Acetic acid accumulation avoiding acrylic acid refining process and apparatus

Abstract

The present application relates to a kind of acrylic acid refining process method and device for avoiding acetic acid accumulation, mainly including dehydration tower T110, de-acetic acid tower T120, light removal tower T130;Process steps are as follows: the non-condensable gas in reaction gas is discharged from the top of dehydration tower T110, more than 90% water, and liquid phase in tower pot enters de-acetic acid tower T120;De-acetic acid tower T120 top is extracted and enters light removal tower T130, and the crude acrylic acid that is substantially free of acetic acid is obtained in lower part of tower;Acid water containing acetic acid is discharged from the top of light removal tower T130, and liquid phase in tower pot enters de-acetic acid tower T120.The present application can be used in the process of obtaining crude acrylic acid product from propylene oxidation reaction gas by continuous absorption, dehydration, de-acetic acid, and is particularly suitable for different concentrations of propylene oxidation reaction gas raw material;Not only need to introduce azeotrope dehydration, de-acetic acid, but also effectively avoid the accumulation of acetic acid in system, improve the system operation stability, also improve the yield of acrylic acid, with extremely significant economic benefits and broad application prospect.

Description

Technical Field

[0001] This invention relates to an acrylic acid refining process and apparatus that avoids acetic acid accumulation. It can be used in a process to obtain crude acrylic acid from propylene oxidation reaction gas through continuous absorption, dehydration, and deacetic acid removal. This invention not only eliminates the need for azeotropic agents for dehydration and deacetic acid removal but also effectively prevents acetic acid accumulation in the system, thereby improving both system operational stability and acrylic acid yield. Background Technology

[0002] Acrylic acid is an unsaturated fatty acid, an important industrial derivative of propylene, and one of the most important organic chemical raw materials. Containing active double bonds and carboxyl functional groups, acrylic acid is particularly suitable for preparing superabsorbent materials, dispersants, flocculants, thickeners, etc., and is widely used in chemical fibers, textiles, coatings, water treatment, daily necessities, and many other fields.

[0003] In existing acrylic acid production processes, the propylene gas-phase oxidation method is widely used. This method uses propylene and air as raw materials and carries out the oxidation reaction in the presence of water vapor and other inert gases through a fixed-bed catalyst bed. 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. The reactor outlet yields an acrylic acid gas-phase mixture, which mainly consists of acrylic acid gas, nitrogen, aldehyde compounds, carboxylic acid compounds, carbon dioxide, carbon monoxide, and oxygen. The acrylic acid gas-phase mixture is then purified and separated to obtain the acrylic acid product.

[0004] Currently, commonly used methods for acrylic acid gas-phase separation 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; however, it requires the use of a solvent to absorb acrylic acid, involves high operating temperatures, is prone to polymerization, and has a short operating cycle. Water absorption azeotropic distillation has the advantages of a short process and low investment costs; however, it requires the use of an azeotropic agent, resulting in higher energy consumption and operating costs. Water absorption extractive distillation has the advantages of low energy consumption and low operating costs; however, it has the disadvantages of a longer process, higher investment costs, and higher consumption of extractants and polymerization inhibitors.

[0005] Chinese patent CN1903738A discloses an "acrylic acid wastewater treatment process" applicable to acrylic acid wastewater discharged from acrylic acid plants. The acrylic acid wastewater treatment employs reverse osmosis membrane separation and distillation processes. After membrane separation, the purified water from the permeate side is discharged to the boundary area, while the organic matter from the residual side is sent to a distillation column to separate acrylic acid and toluene from acetic acid and water, and toluene, toluene, and acetic acid are recovered separately. However, the acrylic acid and toluene obtained by this process need to be further processed in the light component tower of the acrylic acid plant to recover acrylic acid and toluene, and the acetic acid and water obtained need to be further processed in the acetic acid recovery system to recover acetic acid, making it impossible to obtain a high-concentration product. Furthermore, the reverse osmosis membrane operates at a high pressure (1–10 MPa) and has a limited lifespan, requiring frequent replacement, which also results in high operating costs for this process.

[0006] CN1865216A discloses a "process for azeotropic purification of acrylic acid and recovery of acetic acid," which uses ethylcyclohexane and toluene, and ethyl propionate and toluene as azeotropic agents in the azeotropic distillation of acrylic acid. It includes an acrylic acid azeotropic tower and an acetic acid removal tower to remove water and acetic acid from the crude acrylic acid solution. Additionally, it includes an organic membrane and stripping tower, and an acetic acid azeotropic tower to concentrate the by-product acetic acid, which has a concentration of 2-8% (unless otherwise specified, all concentrations in this specification refer to mass percentages), to a concentration ≥85%. While this process achieves high dehydration and acetic acid removal rates, its azeotropic distillation consumes a large amount of energy. Furthermore, the use of multiple material mixtures as azeotropic agents introduces more components to be separated into the system, increasing the separation difficulty and energy consumption. Additionally, the organic membrane is a three-stage reverse osmosis membrane, which is expensive and has a limited lifespan, requiring periodic replacement, further increasing equipment costs and operating expenses.

[0007] CN102775295A discloses a method for purifying acrylic acid. This method includes a two-tower process flow consisting of an absorption tower and a purification tower. By coupling the cooling, absorption, and purification processes of acrylic acid, a device composed of two towers is used to complete the recovery and purification of acrylic acid. Simultaneously, water is recycled as both the absorbent and coolant, avoiding the use of other solvents (extractants, azeotropic agents), thus preventing solvent pollution to the environment. This method has a relatively simple process flow and reduces equipment investment and operating costs. However, because this method uses an aqueous acetic acid solution from the top of the absorption tower as the absorbent, both acetic acid and water have only one outlet at the top of the absorption tower. Water has a normal boiling point of 100℃, acetic acid has a normal boiling point of 117.9℃, and acrylic acid has a normal boiling point of 141℃. 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 complete removal from the top of the absorption tower difficult. The acetic acid content discharged from the top of the absorption tower with non-condensable gases is in equilibrium with the acetic acid concentration in the liquid phase at the top of the tower. According to actual operating data, acetic acid needs to accumulate to approximately 9% (unless otherwise specified, all values ​​below are by mass) at the top of the absorber to ensure complete removal of acetic acid from the reaction gas. This results in a large accumulation of acetic acid within the absorber. Furthermore, as the acetic acid concentration shifts towards the top of the absorber, the acrylic acid concentration inevitably shifts as well, leading to a higher acrylic acid content (approximately 0.3 wt%) in the tail gas at the top of the absorber. This increases propylene consumption and production costs. Simultaneously, because the unit lacks a liquid-phase extraction system for the acetic acid solution, a large amount of acetic acid-containing material from the top of the purification tower returns to the lower part of the absorber when reducing the acetic acid content in the acrylic acid product. This causes a significant amount of acetic acid to circulate and accumulate between the absorber and purification towers, hindering acetic acid removal, exacerbating the increase in acrylic acid content at the top of the absorber, and negatively impacting the quality of the acrylic acid product from the purification tower.

