Liquid phase method methanol synthesis system based on reactive distillation

Abstract

The invention provides a liquid phase method methanol synthesis system based on reactive distillation, which comprises the following steps: mixing hydrogen and carbon dioxide into a raw material gas stream, passing through a multi-stage compressor and then passing through a first heat exchanger to obtain a pretreated raw material gas stream; the solvent stream passes through a booster pump and then passes through a second heat exchanger to obtain a pretreated solvent stream; a pretreated raw material gas stream enters the reactive distillation tower from the bottom of the reactive distillation tower, a pretreated solvent stream enters the reactive distillation tower from the top of the reactive distillation tower to obtain a top stream and a bottom stream, the top stream passes through a condenser and then enters a flash tank, a crude methanol stream and an unreacted gas stream are separated, the crude methanol stream enters the distillation tower, and the unreacted gas stream enters the bottom of the distillation tower; a refined methanol product stream and a purge stream are obtained at the top of the rectifying tower, and a solvent and water mixture stream flows out from the bottom of the rectifying tower and is recycled. According to the method, methanol is synthesized through carbon dioxide hydrogenation in the solvent, the reaction conditions are mild, the process is simple, and the high carbon dioxide conversion per pass is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of methanol synthesis, and in particular relates to a liquid phase methanol synthesis system based on reactive distillation. Background Art

[0002] As carbon dioxide emissions continue to increase, environmental problems such as global warming are becoming increasingly serious. Reducing carbon dioxide emissions has become a common challenge faced by the world, and the development of carbon dioxide utilization technology is of great strategic significance. Methanol (CH3OH), as an important chemical raw material, has a wide range of applications in energy, chemical industry, and medicine. The technical route of producing methanol from carbon dioxide hydrogenation can not only reduce greenhouse gas emissions and realize the resource utilization of CO2, but also connect with the new energy electrolysis water hydrogen production industry to realize the storage of hydrogen energy, and also provide a low-carbon, environmentally friendly, efficient and feasible technical route for the methanol synthesis process.

[0003] At present, the process of synthesizing methanol by hydrogenation of carbon dioxide faces the challenge of thermodynamic equilibrium limitations in practical applications, and it is difficult to significantly improve the CO2 conversion rate. Therefore, during the reaction process, in order to avoid the waste of raw gas, a large amount of unreacted gas needs to be circulated in the system, which leads to an increase in the energy consumption of the reaction process, thereby increasing the production cost of methanol.

[0004] After searching, the invention patent with publication number CN112645797A discloses a process for synthesizing methanol from carbon dioxide-carbon-water, in which carbon monoxide and hydrogen are prepared from carbon dioxide-carbon-water, and the generated carbon monoxide and hydrogen are then synthesized into methanol. The main process includes: gasification unit, hydrogen production unit and methanol synthesis unit. In this process, the total conversion rate of carbon dioxide can reach up to 99.99%, and the total yield of methanol can reach up to 99.99%, but the problem of low single-pass conversion rate of carbon dioxide is not solved in this process, and the gasification and hydrogen production processes increase product costs.

[0005] The invention patent with publication number CN112194566A discloses a device and process for synthesizing methanol based on the hydrogenation of carbon dioxide. In this process, three fresh raw gases, carbon dioxide, hydrogen and carbon monoxide, are mixed through a mixer, and the mixed mixture enters a reactor for a methanol synthesis reaction. However, the single-pass conversion rate of carbon dioxide in this process is still relatively low.

[0006] The invention patent with publication number CN118162090 discloses a process system for synthesizing methanol by hydrogenation of carbon dioxide using membrane separation. A membrane component with high selective permeability to water or methanol is arranged in the carbon dioxide hydrogenation reaction system to overcome thermodynamic limitations and shift the reaction equilibrium in a favorable direction. The single-pass conversion rate of carbon dioxide in the process system reaches 47.12%.

[0007] Based on this, a liquid phase methanol synthesis system based on reactive distillation was proposed. By introducing a solvent during the reaction process and changing the reaction path of carbon dioxide hydrogenation to methanol to overcome the limitations of thermodynamic equilibrium, the single-pass conversion rate of carbon dioxide can be significantly improved, the gas circulation volume of the reaction system can be reduced, the methanol yield can be increased, and the process energy consumption can be reduced. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a liquid phase methanol synthesis system based on reactive distillation in view of the deficiencies of the above-mentioned prior art, so as to solve the problems raised in the above-mentioned background technology.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is: a liquid phase methanol synthesis system based on reactive distillation, comprising the following steps:

