Process method and system for preparing methanol through hydrogenation of carbon dioxide

Abstract

The invention provides a process and a system for preparing methanol through hydrogenation of carbon dioxide, and the process method comprises the following steps: carrying out primary reaction on raw material gas at least containing carbon dioxide and hydrogen in the presence of a first catalyst under the pressure of 1-15.0 MPa and the temperature of 200-350 DEG C, separating a primary methanol crude product in primary reaction products, and separating the primary methanol crude product from the primary reaction products; and carrying out second-stage reaction on the first-stage residues in the presence of a second catalyst at the pressure of 5-20.0 MPa and the temperature of 150-320 DEG C. And separating the secondary reaction product to obtain a secondary methanol crude product. Wherein in the same process operation, the operation pressure of the first-stage reaction is lower than that of the second-stage reaction, and the reaction temperature of the first-stage reaction is higher than that of the second-stage reaction. The process method comprises the following steps: carrying out primary reaction on raw material gas under low-pressure and high-temperature conditions, separating methanol and water from a system after the primary reaction, and carrying out secondary reaction on a primary reaction product under high-pressure and low-temperature conditions to obtain a final product, the conversion per pass of carbon dioxide is improved and the yield of methanol is improved through two-step reaction under different operation conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of methanol preparation, and particularly relates to a process method and system for hydrogenating carbon dioxide to methanol. Background Art

[0002] Carbon dioxide is often used to represent all greenhouse gases in the national carbon neutrality or net-zero emission targets. It is a typical greenhouse gas, and at the same time, it is an abundant, non-toxic, non-flammable and easily available renewable resource. Methanol is an important industrial basic raw material, widely used in the chemical and pharmaceutical industries, and is also a type of clean liquid fuel.

[0003] At present, methanol synthesis is mainly obtained by the hydrogenation reaction of the conversion gas from natural gas conversion and the coal-based synthesis gas from coal gasification. Utilizing the carbon and oxygen resources in carbon dioxide and synthesizing methanol through the hydrogenation reaction can achieve the recycling of carbon resources, enabling humans to gradually get rid of the dependence on the increasingly scarce fossil energy, reducing the environmental burden, and promoting the sustainable development of society.

[0004] However, due to the low activity of carbon dioxide, the methanol synthesis process is restricted by thermodynamics, and the single-pass conversion rate is relatively low. At the same time, the CO selectivity of the currently developed catalysts is relatively high. Therefore, when applied industrially, it is necessary to increase the recycle ratio of the tail gas to achieve high conversion of carbon dioxide and high selectivity of methanol. This will lead to an increase in energy consumption during industrial production, and thus an increase in the production cost of methanol.

[0005] Therefore, in order to improve the methanol yield and reduce the energy consumption of the synthesis device, the present application aims to develop a large-scale methanol synthesis process method and a supporting system that match the reaction mechanism. Summary of the Invention

[0006] In view of the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a process method and system for hydrogenating carbon dioxide to methanol. The process method first performs a primary reaction on carbon dioxide and hydrogen under low pressure and high temperature conditions. After the primary reaction, the generated methanol and water are separated from the system, and then the primary reaction product is subjected to a secondary reaction under high pressure and low temperature conditions to obtain the final product, that is, through two reactions with different operating conditions, the single-pass conversion rate of carbon dioxide is increased and the methanol yield is increased.

[0007] To achieve the above purpose and other related purposes, the first aspect of the present invention provides a process method for hydrogenating carbon dioxide to methanol, and the process method includes the following steps:

[0008] S1. A raw material gas containing at least carbon dioxide and hydrogen is subjected to a primary reaction in the presence of a first catalyst to obtain a primary reaction product; the operating pressure of the primary reaction is 1 MPa to 15.0 MPa, and the reaction temperature is 200 °C to 350 °C;

[0009] S2. After separating the crude primary methanol in the primary reaction product, subject the primary residue to a secondary reaction in the presence of a second catalyst to obtain a secondary reaction product; the operating pressure of the secondary reaction is 5 MPa to 20.0 MPa, and the reaction temperature is 150 °C to 320 °C;

[0010] S3. Separate the crude secondary methanol from the secondary reaction product;

[0011] S4. Refine the crude primary methanol and the crude secondary methanol to obtain methanol;

[0012] Wherein, in the same process operation, the operating pressure of the primary reaction is lower than that of the secondary reaction, and the reaction temperature of the primary reaction is higher than that of the secondary reaction.

[0013] In a second aspect of the present invention, a process system for hydrogenating carbon dioxide to methanol is provided. The process system includes a low-pressure reaction device and a high-pressure reaction device connected in series;

[0014] The low-pressure reaction device is used to carry out a primary reaction on a raw material gas containing at least carbon dioxide and hydrogen in the presence of a first catalyst to obtain a primary reaction product, and the operating pressure of the low-pressure reaction device is 1 MPa to 15.0 MPa, and the reaction temperature is 200 °C to 350 °C;

[0015] The high-pressure reaction device is used to carry out a secondary reaction on the primary residue in the presence of a second catalyst to obtain a secondary reaction product, and the operating pressure of the high-pressure reaction device is 5 MPa to 20.0 MPa, and the reaction temperature is 150 °C to 320 °C.

[0016] The present invention has the following beneficial effects:

[0017] 1) The process method of the present invention connects two reactions with different operating conditions in series. First, the raw material gas undergoes a primary reaction at low pressure and high temperature, and most of the carbon dioxide is converted. The remaining carbon dioxide, hydrogen, and generated carbon monoxide and other primary residues then undergo a secondary reaction at high pressure and low temperature. The single-pass conversion rate of carbon dioxide using this process is high, and the methanol yield is high;

[0018] 2) The process method of the present invention connects two reactions with different operating conditions in series. After the raw material gas undergoes two reactions with different operating conditions, most of the carbon dioxide, hydrogen, and carbon monoxide are converted in the primary reaction and the secondary reaction, and only a small part enters the circulation, that is, the gas circulation volume is small and the energy consumption is low;

[0019] 3) The two reactions with different operating conditions (corresponding to two reactors with different operating conditions) connected in series in the present invention can be flexibly adjusted according to the actual working conditions, and it is easy to realize large-scale production.

[0020] 4) The raw material gas first passes through a low-pressure reaction device and reacts under the conditions of low pressure and high temperature. Most of the carbon dioxide is converted, and the generated methanol and water are condensed and separated. The remaining unreacted carbon dioxide, hydrogen, and the generated carbon monoxide enter a high-pressure reaction device and continue to react under the conditions of high pressure and low temperature. A small part of the unreacted carbon dioxide, hydrogen, and carbon monoxide enters the circulation. The circulating gas is divided by a shunt device, and a part of it circulates back to participate in the primary reaction, and the other part circulates back to participate in the secondary reaction. That is, through the shunt device, the intake gas volume after connecting two reactors in series is adapted, and when applied to large-scale production, the situation that one reactor is restricted by another reaction device will not occur. Description of the Drawings

[0021] Figure 1 It shows a schematic diagram of the process system for hydrogenating carbon dioxide to methanol according to an embodiment of the present application.

