CN111908425A - Process for removing arsenic in process of preparing anhydrous hydrogen fluoride by using fluosilicic acid method - Google Patents
Process for removing arsenic in process of preparing anhydrous hydrogen fluoride by using fluosilicic acid method Download PDFInfo
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- 239000002253 acid Substances 0.000 title claims abstract description 108
- 229910052785 arsenic Inorganic materials 0.000 title claims abstract description 86
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 title claims abstract description 86
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 title claims abstract description 65
- 229910000040 hydrogen fluoride Inorganic materials 0.000 title claims abstract description 63
- 238000000034 method Methods 0.000 title claims abstract description 48
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 69
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 47
- 238000006243 chemical reaction Methods 0.000 claims abstract description 34
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 claims abstract description 28
- 238000001035 drying Methods 0.000 claims abstract description 23
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 22
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 20
- 230000001590 oxidative effect Effects 0.000 claims abstract description 13
- CQXADFVORZEARL-UHFFFAOYSA-N Rilmenidine Chemical compound C1CC1C(C1CC1)NC1=NCCO1 CQXADFVORZEARL-UHFFFAOYSA-N 0.000 claims abstract description 11
- 230000003197 catalytic effect Effects 0.000 claims abstract description 10
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 9
- 239000003054 catalyst Substances 0.000 claims abstract description 7
- 238000012216 screening Methods 0.000 claims abstract description 7
- 230000003647 oxidation Effects 0.000 claims abstract description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 49
- 239000007789 gas Substances 0.000 claims description 33
- 239000012071 phase Substances 0.000 claims description 16
- 239000002994 raw material Substances 0.000 claims description 15
- 238000001914 filtration Methods 0.000 claims description 14
- 238000002156 mixing Methods 0.000 claims description 14
- 238000000926 separation method Methods 0.000 claims description 14
- 239000000463 material Substances 0.000 claims description 11
- 239000007787 solid Substances 0.000 claims description 11
- ABTOQLMXBSRXSM-UHFFFAOYSA-N silicon tetrafluoride Chemical compound F[Si](F)(F)F ABTOQLMXBSRXSM-UHFFFAOYSA-N 0.000 claims description 10
- 239000011148 porous material Substances 0.000 claims description 9
- 239000012535 impurity Substances 0.000 claims description 8
- 239000007791 liquid phase Substances 0.000 claims description 8
- GCPXMJHSNVMWNM-UHFFFAOYSA-N arsenous acid Chemical compound O[As](O)O GCPXMJHSNVMWNM-UHFFFAOYSA-N 0.000 claims description 7
- 238000000746 purification Methods 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 238000012856 packing Methods 0.000 claims description 6
- 230000002572 peristaltic effect Effects 0.000 claims description 6
- 230000007797 corrosion Effects 0.000 claims description 5
- 238000005260 corrosion Methods 0.000 claims description 5
- 238000002425 crystallisation Methods 0.000 claims description 5
- 230000008025 crystallization Effects 0.000 claims description 5
- 238000005516 engineering process Methods 0.000 claims description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 4
- 238000010521 absorption reaction Methods 0.000 claims description 4
- 230000032683 aging Effects 0.000 claims description 4
- 230000000903 blocking effect Effects 0.000 claims description 4
- 239000007788 liquid Substances 0.000 claims description 4
- 239000011259 mixed solution Substances 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 4
- 229910052710 silicon Inorganic materials 0.000 claims description 4
- 239000010703 silicon Substances 0.000 claims description 4
- 239000002893 slag Substances 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 3
- 229960002594 arsenic trioxide Drugs 0.000 claims description 3
- 159000000007 calcium salts Chemical class 0.000 claims description 3
- 125000004122 cyclic group Chemical group 0.000 claims description 3
- 238000000354 decomposition reaction Methods 0.000 claims description 3