[0010] S1, pretreatment system, hydrogen and carbon dioxide are mixed into a raw gas stream, which passes through a multi-stage compressor and then passes through a first heat exchanger to obtain a pretreated raw gas stream; the solvent stream passes through a pressure pump and then passes through a second heat exchanger to obtain a pretreated solvent stream;

[0011] S2, a methanol synthesis system, wherein a pre-treated raw material gas stream enters a reaction distillation tower from the bottom of the tower, and a pre-treated solvent stream enters the tower from the top of the tower, and reacts to generate methanol and water, wherein part of the methanol, water, solvent and unreacted gas flows out from the top of the reaction distillation tower to obtain a top stream, and the rest flows out from the bottom of the reaction distillation tower to obtain a bottom stream;

[0012] S3, methanol refining system, the top stream passes through the condenser and enters the flash tank to separate the crude methanol stream and the unreacted gas stream, the crude methanol stream enters the distillation tower, and the refined methanol product stream and the purge gas stream are obtained at the top of the distillation tower, and the solvent and water mixture stream flows out at the bottom of the distillation tower;

[0013] S4, a circulating operation system, in which the unreacted gas stream is circulated back to the pretreatment system and mixed with the raw gas stream to enter the system, and the bottom stream out of the bottom flow of the reaction distillation tower is circulated back to the pretreatment system; the mixed stream out of the bottom flow of the distillation tower passes through a pressure reducing valve and enters a permeation vaporization solvent recovery device to separate a high-purity alcohol solvent stream, which is circulated back to the pretreatment system and mixed with the solvent stream for recycling.

[0014] As a further illustration of the present invention, the solvent stream is an alcohol solvent, and the alcohol solvent is ethanol, propanol, 2-propanol, n-butanol, 2-butanol, 1-pentanol, 2-pentanol, 3-pentanol or 1-hexanol.

[0015] As a further illustration of the present invention, the molar ratio of hydrogen to carbon dioxide in the raw gas stream is 2 to 3.5, the pressure is 2.0 to 5.0 MPa, and the temperature is 180°C to 220°C.

[0016] As a further illustration of the present invention, the molar ratio of the solvent in the solvent stream to the molar ratio of the raw gas in the raw gas stream is 2 to 3, the pressure is 2.0 to 5.0 MPa, and the temperature is 180°C to 220°C.

[0017] As a further illustration of the present invention, the methanol synthesis catalyst in the reaction distillation tower in S2 is a copper-based catalyst, the synthesis pressure is 2.0-5.0 MPa, the temperature is 180° C.-220° C., and the reflux ratio of the reaction distillation tower 5 is 3-5.

[0018] As a further illustration of the present invention, the pressure in the distillation tower is 0.5-0.7 MPa, the temperature is 120° C.-150° C., and the reflux ratio is 2-3.

[0019] As a further illustration of the present invention, the solvent circulation feed ratio of the high-purity alcohol solvent in S4 is 200-300.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The present invention realizes the synthesis of methanol by hydrogenation of carbon dioxide in a solvent under the following reaction conditions: pressure 2.0-5.0 MPa, temperature 180° C.-220° C., mild conditions, simple process and easy operation.

[0022] 2. The present invention introduces an alcohol solvent into the carbon dioxide hydrogenation methanol synthesis reaction to change the reaction path and achieve a higher carbon dioxide single-pass conversion rate.

[0023] 3. The present invention allows synthesis and separation to be carried out simultaneously, and utilizes reaction heat to supply product separation, so that the products or intermediates generated by the reaction can be separated in time, thereby improving the yield of the product, reducing equipment costs, and achieving the purpose of energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the system of the present invention;

[0025] Figure 2 This is a schematic diagram showing the effect of the molar amount of n-butanol on the reaction of hydrogenating carbon dioxide to produce methanol in Example 1 of the present invention.

[0026] Description of reference numerals:

[0027] 1-multi-stage compressor; 2-first heat exchanger; 3-boosting pump; 4-second heat exchanger; 5-reaction distillation tower; 6-condenser; 7-flash tank; 8-distillation tower; 9-permeation vaporization solvent recovery device. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Embodiment 1, as Figure 1 and Figure 2 As shown, the present invention provides a technical solution: a liquid phase methanol synthesis system based on reactive distillation, comprising the following steps:

[0030] S1, pretreatment system, hydrogen and carbon dioxide are mixed into a raw gas stream, which passes through a multi-stage compressor 1 and then passes through a first heat exchanger 2 to obtain a pretreated raw gas stream; the solvent stream passes through a pressure pump 3 and then passes through a second heat exchanger 4 to obtain a pretreated solvent stream;

[0031] The alcohol solvent is n-butanol, and the experimental conditions are temperature 200°C, pressure 2.5 MPa, feed hydrogen 3 kmol / h, and carbon dioxide 1 kmol / h. The effect of the molar amount of n-butanol on the reaction of carbon dioxide hydrogenation to produce methanol is shown in Figure 2.

