Device and method for preparing electronic-grade phosphoric acid by purifying high-purity phosphoric acid

Abstract

The invention discloses a device and a method for preparing electronic-grade phosphoric acid by purifying high-purity phosphoric acid, the device comprises a cooling crystallization tank, a separation device and a crystal melting device, a discharge port of the cooling crystallization tank is communicated with a feed port of the separation device, one discharge port of the separation device is communicated with a feed port of the crystal melting device, the device further comprises a pre-cooling device, and the pre-cooling device is communicated with the feed port of the crystal melting device. A feed port of the pre-cooling device is used for introducing raw material acid, and a discharge port of the pre-cooling device is communicated with a feed port of the cooling crystallization tank. The phosphoric acid cooling process and the phosphoric acid crystallization process are separated, the cooling time in the cooling crystallization process is shortened, the wall sticking phenomenon of crystals in the crystallization process is avoided, and the yield is increased.

Description

Technical Field

[0001] The invention relates to the technical field of electronic grade phosphoric acid purification, and in particular to a device and a method for purifying high-purity phosphoric acid to prepare electronic grade phosphoric acid. Background Art

[0002] Electronic grade phosphoric acid is a high-purity phosphoric acid, which is mainly used for chip cleaning and etching. It is an important wet electronic chemical in semiconductor manufacturing, and its quality depends on purity. High-quality electronic grade phosphoric acid requires extremely low metal element content. The main purification methods currently include crystallization, ion exchange, extraction, etc. Crystallization has the advantages of low energy consumption and no introduction of other impurities, and has attracted widespread attention.

[0003] Phosphoric acid crystallization purification usually refers to melt crystallization, which is a process of precipitating phosphoric acid crystals from mother liquor by cooling to obtain high-purity phosphoric acid crystals, and then melting the crystals to obtain high-purity phosphoric acid. Melt crystallization is divided into suspension crystallization and layer crystallization. Suspension crystallization has the advantages of simple equipment and is suitable for continuous production. Layer crystallization has higher requirements for equipment purification capacity, so industrial production mainly focuses on suspension crystallization.

[0004] At present, the suspended crystallization devices used in industrial production are mainly jacketed reactors with inner walls lined or sprayed with PFA materials. The jacketed reactors have a small specific surface area and a low heat transfer coefficient of the inner wall material, resulting in a too long cooling time in the initial cooling stage before crystallization.

[0005] For example, Chinese patent document CN104030261A, published (announced) date: 2014.09.10, discloses a method for producing high-purity electronic grade phosphoric acid, which includes adding raw acid to a stirred crystallizer, adding seed crystals, stirring and crystallizing to 30-60%, vacuum filtration to completely separate the crystal and liquid phases, then washing the crystals, heating and stirring the molten crystals with jacket hot water, and finally adjusting the acid to produce the product. The advantages are: the phosphoric acid is crystallized into sand-like crystals by stirring crystallization, the heat exchange rate between phosphoric acid and cooling medium is increased, and the crystallization speed is accelerated; the separation of crystal and liquid phases is more thorough and rapid by vacuum filtration, and the stirring of molten crystal also accelerates the crystallization melting speed, thereby greatly shortening the production cycle of electronic-grade phosphoric acid, greatly improving the production efficiency, and having good economic benefits; the disadvantages are: in this method, cooling is only performed by stirring crystallizer, the cooling time is long, and the temperature near the stirring crystallizer or the inner wall of the reactor is low, which easily causes the phenomenon of crystal scars sticking to the wall, and the crystal scars further reduce the heat transfer efficiency between the refrigerant and the mother liquor (raw acid), prolong the crystallization time, and finally part of the mother liquor is discharged as residual liquid because the temperature cannot be lowered below the crystallization temperature, resulting in a low mother liquor purification yield. Summary of the invention

[0006] In order to solve the current technical problems, the main purpose of the present invention is to provide a device and method for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid. By arranging a pre-cooling device upstream of a cooling crystallization tank, the raw acid is pre-cooled to solve the problems of long purification time and low yield of existing electronic-grade phosphoric acid.