- 238000009826 distribution Methods 0.000 claims description 3
- 238000002309 gasification Methods 0.000 claims description 3
- 229910002804 graphite Inorganic materials 0.000 claims description 3
- 239000010439 graphite Substances 0.000 claims description 3
- 239000011859 microparticle Substances 0.000 claims description 3
- 239000004033 plastic Substances 0.000 claims description 3
- 238000005086 pumping Methods 0.000 claims description 3
- 239000000741 silica gel Substances 0.000 claims description 3
- 229910002027 silica gel Inorganic materials 0.000 claims description 3
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 3
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 3
- 238000007865 diluting Methods 0.000 claims description 2
- 238000003795 desorption Methods 0.000 claims 1
- 238000001471 micro-filtration Methods 0.000 abstract description 6
- 238000009835 boiling Methods 0.000 abstract description 4
- 229940000489 arsenate Drugs 0.000 abstract description 3
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- 230000002378 acidificating effect Effects 0.000 description 3
- 229910004014 SiF4 Inorganic materials 0.000 description 2
- 150000001495 arsenic compounds Chemical class 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- DJHGAFSJWGLOIV-UHFFFAOYSA-N Arsenic acid Chemical compound O[As](O)(O)=O DJHGAFSJWGLOIV-UHFFFAOYSA-N 0.000 description 1
- GOLCXWYRSKYTSP-UHFFFAOYSA-N Arsenious Acid Chemical compound O1[As]2O[As]1O2 GOLCXWYRSKYTSP-UHFFFAOYSA-N 0.000 description 1
- 229910017050 AsF3 Inorganic materials 0.000 description 1
- ATHWXKDKFYQXTM-UHFFFAOYSA-N F.[As] Chemical compound F.[As] ATHWXKDKFYQXTM-UHFFFAOYSA-N 0.000 description 1
- 229910003638 H2SiF6 Inorganic materials 0.000 description 1
- 229910004074 SiF6 Inorganic materials 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 229940000488 arsenic acid Drugs 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 229920002313 fluoropolymer Polymers 0.000 description 1
- 239000004811 fluoropolymer Substances 0.000 description 1
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000001117 sulphuric acid Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
- ZEFWRWWINDLIIV-UHFFFAOYSA-N tetrafluorosilane;dihydrofluoride Chemical compound F.F.F[Si](F)(F)F ZEFWRWWINDLIIV-UHFFFAOYSA-N 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
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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
- C01B7/00—Halogens; Halogen acids
- C01B7/19—Fluorine; Hydrogen fluoride
- C01B7/191—Hydrogen fluoride
- C01B7/193—Preparation from silicon tetrafluoride, fluosilicic acid or fluosilicates
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B7/00—Halogens; Halogen acids
- C01B7/19—Fluorine; Hydrogen fluoride
- C01B7/191—Hydrogen fluoride
- C01B7/195—Separation; Purification
- C01B7/196—Separation; Purification by distillation
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Silicon Compounds (AREA)
Abstract
The invention relates to the technical field of dearsenification of anhydrous hydrogen fluoride, in particular to a process for removing arsenic in the process of preparing the anhydrous hydrogen fluoride by a fluosilicic acid method, which comprises the following steps: pre-purifying fluosilicic acid; step two: pre-oxidizing trivalent arsenic in fluosilicic acid; step three: performing further catalytic oxidation on trivalent arsenic by using hydrogen peroxide through microfiltration II; step four: a concentration and reaction system; step five: screening silicon dioxide; step six: gasifying and decomposing; step seven: a hydrogen fluoride reboiling system and a drying and separating system; step eight: drying and purifying, and has the beneficial effects that: the arsenic in the fluosilicic acid is oxidized into pentavalent arsenic by adding hydrogen peroxide and manganese dioxide as a catalyst under the conditions of normal temperature and acidity, and because the boiling point of an arsenate radical is 160 ℃, a small amount of trivalent arsenic is not enough to react with hydrogen fluoride to generate arsenic trifluoride which is difficult to separate, the oxidation operation and cost are low, the mass production is convenient, and the obtained anhydrous hydrogen fluoride has high purity and small harm.
