A system for recovering and purifying dicarboxylic acids from adipic acid production waste liquid

Abstract

This application belongs to the technical field of chemical machinery and equipment, specifically relating to a system for recovering and purifying dicarboxylic acid from adipic acid production waste liquid. The system includes: a rising film evaporator, a separator, a dicarboxylic acid recovery crystallization unit, a centrifugal separator, a decolorizing tank, and a dicarboxylic acid evaporation and slaking unit, connected sequentially by pipelines. This application, through appropriate concentration (increasing the material concentration entering the dicarboxylic acid evaporation and slaking system from the existing 20% ​​to 50%), cooling centrifugation, and dissolution decolorization, can further improve and enhance the quality of DBA finished products. Preliminary application results, combined with adjustments to relevant process parameters, show that the purity of the existing finished product (approximately 99.3%) can be further increased to 99.7%, and the nitric acid content (0.5%) and water content (0.5%) of the existing finished product can be further reduced to nitric acid ≤0.1% and water ≤0.3%, which has significant technical implications for improving the quality and value of DBA products.

Description

Technical Field

[0001] This application belongs to the field of chemical machinery and equipment technology, specifically relating to a system for recovering and purifying dicarboxylic acids from adipic acid production waste liquid. Background Technology

[0002] Adipic acid is an important raw material for chemical production, with wide applications in organic synthesis, pharmaceuticals, lubricant manufacturing, nylon 66 production, and engineering plastics.

[0003] The earliest industrial production of adipic acid used cyclohexanol as a raw material, which was then obtained through nitric acid oxidation (hydrogenation of phenol). After the 1960s, with the development of other chemical industries, industrial production gradually shifted to a process using cyclohexane as a raw material. That is, cyclohexane is first used to produce an intermediate product, a mixture of cyclohexanone and cyclohexanol (i.e., ketol oil, also known as KA oil), which is then oxidized to produce adipic acid. In the oxidation of KA oil, one process route uses excess nitric acid as an oxidant, and the oxidation reaction is achieved under appropriate catalyst and reaction conditions. Because this process route yields adipic acid with high yield and purity, it is widely used in industrial production.

[0004] In actual production, the main components of adipic acid production waste liquid include: approximately 4% SA (succinic acid), approximately 13% GA (glutaric acid), and approximately 4% ADA (adipic acid). The mixture of SA / GA / ADA is often referred to as DBA, which accounts for about 20% of the total waste liquid. The waste liquid also contains less than 3% nitric acid. DBA, as a chemical raw material, has a wide range of applications. Therefore, in actual production, it is necessary to recover DBA from adipic acid production waste liquid to increase industrial output value and reduce environmental treatment costs. In existing technologies, when extracting DBA, the waste liquid is usually directly fed into a dicarboxylic acid evaporation and flake-forming system for evaporation and flake-forming. However, the DBA flakes prepared by this direct production method have poor purity (around 99.3%), are mostly yellowish-green in color, and have a high nitric acid content (around 0.5%). Therefore, this severely restricts the production and application range of the recovered DBA product and also limits the added value of the extracted DBA product. Summary of the Invention

[0005] The purpose of this application is to provide a system for recovering and purifying dicarboxylic acids from adipic acid production waste liquid, thereby laying a certain technical foundation for effectively extracting high-purity DBA products.

[0006] The technical solution adopted in this application is described in detail below.

[0007] A system for recovering and purifying dicarboxylic acid from adipic acid production waste liquid includes: a rising film evaporator, a separator, a dicarboxylic acid recovery crystallization unit, a centrifugal separation device, a decolorization tank, and a dicarboxylic acid evaporation and condensation unit connected in sequence by pipelines;

[0008] in:

[0009] The rising film evaporator is connected to a raw material tank containing adipic acid production waste liquid to be purified via pipelines. In actual design, a raw material tank discharge pump is designed on the connecting pipeline between the evaporator and the raw material tank to pump the adipic acid production waste liquid in the raw material tank into the evaporator.

[0010] The rising film evaporator uses low-pressure steam as a heat source to perform preliminary evaporation treatment on adipic acid production waste liquid, and controls the discharge temperature to be around 85°C.

[0011] The separator, specifically, for example, is a cyclone separator, used to separate the gas-liquid mixture after evaporation by the rising film evaporator, wherein the gas phase is further recovered and discharged into the atmosphere, and the liquid phase enters the subsequent dicarboxylic acid recovery and crystallization unit.

