A device and method for purifying crude acrylic acid by refining crystallization

Abstract

The application relates to a device and a method for refining and crystallizing crude acrylic acid, and relates to the field of chemical product purification, and comprises an acrylic acid refining unit, a rectifying unit, a falling film crystallization purification unit and a condensation sweating heat pump system; crude acrylic acid and weak alkaline materials are mixed in the acrylic acid refining unit and are pumped into the rectifying unit through a pipeline; the rectifying unit is used for rectification to obtain overhead gas; the overhead gas is condensed and pumped into the falling film crystallization purification unit through a pipeline; the condensation sweating heat pump system is connected with the falling film crystallization purification unit so that the temperature in the falling film crystallization purification unit is lower than 13 DEG C; and the application has the advantages that the efficiency of obtaining high-purity acrylic acid can be improved.

Description

Technical Field

[0001] This invention relates to the field of chemical product purification technology, and in particular to an apparatus and method for the purification and crystallization of crude acrylic acid. Background Technology

[0002] Acrylic acid is a monomer with significant polymerization capabilities, capable of copolymerizing with other substances to produce polymer materials such as polypropylene and polyacrylic acid. Acrylic acid possesses strong adhesion and shear strength, making it a crucial industrial raw material used in the production of polymers, coatings, pharmaceuticals, and building materials. In recent years, acrylic acid and its derivatives have been increasingly used as pharmaceutical intermediates in the production of various drugs, requiring extremely high purity. The purity of products obtained through ordinary absorption and distillation does not meet current requirements, necessitating purification to over 99.98%. However, existing distillation purification methods not only cause severe corrosion to the equipment but also only achieve a purity of around 99.10%, failing to reach the pharmaceutical-grade 99.99%.

[0003] Therefore, to address the above shortcomings, there is a need to provide an apparatus and method for the purification and crystallization of crude acrylic acid. Summary of the Invention

[0004] (a) Technical problems to be solved The technical problem to be solved by this invention is to address the issue that traditional distillation methods cannot purify acrylic acid to 99.99%.

[0005] (II) Technical Solution To address the aforementioned technical problems, this invention provides an apparatus for the refining and crystallization of crude acrylic acid, comprising an acrylic acid purification unit, a distillation unit, a falling film crystallization purification unit, and a condensation and sweating heat pump system. In the acrylic acid purification unit, crude acrylic acid and a weakly alkaline material are mixed and pumped into the distillation unit via pipelines. The distillation unit performs distillation to obtain overhead gas, which is then condensed and pumped into the falling film crystallization purification unit via pipelines. The condensation and sweating heat pump system is connected to the falling film crystallization purification unit to maintain a temperature below 13°C within the unit.

[0006] As a further explanation of the present invention, preferably, the acrylic acid purification unit includes a crude acrylic acid feed buffer tank, a reactant feed buffer tank, a purification reactor, and a distillation column feed buffer tank. The crude acrylic acid feed buffer tank containing acrylic acid with a concentration of 99.0-99.5% and the reactant feed buffer tank containing weakly alkaline materials are connected in parallel with the purification reactor through pipelines. The distillation column feed buffer tank is connected to the outlet end of the purification reactor through a pipeline.

[0007] As a further explanation of the present invention, preferably, the reactant feed buffer tank contains hydrazine with a concentration of 80%.

[0008] As a further explanation of the present invention, preferably, the distillation unit includes a distillation column, a distillation column reboiler, a condensate intermediate tank, and a distillation column condenser connected in sequence by pipelines. The distillation column uses the distillation column reboiler to provide heat to vaporize acrylic acid, the gaseous material is passed into the distillation column condenser for condensation, and the liquid material is then introduced into the condensate intermediate tank for storage.

[0009] As a further explanation of the present invention, preferably, the distillation unit further includes a recovery tower feed buffer tank, an acrylic acid recovery tower, a recovery tower reboiler, a recovery tower condenser, and a recovery tower condenser intermediate tank connected in sequence by pipelines. The recovery tower feed buffer tank is connected to the distillation tower reboiler and stores liquid phase material. The recovery tower feed buffer tank feeds the liquid phase material into the acrylic acid recovery tower for distillation via the recovery tower reboiler. The gas phase material is condensed into liquid phase by the recovery tower condenser and then stored in the recovery tower condenser intermediate tank.

