CN114477196A - Method for preparing fumed silica by fluorination method - Google Patents
Method for preparing fumed silica by fluorination method Download PDFInfo
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- CN114477196A CN114477196A CN202011165061.5A CN202011165061A CN114477196A CN 114477196 A CN114477196 A CN 114477196A CN 202011165061 A CN202011165061 A CN 202011165061A CN 114477196 A CN114477196 A CN 114477196A
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- 238000000034 method Methods 0.000 title claims abstract description 106
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 72
- 229910021485 fumed silica Inorganic materials 0.000 title claims abstract description 25
- 238000003682 fluorination reaction Methods 0.000 title claims abstract description 17
- ABTOQLMXBSRXSM-UHFFFAOYSA-N silicon tetrafluoride Chemical compound F[Si](F)(F)F ABTOQLMXBSRXSM-UHFFFAOYSA-N 0.000 claims abstract description 48
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims abstract description 46
- 239000007789 gas Substances 0.000 claims abstract description 46
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 43
- 239000000843 powder Substances 0.000 claims abstract description 36
- 239000002253 acid Substances 0.000 claims abstract description 34
- 238000001035 drying Methods 0.000 claims abstract description 32
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 25
- 238000001816 cooling Methods 0.000 claims abstract description 24
- 239000003546 flue gas Substances 0.000 claims abstract description 24
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 23
- 238000004090 dissolution Methods 0.000 claims abstract description 23
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 23
- 238000001179 sorption measurement Methods 0.000 claims abstract description 22
- 238000001556 precipitation Methods 0.000 claims abstract description 21
- 239000000047 product Substances 0.000 claims abstract description 18
- 239000006229 carbon black Substances 0.000 claims abstract description 14
- 238000005243 fluidization Methods 0.000 claims abstract description 14
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 14
- 238000005406 washing Methods 0.000 claims abstract description 14
- 238000000746 purification Methods 0.000 claims abstract description 11
- 239000002244 precipitate Substances 0.000 claims abstract description 8
- 229910001515 alkali metal fluoride Inorganic materials 0.000 claims abstract description 7
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 6
- 239000001257 hydrogen Substances 0.000 claims abstract description 6
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 6
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 21
- 229910052708 sodium Inorganic materials 0.000 claims description 21
- 239000011734 sodium Substances 0.000 claims description 21
- 229910052783 alkali metal Inorganic materials 0.000 claims description 15
- 150000001340 alkali metals Chemical class 0.000 claims description 15
- 239000000446 fuel Substances 0.000 claims description 8
- 229910000040 hydrogen fluoride Inorganic materials 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 6
- 230000018044 dehydration Effects 0.000 claims description 6
- 238000006297 dehydration reaction Methods 0.000 claims description 6
- 239000001301 oxygen Substances 0.000 claims description 6
- 229910052760 oxygen Inorganic materials 0.000 claims description 6
- 229940104869 fluorosilicate Drugs 0.000 claims description 4
- 238000001291 vacuum drying Methods 0.000 claims description 4
- 238000001914 filtration Methods 0.000 claims description 3
- 238000000197 pyrolysis Methods 0.000 claims description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 2
- 229930195733 hydrocarbon Natural products 0.000 claims description 2
- 150000002430 hydrocarbons Chemical class 0.000 claims description 2
- 239000007788 liquid Substances 0.000 claims description 2
- 229910052744 lithium Inorganic materials 0.000 claims description 2
- 230000014759 maintenance of location Effects 0.000 claims description 2
- 229910052700 potassium Inorganic materials 0.000 claims description 2
- 239000011591 potassium Substances 0.000 claims description 2
- 235000012239 silicon dioxide Nutrition 0.000 claims description 2
- 239000004215 Carbon black (E152) Substances 0.000 claims 1
