CN112661598B - Method for preparing chloromethane by using chlorine-based CVD (chemical vapor deposition) process tail gas generated by growing Si or SiC crystal film - Google Patents
Method for preparing chloromethane by using chlorine-based CVD (chemical vapor deposition) process tail gas generated by growing Si or SiC crystal film Download PDFInfo
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- NEHMKBQYUWJMIP-UHFFFAOYSA-N chloromethane Chemical compound ClC NEHMKBQYUWJMIP-UHFFFAOYSA-N 0.000 title claims abstract description 318
- 238000000034 method Methods 0.000 title claims abstract description 199
- 238000005229 chemical vapour deposition Methods 0.000 title claims abstract description 31
- 239000013078 crystal Substances 0.000 title claims abstract description 30
- 239000000460 chlorine Substances 0.000 title claims description 30
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 title claims description 28
- 229910052801 chlorine Inorganic materials 0.000 title claims description 28
- 239000007789 gas Substances 0.000 claims abstract description 180
- 239000005046 Chlorosilane Substances 0.000 claims abstract description 114
- KOPOQZFJUQMUML-UHFFFAOYSA-N chlorosilane Chemical compound Cl[SiH3] KOPOQZFJUQMUML-UHFFFAOYSA-N 0.000 claims abstract description 112
- 238000010521 absorption reaction Methods 0.000 claims abstract description 85
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims abstract description 54
- 238000007038 hydrochlorination reaction Methods 0.000 claims abstract description 39
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical class C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 35
- 238000005406 washing Methods 0.000 claims abstract description 33
- 238000009833 condensation Methods 0.000 claims abstract description 30
- 230000005494 condensation Effects 0.000 claims abstract description 30
- 238000007670 refining Methods 0.000 claims abstract description 22
- 239000007921 spray Substances 0.000 claims abstract description 22
- 238000001704 evaporation Methods 0.000 claims abstract description 20
- 230000008020 evaporation Effects 0.000 claims abstract description 20
- 238000001179 sorption measurement Methods 0.000 claims abstract description 20
- 230000006835 compression Effects 0.000 claims abstract description 17
- 238000007906 compression Methods 0.000 claims abstract description 17
- 239000002737 fuel gas Substances 0.000 claims abstract description 12
- 230000008929 regeneration Effects 0.000 claims abstract description 8
- 238000011069 regeneration method Methods 0.000 claims abstract description 8
- 125000001309 chloro group Chemical group Cl* 0.000 claims abstract description 7
- 238000010438 heat treatment Methods 0.000 claims abstract description 7
- 238000004064 recycling Methods 0.000 claims abstract description 7
- 239000012159 carrier gas Substances 0.000 claims abstract description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 111
- IXCSERBJSXMMFS-UHFFFAOYSA-N hcl hcl Chemical compound Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 claims description 96
- 229910000041 hydrogen chloride Inorganic materials 0.000 claims description 95
- 239000007788 liquid Substances 0.000 claims description 61
- 239000000047 product Substances 0.000 claims description 54
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 47
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 claims description 44
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 41
- 238000006243 chemical reaction Methods 0.000 claims description 35
- 238000005507 spraying Methods 0.000 claims description 35
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 claims description 32
- 239000002994 raw material Substances 0.000 claims description 27
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 24
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 22
- 239000010408 film Substances 0.000 claims description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 17
- 239000012535 impurity Substances 0.000 claims description 17
- 229960001701 chloroform Drugs 0.000 claims description 15
- 239000002250 absorbent Substances 0.000 claims description 14
- 230000002745 absorbent Effects 0.000 claims description 14
- 238000005660 chlorination reaction Methods 0.000 claims description 13
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 12
- 229910052739 hydrogen Inorganic materials 0.000 claims description 12
- 239000001257 hydrogen Substances 0.000 claims description 11
- 239000007791 liquid phase Substances 0.000 claims description 11
- 238000010791 quenching Methods 0.000 claims description 11
- 230000000171 quenching effect Effects 0.000 claims description 11
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 10
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 10
- FBBDOOHMGLLEGJ-UHFFFAOYSA-N methane;hydrochloride Chemical compound C.Cl FBBDOOHMGLLEGJ-UHFFFAOYSA-N 0.000 claims description 10
- 238000000926 separation method Methods 0.000 claims description 10
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 9
- 239000012071 phase Substances 0.000 claims description 9
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 8
- 239000003054 catalyst Substances 0.000 claims description 8
- 239000004215 Carbon black (E152) Substances 0.000 claims description 7
- 229910052710 silicon Inorganic materials 0.000 claims description 7
- 239000010703 silicon Substances 0.000 claims description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 6
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 6
- 239000006227 byproduct Substances 0.000 claims description 6
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 6
- 239000000428 dust Substances 0.000 claims description 6
- 239000003595 mist Substances 0.000 claims description 6
- 239000003921 oil Substances 0.000 claims description 6
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 claims description 6
- 229910052799 carbon Inorganic materials 0.000 claims description 5
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 claims description 4
- 239000001569 carbon dioxide Substances 0.000 claims description 4
- 230000007613 environmental effect Effects 0.000 claims description 4
- 229930195733 hydrocarbon Natural products 0.000 claims description 4
- 150000002430 hydrocarbons Chemical class 0.000 claims description 4
- 238000006386 neutralization reaction Methods 0.000 claims description 4
- 229910000077 silane Inorganic materials 0.000 claims description 4
- 239000000377 silicon dioxide Substances 0.000 claims description 4
- 235000012239 silicon dioxide Nutrition 0.000 claims description 4
- 238000011272 standard treatment Methods 0.000 claims description 4
- 239000010409 thin film Substances 0.000 claims description 4
- 239000003513 alkali Substances 0.000 claims description 3
- 239000007864 aqueous solution Substances 0.000 claims description 3
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical group O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 claims description 3
- 239000012495 reaction gas Substances 0.000 claims description 3
- 239000011541 reaction mixture Substances 0.000 claims description 3
- 238000010992 reflux Methods 0.000 claims description 3
- 239000011949 solid catalyst Substances 0.000 claims description 3
- 239000011592 zinc chloride Substances 0.000 claims description 3
- 235000005074 zinc chloride Nutrition 0.000 claims description 3
- 239000011787 zinc oxide Substances 0.000 claims description 3
- 230000005587 bubbling Effects 0.000 claims description 2
