Integrated crystallizer and crystallization device for multi-stage crystallization of oxalic acid

Abstract

The utility model relates to the technical field of oxalic acid crystallization, in particular to an integrated crystallizer and crystallization device for multi-stage crystallization of oxalic acid, which is characterized in that a plurality of stages of crystallization units connected in series are arranged in a shell from top to bottom, so that continuous multi-stage crystallization of oxalic acid is realized, the oxalic acid crystallization process is simplified, and the occupied area of equipment is reduced; meanwhile, the production efficiency of oxalic acid crystallization is improved; the crystallization environment of each crystallization chamber is accurately controlled by arranging a stirring jacket, a cooling jacket or a cooling pipe, so that oxalic acid crystals can grow in a proper environment, the problem of non-uniform crystal particle size distribution is effectively solved, and the purity and the quality of products are improved; clear liquid and mother liquid are subjected to reflux circulating crystallization by arranging the reflux inlet, so that complete crystallization of an oxalic acid solution is realized, the yield of an oxalic acid product is improved, the production cost is reduced, and meanwhile, environmental pollution caused by the oxalic acid mother liquid is avoided; the crystallization process is automatically controlled by arranging the temperature control system, manual intervention is reduced, and the stability and reliability of the production process are improved.

Description

Technical Field

[0001] This utility model relates to the field of oxalic acid crystallization technology, specifically to an integrated crystallizer and crystallization device for multi-stage oxalic acid crystallization. Background Technology

[0002] Oxalic acid, also known as ethanedioic acid, is an important organic chemical raw material widely used in industries such as pharmaceuticals, printing and dyeing, and metallurgy. In the production process of oxalic acid, crystallization is a crucial separation and purification step, the purpose of which is to separate oxalic acid from the solution to obtain high-purity oxalic acid crystals.

[0003] Traditional oxalic acid crystallization processes typically employ batch crystallizers, single-stage continuous crystallizers, double-stage continuous crystallizers, or triple-stage continuous crystallizers. Batch crystallizers offer flexible operation but suffer from low production efficiency, inconsistent product quality, and high labor intensity. Single-stage continuous crystallizers are time-consuming and inefficient. While double-stage or triple-stage continuous crystallizers improve efficiency, they require more equipment, involve more complex processes, and occupy a larger area. Furthermore, during crystallization, the solute concentration in the solution gradually decreases as crystals precipitate, leaving a certain amount of oxalic acid in the mother liquor. Directly discharging this mother liquor not only wastes resources but also pollutes the environment. Therefore, it is necessary to research and develop an integrated crystallizer and crystallization method for multi-stage oxalic acid crystallization to improve production efficiency, simplify the process, and reduce the amount of mother liquor. Utility Model Content

[0004] The purpose of this invention is to provide an integrated crystallizer and crystallization device for multi-stage oxalic acid crystallization, in order to solve the problems mentioned in the background art, such as the large number of equipment, complex processes, large footprint, and large amount of crystallization mother liquor in traditional multi-stage oxalic acid crystallization processes.

[0005] To achieve the above objectives, this utility model provides the following technical solution: an integrated crystallizer for multi-stage oxalic acid crystallization, comprising an outer shell, wherein multiple crystallization chambers are arranged in series vertically from top to bottom within the outer shell, namely, a first crystallization chamber, a second crystallization chamber, ..., an nth crystallization chamber (n≥2); each crystallization chamber is separated by a partition, and the partition is provided with through holes to allow adjacent crystallization chambers to communicate; an inlet is provided on the outer shell and communicates with the first crystallization chamber, the inlet being used to input the oxalic acid solution to be crystallized; an outlet is provided at the bottom of the outer shell and communicates with the nth crystallization chamber, for discharging the crystallized oxalic acid crystals and mother liquor; and an exhaust port is provided at the upper end of the side wall of each crystallization chamber.

[0006] Furthermore, the outer shell is a sealed cylindrical tank, and the outer shell and partition are made of stainless steel, which has good corrosion resistance and mechanical strength.