[0008] CN109232232A discloses a method for refining acrylic acid. This method involves high-concentration gas rapid cooling absorption, low-concentration gas re-absorption, purification, extraction, and stripping of acrylic acid process gas. The cooling, absorption, and purification processes of the acrylic acid gas phase mixture are coupled, and subsequent acid water treatment is performed. The absorption process is improved, and the refining process does not use an azeotropic agent. This method has a relatively simple process and lower operating costs. However, the reabsorption process requires the addition of demineralized water from the top of the light mineral removal tower, which not only consumes demineralized water but also increases the amount of acid water discharged from the system. The stripping gas required by the stripping tower comes from the gas phase discharged from the top of the absorption tower. Acrylic acid containing stripping gas is discharged from the top of the stripping tower and returned to the bottom 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. The solvent regeneration in the stripping tower bottom requires additional heat and operates at a high temperature, posing a 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 material at the top of the purification tower is returned 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. This not only hinders the removal of acetic acid but also exacerbates the increase in acrylic acid content at the top of the absorption tower and affects the quality of the acrylic acid product from the purification tower.

[0009] The process methods provided by CN102775295A and CN109232232A share 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 acetic acid, its concentration needs to be accumulated and increased to a high level before it can be discharged from the top outlet of the absorption tower. The lack of a liquid phase extraction for the acetic acid solution leads to the accumulation and increased content of acetic acid within the system, thus affecting the quality of the acrylic acid product from the purification tower. When reducing the acetic acid content in the acrylic acid product, a large amount of acetic acid-containing material from the top of the purification tower returns to the bottom of the absorption tower, causing acetic acid to circulate and accumulate extensively between the absorption tower and the purification tower. To reduce the acetic acid content in the system and meet the quality requirements of the acrylic acid product, the temperature of the tail gas at the top of the absorption tower is forced to increase, resulting in some acrylic acid being sent to the tail gas incineration system along with the tail gas and acetic acid, leading to increased material consumption and reduced yield.

[0010] Figure 1 This is a process flow diagram of a commonly used three-tower (absorption tower T110, light oil removal tower T120, and acetic acid removal tower T130) conventional process for obtaining crude acrylic acid product from the raw material reaction gas through rapid quenching absorption, azeotropic distillation, and conventional distillation to remove acetic acid. The above-mentioned commonly used conventional three-tower process is relatively simple and has a high dehydration rate, but its azeotropic distillation has high energy consumption. Summary of the Invention

[0011] The purpose of this invention is to provide an acrylic acid refining process and apparatus that avoids acetic acid accumulation. This process can be used to obtain crude acrylic acid from propylene oxidation reaction gas through continuous absorption, dehydration, and acetic acid removal. This invention not only eliminates the need for azeotropic agents for dehydration and acetic acid removal but also effectively prevents acetic acid accumulation in the system, thus improving both system operational stability and acrylic acid yield. This invention overcomes the shortcomings of existing technologies, is applicable to propylene oxidation reaction gas feedstocks of varying concentrations, and possesses significant economic benefits and broad application prospects.

[0012] This invention provides an acrylic acid refining process that avoids acetic acid accumulation. The process involves continuous absorption, dehydration, and acetic acid removal from the propylene oxidation reaction gas to obtain crude acrylic acid. This method not only eliminates the need for azeotropic agents for dehydration and acetic acid removal but also effectively prevents acetic acid accumulation in the system. This improves both system operational stability and acrylic acid yield. The main steps include: 1) It includes at least a dehydration tower T110, an acetic acid removal tower T120, and a light oil removal tower T130; 2) The reaction gas from the reaction system enters the bottom of the dehydration tower T110; 3) The non-condensable gas and more than 90% water in the reaction gas are discharged from the top of the dehydration tower T110, and the liquid phase in the bottom of the tower enters the deacetic acid removal tower (T120); 4) The product collected from the top of the acetic acid removal tower T120 enters the light acetic acid removal tower T130, and crude acrylic acid, which is basically free of acetic acid, is obtained at the bottom of the tower. 5) The acidic water containing acetic acid is discharged from the top of the light acetic acid removal tower T130, and the liquid phase in the bottom of the tower enters the acetic acid removal tower T120.

[0013] The process method provided by this invention comprises the following steps: 1) The raw material reaction gas 1 enters the bottom of the dehydration tower T110, and the tail gas 2 is discharged from the top of the dehydration tower T110. The upper part of the dehydration tower T110 is equipped with a liquid phase circulation cooling section S1101. The circulating liquid phase 3 is cooled by the dehydration tower circulation cooler E1101 and the material 4 returns to the top of the dehydration tower T110. The bottom material 5 of the dehydration tower T110 enters the deacetic acid removal tower T120. 2) The gas phase 6 at the top of the acetic acid removal tower T120 enters the first-stage condenser E1202 of the acetic acid removal tower for condensation. The uncondensed gas 7 after cooling enters the second-stage condenser E1203 of the acetic acid removal tower for condensation. All the condensate 8 from the first-stage condenser E1202 of the acetic acid removal tower is returned to the top of the acetic acid removal tower T120. The non-condensable gas 9 from the second-stage condenser E1203 of the acetic acid removal tower enters the vacuum steam jet pump VP1201, mixes with the power steam 11, and then enters the middle of the light acetic acid removal tower T130 after being condensed by the vacuum pump condenser E1204 of the acetic acid removal tower. The condensate 10 from the second-stage condenser E1203 of the acetic acid removal tower enters the light acetic acid removal tower T130. The liquid phase material collected from the bottom of the acetic acid removal tower T120 is used as crude acrylic acid product 13. 3) The gas phase 14 at the top of the light-light removal tower T130 enters the first-stage condenser E1302 of the light-light removal tower for condensation. The cooled non-condensable gas 15 enters the second-stage condenser E1303 of the light-light removal tower for condensation. The condensate 16 from the first-stage condenser E1302 of the light-light removal tower is completely returned to the top of the light-light removal tower T130. The non-condensable gas 17 from the second-stage condenser E1303 of the light-light removal tower enters the vacuum system. The condensate from the second-stage condenser E1303 of the light-light removal tower is sent out as acidic water containing acetic acid. The liquid phase material 19 collected from the bottom of the light-light removal tower T130 enters the acetic acid removal tower T120.

