Large-scale method and device for synthesizing methanol through carbon dioxide hydrogenation

Abstract

The invention provides a method for synthesizing industrial methanol by using industrial carbon dioxide and industrial hydrogen, which comprises the following steps of: preparing raw material gas, synthesizing methanol and separating and recycling a product, preparing qualified carbon dioxide by using different physical or chemical methods and storing the qualified carbon dioxide in a CO2 storage tank, preparing qualified hydrogen by using electrolyzed water or other chemical products and storing the qualified hydrogen in a hydrogen storage tank, the method comprises the following steps: introducing a synthetic methanol gas into a raw material gas mixing storage tank with normal temperature and low pressure through a pipeline with a valve, mixing H2 and CO2 in the raw material gas in the synthetic methanol mixing storage tank according to a certain proportion, boosting the mixed raw material gas by using a compressor or a raw material gas-recycle gas mixed circulator, heating by using a tower gas preheater, and feeding into a methanol synthesis tower; carrying out CO2 and H2 synthesis of methanol, carrying out CO2 reverse water vapor shift RGWS to generate CO, and carrying out CO and H2 reaction to synthesize methanol. The invention further discloses a synthesis device suitable for the process.

Description

Technical Field

[0001] The invention relates to the field of chemical engineering, in particular to a method and a device for synthesizing industrial methanol from industrial carbon dioxide and industrial hydrogen. Technical Background

[0003] The single-pass conversion rate of CO2 hydrogenation to methanol is lower than that of CO synthesis, generally only 20%. In order to improve the conversion rate of CO2 to methanol, in addition to using precious metal catalysts, CO2 is reversed into CO and water, and then the liquid product H2O is separated, and then CO is used to synthesize methanol. However, this method not only increases the equipment and process, and increases investment, but also wastes energy due to the use of high-temperature reverse conversion, cooling and separation, and reheating to synthesize methanol, which reduces the amount of steam produced as a by-product of methanol synthesis.

[0004] Another proposal is to synthesize methanol from CO2 and H2 in stages, use water-cooled tubular heat exchange in the upper part to generate methanol and water, and then use membrane separation to remove the reaction product water to break the reaction equilibrium. However, the problem is how to successfully separate water without separating hydrogen molecules smaller than water when the hydrogen content in the reaction gas is >50%. In addition, the CO2 and H2 reactors that have been subjected to >200℃ need to be cooled down to around 100℃ for membrane separation of hydrogen, and then further heated up to >200℃ for CO2 synthesis of methanol. The heating and temperature raising reaction - cooling membrane separation to remove water and then heating and temperature raising for CO2 hydrogenation reaction not only increases equipment but also reduces energy efficiency. For this reason, industrial carbon dioxide and industrial hydrogen that meet national standards are used, with a hydrogen to carbon dioxide volume ratio of 3, or physical, chemical, biomass or factory or urban garbage waste, steel mills, power plant flue gas emissions, to capture CO2 and purify it into a CO2 storage tank. Similarly, industrial hydrogen from new energy, wind, solar, hydropower or thermal power, hydropower media is stored in a storage tank, and then loaded into a CO2 and hydrogen mixed raw gas storage tank to synthesize methanol, and then the methanol is made into various chemical products, or aviation gasoline, diesel and marine power energy according to market needs. Summary of the invention

[0005] The object of the present invention is to provide a method and device for synthesizing industrial methanol from industrial carbon dioxide and industrial hydrogen.

[0006] A large-scale method for synthesizing methanol from carbon dioxide includes raw gas preparation, methanol synthesis and product separation and recovery, including the following steps:

[0007] (I) Raw gas preparation: qualified carbon dioxide is produced by different physical or chemical methods and stored in a CO2 storage tank, qualified hydrogen is produced by electrolysis of water or other chemical products and stored in a hydrogen storage tank, and connected to a raw gas mixed storage tank at room temperature and low pressure by a pipeline with a valve. The volume ratio of H2 to CO2 in the raw gas in the synthetic methanol mixed storage tank is 3.0±0.3;

[0008] (ii) Methanol synthesis: first, the mixed raw gas in the raw gas mixing storage tank is pressurized to 5-10 MPa by a compressor or a circulating machine for mixing raw gas and circulating gas, and then heated by an inlet gas preheater, and enters the methanol synthesis tower at a temperature above the activity of the CO2 synthesis methanol catalyst, and CO2 and H2 are synthesized into methanol and CO2 reverse water vapor shift RGWS are generated to CO at a temperature of 210-280°C and a temperature difference of <5°C in the same plane on a copper-based Cu / Zn / Ae or other high-activity small-particle catalyst with heat exchange tubes in the catalyst layer, and CO2 and H2 are reacted to synthesize methanol;

