Method for industrially and continuously preparing silicon tetrafluoride

Abstract

The invention provides a method for industrially and continuously preparing silicon tetrafluoride, and belongs to the technical field of chemical processes. The method comprises the following steps that fluosilicate is subjected to heat treatment in a heating bin at the temperature of 60-500 DEG C for 30-100 minutes, and the fluosilicate is fed into a feeding bin, stays for 30-100 minutes and then is fed into a rotary furnace; after all the fluosilicate subjected to heat treatment enters the feeding bin, the heat treatment step is repeated; the temperature of the rotary furnace is 200-850 DEG C, and reacting for 30-100 minutes to obtain silicon tetrafluoride after thermal cracking reaction; cooling and collecting to obtain high-purity silicon tetrafluoride gas; the steps are repeated, so that the fluosilicate subjected to heat treatment always participates in the reaction in the rotary furnace, and circulation is formed; according to the method, continuous feeding and continuous discharging are achieved, the production efficiency of silicon tetrafluoride is greatly improved, and the disadvantage that industrial production is difficult to achieve through a fluosilicate thermal decomposition method is overcome.

Description

Technical Field

[0001] The invention relates to the field of chemical process technology, in particular to a method for industrially continuously preparing silicon tetrafluoride. Background Art

[0002] SiF 4 In the electronics and semiconductor industries, it is mainly used as an etchant for silicon nitride, tantalum silicide, etc., a P-type dopant, an epitaxial deposition diffusion silicon source, etc. It can also be used to prepare electronic grade silane or polysilicon. 4 It can also be used as a raw material for high-purity quartz glass for optical fibers. It can be hydrolyzed in a high-temperature flame to produce a heat sink SiO with a high specific surface area. 2 In addition, SiF 4 It is also widely used in the preparation of solar cells, fluorosilicic acid and aluminum fluoride, chemical analysis, fluorination agent, oil well drilling, magnesium alloy casting, catalyst, fumigant, cement and artificial marble hardener, etc. 4 After that, its corrosion resistance and wear resistance can be improved, its porosity can be improved and its compressive strength can be increased.

[0003] Currently, SiF 4 Industrialized production is mainly concentrated in the United States, Japan and Italy; in China, several SiF companies have also emerged in the past decade. 4 However, the more mature SiF 4 The production process mainly includes sulfuric acid method, fluorosilicic acid method, hydrofluoric acid method, by-product recovery method, calcium fluorosilicate method, etc. Most of them have problems such as high cost, low conversion rate, and many by-products. 4 The key issue for the manufacturing industry to achieve efficient production.

[0004] Sulfuric acid method 2 SO 4 、SiO 2 Silicon tetrafluoride is prepared by mixing fluoride salts or fluorosilicates through a "one-pot" reaction. This method can be divided into fluorosilicate-H 2 SO 4 Method, Fluorosilicic acid-H 2 SO 4 Fluorite-H 2 SO 4 Fluorosilicate-H 2 SO 4 The method has many by-products, impurities are difficult to remove, the purity of the generated silicon tetrafluoride is not high enough, it pollutes the environment and is prone to serious corrosion of equipment, and the feasibility of industrial production is low. 2 SO 4 The production method requires high equipment conditions and will produce a large amount of fluorine-containing dilute sulfuric acid, which has a great impact on the environment.2 SO 4 This method has the advantages of simple production process and high material utilization rate, but the mining of fluorite is restricted, which greatly increases the cost and is not conducive to industrial production.

[0005] The hydrofluoric acid-quartz sand and sulfuric acid method is similar to the sulfuric acid method mentioned above. The reaction equation is: SiO 2 +4HF→SiF 4 ↑+2H 2 O. The reaction does not require a high acid content, and the reaction residue and slurry can be used. However, the two-step method increases the reaction steps, making the production process complicated, causing serious corrosion to the equipment, and is not convenient for industrial mass production.

[0006] Fluorosilicate pyrolysis is to prepare silicon tetrafluoride gas by directly heating the fluorination reagent fluorosilicate to decompose it. The reaction equation is: NaSiF 6 →SiF 4 ↑+2NaF. BULANOV et al. used thermal decomposition of pure sodium hexafluorosilicate (Na 2 SiF 6 ) method to prepare high-purity silicon tetrafluoride. 2 SiF 6 Add to a reactor equipped with a resistance heater, preliminarily dry at 250°C in a vacuum or helium stream, and then thermally decompose under vacuum conditions at 500°C-620°C. 2 SiF 6 The thermal decomposition of is a reversible reaction, so the SiF 4 It is continuously transferred to a metal container and cooled with liquid nitrogen, and finally the suspended particles are removed by a filter. Zhang Yueqiang et al. used a mixed acid dissolution method to dissolve single crystal silicon to prepare silicon tetrafluoride. This method uses a mixed acid obtained by mixing hydrofluoric acid and nitric acid in proportion to digest the single crystal silicon to obtain fluorosilicic acid, and then adds barium chloride solution to the fluorosilicic acid to prepare barium fluorosilicate. The prepared barium fluorosilicate is decomposed in a reactor under vacuum and 200°C for 60 minutes to prepare SiF 4 gas.

[0007] The fluorosilicate thermal decomposition method has the advantages of a single reaction, fewer by-products and high product purity, which solves the bottleneck of environmental protection issues in the development of the industry. However, the output of the experimental device is low, and industrial production is difficult to achieve. Therefore, a method for continuously producing silicon tetrafluoride using fluorosilicate is urgently needed. Summary of the invention

[0008] The purpose of the present invention is to provide a method for industrially continuously preparing silicon tetrafluoride using fluorosilicate, which greatly improves production efficiency and saves production time.