Description
Technical Field
The invention relates to the technical field of arsenic removal of anhydrous hydrogen fluoride, in particular to a process for removing arsenic in the process of preparing anhydrous hydrogen fluoride by a fluorosilicic acid method.
Background
At present, the product obtained by preparing anhydrous hydrogen fluoride from fluosilicic acid has high impurity content, and the impurity removal is reported in a few researches, but the case of industrial removal is rare. Van Fulan sky company is the exclusive unit of realizing the industrial application of fluorosilicic acid preparation anhydrous hydrogen fluoride technique, and impurity can influence product quality, is unfavorable for the use of product in various hydrogen fluoride downstream trades, and anhydrous hydrogen fluoride edulcoration is the common difficult problem of trade nature, and other villiaumite, fluoropolymer are produced to the hydrogen fluoride and have great influence to product quality equally.
The arsenic content of the existing raw material fluosilicic acid is high, and can be over 50ppm when the arsenic content is high, and the arsenic removal effect of a subsequent system is limited, so that the arsenic content of a rectification system is high, and mainly AsF is used3The form exists. Arsenic in anhydrous hydrogen fluoride is generally present as a trivalent ion, whereas AsF3The boiling point of the arsenic compound is very close to that of hydrofluoric acid, the normal pressure is 57.8 ℃, and the arsenic compound is difficult to be effectively separated by rectification after being rectified, so that the content of As in the product is high.
Disclosure of Invention
The invention aims to provide a technology for removing arsenic in the process of preparing anhydrous hydrogen fluoride by a fluorosilicic acid method, so as to solve the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme:
a technology for removing arsenic in the process of preparing anhydrous hydrogen fluoride by a fluosilicic acid method comprises the following steps:
the method comprises the following steps: pre-purifying fluosilicic acid, namely pre-purifying raw material fluosilicic acid by a filter on a micro-pore filter I, intercepting a small amount of solid micro particles such as silica gel, calcium salt and the like in the raw material fluosilicic acid in a filtering mode, and screening to avoid solid impurities from blocking a subsequent micro-pore filter II, so as to obtain high-purity fluosilicic acid;
step two: pre-oxidizing trivalent arsenic in fluosilicic acid, namely placing the fluosilicic acid which is pre-purified by the micro-pore filtration I in the step I into a mixing tank consisting of fluosilicic acid and hydrogen peroxide under the conditions of normal temperature and acidity, carrying out primary oxidation reaction on the fluosilicic acid, and pre-oxidizing the fluosilicic acid in the mixing tank for 30-60min by adding the hydrogen peroxide, so that nearly 50% of trivalent arsenic in the fluosilicic acid is oxidized into pentavalent arsenic;
step three: further catalytic oxidation of trivalent arsenic by hydrogen peroxide in the microporous filter II, adding a manganese dioxide catalyst into a chamber of the microporous filter II, pumping the fluosilicic acid pre-oxidized in the step II into the microporous filter II through a peristaltic pump, and further oxidizing the trivalent arsenic into pentavalent arsenic by the unreacted trivalent arsenic and hydrogen peroxide components in the step II through the catalytic action of manganese dioxide to obtain the fluosilicic acid with the conversion rate of 80-90%;
step four: a concentration and reaction system, wherein fluosilicic acid after being oxidized and filtered in the third step is sent into a fluosilicic acid concentration system through a buffer tank and a feeding pump, and as the dilute fluosilicic acid absorbs silicon tetrafluoride gas generated by the reaction system to continuously release heat, trivalent arsenic in a fluosilicic acid system further reacts with excessive hydrogen peroxide in the concentration system at the temperature of 40-60 ℃, and the conversion rate of the trivalent arsenic into pentavalent arsenic is close to 95%;
step five: screening silicon dioxide, wherein concentrated fluosilicic acid generates silicon dioxide solid, after the silicon dioxide grows up through a silicon dioxide aging crystallization tank, the mixed solution of fluosilicic acid and silicon dioxide is sent into a plate-and-frame filter for filtration and separation, and part of pentavalent arsenic is separated from silicon slag and is about 5 to 10 percent;
