High-efficiency continuous separation and purification device and process for crude adipic acid process

Abstract

The application discloses a kind of high-efficiency continuous separation and purification device and process of crude adipic acid process, belong to chemical separation technical field.The process aims at solving the problems of low efficiency, discontinuity, high moisture content of product, impurities, large wastewater discharge and other problems existing in traditional segmented separation process.The core of this process is to use a set of sedimentation, filtration, washing function in one of the sedimentation filter centrifuge, and the crude adipic acid slurry is continuously and integrally processed, and low-moisture, low-impurity filter cake is directly obtained.Meanwhile, the separated mother liquor and washing water are innovatively introduced into a monobasic acid removal tower in parallel, and after removing impurities such as monobasic acid, the purified liquid is returned to the system for recycling.The application realizes the great simplification of process flow, the continuous automation of production process, the significant improvement of product quality and the internal circulation of resources, and is especially suitable for large-scale industrial application of adipic acid production.

Description

Technical Field

[0001] This invention relates to the field of organic carboxylic acid separation and purification technology, and in particular to a highly efficient continuous separation and purification device and process for crude adipic acid production. Background Technology

[0002] Adipic acid (AA) is one of the world's largest-produced aliphatic dicarboxylic acids, with a global annual production capacity exceeding 4 million tons in 2024. It is mainly used in the production of nylon 66, polyurethane foam, and plasticizers. In the industrial production of adipic acid (primarily via cyclohexane oxidation), the crude adipic acid slurry produced in the crude processing stage typically contains: 20-30 wt% adipic acid crystals, 60-70 wt% mother liquor (containing monobasic acids such as formic acid, acetic acid, succinic acid, glutaric acid, etc.), and 5-10 wt% free water. Its separation and purification are the core steps determining product purity and production efficiency.

[0003] Existing adipic acid production facilities primarily use static cluster thickeners (structure shown in Chinese Patent Publication No. CN102731289 A, "A Thickening Process for Crude Adipic Acid") and mechanical filter-driven thickeners (structure shown in Chinese Patent Publication No. CN113975887 A, "A Continuous Thickening System for Crude Adipic Acid Slurry"). However, these traditional crude adipic acid separation processes have numerous technical defects, severely hindering the high-quality development of the adipic acid production industry.

[0004] First, the separation unit is fragmented. Traditional processes typically employ a segmented, intermittent equipment combination of "sedimentation concentration - mechanical filtration - multi-stage washing - impurity removal." This decentralized process layout results in a lengthy and complex overall process. Each step requires independent equipment operation, and the connection between the equipment requires manual intervention or complex control systems for coordination, making the processing time for a single batch too long to meet the needs of large-scale continuous production.

[0005] Secondly, the separation efficiency is low. The settling tank uses a static concentration method, resulting in slow settling of the slurry within the tank. This makes it difficult to quickly increase the solids content of the slurry, leading to an increased processing load on subsequent filtration processes. Furthermore, the multi-stage pusher centrifuge has poor dewatering performance, resulting in a high moisture content in the final filter cake. High moisture content in the filter cake not only affects the efficiency of subsequent dissolution processes but also significantly increases energy consumption during dissolution, leading to energy waste and increased production costs.

[0006] Furthermore, production continuity is poor. The mechanical filter-driven forced thickener has structural design flaws, resulting in a high failure rate during operation. Its limited capacity cannot match the processing capacity of subsequent processes, easily creating production bottlenecks. The filter rods of the static cluster thickener are not strong enough and are prone to breakage during long-term use, affecting the normal operation of the equipment. At the same time, this equipment occupies a large area and has high requirements for production space, limiting its application in some production scenarios.

[0007] Finally, the product quality and economic benefits are relatively low. In the mechanical filter-forced thickener, during the filter plate rotation, extraction, peeling, and backwashing process, adipic acid slurry experiences "crystal escape." These escaped crystals enter the mother liquor acid system, not only wasting raw materials but also affecting subsequent mother liquor treatment and reducing resource utilization. In the static cluster thickener, filter cake removal requires the use of factory air for peeling, which contains dust, oil, and other impurities. These impurities mix into the filter cake, leading to a decrease in product purity and affecting product quality and market competitiveness.

[0008] In summary, traditional segmented processes suffer from a series of prominent problems, including lengthy processes, numerous equipment, large floor space requirements, discontinuous operation, low automation, high moisture and impurity content in products, difficulty in mother liquor treatment, and serious resource waste.

