Process for the production of hydrogen fluoride from fluosilicic acid and a production system

Abstract

The application relates to a method and a preparation system for preparing hydrogen fluoride from fluosilicic acid, which comprises a reaction kettle, a hydrogen fluoride absorption tower, a condenser and a silicon tetrafluoride absorption tower which are sequentially communicated; a gas outlet of the reaction kettle is communicated with a gas inlet of the hydrogen fluoride absorption tower, and a gas outlet of the hydrogen fluoride absorption tower is communicated with a gas inlet of the condenser; the generated fluorosulfonic acid in the reaction kettle is introduced into a stripping tower, fluorosulfonic acid generated in a side reaction is re-generated into hydrogen fluoride, the generation of intermediate products is reduced, the process route of the application is free of waste residues and waste gas, and fluosilicic acid is effectively utilized.

Description

TECHNICAL FIELD

[0001] The present application relates to hydrogen fluoride preparation technology field, especially to the method and preparation system for preparing hydrogen fluoride from fluosilicic acid. BACKGROUND

[0002] In the process of producing hydrogen fluoride with calcium fluoride and sulfuric acid, because calcium fluoride contains silicon dioxide, silicon dioxide reacts with hydrogen fluoride to generate silicon tetrafluoride, and silicon tetrafluoride is absorbed with water and a small amount of hydrofluoric acid to become a by-product of fluosilicic acid. In recent years, the market demand for fluosilicic acid has shrunk sharply, and fluosilicic acid has changed from a sellable by-product to a waste acid that needs to be treated, so it is necessary to treat fluosilicic acid.

[0003] The Chinese patent with publication number CN107601434A uses a decomposition kettle to decompose fluosilicic acid, but a side reaction occurs in the decomposition kettle to generate fluorosulfonic acid, which is another intermediate product that needs to be treated, and the yield of hydrogen fluoride is reduced. Therefore, the method and preparation system for preparing hydrogen fluoride from fluosilicic acid are proposed to solve this problem. SUMMARY

[0004] The present application provides a method and preparation system for preparing hydrogen fluoride from fluosilicic acid to solve the problems in the prior art, and the specific technical solutions are as follows:

[0005] The preparation system for preparing hydrogen fluoride from fluosilicic acid comprises a reaction kettle, a hydrogen fluoride absorption tower, a condenser and a silicon tetrafluoride absorption tower connected in sequence;

[0006] The gas outlet of the reaction kettle is connected to the gas inlet of the hydrogen fluoride absorption tower, the gas outlet of the hydrogen fluoride absorption tower is connected to the gas inlet of the condenser, the side wall of the hydrogen fluoride absorption tower is provided with a concentrated sulfuric acid inlet pipe, the condenser is used to condense hydrogen fluoride gas into liquid and separate it from silicon tetrafluoride gas, the liquid outlet of the condenser is connected to a hydrogen fluoride storage tank, the gas outlet of the condenser is connected to the gas inlet of the silicon tetrafluoride absorption tower, the silicon tetrafluoride absorption tower is provided with a fluosilicic acid inlet pipe, and the liquid outlet of the reaction kettle is connected to a stripping tower, and the gas outlet of the stripping tower is connected to the gas inlet of the hydrogen fluoride absorption tower;

[0007] The silicon tetrafluoride absorption tower includes a tower body, a spray mechanism is provided inside the tower body and near one end of the top, a U-shaped sedimentation pipe is provided at the bottom of the tower body through a support frame, a sedimentation pipe is provided in the center of the bottom of the sedimentation pipe, and the sedimentation pipe has an expansion joint to store fixed particles, a guide cover is provided inside the tower body and at the top of the sedimentation pipe, so the air inlet of the tower body is located between the guide cover and the distribution plate, the bottom of the guide cover is connected to one end of the sedimentation pipe, a connecting pipe is provided between the two ends of the sedimentation pipe, a circulation pipe is provided on the side wall of the other end of the sedimentation pipe, the top of the circulation pipe is connected to the fluorosilicic acid inlet pipe, and the inner walls of the inner cavity on both sides of the sedimentation pipe are staggered with multiple groups of downflow plates for reducing the fluid velocity so that the solid particles settle in the sedimentation pipe.

