A crystallization apparatus for adipic acid
By employing a multi-crystallization chamber series structure and a negative pressure source coordinated control method in the adipic acid crystallization device, the scaling problem was solved, a highly efficient and low-energy-consumption crystallization process was achieved, the operating cycle was extended, and product quality was improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- CHONGQING HUAFON CHEM
- Filing Date
- 2025-07-02
- Publication Date
- 2026-07-31
AI Technical Summary
Existing adipic acid crystallization equipment causes the slurry to boil violently due to large temperature differences in a vacuum environment, resulting in scaling, which affects the crystallization quality, requires frequent shutdowns for maintenance, and wastes heat.
Design a crystallization device comprising multiple independent crystallization chambers connected in series via connecting pipes. Each crystallization chamber has a gas phase outlet at the top, and some crystallization chambers are equipped with heat exchange mechanisms. By utilizing a negative pressure source and a gas phase regulating valve to collaboratively control the pressure and temperature gradient, zero-steam-consumption crystallization can be achieved.
It effectively prevents the formation of scale, extends the operating cycle of the device to more than 85 days, improves steam utilization, ensures crystallization quality, and reduces control difficulty and cost.
Smart Images
Figure CN224573259U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the chemical industry, and in particular to a crystallization apparatus for adipic acid. Background Technology
[0002] Adipic acid belongs to the aliphatic carboxylic acids, commonly known as fatty acids, and has the molecular formula C6H12O. 10 O4 is a white crystalline powder, stable and non-hygroscopic. It is mainly used in the manufacture of nylon 66 and polyurethane resins, and secondarily in the manufacture of plasticizers and lubricants. In small quantities, it is used as an acidulant in food and as a substitute for tartaric acid in baking powder. It can also be used in the manufacture of pesticides and adhesives, and in the production of pharmaceuticals and fragrances. Currently, the fastest-growing industries in China using O4 include the synthetic leather resin industry, the polyurethane shoe sole resin industry, and the polyurethane adhesive and TPU polyol industry.
[0003] The production process of adipic acid involves the oxidation of cyclohexanol / cyclohexanone with nitric acid in the presence of a copper-vanadium catalyst. The resulting oxidized solution undergoes a series of processes including crystallization, concentration, dehydration, dissolution, decolorization, recrystallization, and drying to obtain the finished adipic acid. In large-scale industrial production of adipic acid, crystallization is necessary.
[0004] Currently, adipic acid crystallization equipment uses multiple continuous crystallization chambers, relying on vacuum evaporation and stepped cooling to form a supersaturated solution. However, because chemical plants typically use fixed specifications for chilled water and saturated steam, controlling stepped cooling with chilled water and saturated steam is complex. This results in a large temperature difference between the heat exchange medium and the adipic acid slurry in the crystallization chamber. Under high vacuum, this causes the adipic acid slurry in the crystallization chamber to boil violently, forming scale at the bottom of the chamber, affecting the crystallization quality of adipic acid. Frequent shutdowns for maintenance are also required, impacting production efficiency and causing significant heat waste.
[0005] Therefore, how to design a low-energy-consumption, long-operation-cycle adipic acid crystallization scheme is a problem that urgently needs to be solved by those skilled in the art. Utility Model Content
[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a crystallization device for adipic acid. This device has a simple structure and low modification cost. It can effectively prevent scaling inside the crystallizer and extend the operating cycle of the device while achieving zero steam consumption for crystallizing adipic acid slurry.
[0007] The technical solution to achieve the purpose of this utility model is: a crystallization device for adipic acid, comprising M independent crystallization chambers, with a connecting pipe between adjacent crystallization chambers, the M independent crystallization chambers forming a series structure through the connecting pipe, the upstream end of the connecting pipe being located below the liquid level of the upper crystallization chamber, a gas phase outlet being provided at the top of each crystallization chamber, and a heat exchange mechanism being provided in the 2nd to Mth crystallization chambers, the gas phase outlet of the upper crystallization chamber being connected to a negative pressure source through the connecting pipe and the heat exchange medium channel of the lower heat exchange mechanism; M≥3.
[0008] The heat exchange area of the heat exchange mechanism is adapted to the liquid level of the adipic acid slurry in the crystallization chamber.