[0009] With the increasing scale of adipic acid production and the growing market demands for product quality, cost control, and environmental protection, the design of an efficient and continuous separation and purification device and process for crude adipic acid production that can achieve continuous, integrated, efficient, and resource-efficient production has become an urgent need for the industry. This has significant practical and strategic value for promoting the sustainable development of the adipic acid production industry. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention discloses a highly efficient continuous separation and purification device and process for the crude adipic acid production process. This invention achieves continuous, integrated, efficient, and resource-efficient production, and has significant practical and strategic value for promoting the sustainable development of the adipic acid production industry. The technical solution adopted by this invention is as follows: A highly efficient continuous separation and purification device for the crude adipic acid production process is disclosed. The system includes a crude adipic acid slurry tank, a slurry conveying unit, a first flow control unit, a second flow control unit, a sedimentation and filtration unit, a mother liquor treatment unit, and a washing unit. The crude adipic acid slurry tank is equipped with a temperature sensor, a level gauge, and a stirring device. The top of the crude adipic acid slurry tank is connected to the discharge pipeline of the crude adipic acid crystallizer. The slurry conveying unit includes an adipic acid slurry pump, the inlet of which is connected to the outlet of the crude adipic acid slurry tank. The outlet of the adipic acid slurry pump is connected to the inlet pipeline of the sedimentation and filtration centrifuge via the first flow control unit. The sedimentation and filtration unit includes a sedimentation and filtration centrifuge. The feed end of the centrifuge is connected to an adipic acid slurry pump, the outlet of the sedimentation filtrate is connected to a mother liquor acid tank, and the outlet of the washed filter cake is connected to a centrifuge washing water tank. The washing liquid is connected inside the sedimentation centrifuge via a second flow control unit. The mother liquor treatment unit includes a mother liquor acid tank and a mother liquor acid pump. The mother liquor acid pump delivers the mother liquor acid to a monobasic acid removal tower. A heater is installed at the bottom of the monobasic acid removal tower. After being heated by the heater to remove the monobasic acid, the product is sent to the reaction process, and the filter cake is sent to a dissolving tank. The washing unit includes a centrifuge washing water pump and a centrifuge washing water tank. The washing liquid from the sedimentation centrifuge passes through a filter screen and enters the centrifuge washing water tank. The centrifuge washing water pump then delivers the washing liquid to the upper trays of the monobasic acid removal tower.

[0011] As a further optimization of the efficient continuous separation and purification device for the crude adipic acid process described above, the first flow control unit and the second flow control unit are two independent flow control loops. Each loop includes a flow meter, a flow control valve, and a control module for precisely adjusting the feed rate and the washing liquid rate. The discharge end of the sedimentation filter centrifuge is equipped with a pressure control unit for stabilizing the operating pressure inside the centrifuge.

[0012] As a further optimization of the efficient continuous separation and purification device for the crude adipic acid process described above, the discharge end of the monobasic acid removal tower is connected to the reaction process, and the tower body is equipped with a pressure control device; the heat source of the heater is steam, and the steam pipeline is equipped with a flow regulating valve to regulate the heating temperature of the mother liquor acid.

[0013] As a further optimization of the efficient continuous separation and purification device for the crude adipic acid production process described above, the discharge pipeline of the crude adipic acid slurry tank is equipped with multiple solenoid valves for switching different discharge paths; a one-way valve is installed between the mother liquor outlet of the sedimentation filter centrifuge and the mother liquor acid tank to prevent the mother liquor acid from flowing back.

[0014] An efficient and continuous separation and purification process for crude adipic acid includes the following steps: S1: The crude adipic acid slurry is temporarily stored in a crude adipic acid slurry tank and kept uniform, and then quantitatively transported to a sedimentation filter centrifuge. S2: The crude adipic acid slurry is centrifuged and concentrated in the sedimentation section of the sedimentation filter centrifuge. The separated sedimentation mother liquor is sent to the mother liquor acid tank. The concentrated slurry is pushed to the filtration section of the sedimentation filter centrifuge, where it is centrifuged, dehydrated, and washed in a countercurrent manner. The crude adipic acid filter cake is discharged and sent to the dissolving tank. At the same time, the filtrate and washing wastewater generated in the filtration section are sent to the centrifuge washing water tank. S3: After mixing the settling mother liquor in the mother liquor acid tank and the filtrate in the centrifuge washing water tank, the mixture is heated by a heater and sent to the monobasic acid removal tower to remove monobasic acid impurities. The purified liquid after removing impurities is returned to the process system for recycling. S4: Dissolve the crude adipic acid filter cake obtained in step S2 in a dissolving tank to obtain a refined adipic acid solution for subsequent purification processes.

[0015] As a further optimization of the efficient continuous separation and purification process for the crude adipic acid production process described above, the sedimentation filtration centrifuge used in step S1 is a horizontal screw discharge centrifuge, whose drum is composed of a sedimentation section and a filtration section connected coaxially. The sedimentation section is a non-porous cylindrical-conical structure used to achieve liquid-phase sedimentation separation; the filtration section is an open cylindrical structure with its inner wall covered with filter media used to achieve solid-phase dehydration and washing.

[0016] As a further optimization of the efficient continuous separation and purification process for the crude adipic acid production process described above, in step S2, the washing liquid for countercurrent washing is hot water or dilute adipic acid solution, and the washing liquid is evenly sprayed onto the filter cake layer through a washing tube set in the filtration section.

[0017] As a further optimization of the efficient continuous separation and purification process for the crude adipic acid production process described above, in step S3, the monocarboxylic acid removal tower is a distillation tower; when a distillation tower is used, a suitable operating temperature and operating pressure are set to ensure the removal effect of the monocarboxylic acid; the return to the process system for recycling in step S3 refers to the purified liquid being returned to the upstream crystallization process for use as process water, or returned to step S3 for use as washing liquid.