- 239000000243 solution Substances 0.000 abstract description 20
- 239000002994 raw material Substances 0.000 abstract description 12
- 238000006243 chemical reaction Methods 0.000 abstract description 10
- 239000000779 smoke Substances 0.000 abstract description 3
- 239000011259 mixed solution Substances 0.000 abstract description 2
- FFBHFFJDDLITSX-UHFFFAOYSA-N benzyl N-[2-hydroxy-4-(3-oxomorpholin-4-yl)phenyl]carbamate Chemical compound OC1=C(NC(=O)OCC2=CC=CC=C2)C=CC(=C1)N1CCOCC1=O FFBHFFJDDLITSX-UHFFFAOYSA-N 0.000 description 17
- 239000007787 solid Substances 0.000 description 9
- 239000006227 byproduct Substances 0.000 description 6
- 208000005156 Dehydration Diseases 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000007795 chemical reaction product Substances 0.000 description 4
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 description 3
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 3
- 229910052731 fluorine Inorganic materials 0.000 description 3
- 239000011737 fluorine Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 239000005049 silicon tetrachloride Substances 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 239000002686 phosphate fertilizer Substances 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000007791 dehumidification Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 150000004673 fluoride salts Chemical class 0.000 description 1
- 238000006459 hydrosilylation reaction Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
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- 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
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
- C01B33/181—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Silicon Compounds (AREA)
Abstract
The invention discloses a method for preparing fumed silica by a fluorination method. The method mainly comprises the working procedures of cooling absorption-dissolution, adsorption precipitation, washing purification, drying, fluidized decomposition and flame synthesis, and specifically comprises the following steps: taking high-quality silica powder as a raw material, cooling and absorbing smoke generated by silicon tetrafluoride flame synthesis to obtain hydrofluoric acid in solution, and carrying out dissolution reaction to obtain a fluosilicic acid solution; then, adding the fluidized decomposition powder product into a fluosilicic acid solution to enable fluosilicic acid and alkali metal fluoride to form fluosilicate precipitate and hydrofluoric acid, and circularly returning the fluosilicic acid solution for cooling, absorbing and dissolving; after being washed, purified, filtered and dried, the fluosilicate is decomposed in a fluidization way to obtain silicon tetrafluoride gas and powder products; the silicon tetrafluoride gas is purified and then synthesized into gas phase white carbon black by a hydrogen flame method, and the generated flue gas is cooled and absorbed to form hydrofluoric acid and fluosilicic acid mixed solution which is circularly used for dissolving the silica.
Description
Technical Field
The invention relates to the field of chemical industry and materials, in particular to a method for preparing fumed silica by a fluorination method.
Background
Fumed silica (nano-silica) is one of the most important high-tech superfine inorganic new materials, and has outstanding importance in numerous disciplines and fields due to its small particle size, large surface area, strong surface adsorption, large surface energy, high chemical purity, good dispersibility, thermal resistance, electrical resistance and other specific properties, and its excellent stability, reinforcement, thickening and thixotropy. Silicon tetrachloride is mainly used as a raw material in industry, and the production is carried out by adopting a hydrogen flame method and high-temperature flame synthesis. For example, chinese patent CN1282603C discloses that fumed silica is synthesized by a high-temperature flame method using silicon tetrachloride as a raw material, but the cost of the silicon tetrachloride raw material is high, and the by-product hydrochloric acid is difficult to treat. Therefore, a new technology of more efficient and clean fumed silica is yet to be developed.