[0014] Water has a normal boiling point of 100℃, acetic acid 117.9℃, and acrylic acid 141℃. In conventional processes, both acetic acid and water need to be removed from the top of dehydration tower T110. Acetic acid, with its higher boiling point, is difficult to remove completely from the top of T110. The acetic acid content discharged from the top of T110 with the non-condensable gas is in equilibrium with the acetic acid concentration in the liquid phase at the top of the tower. According to actual operating data, acetic acid needs to accumulate to approximately 9% at the top of T110 for all acetic acid in the reaction gas to be removed from the top of T110, resulting in a large accumulation of acetic acid in T110. Furthermore, as the acetic acid concentration shifts towards the top of T110, the acrylic acid concentration also shifts towards the top of T110, resulting in a high acrylic acid content (approximately 3000 ppm) in the tail gas, with approximately 1.85% acrylic acid lost with the tail gas, leading to a low acrylic acid product yield.

[0015] The process method provided by this invention overcomes the shortcomings of existing processes (CN102775295A and CN109232232A). Acetic acid passes through the system only once. Acetic acid in the reaction gas that has not been removed from the top of the dehydration tower enters the deacetic acid removal tower from the bottom of the dehydration tower, enters the light component removal tower from the top of the deacetic acid removal tower, and exits the system from the top of the light component removal tower. The material at the top of the deacetic acid removal tower T120 does not return to the dehydration tower T110, effectively avoiding the accumulation of acetic acid in the dehydration tower T110 and the deacetic acid removal tower T120. The system allows for extensive circulation and accumulation of acetic acid within a certain range, providing an alternative outlet – the top of the light-light residue removal tower. Unlike existing processes (CN102775295A and CN109232232A), where all acetic acid is removed from the top of dehydration tower T110, the concentrations of acetic acid and acrylic acid within dehydration tower T110 are reduced downwards. This significantly lowers the acrylic acid content in the tail gas from the top of dehydration tower T110 to below 500 ppm, reducing acrylic acid loss and increasing the acrylic acid yield of the unit by approximately 1.5%. This results in substantial economic benefits.

[0016] According to the process method provided by this invention, a liquid stream with low acrylic acid content and high acetic acid content can be drawn from the lower part of the dehydration tower T110 to avoid the accumulation of acetic acid in the dehydration tower T110. The liquid stream can be sent to the light removal tower T130 (when the acrylic acid content is less than 50%) or the acetic acid removal tower T120 (when the acrylic acid content is greater than 50%).

[0017] According to the process method provided by this invention, 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 enters above 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 it can be a separate evaporation tower T140. The gas phase at the top of the dehydration tower T110 can all enter the acid water evaporation section S1102 or the evaporation tower T140, or a stream of circulating tail gas with a lower acetic acid content can be diverted to the reactor, and the remaining gas phase can enter the acid water evaporation section S1102 or the evaporation tower T140.

[0018] According to the process method provided by the present invention, the top of the acetic acid removal tower T120 can also be a single-stage or two-stage condenser: part of the first-stage condensate is refluxed and the other part is taken out to the light removal tower T130; the first-stage uncondensed material can go to the second-stage condenser or directly to the vacuum pump; the material at the outlet of the vacuum pump can be condensed by the vacuum pump condenser and then go to the light removal tower T130 or the dehydration tower T110.

[0019] According to the process method provided by the present invention, the material collected from the bottom of the acetic acid removal tower T120 is crude acrylic acid that is basically free of acetic acid. It can be connected to an acrylic acid refining tower to obtain acrylic acid products from the top of the tower; or the gaseous side stream material can be collected from the bottom of the acetic acid removal tower T120 and obtained as acrylic acid products after condensation.

[0020] According to the process method provided by this invention, the dehydration tower T110 can be a single tower or a double tower connected in series with a reduced tower height. In this case, if a liquid phase side stream needs to be collected from the upper tower bottom or the lower tower side stream, it can be collected from the dehydration tower T110. The dehydration tower T110 can be equipped with a top liquid phase circulation cooling section S1101 to condense some of the condensable substances in the rising gas phase in the tower and provide liquid phase reflux; or process water or other wastewater with low acrylic acid content in the system (including but not limited to steam jet pump condensate) can be introduced as reflux liquid; or the top liquid phase circulation cooling section S1101 can be combined with supplementary process water or other wastewater with low acrylic acid content. The T110 dehydration tower appears to be an acrylic acid absorption tower, but it is actually an acrylic acid dehydration distillation tower. The non-condensable gas in the reaction gas greatly reduces the partial pressure of acrylic acid in the gas phase, 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 T110 dehydration tower removes more than 90% of the water in the reaction gas along with the non-condensable gas at the top, and obtains crude acrylic acid with a water content of ~5%, an acetic acid content of ~4%, and an acrylic acid content of ~90% from the bottom of the tower.

[0021] According to the process method provided by the present invention, the light component removal tower T210 and the solvent recovery tower T220 can be used instead of the light component removal tower T130. The light component removal tower T210 adopts solvent azeotropic dehydration and acetic acid removal. The acid water at the top of the light component removal tower T210 enters the acid water evaporation section S1102 at the top of the dehydration tower T110 or is 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 basically free of acetic acid is obtained from the bottom of the solvent recovery tower T220.

[0022] According to the process method provided by this 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. The higher-temperature circulating liquid is extracted and heated by the evaporation heater E1102 of the acid water evaporation section S1102 or the evaporation heater E1102 of the independent evaporation tower T140, evaporating the liquid-phase acid water 18 from the light-phase removal tower T130. The cooled liquid phase returns to the area above the pre-cooling section S1103. No additional steam consumption is added, and the liquid-phase acid water 18 from the light-phase removal tower T130 is completely vaporized with the tail gas, eliminating the need for external discharge of the liquid-phase acid water. To simplify the process and equipment structure, the pre-cooling section S1103 can also be omitted; in this case, the evaporation heater E1102 is heated by an external heat source.

[0023] According to the process method provided by the present invention, the material with an acrylic acid content of ~50%, an acetic acid content of >20%, and a water content of >20% is collected from the top of the acetic acid removal tower T120 and sent to the light removal tower T130; the crude acrylic acid product with an acetic acid content of less than 500ppm is obtained from the bottom of the acetic acid removal tower T120.

[0024] According to the process method provided by the present invention, the top of the light component removal tower T130 is acidic water (a mixture of acetic acid, water and other light components) with an acrylic acid content of <1%; the bottom of the light component removal tower T130 is crude acrylic acid with an acetic acid content of less than 2%, which is returned to the acetic acid removal tower T120.

[0025] According to the process method provided by the present invention, the energy-saving method adopted is as follows: the steam condensate can be preheated sequentially or separately as feed to the acetic acid removal tower T120 and the light acetic acid removal tower T130.

[0026] The condensate vapor can be used to preheat any tower or combination thereof within the system. The various heat exchange methods and combinations described above are merely supplements to the acrylic acid refining process provided by this invention to avoid acetic acid accumulation, and are not intended to limit the spirit of this invention. Those skilled in the art can make appropriate modifications, alterations, and combinations based on the methods provided by this invention to achieve the same technology. It should be particularly noted that all such modifications, alterations, and recombinations of the process flow provided by this invention are obvious to those skilled in the art and are considered to be within the spirit, scope, and content of this invention.