[0012] In actual design, a vacuum system is connected to the top of the cyclone separator to maintain a negative pressure state inside the cyclone separator (absolute pressure of 70-80 kPa), which is conducive to the rapid evaporation of the rising film evaporator;

[0013] The dicarboxylic acid recovery and crystallization unit includes several dicarboxylic acid recovery crystallizers connected in series; the dicarboxylic acid recovery crystallizers are used to cool and crystallize the liquid phase separated by the separator (to precipitate dicarboxylic acid); each dicarboxylic acid recovery crystallizer is connected to a corresponding cooling device (usually a cooling coil with chilled water inlet and chilled water outlet pipes, so that the cooling and crystallization temperature of each dicarboxylic acid recovery crystallizer can be adjusted as needed);

[0014] In the preferred design, the top of the dicarboxylic acid recovery crystallizer is equipped with a recovery crystallization stirring device to ensure uniform cooling of the recovery liquid;

[0015] In the specific design, three dicarboxylic acid recovery crystallizers can be designed. To save power, after cooling, the recovered liquid can overflow from high to low into the next dicarboxylic acid recovery crystallizer based on the position difference between different dicarboxylic acid recovery crystallizers. In the actual design, each dicarboxylic acid recovery crystallizer can be connected to the existing negative pressure system to maintain a slight negative pressure state inside the dicarboxylic acid recovery crystallizer (vacuum degree of about 140 mm water column), thereby ensuring the stable and orderly flow of the recovered liquid.

[0016] After running for a certain period of time, in order to clean the dicarboxylic acid recovery crystallizer, the dicarboxylic acid recovery crystallizer is connected to a low-pressure steam pipeline and a condensate discharge pipeline. The low-pressure cleaning steam enters the dicarboxylic acid recovery crystallizer through the coil to heat and clean it.

[0017] The centrifugal separation device is specifically a centrifuge connected to a filter cake washing water (cold high-purity water, 0.6MPa, 10℃) pipeline, used to centrifuge and dehydrate the recovered liquid after the crystallization of dicarboxylic acid. After centrifugation and washing, the impurity content in the filter cake, which is mainly composed of dicarboxylic acid, is further reduced. The obtained filter cake enters a dissolution and decolorization tank for further processing.

[0018] The dissolving and decolorizing tank is used to further decolorize and remove impurities from the filter cake obtained by the centrifugal separation device after dissolving it. The upper part of the tank is designed with an activated carbon inlet for decolorization and impurity removal and a dissolving water inlet for dissolving.

[0019] To further ensure thorough dissolution and decolorization, a decolorization tank agitator is designed at the top of the tank, and / or a low-pressure steam inlet and a corresponding condensate outlet are designed on the tank (to appropriately increase the temperature of the dissolving solution, thereby accelerating dissolution).

[0020] The carbon filter is used to filter and remove activated carbon from the solution after dissolution and decolorization. In actual production, a dissolution and decolorization tank discharge pump is designed on the connecting pipeline between the carbon filter and the dissolution and decolorization tank to pump the solution after dissolution and decolorization into the carbon filter.

[0021] Furthermore, the carbon filter is also equipped with a sight glass and a carbon protection filter, so as to more intuitively judge the filtration status of the carbon filter and ensure the stable operation of the carbon filter;

[0022] The dicarboxylic acid evaporation and slagging unit includes: a dicarboxylic acid evaporation and slagging feed tank, a dicarboxylic acid evaporation and slagging feed pump, and a slagging machine connected in sequence; the solution after filtration to remove activated carbon is uniformly stored in the feed tank, and then pumped into the slagging machine by the feed pump to slag and prepare DBA sheet products.

[0023] The adipic acid production waste liquid recovery and purification system provided in this application can further improve and enhance the quality of DBA finished products through appropriate concentration (increasing the material concentration entering the dipic acid evaporation and flake formation system from the existing 20% ​​to 50%, which can reduce energy consumption during the flake formation process and reduce the moisture content of the final product), cooling centrifugation, and dissolution and decolorization operations.

