Carbon dioxide hydrogenation methanol preparation system with local circulation

Abstract

The utility model discloses a system for preparing methanol by hydrogenating carbon dioxide with local circulation, which belongs to the technical field of CCUS and comprises a feed gas treatment section, a primary synthesis section and a secondary synthesis section for synthesizing methanol in a non-circulation one-way manner, and a tertiary synthesis section for synthesizing methanol by circulating partial synthesis gas, which are connected in sequence, each stage of synthesis section comprises a gas-gas heat exchanger, a methanol synthesis tower, a synthesis gas cooler and a gas-liquid separation device; in each stage of synthesis section, an inlet and an outlet of the methanol synthesis tower are connected with a gas-gas heat exchanger in the synthesis section, an outlet of the gas-gas heat exchanger is connected with a synthesis gas cooler in the synthesis section, and an outlet of the synthesis gas cooler is connected with a gas-liquid separation device in the synthesis section. According to the utility model, the two stages of methanol synthesis towers without circulation are connected in series with the one-stage methanol synthesis tower with circulation, so that the equipment energy consumption and the investment cost are reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of CCUS, and particularly relates to a carbon dioxide hydrogenation to methanol system with local circulation. Background Art

[0002] With the continuous development and progress of renewable resource power generation technology and large-scale electrolytic water hydrogen production technology, the production cost of electrolytic water hydrogen production is gradually approaching the existing industrial hydrogen production cost level, and it is expected to drop to 0.8 - 1.0 yuan / Nm 3 , and large-scale industrial production is gradually realized. Currently, the single-set electrolytic water hydrogen production scale in China can reach more than 1000 Nm 3 / h. The significant reduction in the cost of green hydrogen provides a major opportunity for the industrial promotion of the technical route of carbon dioxide hydrogenation to high-value chemicals. Among them, carbon dioxide hydrogenation to methanol is one of the important technical routes, because methanol can be directly used as a transportation and thermal power fuel, can be used as a raw material for methanol fuel cell vehicles, and can also be used as an important chemical raw material to further synthesize chemicals such as olefins, aromatics, and oxygen-containing compounds, thereby realizing carbon dioxide circulation and the "methanol economy".

[0003] Carbon dioxide hydrogenation to methanol has a significant carbon reduction effect. Each ton of methanol can absorb and convert 1.375 tons of carbon dioxide. The existing industrial methanol production capacity in China reaches 100 million tons / year, and the output is close to 80 million tons / year. If it is all replaced by methanol produced from carbon dioxide in the future, 110 million tons of carbon dioxide can be directly absorbed and converted annually. Calculated based on the proportion of coal-to-methanol (~3.20 tons of CO2 / ton of methanol) accounting for 76.93%, natural gas-to-methanol accounting for 10.01% (1.911 tons of CO2 / ton of methanol), and coke oven gas-to-methanol accounting for 13.06% (2.963 tons of CO2 / ton of methanol) in China's methanol industry in recent years, the total carbon dioxide emissions from the methanol industry are about 246.6 million tons / year, and the total annual emission reduction from the methanol industry alone is about 356.6 million tons.

[0004] In this context, an effective carbon dioxide hydrogenation to methanol process technology is particularly important.

[0005] In the current carbon dioxide hydrogenation to methanol process technology, without recycling, two-stage methanol synthesis towers in series are required to convert 50% of carbon dioxide, seven-stage methanol synthesis towers in series are required to convert 90% of carbon dioxide, and thirteen-stage methanol synthesis towers in series are required to convert 99% of carbon dioxide. Obviously, the equipment investment for too many series-connected methanol synthesis towers will also increase continuously. Recycle gas can synthesize methanol from feed gas with a low carbon dioxide content at a higher conversion rate. In the prior art, Chinese Patent CN102516029A discloses a method for synthesizing methanol with full recycle. This method has a large recycle volume and high energy consumption. Chinese Patent CN105622344A discloses a methanol synthesis method that couples reverse conversion and synthesis. This method also adopts a full recycle process and has high energy consumption. Chinese Patent CN215288580U discloses a method for synthesizing methanol by hydrogenating carbon dioxide without recycle, which requires more than three stages of methanol synthesis towers in series. The energy consumption is very low, but the equipment investment and catalyst consumption are relatively high. Utility Model Content

[0006] The utility model aims to solve the problems of large recycle volume and high energy consumption when using the full recycle method for carbon dioxide hydrogenation to methanol in the prior art, and proposes a carbon dioxide hydrogenation to methanol system with partial recycle. Two stages of methanol synthesis towers without recycle are designed in series with one stage of methanol synthesis tower with recycle, so as to reduce the equipment energy consumption and investment cost.