[0010] As a further explanation of the present invention, preferably, the falling film crystallization purification unit includes an acrylic acid crystallization feed tank, a primary falling film crystallizer, a primary liquid phase collection tank, a primary product buffer tank, and a condensation and sweating heat pump system connected in sequence by pipelines. The condensation and sweating heat pump system injects cooled HTM into the primary falling film crystallizer. The acrylic acid crystallization feed tank injects liquid phase material into the primary falling film crystallizer. The acrylic acid in the liquid phase material is crystallized by the HTM and passed into the primary product buffer tank. The remaining liquid phase material enters the primary liquid phase collection tank.

[0011] As a further explanation of the present invention, preferably, the falling film crystallization purification unit further includes a secondary falling film crystallizer, a secondary liquid phase collection tank, a secondary product buffer tank, and an acrylic acid product tank connected in sequence by pipelines. The secondary falling film crystallizer is connected to the primary liquid phase collection tank by pipelines. A condensing and sweating heat pump system injects cooled HTM into the secondary falling film crystallizer. The liquid phase in the primary liquid phase collection tank is injected into the secondary falling film crystallizer. The acrylic acid in the liquid phase material is crystallized by HTM and passed into the secondary product buffer tank. The remaining liquid phase material enters the secondary liquid phase collection tank. The liquid phase in the secondary liquid phase collection tank flows back into the primary liquid phase collection tank. The high-purity acrylic acid in the primary product buffer tank and the secondary product buffer tank enters the acrylic acid product tank.

[0012] This invention also provides a method for refining and purifying crude acrylic acid by crystallization, comprising the following steps: I. 99.0-99.5% acrylic acid and 80% hydrazine are injected into the acrylic acid purification unit at a mass ratio of (1900-2100):1 to preliminarily purify the crude acrylic acid. Then all the reactants are passed into the distillation unit. II. The distillation unit is divided into a distillation section and a recovery section. The reactants enter the distillation section at a temperature of 58–67°C and a top pressure of 2.5–5.3 kPa for distillation. During this process, the gaseous material is extracted from the distillation section and condensed at a temperature of 20–25°C. The liquid material enters the recovery section, where the temperature is maintained at 58–67°C. The generated gaseous material is condensed at an environment of 20–25°C. The materials condensed in both the distillation section and the recovery section are fed into the falling film crystallization purification unit. III. The falling film crystallization purification unit evaporates the liquid phase material and then crystallizes it at a temperature of -25 to -15°C. The uncrystallized liquid phase enters the condensation and sweating heat pump system for sweating and cooling at a temperature of 13 to 18°C. The acrylic acid purity of the sweated material and the crystallized material reaches 99.99%.

[0013] As a further explanation of the present invention, preferably, a mixture of oxygen and polymerization inhibitor is introduced into the falling film crystallization purification unit.

[0014] As a further explanation of the present invention, preferably, a DCS decentralized control system is used to control the flow of liquid and gas phases, thereby automating the adjustment of feed ratio and flow rate.

[0015] (III) Beneficial Effects The above-described technical solution of the present invention has the following advantages: This invention uses hydrazine to react with related impurities, and then uses vacuum distillation, falling film crystallization and sweating cooling to purify acrylic acid. During the purification process, a polymerization inhibitor is added to prevent the acrylic acid from polymerizing, further increasing the concentration of the obtained acrylic acid to about 99.99%. Attached Figure Description

[0016] Figure 1 This is a simplified diagram of the device of the present invention.

[0017] In the diagram: 11. Crude acrylic acid feed buffer tank; 12. Reactant feed buffer tank; 13. Purification reactor; 14. Distillation column feed buffer tank; 21. Distillation column; 22. Distillation column reboiler; 23. Condensate intermediate tank; 24. Distillation column condenser; 25. Recovery column feed buffer tank; 26. Acrylic acid recovery column; 27. Recovery column reboiler; 28. Recovery column condenser; 29. ​​Recovery column condenser intermediate tank; 31. Acrylic acid crystallization feed tank; 32. Primary falling film crystallizer; 33. Primary liquid phase collection tank; 34. Primary product buffer tank; 35. Secondary falling film crystallizer; 36. Secondary liquid phase collection tank; 37. Secondary product buffer tank; 38. Acrylic acid product tank; 39. Condensation and sweating heat pump system. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] An apparatus and method for refining, crystallizing, and purifying crude acrylic acid, such as... Figure 1 As shown, it includes an acrylic acid purification unit, a distillation unit, and a falling film crystallization purification unit, wherein: like Figure 1 As shown, the acrylic acid purification unit includes a crude acrylic acid feed buffer tank 11, a reactant feed buffer tank 12, a purification reactor 13, and a distillation column feed buffer tank 14. The crude acrylic acid feed buffer tank 11, containing acrylic acid with a concentration of 99.0-99.5%, and the reactant feed buffer tank 12, containing a weakly alkaline material, are connected in parallel with the purification reactor 13 via pipelines. The distillation column feed buffer tank 14 is connected to the outlet end of the purification reactor 13 via a pipeline. Hydrazine is preferably used in the reactant feed buffer tank 12. Hydrazine, as a highly polar compound, can react with aldehyde impurities in the crude acrylic acid to generate heavy compounds. During distillation, these heavy compounds remain at the bottom of the column and are discharged from there, achieving separation from the acrylic acid that has become a gaseous phase.