step six: gasifying and decomposing, mixing the concentrated fluosilicic acid filtered by the plate and frame filter in a reaction system with high-temperature sulfuric acid dried and absorbed by hydrogen fluoride, reacting, diluting with concentrated sulfuric acid to release heat, decomposing the concentrated fluosilicic acid, introducing the generated gas-phase silicon tetrafluoride into the concentration system for cyclic absorption, and obtaining a liquid phase H2SO4HF and H2A mixed system of O;
step seven: a hydrogen fluoride reboiling system and a drying separation system, wherein a liquid phase mixed system obtained from the sixth reactor is heated to 150-168 ℃ by a reboiler, then hydrogen fluoride is separated by a flash evaporator, and simultaneously the generated dilute sulfuric acid is separated from the system after being cooled;
step eight: drying and purifying, namely fully absorbing the flash-evaporated hydrogen fluoride gas phase system containing water vapor by a hydrogen fluoride drying tower and cold concentrated sulfuric acid gas liquid, wherein the temperature of the top of the drying tower is controlled to be 60-80 ℃, the temperature of the concentrated sulfuric acid is 25-30 ℃, most of water is absorbed, the gas phase of the drying tower is mainly hydrogen fluoride gas, and the high-purity industrial anhydrous hydrogen fluoride is obtained after subsequent separation and purification, wherein the arsenic content is reduced to below 6 ppm.
Preferably, the adding amount of the hydrogen peroxide in the mixing tank in the second step is determined according to the content of arsenic in the raw material fluosilicic acid, and the adding proportion of the hydrogen peroxide to the fluosilicic acid is between 0.1 and 1 percent.
Preferably, the manganese dioxide catalytic particles are loaded at 0.5m in the third step, and the pressure of the peristaltic pump is 0.3 MPa.
Preferably, the reaction temperature in the gasification decomposition reactor in the sixth step is 85 ℃ to 135 ℃, and the reactor is high-temperature corrosion resistant steel lining plastic equipment.
Preferably, the dry absorbed hydrogen fluoride gas phase system in the step eight contains a very small amount of arsenic trifluoride gas, and the arsenic trifluoride gas reacts with the sulfuric acid absorbing moisture at the tower bottom to generate arsenous acid, and the arsenous acid enters the reactor and is finally carried out from the dilute sulfuric acid.
Preferably, in the first step, the concentration of the raw material fluosilicic acid is between 15 and 30 percent, the arsenic content is between 10 and 50ppm, and the hydrogen peroxide content in the hydrogen peroxide is between 25 and 40 percent.
Preferably, a heat exchanger and a reaction tower are required to be used in the removing process, the heat exchanger is made of graphite or silicon carbide and other corrosion-resistant materials, the tower packing of the reaction tower is structured packing, the support disc, the distribution disc and the wire mesh demister of the reaction tower are made of pure tetrafluoro materials, and the support ring and the negative pressure ring are made of special materials.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the invention, hydrogen peroxide is added under normal temperature and acidic conditions, manganese dioxide is added as a catalyst, arsenic in fluosilicic acid is oxidized into pentavalent arsenic, the boiling point of arsenate radical is 160 ℃, the temperature of the outlet of a hydrogen fluoride drying tower is controlled to be lower than 120 ℃ by improving the tower efficiency, a small amount of trivalent arsenic is not enough to react with hydrogen fluoride under the condition to generate difficultly-separated arsenic trifluoride, the oxidation operation and cost are low, and the mass production is facilitated;
2. the invention carries a large amount of arsenic in the fluosilicic acid out of the dilute sulphuric acid in the form of arsenic acid and arsenious acid, and a small amount of arsenic exists in a gaseous state as a small amount of AsF after entering a hydrogen fluoride separation and purification system5Light components can be removed through rectification, high boiling point impurities such as arsenate radicals and the like are removed through rectification, a large amount of arsenic is removed from dilute sulfuric acid after system optimization, the content of the obtained industrial anhydrous arsenic hydrofluoride is reduced to below 6ppm, the purity is high, and the harm is small.
