CN116462200B - Fluosilicic acid concentration method based on vacuum membrane distillation method - Google Patents
Fluosilicic acid concentration method based on vacuum membrane distillation method Download PDFInfo
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- 239000002253 acid Substances 0.000 title claims abstract description 134
- 239000012528 membrane Substances 0.000 title claims abstract description 74
- 238000004821 distillation Methods 0.000 title claims abstract description 58
- 238000000034 method Methods 0.000 title claims abstract description 44
- 239000007788 liquid Substances 0.000 claims abstract description 75
- 238000000926 separation method Methods 0.000 claims abstract description 42
- 239000007789 gas Substances 0.000 claims abstract description 32
- ABTOQLMXBSRXSM-UHFFFAOYSA-N silicon tetrafluoride Chemical compound F[Si](F)(F)F ABTOQLMXBSRXSM-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000000243 solution Substances 0.000 claims abstract description 19
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910000040 hydrogen fluoride Inorganic materials 0.000 claims abstract description 8
- 239000011550 stock solution Substances 0.000 claims abstract description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 30
- 230000002209 hydrophobic effect Effects 0.000 claims description 17
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 8
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 8
- -1 polytetrafluoroethylene Polymers 0.000 claims description 6
- 239000012510 hollow fiber Substances 0.000 claims description 5
- 230000000694 effects Effects 0.000 abstract description 13
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract description 10
- 239000000741 silica gel Substances 0.000 abstract description 10
- 229910002027 silica gel Inorganic materials 0.000 abstract description 10
- 238000000354 decomposition reaction Methods 0.000 abstract description 7
- 238000000746 purification Methods 0.000 abstract description 5
- 238000011084 recovery Methods 0.000 abstract description 3
- 238000006243 chemical reaction Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 5
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 4
- 229910052731 fluorine Inorganic materials 0.000 description 4
- 239000011737 fluorine Substances 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 3
- 239000002826 coolant Substances 0.000 description 3
- 238000005265 energy consumption Methods 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 239000011552 falling film Substances 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000003204 osmotic effect Effects 0.000 description 2
- 239000002367 phosphate rock Substances 0.000 description 2
- OJMIONKXNSYLSR-UHFFFAOYSA-N phosphorous acid Chemical compound OP(O)O OJMIONKXNSYLSR-UHFFFAOYSA-N 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- PASHVRUKOFIRIK-UHFFFAOYSA-L calcium sulfate dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])(=O)=O PASHVRUKOFIRIK-UHFFFAOYSA-L 0.000 description 1
- 238000001311 chemical methods and process Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000011143 downstream manufacturing Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 150000004673 fluoride salts Chemical class 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 239000012982 microporous membrane Substances 0.000 description 1
- 239000002686 phosphate fertilizer Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 238000009489 vacuum treatment Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/08—Compounds containing halogen
- C01B33/10—Compounds containing silicon, fluorine, and other elements
- C01B33/103—Fluosilicic acid; Salts thereof
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D1/00—Evaporating
- B01D1/22—Evaporating by bringing a thin layer of the liquid into contact with a heated surface
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D1/00—Evaporating
- B01D1/28—Evaporating with vapour compression
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/007—Energy recuperation; Heat pumps
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/10—Vacuum distillation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
Abstract
The invention discloses a fluosilicic acid concentration method based on a vacuum membrane distillation method, which solves the problems that the existing fluosilicic acid concentration process is high in temperature, easy to block and the concentration efficiency is required to be further improved. The technical scheme is that dilute fluosilicic acid is heated by a first heat exchanger and then is sent into a fluosilicic acid stock solution tank, bottom liquid is sent into a first gas-liquid separation tank for gas-liquid separation, after silicon tetrafluoride and hydrogen fluoride gas are separated, the bottom liquid is sent into a membrane distillation system for distillation concentration, the concentrated fluosilicic acid is sent into a second gas-liquid separation tank for secondary gas-liquid separation, residual steam is separated out, the bottom liquid is sent back into the fluosilicic acid stock solution tank until fluosilicic acid solution is concentrated to target concentration and then flows into a fluosilicic acid storage tank; the fluosilicic acid raw liquid tank is a constant-temperature storage tank. The method is simple and easy to control, can effectively inhibit the decomposition of the fluosilicic acid, avoids the blockage problem caused by silica gel, and has good concentration and purification effects, high fluosilicic acid recovery rate, low running and equipment investment cost and small occupied area.
