Acrylic acid refining system and process

Abstract

This invention discloses an acrylic acid refining system, comprising a light-weight removal tower, a washing tower, an azeotropic distillation tower, and a product tower. Reaction gas from the acrylic acid reaction system circulates through these towers, yielding refined acrylic acid with a purity greater than 99.5 wt% via a side stream from the product tower. This invention also discloses an acrylic acid refining process operating within the aforementioned system. The acrylic acid refining system and process provided by this invention couple quench absorption, reabsorption, azeotropic distillation, and purification, improving the acrylic acid absorption and azeotropic distillation processes. No wastewater is generated, the acrylic acid concentration in the top gas of the washing tower is ≤200 ppm, propylene consumption is reduced, and production costs are lowered. The acrylic acid refining system and process provided by this invention have significant practicality and economic benefits, yielding a high-purity product that is easily mass-produced industrially.

Description

Technical Field

[0001] This invention relates to an acrylic acid refining system and process. Background Technology

[0002] Acrylic acid is mainly used in the preparation of superabsorbent materials, dispersants, and flocculants, and is widely used in chemical fibers, textiles, coatings, and many other fields. The crude acrylic acid aqueous solution obtained by the propylene oxidation method mainly consists of acrylic acid gas, nitrogen, aldehydes, carboxylic acids, carbon dioxide, carbon monoxide, and oxygen. Due to the strong hydrogen bonds, dehydration is difficult. Currently, there are three main methods for the gas-phase separation of acrylic acid: organic solvent absorption distillation, azeotropic distillation, and extractive distillation.

[0003] CN1865216A discloses a "process for azeotropic purification of acrylic acid and recovery of acetic acid," which uses a complex of ethylcyclohexane and toluene, or ethyl propionate and toluene, as an azeotropic agent in the azeotropic distillation of acrylic acid. Although this process has a high dehydration rate and a high acetic acid removal rate, it has high energy consumption. Furthermore, the azeotropic agent is a complex of multiple materials, which introduces more components to be separated into the system, increasing the separation difficulty and energy consumption.

[0004] CN102775295A discloses a method for purifying acrylic acid, which includes a two-tower process involving an absorption tower and a purification tower. This method is relatively simple and reduces equipment investment and operating costs. However, the high acrylic acid content (approximately 0.3 wt%) in the exhaust gas from the top of the absorption tower increases propylene consumption, leading to a significant increase in production costs. Summary of the Invention

[0005] In view of the above problems, the present invention is proposed to provide an acrylic acid refining system and process that overcomes or at least partially solves the above problems. The acrylic acid refining system and process provided by the present invention are characterized by low energy consumption and zero waste liquid.

[0006] As one aspect of the present invention, an acrylic acid refining system is disclosed, the system comprising:

[0007] In the light-light ...

[0008] The washing tower, at the top of the light removal tower, the inert gas containing acrylic acid is absorbed by the acetic acid aqueous solution, the tail gas is discharged at the top of the washing tower, and the bottom liquid containing acrylic acid, acetic acid and water is obtained at the bottom of the washing tower.

[0009] In the azeotropic tower, the bottom liquid of the washing tower is azeotropically removed from acetic acid and water. The bottom liquid obtained in the azeotropic tower is returned to the top of the light-light removal tower, and after passing through the tray of the light-light removal tower, it falls back to the bottom of the light-light removal tower and mixes with the condensed acrylic acid solution in the bottom of the light-light removal tower as the bottom liquid of the light-light removal tower.

[0010] In the product tower, the bottom liquid of the light-light removal tower is further decomposed to remove acetic acid and water. A refined acrylic acid product is obtained on the side stream of the product tower, and a gas containing acrylic acid, acetic acid and water is obtained at the top of the tower. After condensation, the gas is returned to the light-light removal tower as a coolant.

[0011] In a feasible specific implementation, the above-mentioned acrylic acid refining system further includes:

[0012] Intermediate reboiler for product column: The bottom liquid of the light component removal column is cooled by passing through the intermediate reboiler for product column before entering the product column;

[0013] Product tower condenser and product tower aftercooler: The gas containing acrylic acid, acetic acid and water at the top of the product tower is cooled by the product tower condenser and product tower aftercooler to obtain a crude acrylic acid solution containing acetic acid and water, which is then used as a coolant in the light-weight removal tower.