[0027] According to the process method provided by the present invention, the heat source used in the acetic acid removal tower reboiler E1201 and the light acetic acid removal tower reboiler E1301 can be fresh steam, heat transfer oil, or material steam generated inside the system.

[0028] According to the process method provided by this invention, the typical operating conditions for each tower are as follows: The operating pressure range at the top of the T110 dehydration tower is 50–350 kPa. The operating pressure range at the top of the T120 acetic acid removal tower is 2–80 kPa. The operating pressure range at the top of the T130 light-duty removal tower is 5–50 kPa.

[0029] The preferred operating conditions for each tower are as follows: The operating pressure at the top of the T110 dehydration tower is 100–150 kPa, the operating temperature at the top of the tower is 55–70℃, and the operating temperature at the bottom of the tower is 80–105℃. The T120 acetic acid removal tower has an operating pressure of 2.5–12 kPa at the top, an operating temperature of 42–65°C at the top, and an operating temperature of 70–105°C at the bottom. The operating pressure at the top of the T130 light-light removal tower is 6–12 kPa, the operating temperature at the top is 35–50℃, and the operating temperature at the bottom is 75–105℃.

[0030] An acrylic acid refining process apparatus according to the present invention for avoiding acetic acid accumulation mainly includes connecting pipelines between three towers: dehydration tower T110, acetic acid removal tower T120, and light acetic acid removal tower T130.

[0031] 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 emission pipeline. The upper part of the dehydration tower T110 is equipped 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 dehydration tower T110 above the liquid phase circulation cooling section S1101. The bottom of the dehydration tower T110 is connected to the feed port of the acetic acid removal tower T120. The top of the acetic acid removal tower T120 is connected to the shell-side inlet of the first-stage condenser E1202. The non-condensable gas outlet of the first-stage condenser E1202 is connected to the shell-side inlet of the second-stage condenser E1203. The condensate outlet of the first-stage condenser E1202 is connected to the top of the acetic acid removal tower T120. The non-condensable gas outlet of the second-stage condenser E1203 is connected to the non-condensable gas inlet of the vacuum steam jet pump VP1201. The condensate outlet of the second-stage condenser E1203 is connected to the light condensate removal tower T13. The middle section is connected to the vacuum pump power steam supply pipeline, which 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 vacuum pump condenser E1204 in the acetic acid removal tower. The shell-side outlet of the vacuum pump condenser E1204 in the acetic acid removal tower is connected to the middle section of the light acetic acid removal tower T130. The bottom of the acetic acid removal tower T120 is connected to the tube-side inlet of the reboiler E1201 in the acetic acid removal tower and the crude acrylic acid outlet pipeline. The tube-side outlet of the reboiler E1201 in the acetic acid removal tower is connected to the bottom of the acetic acid removal tower T120.

[0032] The top of the light-weight gas removal tower T130 is connected to the shell-side inlet of the first-stage condenser E1302. The non-condensable gas outlet of the first-stage condenser E1302 is connected to the shell-side inlet of the second-stage condenser E1303. The condensate outlet of the first-stage condenser E1302 is connected to the top of the light-weight gas removal tower T130. The non-condensable gas outlet of the second-stage condenser E1303 is connected to the vacuum system. The condensate outlet of the second-stage condenser E1303 is connected to the acid water discharge pipeline. The bottom of the light-weight gas removal tower T130 is connected to the tube-side inlet of the reboiler E1301 and the upper part of the acetic acid removal tower T120. The tube-side outlet of the reboiler E1301 is connected to the bottom of the light-weight gas removal tower T130.

[0033] To highlight the acrylic acid refining process provided by this invention that avoids acetic acid accumulation, some heat exchangers in the process are omitted.

[0034] According to the process method provided by this invention, those skilled in the art can implement appropriate internal heat exchange methods based on specific device conditions. All resulting variations in the process flow should be considered within the spirit, scope, and content of this invention. The heat exchanger in the simplified flow diagram is merely illustrative, and its specific structural form does not constitute any limitation on this invention.

[0035] This invention provides an acrylic acid refining process and apparatus that avoids acetic acid accumulation, as well as various modified processes. It can be used in a process to obtain crude acrylic acid from propylene oxidation reaction gas through continuous absorption, dehydration, and acetic acid removal. This method not only eliminates the need for azeotropic agents for dehydration and acetic acid removal but also effectively prevents acetic acid accumulation in the system, thus improving both system operational stability and acrylic acid yield. This invention overcomes the shortcomings of existing technologies, is applicable to propylene oxidation reaction gas feedstocks of varying concentrations, and offers significant economic benefits and broad application prospects. Attached Figure Description

[0036] Figure 1 This is a process flow diagram of the commonly used three-tower (absorption tower T110, light acetic acid removal tower T120, and acetic acid removal tower T130) conventional process method for obtaining crude acrylic acid products by means of rapid cooling absorption, azeotropic distillation, and conventional distillation to remove acetic acid from the raw material reaction gas.

[0037] Figure 2 This is a process flow diagram of a typical acrylic acid refining process to avoid acetic acid accumulation provided by the present invention.

[0038] Figure 3 yes Figure 2 One type of evolutionary process, namely, modified process method one, is relatively... Figure 2 The provided process allows a stream of water and a liquid side stream 20 with low acrylic acid content and high acetic acid content to be drawn from the lower part of the dehydration tower T110 to the acetic acid desulfurization tower T120, in order to avoid the accumulation of acetic acid in the dehydration tower T110.

[0039] Figure 4 yes Figure 2 One type of evolutionary process, namely, modified process method two, is relatively... Figure 2 The provided process involves adding an acid water evaporation section S1102 at the top of the dehydration tower T110, and the acid water 18 discharged from the light removal tower T130 entering the acid water evaporation section S1102 at the top of the dehydration tower T110.

[0040] Figure 5 yes Figure 2 One of the evolutionary process methods, namely the modified process method three, is relatively... Figure 2The provided process includes the addition of an independent evaporation tower T140. Acid water 18 discharged from the light-removing tower T130 is fed into the top of the evaporation tower T140. Gas phase 21 from the top of the dehydration tower T110 is fed into the bottom of the evaporation tower T140. Liquid phase 22 from the bottom of the evaporation tower T140 is fed into the top of the dehydration tower T110.

[0041] Figure 6 yes Figure 5 One type of evolutionary process, namely, modified process method four, is relatively... Figure 5 The provided process involves a heated bottom section of the independent evaporator T140, which vaporizes all materials entering the evaporator T140 and discharges tail gas 2 from the top of the tower. No liquid phase is collected from the bottom of the evaporator T140. The gas phase 21 at the top of the dehydration tower T110 can be diverted to a circulating tail gas 23 with a low acetic acid content to the reactor, while the remaining gas phase 24 enters the evaporator T140.