[0022] Reference Signs:

[0023] V1 Raw material gas delivery pipeline

[0024] B1 Primary compressor

[0025] M1-IN Input pipeline of the primary splitter

[0026] M1 Primary splitter

[0027] H1 Primary heat exchange device

[0028] V2 Output pipeline of the primary heat exchange device

[0029] R1 Low-pressure reaction device

[0030] V3 Pipeline for transporting primary reaction products

[0031] C1-IN Input pipeline of the primary condensation device

[0032] C1 Primary condensation device

[0033] V4 Pipeline for primary residues

[0034] L4 Pipeline for crude primary methanol products

[0035] M2 Secondary splitter

[0036] B2-IN Input pipeline of the secondary compressor

[0037] B2 Secondary compressor

[0038] H2 Secondary heat exchange device

[0039] V5 Output pipeline of the secondary heat exchange device

[0040] R2 High-pressure reaction device

[0041] V6 Secondary reaction product transfer pipeline

[0042] C2-IN Secondary condensation device input pipeline

[0043] C2 Secondary condensation device

[0044] V7 Secondary residue pipeline

[0045] S1 Shunt device

[0046] V8 Bleed gas pipeline

[0047] V9-1 Secondary circulation pipeline

[0048] V9-2 Primary circulation pipeline

[0049] L7 Secondary crude methanol product pipeline Detailed implementation mode

[0050] Based on the problems of energy consumption and yield in current methanol production, the inventors of this application aim to analyze from the reaction mechanism and develop a large-scale methanol synthesis process method and supporting system that matches the reaction mechanism.

[0051] Specifically, in the process of preparing methanol from the raw material gas containing carbon dioxide and hydrogen, the following reactions mainly occur:

[0052]

[0053] As can be seen from the above, the reaction of methanol synthesis is an exothermic reaction with a decrease in volume, while the reverse water-gas shift reaction is an endothermic reaction with a constant volume. Considering the combined influence of reaction thermodynamics and kinetics, the applicant has developed a series connection of two reactions under different operating conditions. First, a primary reaction at low pressure and high temperature is carried out. After separating methanol and water, a secondary reaction at high pressure and low temperature is carried out again. The experimental results prove that this method has a high single-pass conversion rate of carbon dioxide and increases the methanol output. In addition, a set of adapted process system has been developed, which can be flexibly adjusted according to the actual working conditions, is easy to realize large-scale production, and reduces energy consumption. On this basis, the present invention has been completed.

[0054] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 1-3, 5-8, and 8-10 are listed for a specific parameter, ranges of 3-8 and 5-10 are also contemplated. In this application, unless otherwise specified, the numerical range "a-b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers.

[0055] The following illustrates the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0056] The first aspect of the present invention provides a process for hydrogenating carbon dioxide to methanol, and the process includes the following steps:

[0057] S1. React a raw material gas containing at least carbon dioxide and hydrogen in the presence of a first catalyst to obtain a primary reaction product; the operating pressure of the primary reaction is 1 MPa to 15.0 MPa, and the reaction temperature is 200 °C to 350 °C;

[0058] Specifically, the raw material gas may only contain carbon dioxide and hydrogen. Generally, the molar ratio of hydrogen to carbon dioxide is required to be 0.2:1 to 9:1, and options include 0.2:1 to 1:1 or 1:1 to 2:1 or 2:1 to 4:1 or 4:1 to 6:1 or 6:1 to 9:1. Of course, depending on the source of the raw material gas, it may also contain a certain amount of CO or other impurity gases, and the molar ratio of carbon monoxide to carbon dioxide more suitable for this example is less than 1. Preferably, the molar ratio of (H2-CO 2) / (CO+CO2) is 1.9 to 2.1, and options include the molar ratio of (H2-CO 2) / (CO+CO2) being 1.9 to 2.0 or 2.0 to 2.1.

[0059] More specifically, the first catalyst is selected from at least one of a copper-based catalyst, a zirconium-based catalyst, or an indium-based catalyst. Different catalysts have different effects on the reaction rate and product selectivity. The focus of this application is on the selection of operating conditions for two consecutive reactions, and the catalyst can be selected according to actual needs. In this example, the first catalyst used is a ZnO-ZrO2 solid solution catalyst, such as 13wt% ZnO-ZrO2. The operating space velocity of the primary reaction is 1000 - 100000 h -1 , such as 1000 - 10000 h -1 or 10000 - 50000 h -1 or 50000 - 100000 h -1 , and it can be selected according to the actual working conditions.

[0060] More specifically, the operating pressure of the primary reaction can be 1 MPa - 3 MPa, or 3 MPa - 5 MPa, or 5 MPa - 10 MPa, or 10 MPa - 15 MPa. Or the reaction temperature can be 280°C - 350°C, or 200°C - 250°C, or 250°C - 300°C, or 300°C - 350°C.

[0061] More specifically, most of the carbon dioxide in the primary reaction product obtained under the operating conditions of low pressure and high temperature in the primary reaction is converted, and the remaining unreacted carbon dioxide, hydrogen, or carbon monoxide and the newly generated carbon monoxide enter the secondary reaction.

[0062] S2. After separating the crude primary methanol in the primary reaction product, the primary residue is subjected to a secondary reaction in the presence of a second catalyst to obtain a secondary reaction product; the operating pressure of the secondary reaction is 5 MPa - 20.0 MPa, and the reaction temperature is 150°C - 320°C;

[0063] Specifically, first cool down to separate the crude methanol and water generated in the primary reaction from the product system, and subject the primary residue (the remaining unreacted carbon dioxide, hydrogen, or carbon monoxide and the newly generated carbon monoxide) to a secondary reaction under high pressure and low temperature.

[0064] More specifically, the second catalyst is selected from at least one of a copper-based catalyst, a zirconium-based catalyst, or a zinc-chromium catalyst. Similarly, different catalysts have different effects on the reaction rate and product selectivity. The focus of this application is on the selection of operating conditions for two consecutive reactions, and the catalyst can be selected according to actual needs. In this example, the second catalyst used is a CuO-ZnO-Al2O3 catalyst, such as 5wt% CuO - 30wt% ZnO-Al2O3. The operating space velocity of the secondary reaction is 1000 - 100000 h -1 , such as 1000 - 10000 h -1 or 10000 - 50000 h-1 or 50,000 - 100,000 h -1 , and it can be selected according to the actual working condition requirements.

[0065] More specifically, the operating pressure of the secondary reaction can be 5 MPa - 20.0 MPa, 5 MPa - 15.0 MPa, 5 MPa - 8 MPa, 8 MPa - 10 MPa, 10 MPa - 15.0 MPa, or 15 MPa - 20.0 MPa. The reaction temperature can be 150°C - 320°C, 180°C - 250°C, 150°C - 180°C, 180°C - 200°C, 200°C - 250°C, or 200°C - 320°C.

[0066] S3. The secondary reaction product is separated to obtain a crude secondary methanol product;

[0067] Specifically, after the secondary reaction product is cooled, a crude secondary methanol product and a secondary residue in the gas phase are obtained. After separation, a secondary methanol product is obtained; a part of the secondary residue is discharged, and the other part is used as recycle gas to enter the primary reaction and / or the secondary reaction. Preferably, 3 - 10 V% of the gas is discharged, and the other part of the recycle gas enters the primary reaction and the secondary reaction respectively to adjust the intake air volume of the two series reactions, so as to ensure the matching of the two reactors during large-scale production.

[0068] S4. The crude primary methanol product and the crude secondary methanol product are refined to obtain methanol;

[0069] Specifically, the refinement of the crude product can be carried out by conventional separation methods.