Drawings
FIG. 1 is a process system flow diagram of the present invention;
FIG. 2 is a flow chart of pre-purification of fluorosilicic acid;
FIG. 3 is a flow diagram of a silica filtration and crystallization system;
FIG. 4 is a flow chart of a hydrogen fluoride separation and purification system.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1-4, the present invention provides a technical solution:
a technology for removing arsenic in the process of preparing anhydrous hydrogen fluoride by a fluosilicic acid method comprises the following steps:
the method comprises the following steps: the method comprises the steps of pre-purifying fluosilicic acid, pre-purifying raw material fluosilicic acid through a filter on a micro-pore filtration I, intercepting a small amount of solid micro particles such as silica gel and calcium salt in the raw material fluosilicic acid in a filtering mode, screening, and avoiding solid impurities from blocking a subsequent micro-pore filtration II, so that the fluosilicic acid with high purity is obtained, wherein the concentration of the raw material fluosilicic acid is between 15% and 30%, the arsenic content is between 10ppm and 50ppm, and the hydrogen peroxide content in hydrogen peroxide is between 25% and 40%.
Step two: pre-oxidizing trivalent arsenic in fluosilicic acid, under normal temperature and acidic conditions, placing fluosilicic acid which is pre-purified by a micro-pore filter I in the step I into a mixing tank consisting of fluosilicic acid and hydrogen peroxide, wherein the adding amount of the hydrogen peroxide in the mixing tank is determined according to the content of arsenic in raw material fluosilicic acid, the adding proportion of the hydrogen peroxide and the fluosilicic acid is between 0.1 percent and 1 percent, carrying out preliminary oxidation reaction on the fluosilicic acid, and pre-oxidizing the fluosilicic acid in the mixing tank for 30-60min by adding the hydrogen peroxide, so that nearly 50 percent of the trivalent arsenic in the fluosilicic acid is oxidized into pentavalent arsenic.
Step three: and (2) further catalytically oxidizing trivalent arsenic by hydrogen peroxide in the microfiltration II, adding a manganese dioxide catalyst into a cavity of the microfiltration II, wherein the adding amount of manganese dioxide catalyst particles is 0.5m, pumping the fluosilicic acid preoxidized in the step (2) into the microfiltration II through a peristaltic pump, wherein the pressure of the peristaltic pump is 0.3MPa, and further oxidizing the trivalent arsenic into pentavalent arsenic by the unreacted trivalent arsenic and hydrogen peroxide components under the catalytic action of manganese dioxide in the step (II) to obtain the fluosilicic acid with the conversion rate of 80-90%.
Step four: and in the concentration and reaction system, fluosilicic acid oxidized and filtered in the third step is sent into a fluosilicic acid concentration system through a buffer tank and a material injection pump, and as the dilute fluosilicic acid absorbs silicon tetrafluoride gas generated by the reaction system to continuously release heat, trivalent arsenic in the fluosilicic acid system further reacts with excessive hydrogen peroxide in the concentration system at the temperature of 40-60 ℃, and the conversion rate of the trivalent arsenic into pentavalent arsenic is close to 95%.
Step five: screening silicon dioxide, generating silicon dioxide solid from the concentrated fluosilicic acid, growing silicon dioxide crystals in a silicon dioxide aging crystallization tank, sending the mixed solution of the fluosilicic acid and the silicon dioxide into a plate-and-frame filter for filtration and separation, and separating partial pentavalent arsenic from silicon slag, wherein the pentavalent arsenic is about 5-10%.
Step six: gasifying and decomposing, the concentrated fluosilicic acid filtered by the plate and frame filter enters a reaction system to be mixed and reacted with the high-temperature sulfuric acid dried and absorbed by the hydrogen fluoride, the concentrated fluosilicic acid is decomposed after the concentrated sulfuric acid is diluted and releases heat,the generated gas-phase silicon tetrafluoride enters a concentration system for cyclic absorption, and the liquid phase is H2SO4HF and H2And in the O mixing system, the reaction temperature in a gasification and decomposition reactor is 85-135 ℃, the reactor is high-temperature corrosion resistant steel-lined plastic equipment, pentavalent arsenic does not react with generated hydrogen fluoride under the temperature condition, the reaction condition that trivalent arsenic reacts with hydrogen fluoride does not reach 140 ℃ is achieved, and arsenic trifluoride gas is not generated.