[0008] An improvement of the above technical solution, the spray assembly includes a drive assembly arranged at the top of the tower body, the top of the drive assembly is connected to the fluorosilicic acid inlet pipe, the drive assembly is provided with a distribution plate at one end inside the tower body, and the bottom of the distribution plate is connected to multiple groups of nozzles.

[0009] An improvement of the above technical solution, the driving assembly includes a rotating shaft and a motor, a hollow rotating shaft is rotatably connected to the top of the tower body, a distribution plate is connected to the bottom of the rotating shaft, a motor is provided on one side of the top of the tower body, the output shaft of the motor is connected to the surface of the rotating shaft through a transmission belt, and a fluorosilicic acid liquid inlet pipe is rotatably connected to the top of the rotating shaft.

[0010] An improvement of the above technical solution is that a spoiler is provided at the bottom of the distribution plate, and the spoiler includes a fixed shaft provided at the bottom of the distribution plate, and multiple groups of spoiler rods are staggeredly distributed on the surface of the fixed shaft, and the air inlet of the tower body is located between the spoiler and the guide cover.

[0011] The method for preparing hydrogen fluoride from fluosilicic acid comprises the following steps:

[0012] S1: Add 31% fluorosilicic acid and 98% sulfuric acid to the reactor, use the external circulation heat exchanger to raise the reaction temperature inside the reactor to 90-100°C, open the gas phase valve, and allow the gas phase to flow into the hydrogen fluoride absorption tower through the pipeline. The pressure of reactor 1 is controlled at ≤0.05MPa, open the bottom valve of the reactor, and control the flow to the stripping tower through the regulating valve.

[0013] S2: Use the external circulating steam of the stripping tower to control the temperature of the stripping tower at 110-120℃, open the compressed air valve, and introduce compressed air. The stripping tower is controlled at a pressure of ≤0.05MPa. The gas phase inside the stripping tower is transported to the hydrogen fluoride absorption tower through a pipeline, and the liquid phase inside the stripping tower enters the sulfuric acid storage tank after condensation.

[0014] S3: The gas phase of the reactor flows into the hydrogen fluoride absorption tower through a pipeline. 98% sulfuric acid is added into the hydrogen fluoride absorption tower to absorb a small amount of water entrained in the hydrogen fluoride and silicon tetrafluoride gases.

[0015] S4: The gas dried in the hydrogen fluoride absorption tower, consisting of hydrogen fluoride and silicon tetrafluoride, is transported to the condenser for cooling, and the hydrogen fluoride is cooled to liquid. The cooled hydrogen fluoride is transported to the hydrogen fluoride storage tank, and the silicon tetrafluoride in the condenser is transported to the silicon tetrafluoride absorption tower.

[0016] S5: Add 11% fluorosilicic acid to the silicon tetrafluoride absorption tower for circulated spraying to absorb silicon tetrafluoride gas. Solid silicon dioxide is precipitated in the tower and the silicon dioxide is settled at the bottom of the silicon tetrafluoride absorption tower. The fluorosilicic acid is refluxed to the silicon tetrafluoride absorption tower.

[0017] S6: The silicon dioxide settled at the bottom of the silicon tetrafluoride absorption tower is output through a precipitation pipe.

[0018] An improvement of the above technical solution is that in S1, the flow rate of 31% fluorosilicic acid is 100 kg / h, the flow rate of 98% sulfuric acid is 225 kg / h, and the flow rate of the stripping tower is 300 kg / h.

[0019] An improvement of the above technical solution is that the compressed air flow rate in S2 is 60Nm3 / h.

[0020] An improvement of the above technical solution is that in S3, the flow rate of 98% sulfuric acid is 2.8 kg / h.