[0009] To achieve the above-mentioned purpose of the invention, the technical solution of the present invention is as follows:

[0010] In one aspect, the present invention provides a method for industrially continuously preparing silicon tetrafluoride, the method being implemented by a roasting device comprising a heating bin, a feeding bin and a rotary kiln; the method comprising the following steps:

[0011] Step 1: The fluorosilicate is heat-treated in a heating chamber at 60-500° C. for 30-100 minutes to obtain the heat-treated fluorosilicate;

[0012] Step 2: The heat-treated fluorosilicate in step 1 is fed into a feed bin, and the heat-treated fluorosilicate is fed into a rotary kiln within 30-100 minutes; when all the heat-treated fluorosilicate in step 1 has entered the feed bin, step 1 is repeated;

[0013] Step 3: maintaining the temperature of the rotary kiln at 200-850° C., reacting the fluorosilicate after the heat treatment in step 2 for 30-100 minutes to obtain silicon tetrafluoride after thermal cracking reaction;

[0014] Step 4: Cooling and collecting the silicon tetrafluoride after the thermal cracking reaction to obtain high-purity silicon tetrafluoride gas;

[0015] Repeat steps 1-2, so that the fluorosilicate heat-treated in step 2 always participates in the reaction in the rotary kiln in step 3 to form a cycle;

[0016] Performed in the following devices:

[0017] An industrial continuous preparation device of silicon tetrafluoride comprises a feeding mechanism, a stirring mechanism, a conveying mechanism, a vacuum mechanism, a rotary kiln, a discharging mechanism and a storage mechanism. Materials are sequentially fed into the feeding mechanism, the vacuum mechanism, the conveying mechanism, the rotary kiln, the discharging mechanism and the storage mechanism for processing operations, and the stirring mechanism stirs the materials in the feeding mechanism; the feeding mechanism is arranged above the vacuum mechanism, the vacuum mechanism comprises a heating bin, a discharge pipe, a first sheet vacuum pump and a filter, the discharge pipe outlet end of the vacuum mechanism is connected to the feed port end of the conveying mechanism, and then the materials conveyed by the conveying mechanism enter the rotary kiln for processing; the heating bin and the feeding mechanism are connected to the filter through a pipeline, and the filter is connected to the first sheet vacuum pump.

[0018] Preferably, in step 1, the heat treatment is carried out under vacuum conditions; the vacuum degree is ≤10Pa.

[0019] Preferably, in the first cycle of the cycle, in step 2, before the heat-treated fluorosilicate is fed into the rotary kiln, the rotary kiln is evacuated to a vacuum degree of ≤10Pa, and helium is replaced 1-10 times; in the subsequent reaction, the pressure of the rotary kiln is the equilibrium pressure, and the absolute pressure is 0.03MPa-0.07MPa.

[0020] Preferably, in step 1, the fluorosilicate is selected from at least one of sodium fluorosilicate, potassium fluorosilicate, barium fluorosilicate and calcium fluorosilicate.

[0021] Preferably, the reaction equation of the fluorosilicate is:

[0022] Na 2 SiF 6 →SiF 4 ↑+2NaF;

[0023] 3K 2 SiF 6 →SiF 4 ↑+2K 3 SiF 7 ;

[0024] FWf 6 →SiF 4 ↑+BaF 2 ;

[0025] CaSiF 6 →SiF 4 ↑+CaF 2 .

[0026] Preferably, in step 1, the temperature of the heat treatment is 60-450°C;

[0027] Further preferably, in step 1, when the fluorosilicate is sodium fluorosilicate, the heat treatment temperature is 250-350°C; in step 1, when the fluorosilicate is potassium fluorosilicate, the heat treatment temperature is 250-450°C; in step 1, when the fluorosilicate is barium fluorosilicate, the heat treatment temperature is 100-300°C; in step 1, when the fluorosilicate is calcium fluorosilicate, the heat treatment temperature is 60-150°C;

[0028] Preferably, in step 1, the heat treatment time is 40-70 minutes; further preferably, in step 1, the heat treatment time is 60 minutes.

[0029] Preferably, in step 2, the heat-treated fluorosilicate is fed into a rotary kiln within 50-80 minutes; further preferably, in step 2, the heat-treated fluorosilicate is fed into a rotary kiln within 50-60 minutes.

[0030] Preferably, in step 3, the temperature is 200°C-800°C; further preferably, in step 3, when the fluorosilicate is sodium fluorosilicate, the temperature is 500-750°C; in step 3, when the fluorosilicate is potassium fluorosilicate, the temperature is 550-800°C; in step 3, when the fluorosilicate is barium fluorosilicate, the temperature is 400-650°C; in step 3, when the fluorosilicate is calcium fluorosilicate, the temperature is 200-400°C;

[0031] Preferably, in step 3, the reaction time is 30-90 minutes; further preferably, in step 3, the reaction time is 60 minutes.

[0032] Preferably, the rotary kiln uses magnetic fluid sealing.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention provides a novel industrial continuous preparation method of silicon tetrafluoride, which realizes continuous feeding and continuous discharging. On the one hand, the production efficiency of silicon tetrafluoride is greatly improved, which makes up for the disadvantage that the fluorosilicate thermal decomposition method is difficult to achieve industrial production. On the other hand, the incorporation of impurities is avoided as much as possible, and the purity of silicon tetrafluoride gas is significantly improved.

[0035] (2) The method for industrial continuous preparation of silicon tetrafluoride provided by the present invention controls the vacuum degree, temperature and reaction time during the heat treatment process to remove moisture and air from the raw materials, controls the vacuum degree of the rotary kiln before the first roasting, and replaces the silicon tetrafluoride with helium multiple times, thereby significantly improving the purity of silicon tetrafluoride.

[0036] (3) The production process of the method for industrial continuous preparation of silicon tetrafluoride provided by the present invention is more automated, reducing the risk of workers being exposed. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a front view of the roasting device diagram of Example 1 of the present invention.

[0038] Figure 2 This is a diagram of the roasting device of Example 1 of the present invention.