[0032] Figure 2 The results show that when the solvent molar amount is 9 kmol / h, the carbon dioxide conversion rate reaches 90.34%, the methanol yield reaches 90.21%, the methanol selectivity is 99.85%, and the carbon monoxide selectivity is 0.15%.

[0033] The molar ratio of hydrogen to carbon dioxide is 3, the pressure is 2.5 MPa, and the temperature is 200°C; the molar ratio of the solvent in the solvent stream to the molar ratio of the raw gas in the raw gas stream is 2.5, the pressure is 2.5 MPa, and the temperature is 200°C.

[0034] S2, methanol synthesis system, the pre-treated raw material gas stream enters the reaction distillation tower 5 from the bottom of the tower, the pre-treated solvent stream enters the tower from the top of the reaction distillation tower 5, and reacts to generate methanol and water, wherein part of the methanol, water and solvent and unreacted gas flow out from the top of the reaction distillation tower 5 to obtain a top stream, and the rest flow out from the bottom of the reaction distillation tower 5 to obtain a bottom stream;

[0035] The methanol synthesis catalyst in the reaction distillation tower 5 is a copper-based catalyst, the synthesis pressure is 2.45 MPa, the temperature is 200° C., and the reflux ratio of the reaction distillation tower 5 is 4.5.

[0036] S3, methanol refining system, the top stream passes through the condenser 6 and enters the flash tank 7 to separate the crude methanol stream and the unreacted gas stream, the crude methanol stream enters the distillation tower 8, the refined methanol product stream and the purge gas stream are obtained at the top of the distillation tower 8, and the solvent and water mixture stream flows out at the bottom of the distillation tower 8;

[0037] The pressure of distillation tower 8 is 0.65Mpa, the temperature is 40℃, and the reflux ratio of distillation tower 8 is 2.5.

[0038] S4, circulating operation system, the unreacted gas stream is circulated back to the pretreatment system and mixed with the raw gas stream to enter the system, the bottom stream out of the bottom flow of the reaction distillation tower 5 is circulated back to the pretreatment system; the mixed stream out of the bottom flow of the distillation tower 8 enters the permeation vaporization solvent recovery device 9 after passing through the pressure reducing valve to separate the high-purity alcohol solvent stream, the high-purity alcohol solvent stream is circulated back to the pretreatment system and mixed with the solvent stream for recycling, and the solvent circulation feed ratio is 250.

[0039] The specific material data is shown in Table 1:

[0040] Table 1

[0041]

[0042] The results show that the methanol output of this process is 100.29kt / y, the purity is 99.69%, the single-pass conversion rate of carbon dioxide is 99.98%, and the carbon dioxide utilization rate is 98.99%.

[0043] Embodiment 2, the present invention provides a technical solution: a liquid phase methanol synthesis system based on reactive distillation, comprising the following steps:

[0044] S1, pretreatment system, hydrogen and carbon dioxide are mixed into a raw gas stream, which passes through a multi-stage compressor 1 and then passes through a first heat exchanger 2 to obtain a pretreated raw gas stream; the solvent stream passes through a pressure pump 3 and then passes through a second heat exchanger 4 to obtain a pretreated solvent stream;

[0045] The alcohol solvent is the same as that in Example 1, which is n-butanol. The molar ratio of hydrogen to carbon dioxide is 3, the pressure is 2 MPa, and the temperature is 180°C; the molar amount of solvent to the raw gas; the molar amount of solvent in the solvent stream to the molar amount of raw gas in the raw gas stream is 2, the pressure is 2 MPa, and the temperature is 180°C.

[0046] S2, methanol synthesis system, the pre-treated raw material gas stream enters the reaction distillation tower 5 from the bottom of the tower, the pre-treated solvent stream enters the tower from the top of the reaction distillation tower 5, and reacts to generate methanol and water, wherein part of the methanol, water and solvent and unreacted gas flow out from the top of the reaction distillation tower 5 to obtain a top stream, and the rest flow out from the bottom of the reaction distillation tower 5 to obtain a bottom stream;

[0047] The methanol synthesis catalyst in the reaction distillation tower 5 is a copper-based catalyst, the synthesis pressure is 1.95 MPa, the temperature is 180° C., and the reflux ratio of the reaction distillation tower is 4.5.

