A method for treating waste gas from an organosilicon workshop

Abstract

The present invention provides a method for treating waste gas from an organosilicon workshop, belonging to the technical field of waste gas treatment. The method comprises the following steps: collecting the waste gas through a gas collection hood and then sending it to an inorganic alkali spray tower; spraying the waste gas within the inorganic alkali spray tower; using a KOH aqueous solution with a mass concentration greater than 20% to hydrolyze CH3SiCl3, CH3SiCl2(OH), and CH3SiCl(OH)2; neutralizing the hydrochloric acid produced by the hydrolysis; and dissolving the CH3Si(OH)3 formed after the hydrolysis; collecting the mixed liquid produced after the spraying; sending the gas after the inorganic alkali spraying treatment to a water spray tower for cleaning; and then sending the cleaned gas to a chimney via a centrifugal fan for external discharge. The present invention has the advantages of high efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of waste gas treatment and relates to a method for treating waste gas from an organosilicon workshop. Background Art

[0002] From the moment organosilicon raw materials (the raw material for organic silica gel solution) are loaded and unloaded in the mica production workshop, large amounts of monomethyltrichlorosilane ("MTS") gas are released during the process of uncapping, packaging, loading, and cleaning. MTS hydrolyzes with moisture in the air, reacting as follows: CH3SiCl3+H20=CH3SiCl2(OH)+HCl. The resulting CH3SiCl2(OH) further hydrolyzes to form methylsilicic acid and HCl. Because this raw material is highly volatile at room temperature and undergoes the aforementioned reaction, large amounts of white smoke (hydrogen chloride gas) and a white or slightly yellowish powdery crystal (primarily a mixture of various hydrolysis byproducts) are easily formed in the air. Hydrogen chloride has a strong pungent odor, and the accompanying white or yellowish granular solid is highly susceptible to clogging pipes and equipment.

[0003] The previous treatment method was: water spray + double-layer swirl plate + top filler treatment process. Since the silicone raw materials easily form white solid powder crystals when they come into contact with water, they block the top filler, nozzle and the air passage between the swirl plates, causing the exhaust tower to be blocked and the workshop exhaust gas cannot be continuously collected and treated. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for treating waste gas from an organosilicon workshop in order to solve the above-mentioned problems existing in the existing technology. The technical problem to be solved by the present invention is how to efficiently treat the waste gas from the organosilicon workshop.

[0005] The object of the present invention can be achieved through the following technical solutions: A method for treating waste gas from an organosilicon workshop, characterized in that it comprises the following steps: first, the waste gas is collected through a gas collecting hood and then sent into an inorganic alkali spray tower, the waste gas is sprayed in the inorganic alkali spray tower, the liquid used for spraying is a KOH aqueous solution with a mass concentration greater than 20%, CH3SiCl3, CH3SiCl2(OH), and CH3SiCl(OH)2 are hydrolyzed, the hydrochloric acid produced by the hydrolysis is neutralized, and the CH3Si(OH)3 formed after the hydrolysis is dissolved, the mixed liquid produced after the spraying is collected, the gas after the inorganic alkali spray treatment is sent to a water spray tower for cleaning, and the cleaned gas is sent to a chimney through a centrifugal fan for external discharge.

[0006] Furthermore, the mass concentration of the KOH aqueous solution is greater than 30%.

[0007] Furthermore, the exhaust gas velocity entering the inorganic alkali spray tower is 1.3m / s to 5.0m / s.

[0008] To treat the monomethyltrichlorosilane waste gas generated in the workshop, two major problems need to be solved: dealing with the acidic hydrogen chloride gas formed when the silicone raw material meets water; and recovering the white or yellow powder crystalline substance formed when it meets water.

[0009] The results of the experiment showed that the generated white or yellow powdery crystalline substance did not dissolve in a KOH solution with a mass concentration of 10%, dissolved in a KOH solution with a mass concentration of 20% after 24 hours, and dissolved in a KOH solution with a mass concentration of 30% or more within 2 hours.

[0010] If an excess of KOH solution (mass concentration > 30%) can be used to dissolve the resulting white or yellow powdery crystalline substance and simultaneously neutralize the generated hydrochloric acid, promoting the absorption of the monomethyl waste gas, the treated wastewater can be discharged to the workshop's wastewater treatment system for subsequent neutralization treatment. This can solve both of the above two problems and fully address the treatment and discharge of wastewater and waste gas.

[0011] Based on the above ideas, the biggest challenge in continuous waste gas treatment is to quickly hydrolyze CH3SiCl3, CH3SiCl2(OH), and CH3SiCl(OH)2. By using a spraying method, monomethyltrichlorosilane gas and its hydrolysis intermediates can be brought into high-frequency and full contact with water, accelerating the hydrolysis while neutralizing hydrochloric acid and dissolving methylsilicic acid. The removal rate of CH3SiCl3 in the waste gas can be achieved within 3 minutes at not less than 98%, and then it can be discharged into the air after further purification by water washing.