[0070] It should be noted that in the same process operation, the operating pressure of the primary reaction is lower than that of the secondary reaction, and the reaction temperature of the primary reaction is higher than that of the secondary reaction. For example, 1) the operating pressure of the primary reaction is 1 MPa - 3 MPa, and the reaction temperature is 250°C - 300°C. The operating pressure of the secondary reaction is 5 MPa - 10 MPa, and the reaction temperature is 180°C - 200°C. 2) The operating pressure of the primary reaction is 3 MPa - 5 MPa, and the reaction temperature is 300°C - 320°C. The operating pressure of the secondary reaction is 10 MPa - 15 MPa, and the reaction temperature is 180°C - 200°C. It can be selected according to the actual situation, but it is necessary to ensure that the operating pressure of the primary reaction is lower than that of the secondary reaction, and the reaction temperature of the primary reaction is higher than that of the secondary reaction.

[0071] The second aspect of the present application provides a process system adapted to the above process method. The process system includes a low-pressure reaction device and a high-pressure reaction device connected in series. The low-pressure reaction device is used to carry out a primary reaction on a raw material gas containing at least carbon dioxide and hydrogen in the presence of a first catalyst to obtain a primary reaction product, and the operating pressure of the low-pressure reaction device is 1 MPa to 15.0 MPa, and the reaction temperature is 200 °C to 350 °C; the high-pressure reaction device is used to carry out a secondary reaction on the primary residue in the presence of a second catalyst to obtain a secondary reaction product, and the operating pressure of the high-pressure reaction device is 5 MPa to 20.0 MPa, and the reaction temperature is 150 °C to 320 °C.

[0072] In some feasible examples, a secondary reaction product delivery pipeline V6 is provided at the output end of the high-pressure reaction device R2, and a secondary condensation device C2 is further provided downstream of the high-pressure reaction device R2;

[0073] The secondary reaction product delivery pipeline V6 is communicated with the secondary condensation device C2, and the secondary reaction product branches into a secondary crude methanol pipeline L7 and a secondary residue pipeline V7 after passing through the secondary condensation device C2, which are respectively used to transport the secondary crude methanol and the secondary residue.

[0074] In a specific example, a shunt device S1 is further provided; the secondary residue pipeline V7 is connected to the shunt device S1 and then branches into a purge gas pipeline V8, a primary circulation pipeline V9-2, and a secondary circulation pipeline V9-1;

[0075] The primary circulation pipeline V9-2 is communicated with the raw material gas delivery pipeline V1, and the secondary circulation pipeline V9-1 is communicated with the primary residue pipeline V4. Through the shunt device, the intake air volume after the two reactors are connected in series is adapted, and when applied to large-scale production, the situation that one reactor is restricted by another reactor will not occur.

[0076] In some feasible examples, a raw material gas delivery pipeline V1, a primary compressor B1, and a primary heat exchange device H1 are further provided upstream of the low-pressure reaction device R1;

[0077] The raw material gas delivery pipeline V1 is used to transport the raw material gas, and after the raw material gas delivery pipeline V1 is sequentially communicated with the primary compressor B1 and the primary heat exchange device H1, it is then communicated with the low-pressure reaction device R1.

[0078] In a specific example, a primary shunt device M1 is provided upstream of the low-pressure reaction device R1. The primary circulation pipeline V9-2 and the raw material gas delivery pipeline V1 are respectively communicated with the primary shunt device M1. Similarly, through the shunt device, the intake air volume after the two reactors are connected in series is adapted, and when applied to large-scale production, the situation that one reactor is restricted by another reactor will not occur.

[0079] In a specific example, after the first-stage reaction product delivery pipeline V3 is connected to the first-stage heat exchange device H1, it is then connected to the first-stage condensation device C1.

[0080] In some feasible examples, the output end of the low-pressure reaction device R1 is provided with a first-stage reaction product delivery pipeline V3, and a first-stage condensation device C1 is further provided downstream of the low-pressure reaction device R1;

[0081] The first-stage reaction product delivery pipeline V3 is connected to the first-stage condensation device C1, and after passing through the first-stage condensation device C1, the first-stage reaction product branches into a first-stage crude methanol pipeline L4 and a first-stage residue pipeline V4, which are respectively used to transport the first-stage crude methanol and the first-stage residue.

[0082] In a specific example, a second-stage diverter M2 is provided upstream of the high-pressure reaction device R2, and the second-stage circulation pipeline V9-1 and the first-stage residue pipeline V4 are respectively connected to the second-stage diverter M2. Similarly, the intake air volume after the two reactors are connected in series is adapted by the diverter, and when applied to large-scale production, the situation where one reactor is restricted by another reactor will not occur.

[0083] In a specific example, a second-stage compressor B2 and a second-stage heat exchange device H2 are further included upstream of the high-pressure reaction device R2; after the first-stage residue pipeline V4 is sequentially connected to the second-stage compressor B2 and the second-stage heat exchange device H2, it is then connected to the high-pressure reaction device R2.

[0084] In a specific example, the second-stage reaction product delivery pipeline V6 is connected to the second-stage heat exchange device H2 and then connected to the second-stage condensation device C2.

[0085] To better understand the present invention, the following refers to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0086] Example 1

[0087] Provide a process system applicable to the process method of the present application. Please refer to Figure 1, The feed gas pipeline V1 is connected to the input end of the first-stage compressor B1. After reaching the required first-stage reaction pressure, it is then transported through the output end of the first-stage compressor B1 to the input pipeline M1-IN of the first-stage splitter. The input pipeline M1-IN of the first-stage splitter is connected to the first-stage splitter M1 and then enters the first-stage heat exchanger H1. After heat exchange and reaching the temperature required for the first-stage reaction, it is transported from the output pipeline V2 of the first-stage heat exchanger to the low-pressure reaction device R1 for the first-stage reaction. The output end of the low-pressure reaction device R1 is provided with a first-stage reaction product pipeline V3, and a first-stage condensation device C1 is also provided downstream of the low-pressure reaction device R1. The first-stage reaction product pipeline V3 is connected to the first-stage condensation device C1, and the first-stage reaction product branches into a first-stage crude methanol pipeline L4 and a first-stage residue pipeline V4 after passing through the first-stage condensation device C1, which are respectively used to transport the first-stage crude methanol and the first-stage residue.

[0088] Specifically, the first-stage reaction product pipeline V3 is connected to the first-stage heat exchanger H1 and then to the first-stage condensation device C1, so that the heat generated by the reaction is fully utilized. More specifically, after passing through the first-stage heat exchanger H1, it then enters the first-stage condensation device C1 through the first-stage condensation device input pipeline C1-IN, and then the first-stage crude methanol pipeline L4 is connected to the input end of the second-stage splitter M2. The output end of the second-stage splitter M2 is connected to the second-stage compressor input pipeline B2-IN. The second-stage compressor input pipeline B2-IN is connected to the second-stage compressor B2. After reaching the pressure required for the second-stage reaction, the second-stage compressor B2 is connected to the second-stage heat exchanger H2 through a pipeline. After reaching the temperature required for the second-stage reaction, the output end of the second-stage heat exchanger H2 is transported to the high-pressure reaction device R2 through the second-stage heat exchanger output pipeline V5 for the second-stage reaction.

[0089] Then, the output end of the high-pressure reaction device R2 is connected to the second-stage reaction product pipeline V6, and a second-stage condensation device C2 is also provided downstream of the high-pressure reaction device R2. The second-stage reaction product pipeline V6 is connected to the second-stage condensation device C2, and the second-stage reaction product branches into a second-stage crude methanol pipeline L7 and a second-stage residue pipeline V7 after passing through the second-stage condensation device C2, which are respectively used to transport the second-stage crude methanol and the second-stage residue.