[0009] (III) Product separation and recovery: The methanol gas out of the tower is cooled by transferring heat to the inlet gas through the inlet gas preheater or further cooled to <100°C by recovering heat through the boiler water heater. It is then cooled to <40°C by air cooling and water cooling or by using a water cooler before entering the methanol separator. The methanol and water in the gas out of the tower are condensed into crude alcohol. The pressure is reduced from 5-10MPa to <0.8MPa and sent to the methanol evaporator. The liquid methanol is sent to methanol distillation, and the decompression expansion function of the methanol liquid is used to recover energy by the expander.

[0010] During the methanol synthesis, CO2 is heated on a small-particle copper-based methanol synthesis or a small-particle Cu / Zn / Ae to react with H2 methanol to generate methanol and water. CO2 is reversely transformed to generate CO. The generated CO generates methanol at a higher rate than CO2 and releases greater reaction heat. The reaction gas is transmitted through a heat exchanger pipe to generate saturated steam with a pressure of 3 to 5 MPa, which is drawn out from the drum to drive the compressor circulation machine turbine power. The methanol tower gas is passed through the inlet and outlet tower gas heat exchanger and the boiler water heater to recover heat. It is reduced to 35°C in the water cooler and sent to the methanol gas-liquid separator. The crude methanol is depressurized and sent to the flash tank and then to the methanol refiner. Distillation, except for a small part of the purge gas <10%, which is washed with water and recovers methanol, H2 and CO2, most of the gas >90% is pressurized by a circulating machine to synthesize methanol; it is then cooled by a water cooler and enters a methanol separator, and the methanol is directly or twice decompressed to remove methanol distillation. The CO2 content in the flash gas generated during the decompression is >60%, and the separated CO2 and H2 are pressurized and merged with the circulating gas to further synthesize methanol. The by-product steam in the CO2 synthesis of methanol is >0.6 tons / T of methanol, which is used to drive the methanol synthesis circulating compressor. The crude methanol is sent from the alcohol separator to the methanol distillation tank and expanded by the expander, which is also used as the power for methanol synthesis.

[0011] When supercritical water is used to produce hydrogen, biochemical methods are used to produce hydrogen and store it in hydrogen tanks, and biomass is used to produce raw gas, if the raw gas contains sulfur, chlorine, oxygen and other substances that are harmful to the catalyst, a dry chemical reaction purifier is set up to use ZnO and other dry purification methods at 220-270°C, the same temperature range as methanol synthesis, reaction temperature and pressure conditions, to purify and remove harmful substances to the catalyst, store it in a carbon raw gas tank, and then send it to the raw mixed gas tank for compression to remove methanol synthesis.

[0012] As a preferred embodiment, when the reaction rate of the CO2 to methanol catalyst is low, a small amount of low-temperature CO shift catalyst under the same temperature and pressure conditions as the CO2 hydrogenation to methanol can be used, and mixed on the upper part of the catalyst layer to carry out CO2 reverse water vapor shift, i.e., RGWS, to improve the CO2 single-pass conversion rate.

[0013] As a preferred embodiment, a higher circulating gas to raw gas circulation ratio of >5 is adopted.

[0014] As a preferred embodiment, when high-carbon raw materials are gasified to produce CO2, the high-temperature CO2 gas is produced to recover heat, and the by-product steam is reduced in pressure, temperature, and dust to <300°C, and is dry-processed with ZnO and other catalysts for desulfurization, dechlorination, and deoxygenation to remove substances that are harmful to methanol synthesis catalysts, and then sent to a CO2 storage tank that meets the national CO2 standards for methanol synthesis.

[0015] As a preferred embodiment, when the activity of the copper-based CuO / ZnO / Al2O3 carbon dioxide to methanol synthesis catalyst is not high enough, a copper-based low-temperature shift catalyst with a total catalyst weight ratio of 20 to 35% and the same operating temperature of 210 to 280°C and the same pressure of 4 to 10 MPa as the copper-based methanol synthesis catalyst can be mixed with the copper-based methanol catalyst in the upper part of the methanol synthesis tower to cause a reverse shift reaction to occur in the methanol synthesis production to generate CO and then carry out a methanol synthesis reaction.