[0020] like Figure 1 As shown, the distillation unit consists of an acrylic acid distillation section and a recovery section. The distillation section includes a distillation column 21, a distillation column reboiler 22, a condensate intermediate tank 23, and a distillation column condenser 24, which are connected in sequence by pipelines. The distillation column 21 uses heat provided by the distillation column reboiler 22 to vaporize acrylic acid. The gaseous material is then passed into the distillation column condenser 24 for condensation, and the condensed liquid material is then transferred to the condensate intermediate tank 23 for storage. Part of the condensate is refluxed by the distillation column reflux pump to control product purity. Once the specified liquid level is reached, the distillation column condensate external pump is activated to send the condensate in the condensate intermediate tank 23 to the falling film crystallization purification unit.

[0021] The recovery section includes a recovery tower feed buffer tank 25, an acrylic acid recovery tower 26, a recovery tower reboiler 27, a recovery tower condenser 28, and a recovery tower condenser intermediate tank 29, all connected sequentially by pipelines. The recovery tower feed buffer tank 25 is connected to the distillation tower reboiler 22 and stores liquid materials. The liquid materials from the recovery tower feed buffer tank 25 are fed into the acrylic acid recovery tower 26 via the recovery tower reboiler 27 for distillation. The acrylic acid recovery tower 26 is also a distillation tower. The gaseous materials are condensed into liquid phase by the recovery tower condenser 28 and then stored in the recovery tower condenser intermediate tank 29. Part of the condensate is refluxed via the acrylic acid recovery tower reflux pump to control product purity. Waste oil from the bottom of the tower enters the waste oil intermediate tank 20. A waste oil external pump, once the specified liquid level is reached, activates the acrylic acid recovery tower condensate external pump to send the condensate to the condensate intermediate tank 23. Finally, the distillation tower condensate external pump sends it to the falling film crystallization purification unit.

[0022] like Figure 1 As shown, the falling film crystallization purification unit consists of a two-stage falling film crystallization device, which includes an acrylic acid crystallization feed tank 31, a first-stage falling film crystallizer 32, a first-stage liquid phase collection tank 33, a first-stage product buffer tank 34, and a condensation and sweating heat pump system 39 connected in sequence by pipelines. The condensation and sweating heat pump system 39 injects cooled HTM (heat transfer material, commonly known as heat carrier) into the first-stage falling film crystallizer. The acrylic acid crystallization feed tank 31 injects liquid phase material into the first-stage falling film crystallizer 32. The acrylic acid in the liquid phase material is crystallized by the HTM and passed into the first-stage product buffer tank 34. The remaining liquid phase material enters the first-stage liquid phase collection tank 33.

[0023] The secondary falling film crystallization equipment includes a secondary falling film crystallizer 35, a secondary liquid phase collection tank 36, a secondary product buffer tank 37, and an acrylic acid product tank 38, which are connected in sequence by pipelines. The secondary falling film crystallizer 35 is connected to the primary liquid phase collection tank 33 by pipelines. A condensing and sweating heat pump system 39 injects cooling HTM into the secondary falling film crystallizer 35. The liquid phase in the primary liquid phase collection tank 33 is injected into the secondary falling film crystallizer 35. The acrylic acid in the liquid phase material is crystallized by the HTM and passed into the secondary product buffer tank 37. The remaining liquid phase material enters the secondary liquid phase collection tank 36. The liquid phase in the secondary liquid phase collection tank 36 flows back into the primary liquid phase collection tank 33. The high-purity acrylic acid in the primary product buffer tank 34 and the secondary product buffer tank 37 enters the acrylic acid product tank 38.

