Organic silicon storage tank emptying tail gas treatment method and device

Abstract

The invention provides an organic silicon storage tank emptying tail gas treatment device and method.The device comprises a tail gas buffer tank, the tail gas buffer tank is connected with an inlet of a compressor through a pipeline, an outlet of the compressor is connected with a heater through a pipeline, and an outlet of the heater is connected with an inlet of a first reactor through a pipeline; the first reactor outlet is connected with the second reactor inlet through a pipeline. The tail gas treatment method comprises the following steps: mixing vented tail gas from a chloromethane storage tank with vented tail gas from a chlorosilane storage tank to obtain mixed gas; the mixed gas reacts after being compressed and preheated in sequence; and condensing a gas phase after reaction, condensing light components into a liquid phase, collecting the liquid phase, and incinerating non-condensable gas-phase tail gas. The tail gas of the chloromethane storage tank and the tail gas of the chlorosilane storage tank are collected and react with each other in the reactor, on one hand, light components such as olefin and chlorohydrocarbon are removed through the reaction, the emptying partial pressure of chloromethane is reduced, and the emptying amount of chloromethane is reduced;

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organosilicon, and particularly relates to a method and device for treating venting tail gas of an organosilicon storage tank. BACKGROUND

[0002] Organosilicon compounds are widely used in many fields such as aerospace, cutting-edge technology, military technology, electronic appliances, building materials, new energy power, automobile transportation, medical care, daily chemicals and textiles, industrial aids, national defense and military industry, and the like, due to their unique physical structure and excellent performance. More than 90% of organosilicon material products are derived from methyl chlorosilane monomers. The methyl chlorosilane monomers are obtained by catalytic reaction of silicon powder and chloromethane in a fluidized bed reactor to obtain an organosilicon monomer mixture. The organosilicon monomer mixture is further separated by rectification to obtain dimethyldichlorosilane, monomethyltrichlorosilane, trimethylmonochlorosilane, monomethylhydrodichlorosilane, low-boiling substances and the like into a storage tank for storage. In the monomer synthesis process, the conversion rate of chloromethane is 30-50%, and the chloromethane is recycled in the device for recycling. The recycled chloromethane contains alkane and olefin substances, and the storage tank tail gas contains alkane, olefin and chloromethane gas.

[0003] The boiling point of chlorosilane products is less than 70.2℃, the saturated vapor pressure at room temperature is less than 200mmHg, and the chlorosilane products contain hydrocarbon substances, which are easy to vaporize and volatilize in hot summer. The tank area also emits a large amount of breathing gas, which contains chlorosilane, hydrocarbon, chloromethane and other volatile organic compounds (VOCs) waste gas and nitrogen. The release of these waste gases not only pollutes the environment, but also causes waste of materials. Usually, enterprises use a set of water washing + alkali washing device to wash the chlorosilane waste gas and then discharge it at high altitude. Although this method can remove chlorosilane substances by reacting with water, it will produce high-salt and high-COD waste water, and non-water-soluble waste gas will still be vented to pollute the environment.

[0004] In the treatment of organosilicon waste gas, another effective engineering example is to use the adsorption method combined with catalytic combustion technology. First, the waste gas is removed through an activated carbon adsorption device, and then the remaining VOCs are completely decomposed into carbon dioxide and water through a catalytic combustion device, so as to realize the harmless treatment of waste gas. However, this method requires a large amount of activated carbon, the treatment cost is high, and the hydrolysis of chlorosilane will block the surface of activated carbon, resulting in failure. Therefore, it is generally used after the water washing system as a strengthening measure to treat VOCs.

[0005] Some enterprises collect organosilicon tail gas through a pipeline and then burn it. Although this method can efficiently remove the tail gas and produce a certain amount of steam, it produces a large amount of waste hydrochloric acid and causes resource waste.