[0042] Figure 7 yes Figure 2 One type of evolutionary process, namely, modified process method six, is relatively... Figure 2 The provided process involves extracting gaseous side stream material 25 from the bottom of the acetic acid removal tower T120, condensing it in the product condenser E1205 to obtain acrylic acid product 26, and discharging heavy component 13 from the bottom of the acetic acid removal tower T120.

[0043] Figure 8 yes Figure 2 One type of evolutionary process, namely, variation process method eight, relative to Figure 2 The provided process involves setting up a circulating cooling section at the top of the dehydration tower T110, while introducing process water 27 as reflux liquid.

[0044] Figure 9 yes Figure 4 One of the evolutionary process methods, namely, the modified process method nine, is relatively... Figure 4 The provided process uses a light component removal tower T210 and a solvent recovery tower T220 instead of a light component removal tower T130. The light component removal tower T210 uses solvent azeotropic dehydration and acetic acid removal. The acid water 32 at the top of the light component removal tower T210 enters 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, which is basically free of acetic acid, is obtained from the bottom of the solvent recovery tower T220.

[0045] Figure 10 yes Figure 4 One type of evolutionary process, namely, the modified process method ten, relative to Figure 4The provided process allows for the use of two towers in series in the dehydration tower T110 to reduce the tower height. A pre-cooling section S1103 can be set below the liquid phase circulation cooling section S1101 in the upper tower T110B of the dehydration tower. The circulating liquid 39 with a higher temperature is extracted and heated by the evaporation heater E1102 in the acid water evaporation section S1102 to evaporate the liquid phase acid water 18 in the light dehydration tower T130. The cooled liquid phase 40 is then returned to the upper part of the pre-cooling section S1103. Detailed Implementation

[0046] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, but are for illustrative purposes only and not for limiting the present invention.

[0047] Unless otherwise specified, the composition, structure, materials (such as connecting pipelines between towers), reagents, etc., of the process equipment used in the embodiments that are not specifically described can all be obtained commercially or by methods known to those skilled in the art. The specific experimental methods and operating conditions involved are generally in accordance with conventional process conditions and the conditions described in the manual, or the conditions recommended by the manufacturer.

[0048] Figure 1 This is a process flow diagram of the commonly used three-tower (absorption tower T110, light acetic acid removal tower T120, and acetic acid removal tower T130) conventional process method for obtaining crude acrylic acid products by means of rapid cooling absorption, azeotropic distillation, and conventional distillation to remove acetic acid from the raw material reaction gas.

[0049] The raw material reaction gas enters the bottom of the absorption tower T110, and the fresh process water enters the top of the absorption tower T110.

[0050] The exhaust gas is discharged from the top of the absorption tower T110; the liquid phase in the bottom of the absorption tower T110 is divided into two streams. The first stream enters the light precipitator T120, and the second stream is the circulating liquid, which returns to the bottom of the absorption tower T110 after being cooled by the absorption tower circulating cooler.

[0051] The condensate from the top gas phase of the light precipitate removal tower T120 is separated into two phases. The separated oil phase flows back to the top of the light precipitate removal tower T120, and the separated water phase is divided into two streams. The first stream is used as recycled absorption water and enters the upper part of the absorption tower T110, and the second stream is used as discharged acid water and sent out to the device. The bottom material of the light precipitate removal tower T120 enters the acetic acid removal tower T130.

[0052] The condensate from the top gas phase of the acetic acid removal tower T130 is divided into two streams. The first stream flows back to the top of the acetic acid removal tower T130, and the second stream enters the light precipitator T120. The crude acrylic acid product collected from the bottom of the acetic acid removal tower T130 is sent out of the equipment.

[0053] The commonly used conventional three-tower process is relatively simple and has a high dehydration rate, but its azeotropic distillation has high energy consumption.

[0054] This invention provides an acrylic acid refining process and apparatus to avoid acetic acid accumulation, wherein the typical composition of the raw material reaction gas is as follows: Component mass percentage (%) Non-condensable gas 77.44 Water 7.66 Formic acid 0.01 Acetic acid 0.57 Acrylic acid 14.27 Recombinant component 0.05 Total: 100.00.

[0055] The above-mentioned range of raw material composition does not constitute any limitation on the present invention, which can be used for the purification of acrylic acid from raw material reaction gases with various compositions.

[0056] Specific application examples are as follows. Example 1

[0057] The acrylic acid refining process apparatus provided by this invention to avoid acetic acid accumulation mainly includes three towers: a dehydration tower T110, an acetic acid removal tower T120, and a light acetic acid removal tower T130, as well as 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 emission pipeline; a liquid phase circulation cooling section S1101 is arranged in the upper part 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, the hot side outlet of the dehydration tower circulation cooler E1101 is connected to the top of the liquid phase circulation cooling section S1101 in the dehydration tower T110, and the bottom of the dehydration tower T110 is connected to the upper part of the acetic acid removal tower T120; The top of the acetic acid removal tower T120 is connected to the shell-side inlet of the first-stage condenser E1202. The non-condensable gas outlet of the first-stage condenser E1202 is connected to the shell-side inlet of the second-stage condenser E1203. The condensate outlet of the first-stage condenser E1202 is connected to the top of the acetic acid removal tower T120. The non-condensable gas outlet of the second-stage condenser E1203 is connected to the non-condensable gas inlet of the vacuum steam jet pump VP1201. The condensate outlet of the second-stage condenser E1203 is connected to the light condensate removal tower T13. The middle section is connected to the vacuum pump power steam supply pipeline, which 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 vacuum pump condenser E1204 in the acetic acid removal tower. The shell-side outlet of the vacuum pump condenser E1204 in the acetic acid removal tower is connected to the middle section of the light acetic acid removal tower T130. The bottom of the acetic acid removal tower T120 is connected to the tube-side inlet of the reboiler E1201 in the acetic acid removal tower and the crude acrylic acid outlet pipeline. The tube-side outlet of the reboiler E1201 in the acetic acid removal tower is connected to the bottom of the acetic acid removal tower T120.

[0058] The top of the light-weight gas removal tower T130 is connected to the shell-side inlet of the first-stage condenser E1302. The non-condensable gas outlet of the first-stage condenser E1302 is connected to the shell-side inlet of the second-stage condenser E1303. The condensate outlet of the first-stage condenser E1302 is connected to the top of the light-weight gas removal tower T130. The non-condensable gas outlet of the second-stage condenser E1303 is connected to the vacuum system. The condensate outlet of the second-stage condenser E1303 is connected to the acid water discharge pipeline. The bottom of the light-weight gas removal tower T130 is connected to the tube-side inlet of the reboiler E1301 and the upper part of the acetic acid removal tower T120. The tube-side outlet of the reboiler E1301 is connected to the bottom of the light-weight gas removal tower T130.