[0007] Furthermore, each crystallization chamber is equipped with a stirring device, which includes a stirring shaft and stirring blades. The stirring shaft passes through a partition and is connected to a drive motor. The drive motor is located on the top of the outer shell. Except for the first crystallization chamber, the drive motor drives the stirring shaft to rotate, thereby causing the stirring blades to stir the solution in the crystallization chamber and promote the crystallization process.

[0008] Furthermore, the first crystallization chamber, the second crystallization chamber, ... the (n-1)th crystallization chamber are all equipped with reflux ports, where n ≥ 2. The clear liquid outlet is provided on the side wall of the nth crystallization chamber, and the reflux port is used to return the clear liquid in the nth crystallization chamber.

[0009] Furthermore, each crystallization chamber is equipped with an independent cooling jacket or cooling pipe; a cooling medium, such as cold water or coolant, is introduced into the cooling jacket or cooling pipe. By controlling the flow rate and temperature of the cooling medium, precise temperature control of each crystallization chamber is achieved. In the first crystallization chamber near the feed inlet, the solution temperature is relatively high. As the solution flows through subsequent crystallization chambers, the temperature gradually decreases, and water vapor continuously evaporates, thereby achieving multi-stage crystallization of oxalic acid.

[0010] An integrated crystallization device for multi-stage crystallization of oxalic acid includes a crystallizer. The clear liquid outlet of the nth crystallization chamber of the crystallizer is connected to the reflux port of the first crystallization chamber, the second crystallization chamber, ..., or the (n-1)th crystallization chamber via a clear liquid reflux pump and pipeline, realizing the cyclic crystallization of the clear liquid. The air extraction port of the crystallizer is connected to a water-gas separator via a pipeline, and the water-gas separator is connected to a vacuum unit via a pipeline. The integrated crystallization device also includes a slurry tank, a crystal separation device, and a mother liquor tank. The discharge port of the crystallizer is connected to the slurry tank via a pipeline, the slurry tank is connected to the crystal separation device via a pipeline and a slurry pump, the crystal outlet of the crystal separation device is connected to a drying device, the mother liquor outlet of the crystal separation device is connected to the mother liquor tank via a pipeline, and the mother liquor tank is connected to the reflux port of the crystallizer via a mother liquor reflux pump, so as to recrystallize the mother liquor and improve the crystallization yield of oxalic acid.

[0011] Furthermore, it also includes a temperature control system, which includes a temperature sensor, a controller, and a cooling medium flow regulating valve. The temperature sensor is installed in each crystallization chamber to monitor the solution temperature in real time. The controller is connected to the temperature sensor and the cooling medium flow regulating valve, and automatically adjusts the opening of the cooling medium flow regulating valve according to the set temperature range to control the flow rate of the cooling medium, thereby precisely controlling the temperature of each crystallization chamber.

[0012] Furthermore, the controller is also connected to the drive motor, and adjusts the speed of the drive motor according to the solution temperature and crystallization status.

[0013] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0014] (1) Improve production efficiency: This utility model can realize continuous multi-level stepwise crystallization of oxalic acid by setting up multiple crystallization units in series from top to bottom in a shell, which simplifies the oxalic acid crystallization process, reduces the equipment footprint, and improves the production efficiency of oxalic acid crystallization.

[0015] (2) Improve product quality: By precisely controlling the temperature and stirring conditions of each crystallization chamber, oxalic acid crystals can grow in a suitable environment, which effectively improves the problem of uneven crystal particle size distribution and improves product purity and quality.

[0016] (3) Realize the reflux of clear liquid and mother liquor: The reflux of clear liquid and mother liquor for crystallization avoids the discharge of oxalic acid in the mother liquor, increases the yield of oxalic acid products, reduces production costs, and also reduces environmental pollution.

[0017] (4) Automated control: The temperature control system can automatically adjust the flow rate of the cooling medium and the speed of the drive motor according to the set temperature, realizing the automated control of the crystallization process, reducing manual intervention, and improving the stability and reliability of the production process. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the main structure of the crystallizer of this utility model, showing a partial cross-section.

