Device and method for pressure-swing distillation of acrylic acid mixture using heat-integrated double towers

Abstract

The present application discloses a device and method for pressure-swing distillation of acrylic acid mixture using heat-integrated double towers, including a mixing tank, an atmospheric tower, a tower top heat exchanger, an atmospheric tower diversion tank, a pressure-swing tower heat exchanger, a gas-liquid separation tank and a pressure-swing tower. The unique double-tower pressure-swing distillation design and heat-integrated concept are adopted. By introducing two independent operating units, the atmospheric tower and the pressure-swing tower, the limitation of water-acrylic acid azeotrope is effectively broken. Even if the content of acrylic acid in the raw material is not high, high-quality acrylic acid products with a purity of up to 99.93% and a recovery rate of 99.93% can still be produced; at the same time, energy consumption is reduced, and additional cooling devices are avoided, making the entire system more compact and easy to manage, ensuring the stability and reliability of the system, not easily disturbed by external factors, and conducive to long-term continuous operation.

Description

Technical Field

[0001] The present application relates to the technical field of chemical separation and purification, and in particular to a device and method for pressure-swing distillation of acrylic acid mixture using a heat-integrated double-tower. Background Art

[0002] Acrylic acid is an important chemical raw material and an important monomer for synthetic resins. Its main derivatives are various acrylates and acrylate salts. The most famous ester and salt products are methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate and sodium acrylate. Since acrylic acid molecules have unsaturated double bonds and carboxyl functional groups, they can undergo copolymerization and homopolymerization reactions with many monomers. They are used as raw materials for coatings, adhesives and various additives, and are widely used in industries and fields such as chemicals, light industry, textiles, building materials and medicine.

[0003] Industrial production method of acrylic acid: In industry, acrylic acid is mainly prepared by formaldehyde acetaldehyde condensation method, propylene ether thermal decomposition method, glycerol dehydration method and propylene oxidation method. Water and acrylic acid will form an azeotrope under normal pressure. The azeotropic composition contains 19.6% water and its azeotropic point is 84.1℃. Due to the presence of azeotropes in the mixture, it is impossible to achieve effective separation by simple distillation method.

[0004] In order to improve the separation efficiency, the prior art often uses a multi-tower system to improve the separation effect. For example, patents CN115738333A and CN218793944U both use a three-tower separation process to obtain the product acrylic acid through distillation separation, but such a system increases the complexity and maintenance difficulty of the equipment, and also has a higher energy demand; moreover, when the mixture to be separated of different concentrations enters the system, more complex operation adjustments are required to achieve the best separation effect. Patent CN1321968C adopts a method for purifying acrylic acid by azeotropic distillation, but it is necessary to add an entrainer, which will introduce additional operating steps and require a special recovery process to remove the entrainer, which will also increase the complexity of the system, and the addition and separation process of the entrainer will also increase additional energy consumption, and this azeotropic distillation method is highly dependent on a specific type of entrainer. If the feed composition changes, it is necessary to reselect a suitable entrainer, which limits its application. Although the prior art provides many methods for treating azeotropes, there is still a problem that the azeotropic phenomenon cannot be completely avoided in some cases. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present application is to provide a device and method for pressure swing distillation of an acrylic acid mixture using a heat-integrated double-tower, so as to solve the problems in the prior art of high complexity of separation equipment, great difficulty in maintenance, high energy consumption, many system operation steps, high system complexity, reliance on the use of entrainer, and selection of entrainer caused by changes in feed composition.

[0006] In order to solve the above technical problems, this application adopts the following technical solutions:

[0007] A device for pressure-swing distillation of acrylic acid mixture using heat-integrated double towers comprises a mixing tank, an atmospheric tower, a tower top heat exchanger, an atmospheric tower diverter tank, a pressure-swing tower heat exchanger, a gas-liquid separation tank and a pressure-swing tower; wherein a crude acrylic acid aqueous solution enters from the top of the mixing tank, and the mixing tank is fluidly connected to the atmospheric tower; the top of the atmospheric tower is fluidly connected to the tower top heat exchanger, the tower top heat exchanger is fluidly connected to the atmospheric tower diverter tank, the top of the atmospheric tower diverter tank is fluidly connected to the atmospheric tower top, and the bottom of the atmospheric tower diverter tank is fluidly connected to the pressure-swing tower top; the tower top heat exchanger is fluidly connected to the pressure-swing tower heat exchanger, the pressure-swing tower heat exchanger is fluidly connected to the gas-liquid separation tank, the top of the gas-liquid separation tank is fluidly connected to the bottom of the pressure-swing tower, and the bottom of the gas-liquid separation tank is fluidly connected to the bottom of the mixing tank through a reflux pump; the bottom of the pressure-swing tower is fluidly connected to the tower top heat exchanger; acrylic acid is extracted from the bottom of the atmospheric tower, and the pressure-swing tower distillate is extracted from the top of the pressure-swing tower.

[0008] Preferably, the atmospheric tower reboiler is further included, and the bottom distillate of the atmospheric tower returns to the atmospheric tower after passing through the atmospheric tower reboiler.

[0009] Preferably, a transformer tower condenser is further included, and the top distillate of the transformer tower passes through the transformer tower condenser and then returns to the transformer tower from the top of the transformer tower.

[0010] Preferably, the atmospheric tower has 20 to 50 plates, and the feed plate is one of the 10th to 30th plates; the transformer tower has 15 to 40 plates, and the feed plate is one of the 5th to 20th plates.

[0011] The present application provides a method for pressure-swing distillation of acrylic acid mixture using a heat-integrated double-tower, the method using the above-mentioned device, and the method specifically includes the following loops:

[0012] Circuit 1: Crude acrylic acid aqueous solution enters from the top of the mixing tank, and then the mixed material fluid in the mixing tank enters the atmospheric pressure tower for distillation, and acrylic acid is extracted from the bottom of the atmospheric pressure tower;

[0013] Loop 2: The top effluent of the atmospheric tower enters the top heat exchanger for heat exchange, and then enters the atmospheric tower split tank. The first split stream of the atmospheric tower split tank flows out from the tank top, enters from the top of the atmospheric tower, and returns to the atmospheric tower; the second split stream of the atmospheric tower split tank enters from the top of the transformer tower into the transformer tower;

[0014] Loop 3: The bottom distillate of the transformer tower enters the tower top heat exchanger, exchanges heat with the tower top effluent, enters the transformer tower heat exchanger for heat exchange, and then enters the gas-liquid separation tank; the transformer tower top liquid condensate is extracted from the transformer tower top;

[0015] Loop 4: The gas phase separated in the gas-liquid separation tank enters the transformer tower from the bottom of the transformer tower, and the separated liquid phase leaves from the bottom of the gas-liquid separation tank, returns to the mixing tank through the reflux pump, and mixes with the crude acrylic acid aqueous solution.