- 238000010924 continuous production Methods 0.000 claims description 2
- 238000007599 discharging Methods 0.000 claims description 2
- 229910052681 coesite Inorganic materials 0.000 claims 1
- 229910052906 cristobalite Inorganic materials 0.000 claims 1
- JEGUKCSWCFPDGT-UHFFFAOYSA-N h2o hydrate Chemical compound O.O JEGUKCSWCFPDGT-UHFFFAOYSA-N 0.000 claims 1
- 239000011859 microparticle Substances 0.000 claims 1
- 229910052682 stishovite Inorganic materials 0.000 claims 1
- 229910052905 tridymite Inorganic materials 0.000 claims 1
- 238000005516 engineering process Methods 0.000 abstract description 4
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 abstract 1
- 229910052731 fluorine Inorganic materials 0.000 abstract 1
- 239000011737 fluorine Substances 0.000 abstract 1
- 238000004519 manufacturing process Methods 0.000 description 8
- 239000000463 material Substances 0.000 description 5
- 229940050176 methyl chloride Drugs 0.000 description 5
- 150000002431 hydrogen Chemical class 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
- 229910004298 SiO 2 Inorganic materials 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 239000000575 pesticide Substances 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000005052 trichlorosilane Substances 0.000 description 2
- ZDHXKXAHOVTTAH-UHFFFAOYSA-N trichlorosilane Chemical compound Cl[SiH](Cl)Cl ZDHXKXAHOVTTAH-UHFFFAOYSA-N 0.000 description 2
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- NEHMKBQYUWJMIP-NJFSPNSNSA-N chloro(114C)methane Chemical compound [14CH3]Cl NEHMKBQYUWJMIP-NJFSPNSNSA-N 0.000 description 1
- YGZSVWMBUCGDCV-UHFFFAOYSA-N chloro(methyl)silane Chemical compound C[SiH2]Cl YGZSVWMBUCGDCV-UHFFFAOYSA-N 0.000 description 1
- 238000009841 combustion method Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 239000000645 desinfectant Substances 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 238000000407 epitaxy Methods 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- -1 extractants Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000003193 general anesthetic agent Substances 0.000 description 1
- 239000000543 intermediate Substances 0.000 description 1
- 229920000609 methyl cellulose Polymers 0.000 description 1
- 239000001923 methylcellulose Substances 0.000 description 1
- 235000010981 methylcellulose Nutrition 0.000 description 1
- 229940073584 methylene chloride Drugs 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 150000003961 organosilicon compounds Chemical class 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- 239000003380 propellant Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 239000003507 refrigerant Substances 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000011863 silicon-based powder Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
Abstract
The invention discloses a method for preparing chloromethane by utilizing a chloro-based CVD (chemical vapor deposition) process tail gas FTrPSA (fluorine-containing PSA) for growing Si/SiC crystal films, which utilizes the effective components HCl, chlorosilane and the like in the chloro-based CVD process tail gas for growing Si/SiC crystals or films to react with methanol through pretreatment, chlorosilane spray absorption, multistage evaporation/compression/condensation, HCl refining, chlorosilane hydrochlorination reaction, washing absorption, chloromethane rectification and shallow cold rectification processes in the chlorosilane, thereby obtaining chloromethane and polychlorinated methane products with high purity and high yield, solving the problem of recycling the difficult-to-burn HCl component contained in the chloro-based CVD process tail gas, and utilizing main combustible components such as H2, CH4 and the like in the tail gas as fuel gas for heating or adsorption regeneration carrier gas for chloromethane hydrochlorination reaction in the invention, reducing tail gas emission and making up the blank of the chloro-based CVD process tail gas treatment technology.
Description
Technical Field
The invention relates to the field of comprehensive recycling of process tail gas in the growth process of semiconductor material silicon (Si) or silicon carbide (SiC) crystals or epitaxial films and environmental protection of semiconductor processes, in particular to a method for preparing chloromethane by utilizing chlorine-based CVD (chemical vapor deposition) process tail gas generated in the growth process of Si/SiC (silicon/silicon carbide) crystal films.
Background
Methyl chloride or methane Chloride (CMS) includes methyl chloride, methylene chloride, chloroform and chloroform (carbon tetrachloride). Methyl chloride is often referred to as mono-chloromethane (CH 3 Cl), with the remainder of the methane chloride being further chlorinated on the basis of CH3 Cl.
Methyl chloride is mainly used as a production raw material of organosilicon compounds, namely methyl chlorosilane and methyl cellulose, about 50-90% of the methyl chloride is used for the production, and further chloridizing to produce methylene dichloride, chloroform and carbon tetrachloride, wherein the serial products of the methane chloride can be widely used for producing intermediates of pesticides and medicines or direct products, such as pesticides, refrigerants, anesthetic agents, extractants, propellants, disinfectants, solvents and the like.
The current industrial chloromethane production methods mainly comprise a methanol method and a methane method. The methanol method is to take methanol and HCl as raw materials, perform hydrochlorination reaction under certain reaction conditions to generate a mixture of chloromethane and water, and then perform separation steps of washing, condensation, drying and rectification to finally obtain a chloromethane product. In addition, the chloromethane can be further reacted with chlorine to generate methane chloride products such as methylene dichloride, chloroform, carbon tetrachloride and the like. The methanol process has a gas phase (or catalyst solid phase) and a liquid phase reaction mode, and the rest of process equipment is almost the same except for the catalyst and the hydrochlorination reactor. The methane method is to directly carry out thermal chlorination reaction on methane or natural gas serving as raw material gas and chlorine to obtain chloromethane and byproduct HCl, and then obtain chloromethane products through separation units such as condensation cooling, absorption washing, neutralization, drying, rectification and the like, and directly prepare the chloromethane products such as dichloromethane and the like, wherein the types of the chloromethane products are controlled by adjusting the excess or circulation of the raw material gas of the methane, such as increasing the methane inflow or circulation, so that chloromethane can be produced in a more-way and the generation of chloromethane can be reduced. In addition, the methane method of the oxychlorination reaction is developed at home and abroad, the production cost is further reduced, and the proportion of methane chloride products is more convenient to adjust. But the main technology of the domestic chloromethane production at present is a methanol method, and the obtained chloromethane product has high purity, relatively low cost, relatively mature technology and high controllability. In general, the preparation of methyl chloride by adopting a methanol gas phase process is common in China, because the yield of the methanol gas phase process is relatively high, and the production cost is relatively lower.