[0024] like Figure 1As shown, the condensing-sweating heat pump system 39 includes the shell side of a falling film crystallizer, an energy storage tank, a compressor, an energy cycle, and pipelines containing valves. To maximize energy utilization, two energy loops are equipped with energy buffer tanks, one for storing cold HTM and the other for heating HTM. The crystallizer is equipped with a separate secondary energy loop for easy energy flow exchange control, where HTM is transported to the falling film crystallizer by an HTM circulation pump for energy circulation. When the heat pump system is operating normally, one falling film crystallizer crystallizes while the other sweats. After the crystallization process, the HTM absorbs heat and its temperature rises, entering the heating buffer tank; after the sweating process, the HTM releases heat and its temperature decreases. When the two crystallizers switch processes, the flow direction of the medium in the buffer tank is controlled by valves to achieve rational energy utilization. The condensing-sweating heat pump system 39 realizes alternating operation of condensation and sweating heat exchange in two stages of falling film crystallizers.

[0025] To prevent the polymerization reaction of acrylic acid during purification and to maximize the polymerization inhibition effect of the inhibitor, oxygen and the inhibitor are thoroughly mixed. The gas supply system is controlled by a solenoid valve in the gas supply section to maintain a slight positive pressure of 0.001 to 0.005 MPa (g). Air is continuously supplied to the acrylic acid product tank 38 at a low flow rate (20 kg / h) and enters the primary product buffer tank 34 and the secondary product buffer tank 37 from the acrylic acid product tank 38 through the gas phase balance line between the two storage tanks.

[0026] In addition, nitrogen is introduced into the gas supply section to inhibit system corrosion. Temperature changes are compensated for by the nitrogen pressure within the system, thus the gas supply section operates under pressure fluctuations. The pressure controller uses nitrogen supply and discharge valves to maintain the pressure below the limit of 0.08 MPa(g). Small amounts of exhaust gas produced in each process are treated in the plant's waste gas treatment system and then discharged at high altitude through a 30m-high exhaust stack.

[0027] This unit also employs an advanced and reliable distributed control system (DCS) to monitor, control, operate, record, and alarm critical process parameters. Both the liquid and gas phase discharges are equipped with solenoid valves, which automatically control the valve opening online to regulate flow, automating the feed / discharge ratio and flow rate adjustment, thereby optimizing the ratio of limiting reactants to excess reactants during production. Due to the flammability, explosiveness, corrosiveness, and toxicity of some process media, a safety instrumented system (SIS) and combustible gas detectors are used to implement safety interlocks. Local instrument panels are installed for critical areas on-site for monitoring and control. Key parameters are displayed in the central control room's DCS system. The interlock system is also integrated into the control room, with interfaces reserved for integration with other units to form a plant control and management network, preserving system expandability and maximizing personnel safety.

[0028] This invention also provides a method for refining and purifying crude acrylic acid by crystallization, comprising the following steps: I. Acrylic acid with a concentration of 99.0-99.5% and hydrazine with a concentration of 80% are injected into the purification reactor 13 from the crude acrylic acid feed buffer tank 11 and the reactant feed buffer tank 12 respectively at a mass ratio of (1900-2100):1, preferably 2000:1. The motor speed in the purification reactor 13 is 60-90 r / min, preferably 60 r / min. The purification reactor 13 is equipped with a cooling water jacket to suppress temperature rise and maintain the reaction at room temperature. In the purification reactor 13, the aldehydes and ketones contained in the crude acrylic acid undergo an addition reaction with hydrazine to generate high-boiling-point compounds. The reacted material is pumped from the reactor to the distillation unit feed buffer tank 14 of the distillation column to achieve preliminary purification of the crude acrylic acid. Subsequently, all reactants are passed into the distillation unit.

[0029] II. The liquid-phase reactants enter distillation column 21. Distillation column 21 is heated by reboiler 22, maintaining a reboiler temperature of 58–67°C. The overhead gas outlet temperature of distillation column 21 is 53–66°C. Condenser 24 condenses the overhead gas to 20–25°C, which then enters intermediate condensate tank 23. The pressure at the top of distillation column 21 is 5.3–2.5 kPa. Acrylic acid recovered from distillation column 21 enters acrylic acid recovery column 26. Acrylic acid recovery column 26 is heated by reboiler 27, maintaining a reboiler temperature of 58–67°C. The overhead gas outlet temperature of acrylic acid recovery column 26 is 53–66°C. Condenser 28 condenses the overhead gas to 20–25°C, which then enters intermediate condenser tank 29. The pressure at the top of acrylic acid recovery column 26 is 5.3–2.5 kPa.