Of the many routes of development, the hydrosilylation process is considered to be one of the most promising routes. The silicon tetrafluoride gas can be obtained by decomposing a byproduct, namely fluosilicic acid or sodium fluosilicate, in the phosphate fertilizer industry, is easy to purify to the high purity required by the production of the white carbon black, and the hydrogen fluoride byproduct generated by synthesizing the white carbon black has good market demand. For example, in chinese patent CN102351150B, coarse silicon tetrafluoride by-produced from phosphate fertilizer is used as a silicon source, and after dust removal and dehumidification, the silicon source reacts with water vapor to prepare fumed silica. However, this route has three prominent problems: (1) if the sodium fluosilicate is used for decomposing to obtain the silicon tetrafluoride gas, the problem of adhesion of materials decomposed at high temperature due to incomplete low-temperature decomposition exists, and a complex decomposition method needs to be further developed and adopted, which is specifically described in the Chinese patent application CN 110683548A; (2) the thermodynamic equilibrium conversion rate of a white carbon black preparation reaction system by a silicon tetrafluoride hydrogen flame method is low (only 70 percent at 1500 ℃), and a difficult-to-treat fluosilicic acid solution can be generated by the absorption treatment of flue gas after powder is separated and recovered; (3) flue gas generated by decomposing silicon tetrafluoride and hydrogen fluoride products generated by treating fluosilicic acid need to be subjected to refining/dehydration treatment and the like, and then the products are sold, so that the operation cost and market uncertainty risk factors of white carbon black manufacturers are increased.
In conclusion, the existing fumed silica preparation technology has the problems of low conversion rate, high cost caused by refining of discharged flue gas and the like. Therefore, the development of green, environment-friendly and economic production technology has important significance through technological innovation.
Disclosure of Invention
Aiming at the problems of the existing gas-phase white black preparation technology, the invention provides a method for preparing gas-phase white carbon black by a fluorination method. The whole process takes high-quality silica as a raw material, and three wastes and byproducts are effectively avoided through fluorine medium circulation, so that low-cost and high-efficiency clean production of the fumed silica is realized. Therefore, the method has the characteristics of environmental friendliness, low energy consumption, high product added value and the like.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for preparing fumed silica by a fluorination method comprises the following steps: the method comprises a cooling absorption-dissolution process 1, an adsorption precipitation process 2, a washing and purification process 3, a drying process 4, a fluidization decomposition process 5 and a flame synthesis process 6, and specifically comprises the following steps:
1) sending the flue gas generated in the flame synthesis process 6 into a cooling absorption-dissolution process 1, so that the hydrogen fluoride gas and the residual silicon tetrafluoride gas in the flue gas are dissolved and absorbed to form hydrofluoric acid and fluorosilicic acid solution, and the hydrofluoric acid reacts with high-quality silica to form fluosilicic acid;
2) sending the fluosilicic acid solution obtained in the cooling absorption-dissolution process 1 into an adsorption precipitation process 2, adding a decomposition powder product generated in a fluidization decomposition process 5, so that silicon tetrafluoride and alkali metal fluoride in the fluosilicic acid form alkali metal fluosilicate precipitates, and circulating the hydrofluoric acid solution back to the cooling absorption-dissolution process 1;
3) sending the alkali metal fluosilicate precipitate obtained in the adsorption precipitation step 2 into a washing and purification step 3, carrying out washing and purification treatment, and then filtering to obtain pure alkali metal fluosilicate powder;
4) sending the fluosilicate powder obtained in the washing and purifying step 3 into a drying step 4, and carrying out drying and dehydration treatment to obtain dry alkali metal fluosilicate powder;
5) feeding the alkali metal fluosilicate powder obtained in the drying process 4 into a fluidization decomposition process 5, realizing fluidization partial decomposition of fluosilicate by using silicon tetrafluoride circulating gas to obtain silicon tetrafluoride gas, and feeding the decomposed powder product into an adsorption precipitation process 2;
6) and (3) purifying the silicon tetrafluoride gas obtained in the fluidized decomposition step 5, then sending the purified silicon tetrafluoride gas into a flame synthesis step 6, obtaining white carbon black powder and flue gas through pyrolysis, and sending the hydrogen fluoride gas and the residual silicon tetrafluoride gas in the flue gas into a cooling absorption-dissolution step 1.
Preferably, the mass content of the silicon dioxide in the silica raw material in the absorption-dissolution process 1 is not less than 99.0%, and the particle size range is 0.1-2.0 mm.