[0018] As a further optimization of the efficient continuous separation and purification process for the crude adipic acid production process described above, the drum speed of the sedimentation filter centrifuge and the differential speed between the screw feeder and the drum are both set within a reasonable range to ensure sedimentation, filtration and feeding effects.

[0019] As a further optimization of the efficient continuous separation and purification process for the above-mentioned crude adipic acid production process, the present invention includes a crude adipic acid slurry tank, a sedimentation filtration centrifuge, and a dissolving tank connected sequentially by pipelines; a mother liquor acid tank is connected to the sedimentation mother liquor outlet of the sedimentation filtration centrifuge; a centrifuge wash water tank is connected to the filtrate outlet of the sedimentation filtration centrifuge; a monobasic acid removal tower is connected to the outlets of the mother liquor acid tank and the centrifuge wash water tank respectively by pipelines, and a heater is provided on the feed pipeline of the monobasic acid removal tower; the purified liquid outlet of the monobasic acid removal tower is connected to the process recycling point by pipelines.

[0020] Beneficial effects Compared with the prior art, the present invention has significant advantages and beneficial effects, achieving considerable technological progress and practicality, and possessing broad application value. It has at least the following advantages: 1. Regarding separation efficiency, traditional processes employ batch operations, resulting in cumbersome connections between stages, long processing times per batch, and low production efficiency. In contrast, this invention achieves continuous operation throughout the entire process, with materials flowing continuously within the system without interruption, significantly shortening the production cycle and resulting in a qualitative leap in production capacity. Furthermore, the integrated equipment design reduces the number of devices and floor space required. Compared to traditional processes, the significantly reduced equipment footprint greatly improves the utilization rate of production space, lowers fixed asset investment costs, and saves enterprises substantial space resources and capital investment. 2. The quality of the filter cake has been fundamentally optimized. Traditional processes produce crude adipic acid filter cakes with high moisture content and high impurity content. This not only affects the efficiency of subsequent dissolution processes but also increases energy consumption and negatively impacts the purity of the final product. This invention, through a combined process of "centrifugal concentration-deep dehydration-countercurrent washing" and monocarboxylic acid directional removal technology, significantly reduces the moisture content of the crude adipic acid filter cake and controls the impurity content to extremely low levels. The reduced moisture content of the filter cake significantly reduces the energy consumption required for subsequent dissolution processes, lowering production costs for enterprises; the reduced impurity content lays a solid foundation for improving the purity of the final product and enhancing its market competitiveness. 3. A significant improvement in impurity removal rate. Monobasic acid, as the main impurity in crude adipic acid slurry, directly determines the purity of the product. Traditional processes have a low removal rate of monobasic acid, resulting in product purity that fails to meet the demands of the high-end market. This invention, through a specially designed monobasic acid removal tower and optimized operating parameters, achieves targeted and efficient removal of monobasic acid, significantly improving the removal rate. The high removal rate keeps the accumulation of impurities in the circulating material at an extremely low level, effectively preventing impurity enrichment within the system, ensuring the stability of product purity, and maintaining a consistently high level of purity to meet the requirements of high-end product production. 4. Resource utilization has been significantly improved. In traditional processes, the treatment of mother liquor and wash water is relatively simple, with most of it being directly discharged, resulting in serious waste of water resources and environmental pollution. This invention achieves highly efficient recycling of mother liquor and wash water, significantly increasing the recycling rate, significantly reducing the consumption of fresh water, and also significantly reducing wastewater discharge. This not only reduces water consumption and wastewater treatment costs in the production process but also reduces environmental pollution, aligning with the current concepts of green chemistry and sustainable development. It establishes a positive environmental image for enterprises and provides a valuable example for the industry's green transformation. 5. Operational stability is greatly enhanced. Traditional processes involve numerous pieces of equipment with complex inter-equipment connections, making them prone to malfunctions, production interruptions, and reduced efficiency. The process system of this invention features a simple structure, high equipment integration, smooth coordination between units, high equipment reliability, long continuous operating time, and extremely low downtime for maintenance. Stable operation ensures continuous production, reduces production interruptions due to equipment failures, improves efficiency, meets the demands of large-scale industrial production, and provides strong support for stable production in enterprises. 6. In summary, the process of the present invention has many advantages such as high separation efficiency, excellent product quality, high impurity removal rate, high resource utilization rate, and strong operational stability. It can bring significant economic, environmental and social benefits to enterprises, has broad prospects for industrial application, and will surely promote the development of the adipic acid production industry towards high efficiency, environmental protection and high quality. Attached Figure Description

[0021] Figure 1 This is a flowchart of the process described in this invention.

[0022] Figure 2 This is a schematic diagram of the sedimentation filtration centrifuge described in this invention.

[0023] Marked in the image: 1: Crude adipic acid slurry tank; 2: Adipic acid slurry pump; 3: First flow control unit; 4: First solenoid valve; 5: Second solenoid valve; 6: Sedimentation filter centrifuge; 7: Second flow control unit; 8: Dissolving tank; 9: Mother liquor acid tank; 10: Centrifuge wash water tank; 11: Mother liquor acid pump; 12: Centrifuge wash water pump; 13: Monobasic acid removal tower; 14: Heater.

