Method for preparing methanol from carbon dioxide by coupling biomass direct combustion with wind, light, green and hydrogen

Abstract

The invention discloses a method for preparing methanol from carbon dioxide by coupling biomass direct combustion with wind, light, green and hydrogen. The method comprises the following steps: feeding biomass into a biomass boiler through a screw feeder and a trestle for direct combustion to obtain flue gas with high carbon dioxide content; the flue gas is treated to generate carbon dioxide gas with the pressure ranging from 1.4 MPaG to 1.6 MPaG; the method comprises the following steps: mixing carbon dioxide gas and hydrogen according to a molar ratio of about 1: 3, and compressing the mixture into 9.0 MPaG synthesis gas through a synthesis gas compressor; the synthesis gas flows to a gas-gas heat exchanger for heat exchange and temperature rise, and then is introduced into a methanol synthesis tower to form a material; the materials are subjected to heat exchange and cooling through a gas-gas heat exchanger and then flow to a high-pressure flash tank to be separated to form first gas and first liquid; the first liquid flows to a low-pressure flash tank to be separated to form second gas and second liquid conveyed to a crude methanol rectifying tower; separating and purifying the crude methanol in a rectifying tower to form methanol, fusel and overhead gas flowing to the biomass boiler; the utilization rate of the biomass carbon is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of methanol preparation, and in particular to a method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind, solar and green hydrogen. Background Art

[0002] Carbon neutrality refers to the total amount of carbon dioxide or greenhouse gas emissions generated directly or indirectly within a certain period of time. Through afforestation, energy conservation and emission reduction, etc., the carbon dioxide or greenhouse gas emissions generated by itself can be offset to achieve positive and negative offsets; wind and solar power generation, electrolysis to produce hydrogen and methanol are of great significance to achieving carbon neutrality.

[0003] With the rapid development of renewable energy, the scale of hydrogen production from wind and solar power generation is huge, and coupling CO2 to produce green methanol has become one of the best decarbonization fuels. Biomass is a renewable energy source, and biomass energy is considered to be one of the potential green alternative energy sources. Compared with traditional CO to methanol, CO2 to methanol has higher requirements for catalysts, but traditional CO to methanol has high carbon emissions, which is not conducive to carbon neutrality.

[0004] Therefore, how to provide a method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind, solar and green hydrogen to improve the above-mentioned drawbacks is a technical problem that technical personnel in this field currently need to solve. Summary of the invention

[0005] The purpose of the present invention is to provide a method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind, solar and green hydrogen. The reaction raw materials are only carbon dioxide and hydrogen. Methanol is synthesized using a special CO2 hydrogenation catalyst. The top gas of the crude methanol distillation tower is returned to the biomass boiler and reconverted into carbon dioxide, thereby improving the utilization rate of biomass carbon, improving the atomic economy of the system, avoiding the waste of resources caused by a high carbon abandonment rate, and ensuring that the produced methanol meets the European green methanol certification standards.

[0006] To achieve the above object, the present invention provides a method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind and solar green hydrogen, comprising:

[0007] The biomass is fed into the biomass boiler through a screw feeder and a trestle and directly burned to obtain flue gas with a high proportion of carbon dioxide;

[0008] Treating the flue gas to generate carbon dioxide gas at a pressure of 1.4-1.6MPaG;

[0009] The carbon dioxide gas and hydrogen gas are mixed in a molar ratio of about 1:3 and compressed into a synthesis gas of 9.0 MPaG by a synthesis gas compressor;

[0010] The synthesis gas is passed to a gas-to-gas heat exchanger for heat exchange and then passed into a methanol synthesis tower to form a material;

[0011] The material is cooled by heat exchange in a gas-to-gas heat exchanger and then flows to a high-pressure flash tank for separation to form a first gas and a first liquid;

[0012] The first liquid is passed to a low-pressure flash tank for separation to form a second gas and a second liquid which is conveyed to a crude methanol distillation tower;

[0013] The crude methanol is separated and purified by a crude methanol distillation tower to form methanol, fusel alcohols and overhead gas which is circulated to the biomass boiler.

[0014] Preferably, the step of circulating the first liquid to a low-pressure flash tank for separation to form a second gas and conveying the second liquid to a crude methanol distillation tower further comprises:

[0015] The second gas, which contains about 60% carbon dioxide and 35% hydrogen, is transported to the biomass boiler for recycling.

