Methanol preparation method and device

Abstract

The invention provides a zero-carbon-emission green methanol production method and device by coupling biomass gasification, green electricity hydrogen production and inverse transformation, and the production method comprises the following steps: 1) pre-treating a raw material biomass, and sending the pretreated raw material biomass to a gasification unit to obtain crude synthesis gas; 2) recovering heat of the crude synthesis gas in a heat recovery unit and producing a byproduct steam, and removing sulfur-containing compounds and CO2 in a desulfurization and decarbonization unit to obtain purified synthesis gas; 3) carrying out reaction on CO2 and H2 in an inverse transformation unit to generate inverse transformation gas; 4) mixing the reverse shift gas with the crude synthesis gas, recovering heat in a heat recovery unit, cooling and separating liquid step by step, separating unreacted CO2 in a desulfurization and decarbonization unit, and circulating the unreacted CO2 back to the reverse shift unit for continuous reaction; 5) feeding the purified synthesis gas to a methanol synthesis unit, and reacting to obtain crude methanol; and 6) feeding the crude methanol to a methanol rectification unit, and rectifying to obtain green methanol. The method for producing green methanol provided by the invention can save equipment investment and reduce energy consumption.

Description

Technical Field

[0001] The invention belongs to the field of synthesis technology, and in particular relates to a method and a device for preparing methanol. Background Art

[0002] Methanol is an important organic chemical raw material, as well as an excellent energy source and vehicle fuel. The price and demand for methanol in the domestic market are also increasing year by year, which shows that methanol has huge market potential. The high-grade conversion of biomass can be achieved by catalyzing the synthesis of methanol from cheap biomass such as straw and wood through thermochemical methods, which can not only increase agricultural income, but also significantly reduce the greenhouse effect caused by carbon dioxide, and has significant economic, social and environmental benefits. It can be foreseen that the biomass to methanol project will become an important industry with a very broad market prospect.

[0003] At present, the process of preparing green methanol from biomass requires large equipment investment and high energy consumption. Therefore, developing a method for producing green methanol with small equipment investment and low energy consumption is a technical problem that needs to be solved urgently at this stage. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for producing green methanol with zero carbon emissions by coupling biomass gasification-green electricity hydrogen production-reverse transformation. The production method has small equipment investment and low energy consumption.

[0005] The present invention also provides a production device for executing the above production method, which can achieve the purpose of small equipment investment and low energy consumption.

[0006] In a first aspect, the present invention provides a method for producing green methanol with zero carbon emission by coupling biomass gasification-green electricity hydrogen production-reverse conversion, comprising the following steps:

[0007] 1) The raw biomass is sent to the gasification unit after pretreatment, and the crude synthesis gas is obtained after gasification;

[0008] 2) sending the crude synthesis gas to a synthesis gas purification system, in which the crude synthesis gas first recovers heat in a heat recovery unit and produces steam as a by-product, is cooled step by step, and then enters a desulfurization and decarbonization unit to remove sulfur-containing compounds and CO2 to obtain purified synthesis gas after gas-liquid separation and removal of condensate.

[0009] 3) The CO2 separated by the desulfurization and decarbonization unit is sent to the inverse conversion unit to react with the H2 from the green electricity hydrogen production unit to generate CO and H2O;

[0010] 4) The reverse conversion gas from the reverse conversion unit is mixed with the crude synthesis gas and sent to the synthesis gas purification system together, and the heat is recovered in the heat recovery unit and the liquid is cooled and separated step by step, and the unreacted CO2 is separated in the desulfurization and decarbonization unit and circulated back to the reverse conversion unit for further reaction;

[0011] 5) sending the purified synthesis gas from the synthesis gas purification system to a methanol synthesis unit to obtain crude methanol after reaction;

[0012] 6) The crude methanol is sent to a methanol distillation unit, and green methanol is obtained as a product after distillation.

[0013] In the method described above, the electric energy used by the green electricity hydrogen production unit for electrolyzing water comes from wind and / or solar power generation.

[0014] According to the method described above, part of the heat generated by the reverse conversion process performed by the reverse conversion unit is obtained by performing heat recovery processing on the reverse conversion gas and / or the raw synthesis gas.

[0015] In the method described above, the temperature at which the inverse transformation unit performs the inverse transformation process is 400° C.-600° C.

[0016] According to the method described above, the content of carbon dioxide in the purified synthesis gas is 2v%-5v%.