[0024] 6-1: Main drive motor; 6-2: Differential; 6-3: Bearing housing; 6-4: Rotary drum (6-4A: Settling section, 6-4B: Filtration section); 6-5: Screw feeder; 6-6: Feed pipe; 6-7: Overflow port; 6-8: Washing pipe; 6-9: Filter medium; 6-10: Filtrate collection hood; 6-11: Filter cake discharge port; 6-12: Settling mother liquor outlet; 6-13: Filtrate outlet. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of protection. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort, such as formal modifications to the technical solutions described in the following embodiments or equivalent substitutions for some technical features, within the scope of the present invention's conceptual framework, are within the scope of protection of the present invention.

[0026] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] like Figure 1 , 2As shown, a high-efficiency continuous separation and purification device for the crude adipic acid process is disclosed. The system includes a crude adipic acid slurry tank 1, a slurry conveying unit, a first flow control unit 3, a second flow control unit 7, a sedimentation filtration unit, a mother liquor treatment unit, and a washing unit. The crude adipic acid slurry tank 1 is equipped with a temperature sensor, a level gauge, and a stirring device. The top of the crude adipic acid slurry tank 1 is connected to the discharge pipeline of the crude acid crystallizer. The slurry conveying unit includes an adipic acid slurry pump 2, the inlet of which is connected to the outlet of the crude adipic acid slurry tank 1. The outlet of the adipic acid slurry pump 2 is connected to the inlet pipeline of the sedimentation filtration centrifuge 6 via the first flow control unit 3. The sedimentation filtration unit includes the sedimentation filtration centrifuge 6. The inlet of the sedimentation filtration centrifuge 6 is connected to the discharge pipeline of the sedimentation filtration centrifuge 6. The material end is connected to the adipic acid slurry pump 2, the sedimentation filtrate outlet is connected to the mother liquor acid tank 9, and the washing filter cake outlet is connected to the centrifuge washing water tank 10; wherein, the washing liquid is connected to the inside of the sedimentation filter centrifuge 6 via the second flow control unit 7; the mother liquor treatment unit includes the mother liquor acid tank 9 and the mother liquor acid pump 11, the mother liquor acid pump 11 transports the mother liquor acid to the monobasic acid removal tower 13, the bottom of the monobasic acid removal tower 13 is equipped with a heater 14, after which the monobasic acid is removed by the heater 14 and sent to the reaction process, and the filter cake is sent to the dissolving tank 8; the washing unit includes the centrifugal washing water pump 12 and the centrifuge washing water tank 10, the washing liquid of the sedimentation filter centrifuge 6 enters the centrifuge washing water tank 10 after passing through the filter screen, and then the centrifugal washing water pump 12 transports the washing liquid to the upper tray of the monobasic acid removal tower 13.

[0028] The first flow control unit 3 and the second flow control unit 7 are two independent flow control loops. Each loop includes a flow meter, a flow control valve and a control module for precisely adjusting the feed rate and the washing liquid rate. The discharge end of the sedimentation filter centrifuge 6 is equipped with a pressure control unit for stabilizing the operating pressure inside the centrifuge.

[0029] The discharge end of the monobasic acid removal tower 13 is connected to the reaction process, and the tower body is equipped with a pressure control device; the heat source of the heater 14 is steam, and the steam pipeline is equipped with a flow regulating valve to regulate the heating temperature of the mother liquor acid.

[0030] Multiple solenoid valves are installed on the discharge pipeline of the crude adipic acid slurry tank 1 to switch different discharge paths; a one-way valve is installed between the mother liquor outlet of the sedimentation filter centrifuge 6 and the mother liquor acid tank 9 to prevent the mother liquor acid from flowing back.

[0031] refer to Figure 1 The material flow path of the present invention is as follows: crude adipic acid slurry crystallizer → crude adipic acid slurry tank 1 → adipic acid slurry pump 2 → through the first flow control unit 3 and the first solenoid valve 4 → sedimentation filter centrifuge 6 (sedimentation-filtration-washing) → filter cake → dissolving tank 8 → refined adipic acid solution. The media-assisted flow path of the present invention is as follows: mother liquor → mother liquor acid tank 9 → mother liquor acid pump 11 → bottom tray of monoprotic acid removal tower 13 → heater 14 → circulating material tank; Washing water flows from the second flow control unit 7 to the sedimentation filter centrifuge 6, then to the centrifuge wash water tank 10, the centrifuge wash water pump 12, the monobasic acid removal tower 13 (high-level tray), the heater 14, the monobasic acid removal tower 13, and finally to the circulating tank.

[0032] An efficient and continuous separation and purification process for crude adipic acid includes the following steps: S1: The crude adipic acid slurry is temporarily stored in crude adipic acid slurry tank 1 and kept uniform. It is then quantitatively transferred to sedimentation filter centrifuge 6. During the transfer process, the pipeline must be kept unobstructed to avoid slurry blockage or leakage. After the slurry enters the slurry tank, the variable frequency agitator is turned on. The agitator speed is adjusted according to the actual state of the slurry to ensure uniform suspension within the tank and prevent crystal sedimentation.