[0016] Preferably, the step of separating and purifying by a crude methanol rectification tower to form methanol, fusel alcohols and overhead gas flowing to the biomass boiler further comprises:

[0017] The fusel alcohol is directed to the fusel alcohol tank and then circulated to the biomass boiler for recycling.

[0018] Preferably, after the step of separating and purifying by a crude methanol rectification tower to form methanol, fusel alcohols and overhead gas flowing to a biomass boiler, the step further includes:

[0019] Collect the methanol in a methanol tank;

[0020] The methanol flowing along the methanol tank to the loading and unloading platform is loaded according to a preset loading amount to form a methanol product;

[0021] The methanol-containing tail gas discharged from the loading and unloading platform and the methanol tank is recovered.

[0022] Preferably, before the step of feeding the biomass into the biomass boiler through a screw feeder and a trestle for direct combustion to obtain flue gas with a high proportion of carbon dioxide, the step further includes:

[0023] The biomass is crushed and iron is removed.

[0024] Preferably, the steps of feeding the biomass into the biomass boiler through a screw feeder and a trestle for direct combustion to obtain flue gas with a high proportion of carbon dioxide are specifically as follows:

[0025] Dust removal of flue gas to generate mixed gas;

[0026] Purify the mixed gas to remove impurities such as sulfides, nitrogen oxides, and particulate matter;

[0027] Capturing carbon dioxide gas in the mixed gas by amine liquid;

[0028] The carbon dioxide gas is released at a desorption temperature of 180°C or less and then compressed to 1.4-1.6MPaG by a carbon dioxide compressor.

[0029] Preferably, the biomass is fed into the biomass boiler through a screw feeder and a trestles for direct combustion to obtain flue gas with a high proportion of carbon dioxide and high-temperature and high-pressure steam to flow to the steam turbine for power generation.

[0030] Preferably, the step of treating the flue gas to generate carbon dioxide gas with a pressure of 1.4-1.6 MPaG and the step of mixing the carbon dioxide gas and hydrogen at a molar ratio of about 1:3 and compressing the mixture to a synthesis gas with a pressure of 9.0 MPaG by a synthesis gas compressor further includes:

[0031] Power is supplied to the electrolyzer through wind and solar power stations and / or the downstream grid to electrolyze water to generate hydrogen and oxygen;

[0032] The hydrogen is directly delivered or pressurized by a hydrogen compressor and then delivered to the synthesis gas compressor;

[0033] Oxygen is transported to the biomass boiler to assist combustion.

[0034] Preferably, the steps of passing the synthesis gas to a gas-to-gas heat exchanger for heat exchange and then passing the synthesis gas into a methanol synthesis tower to form a material are specifically as follows:

[0035] The synthesis gas reacts in the methanol synthesis tower to generate materials, and the second shell side of the methanol synthesis tower is provided with a pipeline connected to the steam drum of the synthesis tower to form a steam-water circulation pipeline for absorbing reaction heat;

[0036] The steam generated in the steam-water circulation pipeline is transported to the steam turbine for power generation.

[0037] Preferably, the step of cooling the material by heat exchange in a gas-to-gas heat exchanger and then circulating it to a high-pressure flash tank for separation to form a first gas and a first liquid further includes:

[0038] The first gas containing a relatively high proportion of hydrogen is transported to the circulating gas compressor for compression and then merged into the outlet of the synthesis gas compressor.

[0039] Preferably, the step of cooling the material by heat exchange in a gas-to-gas heat exchanger and then circulating it to a high-pressure flash tank for separation to form the first gas and the first liquid is specifically as follows:

[0040] The material is cooled by heat exchange in a gas-to-gas heat exchanger, and then enters a lithium bromide unit to reduce the temperature to 40° C., and then flows to a high-pressure flash tank for separation to form a first gas and a first liquid.

[0041] The method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind and solar green hydrogen provided by the present invention has at least the following beneficial effects:

[0042] Carbon dioxide gas is prepared by the combustion of biomass, and the carbon dioxide gas and hydrogen are mixed and pressurized in a molar ratio of about 1:3, and then heated by heat exchange in a gas-to-gas heat exchanger and circulated to a methanol synthesis tower to form materials. Methanol is then prepared through a high-pressure flash tank, a low-pressure flash tank, and a crude methanol distillation tower. The reaction raw materials are only carbon dioxide and hydrogen. Methanol is synthesized using a special CO2 hydrogenation catalyst. The top gas of the crude methanol distillation tower is circulated to a biomass boiler and reconverted into carbon dioxide, which improves the utilization rate of biomass carbon, improves the atomic economy of the system, avoids waste of resources caused by a high carbon abandonment rate, and ensures that the produced methanol meets the European green methanol certification standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0044] Figure 1 This is a schematic diagram of the structure of methanol production provided by an embodiment of the present invention.