[0019] Figure 2 This is a schematic diagram of the crystallizer of this utility model from the right side.

[0020] Figure 3 This is a top view of the crystallizer of this utility model;

[0021] Figure 4 This is a schematic diagram of the crystallization apparatus of this utility model;

[0022] In the diagram: 1 - Drive motor; 2 - Outer shell; 3 - Reflux port; 4 - Clear liquid outlet; 5 - Feed inlet; 6 - Air extraction port; 7 - Stirring blade; 8 - Baffle plate; 9 - Through hole; 10 - Stirring shaft; 11 - Discharge port; 12 - First crystallization chamber; 13 - Second crystallization chamber; 14 - Third crystallization chamber; 15 - Crystallizer; 16 - Drying device; 17 - Crystal separation device; 18 - Mother liquor tank; 19 - Clear liquid reflux pump; 20 - Slurry tank; 21 - Mother liquor reflux pump; 22 - Slurry pump; 23 - Water-air separator; 24 - Vacuum unit. Detailed Implementation Example 1

[0023] refer to Figure 1-4To achieve integrated multi-stage crystallization of oxalic acid solution, simplify the oxalic acid crystallization process, reduce equipment footprint, and improve production efficiency, product purity, and quality, this invention provides an integrated crystallizer 15 for multi-stage oxalic acid crystallization. The crystallizer includes an outer shell 2, within which multiple crystallization chambers are arranged vertically from top to bottom in series: a first crystallization chamber 12, a second crystallization chamber 13, and a third crystallization chamber 14. Each crystallization chamber is separated by a partition 8 with through holes 9 to allow communication between adjacent chambers. An inlet 5 connected to the first crystallization chamber 12 is located on the outer shell 2, used to input the oxalic acid solution to be crystallized. An outlet 11 connected to the third crystallization chamber 14 is located at the bottom of the outer shell 2, used to discharge the crystallized oxalic acid crystals and mother liquor. An exhaust port 6 is located at the upper end of the side wall of each crystallization chamber, allowing each chamber to be independently evacuated.

[0024] The outer shell 2 is a sealed cylindrical tank. The outer shell 2 and the partition 8 are made of stainless steel, which has good corrosion resistance and mechanical strength.

[0025] The first and second crystallization chambers are equipped with reflux ports, and the third crystallization chamber has a clear liquid outlet on its side wall. The reflux ports are used to return the clear liquid in the third crystallization chamber.

[0026] Each crystallization chamber is equipped with a stirring device, which includes a stirring shaft 10 and stirring blades 7. The stirring shaft 10 passes through a partition 8 and is connected to a drive motor 1. Figure 1 The stirring shaft 10 passes through the through hole 9 and the partition 8. At this time, a baffle needs to be set on the stirring shaft to prevent the stirring shaft 10 from playing a role in guiding the flow. The drive motor 1 is set on the top of the outer shell 2. The drive motor 1 drives the stirring shaft 10 to rotate, thereby making the stirring blades 7 stir the solution in the crystallization chamber and promote the crystallization process.

[0027] Each crystallization chamber is equipped with an independent cooling jacket; a cooling medium, such as cold water or coolant, is circulated in the cooling jacket. By controlling the flow rate and temperature of the cooling medium, the temperature of each crystallization chamber can be precisely controlled. In the first crystallization chamber near the feed inlet 5, the solution temperature is relatively high. As the solution flows through the subsequent crystallization chambers, the temperature gradually decreases, and water vapor continuously evaporates, thereby achieving multi-stage crystallization of oxalic acid.