[0009] The heat exchange mechanism is a heat exchange jacket, which is installed on the outer wall of the corresponding crystallization chamber.
[0010] Each crystallization chamber is equipped with a stirrer, and the upstream end of each connecting pipe is higher than the downstream end.
[0011] A gas phase regulating valve is installed on the connecting pipeline, and the opening degree of the gas phase regulating valve is 5%~100%.
[0012] The outlet of the heat exchange medium channel of each heat exchange mechanism is connected to the same negative pressure source.
[0013] The gas phase outlet of the upper crystallization chamber is connected to the negative pressure source through the heat exchange medium channel of the heat exchange mechanism of the adjacent lower crystallization chamber; or, the gas phase outlet of the upstream crystallization chamber is connected to the negative pressure source through the heat exchange medium channel of the heat exchange mechanism separated by one crystallization chamber.
[0014] The heat exchange medium channel outlet of each heat exchange mechanism is connected to a negative pressure source via a condenser. The condenser is a surface cooler, and the condensate outlets of each surface cooler are connected in parallel to supply the mother liquor system.
[0015] It also includes a flash tank, whose inlet is connected to the oxidizing liquid source and whose outlet supplies material to the crystallization chamber; it also includes a reflux pipe, whose upstream end is connected to the final crystallization chamber and whose downstream end supplies material to the crystal nucleus control chamber.
[0016] It includes at least two of the above-mentioned crystallization devices, and at least two crystallization devices are connected in series.
[0017] The above technical solution has the following beneficial effects: 1. The adipic acid crystallization apparatus comprises multiple independent crystallization chambers connected in series via connecting pipes. Each crystallization chamber has a gas phase outlet at its top. Heat exchange mechanisms are installed in the second to the final crystallization chambers. The gas phase outlet of the upper crystallization chamber is connected to a negative pressure source via a connecting pipe to the heat exchange medium channel of the lower heat exchange mechanism, thus adapting to the crystallization process of this application. Preferably, the steam generated in the upper crystallization chamber directly provides heat to the adjacent lower crystallization chamber. This improves the utilization rate of the generated steam and minimizes the temperature difference between the slurry in the lower descending crystallization chamber, preventing violent boiling of the slurry and ensuring the crystallization quality of each crystallization chamber.
[0018] 4. Each stage of the connecting pipeline in the crystallization apparatus is equipped with a gas-phase regulating valve. The opening degree of the gas-phase regulating valve is 5%~100%. Through the coordinated control of the gas-phase regulating valve opening and feedback from the negative pressure source, the pressure drop from the first-stage crystallization unit to the Nth-stage crystallization unit is controlled to be 20-30 kPa A, and the pressure drop from the Nth-stage crystallization unit to the Mth-stage crystallization unit is controlled to be 10-20 kPa A, to adapt to the preferred crystallization process of this application. Furthermore, independent control of the gas-phase regulating valve effectively prevents liquid from flowing into adjacent low-pressure compartments or mixing due to abnormal pressure in one compartment, thus avoiding affecting liquid flow and disrupting the preset temperature and pressure gradients.
[0019] 5. The heat exchange medium channel outlets of each heat exchange mechanism are connected to the same negative pressure source. This not only reduces the control difficulty and operating cost of the device, but also allows the heat exchange of each crystallization chamber to be controlled by adjusting the opening of the gas phase regulating valve. Combined with the condenser located between the heat exchange medium channel outlet and the negative pressure source, the crystallization device can achieve the required vacuum gradient.
[0020] According to the applicant's test verification, the crystallization device of this utility model can achieve zero-input steam crystallization to obtain finished slurry, the maintenance cycle of the crystallization device reaches more than 85 days, and the impurity content (glutaric acid and succinic acid) of the adipic acid product obtained by crystallization is less than 10 ppm.
[0021] The following description, in conjunction with the accompanying drawings and specific embodiments, provides further details. Attached Figure Description
[0022] Figure 1 This is a connection diagram for Example 1; Figure 2 This is a connection diagram for Example 2.
