Acrylic acid refining process device capable of avoiding acetic acid accumulation

Abstract

The utility model provides an acrylic acid refining process device capable of avoiding acetic acid accumulation. The acrylic acid refining process device at least comprises a dehydrating tower (T110), an acetic acid removing tower (T120) and a light component removing tower (T130), the device disclosed by the utility model can be used for a technical process of obtaining a crude acrylic acid product from propylene oxidation reaction gas through continuous absorption, dehydration and acetic acid removal, an entrainer does not need to be introduced for dehydration and acetic acid removal, the accumulation of acetic acid in the system is effectively avoided, the operation stability of the system is improved, and the yield of acrylic acid is also improved. The device disclosed by the utility model overcomes the defects in the prior art, can be suitable for propylene oxidation reaction gas raw materials with different concentrations, and has extremely remarkable economic benefits and wide application prospects.

Description

Technical Field

[0001] This utility model relates to an apparatus for a process for refining acrylic acid that prevents acetic acid accumulation. The apparatus can be used in a process for obtaining a crude acrylic acid product from propylene oxidation reaction gas through continuous absorption, dehydration, and deacetic acid removal. This apparatus not only eliminates the need for an entrainer for dehydration and deacetic acid removal, but also effectively prevents acetic acid accumulation in the system, thereby improving system operational stability and increasing acrylic acid yield. Background Art

[0002] Acrylic acid, an unsaturated fatty acid, is an important industrial derivative of propylene and a key organic chemical raw material. Containing active double bonds and carboxyl functional groups, acrylic acid is particularly suitable for the preparation of highly absorbent materials, dispersants, flocculants, thickeners, and more. It is widely used in a variety of fields, including chemical fibers, textiles, coatings, water treatment, and daily necessities.

[0003] In the existing acrylic acid production process, the propylene vapor phase oxidation method is widely used. This method uses propylene and air as raw materials and conducts an oxidation reaction through a fixed bed catalyst bed in the presence of water vapor and other inert gases. The reaction is divided into two steps. In the first step, propylene is oxidized to acrolein. In the second step, acrolein is oxidized to acrylic acid. An acrylic acid vapor mixture is obtained at the reactor outlet. Its main components are acrylic acid gas, nitrogen, aldehyde compounds, carboxylic acid compounds, carbon dioxide, carbon monoxide and oxygen. The acrylic acid vapor mixture is passed through a refining and separation system to obtain the acrylic acid product.

[0004] Currently, commonly used methods for separating acrylic acid from vapor phases mainly include three different technical routes: organic solvent absorption distillation, water absorption azeotropic distillation, and water absorption extractive distillation. Organic solvent absorption distillation has the advantages of a short process and relatively low energy consumption; its disadvantages are the need for solvent absorption of acrylic acid, high operating temperatures, easy polymerization of acrylic acid, and a short operating cycle. Water absorption azeotropic distillation has the advantages of a short process and low investment costs, but the disadvantages are the need for an entrainer, high energy consumption, and high operating costs. Water absorption extractive distillation has the advantages of low energy consumption and low operating costs; its disadvantages are a long process, high investment costs, and the use of extractants and polymerization inhibitors.

[0005] Chinese patent CN1903738A provides an "acrylic acid wastewater treatment process" suitable for acrylic acid wastewater discharged from acrylic acid plants. This process utilizes reverse osmosis membrane separation and distillation. The acrylic acid wastewater is separated by the membrane, with the purified water on the permeate side discharged into a barrier zone. The organic matter on the retentate side is fed into a distillation tower to separate acrylic acid and toluene from acetic acid and water, and the acrylic acid, toluene, and acetic acid are recovered separately. This process requires the acrylic acid and toluene separated to enter the light fraction column of the acrylic acid plant for recovery, while the acetic acid and water separated to enter the acetic acid recovery system for recovery. This prevents the production of highly concentrated products. Furthermore, the reverse osmosis membranes operate at high pressures (1-10 MPa) and have a limited lifespan, requiring frequent replacement, resulting in high operating costs.

[0006] CN1865216A discloses a "process for azeotropic purification of acrylic acid and recovery of acetic acid." Ethylcyclohexane and toluene, or ethyl propionate and toluene, are used as entrainers in the azeotropic distillation of acrylic acid. An acrylic acid azeotrope and an acetic acid removal column are installed to remove water and acetic acid from the crude acrylic acid solution. Additionally, an organic membrane, a stripping column, and an acetic acid azeotrope are provided to concentrate the by-product acetic acid, which has a concentration of 2-8% (all percentages in this specification are by mass unless otherwise specified), to a concentration of ≥85%. While this process achieves high dehydration and acetic acid removal rates, it consumes a lot of energy for azeotropic distillation. The inclusion of multiple materials in the entrainer introduces more components to be separated, increasing the separation difficulty and energy consumption. Furthermore, the organic membrane is a three-stage reverse osmosis membrane, which is expensive and has a limited service life, requiring regular replacement, further increasing equipment and operating costs.

[0007] CN102775295A discloses a method for purifying acrylic acid. The method includes a two-tower process flow, an absorption tower, and a purification tower. By coupling the cooling, absorption, and purification processes of acrylic acid, a two-tower device is used to complete the recovery and purification of acrylic acid. At the same time, water is recycled as an absorbent and coolant, and other solvents (extractants, entrainers) are not used, thus avoiding solvent pollution to the environment. This method has a relatively simple process flow and reduces equipment investment costs and operating costs. However, because the method uses an aqueous acetic acid solution at the top of the absorption tower as the absorbent, the device has only one outlet for acetic acid and water at the top of the absorption tower. Water has a normal boiling point of 100°C, acetic acid has a normal boiling point of 117.9°C, and acrylic acid has a normal boiling point of 141°C. In conventional processes, both acetic acid and water need to be removed from the top of the absorption tower. Acetic acid has a high boiling point, making it difficult to completely remove from the top of the absorption tower. The acetic acid content discharged from the top of the absorption tower along with the non-condensable gas is balanced with the acetic acid concentration in the liquid phase at the top of the tower. According to actual operating data, acetic acid at the top of the absorber must accumulate to ~9% (all percentages are by mass unless otherwise specified) to completely remove the acetic acid in the reaction gas from the absorber overhead, resulting in a significant accumulation of acetic acid in the absorber. Furthermore, as the acetic acid concentration shifts toward the top of the absorber, the acrylic acid concentration inevitably shifts there as well, leading to a higher acrylic acid content (approximately 0.3wt%) in the absorber overhead tail gas, increasing propylene consumption and production costs. Furthermore, because the system lacks a liquid-phase extraction system for aqueous acetic acid solution, when reducing the acetic acid content in the acrylic acid product, a large amount of acetic acid-containing material from the purification tower overhead returns to the lower part of the absorber, causing significant circulation and accumulation of acetic acid between the absorber and purification towers. This not only hinders acetic acid removal but also exacerbates the increase in acrylic acid content at the top of the absorber, compromising the quality of the acrylic acid product extracted from the purification tower.

