CN110003263B - Process for removing and completely recovering dimethyldichlorosilane from HCl - Google Patents
Process for removing and completely recovering dimethyldichlorosilane from HCl Download PDFInfo
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- CN110003263B CN110003263B CN201910183008.9A CN201910183008A CN110003263B CN 110003263 B CN110003263 B CN 110003263B CN 201910183008 A CN201910183008 A CN 201910183008A CN 110003263 B CN110003263 B CN 110003263B
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- LIKFHECYJZWXFJ-UHFFFAOYSA-N dimethyldichlorosilane Chemical compound C[Si](C)(Cl)Cl LIKFHECYJZWXFJ-UHFFFAOYSA-N 0.000 title claims abstract description 151
- 238000000034 method Methods 0.000 title claims abstract description 25
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 108
- 239000007788 liquid Substances 0.000 claims abstract description 104
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 claims abstract description 72
- 229910000041 hydrogen chloride Inorganic materials 0.000 claims abstract description 72
- 239000007789 gas Substances 0.000 claims abstract description 57
- 238000010521 absorption reaction Methods 0.000 claims abstract description 41
- NEHMKBQYUWJMIP-UHFFFAOYSA-N chloromethane Chemical compound ClC NEHMKBQYUWJMIP-UHFFFAOYSA-N 0.000 claims abstract description 38
- 230000005587 bubbling Effects 0.000 claims abstract description 29
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 5
- 125000000118 dimethyl group Chemical group [H]C([H])([H])* 0.000 claims abstract 2
- 238000012856 packing Methods 0.000 claims description 26
- 239000012071 phase Substances 0.000 claims description 25
- 239000002994 raw material Substances 0.000 claims description 19
- 230000003301 hydrolyzing effect Effects 0.000 claims description 11
- 238000001816 cooling Methods 0.000 claims description 8
- KPUWHANPEXNPJT-UHFFFAOYSA-N disiloxane Chemical class [SiH3]O[SiH3] KPUWHANPEXNPJT-UHFFFAOYSA-N 0.000 claims description 7
- 239000006096 absorbing agent Substances 0.000 claims description 6
- 229910000831 Steel Inorganic materials 0.000 claims description 5
- 239000007791 liquid phase Substances 0.000 claims description 5
- 239000010959 steel Substances 0.000 claims description 5
- 239000000919 ceramic Substances 0.000 claims description 4
- 230000008014 freezing Effects 0.000 claims description 4
- 238000007710 freezing Methods 0.000 claims description 4
- 238000005057 refrigeration Methods 0.000 claims description 4
- 230000005514 two-phase flow Effects 0.000 claims description 4
- 238000005903 acid hydrolysis reaction Methods 0.000 claims description 2
- 230000008020 evaporation Effects 0.000 claims description 2
- 238000001704 evaporation Methods 0.000 claims description 2
- 239000005046 Chlorosilane Substances 0.000 claims 1
- KOPOQZFJUQMUML-UHFFFAOYSA-N chlorosilane Chemical compound Cl[SiH3] KOPOQZFJUQMUML-UHFFFAOYSA-N 0.000 claims 1
- 239000011491 glass wool Substances 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 239000012267 brine Substances 0.000 description 5
- 230000007062 hydrolysis Effects 0.000 description 5
- 238000006460 hydrolysis reaction Methods 0.000 description 5
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- 239000002250 absorbent Substances 0.000 description 2
- 230000002745 absorbent Effects 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000010962 carbon steel Substances 0.000 description 2
- 239000000945 filler Substances 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 239000003595 mist Substances 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 230000001174 ascending effect Effects 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000000110 cooling liquid Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000007792 gaseous phase Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000013526 supercooled liquid Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
- C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
- C07F7/02—Silicon compounds
- C07F7/08—Compounds having one or more C—Si linkages
- C07F7/12—Organo silicon halides
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
- C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
- C07F7/02—Silicon compounds
- C07F7/08—Compounds having one or more C—Si linkages
- C07F7/20—Purification, separation
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Treating Waste Gases (AREA)
- Gas Separation By Absorption (AREA)
Abstract
The invention relates to a process for removing and completely recovering dimethyl dichloroalkane from hydrogen chloride, which comprises the following steps: HCl of the feed gas 3 is used as a heat source to enter the stripping tower 523,using liquid HCl and liquid CH3Cl is evaporated to make the dimethyldichlorosilane flow to the tower kettle of the stripping tower 523; the gas phase HCl4 enters a cold exchanger 524, and the dry gas phase HCl6 with the dimethyl dichlorosilane removed exchanges heat and is sent to CH3A Cl synthesis reaction kettle; a bubbling section is arranged at the lower part of the absorption tower 504, and liquid CH circulating in a coil pipe3Cl was subcooled to-50 ℃ and dimethyldichlorosilane in dry HCl5 was condensed in the bubbling layer; the temperature of the dry gaseous HCl6 of the absorption tower 504 from which the dimethyldichlorosilane is removed is less than-50 ℃ to-60 ℃, the dimethyldichlorosilane is completely absorbed, and the dimethyldichlorosilane is less than 100ppm (mol).