[0017] According to the method described above, the water content in the crude methanol is 3wt%-30wt%.

[0018] In the method described above, the raw synthesis gas first recovers heat in a heat recovery unit and produces steam as a by-product, which includes: using the heat recovered in the heat recovery unit to perform heat exchange treatment on boiler water to obtain the steam.

[0019] In a second aspect, the present invention provides an apparatus for performing the method as described above, comprising a pretreatment unit, a gasification unit, a heat recovery unit, a desulfurization and decarbonization unit, a reverse conversion unit, a green electricity hydrogen production unit, a methanol synthesis unit, and a distillation unit;

[0020] The biomass outlet of the pretreatment unit is connected to the biomass inlet of the gasification unit, the synthesis gas outlet of the gasification unit is connected to the synthesis gas inlet of the heat recovery unit, the reverse conversion synthesis gas inlet of the heat recovery unit is connected to the reverse conversion synthesis gas outlet of the reverse conversion unit, the mixed gas outlet of the heat recovery unit is connected to the mixed gas inlet of the desulfurization and decarbonization unit, the purified synthesis gas outlet of the desulfurization and decarbonization unit is connected to the purified synthesis gas inlet of the methanol synthesis unit, the crude methanol outlet of the methanol synthesis unit is connected to the crude methanol inlet of the distillation unit, the carbon dioxide outlet of the desulfurization and decarbonization unit is connected to the carbon dioxide inlet of the reverse conversion unit, and the hydrogen inlet of the reverse conversion unit is connected to the hydrogen outlet of the green electricity hydrogen production unit.

[0021] In the device as described above, the heat recovery unit is a heat exchanger, which includes an inner shell, the synthesis gas outlet of the gasification unit is connected to the synthesis gas inlet of the inner shell, the reverse conversion synthesis gas inlet of the inner shell is connected to the reverse conversion synthesis gas outlet of the reverse conversion unit, and the mixed gas outlet of the inner shell is connected to the mixed gas inlet of the desulfurization and decarbonization unit.

[0022] In the device as described above, the desulfurization and decarbonization unit is an adsorption separator, the purified synthesis gas outlet of the adsorption separator is connected to the purified synthesis gas inlet of the methanol synthesis unit, and the carbon dioxide outlet of the adsorption separator is connected to the carbon dioxide inlet of the inverse conversion unit.

[0023] The method for producing green methanol with zero carbon emissions by coupling biomass gasification-green electricity hydrogen production-reverse conversion provided by the present invention couples biomass gasification, green electricity hydrogen production and reverse conversion, and allows the raw synthesis gas and the reverse conversion gas to enter the synthesis gas purification system together for heat recovery and desulfurization and decarbonization treatment. There is no need to add additional reverse conversion gas cooling and dehydration devices and reverse conversion gas CO2 separation devices, thus saving equipment investment and reducing energy consumption, thereby achieving efficient, energy-saving, zero-carbon or near-zero-carbon emission production of green methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 A diagram of a device for producing green methanol with zero carbon emissions by coupling biomass gasification-green electricity to hydrogen production-reverse transformation provided by the present invention.

[0026] Description of reference numerals:

[0027] 1-heat recovery unit; 2-desulfurization and decarbonization unit; 3-methanol synthesis unit; 4-reverse conversion unit; 5-purification system; 6-pretreatment unit; 7-gasification unit; 8-green electricity hydrogen production unit; 9-distillation unit. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In a first aspect, the present invention provides a method for producing green methanol with zero carbon emission by coupling biomass gasification-green electricity hydrogen production-reverse conversion, comprising the following steps:

[0030] 1) The raw biomass is sent to the gasification unit after pretreatment, and the crude synthesis gas is obtained after gasification;

[0031] 2) The crude synthesis gas is sent to the synthesis gas purification system. In the synthesis gas purification system, the crude synthesis gas first recovers heat in the heat recovery unit and produces steam as a by-product. After being cooled step by step, the crude synthesis gas is separated by gas and liquid to remove condensate and then enters the desulfurization and decarbonization unit to remove sulfur-containing compounds and CO2 to obtain purified synthesis gas;

[0032] 3) The CO2 separated by the desulfurization and decarbonization unit is sent to the inverse conversion unit to react with the H2 from the green power hydrogen production unit to generate CO and H2O;

[0033] 4) The reverse conversion gas from the reverse conversion unit is mixed with the crude synthesis gas and sent to the synthesis gas purification system. The heat is recovered in the heat recovery unit and the liquid is cooled and separated step by step. The unreacted CO2 is separated in the desulfurization and decarbonization unit and circulated back to the reverse conversion unit for further reaction.