Description
Technical Field
The invention relates to the technical field of fluosilicic acid concentration, in particular to a fluosilicic acid concentration method based on a vacuum membrane distillation method.
Background
The fluosilicic acid is mainly used as a byproduct of the wet phosphoric acid process, fluorine in the phosphorite reacts with sulfuric acid to generate HF and phosphogypsum, and the HF continuously reacts with SiO 2 existing in the phosphorite to generate fluosilicic acid. During concentration of the phosphoric acid solution, the fluosilicic acid is decomposed and escapes in the form of a large amount of silicon tetrafluoride gas, and is absorbed by water in a fluorine absorption tower to form fluosilicic acid solution.
The fluosilicic acid has strong toxicity and corrosiveness, and the direct discharge not only pollutes the environment, but also causes the waste of fluorine resources. The concentration of fluosilicic acid which is a byproduct of most phosphate fertilizer enterprises is lower than 18%, and fluoride chemical products such as fluosilicate, fluoride salt, anhydrous hydrogen fluoride and the like which are directly produced by taking fluosilicic acid as raw materials have the following two defects: firstly, the low-concentration fluosilicic acid is directly transported to a downstream processing plant, so that the storage and transportation cost is high; secondly, the fluosilicic acid with low concentration directly participates in the reaction, and a large amount of water is brought into a reaction device, so that the problems of low reaction efficiency, high energy consumption, low product yield and the like are caused, and finally, the economical efficiency of the process is poor. Therefore, it is necessary to concentrate the fluorosilicic acid at a low concentration.
The concentration of fluosilicic acid has the difficulty that the fluosilicic acid is heated and is easily decomposed into silicon tetrafluoride and hydrogen fluoride gas, wherein the silicon tetrafluoride gas can be quickly reacted with water vapor to be converted into silica gel, so that the yield of fluosilicic acid is low, equipment and pipelines are blocked by generated silica gel which is easy to scale, a large amount of manpower and material resources are consumed by frequent shutdown and scale removal, the running continuity of a system is influenced, and the economical efficiency of the system is reduced.
The traditional concentration method of fluosilicic acid mainly adopts concentrated sulfuric acid to decompose fluosilicic acid, and the generated silicon tetrafluoride gas is absorbed by water to obtain concentrated fluosilicic acid. The method has various defects, such as complex process, high energy consumption, high requirement on equipment and pipeline materials by highly corrosive hydrogen fluoride gas, high investment cost for early construction of the device, and low absorption rate of silicon tetrafluoride gas, which not only causes fluorine resource waste, but also aggravates the burden of post-tail gas treatment. The existing concentration technology of fluosilicic acid mainly comprises evaporation concentration, for example, a falling film evaporation method is adopted for concentrating fluosilicic acid in Chinese patent CN 10384842A and CN 111017931A, a good concentration effect is achieved, but in the method, the thermal decomposition of fluosilicic acid and the gasification of water occur in a falling film evaporator, and generated silicon tetrafluoride gas and water vapor directly contact and react to generate silica gel, so that the problem of pipe blockage is caused.
The membrane distillation is a liquid separation technology combining distillation and membrane separation technology, a hydrophobic microporous membrane is used as a barrier, volatile components in a hot side solution are evaporated and vaporized, the volatile components pass through micropores of the hydrophobic membrane in one way under the drive of vapor pressure difference at two sides of the membrane to enter a cold side, and molecules at the cold side cannot pass through the hydrophobic membrane to enter the hot side, so that the solution concentration is realized. Depending on the way in which the cold side vapor condenses or is vented, the membrane distillation process can be divided into: direct contact, air gap, vacuum, air sweep, and osmotic. M. Tomaszewska researches the concentration and purification effects of direct contact type and osmotic type membrane distillation methods on crude fluosilicic acid, and research results show that the purification effect is good, but the concentration effect is not obvious under the restriction of driving force. In addition, with the membrane distillation method, if a large amount of silicon tetrafluoride gas is contained in fluosilicic acid entering a membrane distillation system, the problem that silica gel is blocked by the direct contact reaction of the silicon tetrafluoride gas and water vapor still exists.
Disclosure of Invention
The invention aims to solve the technical problems, and provides the fluosilicic acid concentration method based on the vacuum membrane distillation method, which is simple and easy to control, can effectively inhibit the decomposition of fluosilicic acid, avoid the blockage problem caused by silica gel, and simultaneously can effectively improve the concentration effect, and has the advantages of high fluosilicic acid recovery rate, low running and equipment investment cost and small occupied area.