[0039] Among them, 1. feeding mechanism; 2. stirring mechanism; 3. vacuum mechanism; 4. conveying mechanism; 5. rotary kiln; 6. discharging mechanism; 7. storage mechanism; 8. bracket; 9. filter; 10. first-piece vacuum pump; 11. second-piece vacuum pump; 12. chiller; 13. mechanical vacuum pump; 14. heating bin; 15. discharge pipe; 16. vacuum loader; 17. first vacuum butterfly valve; 18. feed bin; 19. discharge pipe; 20. weighing meter; 21. vacuum ball valve; 22. furnace body; 23. power limit mechanism; 24. discharging bin; 25. second vacuum butterfly valve; 26. cooling storage bin. DETAILED DESCRIPTION

[0040] The following non-limiting examples can enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. The following content is only an exemplary description of the scope of the present invention, and those skilled in the art can make various changes and modifications to the invention of the present invention based on the disclosed content, and they should also fall within the scope of the present application.

[0041] The present invention is further described below by way of specific examples. The various chemical reagents used in the examples of the present invention are obtained through conventional commercial channels unless otherwise specified. Unless otherwise specified, the contents described below are all weight contents. Unless otherwise specified, it is understood that the process is carried out at room temperature.

[0042] Embodiment 1:

[0043] Use as Figure 1 and Figure 2 The device shown prepares silicon tetrafluoride, which includes the following steps:

[0044] (1) Turn on the chiller 12 to provide cooling water to the device to ensure smooth water flow; then perform a vacuum operation, open the second vacuum butterfly valve 25, and turn on the first vacuum pump 10 and the mechanical vacuum pump 13 to perform a vacuum operation, and reduce the pressure in the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to ≤10Pa, and then turn on the heating of the heating chamber 14 to heat it to 300°C; then turn on the heating of the rotary kiln 5 to heat it to 700°C.

[0045] (2) turning on the vacuum feeder 16 and controlling the first vacuum butterfly valve 17 below the vacuum feeder 16 so that the raw material sodium fluorosilicate is heat-treated in the heating chamber 14 at 300° C. for 60 minutes to obtain heat-treated sodium fluorosilicate;

[0046] (3) Control the first vacuum butterfly valve 17 to feed the heat-treated sodium fluorosilicate into the feed bin 18, then open the discharge pipe 19, and feed the heat-treated sodium fluorosilicate into the rotary kiln 5 within 60 minutes. At this time, the rotation speed of the discharge pipe 19 can be manually adjusted by the weighing meter 6 according to the weight change of the feed bin 18; during the first cycle, it is necessary to perform vacuuming and helium replacement operations at the beginning, specifically, opening the second vacuum butterfly valve 25, opening the helium inlet valve, closing the helium outlet valve and the outlet ball valve, and opening the first vacuum pump 1 0. The mechanical vacuum pump 13 is used to evacuate the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to a pressure of ≤10Pa; the first plate vacuum pump 10 and the mechanical vacuum pump 13 are closed, the helium pressure reducing valve is opened, the helium is inflated to the required pressure of 100kPa, and then the helium pressure reducing valve is closed, the first vacuum pump 10 and the mechanical vacuum pump 13 are opened to evacuate the vacuum again. This replacement operation can be performed 1-10 times as required, wherein the first vacuum butterfly valve 17 is closed only when the solid slag in the cooling storage bin 26 is cleared;

[0047] When all the heat-treated sodium fluorosilicate enters the feed bin 18, the next batch of sodium fluorosilicate repeats the process (2);

[0048] Repeat steps (2) to (3) to ensure that the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction, forming a cycle;

[0049] (4) During the subsequent reaction, the absolute pressure of the rotary kiln 5 is maintained at 0.03 MPa-0.07 MPa, and the heat-treated sodium fluorosilicate is reacted at 700° C. for 60 minutes to obtain silicon tetrafluoride after thermal cracking reaction;

[0050] (5) Turn on the product vacuum pump, cool and collect the silicon tetrafluoride after the thermal cracking reaction to obtain high-purity silicon tetrafluoride gas; the pressure of the rotary kiln 5 is maintained at 0.03-0.07 MPa;

[0051] (6) After the silicon tetrafluoride gas is collected, the second vacuum butterfly valve 25 is opened, and the pyrolyzed material is transported to the cooling storage bin 26 through the water-cooling jacket spiral structure, wherein the cooling storage bin 26 can be set to be replaced every 8 hours. The second vacuum butterfly valve 25 is closed only when the storage bin 26 needs to be opened after running for 8 hours.

[0052] As described above, the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction; then steps (4) to (6) are repeated, and the entire reaction process is continuous and ongoing.

[0053] Embodiment 2:

[0054] Use as Figure 1 and Figure 2The device shown prepares silicon tetrafluoride, which includes the following steps:

[0055] (1) Turn on the chiller 12 to provide cooling water to the device to ensure smooth water flow; then perform a vacuum operation, open the second vacuum butterfly valve 25, and turn on the first vacuum pump 10 and the mechanical vacuum pump 13 to perform a vacuum operation, and reduce the pressure in the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to ≤10Pa, and then turn on the heating of the heating chamber 14 to heat it to 300°C; then turn on the heating of the rotary kiln 5 to heat it to 700°C.