[0034] 5) sending the purified synthesis gas from the synthesis gas purification system to the methanol synthesis unit to obtain crude methanol after reaction;

[0035] 6) The crude methanol is sent to the methanol distillation unit, and the product green methanol is obtained after distillation.

[0036] In the present invention, biomass gasification, green electricity hydrogen production and inverse transformation are coupled to prepare green methanol.

[0037] Specifically, in step 1), before gasifying the raw biomass, the step further includes: pre-treating the raw biomass, wherein the pre-treatment may include impurity removal, temperature carbonization, drying and water removal, cutting, baking, grinding, etc. The raw syngas includes carbon monoxide, hydrogen, carbon dioxide and water.

[0038] It can be understood that biomass is a widely existing and renewable resource, including agricultural waste, forestry residues, urban garbage, etc. By gasifying the pre-treated biomass to obtain crude synthesis gas, these biomass resources that may have been regarded as waste can be effectively utilized and converted into valuable energy products, greatly improving the value utilization of resources, helping to reduce dependence on fossil fuels, alleviate the energy crisis, and achieve the goals of sustainable development and recycling.

[0039] In step 2), the synthesis gas purification system includes a heat recovery unit and a desulfurization and decarbonization unit. The crude synthesis gas is subjected to heat recovery treatment in the heat recovery unit, that is, the crude synthesis gas is subjected to heat exchange with water vapor to increase the temperature of the water vapor, and the crude synthesis gas is cooled down after being cooled step by step, and after the condensate is removed by gas-liquid separation, the desulfurization and decarbonization treatment is carried out in the desulfurization and decarbonization unit to remove sulfur-containing compounds and carbon dioxide to obtain purified synthesis gas, wherein the purified synthesis gas contains carbon monoxide, hydrogen and a small amount of carbon dioxide.

[0040] In step 3), the carbon dioxide obtained by desulfurization and decarbonization in step 2) and hydrogen are subjected to reverse conversion treatment in a reverse conversion unit under the action of a catalyst to generate carbon monoxide and water. Therefore, the reverse conversion gas includes carbon monoxide, water, excess hydrogen and unreacted carbon dioxide. Among them, the hydrogen comes from the green electricity hydrogen production unit and is obtained by electrolyzing water.

[0041] In step 4), after the reverse conversion gas and the crude synthesis gas are mixed, the mixed gas enters a heat recovery unit for heat recovery treatment, the mixed gas is cooled step by step, and the condensate is removed by gas-liquid separation. Then, the mixed gas is desulfurized and decarbonized in a desulfurization and decarbonization unit to remove sulfur-containing compounds and carbon dioxide, and unreacted carbon dioxide is separated and circulated back to the reverse conversion unit to continue to participate in the reverse conversion reaction.

[0042] In step 5), the purified synthesis gas from the synthesis gas purification system enters the methanol synthesis unit for a methanol synthesis reaction, i.e., carbon monoxide and hydrogen in the purified synthesis gas react under the action of a catalyst to generate crude methanol, wherein the crude methanol contains methanol, water and a small amount of by-products, such as methane, dimethyl ether, ethanol, and propanol.

[0043] In step 6), the crude methanol is distilled into a methanol distillation unit to remove impurities therein, thereby obtaining a purer green methanol product.

[0044] The method for producing green methanol with zero carbon emissions by coupling biomass gasification-green electricity hydrogen production-reverse conversion provided by the present invention couples biomass gasification, green electricity hydrogen production and reverse conversion, and allows the raw synthesis gas and the reverse conversion gas to enter the synthesis gas purification system together for heat recovery and desulfurization and decarbonization treatment. There is no need to add additional reverse conversion gas cooling and dehydration devices and reverse conversion gas CO2 separation devices, thus saving equipment investment and reducing energy consumption, thereby achieving efficient, energy-saving, zero-carbon or near-zero-carbon emission production of green methanol.

[0045] In some embodiments of the present invention, the electric energy used by the green electricity hydrogen production unit for electrolyzing water comes from wind and / or solar power generation.