[0014] In a feasible specific implementation, the above-mentioned acrylic acid refining system further includes:

[0015] Washing tower circulating cooler: The acetic acid aqueous solution in the upper part of the washing tower is cooled by the washing tower circulating cooler and then returned to the washing tower.

[0016] In a feasible specific implementation, the above-mentioned acrylic acid refining system further includes:

[0017] Azeotropic column condenser and azeotropic column aftercooler: The gas containing acetic acid, water and azeotropic agent obtained from the top of the azeotropic column is cooled by the azeotropic column condenser and azeotropic column aftercooler to obtain a coolant;

[0018] Azeotropic tower reflux tank: The coolant obtained from the azeotropic tower condenser and the azeotropic tower aftercooler is separated into layers in the azeotropic tower reflux tank. The aqueous phase containing acetic acid obtained from the separation enters the washing tower; the oil phase containing azeotropic agent obtained from the separation returns to the azeotropic tower together with the newly added azeotropic agent.

[0019] As another aspect of the present invention, there is a process for refining acrylic acid, which operates in the above-described system, the acrylic acid refining process comprising:

[0020] The reaction gas from the acrylic acid reaction system enters the bottom of the light-light-removal tower and comes into countercurrent contact with the coolant from the top of the product tower at the bottom of the light-light-removal tower. The acrylic acid in the reaction gas is cooled into an acrylic acid solution and remains in the bottom of the light-light-removal tower. The gas in the reaction gas that has not been cooled and liquefied rises to the top of the light-light-removal tower.

[0021] The gas at the top of the light removal tower enters the bottom of the scrubbing tower. The acrylic acid in the gas is absorbed by the acetic acid aqueous solution in the scrubbing tower. The unabsorbed gas is discharged from the top of the scrubbing tower as tail gas. The bottom liquid containing acrylic acid, acetic acid and water is obtained in the bottom of the scrubbing tower.

[0022] The bottom liquid of the light-light removal tower enters the azeotropic tower and mixes with the azeotropic agent in the azeotropic tower to remove acetic acid and water through azeotropy. The bottom liquid of the azeotropic tower containing acrylic acid is obtained. The bottom liquid of the azeotropic tower enters the top of the light-light removal tower, falls back to the bottom of the light-light removal tower after passing through the tower plate of the light-light removal tower, and mixes with the condensed acrylic acid solution in the bottom of the light-light removal tower as the bottom liquid of the light-light removal tower.

[0023] The liquid at the bottom of the light-light removal tower enters the product tower, where acetic acid and water are further removed. Refined acrylic acid is obtained from the side stream of the light-light removal tower, and a gas containing acrylic acid, acetic acid, and water is obtained at the top of the tower. After condensation, the gas returns to the light-light removal tower as a coolant.

[0024] In a specific feasible implementation, the above-mentioned acrylic acid refining process further includes:

[0025] The liquid in the bottom of the light-light-removal tower is cooled by passing it through the intermediate reboiler of the product tower before entering the product tower.

[0026] The gas containing acrylic acid, acetic acid, and water at the top of the product tower enters the product tower condenser and product tower aftercooler for cooling, resulting in a crude acrylic acid solution containing acetic acid and water, which is then used as a coolant in the light component removal tower.

[0027] In a specific feasible implementation, the above-mentioned acrylic acid refining process further includes:

[0028] The acetic acid aqueous solution at the top of the washing tower is cooled by the washing tower circulating cooler and then returned to the washing tower.

[0029] In a specific feasible implementation, the above-mentioned acrylic acid refining process further includes:

[0030] The gas containing acetic acid, water and azeotropic agent obtained from the top of the azeotropic tower enters the azeotropic tower condenser and the azeotropic tower aftercooler for cooling to obtain a coolant;

[0031] The coolant enters the reflux tank of the azeotropic tower and separates into layers. The aqueous phase containing acetic acid obtained from the separation enters the washing tower to absorb the acrylic acid. The oil phase containing the azeotropic agent obtained from the separation returns to the azeotropic tower together with the newly added azeotropic agent.