[0033] S2: The crude adipic acid slurry is centrifuged and concentrated in the sedimentation section of the sedimentation centrifuge 6. The separated mother liquor is sent to the mother liquor acid tank 9. The concentrated slurry is pushed to the filtration section of the sedimentation centrifuge 6, where it undergoes centrifugal dehydration and countercurrent washing. The resulting crude adipic acid filter cake is discharged and sent to the dissolving tank 8. At the same time, the filtrate and washing wastewater generated in the filtration section are sent to the centrifuge washing water tank 10. In actual operation, the slurry enters the drum sedimentation section through the feed pipe. Under the action of centrifugal force, the adipic acid crystals in the slurry, due to their higher density, settle towards the drum wall, gradually forming a concentrated slurry layer. The mother liquor (containing monobasic acid, water, fine crystals, and other impurities), due to its lower density, moves towards the center of the drum and is eventually discharged continuously through the overflow port at the end of the sedimentation section. During the sedimentation process, the solid content of the concentrated slurry is monitored by an online gamma-ray densitometer in the sedimentation section. Based on the solids content monitoring results, operators flexibly adjust the drum speed using a differential gear to ensure the solids content of the concentrated slurry remains within a suitable range. If the solids content is too low, the drum speed can be appropriately increased to enhance centrifugal force and accelerate crystal settling; if the solids content is too high, the drum speed is reduced to prevent the slurry from becoming too viscous and affecting subsequent feeding and filtration. Simultaneously, the discharge flow rate of the mother liquor is recorded using a flow meter, facilitating material balance and process adjustments throughout the entire process. The discharged mother liquor is temporarily stored in a mother liquor acid tank. The concentrated slurry enters the filtration section under the push of a screw conveyor. The screw conveyor is made of corrosion-resistant, high-strength material, capable of meeting the slurry conveying requirements and ensuring the slurry enters the filtration section smoothly and evenly. The inner wall of the filtration section is lined with a special filter medium with suitable pore size and porosity, effectively blocking adipic acid crystals to prevent crystal loss while ensuring smooth passage of the filtrate, achieving solid-liquid separation. Under centrifugal force, residual water in the slurry is discharged through the pores of the filter medium, forming a filter cake layer. The thickness of the filter cake is monitored in real time by a filter cake thickness sensor, and the rotational speed difference of the screw conveyor is adjusted according to the monitoring results. If the filter cake is too thick, it will increase the filtration resistance and affect the filtration efficiency. In this case, the rotational speed difference needs to be increased to speed up the feeding of the filter cake. If the filter cake is too thin, the rotational speed difference is reduced to prolong the residence time of the filter cake in the filtration section and ensure the dewatering effect. Then, the valve of the washing pipe is opened to introduce washing liquid into the filtration section. The washing liquid is hot water or dilute adipic acid solution, which is evenly sprayed onto the filter cake layer through atomizing nozzles. A countercurrent washing method is adopted, that is, the washing liquid is sprayed from the end of the filtration section, opposite to the movement direction of the filter cake. This washing method can ensure that the washing liquid and the filter cake are in full contact, gradually washing away impurities in the filter cake and improving the washing effect. During the washing process, the conductivity of the washing liquid is monitored in real time by a conductivity meter. The change in conductivity reflects the amount of impurities in the washing liquid. When the conductivity reaches the set qualified standard, it indicates that the filter cake washing is qualified; if the conductivity exceeds the standard, the washing effect can be further improved by increasing the washing liquid flow rate or extending the contact time, so as to ensure that the impurity content in the filter cake is reduced to the specified level.After washing, the crude adipic acid filter cake is continuously discharged through the filter cake outlet, which is equipped with a scraper to remove the filter cake adhering to the inner wall of the drum, ensuring smooth discharge. The discharged filter cake is then conveyed into the dissolving tank, taking precautions to prevent moisture, contamination, or loss during transport. The filtrate (including wash water and residual mother liquor) produced in the filtration section is collected by a filtrate collection hood and discharged through the filtrate outlet. The filtrate collection hood is made of corrosion-resistant material, effectively collecting the filtrate and preventing leakage. The discharged filtrate, along with the centrifuge's rinse water, is collected in the centrifuge wash water tank. The tank level is controlled by a level gauge to maintain it within a reasonable range, ensuring the normal operation of the wash water tank and providing a stable material source for subsequent mother liquor and wash water treatment.