The invention relates to a fluosilicic acid concentration method based on a vacuum membrane distillation method, which comprises the steps of heating dilute fluosilicic acid by a first heat exchanger, sending the dilute fluosilicic acid into a fluosilicic acid stock solution tank, sending bottom liquid into a first gas-liquid separation tank for gas-liquid separation, sending the bottom liquid into a membrane distillation system for distillation concentration after separating silicon tetrafluoride and hydrogen fluoride gas, sending the concentrated fluosilicic acid into a second gas-liquid separation tank for secondary gas-liquid separation, separating out residual steam, sending the bottom liquid back into the fluosilicic acid stock solution tank until the fluosilicic acid solution is concentrated to a target concentration, and then flowing into a fluosilicic acid storage tank; the fluosilicic acid raw liquid tank is a constant-temperature storage tank.
The dilute fluosilicic acid is heated to 40-50 ℃ by a first heat exchanger, and the constant temperature of the fluosilicic acid raw solution tank is 40-50 DEG C
The membrane distillation system is a vacuum membrane distillation system.
The vacuum degree of the cold side compartment of the vacuum membrane distillation system is controlled to be-0.03 to-0.09 MPa.
The hydrophobic membrane in the vacuum membrane distillation system is a Polytetrafluoroethylene (PTFE) hollow fiber membrane, and the pore diameter range is 0.1-0.5 mu m.
And pressurizing the bottom liquid of the first gas-liquid separation tank by a circulating pump, filtering by a filter, and then sending the bottom liquid into the membrane distillation system for distillation and concentration.
And the steam discharged by the membrane distillation system is sent to a third gas-liquid separation tank for gas-liquid separation after being subjected to heat exchange and temperature reduction by a second heat exchanger, so that a small amount of noncondensable gas and condensed water are obtained.
The dilute fluosilicic acid is heated by a third heat exchanger, and then is sent into a fluosilicic acid raw liquid tank after being heated by a first heat exchanger; and the steam discharged by the membrane distillation system is compressed and heated by a steam compressor, then is sent to a third heat exchanger to exchange heat with dilute fluosilicic acid, and then is sent to a second heat exchanger to be cooled.
In order to solve the problem of silica gel pipe blockage, the inventor considers that the whole process adopts low-temperature operation (controlling 40-50 ℃) to inhibit the decomposition of fluosilicic acid, and the generation of silicon tetrafluoride gas is reduced from the source; on the other hand, low-temperature operation, while inhibiting the decomposition of fluorosilicic acid, can seriously affect the concentration effect, resulting in difficulty in achieving the intended target concentration; therefore, the invention provides a new idea of concentrating fluosilicic acid by adopting a vacuum membrane distillation method, the fluosilicic acid can be suitable for concentrating fluosilicic acid at lower temperature under vacuum conditions, in the vacuum membrane distillation concentration process, water in a hot side solution is firstly diffused to a boundary layer contacted with the surface of a hydrophobic membrane, then gasified at the interface of the boundary layer and the hydrophobic membrane, gasified water vapor enters a cold side through micropores of the hydrophobic membrane, so that the gasified water only occurs in a region near the hydrophobic membrane and is separated quickly, fluosilicic acid is concentrated, and the concentration and purification effects under vacuum treatment are good. Further, it is contemplated that the silicon tetrafluoride gas may also enter the cold side through a hydrophobic membrane and contact the condensing system with water vapor, so that the silicon tetrafluoride gas is prevented from entering the membrane distillation system as much as possible. From the analysis of the technological process, the silicon tetrafluoride gas is mainly generated in the raw liquid tank and the feeding heater thereof, so that the bottom liquid of the fluosilicic acid raw liquid tank is sent into the first gas-liquid separation tank for gas-liquid separation, the silicon tetrafluoride gas is ensured to be separated as far as possible before fluosilicic acid enters the hot side of the membrane distillation system, the direct contact of the silicon tetrafluoride gas and water vapor is avoided, and the reaction condition of silica gel generation is destroyed.
Further, the concentrated fluosilicic acid is sent to a second gas-liquid separation tank for secondary gas-liquid separation, and water vapor possibly mixed in the fluosilicic acid liquid is effectively separated through the second gas-liquid separation, so that the situation that the concentrated fluosilicic acid is carried into a fluosilicic acid stock solution tank is avoided, the concentration efficiency is ensured, and meanwhile, the water vapor is prevented from being contacted with silicon tetrafluoride gas in the fluosilicic acid stock solution tank.