[0059] This invention can be used in the dehydration and deacetic acid removal processes of acrylic acid from propylene oxidation reaction gas feedstocks of different concentrations. The specific process is described below: like Figure 2 As shown, this is a typical flow of the process method provided by the present invention. The raw material reaction gas 1 enters the bottom of the dehydration tower T110, and the tail gas 2 is discharged from the top of the dehydration tower T110. A liquid phase circulation cooling section S1101 is provided in the upper part 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 after being cooled by the dehydration tower circulation cooler E1101 is returned to the top of the dehydration tower T110 above the liquid phase circulation cooling section S1101. The material 5 in the bottom of the dehydration tower T110 enters the deacetic acid removal tower T120.

[0060] The gas phase 6 at the top of the acetic acid removal tower T120 enters the primary condenser E1202 for condensation. The cooled non-condensable gas 7 enters the secondary condenser E1203 for condensation. All the condensate 8 from the primary condenser E1202 is returned to the top of the acetic acid removal tower T120. The non-condensable gas 9 from the secondary condenser E1203 enters the vacuum steam jet pump VP1201, mixes with the power steam 11, and then enters the middle of the light acetic acid removal tower T130 after being condensed by the vacuum pump condenser E1204. The condensate 10 from the secondary condenser E1203 enters the light acetic acid removal tower T130. The liquid phase material collected from the bottom of the acetic acid removal tower T120 is used as the crude acrylic acid product 13.

[0061] The gas phase 14 at the top of the light-light removal tower T130 enters the first-stage condenser E1302 for condensation. The cooled non-condensed gas 15 enters the second-stage condenser E1303 for condensation. All the condensate 16 from the first-stage condenser E1302 is returned to the top of the light-light removal tower T130. The non-condensable gas 17 from the second-stage condenser E1303 enters the vacuum system. The condensate from the second-stage condenser E1303 is sent out as acidic water containing acetic acid. The liquid phase material 19 collected from the bottom of the light-light removal tower T130 enters the acetic acid removal tower T120.

[0062] The heat source used for the acetic acid removal tower reboiler E1201 and the light acetic acid removal tower reboiler E1301 can be fresh steam, heat transfer oil, or material steam generated inside the system.

[0063] The condensate of the fresh steam added to the system can be used to preheat the feed of the acetic acid removal tower T120 and the light acetic acid removal tower T130, either separately or sequentially.

[0064] The typical operating conditions for each tower in Example 1 are given below: The operating pressure range at the top of the T110 dehydration tower is 50–350 kPa. The operating pressure range at the top of the T120 acetic acid removal tower is 2–80 kPa. The operating pressure range at the top of the T130 light-duty removal tower is 5–50 kPa.

[0065] The preferred operating conditions for each tower in Example 1 are given below: The operating pressure at the top of the T110 dehydration tower is 100–150 kPa, the operating temperature at the top of the tower is 55–70℃, and the operating temperature at the bottom of the tower is 80–105℃. The T120 acetic acid removal tower has an operating pressure of 2.5–12 kPa at the top, an operating temperature of 42–65°C at the top, and an operating temperature of 70–105°C at the bottom. The operating pressure at the top of the T130 light-light removal tower is 6–12 kPa, the operating temperature at the top is 35–50℃, and the operating temperature at the bottom is 75–105℃.

[0066] According to the process method of this embodiment, compared with CN102775295A, the top material of the acetic acid removal tower T120 is not returned to the dehydration tower T110, effectively avoiding the large-scale circulation and accumulation of acetic acid between the dehydration tower T110 and the acetic acid removal tower T120. Acetic acid in the unit does not need to be completely removed from the top of the dehydration tower T110; the concentrations of acetic acid and acrylic acid in the dehydration tower T110 are all lowered, which can significantly reduce the acrylic acid content in the tail gas at the top of the dehydration tower T110 from 3000 ppm to below 500 ppm, reducing acrylic acid loss and increasing the acrylic acid yield of the unit by ~1.5%. This has extremely significant economic benefits.

[0067] Taking a 100,000-ton / year acrylic acid plant as an example, the tail gas flow rate at the top of the T110 dehydration tower is approximately 78 tons / hour. Assuming an acrylic acid price of 6100 yuan / ton, the economic benefits of increasing the acrylic acid yield annually are: 6100 yuan / ton × 78 tons / hour × (3000-500) × 10-6 × 8000 hours / year / 10000 ≈ 9.5 million yuan / year. Example 2

[0068] like Figure 3 As shown, it is Figure 2One type of evolutionary process, namely, modified process method one, is relatively... Figure 2 The provided process allows for the extraction of a liquid stream (20) from the lower part of dehydration tower T110, containing a low concentration of water and a high concentration of acrylic acid, into acetic acid desiccant tower T120. This prevents the accumulation of acetic acid in dehydration tower T110. A typical composition of this liquid stream is: water ~20%, acetic acid ~16%, and acrylic acid ~64%. Example 3

[0069] like Figure 4 As shown, it is Figure 2 One type of evolutionary process, namely, modified process method two, is relatively... Figure 2 The provided process involves adding an acid water evaporation section S1102 at the top of the dehydration tower T110, and the acid water 18 discharged from the light removal tower T130 entering the acid water evaporation section S1102 at the top of the dehydration tower T110. Example 4

[0070] like Figure 5 As shown, it is Figure 2 One of the evolutionary process methods, namely the modified process method three, is relatively... Figure 2 The provided process includes the addition of an independent evaporation tower T140. Acid water 18 discharged from the light-removing tower T130 is fed into the top of the evaporation tower T140. Gas phase 21 from the top of the dehydration tower T110 is fed into the bottom of the evaporation tower T140. Liquid phase 22 from the bottom of the evaporation tower T140 is fed into the top of the dehydration tower T110. Example 5

[0071] like Figure 6 As shown, it is Figure 5 One type of evolutionary process, namely, modified process method four, is relatively... Figure 5 The provided process involves an independent evaporator T140 heated by an external heat source. All materials entering the evaporator T140 are vaporized and discharged as tail gas 2 from the top of the tower. No liquid phase is collected from the bottom of the evaporator T140. The gas phase 21 at the top of the dehydration tower T110 can be diverted to a circulating tail gas 23 with a low acetic acid content to the reactor, while the remaining gas phase 24 enters the evaporator T140. Example 6

[0072] It is Figure 2 One of the evolutionary process methods, namely, the fifth modified process method, is relatively... Figure 2 The provided process allows for a single-stage condensation at the top of the acetic acid removal tower T120: the first-stage condensate is divided into two parts, one part is reflux and the other part is collected and sent to the light condensation tower T130. The uncondensed material from the first stage goes directly to the vacuum pump, and the material at the vacuum pump outlet is condensed by the vacuum pump condenser and then sent to the light condensation tower T130. Example 7