[0046] The electrolysis of water to produce hydrogen in the present invention is a very clean way of producing hydrogen, which does not produce harmful pollutants, only produces hydrogen and oxygen, and is a relatively environmentally friendly way. Moreover, wind energy and / or solar energy, as the source of electricity for the electrolysis of water to produce hydrogen, are inexhaustible renewable energy sources, and do not produce greenhouse gases and pollutants during their use, which helps to reduce dependence on traditional fossil energy and carbon emissions. Combining wind energy and / or solar energy with the electrolysis of water to produce hydrogen can achieve comprehensive utilization and optimal allocation of energy, and improve energy utilization.

[0047] In some embodiments of the present invention, part of the heat generated by the reverse conversion process performed by the reverse conversion unit is obtained by performing heat recovery processing on the reverse conversion gas and / or the raw synthesis gas.

[0048] In the present invention, the heat obtained by heat recovery treatment of reverse conversion gas and / or crude synthesis gas is used for reverse conversion treatment, which can fully utilize the heat and reduce the consumption of external energy. It can not only reduce production costs but also improve the comprehensive utilization rate of energy, which is in line with the concept of sustainable development.

[0049] In some embodiments of the present invention, the temperature of the inverse transformation process is 400°C-600°C, for example, it can be 400°C, 450°C, 500°C, 550°C, 600°C or a range consisting of any two thereof.

[0050] The temperature of the reverse conversion treatment in the present invention is within an appropriate range, which is conducive to the forward progress of the reverse conversion reaction, allowing carbon dioxide and hydrogen to fully react at this temperature to generate carbon monoxide and water, reducing carbon emissions and avoiding waste of resources caused by excessively high temperatures.

[0051] In some embodiments of the present invention, the content of carbon dioxide in the purified synthesis gas is 2v%-5v%, for example, it can be 2v%, 3v%, 3.5v%, 4v%, 5v% or the range of any two thereof.

[0052] The content of carbon dioxide in the purified synthesis gas of the present invention is 2v%-5v%, preferably 2v%-2.5v%. The content of carbon dioxide in the purified synthesis gas is in a relatively low range. Since carbon dioxide reacts with hydrogen to generate one part of methanol and one part of water at the same time, the low carbon dioxide content can make the water content in the crude methanol lower, thereby reducing the energy consumption required for methanol distillation treatment and improving the purity of the final green methanol.

[0053] In some embodiments of the present invention, the water content in crude methanol is 3wt%-30wt%, for example, it can be 3wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt% or any two thereof.

[0054] The water content in the crude methanol of the present invention is 3wt%-30wt%, preferably 3wt%-8wt%. The water content in the crude methanol is in a relatively low range, thereby reducing the energy consumption required for methanol distillation treatment and improving the purity of the final green methanol.

[0055] In some embodiments of the present invention, the raw synthesis gas is firstly heat recovered in a heat recovery unit and steam is produced as a by-product, including: using the heat recovered in the heat recovery unit to perform heat exchange treatment on boiler water to obtain the steam.

[0056] In the present invention, the heat recovered from the heat recovery unit is used to perform heat exchange treatment on boiler water, and steam is produced as a by-product. The heat obtained from the heat recovery treatment can be fully utilized to achieve the purpose of energy saving and consumption reduction.

[0057] In a second aspect, the present invention provides a device for performing the above production method, such as Figure 1 As shown, it includes a pretreatment unit 6, a gasification unit 7, a heat recovery unit 1, a desulfurization and decarbonization unit 2, a reverse conversion unit 4, a green electricity hydrogen production unit 8, a methanol synthesis unit 3, and a distillation unit 9;

[0058] The biomass outlet of the pretreatment unit 6 is connected to the biomass inlet of the gasification unit 7, the synthesis gas outlet of the gasification unit 7 is connected to the synthesis gas inlet of the heat recovery unit 1, the reverse conversion synthesis gas inlet of the heat recovery unit 1 is connected to the reverse conversion synthesis gas outlet of the reverse conversion unit 4, the mixed gas outlet of the heat recovery unit 1 is connected to the mixed gas inlet of the desulfurization and decarbonization unit 2, the purified synthesis gas outlet of the desulfurization and decarbonization unit 2 is connected to the purified synthesis gas inlet of the methanol synthesis unit 3, the crude methanol outlet of the methanol synthesis unit 3 is connected to the crude methanol inlet of the distillation unit 9, the carbon dioxide outlet of the desulfurization and decarbonization unit 2 is connected to the carbon dioxide inlet of the reverse conversion unit 4, and the hydrogen inlet of the reverse conversion unit 4 is connected to the hydrogen outlet of the green electricity hydrogen production unit 8.