Preferably, the vacuum degree of a cold side compartment of the vacuum membrane distillation system is controlled to be-0.03 to-0.09 MPa, and the realization difficulty of an excessive chemical process is high, and the concentration effect of fluosilicic acid is poor due to the excessive low; preferably, the hydrophobic membrane in the vacuum membrane distillation system is Polytetrafluoroethylene (PTFE), the pore diameter range is 0.1-0.5 mu m, too high can enable fluosilicic acid molecules to enter the cold side through the hydrophobic membrane, too low can enable water molecules to be separated from fluosilicic acid through the hydrophobic membrane, and the purpose of concentration cannot be achieved.
Further, the latent heat of steam discharged by the membrane distillation system is fully utilized, and the steam is sent to the first heat exchanger to exchange heat with dilute fluosilicic acid and then is sent to the second heat exchanger to cool.
The invention has the beneficial effects that:
The vacuum membrane distillation technology is firstly put forward to be applied to the concentration of fluosilicic acid, and aiming at the technical difficulty of concentration of fluosilicic acid, the technology process is improved from two angles of low-temperature operation to avoid fluosilicic acid decomposition and gas-liquid separation to avoid direct contact reaction of silicon tetrafluoride and water vapor, and the concentration method suitable for fluosilicic acid characteristics is put forward. The fluosilicic acid is always kept in a low-temperature state in the circulating concentration process, so that the decomposition of the fluosilicic acid can be effectively inhibited, the loss is reduced, meanwhile, the problem of equipment pipeline blockage caused by silica gel can be avoided, the device can continuously operate, and the operating rate is high; the vacuum membrane distillation method is combined with the mechanical vapor recompression method, and the fluosilicic acid raw material is heated by recovering the latent heat of the secondary vapor, so that the energy can be further saved. The method is simple and easy to control, can effectively inhibit the decomposition of the fluosilicic acid, avoid the blockage problem caused by silica gel, and effectively improve the concentration and purification effects, and has the advantages of high fluosilicic acid recovery rate, energy conservation, consumption reduction, low running and equipment investment cost and small occupied area.
Drawings
Fig. 1 is a process flow diagram of example 1 of the present invention.
Fig. 2 is a process flow chart of embodiment 2 of the present invention.
1, A first heat exchanger; 2 fluosilicic acid raw liquid tank; 3, a safety valve; 4, a first gas-liquid separation tank; 5, a circulating pump; 6, a filter; 7, a vacuum membrane distillation system; 8, a hydrophobic membrane; 9, a second gas-liquid separation tank; 10 a second heat exchanger; 11 a third gas-liquid separation tank; 12 a water storage tank; 13 a vacuum pump; 14 a vapor compressor; 15 a third heat exchanger; 16 fluorosilicic acid storage tank.
Detailed Description
The invention is further described in detail by the following embodiments:
Example 1
Referring to the flow chart in fig. 1, dilute fluosilicic acid with the mass concentration of 10% and hot water with the temperature of 65 ℃ enter a fluosilicic acid raw material tank 2 after heat exchange in a first heat exchanger 1, and the temperature of fluosilicic acid in the fluosilicic acid raw material tank 2 is controlled to be 40 ℃. The fluosilicic acid is heated and then enters a fluosilicic acid raw liquid tank 2, the bottom liquid is sent into a first gas-liquid separation tank 4 for gas-liquid separation, silicon tetrafluoride and hydrogen fluoride gas are separated, the bottom liquid is pressurized by a circulating pump 5 and filtered by a filter 6, and then is sent into a vacuum membrane distillation system 7 for distillation concentration;
Delivering the concentrated fluosilicic acid into a second gas-liquid separation tank 11 for secondary gas-liquid separation, delivering the bottom liquid back into a fluosilicic acid raw solution tank 2 until the fluosilicic acid solution is concentrated to the target concentration, and then delivering the concentrated fluosilicic acid solution into a fluosilicic acid storage tank 16; the mass concentration of the finally prepared fluosilicic acid product is 25.62 percent. The gas phase discharged by the safety valves of the first gas-liquid separation tanks 4 and 9 and the fluosilicic acid raw liquid tank 2 is exhausted after the tail gas post-treatment.