[0006] Patent 201811607778 discloses a method and device for purifying silicone fraction tail gas and recovering silicone monomer, which utilizes an adsorption separation system composed of two or more adsorption towers and its program control valve to adsorb and recover the silicone fraction tail gas. The bed temperature of the adsorption tower is constant at 30-180℃, and the adsorption tower sequentially undergoes adsorption, pressure equalization, reverse release, vacuum flushing, and finally pressure increase. Each adsorption tower operates in the above order and in a time staggered manner to improve the total recovery rate of monomers. However, this method cannot effectively adsorb M4 (tetramethylsilane), and the adsorption process is only physical adsorption recovery.

[0007] The above silicone tail gas treatment methods cannot effectively recover and utilize the tail gas resources, and may also cause secondary pollution. Therefore, it is very important to develop a new tail gas recovery process. SUMMARY

[0008] To solve the above problems, the present application provides a silicone storage tank vent gas treatment device, which comprises a tail gas buffer tank, a compressor inlet connected to the tail gas buffer tank through a pipeline, a heater outlet connected to the compressor outlet through a pipeline, a first reactor inlet connected to the heater outlet through a pipeline, and a second reactor inlet connected to the first reactor outlet through a pipeline.

[0009] Further, the second reactor outlet is connected to the heater shell inlet through a pipeline, the heater shell outlet is connected to the first condenser, the first condenser condensate outlet is connected to the liquid collecting tank through a pipeline, the first condenser gas phase outlet is connected to the second condenser inlet through a pipeline, the second condenser condensate outlet is connected to the liquid collecting tank through a pipeline, and the second condenser gas phase outlet is connected to the tail gas incineration device through a pipeline.

[0010] Further, the first reactor and the second reactor shell are provided with a heating jacket or a half pipe, and are internally filled with solid catalysts.

[0011] The present application also provides a silicone storage tank vent gas treatment method, comprising the following steps: (1) mixing the vent gas from the chloromethane storage tank with the vent gas from the chlorosilane storage tank to obtain a mixed gas; (2) compressing and preheating the mixed gas, and then reacting; the reaction is divided into two stages, the first stage reaction temperature is 150-200℃, and the second stage reaction temperature is 180-300℃; (3) condensing the gas phase after reaction, collecting the light components condensed into liquid phase, and incinerating the non-condensable gas phase tail gas.

[0012] Further, the pressure of the mixed gas in step (1) is 0.05-0.3 MPa.

[0013] Further, the pressure of the mixed gas after compression in step (2) is 0.45-0.9 MPa; and the temperature of the mixed gas after preheating in step (2) is 150-200℃.

[0014] Further, the first-stage reaction time in step (2) is 0.5-5 min; and the second-stage reaction time in step (2) is 3-15 min.

[0015] Further, the first-stage reaction catalyst in step (2) is selected from one or more of palladium, platinum, rhodium, ruthenium, nickel, osmium, iridium and compounds thereof, preferably one or more of palladium, platinum or nickel. The second-stage reaction catalyst is selected from Lewis acid materials, preferably one or more of aluminum chloride, cobalt chloride, iron chloride, aluminum oxide or silicon-aluminum mixture.

[0016] Further, the reaction gas after step (3) is first exchanged with the compressed gas after step (2) to heat the compressed gas after step (2); and then the reaction gas after the heat exchange is condensed.

[0017] Further, the condensation includes two times of condensation, the first condensation temperature is 40-60℃, and the second condensation temperature is -15~-35℃.

[0018] The first-stage reaction catalyst is loaded on a solid carrier, which can be inert materials such as granular carbon and silicon, etc. with suitable size and adsorption force for metals or metal compounds. The concentration of the preferred metal and its compound is in the range of 0.2-10 % of the mass of the carrier.

[0019] The present application has the following advantages: 1. The present application collects the tail gas of the chloromethane storage tank and the tail gas of the chlorosilane storage tank, and makes them react with each other in the reactor, which removes light components such as olefins and chlorohydrocarbons, reduces the venting partial pressure of chloromethane, and reduces the venting amount.

[0020] 2. The components in the mixed tail gas react to obtain high-value-added products such as dimethyldichlorosilane and trimethylmonochlorosilane, which has certain economic benefits.