[0007] In order to overcome the problems existing in the prior art, the technical solution adopted by the present invention is: a device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid, comprising a cooling crystallization tank, a separation device and a crystal melting device, wherein the discharge port of the cooling crystallization tank is connected to the feed port of the separation device, one of the discharge ports of the separation device is connected to the feed port of the crystal melting device, and also comprises a pre-cooling device, the feed port of the pre-cooling device is used to introduce raw acid, and the discharge port of the pre-cooling device is connected to the feed port of the cooling crystallization tank.

[0008] The precooling device is a heat exchanger structure, and a refrigerant is introduced into the precooling device to precool the raw acid passing through the precooling device.

[0009] The separation device has two discharge ports, one of which is connected to the feed port of the crystal melting device, and the other is connected to the residual liquid tank.

[0010] The separation device is a centrifuge.

[0011] At least two separation devices are provided.

[0012] One outlet of the residual liquid tank is connected to the feed inlet of the pre-cooling device, and the other outlet is connected to the tail acid tank.

[0013] The crystal melting device comprises a buffer tank, in which an isolation net is arranged, the isolation net divides the buffer tank into two spaces, the upper and lower spaces of the buffer tank are provided with a circulation pipeline, a circulation pump is installed on the circulation pipeline, and the circulation pump is used to pump the hot acid in the lower space of the buffer tank to the upper space.

[0014] It also includes a raw material tank, the discharge port of which is connected to the feed port of the pre-cooling device.

[0015] A method for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid, using the device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid, the method is used for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid, the method comprises the following steps: S1. Precooling of raw acid: transporting the raw acid into the precooling device to cool the raw acid to below the crystallization temperature of the corresponding concentration; S2, crystallization: after the pre-cooled raw acid enters the cooling crystallization tank, seed crystals are added, and the crystallization process ends when the temperature of the slurry is constant after the nuclear explosion crystallization. During the crystallization process, the cooling crystallization tank is used for cooling and stirring; S3, discharging centrifugation: discharging the cooling crystallization tank, obtaining residual liquid and crystals through a separation device, and the crystals enter a melting device; S4. Crystal melting: The hot acid reserved in the crystal melting device is used to melt the crystals through self-circulation to obtain the finished product of high-purity phosphoric acid.

[0016] The method also includes detecting the concentration of residual liquid, precooling the residual liquid exceeding the threshold concentration in a precooling device as a second batch of crystallization raw acid, and repeating the processes of S2, S3 and S4 to obtain a second batch of crystallization finished high-purity phosphoric acid.

[0017] The present invention has the following beneficial effects: 1. The cooling crystallization tank of the present invention is used for cooling crystallization, the separation device is used for separating residual liquid and crystals, and the melting crystal device is used for melting crystals to obtain finished high-purity phosphoric acid. The pre-cooling device is used to pre-cool the raw acid to cool the raw acid to below the crystallization temperature of the corresponding concentration. Since phosphoric acid has a high degree of supercooling, it often does not crystallize below the crystallization temperature, and supercooled phosphoric acid will burst into nucleation crystallization when it is put into seed crystals. Therefore, the present invention separates the phosphoric acid cooling process and the crystallization process, shortens the cooling process time during the cooling crystallization process, avoids the wall sticking phenomenon of crystals during the crystallization process, and improves the yield at the same time.

[0018] 2. The present invention shortens the time for separating crystals from mother liquor by setting up multiple separation devices, thereby improving the efficiency of the entire purification process.

[0019] 3. It is easier to recycle the residual liquid. The temperature and supercooling degree of low-concentration residual liquid in the pre-cooling device are easy to control, which improves the utilization rate of the residual liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 The present invention is a schematic diagram of a device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid.

[0022] Reference numerals: Raw material tank V01, pre-cooling device E01, cooling crystallization tank R01, centrifuge one C01, centrifuge two C02, residual liquid tank V02, melting crystal device V03, conveying pump one P01, conveying pump two P02, circulation pump P03, conveying pump three P04. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Embodiment 1: See also Figure 1 The present invention provides a device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid, comprising a cooling crystallization tank R01, a separation device and a melting crystal device V03, wherein the discharge port of the cooling crystallization tank R01 is connected to the feed port of the separation device, and one of the discharge ports of the separation device is connected to the feed port of the melting crystal device V03, and further comprising a precooling device E01, wherein the feed port of the precooling device E01 is used to introduce raw acid, and the discharge port of the precooling device E01 is connected to the feed port of the cooling crystallization tank R01. The cooling crystallization tank R01 is used for cooling crystallization, the separation device is used for separating residual liquid and crystals, and the melting crystal device V03 is used for melting crystals to obtain finished high-purity phosphoric acid. The precooling device E01 is used for precooling the raw acid to reduce the temperature of the raw acid to below the crystallization temperature of the corresponding concentration.