[0016] Preferably, the bottom distillate of the atmospheric tower enters the atmospheric tower reboiler and then returns to the atmospheric tower, and the atmospheric tower reboiler provides heat for the atmospheric tower.

[0017] Preferably, the overhead distillate of the transformer tower passes through a transformer tower condenser and then returns to the transformer tower from the top of the transformer tower.

[0018] Preferably, the top temperature of the atmospheric tower is 82°C-100°C, and the bottom temperature is 123°C-140°C; the top temperature of the pressure-changing tower is 33°C-46°C, and the bottom temperature is 46°C-54°C.

[0019] Preferably, the mass fraction of acrylic acid in the water-acrylic acid mixture to be separated entering the mixing tank (1) is less than 33%.

[0020] Preferably, the pressure of the atmospheric tower is 0.1-0.15 MPa, and the reflux ratio is 0.6-0.7; the pressure of the transformer tower is 0.01-0.08 MPa, and the reflux ratio is 2.8-2.9.

[0021] Compared with the prior art, this application has the following beneficial effects:

[0022] 1. The core of the present application is the unique double-tower pressure swing distillation design. Different from the traditional single-tower and heat pump distillation system, the present application effectively breaks the limitation of water-acrylic acid azeotrope by introducing two independent operating units, namely the atmospheric pressure tower and the pressure swing tower, and combines precise pressure control. The atmospheric pressure tower is used for preliminary separation, and then the pressure swing tower is used for further separation, thereby ensuring the high purity of the final product. Even if the content of acrylic acid in the raw material is not high, the present application can still produce high-quality acrylic acid products with a purity of up to 99.93% and a recovery rate of 99.93%, which provides purer raw materials for subsequent processing and reduces the impact of impurities on the production process.

[0023] 2. This application has made bold innovations in equipment design and adopted the concept of heat integration, which greatly simplifies the complexity and maintenance costs of the system. Traditional multi-tower systems often require complex pipeline connections and control logic, which increases the investment and operation risks of equipment. In contrast, this application achieves effective recovery and reuse of heat by optimizing the heat exchange network, reducing the need for external heating sources. For example, the heat exchange between the top effluent of the atmospheric tower and the liquid at the bottom of the transformer tower not only reduces energy consumption, but also avoids additional cooling devices, making the entire system more compact and easy to manage. At the same time, this application finely controls the operating parameters in the atmospheric tower and the transformer tower to ensure the stability and reliability of the system, which is not easily disturbed by external factors and is conducive to long-term continuous operation.

[0024] 3. The device and method described in this application also have excellent operational flexibility. Traditional distillation methods usually require customized designs for specific types of raw materials. Once the feed composition changes, the process parameters need to be readjusted, and even the equipment needs to be replaced. This application can maintain good separation performance within a wider operating window by adjusting the operating conditions of the atmospheric tower and the transformer tower (such as reflux ratio, feed position, etc.). This means that no matter how the initial concentration of acrylic acid in the feed changes, this application can adapt quickly, enter the optimal separation state in time, and maintain the optimal operating state. This flexibility not only improves the adaptability of the system, especially when dealing with feeds of different concentrations, the advantages shown by this application are particularly obvious, and it has great industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic structural diagram of a device for pressure-swing distillation of acrylic acid mixture using a heat-integrated double-tower system according to the present application.

[0026] In the figure: mixing tank 1, atmospheric tower 2, atmospheric tower reboiler 3, tower top heat exchanger 4, atmospheric tower diversion tank 5, transformer tower heat exchanger 6, gas-liquid separation tank 7, transformer tower 8, transformer tower condenser 9, reflux pump 10, crude acrylic acid aqueous solution A, tower top effluent B, first diversion stream C, acrylic acid D, transformer tower top liquid phase condensate E, tower bottom distillate F, liquid phase G. DETAILED DESCRIPTION

[0027] This application will combine the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on this application belong to the scope of protection of this application.

[0028] Unless otherwise indicated in specific cases in this application, the numerical ranges listed herein include the upper and lower limits, as well as all integers and fractions within the range, and are not limited to the specific values ​​listed when defining the range.

[0029] 1. A device for pressure-swing distillation of acrylic acid mixture using heat-integrated double towers

[0030] The device described in the present application comprises a mixing tank 1, an atmospheric tower 2, a tower top heat exchanger 4, an atmospheric tower splitter tank 5, a transformer tower heat exchanger 6, a gas-liquid separation tank 7 and a transformer tower 8;

[0031] The crude acrylic acid aqueous solution A enters from the top of the mixing tank 1, and the mixing tank 1 is fluidly connected to the atmospheric tower 2; the top of the atmospheric tower 2 is fluidly connected to the tower top heat exchanger 4, the tower top heat exchanger 4 is fluidly connected to the atmospheric tower diversion tank 5, the top of the atmospheric tower diversion tank 5 is fluidly connected to the atmospheric tower top, and the bottom of the atmospheric tower diversion tank 5 is fluidly connected to the top of the transformer tower 8; the tower top heat exchanger 4 is fluidly connected to the transformer tower heat exchanger 6, the transformer tower heat exchanger 6 is fluidly connected to the gas-liquid separation tank 7, the top of the gas-liquid separation tank 7 is fluidly connected to the bottom of the transformer tower 8, and the bottom of the gas-liquid separation tank 7 is fluidly connected to the bottom of the mixing tank 1 through a reflux pump 10; the bottom of the transformer tower 8 is fluidly connected to the tower top heat exchanger 4; acrylic acid D is produced from the bottom of the atmospheric tower 2, and the transformer tower overhead distillate E is produced from the top of the transformer tower 8.