[0016] As a preferred method, the high-concentration CO2 of >50% in the recovered crude methanol flash gas is sent to the raw gas tank for mixing and compression and returned to the methanol synthesis.

[0017] The methanol synthesis tower adopts a small-diameter seamless stainless steel pipe, and heat exchange tubes are arranged throughout the catalyst layer from the top to the bottom. Since the reaction heat released by CO2 hydrogenation to synthesize methanol is only half of that released by CO synthesis to synthesize methanol, the methanol synthesis reactor in the methanol synthesis steam production has an inlet temperature of 210-240°C, a 4MPa steam saturation temperature of 250°C, an upper synthetic methanol temperature of 240-260°C, and after the hot spot temperature of 260°C in the middle and upper part, the methanol synthesis reaction heat releases through the heat exchange tubes to generate 4MPa saturated steam to the bottom outlet to reach 240-250°C, thereby increasing steam production.

[0018] After replacing the new catalyst in a new device or an existing methanol tower and completing the catalyst reduction, gradually increase the temperature and pressure and slowly raise the pressure from 2-3MPa in the reduction period to 5MPa, and the temperature to 260℃. First produce at a light load for a few days and then increase to full load and pay close attention to the temperature difference of the catalyst layer on the same plane ≤5℃, the hot spot temperature is 260℃, the tower inlet pressure is around 7.5-8MPa, and later increased to 8-8.5MPa.

[0019] The carbon dioxide is a gas product obtained by further processing or heat treatment or combustion of exhaust gas from refineries, chemical plants, steel plants and other factories. It contains CO2 and CO, and is a harmless gas after being detoxified to remove sulfides and chlorides that are toxic to catalysts. Industrial hydrogen can be synthesized by electrolyzing water or other hydrocarbons or alcohols, ethers, hydrides or biomass to produce raw gas.

[0020] The heat of reaction of CO2 and H2 to produce methanol is only half of the heat of reaction of CO and H2 to synthesize methanol, and the reaction temperature is around 260°C. It is advisable to select a small-diameter uniform temperature reactor with continuous heat exchange and methanol tower air cooling in the heat exchange tube to increase the catalyst filling rate of the reactor and reduce investment.

[0021] The methanol synthesis reactor uses a coiled water-cooled, uniform temperature reactor. Per ton of CO2 synthesized methanol, 0.6 tons of 4MPa medium-pressure steam is produced as a by-product, which is used as power steam or process steam for methanol synthesis compressors and water pumps.

[0022] The synthesis pressure of CO2 and H2 is 5-10MPa. The pressure is reduced to <0.8MPa from the methanol high-pressure separator. The methanol distillation system reduces the pressure by more than 9MPa. The expansion agent turbine is used to recover energy to achieve the purpose of energy saving and consumption reduction.

[0023] The synthesis of methanol by hydrogenation of rich CO2 is carried out by gasifying carbon-rich raw materials to produce coal gas containing H2 gas in different ratios of CO and CO2. After cooling and recovering heat and removing dust, the ZnO and other catalysts at around 300°C are used to desulfurize chlorine and oxygen, which are poisonous to the catalyst, and store the mixed gas in a safe tank outside the explosion range of the mixed gas. Hydrogen is produced by electrolyzing water with new energy such as wind, solar and water, or traditional thermal power, chemical and electric power cogeneration, and is loaded into the hydrogen storage tank. Then the gasified coal gas in the CO2 storage tank and the industrial hydrogen in the hydrogen storage tank are sent to the mixed raw material gas storage tank in different proportions of hydrogen, CO2 and CO according to the amount of carbon and hydrogen elements in the selected synthetic products such as methanol, dimethyl ether, Fischer-Tropsch synthetic oil, ethylene, propylene and other hydrocarbon alcohol ether esters.