[0007] In order to achieve the above utility model purpose, the technical solution of the utility model is as follows:

[0008] A carbon dioxide hydrogenation to methanol system with partial recycle includes a feed gas treatment section, a first-stage synthesis section and a second-stage synthesis section for synthesizing methanol without recycle in a single pass, and a third-stage synthesis section for synthesizing methanol with partial syngas recycle, which are connected in sequence; each stage of the synthesis section includes a gas-gas heat exchanger, a methanol synthesis tower, a syngas cooler and a vapor-liquid separation device; in each stage of the synthesis section, the inlet and outlet of the methanol synthesis tower are connected to the gas-gas heat exchanger in this synthesis section, the outlet of the gas-gas heat exchanger is connected to the syngas cooler in this synthesis section, and the outlet of the syngas cooler is connected to the vapor-liquid separation device in this synthesis section.

[0009] Further, the exhaust port of the vapor-liquid separation device in the first-stage synthesis section is connected to the gas-gas heat exchanger in the second-stage synthesis section, and the exhaust port of the vapor-liquid separation device in the second-stage synthesis section is connected to the gas-gas heat exchanger in the third-stage synthesis section.

[0010] Further, a recycle gas compressor is connected to the gas outlet end of the vapor-liquid separation device in the third-stage synthesis section, and the outlet of the recycle gas compressor is connected to the gas-gas heat exchanger in the third-stage synthesis section.

[0011] Further, the liquid discharge ports of the vapor-liquid separation devices in the primary synthesis section, secondary synthesis section, and tertiary synthesis section are all connected to a flash tank.

[0012] Further, the vapor-liquid separation device includes a primary vapor-liquid separator and a high-efficiency vapor-liquid separator connected in series.

[0013] Further, the raw gas treatment section includes a carbon dioxide compressor, and the inlet of the carbon dioxide compressor is connected to a carbon dioxide raw gas source; the outlet end of the carbon dioxide compressor is connected to a hydrolysis desulfurization device and a hydrodesulfurization device, and the hydrolysis desulfurization device and the hydrodesulfurization device are connected.

[0014] Further, the hydrolysis desulfurization device includes a desulfurization heater and a desulfurization steam heater, the hydrodesulfurization device includes a hydrogenerator and a desulfurization tower, the desulfurization heater, the desulfurization steam heater, the hydrogenerator, and the desulfurization tower are connected in sequence, the outlet of the desulfurization tower is connected to the desulfurization heater, and the desulfurization heater is further connected to a gas-gas heat exchanger in the primary synthesis section.

[0015] Further, a part of the hydrogen raw gas source is connected to the pipeline where the desulfurization heater is connected to the carbon dioxide compressor, and another part is connected to the pipeline where the desulfurization heater outputs to the primary synthesis section.

[0016] Further, the methanol synthesis towers in the primary synthesis section, secondary synthesis section, and tertiary synthesis section are all isothermal reactors with temperature control, using water as a heat transfer medium to by-produce steam.

[0017] Further, the high-efficiency vapor-liquid separator includes a baffle plate, a gas guide barrel, and a wire mesh. The high-efficiency vapor-liquid separator uses baffle separation, cyclone separation, and packed separation to perform composite and efficient water separation on the cooled synthesis gas.

[0018] In summary, the present utility model has the following advantages:

[0019] 1) Using carbon dioxide and hydrogen as raw materials, after balancing investment and energy consumption, this system designs two non-circulating methanol synthesis towers in series with one circulating methanol synthesis tower. Compared with the full-circulation process, the energy consumption is reduced by more than 20%, and the investment is reduced by more than 30%.