[0032] The present application found in the study of the separation technology of water-acrylic acid azeotrope formation that the idea of ​​traditional distillation methods to solve this technical problem is often to use multiple towers in series or introduce an azeotropic agent to achieve separation. In order to solve this problem, the present application considers introducing the design concept of double-tower pressure-swing distillation, by combining the atmospheric pressure tower and the pressure-swing tower, and using the phase equilibrium difference under different pressure conditions to break the limitation of the water-acrylic acid azeotrope. The atmospheric pressure tower is used for preliminary separation, and the material after preliminary separation is sent to the pressure-swing tower, so that it can further purify acrylic acid under a lower pressure to ensure the high purity of the final product. At the same time, the present application also considers the problem of energy consumption. Traditional multi-tower distillation systems usually require a large amount of external heating sources to maintain the operating temperature of each tower, resulting in high energy consumption. To this end, the present application realizes the effective recovery and reuse of heat by introducing a heat integration design, which significantly reduces the overall energy consumption. Heat exchange is carried out between the atmospheric pressure tower top effluent and the pressure-swing tower bottom liquid, reducing the demand for external heating sources. In addition, the energy efficiency is further improved by finely regulating the operating parameters (such as temperature and pressure) in each tower. This application also takes into account the stability of the entire system and operational flexibility, because traditional distillation processes are usually customized for specific types of raw materials. Once the feed composition changes, the process parameters need to be readjusted, and sometimes even equipment needs to be replaced. This application can maintain good separation performance within a wider operating window by adjusting the operating conditions of the atmospheric tower and the transformer tower (such as reflux ratio, feed position, etc.). Regardless of how the initial concentration of acrylic acid in the feed changes, this application can quickly adapt and enter the optimal separation state, thereby maintaining the optimal operating state. This flexibility improves the adaptability of the system, especially when the feed concentration changes, making this application more adaptable to industrial application scenarios.

[0033] In some embodiments of the present application, an atmospheric tower reboiler 3 is further included, and the bottom distillate of the atmospheric tower 2 is returned to the atmospheric tower after passing through the atmospheric tower reboiler. The present application uses the atmospheric tower reboiler to provide heat for the entire atmospheric tower.

[0034] In some embodiments of the present application, a transformer tower condenser 9 is further included, and the top distillate of the transformer tower 8 returns to the transformer tower from the top of the transformer tower after passing through the transformer tower condenser.

[0035] In some embodiments of the present application, the number of plates of the atmospheric tower is 20 to 50, and the feed plate is one of the 10th to 30th plates. The number of plates of the transformer tower is 15 to 40, and the feed plate is one of the 5th to 20th plates. The distillation tower is designed according to the prior art, wherein the feed plates of the atmospheric tower and the transformer tower are both counted from the top of the tower, that is, counting from the top of the atmospheric tower, one of the 10th to 30th plates is the feed plate, and the transformer tower is the same by analogy.

[0036] 2. A method for pressure-swing distillation of acrylic acid mixture using heat-integrated double towers

[0037] The method described in the present application adopts the above-mentioned device, and the method specifically includes the following circuit:

[0038] Loop 1: Crude acrylic acid aqueous solution A enters from the top of mixing tank 1, and at the same time, the liquid phase G produced by loop 4 will also enter the mixing tank 1 and mix with the crude acrylic acid aqueous solution A in the mixing tank 1. Then the mixed material fluid in the mixing tank 1 enters the atmospheric pressure tower 2 for distillation, and acrylic acid D is extracted from the bottom of the atmospheric pressure tower 2. In this process, the role of the atmospheric pressure tower 2 is to use the volatility difference between different components to achieve effective separation of light and heavy components under lower pressure conditions. Acrylic acid D extracted from the bottom of the tower is a product that has been preliminarily purified and usually has a high purity. It can be directly used as a final product or further processed. Mixing tank 1 ensures the uniformity and stability of the feed, which is crucial for subsequent distillation operations. Uniform feed can improve separation efficiency and reduce fluctuations in the tower, thereby ensuring consistency in product quality. Atmospheric pressure tower 2 operates at a lower pressure, which reduces the difficulty of operation and energy consumption, while avoiding the requirements of high pressure on equipment.

[0039] Loop 2: The top effluent B of the atmospheric tower 2 enters the top heat exchanger 4, exchanges heat with the bottom distillate F of the transformer tower 8, and then the top effluent B enters the atmospheric tower diversion tank 5. The first diversion stream C of the atmospheric tower diversion tank 5 flows out from the top of the atmospheric tower diversion tank 5, enters from the top of the atmospheric tower 2, and returns to the atmospheric tower 2; the second diversion stream of the atmospheric tower diversion tank 5 enters into the transformer tower 8 from the top of the transformer tower 8. The top heat exchanger 4 is used to cool the top effluent B and partially condense it, effectively recovering the heat of the top gas phase, reducing the demand for external cooling sources, and thus reducing energy consumption; at the same time, the first diversion stream C is returned to the atmospheric pressure tower 2 as a reflux liquid, maintaining the material balance and gas-liquid contact in the tower, and enhancing the separation effect. The size of the reflux volume directly affects the mass transfer efficiency in the tower. The present application can improve the purity of the product by adjusting the reflux ratio; the second diversion stream is sent to the transformer tower 8. This step realizes further separation of the mixture under different pressure conditions, breaking through the separation limit of a single tower body.

[0040] Loop 3: The bottom distillate F of the transformer tower 8 enters the top heat exchanger 4, exchanges heat with the top effluent B, enters the transformer tower heat exchanger 6 for heat exchange, and then enters the gas-liquid separation tank 7; the top of the transformer tower 8 produces the top liquid condensate E of the transformer tower. A closed-loop system is formed between the transformer tower 8 and the atmospheric pressure tower 2. The heat transfer is achieved through the top heat exchanger 4, which improves the energy utilization rate and promotes the coordinated work between the two tower bodies, making the separation process more efficient. The transformer tower 8 operates at a higher pressure and can more thoroughly separate the light components, especially those components that are easy to form azeotropes under normal pressure. After two heat exchanges, the bottom distillate F has a lower temperature, which is conducive to the subsequent gas-liquid separation; the gas-liquid separation tank 7 is used to separate the gas-liquid mixture flowing out of the bottom of the transformer tower 8, ensuring that the gas phase and the liquid phase are properly treated respectively. The separated gas phase re-enters the transformer tower 8, while the liquid phase is treated by other means, such as reflux or collection.

