synthesis gas, 50% of CO and H2 are separated, and the remaining gas is hydrogen-rich gas.

[0013] S6: Hydrogen-rich gas is fed into the methanol production unit for reaction and then distilled to obtain methanol;

[0014] S7: CO and methanol are fed into the methanol carbonylation unit and reacted with CO under the action of RhI3 or IrI3 catalyst to obtain a mixture of acetic acid.

[0015] S8: After purification, the acetic acid mixture is fed into the acetic acid esterification unit and undergoes esterification reaction under the action of catalyst A-15 in distillation mode to obtain ethyl acetate-water azeotrope.

[0016] S9: After purification, the ethyl acetate-water azeotrope is fed into a hydrogenation reactor and hydrogenated under the action of a 20% Cu / SiO2 hydrogenation catalyst. After purification, ethanol is obtained.

[0017] Preferably, the non-grain biomass raw material mentioned in S1 is any one of straw, agricultural and forestry waste, and fermentation residue;

[0018] The non-grain biomass raw materials mentioned in S1 have a moisture content of 8%-20% after pretreatment;

[0019] The temperature during the thermal fractionation of biomass described in S1 is 400-700℃.

[0020] Preferably, the gasification medium during the gasification process in S3 is oxygen and water vapor, and the temperature is 800-1200℃;

[0021] The crude synthesis gas described in S3 has a volume ratio of H2 to CO of 1:1, and the crude synthesis gas contains a small amount of CO2.

[0022] Preferably, the volume ratio of H2 to CO in the synthesis gas in S4 is 2:1.

[0023] Preferably, the CO2 removal process in S5 is a pressure swing adsorption process;

[0024] The volume ratio of H2 to CO in the hydrogen-rich gas described in S5 is 2:1; the separated CO gas is directly transported to the methanol carbonylation unit, and the hydrogen-rich gas is directly transported to the methanol synthesis unit.

[0025] Preferably, the reaction temperature in S6 is 240-280℃ and the pressure is 4-8MPa.

[0026] Preferably, the molar ratio of CO to methanol in S7 is 1:1;

[0027] The reaction with CO described in S7 is carried out at a temperature of 170-200℃ and a pressure of 3-5MPa.

[0028] Preferably, the raw materials for the esterification reaction in S8 are ethanol and acetic acid in a mass ratio of 1.1-1.3:1, the reaction temperature is 80-90℃, and an ethyl acetate-water azeotrope is obtained at the top of the esterification unit during the reaction. Unreacted ethanol is collected from the side stream of the tower and recycled back to the esterification unit.

[0029] Preferably, in the hydrogenation reaction described in S9, the molar ratio of ethyl acetate to H2 is 1:1, the temperature is 200-250℃, and the pressure is 3-5MPa.

[0030] The beneficial effects of this invention are:

[0031] This invention provides a method for producing ethanol through the thermochemical conversion of biomass. The invention improves the raw material utilization rate and industrial adaptability of the biomass thermochemical conversion process for ethanol production, while reducing production energy consumption.

[0032] The production process of this invention features a pre-heated fractionation and fractional utilization design for biomass, reducing carbon loss at the source and solving the persistent problems of tar clogging pipes and corroding equipment in traditional direct gasification processes, significantly improving the continuity and stability of the production process. The biochar gasification feed component of this invention is singular, the gasification reaction is highly controllable, the effective gas content in the crude syngas is higher, and carbon loss in the purification stage is lower, directly improving the carbon yield from biomass to syngas. The staged pressure swing adsorption of this invention achieves precise separation of CO and H2, with the separated high-purity CO and H2 directly matching the feedstock requirements of the carbonylation and hydrogenation units. The remaining hydrogen-rich gas is still fed into the methanol synthesis unit at a 2:1 ratio, achieving 100% full utilization of the effective components of the syngas, fundamentally improving the utilization rate of carbon and hydrogen elements in the syngas. The high conversion rate of the hydrogenation unit reduces the amount of ethyl acetate recycled, further reducing losses during material circulation, and the closed-loop recycling of raw materials throughout the process further improves the utilization rate of raw materials. This invention utilizes the combustion heat energy of biogas produced by thermal deoxygenation to supply the thermal fractionation unit, gasifier jacket, and reboilers of each distillation column in tiered temperature stages, achieving "one-time heat generation and full-process reuse." This directly reduces the supplementary consumption of fossil fuels such as natural gas, improves energy utilization efficiency, and lowers the energy consumption of the entire heat exchange system. The precise control of the hydrogen-to-carbon ratio of the syngas reduces the power consumption of circulating gas compression. Each unit of this invention is equipped with a buffer chamber, giving the system strong resistance to load fluctuations and adapting to the dynamic adjustment needs of raw materials and loads in industrial production.