[0030] III. The distillation condensate pumped from the distillation column condensate feeder enters the acrylic acid crystallization feeder 31, and then enters the first-stage falling film crystallizer 32 via the first-stage falling film crystallizer feeder pump for evaporation and crystallization. The uncrystallized liquid phase enters the first-stage liquid phase collection tank 33. The first-stage falling film crystallizer enters the sweating process, and the heat pump system enters the heating program. The high-purity product after sweating enters the first-stage product buffer tank 34.

[0031] The acrylic acid-containing liquid phase from the primary liquid phase collection tank 33 is fed into the secondary falling film crystallizer 35 via the secondary falling film crystallizer feed pump. The uncrystallized liquid phase enters the secondary liquid phase collection tank 36. The secondary falling film crystallizer then enters the sweating process, and the heat pump system enters the heating program. The high-purity product after sweating enters the secondary product buffer tank 37. The liquid phase in the secondary liquid phase collection tank 36 is recycled back into the primary liquid phase collection tank 33 via the secondary falling film crystallizer liquid phase reuse pump. The primary falling film crystallizer 32 and the secondary falling film crystallizer 35 are maintained at atmospheric pressure, with a crystallization temperature of -15 to -25°C and a sweating temperature of 13 to 18°C. The temperature is adjusted according to the gradient. The crystallization process takes 2 hours, and the sweating process takes 2 hours. The entire system maintains a stable set pressure and flow rate of oxygen and nitrogen in proportion through the gas supply section.

[0032] To further determine which ratio and temperature will maximize the concentration of purified acrylic acid, the following examples are provided for verification. The method in Example 1 is as follows: 1. Acrylic acid purification reaction Acrylic acid purification reaction: 99.0% acrylic acid from crude acrylic acid feed buffer tank 11 is pumped into purification reactor 13 via a crude acrylic acid feed pump. 80% hydrazine feed from reactant feed buffer tank 12 is pumped into purification reactor 13 via a hydrazine feed pump. The mass ratio of crude acrylic acid to hydrazine solution in the feed is 1900:1. Purification reactor 13 is equipped with a cooling water jacket to maintain a normal reaction temperature. Aldehydes and ketones contained in the crude acrylic acid undergo an addition reaction with hydrazine to generate high-boiling-point compounds. The reacted material is pumped from the reactor to the distillation unit's distillation column feed buffer tank 14 via an external pump. The reactor motor speed is 60 r / min.

[0033] 2. Liquid-phase reactant distillation The liquid reactants enter the distillation column 21, which is heated by the distillation column reboiler 22 to maintain the column bottom temperature at 67°C. The overhead gas outlet temperature of the distillation column 21 is 66°C. The distillation column condenser 24 condenses the overhead gas to 25°C and sends it into the intermediate condensate tank 23. The top pressure of the distillation column 21 is 5.3 kPa.

[0034] Acrylic acid is recovered from distillation column 21 and fed into acrylic acid recovery column 26. Acrylic acid recovery column 26 is heated by recovery column reboiler 27 to maintain column bottom temperature at 67°C. The outlet temperature of the top gas of acrylic acid recovery column 26 is 66°C. Recovery column condenser 28 condenses the top gas to 25°C and feeds it into acrylic acid recovery column condenser intermediate tank 29. The top pressure of acrylic acid recovery column 26 is 5.3 kPa.

[0035] 3. Purification by falling film crystallization Falling film crystallization purification is carried out by a two-stage falling film crystallizer: the distillation condensate pumped from the distillation column condensate enters the acrylic acid crystallization feed tank 31, and then enters the first-stage falling film crystallizer 32 through the first-stage falling film crystallizer feed pump. The crystallization temperature is finally reduced to -15℃ according to the gradient. The uncrystallized liquid phase enters the first-stage liquid phase collection tank 33, and the system enters the sweating process. The heat pump system enters the heating program, and the sweating temperature is finally increased to 13℃ according to the gradient. The high-purity product after sweating enters the first-stage product buffer tank 34.