Preferably, the alkali metal in the alkali metal fluoride salt is one or a combination of lithium, potassium, sodium and the like.
Preferably, the dehydration drying process 3 adopts one or more of vacuum drying, fixed bed drying and fluidized bed drying, the dehydration drying temperature is 20-200 ℃, and the drying time is 0.1-36 h.
Preferably, the low-temperature decomposition process 4 adopts a fluidized bed reactor, the fluidized gas is silicon tetrafluoride gas, the decomposition temperature is 400-700 ℃, and the retention time is 0.5-3.0 h.
Preferably, the fuel used in the flame synthesis process 5 may be hydrogen and/or carbon monoxide, or may be one or a combination of gaseous or liquid combustible hydrocarbons, the temperature is 1000 to 2000 ℃, and the molar ratio of the silicon tetrafluoride gas, the oxygen and the fuel is 1:2 to 15:1.5 to 8.
The method takes high-quality silica powder as a raw material, utilizes the flue gas generated by silicon tetrafluoride flame synthesis to cool and absorb to obtain hydrofluoric acid in solution, and carries out dissolution reaction to obtain fluosilicic acid solution; then, adding the fluidized decomposition powder product into a fluosilicic acid solution to enable fluosilicic acid and alkali metal fluoride to form fluosilicate precipitate and hydrofluoric acid, and circularly returning the fluosilicic acid solution for cooling, absorbing and dissolving; after being washed, purified, filtered and dried, fluosilicate is subjected to fluidized decomposition to obtain silicon tetrafluoride gas and powder products; the silicon tetrafluoride gas is purified and then synthesized into gas phase white carbon black by a hydrogen flame method, and the generated flue gas is cooled and absorbed to form hydrofluoric acid and fluosilicic acid mixed solution which is circularly used for dissolving the silica. The whole process takes high-quality silica as a raw material, and three wastes and byproducts are effectively avoided through fluorine medium circulation, so that low-cost and high-efficiency clean production of the fumed silica is realized.
Compared with the prior art, the invention has the following outstanding advantages:
(1) the low-temperature decomposition process adopts a fluidization technology to strengthen the heat and mass transfer process of the sodium fluosilicate decomposition process, has a faster reaction rate under the condition of lower temperature, and effectively avoids melting agglomeration;
(2) the problems of utilization of fluosilicic acid generated in the absorption process and solid decomposition products generated in the decomposition process are effectively solved, and the cyclic utilization of the fluorine medium is realized;
(3) the whole process effectively avoids the generation of three wastes and byproducts.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.
FIG. 1 is a schematic flow chart of a method for preparing fumed silica by a fluorination method according to the present invention;
reference numerals: 1. cooling, absorbing and dissolving, 2, adsorbing and precipitating, 3, washing and purifying, 4, drying, 5, fluidizing and decomposing, 6 and flame synthesizing.
Detailed Description
Any feature disclosed in this specification may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. Unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features. The description is only for the purpose of facilitating understanding of the present invention and should not be construed as specifically limiting the present invention.
The invention is described in further detail below with reference to the figures and the detailed description.
