Preparation process of large-particle ammonium bifluoride

Abstract

The invention discloses a preparation process of large-particle ammonium bifluoride, which comprises the following steps: introducing an ammonium bifluoride concentrated solution and ammonium bifluoride seed crystal slurry into a circulating crystallizer, and circulating a mixture in the circulating crystallizer between a crystallization cooler and the circulating crystallizer through a circulating pump, and leading out crystals generated at the bottom of the circulating crystallizer, centrifuging and drying to obtain the large-particle ammonium bifluoride. The ammonium bifluoride concentrated solution and the ammonium bifluoride seed crystal slurry are cyclically crystallized between the circulating crystallizer and the crystallization cooler, so that the crystal granularity is increased, the crystal moisture content is reduced, the energy consumption of an ammonium bifluoride drying procedure is reduced, and storage is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of waste liquid utilization, in particular to a preparation process of large-particle ammonium bifluoride. Background Art

[0002] At a time when semiconductor and electronics industries are in mass production, the recycling of fluorine-containing etching waste liquid (BOE) has become a key focus in the field of hazardous solid waste recycling. Fluorine-containing etching waste liquid mainly includes ammonium fluoride, hydrofluoric acid, etc. After removing impurities, the remaining ammonium bifluoride concentrate will generally crystallize into ammonium bifluoride products for reuse.

[0003] Patent application CN202410820630.7 discloses an efficient and energy-saving method for purifying ammonium bifluoride, which belongs to the technical field of ammonium fluoride salt purification. The method for purifying ammonium bifluoride adopts recrystallization to achieve the effects of high yield, high efficiency, environmental protection, simplicity and ease of large-scale production. However, the method involves repeated heating and cooling, and the energy consumption is relatively high. In addition, the method does not take into account the crystal size of ammonium bifluoride, and the size of the crystal will directly affect the water content of the ammonium bifluoride crystal. The larger the crystal, the lower the water content, and the lower the energy consumption of the rear-end drying equipment. In addition, large particles of ammonium bifluoride have a small specific surface area, which can reduce the contact surface with the air, slow down the moisture resorption, and are more conducive to storage. Summary of the invention

[0004] The main purpose of the present invention is to provide a preparation process of large-particle ammonium bifluoride.

[0005] To achieve the above object, the present invention provides a process for preparing large-particle ammonium bifluoride, comprising the following steps: The ammonium bifluoride concentrate and the ammonium bifluoride seed slurry are introduced into a circulating crystallizer, and the materials in the circulating crystallizer are continuously circulated between the circulating crystallizer and the crystallization cooler through a circulating pump, and then the crystals produced at the bottom of the circulating crystallizer are led out, and the large-particle ammonium bifluoride is obtained through centrifugation and drying.

[0006] Further, the concentration of the ammonium bifluoride concentrate is 48 to 53 wt %, and the ammonium bifluoride concentrate is 1 to 1.2 m 3 / h feed rate continuously feed; the concentration of ammonium bifluoride seed slurry is 55-65wt%, and the ammonium bifluoride seed slurry is intermittently fed at a cycle of every 12h, and the feed rate of each feed is 0.5m 3 / h, feeding time 1h, circulation flow rate of circulation pump is 180~250m 3 / h.

[0007] Furthermore, the feed temperature of the ammonium bifluoride concentrate is 75-85°C, the feed temperature of the ammonium bifluoride seed slurry is 60-70°C, and the temperature of the crystallization cooler is 18-23°C.

[0008] Furthermore, except for the first feed, the subsequent feeds of the ammonium bifluoride seed slurry are prepared from the large-particle ammonium bifluoride and the supernatant obtained by centrifugation.

[0009] Furthermore, the average particle size of the seeds of the first feed of the ammonium bifluoride seed slurry is 0.45 to 0.55 mm.

[0010] Furthermore, the drying treatment conditions are a temperature of 68 to 76° C. and a pressure of -1500 to -1000 Pa.