[0024] A large-scale carbon dioxide synthesis methanol device, comprising a raw gas preparation area, a methanol synthesis area and a product separation area, wherein the raw gas preparation area comprises a water electrolysis device, an H2 storage tank, a CO2 storage tank, a raw gas mixing storage tank, a biomass gasification furnace, a dust collector, and a detoxifier, the methanol synthesis area comprises a circulating compressor, a methanol synthesis reactor, a heat exchanger, and a water cooler, and the product separation area comprises an alcohol separator, a water scrubber, a flash steam tank and a gas recovery device, the raw gas preparation area, the methanol synthesis area and the product separation area are connected in sequence, and the The water electrolysis equipment is connected to the H2 storage tank, the H2 storage tank and the CO2 storage tank are connected to the raw gas mixing storage tank at the same time, the biomass gasification furnace, the dust collector, and the detoxifier are connected in sequence and connected to the CO2 storage tank, the raw gas mixing storage tank is connected to the heat exchanger, the circulating compressor, the methanol synthesis reactor, and the water cooler in sequence, the methanol synthesis reactor is connected to an external steam drum, the water cooler is connected to the alcohol separator, the outlet of the alcohol separator is respectively connected to the water washing tower and the flash steam tank, and the outlets of the water washing tower and the flash steam tank are both connected to the gas recovery device.

[0025] As a preferred embodiment, the methanol synthesis reactor is an air-cooled small-diameter uniform temperature reactor.

[0026] As a preferred embodiment, the methanol synthesis reactor uses a coiled water-cooled even-temperature heat exchange reactor. The stainless steel heat exchange tubes between the reactor and the boiler water-produced steam in the reactor are more than twice as long as the shell-and-tube or insulated shell-and-tube heat exchangers used in other water-tube byproduct steam reactors used at home and abroad, reaching >20 meters. The tube diameter is reduced by 50% (shell-and-tube 32-38mm), and there is no weld on the entire tube. The heat exchange tubes inside the reactor do not have a weld, which avoids the reactor from stopping due to weld leakage after being put into operation.

[0027] The above-mentioned device can be used for existing traditional coal gas planning devices or new coal gasification-steam gas power generation devices. The emitted carbon dioxide is loaded into the carbon dioxide storage tank as raw material, and is connected to the new energy, photovoltaic power generation, wind power, and hydropower water electrolysis hydrogen production tanks. The input CO2 and H2 mixed gas raw gas storage tanks are respectively connected by pipelines to send them into the CO2 and H2 synthetic methanol devices, so as to realize the existing coal gasification methanol or coal gasification-steam gas power generation cogeneration device to achieve zero carbon dioxide emissions.

[0028] The beneficial effects of the present invention are as follows:

[0029] 1. It can be used for methanol plants that have already been built and use coal-to-syngas to emit a large amount of CO2 through CO conversion and low-temperature methanol washing. The emitted CO2 will be collected and pressurized and sent to the CO2 storage tank, and then electrolyzed with water to produce hydrogen. After purification, it will be sent to the raw gas mixing tank and then to the CO2 synthesis methanol device to achieve zero emission of methanol synthesis in the whole system.

[0030] 2. The single-pass conversion rate of methanol synthesized from CO2 and hydrogen by non-precious metal copper-based methanol synthesis catalyst is lower than that of methanol synthesized from CO and H2. The circulation ratio is increased to achieve the goal of increasing the total conversion rate of CO2 and hydrogen.

[0031] 3. Traditional coal gasification is used in polygeneration, and CO2 is produced in gas-steam-gas power generation. The CO2 emitted can be synthesized by electrolyzing water to produce H2 and methanol to achieve the goal of zero carbon emissions.

[0032] 4. For newly built methanol plants, kerosene, natural gas and biomass are used as raw materials to produce CO2-rich and CO-poor H2 gas, which are then combined with new energy sources such as wind, photovoltaic and hydropower to produce hydrogen by electrolyzing water, and CO2 and CO gas are added to hydrogen to synthesize methanol, which greatly reduces the raw gas consumption and cost of synthesizing methanol and reduces investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a diagram of the device of the present invention.

[0034] Description of reference numerals:

[0035] 1-Electrolysis water equipment 2-H2 storage tank 3-CO2 storage tank 4-Raw gas mixing storage tank

[0036] 5-Biomass gasifier 6-Dust collector 7-Detoxifier 8-1-Compressor

[0037] 8-2-Circulation machine 8-3-Second compressor 9-Methanol synthesis reactor 10-Steam drum

[0038] 11- Heat exchanger before tower 12- Heat exchanger 13- Water cooler 14- Alcohol separator

[0039] 15-Flash Tank 16-Water Scrubber 17-Gas Recovery Device DETAILED DESCRIPTION

