Methanol synthesis device and synthesis method

Abstract

The present invention provides a methanol synthesis device and method. The synthesis device includes a conversion device, a primary purification device, a secondary purification device, and a reaction device. The conversion device is used to perform conversion treatment on a portion of the raw coal gas in the gasifier to obtain converted coal gas; the primary purification device is used to perform acid gas removal treatment on the converted coal gas and the remaining unconverted raw coal gas in the gasifier, respectively, to obtain converted synthesis gas and first carbon dioxide and second carbon dioxide; the secondary purification device is used to perform fine desulfurization treatment on the converted synthesis gas, unconverted synthesis gas, and carbon dioxide gas to obtain desulfurized synthesis gas; and the reaction device is used to use the desulfurized synthesis gas to perform a methanol synthesis reaction to obtain a product system including methanol. By optimizing the methanol synthesis gas distribution method, the present invention not only reduces the unit consumption of methanol synthesis gas, but also extends the service life of the catalyst, significantly reduces the production cost and energy consumption of methanol, and achieves significant economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of methanol synthesis, and in particular to a methanol synthesis device and a methanol synthesis method. Background Art

[0002] Methanol, as an industrial raw material, can be used to manufacture chemical products such as polyolefins, polyoxymethylene, ethylene glycol, acetic acid, and methyl formate. It is widely used in fine chemical industries such as pesticides and pharmaceuticals, and plays a vital role. Consequently, methanol synthesis technology has developed rapidly in recent years, with production scales increasing. There are two main methanol production processes in China: coal-to-methanol and natural gas-to-methanol. Due to rising industrial natural gas prices, coal-to-methanol is currently the dominant method for methanol synthesis in China.

[0003] The most significant indicator influencing methanol production costs is syngas consumption per unit. This refers to the amount of syngas consumed per ton of methanol produced, which accounts for over 95% of the total cost. Therefore, reducing syngas consumption per unit is a key area of energy conservation and cost reduction for methanol synthesis plants. Syngas consumption is primarily influenced by catalyst activity, hydrogen-to-carbon ratio (H2C = (VH2-VCO2) / (VCO+VCO2)), inert gas content, and space velocity. Catalyst activity is directly related to the performance of the catalyst itself, inert gas content is related to gasifier operation, and space velocity is related to system load. These three indicators cannot be adjusted in real time; only the H2C ratio requires real-time adjustment based on reaction conditions during daily operation. Therefore, optimizing the H2C ratio is crucial for energy conservation and cost reduction in methanol synthesis plants.

[0004] However, the conventional methanol synthesis process adjusts the carbon dioxide content in the synthesis gas by adjusting the circulation volume of the low-temperature methanol wash and the conversion depth of the conversion device. Since the adjustment of the low-temperature methanol wash and the conversion device is relatively delayed, the carbon dioxide content in the methanol device fluctuates widely (the carbon dioxide content in the fresh synthesis gas fluctuates between 2 and 3%), and cannot be accurately controlled. As a result, the methanol synthesis catalyst cannot always maintain its optimal activity state. As a result, the conventional technology can only achieve a minimum unit consumption of 2180Nm per ton of methanol synthesis gas. 3 / h, which ultimately results in higher methanol production costs and higher energy consumption. Summary of the Invention

[0005] The main purpose of the present invention is to provide a methanol synthesis device and synthesis method to solve the problem in the prior art that the unit consumption of refined methanol synthesis gas per ton is high, resulting in high methanol production costs.

[0006] To achieve the above-mentioned objectives, according to one aspect of the present invention, a methanol synthesis device is provided, which includes a shift converter, a primary purification device, a secondary purification device, and a reaction device. The inlet of the shift converter is connected to the outlet of the gasifier, and is used to perform shift processing on a portion of the raw coal gas in the gasifier to obtain shifted coal gas; the inlet of the primary purification device is connected to the outlet of the shift converter and the outlet of the gasifier, respectively, and the primary purification device is used to perform acid gas removal processing on the shifted coal gas obtained by the shift converter to obtain shifted synthesis gas and a first carbon dioxide gas; the primary purification device is used to perform acid gas removal processing on the remaining unshifted raw coal gas in the gasifier to obtain unshifted synthesis gas and a second carbon dioxide gas, wherein the shifted synthesis gas and the unshifted synthesis gas are separately transported, and the first carbon dioxide and the second carbon dioxide are combined to form a separately transported carbon dioxide gas; the inlet of the secondary purification device is connected to the outlet of the primary purification device, and the secondary purification device is used to perform fine desulfurization processing on the shifted synthesis gas, unshifted synthesis gas, and carbon dioxide gas obtained by the primary purification device to obtain a desulfurized synthesis gas; and the inlet of the reaction device is connected to the outlet of the secondary purification device, and the reaction device is used to use the desulfurized synthesis gas obtained by the secondary purification device to perform a methanol synthesis reaction to obtain a product system including methanol.

