Process and device for purifying byproduct waste acid generated by incineration of tail gas in production of methyl chlorosilane

Abstract

The invention provides a process and a device for purifying byproduct waste hydrochloric acid generated by incineration of tail gas in production of methyl chlorosilane. The waste hydrochloric acid is firstly subjected to plate-frame pressure filtration to remove most fumed silica and other large-particle impurities, then is subjected to precision filtration to remove residual fumed silica and other solid impurities, then is subjected to special adsorption material to remove metal ions, and finally is filtered by a filter to obtain clear and transparent hydrochloric acid. High-purity hydrochloric acid can be obtained by purifying the waste hydrochloric acid, and the method has remarkable economic benefits and environmental protection benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of organic silicon, and in particular relates to a purification process and device for waste hydrochloric acid produced as a by-product of the incineration of tail gas in the production of methylchlorosilane. Background Art

[0002] Organic silicon materials have excellent properties such as high and low temperature resistance and electrical insulation. They are widely used in aerospace, electronics, medical and health industries. They are a new type of material that cannot be replaced by modern high-tech industries. More than 90% of organic silicon material products are derived from methylchlorosilane monomers. A large amount of chlorine-containing organic tail gas is generated during the synthesis and distillation separation of methylchlorosilane monomers, which is generally treated by incineration.

[0003] The exhaust gas produced during the production of organosilicon has complex components, including dusty exhaust gas containing silicon powder, non-condensable exhaust gas of methyl chloride and hydrocarbons, and low-boiling-point chlorosilane exhaust gas. Organosilicon exhaust is a chlorine-containing organic substance, and the incineration temperature is generally 1100-1200℃. The main components of the flue gas generated at this time are H2O, HCl, CO2 and SiO2, as well as a large amount of N2 and some excess O2, and a trace amount of Cl2. The exhaust gas enters the incinerator and is incinerated in the waste heat boiler to produce steam as a by-product. After leaving the waste heat boiler, the flue gas enters the quenching tower and is quickly cooled to below 80℃. Most of the hydrogen chloride and the gas-phase silica obtained by incineration are captured in the quenching tower and discharged from the system. The remaining hydrogen chloride is absorbed in the hydrochloric acid absorption tower and returned to the quenching tower.

[0004] The concentration of hydrochloric acid discharged from the quenching tower is only 17%-22%. It contains a large amount of silicon dioxide, metal ions and mechanical impurities, which cannot be directly utilized and sold. It is usually treated as hazardous waste or simply removed solid impurities and then sent to the sewage treatment device for alkali neutralization. This consumes a large amount of alkali solution and produces waste salt, and the comprehensive treatment cost is high. Based on a 400,000-ton organosilicon monomer production unit, about 15,000 tons of waste hydrochloric acid is produced per year, and the cost of waste hydrochloric acid treatment is about 22.5 million yuan per year. It not only increases the cost of the enterprise, but also wastes chlorine resources and pollutes the environment.

[0005] The production of silicone monomers itself is a process that requires chlorine resources. Generally, it is necessary to purchase methyl chloride or purchase hydrochloric acid to decompose hydrogen chloride to synthesize methyl chloride as the raw material for the production of methylchlorosilane. If the hydrochloric acid is purified and utilized as a resource on site, it will not only reduce the company's production costs but also reduce environmental pressure. Summary of the invention

[0006] In view of the above technical problems, the present invention develops a process for purifying waste hydrochloric acid produced by incineration of tail gas from methylchlorosilane production, and the specific steps are as follows: A purification device for waste hydrochloric acid produced as a by-product of tail gas incineration in the production of methylchlorosilane, wherein the waste hydrochloric acid pipeline from the incineration device is connected to the feed port at the top of the stirring tank, the discharge port at the bottom of the stirring tank is connected to the feed pump inlet via a pipeline, and the pump outlet is connected to the inlet pipeline of the plate and frame filter press; the hydrochloric acid outlet of the plate and frame filter press is connected to the inlet pipeline of the intermediate tank; the bottom outlet of the intermediate tank is connected to the inlet pipeline of the intermediate feed pump, and the outlet of the intermediate feed pump is connected to the inlet pipeline of the precision filter; the outlet of the precision filter is connected to the filter pipeline, and the filter outlet is connected to the hydrochloric acid buffer tank.