[0059] In the device for producing green methanol with zero carbon emissions by coupling biomass gasification-green electricity hydrogen production-reverse conversion of the present invention, the biomass is pretreated by the pretreatment unit 6 to obtain pretreated biomass, the pretreated biomass is output through the biomass outlet of the pretreatment unit 6, enters the gasification unit 7 through the biomass inlet of the gasification unit 7 for gasification treatment to obtain crude synthesis gas, the crude synthesis gas is output through the synthesis gas outlet of the gasification unit 7, enters the heat recovery unit 1 through the synthesis gas inlet of the heat recovery unit 1 to exchange heat with water vapor, and steam is produced as a by-product. The crude synthesis gas is cooled step by step to remove condensate, and is output through the mixed gas outlet of the heat recovery unit 1, and enters the desulfurization and decarbonization unit 2 through the mixed gas inlet of the desulfurization and decarbonization unit 2 for desulfurization and decarbonization treatment to remove sulfur-containing compounds and carbon dioxide, and obtain purified synthesis gas. Carbon dioxide is output through the carbon dioxide outlet of the desulfurization and decarbonization unit 2, and enters the inverse conversion unit 4 through the carbon dioxide inlet of the inverse conversion unit 4. The hydrogen obtained by electrolyzing water in the green power hydrogen production unit 8 (the electric energy for the electrolysis treatment comes from solar energy) is output through the hydrogen outlet of the green power hydrogen production unit 8, and enters the inverse conversion unit 4 through the hydrogen inlet of the inverse conversion unit 4. In the inverse conversion unit 4, carbon dioxide and hydrogen are subjected to inverse conversion treatment to obtain inverse conversion gas. The inverse conversion gas is output through the inverse conversion gas outlet of the inverse conversion unit 4, and then enters the heat recovery unit 1 through the inverse conversion gas inlet of the heat recovery unit 1, and forms a mixed gas with the crude synthesis gas, and heat exchange is performed to produce steam as a by-product. The mixed gas is cooled down after step-by-step cooling, and after the condensate is removed by gas-liquid separation, it is output through the mixed gas outlet of the heat recovery unit 1, and enters the desulfurization and decarbonization unit 2 through the mixed gas inlet of the desulfurization and decarbonization unit 2 for desulfurization and decarbonization treatment, removing sulfur-containing compounds and carbon dioxide, and obtaining purified synthesis gas. The purified synthesis gas is outputted through the purified synthesis gas outlet of the desulfurization and decarbonization unit 2, and then enters the methanol synthesis unit 3 through the purified synthesis gas inlet of the methanol synthesis unit 3 for methanol synthesis reaction to obtain crude methanol. The crude methanol is outputted through the crude methanol outlet of the methanol synthesis unit 3, and enters the distillation unit 9 through the crude methanol inlet of the distillation unit 9 for distillation treatment to obtain pure product green methanol.

[0060] The device for producing green methanol with zero carbon emissions by coupling biomass gasification-green electricity hydrogen production-reverse conversion provided by the present invention can realize the coupling of biomass gasification, green electricity hydrogen production and reverse conversion, and make the raw synthesis gas and the reverse conversion gas enter the synthesis gas purification system together for heat recovery and desulfurization and decarbonization treatment, without adding additional reverse conversion gas cooling and dehydration devices and reverse conversion gas CO2 separation devices, saving equipment investment and reducing energy consumption, thereby realizing efficient, energy-saving, zero-carbon or near-zero-carbon emission production of green methanol.

[0061] In some embodiments of the present invention, the heat recovery unit 1 is a heat exchanger, which includes an inner shell, the synthesis gas outlet of the gasification unit 7 is connected to the synthesis gas inlet of the inner shell, the reverse conversion synthesis gas inlet of the inner shell is connected to the reverse conversion synthesis gas outlet of the reverse conversion unit 4, and the mixed gas outlet of the inner shell is connected to the mixed gas inlet of the desulfurization and decarbonization unit 2.

[0062] The heat recovery unit in the present invention may specifically be a heat exchanger, which includes an inner shell and an outer shell. The raw synthesis gas is output through the synthesis gas outlet of the gasification unit 7, enters the heat exchanger through the synthesis gas inlet of the heat exchanger, and exchanges heat with water vapor to produce steam as a byproduct. The outer shell is used to contain water vapor.