Step seven: a hydrogen fluoride reboiling system and a drying separation system, wherein a liquid phase mixed system discharged from the six reactors in the step is heated to 150-168 ℃ by a reboiler, then hydrogen fluoride is separated by a flash evaporator, and simultaneously the generated dilute sulfuric acid is separated from the system after being cooled.
Step eight: drying and purifying, namely fully absorbing the flashed hydrogen fluoride gas phase system containing water vapor with a hydrogen fluoride drying tower and cold concentrated sulfuric acid gas liquid, wherein the temperature of the top of the drying tower is controlled to be 60-80 ℃, the temperature of the concentrated sulfuric acid is 25-30 ℃, the dried and absorbed hydrogen fluoride gas phase system contains a very small amount of arsenic trifluoride gas, the arsenic trifluoride gas reacts with sulfuric acid absorbing moisture at the tower bottom to generate arsenous acid, the arsenous acid enters a reactor and is finally taken out from dilute sulfuric acid, most of the moisture is absorbed, the gas phase of the drying tower is mainly hydrogen fluoride gas, and the high-purity industrial anhydrous hydrogen fluoride is obtained after subsequent separation and purification, wherein the arsenic content is reduced to below 6 ppm.
The heat exchanger and the reaction tower are needed in the removing process, the heat exchanger is made of graphite or silicon carbide and other corrosion-resistant materials, the tower packing of the reaction tower is regular packing, the reaction tower internal part supporting disc, the distribution disc and the wire mesh demister are made of pure tetrafluoro materials, and the supporting ring and the negative pressure ring are made of special materials.
The working principle is as follows: firstly, filtering raw material fluosilicic acid through a microfiltration I to avoid solid impurities from blocking a subsequent microfiltration II so as to obtain fluosilicic acid with high purity, then placing the filtered fluosilicic acid into a mixing tank consisting of fluosilicic acid and hydrogen peroxide under normal temperature and acidic conditions, wherein the adding amount of the hydrogen peroxide in the mixing tank is determined according to the content of arsenic in the raw material fluosilicic acid, the adding ratio of the hydrogen peroxide to the fluosilicic acid is between 0.1 and 1 percent, and pre-oxidizing for 30 to 60 minutes so as to oxidize nearly 50 percent of trivalent arsenic in the fluosilicic acid into pentavalent arsenic.
Adding a manganese dioxide catalyst into a chamber of the microporous filter II, and further oxidizing trivalent arsenic into pentavalent arsenic through the catalytic action of manganese dioxide to obtain fluosilicic acid with the conversion rate of between 80 and 90 percent.
And (3) sending the fluosilicic acid subjected to oxidation filtration into a fluosilicic acid concentration system through a buffer tank and a material injection pump, wherein the dilute fluosilicic acid absorbs silicon tetrafluoride gas generated by a reaction system to continuously release heat, trivalent arsenic in the fluosilicic acid system further reacts with excessive hydrogen peroxide in the concentration system at the temperature of 40-60 ℃, and the conversion rate of the trivalent arsenic into pentavalent arsenic is close to 95%.
The concentrated fluosilicic acid generates silicon dioxide solid, after the silicon dioxide crystal grows up through a silicon dioxide aging crystallization tank, the mixed solution of the fluosilicic acid and the silicon dioxide is sent to a plate-and-frame filter for filtration and separation, and part of pentavalent arsenic is separated from the silicon slag and is about 5 to 10 percent.