[0056] (2) turning on the vacuum feeder 16 and controlling the first vacuum butterfly valve 17 below the vacuum feeder 16 so that the auxiliary silicon dioxide and the raw material sodium fluorosilicate are heat-treated in the heating chamber 14 at 300° C. for 60 minutes to obtain heat-treated sodium fluorosilicate; wherein the mass ratio of the auxiliary silicon dioxide to the raw material sodium fluorosilicate is 5:1;

[0057] (3) Control the first vacuum butterfly valve 17 to feed the heat-treated sodium fluorosilicate into the feed bin 18, then open the discharge pipe 19, and feed the heat-treated sodium fluorosilicate into the rotary kiln 5 within 60 minutes. At this time, the rotation speed of the discharge pipe 19 can be manually adjusted by the weighing meter 6 according to the weight change of the feed bin 18; during the first cycle, it is necessary to perform vacuuming and helium replacement operations at the beginning, specifically, opening the second vacuum butterfly valve 25, opening the helium inlet valve, closing the helium outlet valve and the outlet ball valve, and opening the first vacuum pump 1 0. The mechanical vacuum pump 13 is used to evacuate the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to a pressure of ≤10Pa; the first plate vacuum pump 10 and the mechanical vacuum pump 13 are closed, the helium pressure reducing valve is opened, the helium is inflated to the required pressure of 100kPa, and then the helium pressure reducing valve is closed, the first vacuum pump 10 and the mechanical vacuum pump 13 are opened to evacuate the vacuum again. This replacement operation can be performed 1-10 times as required, wherein the first vacuum butterfly valve 17 is closed only when the solid slag in the cooling storage bin 26 is cleared;

[0058] When all the heat-treated sodium fluorosilicate enters the feed bin 18, the next batch of sodium fluorosilicate repeats the process (2);

[0059] Repeat steps (2) to (3) to ensure that the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction, forming a cycle;

[0060] (4) During the subsequent reaction, the absolute pressure of the rotary kiln 5 is maintained at 0.03 MPa-0.07 MPa, and the heat-treated sodium fluorosilicate is reacted at 700° C. for 60 minutes to obtain silicon tetrafluoride after thermal cracking reaction;

[0061] (5) Turn on the product vacuum pump, cool and collect the silicon tetrafluoride after the thermal cracking reaction to obtain high-purity silicon tetrafluoride gas; the pressure of the rotary kiln 5 is maintained at 0.03-0.07 MPa;

[0062] (6) After the silicon tetrafluoride gas is collected, the second vacuum butterfly valve 25 is opened, and the pyrolyzed material is transported to the cooling storage bin 26 through the water-cooling jacket spiral structure, wherein the cooling storage bin 26 can be set to be replaced every 8 hours. The second vacuum butterfly valve 25 is closed only when the storage bin 26 needs to be opened after running for 8 hours.

[0063] As described above, the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction; then steps (4) to (6) are repeated, and the entire reaction process is continuous and ongoing.

[0064] Embodiment 3:

[0065] The steps of Example 3 are the same as those of Example 2, except that Example 3 uses auxiliary agent alumina instead of auxiliary agent silica.

[0066] Embodiment 4:

[0067] The steps of Example 4 are the same as those of Example 1, except that the temperature of the rotary kiln 5 of Example 4 is 750°C.

[0068] Embodiment 5:

[0069] The steps of Example 5 are the same as those of Example 1, except that the temperature of the rotary kiln 5 of Example 5 is 650°C.

[0070] Example 6

[0071] The steps of Example 6 are the same as those of Example 1, except that sodium fluorosilicate is replaced by potassium fluorosilicate, and in step 1, the temperature of the heat treatment is 350°C; in step 3, the temperature of the rotary kiln 5 is 700°C.

[0072] Example 7

[0073] The steps of Example 7 are the same as those of Example 1, except that sodium fluorosilicate is replaced by barium fluorosilicate, and in step 1, the heat treatment temperature is 250°C; in step 3, the temperature of the rotary kiln 5 is 550°C.

[0074] Example 8

[0075] The steps of Example 8 are the same as those of Example 1, except that sodium fluorosilicate is replaced by calcium fluorosilicate, and in step 1, the temperature of the heat treatment is 180°C; in step 3, the temperature of the rotary kiln 5 is 250°C.

[0076] Comparative Example 1:

[0077] Use as Figure 1 and Figure 2 The device shown prepares silicon tetrafluoride, which includes the following steps:

[0078] (1) Turn on the chiller 12 to provide cooling water to the device to ensure smooth water flow; then perform vacuum operation, open the second vacuum butterfly valve 25, and turn on the first vacuum pump 10 and the mechanical vacuum pump 13 to perform vacuum operation, reduce the pressure in the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to 50Pa, then turn on the heating of the heating chamber 14 and heat it to 300℃; then turn on the heating of the rotary kiln 5 and heat it to 700℃.

[0079] (2) turning on the vacuum feeder 16 and controlling the first vacuum butterfly valve 17 below the vacuum feeder 16 so that the raw material sodium fluorosilicate is heat-treated in the heating chamber 14 at 300° C. for 60 minutes to obtain heat-treated sodium fluorosilicate;

[0080] (3) Control the first vacuum butterfly valve 17 to feed the heat-treated sodium fluorosilicate into the feed bin 18, then open the discharge pipe 19, and feed the heat-treated sodium fluorosilicate into the rotary kiln 5 within 60 minutes. At this time, the rotation speed of the discharge pipe 19 can be manually adjusted by the weighing meter 6 according to the weight change of the feed bin 18; during the first cycle, it is necessary to perform vacuuming and helium replacement operations at the beginning, specifically, opening the second vacuum butterfly valve 25, opening the helium inlet valve, closing the helium outlet valve and the outlet ball valve, and opening the first vacuum pump 1 0, the mechanical vacuum pump 13 is used to evacuate, and the pressure in the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) is reduced to 50Pa; the first sheet vacuum pump 10 and the mechanical vacuum pump 13 are closed, and the helium pressure reducing valve is opened, and the helium is inflated to the required pressure of 100kPa, and then the helium pressure reducing valve is closed, and the first vacuum pump 10 and the mechanical vacuum pump 13 are opened to evacuate again. This replacement operation can be performed 1-10 times as required, wherein the first vacuum butterfly valve 17 is closed only when the solid slag in the cooling storage bin 26 is cleared;

[0081] When all the heat-treated sodium fluorosilicate enters the feed bin 18, the next batch of sodium fluorosilicate repeats the process (2);

[0082] Repeat steps (2) to (3) to ensure that the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction, forming a cycle;

[0083] (4) During the subsequent reaction, the absolute pressure of the rotary kiln 5 is maintained at 0.03 MPa-0.07 MPa, and the heat-treated sodium fluorosilicate is reacted at 700° C. for 60 minutes to obtain silicon tetrafluoride after thermal cracking reaction;

[0084] (5) Turn on the product vacuum pump, cool and collect the silicon tetrafluoride after the thermal cracking reaction to obtain high-purity silicon tetrafluoride gas; the pressure of the rotary kiln 5 is maintained at 0.03-0.07 MPa;

[0085] (6) After the silicon tetrafluoride gas is collected, the second vacuum butterfly valve 25 is opened, and the pyrolyzed material is transported to the cooling storage bin 26 through the water-cooling jacket spiral structure, wherein the cooling storage bin 26 can be set to be replaced every 8 hours. The second vacuum butterfly valve 25 is closed only when the storage bin 26 needs to be opened after running for 8 hours.