[0023] In the attached diagram, 1 is the crystallization chamber, 2 is the connecting pipe, 3 is the gas phase outlet, 4 is the heat exchange mechanism, 5 is the condenser, and 6 is the stirrer. Detailed Implementation Example 1
[0024] See Figure 1The adipic acid crystallization apparatus comprises twelve independent crystallization units, each represented by a crystallization chamber 1 in this embodiment. Each crystallization chamber 1 is equipped with a stirrer 6. A connecting pipe 2 connects adjacent crystallization chambers, forming a series structure. The upstream end of the connecting pipe 2 is below the liquid level of the upstream crystallization chamber, and the upstream end of each connecting pipe 2 is higher than the downstream end. Each crystallization chamber 1 is equipped with a heat exchange mechanism 4, specifically a heat exchange jacket. The heat exchange jacket is mounted on the outer wall of the corresponding crystallization chamber, and its height is adapted to the liquid level of the adipic acid slurry within the crystallization chamber. Each crystallization chamber 1 has a gas phase outlet 3 at its top. The gas phase outlet of the upstream crystallization chamber is connected to a negative pressure source via a connecting pipe, the heat exchange medium channel of the adjacent downstream heat exchange mechanism, and a condenser 5. That is, the gas phase outlet of the first crystallization chamber is connected to the inlet of the heat exchange medium channel of the heat exchange jacket in the second crystallization chamber, the gas phase outlet of the second crystallization chamber is connected to the inlet of the heat exchange medium channel of the heat exchange jacket in the third crystallization chamber, and so on. Condenser 5 is a surface cooler, and the condensate outlets of each surface cooler are connected in parallel to supply the mother liquor system. A gas phase regulating valve is installed on the connecting pipeline. By adjusting the opening of the gas phase regulating valve, the absolute pressure of each compartment is independently controlled within a preset target value. For ease of industrial operation, a pressure sensor is also installed on the connecting pipeline. The gas phase regulating valve and the pressure sensor are uniformly connected to an external central controller. The central controller receives signals from the pressure sensors and adaptively adjusts the opening of the gas phase regulating valve between 5% and 100% to precisely control the pressure of each crystallization chamber within the preset target value.
[0025] The twelfth crystallization chamber also supplies material to the third crystallization chamber through a reflux pipe, which is obviously equipped with valves and pumps.
[0026] The crystallization apparatus also includes a flash tank, whose inlet is connected to an oxidation liquid source, and whose outlet supplies material to the upstream crystallization chamber. Example 2
[0027] See Figure 2 The difference from Example 1 is that the gas phase outlet of the upstream crystallization chamber is connected to the heat exchange medium channel of the heat exchange mechanism that is separated by one crystallization chamber, the condenser and the negative pressure source. That is, the gas phase outlet of the first crystallization chamber is connected to the heat exchange medium channel inlet of the heat exchange jacket in the third crystallization chamber, the gas phase outlet of the second crystallization chamber is connected to the heat exchange medium channel inlet of the heat exchange jacket in the fourth crystallization chamber, and so on. The other structures are the same. Example 3
[0028] In this embodiment, there are two sets of adipic acid crystallization devices from Example 1. The finished slurry produced by the first crystallization device is thickened, centrifuged, and decolorized, and then used as the primary slurry for the second crystallization device. Comparative Example 1
[0029] Each crystallization chamber has its own heat exchange jacket for heating, and each crystallization chamber is directly connected to a negative pressure source, using 0.5 MPaG saturated steam to heat the heat exchange jacket of each crystallization chamber. Comparative Example 2
[0030] In this embodiment, there are two sets of Comparative Example 1 devices. The finished slurry produced by the first crystallization device is thickened, centrifuged, and decolorized, and then used as the primary slurry for the second crystallization device.
[0031] Application Example 1
[0032] Adipic acid was crystallized using the crystallization apparatus of Example 1, with M=12 and N=4.