[0011] Furthermore, the circulation pump adopts a submersible pump, and the circulation pump extends into the bottom of the circulation crystallizer.

[0012] Furthermore, the medium flows in the shell and tube of the crystallizer in the same direction. With this design, the heat exchange material and the refrigerant keep relatively parallel material flows, which can buffer the cooling capacity, reduce the temperature difference between the two borings, achieve the effect of slow cooling and reduce vibration, and make the crystallization stable.

[0013] The present invention also provides a production system for implementing the above-mentioned preparation process, comprising a circulating crystallizer, a circulating pump, a crystal cooler, and a crystal temporary storage tank, a centrifuge and a dryer connected in sequence, wherein the feed port of the circulating pump is connected to the top of the circulating crystallizer, the discharge port of the circulating pump is connected to the feed port of the crystal cooler, the discharge port of the crystal cooler is connected to the circulating crystallizer, and the crystal temporary storage tank is connected to the bottom of the circulating crystallizer.

[0014] Furthermore, it also includes a seed slurry tank and a seed slurry pump, the seed slurry tank is connected to the liquid outlet of the centrifuge, the feed port of the seed slurry pump is connected to the seed slurry tank, and the discharge port of the seed slurry pump is connected to the circulation crystallizer.

[0015] The beneficial effects of the present invention are embodied in: The invention circulates and crystallizes the ammonium bifluoride concentrated liquid and the ammonium bifluoride seed slurry between a circulating crystallizer and a crystallization cooler to increase the crystal particle size, thereby reducing the crystal water content, reducing the energy consumption of the ammonium bifluoride drying procedure, and facilitating storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a schematic structural diagram of a production system for implementing a process for preparing large-particle ammonium bifluoride according to an embodiment of the present invention.

[0017] Figure 2This is a physical photo of the ammonium bifluoride crystals of Example 1.

[0018] Figure 3 This is a physical photo of the ammonium bifluoride crystals of Comparative Example 3.

[0019] Description of reference numerals: 1. Circulation crystallizer; 2. Circulation pump; 3. Crystallization cooler; 4. Crystallization cooler; 5. Refrigerant buffer tank; 6. Refrigerant buffer tank; 7. Refrigerant pump; 8. Refrigerant heater; 9. Seed slurry tank; 10. Crystal temporary storage tank; 11. Seed slurry pump; 12. Centrifuge; 13. Dryer. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0021] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or can be obtained by existing known methods; unless otherwise specified, the methods used in the examples of the present invention are methods known to those skilled in the art.

[0022] The present invention is equipped with a production system for implementing a preparation process of large-particle ammonium bifluoride. The system includes a circulating crystallizer 1, a circulating pump 2, a crystal cooler, and a crystal temporary storage tank 10, a centrifuge 12 and a dryer 13 which are connected in sequence. The feed port of the circulating pump 2 is connected to the top of the circulating crystallizer 1, the discharge port of the circulating pump 2 is connected to the feed port of the crystal cooler, the discharge port of the crystal cooler is connected to the circulating crystallizer 1, the crystal temporary storage tank 10 is connected to the bottom of the circulating crystallizer 1, the circulating pump 2 adopts a submersible pump, and the circulating pump 2 extends to the bottom of the circulating crystallizer 1; the dryer 13 uses a cyclone separator; The system further comprises a seed slurry tank 9 and a seed slurry pump 11, wherein the seed slurry tank 9 is connected to the liquid outlet of the centrifuge 12, the feed inlet of the seed slurry pump 11 is connected to the seed slurry tank 9, and the discharge port of the seed slurry pump 11 is connected to the circulation crystallizer 1; The medium in the shell side and the tube side of the crystallizer cooler 43 is in the same direction, and the refrigeration system of the crystallizer cooler 43 includes a refrigerant pump 7, a refrigerant buffer tank, and a refrigerant heater 8. The liquid inlet of the refrigerant pump 7 is connected to the refrigerant water source, the liquid outlet of the refrigerant pump 7 is connected to one end of the shell side of the crystallizer cooler, and the other end of the shell side of the crystallizer cooler is connected to the refrigerant buffer tank, and the refrigerant buffer tank is connected to the refrigerant heater 8. Specifically, two crystallizer coolers 3, 4 and two refrigerant buffer tanks 5, 6 are used, and the two crystallizer coolers 3, 4 share one refrigerant pump 7 and one refrigerant heater 8.