[0045] in:

[0046] 1-Biomass boiler, 2-Bag dust removal device, 3-Carbon dioxide pre-treatment device, 4-Carbon dioxide capture device, 5-Carbon dioxide post-treatment device, 6-Carbon dioxide compressor, 7-Carbon dioxide storage tank, 8-Steam turbine, 9-Wind and solar power station, 10-Electrolyzer, 11-Hydrogen storage tank, 12-Hydrogen compressor, 13-Synthesis gas compressor, 14-Circulating gas compressor, 15-Gas heat exchanger, 16-Methanol synthesis tower, 17-Synthesis tower steam drum, 18-Lithium bromide Unit, 19-high-pressure flash tank, 20-low-pressure flash tank, 21-crude methanol tank, 22-crude methanol distillation tower, 23-methanol tank, 24-loading and unloading platform, 25-fusel tank, 26-oil and gas recovery device, 27-first pipeline, 28-second pipeline, 29-third pipeline, 30-fourth pipeline, 31-third pipeline, 32-fourth pipeline, 100-carbon dioxide production system, 200-hydrogen production system, 300-methanol synthesis system, 400-methanol distillation system. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0048] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0049] In the description of the present invention, it is necessary to understand that the orientations or positional relationships indicated by the terms "top", "bottom", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the position or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0050] The purpose of the present invention is to provide a method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind-solar green hydrogen. The reaction raw materials are only carbon dioxide and hydrogen. Methanol is synthesized using a special CO2 hydrogenation catalyst. The top gas of the crude methanol distillation tower 22 is returned to the biomass boiler 1 and then reconverted into carbon dioxide, thereby improving the utilization rate of biomass carbon, improving the atomic economy of the system, avoiding waste of resources caused by a high carbon abandonment rate, and ensuring that the produced methanol meets the European green methanol certification standards.

[0051] See also Figure 1 To achieve the above-mentioned purpose, the present invention provides a method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind-solar green hydrogen, comprising: feeding biomass into a biomass boiler 1 through a screw feeder and a trestle for direct combustion to obtain flue gas with a relatively high proportion of carbon dioxide; treating the flue gas to generate carbon dioxide gas with a pressure of 1.4-1.6 MPaG; mixing carbon dioxide gas and hydrogen in a molar ratio of about 1:3 and compressing the mixture to a synthesis gas of 9.0 MPaG through a synthesis gas compressor 13; passing the synthesis gas to a gas-to-gas heat exchanger 15 for heat exchange and temperature increase, and then passing the synthesis gas to a methanol synthesis tower 16 to form a material; passing the material to a high-pressure flash tank 19 for separation to form a first gas and a first liquid after heat exchange and temperature reduction through the gas-to-gas heat exchanger 15; passing the first liquid to a low-pressure flash tank 20 for separation to form a second gas and a second liquid transported to a crude methanol distillation tower 22; and separating and purifying through the crude methanol distillation tower 22 to form methanol, fusel alcohols and a tower top gas that flows to the biomass boiler 1.

[0052] Carbon dioxide gas is prepared by the combustion of biomass, and the carbon dioxide gas and hydrogen are mixed and pressurized in a molar ratio of about 1:3, and the mixture is heated by heat exchange in a gas-to-gas heat exchanger 15 and then circulated to a methanol synthesis tower 16 to form a material. Methanol is then prepared through a high-pressure flash tank 19, a low-pressure flash tank 20, and a crude methanol distillation tower 22. The reaction raw materials are only carbon dioxide and hydrogen. Methanol is synthesized using a special CO2 hydrogenation catalyst. The top gas of the crude methanol distillation tower 22 is circulated to a biomass boiler 1 and then converted back into carbon dioxide, thereby improving the utilization rate of biomass carbon, improving the atomic economy of the system, avoiding waste of resources caused by a high carbon abandonment rate, and ensuring that the prepared methanol meets the European green methanol certification standards.