[0040] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0041] Example 1

[0042] See also Figure 1, H2 and CO2 gases are input into the raw gas mixing storage tank 4 through pipelines from the H2 storage tank 2 and CO2 storage tank 3 with inlet and outlet valves. The storage tank is 2-3MPa pressure room temperature according to different raw gas preparation methods. The raw gas in the storage tank is sent to the dry purification reactor equipped with desulfurization, chlorine, oxygen and other catalyst harmful substances according to the purity, or the pure gas without harmful substances is directly sent to the circulating compressor 8 for compression, or mixed with the circulating gas and pressurized to 5-10MPa methanol synthesis pressure, and then heated to 220-2 by the hot gas from the tower through the pre-tower heat exchanger 11. 40℃, enters from the top of methanol synthesis reactor 9, a small amount of reverse low-speed conversion catalyst is mixed in the upper part to react CO2 and H2 to generate CO (for example, mass ratio <30%) CO2+3H2=CH3OH+H2O and CO+2H2=CH3OH, the mixed gas in the methanol synthesis reactor passes through the shell and the heat exchange coil to react CO2 to methanol, the lower part of the reactor can be equipped with less or no catalyst depending on the performance of different processes, CO low-temperature reverse catalyst is all CO2 methanol synthesis catalyst, the hot spot temperature in the synthesis reactor is 260℃, The temperature out of the methanol synthesis reactor is 250℃, and the temperature difference in the same plane of the reactor is less than 5℃. The temperature is adjusted by the saturated steam pressure of the saturated water in the heat exchange tube through the saturated steam coil connected to the heat exchange coil at the top of the tower. The CO2 and H2 reach a total conversion rate of CO2 and H2 of more than 98% through a large circulation ratio. The heat out of the reactor is recovered by the heat exchanger 11 before the tower and the heat is recovered by the boiler water heater. Then, the temperature is reduced to 35℃ by the water cooler 13 or the air cooler and the water tower to the methanol gas-liquid separator to separate the crude methanol. The pressure is reduced to <1MPa by the high-pressure synthesis 8MPa pressure expander, and the heat is recovered to the flash tank. The liquid crude steam sent out from the steam tank contains >80% CO2, which is nearly 90% of the gas when H2 is added. The separated CO2 is returned to the synthesis reactor, and the liquid crude methanol is sent to the methanol distillation section to improve the overall conversion rate of CO2 and H2. A small part of the purge gas from the methanol separator is recovered as CO2 and H2. Most of the gas other than the raw gas is circulating gas, which is pressurized by the circulating machine and enters the synthesis reactor again to synthesize methanol. The water in the bypass tube absorbs the CO2 outside the tube to synthesize methanol reaction heat, generating 4MPa pressure>1 ton steam / ton alcohol, which is sent out through the steam drum 10 and can be used as power steam for the compression circulating machine.

[0043] Example 2

[0044] The annual production of 120,000 tons of carbon dioxide and hydrogen synthesis methanol plant uses industrial-grade hydrogen and industrial-grade carbon dioxide, with a raw gas volume of 43429NM at a ratio of hydrogen to carbon dioxide of 3. 3 / h in Figure 1 The raw gas at room temperature of 2MPa is mixed in the storage tank 4, compressed to 8.1MPa by the compressor and then enters the raw gas purifier to remove the catalyst harmful substances such as sulfur, chlorine and oxygen by dry method with ZnO catalyst at 250℃, and then mixed with 322504NM pressurized to the same pressure of 8.1MPa by the circulation machine. 3 / h mixture, heated to 230℃ by methanol in and out, and then enters the coiled water-cooled heat exchanger methanol synthesis tower, with an inner diameter of 4.2 meters and a total catalyst bed height of 7.6 meters. The upper 2 meters are filled with NC307 methanol synthesis catalyst and B206 CO low-temperature shift catalyst with a weight ratio of 1:1, and the middle and lower 5.6 meters are all filled with CO2 methanol synthesis catalyst, with a total of 91M 3 , using 4MPa saturated steam pressure water heat exchange in the coil to control the middle hot spot temperature at 263℃, the low part at 252℃, the CO2 conversion rate out of the tower is 29%, the total conversion rate is 94%, and the by-product of each ton of methanol is 700kg / ton of methanol. The raw gas consumption per ton of methanol is 2816NM 3 / T, daily production of refined methanol 371 tons, when the flash gas is recovered 746NM 3 72.9% CO2544NM / h 3 The total conversion rate is 99% when the pressurized cycle is used to synthesize methanol.