[0036] The acrylic acid-containing liquid phase from the primary liquid phase collection tank 33 is fed into the secondary falling film crystallizer 35 via the secondary falling film crystallizer feed pump, where the crystallization temperature is gradually reduced to -15℃. The uncrystallized liquid phase enters the secondary liquid phase collection tank 36, and the system enters the sweating process. The heat pump system enters the heating program, and the sweating temperature gradually rises to 13℃. The high-purity product after sweating enters the secondary product buffer tank 37. The liquid phase in the secondary liquid phase collection tank 36 is recycled back into the primary liquid phase collection tank 33 via the secondary falling film crystallizer liquid phase reuse pump.

[0037] The specific parameters of Examples 2 and 3 are compared with those of Example 1 in the following table: The concentration of crude acrylic acid in the feed was 99%.

[0038] The following table shows a comparison of the acquired product properties and related information: Based on the comparison of Examples 1 to 3, the optimal feed ratio of crude product to hydrazine should be 2000:1.

[0039] The specific parameters of Examples 4 to 8 are compared in the table below:

[0040] The concentration of crude acrylic acid in the feed was 99%.

[0041] The following table shows a comparison of the acquired product properties and related information: By comparing Examples 4-8, under the optimal feed ratio, within a certain range, as the pressure at the top of the column decreases, the temperature at the top of the column decreases, and the recovery efficiency also increases, although energy consumption also increases accordingly. Subsequently, the crystallization and sweating temperatures were compared using the purification method of Example 6 as the standard.

[0042] The specific parameters of Examples 4-8 are compared with those of Example 6 in the following table: The concentration of crude acrylic acid in the feed was 99%.

[0043] The following table shows a comparison of the acquired product properties and related information: By comparing Examples 6, 9, and 10, it was found that under the optimal feed ratio, within a certain range, a slightly lower crystallization temperature is beneficial for improving product purity; however, a lower temperature also results in higher energy consumption. Subsequently, the crystallization and sweating temperatures were compared using the purification method of Example 9 as the standard.

[0044] The specific parameters of Examples 11-12 are compared with those of Example 9 in the following table: The concentration of crude acrylic acid in the feed was 99%.

[0045] The following table shows a comparison of the acquired product properties and related information: By comparing Examples 6, 9 and 10, it can be seen that under the optimal feed ratio, within a certain range, a slightly lower sweating temperature is beneficial to improving product purity. If the temperature is too low, energy consumption will increase accordingly, and if the temperature is too high, product purity will decrease.

[0046] In summary, the 12 sets of experiments conducted within the defined range of this invention yielded acrylic acid products with a concentration of approximately 99.97%, with some reaching 99.99%. Compared to traditional purification methods relying solely on distillation, this invention achieves the highest acrylic acid concentration, thereby increasing product concentration and production efficiency. Simultaneously, a heat pump system is used for the circulating cooling and heating of the falling film crystallization unit, fully utilizing the waste heat from the heat exchange. Furthermore, the gas supply system employed in this invention helps regulate system temperature, maximizing the effect of the polymerization inhibitor and reducing equipment corrosivity.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An apparatus for refining, crystallizing, and purifying crude acrylic acid, characterized in that: The system includes an acrylic acid purification unit, a distillation unit, and a falling film crystallization purification unit. The acrylic acid purification unit includes a crude acrylic acid feed buffer tank (11), a reactant feed buffer tank (12), a purification reactor (13), and a distillation column feed buffer tank (14). The crude acrylic acid feed buffer tank (11), containing 99.0-99.5% acrylic acid, and the reactant feed buffer tank (12), containing weakly alkaline materials, are connected in parallel to the purification reactor (13) via pipelines. The distillation column feed buffer tank (14) is connected to the outlet end of the purification reactor (13) via a pipeline. The crude acrylic acid and weakly alkaline materials are mixed and pumped into the distillation unit through pipelines. The distillation unit is used to obtain overhead gas, which is then condensed and pumped into the falling film crystallization purification unit through pipelines. The falling film crystallization purification unit includes an acrylic acid crystallization feed tank (31), a primary falling film crystallizer (32), a primary liquid phase collection tank (33), a primary product buffer tank (34), a secondary falling film crystallizer (35), a secondary liquid phase collection tank (36), a secondary product buffer tank (37), an acrylic acid product tank (38), and a condensation and sweating heat pump, all connected in sequence through pipelines. The system (39) injects cooling HTM into the primary falling film crystallizer (32), and the acrylic acid crystallization feed tank (31) injects liquid phase material into the primary falling film crystallizer (32). The acrylic acid in the liquid phase material is crystallized by HTM and passed into the primary product buffer tank (34). The remaining liquid phase material enters the primary liquid phase collection tank (33). The secondary falling film crystallizer (35) is connected to the primary liquid phase collection tank (33) through a pipeline. The condensing and sweating heat pump system (39) injects cooling HTM into the secondary falling film crystallizer (35) to make the falling film crystallizer (35) cool. The temperature inside the crystallization and purification unit is below 13°C. The liquid phase in the primary liquid phase collection tank (33) is injected into the secondary falling film crystallizer (35). The acrylic acid in the liquid phase material is crystallized by HTM and passed into the secondary product buffer tank (37). The remaining liquid phase material enters the secondary liquid phase collection tank (36). The liquid phase in the secondary liquid phase collection tank (36) flows back into the primary liquid phase collection tank (33). The high-purity acrylic acid in the primary product buffer tank (34) and the secondary product buffer tank (37) enters the acrylic acid product tank (38). A mixture of oxygen and polymerization inhibitor is introduced into the falling film crystallization and purification unit.