[0021] Beneficial effects of the present invention:

[0022] 1. The fluorosulfonic acid generated in the reactor is passed into the stripping tower, and the fluorosulfonic acid generated by the side reaction can be regenerated into hydrogen fluoride, reducing the generation of intermediate products, so that the process route of the present invention is free of waste residue and waste gas, and the fluorosilicic acid is effectively utilized.

[0023] 2. The U-shaped structure of the settling tube inside the silicon tetrafluoride absorption tower can extend the travel of the solid-solution mixed solution in the settling tube, extend the time the solution stays in the settling tube, reduce the floor space, and improve the sedimentation efficiency of the particles. Under the action of the U-shaped structure, the settled particles can easily enter the sedimentation tube for storage, and through the expansion joint, not only can the problem of fluorosilicic acid reflux failure caused by blockage be effectively avoided, but the solution residence time can also be further extended. The downflow plate in the inner cavity at one end of the settling tube connected to the guide cover can reduce the flow rate of the liquid, avoid the problem of the precipitate being swirled due to excessive flow rate, and the downflow plate in the inner cavity at the other end of the settling tube can intercept the fixed particles, avoid the particles from entering the circulation pipe, reduce the problem of particles clogging the circulation pipe, and improve the sedimentation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the system structure for preparing hydrogen fluoride from fluosilicic acid in the present invention;

[0025] Figure 2 Schematic diagram of the structure of the silicon tetrafluoride absorption tower in the present invention;

[0026] Figure 3 It is a structural schematic diagram of the sedimentation tube in the present invention.

[0027] Figure numerals: 1. Reactor; 2. Hydrogen fluoride absorption tower; 3. Condenser; 4. Silicon tetrafluoride absorption tower; 41. Tower body; 42. Flow guide cover; 43. Settling pipe; 431. Downflow plate; 44. Sedimentation pipe; 45. Circulation pipe; 46. Spoiler; 47. Distribution plate; 48. Rotating shaft; 49. Motor; 5. Stripping tower; 6. Hydrogen fluoride storage tank. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] A preparation system for preparing hydrogen fluoride from fluorosilicic acid comprises a reaction kettle 1, a hydrogen fluoride absorption tower 2, a condenser 3 and a silicon tetrafluoride absorption tower 4 which are connected in sequence;

[0030] The gas outlet on the reactor 1 is connected to the gas inlet of the hydrogen fluoride absorption tower 2, and the gas outlet of the hydrogen fluoride absorption tower 2 is connected to the gas inlet of the condenser 3. A concentrated sulfuric acid liquid inlet pipe is provided on the side wall of the hydrogen fluoride absorption tower 2. The condenser 3 is used to condense the hydrogen fluoride gas into liquid to separate it from the silicon tetrafluoride gas. The liquid outlet of the condenser 3 is connected to the hydrogen fluoride storage tank 6. The gas outlet of the condenser 3 is connected to the gas inlet of the silicon tetrafluoride absorption tower 4. The silicon tetrafluoride absorption tower 4 is provided with a fluosilicic acid liquid inlet pipe. The liquid outlet of the reactor 1 is connected to the stripping tower 5, and the gas outlet of the stripping tower 5 is connected to the gas inlet of the hydrogen fluoride absorption tower 2.