[0008] CN109232232A discloses a method for refining acrylic acid. The method subjects acrylic acid process gas to a high-concentration gas rapid cooling absorption, low-concentration gas reabsorption, purification, extraction and stripping process. The cooling process, absorption process and purification process of the acrylic acid gas mixture are coupled, and a subsequent acid-water treatment is performed. At the same time, the absorption process is improved, and no entrainer is used in the refining process. This method has a relatively simple process and reduces operating costs. However, since the reabsorption process in this method requires the addition of desalted water from the top of the light-removal tower, it not only consumes desalted water but also increases the amount of acid water discharged from the system. The stripping gas required for the stripping tower comes from the gas phase discharged from the top of the absorption tower. The acrylic acid containing stripping gas is discharged from the top of the stripping tower and returned to the lower part of the absorption tower, which not only increases the gas phase load of the absorption tower, but also increases the amount and difficulty of acrylic acid absorption in the absorption tower. The regeneration of the solvent in the bottom of the stripping tower requires additional heat, and the operating temperature is relatively high, which poses the risk of acrylic acid polymerization and material loss. When reducing the acetic acid content in the acrylic acid product, a large amount of acetic acid-containing materials at the top of the purification tower are all returned to the lower part of the absorption tower, causing a large amount of acetic acid to circulate and accumulate between the absorption tower and the purification tower, which is not only not conducive to the removal of acetic acid, but also aggravates the increase in the acrylic acid content at the top of the absorption tower and affects the quality of the acrylic acid product produced by the purification tower.

[0009] The process methods provided by CN102775295A and CN109232232A both have the following common problems: the outlets for acetic acid and water in the system are both located at the top of the absorption tower. To discharge the acetic acid, the acetic acid concentration must be accumulated and increased to a high concentration before it can be discharged from the outlet at the top of the absorption tower. The lack of a liquid phase extraction system for the acetic acid aqueous solution leads to the accumulation of acetic acid in the system and an increase in its content, thus affecting the quality of the acrylic acid product extracted from the purification tower. When reducing the acetic acid content in the acrylic acid product, a large amount of acetic acid-containing material at the top of the purification tower returns to the bottom of the absorption tower, causing a large amount of acetic acid to circulate and accumulate between the absorption tower and the purification tower. In order to reduce the acetic acid content in the system and meet the quality requirements of the acrylic acid product, the temperature of the exhaust gas at the top of the absorption tower is forced to be increased, causing some acrylic acid to be discharged to the exhaust gas incineration system along with the exhaust gas and acetic acid, resulting in increased material consumption and reduced yield.

[0010] Figure 1 This is a process flow chart for a commonly used three-tower process (absorption tower T110, lightness removal tower T120, and acetic acid removal tower T130) to produce crude acrylic acid from the raw reaction gas through rapid absorption, azeotropic distillation, and conventional distillation to remove acetic acid. This commonly used three-tower process is relatively simple and offers a high dehydration rate, but the azeotropic distillation process consumes a lot of energy. Summary of the Invention

[0011] The purpose of this utility model is to provide an apparatus for an acrylic acid refining process that prevents acetic acid accumulation. The apparatus can be used in a process for obtaining a crude acrylic acid product from propylene oxidation reaction gas through continuous absorption, dehydration, and deacetication. This apparatus not only eliminates the need for an entrainer for dehydration and deacetication but also effectively prevents acetic acid accumulation in the system, thereby improving both system operational stability and acrylic acid yield. This apparatus overcomes the shortcomings of the prior art and is applicable to propylene oxidation reaction gas feedstocks of varying concentrations, offering significant economic benefits and broad application prospects.

[0012] The utility model provides a method for refining acrylic acid by avoiding acetic acid accumulation. The method obtains a crude acrylic acid product from propylene oxidation reaction gas through continuous absorption, dehydration, and deacetic acid removal. The method not only eliminates the need for introducing an entrainer for dehydration and deacetic acid removal, but also effectively avoids the accumulation of acetic acid in the system, thereby improving the operational stability of the system and the yield of acrylic acid. The method mainly comprises the following steps:

[0013] 1) At least includes dehydration tower T110, deacetic acid tower T120, and lightness removal tower T130;

[0014] 2) The reaction gas from the reaction system enters the bottom of the dehydration tower T110;

[0015] 3) The non-condensable gas and more than 90% of the water in the reaction gas are discharged from the top of the dehydration tower T110, and the liquid phase at the bottom of the tower enters the deacetic acid tower (T120);

[0016] 4) The top of the acetic acid removal tower T120 is drawn into the lightness removal tower T130, and crude acrylic acid substantially free of acetic acid is obtained at the bottom of the tower;

[0017] 5) The acid water containing acetic acid is discharged from the top of the lightness removal tower T130, and the liquid phase at the bottom of the tower enters the deacetylating tower T120.

[0018] According to the process provided by the utility model, it is through the following steps:

[0019] 1) Raw reaction gas 1 enters the bottom of dehydration tower T110, and tail gas 2 is discharged from the top of dehydration tower T110. A liquid phase circulation cooling section S1101 is provided at the top of dehydration tower T110. The circulating liquid phase 3 is cooled by the dehydration tower circulation cooler E1101 and then returned to the top of dehydration tower T110. Material 5 from the bottom of dehydration tower T110 enters deacetation tower T120.

[0020] 2) The top gas phase 6 of the deacetylating tower T120 enters the primary condenser E1202 of the deacetylating tower for condensation. The cooled uncondensed gas 7 enters the secondary condenser E1203 of the deacetylating tower for condensation. The condensate 8 of the primary condenser E1202 of the deacetylating tower is completely refluxed to the top of the deacetylating tower T120. The non-condensable gas 9 of the secondary condenser E1203 of the deacetylating tower enters the vacuum steam jet pump VP1201, mixes with the motive steam 11, and then condenses in the vacuum pump condenser E1204 of the deacetylating tower. The stream 12 enters the middle of the lightness removal tower T130. The condensate 10 of the secondary condenser E1203 of the deacetylating tower enters the lightness removal tower T130. The liquid phase material withdrawn from the bottom of the deacetylating tower T120 is used as the crude acrylic acid product 13.