[0063] The reverse conversion gas is outputted through the reverse conversion gas outlet of the reverse conversion unit 4, and then enters the inner shell through the reverse conversion gas inlet of the inner shell to form a mixed gas with the crude synthesis gas, perform heat exchange, and produce steam as a by-product.

[0064] The mixed gas is outputted through the mixed gas outlet of the inner shell, and enters the desulfurization and decarbonization unit 2 through the mixed gas inlet of the desulfurization and decarbonization unit 2 for desulfurization and decarbonization treatment to remove sulfur-containing compounds and carbon dioxide, and obtain purified synthesis gas.

[0065] The heat recovery unit in the present invention is a heat exchanger, and the heat exchanger includes an inner shell, which can effectively recover waste heat and fully utilize the heat obtained by heat recovery processing to achieve the purpose of energy saving and consumption reduction.

[0066] In some embodiments of the present invention, the desulfurization and decarbonization unit 2 is an adsorption separator, the purified synthesis gas outlet of the adsorption separator is connected to the purified synthesis gas inlet of the methanol synthesis unit 3, and the carbon dioxide outlet of the adsorption separator is connected to the carbon dioxide inlet of the inversion unit 4.

[0067] The desulfurization and decarbonization unit 2 in the present invention can specifically be an adsorption separator. The purified synthesis gas is output through the purified synthesis gas outlet of the adsorption separator, and then enters the methanol synthesis unit 3 through the purified synthesis gas inlet of the methanol synthesis unit 3 to carry out methanol synthesis reaction to obtain crude methanol.

[0068] The carbon dioxide is outputted through the carbon dioxide outlet of the adsorption separator, enters the inverse conversion unit 4 through the carbon dioxide inlet of the inverse conversion unit 4, and is inversely converted with the hydrogen input from the green electricity hydrogen production unit 8 to obtain inverse conversion gas.

[0069] The desulfurization and decarbonization unit in the present invention is an adsorption separator, which can efficiently remove sulfur-containing compounds and carbon dioxide.

[0070] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0071] Example 1

[0072] The device of this embodiment is a device for producing green methanol with zero carbon emission by coupling biomass gasification-green electricity hydrogen production-reverse conversion, such as Figure 1 As shown, it includes a heat recovery unit 1 (heat exchanger); a desulfurization and decarbonization unit 2 (adsorption separator); a methanol synthesis unit 3 (first reactor); a reverse conversion unit 4 (second reactor); a purification system 5; a pretreatment unit 6 (pretreatment unit); a gasification unit 7 (gasifier); a green electricity hydrogen production unit 8 (electrolyzer); and a distillation unit 9 (distillation tower).

[0073] Among them, the biomass outlet of the pretreatment unit 6 is connected to the biomass inlet of the gasification unit 7, the synthesis gas outlet of the gasification unit 7 is connected to the synthesis gas inlet of the heat recovery unit 1, the reverse conversion synthesis gas inlet of the heat recovery unit 1 is connected to the reverse conversion synthesis gas outlet of the reverse conversion unit 4, the mixed gas outlet of the heat recovery unit 1 is connected to the mixed gas inlet of the desulfurization and decarbonization unit 2, the purified synthesis gas outlet of the desulfurization and decarbonization unit 2 is connected to the purified synthesis gas inlet of the methanol synthesis unit 3, the crude methanol outlet of the methanol synthesis unit 3 is connected to the crude methanol inlet of the distillation unit 9, the carbon dioxide outlet of the desulfurization and decarbonization unit 2 is connected to the carbon dioxide inlet of the reverse conversion unit 4, and the hydrogen inlet of the reverse conversion unit 4 is connected to the hydrogen outlet of the water electrolysis unit 8.