Example 1
FIG. 1 is a schematic flow chart of a method for preparing fumed silica by a fluorination method according to the present invention. Referring to fig. 1, a method for preparing fumed silica by a fluorination method comprises the following steps: the cooling absorption-dissolution process 1, the adsorption precipitation process 2, the washing purification process 3, the drying process 4, the fluidization decomposition process 5 and the flame synthesis process 6 are specifically carried out according to the following steps:
1) sending the flue gas generated in the flame synthesis process 6 into a cooling absorption-dissolution process 1, so that the hydrogen fluoride gas and the residual silicon tetrafluoride gas in the flue gas are dissolved and absorbed to form hydrofluoric acid and fluorosilicic acid solution, and the hydrofluoric acid reacts with high-quality silica to form fluosilicic acid;
2) the fluosilicic acid solution obtained in the cooling absorption-dissolution process 1 is sent to an adsorption precipitation process 2, and a decomposition powder product generated in a fluidization decomposition process 5 is added to enable silicon tetrafluoride and alkali metal fluoride in the fluosilicic acid to form alkali metal fluosilicate precipitate, and the hydrofluoric acid solution is circularly returned to the cooling absorption-dissolution process 1;
3) sending the alkali metal fluosilicate precipitate obtained in the adsorption precipitation step 2 into a washing and purification step 3 for washing and purification treatment, and then filtering to obtain pure fluosilicate powder;
4) sending the fluorosilicate powder obtained in the washing and purifying step 3 to a drying step 4, and carrying out drying and dehydration treatment to obtain dry fluorosilicate powder;
5) the fluosilicate powder obtained in the drying step 4 is sent to a fluidized decomposition step 5, the fluidized part of the fluosilicate is decomposed by utilizing the silicon tetrafluoride circulating gas to obtain silicon tetrafluoride gas, and the decomposed powder product is sent to an adsorption precipitation step 2;
6) and (3) purifying the silicon tetrafluoride gas obtained in the fluidized decomposition step 5, then sending the purified silicon tetrafluoride gas into a flame synthesis step 6, obtaining white carbon black powder and flue gas through pyrolysis, and sending the hydrogen fluoride gas and the residual silicon tetrafluoride gas in the flue gas into a cooling absorption-dissolution step 1.
Example 2
In this embodiment, the method for preparing fumed silica by using the fluorination method described in embodiment 1 is adopted. The method comprises the following steps of (1) sending silicon dioxide powder with the mass content of 99.0% and the particle size of 0.5mm serving as a raw material to a cooling-absorbing dissolving process 1, and reacting with hydrofluoric acid solution obtained by absorbing flue gas in a flame synthesis process 6 to form fluosilicic acid; then sending fluosilicic acid into an adsorption precipitation process 2 to react with the solid decomposition product of a low-temperature decomposition process 4 to obtain sodium fluosilicate; sending sodium fluosilicate into a drying process 3, and drying for 5 hours at 100 ℃ in a fixed bed to obtain dry sodium fluosilicate powder; sending the dried sodium fluosilicate powder into a fluidization reaction process 5, reacting for 3.0h at 400 ℃, sending the obtained solid reaction product into an adsorption precipitation process 2, dedusting and purifying the silicon tetrafluoride gas generated by decomposition, then sending the silicon tetrafluoride gas into a flame synthesis process 6, decomposing and oxidizing at 1500 ℃ under the condition that the molar ratio of the silicon tetrafluoride to oxygen to the fuel is 1:5:5 to obtain gas-phase white carbon black, and sending the generated flue gas into a cooling absorption-dissolution process 1.
Example 3
In this embodiment, the method for preparing fumed silica by using the fluorination method described in embodiment 1 is adopted. The method comprises the following steps of (1) sending silicon dioxide powder with the mass content of 99.4% and the particle size of 2.0mm serving as a raw material to a cooling-absorbing dissolving process 1, and reacting with hydrofluoric acid solution obtained by absorbing flue gas in a flame synthesis process 6 to form fluosilicic acid; then sending fluosilicic acid into an adsorption precipitation process 2 to react with the solid decomposition product of a low-temperature decomposition process 4 to obtain sodium fluosilicate; sending sodium fluosilicate into a drying process 3, and drying in a fluidized bed at 200 ℃ for 0.1h to obtain dry sodium fluosilicate powder; sending the dried sodium fluosilicate powder into a fluidization reaction process 5, reacting for 2.0h at 500 ℃, sending the obtained solid reaction product into an adsorption precipitation process 2, dedusting and purifying the silicon tetrafluoride gas generated by decomposition, then sending the silicon tetrafluoride gas into a flame synthesis process 6, decomposing and oxidizing at the temperature of 1000 ℃ under the condition that the molar ratio of the silicon tetrafluoride to oxygen to the fuel is 1:10:8 to obtain gas-phase white carbon black, and sending the generated flue gas into a cooling absorption-dissolution process 1.