[0033] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a flowchart of the biomass thermochemical conversion method for producing ethanol according to the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1: A method for producing ethanol from biomass through thermochemical conversion is as follows:

[0038] S1: First, the mixture of liquor lees, beer lees, soy sauce residue, and vinegar lees is dehydrated and impurity removed to pre-treat the raw materials. Finally, the moisture content of the raw materials is reduced to 8%. Then, it is sent to the biomass thermal fractionation unit to carry out thermal deoxidation and carbonization reaction at 400℃, 0.1MPa, and nitrogen atmosphere to generate biochar and biocombustible gas.

[0039] Tests showed that the calorific value of biochar was 4500 kcal / kg, and the calorific value of biocombustible gas was 2800 kcal / Nm³. 3 The biogas is preferentially transported to the biomass thermal fractionation unit for energy supply, and the remaining part is transported to the gas storage tank of the green steam / electricity production unit for buffering. The biochar is transported to the buffer silo of the biochar gasification unit through a closed pipeline.

[0040] S2: The biocombustible gas buffered in the gas storage tank of the green steam / electricity production unit is burned by a dedicated burner. The high-temperature heat energy generated is transported through a heat exchange system to the heating device of the thermal fractionation unit, the gasifier jacket of the biochar gasification unit, and the reboiler of the distillation column of the methanol synthesis and acetic acid separation and refining unit.

[0041] In this embodiment, the heat generated by the combustion of biogas can meet 72% of the total heat demand of all units in the process, and the remaining 28% of the heat is supplied by natural gas.

[0042] S3: The biochar in the buffer chamber of the biochar gasification unit is fed into the biochar gasification unit, and oxygen and water vapor are introduced as gasification media. The gasification reaction is carried out at 800℃, and crude syngas is generated after the reaction is completed.

[0043] Tests showed that the volume ratio of H2 to CO in the crude syngas was 1:1, and it also contained a small amount of CO2.

[0044] S4: After the crude syngas is purified by dust removal, it is transported to the water-gas conversion unit through pipeline, where the crude syngas reacts with water to convert part of the CO into CO2 and H2, resulting in syngas with a volume ratio of H2 to CO of 2:1.

[0045] S5: After the syngas is introduced into the CO separation unit, it first undergoes pressure swing adsorption (PSA) in the adsorption bed to remove CO2 (CO2 content ≤0.1% after removal). Then, it undergoes secondary adsorption to separate 50% CO (99% purity) and 50% H2 (99% purity). The remaining gas is a hydrogen-rich gas with a H2 to CO volume ratio of 2:1. The separated CO gas is directly sent to the methanol carbonylation unit, the H2 is sent to the ethyl acetate hydrogenation unit, and the hydrogen-rich gas is sent to the methanol production unit.

[0046] S6: Hydrogen-rich gas is fed into the synthesis tower of the methanol production unit and reacted at 240℃, 4MPa, and with the action of Cu-Zn-Al catalyst. The reaction product is cooled by a condenser and then sent to a multi-tower continuous distillation system for purification to obtain methanol with a purity of 99.92%. The methanol is then transported to the methanol carbonylation unit through pipelines.

[0047] S7: Methanol and CO are mixed evenly in a 1:1 molar ratio, and then fed into the reactor of the methanol carbonylation unit. The carbonylation reaction is carried out at 170℃ and 3MPa using RhI3 catalyst to obtain an acetic acid mixture.