Description
Technical Field
The invention relates to the field of chemical industry, in particular to a process for separating and completely recovering dimethyldichlorosilane from HCl.
Background
In the prior art, a large-scale organic silicon device hydrolyzes dimethyldichlorosilane to produce siloxane byproduct hydrochloric acid gas, which is also called HCl gas. The most economical hydrolysis method of dimethyldichlorosilane is the supersaturated hydrochloric acid method, also known as the concentrated hydrochloric acid hydrolysis method. The granted patent No. ZL201410012354.8 discloses a process for removing and recovering dimethyldichlorosilane from hydrochloric acid gas, which comprises the following steps:
1 a first-stage HCl subcooler 507-1 is arranged at the downstream of a frozen brine graphite subcooler 501, HC1 gas 4 with the gas phase containing less than 0.99% (mol) of dimethyldichlorosilane is cooled to the temperature of less than-20 ℃, dry HCl5 with the gas phase containing less than 0.5% (mol) of dimethyldichlorosilane enters a glass wool filter 502, is dehydrated by the glass wool filter 502, more than 90 wt% of concentrated acid mist drops and dimethyldichlorosilane small liquid beads suspended in the HCl gas phase are filtered out, and are gathered into large liquid drops which slide down to a collecting tank at the lower part of the glass wool filter 502 by gravity, and the dry HCl5 with the dimethyldichlorosilane less than 0.5% (mol) is obtained by filtration, wherein the dry HCl5 contains H2O＜100ppm(wt)；
Dry HCl5 (mole) less than 0.5% of 2-dimethyldichlorosilane enters the dimethyldichlorosilane absorption tower 504 and is filled with wire mesh corrugated packing, and the supercooled liquid CH3Cl and dry HCl are in countercurrent contact on the surface of the wire mesh corrugated packing, and liquid CH3Cl is volatilized continuously, the temperature is reduced rapidly, and liquid CH is obtained3The volatilization of Cl provides a large amount of cold energy, so that the temperature of HCl main body of the gas discharged from the tower is reduced to be less than-35 ℃, the temperature of the absorbent is less than-50 ℃, and the dimethyl dichlorosilane is dissolved in the absorbent to ensure the temperature of the absorbentRising, with the dimethyldichlorosilane absorbing excess heat, to bring a portion of the liquid CH3Cl is evaporated into the gas phase and the dried HCl6 after removal of dimethyldichlorosilane contains CH3Cl is less than 2.3 percent (mol), dimethyldichlorosilane is less than 0.01-0.02 percent (mol), and the heat is transferred to CH after passing through a primary HCl subcooler 507-1 and a secondary HCl subcooler 507-23A Cl synthesis reaction kettle;
3 the liquid discharged from the tower bottom of the dimethyldichlorosilane absorption tower 504 and the primary liquid CH3The Cl subcooler 509-1 enters the middle section of the rectifying tower 505 after being cooled, the rectifying tower 505 is provided with an upper section of packing and a lower section of packing, and the upper end of the packing is sprayed with fresh liquid CH3Cl8, dimethyl dichlorosilane < 0.1(wt) from rectifying column vent gas 11 to recycle CH3The absorption liquid is rectified by a Cl compressor through a lower section of packing, so that the rectifying tower 505 contains more than 99.9 percent (wt) of dimethyldichlorosilane and CH3The residue having Cl < 0.1(wt) is cooled with water and then sent to the dimethyldichlorosilane hydrolysis step 400 by the dimethyldichlorosilane return pump 503, as shown in FIG. 1.