[0073] like Figure 7 As shown, it is Figure 2 One type of evolutionary process, namely, modified process method six, is relatively... Figure 2 The provided process involves extracting gaseous side stream material 25 from the bottom of the acetic acid removal tower T120, condensing it in the product condenser E1205 to obtain acrylic acid product 26, and discharging heavy component 13 from the bottom of the acetic acid removal tower T120. Example 8

[0074] It is Figure 2 One of the evolutionary process methods, namely the modified process method seven, is relatively... Figure 2 The provided process allows for a dual-tower series configuration in dehydration tower T110, reducing the tower height. The raw material reaction gas 1 enters the bottom of the lower dehydration tower T110A; the gaseous phase from the top of the lower dehydration tower T110A enters the bottom of the upper dehydration tower T110B; the bottom material 5 from the lower dehydration tower T110A enters the acetic acid removal tower T120; tail gas 2 is discharged from the top of the upper dehydration tower T110B; and the liquid phase material from the bottom of the upper dehydration tower T110B enters the top of the lower dehydration tower T110A. Example 9

[0075] like Figure 8 As shown, it is Figure 2 One type of evolutionary process, namely, variation process method eight, relative to Figure 2 The provided process involves a circulating cooling section at the top of dehydration tower T110, with process water 27 introduced as reflux liquid. Material from the vacuum pump outlet of the acetic acid removal tower T120 is condensed by the vacuum pump condenser before entering dehydration tower T110.

[0076] Example 10: like Figure 9 As shown, it is Figure 4 One of the evolutionary process methods, namely, the modified process method nine, is relatively... Figure 4 The provided process uses a light component removal tower T210 and a solvent recovery tower T220 instead of a light component removal tower T130. The light component removal tower T210 uses solvent azeotropic dehydration and acetic acid removal. The acid water 32 at the top of the light component removal tower T210 enters 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, which is basically free of acetic acid, is obtained from the bottom of the solvent recovery tower T220.

[0077] Example 11: like Figure 10 As shown, it is Figure 4 One type of evolutionary process, namely, the modified process method ten, relative to Figure 4The provided process allows for the dehydration tower T110 to be constructed using a dual-tower series configuration to reduce tower height. A pre-cooling section S1103 can be installed below the liquid phase circulation cooling section S1101 in the upper tower T110B of the dehydration tower. The higher-temperature circulating liquid 39 is extracted and heated by the evaporation heater E1102 in the acid water evaporation section S1102. The acid water 18 is discharged from the evaporation tower T130, and the cooled liquid phase 40 is returned to the area above the pre-cooling section S1103.

[0078] This invention provides a process and apparatus for refining acrylic acid to avoid acetic acid accumulation. It can be used in a process to obtain crude acrylic acid from propylene oxidation reaction gas through continuous absorption, dehydration, and acetic acid removal. This process eliminates the need for azeotropic agents for dehydration and acetic acid removal, effectively preventing acetic acid accumulation in the system, thus improving both system operational stability and acrylic acid yield. This invention overcomes the shortcomings of existing technologies, is applicable to propylene oxidation reaction gas feedstocks of varying concentrations, and offers significant economic benefits and broad application prospects.

[0079] With the specific description of the above embodiments, those skilled in the art can make appropriate modifications, alterations, and combinations to the methods provided by this invention to achieve the technology. It should be particularly noted that all such modifications, alterations, and recombinations of the process flow provided by this invention, and the implementation of suitable internal system heat exchange methods, are obvious to those skilled in the art and are considered to be within the spirit, scope, and content of this invention.

Claims

1. A process for refining acrylic acid to avoid acetic acid accumulation, comprising a process of obtaining crude acrylic acid product from propylene oxidation reaction gas through continuous absorption, dehydration, and deacetic acid removal, characterized in that: The system includes at least a dehydration tower (T110), an acetic acid removal tower (T120), and a light acetic acid removal tower (T130). The reaction gas from the reaction system enters the bottom of the dehydration tower (T110). Non-condensable gases and over 90% water content from the reaction gas are discharged from the top of the dehydration tower (T110), and the liquid phase from the bottom of the tower enters the acetic acid removal tower (T120). The top of the acetic acid removal tower (T120) is collected and enters the light acetic acid removal tower (T130), where crude acrylic acid, essentially free of acetic acid, is obtained at the bottom. Acidic water containing acetic acid is discharged from the top of the light acetic acid removal tower (T130), and the liquid phase from the bottom of the tower enters the acetic acid removal tower (T120). The specific steps are as follows: 1) The raw material reaction gas (1) enters the bottom of the dehydration tower (T110), and the tail gas (2) is discharged from the top of the dehydration tower (T110). The upper part of the dehydration tower (T110) is equipped with a liquid phase circulation cooling section (S1101). The circulating liquid phase (3) is extracted from the bottom of the liquid phase circulation cooling section (S1101). The material (4) after being cooled by the dehydration tower circulation cooler (E1101) returns to the top of the dehydration tower (T110) above the liquid phase circulation cooling section (S1101). The bottom material (5) of the dehydration tower (T110) enters the deacetic acid removal tower (T120). 2) The gas phase (6) at the top of the acetic acid removal tower (T120) enters the first-stage condenser (E1202) of the acetic acid removal tower for condensation. The uncondensed gas (7) after cooling enters the second-stage condenser (E1203) of the acetic acid removal tower for condensation. The condensate (8) of the first-stage condenser (E1202) of the acetic acid removal tower is completely returned to the top of the acetic acid removal tower (T120). The non-condensable gas (9) of the second-stage condenser (E1203) of the acetic acid removal tower enters the vacuum steam jet pump (VP1201), mixes with the power steam (11), and then enters the light-light removal tower (T130) after being condensed by the vacuum pump condenser (E1204). The condensate (10) of the second-stage condenser (E1203) of the acetic acid removal tower enters the light-light removal tower (T130). The liquid phase material collected from the bottom of the acetic acid removal tower (T120) is used as crude acrylic acid product (13). 3) The gas phase (14) at the top of the light-light removal tower (T130) enters the first-stage condenser (E1302) of the light-light removal tower for condensation. The uncondensed gas (15) after cooling enters the second-stage condenser (E1303) of the light-light removal tower for condensation. The condensate (16) of the first-stage condenser (E1302) of the light-light removal tower is completely returned to the top of the light-light removal tower (T130). The non-condensable gas (17) of the second-stage condenser (E1303) of the light-light removal tower enters the vacuum system. The condensate of the second-stage condenser (E1303) of the light-light removal tower is sent out as an acetic acid-containing acid water discharge device. The liquid phase material (19) collected from the bottom of the light-light removal tower (T130) enters the acetic acid removal tower (T120).