[0034] S3: The settling mother liquor in the mother liquor acid tank 9 and the filtrate in the centrifuge wash water tank 10 are mixed separately, heated by the heater 14, and then sent to the monobasic acid removal tower 13 to remove monobasic acid impurities. The purified liquid after impurity removal is returned to the process system for recycling. Monobasic acids (formic acid, acetic acid) are the main impurities in crude adipic acid slurry, and their removal effect directly affects the purity of the final product. Therefore, it is necessary to perform targeted removal treatment of monobasic acids in the mother liquor and wash water. Open the outlet valve of the mother liquor acid tank and start the mother liquor acid pump to deliver the mother liquor to the lower tray of the monobasic acid removal tower. During the delivery process, the mother liquor is heated by the heater. The heater adopts PID regulation to accurately control the heating temperature of the mother liquor, ensuring that the mother liquor is heated to a suitable temperature before entering the removal tower, creating favorable conditions for the removal of monobasic acids. At the same time, start the centrifuge wash water pump to deliver the wash water to the upper tray of the monobasic acid removal tower. The wash water, with its relatively low concentration, flows downwards along the trays of the removal tower, where it comes into full contact with the high-concentration mother liquor acid vapor and monobasic acid flowing upwards, forming an azeotrope. The azeotrope is then cooled by vapor phase and discharged from the system, achieving preliminary separation of the monobasic acid. The mother liquor, after removing the monobasic acid, is concentrated by distillation in a heater and then sent to the oxidation process. There, it is mixed with fresh nitric acid solution in a certain proportion and fed into the oxidizing acid preparation tank, achieving mother liquor recycling, improving resource utilization, and reducing waste. The high-concentration mother liquor acid material is fed into the lower tray inlet of the monobasic acid removal tower via a feed distributor, while the low-concentration centrifuge wash water is fed into the upper tray inlet via the same feed distributor. The feed distributor ensures uniform liquid distribution on the trays, preventing liquid deviation, improving gas-liquid contact efficiency, and thus enhancing the removal effect. The reboiler is heated by saturated steam to provide heat for the vaporization of the material inside the tower. The temperature of the column bottom is controlled within a suitable range by adjusting the steam flow rate. A circulating water condenser is used at the top of the column; the temperature at the top is controlled by adjusting the circulating water flow rate to ensure sufficient condensation of the gas phase. The material inside the column undergoes a thorough gas-liquid mass transfer process within the packing layer. Monobasic acids have relatively low boiling points and, under the temperature and pressure conditions inside the column, easily vaporize and rise to the top of the column in gaseous form. After condensation in the condenser, a high-purity monobasic acid fraction is obtained and sent to a monobasic acid storage tank for storage, where it can be recycled as a byproduct. The liquid phase at the bottom of the column is monitored in real time by an online gas chromatograph, which can accurately detect the content of monobasic acids in the liquid phase. When the content of monobasic acids in the liquid phase decreases to the set acceptable standard, it is discharged from the column bottom outlet and sent to the circulating feed tank. If the content of monobasic acids exceeds the standard, the operating parameters can be adjusted by increasing the reboiler steam pressure or reducing the feed flow rate to extend the residence time of the material in the column and improve the removal efficiency until the content of monobasic acids in the liquid phase at the bottom of the column reaches the acceptable standard. The liquid phase (with a relatively high adipic acid content and a low monocarboxylic acid content) in the circulating tank is pumped to the crude adipic acid slurry tank, where it is mixed with the fresh slurry and then re-enters the separation process.This recycling method can make full use of the useful components in materials, improve the recycling rate of materials, reduce resource waste, and also reduce the amount of wastewater discharged, thus having good economic and environmental benefits.

[0035] S4: The crude adipic acid filter cake obtained in step S2 is dissolved in dissolving tank 8 to obtain a refined adipic acid solution for subsequent purification processes. The washed crude adipic acid filter cake is fed into the dissolving tank, and the solution circulation pump is turned on to promote thorough mixing of the filter cake and solvent, accelerating the dissolution rate. An appropriate amount of hot water is introduced into the dissolving tank as a solvent; the amount of hot water added is rationally controlled according to the mass of the filter cake to ensure complete dissolution. During the dissolution process, the solution concentration is monitored in real time by an online concentration meter in the dissolving tank. The concentration meter uses the refractive index method to quickly and accurately measure the concentration of adipic acid in the solution. Based on the concentration monitoring results, the amount of hot water added or the amount of filter cake fed is adjusted to ensure that the adipic acid concentration reaches a suitable range, allowing the filter cake to dissolve completely and avoiding undissolved solid particles that could affect subsequent purification processes. The final refined adipic acid solution overflows through a baffle to the subsequent activated carbon decolorization process. The baffle acts as a preliminary filter, removing any small amounts of solid impurities that may be present in the solution. During the decolorization process, activated carbon adsorbs pigments and other trace impurities in the solution, further improving the purity of the solution. High-purity adipic acid is obtained after decolorization, meeting the requirements of downstream industries.

[0036] The sedimentation and filtration centrifuge 6 used in step S1 is a horizontal screw discharge centrifuge. Its drum is composed of a sedimentation section and a filtration section connected coaxially. The sedimentation section is a non-porous cylindrical-conical structure used to achieve liquid phase sedimentation and separation. The filtration section is an open cylindrical structure with a filter medium on its inner wall used to achieve solid phase dehydration and washing.

[0037] In step S2, the washing liquid for countercurrent washing is hot water or dilute adipic acid solution, and the washing liquid is evenly sprayed onto the filter cake layer through the washing pipe set in the filtration section.