[0007] Furthermore, the above-mentioned primary purification device includes a methanol washing device, a high-pressure water vapor device and a hydrolysis reactor. The inlet of the methanol washing device is respectively connected to the outlet of the conversion device and the outlet of the gasifier. The methanol washing device is used to perform methanol washing on the converted coal gas obtained by the conversion device to obtain converted synthesis gas and crude carbon dioxide. The methanol washing device is used to perform methanol washing on the remaining unconverted crude coal gas in the gasifier to obtain unconverted synthesis gas and crude carbon dioxide B. The crude carbon dioxide A and the crude carbon dioxide B are jointly used as crude carbon dioxide; the inlet of the high-pressure water vapor device is connected to the high-pressure water vapor source for providing high-pressure water vapor; the inlet of the hydrolysis reactor is respectively connected to the outlet of the methanol washing device and the outlet of the high-pressure water vapor device. The hydrolysis reactor is used to hydrolyze the high-pressure water vapor with the crude carbon dioxide to obtain carbon dioxide gas.

[0008] Furthermore, a high-pressure steam flow orifice plate is provided on the pipeline connecting the above-mentioned high-pressure steam device and the hydrolysis reactor. The high-pressure steam flow orifice plate is used to control the flow of high-pressure steam entering the hydrolysis reactor. Preferably, the aperture of the high-pressure steam flow orifice plate is 0.5-1 mm.

[0009] Furthermore, a carbon dioxide flow regulating valve is provided on the pipeline connecting the methanol washing device and the hydrolysis reactor, and the carbon dioxide flow regulating valve is used to control the flow of crude carbon dioxide entering the hydrolysis reactor.

[0010] Furthermore, a carbon dioxide compressor is provided on the pipeline connecting the above-mentioned methanol washing device and the carbon dioxide flow regulating valve, and the carbon dioxide compressor is used to pressurize the crude carbon dioxide product.

[0011] Furthermore, a converted synthesis gas flow regulating valve is provided on the pipeline connecting the above-mentioned methanol washing device and the reaction device, and the converted synthesis gas flow regulating valve is used to control the flow of the converted synthesis gas; preferably, an unconverted synthesis gas flow regulating valve is provided on the pipeline connecting the methanol washing device and the reaction device, and the unconverted synthesis gas flow regulating valve is used to control the flow of the unconverted synthesis gas.

[0012] Furthermore, the above-mentioned synthesis device also includes a synthesis gas compressor, which is arranged on the pipeline connecting the carbon dioxide flow regulating valve and the reaction device. The synthesis gas compressor is also arranged on the pipeline connecting the converted synthesis gas flow regulating valve and the reaction device. The synthesis gas compressor is also arranged on the pipeline connecting the unconverted synthesis gas flow regulating valve and the reaction device. The synthesis gas compressor is used to mix and pressurize the converted synthesis gas, unconverted synthesis gas and carbon dioxide gas.

[0013] Furthermore, the above-mentioned synthesis device also includes a methanol separator and a circulating gas compressor. The inlet of the methanol separator is connected to the outlet of the reaction device. The methanol separator is used to separate the product system to obtain crude methanol and circulating gas; the circulating gas compressor is arranged on the pipeline connecting the methanol separator and the reaction device, and is used to pressurize the circulating gas and return it to the reaction device for methanol synthesis reaction.

[0014] Furthermore, the above-mentioned synthesis device also includes a heat exchanger, which is arranged on the pipeline connecting the secondary purification device and the reaction device, and is used to preheat the product system and the desulfurized synthesis gas to obtain preheated synthesis gas and a cooled product system; optionally, a cooling device is provided on the pipeline connecting the methanol separator and the heat exchanger, and the cooling device has a cooling water inlet and a cooling water outlet, and the cooling device is used to further cool the cooled product system.

[0015] In another typical embodiment of the present application, a novel method for synthesizing methanol is provided, which includes: step S1, performing a conversion treatment on a portion of the raw coal gas to obtain converted coal gas, and the remaining raw coal gas is used as unconverted raw coal gas; step S2, performing an acid gas removal treatment on the converted coal gas to obtain converted synthesis gas and a first carbon dioxide; performing an acid gas removal treatment on the unconverted raw coal gas to obtain an unconverted synthesis gas and a second carbon dioxide, wherein the converted synthesis gas and the unconverted synthesis gas are stored separately, and the first carbon dioxide and the second carbon dioxide are combined and stored as carbon dioxide gas; step S3, performing a fine desulfurization treatment on the converted synthesis gas, the unconverted synthesis gas and the carbon dioxide gas to obtain a desulfurized synthesis gas; and step S4, performing a methanol synthesis reaction on the desulfurized synthesis gas to obtain a product system including methanol.

[0016] Furthermore, in the above-mentioned step S2, the process of acid gas removal treatment includes: performing methanol washing on the converted coal gas to obtain converted synthesis gas and crude carbon dioxide product A, and performing methanol washing on the unconverted crude coal gas to obtain unconverted synthesis gas and crude carbon dioxide product B; the crude carbon dioxide product A and the crude carbon dioxide product B are jointly used as crude carbon dioxide product; and the crude carbon dioxide product is hydrolyzed with high-pressure water vapor to obtain carbon dioxide gas; preferably, the flow rate of the high-pressure water vapor is less than or equal to one twenty-five thousandth of the flow rate of the crude carbon dioxide product, preferably, the total sulfur content in the carbon dioxide gas is ≤10 ppm, and preferably, the COS content in the carbon dioxide gas is <0.1 ppm.