2. The process method according to claim 1, characterized in that: A liquid side stream with low water and high acrylic acid content is drawn from the lower part of the dehydration tower (T110) to avoid the accumulation of acetic acid in the dehydration tower (T110); the liquid side stream is sent to the light removal tower (T130) or the acetic acid removal tower (T120).

3. The process method according to claim 1, characterized in that: An acid water evaporation section (S1102) is added to the top of the dehydration tower (T110). The acid water (18) discharged from the light removal tower (T130) enters the acid water evaporation section (S1102) at the top of the dehydration tower (T110). The acid water evaporation section (S1102) is located at the top of the dehydration tower (T110) or is an independent evaporation tower (T140). All the gas phase at the top of the dehydration tower (T110) enters the acid water evaporation section (S1102) or the evaporation tower (T140), or a stream of 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).

4. The process method according to claim 1, characterized in that: The top of the acetic acid removal tower (T120) is a single or two-stage condenser: part of the first-stage condensate is refluxed and the other part is taken out to the light removal tower (T130); the uncondensed material from the first stage goes to the second-stage condenser or directly to the vacuum pump; the material at the outlet of the vacuum pump is condensed by the vacuum pump condenser and then goes to the light removal tower (T130) or the dehydration tower (T110).

5. The process method according to claim 1, characterized in that: The material collected from the bottom of the deacetic acid removal tower (T120) is crude acrylic acid that is basically free of acetic acid. It is then connected to an acrylic acid refining tower to obtain acrylic acid products from the top of the tower; or the gaseous side stream material is collected from the bottom of the deacetic acid removal tower (T120), and after condensation, acrylic acid products are obtained.

6. The process method 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 equipped with a liquid phase circulation cooling section (S1101) at the top of the tower to condense some of the condensable substances in the rising gas phase inside the tower and provide liquid phase reflux; Alternatively, process water or other wastewater with low acrylic acid content within the system, including but not limited to steam jet pump condensate, may be introduced as reflux liquid. Alternatively, the top liquid phase circulation cooling section (S1101) can be combined with supplementary process water or other wastewater with low acrylic acid content.

7. The process method according to any one of claims 1 or 3, characterized in that: The light component removal tower (T210) and solvent recovery tower (T220) are used instead of the light component removal tower (T130). The light component removal tower (T210) uses solvent azeotropic dehydration and acetic acid removal. The acid water at the top of the light component removal tower (T210) enters the acid water evaporation section (S1102) at the top of the dehydration tower (T110) or is 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 basically free of acetic acid is obtained from the bottom of the solvent recovery tower (T220).

8. The process method according to claim 1, characterized in that: Typical operating conditions for each tower are as follows: The operating pressure range at the top of the dehydration tower (T110) is 50–350 kPa; The operating pressure range at the top of the acetic acid removal tower (T120) is 2–80 kPa; The operating pressure range at the top of the light-weight removal tower (T130) is 5–50 kPa.

9. The process method according to claim 1, characterized in that: The operating conditions for each tower are as follows: The dehydration tower (T110) has an operating pressure of 100-150 kPa at the top, an operating temperature of 55-70℃ at the top, and an operating temperature of 80-105℃ at the bottom. The acetic acid removal tower (T120) has an operating pressure of 2.5–12 kPa at the top, an operating temperature of 42–65°C at the top, and an operating temperature of 70–105°C at the bottom. The operating pressure at the top of the light-light removal tower (T130) is 6–12 kPa, the operating temperature at the top is 35–50℃, and the operating temperature at the bottom is 75–105℃.

10. An apparatus for an acrylic acid refining process to avoid acetic acid accumulation, characterized in that: It mainly includes three towers: a dehydration tower (T110), an acetic acid removal tower (T120), and a light odor removal tower (T130), as well as connecting pipelines; The feed gas 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 emission pipeline. A liquid-phase circulating cooling section (S1101) is installed at the top of the dehydration tower (T110). The bottom of the liquid-phase circulating cooling section (S1101) is connected to the hot-side inlet of the dehydration tower circulating cooler (E1101), and the hot-side outlet of the dehydration tower circulating cooler (E1101) is connected to the top of the liquid-phase circulating cooling section (S1101) at the top of the dehydration tower (T110). The bottom of the dehydration tower (T110) is connected to the upper part of the acetic acid removal tower (T120). The top of the acetic acid removal tower (T120) is connected to the first-stage condenser of the acetic acid removal tower. The shell-side inlet of the condenser (E1202) is connected; the non-condensable gas outlet of the shell-side of the first-stage condenser (E1202) of the acetic acid removal tower is connected to the shell-side inlet of the second-stage condenser (E1203); the condensate outlet of the shell-side of the first-stage condenser (E1202) of the acetic acid removal tower is connected to the top of the acetic acid removal tower (T120); the non-condensable gas outlet of the shell-side of the second-stage condenser (E1203) of the acetic acid removal tower is connected to the non-condensable gas inlet of the vacuum steam jet pump (VP1201); the condensate outlet of the shell-side of the second-stage condenser (E1203) of the acetic acid removal tower is connected to the middle section of the light condensate removal tower (T130); and the vacuum pump power steam supply line is connected to the vacuum steam jet pump (VP1201). The steam inlet is connected, the outlet of the vacuum steam jet pump (VP1201) is connected to the shell-side inlet of the vacuum pump condenser (E1204) of the acetic acid removal tower, the shell-side outlet of the vacuum pump condenser (E1204) of the acetic acid removal tower is connected to the middle of the light acetic acid removal tower (T130), the bottom of the acetic acid removal tower (T120) is connected to the tube-side inlet of the reboiler (E1201) of the acetic acid removal tower and the crude acrylic acid outlet pipeline, and the tube-side outlet of the reboiler (E1201) of the acetic acid removal tower is connected to the bottom of the acetic acid removal tower (T120); the top of the light acetic acid removal tower (T130) is connected to the shell-side inlet of the first-stage condenser (E1302) of the light acetic acid removal tower, and the first-stage condenser (E1302) of the light acetic acid removal tower (E1302) is connected to the shell-side inlet of the condenser. 302) The shell-side non-condensable gas outlet is connected to the shell-side inlet of the secondary condenser (E1303) of the light-light removal tower. The shell-side condensate outlet of the primary condenser (E1302) of the light-light removal tower is connected to the top of the light-light removal tower (T130). The shell-side non-condensable gas outlet of the secondary condenser (E1303) of the light-light removal tower is connected to the vacuum system. The shell-side condensate outlet of the secondary condenser (E1303) of the light-light removal tower is connected to the acid water discharge pipeline. The bottom of the light-light removal tower (T130) is connected to the tube-side inlet of the reboiler (E1301) of the light-light removal tower and the upper part of the acetic acid removal tower (T120). The tube-side outlet of the reboiler (E1301) of the light-light removal tower is connected to the bottom of the light-light removal tower (T130).

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