[0038] In step S3, the monobasic acid removal tower 13 is a distillation tower. When a distillation tower is used, a suitable operating temperature and operating pressure are set to ensure the removal effect of the monobasic acid. The return to the process system for recycling in step S3 means that the purified liquid is returned to the upstream crystallization process for use as process water, or returned to step S2 for use as washing liquid.

[0039] The rotational speed of the sedimentation filter centrifuge 6 and the differential speed between the screw feeder and the rotational speed are both set within a reasonable range to ensure the sedimentation, filtration and feeding effects.

[0040] The system includes a crude adipic acid slurry tank 1, a sedimentation and filtration centrifuge 6, and a dissolving tank 8, all connected sequentially via pipelines. A mother liquor acid tank 9 is connected to the sedimentation mother liquor outlet of the sedimentation and filtration centrifuge 6. A centrifuge wash water tank 10 is connected to the filtrate outlet of the sedimentation and filtration centrifuge 6. A monobasic acid removal tower 13 is connected to the outlets of the mother liquor acid tank 9 and the centrifuge wash water tank 10 via pipelines. A heater 14 is installed on the feed pipeline of the monobasic acid removal tower 13. The purified liquid outlet of the monobasic acid removal tower 13 is connected to a process recycling point via a pipeline.

[0041] In actual implementation, the parameters and models of each unit are as follows: Raw material is crude adipic acid slurry from a cyclohexanol oxidation crystallizer, temperature 30-40℃, solid content (based on adipic acid) 10-30wt%. Key equipment: Sedimentation filter centrifuge, drum diameter 1200mm, length-to-diameter ratio 1.5:1-3.5:1, sedimentation section to filtration section length ratio approximately 5:1-2:1. Monobasic acid removal tower: adopts an atmospheric distillation tower, theoretical plate number 20-35. Sedimentation filter centrifuge drum speed: 1500-3000 r / min. Differential speed between the screw conveyor and the drum: 5-18 r / min. Washing liquid volume: 1-3 m³. 3 / h. Monobasic acid removal tower reboiler temperature: 100-130℃, operating pressure: 0.1-0.3 MPa (gauge pressure), reflux ratio controlled at 4:1-2:1.

[0042] Operating results: Moisture content of crude adipic acid filter cake: 1-8%. Monobasic acid content (calculated as glutaric acid) in crude adipic acid filter cake: 0.08%. Monobasic acid removal rate of settling mother liquor and wash water after passing through the removal tower: 95-99.5%.

[0043] During continuous operation, the separation system maintained stable processing capacity. All purified liquid was reused in the crystallization process for slurry preparation, reducing wastewater discharge by approximately 60% compared to the old process.

[0044] The above embodiments fully demonstrate that the process of the present invention can stably produce high-quality, low-moisture, and low-impurity crude adipic acid filter cake under different feeding conditions and operating parameters, and efficiently achieves impurity removal and resource recycling. Its comprehensive technical and economic indicators are superior, and it possesses good adaptability and stability, capable of meeting the needs of adipic acid production enterprises of different scales and with different raw material conditions. It has broad prospects for industrial application and enormous promotional value.

[0045] The preferred embodiments and specific implementations of the present invention have been described in detail above with reference to the examples. However, the present invention is not limited to the above-described embodiments and examples. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the concept of the present invention.

Claims

1. A highly efficient continuous separation and purification device for the crude adipic acid production process, characterized in that: The system includes a crude adipic acid slurry tank (1), a slurry conveying unit, a first flow control unit (3), a second flow control unit (7), a sedimentation filtration unit, a mother liquor treatment unit, and a washing unit. The crude adipic acid slurry tank (1) is equipped with a temperature sensor, a level gauge, and a stirring device. The top of the crude adipic acid slurry tank (1) is connected to the discharge pipeline of the crude acid crystallizer. The slurry conveying unit includes an adipic acid slurry pump (2). The inlet of the adipic acid slurry pump (2) is connected to the outlet of the crude adipic acid slurry tank (1). The outlet of the adipic acid slurry pump (2) is connected to the inlet pipeline of the sedimentation filtration centrifuge (6) via the first flow control unit (3). The sedimentation filtration unit includes a sedimentation filtration centrifuge (6). The inlet of the sedimentation filtration centrifuge (6) is connected to the adipic acid slurry pump (2). The sedimentation filtrate... The outlet is connected to the mother liquor acid tank (9), and the washing filter cake outlet is connected to the centrifuge washing water tank (10); wherein, the washing liquid is connected to the interior of the sedimentation filter centrifuge (6) via the second flow control unit (7); the mother liquor treatment unit includes the mother liquor acid tank (9) and the mother liquor acid pump (11), the mother liquor acid pump (11) transports the mother liquor acid to the monobasic acid removal tower (13), the bottom of the monobasic acid removal tower (13) is equipped with a heater (14), the monobasic acid is removed by the heater (14) and sent to the reaction process, and the filter cake is sent to the dissolving tank (8); the washing unit includes the centrifuge washing water pump (12) and the centrifuge washing water tank (10), the washing liquid of the sedimentation filter centrifuge (6) enters the centrifuge washing water tank (10) after passing through the filter screen, and then the centrifuge washing water pump (12) transports the washing liquid to the upper plate of the monobasic acid removal tower (13).

