Methanol carbonylation acetic acid preparation system

Abstract

The utility model relates to the technical field of acetic acid synthesis through methanol low-pressure carbonyl, in particular to a system for preparing acetic acid through methanol carbonylation. The system comprises a reaction kettle 1, a flash tank 2, a light component removal tower 3, a dehydration tower 4 and a heavy component removal tower 5, wherein a micro-interface unit 6 is arranged in the reaction kettle 1; the phase interface size of gas-liquid particles in the micro-interface unit 6 is changed from the traditional centimeter level to the micron level, so that the phase interface mass transfer area between the raw material carbon monoxide and the raw material methanol in the process of producing acetic acid through methanol low-pressure carbonylation is increased, and the methanol carbonylation gas reaction rate is greatly improved. According to the system disclosed by the utility model, the micro-interface is introduced, the micro-interface strengthening effect is better, and the gas-liquid phase boundary mass transfer area can be stably maintained at a high level, so that the methanol carbonylation gas reaction rate is greatly improved, and the prominent technical bottleneck of the traditional methanol carbonylation method acetic acid synthesis process can be effectively solved; the method has good operation flexibility and high practical application value.

Description

Technical Field

[0001] The utility model relates to the technical field of methanol low-pressure carbonylation synthesis of acetic acid, in particular to a methanol carbonylation system for preparing acetic acid. Background Art

[0002] Acetic acid (also known as acetic acid), with the molecular formula CH3COOH and a relative molecular weight of 60.05, is a colorless, transparent liquid with a pungent, sour odor and strong corrosive properties. It is miscible with water, alcohol, chloroform, ether, and glycerin, but insoluble in carbon disulfide. Due to its low freezing point, it solidifies into ice-like crystals at low temperatures, hence its common name, glacial acetic acid. Acetic acid is a weak monoprotic acid that reacts with bases, undergoes esterification with alcohols, reacts with chlorine to form chloroacetic acid, and reacts chemically with metals and their oxides.

[0003] Its physical properties are as follows

[0004] <![CDATA[Molecular formula: CH3COOH]]> Molecular weight: 60.05 <![CDATA[Density: (20 / 4 °C): 1.049 g / cm 3 > Freezing point: 16.7°C Boiling point: 118.1°C Flash point: 42.78℃ (closed cup) Autoignition point: 465℃ Explosion limit: 4%-17%

[0005] Acetic acid possesses a carbonyl functional group, a characteristic of organic acids. As an important chemical intermediate, it is primarily used in the synthesis of acetate esters, acetic anhydride, cellulose acetate, metal acetates, and chloroacetic acid. It is also widely used in the pharmaceutical, dye, pesticide, and rubber industries, and has been a rapidly growing organic chemical raw material worldwide in recent years. The main production processes for acetic acid include methanol carbonylation, acetaldehyde oxidation, ethylene oxidation, and liquid-phase oxidation of light hydrocarbons. Low-pressure methanol carbonylation has become the preferred route for acetic acid production, offering significant advantages: first, it diversifies raw material routes and connects the coal chemical industry chain; second, it offers high methanol yields, minimal by-products, and a high degree of automation. The entire process is a closed system, and aside from the unreacted carbon monoxide that is flared, no other waste is emitted. my country is a major coal resource country, providing a strong supply base for methanol and carbon monoxide. With the rapid development of acetic acid's downstream products, demand for acetic acid and its derivatives is expected to grow in tandem, becoming a vital component of the national economy.

[0006] Traditional process for synthesizing acetic acid by methanol carbonylation Figure 2 As shown, carbon monoxide and methanol enter reactor 1, and are synthesized into acetic acid by low-pressure carbonylation at 180°C and 3 MPa under the action of rhodium triiodide catalyst and hydroiodic acid co-catalyst. After separation and recovery of rhodium and iodine catalyst in flash tank 2, the crude acetic acid enters light removal tower 3 to remove hydroiodic acid, hydrogen iodide, methyl acetate, aldehydes and some water, then enters dehydration tower 4 to remove water, and finally enters heavy removal tower 5 to remove high-boiling-point substances such as propionic acid and heavy metal ions at the bottom, and finished acetic acid is produced by the side line of the heavy removal tower.