[0086] As described above, the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction; then steps (4) to (6) are repeated, and the entire reaction process is continuous and ongoing.

[0087] Comparative Example 2:

[0088] Use as Figure 1 and Figure 2 The device shown prepares silicon tetrafluoride, which includes the following steps:

[0089] (1) Turn on the chiller 12 to provide cooling water to the device to ensure smooth water flow; then perform vacuum operation, open the second vacuum butterfly valve 25, and turn on the first vacuum pump 10 and the mechanical vacuum pump 13 to perform vacuum operation, and reduce the pressure in the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to 100Pa, and then turn on the heating of the heating chamber 14 to heat it to 300℃; then turn on the heating of the rotary kiln 5 to heat it to 700℃.

[0090] (2) turning on the vacuum feeder 16 and controlling the first vacuum butterfly valve 17 below the vacuum feeder 16 so that the raw material sodium fluorosilicate is heat-treated in the heating chamber 14 at 300° C. for 60 minutes to obtain heat-treated sodium fluorosilicate;

[0091] (3) Control the first vacuum butterfly valve 17 to feed the heat-treated sodium fluorosilicate into the feed bin 18, then open the discharge pipe 19, and feed the heat-treated sodium fluorosilicate into the rotary kiln 5 within 60 minutes. At this time, the rotation speed of the discharge pipe 19 can be manually adjusted by the weighing meter 6 according to the weight change of the feed bin 18; during the first cycle, it is necessary to perform vacuuming and helium replacement operations at the beginning, specifically, opening the second vacuum butterfly valve 25, opening the helium inlet valve, closing the helium outlet valve and the outlet ball valve, and opening the first vacuum pump 1 0, the mechanical vacuum pump 13 performs vacuuming, and the pressure in the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) is reduced to 100Pa; the first sheet vacuum pump 10 and the mechanical vacuum pump 13 are closed, the helium pressure reducing valve is opened, the helium is inflated to the required pressure of 100kPa, and then the helium pressure reducing valve is closed, and the first vacuum pump 10 and the mechanical vacuum pump 13 are opened to perform vacuuming again. This replacement operation can be performed 1-10 times as required, wherein the first vacuum butterfly valve 17 is closed only when the solid slag in the cooling storage bin 26 is cleared;

[0092] When all the heat-treated sodium fluorosilicate enters the feed bin 18, the next batch of sodium fluorosilicate repeats the process (2);

[0093] Repeat steps (2) to (3) to ensure that the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction, forming a cycle;

[0094] (4) During the subsequent reaction, the absolute pressure of the rotary kiln 5 is maintained at 0.03 MPa-0.07 MPa, and the heat-treated sodium fluorosilicate is reacted at 700° C. for 60 minutes to obtain silicon tetrafluoride after thermal cracking reaction;

[0095] (5) Turn on the product vacuum pump, cool and collect the silicon tetrafluoride after the thermal cracking reaction to obtain high-purity silicon tetrafluoride gas; the pressure of the rotary kiln 5 is maintained at 0.03-0.07 MPa

[0096] (6) After the silicon tetrafluoride gas is collected, the second vacuum butterfly valve 25 is opened, and the pyrolyzed material is transported to the cooling storage bin 26 through the water-cooling jacket spiral structure, wherein the cooling storage bin 26 can be set to be replaced every 8 hours. The second vacuum butterfly valve 25 is closed only when the storage bin 26 needs to be opened after running for 8 hours.

[0097] As described above, the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction; then steps (4) to (6) are repeated, and the entire reaction process is continuous and ongoing.

[0098] Comparative Example 3:

[0099] Use as Figure 1 and Figure 2The device shown prepares silicon tetrafluoride, which includes the following steps:

[0100] (1) Turn on the chiller 12 to provide cooling water to the device to ensure smooth water flow; then perform a vacuum operation, open the second vacuum butterfly valve 25, and turn on the first vacuum pump 10 and the mechanical vacuum pump 13 to perform a vacuum operation, and reduce the pressure in the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to ≤10Pa, and then turn on the heating of the heating chamber 14 to heat it to 300°C; then turn on the heating of the rotary kiln 5 to heat it to 700°C.

[0101] (2) turning on the vacuum feeder 16 and controlling the first vacuum butterfly valve 17 below the vacuum feeder 16 so that the raw material sodium fluorosilicate is heat-treated in the heating chamber 14 at 300° C. for 25 minutes to obtain heat-treated sodium fluorosilicate;

[0102] (3) Control the first vacuum butterfly valve 17 to feed the heat-treated sodium fluorosilicate into the feed bin 18, then open the discharge pipe 19, and feed the heat-treated sodium fluorosilicate into the rotary kiln 5 within 60 minutes. At this time, the rotation speed of the discharge pipe 19 can be manually adjusted by the weighing meter 6 according to the weight change of the feed bin 18; during the first cycle, it is necessary to perform vacuuming and helium replacement operations at the beginning, specifically, opening the second vacuum butterfly valve 25, opening the helium inlet valve, closing the helium outlet valve and the outlet ball valve, and opening the first vacuum pump 1 0. The mechanical vacuum pump 13 is used to evacuate the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to a pressure of ≤10Pa; the first plate vacuum pump 10 and the mechanical vacuum pump 13 are closed, the helium pressure reducing valve is opened, the helium is inflated to the required pressure of 100kPa, and then the helium pressure reducing valve is closed, the first vacuum pump 10 and the mechanical vacuum pump 13 are opened to evacuate the vacuum again. This replacement operation can be performed 1-10 times as required, wherein the first vacuum butterfly valve 17 is closed only when the solid slag in the cooling storage bin 26 is cleared;