[0021] 3) The gas phase 14 at the top of the lightness removal tower T130 enters the first condenser E1302 of the lightness removal tower for condensation, and the cooled uncondensed gas 15 enters the second condenser E1303 of the lightness removal tower for condensation. The condensate 16 of the first condenser E1302 of the lightness removal tower is completely refluxed to the top of the lightness removal tower T130, and the non-condensable gas 17 of the second condenser E1303 of the lightness removal tower enters the vacuum system. The condensate 18 of the second condenser E1303 of the lightness removal tower is used as the discharge acid water containing acetic acid. The liquid phase material 19 extracted from the bottom of the lightness removal tower T130 enters the deacetate tower T120.

[0022] Water, acetic acid, and acrylic acid have atmospheric boiling points of 100°C, 117.9°C, and 141°C, respectively. In conventional processes, both acetic acid and water must be removed from the top of the dehydration tower T110. Due to the high boiling point of acetic acid, complete removal from the top of the dehydration tower T110 is difficult. The acetic acid content discharged with the non-condensable gas from the top of the dehydration tower T110 must be balanced with the acetic acid concentration in the top liquid phase. According to actual operational data, the acetic acid concentration at the top of the dehydration tower T110 must accumulate to ~9% to completely remove all acetic acid from the reaction gas. This results in a significant accumulation of acetic acid in the dehydration tower T110. Furthermore, as the acetic acid concentration shifts toward the top of the dehydration tower T110, the acrylic acid concentration inevitably shifts toward the top of the dehydration tower T110, resulting in a high acrylic acid content (~3000 ppm) in the overhead off-gas. With ~1.85% of acrylic acid lost in the off-gas, the acrylic acid yield of the unit is low.

[0023] The process provided by the utility model overcomes the defects of the existing process methods (CN102775295A and CN109232232A). The acetic acid passes through the system once. The acetic acid in the reaction gas that is not removed from the top of the dehydration tower enters the deacetylating tower from the dehydration tower kettle, enters the light-removing tower from the top of the deacetylating tower, and exits the system from the top of the light-removing tower. The material at the top of the deacetylating tower T120 does not return to the dehydration tower T110, effectively avoiding the accumulation of acetic acid in the dehydration tower T110 and the deacetylating tower T120. 20, providing an alternative outlet for acetic acid—the overhead discharge from the dehydration tower. This eliminates the need to remove all acetic acid from the dehydration tower T110, as in existing processes (CN102775295A and CN109232232A). The concentrations of acetic acid and acrylic acid in dehydration tower T110 shift downward, significantly reducing the acrylic acid content in the T110 overhead tail gas to below 500 ppm. This reduces acrylic acid loss and increases the acrylic acid yield by 1.5%. This offers significant economic benefits.

[0024] According to the process provided by the present invention, a liquid sidestream with low water and acrylic acid content and high acetic acid content can be drawn from the lower portion of dehydration tower T110 to prevent accumulation of acetic acid in dehydration tower T110. This liquid sidestream can be directed to the lightness removal tower T130 (when the acrylic acid content is less than 50%) or the acetate removal tower T120 (when the acrylic acid content is greater than 50%).

[0025] According to the process provided by the present invention, an acid water evaporation section S1102 is added to the top of the dehydration tower T110. The acid water 18 discharged from the lightness removal tower T130 is fed into the acid water evaporation section S1102 at the top of the dehydration tower T110. The acid water evaporation section S1102 can be located at the top of the dehydration tower or can be a separate evaporation tower T140. The gas phase from the top of the dehydration tower T110 can be fed entirely into the acid water evaporation section S1102 or the evaporation tower T140. Alternatively, a portion of the recycled tail gas with a low acetic acid content can be diverted to the reactor, while the remaining gas phase is fed into the acid water evaporation section S1102 or the evaporation tower T140.

[0026] According to the process method provided by the utility model, the top of the deacetic acid tower T120 can also be a single-stage or two-stage condensation: part of the first-stage condensate is refluxed, and the other part is taken out to the de-lightness tower T130; the first-stage uncondensed material can go to the secondary condenser or directly to the vacuum pump; the material at the vacuum pump outlet can be condensed by the vacuum pump condenser and then go to the de-lightness tower T130 or the dehydration tower T110.

[0027] According to the process provided by the utility model, the material extracted from the bottom of the deacetylating tower T120 is crude acrylic acid that is substantially free of acetic acid. An acrylic acid refining tower can be connected to the tower to obtain an acrylic acid product from the top of the tower. Alternatively, a gaseous side-line material can be extracted from the bottom of the deacetylating tower T120 and condensed to obtain an acrylic acid product.

[0028] According to the process provided by the present invention, dehydration tower T110 can be a single tower or a dual tower connected in series with a reduced tower height. In this case, if a liquid sidestream is required from dehydration tower T110, it can be produced from the upper tower kettle or the lower tower sidestream. Dehydration tower T110 can be equipped with a top liquid phase circulation cooling section S1101 to condense some condensables in the ascending gas phase within the tower to provide liquid reflux. Process water or other wastewater with low acrylic acid content (including but not limited to steam jet pump condensate) can also be introduced as reflux. Alternatively, the top liquid phase circulation cooling section S1101 can be combined with make-up process water or other wastewater with low acrylic acid content. Dehydration tower T110 appears to be an acrylic acid absorption tower, but is actually an acrylic acid dehydration distillation tower. The non-condensable gas in the reaction gas greatly reduces the gas phase partial pressure of acrylic acid, providing operating conditions similar to vacuum distillation for the distillation and dehydration process. Using the heat of the reaction gas as a heat source, the top of the dehydration tower T110 removes more than 90% of the water in the reaction gas along with the non-condensable gas, and obtains crude acrylic acid with a water content of ~5%, acetic acid content of ~4%, and acrylic acid content of ~90% from the bottom of the tower.

[0029] According to the process method provided by the utility model, a light component removal tower T210 and a solvent recovery tower T220 can be used to replace the light component removal tower T130. The light component removal tower T210 uses solvent azeotropic dehydration and deacetic acid removal. The acid water at the top of the light component removal tower T210 is fed into the top of the acid water evaporation section S1102 at the top of the dehydration tower T110 or discharged externally. The solvent recovery tower T220 recovers the solvent and returns it to the bottom of the light component removal tower T210. Crude acrylic acid that is substantially free of acetic acid is obtained from the bottom of the solvent recovery tower T220.