[0041] Loop 4: The gas phase separated in the gas-liquid separation tank 7 enters the transformer tower from the bottom of the transformer tower 8, and the separated liquid phase G leaves the bottom of the gas-liquid separation tank 7, returns to the mixing tank 1 through the reflux pump 10, and mixes with the crude acrylic acid aqueous solution A. The gas phase returns to the transformer tower 8 from the bottom of the gas-liquid separation tank 7 and continues to participate in the separation process in the tower. This recycling helps to maintain the material balance in the tower and ensure the continuity and stability of the separation process. The liquid phase G returns to the mixing tank 1 through the reflux pump 10 and mixes with the new feed to form a closed circulation system, which not only improves the utilization rate of the material, but also reduces the discharge of waste liquid. By reintroducing the liquid phase into the mixing tank 1 through the reflux pump 10, the stability and uniformity of the feed can be maintained, and the separation effect can be avoided from being reduced due to material fluctuations. The reflux amount can also be adjusted as needed to flexibly respond to changes in production.

[0042] In some embodiments of the present application, the bottom distillate of the atmospheric tower 2 enters the atmospheric tower reboiler 3 and then returns to the atmospheric tower, and the atmospheric tower reboiler provides heat for the atmospheric tower.

[0043] In some embodiments of the present application, the overhead distillate of the transformer tower 8 passes through the transformer tower condenser 9 and then returns to the transformer tower from the top of the transformer tower.

[0044] In some embodiments of the present application, the top temperature of the atmospheric tower is 82°C-100°C, and the bottom temperature is 123°C-140°C; the top temperature of the pressure-scaling tower is 33°C-46°C, and the bottom temperature is 46°C-54°C. When the temperature is too low, the fluidity of the liquid deteriorates, and the reflux ratio needs to be increased to achieve the ideal separation effect, which greatly increases the separation energy consumption; when the temperature is too high, it will cause the liquid water to vaporize excessively, affecting the gas-liquid contact and mass transfer efficiency, and also greatly increasing the separation energy consumption. Therefore, the top temperature of the atmospheric tower can be 82°C, 85°C, 99°C, 100°C, etc., and all ranges and sub-ranges between the above values; the bottom temperature of the atmospheric tower can be 123°C, 139°C, 140°C, etc., and all ranges and sub-ranges between the above values; the top temperature of the transformer tower can be 33°C, 45°C, 46°C, etc., and all ranges and sub-ranges between the above values; the bottom temperature of the transformer tower can be 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C, etc., and all ranges and sub-ranges between the above values; it should be understood that in the implementation scheme, any of the above ranges can be combined with any other ranges.

[0045] In some embodiments of the present application, in the water-acrylic acid mixture to be separated entering the mixing tank (1), the mass fraction of acrylic acid is less than 33% calculated by mass percentage.

[0046] In some embodiments of the present application, the pressure of the atmospheric tower is 0.1-0.15MPa, and the reflux ratio is 0.6-0.7; the pressure of the transformer tower is 0.01-0.08MPa, and the reflux ratio is 2.8-2.9. The pressure of the atmospheric tower can be 0.1MPa, 0.13MPa, 0.14MPa, 0.15MPa, etc., and all ranges and sub-ranges between the above values; the reflux ratio of the atmospheric tower can be 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, etc., and all ranges and sub-ranges between the above values; the pressure of the transformer tower can be 0.01MPa, 0.02MPa, 0.03MPa , 0.04MPa, 0.05MPa, 0.06MPa, 0.07MPa, 0.08MPa, etc., and all ranges and sub-ranges between the above values; the reflux ratio of the transformer can be 2.80, 2.81, 2.82, 2.83, 2.84, 2.85, 2.86, 2.87, 2.88, 2.89, 2.90, etc., and all ranges and sub-ranges between the above values; it should be understood that in the embodiment, any of the above ranges can be combined with any other ranges.

[0047] 3. Examples and Comparative Examples

[0048] The crude trihydroxypropionaldehyde obtained by simulating the trihydroxypropionaldehyde production device of acrolein hydration method in a certain factory is used as an example.

[0049] Embodiment 1:

[0050] The feed temperature of the water-acrylic acid mixture entering the mixing tank 1 is 100°C, and the feed temperature entering the atmospheric pressure tower 1 after mixing in the mixing tank 1 is 105°C. The feed contains 67.33% water and 32.62% acrylic acid (mass fraction). The feed flow rate of the atmospheric pressure tower is 932.03kg / h, and the pressure of the atmospheric pressure tower is 0.1MPa (absolute pressure). The material enters the atmospheric pressure tower 1 from the 25th plate. The theoretical number of plates of the atmospheric pressure tower is 48. The reflux ratio of the atmospheric pressure tower is 0.64. The top temperature of the atmospheric pressure tower is 99.57°C, and the bottom temperature is 139.57°C. After heat exchange and diversion, a portion of the top distillate of atmospheric tower 1 is pressurized by a pump and enters transformer tower 2 through the 15th plate. The operating pressure of the transformer tower is 0.01 MPa (absolute pressure), the theoretical number of plates of the transformer tower is 30, the reflux ratio of the transformer tower is 2.89, the feed temperature of the transformer tower is 99.35°C, the top temperature of the transformer tower is 45.33°C, and the bottom temperature of the transformer tower is 52.11°C; the liquid at the bottom of transformer tower 2 enters the top heat exchanger 4 and the transformer tower heat exchanger 6 for heat exchange, and then refluxes back to the transformer tower 8 through the gas-liquid separation tank 7; the mass fraction of the acrylic acid product obtained after separation is 99.5%, and the recovery rate is 99.5%; the mass fraction of the recovered water is 97.53%, and the recovery rate is 97.53%.