[0048] S8: After refining the acetic acid mixture, acetic acid with a purity of 99.82% is fed into the esterification unit. Reactive distillation is used, with A-15 strong acid cation exchange resin as a catalyst. Acetic acid and ethanol react at 80°C in a mass ratio of 1.1:1 to obtain an ethyl acetate-water azeotrope. During the reaction, the ethyl acetate-water azeotrope is continuously distilled off the top of the column and transported through pipeline to the ethyl acetate separation and purification unit. Unreacted ethanol is collected from the side stream of the column, cooled, and recycled back to the feed inlet of the esterification unit to participate in the reaction again. The recovery rate of unreacted ethanol is 96%.

[0049] S9: Ethyl acetate with a purity of 99.53% obtained after purifying the ethyl acetate-water azeotrope was then fed into the ethyl acetate hydrogenation unit. Under the action of 170℃, 2MPa, and 20% Cu / SiO2 hydrogenation catalyst (the amount of hydrogenation catalyst loaded was 6% of the total mass of the reaction system), it was hydrogenated with H2 split from the separation unit at a molar ratio of 1:1 to obtain crude ethanol.

[0050] S10: Crude ethanol is fed into the ethanol refining unit, where a three-stage process of "light component removal - heavy component removal - finished product distillation" is adopted, with the addition of a molecular sieve dehydration step for refining. First, it is fed into the light component removal tower, where the bottom temperature is controlled at 90℃, the top temperature at 78℃, and the operating pressure at 0.15MPa to remove low-boiling-point impurities such as acetal and trace amounts of unreacted ethyl acetate. Then, the bottom material from the light component removal tower is fed into the heavy component removal tower, where the bottom temperature is controlled at 125℃, the top temperature at 93℃, and the operating pressure at 0.15MPa to remove heavy components such as higher alcohols and esters. Finally, the top material from the heavy component removal tower is fed into the finished product distillation tower, where the bottom temperature is controlled at 108℃, the top temperature at 79℃, and the operating pressure at 0.1MPa. After precision distillation, it is sent to a 3A molecular sieve adsorption tower for dehydration to obtain ethanol with a purity of 99.70%.

[0051] Example 2: A method for producing ethanol from biomass through thermochemical conversion is as follows:

[0052] S1: First, the corn stalks are dehydrated and impurities are removed to pre-treat them, and the moisture content of the raw materials is reduced to 14%. Then, they are sent to the biomass thermal fractionation unit to carry out thermal deoxidation and carbonization reaction at 480℃ and under normal pressure nitrogen atmosphere to generate biochar and biocombustible gas.

[0053] Tests showed that the calorific value of biochar was 4806 kcal / kg, and the calorific value of biocombustible gas was 3510 kcal / Nm³. 3 The biogas is preferentially transported to the biomass thermal fractionation unit for energy supply, and the remaining part is transported to the gas storage tank of the green steam / electricity production unit for buffering. The biochar is transported to the buffer silo of the biochar gasification unit through a closed pipeline.

[0054] S2: The biocombustible gas buffered in the gas storage tank of the green steam / electricity production unit is burned by a dedicated burner. The high-temperature heat energy generated is transported through a heat exchange system to the heating device of the thermal fractionation unit, the gasifier jacket of the biochar gasification unit, and the reboiler of the distillation column of the methanol synthesis and acetic acid separation and refining unit.

[0055] In this embodiment, the heat generated by the combustion of biogas can meet 72% of the total heat demand of all units in the process, and the remaining 28% of the heat is supplied by natural gas.

[0056] S3: Biochar in the buffer chamber of the biochar gasification unit is fed into the biochar gasification unit, and oxygen and water vapor are introduced as gasification media. The gasification reaction is carried out at 950°C, and crude syngas is generated after the reaction is completed.

[0057] Tests showed that the volume ratio of H2 to CO in the crude syngas was 1:1, and it also contained a small amount of CO2.

[0058] S4: After the crude syngas is purified by dust removal, it is transported to the water-gas conversion unit through pipeline, where the crude syngas reacts with water to convert part of the CO into CO2 and H2, resulting in syngas with a volume ratio of H2 to CO of 2:1.

[0059] S5: After the syngas is introduced into the CO separation unit, it first undergoes pressure swing adsorption (PSA) in the adsorption bed to remove CO2 (CO2 content ≤0.1% after removal). Then, it undergoes secondary adsorption to separate 50% CO (99% purity) and 50% H2 (99% purity). The remaining gas is a hydrogen-rich gas with a H2 to CO volume ratio of 2:1. The separated CO gas is directly sent to the methanol carbonylation unit, the H2 is sent to the ethyl acetate hydrogenation unit, and the hydrogen-rich gas is sent to the methanol production unit.