[0021] 3. The pressure is increased by the compressor, which not only improves the reaction efficiency, but also improves the condensation yield of the material, reduces the tail gas burning load, and reduces the amount of waste acid.

[0022] 4. Compared with the traditional water washing and alkali washing treatment method, the present application has certain economic benefits, and greatly reduces the emission of VOCs. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The device structure diagram of the present application is shown.

[0024] Legend in the figure: exhaust buffer tank 1, compressor 2, heater 3, first reactor 4, second reactor 5, first condenser 6, second condenser 7, liquid collecting tank 8. DETAILED DESCRIPTION

[0025] The embodiments of the present application will be described in detail below with examples, which are only used to illustrate the present application and should not be regarded as limiting the scope of the present application.

[0026] Example 1 An organic silicon storage tank vent gas treatment device, comprising an exhaust buffer tank 1, the exhaust buffer tank 1 is connected with the compressor 2 inlet through the pipeline, the compressor 2 outlet is connected with the heater 3 through the pipeline, the heater 3 outlet is connected with the first reactor 4 inlet through the pipeline, the first reactor 4 outlet is connected with the second reactor 5 inlet through the pipeline.

[0027] Further, the second reactor 5 outlet is connected with the heater 3 shell inlet through the pipeline, the heater 3 shell outlet is connected with the first condenser 6, the first condenser 6 condensate outlet is connected with the liquid collecting tank 8 through the pipeline, the first condenser 6 gas phase outlet is connected with the second condenser 7 inlet through the pipeline, the second condenser 7 condensate outlet is connected with the liquid collecting tank 8 through the pipeline, and the second condenser 7 gas phase outlet is connected with the exhaust gas incineration device through the pipeline.

[0028] Further, the first reactor 4 and the second reactor 5 shell are provided with heating jacket or half pipe, and the inside is filled with solid catalyst.

[0029] Example 2 Using the device shown in the figure, the organic silicon storage tank vent gas treatment method is as follows: Figure 1 ​The vent gas from the chloromethane storage tank (flow rate of 20-30 Nm3 / h) and the vent gas from the chlorosilane storage tank (flow rate of 50-80 Nm3 / h) are respectively introduced into the tail gas buffer tank 1 through pipes, the internal pressure of the tail gas buffer tank 1 is controlled at 0.05-0.1 MPa (g), the mixed gas is compressed to 0.75-0.8 MPa (g) by the compressor 2, and the temperature of the compressed gas is 90-110°C. Then the compressed gas is introduced into the heater 3, and the gas is superheated to 175-180°C and introduced into the first reactor 4; the gas is subjected to the first stage reaction in the first reactor 4, the palladium catalyst (palladium content of 0.2%) is used, the reaction temperature is 180°C, and the reaction time is 3 min; then the gas is introduced into the second reactor 5 for the second stage reaction, the second reactor is maintained at a reaction temperature of 250°C, the reaction time is 10 min, and the catalyst is aluminum oxide. The mixed gas from the second reactor 5 is heated in the heater 3 after the gas after the compressor, and then introduced into the first cooler 6, the temperature of the condensed liquid is 42-45°C, the condensed liquid phase is introduced into the liquid collecting tank 8, and the non-condensable gas is introduced into the second condenser 7 for further cooling; the temperature of the coolant of the second condenser 7 is -30°C, the light components after condensation are introduced into the liquid collecting tank 8, the liquid collecting tank 8 obtains the mixture of the mixed monomers and chloromethane, and about 10-15 Nm3 / h of the non-condensable gas is introduced into the tail gas incineration device, and the tail gas introduced into the incineration device is reduced by more than 80% in terms of the volume ratio of the non-condensable gas.