[0007] The outlet of the precision filter is connected to the inlet pipeline of the resin bed; the outlet of the resin bed is connected to the filter pipeline.

[0008] Two resin beds are provided and connected by pipelines, so that parallel operation and series operation can be realized.

[0009] The purification process of waste hydrochloric acid produced as a by-product of tail gas incineration in the production of methylchlorosilane comprises the following steps: the waste hydrochloric acid enters a stirring tank, the flow of a feed pump is controlled to lift the waste hydrochloric acid to a plate and frame filter press for filtration, the acid filter cake obtained by filtration is de-alkali-neutralized, and the hydrochloric acid filtrate is obtained by gravity flow to an intermediate tank; the hydrochloric acid in the intermediate tank is transported by a high-pressure pump through a precision filter to filter a small amount of gas-phase silica and mechanical impurities therein, and then removed from the resin bed, and finally filtered to a filter to obtain pure dilute hydrochloric acid to be sent to a buffer tank.

[0010] The waste hydrochloric acid is obtained by burning the flue gas obtained by burning chloromethane exhaust gas, chlorosilane exhaust gas and dust-containing exhaust gas containing silicon powder and catalyst in an incinerator at 1100-1200°C in the production process of organic silicon through a preheating boiler, a quenching tower and a hydrochloric acid tower, including a hydrogen chloride concentration of 17%-22%, 5%-10% of fumed silica, and metal ion iron ion, aluminum ion, calcium ion impurities, and a temperature of ≤45°C. It also contains unknown organic impurities and is gray-black, apricot-yellow, turbid and opaque in appearance.

[0011] The stirring paddle is located at one-third of the bottom of the stirring tank, and the stirring speed is 10-30 rpm.

[0012] The content of fumed silica in the waste hydrochloric acid after plate and frame filtration is less than or equal to 1%.

[0013] The precision filter is a filter with a cartridge structure or a filter bag structure. The filter element is made of polytetrafluoroethylene. After filtration, the hydrochloric acid appears yellow, clear and transparent, and solid impurities such as silicon dioxide are less than 0.01%.

[0014] The resin in the resin bed is mainly composed of a polystyrene skeleton and contains a porous structure amide macroporous adsorption material. The structural characteristics are: , wherein R is a matrix material with an active group, which is a styrene resin, acrylic resin, acrylonitrile resin, phenolic resin, epoxy resin or silica gel matrix material, mainly a polystyrene resin. The active group of the matrix material R with an active group is -CH2Cl, -COOCH3, -CN, -CH2OH, -CH2(O)CH-CH2Cl or other groups that can react with amines and polyamines. R1 is an alkyl or alkyl ketone structure, R2 is a propionamide structure, and N- represents elemental nitrogen.

[0015] The resin used in the present invention is a type of macromolecular adsorbent that does not contain ion exchange groups and has a large mesh network. It relies on the van der Waals attraction between it and the adsorbate and works through physical adsorption through its huge specific surface. Macroporous adsorption resin is a separation material that combines the principles of adsorption and screening. This adsorption performance is the result of van der Waals attraction or the formation of hydrogen bonds; at the same time, due to the porous structure of the macroporous adsorption resin, it has a screening effect on substances of different molecular sizes. The macroporous adsorption resin material in the present invention is prepared by using an amide-containing adsorption material and its synthesis method (CN 105944693A).

[0016] The resin bed adopts a one-on-one-standby mode, when one is working for adsorption, the other is in regeneration operation.

[0017] When the hydrochloric acid passes through the resin bed, the flow rate of the waste hydrochloric acid is 0.5-1BV / h, and analysis is performed after absorbing 20-60BV of hydrochloric acid (BV is a multiple of the volume of the adsorption material).

[0018] After treatment, the waste hydrochloric acid has iron ions ≤0.05ppm, calcium ions ≤10ppm, aluminum ions ≤3ppm, and is colorless and transparent in appearance.