[0023] Example 1 Preparation of Large Particle Ammonium Bifluoride The steps are as follows: The ammonium bifluoride concentrate and the ammonium bifluoride seed slurry are introduced into the circulation crystallizer, and the circulation pump is started at the same time. The materials in the circulation crystallizer are continuously circulated between the circulation crystallizer and the crystallization cooler through the circulation pump. The circulation flow rate of the circulation pump is 220m 3 / h, the temperature of the crystallization cooler is set at 20°C; The concentration of the ammonium bifluoride concentrate is 50.12wt%, the temperature is 75°C, and the ammonium bifluoride concentrate is 1.0m 3 / h feed rate for continuous feeding; The concentration of the ammonium bifluoride seed slurry was 60 wt % and the temperature was 60 ° C. The ammonium bifluoride seed slurry was fed intermittently every 12 hours, and the feed flow rate of each feed was 0.5 m 3 / h, feeding time 1h, the first feeding of ammonium bifluoride seed slurry and the feeding of ammonium bifluoride concentrated solution started simultaneously, and the average particle size of the seed crystals was 0.55mm; As the crystallization proceeds, crystals are gradually generated at the bottom of the circulating crystallizer, and the crystals self-sediment into the crystal temporary storage tank. After that, the material is discharged from the lower end of the crystal temporary storage tank and enters the centrifuge for centrifugal treatment at a speed of 3000r / min. The solid obtained by centrifugation enters the dryer for drying at a temperature of 72°C and a pressure of -1480Pa to obtain large-particle ammonium bifluoride. The second and subsequent feeds of the ammonium bifluoride seed slurry are composed of large-particle ammonium bifluoride and the supernatant obtained by centrifugation. Specifically, the liquid obtained by centrifugation enters the seed slurry tank, and then the large-particle ammonium bifluoride obtained by drying is put into the seed slurry tank. During the feeding, it is pumped into the circulation crystallizer through the seed slurry pump.

[0024] Example 2 Preparation of Large Particle Ammonium Bifluoride The steps are as follows: The ammonium bifluoride concentrate and the ammonium bifluoride seed slurry are introduced into the circulation crystallizer, and the circulation pump is started at the same time. The materials in the circulation crystallizer are continuously circulated between the circulation crystallizer and the crystallization cooler through the circulation pump. The circulation flow rate of the circulation pump is 200m 3 / h, the temperature of the crystallization cooler was set at 23°C; The concentration of the ammonium bifluoride concentrate is 52.14wt%, the temperature is 80°C, and the ammonium bifluoride concentrate is 1.14m 3 / h feed rate for continuous feeding; The concentration of the ammonium bifluoride seed slurry was 55 wt % and the temperature was 65 ° C. The ammonium bifluoride seed slurry was fed intermittently every 12 hours, and the feed flow rate of each feed was 0.5 m 3 / h, feeding time 1h, the first feeding of ammonium bifluoride seed slurry and the feeding of ammonium bifluoride concentrated solution started simultaneously, and the average particle size of the seed crystals was 0.45mm; As the crystallization proceeds, crystals are gradually generated at the bottom of the circulating crystallizer, and the crystals self-sediment into the crystal temporary storage tank. After that, the material is discharged from the lower end of the crystal temporary storage tank and enters the centrifuge for centrifugal treatment at a speed of 3000r / min. The solids obtained by centrifugation enter the dryer and are dried at a temperature of 68°C and a pressure of -1500Pa to obtain large-particle ammonium bifluoride. The second and subsequent feeds of the ammonium bifluoride seed slurry are composed of large-particle ammonium bifluoride and the supernatant obtained by centrifugation. Specifically, the liquid obtained by centrifugation enters the seed slurry tank, and then the large-particle ammonium bifluoride obtained by drying is put into the seed slurry tank. During the feeding, it is pumped into the circulation crystallizer through the seed slurry pump.