[0103] When all the heat-treated sodium fluorosilicate enters the feed bin 18, the next batch of sodium fluorosilicate repeats the process (2);

[0104] Repeat steps (2) to (3) to ensure that the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction, forming a cycle;

[0105] (4) During the subsequent reaction, the absolute pressure of the rotary kiln 5 is maintained at 0.03 MPa-0.07 MPa, and the heat-treated sodium fluorosilicate is reacted at 700° C. for 60 minutes to obtain silicon tetrafluoride after thermal cracking reaction;

[0106] (5) Turn on the product vacuum pump, cool and collect the silicon tetrafluoride after the thermal cracking reaction to obtain high-purity silicon tetrafluoride gas; the pressure of the rotary kiln 5 is maintained at 0.03-0.07 MPa;

[0107] (6) After the silicon tetrafluoride gas is collected, the second vacuum butterfly valve 25 is opened, and the pyrolyzed material is transported to the cooling storage bin 26 through the water-cooling jacket spiral structure, wherein the cooling storage bin 26 can be set to be replaced every 8 hours. The second vacuum butterfly valve 25 is closed only when the storage bin 26 needs to be opened after running for 8 hours.

[0108] As described above, the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction; then steps (4) to (6) are repeated, and the entire reaction process is continuous and ongoing.

[0109] Comparative Example 4:

[0110] Use as Figure 1 and Figure 2 The device shown prepares silicon tetrafluoride, which includes the following steps:

[0111] (1) Turn on the chiller 12 to provide cooling water to the device to ensure smooth water flow; then perform a vacuum operation, open the second vacuum butterfly valve 25, and turn on the first vacuum pump 10 and the mechanical vacuum pump 13 to perform a vacuum operation, and reduce the pressure in the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to ≤10Pa, and then turn on the heating of the heating chamber 14 to heat it to 300°C; then turn on the heating of the rotary kiln 5 to heat it to 700°C.

[0112] (2) turning on the vacuum feeder 16 and controlling the first vacuum butterfly valve 17 below the vacuum feeder 16 so that the raw material sodium fluorosilicate is heat-treated in the heating chamber 14 at 300° C. for 60 minutes to obtain heat-treated sodium fluorosilicate;

[0113] (3) Control the first vacuum butterfly valve 17 to feed the heat-treated sodium fluorosilicate into the feed bin 18, then open the discharge pipe 19, and feed the heat-treated sodium fluorosilicate into the rotary kiln 5 within 60 minutes. At this time, the rotation speed of the discharge pipe 19 can be manually adjusted by the weighing meter 6 according to the weight change of the feed bin 18; during the first cycle, it is necessary to perform vacuuming and helium replacement operations at the beginning, specifically, opening the second vacuum butterfly valve 25, opening the helium inlet valve, closing the helium outlet valve and the outlet ball valve, and opening the first vacuum pump 1 0. The mechanical vacuum pump 13 is used to evacuate the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to a pressure of ≤10Pa; the first plate vacuum pump 10 and the mechanical vacuum pump 13 are closed, the helium pressure reducing valve is opened, the helium is inflated to the required pressure of 100kPa, and then the helium pressure reducing valve is closed, the first vacuum pump 10 and the mechanical vacuum pump 13 are opened to evacuate the vacuum again. This replacement operation can be performed 1-10 times as required, wherein the first vacuum butterfly valve 17 is closed only when the solid slag in the cooling storage bin 26 is cleared;

[0114] When all the heat-treated sodium fluorosilicate enters the feed bin 18, the next batch of sodium fluorosilicate repeats the process (2);

[0115] Repeat steps (2) to (3) to ensure that the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction, forming a cycle;

[0116] (4) During the subsequent reaction, the absolute pressure of the rotary kiln 5 is maintained at 0.03 MPa-0.07 MPa, and the heat-treated sodium fluorosilicate is reacted at 700° C. for 20 minutes to obtain silicon tetrafluoride after thermal cracking reaction;

[0117] (5) Turn on the product vacuum pump, cool and collect the silicon tetrafluoride after the thermal cracking reaction to obtain high-purity silicon tetrafluoride gas; the pressure of the rotary kiln 5 is maintained at 0.03-0.07 MPa;

[0118] (6) After the silicon tetrafluoride gas is collected, the second vacuum butterfly valve 25 is opened, and the pyrolyzed material is transported to the cooling storage bin 26 through the water-cooling jacket spiral structure, wherein the cooling storage bin 26 can be set to be replaced every 8 hours. The second vacuum butterfly valve 25 is closed only when the storage bin 26 needs to be opened after running for 8 hours.

[0119] As described above, the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction; then steps (4) to (6) are repeated, and the entire reaction process is continuous and ongoing.

[0120] Comparative Example 5:

[0121] Use as Figure 1 and Figure 2The device shown prepares silicon tetrafluoride, which includes the following steps:

[0122] (1) Turn on the chiller 12 to provide cooling water to the device to ensure smooth water flow; then perform vacuum operation, open the second vacuum butterfly valve 25, and turn on the first vacuum pump 10 and the mechanical vacuum pump 13 to perform vacuum operation, and reduce the pressure in the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to ≤10Pa, and then turn on the heating of the heating chamber 14 to heat it to 200℃; then turn on the heating of the rotary kiln 5 to heat it to 800℃.