In the process of preparing thin films by crystal growth of semiconductor materials such as silicon (Si) or silicon carbide (SiC) or epitaxy on Si/SiC, it is common to use a "silicon" containing precursor such as silane (SiH 4)/Trichlorosilane (TCS) or a "carbon" containing precursor such as methane (CH 4)/propane (C3H 8)/ethylene (C2H 4) as a reactant while introducing HCl or chlorohydrate, and to carry out Chemical Vapor Deposition (CVD) of Si/SiC single crystal or epitaxial thin film growth in a reaction chamber with carrier gas such as hydrogen (H2), while obtaining single crystal or epitaxial materials, release tail gases containing H2, HCl, CH4 as a main component and small amounts of SiH4, chlorosilane (SiHmCln), carbon monoxide (CO), carbon dioxide (CO 2), two and more light hydrocarbon components (c2+) and trace amounts of silicon powder, carbon powder, and the like. The tail gas contains more nonflammable HCl, inflammable and explosive H2, CH4, a small amount of C2+/SiH4 and the like, so that the combustion method commonly used in the field of semiconductor material production is not applicable. In the air emission standard, HCl, siHmCln, C2+ and other gases in the tail gas are strictly limited, so that the industrial chlorine-containing components such as HCl/SiHmCln and the like are changed into industrial hydrochloric acid by water spray absorption, and then toxic SiH4 and SiHmCln impurity components are oxidized into harmless silicon oxide (SiO 2), water (H2O), CO2 and the like by introducing air/steam, and finally the waste gas can be discharged after further water washing. Valuable H2, HCl and the like in the tail gas cannot be recovered and returned to the CVD process for recycling.
In view of the fact that the tail gas generated in the growth process of the chlorine-based Si/SiC CVD crystal and the epitaxial film contains more HCl except H2, inflammable components such as H2 in the tail gas are used as fuel gas for preparing chloromethane and heating the system by using the more HCl in the tail gas, the problem of exhaust of the CVD process can be effectively solved, and a larger additional value can be generated, so that the method is a work favorable for green development of Si/SiC materials.
Disclosure of Invention
A method for preparing chloromethane by using tail gas of a chlorine-based CVD epitaxial process for growing Si/SiC crystal thin films comprises the following steps:
(1) The raw material gas is prepared by Chemical Vapor Deposition (CVD) growth of Si or silicon carbide (SiC) crystals or epitaxial films by taking silane (SiH 4) or chlorosilane (SiHmCln) as a main silicon (Si) source or hydrogen chloride (HCl) or SiHmCln as a chlorine group, and mainly comprises hydrogen (H2) and HCl, a small amount of methane (CH 4), two or more carbon components (C2+), siH4/SiHmCln, trace carbon monoxide (CO), carbon dioxide (CO 2), water (H2O) and silicon dioxide (SiO 2) and Si/C fine particles, wherein the pressure is normal pressure or low pressure, and the temperature is normal temperature.
(2) Pretreating, namely, feeding raw material gas into a pretreatment unit consisting of a dust remover, a particle removal filter and an oil mist removal catcher through pressurization, sequentially removing dust, particles, oil mist, partial high-chlorosilane, high-chloralkane and high-hydrocarbon impurities under the operating conditions of 0.2-0.3 MPa pressure and normal temperature, and enabling the formed purified raw material gas to enter a next working procedure, namely, chlorosilane spraying absorption.
(3) The method comprises the steps of spraying and absorbing chlorosilane, pressurizing purified raw material gas from a pretreatment process to 0.6-1.0 MPa, carrying out cold-heat exchange to 80-160 ℃, entering from the bottom of a spraying absorption tower, adopting chlorosilane+anhydrous HCl liquid as an absorbent, spraying from the top of the spraying absorption tower, carrying out reverse mass transfer exchange with the purified raw material gas, flowing out an absorption liquid enriched with chlorosilane and HCl from the bottom of the chlorosilane spraying absorption tower, entering a next process, namely a multistage evaporation/compression/condensation process, simultaneously outputting a small amount of residual particles, high chlorosilane, high chloralkane and high hydrocarbon impurities flowing out from the bottom of the chlorosilane spraying absorption tower, and carrying out environmental protection treatment, wherein the non-condensable gas rich in H2 flows out from the top of the chlorosilane spraying absorption tower, is used for heating in a subsequent chloromethane hydrochlorination process after adsorption treatment, or is directly used as fuel gas, or is output as raw material gas for extracting H2.
(4) The method comprises the steps of multistage evaporation/compression/condensation, wherein absorption liquid from a chlorosilane spray absorption process enters multistage evaporation, is directly or depressurized to 0.6-1.0 MPa, enters a condenser, and obtains gas-phase crude HCl gas from the gas-phase crude HCl gas, the crude HCl liquid formed after condensation enters the next process, namely HCl refining, and crude chlorosilane liquid flows out of the condenser and enters the subsequent chlorosilane for shallow cold rectification.
(5) And (3) refining HCl, namely, feeding the crude HCl liquid from the multistage evaporation/compression/condensation process into an HCl refining process consisting of an HCl rectifying tower and a vacuum rectifying tower, wherein the operating pressure of the rectifying tower is 0.3-1.0 MPa, the operating temperature is 60-120 ℃, the operating pressure of the vacuum rectifying tower is-0.08 to-0.1 MPa, the operating temperature is 60-120 ℃, HCl gas with the purity of more than 99.9% is distilled from the top of the rectifying tower, feeding the HCl gas into the next process, namely, chlorosilane hydrogen greening reaction, and feeding the distillate from the bottom of the rectifying tower into the vacuum tower, feeding the overhead gas which mainly contains a small amount of methane chloride and flows out from the top of the rectifying tower into the subsequent chloromethane rectifying process, further recovering chloromethane, and feeding the heavy component which flows out from the bottom of the vacuum tower back into the multistage evaporation/compression/condensation process, or feeding the HCl gas into the shallow-cold rectifying process.
(6) The chloromethane hydrochlorination reaction, namely, HCl gas from an HCl refining process is proportionally mixed with externally-transmitted methanol steam to enter a hydrochlorination reactor for hydrochlorination reaction, wherein the reaction temperature is 230-300 ℃, the reaction pressure is normal pressure or less than 0.3MPa, a solid catalyst is ferric oxide or zinc oxide, crude chloromethane gas generated by the reaction flows out of the reactor, and the crude chloromethane gas enters the next process, namely, washing and absorption after quenching and condensation.
(7) Washing and absorbing, namely, enabling the quenched and condensed crude chloromethane gas from the chloromethane hydrochlorination reaction process to enter a washing and absorbing tower for separating organic matters from inorganic matters, wherein the washing and absorbing operation conditions are normal temperature and pressure or micro-positive pressure, enabling the by-product hydrochloric acid to flow out of the washing and absorbing tower, enabling the flowing-out non-condensable gas to enter an alkali neutralization tower and a rewashing tower, further removing residual HCl and methanol, and enabling the formed purified chloromethane gas to enter the next process, namely chloromethane rectification.
(8) And (3) rectifying chloromethane, mixing the purified chloromethane gas from the washing and absorbing process with the vacuum tower top gas from the HCl refining process, entering a chloromethane rectifying tower, distilling chloromethane product with purity of more than 99.9% from the rectifying tower top, and outputting the distillate at the rectifying tower bottom to process to produce the chloromethane product.