[0024] Based on adjustments to relevant process parameters, preliminary application results show that the recycling and purification system provided in this application can further increase the purity of the existing finished product from approximately 99.3% to 99.7%, and further reduce the nitric acid content (0.5%) and moisture content (0.5%) of the existing finished product to ≤0.1% for nitric acid and ≤0.3% for water. This has significant technical implications for improving the quality and value of DBA products. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the adipic acid production liquid recycling system provided in this application. Example

[0026] like Figure 1 As shown, the adipic acid production waste liquid recovery and purification system provided in this application includes: a rising film evaporator 3, a separator 4, a dipic acid recovery crystallization unit, a centrifugal separation device 7, a decolorizing tank 8, a carbon filter 11, and a dipic acid evaporation and agglomeration unit connected in sequence by pipelines;

[0027] in:

[0028] The rising film evaporator 3 is connected to the raw material tank 1, which stores the adipic acid production waste liquid to be purified, via a pipeline. In the actual design, the connecting pipeline between the evaporator 3 and the raw material tank 1 is equipped with a raw material tank discharge pump 2 to pump the adipic acid production waste liquid 1-1 to be purified from the raw material tank 1 into the evaporator 3.

[0029] The rising film evaporator 3 uses low-pressure steam as a heat source to perform preliminary evaporation treatment on adipic acid production waste liquid, and controls the discharge temperature to be around 85°C.

[0030] The separator 4, specifically, for example, is a cyclone separator, used to separate the gas-liquid mixture after evaporation by the rising film evaporator 3. The gas phase is further recovered and discharged into the atmosphere, while the liquid phase enters the subsequent dicarboxylic acid recovery and crystallization unit.

[0031] In actual design, a vacuum system (not shown in the figure, which can be designed and constructed according to existing technical knowledge) is connected to the top of the cyclone separator to maintain a negative pressure state (absolute pressure of 70-80 kPa) inside the cyclone separator, which is conducive to the rapid evaporation of the rising film evaporator 3.

[0032] The dicarboxylic acid recovery and crystallization unit includes several dicarboxylic acid recovery crystallizers 5 connected in series. The dicarboxylic acid recovery crystallizers 5 are used to cool and crystallize the liquid phase separated by the separator (to precipitate dicarboxylic acid). Therefore, each dicarboxylic acid recovery crystallizer 5 is connected to a cooling device (usually a cooling coil with a chilled water inlet pipe 5-1 and a chilled water outlet pipe 5-3, so that the cooling and crystallization temperature of each dicarboxylic acid recovery crystallizer can be adjusted as needed).

[0033] In the preferred design, the top of the dicarboxylic acid recovery crystallizer 5 is equipped with a recovery crystallization stirring device 6 to ensure uniform cooling of the recovery liquid.

[0034] In this embodiment, three dicarboxylic acid recovery crystallizers are designed. To save power, the recovered liquid after cooling overflows into the next dicarboxylic acid recovery crystallizer from high to low according to the position difference between the different dicarboxylic acid recovery crystallizers.

[0035] In actual design, each dicarboxylic acid recovery crystallizer can be connected to an existing negative pressure system (not shown in the figure, but can be designed according to existing technology) to keep the inside of the dicarboxylic acid recovery crystallizer under a slight negative pressure (vacuum of about 140 mm water column), thereby ensuring the stable and orderly flow of the recovered liquid;

[0036] After running for a certain period of time, in order to clean the dicarboxylic acid recovery crystallizer, the dicarboxylic acid recovery crystallizer is connected to a low-pressure steam pipeline 5-2 and a condensate discharge pipeline 5-4. The low-pressure cleaning steam enters the dicarboxylic acid recovery crystallizer through the coil to heat and clean it.

[0037] In actual production, the temperatures of the three dicarboxylic acid recovery crystallizers are controlled sequentially from high to low as follows: 50℃, 25℃, and 12℃.

[0038] The centrifugal separation device 7 is specifically a centrifuge connected to a filter cake washing water (cold high-purity water, 0.6MPa, 10℃) pipeline, used to centrifuge and dehydrate the recovered liquid after the crystallization of dicarboxylic acid. After centrifugal washing, the impurity content in the filter cake, which is mainly composed of dicarboxylic acid, is further reduced (the washing liquid enters other processes for subsequent processing), and the obtained filter cake enters the dissolution and decolorization tank 8 for further processing.