[0123] (2) turning on the vacuum feeder 16 and controlling the first vacuum butterfly valve 17 below the vacuum feeder 16 so that the raw material sodium fluorosilicate is heat-treated in the heating chamber 14 at 200° C. for 60 minutes to obtain heat-treated sodium fluorosilicate;

[0124] (3) Control the first vacuum butterfly valve 17 to feed the heat-treated sodium fluorosilicate into the feed bin 18, then open the discharge pipe 19, and feed the heat-treated sodium fluorosilicate into the rotary kiln 5 within 60 minutes. At this time, the rotation speed of the discharge pipe 19 can be manually adjusted by the weighing meter 6 according to the weight change of the feed bin 18; during the first cycle, it is necessary to perform vacuuming and helium replacement operations at the beginning, specifically, opening the second vacuum butterfly valve 25, opening the helium inlet valve, closing the helium outlet valve and the outlet ball valve, and opening the first vacuum pump 1 0. The mechanical vacuum pump 13 is used to evacuate the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to a pressure of ≤10Pa; the first plate vacuum pump 10 and the mechanical vacuum pump 13 are closed, the helium pressure reducing valve is opened, the helium is inflated to the required pressure of 100kPa, and then the helium pressure reducing valve is closed, the first vacuum pump 10 and the mechanical vacuum pump 13 are opened to evacuate the vacuum again. This replacement operation can be performed 1-10 times as required, wherein the first vacuum butterfly valve 17 is closed only when the solid slag in the cooling storage bin 26 is cleared;

[0125] When all the heat-treated sodium fluorosilicate enters the feed bin 18, the next batch of sodium fluorosilicate repeats the process (2);

[0126] Repeat steps (2) to (3) to ensure that the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction, forming a cycle;

[0127] (4) During the subsequent reaction, the absolute pressure of the rotary kiln 5 is maintained at 0.03 MPa-0.07 MPa, and the heat-treated sodium fluorosilicate is reacted at 900° C. for 60 minutes to obtain silicon tetrafluoride after thermal cracking reaction;

[0128] (5) Turn on the product vacuum pump, cool and collect the silicon tetrafluoride after the thermal cracking reaction to obtain high-purity silicon tetrafluoride gas; the pressure of the rotary kiln 5 is maintained at 0.03-0.07 MPa;

[0129] (6) After the silicon tetrafluoride gas is collected, the second vacuum butterfly valve 25 is opened, and the pyrolyzed material is transported to the cooling storage bin 26 through the water-cooling jacket spiral structure, wherein the cooling storage bin 26 can be set to be replaced every 8 hours. The second vacuum butterfly valve 25 is closed only when the storage bin 26 needs to be opened after running for 8 hours.

[0130] As described above, the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction; then steps (4) to (6) are repeated, and the entire reaction process is continuous and ongoing.

[0131] Comparative Example 6

[0132] Use as Figure 1 and Figure 2 The device shown prepares silicon tetrafluoride, which includes the following steps:

[0133] (1) Turn on the chiller 12 to provide cooling water to the device to ensure smooth water flow; then perform a vacuum operation, open the second vacuum butterfly valve 25, and turn on the first vacuum pump 10 and the mechanical vacuum pump 13 to perform a vacuum operation, and reduce the pressure in the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to ≤10Pa, and then turn on the heating of the heating chamber 14 to heat it to 300°C; then turn on the heating of the rotary kiln 5 to heat it to 700°C.

[0134] (2) turning on the vacuum feeder 16 and controlling the first vacuum butterfly valve 17 below the vacuum feeder 16 so that the raw material sodium fluorosilicate is heat-treated in the heating chamber 14 at 300° C. for 60 minutes to obtain heat-treated sodium fluorosilicate;

[0135] (3) Control the first vacuum butterfly valve 17 to feed the heat-treated sodium fluorosilicate into the feed bin 18, then open the discharge pipe 19, and feed the heat-treated sodium fluorosilicate into the rotary kiln 5 within 20 minutes. At this time, the rotation speed of the discharge pipe 19 can be manually adjusted by the weighing meter 6 according to the weight change of the feed bin 18; during the first cycle, it is necessary to perform vacuuming and helium replacement operations at the beginning, specifically, opening the second vacuum butterfly valve 25, opening the helium inlet valve, closing the helium outlet valve and the outlet ball valve, and opening the first vacuum pump 1 0. The mechanical vacuum pump 13 is used to evacuate the entire circulation pipeline (including the entire pipeline of the rotary kiln 5) to a pressure of ≤10Pa; the first plate vacuum pump 10 and the mechanical vacuum pump 13 are closed, the helium pressure reducing valve is opened, the helium is inflated to the required pressure of 100kPa, and then the helium pressure reducing valve is closed, the first vacuum pump 10 and the mechanical vacuum pump 13 are opened to evacuate the vacuum again. This replacement operation can be performed 1-10 times as required, wherein the first vacuum butterfly valve 17 is closed only when the solid slag in the cooling storage bin 26 is cleared;

[0136] When all the heat-treated sodium fluorosilicate enters the feed bin 18, the next batch of sodium fluorosilicate repeats the process (2);

[0137] Repeat steps (2) to (3) to ensure that the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction, forming a cycle;

[0138] (4) During the subsequent reaction, the absolute pressure of the rotary kiln 5 is maintained at 0.03 MPa-0.07 MPa, and the heat-treated sodium fluorosilicate is reacted at 700° C. for 60 minutes to obtain silicon tetrafluoride after thermal cracking reaction;

[0139] (5) Turn on the product vacuum pump, cool and collect the silicon tetrafluoride after the thermal cracking reaction to obtain high-purity silicon tetrafluoride gas; the pressure of the rotary kiln 5 is maintained at 0.03-0.07 MPa;

[0140] (6) After the silicon tetrafluoride gas is collected, the second vacuum butterfly valve 25 is opened, and the pyrolyzed material is transported to the cooling storage bin 26 through the water-cooling jacket spiral structure, wherein the cooling storage bin 26 can be set to be replaced every 8 hours. The second vacuum butterfly valve 25 is closed only when the storage bin 26 needs to be opened after running for 8 hours.