2. The apparatus for refining, crystallizing, and purifying crude acrylic acid according to claim 1, characterized in that: The reactant feed buffer tank (12) contains hydrazine with a concentration of 80%.

3. The apparatus for refining, crystallizing, and purifying crude acrylic acid according to claim 1, characterized in that: The distillation unit includes a distillation column (21), a distillation column reboiler (22), a condensate intermediate tank (23), and a distillation column condenser (24) connected in sequence by pipes. The distillation column (21) uses the distillation column reboiler (22) to provide heat to vaporize acrylic acid. The gaseous material is passed into the distillation column condenser (24) for condensation, and the liquid material is then introduced into the condensate intermediate tank (23) for storage.

4. The apparatus for refining, crystallizing, and purifying crude acrylic acid according to claim 3, characterized in that: The distillation unit also includes a recovery tower feed buffer tank (25), an acrylic acid recovery tower (26), a recovery tower reboiler (27), a recovery tower condenser (28), and a recovery tower condenser intermediate tank (29) connected in sequence by pipelines. The recovery tower feed buffer tank (25) is connected to the distillation tower reboiler (22) and stores liquid phase materials. The recovery tower feed buffer tank (25) feeds liquid phase materials into the acrylic acid recovery tower (26) via the recovery tower reboiler (27) for distillation. The gas phase materials are condensed into liquid phase by the recovery tower condenser (28) and then stored in the recovery tower condenser intermediate tank (29).

5. The purification method of the crude acrylic acid refining and crystallization purification device according to claim 1, characterized in that: Includes the following steps, I. 99.0-99.5% acrylic acid and 80% hydrazine are injected into the acrylic acid purification unit at a mass ratio of (1900-2100):1 to perform preliminary purification of crude acrylic acid. Then all the reactants are passed into the distillation unit. II. The distillation unit is divided into a distillation section and a recovery section. The reactants enter the distillation section at a temperature of 58–67°C and a top pressure of 2.5–5.3 kPa for distillation. During this process, the gaseous material is extracted from the distillation section and condensed at a temperature of 20–25°C. The liquid material enters the recovery section, where the temperature is maintained at 58–67°C. The generated gaseous material is condensed at an environment of 20–25°C. The materials condensed in both the distillation section and the recovery section are fed into the falling film crystallization purification unit. III. The falling film crystallization purification unit evaporates the liquid phase material and then crystallizes it at a temperature of -25 to -15°C. The uncrystallized liquid phase enters the condensation and sweating heat pump system (39) for sweating and cooling. The sweating temperature is 13 to 18°C. The purity of acrylic acid in the sweated material and the crystallized material reaches 99.99%. The oxygen and polymerization inhibitor are fully mixed. The gas supply system is controlled by the solenoid valve of the gas supply section to maintain a slight positive pressure of 0.001 to 0.005 MPa (g). The air is continuously supplied to the acrylic acid product tank (38) at a low flow rate (20 kg / h) and enters the primary product buffer tank (34) and the secondary product buffer tank (37) from the acrylic acid product tank (38) through the gas phase balance line between the two tanks.

6. The purification method of the crude acrylic acid refining and crystallization purification device according to claim 5, characterized in that: A DCS distributed control system is used to control the flow of liquid and gas phases, thereby automating the adjustment of feed ratio and flow rate.

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