(9) The method comprises the steps of shallow cold rectification in chlorosilane, carrying out shallow cold rectification in the crude chlorosilane liquid from a multistage evaporation/compression/condensation process, entering the shallow cold rectification process in the chlorosilane, wherein the operating temperature is-35-10 ℃, the operating pressure is 0.6-2.0 MPa, and returning the non-condensable gas flowing out of the top of a rectifying tower to the chlorosilane spraying absorption process as an absorbent for recycling, wherein the non-condensable gas is directly used as fuel gas or returned to the chlorosilane spraying absorption process.
Furthermore, the method for preparing chloromethane by utilizing the tail gas of the chlorine-based CVD epitaxial process for growing the Si/SiC crystal film is characterized in that a secondary medium-temperature chlorosilane absorption process is additionally arranged in the chlorosilane spraying absorption process under the working condition that the concentration of HCl and chlorosilane contained in purified raw material gas is high, namely, non-condensable gas from the chlorosilane spraying absorption process is compressed, condensed and separated from gas-liquid, then the new non-condensable gas is formed and directly or pressurized to 0.2-1.0 MPa, after cold and heat exchange is carried out to 60-120 ℃, the new non-condensable gas enters from the bottom of the additionally arranged secondary chlorosilane spraying absorption process absorption tower, the mixed liquid containing chlorosilane/HCl is adopted as an absorbent, the mixed liquid containing chlorosilane/HCl is sprayed from the secondary chlorosilane spraying absorption tower bottom and reversely exchanges with the new non-condensable gas, the absorption liquid 2 enriched with the HCl flows out from the bottom of the absorption tower, the mixed liquid 1 of the primary chlorosilane absorption process enters the subsequent multistage evaporation/compression/condensation process, the liquid obtained after the gas-liquid separation is returned to the top of the chlorosilane, and the liquid flows out from the top of the absorption tower as fuel gas, and the fuel gas is directly or directly extracted as H after the absorption or is used as the cold gas after the absorption or is directly extracted.
Furthermore, the method for preparing chloromethane by using the tail gas of the chlorine-based CVD epitaxial process for growing the Si/SiC crystal film is characterized in that under the working condition that the purified chloromethane gas from the washing and absorbing process contains more polychlorinated methane and water, the purified chloromethane gas is dehydrated and dried by sulfuric acid and then treated by a chloromethane rectifying process, the top gas is distilled from the top of a rectifying tower and is condensed and separated from gas liquid, the liquid is returned to the rectifying tower as reflux, the gas enters an adsorption and drying process to obtain chloromethane product gas, the purity is more than or equal to 99.99%, and the bottoms of the rectifying tower are the polychlorinated methane, and the products are sent out of a boundary region to be subjected to rectification separation to obtain the respective products.
Furthermore, the method for preparing chloromethane by utilizing the tail gas of the chlorine-based CVD epitaxial process for growing the Si/SiC crystal film is characterized in that the chloromethane hydrochlorination reaction is carried out by adopting liquid phase reaction, anhydrous HCl gas from an HCl refining process, and gasified methanol steam with a certain proportion are mixed into a chloromethane hydrochlorination liquid phase reaction process, 75-85% zinc chloride aqueous solution is used as a liquid catalyst, the liquid catalyst is heated to 120 ℃, the reaction temperature is 120-160 ℃, the reaction pressure is normal pressure or micro-positive pressure, the gas-liquid contact is carried out to generate chloromethane hydrochlorination liquid phase reaction, and the crude chloromethane gas generated by the reaction is subjected to quenching, condensation, washing absorption, sulfuric acid drying and chloromethane rectification, or adsorption drying to obtain chloromethane products, wherein the purity is more than or equal to 99.9-99.99%.
Furthermore, the method for preparing chloromethane by using the tail gas of the chlorine-based CVD epitaxial process for growing the Si/SiC crystal film is characterized in that the rectifying bottom distillate of the chloromethane rectifying process enters a chlorination reactor, wherein chlorine is introduced into the chlorination reactor according to a certain proportion, so that the bottom distillate is further chlorinated, the generated reaction mixture gas firstly enters a carbon tetrachloride rectifying tower, the carbon tetrachloride product is distilled from the top of the tower, the bottom distillate returns to the chloromethane rectifying tower, the chloromethane product is distilled from the top of the tower, the purity is greater than or equal to 99.99%, the yield is greater than 98%, the bottom distillate enters a dichloromethane rectifying tower, the dichloromethane product is distilled from the top of the tower, the chloroform product is distilled from the top of the tower, the rest of heavy component impurities including a small amount of chlorosilane, C2+ and water are discharged from the bottom of the tower, and the residual heavy component impurities are sent into an incinerator for standard treatment and discharge.
Furthermore, the method for preparing chloromethane by utilizing the tail gas of the chlorine-based CVD epitaxial process for growing Si/SiC crystal films is characterized in that when the content of HCl in the purified raw material gas is less than 5 percent and the content of H2 is more than 80 percent, a chlorination reaction step can be additionally arranged, the dried crude chloromethane gas dried by sulfuric acid, non-condensable gas (hydrogen-rich gas) from a chlorosilane spray absorption process and chlorine gas enter a chlorination reactor according to a certain proportion to carry out hydrochlorination reaction, the formed reaction gas enters a rectifying tower of a quenching and HCl rectifying process after cooling, part of crude HCl distilled from the top of the rectifying tower directly enters the chloromethane hydrochlorination process, and the other part or the part of the crude HCl enters a vacuum tower of HCl refining, or directly serving as an absorbent of a chlorosilane spray absorption process, directly entering a chloromethane hydrochlorination process from the distillate flowing out of the bottom of a rectifying tower, quenching, condensing, washing, absorbing and drying by sulfuric acid to obtain crude chloromethane gas, then entering a carbon tetrachloride rectifying tower, distilling carbon tetrachloride products from the top of the tower, feeding the tower bottom distillate into the chloromethane rectifying tower, distilling chloromethane products from the top of the tower, wherein the purity is more than or equal to 99.99%, feeding the tower bottom distillate into a dichloromethane rectifying tower, distilling dichloromethane products from the top of the tower, feeding the tower bottom distillate into a trichloromethane rectifying tower, feeding the tower top distilled trichloromethane products, and discharging other heavy component impurities including a small amount of chlorosilane, C2+ and water reaching standards into an incinerator for treatment and discharge.
Furthermore, the method for preparing the chloromethane by using the tail gas of the chlorine-based CVD epitaxial process for growing the Si/SiC crystal film is characterized in that the chloromethane and water in the purified chloromethane gas in the washing and absorbing process can directly enter a temperature swing adsorption drying mode consisting of at least two adsorption towers under the working condition that the content of the chloromethane and the water is less than 1-3%, one tower adsorbs, the other tower or towers regenerates, and the adsorption and regeneration alternately operate to realize continuous production, the chloromethane product with the purity of more than or equal to 99.9-99.99% flows out of the adsorption tower in an adsorption state, a chloromethane rectification process is not needed, the regeneration carrier gas adopts non-condensable gas flowing out from the chlorosilane spraying and absorbing process, and the regeneration temperature is more than 80-120 ℃.