[0017] Furthermore, the desulfurized synthesis gas comprises, by mass percentage, 66.5-68% hydrogen, 30-31% carbon monoxide, and 2-2.5% carbon dioxide; preferably, the total sulfur content in the desulfurized synthesis gas is less than 50 ppb.

[0018] Furthermore, the hydrogen-carbon ratio of the desulfurized synthesis gas is controlled between 3.5% and 4%, preferably within a fluctuation range of ±0.03, and the unit consumption of refined methanol synthesis gas is reduced to 2150 Nm 3 / t or less.

[0019] Furthermore, the above-mentioned product system is separated to obtain crude methanol and circulating gas, and the circulating gas is preferably pressurized and returned to the methanol synthesis reaction; before separating the product system, the desulfurized synthesis gas is preferably preheated using the product system to obtain preheated synthesis gas and a cooled product system; and the cooled product system is preferably further cooled using cooling water.

[0020] By applying the technical solution of the present application and utilizing the conversion device, primary purification device, secondary purification device and reaction device of the above-mentioned methanol synthesis device, the present invention can change the traditional gas distribution method of the methanol synthesis device, divide the methanol synthesis gas into three gases: conversion synthesis gas, unconverted synthesis gas and carbon dioxide product gas, and proportion them separately, especially for the separate distribution of carbon dioxide gas, and at the same time utilize carbon dioxide hydrolysis desulfurization technology to reduce the sulfur content to an acceptable range. By precisely controlling the amount of carbon dioxide added to the methanol synthesis device, the dual influence of the carbon dioxide content of the traditional methanol synthesis device on the operation of the conversion and low-temperature methanol washing device is eliminated, the fluctuation range of the hydrogen-carbon ratio is reduced to ±0.03, and the unit consumption of refined methanol synthesis gas per ton is reduced to 2150Nm 3 / t or less. In addition, compared with the preparation of synthesis gas by using conversion synthesis gas alone, the preparation of synthesis gas by using conversion synthesis gas with different hydrogen-carbon ratios and unconverted synthesis gas together can further reduce costs. It can be seen that the present invention reduces the unit consumption of methanol synthesis gas and extends the service life of the catalyst by optimizing the methanol synthesis gas distribution method, thereby significantly reducing the production cost and energy consumption of methanol and achieving significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0022] Figure 1 A schematic diagram of a methanol synthesis device provided according to Example 1 of the present invention is shown.

[0023] The above drawings include the following reference numerals:

[0024] 1. Methanol washing device; 2. High-pressure steam device; 3. Hydrolysis reactor; 4. High-pressure steam flow orifice plate; 5. Carbon dioxide flow regulating valve; 6. Carbon dioxide compressor; 7. Converted synthesis gas flow regulating valve; 8. Unconverted synthesis gas flow regulating valve; 10. Converter; 20. Primary purification device; 30. Secondary purification device; 40. Reaction device; 50. Synthesis gas compressor; 60. Methanol separator; 70. Circulating gas compressor; 80. Heat exchanger. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] As analyzed in the background technology of this application, the existing technology has the problem of high unit consumption of refined methanol synthesis gas per ton, which leads to high production cost of methanol. In order to solve this problem, this application provides a methanol synthesis device and synthesis method.

[0027] In a typical embodiment of the present application, a methanol synthesis device is provided, such as Figure 1 As shown, the synthesis device includes a conversion device 10, a primary purification device 20, a secondary purification device 30 and a reaction device 40. The inlet of the conversion device 10 is connected to the outlet of the gasifier, and is used to convert part of the raw gas in the gasifier to obtain converted coal gas; the inlet of the primary purification device 20 is connected to the outlet of the conversion device 10 and the outlet of the gasifier respectively. The primary purification device 20 is used to remove acid gases from the converted coal gas obtained by the conversion device 10 to obtain converted synthesis gas and first carbon dioxide. The primary purification device 20 is used to remove acid gases from the remaining unconverted raw coal gas in the gasifier to obtain unconverted synthesis gas and The second carbon dioxide, wherein the converted synthesis gas and the unconverted synthesis gas are separately transported, and the first carbon dioxide and the second carbon dioxide are combined as a separately transported carbon dioxide gas; the inlet of the secondary purification device 30 is connected to the outlet of the primary purification device 20, and the secondary purification device 30 is used to perform fine desulfurization treatment on the converted synthesis gas, the unconverted synthesis gas, and the carbon dioxide gas obtained by the primary purification device 20 to obtain desulfurized synthesis gas; and the inlet of the reaction device 40 is connected to the outlet of the secondary purification device 30, and the reaction device 40 is used to use the desulfurized synthesis gas obtained by the secondary purification device 30 to carry out a methanol synthesis reaction to obtain a product system including methanol.