[0053] Among them, it should be noted that the method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind-solar green hydrogen requires the use of a methanol production system, which includes a carbon dioxide production system 100, a hydrogen production system 200, a methanol synthesis system 300 and a methanol distillation system 400. The carbon dioxide production system 100 includes a biomass boiler 1 for burning biomass to generate flue gas, and a first processing component for treating the flue gas to obtain carbon dioxide. The hydrogen production system 200 is capable of preparing hydrogen. The methanol synthesis system 300 includes a synthesis gas compressor 13 for receiving carbon dioxide and hydrogen to generate synthesis gas, a second processing component connected to the synthesis gas compressor 13 to receive the synthesis gas and convert it into a material, and a crude methanol tank 21 connected to the second processing component to receive the material. The methanol distillation system 400 includes a crude methanol distillation tower 22 connected to the crude methanol tank 21, and the crude methanol distillation tower 22 is provided with a first outlet for discharging methanol and a second outlet for discharging top gas, and the second outlet is connected to the biomass boiler 1 through a first pipeline 27.

[0054] In this embodiment, the biomass boiler 1 is provided with a first outlet for discharging flue gas, a second outlet for discharging steam and a third outlet for discharging ash, the second outlet is connected to a steam turbine 8 through a first pipeline, and the steam turbine 8 can generate electricity through steam; the first processing component includes a bag dust removal device 2, a carbon dioxide pre-treatment device 3, a carbon dioxide capture device 4, a carbon dioxide post-treatment device 5, a carbon dioxide compressor 6, and a carbon dioxide storage tank 7 connected in sequence. Specifically, the inlet of the bag dust removal device 2 is connected to the first outlet, and the bag dust removal device 2 is provided with a third outlet for gas outflow. a channel and a second channel for fly ash discharge; the inlet of the carbon dioxide pre-treatment device 3 is connected to the first channel; the inlet of the carbon dioxide capture device 4 is connected to the outlet of the carbon dioxide pre-treatment device 3; the inlet of the carbon dioxide post-treatment device 5 is connected to the outlet of the carbon dioxide capture device 4; the inlet of the carbon dioxide compressor 6 is connected to the outlet of the carbon dioxide post-treatment device 5 through a third pipeline 29, and the outlet of the carbon dioxide compressor 6 is connected to the inlet of the synthesis gas compressor 13 through a fourth pipeline 30; the inlet of the carbon dioxide storage tank 7 is connected to the fourth pipeline 30, and the outlet of the carbon dioxide storage tank 7 is connected to the third pipeline 29.

[0055] Among them, before the step of feeding the biomass into the biomass boiler 1 through the screw feeder and the trestle for direct combustion to obtain flue gas with a high proportion of carbon dioxide, the step also includes: crushing and removing iron from the biomass.

[0056] The specific steps of feeding the biomass into the biomass boiler 1 through a screw feeder and a trestle for direct combustion to obtain flue gas with a high proportion of carbon dioxide are: removing dust from the flue gas to generate a mixed gas; purifying the mixed gas to remove impurities such as sulfides, nitrogen oxides, particulate matter, etc.; capturing carbon dioxide gas in the mixed gas by amine liquid; releasing the carbon dioxide gas at a desorption temperature of less than or equal to 180°C and compressing it to 1.4-1.6MPaG through a carbon dioxide compressor 6.

[0057] The biomass is fed into the biomass boiler 1 through a screw feeder and a trestle for direct combustion to obtain flue gas with a high proportion of carbon dioxide and high-temperature and high-pressure steam to flow to the steam turbine 8 for power generation.

[0058] Specifically, after pretreatment such as crushing and iron removal, the biomass is sent to the biomass boiler 1 through a screw feeder and a trestle for direct combustion, obtaining flue gas with a high proportion of carbon dioxide, and at the same time, a by-product of 540°C high-temperature 9.8MPaG high-pressure steam is produced. The high-temperature and high-pressure steam is used to generate electricity for factory use through a steam turbine 8. The flue gas from the biomass boiler 1 is dedusted by a bag filter 2, and impurities such as sulfides, nitrogen oxides, and particulate matter are removed by a carbon dioxide pretreatment device 3, and then enters a carbon dioxide capture device 4 for carbon dioxide capture. The capture medium is an amine liquid, and the desorption temperature is 180≤°C. The desorbed CO2 is compressed to 1.4 to 1.6MPaG by a carbon dioxide post-treatment device 5 and a carbon dioxide compressor 6, and then goes to a synthesis gas compressor 13 to further increase the pressure. A carbon dioxide storage tank 7 is set for buffering to reduce the load limit of the carbon dioxide production system 100 for preparing carbon dioxide from biomass.