And (3) related reaction: 5SiF4 + 2H2O → 2H2SiF6▪ SiF4 +SiO2↓
As3+ + H2O2 → As5+ + H2O
The concentrated fluosilicic acid filtered by the plate and frame filter enters a reaction system to be mixed and reacted with high-temperature sulfuric acid dried and absorbed by hydrogen fluoride, the concentrated fluosilicic acid is decomposed after the concentrated sulfuric acid is diluted to release heat, the generated gas-phase silicon tetrafluoride enters a concentration system to be circularly absorbed, and the liquid phase is H2SO4HF and H2The mixed system of O, a hydrogen fluoride reboiling system and a drying separation system, wherein the liquid-phase mixed system discharged from the six-step reactor is heated to 150-168 ℃ by a reboiler, then hydrogen fluoride is separated by a flash evaporator, and simultaneously the generated dilute sulfuric acid is separated from the system after being cooled.
H2SiF6•SiF4(aq)＋H2SO4 → 2SiF4＋2HF＋H2SO4(aq)
And finally, fully absorbing the hydrogen fluoride gas phase system containing water vapor after flash evaporation with cold concentrated sulfuric acid gas liquid through a hydrogen fluoride drying tower, wherein the temperature of the top of the drying tower is controlled to be 60-80 ℃, the temperature of the concentrated sulfuric acid is 25-30 ℃, the hydrogen fluoride gas phase system subjected to drying absorption contains a very small amount of arsenic trifluoride gas, the arsenic trifluoride gas reacts with sulfuric acid absorbing moisture at the tower bottom to generate arsenous acid, the arsenous acid enters a reactor and is finally taken out from dilute sulfuric acid, most of moisture is absorbed, the gas phase of the drying tower is mainly hydrogen fluoride gas, and high-purity industrial anhydrous hydrogen fluoride is obtained after subsequent separation and purification, and the arsenic content is reduced to below 6 ppm.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (7)
1. A technology for removing arsenic in the process of preparing anhydrous hydrogen fluoride by a fluosilicic acid method is characterized in that: the removal process comprises the following steps:
the method comprises the following steps: pre-purifying fluosilicic acid, namely pre-purifying raw material fluosilicic acid by a filter on a micro-pore filter I, intercepting a small amount of solid micro particles such as silica gel, calcium salt and the like in the raw material fluosilicic acid in a filtering mode, and screening to avoid solid impurities from blocking a subsequent micro-pore filter II, so as to obtain high-purity fluosilicic acid;
step two: pre-oxidizing trivalent arsenic in fluosilicic acid, namely placing the fluosilicic acid which is pre-purified by the micro-pore filtration I in the step I into a mixing tank consisting of fluosilicic acid and hydrogen peroxide under the conditions of normal temperature and acidity, carrying out primary oxidation reaction on the fluosilicic acid, and pre-oxidizing the fluosilicic acid in the mixing tank for 30-60min by adding the hydrogen peroxide, so that nearly 50% of trivalent arsenic in the fluosilicic acid is oxidized into pentavalent arsenic;
step three: further catalytic oxidation of trivalent arsenic by hydrogen peroxide in the microporous filter II, adding a manganese dioxide catalyst into a chamber of the microporous filter II, pumping the fluosilicic acid pre-oxidized in the step 2 into the microporous filter II through a peristaltic pump, and further oxidizing the trivalent arsenic into pentavalent arsenic by the unreacted trivalent arsenic and hydrogen peroxide components in the step II through the catalytic action of manganese dioxide to obtain the fluosilicic acid with the conversion rate of 80-90%;
step four: a concentration and reaction system, wherein fluosilicic acid after being oxidized and filtered in the third step is sent into a fluosilicic acid concentration system through a buffer tank and a feeding pump, and as the dilute fluosilicic acid absorbs silicon tetrafluoride gas generated by the reaction system to continuously release heat, trivalent arsenic in a fluosilicic acid system further reacts with excessive hydrogen peroxide in the concentration system at the temperature of 40-60 ℃, and the conversion rate of the trivalent arsenic into pentavalent arsenic is close to 95%;