[0019] Technical advantages of the present invention: The components of organic silicon tail gas are complex, and the byproduct waste hydrochloric acid after incineration has complex components, many impurities, and extremely poor quality, and is generally treated as hazardous waste. The present invention develops a purification process for the waste hydrochloric acid and obtains high-purity hydrochloric acid, which is of great significance.

[0020] 1. High-purity dilute hydrochloric acid can be obtained by using plate and frame filter pressing, precision filtration and resin adsorption process routes.

[0021] 2. The purified hydrochloric acid can be directly used to synthesize chloromethane in the chloromethane synthesis kettle, or it can be used to analyze hydrogen chloride gas in the analysis device to synthesize chloromethane or trichlorosilane. It can also be used to absorb hydrogen chloride gas in the organosilicon dimethyl hydrolysis device to obtain concentrated hydrochloric acid for sale. It can also analyze hydrogen chloride in part and absorb hydrogen chloride in part to obtain concentrated hydrochloric acid for sale.

[0022] 3. The resin material developed for waste salt from tail gas incineration has high adsorption efficiency. It can not only adsorb inorganic metal ions, but also adsorb organic impurities therein, and has a high processing capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a process flow chart of the present invention, wherein: 1. stirring tank; 2. feed pump; 3. plate and frame filter press; 4. intermediate tank; 5. intermediate feed pump; 6. precision filter; 7. resin bed; 8. filter. DETAILED DESCRIPTION

[0024] Example 1 A set of purification equipment for treating 15,000 tons of methylchlorosilane production tail gas incineration byproduct waste hydrochloric acid annually. The waste hydrochloric acid pipeline from the incineration device is connected to the top feed port of the mixing tank 1, the bottom discharge port of the mixing tank 1 is connected to the inlet of the feed pump 2 through a pipeline, and the outlet of the feed pump 2 is connected to the inlet pipeline of the plate and frame filter press 3; the hydrochloric acid outlet of the plate and frame filter press 3 is connected to the inlet pipeline of the intermediate tank 4; the bottom outlet of the intermediate tank 4 is connected to the inlet pipeline of the intermediate feed pump 5, and the outlet of the intermediate feed pump 5 is connected to the inlet pipeline of the precision filter 6; the outlet of the precision filter 6 is connected to the filter 8 pipeline, and the outlet of the filter 8 is connected to the hydrochloric acid buffer tank. The outlet of the precision filter 6 is connected to the inlet pipeline of the resin bed 7; the outlet of the resin bed 7 is connected to the filter 8 pipeline. The resin bed 7 is two resin beds connected in parallel, realizing one open and one standby. The pipelines and instrument valves are all lined materials. Automatic control valves and instrument monitoring, instrument adjustment, and instrument metering facilities are set according to the process operation needs of each device and the pipelines connecting the devices. The precision filter is set with backwashing measures.

[0025] Example 2 Waste hydrochloric acid from the incineration device is waste hydrochloric acid obtained by burning chloromethane exhaust gas, chlorosilane exhaust gas and dusty exhaust gas containing silicon powder and catalyst in the incinerator at 1100-1200℃ in the production process of organic silicon, and then passing through the preheating boiler, quenching tower and hydrochloric acid tower. The concentration of hydrogen chloride is 18%-22%, and it contains 8%-10% fumed silica, 80-100ppm iron ions, 180-300ppm aluminum ions, 20-50ppm calcium ions, and metal ion impurities such as nickel, chromium, and vanadium. It also contains unknown organic impurities, and its appearance is gray-black, apricot-yellow, turbid and opaque.

[0026] With the waste hydrochloric acid purification device of Example 1, 2t / h of waste hydrochloric acid from the incineration device enters the stirring tank, and stirring makes it evenly distributed in the hydrochloric acid. The waste hydrochloric acid is transported to the plate and frame filter press at a speed of 2t / h by a mud pump for pressure filtration to obtain an acidic silica filter cake and hydrochloric acid liquid. The silica filter cake is de-alkali neutralized, and the hydrochloric acid liquid flows to the hydrochloric acid intermediate tank. The silica content in the hydrochloric acid after pressure filtration is 0.5%, and the flow rate is controlled by the regulating valve after the pump. 1.9t / h is sent to the precision filter to further filter and remove silica and trace mechanical impurities to avoid affecting the effect of material adsorption. 50ppm of silica in the hydrochloric acid after filtering by the precision filter enters the adsorption bed A, and the flow rate in the adsorption bed is 1BV / h. The hydrochloric acid after the adsorption bed A is analyzed by chemical analysis of iron ion removal rate 0ppm, calcium ion 3ppm, aluminum ion 1ppm, appearance colorless and transparent, quality qualified, and enters the buffer tank after passing through the filter.