[0020] 2) By setting two non-circulating methanol synthesis towers in this system, the raw gas with a high carbon-hydrogen ratio is partially converted into methanol, and then added to the circulating tertiary synthesis section to convert the remaining carbon dioxide into methanol under the condition of a high hydrogen-carbon ratio.

[0021] 3) The dehydration method adopted by this system is a combination of a wire mesh vapor-liquid separator and a high-efficiency vapor-liquid separator. Most of the moisture in the syngas is removed in the wire mesh vapor-liquid separator and then enters the high-efficiency vapor-liquid separator. By using the combined effects of baffle separation, cyclone separation, and packed separation, the moisture can be removed as much as possible without wasting heat. The dehydration efficiency is increased by more than 5%, and the methanol conversion rate is increased by more than 3%.

[0022] 4) This system is suitable for the working conditions of hydrogenation of carbon dioxide to methanol with different scales, and has the advantages of simple process, convenient control, remarkable water separation effect, high total conversion rate, appropriate investment and energy consumption, etc.

[0023] 5) In this system, the organic sulfur and inorganic sulfur in the carbon dioxide gas source adopt a combined process of hydrolysis desulfurization and hydrogenation desulfurization, which can ensure that the total sulfur is reduced to less than 1 ppm. Description of the Drawings

[0024] Figure 1 It is the schematic diagram of a carbon dioxide hydrogenation to methanol system with partial circulation of the present utility model;

[0025] Wherein:

[0026] C1101, carbon dioxide compressor; E1101, desulfurization heater; E1102, desulfurization steam heater; R1101, hydrogenator; T1101, desulfurization tower; E1103, primary gas-gas heat exchanger; R1102, primary synthesis tower; E1104, primary syngas cooler; V1101, primary wire mesh vapor-liquid separator; V1102, primary high-efficiency vapor-liquid separator; E1105, primary water cooler; E1106, secondary gas-gas heat exchanger; R1103, secondary synthesis tower; E1107, secondary syngas cooler; V1103, secondary wire mesh vapor-liquid separator; V1104, secondary high-efficiency vapor-liquid separator; E1108, secondary water cooler; E1109, tertiary gas-gas heat exchanger; R1104, tertiary synthesis tower; E1110, tertiary syngas cooler; V1105, tertiary wire mesh vapor-liquid separator; V1106, tertiary high-efficiency vapor-liquid separator; E1111, tertiary water cooler; C1102, recycle gas compressor; V1107, flash tank. Detailed Embodiments

[0027] To better explain the content of the present utility model, the following further illustrates the present utility model through specific embodiments. However, it should not be understood that the protection scope of the present utility model is limited thereto. All features disclosed in the utility model content of the present utility model, or steps in all methods or processes disclosed, except for mutually exclusive features and / or steps, can be combined in any way. Any feature disclosed in the present utility model, unless specifically described, can be replaced by other equivalent or similar-purpose alternative features. That is, unless specifically described, each feature is only an example in a series of equivalent or similar features.

[0028] Embodiment 1

[0029] As a basic implementation mode of the present utility model, the present utility model provides a carbon dioxide hydrogenation to methanol system with local recycling, including a raw material gas treatment section, a primary synthesis section, a secondary synthesis section, and a tertiary synthesis section connected in sequence. Among them, the raw material gas treated by the raw material gas treatment section enters the primary synthesis section and the secondary synthesis section to synthesize methanol by non-recycling single-pass, and the tertiary synthesis section uses partial synthesis gas recycling to synthesize methanol.

[0030] In this embodiment, the source of the carbon dioxide gas source can be carbon dioxide released from low-temperature methanol washing in coal gasification, carbon dioxide capture gas, biomass gas, etc. This system is applicable to working conditions of carbon dioxide hydrogenation to methanol of different scales.