The beneficial effects of the invention are as follows:
(1) According to the invention, the chloromethane can be prepared by utilizing the tail gas of the chloromethane SiC-CVD process in which Si/SiC crystals or epitaxial films grow, so that the reutilization of the HCl component which is difficult to burn and is contained in the tail gas is solved, and the main combustible components in the tail gas, such as H2, CH4 and the like, are used as fuel gas for heating or adsorbing regeneration carrier gas of chloromethane hydrochlorination in the invention, so that the tail gas emission is reduced, and the blank of the tail gas treatment technology of the chloromethane-CVD process is made up;
(2) The invention utilizes the physical chemistry and relative separation coefficient characteristics of tail gas components, adopts organic coupling of separation methods such as reaction, absorption, condensation, rectification and adsorption, obtains a chloromethane product, and simultaneously can be used as an absorbent or reaction heating for recycling in a tail gas recovery system by byproduct chlorosilane and hydrogen-rich gas, thereby solving the technical bottleneck that the tail gas contains HCl and is not easy to burn;
(3) The invention can prepare chloromethane by utilizing the tail gas of the chlorine-based CVD process, and can obtain chloromethane and polychlorinated methane products of dichloromethane, trichloromethane and carbon tetrachloride by arranging the chlorination reactor back and forth.
(4) The invention can flexibly prepare chloromethane by adopting a gas phase method or a liquid phase method by adjusting the proportion of crude HCl or refined HCl gas in the HCl refining process, and the production cost can be further reduced.
(5) According to the invention, aiming at the chlorine adding degree and fluctuation of byproduct chlorosilane/HCl concentration caused by epitaxial operation fluctuation according to the demands of the crystal or epitaxial CVD growth process, the processes of primary and secondary chlorosilane spray absorption and different absorbents are adopted, so that the HCl utilization efficiency in tail gas is greatly improved, and the load and difficulty of subsequent procedures are also reduced.
Drawings
Fig. 1 is a schematic flow chart of embodiment 1 of the present invention.
Fig. 2 is a schematic flow chart of embodiment 2 of the present invention.
Fig. 3 is a schematic flow chart of embodiment 3 of the present invention.
Detailed Description
In order to enable those skilled in the art to better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
Example 1
As shown in fig. 1, a method for preparing chloromethane by using chlorine-based CVD process tail gas FTrPSA of Si/SiC crystal film growth, comprises the following steps,
(1) The raw material gas takes chlorosilane (SiHmCln)/silane (SiH 4) as a main silicon (Si) source, takes hydrogen chloride (HCl) as a chlorine group to carry out Chemical Vapor Deposition (CVD) growth to prepare Si/silicon carbide (SiC) crystal or/and tail gas of an epitaxial film, and the raw material gas mainly comprises hydrogen (H2) and HCl, a small amount of methane (CH 4), two or more carbon components (C2+), siH4/SiHmCln, trace carbon monoxide (CO), carbon dioxide (CO 2), water (H2O), silicon dioxide (SiO 2) and Si/C fine particles, and is normal pressure and normal temperature.
(2) Pretreating, namely feeding raw material gas into a pretreatment unit consisting of a dust remover, a particle removal filter and an oil mist removal catcher through pressurization, sequentially removing dust, particles, oil mist, partial high-chlorosilane, high-chloralkane and high-hydrocarbon impurities under the operating conditions of 0.2-0.3 MPa pressure and normal temperature, and enabling the formed purified raw material gas to enter a chlorosilane spraying absorption process.
(3) The chlorosilane spraying absorption, the purification raw material gas from the pretreatment process is pressurized to 0.6-1.0 MPa, the temperature is changed to 80-160 ℃ after cold and heat exchange, the chlorosilane and anhydrous HCl liquid are adopted as an absorbent from the bottom of the spraying absorption tower, the reverse mass transfer exchange is carried out on the chlorosilane and HCl-enriched absorption liquid from the bottom of the chlorosilane spraying absorption tower after spraying, the multistage evaporation/compression/condensation process is carried out on the chlorosilane and HCl-enriched absorption liquid, and meanwhile, a small amount of residual particles, high chlorosilane, high chloralkane and high hydrocarbon impurities flowing out from the bottom of the chlorosilane spraying absorption tower are output for environmental protection treatment, the non-condensable gas rich in H2 flows out from the top of the chlorosilane spraying absorption tower and is used as fuel gas for heating in the chloromethane hydrochlorination process after adsorption treatment.
(4) The method comprises the steps of multistage evaporation/compression/condensation, wherein absorption liquid from a chlorosilane spray absorption process enters the multistage evaporation, and enters a condenser again at a pressure of 0.6-1.0 MPa to obtain gas-phase crude HCl gas, the crude HCl liquid formed after condensation enters an HCl refining process, crude chlorosilane liquid flows out of the condenser, and the crude HCl liquid enters a shallow-cold rectification process in chlorosilane.
(5) And (3) refining HCl, namely feeding the crude HCl liquid from the multistage evaporation/compression/condensation process into an HCl refining process consisting of an HCl rectifying tower and a vacuum rectifying tower, wherein the operating pressure of the rectifying tower is 0.3-0.6 MPa, the operating temperature is 60-120 ℃, the operating pressure of the vacuum rectifying tower is-0.08 to-0.1 MPa, the operating temperature is 60-120 ℃, HCl gas with the purity of more than 99.9% is distilled from the top of the rectifying tower, the HCl gas enters a chlorosilane hydrogen greening reaction, distillate from the bottom of the rectifying tower enters a vacuum tower, the top gas flowing out from the top of the rectifying tower mainly contains a small amount of methane chloride, the methane chloride enters the chloromethane rectifying process, the chloromethane is further recovered, and heavy components flowing out from the bottom of the vacuum rectifying tower return to the subsequent chlorosilane shallow-cooling rectifying process.
(6) The chlorsilane hydrochlorination reaction is carried out, HCl gas from the HCl refining process is mixed with externally-transmitted methanol steam in proportion to enter a hydrochlorination reactor for hydrochlorination reaction, the reaction temperature is 230-300 ℃, the reaction pressure is normal pressure or less than 0.3MPa, the solid catalyst is ferric oxide or zinc oxide, crude chloromethane gas generated by the reaction flows out of the reactor, and the crude chloromethane gas enters the washing absorption process after quenching and condensation.