[0090] Specifically, the second-stage reaction product pipeline V6 is connected to the second-stage heat exchanger H2 and then to the second-stage condensation device C2, so that the heat generated by the reaction is fully utilized. More specifically, after passing through the second-stage heat exchanger H2, it then enters the second-stage condensation device C2 through the second-stage condensation device input pipeline C2-IN, and after condensation treatment, it branches into a second-stage crude methanol pipeline L7 and a second-stage residue pipeline V7.

[0091] More specifically, after the secondary residue pipeline V7 is connected to the shunt device S1, it branches into a blowdown pipeline V8, a primary circulation pipeline V9-2, and a secondary circulation pipeline V9-1. More specifically, the primary circulation pipeline V9-2 is connected to the input end of the primary diverter M1, and the secondary circulation pipeline V9-1 is connected to the input end of the secondary diverter M2. By means of the shunt device and the diverter, the intake air volume after the two reactors are connected in series is made suitable, so that when applied to large-scale production, the situation where one reactor is restricted by another reactor will not occur.

[0092] Example 2

[0093] The process method of this example is carried out using the process system described in Example 1. Hydrogen and carbon dioxide with a molar ratio of 3:1 are mixed and used as the reaction raw material gas, which is input into the raw material gas pipeline V1 (the temperature of V1 is 30°C and the pressure is 101.25 Pa), and the space velocity is set at 20000 h -1 , pressurized by the primary compressor B1, and after passing through the primary heat exchange device H1, V2 is obtained (the temperature in V2 is 250°C and the pressure is 3 MPa); it enters the low-pressure reaction device R1 for reaction (R1 is a shell-and-tube reactor, the reaction temperature is 280°C, and the loaded catalyst is ZnO-ZrO2 solid solution catalyst). The tail gas after the reaction enters the primary heat exchange device H1 through the primary reaction product pipeline V3. In H1, it exchanges heat with the raw material gas, and then enters the primary condensation device C1 (the primary condensation device C1 is a water-cooled condenser, and the condensation temperature is 40°C). The condensed liquid product is output through the primary methanol crude product pipeline L4 or enters the downstream refining. The obtained carbon dioxide-rich gas-phase product enters the secondary compressor B2 through the primary residue pipeline V4 for pressurization, and then enters the secondary heat exchange device H2 for preheating to obtain a high-temperature and high-pressure reaction gas, which is output through the secondary heat exchange device pipeline V5 (the temperature in V5 is 180°C and the pressure is 5 MPa), and enters the high-pressure reaction device R2 for reaction (R2 is a shell-and-tube reactor, the reaction temperature is 250°C, and the loaded catalyst is CuO-ZnO-Al2O3 catalyst). The reaction product exchanges heat and cools with the high-pressure carbon dioxide-rich gas-phase product in the secondary heat exchange device H2 through the secondary reaction product pipeline V6, and then enters the condensation device C2 (the secondary condensation device C2 is a water-cooled condenser, and the condensation temperature is 40°C). The separated liquid product is output through the secondary methanol crude product pipeline or enters the downstream refining. The gas-phase product is transported to the shunt device S1 through the V7 secondary residue pipeline for shunting. 5v% of the gas is discharged as the blowdown gas V8, and the remaining gas is recycled as the circulating gas to re-enter the reaction. To meet the matching of the processing capacities of the two reactors, a part of the remaining circulation is transported through the primary circulation pipeline V9-2 to the primary diverter M1 to participate in the downstream primary reaction, and the other part is transported through the secondary circulation pipeline V9-1 to the secondary diverter M2 to participate in the downstream secondary reaction, V9-1:V9-2 = 43:5.

[0094] The result of this example is that the single-pass conversion rate of carbon dioxide is 36.5%, and the selectivity of methanol is 72%.

[0095] Example 3

[0096] The process method of this example is carried out using the process system described in Example 1. Hydrogen and carbon dioxide with a molar ratio of 3:1 are mixed and used as the reaction raw material gas, which is input into the raw material gas pipeline V1 (the temperature of V1 is 25 °C and the pressure is 101.25 Pa). The space velocity is set to 20000 h -1 , pressurized by the first-stage compressor B1, and after passing through the first-stage heat exchanger H1, V2 is obtained (the temperature in V2 is 280 °C and the pressure is 3 MPa); it enters the low-pressure reaction device R1 for reaction (R1 is a shell-and-tube reactor, the reaction temperature is 280 °C, and the catalyst loaded is the same as that in Example 1). The tail gas after the reaction enters the first-stage heat exchanger H1 through the first-stage reaction product pipeline V3. In H1, it exchanges heat with the raw material gas, and then enters the first-stage condensation device C1 (the first-stage condensation device C1 is a water-cooled condenser, and the condensation temperature is 40 °C). The condensed liquid product is output through the first-stage crude methanol pipeline L4 or enters downstream refining. The carbon dioxide-rich gas product obtained enters the second-stage compressor B2 for pressurization through the first-stage residue pipeline V4, and then enters the second-stage heat exchanger H2 for preheating to obtain a high-temperature and high-pressure reaction gas, which is output through the second-stage heat exchanger pipeline V5 (the temperature in V5 is 200 °C and the pressure is 5 MPa), and enters the high-pressure reaction device R2 for reaction (R2 is a shell-and-tube reactor, the reaction temperature is 230 °C, and the catalyst loaded is the same as that in Example 1). The reaction product exchanges heat and cools with the high-pressure carbon dioxide-rich gas product in the second-stage heat exchanger H2 through the second-stage reaction product pipeline V6, and then enters the condensation device C2 (the second-stage condensation device C2 is a water-cooled condenser, and the condensation temperature is 40 °C). The separated liquid product is output through the second-stage crude methanol pipeline or enters downstream refining. The gas product is transported to the shunt device S1 through the V7 second-stage residue pipeline for shunting. 5v% of the gas is discharged as the purge gas V8, and the remaining is used as recycle gas to re-enter the reaction. To meet the matching of the processing capacities of the two reactors, a part of the remaining recycle gas is transported through the first-stage recycle pipeline V9-2 to the first-stage splitter M1 to participate in the downstream first-stage reaction, and the other part is transported through the second-stage recycle pipeline V9-1 to the second-stage splitter M2 to participate in the downstream second-stage reaction, V9-1:V9-2 = 13:1.

[0097] The result of this example is that the single-pass conversion rate of carbon dioxide is 38.7%, and the selectivity of methanol is 85.5%.

[0098] Example 4

[0099] The process method of this example is carried out using the process system described in Example 1. Hydrogen and carbon dioxide with a molar ratio of 3:1 are mixed and used as the reaction raw material gas, which is input into the raw material gas pipeline V1 (the temperature of V1 is 25 °C and the pressure is 101.25 Pa). The space velocity is set to 20000 h -1 , pressurized by the first-stage compressor B1, and after passing through the first-stage heat exchanger H1, V2 is obtained (the temperature in V2 is 280 °C and the pressure is 3 MPa); it enters the low-pressure reaction device R1 for reaction (R1 is a shell-and-tube reactor, the reaction temperature is 320 °C, and the catalyst filled is the same as that in Example 1). The tail gas after the reaction enters the first-stage reaction product pipeline V3 and then enters the first-stage heat exchanger H1. In H1, it exchanges heat with the raw material gas, and then enters the first-stage condensation device C1 (the first-stage condensation device C1 is a water-cooled condenser, and the condensation temperature is 40 °C). The condensed liquid product is output through the first-stage crude methanol pipeline L4 or enters the downstream refining. The carbon dioxide-rich gas product obtained enters the second-stage compressor B2 through the first-stage residue pipeline V4 for pressurization, and then enters the second-stage heat exchanger H2 for preheating to obtain a high-temperature and high-pressure reaction gas, which is output through the second-stage heat exchanger pipeline V5 (the temperature in V5 is 200 °C and the pressure is 5 MPa), and enters the high-pressure reaction device R2 for reaction (R2 is a shell-and-tube reactor, the reaction temperature is 230 °C, and the catalyst filled is the same as that in Example 1). The reaction product exchanges heat and cools with the high-pressure carbon dioxide-rich gas product in the second-stage heat exchanger H2 through the second-stage reaction product pipeline V6, and then enters the condensation device C2 (the second-stage condensation device C2 is a water-cooled condenser, and the condensation temperature is 40 °C). The separated liquid product is output through the second-stage crude methanol pipeline or enters the downstream refining. The gas product is transported to the shunt device S1 through the V7 second-stage residue pipeline for shunting. 5v% of the gas is discharged as the purge gas V8, and the remaining is used as the recycle gas to re-enter the reaction. To meet the matching of the processing capacities of the two reactors, a part of the remaining recycle gas is transported through the first-stage recycle pipeline V9-2 to the first-stage splitter M1 to participate in the downstream first-stage reaction, and the other part is transported through the second-stage recycle pipeline V9-1 to the second-stage splitter M2 to participate in the downstream second-stage reaction, V9-1:V9-2 = 22:5.