[0031] Specifically, as Figure 1 shown, the primary synthesis section includes a primary gas-gas heat exchanger E1103, a primary synthesis tower R1102, a primary synthesis gas cooler E1104, a primary gas-liquid wire mesh vapor-liquid separator, and a primary high-efficiency vapor-liquid separator V1102. The inlet and outlet of the primary synthesis tower R1102 are both connected to the primary gas-gas heat exchanger E1103. The outlet of the primary gas-gas heat exchanger E1103 is connected to the primary synthesis gas cooler E1104. The outlet of the primary synthesis gas cooler E1104 is connected to a primary vapor-liquid separation device, and the gas outlet of the primary vapor-liquid separation device is connected to the secondary gas-gas heat exchanger E1106 in the secondary synthesis section.

[0032] The secondary synthesis section includes a secondary gas-gas heat exchanger E1106, a secondary synthesis tower R1103, a secondary synthesis gas cooler E1107, a secondary wire mesh vapor-liquid separator V1103, and a secondary high-efficiency vapor-liquid separator V1104. The inlet and outlet of the secondary synthesis tower R1103 are both connected to the secondary gas-gas heat exchanger E1106. The outlet of the secondary gas-gas heat exchanger E1106 is connected to the secondary synthesis gas cooler E1107. The outlet of the secondary synthesis gas cooler E1107 is connected to a secondary vapor-liquid separation device, and the gas outlet of the secondary vapor-liquid separation device is connected to the tertiary gas-gas heat exchanger E1109 in the tertiary synthesis section.

[0033] The third - stage synthesis section includes a third - stage gas - gas heat exchanger E1109, a third - stage synthesis tower R1104, a third - stage synthesis gas cooler E1110, a third - stage wire - mesh vapor - liquid separator V1105, and a third - stage high - efficiency vapor - liquid separator V1106. Both the inlet and outlet of the third - stage synthesis tower R1104 are connected to the third - stage gas - gas heat exchanger E1109. The outlet of the third - stage gas - gas heat exchanger E1109 is connected to the third - stage synthesis gas cooler E1110. The outlet of the third - stage synthesis gas cooler E1110 is sequentially connected to the third - stage vapor - liquid separation device. The gas outlet of the third - stage high - efficiency vapor - liquid separation device is also connected to a recycle gas compressor C1102, and the outlet of the recycle gas compressor C1102 is connected back into the third - stage gas - gas heat exchanger E1109.

[0034] In this embodiment, the first - stage vapor - liquid separation device, the second - stage vapor - liquid separation device, and the third - stage vapor - liquid separation device are all connected to a flash tank V1107 to perform flash treatment on the mixed liquid of methanol and water separated at each stage, obtaining crude methanol.

[0035] The separation of water in the synthesis gas can effectively promote the reaction in the direction of methanol synthesis. Generally, by lowering the temperature, supersaturated water can be separated out. In this embodiment, the first - stage vapor - liquid separation device, the second - stage vapor - liquid separation device, and the third - stage vapor - liquid separation device all include a primary vapor - liquid separator and a high - efficiency vapor - liquid separator connected in series. Among them, the primary vapor - liquid separator is a wire - mesh vapor - liquid separator, and the high - efficiency vapor - liquid separator includes a baffle plate, a gas guide barrel, and wire mesh. The high - efficiency vapor - liquid separator uses baffle separation, cyclone separation, and packed separation to perform composite and efficient water separation on the water - cooled synthesis gas.

[0036] Preferably, a water cooler is also connected between the primary vapor - liquid separator and the high - efficiency vapor - liquid separator in each stage of the synthesis section.

[0037] Specifically, as Figure 1 shown, the first - stage vapor - liquid separation device includes a first - stage wire - mesh vapor - liquid separator V1101 and a first - stage high - efficiency vapor - liquid separator V1102, and a first - stage water cooler E1105 is connected between the first - stage wire - mesh vapor - liquid separator V1101 and the first - stage high - efficiency vapor - liquid separator V1102. The second - stage vapor - liquid separation device includes a second - stage wire - mesh vapor - liquid separator V1103 and a second - stage high - efficiency vapor - liquid separator V1104, and a second - stage water cooler E1108 is connected between the second - stage wire - mesh vapor - liquid separator V1103 and the second - stage high - efficiency vapor - liquid separator. The third - stage vapor - liquid separation device includes a third - stage wire - mesh vapor - liquid separator V1105 and a third - stage high - efficiency vapor - liquid separator V1106, and a third - stage water cooler E1111 is connected between the third - stage wire - mesh vapor - liquid separator V1105 and the third - stage high - efficiency vapor - liquid separator V1106.