[0027] The adsorption material used is a macroporous adsorption resin with a polystyrene skeleton, a porous structure and amino active groups, which has excellent antioxidant and acid-base resistance. The product obtained by the preparation method of Example 1 in CN 105944693 A patent was used for the experiment.

[0028] Example 3 Using the waste hydrochloric acid treatment process and process parameters of Example 2, when the hydrochloric acid treatment capacity is 50 BV / h, the hydrochloric acid flowing out of adsorption bed A is slightly yellow. The feed valve of adsorption bed B is opened, the feed valve of adsorption bed 4 is closed, the adsorption bed is switched for use, and a qualified hydrochloric acid solution is obtained. Adsorption bed A is regenerated.

[0029] Example 4 According to the treatment process steps and process parameters of the waste hydrochloric acid in Example 2, the flow rate of hydrochloric acid in the adsorption bed is 1.5BV / h, the hydrochloric acid flowing out of the adsorption bed A is slightly yellow, and the feed valve of the adsorption bed B is opened, so that the adsorption beds A and B are used in series to obtain a qualified hydrochloric acid solution.

[0030] Example 5 According to the treatment process steps and process parameters of waste hydrochloric acid in Example 2, the resin is a product obtained by the method of Example 2 in CN 105944693 A. The hydrochloric acid has a flow rate of 0.5 BV / h in the resin bed, and can treat 55 BV of hydrochloric acid. The obtained hydrochloric acid has 0.01 ppm of iron ions, 2 ppm of calcium, and 0.5 ppm of aluminum, and is colorless and transparent in appearance. The dilute hydrochloric acid is transported to the hydrochloric acid absorption device to absorb hydrogen chloride to obtain 31% concentrated hydrochloric acid for sale.

[0031] Example 6 According to the treatment process steps and process parameters of waste hydrochloric acid in Example 2, the resin is a macroporous adsorption resin with a porous structure and amino active groups, which is mainly composed of polystyrene skeleton and RD115 produced by Xi'an Rundong Technology Co., Ltd. The hydrochloric acid has a flow rate of 1BV / h in the resin bed, and can process 50BV of hydrochloric acid. The obtained hydrochloric acid has 0ppm of iron ions, 1ppm of calcium, and 0.2ppm of aluminum, and the appearance is colorless and transparent. After purification, the dilute hydrochloric acid is transported to the hydrochloric acid analysis device for analysis to obtain hydrogen chloride gas, which is transported to the chloromethane synthesis device through a pipeline to produce chloromethane.

[0032] Example 7 According to the treatment process steps and process parameters of the waste hydrochloric acid in Example 2, an ion exchange resin with a sulfonic acid group (-SO3H) as an active group is used (such as a cationic resin of type -001X7 (732)). When the hydrochloric acid treatment volume is 8 BV, the hydrochloric acid flowing out of the adsorption bed A is slightly yellow. The feed valve of the adsorption bed B is opened, the feed valve of the adsorption bed 4 is closed, and the adsorption bed is switched for use. When the adsorption bed B treats 8 BV, the color and metal ions of the hydrochloric acid are unqualified. The ion exchange resin with a sulfonic acid group (-SO3H) as an active group has a poor ability to treat the hydrochloric acid.