[0030] According to the process method provided by the present invention, a pre-cooling section S1103 can be set below the liquid-phase circulating cooling section S1101 at the top of the dehydration tower T110, and the circulating liquid with a higher temperature can be extracted to heat the evaporation heater E1102 of the acid water evaporation section S1102 or the evaporation tower heater E1102 of the independent evaporation tower T140, thereby evaporating the liquid-phase acid water 18 of the delightening tower T130, and the cooled liquid phase is returned to the top of the pre-cooling section S1103. No additional steam consumption is required, and the liquid-phase acid water 18 of the delightening tower T130 is completely vaporized along with the tail gas, without the need to discharge the liquid-phase acid water. To simplify the process and equipment structure, the pre-cooling section S1103 can also be omitted, and the evaporation heater E1102 is heated by an external heat source.

[0031] According to the process provided by the utility model, the material with an acrylic acid content of 50% or less, an acetic acid content of more than 20%, and a water content of more than 20% is extracted from the top of the deacetylating tower T120 and sent to the lightness removal tower T130; the crude acrylic acid product with an acetic acid content of less than 500 ppm is obtained in the bottom of the deacetylating tower T120.

[0032] According to the process provided by the utility model, acid water (a mixture of acetic acid, water and other light components) with an acrylic acid content of less than 1% is produced from the top of the lightness removal tower T130; the bottom of the lightness removal tower T130 is crude acrylic acid with an acetic acid content of less than 2%, which is returned to the deacetate tower T120.

[0033] According to the process provided by the present invention, the energy-saving method adopted is selected as follows: the steam condensate can be used to preheat the feed of the deacetic acid tower T120 and the delight tower T130 in sequence or separately.

[0034] The steam condensate can be preheated in any column within the system, or any combination thereof. The various heat exchange methods and combinations described above merely supplement the acrylic acid refining process for avoiding acetic acid accumulation provided by the present invention, and do not limit the spirit of the present invention. Personnel skilled in the relevant art are fully capable of implementing the technology by making appropriate modifications, alterations, and combinations based on the method provided by the present invention. It should be noted that all such similar modifications, alterations, and rearrangements of the process flow provided by the present invention are obvious to those skilled in the art and are considered to be within the spirit, scope, and content of the present invention.

[0035] According to the process method provided by the present invention, the heat source used by the deacetic acid tower reboiler E1201 and the delight tower reboiler E1301 can be fresh steam, heat transfer oil, or material steam generated inside the system.

[0036] According to the process provided by this utility model, the typical operating conditions of each tower are:

[0037] The operating pressure range of the top of the dehydration tower T110 is 50-350kPa;

[0038] The operating pressure range of the top of the deacetic acid tower T120 is 2 to 80 kPa;

[0039] The operating pressure range of the top of the lightness removal tower T130 is 5 to 50 kPa.

[0040] The preferred operating conditions of each tower are:

[0041] The top operating pressure of dehydration tower T110 is 100-150kPa, the top operating temperature is 55-70℃, and the bottom operating temperature is 80-105℃;

[0042] The top operating pressure of the deacetic acid tower T120 is 2.5-12kPa, the top operating temperature is 42-65℃, and the bottom operating temperature is 70-105℃;

[0043] The top operating pressure of the lightness removal tower T130 is 6-12 kPa, the top operating temperature is 35-50°C, and the bottom operating temperature is 75-105°C.

[0044] The utility model provides an acrylic acid refining process device for avoiding acetic acid accumulation, which mainly includes connecting pipelines between three towers: a dehydration tower T110, a deacetic acid removal tower T120, and a lightness removal tower T130.

[0045] The raw material reaction gas feed pipeline is connected to the bottom of the dehydration tower T110, and the top of the dehydration tower T110 is connected to the tail gas discharge pipeline; the upper part of the dehydration tower T110 is provided with a liquid phase circulation cooling section S1101, the bottom of the liquid phase circulation cooling section S1101 is connected to the hot side inlet of the dehydration tower circulation cooler E1101, and the hot side outlet of the dehydration tower circulation cooler E1101 is connected to the top of the liquid phase circulation cooling section S1101 at the dehydration tower T110, and the bottom of the dehydration tower T110 is connected to the feed port of the deacetic acid removal tower T120;

[0046] The top of the deacetic acid tower T120 is connected to the shell side inlet of the first condenser E1202 of the deacetic acid tower. The shell side uncondensed gas outlet of the first condenser E1202 of the deacetic acid tower is connected to the shell side inlet of the second condenser E1203 of the deacetic acid tower. The shell side condensate outlet of the first condenser E1202 of the deacetic acid tower is connected to the top of the deacetic acid tower T120. The shell side non-condensed gas outlet of the second condenser E1203 of the deacetic acid tower is connected to the non-condensed gas inlet of the vacuum steam jet pump VP1201. The shell side condensate outlet of the second condenser E1203 of the deacetic acid tower is connected to the de-light tower T13. 0, the vacuum pump power steam supply pipeline is connected to the steam inlet of the vacuum steam jet pump VP1201, the outlet of the vacuum steam jet pump VP1201 is connected to the shell side inlet of the deacetic acid tower vacuum pump condenser E1204, the shell side outlet of the deacetic acid tower vacuum pump condenser E1204 is connected to the middle of the delightness removal tower T130, the bottom of the deacetic acid tower T120 is respectively connected to the pipe side inlet of the deacetic acid tower reboiler E1201 and the crude acrylic acid production pipeline, and the pipe side outlet of the deacetic acid tower reboiler E1201 is connected to the bottom of the deacetic acid tower T120.

[0047] The top of the lightness removal tower T130 is connected to the shell side inlet of the first condenser E1302 of the lightness removal tower, the shell side uncondensed gas outlet of the first condenser E1302 of the lightness removal tower is connected to the shell side inlet of the second condenser E1303 of the lightness removal tower, the shell side condensate outlet of the first condenser E1302 of the lightness removal tower is connected to the top of the lightness removal tower T130, the shell side non-condensable gas outlet of the second condenser E1303 of the lightness removal tower is connected to the vacuum system, the shell side condensate outlet of the second condenser E1303 of the lightness removal tower is connected to the acid water discharge pipeline, the bottom of the lightness removal tower T130 is respectively connected to the tube side inlet of the lightness removal tower reboiler E1301 and the upper part of the deacetic acid tower T120, and the tube side outlet of the lightness removal tower reboiler E1301 is connected to the kettle of the lightness removal tower T130.

[0048] In order to highlight the acrylic acid refining process method that avoids acetic acid accumulation provided by the utility model, some heat exchangers in the process are omitted.