[0060] S6: Hydrogen-rich gas is fed into the synthesis tower of the methanol production unit and reacted at 260℃, 5MPa, and with Cu-Zn-Al catalyst. The reaction product is cooled by a condenser and then sent to a multi-tower continuous distillation system for purification to obtain methanol with a purity of 99.92%. The methanol is then transported to the methanol carbonylation unit through pipelines.

[0061] S7: Methanol and CO are mixed evenly in a 1:1 molar ratio and then fed into the reactor of the methanol carbonylation unit. The carbonylation reaction is carried out at 190℃ and 4MPa using IrI3 catalyst to obtain an acetic acid mixture.

[0062] S8: After purifying the acetic acid mixture, the purified acetic acid with a purity of 99.82% is fed into the acetic acid esterification unit. Reactive distillation is used, with A-15 strong acid cation exchange resin as a catalyst. Acetic acid and ethanol react at 85°C with a mass ratio of 1.2:1 to obtain an ethyl acetate-water azeotrope. During the reaction, the ethyl acetate-water azeotrope is continuously distilled off the top of the column and transported through pipeline to the ethyl acetate separation and purification unit. Unreacted ethanol is collected from the side stream of the column, cooled, and recycled back to the feed inlet of the esterification unit to participate in the reaction again. The recovery rate of unreacted ethanol is 96%.

[0063] S9: Ethyl acetate with a purity of 99.53% obtained after purification of ethyl acetate-water azeotrope is then fed into the ethyl acetate hydrogenation unit. Under the action of 180℃, 2.5MPa, and 20% Cu / SiO2 hydrogenation catalyst (the amount of hydrogenation catalyst is 6% of the total mass of the reaction system), it reacts with H2 split from the separation unit at a molar ratio of 1:1 to obtain crude ethanol.

[0064] S10: Crude ethanol is fed into the ethanol refining unit, where a three-stage process of "light component removal - heavy component removal - finished product distillation" is adopted, with the addition of a molecular sieve dehydration step for refining. First, it is fed into the light component removal tower, where the bottom temperature is controlled at 90℃, the top temperature at 78℃, and the operating pressure at 0.15MPa to remove low-boiling-point impurities such as acetal and trace amounts of unreacted ethyl acetate. Then, the bottom material from the light component removal tower is fed into the heavy component removal tower, where the bottom temperature is controlled at 125℃, the top temperature at 93℃, and the operating pressure at 0.15MPa to remove heavy components such as higher alcohols and esters. Finally, the top material from the heavy component removal tower is fed into the finished product distillation tower, where the bottom temperature is controlled at 108℃, the top temperature at 79℃, and the operating pressure at 0.1MPa. After precision distillation, it is sent to a 3A molecular sieve adsorption tower for dehydration to obtain ethanol with a purity of 99.75%.

[0065] Example 3: A method for producing ethanol from biomass through thermochemical conversion is as follows:

[0066] S1: First, the sawdust, bamboo shavings and bamboo and wood scraps are dehydrated and impurities are removed to control the moisture content of the raw materials to 20%. Then, they are sent to the biomass thermal fractionation unit to carry out thermal deoxidation and carbonization reaction at 700℃ and 0.1MPa nitrogen atmosphere to generate biochar and biocombustible gas.

[0067] Tests showed that the calorific value of biochar was 5500 kcal / kg, and the calorific value of biocombustible gas was 3600 kcal / Nm³. 3 The biogas is preferentially transported to the biomass thermal fractionation unit for energy supply, and the remaining part is transported to the gas storage tank of the green steam / electricity production unit for buffering. The biochar is transported to the buffer silo of the biochar gasification unit through a closed pipeline.

[0068] S2: The biocombustible gas buffered in the gas storage tank of the green steam / electricity production unit is burned by a dedicated burner. The high-temperature heat energy generated is transported through a heat exchange system to the heating device of the thermal fractionation unit, the gasifier jacket of the biochar gasification unit, and the reboiler of the distillation column of the methanol synthesis and acetic acid separation and refining unit.