[0074] Specifically, the biomass is pretreated by the pretreatment unit 6 to obtain pretreated biomass, which is output through the biomass outlet of the pretreatment unit 6, and enters the gasification unit 7 through the biomass inlet of the gasification unit 7 for gasification treatment to obtain crude synthesis gas, which is output through the synthesis gas outlet of the gasification unit 7, and enters the heat recovery unit 1 through the synthesis gas inlet of the heat recovery unit 1 to exchange heat with boiler water, and produce steam as a by-product. The crude synthesis gas is cooled step by step to remove condensate, and then output through the mixed gas outlet of the heat recovery unit 1, and enters the desulfurization and decarbonization unit 2 through the mixed gas inlet of the desulfurization and decarbonization unit 2 for desulfurization and decarbonization treatment, removing sulfur-containing compounds and carbon dioxide, and obtaining purified synthesis gas. The content of carbon dioxide in the purified synthesis gas is 2.5v%. Carbon dioxide is output through the carbon dioxide outlet of the desulfurization and decarbonization unit 2, and enters the inverse conversion unit 4 through the carbon dioxide inlet of the inverse conversion unit 4. The hydrogen obtained by electrolyzing water in the green power hydrogen production unit 8 (the electric energy for the electrolysis treatment comes from solar energy) is output through the hydrogen outlet of the green power hydrogen production unit 8, and enters the inverse conversion unit 4 through the hydrogen inlet of the inverse conversion unit 4. In the inverse conversion unit 4, carbon dioxide and hydrogen are subjected to inverse conversion treatment to obtain inverse conversion gas. The inverse conversion gas is output through the inverse conversion gas outlet of the inverse conversion unit 4, and then enters the heat recovery unit 1 through the inverse conversion gas inlet of the heat recovery unit 1, and forms a mixed gas with the crude synthesis gas, and performs heat exchange with boiler water to produce steam as a byproduct. The mixed gas is cooled down after step-by-step cooling, and after the condensate is removed by gas-liquid separation, it is output through the mixed gas outlet of the heat recovery unit 1, and enters the desulfurization and decarbonization unit 2 through the mixed gas inlet of the desulfurization and decarbonization unit 2 for desulfurization and decarbonization treatment, removing sulfur-containing compounds and carbon dioxide, and obtaining purified synthesis gas. The heat of the reverse conversion treatment is obtained by heat recovery treatment of the mixed gas, and the temperature of the reverse conversion treatment is 500°C. The purified synthesis gas is output through the purified synthesis gas outlet of the desulfurization and decarbonization unit 2, and then enters the methanol synthesis unit 3 through the purified synthesis gas inlet of the methanol synthesis unit 3 for methanol synthesis reaction to obtain crude methanol, wherein the water content in the crude methanol is 9wt%, and the crude methanol is output through the crude methanol outlet of the methanol synthesis unit 3, and enters the distillation unit 9 through the crude methanol inlet of the distillation unit 9 for distillation treatment to obtain pure product green methanol.

[0075] For every ton of green methanol produced, the amount of steam and circulating water consumed by the distillation unit is shown in Table 1.

[0076] Example 2

[0077] The apparatus and method for producing green methanol in Example 2 are basically the same as those in Example 1, except that the content of carbon dioxide in the purified synthesis gas is changed to 2% by weight, and the content of water in the crude methanol is changed to 8.8% by weight.

[0078] Example 3

[0079] The apparatus and method for producing green methanol in Example 3 are basically the same as those in Example 1, except that the content of carbon dioxide in the purified synthesis gas is changed to 5% by volume, and the content of water in the crude methanol is changed to 12% by weight.

[0080] Comparative Example 1

[0081] The apparatus and method for producing green methanol in Comparative Example 1 are basically the same as those in Example 1, except that no reverse conversion unit 4 is provided, no reverse conversion gas is obtained, and only the crude synthesis gas is subjected to heat recovery treatment and desulfurization and decarbonization treatment.

[0082] Table 1

[0083] Group Steam consumption of distillation unit / ton Circulating water consumption of distillation unit / ton Example 1 0.9 54 Example 2 0.89 53 Example 3 0.93 56 Comparative Example 1 1.1 66

[0084] As can be seen from Table 1, the method for producing green methanol with zero carbon emissions by coupling biomass gasification-green electricity hydrogen production-reverse transformation provided by the present invention couples biomass gasification, green electricity hydrogen production and reverse transformation, and allows the raw synthesis gas and the reverse transformation gas to enter the synthesis gas purification system together for heat recovery and desulfurization and decarbonization treatment. There is no need to add additional reverse transformation gas cooling and dehydration devices and reverse transformation gas CO2 separation devices, which saves equipment investment and reduces energy consumption, thereby achieving efficient, energy-saving, zero-carbon or near-zero-carbon emission production of green methanol.