[0031] Reactor 1 is heated to decompose fluorosilicic acid. The main reaction in reactor 1 is H2SiF6=2HF+SiF4, and the side reaction is: HF+H2SO4=HSO3F+H2O. Therefore, the gas in reactor 1 is hydrogen fluoride and silicon tetrafluoride, which are transported to hydrogen fluoride absorption tower 2. Concentrated sulfuric acid is used to remove the water entrained in the mixed gas of silicon tetrafluoride and hydrogen fluoride. The liquid generated by the side reaction in reactor 1 is transported to the inside of stripping tower 5. The reaction is HSO3F+H2O=HF+H2SO4. The liquid generated by the side reaction can be regenerated into hydrogen fluoride and then transported. The hydrogen fluoride is dehydrated in the hydrogen fluoride absorption tower 2, and the condenser 3 is used to condense the hydrogen fluoride gas into liquid to separate it from the silicon tetrafluoride gas. The hydrogen fluoride is stored in the hydrogen fluoride storage tank 6, and the silicon tetrafluoride gas is transported to the interior of the silicon tetrafluoride absorption tower 4. The reaction formula is: SiF4+2H2O=4HF+SiO2. Therefore, the dilute hydrofluorosilicic acid is sprayed and circulated multiple times to reduce the water content in the dilute hydrofluorosilicic acid, becoming concentrated hydrofluorosilicic acid and precipitating silicon dioxide at the same time, making sulfuric acid an intermediate, and decomposing the hydrofluorosilicic acid into hydrogen fluoride and silicon dioxide. This preparation system increases the output of hydrogen fluoride and reduces the output of intermediate waste.

[0032] The silicon tetrafluoride absorption tower 4 includes a tower body 41, a spray mechanism is provided inside the tower body 41 and near one end of the top, a U-shaped sedimentation pipe 43 is provided at the bottom of the tower body 41 through a support frame, and a sedimentation pipe 44 is provided in the center of the bottom of the sedimentation pipe 43, and the sedimentation pipe 44 has an expansion joint to store fixed particles, and a guide cover 42 is provided inside the tower body 41 and at the top of the sedimentation pipe 43, so the air inlet of the tower body 41 is located between the guide cover 42 and the distribution plate 47, and the bottom of the guide cover 42 is connected to one end of the sedimentation pipe 43, and a connecting pipe is provided between the two ends of the sedimentation pipe 43, and a circulation pipe 45 is provided on the side wall of the other end of the sedimentation pipe 43, and the top of the circulation pipe 45 is connected to the fluorosilicic acid inlet pipe, and the inner walls of the inner cavity on both sides of the sedimentation pipe 43 are staggered with multiple groups of downflow plates 431, which are used to reduce the fluid velocity so that the solid particles settle in the sedimentation pipe 44.

[0033] The spray mechanism sprays the dilute fluorosilicic acid to contact with silicon tetrafluoride gas to precipitate silicon dioxide solid particles. Since the sedimentation tube 43 is a U-shaped structure, the travel of the solid-solution mixed solution in the sedimentation tube 43 can be extended, the time the solution stays in the sedimentation tube 43 can be extended, the floor space can be reduced, and the sedimentation efficiency of the particles can be improved. Moreover, under the action of the U-shaped structure, the sedimentation particles can easily enter the sedimentation tube 44 for storage, and through the expansion joint, not only can the problem of fluorosilicic acid reflux failure caused by blockage be effectively avoided, but the time the solution stays can also be further extended. The sedimentation tube 43 and the guide cover are connected. The downflow plate 431 in the inner cavity at one end of the 42 connection can reduce the flow rate of the liquid, avoiding the problem of the sediment being stirred up due to excessive flow rate, and the downflow plate 431 in the inner cavity at the other end of the sedimentation tube 43 can intercept the fixed particles, preventing the particles from entering the circulation tube 45, reducing the problem of particles clogging the circulation tube 45, and improving the sedimentation effect. At the same time, the connecting tube can circulate and settle the liquid, further improving the sedimentation effect. Among them, the expansion joint is two symmetrically arranged conical structures, which on the one hand increases the storage space, and on the other hand avoids the particles from being blocked in the sedimentation tube 44.

[0034] In one embodiment, the spray assembly includes a drive assembly arranged at the top of the tower body 41, the top of the drive assembly is connected to the fluorosilicic acid liquid inlet pipe, and the drive assembly is located at one end inside the tower body 41. A distribution plate 47 is provided, and the bottom of the distribution plate 47 is connected and provided with multiple groups of nozzles. The fluorosilicic acid liquid is transported to the distribution plate 47 through the drive assembly, and finally sprayed into the interior of the tower body 41 through the nozzle. The drive assembly drives the distribution plate 47 to rotate, thereby increasing the spraying area and improving the absorption effect of silicon tetrafluoride gas.