The problem exists that the process comprises a freezing brine graphite subcooler 501, a primary HCl subcooler 507-1, a secondary HCl subcooler 507-2, a glass wool filter 502 and a primary liquid CH, although the dimethyl dichlorosilane in the HCl gas phase of the raw material can be completely eliminated, and the separated dimethyl dichlorosilane can be completely returned to the dimethyl dichlorosilane hydrolysis procedure after being processed3Cl subcooler 509-1, secondary liquid CH3Cl subcooler 509-2, dimethyldichlorosilane absorption tower 504, dimethyldichlorosilane return pump 503, reboiling pump 506 and kettle liquid subcooler 508, need above-mentioned 10 equipment just can realize eliminating dimethyldichlorosilane in raw materials HCl gaseous phase completely, and can process qualified all returning dimethyldichlorosilane that separates to the dimethyldichlorosilane hydrolysis process, it uses equipment many, have area big, investment and manufacturing cost are high, the construction cycle is long, the process is complicated, the process control degree of difficulty is big, the problem of production cycle length, the probability of error appearing in the production has also been increased.
The invention content is as follows:
the technical problem to be solved by the invention is as follows: overcomes the defects and shortcomings of the prior art, and provides a process for separating and completely recovering dimethyldichlorosilane from HCl, which simplifies the flow, reduces the investment, has reasonable energy utilization, low operating cost and good safety.
The technical scheme for solving the technical problem is as follows: a process for removing and completely recovering dimethyldichlorosilane from hydrogen chloride comprises a process 400 of hydrolyzing dimethyldichlorosilane by concentrated hydrochloric acid, and is characterized in that: further comprising the steps of:
1) the HCl of the raw material gas 3 from the step 400 of hydrolyzing dimethyldichlorosilane with concentrated hydrochloric acid is introduced into the lower part of the stripping tower 523 as a heat source, and the dephlegmation liquid 13 of the cooling exchanger 524 and the still liquid 7 of the absorption tower 504 are sprinkled on the ceramic corrugated packing of the stripping tower 523; using liquid HCl and liquid CH3Cl is evaporated to reduce the temperature of the raw material gas 3, a part of dimethyldichlorosilane is condensed, simultaneously dimethyldichlorosilane in the kettle liquid 7 and the fractional condensate liquid 13 flows to the tower kettle of the stripping tower 523, the weight of dimethyldichlorosilane in the kettle liquid 15 of the stripping tower 523 is equal to that of dimethyldichlorosilane in the raw material gas, the tower kettle liquid 15 returns to the step 400 of hydrolyzing dimethyldichlorosilane by concentrated hydrochloric acid, and gaseous HCl4 containing less than 0.99 percent of dimethyldichlorosilane flows out of the stripping tower 523;
the raw material gas 3 from the step 400 of hydrolyzing dimethyldichlorosilane with concentrated hydrochloric acid contains HCl and CH3Cl and dimethyldichlorosilane;
the kettle liquid 7 discharged from the absorption tower 504 contains liquid CH3Cl and dimethyldichlorosilane;
the dephlegmation liquid 13 discharged from the cooling exchanger 524 contains dimethyl dichlorosilane and siloxane which are recovered by refrigeration;
2) after raw material gas 3 entering stripping tower 523 comes out of the packing layer, gas-phase HCl4 containing dimethyldichlorosilane less than 0.99% enters cold exchanger 524, dimethyldichlorosilane carried by gas-phase HCl4 is fractionated into dephlegmation liquid 13 in cold exchanger 524, dry HCl5 containing dimethyldichlorosilane less than 0.5% (mol) enters absorption tower 504, and the residual dimethyldichlorosilane is totally condensed into kettle liquid 7 of absorption tower 504, the dimethyldichlorosilane of the two liquid streams is totally recovered, and the cold energy is fully utilized,meanwhile, the dry gas phase HCl6 without the dimethyldichlorosilane is sent to CH after heat exchange between the cold exchanger 524 and the gas phase HCl43A Cl synthesis reaction kettle;
