KR940003212B1 - Continuous treatment of compound including chlorosilane - Google Patents

Abstract

The treatment method comprises (1) introducing the waste solution and gas containing at least one component of chlorosilane into the downpart of a stirring bath, which is filled with suspension solution of water and CaO with its pH being above 9; (2) discharging produced slurry continuously; (3) keeping the level of solution and temperature in the bath within a certain range, and (4) additing and compensating new CaO suspension solution and keeping the pH 9. This method can treat the waste solution and gas simultaneously.

Description

Continuous disposal method of waste containing silane chloride compounds

1 is a flow diagram of an apparatus and process used in an embodiment to illustrate the invention.

* Explanation of symbols for main parts of the drawings

1 CaO Sultry stirring tank 2 Gas-liquid contact device

3: sedimentation tank 5: gas dispersion pipe

8: slurry pump 12: pH measuring instrument

15 cooling coil 18 agitator impeller

CW: Coolant M: Motor

PG: Pressure gauge TC: Temperature controller

V: Valve

The present invention relates to a method for treating a waste containing a silane chloride compound. In more detail, the present invention relates to a liquid or gaseous waste containing at least one component of the silane chloride compound discharged in a high-purity polycrystalline silicon manufacturing process or a synthesis process of organochlorinated silane which is a starting material of an organosilicon product (Silicone). The present invention relates to a method for simple and safe continuous processing with an aqueous alkali solution.

The silane chloride compound in the present invention includes not only silane chlorides such as trichlorosilane and silicon tetrachloride, but also methyl chloride silane, phenyl chloride, etc., which are recently used in large quantities as starting materials of silicone, and include general formulas such as R _a SiH _b Cl _c . I can display it. Where R represents a methyl group or a phenyl group and the subscripts a, b are integers of 0,1,2,3, c is 1,2,3 and a + b + c = 4 relationship is established between them. Examples of the representative silane chloride compounds include trichlorosilane, silicon tetrachloride, trimethylsilane, methyldichloride, dimethyldichloride, methyltrichloride, phenyltrichloride, diphenyldichloride and the like.

As one of the methods for manufacturing high-purity polycrystalline silicon (6N-11N), which are the basic materials of semiconductor ICs and solar cells, (1) metal trichloride (about 98.5% purity) is reacted with hydrogen chloride gas to produce trichlorosilane (SiHCl ₃ ). And (2) purifying the trichlorosilane with high purity, (3) reducing or pyrolysing the purified trichlorosilane with hydrogen at about 1.100 ° C. to deposit and prepare silicon, and (4) byproduct silicon tetrachloride (SiCl _4). ) Is reduced to H ₂ in the presence of metal silicon to prepare trichlorosilane and reuse it. Wastes from these high-purity silicon manufacturing processes include silane chloride liquid containing chlorides of metals such as aluminum, iron, and titanium, and waste gas containing hydrogen silane (hydrogen, nitrogen, etc.) from distillation and purge. have. In addition, a large amount of wastes containing the silane chloride compounds are also loaned in synthetic processes such as methyl chloride silane and phenyl silane, which are silicone starting materials such as silicone oil, rubber and resin, and synthetic quartz glass manufacturing process.

Conventional techniques for treating such waste liquid of the silane chloride compound include a method of hydrating liquid waste into water to form an oxide and treating byproduct hydrochloric acid with a suitable alkali. In this method, a large amount of water and very vigorous stirring are required in order to prevent the reaction vessel from being blocked by the silica solid generated by hydration, resulting in excessive equipment costs and difficult maintenance. Another conventional technique is a combustion method as set forth in US Pat. No. 4,519,999, which also has a high equipment cost and fuel cost. Another prior art for solving the above problems is described in US Pat. No. 4,690,810 as a method of neutralizing by injecting silane chloride liquid into a stirred tank filled with calcium oxide (CaO) suspension water. This method is a batch process that injects silane chloride solution into calcium oxide suspended water initially maintained at pH 9 or above, and stops the waste solution injection at pH 7-8 and recovers the solid reaction product. Solving the problems, but after the reaction is finished, after removing the internal product again to charge the new CaO suspension ballistics to carry out the reaction, there is a problem that continuous operation is impossible.

Conventional techniques for treating the waste gas of the silane chloride compound have been widely used to decompose the chlorine chloride into SiO ₂ and neutralize the HCl produced by washing the waste gas with an aqueous solution of caustic soda (NaOH). the herein generated SiO ₂ is acid to ttuin a slightly alkaline clogging adhering to the surface of the precipitation by the device or devices in a gel state, it will cause and increase pressure loss by adjusting the pH of the rinse solution to 13 to 14 to SiO ₂ Na It needs to be made of ₂ SiO ₃ (sodium metasilicate).