[0025] Since phosphoric acid has a high degree of supercooling, it often does not crystallize even if it is below the crystallization temperature. However, supercooled phosphoric acid will explode into nucleation crystals when seed crystals are added. Therefore, the present invention separates the phosphoric acid cooling process and the crystallization process, shortens the cooling time of the cooling crystallization process, avoids the crystal wall sticking phenomenon during the crystallization process, and improves the yield.

[0026] In this embodiment, the precooling device E01 is a heat exchanger structure, and a refrigerant is introduced into the precooling device E01 to precool the raw acid passing through the precooling device E01. In this embodiment, a delivery pump P04 is installed on the pipeline between the precooling device E01 and the cooling crystallization tank R01.

[0027] Specifically, the heat exchanger can adopt one or more combinations of plate heat exchangers, shell and tube heat exchangers, coil heat exchangers, etc. The inner part of the heat exchanger in contact with the material is made of PTFE or sprayed PFA material, and the medium in contact with the cold and hot media is 316L stainless steel.

[0028] The pre-cooling device E01 has multiple temperature sensors inside, which monitor the temperature of the cold and hot media and the material temperature respectively. If the material temperature rises when the cold media is introduced, the material will crystallize prematurely in the heat exchanger. At this time, the hot media should be introduced to completely eliminate the crystals.

[0029] In this embodiment, the separation device has two discharge ports, one of which is connected to the feed port of the crystal melting device V03, and the other is connected to the residual liquid tank V02.

[0030] In this embodiment, the separation device is a centrifuge.

[0031] Furthermore, at least two separation devices are provided. When in use, the cooling crystallization tank R01 can be discharged to multiple centrifuges alternately to keep the discharge process continuous, avoid the material from being blocked at the discharge port of the cooling crystallization tank R01, and improve the efficiency of crystal separation, so that the efficiency of the entire purification process is improved.

[0032] In this embodiment, see Figure 1 There are two separation devices, including centrifuge 1 C01 and centrifuge 2 C02.

[0033] Further, in the present embodiment, in order to further utilize the residual liquid and improve the yield, the discharge port of the residual liquid tank V02 is connected to the feed port of the precooling device E01 in one way, and is connected to the tail acid tank in another way. When in use, the residual liquid concentration in the residual liquid tank V02 is detected, and the residual liquid exceeding the threshold concentration is precooled in the precooling device E01 as the second batch of crystallization raw acid, thereby obtaining the second batch of crystallization finished product high-purity phosphoric acid. In the present embodiment, a delivery pump P02 is installed on the pipeline connecting the residual liquid tank V02 and the precooling device E01.

[0034] In this embodiment, the crystal melting device V03 includes a buffer tank, in which an isolation net is provided, the isolation net divides the buffer tank into two spaces, the upper and lower spaces of the buffer tank are provided with a circulation pipeline, and a circulation pump P03 is installed on the circulation pipeline. The circulation pump P03 is used to pump the hot acid in the lower space of the buffer tank to the upper space. When in use, the crystal is placed above the isolation net, and the hot acid reserved in the buffer tank is self-circulated to melt the crystal to obtain a finished high-purity phosphoric acid. In this embodiment, a circulation pump P03 is installed on the circulation pipeline.

[0035] Specifically, the buffer tank has a heating and heat preservation device, such as an external coil heating.

[0036] Furthermore, the present embodiment further comprises a raw material tank V01, the discharge port of the raw material tank V01 is connected to the feed port of the pre-cooling device E01. The raw material tank V01 is used to hold the raw acid. In the present embodiment, a delivery pump P01 is also installed on the pipeline connecting the raw material tank V01 and the pre-cooling device E01.