[0038] In this embodiment, the first - stage synthesis tower R1102, the second - stage synthesis tower R1103, and the third - stage synthesis tower R1104 are all isothermal reactors with temperature control, using water as the heat - removal medium to by - produce steam.

[0039] It should be noted that in this embodiment, the number of the first - stage synthesis section and the second - stage synthesis section without circulation is the preferred number set based on economic considerations, and it is not a limitation to the present invention.

[0040] In this embodiment, the working process of the system is as follows:

[0041] A. The carbon dioxide feed gas and the hydrogen feed gas are mixed and then enter the first - stage gas - gas heat exchanger E1103. The temperature is raised to above 200 °C and then enters the first - stage synthesis tower R1102. The synthesis gas is heated to above 230 °C, and the excess heat is used to produce by - product steam.

[0042] B. After the synthesis gas pre - heats the feed gas, it enters the primary vapor - liquid separator, where most of the water and methanol are separated, and the temperature drops to ≤60 °C.

[0043] C. After the initial water separation, the synthesis gas enters the high - efficiency vapor - liquid separator to further separate as much water as possible.

[0044] D. The synthesis gas coming out of the first - stage synthesis section enters the second - stage synthesis section, and the second - stage methanol synthesis is carried out in the same order as in step A, step B, and step C.

[0045] E. The synthesis gas coming out of the second - stage synthesis section enters the third - stage synthesis section, and the third - stage methanol synthesis is carried out in the same order as in step A, step B, and step C. The third - stage methanol synthesis adopts synthesis gas circulation, and the circulation ratio ≥2.

[0046] F. The mixed liquid of methanol and water separated from each stage of the synthesis section is collected in the flash tank V1107, and the flash pressure ≤0.5 MPaG to obtain crude methanol.

[0047] The present utility model uses carbon dioxide and hydrogen as raw materials. After balancing investment and energy consumption, it designs two non - circulating methanol synthesis towers in series with one circulating methanol synthesis tower. By setting two non - circulating methanol synthesis towers, the raw material gas with a high carbon - hydrogen ratio is partially converted into methanol, and then the remaining carbon dioxide is converted into methanol under the condition of a high hydrogen - carbon ratio by adding a circulating third - stage synthesis section. The energy consumption is reduced by more than 20% and the investment is reduced by more than 30% compared with the full - circulation process.

[0048] To further improve the methanol synthesis conversion rate, this system adopts a dehydration method combining a wire - mesh vapor - liquid separator and a high - efficiency vapor - liquid separator. The dehydration efficiency is increased by more than 5%, and the methanol conversion rate is increased by more than 3%.

[0049] This system is suitable for the working conditions of carbon dioxide hydrogenation to methanol with different scales, and has the advantages of simple process, convenient control, significant water - separation effect, high total conversion rate, appropriate investment and energy consumption, etc.

[0050] Embodiment 2

[0051] Based on Embodiment 1, a carbon dioxide hydrogenation to methanol system with a partial loop in this embodiment has the following differences:

[0052] As Figure 1 shown, in this embodiment, the raw material gas treatment section includes a carbon dioxide compressor C1101, a hydrolysis desulfurization device, and a hydrodesulfurization device. The hydrolysis desulfurization device includes a desulfurization heater E1101 and a desulfurization steam heater E1102, and the hydrodesulfurization device includes a hydrodesulfurizer R1101 and a desulfurization tower T1101.