[0069] In this embodiment, the heat generated by the combustion of biogas can meet 73.4% of the total heat demand of all units in the entire process, with the remaining 26.6% of the heat supplied by natural gas as an auxiliary source.

[0070] S3: The biochar in the buffer chamber of the biochar gasification unit is fed into the biochar gasification unit, and oxygen and water vapor are introduced as gasification media. The gasification reaction is carried out at 1200℃, and crude syngas is generated after the reaction is completed.

[0071] Tests showed that the volume ratio of H2 to CO in the crude syngas was 1:1, and it also contained a small amount of CO2.

[0072] S4: After the crude syngas is purified by dust removal, it is transported to the water-gas conversion unit through pipeline, where the crude syngas reacts with water to convert part of the CO into CO2 and H2, resulting in syngas with a volume ratio of H2 to CO of 2:1.

[0073] S5: After the syngas is introduced into the CO separation unit, it first undergoes pressure swing adsorption (PSA) in the adsorption bed to remove CO2 (CO2 content ≤0.1% after removal). Then, it undergoes secondary adsorption to separate 50% CO (99% purity) and 50% H2 (99% purity). The remaining gas is a hydrogen-rich gas with a H2 to CO volume ratio of 2:1. The separated CO gas is directly sent to the methanol carbonylation unit, the H2 is sent to the ethyl acetate hydrogenation unit, and the hydrogen-rich gas is sent to the methanol production unit.

[0074] S6: Hydrogen-rich gas is fed into the synthesis tower of the methanol production unit and reacted at 280℃, 8MPa, and with the action of Cu-Zn-Al catalyst. The reaction product is cooled by a condenser and then sent to a multi-tower continuous distillation system for purification to obtain methanol with a purity of 99.92%. The methanol is then transported to the methanol carbonylation unit through pipelines.

[0075] S7: Methanol and CO are mixed evenly in a 1:1 molar ratio and then fed into the reactor of the methanol carbonylation unit. The carbonylation reaction is carried out at 200℃ and 5MPa using IrI3 catalyst to obtain an acetic acid mixture.

[0076] S8: After refining the acetic acid mixture, acetic acid with a purity of 99.82% is fed into the esterification unit. Reactive distillation is used, with A-15 strong acid cation exchange resin as a catalyst. Acetic acid and ethanol react at 90°C in a mass ratio of 1.3:1 to obtain an ethyl acetate-water azeotrope. During the reaction, the ethyl acetate-water azeotrope is continuously distilled off the top of the column and transported through pipeline to the ethyl acetate separation and purification unit. Unreacted ethanol is collected from the side stream of the column, cooled, and recycled back to the feed inlet of the esterification unit to participate in the reaction again. The recovery rate of unreacted ethanol is 96.3%.

[0077] S9: Ethyl acetate with a purity of 99.53% obtained after purifying the ethyl acetate-water azeotrope is then fed into the ethyl acetate hydrogenation unit. Under the action of 190℃, 3MPa, and 20% Cu / SiO2 hydrogenation catalyst (the amount of hydrogenation catalyst is 6% of the total mass of the reaction system), it undergoes a hydrogenation reaction with H2 split from the separation unit at a molar ratio of 1:1 to obtain crude ethanol.

[0078] S10: Crude ethanol is fed into the ethanol refining unit, where a three-stage process of "light component removal - heavy component removal - finished product distillation" is adopted, with the addition of a molecular sieve dehydration step for refining. First, it is fed into the light component removal tower, where the bottom temperature is controlled at 90℃, the top temperature at 78℃, and the operating pressure at 0.15MPa to remove low-boiling-point impurities such as acetal and trace amounts of unreacted ethyl acetate. Then, the bottom material from the light component removal tower is fed into the heavy component removal tower, where the bottom temperature is controlled at 125℃, the top temperature at 93℃, and the operating pressure at 0.15MPa to remove heavy components such as higher alcohols and esters. Finally, the top material from the heavy component removal tower is fed into the finished product distillation tower, where the bottom temperature is controlled at 108℃, the top temperature at 79℃, and the operating pressure at 0.1MPa. After precision distillation, it is sent to a 3A molecular sieve adsorption tower for dehydration to obtain ethanol with a purity of 99.78%.