[0032] In a specific feasible implementation, in the above-mentioned acrylic acid refining process,

[0033] The pressure at the top of the light-weight removal tower is 115–125 kPa, the temperature at the top of the tower is 70–75°C, the pressure at the bottom of the tower is 125–135 kPa, and the temperature at the bottom of the tower is 90–100°C.

[0034] The scrubbing tower has a top pressure of 110–120 kPa and a top temperature of 55–65°C. The bottom pressure is 115–125 kPa and the bottom temperature is 65–75°C.

[0035] The pressure at the top of the azeotropic column is 15-25 kPa, the temperature at the top is 45-55°C, the pressure at the bottom is 25-35 kPa, and the temperature at the bottom is 70-80°C.

[0036] The product column has a top pressure of 1–5 kPa and a top temperature of 45–55°C. The bottom pressure is 10–20 kPa and the bottom temperature is 85–95°C.

[0037] In a specific implementation, the azeotropic agent in the above-mentioned acrylic acid refining process is toluene.

[0038] The acrylic acid refining system and process provided by the present invention obtains a high-concentration acrylic acid product in the side stream of the product tower, wherein the concentration of acrylic acid in the high-concentration acrylic acid product is greater than 99.5 wt%; and discharges tail gas at the top of the washing tower, wherein the concentration of acrylic acid in the tail gas is ≤200 ppm.

[0039] The beneficial technical effects of the present invention include at least the following:

[0040] 1. By adjusting the top temperature of the scrubbing tower (C-120) and re-spraying the aqueous phase of the azeotropic tower (C-130), the acrylic acid content at the top of the tower can be controlled to be less than 200 ppm.

[0041] 2. The acrylic acid solution in the bottom of the light-light removal tower (C-110) is cooled by passing it through the intermediate reboiler (E-103) of the product tower before entering the top of the product tower, thus reducing energy consumption.

[0042] 3. By using an acrylic acid solution containing acetic acid as a quenching medium (coolant) and an aqueous acetic acid solution as an absorbent for acrylic acid absorption, the consumption of fresh water and wastewater treatment costs are reduced, resulting in increased efficiency. Attached Figure Description

[0043] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0044] Figure 1 This is a schematic diagram of the acrylic acid refining process disclosed in an embodiment of the present invention;

[0045] Among them, C-110 is the light component removal tower, C-120 is the washing tower, C-130 is the azeotropic tower, C-210 is the product tower, E-102 is the washing tower circulating cooler, E-103 is the product tower intermediate reboiler, E-105 is the azeotropic tower condenser, E-106 is the azeotropic tower aftercooler, E-201 is the product tower condenser, E-202 is the product tower aftercooler, P-102 is the washing tower top circulating pump, P-103 is the azeotropic tower azeotropic agent pump, P-104 is the aqueous phase pump, P-106 is the azeotropic tower bottom pump, P-107 is the azeotropic agent pump, P-201 is the product tower reflux pump, P-203 is the product tower bottom pump, V-101 is the azeotropic tower reflux tank, V-102 is the azeotropic agent tank, and V-201 is the product tower reflux tank. Detailed Implementation

[0046] The present invention will be further illustrated below with specific examples.

[0047] Example 1

[0048] like Figure 1 The diagram shows an acrylic acid refining process, including a light-removal tower (C-110), a washing tower (C-120), an azeotropic tower (C-130), and a product tower (C-210).

[0049] (1) Light weight removal tower (C-110): Tower top pressure 115KPa, tower top temperature 70℃, tower bottom pressure 125KPa, tower bottom temperature 90℃.

[0050] The reaction gas from the acrylic acid reaction system enters the bottom of the light-light-removal tower (C-110) and comes into countercurrent contact with the crude acrylic acid solution containing acetic acid and water, which has undergone two-stage condensation from the top of the product tower (C-210) at the bottom of the light-light-removal tower (C-110). The crude acrylic acid solution containing acetic acid and water acts as a coolant, and the reaction gas is rapidly cooled by the coolant. The acrylic acid in the reaction gas is cooled into an acrylic acid solution and remains in the bottom of the light-light-removal tower (C-110). The gas in the reaction gas that has not been cooled and liquefied rises to the top of the light-light-removal tower (C-110) and then enters the bottom of the scrubbing tower (C-120).