[0051] Table 1 Example 1 distillation system operating parameters

[0052]

[0053] Embodiment 2:

[0054] The feed temperature of the water-acrylic acid mixture entering the mixing tank 1 is 99.5°C, and the feed temperature entering the atmospheric pressure tower 1 after mixing in the mixing tank 1 is 104.5°C. The feed contains 70% water and 30% acrylic acid (mass fraction). The feed flow rate of the atmospheric pressure tower is 932.03kg / h, and the pressure of the atmospheric pressure tower is 0.1MPa (absolute pressure). The material enters the atmospheric pressure tower 1 from the 26th plate. The theoretical number of plates of the atmospheric pressure tower is 48. The reflux ratio of the atmospheric pressure tower is 0.65. The top temperature of the atmospheric pressure tower is 99.6°C, and the bottom temperature is 138.57°C. After heat exchange and diversion, a portion of the top distillate of atmospheric tower 1 is pressurized by a pump and enters transformer tower 2 through the 15th plate. The operating pressure of the transformer tower is 0.01 MPa (absolute pressure), the theoretical number of plates of the transformer tower is 30, the reflux ratio of the transformer tower is 2.88, the feed temperature of the transformer tower is 99.4°C, the top temperature of the transformer tower is 45.3°C, and the bottom temperature of the transformer tower is 52.2°C; the liquid at the bottom of transformer tower 2 enters the top heat exchanger 4 and the transformer tower heat exchanger 6 for heat exchange, and then refluxes back to the transformer tower 8 through the gas-liquid separation tank 7; the mass fraction of the acrylic acid product obtained after separation is 99.52%, and the recovery rate is 99.52%; the mass fraction of the recovered water is 97.51%, and the recovery rate is 97.51%.

[0055] Table 2 Example 2 distillation system operating parameters

[0056]

[0057] Embodiment 3:

[0058] The feed temperature of the water-acrylic acid mixture entering the mixing tank 1 is 99.8°C, and the feed temperature entering the atmospheric pressure tower 1 after mixing in the mixing tank 1 is 104.8°C. The feed contains 69% water and 31% acrylic acid (mass fraction). The feed flow rate of the atmospheric pressure tower is 932.03kg / h, and the pressure of the atmospheric pressure tower is 0.1MPa (absolute pressure). The material enters the atmospheric pressure tower 1 from the 26th plate. The theoretical number of plates of the atmospheric pressure tower is 48. The reflux ratio of the atmospheric pressure tower is 0.66. The top temperature of the atmospheric pressure tower is 99.54°C, and the bottom temperature is 139.42°C. After heat exchange and diversion, a portion of the distillate from the top of the atmospheric tower 1 is pressurized by a pump and enters the transformer tower 2 through the 14th plate. The operating pressure of the transformer tower is 0.015 MPa (absolute pressure), the theoretical number of plates of the transformer tower is 31, the reflux ratio of the transformer tower is 2.87, the feed temperature of the transformer tower is 99.38°C, the top temperature of the transformer tower is 45.3°C, and the bottom temperature of the transformer tower is 52.2°C; the liquid at the bottom of the transformer tower 2 enters the top heat exchanger 4 and the transformer tower heat exchanger 6 for heat exchange, and then refluxes back to the transformer tower 8 through the gas-liquid separation tank 7; the mass fraction of the acrylic acid product obtained after separation is 99.55%, and the recovery rate is 99.55%; the mass fraction of the recovered water is 97.48%, and the recovery rate is 97.48%.

[0059] Table 3 Example 3 distillation system operating parameters

[0060]

[0061] Embodiment 4:

[0062] The feed temperature of the water-acrylic acid mixture entering the mixing tank 1 is 99.6°C, and the feed temperature entering the atmospheric pressure tower 1 after mixing in the mixing tank 1 is 104.7°C. The feed contains 69% water and 31% acrylic acid (mass fraction). The feed flow rate of the atmospheric pressure tower is 932.03kg / h, and the pressure of the atmospheric pressure tower is 0.1MPa (absolute pressure). The material enters the atmospheric pressure tower 1 from the 25th plate. The theoretical number of plates of the atmospheric pressure tower is 48. The reflux ratio of the atmospheric pressure tower is 0.66. The top temperature of the atmospheric pressure tower is 99.58°C, and the bottom temperature is 139.36°C. After heat exchange and diversion, a portion of the top distillate of atmospheric tower 1 is pressurized by a pump and enters transformer tower 2 through the 15th plate. The operating pressure of the transformer tower is 0.015 MPa (absolute pressure), the theoretical number of plates of the transformer tower is 31, the reflux ratio of the transformer tower is 2.87, the feed temperature of the transformer tower is 99.36°C, the top temperature of the transformer tower is 45.88°C, and the bottom temperature of the transformer tower is 53°C; the liquid at the bottom of transformer tower 2 enters the top heat exchanger 4 and the transformer tower heat exchanger 6 for heat exchange, and then refluxes back to the transformer tower 8 through the gas-liquid separation tank 7; the mass fraction of the acrylic acid product obtained after separation is 99.44%, and the recovery rate is 99.44%; the mass fraction of the recovered water is 97.67%, and the recovery rate is 97.67%.

[0063] Table 4 Example 4 distillation system operating parameters

[0064]

[0065] Embodiment 5:

[0066] The feed temperature of the water-acrylic acid mixture entering the mixing tank 1 is 99.6°C, and the feed temperature entering the atmospheric pressure tower 1 after mixing in the mixing tank 1 is 104.9°C. The feed contains 69% water and 31% acrylic acid (mass fraction). The feed flow rate of the atmospheric pressure tower is 932.03kg / h, and the pressure of the atmospheric pressure tower is 0.12MPa (absolute pressure). The material enters the atmospheric pressure tower 1 from the 25th plate. The theoretical number of plates of the atmospheric pressure tower is 48. The reflux ratio of the atmospheric pressure tower is 0.67. The top temperature of the atmospheric pressure tower is 100°C, and the bottom temperature is 140°C. After heat exchange and diversion, a portion of the top distillate of atmospheric tower 1 is pressurized by a pump and enters transformer tower 2 through the 15th plate. The operating pressure of the transformer tower is 0.018 MPa (absolute pressure), the theoretical number of plates of the transformer tower is 31, the reflux ratio of the transformer tower is 2.86, the feed temperature of the transformer tower is 99.21°C, the top temperature of the transformer tower is 45.9°C, and the bottom temperature of the transformer tower is 53.1°C; the liquid at the bottom of transformer tower 2 enters the top heat exchanger 4 and the transformer tower heat exchanger 6 for heat exchange, and then refluxes back to the transformer tower 8 through the gas-liquid separation tank 7; the mass fraction of the acrylic acid product obtained after separation is 99.5%, and the recovery rate is 99.5%; the mass fraction of the recovered water is 97.5%, and the recovery rate is 97.5%.