3) the lower part of the absorption tower 504 is provided with a bubbling section which consists of a coil pipe wound outside a central pipe and an annular bubbling pipe arranged at the bottom of the coil pipe and is welded on a channel steel welded firmly with the tower wall, and a two-phase flow containing a plurality of small bubbles flows through a gap between the coil pipe on the outer wall of the central pipe and the tower wall, so that HCl and CH in a liquid phase3Cl is volatilized to refrigerate, so that the freezing temperature of the system is reduced, even a part of HCl is liquefied, and liquid CH flows through the coil3The Cl is subcooled to-50 ℃ to become bottoms 7 of the absorber 504; > 60% liquid CH3Cl is volatilized and refrigerated in the bubbling layer, and more than 80% of dimethyldichlorosilane in the dried HCl5 with dimethyldichlorosilane less than 0.5% (mol) is condensed in the bubbling layer;
4) the wire mesh corrugated packing in the absorber 504 is sufficiently wetted to form a very thin layer of HCl + CH on the large packing surface3Cl film, gas passing from the surface, HCl and CH3Volatilizing Cl, further cooling and refrigerating, wherein the temperature of dry gas phase HCl6 which is taken out of tower gas and is deprived of dimethyl dichlorosilane is lower than minus 50 ℃ to minus 60 ℃, the dimethyl dichlorosilane is completely absorbed, the dimethyl dichlorosilane is lower than 100ppm (mol), and the dry gas phase HCl6 which is deprived of the dimethyl dichlorosilane enters a cold exchanger 524;
5) fresh liquid CH3Cl8 into precooler 520 and portion CH3Cl evaporation, liquid CH3Introducing Cl8 into a bubbling section of the absorption tower 504 after precooling;
6) the kettle liquid 7 of the absorption tower 504 is pumped into the pressure storage tank 522 by the kettle liquid pump, and then flows out of the pressure storage tank 522 into the stripping tower 523.
The invention has the beneficial effects that:
1 stripping tower 521 without reboiler, using raw gas as heat source, separating light components HCl and CH of the kettle liquid (7) and the condensate (13)3Cl is vaporized and rises, so that the heavy component dimethyldichlorosilane is liquefied and flows into the tower kettle;
2, a bubbling layer and a circulating central pipe are arranged at the bottom of the dimethyldichlorosilane absorption tower 504;
3 a plurality of small holes are drilled on the wall of the annular bubbling pipe, and when cold HCl airflow is sprayed out from the small holes at high speed to enter the liquid CH3In Cl, make liquid CH3Cl is strongly volatilized for refrigeration, so that the system is rapidly cooled;
4 a coil pipe is arranged in the bubbling layer of the dimethyldichlorosilane absorption tower 504, and liquid CH outside the pipe3Cl is volatilized; rapidly cooling liquid HCl in a coil pipe at the temperature of-50 to-60 ℃ to T < -50 ℃;
liquid CH in 5 coil3After being supercooled, Cl is sprinkled on the wire mesh corrugated packing of the dimethyldichlorosilane absorption tower 504, and only a small part of liquid CH is3Cl volatilizes on the surface of the filler, the gas temperature is reduced to minus 50 to minus 60 ℃, and enough liquid CH is available3Cl was used to wash the residual dimethyldichlorosilane after > 80% of the dimethyldichlorosilane had been absorbed by the bubbling layer, so that the purified HCl contained < 100ppm (mol) dimethyldichlorosilane (guaranteed value of 200ppm mol).
The method has the advantages of simplified flow, low investment, reasonable energy utilization, low operating cost and good safety, thereby being more competitive.
Drawings
FIG. 1 is a flow diagram of a prior art process for the removal and recovery of dimethyldichlorosilane from hydrochloric acid gas;
FIG. 2 is a flow chart of the process for the removal and complete recovery of dimethyldichlorosilane from HCl in accordance with the present invention.