[0028] By utilizing the conversion device 10, the primary purification device 20, the secondary purification device 30, and the reaction device 40 of the above-mentioned methanol synthesis device, the present invention can change the traditional gas distribution method of the methanol synthesis device, divide the methanol synthesis gas into three gases: conversion synthesis gas, unconverted synthesis gas, and carbon dioxide product gas, and distribute them in different proportions, especially for the separate distribution of carbon dioxide gas. At the same time, the sulfur content is reduced to an acceptable range by utilizing carbon dioxide hydrolysis desulfurization technology. By precisely controlling the amount of carbon dioxide added to the methanol synthesis device, the dual influence of the carbon dioxide content of the traditional methanol synthesis device on the operation of the conversion and low-temperature methanol washing device is eliminated, the fluctuation range of the hydrogen-carbon ratio is reduced to ±0.03, and the unit consumption of refined methanol synthesis gas per ton is reduced to 2150Nm 3 / t or less. In addition, compared with the preparation of synthesis gas by using conversion synthesis gas alone, the preparation of synthesis gas by using conversion synthesis gas with different hydrogen-carbon ratios and unconverted synthesis gas together can further reduce costs. It can be seen that the present invention reduces the unit consumption of methanol synthesis gas and extends the service life of the catalyst by optimizing the methanol synthesis gas distribution method, thereby significantly reducing the production cost and energy consumption of methanol and achieving significant economic benefits.

[0029] In one embodiment of the present application, the above-mentioned primary purification device 20 includes a methanol washing device 1, a high-pressure water vapor device 2 and a hydrolysis reactor 3. The inlet of the methanol washing device 1 is connected to the outlet of the conversion device 10 and the outlet of the gasifier respectively. The methanol washing device 1 is used to perform methanol washing on the converted coal gas obtained by the conversion device 10 to obtain converted synthesis gas and crude carbon dioxide product A. The methanol washing device 1 is used to perform methanol washing on the remaining unconverted crude coal gas in the gasifier to obtain unconverted synthesis gas and crude carbon dioxide product B. The crude carbon dioxide product A and the crude carbon dioxide product B are jointly used as crude carbon dioxide product; the inlet of the high-pressure water vapor device 2 is connected to the high-pressure water vapor source for providing high-pressure water vapor; the inlet of the hydrolysis reactor 3 is connected to the outlet of the methanol washing device 1 and the outlet of the high-pressure water vapor device 2 respectively. The hydrolysis reactor 3 is used to hydrolyze the high-pressure water vapor with the crude carbon dioxide product to obtain carbon dioxide gas.

[0030] The crude carbon dioxide is fed into the carbon dioxide hydrolysis reactor 3 together with high-pressure water vapor (of course, if the reaction conditions of the hydrolysis catalyst have special requirements, temperature increase measures need to be considered). Under the action of the hydrolysis catalyst, the reaction COS+H2O→CO2+H2S occurs, converting COS into H2S. The product of the initial hydrolysis reaction is discharged on site after the hydrolysis reactor 3. After 30 minutes, the COS content at the outlet of the hydrolysis reactor 3 is analyzed and tested. If the COS content is less than 0.1 ppm, it indicates that the hydrolysis reaction is normal and the obtained carbon dioxide gas can be used normally.

[0031] In one embodiment of the present application, a high-pressure water steam flow orifice plate 4 is provided on the pipeline connecting the above-mentioned high-pressure water steam device 2 and the hydrolysis reactor 3. The high-pressure water steam flow orifice plate 4 is used to control the flow rate of high-pressure water steam entering the hydrolysis reactor 3. Preferably, the aperture of the high-pressure water steam flow orifice plate 4 is 0.5 to 1 mm.

[0032] Adding too much high-pressure steam to the hydrolysis reaction can generate carbonic acid, causing acid corrosion of the synthesis gas compressor and inlet and outlet pipelines of the synthesis unit. Adding too little high-pressure steam can affect the efficiency and effectiveness of the hydrolysis reaction. It is preferred to use a high-pressure steam flow orifice plate 4 of the above specifications, which helps ensure the hydrolysis effect while reducing the chance of carbonic acid corrosion of the equipment.

[0033] A carbon dioxide flow regulating valve 5 is provided on the pipeline connecting the methanol washing device 1 and the hydrolysis reactor 3 . The carbon dioxide flow regulating valve 5 is used to control the flow of crude carbon dioxide entering the hydrolysis reactor 3 .

[0034] Carbon dioxide is an important activator and protective agent for methanol synthesis catalysts. It significantly increases the reactivity of the methanol catalyst. The water generated by the reaction stabilizes the methanol catalyst bed temperature, extending the service life of the methanol catalyst. A carbon dioxide flow control valve 5 is preferably used to control the amount of carbon dioxide in the synthesis gas.

[0035] In order to facilitate the transportation of crude carbon dioxide and promote its hydrolysis reaction with high-pressure water vapor, a carbon dioxide compressor 6 is preferably provided on the pipeline connecting the above-mentioned methanol washing device 1 and the carbon dioxide flow regulating valve 5. The carbon dioxide compressor 6 is used to pressurize the crude carbon dioxide.

[0036] In one embodiment of the present application, a converted synthesis gas flow regulating valve 7 is provided on the pipeline connecting the above-mentioned methanol washing device 1 and the reaction device 40, and the converted synthesis gas flow regulating valve 7 is used to control the flow of the converted synthesis gas; preferably, an unconverted synthesis gas flow regulating valve 8 is provided on the pipeline connecting the methanol washing device 1 and the reaction device 40, and the unconverted synthesis gas flow regulating valve 8 is used to control the flow of the unconverted synthesis gas.