(7) Washing and absorbing, namely, the crude chloromethane gas obtained after quenching and condensation from the chloromethane hydrochlorination reaction process enters a washing and absorbing process consisting of a washing and absorbing tower to separate organic matters from inorganic matters, washing and absorbing operation conditions are normal temperature and normal pressure, hydrochloric acid which is a byproduct flows out of the washing and absorbing tower is output, the flowing non-condensable gas enters an alkali neutralization tower and a rewashing tower, residual HCl and methanol are further removed, and the formed purified chloromethane gas enters a chloromethane rectification process.
(8) And (3) rectifying chloromethane, mixing the purified chloromethane gas from the washing and absorbing process with the vacuum tower top gas from the HCl refining process, entering a chloromethane rectifying tower, distilling chloromethane product with purity of more than 99.9% from the rectifying tower top, and outputting the distillate at the rectifying tower bottom to process to produce the chloromethane product.
(9) The method comprises the steps of shallow cold rectification in chlorosilane, carrying out shallow cold rectification in the crude chlorosilane liquid from a multistage evaporation/compression/condensation process, entering the shallow cold rectification process in the chlorosilane, wherein the operating temperature is-15-10 ℃, the operating pressure is 0.6-1.0 MPa, returning non-condensable gas flowing out of the top of a rectifying tower to a chlorosilane spray absorption process, and returning the chlorosilane liquid flowing out of the bottom of the rectifying tower as an absorbent to the chlorosilane spray absorption process for recycling.
Example 2
As shown in fig. 2, on the basis of example 1, under the working condition that the concentration of HCl and chlorosilane contained in the purified raw material gas is higher, for example, greater than 5%, the chlorosilane spray absorption process needs to be additionally provided with a secondary medium-temperature chlorosilane absorption process, namely, non-condensable gas from the chlorosilane spray absorption process is compressed, condensed and separated from gas-liquid, new non-condensable gas is formed, the non-condensable gas is subjected to cold-heat exchange to 60-120 ℃, then enters from the bottom of the additionally provided secondary chlorosilane spray absorption process, a mixed liquid containing chlorosilane/HCl is adopted as an absorbent, reverse mass transfer exchange is performed between the secondary chlorosilane spray absorption tower and the new non-condensable gas, an absorption liquid 2 enriched with chlorosilane and HCl flows out from the bottom of the absorption tower, the mixed liquid is mixed with an absorption liquid 1 of the primary chlorosilane spray absorption process, the liquid obtained after gas-liquid separation is returned to the shallow cold rectification process in the chlorosilane, the non-condensable gas flows out from the top of the absorption tower, and is directly used as fuel gas after absorption treatment, wherein the secondary chlorosilane is sprayed from the bottom, and no solid impurity component flows out.
Example 3
As shown in FIG. 3, on the basis of example 1, under the working conditions that the purified chloromethane gas from the washing and absorbing process contains more polychlorinated methane and moisture, for example, the water content is more than 500ppm, the purified chloromethane gas is dehydrated and dried by sulfuric acid and then treated by the chloromethane rectifying process, the overhead gas is distilled from the top of the rectifying tower and is condensed and separated from gas and liquid, the liquid is returned to the rectifying tower as reflux, the gas enters an adsorption and drying process to obtain chloromethane product gas, the purity is more than or equal to 99.99%, and the rectifying tower bottom distillate is the chloromethane, and the chloromethane product gas is sent to the outside of the boundary region for rectification and separation to obtain respective products.
Example 4
On the basis of the embodiment 1, the chloromethane hydrochlorination reaction is to adopt liquid phase reaction, anhydrous HCl gas from an HCl refining process is mixed with gasified methanol steam with a certain proportion (HCl: methanol is 1.3:1.0) to enter a chloromethane hydrochlorination liquid phase reaction process, 75-85% zinc chloride aqueous solution is used as a liquid catalyst, the liquid catalyst is heated to 120 ℃, bubbling gas-liquid contact is carried out under the condition that the reaction temperature is 120-160 ℃ and the reaction pressure is micro positive pressure to generate chloromethane hydrochlorination liquid phase reaction, and the crude chloromethane gas generated by the reaction is subjected to quenching, condensation, washing absorption, sulfuric acid drying and chloromethane rectification or adsorption drying to obtain chloromethane products with the purity of more than or equal to 99.9-99.99%.
Example 5
On the basis of the embodiment 1, the rectifying bottom distillate from the chloromethane rectifying process enters a chlorination reactor, wherein chlorine is introduced into the chlorination reactor according to a certain proportion (the bottom distillate: the chlorine is 0.4-0.6:1.0), so that the bottom distillate is further chlorinated, the generated reaction mixture firstly enters a carbon tetrachloride rectifying tower, the carbon tetrachloride product is distilled from the top of the tower, the bottom distillate returns to the chloromethane rectifying tower, the chloromethane product is distilled from the top of the tower, the purity is greater than or equal to 99.99%, the yield is greater than 98%, the bottom distillate enters a dichloromethane rectifying tower, the dichloromethane product is distilled from the top of the tower, the bottom of the tower enters the trichloromethane rectifying tower, the rest of heavy component impurities including a small amount of chlorosilane, C2+ and water are discharged from the top of the tower, and the rest of heavy component impurities are discharged from the bottom of the tower to an incinerator for standard treatment.
Example 6
As shown in the drawing, on the basis of example 1, the HCl content in the purified feed gas is less than 5% and H 2 When the content is more than 80%, a chlorination reaction step can be additionally arranged, the dry crude chloromethane gas obtained by drying sulfuric acid, noncondensable gas (hydrogen-rich gas) obtained by spraying and absorbing chlorosilane and chlorine gas enter a chlorination reactor according to a certain proportion (hydrogen-rich gas: chlorine gas is 1.0:1.0-1.2), hydrochlorination reaction is carried out, the formed reaction gas is cooled by a rectifying tower of a quenching and HCl rectifying process, a part of crude HCl distilled from the top of the rectifying tower directly enters the chloromethane hydrochlorination process and is directly used as an absorbent of the chlorosilane spraying and absorbing process, the fraction flowing out from the bottom of the rectifying tower directly enters the chloromethane hydrochlorination process, the obtained crude chloromethane gas is quenched, condensed, washed and absorbed and dried by sulfuric acid, then enters a carbon tetrachloride rectifying tower, the carbon tetrachloride product is distilled from the top of the rectifying tower, the chloromethane product is distilled from the top of the rectifying tower, and the chloromethane product is high in purity99.99%, wherein the bottom distillate enters a methylene dichloride rectifying tower, the top of the tower is distilled with a methylene dichloride product, the bottom distillate enters a chloroform rectifying tower, the top of the tower is distilled with a chloroform product, and the bottom of the tower is discharged with other heavy component impurities including a small amount of chlorosilane, C2+ and water, and the heavy component impurities are sent into an incinerator for standard treatment and discharge.