step five: screening silicon dioxide, wherein concentrated fluosilicic acid generates silicon dioxide solid, after the silicon dioxide grows up through a silicon dioxide aging crystallization tank, the mixed solution of fluosilicic acid and silicon dioxide is sent into a plate-and-frame filter for filtration and separation, and part of pentavalent arsenic is separated from silicon slag and is about 5 to 10 percent;
step six: gasifying and decomposing, mixing the concentrated fluosilicic acid filtered by the plate and frame filter in a reaction system with high-temperature sulfuric acid dried and absorbed by hydrogen fluoride, reacting, diluting with concentrated sulfuric acid to release heat, decomposing the concentrated fluosilicic acid, introducing the generated gas-phase silicon tetrafluoride into the concentration system for cyclic absorption, and obtaining a liquid phase H2SO4HF and H2A mixed system of O;
step seven: a hydrogen fluoride reboiling system and a drying separation system, wherein a liquid phase mixed system obtained from the sixth reactor is heated to 150-168 ℃ by a reboiler, then hydrogen fluoride is separated by a flash evaporator, and simultaneously the generated dilute sulfuric acid is separated from the system after being cooled;
step eight: drying and purifying, namely fully absorbing the flash-evaporated hydrogen fluoride gas phase system containing water vapor by a hydrogen fluoride drying tower and cold concentrated sulfuric acid gas liquid, wherein the temperature of the top of the drying tower is controlled to be 60-80 ℃, the temperature of the concentrated sulfuric acid is 25-30 ℃, most of water is absorbed, the gas phase of the drying tower is mainly hydrogen fluoride gas, and the high-purity industrial anhydrous hydrogen fluoride is obtained after subsequent separation and purification, wherein the arsenic content is reduced to below 6 ppm.
2. The process for removing arsenic in the process of preparing anhydrous hydrogen fluoride by a fluorosilicic acid method according to claim 1, which is characterized in that: and step two, the adding amount of hydrogen peroxide in the mixing tank is determined according to the content of arsenic in the raw material fluosilicic acid, and the adding ratio of the hydrogen peroxide to the fluosilicic acid is between 0.1 and 1 percent.
3. The process for removing arsenic in the process of preparing anhydrous hydrogen fluoride by a fluorosilicic acid method according to claim 1, which is characterized in that: and (3) carrying out manganese dioxide catalytic particle growing according to the third step, wherein the adding amount of the manganese dioxide catalytic particles is 0.5m, and the pressure of the peristaltic pump is 0.3 MPa.
4. The process for removing arsenic in the process of preparing anhydrous hydrogen fluoride by a fluorosilicic acid method according to claim 1, which is characterized in that: and sixthly, the reaction temperature in the gasification and decomposition reactor is 85-135 ℃, and the reactor is high-temperature corrosion resistant steel-lined plastic equipment.
5. The process for removing arsenic in the process of preparing anhydrous hydrogen fluoride by a fluorosilicic acid method according to claim 1, which is characterized in that: and eighthly, the dry and absorbed hydrogen fluoride gas phase system contains a very small amount of arsenic trifluoride gas, and the arsenic trifluoride gas reacts with the sulfuric acid absorbing moisture at the tower bottom to generate arsenous acid which enters a reactor and is finally carried out of dilute sulfuric acid.
6. The process for removing arsenic in the process of preparing anhydrous hydrogen fluoride by a fluorosilicic acid method according to claim 1, which is characterized in that: in the first step, the concentration of the raw material fluosilicic acid is between 15% and 30%, the arsenic content is between 10ppm and 50ppm, and the hydrogen peroxide content in the hydrogen peroxide is between 25% and 40%.
7. The process for removing arsenic in the process of preparing anhydrous hydrogen fluoride by a fluorosilicic acid method according to claim 1, which is characterized in that: the desorption process needs to use a heat exchanger and a reaction tower, wherein the heat exchanger is made of graphite or silicon carbide and other corrosion-resistant materials, the tower packing of the reaction tower is regular packing, the reaction tower internal part supporting disc, the distribution disc and the wire mesh demister are made of pure tetrafluoro materials, and the supporting ring and the negative pressure ring are made of special materials.
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