[0037] The synthesis gas flow regulating valve 7 and the unconverted synthesis gas flow regulating valve 8 help control the flow rates of the converted synthesis gas and the unconverted synthesis gas, thereby obtaining a synthesis gas that meets the hydrogen-to-carbon ratio requirements.

[0038] Preferably, the above-mentioned synthesis device also includes a synthesis gas compressor 50, which is arranged on the pipeline connecting the carbon dioxide flow regulating valve 5 and the reaction device 40. The synthesis gas compressor 50 is also arranged on the pipeline connecting the converted synthesis gas flow regulating valve 7 and the reaction device 40. The synthesis gas compressor 50 is also arranged on the pipeline connecting the unconverted synthesis gas flow regulating valve 8 and the reaction device 40. The synthesis gas compressor 50 is used to mix and pressurize the converted synthesis gas, unconverted synthesis gas and carbon dioxide gas, thereby helping to adjust the synthesis gas to a suitable pressure.

[0039] In one embodiment of the present application, the above-mentioned synthesis device also includes a methanol separator 60 and a circulating gas compressor 70. The inlet of the methanol separator 60 is connected to the outlet of the reaction device 40. The methanol separator 60 is used to separate the product system to obtain crude methanol and circulating gas; the circulating gas compressor 70 is arranged on the pipeline connecting the methanol separator 60 and the reaction device 40, and is used to pressurize the circulating gas and return it to the reaction device 40 for methanol synthesis reaction.

[0040] In one embodiment of the present application, the above-mentioned synthesis device also includes a heat exchanger 80, which is arranged on the pipeline connecting the secondary purification device 30 and the reaction device 40, and is used to preheat the product system and the desulfurized synthesis gas to obtain preheated synthesis gas and a cooled product system; optionally, a cooling device is provided on the pipeline connecting the methanol separator 60 and the heat exchanger 80, and the cooling device has a cooling water inlet and a cooling water outlet, and the cooling device is used to further cool the cooled product system.

[0041] The heat exchanger 80 helps to transfer most of the waste heat in the product system to the desulfurized synthesis gas, thereby reducing the cooling load of the cooling device on the cooling product system and utilizing the waste heat of the product system to preheat the desulfurized synthesis gas, thereby greatly reducing energy consumption.

[0042] In another typical embodiment of the present application, a novel method for synthesizing methanol is provided, which includes: step S1, performing a conversion treatment on a portion of the raw coal gas to obtain converted coal gas, and the remaining raw coal gas is used as unconverted raw coal gas; step S2, performing an acid gas removal treatment on the converted coal gas to obtain converted synthesis gas and a first carbon dioxide; performing an acid gas removal treatment on the unconverted raw coal gas to obtain an unconverted synthesis gas and a second carbon dioxide, wherein the converted synthesis gas and the unconverted synthesis gas are stored separately, and the first carbon dioxide and the second carbon dioxide are combined and stored as carbon dioxide gas; step S3, performing a fine desulfurization treatment on the converted synthesis gas, the unconverted synthesis gas and the carbon dioxide gas to obtain a desulfurized synthesis gas; and step S4, performing a methanol synthesis reaction on the desulfurized synthesis gas to obtain a product system including methanol.

[0043] The above synthesis method can change the traditional gas distribution mode of methanol synthesis unit, and divide the methanol synthesis gas into three gases: conversion synthesis gas, unconverted synthesis gas and carbon dioxide product gas, and distribute them in different proportions. In particular, the separate distribution of carbon dioxide gas can be used. At the same time, the sulfur content can be reduced to the qualified range by using carbon dioxide hydrolysis desulfurization technology. By accurately controlling the amount of carbon dioxide added to the methanol synthesis unit, the dual influence of the conversion and low-temperature methanol washing unit operations on the carbon dioxide content of the traditional methanol synthesis unit is eliminated, and the fluctuation range of the hydrogen-carbon ratio is reduced to ±0.03. The unit consumption of refined methanol synthesis gas per ton is reduced to 2150Nm 3 / t or less. In addition, compared with the preparation of synthesis gas by using conversion synthesis gas alone, the preparation of synthesis gas by using conversion synthesis gas with different hydrogen-carbon ratios and unconverted synthesis gas together can reduce the cost in one step. It can be seen that the present invention reduces the unit consumption of methanol synthesis gas and extends the service life of the catalyst by optimizing the methanol synthesis gas distribution method, thereby significantly reducing the production cost and energy consumption of methanol and achieving significant economic benefits.

[0044] In one embodiment of the present application, in the above-mentioned step S2, the process of acid gas removal treatment includes: performing methanol washing on the converted coal gas to obtain converted synthesis gas and crude carbon dioxide product A, and performing methanol washing on the unconverted crude coal gas to obtain unconverted synthesis gas and crude carbon dioxide product B; the crude carbon dioxide product A and the crude carbon dioxide product B are jointly used as crude carbon dioxide product; the crude carbon dioxide product is hydrolyzed with high-pressure water vapor to obtain carbon dioxide gas; preferably, the flow rate of the high-pressure water vapor is less than or equal to one twenty-five thousandth of the flow rate of the crude carbon dioxide product, preferably, the total sulfur content in the carbon dioxide gas is ≤10ppm, and preferably, the COS content in the carbon dioxide gas is <0.1ppm.