[0045] Example 3

[0046] The annual production of 260,000 tons of carbon dioxide synthesis methanol zero emission gas device uses a 4.2-meter diameter internal domestic NC307 catalyst 90M 3 One, bed height 7.6 meters, using mixed raw gas with hydrogen and carbon dioxide ratio of 3 92KM 3 / h Under 8MPa methanol synthesis pressure, the cold surface is 42m -1 The coiled water-cooled heat exchange methanol synthesis tower uses a circulating gas volume of 600,000 standard cubic meters per hour and an air velocity of 7600 h -1 When the saturated steam pressure in the lower tube is 4MPa and the saturated temperature is 251℃, and the relaxation gas volume is zero, the methanol volume fraction in the outlet gas reaches 3.81%, the net value is 3.66%, the CO2 single-pass conversion rate reaches 33%, the total conversion rate reaches 95%, and the total CO2 reaches 99% when CO2 is recovered in the steam. The raw gas consumption per ton of methanol is 2822NM 3 / h, 670kg of 4MPa steam is produced as a by-product per ton of methanol, and the total methanol output reaches 260,000 tons / year.

Claims

1. A large-scale method for synthesizing methanol from carbon dioxide, comprising raw gas preparation, methanol synthesis and product separation and recovery, characterized in that: The specific contents include: (I) Raw gas preparation: qualified carbon dioxide is produced by different physical or chemical methods and stored in a CO2 storage tank, qualified hydrogen is produced by electrolysis of water or other chemical products and stored in a hydrogen storage tank, and connected to a raw gas mixed storage tank at room temperature and low pressure by a pipeline with a valve. The volume ratio of H2 to CO2 in the raw gas in the synthetic methanol mixed storage tank is 3.0±0.3; (ii) Methanol synthesis: first, the mixed raw gas in the raw gas mixing storage tank is pressurized to 5-10 MPa by a compressor or a circulating machine for mixing raw gas and circulating gas, and then heated by an inlet gas preheater, and enters the methanol synthesis tower at a temperature above the activity of the CO2 synthesis methanol catalyst, and CO2 and H2 are synthesized into methanol and CO2 reverse water vapor shift RGWS are generated to CO at a temperature of 210-280°C and a temperature difference of <5°C in the same plane on a copper-based Cu / Zn / Ae or other high-activity small-particle catalyst with heat exchange tubes in the catalyst layer, and CO2 and H2 are reacted to synthesize methanol; (III) Product separation and recovery: The methanol gas out of the tower is cooled by transferring heat to the inlet gas through the inlet gas preheater or further cooled to <100°C by recovering heat through the boiler water heater. It is then cooled to <40°C by air cooling and water cooling or by using a water cooler before entering the methanol separator. The methanol and water in the gas out of the tower are condensed into crude alcohol. The pressure is reduced from 5-10MPa to <0.8MPa and sent to the methanol evaporator. The liquid methanol is sent to methanol distillation, and the decompression expansion function of the methanol liquid is used to recover energy by the expander.

2. The large-scale method for synthesizing methanol from carbon dioxide according to claim 1, characterized in that: During the methanol synthesis, CO2 is heated on a small-particle copper-based methanol synthesis or a small-particle Cu / Zn / Ae to react with H2 methanol to generate methanol and water. CO2 is reversely transformed to generate CO. The generated CO generates methanol at a higher rate than CO2 and releases greater reaction heat. The reaction gas is transmitted through a heat exchanger pipe to generate saturated steam with a pressure of 3 to 5 MPa, which is drawn out from the drum to drive the compressor circulation machine turbine power. The methanol tower gas is passed through the inlet and outlet tower gas heat exchanger and the boiler water heater to recover heat. It is reduced to 35°C in the water cooler and sent to the methanol gas-liquid separator. The crude methanol is depressurized and sent to the flash tank and then to the methanol refiner. Distillation, except for a small part of the purge gas <10%, which is washed with water and recovers methanol, H2 and CO2, most of the gas >90% is pressurized by a circulating machine to synthesize methanol; it is then cooled by a water cooler and enters a methanol separator, and the methanol is directly or twice decompressed to remove methanol distillation. The CO2 content in the flash gas generated during the decompression is >60%, and the separated CO2 and H2 are pressurized and merged with the circulating gas to further synthesize methanol. The by-product steam in the CO2 synthesis of methanol is >0.6 tons / T of methanol, which is used to drive the methanol synthesis circulating compressor. The crude methanol is sent from the alcohol separator to the methanol distillation tank and expanded by the expander, which is also used as the power for methanol synthesis.