[0025] Example 3 Preparation of Large Particle Ammonium Bifluoride The steps are as follows: The ammonium bifluoride concentrate and the ammonium bifluoride seed slurry are introduced into the circulation crystallizer, and the circulation pump is started at the same time. The materials in the circulation crystallizer are continuously circulated between the circulation crystallizer and the crystallization cooler through the circulation pump. The circulation flow rate of the circulation pump is 240m 3 / h, the temperature of the crystallization cooler was set at 18°C; The concentration of the ammonium bifluoride concentrate is 48.55wt%, the temperature is 85°C, and the ammonium bifluoride concentrate is 1.0m 3 / h feed rate for continuous feeding; The concentration of the ammonium bifluoride seed slurry was 65wt%, the temperature was 70°C, and the ammonium bifluoride seed slurry was fed intermittently every 12h, with a feed flow rate of 0.5m 3 / h, feeding time 1h, the first feeding of ammonium bifluoride seed slurry and the feeding of ammonium bifluoride concentrated solution started simultaneously, and the average particle size of the seed crystals was 0.50mm; As the crystallization proceeds, crystals are gradually generated at the bottom of the circulating crystallizer, and the crystals self-sediment into the crystal temporary storage tank. After that, the material is discharged from the lower end of the crystal temporary storage tank and enters the centrifuge for centrifugal treatment at a speed of 3000r / min. The solids centrifuged enter the dryer and are dried at a temperature of 76°C and a pressure of -1000Pa to obtain large-particle ammonium bifluoride. The second and subsequent feeds of the ammonium bifluoride seed slurry are composed of large-particle ammonium bifluoride and the supernatant obtained by centrifugation. Specifically, the liquid obtained by centrifugation enters the seed slurry tank, and then the large-particle ammonium bifluoride obtained by drying is put into the seed slurry tank. During the feeding, it is pumped into the circulation crystallizer through the seed slurry pump.

[0026] Comparative Example 1 Preparation of Ammonium Bifluoride This comparative example is operated in the same manner as in Example 1, except that the operation of continuously circulating the material in the circulating crystallizer between the circulating crystallizer and the crystallization cooler by means of a circulating pump is eliminated.

[0027] Comparative Example 2 Preparation of Ammonium Bifluoride This comparative example is operated in the same manner as in Example 1, except that the medium flow directions in the shell side and the tube side of the crystallization cooler are changed to the opposite direction.

[0028] Comparative Example 3 Preparation of Ammonium Bifluoride This comparative example was operated in the same manner as in Example 1, except that the addition of seed slurry was omitted.

[0029] Comparative Example 4 Preparation of Ammonium Bifluoride This comparative example was operated in the same manner as in Example 1, except that the temperature of the crystallization cooler was adjusted to 15°C.

[0030] Comparative Example 5 Preparation of Ammonium Bifluoride This comparative example was operated in the same manner as in Example 1, except that the temperature of the crystallization cooler was adjusted to 26°C.

[0031] Comparative Example 6 Preparation of Ammonium Bifluoride This comparative example is operated in the same manner as in Example 1, except that the flow rate of the circulating pump is adjusted to 260 m 3 / h.

[0032] Comparative Example 7 Preparation of Ammonium Bifluoride This comparative example is operated in the same manner as in Example 1, except that the flow rate of the circulating pump is adjusted to 180 m 3 / h.

[0033] Crystallization Effect and Size Analysis of Large Particle Ammonium Bifluoride The product in the crystal temporary storage tank of Example 1 was taken out for observation (sampling was performed after 72 hours of operation). Figure 1 As shown, it can be seen that the particle size of the ammonium bifluoride crystals is significantly larger than that of the ammonium bifluoride crystals, and exhibits a distinct needle-shaped crystal form.