[0039] The dissolving and decolorizing tank 8 is used to further decolorize and remove impurities from the filter cake obtained by the centrifugal separator 7 after dissolving it. Therefore, the upper part of the tank is designed with an activated carbon inlet 8-1 for decolorization and impurity removal and a dissolving water inlet 8-2 for dissolving. To further ensure sufficient dissolving and decolorization, a decolorizing tank agitator 9 can be designed at the top of the tank, and / or a decolorizing tank low-pressure steam inlet 8-3 and a corresponding decolorizing tank condensate outlet 8-4 can be designed on the tank (to appropriately increase the temperature of the dissolving liquid, thereby accelerating dissolution).

[0040] In actual production, activated carbon can be added at a mass ratio of 0.5% of the filter cake. After dissolution, the concentration of DBA solution is controlled at 50%, which is beneficial for decolorization and impurity removal.

[0041] The carbon filter 11 is used to filter and remove activated carbon from the solution after dissolution and decolorization. In actual production, a dissolution and decolorization tank discharge pump 10 is designed on the connecting pipeline between the carbon filter 11 and the dissolution and decolorization tank 8 to pump the solution after dissolution and decolorization into the carbon filter.

[0042] Furthermore, the carbon filter 11 is also equipped with a sight glass 12 and a carbon protection filter 13, so as to more intuitively judge the filtration status of the carbon filter and ensure the stable operation of the carbon filter.

[0043] The dicarboxylic acid evaporation and slagging unit includes: a dicarboxylic acid evaporation and slagging feed tank 14, a dicarboxylic acid evaporation and slagging feed pump 15, and a slagging machine 16 connected in sequence;

[0044] After the activated carbon is removed by filtration, the solution is stored in the feed tank 14 and then pumped into the sheeter 16 by the feed pump 15 to form DBA sheet products.

[0045] Using the above system, taking adipic acid waste liquid with a capacity of 4t / h as an example, and combining some process parameters, we conducted actual production on the yield and quality of DBA prepared under different process parameters. The results are shown in Table 1 below.

[0046] Table 1. DBA obtained under different process parameters

[0047] .

[0048] The results in the table above show that the quality of DBA products prepared under different process parameters varies slightly, but the overall purity is high and the nitric acid content is significantly reduced, demonstrating good technical results.

[0049] Overall, the adipic acid recovery and purification system for adipic acid production waste liquid provided in this application, through appropriate concentration (increasing the material concentration entering the dipic acid evaporation and flake formation system from the existing 20% ​​to 50%, which can reduce energy consumption during flake formation and reduce the moisture content of the final product), cooling centrifugation, and dissolution and decolorization operations, can further improve and enhance the quality of DBA finished products. It can further increase the existing purity of about 99.3% to 99.7%, and further reduce the existing 0.5% nitric acid content and 0.5% moisture content of the finished product to nitric acid ≤0.1% and water ≤0.3%. This has good technical significance for improving the quality and value of DBA products.

Claims

1. A process for recovering and purifying dicarboxylic acids from adipic acid production waste liquid, characterized in that, This process utilizes a dicarboxylic acid recovery and purification system from adipic acid production waste liquid; The dicarboxylic acid recovery and purification system for adipic acid production waste liquid includes: The system is connected in sequence via pipelines to a rising film evaporator, a separator, a diacid recovery and crystallization unit, a centrifugal separator, a decolorization tank, and a diacid evaporation and condensation unit; wherein: The rising film evaporator is connected to a raw material tank containing adipic acid production waste liquid to be purified via pipelines; The rising film evaporator uses low-pressure steam as a heat source for the preliminary evaporation treatment of adipic acid production waste liquid; The dicarboxylic acid recovery and crystallization unit includes several dicarboxylic acid recovery crystallizers connected in series; the dicarboxylic acid recovery crystallizers are used to cool and crystallize the liquid phase separated by the separator to precipitate dicarboxylic acid; each dicarboxylic acid recovery crystallizer is connected to a corresponding cooling device. The centrifugal separation device is specifically a centrifuge connected to a filter cake washing water pipeline, used to centrifuge, dehydrate, and wash the recovered liquid after crystallization of dicarboxylic acid. The decolorization tank is used to further decolorize and remove impurities from the filter cake obtained by the centrifugal separator after dissolving it. The upper part of the tank is designed with an activated carbon inlet for decolorization and impurity removal and a dissolving water inlet for dissolution. At the same time, a decolorization tank agitator is designed at the top of the tank, and / or a low-pressure steam inlet and a corresponding decolorization tank condensate outlet are designed on the tank. A decolorization tank discharge pump is designed on the connecting pipeline between the carbon filter and the decolorization tank to pump the dissolved and decolorized solution into the carbon filter. The dicarboxylic acid evaporation and slagging unit includes: a dicarboxylic acid evaporation and slagging feed tank, a dicarboxylic acid evaporation and slagging feed pump, and a slagging machine connected in sequence; When recovering and purifying dicarboxylic acid from adipic acid production waste liquid, the dicarboxylic acid recovery crystallizer consists of three dicarboxylic acid recovery crystallizers connected in sequence. The temperatures of the three dicarboxylic acid recovery crystallizers from high to low are 50℃, 25℃, and 10~20℃, respectively. Activated carbon is added at a mass ratio of 0.3~1% of the filter cake. The material concentration entering the dicarboxylic acid evaporation and slaking unit is 50%.