[0007] As the load increases, the traditional methanol carbonylation process for synthesizing acetic acid gradually highlights certain technical bottlenecks, including:

[0008] (1) Traditionally, carbon monoxide raw gas enters the reactor in the form of bubbles. The carbon monoxide bubbles are large in size (their average diameter is at the milli-centimeter level), the interfacial area between the gas and liquid phases is small, the bubble coalescence phenomenon is serious, and the residence time is short, resulting in low gas-liquid mass transfer efficiency and reaction rate.

[0009] (2) Traditionally, mechanical stirring is done with an agitator, which consumes a lot of electricity during operation. Annual inspection and replacement of the mechanical seals increase maintenance costs. In addition, there is a risk of mechanical collision with the zirconium reactor during operation.

[0010] (3) As the load continues to increase, in order to ensure the expected carbonylation reaction rate in the reactor, the reactor temperature is often increased, which will affect the service life of the catalyst.

[0011] (4) The overall production efficiency of the reaction unit is relatively low, and the single-pass utilization rate of carbon monoxide raw materials and the reaction space velocity both have a large room for improvement.

[0012] Therefore, it is of great significance to develop a new methanol carbonylation reaction device to produce acetic acid with a built-in micro-interface. Utility Model Content

[0013] Purpose of the utility model: The technical problem to be solved by the utility model is to provide a methanol carbonylation system for producing acetic acid with a built-in micro-interface reaction in the industrial production of low-pressure methanol carbonylation to acetic acid.

[0014] In order to solve the above technical problems, the utility model discloses a methanol carbonylation system for producing acetic acid, comprising a reactor 1, a flash tank 2, a lightness removal tower 3, a dehydration tower 4 and a weight removal tower 5. The reactor 1 is provided with a micro-interface unit 6; the reactor 1 is provided with a product outlet on the side line, and the product outlet is connected to the flash tank 2; the flash tank 2 is provided with a gas phase production outlet on the top, and the gas phase production outlet is connected to the lightness removal tower 3; the side of the lightness removal tower 3 is provided with a first side line production outlet, and the first side line production outlet is connected to the dehydration tower 4; the bottom of the dehydration tower 4 is provided with a bottom production outlet, and the bottom production outlet is connected to the weight removal tower 5; the side of the weight removal tower 5 is provided with a second side line production outlet, and the second side line production outlet is used to obtain finished acetic acid.

[0015] Among them, the side line of the reactor 1 is provided with a reactor external circulation outlet, which enters the reactor external circulation pipeline 10 after passing through the reactor circulation pump and the reactor cooler. The reactor external circulation pipeline 10 is connected to the micro-interface unit 6 from the top of the reactor 1.

[0016] The bottom of the flash tank 2 is provided with a liquid phase outlet, and the liquid phase outlet is connected to the flash tank external circulation pipeline 9, and the flash tank external circulation pipeline 9 is connected to the micro-interface unit 6 from the top of the reactor 1.

[0017] Among them, the tops of the light removal tower 3 and the dehydration tower 4 are provided with dilute acid reflux outlets, and the dilute acid reflux outlets are connected to the dilute acid reflux pipeline 8, and the dilute acid reflux pipeline 8 is connected to the micro-interface unit 6 from the top of the reactor 1.

[0018] Among them, a heavy phase reflux outlet is provided on the top of the light-removal tower 3, and the heavy phase reflux outlet is connected to a heavy phase reflux pipeline 7, and the heavy phase reflux pipeline 7 is connected to the micro-interface unit 6 from the top of the reactor 1.

[0019] A raw material methanol pipeline and a raw material carbon monoxide pipeline are further provided on the top of the reactor 1 ; the raw material methanol pipeline and the raw material carbon monoxide pipeline are connected to the micro-interface unit 6 .