[0034] The product in the crystal temporary storage tank of Comparative Example 3 was taken out for observation (sampling was performed after 72 hours of operation). Figure 2 As shown, it can be seen that the particle size of the ammonium bifluoride crystals is significantly reduced relative to that of Example 1.

[0035] The crystals of other proportions were observed, and it was also found that the particle sizes of the ammonium bifluoride crystals were all smaller than those of Example 1. For the sake of brevity, they are not further described with reference to the figures.

[0036] The ammonium bifluoride products obtained in the above-mentioned embodiments and comparative examples (sampled after running for 72 hours) were tested for particle size, and the results are shown in Table 1 below: Table 1 The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A process for preparing large-particle ammonium bifluoride, characterized in that: The following steps are involved: The ammonium bifluoride concentrate and the ammonium bifluoride seed slurry are introduced into a circulating crystallizer, and the materials in the circulating crystallizer are continuously circulated between the circulating crystallizer and the crystallization cooler through a circulating pump, and then the crystals produced at the bottom of the circulating crystallizer are led out, and the large-particle ammonium bifluoride product is obtained through centrifugation and drying.

2. The process for preparing large-particle ammonium bifluoride according to claim 1, characterized in that: The concentration of the ammonium bifluoride concentrate is 48-53 wt %, and the ammonium bifluoride concentrate is 1-1.2 m 3 / h feed rate continuously feed; the concentration of ammonium bifluoride seed slurry is 55-65wt%, and the ammonium bifluoride seed slurry is intermittently fed at a cycle of every 12h, and the feed rate of each feed is 0.5m 3 / h, feeding time 1h, circulation flow rate of circulation pump is 200~240m 3 / h.

3. The process for preparing large-particle ammonium bifluoride according to claim 1 or 2, characterized in that: The feed temperature of the ammonium bifluoride concentrated solution is 75-85°C, the feed temperature of the ammonium bifluoride seed slurry is 60-70°C, and the temperature of the crystallization cooler is 18-23°C.

4. The process for preparing large-particle ammonium bifluoride according to claim 1 or 2, characterized in that: Except for the first feed, the subsequent feeds of the ammonium bifluoride seed slurry are prepared from the large-particle ammonium bifluoride and the supernatant obtained by centrifugation.

5. The process for preparing large-particle ammonium bifluoride according to claim 4, characterized in that: The average particle size of the seeds of the first charge of ammonium bifluoride seed slurry is 0.45 to 0.55 mm.

6. The process for preparing large-particle ammonium bifluoride according to claim 1 or 2, characterized in that: The drying treatment conditions are a temperature of 68 to 76°C and a pressure of -1500 to -1000Pa.

7. The process for preparing large-particle ammonium bifluoride according to claim 1 or 2, characterized in that: The circulation pump adopts a submersible pump, and the circulation pump extends into the bottom of the circulation crystallizer.

8. The process for preparing large-particle ammonium bifluoride according to claim 1 or 2, characterized in that: The medium flows in the shell side and tube side of the crystallizer in the same direction.

9. A production system for implementing the preparation process according to any one of claims 1 to 8, characterized in that: The invention comprises a circulating crystallizer, a circulating pump, a crystal cooler, and a crystal temporary storage tank, a centrifuge and a dryer which are connected in sequence. The feed port of the circulating pump is connected to the top of the circulating crystallizer, the discharge port of the circulating pump is connected to the feed port of the crystal cooler, the discharge port of the crystal cooler is connected to the circulating crystallizer, and the crystal temporary storage tank is connected to the bottom of the circulating crystallizer.

10. The production system according to claim 9, characterized in that It also includes a seed slurry tank and a seed slurry pump. The seed slurry tank is connected to the liquid outlet of the centrifuge, the feed port of the seed slurry pump is connected to the seed slurry tank, and the discharge port of the seed slurry pump is connected to the circulation crystallizer.

Images