SiO ₂ +2 NaOH → Na ₂ SiO ₃ + H ₂ 0

Therefore, a large amount of caustic soda is usually required and the maintenance of the device is difficult. Conventional techniques for solving this problem include calcium oxide suspended water and jet scrubber in a pH range of 9.5 to 10.5 circulating by pumping silane chloride waste gas as disclosed in Japanese Patent Laid-Open No. 63-214,321. The slurry produced after the reaction in the same gas-liquid contacting apparatus is precipitated and separated, and calcium oxide is added to the mother liquor to adjust the pH to circulate and reuse. This method is effective for treating silane chloride waste gas, but the equipment cost is relatively high and it is inadequate for treating silane chloride waste liquid.

The present invention solves the problems of the conventional method as described above to provide an inexpensive and simple method that can simultaneously process the waste gas and waste liquid of the silane chloride compound discharged from a high-purity polycrystalline silicon manufacturing process or organochlorinated silane synthesis process.

The conventional method divides waste containing silane chloride compound into gas and liquid, and waste gas is treated with NaOH aqueous solution in the range of pH 13 to 14 or CaO suspension in the range of pH 9.5 to 10.5, and the waste liquid is treated separately in batch. Is characterized in that all the wastes are treated continuously at the same time using a continuous stirring tank filled with CaO suspension of pH 9 or more.

탱크와 같은 내산, 내알칼리성 재질의 탱크로서 그 내부에 2개의 임펠러(impeller)가 부착된 교반기와 냉각용 코일이, 그 하부에는 염화실란 화합물 도입용 분산 파이프가 설치되어 있다. pH 9 이상의 CaO 현탁수를 상기 교반조 내에 채운다음 염화실란 화합물 함유 폐기물을 반응열에 의한 증기(fume)가 발생하지 않을 정도의 속도로 현탁액의 하부에 주입한다. 염화실란 화합물이 CaO 현탁수와 접촉하면 우선 물과 반응하여 SiO₂가 생성됨과 동시에 HCI은 CaO에 의해 중화되고 SiO₂는 겔 상으로 석출하는데 이때 현탁수의 pH를 9 이상으로 유지하면 석출한 SiO₂와 CaO, H₂O가 반응하여 Ca(HSiO₃)₂로 되어 겔 상 SiO₂를 수반하므로 침강하기 쉬운 슬러리가 된다. pH 9 이하에서는 CaO가 거의 다 소비되어 Ca(HSi0₃)₂에 수반되지 않은 겔 상 SiO₂가 많이 남아 있어 침강 분리가 어렵고 장치, 기기등에 부착하기가 쉽다.Referring to one embodiment of the present invention, a continuous stirring bath for treating a silane chloride compound is for example polyethylene ELPAI.

An acid and alkali resistant tank, such as a tank, is provided with a stirrer with two impellers inside it and a cooling coil, and a dispersing pipe for introducing a chlorinated silane compound at the lower portion thereof. The CaO suspension having a pH of 9 or above is filled into the stirring vessel, and then the waste containing the silane chloride compound is injected into the lower portion of the suspension at a rate such that no fume is generated by the heat of reaction. When the silane compound contacts with CaO suspended water, it first reacts with water to form SiO ₂ , while HCI is neutralized by CaO and SiO ₂ is precipitated in a gel phase. When the pH of the suspended water is maintained above 9, the precipitated SiO ₂ reacts with CaO and H ₂ O to form Ca (HSiO ₃ ) ₂ , which is accompanied by gel phase SiO ₂ , and thus becomes a slurry that is easily precipitated. Below pH 9, CaO is almost consumed, and much SiO ₂ remains on the gel, which is not accompanied by Ca (HSi0 ₃ ) ₂ , making sedimentation separation difficult and easy to attach to devices and devices.

The chemical formula involved in the reaction is represented by the following formula in the case of trichlorosilane and dimethyldichloride.