[0048] S3, methanol refining system, the top stream passes through the condenser 6 and enters the flash tank 7 to separate the crude methanol stream and the unreacted gas stream, the crude methanol stream enters the distillation tower 8, the refined methanol product stream and the purge gas stream are obtained at the top of the distillation tower 8, and the solvent and water mixture stream flows out at the bottom of the distillation tower 8;

[0049] The pressure of distillation tower 8 is 0.65 MPa, the temperature is 40°C, and the reflux ratio of the methanol distillation tower is 2.5.

[0050] S4, circulating operation system, the unreacted gas stream is circulated back to the pretreatment system and mixed with the raw gas stream to enter the system, the bottom stream out of the bottom flow of the reaction distillation tower 5 is circulated back to the pretreatment system; the mixed stream out of the bottom flow of the distillation tower 8 enters the permeation vaporization solvent recovery device 9 after passing through the pressure reducing valve to separate the high-purity alcohol solvent stream, the high-purity alcohol solvent stream is circulated back to the pretreatment system and mixed with the solvent stream for recycling, and the solvent circulation feed ratio is 409.

[0051] The specific material data is shown in Table 2:

[0052] Table 2

[0053]

[0054] The results show that the methanol output of this process is 99.84kt / y, the purity is 99.81%, the single-pass conversion rate of carbon dioxide is 98.94%, and the carbon dioxide utilization rate is 98.66%.

[0055] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0056] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A liquid phase methanol synthesis system based on reactive distillation, characterized in that: The following steps are involved: S1, pretreatment system, hydrogen and carbon dioxide are mixed into a raw gas stream, which passes through a multi-stage compressor (1) and then passes through a first heat exchanger (2) to obtain a pretreated raw gas stream; the solvent stream passes through a pressure pump (3) and then passes through a second heat exchanger (4) to obtain a pretreated solvent stream; S2, a methanol synthesis system, wherein a pre-treated raw material gas stream enters a reaction distillation tower (5) from the bottom of the tower, and a pre-treated solvent stream enters the tower from the top of the tower, and reacts to generate methanol and water, wherein part of the methanol, water and solvent and unreacted gas flow out from the top of the reaction distillation tower (5) to obtain a top stream, and the rest flow out from the bottom of the reaction distillation tower (5) to obtain a bottom stream; S3, methanol refining system, the top stream passes through the condenser (6) and enters the flash tank (7), where a crude methanol stream and an unreacted gas stream are separated, and the crude methanol stream enters the distillation tower (8), where a refined methanol product stream and a purge gas stream are obtained at the top of the distillation tower (8), and a solvent and water mixture stream flows out at the bottom of the distillation tower (8); S4, a circulating operation system, wherein the unreacted gas stream is circulated back to the pretreatment system and mixed with the raw gas stream to enter the system, and the bottom stream flowing out of the bottom of the reaction distillation tower (5) is circulated back to the pretreatment system; the mixed stream flowing out of the bottom of the distillation tower (8) passes through a pressure reducing valve and enters a permeation vaporization solvent recovery device (9) to separate a high-purity alcohol solvent stream, and the high-purity alcohol solvent stream is circulated back to the pretreatment system and mixed with the solvent stream for recycling.

2. A liquid phase methanol synthesis system based on reactive distillation according to claim 1, characterized in that: The solvent stream is an alcohol solvent, and the alcohol solvent is ethanol, propanol, 2-propanol, n-butanol, 2-butanol, 1-pentanol, 2-pentanol, 3-pentanol or 1-hexanol.

3. A liquid phase methanol synthesis system based on reactive distillation according to claim 1, characterized in that: The molar ratio of hydrogen to carbon dioxide in the raw gas stream is 2-3.5, the pressure is 2.0-5.0 MPa, and the temperature is 180°C-220°C.

4. A liquid phase methanol synthesis system based on reactive distillation according to claim 1, characterized in that: The molar ratio of the solvent in the solvent stream to the molar ratio of the raw gas in the raw gas stream is 2 to 3, the pressure is 2.0 to 5.0 MPa, and the temperature is 180° C. to 220° C.

5. The liquid phase methanol synthesis system based on reactive distillation according to claim 1, characterized in that: In S2, the methanol synthesis catalyst in the reaction distillation tower (5) is a copper-based catalyst, the synthesis pressure is 2.0-5.0 MPa, the temperature is 180° C.-220° C., and the reflux ratio of the reaction distillation tower (5) is 3-5.

6. The liquid phase methanol synthesis system based on reactive distillation according to claim 1, characterized in that: The pressure in the distillation tower (8) is 0.5-0.7 MPa, the temperature is 120° C.-150° C., and the reflux ratio is 2-3.

7. The liquid phase methanol synthesis system based on reactive distillation according to claim 1, characterized in that: The solvent circulation feed ratio of the high-purity alcohol solvent in S4 is 200-300.

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