[0085] From the comparison between Examples 1-3 and Comparative Example 1, it can be seen that the method for producing green methanol with zero carbon emissions by coupling biomass gasification-green electricity hydrogen production-reverse transformation provided by the present invention couples biomass gasification, green electricity hydrogen production and reverse transformation, and allows the crude synthesis gas and the reverse transformation gas to enter the synthesis gas purification system together for heat recovery and desulfurization and decarbonization treatment, which can reduce the consumption of steam and circulating water in the distillation unit.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing green methanol with zero carbon emission by coupling biomass gasification-green electricity hydrogen production-reverse conversion, characterized in that: The following steps are involved: 1) The raw biomass is sent to the gasification unit after pretreatment, and the crude synthesis gas is obtained after gasification; 2) sending the crude synthesis gas to a synthesis gas purification system, in which the crude synthesis gas first recovers heat in a heat recovery unit and produces steam as a by-product, is cooled step by step, and then enters a desulfurization and decarbonization unit to remove sulfur-containing compounds and CO2 to obtain purified synthesis gas after gas-liquid separation and removal of condensate. 3) The CO2 separated by the desulfurization and decarbonization unit is sent to the inverse conversion unit to react with the H2 from the green electricity hydrogen production unit to generate CO and H2O; 4) The reverse conversion gas from the reverse conversion unit is mixed with the crude synthesis gas and sent to the synthesis gas purification system together, and the heat is recovered in the heat recovery unit and the liquid is cooled and separated step by step, and the unreacted CO2 is separated in the desulfurization and decarbonization unit and circulated back to the reverse conversion unit for further reaction; 5) sending the purified synthesis gas from the synthesis gas purification system to a methanol synthesis unit to obtain crude methanol after reaction; 6) The crude methanol is sent to a methanol distillation unit, and green methanol is obtained as a product after distillation.

2. The method according to claim 1, characterized in that The electric energy used by the green electricity hydrogen production unit for electrolyzing water comes from wind and / or solar power generation.

3. The method according to claim 1 or 2, characterized in that: Part of the heat of the reverse conversion process performed by the reverse conversion unit is obtained by performing heat recovery processing on the reverse conversion gas and / or the raw synthesis gas.

4. The method according to any one of claims 1 to 3, characterized in that: The inverse conversion unit performs inverse conversion at a temperature of 400°C-600°C.

5. The method according to any one of claims 1 to 4, characterized in that: The content of carbon dioxide in the purified synthesis gas is 2v%-5v%.

6. The method according to any one of claims 1 to 5, characterized in that: The water content in the crude methanol is 3wt%-30wt%.

7. The method according to any one of claims 1 to 6, characterized in that: The raw synthesis gas first recovers heat in a heat recovery unit and produces steam as a by-product, including: using the heat recovered in the heat recovery unit to perform heat exchange treatment on boiler water to obtain the steam.

8. A device for executing the method according to any one of claims 1 to 7, characterized in that: It includes pretreatment unit, gasification unit, heat recovery unit, desulfurization and decarbonization unit, reverse conversion unit, green electricity hydrogen production unit, methanol synthesis unit and distillation unit; The biomass outlet of the pretreatment unit is connected to the biomass inlet of the gasification unit, the synthesis gas outlet of the gasification unit is connected to the synthesis gas inlet of the heat recovery unit, the reverse conversion synthesis gas inlet of the heat recovery unit is connected to the reverse conversion synthesis gas outlet of the reverse conversion unit, the mixed gas outlet of the heat recovery unit is connected to the mixed gas inlet of the desulfurization and decarbonization unit, the purified synthesis gas outlet of the desulfurization and decarbonization unit is connected to the purified synthesis gas inlet of the methanol synthesis unit, the crude methanol outlet of the methanol synthesis unit is connected to the crude methanol inlet of the distillation unit, the carbon dioxide outlet of the desulfurization and decarbonization unit is connected to the carbon dioxide inlet of the reverse conversion unit, and the hydrogen inlet of the reverse conversion unit is connected to the hydrogen outlet of the green electricity hydrogen production unit.

9. The device according to claim 8, characterized in that The heat recovery unit is a heat exchanger, which includes an inner shell. The synthesis gas outlet of the gasification unit is connected to the synthesis gas inlet of the inner shell, the reverse conversion synthesis gas inlet of the inner shell is connected to the reverse conversion synthesis gas outlet of the reverse conversion unit, and the mixed gas outlet of the inner shell is connected to the mixed gas inlet of the desulfurization and decarbonization unit.

10. The device according to claim 8 or 9, characterized in that The desulfurization and decarbonization unit is an adsorption separator, the purified synthesis gas outlet of the adsorption separator is connected to the purified synthesis gas inlet of the methanol synthesis unit, and the carbon dioxide outlet of the adsorption separator is connected to the carbon dioxide inlet of the inverse conversion unit.

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