[0020] Among them, the phase interface size of the gas-liquid particles in the micro-interface unit 6 is changed from the traditional centimeter level to the micron level, so as to increase the phase interface mass transfer area between the raw material carbon monoxide and the raw material methanol during the low-pressure carbonylation of methanol to produce acetic acid, thereby greatly improving the methanol carbonylation gas reaction rate.

[0021] The micro-interface unit (6) collects unreacted raw materials, catalysts, by-products and impurities in the reaction through the heavy phase reflux line (7), the dilute acid reflux line (8), the flash tank external circulation line (9) and the reactor external circulation line (10), thereby cooling the reaction liquid temperature and enhancing the micro-interface effect.

[0022] Beneficial effects: The system disclosed in the present invention introduces a micro-interface, which has a better micro-interface strengthening effect, and the mass transfer area of the gas-liquid phase interface can be stably maintained at a high level, thereby greatly improving the methanol carbonylation gas reaction rate, and can effectively solve the technical bottlenecks highlighted in the traditional methanol carbonylation process for synthesizing acetic acid, and has good operational flexibility and strong practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0024] Figure 1 This is a schematic diagram of a methanol carbonylation to acetic acid reaction device with a built-in micro-interface according to the present invention, wherein 1-reactor, 2-flash tank, 3-lightness removal column, 4-dehydration column, 5-heavyness removal column, 6-micro-interface unit, 7-heavy phase reflux line, 8-dilute acid reflux line, 9-flash tank external circulation line, 10-reactor external circulation line;

[0025] Figure 2This is a schematic diagram of the traditional acetic acid process flow, where 1-reactor, 2-flash tank, 3-light removal tower, 4-dehydration tower, 5-heavy removal tower, 6-accelerator separator. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to the following embodiments. The embodiments will help to better understand the present invention, but the present invention is not limited to the following examples.

[0027] This embodiment discloses a system for producing acetic acid by carbonylation of methanol, comprising: a reactor 1, a flash tank 2, a light removal tower 3, a dehydration tower 4, a heavy removal tower 5, and a micro-interface unit 6.

[0028] Reactor 1 is provided with a product outlet on the side line, which is connected to flash tank 2. In flash tank 2, the reaction liquid undergoes instantaneous flash evaporation, consuming a large amount of heat energy to provide the necessary heat of vaporization to convert the reaction liquid from liquid to gas, thereby cooling the reaction liquid in the reactor. Flash tank 2 is provided with a liquid phase outlet at the bottom, which is connected to the flash tank external circulation pipeline 9.

[0029] A gas phase production port is provided on the top of the flash tank 2, and the gas phase production port is connected to the light removal tower 3. In the light removal tower 3, light components and non-condensable gases are removed to reduce the water content in the acetic acid product.

[0030] A side line outlet is provided on the side of the light removal tower 3, and the side line outlet is connected to the dehydration tower 4. In the dehydration tower 4, water and light components in the acetic acid product are further removed.

[0031] The bottom of the dehydration tower 4 is provided with a bottom outlet, and the bottom outlet is connected to the deweighting tower 5. In the deweighting tower 5, heavy components such as propionic acid are removed.

[0032] A side line outlet is provided on the side of the deweighting tower 5, and the side line outlet obtains finished acetic acid.

[0033] The reactor 1 of the present invention is provided with a reactor external circulation outlet on the side line. After passing through the reactor circulation pump and the reactor cooler, the liquid enters the reactor external circulation pipeline 10. The reactor external circulation pipeline 10 enters the micro-interface unit 6 from the top of the reactor 1. This can cool the reaction liquid in the reactor and enhance the micro-interface effect.

[0034] In flash tank 2, as the reaction liquid flashes, low-boiling-point substances vaporize into steam and enter lightness removal tower 3. Unvaporized high-boiling-point liquid accumulates at the bottom of flash tank 2. A liquid phase outlet is provided at the bottom of flash tank 2, connected to flash tank external circulation pipeline 9, which enters micro-interface unit 6 from the top of reactor 1. This cools the reaction liquid in the reactor, enabling the recycling of high-boiling-point catalysts and enhancing the micro-interface effect.