2. A high efficiency continuous separation and purification device for crude adipic acid process as claimed in claim 1, wherein: The first flow control unit (3) and the second flow control unit (7) are two independent flow control loops. Each loop includes a flow meter, a flow control valve and a control module for precisely adjusting the feed rate and the washing liquid rate. The discharge end of the sedimentation filter centrifuge (6) is equipped with a pressure control unit for stabilizing the operating pressure inside the centrifuge.

3. A high efficiency continuous separation and purification device for crude adipic acid process as claimed in claim 1, wherein: The discharge end of the monobasic acid removal tower (13) is connected to the reaction process, and the tower body is equipped with a pressure control device; the heat source of the heater (14) is steam, and the steam pipeline is equipped with a flow regulating valve to regulate the heating temperature of the mother liquor acid.

4. A high efficiency continuous separation and purification device for crude adipic acid process as claimed in claim 1, wherein: The crude adipic acid slurry tank (1) is equipped with multiple solenoid valves on its discharge pipeline for switching different discharge paths; a one-way valve is provided between the mother liquor outlet of the sedimentation filter centrifuge (6) and the mother liquor acid tank (9) to prevent the mother liquor acid from flowing back.

5. The purification process of a high-efficiency continuous separation and purification device for a crude adipic acid process according to any one of claims 1 to 4, characterized in that: Includes the following steps, S1: The crude adipic acid slurry is temporarily stored in the crude adipic acid slurry tank (1) and kept uniform, and then quantitatively transported to the sedimentation filter centrifuge (6). S2: The crude adipic acid slurry is centrifuged and concentrated in the sedimentation section of the sedimentation filter centrifuge (6), and the separated sedimentation mother liquor is sent to the mother liquor acid tank (9); the concentrated slurry is pushed to the filtration section of the sedimentation filter centrifuge (6), and centrifugation dewatering and countercurrent washing are performed in sequence. The crude adipic acid filter cake is discharged and sent to the dissolving tank (8). At the same time, the filtrate and washing wastewater generated in the filtration section are sent to the centrifuge washing water tank (10). S3: After mixing the sedimentation mother liquor in the mother liquor acid tank (9) and the filtrate in the centrifuge washing water tank (10), the mixture is heated by the heater (14) and sent to the monobasic acid removal tower (13) to remove monobasic acid impurities. The purified liquid after removing impurities is returned to the process system for recycling. S4: Dissolve the crude adipic acid filter cake obtained in step S2 in a dissolving tank (8) to obtain a refined adipic acid solution for subsequent purification processes.

6. A highly efficient continuous separation and purification process of crude adipic acid process as claimed in claim 5, wherein: The sedimentation and filtration centrifuge (6) used in step S1 is a horizontal screw discharge centrifuge. Its drum is composed of a sedimentation section and a filtration section connected coaxially. The sedimentation section is a non-porous cylindrical-conical structure used to achieve liquid phase sedimentation and separation. The filtration section is an open cylindrical structure with a filter medium covering its inner wall, used to achieve solid phase dehydration and washing.

7. A highly efficient continuous separation and purification process of crude adipic acid process as claimed in claim 5, wherein: In step S2, the washing liquid for countercurrent washing is hot water or dilute adipic acid solution, and the washing liquid is evenly sprayed onto the filter cake layer through the washing pipe set in the filtration section.

8. A highly efficient continuous separation and purification process of crude adipic acid process as claimed in claim 5, wherein: In step S3, the monobasic acid removal tower (13) is a distillation tower; When using a distillation column, set appropriate operating temperature and operating pressure to ensure the removal effect of monobasic acid; the return to the process system for recycling in step S3 means that the purified liquid is returned to the upstream crystallization process for use as process water, or returned to step S2 for use as washing liquid.

9. A highly efficient continuous separation and purification process of crude adipic acid process as claimed in claim 5, wherein: The rotational speed of the drum of the sedimentation filter centrifuge (6) and the differential speed between the screw feeder and the drum are both set within a reasonable range to ensure the sedimentation, filtration and feeding effects.

10. A highly efficient continuous separation and purification process of crude adipic acid process as claimed in claim 5, wherein: The present invention includes a crude adipic acid slurry tank (1), a sedimentation filtration centrifuge (6), and a dissolving tank (8) connected sequentially by pipelines; a mother liquor acid tank (9) is connected to the sedimentation mother liquor outlet of the sedimentation filtration centrifuge (6); a centrifuge washing water tank (10) is connected to the filtrate outlet of the sedimentation filtration centrifuge (6); a monobasic acid removal tower (13) is connected to the outlets of the mother liquor acid tank (9) and the centrifuge washing water tank (10) by pipelines respectively, and a heater (14) is provided on the feed pipeline of the monobasic acid removal tower (13); the purified liquid outlet of the monobasic acid removal tower (13) is connected to the process recycling point by pipelines.

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