[0051] (2) Scrubber (C-120): Top pressure 110KPa, top temperature 55℃, bottom pressure 115KPa, bottom temperature 65℃.

[0052] Gas from the top of the light-light removal tower (C-110) enters the bottom of the scrubbing tower (C-120). Acrylic acid in the gas is absorbed by the cooled acetic acid aqueous solution (absorbent) in the scrubbing tower (C-120). The unabsorbed gas is discharged from the top of the scrubbing tower (C-120) as tail gas, with an acrylic acid content of 140 ppm, and enters the waste gas treatment unit. The acetic acid aqueous solution in the upper part of the light-light removal tower (C-110) is extracted by the scrubbing tower top circulation pump (P-102), cooled by the scrubbing tower circulation cooler (E-102), and returned to the scrubbing tower (C-120) as an absorbent. The bottom of the light-light removal tower (C-110) yields a bottom liquid containing acrylic acid, acetic acid, and water.

[0053] (3) Azeotropic tower (C-130): Top pressure 15KPa, top temperature 45℃, bottom pressure 25KPa, bottom temperature 70℃.

[0054] The bottom liquid of the light-removal tower (C-110) enters the azeotropic tower (C-130), where it mixes with the azeotropic agent to remove acetic acid and water through azeotropic extraction. The bottom liquid of the azeotropic tower (C-130) contains acrylic acid. The gas from the top of the azeotropic tower (C-130) undergoes two stages of condensation in the azeotropic tower condenser (E-105) and aftercooler (E-106). The uncondensed gas enters the vacuum system, and the resulting liquid is transferred to the azeotropic tower reflux tank (V-101) for stratification. The aqueous phase containing acetic acid that separates from the azeotropic tower reflux tank (V-101) is returned to the top of the scrubbing tower (C-120) via the azeotropic tower aqueous phase pump (P-104). The acrylic acid is sprayed again to absorb the gas. The oil phase containing the azeotropic agent separated from the azeotropic tower reflux tank (V-101) is pumped into the azeotropic agent tank (V-102) through the azeotropic agent pump (P-103), where it is mixed with the azeotropic agent added to the azeotropic agent tank (V-102). The mixture is then pumped back to the azeotropic tower (C-130) through the azeotropic agent pump (P-107). The azeotropic agent is toluene. The bottom liquid of the azeotropic tower (C-130) is returned to the top of the light-light removal tower (C-110), and after passing through the trays of the light-light removal tower (C-110), it falls back to the bottom of the light-light removal tower (C-110) and mixes with the condensed acrylic acid solution in the bottom of the light-light removal tower as the bottom liquid of the light-light removal tower.

[0055] (4) Product tower (C-210): Top pressure 1KPa, top temperature 45℃, bottom pressure 10KPa, bottom temperature 85℃.

[0056] The liquid in the bottom of the light component removal tower (C-110) is cooled by passing through the intermediate reboiler (E-103) of the product tower and then enters the top of the product tower (C-210) as reflux. The gas at the top of the product tower (C-210) undergoes two stages of condensation in the product tower condenser (E-201) and the product tower aftercooler (E-202). The uncondensed gas enters the vacuum system, and the liquid obtained from the condensation enters the product tower reflux tank (V-201), which is a crude acrylic acid solution containing acetic acid and water. The product is then pumped back to the bottom of the light component removal tower (C-110) via the product tower reflux pump (P-201) as a coolant. The bottom liquid of the product tower (C-210) is pumped to the thin-film evaporator via the product tower bottom pump (P-203) to remove heavy component impurities. The gas evaporated by the thin-film evaporator is returned to the bottom of the product tower (C-210) and circulated within the product tower. A high-concentration acrylic acid product with a purity of 99.79 wt% is obtained from the side stream of the product tower (C-210).

[0057] Example 2

[0058] like Figure 1 The diagram shows an acrylic acid refining process, including a light-removal tower (C-110), a washing tower (C-120), an azeotropic tower (C-130), and a product tower (C-210).

[0059] (1) Light weight removal tower (C-110): Tower top pressure 125KPa, tower top temperature 75℃, tower bottom pressure 135KPa, tower bottom temperature 100℃.