[0059] In this embodiment, the hydrogen production system 200 includes an electrolyzer 10, a hydrogen storage tank 11, and a hydrogen compressor 12. The electrolyzer 10 is connected to a wind and solar power station 9 and / or a downstream power grid through a circuit system to electrolyze water to generate hydrogen and oxygen. The electrolyzer 10 is provided with a hydrogen outlet for hydrogen discharge and an oxygen outlet for oxygen discharge. The biomass boiler 1 is connected to the oxygen outlet through a second pipeline, and the inlet of the synthesis gas compressor 13 is connected to the hydrogen outlet through a third pipeline 31; the inlet of the hydrogen storage tank 11 is connected to the hydrogen outlet; the inlet of the hydrogen compressor 12 is connected to the outlet of the hydrogen storage tank 11, and the outlet of the hydrogen compressor 12 is connected to the inlet of the synthesis gas compressor 13 through a fourth pipeline 32.

[0060] Among them, between the step of treating the flue gas to generate carbon dioxide gas with a pressure of 1.4-1.6MPaG and the step of mixing the carbon dioxide gas and hydrogen in a molar ratio of about 1:3 and then compressing it to 9.0MPaG synthesis gas through the synthesis gas compressor 13, it also includes: supplying power to the electrolyzer 10 through the wind and solar power station 9 and / or the downstream power grid to electrolyze water to generate hydrogen and oxygen; hydrogen is directly transported or pressurized by the hydrogen compressor 12 and then transported to the synthesis gas compressor 13; oxygen is transported to the biomass boiler 1 to assist combustion.

[0061] It should be noted that part of the oxygen generated by electrolysis of water is introduced into the biomass boiler 1 to reduce the air flow rate (the air contains a large amount of nitrogen), thereby increasing the CO2 concentration in the flue gas generated in the biomass boiler 1, increasing the driving force for carbon capture mass transfer, and reducing the energy consumption of carbon capture operation. The amount of oxygen introduced will be adjusted according to the temperature of the biomass boiler to prevent the biomass ash from melting and coking easily due to excessive temperature.

[0062] Specifically, the 220kV green electricity obtained by the wind and solar power station 9 is transmitted to the electrolyzer 10 through the circuit system to provide electricity for the electrolysis of water to produce hydrogen. When necessary, in order to maintain the minimum load operation of the electrolyzer 10, an appropriate amount of grid power can be disconnected. Most of the oxygen generated by the electrolyzer 10 is directly discharged into the air, and a second pipeline is reserved for the biomass boiler 1 to reduce the amount of air used. The purity of the separated and purified hydrogen reaches 99.99%, which can be directly used for methanol synthesis. A hydrogen storage tank 11 and a reciprocating hydrogen compressor 12 are set to adapt to the fluctuation of wind power output of the wind and solar power station 9 and reduce the abandonment rate.

[0063] In this embodiment, the second processing component includes a high-pressure flash tank 19 and a low-pressure flash tank 20, the inlet of the low-pressure flash tank 20 is connected to the first liquid outlet of the high-pressure flash tank 19, the high-pressure flash tank 19 and the low-pressure flash tank 20 are both used for separation of gas-liquid two-phase fluid, the low-pressure flash tank 20 is provided with a second liquid outlet and a second gas outlet, the second liquid outlet is connected to the inlet of the crude methanol tank 21 for liquid circulation to the crude methanol tank 21, the second gas outlet is connected to the first pipeline 27, for the purge gas to flow to the biomass boiler 1; the high-pressure flash tank 19 is also provided with a first gas outlet, the second processing component also includes a circulating gas compressor 14, a gas-to-gas heat exchanger 15, a methanol synthesis tower 16 and a lithium bromide unit 18, the circulating gas pressure The inlet of the compressor 14 is connected to the first gas outlet; the gas-to-gas heat exchanger 15 is provided with a first tube side and a first shell side, the inlet of the first tube side is connected to the outlet of the synthesis gas compressor 13 and the outlet of the circulating gas compressor 14, that is, the outlet of the synthesis gas compressor 13 and the outlet of the circulating gas compressor 14 are connected to the inlet of the first tube side after merging; the inlet of the methanol synthesis tower 16 is connected to the outlet of the first tube side, the methanol synthesis tower 16 is provided with a second shell side, and the second shell side is provided with a pipeline connected to the synthesis tower steam drum 17 to form a steam-water circulation pipeline; the outlet of the methanol synthesis tower 16 is connected to the inlet of the first shell side; the inlet of the lithium bromide unit 18 is connected to the outlet of the first shell side, and the outlet of the lithium bromide unit 18 is connected to the inlet of the high-pressure flash tank 19.