It will be apparent that the embodiments described above are only some, but not all, of the embodiments of the present invention. All other embodiments, or structural changes made by those skilled in the art without inventive effort, based on the embodiments described herein, are intended to be within the scope of the invention, as long as the same or similar technical solutions as the invention are provided.
Claims (7)
1. A method for preparing chloromethane by using chlorine-based CVD process tail gas generated by Si/SiC crystal film growth is characterized by comprising the following steps: the raw material gas takes silane SiH4 or chlorosilane SiHmCln as a main silicon Si source or takes hydrogen chloride HCl or SiHmCln as chlorine groups to carry out chemical vapor deposition CVD growth to prepare tail gas of Si or silicon carbide SiC crystal or epitaxial film, the main components of the raw material gas are hydrogen H2 and HCl, and a small amount of methane CH4, carbon two and more than carbon components C2+, siH4/SiHmCln, a small amount of carbon monoxide CO, carbon dioxide CO2, water H2O, silicon dioxide SiO2 and Si/C micro particles, wherein the pressure is normal pressure or low pressure, and the temperature is normal temperature; pretreating, namely, feeding raw material gas into a pretreatment unit consisting of a dust remover, a particle removal filter and an oil mist removal catcher through pressurization, sequentially removing dust, particles, oil mist, partial high-chlorosilane, high-chloralkane and high-hydrocarbon impurities under the operating conditions of 0.2-0.3 MPa pressure and normal temperature, and enabling the formed purified raw material gas to enter the next working procedure, namely, chlorosilane spraying absorption; the method comprises the steps of spraying and absorbing chlorosilane, pressurizing purified raw material gas from a pretreatment process to 0.6-1.0 MPa, carrying out cold-heat exchange to 80-160 ℃, entering from the bottom of a spraying absorption tower, adopting chlorosilane+anhydrous HCl liquid as an absorbent, spraying from the top of the spraying absorption tower and carrying out reverse mass transfer exchange with the purified raw material gas, flowing out an absorption liquid enriched with chlorosilane and HCl from the bottom of the chlorosilane spraying absorption tower, entering a next process, namely a multistage evaporation/compression/condensation process, simultaneously outputting a small amount of residual particles, high chlorosilane, high chloralkane and high hydrocarbon impurities flowing out from the bottom of the chlorosilane spraying absorption tower, and carrying out environmental protection treatment, wherein the non-condensable gas rich in H2 flows out from the top of the chlorosilane spraying absorption tower, is used for heating in a subsequent chloromethane hydrochlorination process after adsorption treatment, or is directly used as fuel gas, or is output as raw material gas for extracting H2; the method comprises the steps of multistage evaporation/compression/condensation, wherein an absorption liquid from a chlorosilane spray absorption process enters multistage evaporation, is directly or depressurized to 0.6-1.0 MPa, enters a condenser, and obtains gas-phase crude HCl gas from the gas-phase crude HCl gas, wherein the crude HCl liquid formed after condensation enters the next process, namely HCl refining, flows out of the condenser, and enters the subsequent chlorosilane for shallow cold rectification; HCl refining, namely, feeding crude HCl liquid from a multistage evaporation/compression/condensation process into an HCl refining process consisting of an HCl rectifying tower and a vacuum rectifying tower, wherein the operating pressure of the rectifying tower is 0.3-1.0 MPa, the operating temperature is 60-120 ℃, the operating pressure of the vacuum rectifying tower is-0.08 to-0.1 MPa, the operating temperature is 60-120 ℃, HCl gas with the purity of more than 99.9% is distilled from the top of the rectifying tower, the HCl gas enters a next process, namely chlorosilane hydrochlorination, distillate from the bottom of the rectifying tower enters the vacuum tower, overhead gas flowing out from the top of the rectifying tower mainly contains a small amount of methane chloride, enters a subsequent chloromethane rectifying process, chloromethane is further recovered, heavy components flowing out from the bottom of the vacuum rectifying tower are returned to the multistage evaporation/compression/condensation process, or returned to a shallow cold rectifying process in the subsequent chlorosilane; the hydrochlorination of chloromethane, namely, HCl gas from an HCl refining process is proportionally mixed with externally-transmitted methanol steam to enter a hydrochlorination reactor for hydrochlorination, the reaction temperature is 230-300 ℃, the reaction pressure is normal pressure or less than 0.3MPa, a solid catalyst is ferric oxide or zinc oxide, crude chloromethane gas generated by the reaction flows out of the reactor, and the crude chloromethane gas enters the next process, namely, washing and absorption after quenching and condensation; washing and absorbing, namely, enabling the quenched and condensed crude chloromethane gas from the chloromethane hydrochlorination reaction process to enter a washing and absorbing tower for separating organic matters from inorganic matters, wherein the washing and absorbing operation conditions are normal temperature and normal pressure or micro-positive pressure, enabling the by-product hydrochloric acid to flow out of the washing and absorbing tower, enabling the flowing-out non-condensable gas to enter an alkali neutralization tower and a rewashing tower, further removing residual HCl and methanol, and enabling the formed purified chloromethane gas to enter the next process, namely chloromethane rectification; rectifying chloromethane, mixing the purified chloromethane gas from the washing and absorbing process with the vacuum tower top gas from the HCl refining process, entering a chloromethane rectifying tower, distilling chloromethane product with purity of more than 99.9% from the rectifying tower top, and outputting the distillate at the rectifying tower bottom to process to produce a polychlorinated methane product; the method comprises the steps of shallow cold rectification in chlorosilane, a crude chlorosilane liquid from a multistage evaporation/compression/condensation process, a shallow cold rectification process in the entered chlorosilane, wherein the operating temperature is-35-10 ℃, the operating pressure is 0.6-2.0 MPa, non-condensable gas flowing out of the top of a rectifying tower is directly used as fuel gas or returned to a chlorosilane spraying absorption process, and the chlorosilane liquid flowing out of the bottom of the rectifying tower is used as an absorbent and returned to the chlorosilane spraying absorption process for recycling.
2. The method for preparing chloromethane by utilizing chlorine-based CVD process tail gas grown by Si/SiC crystal films as claimed in claim 1, wherein the chlorosilane spray absorption process is additionally provided with a secondary medium-temperature chlorosilane absorption process under the working condition that HCl and chlorosilane contained in purified raw material gas are high in concentration, namely, non-condensable gas from the chlorosilane spray absorption process is compressed, condensed and separated from gas-liquid, then the new non-condensable gas is formed and directly or pressurized to 0.2-1.0 MPa, after cold and heat exchange is carried out, the new non-condensable gas enters from the bottom of the additionally provided secondary chlorosilane spray absorption process absorption tower, a mixed liquid containing chlorosilane/HCl is adopted as an absorbent, the mixed liquid containing chlorosilane/HCl is sprayed from the secondary chlorosilane spray absorption tower, the mixed liquid 2 enriched with the HCl flows out from the bottom of the absorption tower, the mixed liquid 1 of the primary chlorosilane spray absorption process enters a subsequent multistage evaporation/compression/condensation process, the liquid obtained after gas-liquid separation returns to the top of the chlorosilane, and flows out from the bottom of the absorption tower as fuel gas, and is directly or directly extracted as the mass transfer gas after absorption or is carried out as the mass transfer gas after absorption.