[0049] According to the process provided by this utility model, those skilled in the relevant professional field can fully implement appropriate internal system logistics heat exchange methods based on specific equipment conditions. Any resulting process flow should be considered within the spirit, scope, and content of this utility model. The heat exchanger in the flow diagram is for illustration only, and its specific structure does not constitute any limitation to this utility model.

[0050] This utility model provides an apparatus for an acrylic acid refining process that avoids acetic acid accumulation, and various modified process methods thereof. These apparatus can be used to obtain a crude acrylic acid product from propylene oxidation reaction gas through continuous absorption, dehydration, and deacetic acid removal. This process not only eliminates the need for an entrainer for dehydration and deacetic acid removal, but also effectively avoids acetic acid accumulation in the system, improving both system operational stability and acrylic acid yield. This utility model overcomes the shortcomings of the prior art, is applicable to propylene oxidation reaction gas feedstocks of varying concentrations, and offers significant economic benefits and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a process flow chart of the currently commonly used three-tower (absorption tower T110, lightness removal tower T120, and acetic acid removal tower T130) conventional process method for obtaining crude acrylic acid product through the steps of rapid cooling absorption, azeotropic distillation, and conventional distillation to remove acetic acid from the raw reaction gas.

[0052] Figure 2 The utility model provides a typical process flow chart of an acrylic acid refining process method for avoiding acetic acid accumulation.

[0053] Figure 3 yes Figure 2 An evolutionary process method, namely deformation process method 1, is relatively Figure 2 In the provided process, a liquid phase side line 20 with low water and acrylic acid content and high acetic acid content can be drawn from the lower part of the dehydration tower T110 to the deacetate tower T120 to avoid the accumulation of acetic acid in the dehydration tower T110.

[0054] Figure 4 yes Figure 2 An evolutionary process method, namely deformation process method 2, is relatively Figure 2 In the provided process, an acid water evaporation section S1102 is added to the top of the dehydration tower T110, and the acid water 18 discharged from the light removal tower T130 is fed into the top of the acid water evaporation section S1102 at the top of the dehydration tower T110.

[0055] Figure 5 yes Figure 2 An evolutionary process method, namely deformation process method three, relatively Figure 2The provided process adds an independent evaporation tower T140, the acid water 18 discharged from the light removal tower T130 enters the top of the evaporation tower T140, the gas phase 21 at the top of the dehydration tower T110 enters the bottom of the evaporation tower T140, and the liquid phase 22 at the bottom of the evaporation tower T140 enters the top of the dehydration tower T110.

[0056] Figure 6 yes Figure 5 An evolutionary process method, namely deformation process method 4, is relatively Figure 5 In the proposed process, the independent evaporation tower T140 is equipped with a heated bottom. This vaporizes all incoming material and discharges tail gas 2 from the top of the tower. No liquid phase is extracted from the bottom of the evaporation tower T140. A stream of recycled tail gas 23 with a low acetic acid content is diverted from the top of the dehydration tower T110, sending it to the reactor. The remaining gas phase 24 flows into the evaporation tower T140.

[0057] Figure 7 yes Figure 2 An evolutionary process method, namely deformation process method 6, relatively Figure 2 The provided process extracts the gaseous side-line material 25 from the lower part of the deacetylating tower T120, condenses it in the product condenser E1205 to obtain the acrylic acid product 26, and discharges the heavy component 13 from the bottom of the deacetylating tower T120.

[0058] Figure 8 yes Figure 2 An evolutionary process method, namely deformation process method eight, relatively Figure 2 In the provided process, a circulating cooling section is set at the top of the dehydration tower T110, and process water 27 is introduced as reflux liquid.

[0059] Figure 9 yes Figure 4 An evolutionary process method, namely deformation process method nine, relatively Figure 4 The provided process uses a light component removal tower T210 and a solvent recovery tower T220 instead of the light component removal tower T130. The light component removal tower T210 uses solvent azeotropic dehydration and deacetic acid removal. The acid water 32 at the top of the light component removal tower T210 is fed above the acid water evaporation section S1102 at the top of the dehydration tower T110. The solvent 37 recovered at the top of the solvent recovery tower T220 is returned to the bottom of the light component removal tower T210. Crude acrylic acid (II) 38 substantially free of acetic acid is obtained from the bottom of the solvent recovery tower T220.

[0060] Figure 10 yes Figure 4 An evolutionary process method, namely deformation process method 10, relatively Figure 4In the provided process, the dehydration tower T110 can be connected in series with two towers to reduce the tower height; a pre-cooling section S1103 can be set below the liquid phase circulation cooling section S1101 of the upper tower T110B of the dehydration tower, and the circulating liquid 39 with a higher temperature can be extracted to heat the evaporation heater E1102 of the acid water evaporation section S1102, evaporate the liquid phase acid water 18 of the dehydration tower T130, and the cooled liquid phase 40 returns to the top of the pre-cooling section S1103. DETAILED DESCRIPTION

[0061] The specific implementation scheme of the present invention is described in detail below with reference to the accompanying drawings, but it is only for illustration rather than limitation of the present invention.

[0062] Unless otherwise noted, the components and structures of process equipment, such as tower components, materials (such as connecting pipelines between tower components), and reagents not specifically used in the examples are commercially available or can be obtained by methods well known to those skilled in the art. Specific experimental methods and operating conditions generally follow conventional process conditions, those described in manuals, or those recommended by the manufacturer.

[0063] Figure 1 This is a process flow chart of the currently commonly used three-tower (absorption tower T110, lightness removal tower T120, and acetic acid removal tower T130) conventional process method for obtaining crude acrylic acid product through the steps of rapid cooling absorption, azeotropic distillation, and conventional distillation to remove acetic acid from the raw reaction gas.

[0064] The raw reaction gas enters the bottom of the absorption tower T110, and the fresh process water enters the top of the absorption tower T110.

[0065] Tail gas is discharged from the top of absorption tower T110; the liquid phase in the bottom of absorption tower T110 is divided into two streams, the first stream enters the light removal tower T120, and the second stream is the circulating liquid, which is cooled by the absorption tower circulation cooler and returns to the lower part of absorption tower T110.

[0066] The condensate after condensation of the gas phase at the top of the de-lightness tower T120 is phase-separated, and the oil phase after phase separation is refluxed to the top of the de-lightness tower T120. The water phase after phase separation is divided into two streams, the first stream enters the upper part of the absorption tower T110 as recycled absorption water, and the second stream is used as an external acid water delivery device; the material in the bottom of the de-lightness tower T120 enters the deacetic acid tower T130.

[0067] The condensate after condensation of the top gas phase of the deacetylating tower T130 is divided into two streams, the first stream is refluxed to the top of the deacetylating tower T130, and the second stream enters the lightness removal tower T120; the crude acrylic acid product is taken out of the bottom of the deacetylating tower T130 and sent to the delivery device.