[0060] The reaction gas from the acrylic acid reaction system enters the bottom of the light-light-removal tower (C-110) and comes into countercurrent contact with the crude acrylic acid solution containing acetic acid and water, which has undergone two-stage condensation from the top of the product tower (C-210) at the bottom of the light-light-removal tower (C-110). The crude acrylic acid solution containing acetic acid and water acts as a coolant, and the reaction gas is rapidly cooled by the coolant. The acrylic acid in the reaction gas is cooled into an acrylic acid solution and remains in the bottom of the light-light-removal tower (C-110). The gas in the reaction gas that has not been cooled and liquefied rises to the top of the light-light-removal tower (C-110) and then enters the bottom of the scrubbing tower (C-120).

[0061] (2) Scrubber (C-120): Top pressure 120KPa, top temperature 65℃, bottom pressure 125KPa, bottom temperature 75℃.

[0062] Gas from the top of the light-light removal tower (C-110) enters the bottom of the scrubbing tower (C-120). Acrylic acid in the gas is absorbed by the cooled acetic acid aqueous solution (absorbent) in the scrubbing tower (C-120). The unabsorbed gas is discharged from the top of the scrubbing tower (C-120) as tail gas, with an acrylic acid content of 170 ppm, and enters the waste gas treatment unit. The acetic acid aqueous solution in the upper part of the light-light removal tower (C-110) is extracted by the scrubbing tower top circulation pump (P-102), cooled by the scrubbing tower circulation cooler (E-102), and returned to the scrubbing tower (C-120) as an absorbent. The bottom of the light-light removal tower (C-110) yields a bottom liquid containing acrylic acid, acetic acid, and water.

[0063] (3) Azeotropic tower (C-130): Top pressure 25KPa, top temperature 55℃, bottom pressure 35KPa, bottom temperature 80℃.

[0064] The bottom liquid of the light-removal tower (C-110) enters the azeotropic tower (C-130), where it mixes with the azeotropic agent to remove acetic acid and water through azeotropic extraction. The bottom liquid of the azeotropic tower (C-130) contains acrylic acid. The gas from the top of the azeotropic tower (C-130) undergoes two stages of condensation in the azeotropic tower condenser (E-105) and aftercooler (E-106). The uncondensed gas enters the vacuum system, and the resulting liquid is transferred to the azeotropic tower reflux tank (V-101) for stratification. The aqueous phase containing acetic acid that separates from the azeotropic tower reflux tank (V-101) is returned to the top of the scrubbing tower (C-120) via the azeotropic tower aqueous phase pump (P-104). The acrylic acid is sprayed again to absorb the gas. The oil phase containing the azeotropic agent separated from the azeotropic tower reflux tank (V-101) is pumped into the azeotropic agent tank (V-102) through the azeotropic agent pump (P-103), where it is mixed with the azeotropic agent added to the azeotropic agent tank (V-102). The mixture is then pumped back to the azeotropic tower (C-130) through the azeotropic agent pump (P-107). The azeotropic agent is toluene. The bottom liquid of the azeotropic tower (C-130) is returned to the top of the light-light removal tower (C-110), and after passing through the trays of the light-light removal tower (C-110), it falls back to the bottom of the light-light removal tower (C-110) and mixes with the condensed acrylic acid solution in the bottom of the light-light removal tower as the bottom liquid of the light-light removal tower.

[0065] (4) Product tower (C-210): Top pressure 5KPa, top temperature 55℃, bottom pressure 20KPa, bottom temperature 95℃.

[0066] The liquid in the bottom of the light component removal tower (C-110) is cooled by passing through the intermediate reboiler (E-103) of the product tower and then enters the top of the product tower (C-210) as reflux. The gas at the top of the product tower (C-210) undergoes two stages of condensation in the product tower condenser (E-201) and the product tower aftercooler (E-202). The uncondensed gas enters the vacuum system, and the liquid obtained from the condensation enters the product tower reflux tank (V-201), which is a crude acrylic acid solution containing acetic acid and water. The product is then pumped back to the bottom of the light component removal tower (C-110) via the product tower reflux pump (P-201) as a coolant. The bottom liquid of the product tower (C-210) is pumped to the thin-film evaporator via the product tower bottom pump (P-203) to remove heavy component impurities. The gas evaporated by the thin-film evaporator is returned to the bottom of the product tower (C-210) and circulated within the product tower. A high-concentration acrylic acid product with a purity of 99.75 wt% is obtained from the side stream of the product tower (C-210).