The steam discharged by the membrane distillation system 7 is sent to a third steam-liquid separation tank 11 for gas-liquid separation after heat exchange and temperature reduction by a second heat exchanger 10 to obtain a small amount of non-condensable gas and condensed water, the non-condensable gas is directly emptied, and the condensed water enters a water storage tank 12;
The fluosilicic acid raw solution tank 1 is a constant-temperature storage tank, the temperature of fluosilicic acid in the fluosilicic acid raw solution tank 1 is controlled to be 40 ℃, and the hydrophobic membrane 8 of the vacuum membrane distillation system 7 is a polytetrafluoroethylene hollow fiber membrane with the aperture of 0.3 mu m. The vacuum degree of the cold side compartment of the vacuum membrane distillation system 7 is controlled to be-0.07 MPa by utilizing a vacuum pump 13, and the third heat exchanger 15 takes circulating water at 30 ℃ as a cooling medium.
After the method is adopted, the system runs stably, the system is free from blocking in 2000 hours of experiment, and the fluosilicic acid concentration effect is good.
Example 2
Referring to fig. 2, dilute fluosilicic acid with the mass concentration of 12% exchanges heat with steam from the steam compressor 14 after being heated in the third heat exchanger 15, exchanges heat with hot water with the temperature of 70 ℃ in the first heat exchanger 1, and enters the fluosilicic acid raw liquid tank 2, and the temperature of fluosilicic acid in the fluosilicic acid raw liquid tank 2 is controlled to be 45 ℃; the fluosilicic acid is heated and then enters a fluosilicic acid raw liquid tank 2, the bottom liquid is sent into a first gas-liquid separation tank 4 for gas-liquid separation, silicon tetrafluoride and hydrogen fluoride gas are separated, the bottom liquid is pressurized by a circulating pump 5 and filtered by a filter 6, and then is sent into a vacuum membrane distillation system 7 for distillation concentration;
the concentrated fluosilicic acid is sent to a second gas-liquid separation tank 11 for three times of gas-liquid separation, the bottom liquid returns to the fluosilicic acid raw liquid tank 2 until the fluosilicic acid solution is concentrated to the target concentration and then flows into a fluosilicic acid storage tank 16; the final product fluosilicic acid mass concentration is 27.54%. The gas phase discharged by the safety valves of the first gas-liquid separation tanks 4 and 9 and the fluosilicic acid raw liquid tank 2 is exhausted after the tail gas post-treatment.
The steam discharged by the membrane distillation system 7 is heated by the steam compressor 14 and then is sent to the third heat exchanger 10 to heat dilute fluosilicic acid, latent heat of the steam is released, the steam is cooled by the second heat exchanger 10 and then is sent to the third steam-liquid separation tank 11 to carry out gas-liquid separation to obtain a small amount of non-condensable gas and condensed water, the non-condensable gas is directly emptied, and the condensed water enters the water storage tank;
The fluosilicic acid raw solution tank 1 is a constant-temperature storage tank, the temperature of fluosilicic acid in the fluosilicic acid raw solution tank 1 is controlled to be 45 ℃, and the hydrophobic membrane 8 of the vacuum membrane distillation system 7 is a polytetrafluoroethylene hollow fiber membrane with the aperture of 0.4 mu m. The vacuum degree of the cold side compartment of the vacuum membrane distillation system 7 is controlled to be-0.09 MPa by utilizing a vacuum pump 13, and the third heat exchanger 15 takes circulating water at 30 ℃ as a cooling medium.
After the method is adopted, the system stably operates, the problem of blockage of the system does not occur within 2000 hours of the experiment, the fluosilicic acid concentration effect is good, and the energy consumption is reduced by about 20 percent compared with the method in the embodiment 1.
Example 3
Except for the following parameters, the fluorosilicic acid raw solution tank 1 is a constant temperature storage tank, the temperature of the fluorosilicic acid in the fluorosilicic acid raw solution tank 1 is controlled to be 50 ℃, and the hydrophobic membrane of the vacuum membrane distillation system 7 is a polytetrafluoroethylene hollow fiber membrane with the pore diameter of 0.4 μm. The vacuum degree of the cold side compartment of the vacuum membrane distillation system 7 is controlled to be-0.09 MPa by utilizing a vacuum pump 13, and the third heat exchanger 15 takes circulating water at 30 ℃ as a cooling medium. The final product fluosilicic acid mass concentration is 27.38%.