[0068] The conventional three-tower process commonly used above is relatively simple and has a high dehydration rate, but its energy consumption of azeotropic distillation is high.

[0069] The utility model provides a device for a process for refining acrylic acid to avoid the accumulation of acetic acid. The typical raw material reaction gas composition is:

[0070] Component mass percentage (%)

[0071] Non-condensable gas 77.44

[0072] Water 7.66

[0073] Formic acid 0.01

[0074] Acetic acid 0.57

[0075] Acrylic acid 14.27

[0076] Heavy fraction 0.05

[0077] Total 100.00.

[0078] The above raw material composition range does not constitute any limitation to the present invention, and the present invention can be used for refining acrylic acid from raw material reaction gases of various compositions.

[0079] Specific application examples are as follows. Example

[0080] The utility model provides an acrylic acid refining process device for avoiding acetic acid accumulation, which mainly includes three towers: a dehydration tower T110, a deacetic acid removal tower T120, a lightness removal tower T130, and connecting pipelines:

[0081] The raw material reaction gas feed pipeline is connected to the bottom of the dehydration tower T110, and the top of the dehydration tower T110 is connected to the tail gas discharge pipeline; the upper part of the dehydration tower T110 is provided with a liquid phase circulation cooling section S1101, the bottom of the liquid phase circulation cooling section S1101 is connected to the hot side inlet of the dehydration tower circulation cooler E1101, and the hot side outlet of the dehydration tower circulation cooler E1101 is connected to the top of the liquid phase circulation cooling section S1101 at the top of the dehydration tower T110, and the bottom of the dehydration tower T110 is connected to the upper part of the deacetic acid removal tower T120;

[0082] The top of the deacetic acid tower T120 is connected to the shell side inlet of the first condenser E1202 of the deacetic acid tower. The shell side uncondensed gas outlet of the first condenser E1202 of the deacetic acid tower is connected to the shell side inlet of the second condenser E1203 of the deacetic acid tower. The shell side condensate outlet of the first condenser E1202 of the deacetic acid tower is connected to the top of the deacetic acid tower T120. The shell side non-condensed gas outlet of the second condenser E1203 of the deacetic acid tower is connected to the non-condensed gas inlet of the vacuum steam jet pump VP1201. The shell side condensate outlet of the second condenser E1203 of the deacetic acid tower is connected to the de-light tower T13. 0, the vacuum pump power steam supply pipeline is connected to the steam inlet of the vacuum steam jet pump VP1201, the outlet of the vacuum steam jet pump VP1201 is connected to the shell side inlet of the deacetic acid tower vacuum pump condenser E1204, the shell side outlet of the deacetic acid tower vacuum pump condenser E1204 is connected to the middle of the delightness removal tower T130, the bottom of the deacetic acid tower T120 is respectively connected to the pipe side inlet of the deacetic acid tower reboiler E1201 and the crude acrylic acid production pipeline, and the pipe side outlet of the deacetic acid tower reboiler E1201 is connected to the bottom of the deacetic acid tower T120.

[0083] The top of the lightness removal tower T130 is connected to the shell side inlet of the first condenser E1302 of the lightness removal tower, the shell side uncondensed gas outlet of the first condenser E1302 of the lightness removal tower is connected to the shell side inlet of the second condenser E1303 of the lightness removal tower, the shell side condensate outlet of the first condenser E1302 of the lightness removal tower is connected to the top of the lightness removal tower T130, the shell side non-condensable gas outlet of the second condenser E1303 of the lightness removal tower is connected to the vacuum system, the shell side condensate outlet of the second condenser E1303 of the lightness removal tower is connected to the acid water discharge pipeline, the bottom of the lightness removal tower T130 is respectively connected to the tube side inlet of the lightness removal tower reboiler E1301 and the upper part of the deacetic acid tower T120, and the tube side outlet of the lightness removal tower reboiler E1301 is connected to the kettle of the lightness removal tower T130.

[0084] The utility model can be used for the dehydration and deacetic acid process of acrylic acid from propylene oxidation reaction gas raw materials of different concentrations. The specific process is described as follows:

[0085] like Figure 2 As shown, a typical process of the process method provided by the present invention is as follows: the raw reaction gas 1 enters the bottom of the dehydration tower T110, the tail gas 2 is discharged from the top of the dehydration tower T110, a liquid phase circulation cooling section S1101 is provided on the top of the dehydration tower T110, the circulating liquid phase 3 is extracted from the bottom of the liquid phase circulation cooling section S1101, and the material 4 cooled by the dehydration tower circulation cooler E1101 returns to the top of the liquid phase circulation cooling section S1101 at the top of the dehydration tower T110, and the material 5 in the bottom of the dehydration tower T110 enters the deacetation tower T120.

[0086] The top gas phase 6 of the deacetylating tower T120 enters the first condenser E1202 of the deacetylating tower for condensation, and the cooled uncondensed gas 7 enters the second condenser E1203 of the deacetylating tower for condensation. The condensate 8 of the first condenser E1202 of the deacetylating tower is completely refluxed to the top of the deacetylating tower T120. The non-condensable gas 9 of the second condenser E1203 of the deacetylating tower enters the vacuum steam jet pump VP1201, and after mixing with the power steam 11, the logistics 12 after condensation by the vacuum pump condenser E1204 of the deacetylating tower enters the middle part of the lightness removal tower T130. The condensate 10 of the second condenser E1203 of the deacetylating tower enters the lightness removal tower T130, and the liquid phase material extracted from the bottom of the deacetylating tower T120 is used as the crude acrylic acid product 13.

[0087] The gas phase 14 at the top of the lightness removal tower T130 enters the first condenser E1302 of the lightness removal tower for condensation, and the cooled uncondensed gas 15 enters the second condenser E1303 of the lightness removal tower for condensation. The condensate 16 of the first condenser E1302 of the lightness removal tower is all refluxed to the top of the lightness removal tower T130, and the non-condensable gas 17 of the second condenser E1303 of the lightness removal tower enters the vacuum system. The condensate 18 of the second condenser E1303 of the lightness removal tower is used as the discharge acid water delivery device containing acetic acid, and the liquid phase material 19 extracted from the bottom of the lightness removal tower T130 enters the deacetate tower T120.

[0088] The heat sources used by the deacetic acid tower reboiler E1201 and the delight tower reboiler E1301 can be fresh steam, heat transfer oil, or material steam generated inside the system.

[0089] The condensate of fresh steam added to the system can be used to preheat the feed of the deacetic acid tower T120 and the delight tower T130 separately or successively.