[0100] The results of this example show that the single-pass conversion rate of carbon dioxide is 40.4% and the selectivity of methanol is 84.5%.

[0101] Example 5

[0102] The process method of this example is carried out using the process system described in Example 1. Hydrogen and carbon dioxide with a molar ratio of 3:1 are mixed and used as the reaction raw material gas, which is input into the raw material gas pipeline V1 (the temperature of V1 is 25 °C and the pressure is 101.25 Pa). The space velocity is set to 20000 h -1, pressurized by the first-stage compressor B1, and after passing through the first-stage heat exchange device H1, V2 is obtained (the temperature in V2 is 280 °C and the pressure is 3 MPa); it enters the low-pressure reaction device R1 for reaction (R1 is a shell-and-tube reactor, the reaction temperature is 320 °C, and the catalyst filled is the same as that in Example 1). The tail gas after the reaction enters the first-stage heat exchange device H1 through the first-stage reaction product pipeline V3. In H1, it exchanges heat with the raw material gas and then enters the first-stage condensation device C1 (the first-stage condensation device C1 is a water-cooled condenser, and the condensation temperature is 40 °C). The condensed liquid product is output through the first-stage crude methanol pipeline L4 or enters downstream refining. The obtained carbon dioxide-rich gas-phase product enters the second-stage compressor B2 through the first-stage residue pipeline V4 for pressurization, and then enters the second-stage heat exchange device H2 for preheating to obtain a high-temperature and high-pressure reaction gas, which is output through the second-stage heat exchange device pipeline V5 (the temperature in V5 is 200 °C and the pressure is 10 MPa), and enters the high-pressure reaction device R2 for reaction (R2 is a shell-and-tube reactor, the reaction temperature is 250 °C, and the catalyst filled is the same as that in Example 1). The reaction product exchanges heat and cools with the high-pressure carbon dioxide-rich gas-phase product in the second-stage heat exchange device H2 through the second-stage reaction product pipeline V6, and then enters the condensation device C2 (the second-stage condensation device C2 is a water-cooled condenser, and the condensation temperature is 40 °C). The separated liquid product is output through the second-stage crude methanol pipeline or enters downstream refining. The gas-phase product is transported to the shunt device S1 through the V7 second-stage residue pipeline for shunting. 5v% of the gas is discharged as the purge gas V8, and the remaining is used as recycle gas to re-enter the reaction. To meet the matching of the processing capacities of the two reactors, a part of the remaining recycle gas is transported through the first-stage recycle pipeline V9-2 to the first-stage splitter M1 to participate in the downstream first-stage reaction, and the other part is transported through the second-stage recycle pipeline V9-1 to the second-stage splitter M2 to participate in the downstream second-stage reaction, V9-1:V9-2 = 1:9.

[0103] The result of this example is that the single-pass conversion rate of carbon dioxide is 48.2%, and the selectivity of methanol is 90.0%.

[0104] Example 6

[0105] Using the process system described in Example 1 for the process method of this example, hydrogen and carbon dioxide with a molar ratio of 3:1 are mixed and used as the reaction raw material gas, which is input into the raw material gas pipeline V1 (the temperature of V1 is 25 °C and the pressure is 101.25 Pa), and the space velocity is set to 20000 h -1, pressurized by the primary compressor B1, and after passing through the primary heat exchange device H1, V2 is obtained (the temperature in V2 is 280 °C and the pressure is 5 MPa); it enters the low-pressure reaction device R1 for reaction (R1 is a shell-and-tube reactor, the reaction temperature is 320 °C, and the catalyst loaded is the same as that in Example 1). The tail gas after the reaction enters the primary heat exchange device H1 through the primary reaction product pipeline V3. In H1, it is heat-exchanged with the raw material gas and then enters the primary condensation device C1 (the primary condensation device C1 is a water-cooled condenser, and the condensation temperature is 40 °C). The condensed liquid-phase product is output through the primary crude methanol pipeline L4 or enters downstream refining. The carbon dioxide-rich gas-phase product obtained enters the secondary compressor B2 through the primary residue pipeline V4 for pressurization, and then enters the secondary heat exchange device H2 for preheating to obtain a high-temperature and high-pressure reaction gas, which is output through the secondary heat exchange device pipeline V5 (the temperature in V5 is 200 °C and the pressure is 10 MPa), and enters the high-pressure reaction device R2 for reaction (R2 is a shell-and-tube reactor, the reaction temperature is 250 °C, and the catalyst loaded is the same as that in Example 1). The reaction product is heat-exchanged and cooled with the high-pressure carbon dioxide-rich gas-phase product in the secondary heat exchange device H2 through the secondary reaction product pipeline V6, and then enters the condensation device C2 (the secondary condensation device C2 is a water-cooled condenser, and the condensation temperature is 40 °C). The separated liquid-phase product is output through the secondary crude methanol pipeline or enters downstream refining. The gas-phase product is transported to the shunt device S1 through the secondary residue pipeline V7 for shunting. 5v% of the gas is discharged as the purge gas V8, and the remaining is used as recycle gas to re-enter the reaction. To meet the matching of the processing capacities of the two reactors, a part of the remaining recycle gas is transported to the primary splitter M1 through the primary recycle pipeline V9-2 to participate in the downstream primary reaction, and the other part is transported to the secondary splitter M2 through the secondary recycle pipeline V9-1 to participate in the downstream secondary reaction, V9-1:V9-2 = 7:3.

[0106] The result of this example is that the single-pass conversion rate of carbon dioxide is 49.0% and the selectivity of methanol is 90.3%.