[0045] The crude carbon dioxide is fed together with high-pressure steam and reacts under the action of a hydrolysis catalyst to form COS+H2O→CO2+H2S (of course, if the reaction conditions of the hydrolysis catalyst have special requirements, temperature increase measures need to be considered), converting COS into H2S. The initial hydrolysis reaction product is vented on site, and the COS content in the hydrolysis reaction product is analyzed after 30 minutes. If the COS content is less than 0.1ppm, it indicates that the hydrolysis reaction is normal and the obtained carbon dioxide gas can be used normally. If the amount of high-pressure steam added to the hydrolysis reaction is too large, carbonic acid may be generated, causing acid corrosion of the synthesis gas compressor body and the inlet and outlet pipelines of the synthesis unit. If the amount of high-pressure steam added is too small, the efficiency and effect of the hydrolysis reaction will be affected. It is preferred to control the flow rate of high-pressure steam within the above range, which not only helps to ensure the hydrolysis effect, but also reduces the probability of carbonic acid corrosion of equipment.

[0046] In some embodiments of the present application, the above-mentioned desulfurized synthesis gas preferably includes 66.5-68% hydrogen, 30-31% carbon monoxide and 2-2.5% carbon dioxide, in terms of mass percentage; the total sulfur content in the desulfurized synthesis gas is preferably less than 50ppb, which is more conducive to improving the efficiency and effect of the methanol synthesis reaction.

[0047] In one embodiment of the present application, the hydrogen-carbon ratio of the desulfurized synthesis gas is controlled between 3.5% and 4%, preferably with a fluctuation range of ±0.03, and preferably the unit consumption of refined methanol synthesis gas per ton is reduced to 2150 Nm 3 / t or less.

[0048] The above conditions help to further reduce costs, extend the service life of the catalyst, significantly reduce the production cost and energy consumption of methanol, and achieve significant economic benefits.

[0049] In one embodiment of the present application, the above-mentioned product system is separated to obtain crude methanol and circulating gas, and the circulating gas is preferably pressurized and returned to the methanol synthesis reaction; before separating the product system, the desulfurized synthesis gas is preferably preheated using the product system to obtain preheated synthesis gas and a cooled product system; and cooling water is preferably used to further cool the cooled product system.

[0050] The cost can be further reduced by using the above-mentioned recycled gas as part of the reaction raw material for the methanol synthesis reaction.

[0051] The beneficial effects of the present application will be further illustrated below with reference to examples.

[0052] Example 1

[0053] according to Figure 1 The device shown in the figure is applied to methanol synthesis in a large coal chemical plant. A portion of the crude gas from the gasifier is converted after the converter to obtain converted gas. The converted gas enters the methanol scrubber for methanol washing to obtain converted synthesis gas and crude carbon dioxide product A. Another portion of the crude gas from the gasifier enters the methanol scrubber for methanol washing to obtain unconverted synthesis gas and crude carbon dioxide product B. The crude carbon dioxide including crude carbon dioxide product A and crude carbon dioxide product B is pressurized by the carbon dioxide compressor 6 and then controlled by the carbon dioxide flow control valve 5 to enter the hydrolysis reactor 3 at a flow rate of 4000 Nm 3 / h, a high-pressure steam generator is connected to a high-pressure steam source, and the generated high-pressure steam enters the hydrolysis reactor 3 through a high-pressure steam flow orifice 4 (1 mm), and the high-pressure steam in the hydrolysis reactor 3 undergoes a hydrolysis reaction (potassium salt hydrolyzing agent) with the crude carbon dioxide to obtain carbon dioxide gas, wherein the converted synthesis gas and the unconverted synthesis gas are separately transported, and the crude carbon dioxide A and the crude carbon dioxide B are combined as a separately transported carbon dioxide gas.

[0054] The conversion synthesis gas flow regulating valve 7 is used to control the conversion synthesis gas flow rate to 219,000 Nm 3 / h, the flow rate of the unconverted synthesis gas is controlled by the unconverted synthesis gas flow control valve 8 to be 61,000 Nm 3 The converted synthesis gas, unconverted synthesis gas and carbon dioxide gas are mixed and pressurized by the synthesis gas compressor 50 and then subjected to fine desulfurization treatment (zinc oxide desulfurizer) in a fine desulfurization tower to obtain desulfurized synthesis gas (hydrogen-carbon ratio controlled between 2.03±0.03).

[0055] The desulfurized syngas undergoes a methanol synthesis reaction in the reactor (using a Topsoe MK121 catalyst from Denmark), producing a product system including methanol. This product system is separated in a methanol separator 60 to produce crude methanol and recycle gas. The recycle gas is pressurized by a recycle gas compressor 70 and returned to the reactor to continue the methanol synthesis reaction.

[0056] The above synthesis gas consumption is as low as 2140Nm 3 / t, the energy consumption per ton of methanol production has reached the industry benchmark value of less than 1,400 kg of standard coal per ton, the high-pressure steam flow rate has been stabilized at 10 kg / h, the risk of carbonic acid corrosion caused by carbon dioxide product gas has been completely eliminated, and the cost of methanol production has been significantly reduced.