[0067] Example 3

[0068] like Figure 1 The diagram shows a new process for refining acrylic acid, including a light-removal tower (C-110), a washing tower (C-120), an azeotropic tower (C-130), and a product tower (C-210).

[0069] (1) Light weight removal tower (C-110): Tower top pressure 120KPa, tower top temperature 73℃, tower bottom pressure 130KPa, tower bottom temperature 95℃.

[0070] The reaction gas from the acrylic acid reaction system enters the bottom of the light-light-removal tower (C-110) and comes into countercurrent contact with the crude acrylic acid solution containing acetic acid and water, which has undergone two-stage condensation from the top of the product tower (C-210) at the bottom of the light-light-removal tower (C-110). The crude acrylic acid solution containing acetic acid and water acts as a coolant, and the reaction gas is rapidly cooled by the coolant. The acrylic acid in the reaction gas is cooled into an acrylic acid solution and remains in the bottom of the light-light-removal tower (C-110). The gas in the reaction gas that has not been cooled and liquefied rises to the top of the light-light-removal tower (C-110) and then enters the bottom of the scrubbing tower (C-120).

[0071] (2) Scrubber (C-120): Top pressure 114KPa, top temperature 58℃, bottom pressure 119KPa, bottom temperature 72℃.

[0072] Gas from the top of the light-light removal tower (C-110) enters the bottom of the scrubbing tower (C-120). Acrylic acid in the gas is absorbed by the cooled acetic acid aqueous solution (absorbent) in the scrubbing tower (C-120). The unabsorbed gas is discharged from the top of the scrubbing tower (C-120) as tail gas, with an acrylic acid content of 160 ppm, and enters the waste gas treatment unit. The acetic acid aqueous solution in the upper part of the light-light removal tower (C-110) is extracted by the scrubbing tower top circulation pump (P-102), cooled by the scrubbing tower circulation cooler (E-102), and returned to the scrubbing tower (C-120) as an absorbent. The bottom of the light-light removal tower (C-110) yields a bottom liquid containing acrylic acid, acetic acid, and water.

[0073] (3) Azeotropic tower (C-130): Top pressure 20KPa, top temperature 50℃, bottom pressure 30KPa, bottom temperature 73℃.

[0074] The bottom liquid of the light-removal tower (C-110) enters the azeotropic tower (C-130), where it mixes with the azeotropic agent to remove acetic acid and water through azeotropic extraction. The bottom liquid of the azeotropic tower (C-130) contains acrylic acid. The gas from the top of the azeotropic tower (C-130) undergoes two stages of condensation in the azeotropic tower condenser (E-105) and aftercooler (E-106). The uncondensed gas enters the vacuum system, and the resulting liquid is transferred to the azeotropic tower reflux tank (V-101) for stratification. The aqueous phase containing acetic acid that separates from the azeotropic tower reflux tank (V-101) is returned to the top of the scrubbing tower (C-120) via the azeotropic tower aqueous phase pump (P-104). The acrylic acid is sprayed again to absorb the gas. The oil phase containing the azeotropic agent separated from the azeotropic tower reflux tank (V-101) is pumped into the azeotropic agent tank (V-102) through the azeotropic agent pump (P-103), where it is mixed with the azeotropic agent added to the azeotropic agent tank (V-102). The mixture is then pumped back to the azeotropic tower (C-130) through the azeotropic agent pump (P-107). The azeotropic agent is toluene. The bottom liquid of the azeotropic tower (C-130) is returned to the top of the light-light removal tower (C-110), and after passing through the trays of the light-light removal tower (C-110), it falls back to the bottom of the light-light removal tower (C-110) and mixes with the condensed acrylic acid solution in the bottom of the light-light removal tower as the bottom liquid of the light-light removal tower.

[0075] (4) Product tower (C-210): Top pressure 3KPa, top temperature 52℃, bottom pressure 15KPa, bottom temperature 90℃.