[0090] The typical operating conditions of each tower in Example 1 are given below:

[0091] The operating pressure range of the top of the dehydration tower T110 is 50-350kPa;

[0092] The operating pressure range of the top of the deacetic acid tower T120 is 2 to 80 kPa;

[0093] The operating pressure range of the top of the lightness removal tower T130 is 5 to 50 kPa.

[0094] The preferred operating conditions of each tower in Example 1 are given below:

[0095] The top operating pressure of dehydration tower T110 is 100-150kPa, the top operating temperature is 55-70℃, and the bottom operating temperature is 80-105℃;

[0096] The top operating pressure of the deacetic acid tower T120 is 2.5-12kPa, the top operating temperature is 42-65℃, and the bottom operating temperature is 70-105℃;

[0097] The top operating pressure of the lightness removal tower T130 is 6-12 kPa, the top operating temperature is 35-50°C, and the bottom operating temperature is 75-105°C.

[0098] According to the process of this embodiment, compared to CN102775295A, the overhead material from deacetation tower T120 is not returned to dehydration tower T110, effectively preventing the extensive circulation and accumulation of acetic acid between dehydration tower T110 and deacetation tower T120. This eliminates the need to remove all acetic acid from the top of dehydration tower T110. The concentrations of acetic acid and acrylic acid in dehydration tower T110 are completely shifted downward, significantly reducing the acrylic acid content in the exhaust gas from the top of dehydration tower T110 from 3000 ppm to below 500 ppm. This reduces acrylic acid loss and increases the acrylic acid yield of the device by 1.5%. This provides significant economic benefits.

[0099] Taking a 100,000 t / a acrylic acid unit as an example, the tail gas flow rate at the top of the dehydration tower T110 is about 78 t / h. The unit price of acrylic acid is calculated at RMB 6,100 / ton. The economic benefits of increasing the acrylic acid yield each year are:

[0100] 6100 yuan / ton×78 tons / hour×(3000-500)×10 -6 ×8000 hours / year / 10000≈9.5 million yuan / year. Example

[0101] like Figure 3 As shown, it is Figure 2 An evolutionary process method, namely deformation process method 1, is relatively Figure 2 In the proposed process, a liquid side stream 20, low in water and acrylic acid and high in acetic acid, can be drawn from the lower middle portion of dehydration tower T110 to be sent to deacetate tower T120 to prevent acetic acid accumulation in dehydration tower T110. The typical composition of this liquid side stream is approximately 20% water, approximately 16% acetic acid, and approximately 64% acrylic acid. Example

[0102] like Figure 4 As shown, it is Figure 2 An evolutionary process method, namely deformation process method 2, is relatively Figure 2 In the provided process, an acid water evaporation section S1102 is added to the top of the dehydration tower T110, and the acid water 18 discharged from the light removal tower T130 is fed into the top of the acid water evaporation section S1102 at the top of the dehydration tower T110. Example

[0103] like Figure 5 As shown, it is Figure 2 An evolutionary process method, namely deformation process method three, relatively Figure 2The provided process adds an independent evaporation tower T140, the acid water 18 discharged from the light removal tower T130 enters the top of the evaporation tower T140, the gas phase 21 at the top of the dehydration tower T110 enters the bottom of the evaporation tower T140, and the liquid phase 22 at the bottom of the evaporation tower T140 enters the top of the dehydration tower T110. Example

[0104] like Figure 6 As shown, it is Figure 5 An evolutionary process method, namely deformation process method 4, is relatively Figure 5 In the proposed process, the independent evaporation tower T140 is heated by an external heat source, vaporizing all incoming material and discharging tail gas 2 from the top. No liquid phase is extracted from the bottom of the evaporation tower T140. A recycle tail gas 23 with a low acetic acid content is diverted from the top gas phase 21 of the dehydration tower T110 and sent to the reactor. The remaining gas phase 24 flows into the evaporation tower T140. Example

[0105] It is Figure 2 An evolutionary process method, namely deformation process method 5, is relatively Figure 2 According to the provided process, the top of the deacetic acid tower T120 can also be a first-stage condensation: the first-stage condensate is divided into two parts, one part is reflux 8, and the other part is produced 10 to go to the de-light tower T130. The first-stage uncondensed material 7 goes directly to the vacuum pump, and the material at the vacuum pump outlet is condensed by the vacuum pump condenser and then goes to the de-light tower T130. Example

[0106] like Figure 7 As shown, it is Figure 2 An evolutionary process method, namely deformation process method 6, relatively Figure 2 The provided process extracts the gaseous side-line material 25 from the lower part of the deacetylating tower T120, condenses it in the product condenser E1205 to obtain the acrylic acid product 26, and discharges the heavy component 13 from the bottom of the deacetylating tower T120. Example

[0107] It is Figure 2 An evolutionary process method, namely deformation process method seven, relatively Figure 2 In the proposed process, dehydration tower T110 can be connected in series as two towers to reduce tower height. Raw reaction gas 1 enters the bottom of lower dehydration tower T110A. The gas phase at the top of lower dehydration tower T110A enters the bottom of upper dehydration tower T110B. Liquid phase 5 in the bottom of lower dehydration tower T110A enters deacetation tower T120. Tail gas 2 is discharged from the top of upper dehydration tower T110B. Liquid phase in the bottom of upper dehydration tower T110B enters the top of lower dehydration tower T110A. Example

[0108] like Figure 8 As shown, it is Figure 2 An evolutionary process method, namely deformation process method eight, relatively Figure 2 In the proposed process, a circulating cooling section is installed at the top of dehydration tower T110, and process water 27 is introduced as reflux. The material exiting the vacuum pump at the top of deacetation tower T120 is condensed in the vacuum pump condenser and then fed into dehydration tower T110.

[0109] Example 10:

[0110] like Figure 9 As shown, it is Figure 4 An evolutionary process method, namely deformation process method nine, relatively Figure 4 The provided process uses a light component removal tower T210 and a solvent recovery tower T220 instead of the light component removal tower T130. The light component removal tower T210 uses solvent azeotropic dehydration and deacetic acid removal. The acid water 32 at the top of the light component removal tower T210 is fed above the acid water evaporation section S1102 at the top of the dehydration tower T110. The solvent 37 recovered at the top of the solvent recovery tower T220 is returned to the bottom of the light component removal tower T210. Crude acrylic acid (II) 38 substantially free of acetic acid is obtained from the bottom of the solvent recovery tower T220.