After the method is adopted, the system runs stably, the system is free from blocking in 2000 hours of experiment, and the fluosilicic acid concentration effect is good.
Claims (4)
1. A fluosilicic acid concentration method based on a vacuum membrane distillation method is characterized in that dilute fluosilicic acid is heated to 40-50 ℃ by a first heat exchanger and then is sent to a fluosilicic acid stock solution tank, bottom liquid is sent to a first gas-liquid separation tank for gas-liquid separation, after silicon tetrafluoride and hydrogen fluoride gas are separated, the bottom liquid is pressurized by a circulating pump and filtered by a filter and then is sent to a membrane distillation system for distillation concentration, the concentrated fluosilicic acid is sent to a second gas-liquid separation tank for secondary gas-liquid separation, residual steam is separated, the bottom liquid is sent back to the fluosilicic acid stock solution tank until the fluosilicic acid solution is concentrated to a target concentration and then flows into a fluosilicic acid storage tank; the fluosilicic acid raw liquid tank is a constant-temperature storage tank with constant temperature of 40-50 ℃; the membrane distillation system is a vacuum membrane distillation system, the hydrophobic membrane in the vacuum membrane distillation system is a polytetrafluoroethylene hollow fiber membrane, and the aperture range is 0.1-0.5 mu m.
2. The method for concentrating fluorosilicic acid by vacuum membrane distillation according to claim 1, wherein the vacuum degree of the cold side compartment of said vacuum membrane distillation system is controlled to be-0.03 to-0.09 MPa.
3. The fluosilicic acid concentration method based on the vacuum membrane distillation method according to claim 1 or 2, wherein the steam discharged by the membrane distillation system is sent to a third gas-liquid separation tank for gas-liquid separation after heat exchange and temperature reduction by a second heat exchanger, so as to obtain a small amount of noncondensable gas and condensed water.
4. The method for concentrating fluosilicic acid based on vacuum membrane distillation according to claim 3, wherein said diluted fluosilicic acid is heated by a third heat exchanger and then sent to a fluosilicic acid raw liquid tank after being heated by a first heat exchanger; and the steam discharged by the membrane distillation system is compressed and heated by a steam compressor, then is sent to a third heat exchanger to indirectly exchange heat with dilute fluosilicic acid, and then is sent to a second heat exchanger to be cooled.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2018065101A (en) * | 2016-10-20 | 2018-04-26 | オルガノ株式会社 | Method and apparatus for treating fluorine-containing water |
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| CN104211031B (en) * | 2013-06-04 | 2017-02-08 | 四川玖长科技有限公司 | Equipment and process for recovery of fluorine from flue gas of hydration absorption of phosphorus in kiln-method phosphoric acid technology |
| CN103848426B (en) * | 2014-02-25 | 2015-08-26 | 瓮福（集团）有限责任公司 | Vacuum falling film method of evaporation is utilized to concentrate the method for silicofluoric acid |
| CN109678160A (en) * | 2019-01-23 | 2019-04-26 | 瓮福（集团）有限责任公司 | A kind of fluosilicic acid energy conservation method for concentration |
| CN110240164A (en) * | 2019-06-26 | 2019-09-17 | 威海恒邦化工有限公司 | The method and device of fluosilicic acid concentration |
| CN110510591A (en) * | 2019-09-27 | 2019-11-29 | 瓮福达州化工有限责任公司 | A kind of high purity phosphorus hydrochlorate concentration technology |
| CN113603058A (en) * | 2021-09-06 | 2021-11-05 | 瓮福（集团）有限责任公司 | Method for separating and concentrating fluorine-containing water vapor by utilizing vacuum membrane separation technology |
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| JP2018065101A (en) * | 2016-10-20 | 2018-04-26 | オルガノ株式会社 | Method and apparatus for treating fluorine-containing water |
| CN109678159A (en) * | 2019-01-23 | 2019-04-26 | 瓮福（集团）有限责任公司 | A kind of fluosilicic acid cleaning method for concentration |
| CN114225443A (en) * | 2022-01-18 | 2022-03-25 | 何浩明 | Vacuum low-temperature circulating concentration system and method for fluosilicic acid |
| CN114735653A (en) * | 2022-03-31 | 2022-07-12 | 贵州省化工研究院 | Method and device for preparing hydrogen fluoride by taking silicon tetrafluoride as raw material through centrifugal separation |
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