[0057] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0058] By utilizing the conversion device, primary purification device, secondary purification device and reaction device of the above-mentioned methanol synthesis device, the present invention can change the traditional gas distribution method of the methanol synthesis device, divide the methanol synthesis gas into three gases: conversion synthesis gas, unconverted synthesis gas and carbon dioxide product gas, and proportion them separately, especially for the separate distribution of carbon dioxide gas, while using carbon dioxide hydrolysis desulfurization technology to reduce the sulfur content to an acceptable range. By accurately controlling the amount of carbon dioxide added to the methanol synthesis device, the dual influence of the carbon dioxide content of the traditional methanol synthesis device on the operation of the conversion and low-temperature methanol washing device is eliminated, the fluctuation range of the hydrogen-carbon ratio is reduced to ±0.03, and the unit consumption of refined methanol synthesis gas per ton is reduced to 2150Nm 3 / t or less. In addition, compared with the preparation of synthesis gas by using conversion synthesis gas alone, the preparation of synthesis gas by using conversion synthesis gas with different hydrogen-carbon ratios and unconverted synthesis gas together can further reduce costs. It can be seen that the present invention reduces the unit consumption of methanol synthesis gas and extends the service life of the catalyst by optimizing the methanol synthesis gas distribution method, thereby significantly reducing the production cost and energy consumption of methanol and achieving significant economic benefits.

[0059] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A methanol synthesis device, characterized in that: The synthesis device comprises: a conversion device (10), the inlet of which is connected to the outlet of the gasifier, for performing conversion processing on a portion of the raw coal gas in the gasifier to obtain converted coal gas; a first-stage purification device (20), the inlet of which is connected to the outlet of the conversion device (10) and the outlet of the gasifier, respectively; the first-stage purification device (20) is used to perform acid gas removal treatment on the converted coal gas obtained by the conversion device (10) to obtain converted synthesis gas and first carbon dioxide; the first-stage purification device (20) is used to perform acid gas removal treatment on the unconverted raw coal gas remaining in the gasifier to obtain unconverted synthesis gas and second carbon dioxide, wherein the converted synthesis gas and the unconverted synthesis gas are separately transported, and the first carbon dioxide and the second carbon dioxide are combined as a separately transported carbon dioxide gas; a secondary purification device (30), the inlet of which is connected to the outlet of the primary purification device (20), the secondary purification device (30) being used to perform fine desulfurization treatment on the shifted synthesis gas, the unshifted synthesis gas, and the carbon dioxide gas obtained by the primary purification device (20) to obtain desulfurized synthesis gas; and a reaction device (40), the inlet of which is connected to the outlet of the secondary purification device (30), the reaction device (40) being used to perform a methanol synthesis reaction using the desulfurized synthesis gas obtained from the secondary purification device (30) to obtain a product system including methanol; The primary purification device (20) comprises: A methanol washing device (1), the inlet of which is connected to the outlet of the conversion device (10) and the outlet of the gasifier, respectively. The methanol washing device (1) is used to perform a methanol washing treatment on the converted coal gas obtained by the conversion device (10) to obtain a converted synthesis gas and a crude carbon dioxide product A. The methanol washing device (1) is used to perform a methanol washing treatment on the unconverted crude coal gas remaining in the gasifier to obtain an unconverted synthesis gas and a crude carbon dioxide product B. The crude carbon dioxide product A and the crude carbon dioxide product B are used together as a crude carbon dioxide product. a high-pressure water steam device (2), the inlet of which is connected to a high-pressure water steam source and is used to provide high-pressure water steam; The hydrolysis reactor (3) has an inlet connected to the outlet of the methanol washing device (1) and the outlet of the high-pressure water vapor device (2), respectively. The hydrolysis reactor (3) is used to cause the high-pressure water vapor to hydrolyze the crude carbon dioxide product to obtain the carbon dioxide gas.

2. The synthesis device according to claim 1, characterized in that A high-pressure water steam flow orifice plate (4) is provided on a pipeline connecting the high-pressure water steam device (2) and the hydrolysis reactor (3), and the high-pressure water steam flow orifice plate (4) is used to control the flow rate of the high-pressure water steam entering the hydrolysis reactor (3).

3. The synthesis device according to claim 2, characterized in that The aperture of the high-pressure water vapor flow orifice plate (4) is 0.5-1 mm.

4. The synthesis device according to claim 1 or 2, characterized in that A carbon dioxide flow regulating valve (5) is provided on the pipeline connecting the methanol washing device (1) and the hydrolysis reactor (3), and the carbon dioxide flow regulating valve (5) is used to control the flow of the crude carbon dioxide entering the hydrolysis reactor (3).

5. The synthesis device according to claim 4, characterized in that A carbon dioxide compressor (6) is provided on the pipeline connecting the methanol washing device (1) and the carbon dioxide flow regulating valve (5), and the carbon dioxide compressor (6) is used to pressurize the crude carbon dioxide product.

6. The synthesis device according to claim 4, characterized in that A conversion synthesis gas flow regulating valve (7) is provided on a pipeline connecting the methanol washing device (1) and the reaction device (40), and the conversion synthesis gas flow regulating valve (7) is used to control the flow of the conversion synthesis gas.