[0064] The step of circulating the first liquid to the low-pressure flash tank 20 for separation to form a second gas and conveying the second liquid to the crude methanol distillation tower 22 also includes: conveying the second gas containing about 60% carbon dioxide and about 35% hydrogen to the biomass boiler 1 for recycling.

[0065] The step of separating and purifying by the crude methanol distillation tower 22 to form methanol, fusel alcohols and the top gas flowing to the biomass boiler 1 also includes: directing the fusel alcohols to the fusel alcohol tank 25 and flowing to the biomass boiler 1 for recycling.

[0066] The specific steps of passing the synthesis gas to the gas-to-gas heat exchanger 15 for heat exchange and temperature rise and then passing it into the methanol synthesis tower 16 to form the material are as follows: the synthesis gas reacts in the methanol synthesis tower 16 to generate the material, and the second shell side of the methanol synthesis tower 16 is provided with a pipeline connected to the synthesis tower steam drum 17 to form a steam-water circulation pipeline for absorbing the reaction heat; the steam generated in the steam-water circulation pipeline is transported to the steam turbine 8 for power generation.

[0067] It should be noted that the steam generated by the steam-water circulation pipeline can also be used as a heat source for the entire plant. The steam can be used in different ways within a certain proportion range. For example, one-third of the steam generated by the steam-water circulation pipeline is used as a steam turbine 8 for power generation, and two-thirds of the steam generated by the steam-water circulation pipeline is used as a heat source for the entire plant.

[0068] The step of cooling the material through heat exchange in the gas-to-gas heat exchanger 15 and then circulating it to the high-pressure flash tank 19 for separation into the first gas and the first liquid also includes: conveying the first gas with a higher proportion of hydrogen to the circulating gas compressor 14 for compression and then merging it into the outlet of the synthesis gas compressor 13.

[0069] The step of cooling the material through heat exchange in the gas-to-gas heat exchanger 15 and then circulating it to the high-pressure flash tank 19 for separation to form the first gas and the first liquid is specifically as follows: cooling the material through heat exchange in the gas-to-gas heat exchanger 15 and then entering the lithium bromide unit 18 to reduce the temperature to 40° C. and then circulating it to the high-pressure flash tank 19 for separation to form the first gas and the first liquid.

[0070] Specifically, CO2 and H2 are mixed in a molar ratio of ≈1:3 and compressed to 9.0 MPaG by the synthesis gas compressor 13. After heat exchange with the material at the outlet of the methanol synthesis tower 16, the temperature is increased and the methanol synthesis tower 16 is entered into the methanol synthesis tower 16 for methanol synthesis reaction. There is a two-phase water vapor natural circulation stream between the second shell side of the methanol synthesis tower 16 and the steam drum of the synthesis tower 17 to remove the reaction heat. Steam is obtained after decompression. The steam can also be directed to the steam turbine 8 for power generation and used in the factory. The temperature of the material after heat exchange in the gas-to-gas heat exchanger 15 is reduced, and the heat is further recovered in the lithium bromide unit 18 to reduce the temperature to 40°C. The 12°C water introduced into the lithium bromide unit 18 is prepared into 7°C water, which is used for separation and purification in the electrolyzer 10 and summer air conditioning in the factory area. The material cooled by the lithium bromide unit 18 is separated into gas and liquid through the high-pressure flash tank 19. The gas phase with a higher proportion of H2 is compressed by the circulating gas compressor 14 and then merged into the outlet of the synthesis gas compressor 13, and enters the methanol synthesis tower 16 again. The liquid phase is passed through the low-pressure flash tank 20 to obtain crude methanol which is stored in the crude methanol tank 21. The gas phase (purge gas) with a CO2 proportion of about 60% and a H2 proportion of about 35% is discharged from the low-pressure flash tank 20 to the first pipeline 27 and then returns to the biomass boiler 1 to recover the carbon source.