2. A system for recovering and purifying dicarboxylic acids from adipic acid production waste liquid, characterized in that, The system includes: a rising film evaporator, a separator, a diacid recovery and crystallization unit, a centrifugal separator, a decolorization tank, and a diacid evaporation and condensation unit, all connected sequentially by pipelines; wherein: The rising film evaporator is connected to a raw material tank containing adipic acid production waste liquid to be purified via pipelines; The rising film evaporator uses low-pressure steam as a heat source for the preliminary evaporation treatment of adipic acid production waste liquid; The dicarboxylic acid recovery and crystallization unit includes several dicarboxylic acid recovery crystallizers connected in series; the dicarboxylic acid recovery crystallizers are used to cool and crystallize the liquid phase separated by the separator to precipitate dicarboxylic acid; each dicarboxylic acid recovery crystallizer is connected to a corresponding cooling device. The centrifugal separation device is specifically a centrifuge connected to a filter cake washing water pipeline, used to centrifuge, dehydrate, and wash the recovered liquid after crystallization of dicarboxylic acid. The decolorization tank is used to further decolorize and remove impurities from the filter cake obtained by the centrifugal separator after dissolving it. The upper part of the tank is designed with an activated carbon inlet for decolorization and impurity removal and a dissolving water inlet for dissolution. At the same time, a decolorization tank agitator is designed at the top of the tank, and / or a low-pressure steam inlet and a corresponding decolorization tank condensate outlet are designed on the tank. A decolorization tank discharge pump is designed on the connecting pipeline between the carbon filter and the decolorization tank to pump the dissolved and decolorized solution into the carbon filter. The dicarboxylic acid evaporation and slagging unit includes: a dicarboxylic acid evaporation and slagging feed tank, a dicarboxylic acid evaporation and slagging feed pump, and a slagging machine connected in sequence; A raw material tank discharge pump is designed on the connecting pipeline between the evaporator and the raw material tank to pump the adipic acid production waste liquid in the raw material tank into the evaporator. The separator is a cyclone separator; a vacuum system is connected to the top of the cyclone separator to maintain a negative pressure state inside the cyclone separator.

3. The adipic acid recovery and purification system for adipic acid production waste liquid as described in claim 2, characterized in that, The cooling device installed in the dicarboxylic acid recovery crystallizer is a cooling coil with chilled water inlet and chilled water outlet pipes.

4. The adipic acid recovery and purification system for adipic acid production waste liquid as described in claim 2, characterized in that, The top of the dicarboxylic acid recovery crystallizer is equipped with a recovery crystallization stirring device.

5. The adipic acid recovery and purification system for adipic acid production waste liquid as described in claim 2, characterized in that, Each dicarboxylic acid recovery crystallizer is connected to a negative pressure system to maintain a slight negative pressure inside the crystallizer, thereby ensuring the stable and orderly flow of the recovered liquid. At the same time, the dicarboxylic acid recovery crystallizer is connected to a low-pressure steam pipeline and a condensate discharge pipeline for heating and cleaning.

6. The adipic acid recovery and purification system for adipic acid production waste liquid as described in claim 2, characterized in that, The carbon filter is equipped with a sight glass and a carbon protection filter to visually assess the filtration status of the carbon filter and ensure its stable operation.

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