2HSiCl ₃ + 3ca0 + H ₂ O → 2SiO ₂ + 3CaCl ₂ + H ₂

(CH _{3) 2} SiCl ₂ + H ₂ 0 → Ca0 + SiO ₂ + CaC1 ₂ + 2CH ₄

Since the above reactions are very exothermic, the temperature of the reaction mixture increases in proportion to the injection rate of the silane chloride compound. The temperature of the stirring bath is controlled by cooling the suspension with a cooling coil installed in the vessel while limiting the silane chloride injection rate. Maintaining the temperature inside the stirring tank below about 60 ° C. can avoid fume generation. The resulting slurry is automatically discharged to the outside of the stirring tank through the overflow tube so that the level of the stirring tank is kept constant. The pH of the discharged slurry is measured, and the stirring tank is added with a new CaO suspension of pH 9 or higher in conjunction with this value. The internal slurry is kept constant above pH 9 to allow for treatment of the silane chloride compound. The discharged slurry is introduced into a sedimentation separation tank and separated into a solid mainly composed of silica and an aqueous solution of CaCl ₂ . Aqueous CaCl ₂ solution can be concentrated and prepared commercially at about 35 wt.% Through an evaporation process, and the solid is an environmentally harmless material. The stirring tank is capable of sealing by applying a positive pressure, for example, about 10 psi or more above the vapor pressure of the injected silane chloride compound, and the rotating shaft of the stirrer and the stirring tank are sealed using a mechanical chamber. In addition, a gas-liquid contact device such as a separate Rasching Ring packed column is installed, and newly supplied CaO suspension water is passed through the device to be supplied to the stirring tank, and the gas discharged from the stirring tank is passed through the device to finally remain there. To neutralize and remove silane chloride compounds.

In the prior art, as shown in US Pat. No. 4,690,810, the silane chloride waste solution is treated batchwise in a stirred tank filled with CaO suspension, whereby the adjustment of the silane chloride injection rate is difficult and continuous operation is not possible. Wastes containing all types of silane chloride compounds were removed using a continuous stirred tank reactor (CSTR) type treatment tank that continuously discharged the resulting slurry and replenished the spent CaO with fresh CaO suspended water. It can be processed continuously in one device.

Hereinafter, the present invention will be described in detail with reference to the drawings. The figure shows a flowchart of an embodiment of the present invention, where (1) is a stirring vessel, (2) a gas-liquid contact device, and (3) is a sedimentation separation tank.

Waste gas or waste liquid containing a chlorosilane compound is dispersed in a dispersion pipe (5) through an introduction pipe (4), introduced into a stirring vessel (1), and brought into contact with CaO suspended water to change into SiO ₂ , Ca (HSi0 ₃ ) ₂ . The resulting slurry-containing liquid is introduced into the sedimentation separation tank 3 continuously through an overflow tube 6, where the sedimentation-separated slurry is introduced by the pump 8 through the tube 7 The supernatant CaCl ₂ aqueous solution is discharged through the tube (9).

On the other hand, the waste gas in which the silane chloride compound, HCI gas and the like are mostly removed by contacting and reacting with CaO suspended water in the stirring vessel and the hydrogen gas generated by the reaction are passed through the tube 10 to the gas-liquid contact device 2. It is introduced and reacted with CaO strong alkaline suspension water of pH 9 or higher injected therein to remove the trace amount of residual silane compound and then discharged out of the system through the pipe (11).

재질의 냉각코일로서 (16),(17)을 통해 냉각수를 흘려 염화실란 화합물이 CaO 접촉하여 발생하는 반응열을 제거하여 액의 과열에 의한 유독성 증기(fume) 발생을 억제하도록 한다.(12) measures the pH of the suspension overflowed from the stirring tank with a measuring device, in conjunction with this to operate the valve 13 to inject fresh CaO suspension water into the stirring tank through the tube 14, the pH of the stirring tank is constant To be maintained. 15 is polystyrene XL for heat exchange

Cooling water flows through the cooling coils (16) and (17) as a cooling coil of the material to remove the reaction heat generated by the contact of the silane chloride compound with CaO to suppress the generation of toxic fumes due to overheating of the liquid.

Although the Rasching Ring is used as the gas-liquid contacting device 2 in the above embodiment, other gas-liquid contacting devices such as a jet scrubber and a sieve tray may be used. In addition, although a dispersion pipe 5 having several holes drilled down was used as an injection facility for the silane chloride compound, various types of dispersion devices such as screens and filters may be used.

As shown in the above description, according to the conventional method, when the waste gas and the waste liquid of the silane chloride compound discharged from the high purity polycrystalline silicon manufacturing process, etc. are treated in a separate apparatus, and the NaOH is used in the waste gas treatment method, the apparatus and the apparatus are clogged. Since the pH of the NaOH aqueous solution must be maintained at 13 to 14, a large amount of NaOH is required, maintenance is difficult, and a circulatory system using CaO suspended water is complicated in equipment and incapable of treating waste liquids, and in waste liquid treatment methods. In the glass-lined agitator tank equipped with a cooling jacket filled with CaO suspension water, it is treated as a potted plant, so the equipment cost and operation cost are relatively high. And waste liquid can be processed continuously in one stirring tank at the same time. By keeping constant the gel SiO ₂ is an easy-slurry (Slurry) to extremely sedimentation to coexist with the generated Ca (HSi0 _{3) 2} can operate reliably without the concern that attached to the device, the device because it is easy to separate the conventional According to the method of the present invention, compared to the method, all gas / liquid chlorine chloride wastes generated in polycrystalline silicon manufacturing process or organochlorinated silane synthesis process can be continuously and stably processed in one device, and the equipment cost is low, maintenance, Easy to repair

Example 1

500 liters of suspended water (CaO 15% by weight) of calcium oxide (CaO) in the form of fine powder of 60 mesh or less was prepared in a polyethylene stirring tank as shown in the drawing. Initially, the pH of the suspended water was above 13. The chlorine silane waste gas of the composition shown in Table 1 discharged from the high-purity polycrystal test plant was injected into the apparatus through a distribution pipe installed at the bottom of the stirring vessel to neutralize and process the same.