[0035] In one embodiment, the driving assembly includes a rotating shaft 48 and a motor 49. A hollow rotating shaft 48 is rotatably connected to the top of the tower body 41, and a distribution plate 47 is provided at the bottom of the rotating shaft 48. A motor 49 is provided on one side of the top of the tower body 41. The output shaft of the motor 49 is connected to the surface of the rotating shaft 48 through a transmission belt. A fluorosilicic acid liquid inlet pipe is rotatably connected to the top of the rotating shaft 48. The motor 49 drives the rotating shaft 48 to rotate through the transmission belt, and the rotating shaft 48 drives the distribution plate to rotate, thereby increasing the spraying area and increasing the contact area between the spray liquid and the liquid, thereby improving the absorption effect. Fluorosilicic acid is transported to the distribution plate 47 through the hollow rotating shaft 48.

[0036] In order to further improve the absorption effect of silicon tetrafluoride gas, a spoiler 46 is provided at the bottom of the distribution plate 47. The spoiler 46 includes a fixed shaft provided at the bottom of the distribution plate 47. A plurality of spoiler rods are staggeredly distributed on the surface of the fixed shaft. The air inlet of the tower body 41 is located between the spoiler 46 and the guide cover 42. The fixed shaft is driven to rotate during the rotation of the distribution plate 47, and the fixed shaft drives the spoiler rods to rotate, which can break up the gas and increase the contact area between the gas and the liquid, thereby improving the absorption effect.

[0037] The method for preparing hydrogen fluoride from fluosilicic acid comprises the following steps:

[0038] S1: Add 31% hydrosilicic acid and 98% sulfuric acid to reactor 1, use an external circulation heat exchanger to raise the reaction temperature inside reactor 1 to 90-100°C, open the gas phase valve, and allow the gas phase to flow into hydrogen fluoride absorption tower 2 through the pipeline. The pressure of reactor 1 is controlled at ≤0.05MPa, open the bottom valve of the reactor, and control the flow rate to stripping tower 5 through the regulating valve;

[0039] Reactor 1 is heated to decompose fluorosilicic acid. The main reaction in reactor 1 is H2SiF6=2HF+SiF4, and the side reaction is: HF+H2SO4=HSO3F+H2O. Therefore, the gas in reactor 1 is hydrogen fluoride and silicon tetrafluoride, which are transported to hydrogen fluoride absorption tower 2 through pipeline, and the liquid in the reactor is transported to stripping tower 5.

[0040] S2: Use the external circulating steam of the stripping tower 5 to control the temperature of the stripping tower at 110-120°C, open the compressed air valve, and introduce compressed air. The pressure of the stripping tower 5 is controlled at ≤0.05MPa. The gas phase inside the stripping tower 5 is transported to the hydrogen fluoride absorption tower 2 through a pipeline, and the liquid phase inside the stripping tower 5 enters the sulfuric acid storage tank after condensation.

[0041] The reaction in the stripping tower 5 is HSO3F+H2O=HF+H2SO4, and the HSO3F generated by the side reaction can be regenerated into hydrogen fluoride, which is then transported to the hydrogen fluoride absorption tower 2 for dehydration, thereby increasing the yield of hydrogen fluoride and reducing the loss of sulfuric acid.

[0042] S3: The gas phase of the reactor 1 flows into the interior of the hydrogen fluoride absorption tower 2 through a pipeline. 98% sulfuric acid is added into the hydrogen fluoride absorption tower 2 to absorb a small amount of water entrained in the hydrogen fluoride and silicon tetrafluoride gases.

[0043] Concentrated sulfuric acid is used to remove moisture from the mixed gas of silicon tetrafluoride and hydrogen fluoride.