[0030] In the above process, the vent gas from the chloromethane storage tank contains a mixture of chloromethane, methane, olefins, etc., and the vent gas from the chlorosilane storage tank contains a mixture of tetramethylsilane, monomethyltrichlorosilane, trimethylmonochlorosilane, dimethyldichlorosilane, monomethyldichlorohydrosilane, chlorinated hydrocarbon, olefin, alkane, nitrogen, etc. The conversion reaction of the olefins and the hydrogen-containing chlorosilane monomers occurs in the first reactor 4, and the conversion reaction between the tetramethylsilane, the hydrogen-containing chlorosilane monomers, the monomethyltrichlorosilane, the trimethylmonochlorosilane and the product of the first reactor occurs in the second reactor 5, to obtain chlorosilane components such as dimethyldichlorosilane and trimethylmonochlorosilane. The reactants passing through the second reactor 5 and the unreacted chlorosilane and part of the chloromethane are condensed and recovered in the first condenser 6 and the second condenser 7, and the alkanes with lower boiling points and part of the chloromethane are vented to the tail gas incineration.

Claims

1. A device for treating vented exhaust gas from an organosilicon storage tank, characterized in that, It includes an exhaust gas buffer tank (1), which is connected to the inlet of the compressor (2) through a pipe. The outlet of the compressor (2) is connected to the heater (3) through a pipe. The outlet of the heater (3) is connected to the inlet of the first reactor (4) through a pipe. The outlet of the first reactor (4) is connected to the inlet of the second reactor (5) through a pipe.

2. The organosilicon storage tank venting tail gas treatment device according to claim 1, characterized in that, The outlet of the second reactor (5) is connected to the shell-side inlet of the heater (3) via a pipe. The shell-side outlet of the heater (3) is connected to the first condenser (6). The condensate outlet of the first condenser (6) is connected to the liquid collection tank (8) via a pipe. The gas phase outlet of the first condenser (6) is connected to the inlet of the second condenser (7) via a pipe. The condensate outlet of the second condenser (7) is connected to the liquid collection tank (8) via a pipe. The gas phase outlet of the second condenser (7) is connected to the tail gas incinerator via a pipe.

3. The organosilicon storage tank venting exhaust gas treatment device according to claim 1, characterized in that, The first reactor (4) and the second reactor (5) have heating jackets or half-pipes on their shells and are filled with solid catalysts inside.

4. A method for treating vented exhaust gas from an organosilicon storage tank, characterized in that, Includes the following steps: (1) The vent gas from the chloromethane storage tank is mixed with the vent gas from the chlorosilane storage tank to obtain a mixed gas; (2) The mixed gas is compressed and preheated in sequence before the reaction is carried out; the reaction is divided into two stages, the first stage reaction temperature is 150-200℃, and the second stage reaction temperature is 180-300℃. (3) The gas phase after the reaction is condensed, the light components are condensed into liquid phase for collection, and the non-condensable gas phase is incinerated.

5. The method for treating vented exhaust gas from an organosilicon storage tank according to claim 4, characterized in that, The pressure of the mixed gas in step (1) is 0.05-0.3 MPa.

6. The method for treating vented exhaust gas from an organosilicon storage tank according to claim 4, characterized in that, The pressure of the mixed gas in step (2) after compression is 0.45-0.9 MPa; the temperature after preheating is 150-200℃.

7. The method for treating vented exhaust gas from an organosilicon storage tank according to claim 4, characterized in that, Step (2) The reaction time of the first stage is 0.5-5 min; the reaction time of the second stage is 3-15 min.

8. The method for treating vented exhaust gas from an organosilicon storage tank according to claim 4, characterized in that, In step (2), the catalyst for the first stage reaction is selected from one or more combinations of palladium, platinum, rhodium, ruthenium, nickel, osmium, iridium and their compounds, preferably one or more of palladium, platinum or nickel; The catalyst for the second-stage reaction is selected from Lewis acid materials, preferably one or more of aluminum chloride, cobalt chloride, ferric chloride, alumina, or a silicon-aluminum mixture.

9. The method for treating vented exhaust gas from an organosilicon storage tank according to claim 4, characterized in that, In step (3), the gas phase after the reaction is first heated by exchanging heat with the gas compressed in step (2); the gas phase after the reaction is then condensed.

10. A method for treating vented exhaust gas from an organosilicon storage tank according to claim 4 or 9, characterized in that, The condensation includes two condensation processes: the first condensation temperature is 40-60℃, and the second condensation temperature is -15~-35℃.

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