[0037] Embodiment 2: On the basis of Example 1, a method for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid is provided, which uses a device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid. The method is used for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid, and the method comprises the following steps: S1. Precooling of raw acid: The raw acid is transported into the precooling device E01 to cool the raw acid to below the corresponding concentration crystallization temperature. In this embodiment, the raw acid is cooled to 5-10°C below the corresponding crystallization temperature.

[0038] S2, crystallization: After the pre-cooled raw acid enters the cooling crystallization tank R01, seed crystals are added. The crystallization process ends when the temperature of the slurry is constant after the nuclear explosion crystallization. During the crystallization process, the cooling crystallization tank R01 is used for cooling and stirring. In this embodiment, the seed crystal dosage is 0.1-0.5%, and the cooling crystallization tank R01 is passed through a constant temperature refrigerant of 0-10°C.

[0039] S3, discharging centrifuge: discharging from cooling crystallization tank R01, obtaining residual liquid and crystals through separation device, and the crystals enter into melting crystal device V03.

[0040] S4, crystal melting: The reserved hot acid in the crystal melting device V03 is used to melt the crystals by self-circulation to obtain the finished high-purity phosphoric acid. In this embodiment, the mass ratio of the reserved hot acid to the crystal is 3:1-5:1, and the hot acid temperature is 40-60°C. Embodiment 3: On the basis of Example 2, it also includes detecting the concentration of residual liquid, precooling the residual liquid exceeding the threshold concentration as the second batch of crystallization raw acid in the precooling device E01, repeating the processes of S2, S3 and S4 to obtain the second batch of crystallization finished high-purity phosphoric acid, so as to further improve the yield.

[0041] Embodiment 4: The device of Example 1 of the present application is used for purification, and the raw acid is phosphoric acid with a concentration of 88%. Cooling: the raw acid is passed into a shell-and-tube heat exchanger, and a 15°C refrigerant is passed. When the acid temperature is measured to be 18°C, the acid is transported to the cooling crystallization tank R01, and the cooling crystallization tank R01 is stirred at a stirring rate of 150r / min, and a 18°C ​​refrigerant is passed into the jacket; crystallization: seed crystals are added, and the bottom discharge valve is opened 10 minutes after the acid temperature rises to 25°C to discharge the material into the centrifuge. During the process, the material is discharged and centrifuged alternately to obtain crystals and residual liquid. The crystals are discharged into the melting crystal device V03 for melting to obtain finished phosphoric acid; the concentration of the residual liquid is measured, and the temperature is returned to the heat exchanger for cooling, and a 10°C refrigerant is passed. When the acid temperature is 13°C, it is transported to the crystallization tank and the above process is repeated for crystallization, centrifugation and melting.

[0042] Comparative Example 1: A jacketed crystallization kettle is used for purification, and the raw acid is phosphoric acid with a concentration of 88%. Cooling: the raw acid is passed into a crystallization tank, and a 25°C refrigerant is passed into the crystallization tank. The stirring is started in the crystallization tank, and the stirring rate is 150r / min. Crystallization: when the acid temperature drops to 26°C, seed crystals are added, and the refrigerant is cooled to 10°C at 2°C / h. After the acid temperature is constant, the bottom discharge valve is opened 10 minutes after the acid temperature is constant to discharge the material into a centrifuge for centrifugation to obtain crystals and residual liquid. The crystals are discharged into a finished product buffer tank for melting to obtain finished phosphoric acid; the concentration of the residual liquid is measured, and the liquid is returned to the heat exchanger for cooling, and a 10°C refrigerant is passed into the acid. When the acid temperature is 13°C, it is transported to the crystallization tank and the above process is repeated for crystallization, centrifugation and melting.

[0043] Comparative Example 2: A jacketed crystallization kettle is used for purification. The raw acid is phosphoric acid with a concentration of 88%. Cooling: the raw acid is passed into the crystallization tank, and a 25°C refrigerant is passed into the crystallization tank. The crystallization tank is stirred at a stirring rate of 150r / min. Crystallization: When the acid temperature is 26°C, seed crystals are added, and the refrigerant is cooled to 10°C at 2°C / h. After the acid temperature is constant, the bottom discharge valve is opened 10 minutes later. Sweating: the material is discharged into the suction filtration kettle, and a 40°C heat medium is passed into the jacket of the suction filtration kettle, and the residual sweat is discharged into the residual liquid tank. Melting: When the mass of the residual sweat accounts for 50% of the raw acid, the heat medium temperature rises to 50°C, and the molten hot acid is discharged into the finished product buffer tank to obtain the finished phosphoric acid; the concentration of the residual sweat is measured, and the crystallization tank is returned to repeat the above process of crystallization, sweating and melting.