[0028] An integrated crystallization device for multi-stage crystallization of oxalic acid includes a crystallizer 15. The clear liquid outlet 4 of the third crystallization chamber 14 of the crystallizer 15 is connected to the return port 3 of the first crystallization chamber 12 via a clear liquid return pump 19 and a pipeline to achieve circulating crystallization of the clear liquid. The exhaust port 6 of each crystallization chamber of the crystallizer 15 is connected to a water-gas separator 23 via a pipeline. The water-gas separator 23 is connected to a vacuum unit 24 via a pipeline. The water-gas separator 23 also acts as a pressure buffer tank to stabilize the exhaust pressure. The integrated crystallization device also includes a slurry tank 20, a crystal separation device 17, and a mother liquor tank 18. The outlet of the crystallizer 15... The feed inlet 11 is connected to the slurry tank 20 via a pipe. The slurry tank 20 is connected to the crystal separation device 17 via a pipe and a slurry pump 22. The crystal outlet of the crystal separation device 17 is connected to the drying device 16. The mother liquor outlet of the crystal separation device 17 is connected to the mother liquor tank 18 via a pipe. The mother liquor tank 18 is connected to the reflux port 3 of the first crystallization chamber 12 via a mother liquor reflux pump 21, so that the mother liquor recrystallizes and the oxalic acid crystallization yield is improved. The crystal separation device 17 can separate oxalic acid crystals and mother liquor, such as a vacuum bag filter, but is not limited to a vacuum bag filter. Other equipment that can separate oxalic acid crystals and mother liquor can also be used.

[0029] The crystallization apparatus also includes a temperature control system, which includes a temperature sensor, a controller, and a cooling medium flow regulating valve. The temperature sensor is installed in each crystallization chamber to monitor the solution temperature in real time. The controller is connected to the temperature sensor and the cooling medium flow regulating valve, and automatically adjusts the opening of the cooling medium flow regulating valve according to the set temperature range to control the flow rate of the cooling medium, thereby precisely controlling the temperature of each crystallization chamber.

[0030] Another embodiment differs from Embodiment 1 in that: the second crystallization chamber 13 is also provided with a reflux port 3 for refluxing the clear liquid and separated mother liquor in the third crystallization chamber 14.

[0031] Another embodiment differs from Embodiment 1 in that each crystallization chamber is equipped with an independent cooling pipe, and a cooling medium, such as cold water or coolant, is circulated in the cooling pipe. By controlling the flow rate and temperature of the cooling medium, precise control of the temperature of each crystallization chamber can be achieved.

[0032] Another embodiment differs from Embodiment 1 in that: the clear liquid outlet 4 of the third crystallization chamber 14 of the crystallizer 15 is connected to the return port 3 of the second crystallization chamber 13 through the clear liquid return pump 19 and the pipeline.

[0033] Another embodiment differs from Embodiment 1 in that the mother liquor tank 18 is connected to the reflux port 3 of the second crystallization chamber 13 via the mother liquor reflux pump 21.

[0034] Another embodiment differs from Embodiment 1 in that the controller is also connected to the drive motor 1, and adjusts the speed of the drive motor 1 according to the solution temperature and crystallization conditions.

[0035] In use, the oxalic acid solution enters the first crystallization chamber 12 through the feed port 5 of the crystallizer 15. The vacuum unit 24 draws a vacuum to evaporate and crystallize the solution. After crystallization in the first crystallization chamber 12, the solution enters the second crystallization chamber 13 for crystallization, and then enters the third crystallization chamber 14 for crystallization. The water vapor extracted by the vacuum unit 24 is separated into gas and water in the water-gas tank. The clear liquid in the third crystallization chamber is returned to the first crystallization chamber 12 through the clear liquid return pump 19. The oxalic acid crystals and mother liquor in the third crystallization chamber flow out through the discharge port 11 and enter the slurry tank 20. The oxalic acid crystals and mother liquor in the slurry tank 20 are transported to the crystal separation device 17 by the slurry pump 22. The oxalic acid crystals and mother liquor are separated in the crystal separation device 17. The oxalic acid crystals are sent to the drying device 16 for drying. The mother liquor enters the mother liquor tank 18 and is returned to the first crystallization chamber 12 or the second crystallization chamber 13 by the mother liquor return pump 21 to recrystallize the mother liquor.