[0044] S4: The gas dried in the hydrogen fluoride absorption tower 2, consisting of hydrogen fluoride and silicon tetrafluoride, is transported to the condenser 3 for cooling, and the hydrogen fluoride is cooled to liquid. The cooled hydrogen fluoride is transported to the hydrogen fluoride storage tank 6, and the silicon tetrafluoride in the condenser 3 is transported to the silicon tetrafluoride absorption tower 4.

[0045] The condenser 3 is used to condense the hydrogen fluoride gas into liquid to separate it from the silicon tetrafluoride gas. The hydrogen fluoride is stored in the hydrogen fluoride storage tank 6, while the silicon tetrafluoride gas is transported to the inside of the silicon tetrafluoride absorption tower 4.

[0046] S5: Add 11% fluorosilicic acid to the silicon tetrafluoride absorption tower 4 for circulated spraying to absorb silicon tetrafluoride gas. Solid silicon dioxide is precipitated in the tower and the silicon dioxide is settled at the bottom of the silicon tetrafluoride absorption tower. The fluorosilicic acid is refluxed to the silicon tetrafluoride absorption tower 4.

[0047] S6: The silicon dioxide settled at the bottom of the silicon tetrafluoride absorption tower 4 is output through the precipitation pipe 44.

[0048] In S1, the flow rate of 31% fluorosilicic acid is 100 kg / h, the flow rate of 98% sulfuric acid is 225 kg / h, and the flow rate of the stripping tower is 300 kg / h.

[0049] The compressed air flow rate in S2 is 60Nm 3 h.

[0050] In S3, the flow rate of 98% sulfuric acid is 2.8 kg / h.

[0051] 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 and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A system for preparing hydrogen fluoride from fluosilicic acid, characterized by: It comprises a reaction kettle (1), a hydrogen fluoride absorption tower (2), a condenser (3) and a silicon tetrafluoride absorption tower (4) which are connected in sequence; The silicon tetrafluoride absorption tower (4) includes a tower body (41), a spray mechanism is provided inside the tower body (41) and near one end of the top, a U-shaped sedimentation pipe (43) is provided at the bottom of the tower body (41) through a support frame, a sedimentation pipe (44) is provided at the center of the bottom of the sedimentation pipe (43), and the sedimentation pipe (44) has an expansion joint for storing fixed particles, a guide cover (42) is provided inside the tower body (41) and at the top of the sedimentation pipe (43), so that the air inlet of the tower body (41) is located between the guide cover (42) and the distribution plate (47), the bottom of the guide cover (42) is communicated with one end of the sedimentation pipe (43), a connecting pipe is provided between the two ends of the sedimentation pipe (43), a circulation pipe (45) is provided on the side wall of the other end of the sedimentation pipe (43), and the top of the circulation pipe (45) is communicated with the fluosilicic acid inlet pipe; The spray assembly includes a drive assembly arranged at the top of the tower body (41), the top of the drive assembly is connected to the fluosilicic acid liquid inlet pipe, one end of the drive assembly located inside the tower body (41) is provided with a distribution plate (47), and the bottom of the distribution plate (47) is connected to multiple groups of nozzles; The driving assembly includes a rotating shaft (48) and a motor (49); a hollow rotating shaft (48) is rotatably plugged into the top of the tower body (41); a distribution plate (47) is provided at the bottom of the rotating shaft (48); a motor (49) is provided on one side of the top of the tower body (41); an output shaft of the motor (49) is connected to the surface of the rotating shaft (48) through a transmission belt; and a fluorosilicic acid liquid inlet pipe is rotatably plugged into the top of the rotating shaft (48); A spoiler (46) is provided at the bottom of the distribution plate (47), and the spoiler (46) comprises a fixed shaft provided at the bottom of the distribution plate (47), and a plurality of groups of spoiler rods are staggeredly distributed on the surface of the fixed shaft.