[0079] Determination of total carbon yield of ethanol:

[0080] The total carbon yield (%) of ethanol in the whole process of the ethanol production method of Examples 1-3 of the present invention was determined, and the total carbon content in the final ethanol product was determined as a proportion of the total carbon content in the initial biomass feedstock. The results are shown in Table 1.

[0081] Determination of hydrogen utilization efficiency and ethyl acetate single-pass conversion rate:

[0082] The effective utilization rate of hydrogen (%) and the proportion of hydrogen participating in the production of ethanol to the total feed hydrogen of the hydrogenation unit, as well as the single-pass conversion rate of ethyl acetate (%), in process S9 of the method for producing ethanol in Examples 1-3 of the present invention were determined. The results are shown in Table 1.

[0083] Table 1: Performance test results of Examples 1-3

[0084]

[0085] Data Analysis:

[0086] As can be seen from Table 1, the ethanol production process of the present invention has both excellent raw material utilization and low production energy consumption.

[0087] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for producing ethanol through the thermochemical conversion of biomass, characterized in that, Includes the following steps: S1: Non-grain biomass raw materials are dehydrated and impurity removed before being sent to the biomass thermal fractionation unit for thermal deoxygenation and carbonization reaction to generate biochar and biocombustible gas, which are then diverted and transported. S2: The diverted biogas is introduced into the green steam / electricity production unit for combustion treatment, and the heat generated by combustion powers all units in the process. S3: The diverted biochar is sent to the biochar gasification unit for gasification to obtain crude syngas; S4: After dust removal and purification, the crude syngas is sent to the water-gas shift reaction unit to react with water to obtain syngas; S5: After CO2 removal treatment of the synthesis gas, 50% of CO and H2 are separated, and the remaining gas is hydrogen-rich gas. S6: Hydrogen-rich gas is fed into the methanol production unit for reaction and then distilled to obtain methanol; S7: CO and methanol are fed into the methanol carbonylation unit, where they react with CO under the action of a catalyst to obtain a mixture of acetic acid; S8: After purification, the acetic acid mixture is fed into the acetic acid esterification unit and carried out in distillation mode to obtain ethyl acetate-water azeotrope. S9: After purification, the ethyl acetate-water azeotrope is fed into a hydrogenation reactor and hydrogenated under the action of a hydrogenation catalyst. After purification, ethanol is obtained.

2. The method for producing ethanol from biomass through thermochemical conversion according to claim 1, characterized in that, The non-grain biomass raw materials mentioned in S1 are any one of straw, agricultural and forestry waste, and fermentation residue; The non-grain biomass raw materials mentioned in S1 have a moisture content of 8%-20% after pretreatment; The temperature during the thermal fractionation of biomass described in S1 is 400-700℃.

3. The method for producing ethanol from biomass through thermochemical conversion according to claim 1, characterized in that, The gasification medium used in the gasification process described in S3 is oxygen and water vapor, and the temperature is 800-1200℃.

4. The method for producing ethanol from biomass through thermochemical conversion according to claim 1, characterized in that, The volume ratio of H2 to CO in the synthesis gas described in S4 is 2:

1.

5. The method for producing ethanol from biomass through thermochemical conversion according to claim 1, characterized in that, The volume ratio of H2 to CO in the hydrogen-rich gas described in S5 is 2:

1.

6. The method for producing ethanol from biomass through thermochemical conversion according to claim 1, characterized in that, The reaction in S6 takes place at a temperature of 240-280℃ and a pressure of 4-8MPa.

7. The method for producing ethanol from biomass through thermochemical conversion according to claim 1, characterized in that, The molar ratio of CO to methanol mentioned in S7 is 1:1; The catalyst mentioned in S7 is either RhI3 or IrI3 catalyst, and the reaction temperature is 170-200℃ and the pressure is 3-5MPa.

8. The method for producing ethanol from biomass through thermochemical conversion according to claim 1, characterized in that, The esterification reaction described in S8 uses ethanol and acetic acid in a mass ratio of 1.1-1.3:1, and the reaction temperature is 80-90℃.

9. The method for producing ethanol from biomass through thermochemical conversion according to claim 1, characterized in that, In the hydrogenation reaction described in S9, the molar ratio of ethyl acetate to H2 is 1:1, the temperature is 200-250℃, and the pressure is 3-5MPa.

Images