[0141] As described above, the heat-treated sodium fluorosilicate is always present in the rotary kiln to participate in the reaction; then steps (4) to (6) are repeated, and the entire reaction process is continuous and ongoing.

[0142] Silicon tetrafluoride (SiF) of Examples 1-8 and Comparative Examples 1-6 4 )'s purity (volume fraction) and yield are shown in Table 1:

[0143] Table 1. Purity and yield of silicon tetrafluoride

[0144]

[0145]

[0146] From the data in Table 1, it can be seen that compared with Examples 1-8, the silicon tetrafluoride (SiF 4 ) purity is significantly reduced, indicating that the specific process of the present invention has played a significant role in improving the production efficiency of silicon tetrafluoride, especially the specific process parameters, such as the pressure, temperature, and time of the heat treatment, the material stays in the feed bin for a period of time after the heat treatment before entering the rotary kiln, and the pressure, temperature, and time of the thermal cracking, which significantly improves the production efficiency of silicon tetrafluoride (SiF 4 ) purity and yield. Compared with Example 1, Comparative Examples 1 and 2 increase the vacuum pressure, resulting in more residual impurities, and the yield of silicon tetrafluoride does not change much, but the purity decreases significantly. Comparative Example 3 shortens the heat treatment time, and the impurities in the raw material are not completely removed, resulting in a significant decrease in the purity of silicon tetrafluoride. Comparative Example 4 shortens the roasting time, resulting in incomplete decomposition of sodium fluorosilicate, a significant decrease in the yield of silicon tetrafluoride, and a significant decrease in purity. Comparative Example 5 reduces the heat treatment temperature and increases the roasting temperature. Some impurities in the raw material decompose at high temperature, and sodium fluorosilicate melts before it is decomposed, causing a significant decrease in the purity and yield of silicon tetrafluoride. Comparative Example 6 reduces the residence time of the feed bin. Since the residence time of the feed bin does not match the residence time of the rotary kiln, materials accumulate and eventually block the pipe.

[0147] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the disclosure disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. It should be understood that the present invention is not limited to the precise structure that has been described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from the scope thereof.

Claims

1. A method for industrial continuous preparation of silicon tetrafluoride, characterized in that: The method is implemented by a roasting device comprising a heating bin, a feeding bin and a rotary kiln; the method comprises the following steps: Step 1: The fluorosilicate is heat-treated in a heating chamber at 60-500° C. for 30-100 minutes to obtain the heat-treated fluorosilicate; Step 2: The heat-treated fluorosilicate in step 1 is fed into a feed bin, and the heat-treated fluorosilicate is fed into a rotary kiln within 30-100 minutes; when all the heat-treated fluorosilicate in step 1 has entered the feed bin, step 1 is repeated; Step 3: maintaining the temperature of the rotary kiln at 200-850° C., reacting the fluorosilicate after the heat treatment in step 2 for 30-100 minutes to obtain silicon tetrafluoride after thermal cracking reaction; Step 4: Cooling and collecting the silicon tetrafluoride after the thermal cracking reaction to obtain high-purity silicon tetrafluoride gas; Repeat steps 1-2, so that the fluorosilicate heat-treated in step 2 always participates in the reaction in the rotary kiln in step 3 to form a cycle; Performed in the following devices: An industrial continuous preparation device of silicon tetrafluoride comprises a feeding mechanism, a stirring mechanism, a conveying mechanism, a vacuum mechanism, a rotary kiln, a discharging mechanism and a storage mechanism. Materials are sequentially fed into the feeding mechanism, the vacuum mechanism, the conveying mechanism, the rotary kiln, the discharging mechanism and the storage mechanism for processing operations, and the stirring mechanism stirs the materials in the feeding mechanism; the feeding mechanism is arranged above the vacuum mechanism, the vacuum mechanism comprises a heating bin, a discharge pipe, a first sheet vacuum pump and a filter, the discharge pipe outlet end of the vacuum mechanism is connected to the feed port end of the conveying mechanism, and then the materials conveyed by the conveying mechanism enter the rotary kiln for processing; the heating bin and the feeding mechanism are connected to the filter through a pipeline, and the filter is connected to the first sheet vacuum pump.

2. The method according to claim 1, characterized in that: In step 1, the fluorosilicate is selected from at least one of sodium fluorosilicate, potassium fluorosilicate, barium fluorosilicate and calcium fluorosilicate.

3. The method according to claim 1, characterized in that In step 1, the heat treatment is carried out under vacuum conditions; the vacuum degree is ≤10Pa.

4. The method according to claim 1, characterized in that: In the first cycle of the cycle, in step 2, before the heat-treated fluorosilicate is fed into the rotary kiln, the rotary kiln is evacuated to a vacuum degree of ≤10Pa, and helium is replaced 1-10 times; in the subsequent reaction, the pressure of the rotary kiln is the equilibrium pressure, and the absolute pressure is 0.03MPa-0.07MPa.

5. The method according to claim 1, characterized in that In step 1, the temperature of the heat treatment is 60-450°C.

6. The method according to claim 5, characterized in that In step 1, when the fluorosilicate is sodium fluorosilicate, the heat treatment temperature is 250-350°C; when the fluorosilicate is potassium fluorosilicate, the heat treatment temperature is 250-450°C; when the fluorosilicate is barium fluorosilicate, the heat treatment temperature is 100-300°C; when the fluorosilicate is calcium fluorosilicate, the heat treatment temperature is 60-150°C.

7. The method according to claim 1, characterized in that In step 1, the heat treatment time is 40-70 minutes.

8. The method according to claim 1, characterized in that In step 2, the heat treated fluorosilicate is fed into a rotary kiln within 50-80 minutes.

9. The method according to claim 1, characterized in that: In step 3, the temperature is 200-800°C.

10. The method according to claim 1, characterized in that In step 3, the reaction time is 30-90 minutes.

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