[0107] Example 7

[0108] The process method of this example is carried out using the process system described in Example 1. Hydrogen and carbon dioxide with a molar ratio of 3:1 are mixed and used as the reaction raw material gas, which is input into the raw material gas pipeline V1 (the temperature of V1 is 25 °C and the pressure is 101.25 Pa), and the space velocity is set to 20000 h -1, pressurized by the first-stage compressor B1, and after passing through the first-stage heat exchange device H1, V2 is obtained (the temperature in V2 is 280 °C and the pressure is 5 MPa); it enters the low-pressure reaction device R1 for reaction (R1 is a shell-and-tube reactor, the reaction temperature is 320 °C, and the catalyst filled is the same as that in Example 1). The tail gas after the reaction enters the first-stage heat exchange device H1 through the first-stage reaction product pipeline V3. In H1, it exchanges heat with the raw material gas and then enters the first-stage condensation device C1 (the first-stage condensation device C1 is a water-cooled condenser, and the condensation temperature is 40 °C). The condensed liquid product is output through the first-stage crude methanol pipeline L4 or enters downstream refining. The obtained carbon dioxide-rich gas-phase product enters the second-stage compressor B2 through the first-stage residue pipeline V4 for pressurization, and then enters the second-stage heat exchange device H2 for preheating to obtain a high-temperature and high-pressure reaction gas, which is output through the second-stage heat exchange device pipeline V5 (the temperature in V5 is 200 °C and the pressure is 5 MPa). It enters the high-pressure reaction device R2 for reaction (R2 is a shell-and-tube reactor, the reaction temperature is 250 °C, and the catalyst filled is the same as that in Example 1). The reaction product exchanges heat and cools with the high-pressure carbon dioxide-rich gas-phase product in the second-stage heat exchange device H2 through the second-stage reaction product pipeline V6, and then enters the condensation device C2 (the second-stage condensation device C2 is a water-cooled condenser, and the condensation temperature is 40 °C). The separated liquid product is output through the second-stage crude methanol pipeline or enters downstream refining. The gas-phase product is transported to the shunt device S1 through the V7 second-stage residue pipeline for shunting. 5v% of the gas is discharged as the purge gas V8, and the remaining is used as recycle gas to re-enter the reaction. To meet the matching of the throughput of the two reactors, a part of the remaining recycle passes through the first-stage recycle pipeline V9-2 and is transported to the first-stage shunt M1 to participate in the downstream first-stage reaction, and the other part passes through the second-stage recycle pipeline V9-1 and is transported to the second-stage shunt M2 to participate in the downstream second-stage reaction, V9-1:V9-2 = 47:3.

[0109] The result of this example is that the single-pass conversion rate of carbon dioxide is 42.5%, and the selectivity of methanol is 79.8%.

[0110] Example 8

[0111] Using the process system described in Example 1 for the process method of this example, hydrogen and carbon dioxide with a molar ratio of 3:1 are mixed and used as the reaction raw material gas, which is input into the raw material gas pipeline V1 (the temperature of V1 is 25 °C and the pressure is 101.25 Pa), and the space velocity is set to 20000 h -1, pressurized by the primary compressor B1, and after passing through the primary heat exchange device H1, V2 is obtained (the temperature in V2 is 280 °C and the pressure is 5 MPa); it enters the low-pressure reaction device R1 for reaction (R1 is a shell-and-tube reactor, the reaction temperature is 320 °C, and the catalyst loaded is the same as that in Example 1). The tail gas after the reaction enters the primary heat exchange device H1 through the primary reaction product pipeline V3. In H1, it exchanges heat with the raw material gas and then enters the primary condensation device C1 (the primary condensation device C1 is a water-cooled condenser, and the condensation temperature is 40 °C). The condensed liquid product is output through the primary crude methanol pipeline L4 or enters downstream refining. The carbon dioxide-rich gas product obtained enters the secondary compressor B2 for pressurization through the primary residue pipeline V4, and after being preheated in the secondary heat exchange device H2, the high-temperature and high-pressure reaction gas is obtained and output through the secondary heat exchange device pipeline V5 (the temperature in V5 is 280 °C and the pressure is 5 MPa), and enters the high-pressure reaction device R2 for reaction (R2 is a shell-and-tube reactor, the reaction temperature is 320 °C, and the catalyst loaded is the same as that in Example 1). The reaction product exchanges heat and cools with the high-pressure carbon dioxide-rich gas product in the secondary heat exchange device H2 through the secondary reaction product pipeline V6, and then enters the condensation device C2 (the secondary condensation device C2 is a water-cooled condenser, and the condensation temperature is 40 °C). The separated liquid product is output through the secondary crude methanol pipeline or enters downstream refining. The gas product is transported to the shunt device S1 through the V7 secondary residue pipeline for shunting. 5v% of the gas is discharged as the purge gas V8, and the remaining is used as recycle gas to re-enter the reaction. To adapt to the throughput of the two reactors, all the recycle gas is transported through the primary recycle pipeline V9-2 to the primary splitter M1 to participate in the downstream primary reaction.

[0112] The result of this example is that the single-pass conversion rate of carbon dioxide is 45.3% and the selectivity of methanol is 63.5%.

[0113] Example 9

[0114] The process method of this example is carried out using the process system described in Example 1. Hydrogen and carbon dioxide with a molar ratio of 3:1 are mixed and used as the reaction raw material gas and input into the raw material gas pipeline V1 (the temperature of V1 is 25 °C and the pressure is 101.25 Pa), and the space velocity is set to 20000 h -1, pressurized by the primary compressor B1, and after passing through the primary heat exchange device H1, V2 is obtained (the temperature in V2 is 280 °C and the pressure is 5 MPa); it enters the low-pressure reaction device R1 for reaction (R1 is a shell-and-tube reactor, the reaction temperature is 320 °C, and the catalyst loaded is the same as that in Example 1). The tail gas after the reaction enters the primary heat exchange device H1 through the primary reaction product pipeline V3. In H1, it exchanges heat with the raw material gas and then enters the primary condensation device C1 (the primary condensation device C1 is a water-cooled condenser, and the condensation temperature is 40 °C). The condensed liquid-phase product is output through the primary crude methanol pipeline L4 or enters downstream refining. The carbon dioxide-rich gas-phase product obtained enters the secondary compressor B2 through the primary residue pipeline V4 for boosting, and then enters the secondary heat exchange device H2 for preheating to obtain a high-temperature and high-pressure reaction gas, which is output through the secondary heat exchange device pipeline V5 (the temperature in V5 is 200 °C and the pressure is 10 MPa), and enters the high-pressure reaction device R2 for reaction (R2 is a shell-and-tube reactor, the reaction temperature is 230 °C, and the catalyst loaded is the same as that in Example 1). The reaction product exchanges heat and cools with the high-pressure carbon dioxide-rich gas-phase product in the secondary heat exchange device H2 through the secondary reaction product pipeline V6, and then enters the condensation device C2 (the secondary condensation device C2 is a water-cooled condenser, and the condensation temperature is 40 °C). The separated liquid-phase product is output through the secondary crude methanol pipeline or enters downstream refining. The gas-phase product is transported to the shunt device S1 through the V7 secondary residue pipeline for shunting. 5v% of the gas is discharged as the purge gas V8, and the remaining is used as recycle gas to re-enter the reaction. To meet the matching of the treatment capacities of the two reactors, a part of the remaining recycle gas is transported through the primary recycle pipeline V9-2 to the primary splitter M1 to participate in the downstream primary reaction, and the other part is transported through the secondary recycle pipeline V9-1 to the secondary splitter M2 to participate in the downstream secondary reaction, V9-1:V9-2 = 2:1.

[0115] The result of this example is that the single-pass conversion rate of carbon dioxide is 53.5%, and the selectivity of methanol is 95.6%.