[0033] Includes the following steps: 1) The primary slurry containing the target product (composed of 25 wt% adipic acid, 4.5 wt% glutaric acid, 1.5 wt% succinic acid, approximately 30 wt% nitric acid, no more than 5 wt% monoacids, and the balance being water) is fed to a flash tank. The flash temperature is 90°C, and the time is 20-40 minutes. The flash-frozen slurry is then fed to the first crystallization chamber at 90°C. The flow rate of the primary slurry is 40 m³ / min. 3 / h; 2) By coordinating the control of the negative pressure source, surface cooler, and gas phase regulating valve opening, the pressure in each crystallization chamber is controlled to be negative, and the pressure decreases sequentially to 48KPaA, 38KPaA, 30KPaA, 22KPaA, 20KPaA, 19KPaA, 16KPaA, 13KPaA, 11KPaA, 9KPaA, 6KPaA, and 4KPaA, respectively. The temperatures are 75℃, 68℃, 60℃, 52℃, 50℃, 48℃, 45℃, 42℃, 39℃, 36℃, 33℃, and 30℃, respectively. The stirring speed in each crystallization chamber is controlled to be 350RPM. 3) The target slurry containing adipic acid crystals is discharged from the twelfth crystallization chamber. 10 wt% of the target slurry is returned to the third crystallization chamber to form a cycle. After the system reaches equilibrium, the temperature of the primary target slurry containing adipic acid crystals is 25℃, and the composition is: adipic acid content 38 wt%, other by-product dicarboxylic acids content 2.2 wt% (by-product dicarboxylic acids are glutaric acid and succinic acid), nitric acid content 30 wt%, and the remainder is water. The entire crystallization process consumes zero external steam, and the crystallization device has an operating cycle of more than 85 days, meaning it can still operate normally after 85 days.
[0034] Application Example 2
[0035] The method for crystallizing adipic acid using the crystallization apparatus of Example 2 includes the following steps: 1) The primary slurry containing the target product (composed of 35 wt% adipic acid, 3.6 wt% glutaric acid, 2.1 wt% succinic acid, approximately 25 wt% nitric acid, no more than 5 wt% monoacids, and the balance being water) is fed to a flash tank. The flash temperature is 85°C, and the time is 20-40 min. The slurry obtained after flash evaporation is then fed to the first crystallization chamber at 90°C. The flow rate of the primary slurry is 45 m³ / min. 3 / h; 2) Control the pressure in each crystallization chamber to be negative, the pressure control is the same as in Application Example 1, and control the stirring speed in each crystallization chamber to be 350 RPM; 3) The target slurry containing adipic acid crystals is discharged from the twelfth crystallization chamber. 10 wt% of the target slurry is returned to the third crystallization chamber to form a cycle. After the system reaches equilibrium, the temperature of the primary target slurry containing adipic acid crystals is 23℃, and the composition is as follows: adipic acid content 39 wt%, other by-product dicarboxylic acids content 2.4 wt% (by-product dicarboxylic acids are glutaric acid and succinic acid), nitric acid content 30 wt%, and the remainder is water. The entire crystallization process consumes zero external steam, and the crystallization device has an operating cycle of more than 85 days, meaning it can still operate normally after 85 days.
[0036] Application Example 3
[0037] The method for crystallizing adipic acid using the adipic acid crystallization apparatus of Example 3 includes the following steps: 1) The primary target slurry obtained in Application Example 1 was thickened, centrifuged, dissolved and decolorized to obtain a primary slurry. The primary slurry composition was 40 wt% adipic acid, 2.4 wt% by-product dicarboxylic acid, 1 wt% nitric acid, and the remainder was water. 2) The primary slurry is fed into the first crystallization chamber of the second crystallization unit (M=12, N=3) at a temperature of 92℃, and the flow rate of the primary slurry is 35m³ / h. 3 / h; 6) By coordinating the control of the negative pressure source, surface cooler, and gas phase regulating valve opening, the pressure in each crystallization chamber of the second crystallization unit is controlled to be negative, and the pressure decreases sequentially as follows: 50 kPaA, 40 kPaA, 30 kPaA, 27 kPaA, 24 kPaA, 21 kPaA, 18 kPaA, 15 kPaA, 11 kPaA, 9 kPaA, 7 kPaA, and 5 kPaA. The temperatures are 80℃, 70℃, 60℃, 58℃, 56℃, 53℃, 50℃, 49℃, 45℃, 39℃, 33℃, and 27℃, respectively. The stirring shaft speed is 450 RPM. 7) The twelfth crystallization chamber of the second crystallization unit discharges finished slurry containing the target product at a flow rate of 30 m³ / s. 3 / h; temperature is 30℃, component content is adipic acid 42wt%, by-product dicarboxylic acid (glutaric acid and succinic acid) content <1wt%, nitric acid content <0.5wt%, the remainder is water.