[0076] The liquid in the bottom of the light component removal tower (C-110) is cooled by passing through the intermediate reboiler (E-103) of the product tower and then enters the top of the product tower (C-210) as reflux. The gas at the top of the product tower (C-210) undergoes two stages of condensation in the product tower condenser (E-201) and the product tower aftercooler (E-202). The uncondensed gas enters the vacuum system, and the liquid obtained from the condensation enters the product tower reflux tank (V-201), which is a crude acrylic acid solution containing acetic acid and water. The product is then pumped back to the bottom of the light component removal tower (C-110) via the product tower reflux pump (P-201) as a coolant. The bottom liquid of the product tower (C-210) is pumped to the thin-film evaporator via the product tower bottom pump (P-203) to remove heavy component impurities. The gas evaporated by the thin-film evaporator is returned to the bottom of the product tower (C-210) and circulated within the product tower. A high-concentration acrylic acid product with a purity of 99.77 wt% is obtained from the side stream of the product tower (C-210).

[0077] As can be seen from the above embodiments, the acrylic acid refining system and process provided by the present invention obtains a high-concentration acrylic acid product in the side stream of the product tower, wherein the concentration of acrylic acid in the high-concentration acrylic acid product is greater than 99.5 wt%; and discharges tail gas at the top of the washing tower, wherein the concentration of acrylic acid in the tail gas is ≤200 ppm.

[0078] The beneficial technical effects of the present invention include at least the following:

[0079] 1. By adjusting the top temperature of the scrubbing tower (C-120) and re-spraying the aqueous phase of the azeotropic tower (C-130), the acrylic acid content at the top of the tower can be controlled to be less than 200 ppm.

[0080] 2. The acrylic acid solution in the bottom of the light-light removal tower (C-110) is cooled by passing it through the intermediate reboiler (E-103) of the product tower before entering the top of the product tower, thus reducing energy consumption.

[0081] 3. By using an acrylic acid solution containing acetic acid as a quenching medium (coolant) and an aqueous acetic acid solution as an absorbent for acrylic acid absorption, the consumption of fresh water and wastewater treatment costs are reduced, resulting in increased efficiency.

[0082] The above description is merely one embodiment of the present invention and is not intended to limit the invention. Those skilled in the art will recognize that the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An acrylic acid refining system, characterized in that, The system includes: In the light-light ... The washing tower, at the top of the light removal tower, the inert gas containing acrylic acid is absorbed by the acetic acid aqueous solution, the tail gas is discharged at the top of the washing tower, and the bottom liquid containing acrylic acid, acetic acid and water is obtained at the bottom of the washing tower. In the azeotropic tower, the bottom liquid of the washing tower is azeotropically removed from acetic acid and water. The bottom liquid obtained in the azeotropic tower is returned to the top of the light-light removal tower, and after passing through the tray of the light-light removal tower, it falls back to the bottom of the light-light removal tower and mixes with the condensed acrylic acid solution in the bottom of the light-light removal tower as the bottom liquid of the light-light removal tower. In the product tower, the bottom liquid of the light-light removal tower is further decomposed to remove acetic acid and water. A refined acrylic acid product is obtained on the side stream of the product tower, and a gas containing acrylic acid, acetic acid and water is obtained at the top of the tower. After condensation, the gas is returned to the light-light removal tower as a coolant.

2. The acrylic acid refining system of claim 1, characterized in that, Also includes: Intermediate reboiler for product column: The bottom liquid of the light component removal column is cooled by passing through the intermediate reboiler for product column before entering the product column; Product tower condenser and product tower aftercooler: The gas containing acrylic acid, acetic acid and water at the top of the product tower is cooled by the product tower condenser and product tower aftercooler to obtain a crude acrylic acid solution containing acetic acid and water, which is then used as a coolant in the light-weight removal tower.

3. The acrylic acid refining system of claim 1, characterized in that, Also includes: Washing tower circulating cooler: The acetic acid aqueous solution in the upper part of the washing tower is cooled by the washing tower circulating cooler and then returned to the washing tower.

4. The acrylic acid refining system of claim 1, characterized in that, Also includes: Azeotropic column condenser and azeotropic column aftercooler: The gas containing acetic acid, water and azeotropic agent obtained from the top of the azeotropic column is cooled by the azeotropic column condenser and azeotropic column aftercooler to obtain a coolant; Azeotropic tower reflux tank: The coolant obtained from the azeotropic tower condenser and the azeotropic tower aftercooler is separated into layers in the azeotropic tower reflux tank. The aqueous phase containing acetic acid obtained from the separation enters the washing tower; the oil phase containing azeotropic agent obtained from the separation returns to the azeotropic tower together with the newly added azeotropic agent.