[0053] The inlet of the carbon dioxide compressor C1101 is connected to the carbon dioxide raw material gas source for compressing the raw material carbon dioxide. The desulfurization heater E1101, the desulfurization steam heater E1102, the hydrodesulfurizer R1101, and the desulfurization tower T1101 are sequentially connected to the outlet end of the carbon dioxide compressor C1101. The outlet of the desulfurization tower T1101 is connected into the desulfurization heater E1101, and the desulfurization heater E1101 is further connected into the first-stage gas-gas heat exchanger E1103 in the first-stage synthesis section.

[0054] In this embodiment, the organic sulfur and inorganic sulfur in the carbon dioxide gas source can adopt a combined process of hydrolysis desulfurization and hydrodesulfurization, which can ensure that the total sulfur is reduced to less than 1 ppm.

[0055] A part of the hydrogen raw material gas is connected to the pipeline where the carbon dioxide compressor C1101 is connected to the desulfurization heater E1101, and enters the desulfurization heater E1101 and the desulfurization steam heater E1102 together with the pressurized carbon dioxide. After heat exchange with the desulfurized syngas, the temperature is increased; the other part is connected to the pipeline where the desulfurization heater E1101 outputs to the gas-gas heat exchanger in the first-stage synthesis section, and is mixed with the heated carbon dioxide and then enters the first-stage gas-gas heat exchanger E1103 in the first-stage synthesis section together to further increase the temperature of the mixed raw material gas.

[0056] In this embodiment, taking the utilization of carbon dioxide from low-temperature methanol washing of coal gasification as an example, the working process of the system is as follows:

[0057] The temperature of the raw material carbon dioxide is 25 °C, the pressure is 0.15 MPaG, the flow rate is 13403 kg / hr, and the mass composition of carbon dioxide is CO2: 98.5%; H2: 1.5%, and both organic sulfur and inorganic sulfur are 10 ppm.

[0058] The temperature of the raw material hydrogen is 25 °C, the pressure is 2.5 MPaG, the flow rate is 1815 kg / hr, and the mass composition of hydrogen is H2: 99.9%; CH4: 0.1%.

[0059] 1) The raw material carbon dioxide first enters the carbon dioxide compressor C1101 for compression, and the pressure is increased to 2.5 MPaG;

[0060] 2) After pressurization, 1% of raw material hydrogen is incorporated into carbon dioxide. After heat exchange with desulfurized syngas, the temperature is increased to 150 °C, and then it enters a steam heater to be heated to 180 °C. The steam used is by-product steam from synthesis;

[0061] 3) After the temperature is increased, carbon dioxide successively enters two-stage hydrogenation and one-stage desulfurization to reduce the total sulfur to below 1 ppm;

[0062] 4) After desulfurization, carbon dioxide is mixed with the remaining raw material hydrogen and enters the tube side of a gas-gas heat exchanger, where it exchanges heat with the gas from the outlet of the synthesis tower. The temperature is increased to 200 °C and then it enters the first-stage synthesis tower R1102. The outlet temperature of the syngas is 230 °C, and the excess heat is used to produce by-product steam;

[0063] 5) After the syngas preheats the raw material gas, it enters a primary vapor-liquid separator to separate most of the water and methanol, and the temperature drops to 40 °C;

[0064] 6) After the initial water separation, the syngas enters a high-efficiency vapor-liquid separator to continue separating as much water as possible;

[0065] 7) The syngas coming out of the first-stage synthesis section is incorporated with a part of carbon dioxide to make the hydrogen-carbon ratio at the inlet of the second stage 2, and then continue with second-stage synthesis and second-stage water separation;

[0066] 8) The syngas coming out of the second-stage synthesis section enters the third-stage synthesis section to continue with third-stage synthesis and third-stage water separation; The third-stage synthesis uses a reciprocating machine to compress and recycle the syngas, and the recycle ratio is 3.2;

[0067] 9) The mixed liquid of methanol and water separated from each stage of the synthesis section is collected in a flash tank V1107, and the flash pressure is 0.4 MPaG to obtain crude methanol for rectification and separation.

[0068] Methanol is produced through the above process, and the carbon dioxide emissions from the low-temperature methanol wash in coal gasification are also reduced. The entire system has the advantages of simple process, convenient control, remarkable water separation effect, high total conversion rate, and appropriate investment and energy consumption.