Example 4
In this embodiment, the method for preparing fumed silica by using the fluorination method described in embodiment 1 is adopted. The method comprises the following steps of (1) sending silicon dioxide powder with the mass content of 99.5% and the particle size of 0.1mm serving as a raw material to a cooling-absorbing dissolving process 1, and reacting the silicon dioxide powder with a hydrofluoric acid solution obtained by absorbing smoke in a flame synthesis process 6 to form fluosilicic acid; then sending fluosilicic acid into an adsorption precipitation process 2 to react with the solid decomposition product of a low-temperature decomposition process 4 to obtain sodium fluosilicate; sending sodium fluosilicate into a drying process 3, and drying in a vacuum drying oven at 20 ℃ for 36h to obtain dry sodium fluosilicate powder; sending the dried sodium fluosilicate powder into a fluidization reaction process 5, reacting for 3.0h at 400 ℃, sending the obtained solid reaction product into an adsorption precipitation process 2, dedusting and purifying the silicon tetrafluoride gas generated by decomposition, then sending the silicon tetrafluoride gas into a flame synthesis process 6, decomposing and oxidizing at 2000 ℃ under the condition that the molar ratio of the silicon tetrafluoride to oxygen to the fuel is 1:4:2 to obtain gas-phase white carbon black, and sending the generated flue gas into a cooling absorption-dissolution process 1.
Example 5
In this embodiment, the method for preparing fumed silica by using the fluorination method described in embodiment 1 is adopted. The method comprises the following steps of (1) sending silicon dioxide powder with the mass content of 99.0% and the particle size of 1.0mm serving as a raw material to a cooling-absorbing dissolving process 1, and reacting the silicon dioxide powder with a hydrofluoric acid solution obtained by absorbing smoke in a flame synthesis process 6 to form fluosilicic acid; then sending fluosilicic acid into an adsorption precipitation process 2 to react with the solid decomposition product of a low-temperature decomposition process 4 to obtain sodium fluosilicate; sending sodium fluosilicate into a drying process 3, and drying for 24 hours in a vacuum drying oven at 100 ℃ to obtain dry sodium fluosilicate powder; feeding the dried sodium fluosilicate powder into a fluidization reaction process 5, reacting for 0.5h at 700 ℃, feeding the obtained solid reaction product into an adsorption precipitation process 2, performing dust removal and purification on the decomposed silicon tetrafluoride gas, feeding the silicon tetrafluoride gas into a flame synthesis process 6, performing decomposition and oxidation at 1500 ℃ under the condition that the molar ratio of the silicon tetrafluoride to oxygen to the fuel is 1:15:8, obtaining gas-phase white carbon black, and feeding the generated flue gas into a cooling absorption-dissolution process 1.
The method can be realized by upper and lower limit values and interval values of intervals of process parameters (such as temperature, time and the like), and embodiments are not listed.