[0044] The crystallization purification time and yield of Example 4 and Comparative Examples 1 and 2 are shown in the following table:

[0045] The present invention shortens the cooling time of the cooling crystallization process, avoids the wall sticking phenomenon of the crystals during the crystallization process, and improves the yield. At the same time, the time for separating the crystals from the mother liquor is shortened, so that the efficiency of the entire crystallization process is improved. At the same time, it is easier to recycle the residual liquid, and the temperature and supercooling degree of the low-concentration residual liquid in the external heat exchanger are easy to control, thereby improving the utilization rate of the residual liquid.

Claims

1. A device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid, comprising a cooling crystallization tank (R01), a separation device and a crystal melting device (V03), wherein the discharge port of the cooling crystallization tank (R01) is connected to the feed port of the separation device, and one of the discharge ports of the separation device is connected to the feed port of the crystal melting device (V03), characterized in that: It also includes a pre-cooling device (E01), wherein the feed port of the pre-cooling device (E01) is used to introduce raw acid, and the discharge port of the pre-cooling device (E01) is connected to the feed port of the cooling crystallization tank (R01).

2. The device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid according to claim 1, characterized in that: The precooling device (E01) is a heat exchanger structure, and a refrigerant is introduced into the precooling device (E01) to precool the raw acid passing through the precooling device (E01).

3. The device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid according to claim 1, characterized in that: The separation device has two discharge ports, one of which is connected to the feed port of the crystal melting device (V03), and the other is connected to the residual liquid tank (V02).

4. The device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid according to claim 3, characterized in that: The separation device is a centrifuge.

5. The device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid according to claim 1, 3 or 4, characterized in that: At least two separation devices are provided.

6. The device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid according to claim 3, characterized in that: One outlet of the residual liquid tank (V02) is connected to the feed inlet of the pre-cooling device (E01), and the other outlet is connected to the tail acid tank.

7. The device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid according to claim 1, characterized in that: The crystal melting device (V03) includes a buffer tank, in which an isolation net is arranged, the isolation net divides the buffer tank into two upper and lower spaces, the upper and lower spaces of the buffer tank are provided with a circulation pipeline, and a circulation pump is installed on the circulation pipeline, and the circulation pump is used to pump the hot acid in the lower space of the buffer tank to the upper space.

8. The device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid according to claim 1, characterized in that: It also includes a raw material tank (V01), wherein the discharge port of the raw material tank (V01) is connected to the feed port of the pre-cooling device (E01).

9. A method for purifying high-purity phosphoric acid to prepare electronic grade phosphoric acid, characterized in that: The device for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid according to any one of claims 1 to 8 is used, and the method is used for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid, and the method comprises the following steps: S1, raw acid precooling: the raw acid is transported into the precooling device (E01) to cool the raw acid to below the corresponding concentration crystallization temperature; S2, crystallization: After the pre-cooled raw acid enters the cooling crystallization tank (R01), seed crystals are added. The crystallization process ends when the slurry temperature is constant after the nuclear explosion crystallization. During the crystallization process, the cooling crystallization tank (R01) is used for cooling and stirring; S3, discharging centrifuge: discharging from the cooling crystallization tank (R01), obtaining residual liquid and crystals through a separation device, and the crystals enter the melting crystal device (V03); S4. Crystal melting: The hot acid reserved in the crystal melting device (V03) is used to melt the crystals through self-circulation to obtain the finished high-purity phosphoric acid.

10. The method for purifying high-purity phosphoric acid to prepare electronic-grade phosphoric acid according to claim 9, characterized in that: The method also includes detecting the concentration of residual liquid, precooling the residual liquid exceeding the threshold concentration in a precooling device (E01) as the second batch of crystallization raw acid, and repeating the processes of S2, S3 and S4 to obtain the second batch of crystallization finished high-purity phosphoric acid.

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