[0116] Example 10

[0117] The process method of this example is carried out using the process system described in Example 1. The reaction raw material gas is input into the raw material gas pipeline V1 (the temperature of V1 is 30 °C and the pressure is 101.25 Pa), and the space velocity is set to 20000 h -1, wherein in the feed gas, the mole fraction of hydrogen is 74%, the mole fraction of carbon dioxide is 22%, and the mole fraction of carbon monoxide is 4%. It is pressurized by a first-stage compressor B1 and then passes through a first-stage heat exchange device H1 to obtain V2 (the temperature in V2 is 280 °C and the pressure is 5 MPa); it enters a low-pressure reaction device R1 for reaction (R1 is a shell-and-tube reactor, the reaction temperature is 320 °C, and the loaded catalyst is a commercial copper-zinc-aluminum catalyst). The tail gas after the reaction enters the first-stage heat exchange device H1 through a first-stage reaction product pipeline V3. In H1, it exchanges heat with the feed gas and then enters a first-stage condensation device C1 (the first-stage condensation device C1 is a water-cooled condenser, and the condensation temperature is 40 °C). The condensed liquid product is output through a first-stage crude methanol pipeline L4 or enters downstream refining. The carbon dioxide-rich gas product obtained enters a second-stage compressor B2 through a first-stage residue pipeline V4 for boosting, and then enters a second-stage heat exchange device H2 for preheating to obtain a high-temperature and high-pressure reaction gas, which is output through a second-stage heat exchange device pipeline V5 (the temperature in V5 is 200 °C and the pressure is 10 MPa). It enters a high-pressure reaction device R2 for reaction (R2 is a shell-and-tube reactor, the reaction temperature is 250 °C, and the loaded catalyst is a commercial zinc-chromium catalyst). The reaction product exchanges heat and cools with the high-pressure carbon dioxide-rich gas product in the second-stage heat exchange device H2 through a second-stage reaction product pipeline V6, and then enters a condensation device C2 (the second-stage condensation device C2 is a water-cooled condenser, and the condensation temperature is 40 °C). The separated liquid product is output through a second-stage crude methanol pipeline or enters downstream refining. The gas product is transported to a shunt device S1 through a V7 second-stage residue pipeline for shunting. 5v% of the gas is discharged as purge gas V8, and the remaining is used as recycle gas to re-enter the reaction. To meet the matching of the processing capacities of the two reactors, a part of the remaining recycle gas is transported to a first-stage splitter M1 through a first-stage recycle pipeline V9-2 to participate in the downstream first-stage reaction, and the other part is transported to a second-stage splitter M2 through a second-stage recycle pipeline V9-1 to participate in the downstream second-stage reaction, V9-1:V9-2 = 2:1.

[0118] The result of this example is that the single-pass total carbon conversion rate is 64% and the selectivity of methanol is 93%.

[0119] Example 11

[0120] The process method of this example is carried out using the process system described in Example 1. The reaction raw material gas is input into the feed gas pipeline V1 (the temperature of V1 is 30 °C and the pressure is 101.25 Pa), and the space velocity is set to 20000 h -1, in which in the feed gas, the mole fraction of hydrogen is 74%, the mole fraction of carbon dioxide is 22%, and the mole fraction of carbon monoxide is 4%. It is pressurized by a first-stage compressor B1 and then passes through a first-stage heat exchange device H1 to obtain V2 (the temperature in V2 is 280 °C and the pressure is 5 MPa); it enters a low-pressure reaction device R1 for reaction (R1 is a shell-and-tube reactor, the reaction temperature is 320 °C, and the catalyst loaded is the same as that in Example 1). The tail gas after the reaction enters the first-stage heat exchange device H1 through a first-stage reaction product pipeline V3. In H1, it exchanges heat with the feed gas and then enters a first-stage condensation device C1 (the first-stage condensation device C1 is a water-cooled condenser, and the condensation temperature is 40 °C). The condensed liquid product is output through a first-stage crude methanol pipeline L4 or enters downstream refining. The carbon dioxide-rich gas product obtained enters a second-stage compressor B2 through a first-stage residue pipeline V4 for pressurization, and then enters a second-stage heat exchange device H2 for preheating to obtain a high-temperature and high-pressure reaction gas, which is output through a second-stage heat exchange device output pipeline V5 (the temperature in V5 is 200 °C and the pressure is 15 MPa), and enters a high-pressure reaction device R2 for reaction (R2 is a shell-and-tube reactor, the reaction temperature is 230 °C, and the catalyst loaded is the same as that in Example 1). The reaction product exchanges heat and cools with the high-pressure carbon dioxide-rich gas product in the second-stage heat exchange device H2 through a second-stage reaction product pipeline V6, and then enters a condensation device C2 (the second-stage condensation device C2 is a water-cooled condenser, and the condensation temperature is 40 °C). The separated liquid product is output through a second-stage crude methanol pipeline or enters downstream refining. The gas product is transported to a shunt device S1 through a V7 second-stage residue pipeline for shunting. 5v% of the gas is discharged as purge gas V8, and the remaining is used as recycle gas to re-enter the reaction. To meet the matching of the throughput of the two reactors, a part of the remaining recycle passes through a first-stage recycle pipeline V9-2 and is transported to a first-stage splitter M1 to participate in the downstream first-stage reaction, and another part passes through a second-stage recycle pipeline V9-1 and is transported to a second-stage splitter M2 to participate in the downstream second-stage reaction, V9-1:V9-2 = 1:4.

[0121] The result of this example is that the single-pass total carbon conversion rate is 69% and the selectivity of methanol is 99%.

[0122] Example 12

[0123] The process method of this example is carried out using the process system described in Example 1. Hydrogen and carbon dioxide with a molar ratio of 9:1 are mixed and then input into a feed gas pipeline V1 (the temperature of V1 is 30 °C and the pressure is 101.25 Pa) as the reaction raw material gas, and the space velocity is set to 20000 h -1, pressurized by the first-stage compressor B1, and after passing through the first-stage heat exchange device H1, V2 is obtained (the temperature in V2 is 280 °C and the pressure is 5 MPa); it enters the low-pressure reaction device R1 for reaction (R1 is a shell-and-tube reactor, the reaction temperature is 320 °C, and the catalyst filled is the same as that in Example 1). The tail gas after the reaction enters the first-stage heat exchange device H1 through the first-stage reaction product pipeline V3. In H1, it exchanges heat with the raw material gas and then enters the first-stage condensation device C1 (the first-stage condensation device C1 is a water-cooled condenser, and the condensation temperature is 40 °C). The condensed liquid-phase product is output through the first-stage crude methanol pipeline L4 or enters the downstream refining. The obtained carbon dioxide-rich gas-phase product enters the second-stage compressor B2 through the first-stage residue pipeline V4 for pressurization, and then enters the second-stage heat exchange device H2 for preheating to obtain a high-temperature and high-pressure reaction gas, which is output through the second-stage heat exchange device pipeline V5 (the temperature in V5 is 180 °C and the pressure is 15 MPa), and enters the high-pressure reaction device R2 for reaction (R2 is a shell-and-tube reactor, the reaction temperature is 230 °C, and the catalyst filled is the same as that in Example 1). The reaction product exchanges heat and cools with the high-pressure carbon dioxide-rich gas-phase product in the second-stage heat exchange device H2 through the second-stage reaction product pipeline V6, and then enters the condensation device C2 (the second-stage condensation device C2 is a water-cooled condenser, and the condensation temperature is 40 °C). The separated liquid-phase product is output through the second-stage crude methanol pipeline or enters the downstream refining. The gas-phase product is transported to the shunt device S1 through the V7 second-stage residue pipeline for shunting. 5v% of the gas is discharged as the purge gas V8, and the remaining is used as the recycle gas to re-enter the reaction. To meet the matching of the throughput of the two reactors, a part of the remaining recycle gas is transported through the first-stage recycle pipeline V9-2 to the first-stage splitter M1 to participate in the downstream first-stage reaction, and the other part is transported through the second-stage recycle pipeline V9-1 to the second-stage splitter M2 to participate in the downstream second-stage reaction, V9-1:V9-2 = 1:4.