5. Acrylic acid refining process, characterized in that, Operating in any one of the acrylic acid refining systems described in claims 1-4, the acrylic acid refining process includes: The reaction gas from the acrylic acid reaction system enters the bottom of the light-light-removal tower and comes into countercurrent contact with the coolant from the top of the product tower at the bottom of the light-light-removal tower. The acrylic acid in the reaction gas is cooled into an acrylic acid solution and remains in the bottom of the light-light-removal tower. The gas in the reaction gas that has not been cooled and liquefied rises to the top of the light-light-removal tower. The gas at the top of the light removal tower enters the bottom of the scrubbing tower. The acrylic acid in the gas is absorbed by the acetic acid aqueous solution in the scrubbing tower. The unabsorbed gas is discharged from the top of the scrubbing tower as tail gas. The bottom liquid containing acrylic acid, acetic acid and water is obtained in the bottom of the scrubbing tower. The bottom liquid of the light-light removal tower enters the azeotropic tower and mixes with the azeotropic agent in the azeotropic tower to remove acetic acid and water through azeotropy. The bottom liquid of the azeotropic tower containing acrylic acid is obtained. The bottom liquid of the azeotropic tower enters the top of the light-light removal tower, falls back to the bottom of the light-light removal tower after passing through the tower plate of the light-light removal tower, and mixes with the condensed acrylic acid solution in the bottom of the light-light removal tower as the bottom liquid of the light-light removal tower. The liquid at the bottom of the light-light removal tower enters the product tower, where acetic acid and water are further removed. Refined acrylic acid is obtained from the side stream of the light-light removal tower, and a gas containing acrylic acid, acetic acid, and water is obtained at the top of the tower. After condensation, the gas returns to the light-light removal tower as a coolant.

6. The acrylic acid refining process according to claim 5, characterized in that, Also includes: The liquid in the bottom of the light-light-removal tower is cooled by passing it through the intermediate reboiler of the product tower before entering the product tower. The gas containing acrylic acid, acetic acid, and water at the top of the product tower enters the product tower condenser and product tower aftercooler for cooling, resulting in a crude acrylic acid solution containing acetic acid and water, which then enters the light-weight removal tower as a coolant.

7. The acrylic acid refining process according to claim 5, characterized in that, Also includes: The acetic acid aqueous solution at the top of the washing tower is cooled by the washing tower circulating cooler and then returned to the washing tower.

8. The acrylic acid refining process according to claim 5, characterized in that, Also includes: The gas containing acetic acid, water and azeotropic agent obtained from the top of the azeotropic tower enters the azeotropic tower condenser and the azeotropic tower aftercooler for cooling to obtain a coolant; The coolant enters the reflux tank of the azeotropic tower and separates into layers. The aqueous phase containing acetic acid obtained from the separation enters the washing tower to absorb the acrylic acid. The oil phase containing the azeotropic agent obtained from the separation returns to the azeotropic tower together with the newly added azeotropic agent.

9. The acrylic acid refining process according to any one of claims 5-8, characterized in that, The pressure at the top of the light-weight removal tower is 115–125 kPa, the temperature at the top of the tower is 70–75°C, the pressure at the bottom of the tower is 125–135 kPa, and the temperature at the bottom of the tower is 90–100°C. The scrubbing tower has a top pressure of 110–120 kPa and a top temperature of 55–65°C. The bottom pressure is 115–125 kPa and the bottom temperature is 65–75°C. The pressure at the top of the azeotropic column is 15-25 kPa, the temperature at the top is 45-55°C, the pressure at the bottom is 25-35 kPa, and the temperature at the bottom is 70-80°C. The product column has a top pressure of 1–5 kPa and a top temperature of 45–55°C. The bottom pressure is 10–20 kPa and the bottom temperature is 85–95°C.

10. The acrylic acid refining process according to any one of claims 5-8, characterized in that, The azeotropic agent is toluene.

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