[0071] In this embodiment, the methanol distillation system 400 also includes a fusel tank 25, a methanol tank 23, a loading and unloading platform 24 and an oil and gas recovery device 26. The crude methanol distillation tower 22 is provided with a third outlet for discharging fusel products, and the third outlet is connected to the inlet of the fusel tank 25, that is, the by-products of methanol distillation are connected to the inlet of the fusel tank 25, and the outlet of the fusel tank 25 is connected to the biomass boiler 1 through the second pipeline 28; the inlet of the methanol tank 23 is connected to the first outlet of the crude methanol distillation tower 22 for collecting refined methanol; the inlet of the loading and unloading platform 24 is connected to the outlet of the methanol tank 23.

[0072] After the steps of separation and purification by the crude methanol distillation tower 22 to form methanol, fusel alcohols and top gas flowing to the biomass boiler 1, the process also includes: collecting methanol in the methanol tank 23; loading the methanol flowing along the methanol tank 23 to the loading and unloading platform 24 according to a preset loading amount to form a methanol product; and recovering the methanol-containing tail gas discharged from the loading and unloading platform 24 and the methanol tank 23.

[0073] Specifically, the oil and gas recovery device 26 is connected to the exhaust port of the methanol tank 23 and the exhaust port of the loading and unloading platform 24 for oil and gas recovery; the crude methanol is distilled into methanol by the crude methanol distillation tower 22 to obtain refined methanol and stored in the methanol tank 23, the fusel alcohol and the waste gas from the top of the distillation tower (tower top gas) are recycled to the biomass boiler 1, the refined methanol is loaded as a green fuel through the loading and unloading platform 24 and sold as a product, and the methanol-containing tail gas is discharged after the methanol is recovered by the oil and gas recovery device 26 and meets the emission standards.

[0074] In summary, the method for producing methanol by direct combustion of biomass coupled with wind-solar green hydrogen provided by the present application will not affect the downstream methanol synthesis operation load by adjusting the biomass boiler 1 with wind-solar output and factory electricity consumption; direct combustion of biomass coupled with wind-solar green hydrogen to produce methanol is green and environmentally friendly; the methanol synthesis relaxation gas, the top gas of the crude methanol distillation tower 22 and the fusel alcohol by-products are returned to the biomass boiler 1 and reconverted into carbon dioxide, thereby improving the utilization rate of biomass carbon and the atomic economy of the system; a lithium bromide unit 18 is arranged to fully utilize the heat of the methanol synthesis reaction to prepare 7°C low-temperature water, providing a cold source for the plant air conditioning and water electrolysis hydrogen production and purification equipment, thereby improving the energy utilization efficiency of the system.

[0075] It should be noted that, in this specification, relational terms such as first and second are merely used to distinguish one entity from other entities, but do not necessarily require or imply any actual relationship or order between these entities.

[0076] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0077] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core ideas of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the present invention.

Claims

1. A method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind and solar green hydrogen, characterized in that: include: The biomass is fed into the biomass boiler (1) through a screw feeder and a trestle and directly burned to produce flue gas with a high proportion of carbon dioxide; Treating the flue gas to generate carbon dioxide gas with a pressure of 1.4-1.6 MPaG; The carbon dioxide gas and hydrogen gas are mixed in a molar ratio of about 1:3 and compressed into a synthesis gas of 9.0 MPaG by a synthesis gas compressor (13); The synthesis gas is passed to a gas-to-gas heat exchanger (15) for heat exchange and temperature increase, and then passed into a methanol synthesis tower (16) to form a material; The material is passed through the gas-to-gas heat exchanger (15) for heat exchange and temperature reduction, and then flows to the high-pressure flash tank (19) for separation into a first gas and a first liquid; The first liquid is passed to a low-pressure flash tank (20) for separation to form a second gas and a second liquid which is transported to a crude methanol distillation tower (22); The crude methanol distillation tower (22) is used for separation and purification to form methanol, fusel alcohols and a tower top gas which is circulated to the biomass boiler (1).

2. The method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind and solar green hydrogen according to claim 1 is characterized in that: The step of circulating the first liquid to the low-pressure flash tank (20) for separation to form a second gas and a second liquid transported to the crude methanol distillation tower (22) further comprises: The second gas, which contains about 60% carbon dioxide and about 35% hydrogen, is transported to the biomass boiler (1) for recycling.