In the figure: 1 dimethyldichlorosilane, 2 acid condensate, 3 feed gas containing less than 4.3% (mol) dimethyldichlorosilane, 4 gaseous HCl containing less than 0.99% dimethyldichlorosilane, 5 dry HCL containing less than 0.5% (mol) dimethyldichlorosilane, 6 dry gaseous HCl from which dimethyldichlorosilane is removed, 7 kettle solution, 8 fresh liquid CH3Cl, 9 circulating liquid CH3Cl, 10 cycle gas CH3Cl, 11 gas outlet of rectifying tower, 12 hot dimethyldichlorosilane and siloxane liquid, 13 frozen and recovered dimethyldichlorosilane and siloxane, 14 frozen brine, 15 kettle liquid, 400 dimethyldichlorosilane hydrolysis process, 501 frozen brine graphite cooler, 502 glass wool filter, 503 dimethyldichlorosilane return pump, 504 absorption tower and 505 refining towerA distillation tower, a 506 reboiler, a 507-1 first-stage HCl heat exchanger, a 507-2 second-stage HCl heat exchanger, a 508 kettle liquid water cooler, a 509-1 first-stage CH3Cl subcooler, 509-2 two-stage CH3Cl subcooler, 520 liquid CH3Cl precooler, 521 bottom pump, 522 pressure storage tank, 523 stripping column, 524 cold exchanger.
Detailed Description
The invention is further illustrated by the figures and the specific examples.
Referring to fig. 1, example 1, this example is a process for removing and completely recovering dimethyldichlorosilane from hydrogen chloride, which includes a process 400 of hydrolyzing dimethyldichlorosilane with concentrated hydrochloric acid, and further includes the following steps:
1) the HCl of the raw material gas 3 containing less than 4.3% (mol) of dimethyldichlorosilane from the step 400 of hydrolyzing dimethyldichlorosilane with concentrated hydrochloric acid enters the lower part of the stripping tower 523 as a heat source, and the dephlegmation liquid 13 of the cooling exchanger 524 and the kettle liquid 7 of the absorption tower 504 are sprinkled on the ceramic corrugated packing of the stripping tower 523; using liquid HCl and liquid CH3Cl is evaporated to reduce the temperature of the raw material gas 3, a part of dimethyldichlorosilane is condensed, simultaneously dimethyldichlorosilane in the kettle liquid 7 and the fractional condensate liquid 13 flows to the tower kettle of the stripping tower 523, the weight of dimethyldichlorosilane in the kettle liquid 15 of the stripping tower 523 is equal to that of dimethyldichlorosilane in the raw material gas 3, the tower kettle liquid 15 returns to the step 400 of hydrolyzing dimethyldichlorosilane by concentrated hydrochloric acid, and gaseous HCl4 containing less than 0.99 percent of dimethyldichlorosilane flows out of the stripping tower 523;
the raw material gas 3 from the step 400 of hydrolyzing dimethyldichlorosilane with concentrated hydrochloric acid contains HCl and CH3Cl and dimethyldichlorosilane, with only droplets of concentrated hydrochloric acid and siloxane entrained in the mist being corrosive to carbon steel;
the kettle liquid 7 discharged from the absorption tower 504 contains 49.3 percent of HClC and CH when the temperature is minus 42 DEG C3Cl 47% and dimethyldichlorosilane 3.5% (mol%);
the temperature of the partial condensate 13 discharged from the cooling exchanger 524 is-32 ℃, and the partial condensate contains HCl36.6% and CH3Cl 6.7%, dimethyldichlorosilane 56.2% (mol%), dry HCl6 for dimethyldichlorosilane removal was virtually free of normal handlingDimethyldichlorosilane, and therefore the weight of dimethyldichlorosilane in feed gas 3 is equal to the weight of dimethyldichlorosilane in bottoms 15 from stripping column 523;
2) after raw material gas 3 entering stripping tower 523 comes out of the packing layer, gas-phase HCl4 containing dimethyldichlorosilane less than 0.99% enters cold exchanger 524, dimethyldichlorosilane carried by gas-phase HCl4 is fractionated into dephlegmation liquid 13 in cold exchanger 524, dry HCl5 containing dimethyldichlorosilane less than 0.5% (mol) enters absorption tower 504, and residual dimethyldichlorosilane is completely condensed into kettle liquid 7 of absorption tower 504, dimethyldichlorosilane of the two liquid streams is completely recovered, the cold energy is fully utilized, and meanwhile, dry gas-phase HCl6 without dimethyldichlorosilane is sent to CH after heat exchange between cold exchanger 524 and gas-phase HCl43A Cl synthesis reaction kettle;