7. The synthesis device according to claim 6, characterized in that An unconverted synthesis gas flow regulating valve (8) is provided on a pipeline connecting the methanol washing device (1) and the reaction device (40), and the unconverted synthesis gas flow regulating valve (8) is used to control the flow of the unconverted synthesis gas.

8. The synthesis device according to claim 7, characterized in that The synthesis device also includes: The synthesis gas compressor (50) is provided on the pipeline connecting the carbon dioxide flow regulating valve (5) and the reaction device (40), and the synthesis gas compressor (50) is also provided on the pipeline connecting the converted synthesis gas flow regulating valve (7) and the reaction device (40). The synthesis gas compressor (50) is also provided on the pipeline connecting the unconverted synthesis gas flow regulating valve (8) and the reaction device (40). The synthesis gas compressor (50) is used to mix and pressurize the converted synthesis gas, the unconverted synthesis gas and the carbon dioxide gas.

9. The synthesis device according to claim 1, characterized in that The synthesis device also includes: a methanol separator (60), the inlet of which is connected to the outlet of the reaction device (40), and the methanol separator (60) is used to separate the product system to obtain crude methanol and circulating gas; A circulating gas compressor (70) is provided on a pipeline connecting the methanol separator (60) and the reaction device (40), and is used to pressurize the circulating gas and return it to the reaction device (40) for the methanol synthesis reaction.

10. The synthesis device according to claim 9, characterized in that The synthesis device also includes: The heat exchanger (80) is provided on a pipeline connecting the secondary purification device (30) and the reaction device (40), and is used to preheat the product system and the desulfurized synthesis gas to obtain preheated synthesis gas and a cooled product system.

11. The synthesis device according to claim 10, characterized in that A cooling device is provided on the pipeline connecting the methanol separator (60) and the heat exchanger (80), wherein the cooling device has a cooling water inlet and a cooling water outlet, and the cooling device is used to further cool the cooled product system.

12. A method for synthesizing methanol, characterized in that: The synthesis method comprises: Step S1, converting part of the crude gas to obtain converted gas, and the remaining crude gas is used as unconverted crude gas; Step S2: performing acid gas removal treatment on the shifted coal gas to obtain shifted synthesis gas and first carbon dioxide; performing acid gas removal treatment on the unshifted raw coal gas to obtain unshifted synthesis gas and second carbon dioxide, wherein the shifted synthesis gas and the unshifted synthesis gas are stored separately, and the first carbon dioxide and the second carbon dioxide are combined and stored as carbon dioxide gas; Step S3, performing fine desulfurization treatment on the shifted synthesis gas, the unshifted synthesis gas and the carbon dioxide gas to obtain desulfurized synthesis gas; and Step S4, performing a methanol synthesis reaction on the desulfurized synthesis gas to obtain a product system including methanol; The synthesis method is carried out in the synthesis apparatus according to any one of claims 1 to 11.

13. The synthesis method according to claim 12, characterized in that In step S2, the acid gas removal process includes: The shifted coal gas is subjected to methanol washing to obtain shifted synthesis gas and crude carbon dioxide product A, and the unshifted crude coal gas is subjected to methanol washing to obtain unshifted synthesis gas and crude carbon dioxide product B; the crude carbon dioxide product A and the crude carbon dioxide product B are collectively referred to as crude carbon dioxide product; The crude carbon dioxide product is subjected to a hydrolysis reaction with high-pressure water vapor to obtain the carbon dioxide gas.

14. The synthesis method according to claim 13, characterized in that The flow rate of the high-pressure water vapor is less than or equal to one twenty-five thousandth of the flow rate of the crude carbon dioxide product.

15. The synthesis method according to claim 14, characterized in that The total sulfur content in the carbon dioxide gas is ≤10 ppm.

16. The synthesis method according to claim 14, characterized in that The COS content in the carbon dioxide gas is less than 0.1 ppm.

17. The synthesis method according to claim 12, characterized in that In terms of mass percentage, the desulfurized synthesis gas comprises: 66.5~68% hydrogen; 30-31% carbon monoxide; and 2~2.5% carbon dioxide.

18. The synthesis method according to claim 17, characterized in that The total sulfur content in the desulfurized synthesis gas is less than 50 ppb.

19. The synthesis method according to claim 12, characterized in that The hydrogen-to-carbon ratio of the desulfurized synthesis gas is controlled between 3.5% and 4%, wherein the hydrogen-to-carbon ratio = (VH2-VCO2) / (VCO+VCO2).

20. The synthesis method according to claim 19, characterized in that The fluctuation range of the hydrogen-to-carbon ratio is ±0.

03.

21. The synthesis method according to claim 19, characterized in that The unit consumption of syngas per ton of refined methanol is reduced to 2150Nm 3 / t or less.

22. The synthesis method according to claim 12, characterized in that The product system is separated to obtain crude methanol and circulating gas.

23. The synthesis method according to claim 22, characterized in that The circulating gas is pressurized and then returned to the methanol synthesis reaction.

24. The synthesis method according to claim 22, characterized in that Before separating the product system, the desulfurized synthesis gas is preheated using the product system to obtain preheated synthesis gas and a cooled product system.

25. The synthesis method according to claim 24, characterized in that The cooled product system is further cooled by using cooling water.

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