3. The large-scale method for synthesizing methanol from carbon dioxide according to claim 1, characterized in that: When supercritical water is used to produce hydrogen, biochemical methods are used to produce hydrogen and store it in hydrogen tanks, and biomass is used to produce raw gas, if the raw gas contains sulfur, chlorine, oxygen and other substances that are harmful to the catalyst, a dry chemical reaction purifier is set up to use ZnO and other dry purification methods at 220-270°C, the same temperature range as methanol synthesis, reaction temperature and pressure conditions, to purify and remove harmful substances to the catalyst, store it in a carbon raw gas tank, and then send it to the raw mixed gas tank for compression to remove methanol synthesis.

4. The large-scale method for synthesizing methanol from carbon dioxide according to claim 1, characterized in that: The circulation ratio of circulating gas to raw gas is >5.

5. The large-scale method for synthesizing methanol from carbon dioxide according to claim 1, characterized in that: When high-carbon raw materials are gasified to produce CO2, the high-temperature CO2 gas is produced to recover heat, and the by-product steam is reduced in pressure, cooled and dusted to <300℃. It is then dry-processed with ZnO and other catalysts to remove sulfur, chlorine and oxygen, which are harmful to the methanol synthesis catalyst, and then sent to the CO2 storage tank for methanol synthesis.

6. The large-scale method for synthesizing methanol from carbon dioxide according to claim 1, characterized in that: When the activity of the copper-based CuO / ZnO / Al2O3 carbon dioxide to methanol synthesis catalyst is not high enough, a copper-based low-temperature shift catalyst with a total catalyst weight ratio of 20-35% under the same operating temperature of 210-280°C and the same pressure of 4-10 MPa as the copper-based methanol synthesis catalyst can be mixed with the copper-based methanol catalyst in the upper part of the methanol synthesis tower to cause a reverse shift reaction to occur in the methanol synthesis production to generate CO and then carry out a methanol synthesis reaction.

7. The large-scale method for synthesizing methanol from carbon dioxide according to claim 1, characterized in that: The high concentration CO2 of >50% in the recovered crude methanol flash gas is sent to the raw gas tank for mixing and compression and returned to methanol synthesis.

8. A large-scale carbon dioxide to methanol synthesis device, comprising a feed gas preparation area, a methanol synthesis area and a product separation area, characterized in that: The raw gas preparation area includes an electrolytic water device, an H2 storage tank, a CO2 storage tank, a raw gas mixing storage tank, a dust collector, and a detoxifier. The methanol synthesis area includes a circulating compressor, a methanol synthesis reactor, a heat exchanger, and a water cooler. The product separation area includes an alcohol separator, a water scrubber, a flash steam tank, and a gas recovery device. The raw gas preparation area, the methanol synthesis area, and the product separation area are connected in sequence. The electrolytic water device is connected to the H2 storage tank. The H2 storage tank and the CO2 storage tank are simultaneously connected to the raw gas mixing storage tank. The dust collector and the detoxifier are connected in sequence and connected to the CO2 storage tank. The raw gas mixing storage tank is connected to the heat exchanger, the circulating compressor, the methanol synthesis reactor, and the water cooler in sequence. The methanol synthesis reactor is connected to an external steam drum. The water cooler is connected to the alcohol separator. The outlet of the alcohol separator is connected to the water scrubber and the flash steam tank respectively, and the outlets of the water scrubber and the flash steam tank are both connected to the gas recovery device.

9. The large-scale carbon dioxide to methanol synthesis device according to claim 8, characterized in that: The methanol synthesis reactor is an air-cooled small-diameter uniform temperature reactor.

10. The large-scale carbon dioxide to methanol synthesis device according to claim 8, characterized in that: The methanol synthesis reactor is a coiled water-cooled, uniform temperature reactor.

11. The large-scale carbon dioxide to methanol synthesis device according to claim 8, characterized in that: The methanol synthesis reactor uses a coiled water-cooled uniform temperature heat exchange reactor. The stainless steel heat exchange tube in the reactor is greater than 20 meters, and the tube diameter is 50% smaller than the 32-38 mm of the shell and tube heat exchange tube.

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