[0067] Table 5 Example Table 5 Example 5 Distillation system operating parameters

[0068]

[0069] Embodiment 6:

[0070] The feed temperature of the water-acrylic acid mixture entering the mixing tank 1 is 99.6°C, and the feed temperature entering the atmospheric pressure tower 1 after mixing in the mixing tank 1 is 105°C. The feed contains 69% water and 31% acrylic acid (mass fraction). The feed flow rate of the atmospheric pressure tower is 932.03kg / h, and the pressure of the atmospheric pressure tower is 0.13MPa (absolute pressure). The material enters the atmospheric pressure tower 1 from the 25th plate. The theoretical number of plates of the atmospheric pressure tower is 48. The reflux ratio of the atmospheric pressure tower is 0.68. The top temperature of the atmospheric pressure tower is 99.79°C, and the bottom temperature is 139.82°C. After heat exchange and diversion, a portion of the top distillate of atmospheric tower 1 is pressurized by a pump and enters transformer tower 2 through the 15th plate. The operating pressure of the transformer tower is 0.02MPa (absolute pressure), the theoretical number of plates of the transformer tower is 31, the reflux ratio of the transformer tower is 2.86, the feed temperature of the transformer tower is 99.67°C, the top temperature of the transformer tower is 46°C, and the bottom temperature of the transformer tower is 53.6°C; the liquid at the bottom of transformer tower 2 enters the top heat exchanger 4 and the transformer tower heat exchanger 6 for heat exchange, and then refluxes back to the transformer tower 8 through the gas-liquid separation tank 7; the mass fraction of the acrylic acid product obtained after separation is 99.6%, and the recovery rate is 99.6%; the mass fraction of the recovered water is 97.4%, and the recovery rate is 97.4%.

[0071] Table 6 Example 6 distillation system operating parameters

[0072]

[0073] Comparative Example 1:

[0074] The feed temperature of the water-acrylic acid mixture entering the mixing tank 1 is 99.6°C, and the feed temperature entering the atmospheric pressure tower 1 after mixing in the mixing tank 1 is 105°C. The feed contains 69% water and 31% acrylic acid (mass fraction). The feed flow rate of the atmospheric pressure tower is 932.03kg / h, and the pressure of the atmospheric pressure tower is 0.1MPa (absolute pressure). The material enters the atmospheric pressure tower 1 from the 25th plate. The theoretical number of plates of the atmospheric pressure tower is 48. The reflux ratio of the atmospheric pressure tower is 0.63. The top temperature of the atmospheric pressure tower is 102°C, and the bottom temperature is 141.2°C. After heat exchange and diversion, a portion of the top distillate of atmospheric tower 1 is pressurized by a pump and enters transformer tower 2 through the 15th plate. The operating pressure of the transformer tower is 0.01 MPa (absolute pressure), the theoretical number of plates of the transformer tower is 31, the reflux ratio of the transformer tower is 2.86, the feed temperature of the transformer tower is 99.35°C, the top temperature of the transformer tower is 45.33°C, and the bottom temperature of the transformer tower is 52.73°C; the liquid at the bottom of transformer tower 2 enters the top heat exchanger 4 and the transformer tower heat exchanger 6 for heat exchange, and then refluxes back to the transformer tower 8 through the gas-liquid separation tank 7; the mass fraction of the acrylic acid product obtained after separation is 92.6%, and the recovery rate is 92.6%; the mass fraction of the recovered water is 91.4%, and the recovery rate is 91.4%.

[0075] Table 7 Comparative Example 1 Distillation System Operating Parameters

[0076]

[0077] This comparative example 1 studies the influence of temperature on the separation effect of the atmospheric tower. Compared with Example 1, when the temperature at the top and bottom of the atmospheric tower exceeds the range, the mass fraction and recovery rate of the acrylic acid product are greatly reduced, the separation effect is reduced, and the energy consumption is increased.

[0078] Comparative Example 2:

[0079] The feed temperature of the water-acrylic acid mixture entering the mixing tank 1 is 99.5°C, and the feed temperature entering the atmospheric pressure tower 1 after mixing in the mixing tank 1 is 104.5°C. The feed contains 70% water and 30% acrylic acid (mass fraction). The feed flow rate of the atmospheric pressure tower is 932.03kg / h, and the pressure of the atmospheric pressure tower is 0.2MPa (absolute pressure). The material enters the atmospheric pressure tower 1 from the 26th plate. The theoretical number of plates of the atmospheric pressure tower is 48. The reflux ratio of the atmospheric pressure tower is 0.65. The top temperature of the atmospheric pressure tower is 99.6°C, and the bottom temperature is 138.57°C. After heat exchange and diversion, a portion of the top distillate of atmospheric tower 1 is pressurized by a pump and enters transformer tower 2 through the 15th plate. The operating pressure of the transformer tower is 0.01 MPa (absolute pressure), the theoretical number of plates of the transformer tower is 30, the reflux ratio of the transformer tower is 2.88, the feed temperature of the transformer tower is 99.4°C, the top temperature of the transformer tower is 45.3°C, and the bottom temperature of the transformer tower is 52.2°C; the liquid at the bottom of transformer tower 2 enters the top heat exchanger 4 and the transformer tower heat exchanger 6 for heat exchange, and then refluxes back to the transformer tower 8 through the gas-liquid separation tank 7; the mass fraction of the acrylic acid product obtained after separation is 92.52%, and the recovery rate is 92.52%; the mass fraction of the recovered water is 91.51%, and the recovery rate is 91.51%.

[0080] Table 8 Comparative Example 2 Distillation System Operating Parameters

[0081]

[0082] This comparative example 2 studies the influence of pressure on the separation effect of the atmospheric tower. Compared with Example 2, when the atmospheric tower pressure exceeds the range, the mass fraction and recovery rate of acrylic acid product are greatly reduced, the separation effect is reduced, and the energy consumption is increased.