3) the lower part of the absorption tower 504 is provided with a bubbling section which consists of a coil pipe wound outside a central pipe and an annular bubbling pipe arranged at the bottom of the coil pipe and is welded on a channel steel welded firmly with the tower wall, and a two-phase flow containing a plurality of small bubbles flows through gaps among the central pipe, an outer wall coil pipe and the tower wall, so that HCl and CH in a liquid phase3Cl is volatilized to refrigerate, so that the freezing temperature of the system is reduced, even a part of HCl is liquefied, and liquid CH flows through the coil3The Cl is subcooled to-50 ℃ to become bottoms 7 of the absorber 504; > 60% liquid CH3Cl is volatilized and refrigerated in the bubbling layer, and more than 80% of dimethyldichlorosilane in the dried HCl5 with dimethyldichlorosilane less than 0.5% (mol) is condensed in the bubbling layer;
4) the wire mesh corrugated packing in the absorber 504 is sufficiently wetted to form a very thin layer of HCl + CH on the large packing surface3Cl film, gas passing from the surface, HCl and CH3Cl is volatilized, the temperature is further reduced and refrigerated, the temperature of the dry gas phase HCl6 which is taken out of the tower and is deprived of the dimethyldichlorosilane is lower than minus 50 ℃ to minus 60 ℃, the dimethyldichlorosilane is completely absorbed, the dimethyldichlorosilane is less than 100ppm (mol), and the dry gas phase HCl6 which is deprived of the dimethyldichlorosilane enters a cold exchanger 524;
5) fresh liquid CH3Cl8 enters precooler 520 and a portion of CH3Cl between the tubesEvaporating, precooling and then entering a bubbling section of the absorption tower 504;
6) the kettle liquid 7 of the absorption tower 504 is pumped into the pressure storage tank 522 by the kettle liquid pump, and then flows out of the pressure storage tank 522 into the stripping tower 523.
The technical and economic effects of the embodiment are obvious and are embodied as follows:
1) the stripping tower 523 has good technology and remarkable effect;
(1) the weight of the dimethyl dichlorosilane frozen and recovered from the stripping tower 523 is more than that of the dimethyl dichlorosilane recovered from the frozen brine graphite cooler 501 in the technical scheme disclosed in the issued patent with the patent number ZL 201410012354.8;
(2) the stripping tower 523 can recover cold energy and dimethyl dichlorosilane, simplify the process and reasonably utilize energy;
due to HCl and CH3The Cl and dimethyl dichlorosilane ternary system can be liquefied at low temperature, and the lower the temperature is, the higher the concentration of HCl dissolved in a liquid phase is; for example: the temperature of the bottom liquid 7 of the absorption tower 504 is-42 ℃, and the bottom liquid contains 49.3% of HClC and CH3Cl 47%, dimethyldichlorosilane 3.5% (mol%), condensate 13 discharged from cooling exchanger 524 at-32 deg.C, HCl 36.6%, and CH3Cl 6.7%, dimethyldichlorosilane 56.2% (mol%), as reflux for stripping column 523, liquid HCl and CH3Cl evaporates and absorbs heat, so that the temperature of the system is reduced, the dimethyl dichlorosilane in the raw material gas 3 is mostly liquefied, and the liquid dimethyl dichlorosilane in the kettle liquid 7 of the absorption tower 504 and the partial condensate liquid 13 discharged from the cold exchanger 524 also flows into the tower kettle of the stripping tower 523. Moreover, the weight of the dimethyldichlorosilane discharged from the residue 15 of the stripping tower 523 is exactly equal to that of the dimethyldichlorosilane in the raw material gas 3; most of the uncondensed dimethyldichlorosilane in the feed gas 3 is liquefied in the cold exchanger 524, and returns to the stripping tower 523 along with the condensate 13, and the residual dimethyldichlorosilane is completely absorbed by the absorption tower 504 and returns to the top of the stripping tower 523 along with the kettle liquid 7 of the absorption tower 504; in the technical solution disclosed in the granted patent No. ZL201410012354.8, HCl + CH in the bottom liquid 7 of the absorption tower 5043Cl: dimethyldichlorosilane 27 to 30:1(mol ratio)) Large amount of liquid HCl and CH3Cl is distilled out through a reboiler 506 in the rectifying tower 505, precious cold energy between-32 ℃ and-42 ℃ cannot be utilized, water vapor is consumed, and energy waste is large! Furthermore, it has been found that reboiler 506 is absolutely leak-free, even though only 0.1 orifice is required due to H2The O meets with the dimethyldichlorosilane to generate hydrochloric acid, the area of a leakage point is rapidly enlarged, once the water vapor leaks into the rectifying tower 505, all the wire mesh filler is scrapped;