Conventional technical knowledge in the art can be used for the details which are not described in the present invention.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (6)
1. A method for preparing fumed silica by a fluorination method comprises the following steps: the method comprises a cooling absorption-dissolution process (1), an adsorption precipitation process (2), a washing and purification process (3), a drying process (4), a fluidization decomposition process (5) and a flame synthesis process (6), and specifically comprises the following steps:
1) sending the flue gas generated in the flame synthesis process (6) into a cooling absorption-dissolution process (1) to dissolve and absorb hydrogen fluoride gas and residual silicon tetrafluoride gas in the flue gas to form hydrofluoric acid and fluorosilicic acid solution, wherein the hydrofluoric acid reacts with added silica to form fluorosilicic acid;
2) sending the fluosilicic acid solution obtained in the cooling absorption-dissolution process (1) into an adsorption precipitation process (2), adding a decomposition powder product generated in a fluidization decomposition process (5), so that silicon tetrafluoride and alkali metal fluoride in the fluosilicic acid form alkali metal fluosilicate precipitate, and circularly returning the hydrofluoric acid solution to the cooling absorption-dissolution process (1);
3) sending the alkali metal fluosilicate precipitate obtained in the adsorption precipitation step (2) into a washing and purification step (3), carrying out washing and purification treatment, and then filtering to obtain pure alkali metal fluosilicate powder;
4) feeding the alkali metal fluorosilicate powder obtained in the washing and purifying step (3) to a drying step (4), and drying and dehydrating to obtain dry alkali metal fluorosilicate powder;
5) feeding the alkali metal fluosilicate powder obtained in the drying step (4) into a fluidized decomposition step (5), realizing fluidized decomposition of fluosilicate by using silicon tetrafluoride circulating gas to obtain silicon tetrafluoride gas, and feeding the decomposed powder product into an adsorption precipitation step (2);
6) and (3) purifying the silicon tetrafluoride gas obtained in the fluidized decomposition step (5), then sending the silicon tetrafluoride gas into a flame synthesis step (6), obtaining white carbon black powder and flue gas through pyrolysis, and sending the hydrogen fluoride gas and the residual silicon tetrafluoride gas in the flue gas into a cooling absorption-dissolution step (1).
2. The method for preparing fumed silica according to claim 1, wherein the silica has a silicon dioxide content of not less than 98.0% by mass and a particle size of 0.01-2.0 mm.
3. The method for preparing fumed silica according to claim 1, wherein the alkali metal of the alkali metal fluoride is selected from one or more of lithium, potassium and sodium.
4. The method for preparing fumed silica by fluorination according to claim 1, wherein one or more of vacuum drying, fixed bed drying and fluidized bed drying is adopted in the drying step (4), the dehydration drying temperature is 0-200 ℃, and the drying time is 0.1-36 h.
5. The method for preparing fumed silica by fluorination according to claim 1, wherein the fluidized decomposition step (5) adopts a fluidized bed reactor, the fluidized gas is silicon tetrafluoride gas, the decomposition temperature is 400-700 ℃, and the retention time is 0.5-3.0 h.
6. The method for preparing fumed silica by fluorination according to claim 1, wherein the fuel used in the flame synthesis step (5) is one or a combination of hydrogen and gaseous or liquid combustible hydrocarbon, the temperature is 1200-2000 ℃, and the molar ratio of silicon tetrafluoride gas, oxygen and fuel is 1: 2-15: 1.5-8.
Priority Applications (1)
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| CN85101690A (en) * | 1984-05-15 | 1987-01-31 | 住友电器工业株式会社 | Method for producing optical fiber glass preform |
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| CN102220036A (en) * | 2011-06-02 | 2011-10-19 | 北京化工大学 | Method for preparing white carbon black modified by silane coupling agent |
| US20140080752A1 (en) * | 2012-09-17 | 2014-03-20 | Tocad America, Inc. | White Carbon Black Formulations and Methods |
| CN106219557A (en) * | 2016-07-08 | 2016-12-14 | 黄冈师范学院 | A kind of technique preparing gas-phase silica for raw material low temperature with SILICA FUME/diatomite in powder/albumen stone powder |
| CN110683548A (en) * | 2018-07-04 | 2020-01-14 | 中国科学院过程工程研究所 | Method for efficiently producing silicon tetrafluoride and sodium fluoride by using sodium fluosilicate |
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| CN85101690A (en) * | 1984-05-15 | 1987-01-31 | 住友电器工业株式会社 | Method for producing optical fiber glass preform |
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| CN102220036A (en) * | 2011-06-02 | 2011-10-19 | 北京化工大学 | Method for preparing white carbon black modified by silane coupling agent |
| US20130131357A1 (en) * | 2011-06-02 | 2013-05-23 | Beijing University Of Chemical Technology | Method for preparing white carbon black modified by silane coupling agent |
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