[0111] Example 11:

[0112] like Figure 10 As shown, it is Figure 4 An evolutionary process method, namely deformation process method 10, relatively Figure 4 In the provided process, the dehydration tower T110 can be connected in series with two towers to reduce the tower height; a pre-cooling section S1103 can be set below the liquid phase circulation cooling section S1101 of the upper tower T110B of the dehydration tower, and the circulating liquid 39 with a higher temperature can be extracted to heat the evaporation heater E1102 of the acid water evaporation section S1102, evaporate the liquid phase acid water 18 of the dehydration tower T130, and the cooled liquid phase 40 returns to the top of the pre-cooling section S1103.

[0113] The utility model provides an apparatus for an acrylic acid refining process that avoids acetic acid accumulation. The apparatus can be used to obtain a crude acrylic acid product from propylene oxidation reaction gas through continuous absorption, dehydration, and deacetic acid removal. This process not only eliminates the need for an entrainer for dehydration and deacetic acid removal, but also effectively avoids acetic acid accumulation in the system, improving both system operational stability and acrylic acid yield. The utility model overcomes the shortcomings of the prior art and is applicable to propylene oxidation reaction gas feedstocks of varying concentrations, offering significant economic benefits and broad application prospects.

[0114] With reference to the above embodiments, it is clear that those skilled in the art can implement the technology by making appropriate modifications, alterations, and combinations based on the methods provided by the present invention. It should be noted that all such modifications, alterations, and recombinations of the process flow provided by the present invention, as well as implementation of appropriate internal system logistics heat exchange methods, are obvious to those skilled in the art and are considered to be within the spirit, scope, and content of the present invention.

Claims

1. A device for a process for refining acrylic acid to avoid acetic acid accumulation, characterized in that: It mainly includes three towers: dehydration tower (T110), deacetic acid tower (T120), delight tower (T130) and connecting pipelines; The raw material reaction gas supply pipeline is connected to the bottom of the dehydration tower (T110), and the top of the dehydration tower (T110) is connected to the tail gas discharge pipeline; a liquid phase circulation cooling section (S1101) is provided on the top of the dehydration tower (T110), the bottom of the liquid phase circulation cooling section (S1101) is connected to the hot side inlet of the dehydration tower circulation cooler (E1101), and the hot side outlet of the dehydration tower circulation cooler (E1101) is connected to the top of the liquid phase circulation cooling section (S1101) of the dehydration tower (T110), and the bottom of the dehydration tower (T110) is connected to the top of the deacetic acid removal tower (T120); The top of the deacetic acid tower (T120) is connected to the shell side inlet of the first condenser (E1202) of the deacetic acid tower. The shell side non-condensable gas outlet of the first condenser (E1202) of the deacetic acid tower is connected to the shell side inlet of the second condenser (E1203) of the deacetic acid tower. The shell side condensate outlet of the first condenser (E1202) of the deacetic acid tower is connected to the top of the deacetic acid tower (T120). The shell side non-condensable gas outlet of the second condenser (E1203) of the deacetic acid tower is connected to the non-condensable gas inlet of the vacuum steam jet pump (VP1201). The shell side condensate outlet of the second condenser (E1203) of the deacetic acid tower is connected to the de-light tower (T13 0) is connected in the middle, the vacuum pump power steam supply pipeline is connected to the steam inlet of the vacuum steam jet pump (VP1201), the vacuum steam jet pump (VP1201) outlet is connected to the shell side inlet of the deacetic acid tower vacuum pump condenser (E1204), the shell side outlet of the deacetic acid tower vacuum pump condenser (E1204) is connected to the middle of the delight tower (T130), the bottom of the deacetic acid tower (T120) is respectively connected to the tube side inlet of the deacetic acid tower reboiler (E1201) and the crude acrylic acid production pipeline, and the tube side outlet of the deacetic acid tower reboiler (E1201) is connected to the tower kettle of the deacetic acid tower (T120); The top of the de-lightness tower (T130) is connected to the shell side inlet of the first condenser (E1302) of the de-lightness tower, the shell side uncondensed gas outlet of the first condenser (E1302) of the de-lightness tower is connected to the shell side inlet of the second condenser (E1303) of the de-lightness tower, the shell side condensate outlet of the first condenser (E1302) of the de-lightness tower is connected to the top of the de-lightness tower (T130), the shell side non-condensable gas outlet of the second condenser (E1303) of the de-lightness tower is connected to the vacuum system, the shell side condensate outlet of the second condenser (E1303) of the de-lightness tower is connected to the acid water discharge pipeline, the bottom of the de-lightness tower (T130) is respectively connected to the tube side inlet of the de-lightness tower reboiler (E1301) and the upper part of the deacetic acid tower (T120), and the tube side outlet of the de-lightness tower reboiler (E1301) is connected to the kettle of the de-lightness tower (T130).

2. The device according to claim 1, characterized in that: An acid water evaporation section (S1102) is additionally provided on the top of the dehydration tower (T110), and the acid water (18) discharged from the lightness removal tower (T130) enters the top of the acid water evaporation section (S1102) on the top of the dehydration tower (T110); the acid water evaporation section (S1102) is placed on the top of the dehydration tower (T110), or is an independent evaporation tower (T140); all the gas phase on the top of the dehydration tower (T110) enters the acid water evaporation section (S1102) or the evaporation tower (T140), or a circulating tail gas with a low acetic acid content is diverted to the reactor, and the remaining gas phase enters the acid water evaporation section (S1102) or the evaporation tower (T140).

3. The device according to claim 1, characterized in that: The dehydration tower (T110) is a single tower, or a double tower connected in series to reduce the tower height; the dehydration tower (T110) is provided with a liquid phase circulation cooling section (S1101) at the top of the tower to condense part of the condensable matter in the ascending gas phase in the tower and provide liquid phase reflux.

4. The device according to claim 1, characterized in that: Typical operating conditions for each tower are: The operating pressure range of the dehydration tower (T110) top is 50~350kPa; The operating pressure range of the top of the deacetic acid tower (T120) is 2 to 80 kPa; The operating pressure range of the top of the lightness removal tower (T130) is 5 to 50 kPa.

5. The device according to claim 1, characterized in that: Typical operating conditions for each tower are: The dehydration tower (T110) has a top operating pressure of 100-150 kPa, a top operating temperature of 55-70°C, and a bottom operating temperature of 80-105°C. The deacetic acid tower (T120) has a top operating pressure of 2.5-12 kPa, a top operating temperature of 42-65°C, and a bottom operating temperature of 70-105°C. The top operating pressure of the lightness removal tower (T130) is 6~12kPa, the top operating temperature is 35~50℃, and the bottom operating temperature is 75~105℃.

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