[0038] 8) The finished slurry is thickened and dehydrated, and then sent to a fluidized bed dryer to obtain adipic acid powder. After testing, the impurity content (glutaric acid and succinic acid) in the adipic acid powder is less than 10 ppm, and the particle size distribution of the adipic acid powder is D50=100±10μm.
[0039] Application Example 4
[0040] The adipic acid crystallization apparatus used in Example 3 differs from that used in Application Example 3 in that: All the steam generated by the pre-crystallization unit is used to heat the adjacent post-crystallization unit. The pressure drop is controlled by a negative pressure source, and the pressure drop between adjacent crystallization chambers is maintained at 3~10 kPaA to ensure that each crystallization unit can pass material normally.
[0041] After testing, the impurity content (glutaric acid and succinic acid) in the adipic acid powder was less than 15 ppm, and the particle size distribution of the adipic acid powder was D50=110±15μm.
[0042] Comparative Application Example 1
[0043] Using the apparatus of Comparative Example 1 and applying the process of Example 1, under steady-state conditions, approximately 2.8 t / h of 0.5 MPaG saturated steam was consumed. After 30 days of operation, obvious scale appeared in the crystallization chamber, requiring scale removal treatment, which affected production efficiency.
[0044] Comparative Application Example 2
[0045] Using the apparatus of Comparative Example 2 and the process of Example 2, under steady-state conditions, approximately 4.1 t / h of 0.5 MPaG saturated steam was consumed, and the impurity content (glutaric acid and succinic acid) in the obtained adipic acid powder was approximately 100 ppm. The particle size distribution of the adipic acid powder was D50 = 80 ± 40 μm.
Claims
1. A crystallization apparatus for adipic acid, comprising M independent crystallization chambers (1), with a connecting pipe (2) between adjacent crystallization chambers, the M independent crystallization chambers forming a series structure through the connecting pipe (2), the upstream end of the connecting pipe (2) being located below the liquid level of the upper crystallization chamber, characterized in that: Each crystallization chamber (1) is provided with a gas phase outlet (3) at the top. The second to the Mth crystallization chambers (1) are provided with heat exchange mechanisms (4). The gas phase outlet of the upper crystallization chamber is connected to the negative pressure source through the connecting pipeline and the heat exchange medium channel of the lower heat exchange mechanism; M≥3.
2. The crystallization apparatus of adipic acid according to claim 1, characterized in that: The heat exchange area of the heat exchange mechanism (4) is adapted to the liquid level of the adipic acid slurry in the crystallization chamber.
3. The crystallization apparatus of adipic acid according to claim 1 or 2, characterized in that: The heat exchange mechanism (4) is a heat exchange jacket, which is installed on the outer wall of the corresponding crystallization chamber.
4. The crystallization apparatus of adipic acid according to claim 1 or 2, characterized in that: Each crystallization chamber (1) is equipped with a stirrer (6), and the upstream end of each connecting pipe (2) is higher than the downstream end.
5. The crystallization apparatus of adipic acid according to claim 1 or 2, characterized in that: A gas phase regulating valve is installed on the connecting pipeline, and the opening degree of the gas phase regulating valve is 5%~100%.
6. The crystallization apparatus of adipic acid according to claim 1 or 2, characterized in that: The outlet of the heat exchange medium channel of each heat exchange mechanism is connected to the same negative pressure source.
7. The crystallization apparatus of adipic acid according to claim 6, characterized in that: The gas phase outlet of the upper crystallization chamber is connected to the negative pressure source through the heat exchange medium channel of the heat exchange mechanism of the adjacent lower crystallization chamber; or, the gas phase outlet of the upstream crystallization chamber is connected to the negative pressure source through the heat exchange medium channel of the heat exchange mechanism separated by one crystallization chamber.
8. The crystallization apparatus of adipic acid according to claim 1, characterized by: The heat exchange medium channel outlet of each heat exchange mechanism (4) is connected to the negative pressure source via the condenser (5). The condenser (5) is a surface cooler. The condensate outlets of each surface cooler are connected in parallel to supply the mother liquor system.
9. The crystallization apparatus of adipic acid according to claim 1, characterized in that: It also includes a flash tank, whose inlet is connected to the oxidizing liquid source and whose outlet supplies material to the crystallization chamber; it also includes a reflux pipe, whose upstream end is connected to the final crystallization chamber and whose downstream end supplies material to the crystal nucleus control chamber.