[0069] The above is only a preferred embodiment of the present invention, and it does not impose any form of limitation on the present invention. Any simple modification or equivalent change made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A carbon dioxide hydrogenation to methanol system with local recycling, characterized in that, It includes a raw gas treatment section, a first-stage synthesis section for non-circulating one-pass methanol synthesis, a second-stage synthesis section, and a third-stage synthesis section for synthesizing methanol with partial synthesis gas recycle; each synthesis section includes a gas-gas heat exchanger, a methanol synthesis tower, a synthesis gas cooler, and a vapor-liquid separation device; in each synthesis section, the inlet and outlet of the methanol synthesis tower are connected to the gas-gas heat exchanger in this synthesis section, the outlet of the gas-gas heat exchanger is connected to the synthesis gas cooler in this synthesis section, and the outlet of the synthesis gas cooler is connected to the vapor-liquid separation device in this synthesis section.

2. The carbon dioxide hydrogenation to methanol system with partial circulation according to claim 1, wherein The exhaust port of the vapor-liquid separation device in the first-stage synthesis section is connected to the gas-gas heat exchanger in the second-stage synthesis section, and the exhaust port of the vapor-liquid separation device in the second-stage synthesis section is connected to the gas-gas heat exchanger in the third-stage synthesis section.

3. The carbon dioxide hydrogenation to methanol system with partial circulation according to claim 1, characterized in that, The gas outlet end of the vapor-liquid separation device in the third-stage synthesis section is connected with a recycle gas compressor, and the outlet of the recycle gas compressor is connected to the gas-gas heat exchanger in the third-stage synthesis section.

4. A carbon dioxide hydrogenation to methanol system with partial circulation according to claim 1, characterized in that, The liquid discharge ports of the vapor-liquid separation devices in the first-stage synthesis section, the second-stage synthesis section, and the third-stage synthesis section are all connected to a flash tank.

5. A carbon dioxide hydrogenation to methanol system with local circulation according to any one of claims 1 to 4, characterized in that, The vapor-liquid separation device includes a primary vapor-liquid separator and a high-efficiency vapor-liquid separator connected in series.

6. The carbon dioxide hydrogenation to methanol system with partial circulation according to claim 1, characterized in that, The raw gas treatment section includes a carbon dioxide compressor, and the inlet of the carbon dioxide compressor is connected to a carbon dioxide raw gas source; the outlet end of the carbon dioxide compressor is connected with a hydrolysis desulfurization device and a hydrodesulfurization device, and the hydrolysis desulfurization device and the hydrodesulfurization device are connected.

7. A carbon dioxide hydrogenation to methanol system with local circulation according to claim 6, wherein, The hydrolysis desulfurization device includes a desulfurization heater and a desulfurization steam heater, the hydrodesulfurization device includes a hydrogenator and a desulfurization tower, the desulfurization heater, the desulfurization steam heater, the hydrogenator, and the desulfurization tower are connected in sequence, the outlet of the desulfurization tower is connected to the desulfurization heater, and the desulfurization heater is also connected to the gas-gas heat exchanger in the first-stage synthesis section.

8. A carbon dioxide hydrogenation to methanol system with partial circulation according to claim 7, characterized in that, Part of the hydrogen raw gas source is connected to the pipeline where the desulfurization heater is connected to the carbon dioxide compressor, and the other part is connected to the pipeline where the desulfurization heater outputs to the first-stage synthesis section.

9. A carbon dioxide hydrogenation to methanol system with a partial loop according to claim 1, characterized in that, The methanol synthesis towers in the first-stage synthesis section, the second-stage synthesis section, and the third-stage synthesis section are all isothermal reactors with temperature control, using water as the heat transfer medium to by-product steam.

10. A carbon dioxide hydrogenation to methanol system with local circulation according to claim 5, characterized in that, The high-efficiency vapor-liquid separator includes a baffle plate, a gas guide barrel, and a wire mesh. The high-efficiency vapor-liquid separator uses baffle separation, cyclone separation, and packed separation to conduct composite and high-efficiency water separation on the water-cooled synthesis gas.

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