(3) the lower part of the stripping tower 523 is filled with ceramic corrugations, the area is large, and the gas flow rate is low, so that concentrated hydrochloric acid and siloxane fog drops wrapped by the feed gas 3 can be effectively captured, and the effect of the glass wool filter 502 can also be achieved; if the glass wool filter 502 is arranged before HCl of the feed gas 3 enters the stripping tower 523, the stripping tower 523 and the filling materials in the tower can be made of carbon steel;
2) countercurrent exchange is carried out on the outlet gas 4 of the stripping tower and the dry HCl6 which is subjected to the removal of the dimethyldichlorosilane at the temperature of minus 50 ℃ to minus 60 ℃ in a cold exchanger 524, the dephlegmated liquid 13 is dephlegmated at the cold end of the cold exchanger 524, the dephlegmated liquid 13 flows back to the stripping tower 523 by gravity, and the cold energy and related components HCl and CH are recovered3Cl and dimethyldichlorosilane; dry HCl5 with the temperature of-32 ℃ to-40 ℃ and the dimethyl dichlorosilane content of less than 0.5% (mol) enters a bubbling pipe at the bottom of the absorption tower 504;
3) the tower bottom of the absorption tower 504 is provided with a bubbling section, the bubbling section is composed of a bubbling pipe and two layers of coiled pipes wound on a central pipe, the bubbling pipe and the central pipe are welded firmly on a manufactured channel steel, the channel steel is welded firmly with the tower bottom, and the central pipe is used as a liquid circulation pipe of the bubbling layer;
the gas flow at-32 ℃ sprayed out from the small hole of the bubbling tube at high speed is in liquid HCl + liquid CH3Water bubbles formed in the liquid phase of Cl, with a bubble diameter of about 2.0mm, at the bubble boundary, CH3The Cl liquid is volatilized and refrigerated to ensure that the gaseous HCl is rapidly cooled, even a part of HCl is liquefied, meanwhile, the dimethyldichlorosilane in the gas phase is liquefied to be more than 80 percent (wt) and enters the circulating liquid, and the two-phase flow with high turbulence degree passes through the gap of the spiral pipe to ensure that the liquid CH in the spiral pipe3Cl is cooled to-45-50 ℃ and-50 ℃ liquid CH3Cl showerOnto the packing of absorber 504; because the wire netting ripple packing has large specific surface area, a thin liquid layer CH is hung3Cl, when ascending HCl gas passes through, CH3Cl is volatilized to further refrigerate, so that the temperature of the dry HCL gas 6 discharged from the absorption tower 504 is lower than-50 ℃ to-60 ℃, and cold exchange is facilitated;
most of CH3Cl in bubbling layer to volatilize and refrigerate, cooled CH3Cl liquid flows through the packing layer of the absorption tower 504, and the absorption flow formed in the packing layer is 4-5 times of the minimum wetting amount of the packing. The amount of dimethyldichlorosilane actually entering the packing layer is only one tenth of the amount of dimethyldichlorosilane entering stripping column 523, thus ensuring that less than 100ppm (mol) of dimethyldichlorosilane is present in dry HCL gas 4 exiting stripping column 523;
4) for the liquid tank pump 521, a shield pump is recommended in the invention; due to the presence of HCl and CH3Cl, which can corrode severely once in contact with air, causing leaks; in addition, the liquid level of the bubbling layer is less than 3 m, and a part of fluid at the outlet of the pump must return to the inlet of the pump to improve the positive net suction head of the inlet of the pump, so that the pump does not generate air-lock.