[0083] Comparative Example 3:

[0084] The feed temperature of the water-acrylic acid mixture entering the mixing tank 1 is 99.5°C, and the feed temperature entering the atmospheric pressure tower 1 after mixing in the mixing tank 1 is 104.5°C. The feed contains 70% water and 30% acrylic acid (mass fraction). The feed flow rate of the atmospheric pressure tower is 932.03kg / h, and the pressure of the atmospheric pressure tower is 0.2MPa (absolute pressure). The material enters the atmospheric pressure tower 1 from the 26th plate. The theoretical number of plates of the atmospheric pressure tower is 48. The reflux ratio of the atmospheric pressure tower is 0.55. The top temperature of the atmospheric pressure tower is 99.68°C, and the bottom temperature is 139.21°C. After heat exchange and diversion, a portion of the top distillate of atmospheric tower 1 is pressurized by a pump and enters transformer tower 2 through the 15th plate. The operating pressure of the transformer tower is 0.01 MPa (absolute pressure), the theoretical number of plates of the transformer tower is 30, the reflux ratio of the transformer tower is 2.88, the feed temperature of the transformer tower is 99.4°C, the top temperature of the transformer tower is 45.39°C, and the bottom temperature of the transformer tower is 52.28°C; the bottom liquid of transformer tower 2 enters the top heat exchanger 4 and the transformer tower heat exchanger 6 for heat exchange, and then refluxes back to transformer tower 8 through the gas-liquid separation tank 7; the mass fraction of the acrylic acid product obtained after separation is 93.52%, and the recovery rate is 93.52%; the mass fraction of the recovered water is 92.51%, and the recovery rate is 92.51%.

[0085] Table 9 Comparative Example 3 Distillation System Operating Parameters

[0086]

[0087] This comparative example 4 studies the influence of the reflux ratio on the separation effect of the atmospheric tower. Compared with Example 3, when the reflux ratio of the atmospheric tower is lower than the range, the mass fraction and recovery rate of the acrylic acid product are greatly reduced, the separation effect is reduced, and the energy consumption is increased.

[0088] Comparative Example 4:

[0089] The feed temperature of the water-acrylic acid mixture entering the mixing tank 1 is 99.5°C, and the feed temperature entering the atmospheric pressure tower 1 after mixing in the mixing tank 1 is 104.5°C. The feed contains 70% water and 30% acrylic acid (mass fraction). The feed flow rate of the atmospheric pressure tower is 932.03kg / h, and the pressure of the atmospheric pressure tower is 0.2MPa (absolute pressure). The material enters the atmospheric pressure tower 1 from the 26th plate. The theoretical number of plates of the atmospheric pressure tower is 48. The reflux ratio of the atmospheric pressure tower is 0.75. The top temperature of the atmospheric pressure tower is 99.8°C, and the bottom temperature is 139.4°C. After heat exchange and diversion, a portion of the top distillate of atmospheric tower 1 is pressurized by a pump and enters transformer tower 2 through the 15th plate. The operating pressure of the transformer tower is 0.01 MPa (absolute pressure), the theoretical number of plates of the transformer tower is 30, the reflux ratio of the transformer tower is 2.88, the feed temperature of the transformer tower is 99.4°C, the top temperature of the transformer tower is 45.34°C, and the bottom temperature of the transformer tower is 52.3°C; the liquid at the bottom of transformer tower 2 enters the top heat exchanger 4 and the transformer tower heat exchanger 6 for heat exchange, and then refluxes back to the transformer tower 8 through the gas-liquid separation tank 7; the mass fraction of the acrylic acid product obtained after separation is 99.72%, and the recovery rate is 99.72%; the mass fraction of the recovered water is 99.51%, and the recovery rate is 99.51%.

[0090] Table 10 Comparative Example 4 Distillation System Operating Parameters

[0091]

[0092] This comparative example 4 studies the effect of the reflux ratio on the separation effect of the atmospheric tower. Compared with Example 3, when the reflux ratio of the atmospheric tower is higher than the range, the operating cost increases, the system stability decreases, the separation effect decreases, and the energy consumption increases greatly.

[0093] Small test results:

[0094] Compare this scheme with the experimental test results

[0095] The feed temperature of the water-acrylic acid mixture entering the mixing tank 1 is 99.5°C, and the feed temperature entering the atmospheric pressure tower 1 after mixing in the mixing tank 1 is 104.5°C. The feed contains 70% water and 30% acrylic acid (mass fraction). The feed flow rate of the atmospheric pressure tower is 3kg / h, and the pressure of the atmospheric pressure tower is 0.1MPa (absolute pressure). The material enters the atmospheric pressure tower 1 from the 12th plate. The theoretical number of plates of the atmospheric pressure tower is 20. The reflux ratio of the atmospheric pressure tower is 0.65. The top temperature of the atmospheric pressure tower is 99.6°C, and the bottom temperature is 138.57°C. After heat exchange and diversion, a portion of the top distillate of atmospheric tower 1 is pressurized by a pump and enters transformer tower 2 through the 5th plate. The operating pressure of the transformer tower is 0.01MPa (absolute pressure), the theoretical number of plates of the transformer tower is 15, the reflux ratio of the transformer tower is 2.88, the feed temperature of the transformer tower is 99.4°C, the top temperature of the transformer tower is 45.3°C, and the bottom temperature of the transformer tower is 52.2°C; the liquid at the bottom of transformer tower 2 enters the top heat exchanger 4 and the transformer tower heat exchanger 6 for heat exchange, and then refluxes back to the transformer tower 8 through the gas-liquid separation tank 7; the mass fraction of the acrylic acid product obtained after separation is 99.22%, and the recovery rate is 99.22%; the mass fraction of the recovered water is 98.21%, and the recovery rate is 98.21%.

[0096] Table 11 Small test results Distillation system operating parameters

[0097]

[0098] It can be seen from the embodiments and comparative examples that:

[0099] (1) The various parameters in the embodiment are more reasonably set, which can effectively improve the quality and recovery rate of acrylic acid products, reduce energy consumption and operating costs, and have better economic and environmental benefits; moreover, the results of the small test show that the technical solution described in the present application has a good industrialization prospect. However, when the number of theoretical plates of the atmospheric tower is reduced to 20 and the number of theoretical plates of the transformer tower is reduced to 15, although the mass fraction and recovery rate of acrylic acid products are still high (99.22% and 99.22%, respectively), the mass fraction and recovery rate of recycled water are reduced (98.21% and 98.21%, respectively). This shows that the reduction of the number of theoretical plates will affect the separation effect, especially when dealing with large-scale industrial production, more theoretical plates are needed to ensure the high efficiency of separation.