[0035] The dilute acid discharged from the top of the light removal tower 3 and the dehydration tower 4 is connected to the dilute acid reflux pipeline 8, which enters the micro-interface unit 6 from the top of the reactor 1. This can cool the reaction liquid in the reactor and strengthen the micro-interface effect.

[0036] The heavy phase discharged from the top of the light removal tower 3 is connected to the heavy phase reflux line 7, which enters the micro-interface unit 6 from the top of the reactor 1. It can cool the reaction liquid in the reactor and strengthen the micro-interface effect.

[0037] The micro-interface unit 6 is installed inside the reactor 1, and is connected to the heavy phase reflux pipeline 7, the dilute acid reflux pipeline 8, the flash tank external circulation pipeline 9, the reactor external circulation pipeline 10, the raw material methanol pipeline, and the raw material carbon monoxide pipeline.

[0038] In the micro-interface unit 6, the phase interface size of the gas-liquid particles is changed from the traditional centimeter level to the micron level, so as to increase the phase interface mass transfer area between the raw material carbon monoxide and the raw material methanol in the process of producing acetic acid by low-pressure carbonylation of methanol, thereby greatly improving the reaction rate of methanol carbonylation gas.

[0039] The present invention provides a system for producing acetic acid by carbonylation of methanol. There are numerous methods and approaches for implementing this technical solution. The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications should be considered within the scope of protection of the present invention. Any components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A system for producing acetic acid by carbonylation of methanol, comprising a reactor (1), a flash tank (2), a light removal tower (3), a dehydration tower (4) and a heavy removal tower (5), characterized in that: The reactor (1) is provided with a micro-interface unit (6); a product outlet is provided on the side line of the reactor (1), and the product outlet is connected to the flash tank (2); a gas phase extraction outlet is provided on the top of the flash tank (2), and the gas phase extraction outlet is connected to the light removal tower (3); a first side line extraction outlet is provided on the side of the light removal tower (3), and the first side line extraction outlet is connected to the dehydration tower (4); a bottom extraction outlet is provided on the bottom of the dehydration tower (4), and the bottom extraction outlet is connected to the deweight removal tower (5); a second side line extraction outlet is provided on the side of the deweight removal tower (5), and the second side line extraction outlet is used to obtain finished acetic acid.

2. The system according to claim 1, wherein: The reactor (1) side line is provided with a reactor external circulation outlet, which enters the reactor external circulation pipeline (10) after passing through the reactor circulation pump and the reactor cooler. The reactor external circulation pipeline (10) is connected to the micro-interface unit (6) from the top of the reactor (1).

3. The system according to claim 1, wherein: The bottom of the flash tank (2) is provided with a liquid phase outlet, and the liquid phase outlet is connected to the flash tank external circulation pipeline (9), and the flash tank external circulation pipeline (9) is connected to the micro-interface unit (6) from the top of the reactor (1).

4. The system according to claim 1, wherein: The tops of the light-removal tower (3) and the dehydration tower (4) are provided with dilute acid reflux outlets, which are connected to a dilute acid reflux pipeline (8), which is connected to the micro-interface unit (6) from the top of the reactor (1).

5. The system according to claim 1, wherein: A heavy phase reflux outlet is provided at the top of the light-removal tower (3), and the heavy phase reflux outlet is connected to a heavy phase reflux pipeline (7), and the heavy phase reflux pipeline (7) is connected to the micro-interface unit (6) from the top of the reactor (1).

6. The system according to claim 1, wherein: A raw material methanol pipeline and a raw material carbon monoxide pipeline are also provided on the top of the reactor (1); the raw material methanol pipeline and the raw material carbon monoxide pipeline are connected to the micro-interface unit (6).

7. The system according to claim 1, wherein: The interface size of the gas-liquid particles in the micro-interface unit (6) is changed from the traditional centimeter level to the micron level.

8. The system according to claim 7, characterized in that The micro-interface unit (6) collects unreacted raw materials, catalysts, by-products and impurities in the reaction through a heavy phase reflux line (7), a dilute acid reflux line (8), a flash tank external circulation line (9) and a reactor external circulation line (10).

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