Claims (1)
1. A process for removing and completely recovering dimethyldichlorosilane from hydrogen chloride comprises a step (400) of hydrolyzing dimethyldichlorosilane by concentrated hydrochloric acid, and is characterized in that: further comprising the steps of:
1) HCl of a raw material gas (3) from a step (400) of hydrolyzing dimethyldichlorosilane by concentrated hydrochloric acid enters the lower part of a stripping tower (523) as a heat source, and a dephlegmation liquid (13) of a cooling exchanger (524) and a kettle liquid (7) of an absorption tower (504) are sprayed on a ceramic corrugated packing of the stripping tower (523); using liquid HCl and liquid CH3Cl evaporation is carried out to reduce the temperature of the raw material gas (3), a part of dimethyldichlorosilane is condensed, dimethyldichlorosilane in the kettle liquid (7) and the fractional condensate liquid (13) flows to the tower kettle of the stripping tower (523), the weight of dimethyldichlorosilane in the kettle liquid (15) of the stripping tower (523) is equal to that of dimethyldichlorosilane in the raw material gas, the tower kettle liquid (15) reflows to the concentrated hydrochloric acid hydrolysis dimethyldichlorosilane working procedure (400), and the dimethyl-containing dichlorosilaneGas phase HCl (4) with chlorosilane less than 0.99 mol percent flows out of the stripping tower (523);
the raw material gas (3) from the step (400) of hydrolyzing dimethyldichlorosilane with concentrated hydrochloric acid contains HCl and CH3Cl and dimethyldichlorosilane;
the kettle liquid (7) discharged from the absorption tower (504) contains liquid CH3Cl and dimethyldichlorosilane;
the partial condensate (13) discharged from the cold exchanger (524) comprises the dimethyl dichlorosilane and the siloxane which are recovered by refrigeration;
2) after raw material gas (3) entering a stripping tower (523) exits a packing layer, gas-phase HCl (4) containing dimethyldichlorosilane less than 0.99% enters a cold exchanger (524), dimethyldichlorosilane carried by the gas-phase HCl (4) is fractionated into a dephlegmation liquid (13) in the cold exchanger (524), dry HCl (5) containing dimethyldichlorosilane less than 0.5% mol enters an absorption tower (504), and residual dimethyldichlorosilane is completely condensed into kettle liquid (7) of the absorption tower (504), dimethyldichlorosilane of the two liquid streams is completely recycled, cold energy is fully utilized, and meanwhile, dry-phase HCl (6) without dimethyldichlorosilane is sent to CH (CH) after heat exchange between the cold exchanger (524) and the gas-phase HCl (4)3A Cl synthesis reaction kettle;
3) the lower part of the absorption tower (504) is provided with a bubbling section which consists of a coil pipe wound outside a central pipe and an annular bubbling pipe arranged at the bottom of the coil pipe and is welded on a channel steel welded with the tower wall, and a two-phase flow containing a plurality of small bubbles flows through a gap between the coil pipe on the outer wall of the central pipe and the tower wall, so that HCl and CH in a liquid phase3Cl is volatilized to refrigerate, so that the freezing temperature of the system is reduced, even a part of HCl is liquefied, and liquid CH flows through the coil3Cl is subcooled to-50 ℃ and-50 ℃ liquid CH3Cl is sprinkled on the packing on the upper part of the absorption tower (504) to become kettle liquid (7) of the absorption tower (504); > 60% liquid CH3The Cl is volatilized and refrigerated in the bubbling layer, and the dimethyldichlorosilane which is less than 0.5 percent mol and is more than 80 percent in the dry HCl (5) is condensed in the bubbling layer;
4) wire mesh in an absorber tower (504)The corrugated packing is fully wetted, and very thin HCl and CH are formed on the surface of the huge packing3Cl film, gas passing from the surface, HCl and CH3Cl is volatilized, then cooling and refrigeration are carried out, the temperature of the dry gas phase HCl (6) which is taken out of the tower and is deprived of the dimethyldichlorosilane is T which is more than minus 60 ℃ and less than minus 50 ℃, the dimethyldichlorosilane is completely absorbed, the dimethyldichlorosilane is less than 100 ppm/mol, and the dry gas phase HCl (6) which is deprived of the dimethyldichlorosilane enters a cold exchanger (524).
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| CN102250132B (en) * | 2011-04-11 | 2013-12-04 | 余家骧 | Process for recovering siloxane from concentrated hydrochloric acid and refining coarse chloromethane |
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| CN103724367B (en) * | 2014-01-11 | 2016-01-27 | 余家骧 | Remove from HCl gas and reclaim dimethyldichlorosilane(DMCS) technique |
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