[0100] (2) It can be seen from Example 1 and Comparative Example 1 that if the top and bottom temperatures of the atmospheric tower are too high, the quality of the acrylic acid product and the recovery efficiency will be significantly reduced. This shows that too high an operating temperature not only affects the separation effect, but also increases energy consumption and reduces the economy and efficiency of the system.

[0101] (3) It can be seen from Example 1 and Comparative Example 2 that the operating pressure of the atmospheric tower in Comparative Example 2 was increased to 0.2 MPa, which resulted in a significant decrease in the mass fraction and recovery rate of acrylic acid products, which were reduced to 92.52% and 92.52% respectively; the mass fraction and recovery rate of recovered water were also reduced to 91.51% and 91.51% respectively. This shows that too high an operating pressure will have a negative impact on the separation effect, increase energy consumption and reduce the economic benefits of the system.

[0102] (4) It can be seen from Example 1 and Comparative Examples 3 and 4 that the change in reflux ratio has a significant impact on the separation effect. A reflux ratio outside the range described in this application will lead to a significant increase in operating costs, a decrease in system stability, and a significant increase in energy consumption.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application rather than to limit the technical solution. Ordinary technicians in this field should understand that those modifications or equivalent substitutions of the technical solution of the present application that do not depart from the purpose and scope of the technical solution of the present application should be included in the scope of the claims of the present application.

Claims

1. A device for pressure-swing distillation of acrylic acid mixture using heat-integrated double towers, characterized in that: It comprises a mixing tank (1), an atmospheric tower (2), a tower top heat exchanger (4), an atmospheric tower splitter tank (5), a pressure-changing tower heat exchanger (6), a gas-liquid separation tank (7) and a pressure-changing tower (8); The crude acrylic acid aqueous solution (A) enters from the top of the mixing tank (1), and the mixing tank (1) is fluidly connected to the atmospheric tower (2); the top of the atmospheric tower (2) is fluidly connected to the top heat exchanger (4), the top heat exchanger (4) is fluidly connected to the atmospheric tower diversion tank (5), the top of the atmospheric tower diversion tank (5) is fluidly connected to the top of the atmospheric tower, and the bottom of the atmospheric tower diversion tank (5) is fluidly connected to the top of the transformer tower (8); the top heat exchanger (4) is fluidly connected to the transformer tower heat exchanger (6), the transformer tower heat exchanger (6) is fluidly connected to the gas-liquid separation tank (7), the top of the gas-liquid separation tank (7) is fluidly connected to the bottom of the transformer tower (8), and the bottom of the gas-liquid separation tank (7) is fluidly connected to the bottom of the mixing tank (1) through a reflux pump (10); the bottom of the transformer tower (8) is fluidly connected to the top heat exchanger (4); Acrylic acid (D) is taken out from the bottom of the atmospheric tower (2), and a pressure-swing tower overhead product (E) is taken out from the top of the pressure-swing tower (8).

2. The device according to claim 1, characterized in that: It also includes an atmospheric tower reboiler (3), and the bottom distillate of the atmospheric tower (2) returns to the atmospheric tower after passing through the atmospheric tower reboiler.

3. The device according to claim 1, characterized in that: It also includes a transformer tower condenser (9), and the top distillate of the transformer tower (8) passes through the transformer tower condenser and then returns to the transformer tower from the top of the transformer tower.

4. The device according to claim 1, characterized in that: The atmospheric tower has 20 to 50 plates, and the feed plate is one of the 10th to 30th plates; the transformer tower has 15 to 40 plates, and the feed plate is one of the 5th to 20th plates.

5. A method for pressure-swing distillation of an acrylic acid mixture using a heat-integrated double-tower, characterized in that: The method adopts the device described in any of claims 1 to 4, and the method specifically comprises the following circuit: Loop 1: crude acrylic acid aqueous solution (A) enters from the top of the mixing tank (1), and then the mixed material fluid in the mixing tank (1) enters the atmospheric pressure tower (2) for distillation, and acrylic acid (D) is produced at the bottom of the atmospheric pressure tower (2); Loop 2: the top effluent (B) of the atmospheric tower (2) enters the top heat exchanger (4) for heat exchange, and then enters the atmospheric tower split tank (5); the first split stream (C) of the atmospheric tower split tank (5) flows out from the tank top, enters from the top of the atmospheric tower, and returns to the atmospheric tower; the second split stream of the atmospheric tower split tank (5) enters from the top of the transformer tower (8) into the transformer tower; Loop 3: The bottom distillate (F) of the transformer tower (8) enters the tower top heat exchanger (4), exchanges heat with the tower top effluent (B), enters the transformer tower heat exchanger (6) for heat exchange, and then enters the gas-liquid separation tank (7); the transformer tower top liquid phase condensate (E) is extracted from the transformer tower (8); Loop 4: The gas phase separated in the gas-liquid separation tank (7) enters the transformer tower (8) from the bottom of the transformer tower, and the liquid phase separated leaves the bottom of the gas-liquid separation tank (7), returns to the mixing tank (1) through the reflux pump (10), and is mixed with the crude acrylic acid aqueous solution (A).

6. The method according to claim 5, characterized in that: The bottom distillate of the atmospheric tower (2) enters the atmospheric tower reboiler (3) and then returns to the atmospheric tower. The atmospheric tower reboiler provides heat for the atmospheric tower.

7. The method according to claim 5, characterized in that: The top distillate of the transformer tower (8) passes through the transformer tower condenser (9) and then returns to the transformer tower from the top of the transformer tower.

8. The method according to claim 5, characterized in that: The top temperature of the atmospheric tower is 82℃-100℃, and the bottom temperature is 123℃-140℃; the top temperature of the transformer tower is 33℃-46℃, and the bottom temperature is 46℃-54℃.

9. The method according to claim 5, characterized in that: In the water-acrylic acid mixture to be separated entering the mixing tank (1), the mass fraction of acrylic acid is less than 33%.

10. The method according to claim 5, characterized in that: The pressure of the atmospheric tower is 0.1-0.15 MPa, and the reflux ratio is 0.6-0.7; the pressure of the transformer tower is 0.01-0.08 MPa, and the reflux ratio is 2.8-2.9.

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