TABLE 1

Continuously flowing the waste gas, the pH of the suspension flowing in the stirring tank was continuously measured with a pH meter.When the pH value dropped to 9, new CaO suspension water (15% by weight) was automatically replenished to adjust the pH in the stirring tank to 9 The waste gas was treated at steady state.

The rotation speed of the stirrer was 350rpm and the cooling water was flowed into the cooling coil to maintain the temperature in the stirring tank at 50 ° C or lower. After about 100 hours of operation, the total consumption of CaO was 470 kg, which was 18.5 kg per 100 m3 of gas, and the average amount of CaO contained in freshly-injected suspended water was 4.5 kg per hour. Stable operation was possible without any blockages or deposits in the gas injector, impeller, etc., and the content of silane chloride in the outlet gas was 5 ppm or less.

Example 2

As in Example 1, 15% by weight of CaO suspension was initially prepared in a stirring vessel. Silane chloride waste liquid of the composition as shown in Table 2 was injected through the liquid injection pipe installed in the lower part of the stirring tank to neutralize and process.

TABLE 2

In the same manner as in Example 1, while continuously injecting the waste liquid to the pH 9 of the stirred tank was replenished with fresh CaO suspension to treat the waste liquid continuously in a steady state of pH 9. After about 65 hours of operation, the total consumption of CaO was 440 kg, 1.23 kg per liter of waste liquor, and the average amount of newly injected CaO was 6.4 kg per hour. Stable operation was possible without clogging or deposits in the equipment such as liquid injection pipes and impellers, and the content of silane chloride in the outlet gas was 5 ppm or less.

Example 3

The silane chloride waste gas having the same composition as in Example 1 and the waste liquid of Example 2 were continuously injected into the stirring vessel in the same manner as described above at a flow rate of 12.2 m 3 / hr and 3 L / hr, respectively, to be continuously neutralized and treated. After about 100 hours of operation, the total consumption of CaO was about 560 kg, and the average amount of CaO newly injected at steady state was 5.3 kg per hour. Stable operation was possible and the silane chloride content in the outlet gas was less than 5 ppm.

Example 4

For the purpose of the experiment, (CH ₃ ) ₂ SiCl ₂ liquid was injected and neutralized and treated at a rate of about 10 kg / hr through a liquid injection pipe installed in the lower part of the stirring vessel in the same manner as in Example 2. After 20 hours of operation, the total CaO consumption was 102 kg, 0.51 kg per 1 kg of (CH ₃ ) ₂ SiCl ₂ liquid, and the amount of newly added CaO at steady state was 4.9 kg per hour. Stable operation was possible and the chloride silane content in the outlet gas was less than 5 ppm.

Claims (5)

Waste gas and waste liquid containing at least one component of the silane chloride compound are injected into the lower part of the stirring tank filled with a suspension of CaO particles and water of pH 9 or higher, and the resulting slurry is continuously discharged to the outside of the stirring tank, and the temperature and temperature of the stirring tank are constant. Chloride silane, characterized in that it is maintained within the range, and the spent CaO is added and supplemented with fresh CaO suspension water of pH 9 or more to treat the silane chloride compound while maintaining the pH of the slurry in the stirring tank within 9 for a certain range. Process for the continuous disposal of wastes containing compounds. The method of claim 1, wherein the CaO slurry agitator is a container in which a cooling coil is installed inside and sealed to the outside. The chlorinated silane according to claim 1, wherein the newly supplied CaO suspension water is passed through a separate gas-liquid contacting device to be supplied to the stirring tank, and the gas discharged from the stirring tank is also passed through the gas-liquid contacting device. Process for the continuous treatment of wastes containing compounds. The method of claim 1, wherein the pH of the slurry to be discharged is continuously measured and the amount of fresh CaO suspended water is automatically adjusted according to this value. The chlorinated compound according to claim 1, wherein the chlorochloride compound is trichlorosilane, silicon tetrachloride, trimethylsilane, methyldichloride, dimethyldichloride, methyltrichloride, pentyl trichloride, divinyl dichloride. Process for the continuous treatment of waste containing silane compounds.

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