Claims

1. A purification device for waste hydrochloric acid produced by incineration of tail gas from methylchlorosilane production, characterized in that: The waste hydrochloric acid pipeline from the incineration device is connected to the top feed port of the stirring tank (1); the bottom discharge port of the stirring tank (1) is connected to the inlet of the feed pump (2) through a pipeline; the outlet of the pump (2) is connected to the inlet pipeline of the plate and frame filter press (3); the hydrochloric acid outlet of the plate and frame filter press (3) is connected to the inlet pipeline of the intermediate tank (4); the bottom outlet of the intermediate tank (4) is connected to the inlet pipeline of the intermediate feed pump (5), and the outlet of the intermediate feed pump (5) is connected to the inlet pipeline of the precision filter (6); the outlet of the precision filter (6) is connected to the filter (8) pipeline, and the outlet of the filter (8) is connected to the hydrochloric acid buffer tank.

2. The purification device for waste hydrochloric acid produced by incineration of tail gas from methylchlorosilane production according to claim 1, characterized in that: The outlet of the precision filter (6) is connected to the inlet pipeline of the resin bed (7); and the outlet of the resin bed (7) is connected to the pipeline of the filter (8).

3. The purification device for waste hydrochloric acid produced by incineration of tail gas from methylchlorosilane production according to claim 1, characterized in that: The resin beds (7) are provided in two units and connected by pipelines, so that parallel operation and series operation can be realized.

4. A purification process for waste hydrochloric acid produced by incineration of tail gas from methylchlorosilane production, characterized in that: The following steps are involved: The waste hydrochloric acid enters the mixing tank, and the feed pump flow is controlled to lift the waste hydrochloric acid to the plate and frame filter press for filtration. The acid filter cake obtained by filtration is de-alkalied and neutralized, and the hydrochloric acid filtrate is obtained by gravity flow to the intermediate tank; the hydrochloric acid in the intermediate tank is transported by a high-pressure pump through a precision filter to filter a small amount of fumed silica and mechanical impurities, and then to the resin bed, and finally filtered to the filter to obtain pure dilute hydrochloric acid to go to the buffer tank.

5. The purification process of waste hydrochloric acid produced by incineration of tail gas from methylchlorosilane production according to claim 4, characterized in that: The waste hydrochloric acid is obtained by burning chloromethane exhaust gas, chlorosilane exhaust gas and dust-containing exhaust gas containing silicon powder and catalyst in an incinerator at 1100-1200°C, and then passing the flue gas through a preheating boiler, a quenching tower and a hydrochloric acid tower. The waste hydrochloric acid includes a hydrogen chloride concentration of 17%-22%, 5%-10% of gas-phase silicon dioxide, and metal ion impurities such as iron ion, aluminum ion and calcium ion, and the temperature is ≤45°C.

6. The purification process of waste hydrochloric acid produced by incineration of tail gas from methylchlorosilane production according to claim 4, characterized in that: The content of fumed silica in the waste hydrochloric acid after plate and frame filtration is less than or equal to 1%.

7. The purification process of waste hydrochloric acid produced by incineration of tail gas from methylchlorosilane production according to claim 4, characterized in that: The precision filter is a filter with a cartridge structure or a filter bag structure. The filter element is made of polytetrafluoroethylene. After filtration, the hydrochloric acid appears yellow, clear and transparent, and solid impurities such as silicon dioxide are less than 0.01%.

8. The purification process of waste hydrochloric acid produced by incineration of tail gas from methylchlorosilane production according to claim 4, characterized in that: The structural characteristics of the resin in the resin bed are: , the active group of R is -CH2Cl, -COOCH3, -CN, -CH2OH, -CH2(O)CH-CH2Cl or other groups that can react with amines and polyamines; R1 is an alkyl or alkyl ketone structure, R2 is a propionamide structure, and N- represents elemental nitrogen.

9. The purification process for waste hydrochloric acid produced by incineration of tail gas from methylchlorosilane production according to claim 8, characterized in that: When the hydrochloric acid passes through the resin bed, the flow rate of the waste hydrochloric acid is 0.5-1 BV / h.

10. The purification process of waste hydrochloric acid produced as a by-product of the incineration of tail gas from the production of methylchlorosilane according to any one of claims 4 to 9, characterized in that: After treatment, the waste hydrochloric acid has iron ions ≤0.05ppm, calcium ions ≤10ppm, aluminum ions ≤3ppm, and is colorless and transparent in appearance.

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