3. The method for preparing chloromethane by using chlorine-based CVD process tail gas for growing Si/SiC crystal films as claimed in claim 1, wherein under the working condition that the purified chloromethane gas from the washing and absorbing process contains more polychlorinated methane and water, the purified chloromethane gas is dehydrated and dried by sulfuric acid and then treated by a chloromethane rectifying process, overhead gas is distilled from the top of a rectifying tower and is condensed and separated from gas liquid, liquid is returned to the rectifying tower as reflux, the gas enters an adsorption and drying process to obtain chloromethane product gas, the purity is greater than or equal to 99.99%, and the rectifying tower bottom distillate is the polychlorinated methane, and the chloromethane product gas is sent out of a boundary region to be subjected to rectification separation to obtain respective products.
4. The method for preparing chloromethane by utilizing chlorine-based CVD process tail gas for growing Si/SiC crystal films according to any one of claims 1 or 3, wherein the chloromethane hydrochlorination reaction is to adopt liquid phase reaction, anhydrous HCl gas from an HCl refining process is mixed with gasified methanol steam with a certain proportion to enter a chloromethane hydrochlorination liquid phase reaction process, 75-85% zinc chloride aqueous solution is used as a liquid catalyst, the liquid catalyst is heated to 120 ℃, the reaction temperature is 120-160 ℃, the reaction pressure is normal pressure or micro-positive pressure, the chloromethane hydrochlorination liquid phase reaction is carried out by bubbling gas-liquid contact, and crude chloromethane gas generated by the reaction is subjected to quenching, condensation, washing absorption, sulfuric acid drying and chloromethane rectification, or the chloromethane product is obtained after absorption drying, and the purity is more than or equal to 99.9-99.99%.
5. A method for preparing chloromethane by using chlorine-based CVD process tail gas generated by growing Si/SiC crystal thin film according to any one of claims 1 or 3, wherein the rectifying bottom of the chloromethane rectifying process is fed into a chlorination reactor, wherein chlorine is fed in a certain proportion to further chlorinate the bottom of the rectifying tower, the reaction mixture thus produced is fed into a carbon tetrachloride rectifying tower, the carbon tetrachloride product is distilled from the top of the rectifying tower, the bottom of the rectifying tower is returned to the chloromethane rectifying tower, the chloromethane product is distilled from the top of the rectifying tower, the purity is greater than or equal to 99.99%, the yield is greater than 98%, the bottom of the rectifying tower is fed into a dichloromethane rectifying tower, the bottom of the rectifying tower is fed into a trichloromethane rectifying tower, the trichloromethane product is fed from the top of the rectifying tower, and the rest of heavy component impurities including a small amount of chlorosilane, c2+ and water are discharged into an incinerator for standard treatment.
6. A method for preparing chloromethane by utilizing chlorine-based CVD process tail gas for growing Si/SiC crystal films, as claimed in any one of claims 1 or 3, is characterized in that a chlorination reaction step is additionally carried out when the HCl content in the purified raw material gas is less than 5 percent and the H2 content is more than 80 percent under the working condition, dry crude chloromethane gas obtained by drying sulfuric acid, non-condensable hydrogen-rich gas obtained by a chlorosilane spray absorption process and chlorine gas are fed into a chlorination reactor according to a certain proportion to carry out hydrochlorination reaction, the formed reaction gas is quenched by a rectifying tower of an HCl rectifying process, part of crude HCl distilled from the top of the rectifying tower is directly fed into the chloromethane hydrochlorination process after being cooled, and the other part of the crude HCl is fed into a vacuum tower of HCl refining, or directly serving as an absorbent of a chlorosilane spray absorption process, directly entering a chloromethane hydrochlorination process from the distillate flowing out of the bottom of a rectifying tower, quenching, condensing, washing, absorbing and drying by sulfuric acid to obtain crude chloromethane gas, then entering a carbon tetrachloride rectifying tower, distilling carbon tetrachloride products from the top of the tower, feeding the tower bottom distillate into the chloromethane rectifying tower, distilling chloromethane products from the top of the tower, wherein the purity is more than or equal to 99.99%, feeding the tower bottom distillate into a dichloromethane rectifying tower, distilling dichloromethane products from the top of the tower, feeding the tower bottom distillate into a trichloromethane rectifying tower, feeding the tower top distilled trichloromethane products, and discharging other heavy component impurities including a small amount of chlorosilane, C2+ and water reaching standards into an incinerator for treatment and discharge.
7. The method for preparing chloromethane by using chlorine-based CVD process tail gas for growing Si/SiC crystal films according to claim 1, wherein the purified chloromethane gas in the washing and absorbing process can directly enter a temperature swing adsorption drying mode consisting of at least two adsorption towers under the working condition that the content of polychloroethane and water is less than 1-3%, one tower adsorbs, the other tower or towers regenerates, and the adsorption and regeneration alternately operate to realize continuous production, the chloromethane product with the purity of more than or equal to 99.9-99.99% flows out of the adsorption tower in an adsorption state, a chloromethane rectification process is not needed, and the regeneration carrier gas adopts non-condensable gas flowing out from the chlorosilane spraying and absorbing process, and the regeneration temperature is more than 80-120 ℃.
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| CN101870709A (en) * | 2010-06-25 | 2010-10-27 | 天津大学 | Method for refining and reclaiming chloromethane from organic silicon production process |
| RU2404952C1 (en) * | 2009-07-01 | 2010-11-27 | Федеральное государственное унитарное предприятие "Государственный ордена Трудового Красного Знамени научно-исследовательский институт химии и технологии элементоорганических соединений" (ФГУП ГНИИХТЭОС) | Methyl chloride synthesis method |
| CN111333484A (en) * | 2020-04-29 | 2020-06-26 | 高永宝 | Ultrahigh-purity methane chloride production system and process |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| RU2404952C1 (en) * | 2009-07-01 | 2010-11-27 | Федеральное государственное унитарное предприятие "Государственный ордена Трудового Красного Знамени научно-исследовательский институт химии и технологии элементоорганических соединений" (ФГУП ГНИИХТЭОС) | Methyl chloride synthesis method |
| CN101870709A (en) * | 2010-06-25 | 2010-10-27 | 天津大学 | Method for refining and reclaiming chloromethane from organic silicon production process |
| CN111333484A (en) * | 2020-04-29 | 2020-06-26 | 高永宝 | Ultrahigh-purity methane chloride production system and process |
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