[0036] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An integrated crystallizer for multi-stage crystallization of oxalic acid, characterized in that: The device includes an outer shell, within which multiple crystallization chambers are arranged in series vertically from top to bottom, namely the first crystallization chamber, the second crystallization chamber, ..., the nth crystallization chamber, where n≥2; each crystallization chamber is separated by a partition with through holes to allow adjacent crystallization chambers to communicate; an inlet is provided on the outer shell and communicates with the first crystallization chamber for inputting the oxalic acid solution to be crystallized; an outlet is provided at the bottom of the outer shell and communicates with the nth crystallization chamber for discharging the crystallized oxalic acid crystals and mother liquor; and an exhaust port is provided at the upper end of the side wall of each crystallization chamber.

2. The integrated crystallizer for multi-stage crystallization of oxalic acid according to claim 1, characterized in that: The outer shell is a sealed cylindrical tank, and the outer shell and partition are made of stainless steel, which has good corrosion resistance and mechanical strength.

3. The integrated crystallizer for multi-stage crystallization of oxalic acid according to claim 1, characterized in that: Each crystallization chamber is equipped with a stirring device, which includes a stirring shaft and stirring blades. The stirring shaft passes through a partition and is connected to a drive motor. The drive motor is located on the top of the outer casing. The drive motor drives the stirring shaft to rotate, thereby causing the stirring blades to stir the solution in the crystallization chamber and promote the crystallization process.

4. The integrated crystallizer for multi-stage crystallization of oxalic acid according to claim 1, characterized in that: The first crystallization chamber, the second crystallization chamber, ... the (n-1)th crystallization chamber are all equipped with reflux ports, where n ≥ 2. The clear liquid outlet is provided on the side wall of the nth crystallization chamber, and the reflux port is used to return the clear liquid in the nth crystallization chamber.

5. The integrated crystallizer for multi-stage crystallization of oxalic acid according to claim 1, characterized in that: Each crystallization chamber is equipped with an independent cooling jacket or cooling pipe; a cooling medium, such as cold water or coolant, is introduced into the cooling jacket or cooling pipe. By controlling the flow rate and temperature of the cooling medium, the temperature of each crystallization chamber can be precisely controlled. In the first crystallization chamber near the feed inlet, the solution temperature is relatively high. As the solution flows through the subsequent crystallization chambers, the temperature gradually decreases, and water vapor continuously evaporates, thereby achieving multi-stage crystallization of oxalic acid.

6. An integrated crystallization apparatus for multi-stage crystallization of oxalic acid, comprising the crystallizer according to any one of claims 1-5, characterized in that: The clear liquid outlet of the nth crystallization chamber of the crystallizer is connected to the reflux port of the first crystallization chamber, the second crystallization chamber, ..., or the (n-1)th crystallization chamber via a clear liquid reflux pump and pipeline, realizing the circulating crystallization of the clear liquid; the air extraction port of the crystallizer is connected to a water-gas separator via a pipeline, and the water-gas separator is connected to a vacuum unit via a pipeline; the integrated crystallization device also includes a slurry tank, a crystal separation device, and a mother liquor tank; the discharge port of the crystallizer is connected to the slurry tank via a pipeline, the slurry tank is connected to the crystal separation device via a pipeline and a slurry pump, the crystal outlet of the crystal separation device is connected to a drying device, the mother liquor outlet of the crystal separation device is connected to the mother liquor tank via a pipeline, and the mother liquor tank is connected to the reflux port of the crystallizer via a mother liquor reflux pump, so that the mother liquor recrystallizes and the oxalic acid crystallization yield is improved.

7. The integrated crystallization apparatus for multi-stage crystallization of oxalic acid according to claim 6, characterized in that: It also includes a temperature control system, which includes a temperature sensor, a controller, and a cooling medium flow regulating valve. The temperature sensor is installed in each crystallization chamber to monitor the solution temperature in real time. The controller is connected to the temperature sensor and the cooling medium flow regulating valve, and automatically adjusts the opening of the cooling medium flow regulating valve according to the set temperature range to control the flow rate of the cooling medium, thereby precisely controlling the temperature of each crystallization chamber.

8. The integrated crystallization apparatus for multi-stage crystallization of oxalic acid according to claim 6, characterized in that: The controller is also connected to the drive motor, and adjusts the speed of the drive motor according to the solution temperature and crystallization status.

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