3. The method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind and solar green hydrogen according to claim 1 is characterized in that: The step of separating and purifying by the crude methanol rectification tower (22) to form methanol, fusel alcohols and a tower top gas flowing to the biomass boiler (1) further comprises: The fusel alcohol is directed to the fusel alcohol tank (25) and then circulated to the biomass boiler (1) for recycling.

4. The method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind and solar green hydrogen according to claim 1 is characterized in that: After the step of separating and purifying by the crude methanol rectification tower (22) to form methanol, fusel alcohols and the top gas flowing to the biomass boiler (1), the method further comprises: collecting methanol in a methanol tank (23); The methanol flowing along the methanol tank (23) to the loading and unloading platform (24) is loaded according to a preset loading amount to form a methanol product; The methanol-containing tail gas discharged from the loading and unloading platform (24) and the methanol tank (23) is recovered.

5. The method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind and solar green hydrogen according to claim 1 is characterized in that: Before the step of feeding the biomass into the biomass boiler (1) through the screw feeder and the trestle for direct combustion to obtain flue gas with a high proportion of carbon dioxide, the step further includes: The biomass is crushed and iron is removed.

6. The method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind and solar green hydrogen according to claim 1 is characterized in that: The specific steps of feeding the biomass into the biomass boiler (1) through the screw feeder and the trestle for direct combustion to obtain flue gas with a high proportion of carbon dioxide are: removing dust from the flue gas to generate a mixed gas; Purifying the mixed gas to remove impurities such as sulfide, nitrogen oxide, and particulate matter; capturing carbon dioxide gas in the mixed gas by using amine liquid; The carbon dioxide gas is released at a desorption temperature of 180°C or less and then compressed to 1.4-1.6MPaG by a carbon dioxide compressor.

7. The method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind and solar green hydrogen according to claim 1 is characterized in that: The biomass is fed into the biomass boiler (1) through a screw feeder and a trestle for direct combustion to obtain flue gas with a high proportion of carbon dioxide and high-temperature and high-pressure steam to flow to a steam turbine (8) for power generation.

8. The method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind and solar green hydrogen according to claim 1 is characterized in that: The step of treating the flue gas to generate carbon dioxide gas with a pressure of 1.4-1.6 MPaG and the step of mixing carbon dioxide gas and hydrogen at a molar ratio of about 1:3 and then compressing the mixture to 9.0 MPaG synthesis gas by a synthesis gas compressor further includes: Supplying electricity to an electrolyzer (10) through a wind and solar power station (9) and / or a downstream power grid to electrolyze water to generate hydrogen and oxygen; The hydrogen is directly transported or pressurized by a hydrogen compressor (12) and then transported to the synthesis gas compressor (13); The oxygen is transported to the biomass boiler (1) to assist combustion.

9. The method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind and solar green hydrogen according to claim 7 is characterized in that: The step of passing the synthesis gas to the gas-to-gas heat exchanger (15) for heat exchange and temperature increase and then passing the synthesis gas to the methanol synthesis tower (16) to form the material is specifically as follows: The synthesis gas reacts in the methanol synthesis tower (16) to generate the material, and the second shell side of the methanol synthesis tower (16) is provided with a pipeline connected to the synthesis tower steam drum (17) to form a steam-water circulation pipeline for absorbing reaction heat; The steam generated by the steam-water circulation pipeline is transported to the steam turbine (8) to generate electricity.

10. The method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind and solar green hydrogen according to claim 1, characterized in that: The step of passing the material through the gas-to-gas heat exchanger (15) for heat exchange and temperature reduction and then flowing it to the high-pressure flash tank (19) for separation to form the first gas and the first liquid also includes: The first gas containing a relatively high proportion of hydrogen is transported to a circulating gas compressor for compression and then flows into the outlet of the synthesis gas compressor (13).

11. The method for producing methanol from carbon dioxide by direct combustion of biomass coupled with wind and solar green hydrogen according to claim 1, characterized in that: The step of passing the material through the gas-to-gas heat exchanger (15) for heat exchange and temperature reduction and then flowing it to the high-pressure flash tank (19) for separation into the first gas and the first liquid is specifically as follows: The material is cooled by heat exchange in the gas-to-gas heat exchanger (15), then enters the lithium bromide unit to reduce the temperature to 40° C., and then flows to the high-pressure flash tank (19) for separation to form a first gas and a first liquid.

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