2. The system for preparing hydrogen fluoride from hydrosilicic acid according to claim 1, wherein: The gas outlet on the reactor (1) is communicated with the gas inlet of the hydrogen fluoride absorption tower (2), the gas outlet of the hydrogen fluoride absorption tower (2) is communicated with the gas inlet of the condenser (3), a concentrated sulfuric acid liquid inlet pipe is provided on the side wall of the hydrogen fluoride absorption tower (2), the condenser (3) is used to condense the hydrogen fluoride gas into liquid to separate it from the silicon tetrafluoride gas, the liquid outlet of the condenser (3) is communicated with the hydrogen fluoride storage tank (6), the gas outlet of the condenser (3) is communicated with the gas inlet of the silicon tetrafluoride absorption tower (4), the silicon tetrafluoride absorption tower (4) is provided with a fluorosilicic acid liquid inlet pipe, the liquid outlet of the reactor (1) is communicated with the stripping tower (5), and the gas outlet of the stripping tower (5) is communicated with the gas inlet of the hydrogen fluoride absorption tower (2).

3. A method for preparing hydrogen fluoride from fluorosilicic acid, using the system for preparing hydrogen fluoride from fluorosilicic acid according to any one of claims 1-2, characterized in that: The following steps are involved: S1: Add 31% hydrosilicic acid and 98% sulfuric acid to the reactor (1), use the external circulation heat exchanger to raise the reaction temperature inside the reactor (1) to 90-100°C, open the gas phase valve, and allow the gas phase to flow into the hydrogen fluoride absorption tower (2) through the pipeline. The pressure of the reactor (1) is controlled at ≤0.05MPa, open the bottom valve of the reactor, and control the flow rate to the stripping tower through the regulating valve; S2: Using the external circulating steam of the stripping tower (5), the temperature of the stripping tower is controlled at 110-120°C, the compressed air valve is opened, and compressed air is introduced. The pressure of the stripping tower (5) is controlled at ≤0.05MPa, and the gas phase inside the stripping tower (5) is transported to the hydrogen fluoride absorption tower (2) through a pipeline. The liquid phase inside the stripping tower (5) enters the sulfuric acid storage tank after condensation; S3: The gas phase of the reactor (1) flows into the interior of the hydrogen fluoride absorption tower (2) through a pipeline, and 98% sulfuric acid is added into the hydrogen fluoride absorption tower (2) to absorb a small amount of water entrained in the hydrogen fluoride and silicon tetrafluoride gases using the 98% sulfuric acid; S4: The gas dried by the hydrogen fluoride absorption tower (2), which consists of hydrogen fluoride and silicon tetrafluoride, is transported to the condenser (3) for cooling, and the hydrogen fluoride is cooled to liquid. The cooled hydrogen fluoride is transported to the hydrogen fluoride storage tank (6), and the silicon tetrafluoride in the condenser (3) is transported to the silicon tetrafluoride absorption tower (4); S5: Add 11% fluorosilicic acid to the silicon tetrafluoride absorption tower (4) for circulated spraying to absorb silicon tetrafluoride gas, precipitate silicon dioxide solid in the tower, settle silicon dioxide at the bottom of the silicon tetrafluoride absorption tower, and reflux the fluorosilicic acid to the silicon tetrafluoride absorption tower (4); S6: The silicon dioxide settled at the bottom of the silicon tetrafluoride absorption tower (4) is output through a precipitation pipe (44).

4. The method for preparing hydrogen fluoride from hydrosilicic acid according to claim 3, wherein: In S1, the flow rate of 31% hydrosilicic acid is 100 kg / h, the flow rate of 98% sulfuric acid is 225 kg / h, and the flow rate of the stripping tower is 300 kg / h.

5. The method for preparing hydrogen fluoride from hydrosilicic acid according to claim 3, wherein: The compressed air flow rate in S2 is 60Nm 3 / h.

6. The method for preparing hydrogen fluoride from hydrosilicic acid according to claim 3, wherein: In S3, the flow rate of 98% sulfuric acid is 2.8 kg / h.

Images