[0124] The result of this example is that the single-pass total carbon conversion rate is 96%, and the selectivity of methanol is 99%.

[0125] In summary, for the process method and supporting system for hydrogenating carbon dioxide to methanol in this application, two reactions with different operating conditions are connected in series. First, the raw material gas undergoes a first-stage reaction at low pressure and high temperature, and most of the carbon dioxide is converted. The remaining carbon dioxide, hydrogen, and the generated carbon monoxide and other first-stage residues then undergo a second-stage reaction at high pressure and low temperature. The carbon dioxide single-pass conversion rate of this process is high, and the methanol output is high.

[0126] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A process for producing methanol by hydrogenating carbon dioxide, characterized in that, The process method includes the following steps: S1. Feed gas containing at least carbon dioxide and hydrogen is subjected to a primary reaction in the presence of a first catalyst to obtain a primary reaction product; the operating pressure of the primary reaction is 1 MPa to 15.0 MPa, and the reaction temperature is 200 °C to 350 °C; S2. After separating the crude primary methanol product from the primary reaction product, the primary residue is subjected to a secondary reaction in the presence of a second catalyst to obtain a secondary reaction product; the operating pressure of the secondary reaction is 5 MPa to 20.0 MPa, and the reaction temperature is 150 °C to 320 °C; S3. The secondary reaction product is separated to obtain a crude secondary methanol product; S4. The crude primary methanol product and the crude secondary methanol product are refined to obtain methanol; Wherein, in the same process operation, the operating pressure of the primary reaction is lower than that of the secondary reaction, and the reaction temperature of the primary reaction is higher than that of the secondary reaction.

2. The process for hydrogenating carbon dioxide to methanol according to claim 1, characterized in that, It further includes at least one of the following technical features: 1) In step S1, the feed gas further includes carbon monoxide; 2) In step S1, the molar ratio of hydrogen to carbon dioxide is 0.2:1 to 9:1; 3) In step S1, the space velocity of the primary reaction is 1000 to 100000 h -1 ; 4) In step S1, the first catalyst is selected from at least one of a copper-based catalyst, a zirconium-based catalyst or an indium-based catalyst; 5) In step S1, the operating pressure of the primary reaction is 3 MPa to 10.0 MPa, and the reaction temperature is 280 °C to 350 °C; 6) In step S2, the operating pressure of the secondary reaction is 5 MPa to 15.0 MPa, and the reaction temperature is 180 °C to 250 °C; 7) In step S2, the operating space velocity of the secondary reaction is 1000 - 100000 h -1 ; 8) In step S2, the second catalyst is selected from at least one of a copper-based catalyst, a zirconium-based catalyst or a zinc-chromium catalyst.

3. The process for hydrogenating carbon dioxide to methanol according to claim 2, characterized in that, It further includes at least one of the following technical features: 1a) In Feature 1), the molar ratio of carbon monoxide to carbon dioxide is less than 1, and the molar ratio of (H2 - CO 2) / (CO + CO2) is 1.9 to 2.1; 2a) In feature 2), the molar ratio of hydrogen to carbon dioxide is 2:1 to 4:

1.

4. The process for hydrogenating carbon dioxide to methanol according to claim 1 or 2, characterized in that, In step S2, the primary reaction product is cooled to obtain a crude primary methanol product and a gaseous primary residue, and after separation, a primary methanol product is obtained, and the primary residue continues to undergo a secondary reaction; And / or, in step S3, the secondary reaction product is cooled to obtain a crude secondary methanol product and a gaseous secondary residue, and after separation, a secondary methanol product is obtained; Part of the secondary residue is released, and the other part is used as recycle gas to enter the primary reaction and / or the secondary reaction.

5. A process system for hydrogenating carbon dioxide to methanol, characterized in that, The process system includes a low-pressure reaction device (R1) and a high-pressure reaction device (R2) connected in series; The low-pressure reaction device (R1) is used to realize the primary reaction of the feed gas containing at least carbon dioxide and hydrogen in the presence of a first catalyst to obtain a primary reaction product, and the operating pressure of the low-pressure reaction device (R1) is 1 MPa to 15.0 MPa, and the reaction temperature is 200 °C to 350 °C; The high-pressure reaction device (R2) is used to realize the secondary reaction of the primary residue in the presence of a second catalyst to obtain a secondary reaction product, and the operating pressure of the high-pressure reaction device (R2) is 5 MPa to 20.0 MPa, and the reaction temperature is 150 °C to 320 °C.

6. The process system according to claim 5, wherein It further includes one of the following technical features: a) The output end of the high-pressure reaction device (R2) is provided with a secondary reaction product delivery pipeline (V6), and a secondary condensation device (C2) is also provided downstream of the high-pressure reaction device (R2); The secondary reaction product delivery pipeline (V6) is communicated with the secondary condensation device (C2), and after passing through the secondary condensation device (C2), the secondary reaction product branches into a secondary crude methanol pipeline (L7) and a secondary residue pipeline (V7) for delivering the secondary crude methanol and the secondary residue respectively; b) Upstream of the low-pressure reaction device (R1), there are also provided a raw material gas delivery pipeline (V1), a primary compressor (B1), and a primary heat exchange device (H1); The raw material gas delivery pipeline (V1) is used for delivering the raw material gas, and after being sequentially communicated with the primary compressor (B1) and the primary heat exchange device (H1), the raw material gas delivery pipeline (V1) is then communicated with the low-pressure reaction device (R1); c) The output end of the low-pressure reaction device (R1) is provided with a primary reaction product delivery pipeline (V3), and a primary condensation device (C1) is also provided downstream of the low-pressure reaction device (R1); The primary reaction product delivery pipeline (V3) is communicated with the primary condensation device (C1), and after passing through the primary condensation device (C1), the primary reaction product branches into a primary crude methanol pipeline (L4) and a primary residue pipeline (V4) for delivering the primary crude methanol and the primary residue respectively.

7. The process system according to claim 6, wherein, It further includes at least one of the following technical features: d) A shunt device (S1) is also provided; after the secondary residue pipeline (V7) is connected to the shunt device (S1), it branches into a purge gas pipeline (V8), a primary circulation pipeline (V9-2), and a secondary circulation pipeline (V9-1); The primary circulation pipeline (V9-2) is communicated with the raw material gas delivery pipeline (V1), and the secondary circulation pipeline (V9-1) is communicated with the primary residue pipeline (V4); e) Upstream of the high-pressure reaction device (R2), there are also included a secondary compressor (B2) and a secondary heat exchange device (H2); The primary residue pipeline (V4) is sequentially communicated with the secondary compressor (B2) and the secondary heat exchange device (H2) and then communicated with the high-pressure reaction device (R2); f) The primary reaction product delivery pipeline (V3) is communicated with the primary heat exchange device (H1) and then with the primary condensation device (C1).

8. The process system according to claim 7, characterized in that, The secondary reaction product delivery pipeline (V6) is communicated with the secondary heat exchange device (H2) and then with the secondary condensation device (C2).

9. The process system according to claim 7, wherein Upstream of the low-pressure reaction device (R1), there is provided a primary diverter (M1), and the primary circulation pipeline (V9-2) and the raw material gas delivery pipeline (V1) are respectively communicated with the primary diverter (M1).

10. The process system according to claim 7, characterized in that, Upstream of the high-pressure reaction device (R2), there is provided a secondary diverter (M2), and the secondary circulation pipeline (V9-1) and the primary residue pipeline (V4) are respectively communicated with the secondary diverter (M2).

Images