[0012] Furthermore, the inorganic alkali spray tower includes a tower body, an air inlet pipe, a drain pipe, a centrifugal cylinder, a reflux pipe, a water inlet pipe and an air outlet pipe, wherein the air inlet pipe is located in the middle of the tower body, the centrifugal cylinder is located in the tower body below the air inlet pipe, the air outlet pipe is located at the top of the tower body, and the air outlet pipe is connected to the inlet of the water spray tower. The centrifugal cylinder includes a contraction cone, a center tube and a vortex generating cylinder. The air inlet pipe is connected to the eccentric position of the vortex generating cylinder, the contraction cone is located below the vortex generating cylinder, and the two ends of the center tube are respectively located in the middle and above the vortex generating cylinder. The vortex generating cylinder connects the tower The body is divided into a spray chamber and a slow flow chamber from top to bottom. The bottom of the contraction cone is connected to the slow flow chamber. The upper end of the central tube is connected to a diverter cap. The side wall of the diverter cap is provided with a plurality of exhaust holes connected to the central tube. A plurality of spray plates are arranged horizontally in the spray chamber. The spray plates have a closed interlayer. The lower surface of the spray plates is provided with a plurality of nozzles identical to the interlayer. The spray plates are provided with air vents running through the upper and lower surfaces of the spray plates. The return pipe connects the interlayer and the slow flow chamber. The water inlet pipe sends the KOH aqueous solution into the interlayer. The inlet of the drain pipe is located at the bottom of the spray chamber.

[0013] Furthermore, a plurality of flow mixing sheets are provided in the interlayer.

[0014] In order to further save the amount of stepless alkaline solution and improve the efficiency of waste gas treatment, the structure of the stepless alkali spray tower is designed as above. It has two main purposes. One is to enable the hydrochloric acid mixture to offset the mono-Methyl mixture, slow down the sedimentation rate of the mono-Methyl mixture, make the hydrolysis and dissolution more complete, and the neutralization rate of hydrochloric acid and alkali is faster, so that the gas outlet direction is upward, and the hydrolysis and dissolution of mono-Methyl is slow, so that it sprays downward; on the other hand, before the mono-Methyl is sprayed downward, it is mixed with the alkaline solution to achieve preliminary hydrolysis. The preliminary hydrolysis produces a large amount of gas, which can increase the spraying speed. The water-gas mixture spraying method has a better dispersion effect than the liquid spraying method, and also has the effect of improving the hydrolysis efficiency.

[0015] The centrifugal cylinder is a tangential entry separator structure, which can allow the light substances in the mixture to enter the central tube, and the heavy substances to enter the bottom of the contraction cone, and then enter the slow flow chamber. Of course, due to the large variety of substances contained in the exhaust gas, this separation does not have a clear boundary. For example, in addition to air and a small amount of hydrochloric acid gas, the gas discharged from the central tube also contains a small amount of monomethane and monomethane hydrolyzate, while the gas discharged from the contraction cone contains monomethane and monomethane hydrolyzate as well as air. However, this method can generally group the exhaust gas. Since the water content of the exhaust gas at this time is extremely low, it will not cause a lot of adhesion to the reflux pipe and the inner wall of the centrifugal cylinder, and basically will not cause blockage of the channel.

[0016] A monomethyl intermediate is produced in the interlayer of the spray plate due to preliminary hydrolysis, but it will not cause blockage even under the flushing of alkaline solution.

[0017] Since this solution can improve the waste gas treatment efficiency, it can also increase the entry speed of the waste gas. After the entry speed of the waste gas is accelerated, the reflux pipe can achieve unpowered reflux, and the speed at which the stepless alkaline solution enters the spray plate can be appropriately reduced. On the one hand, it reduces the amount used, and on the other hand, it avoids the liquid from interfering with the circulation of the gas in the reflux pipe.

[0018] The exhaust gas entering the interlayer through the reflux pipe can provide atomization power for the spraying of the stepless alkaline solution, thereby improving the spraying effect of the inorganic alkaline solution, saving the amount of alkaline solution, and optimizing the effects of hydrolysis, neutralization and dissolution.

[0019] The degree of hydrolysis of the waste gas before treatment is generally low, and the amount of stepless alkali solution, the concentration of stepless alkali solution and the number of spray plates can be controlled according to actual conditions; since the upward airflow is diverted and slowed down, the residence time of the waste gas in the inorganic alkali spray tower is prolonged and the discharge is slowed down, and the same is true in the water spray tower.

[0020] Furthermore, a demister is provided on the top of the water spray tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural diagram of the equipment used for waste gas treatment.

[0022] Figure 2 It is a schematic diagram of the internal structure of the inorganic alkali spray tower.

[0023] Figure 3 It is a schematic diagram of the principle of the inorganic alkali spray tower.

[0024] Figure 4 It is a structural diagram of the spray plate.

[0025] Figure 5 It is a schematic diagram of the internal structure of the spray plate.

[0026] In the figure, 1. Inorganic alkali spray tower; 11. Tower body; 12. Air inlet pipe; 13. Drain pipe; 14. Centrifugal cylinder; 141. Converging cone; 142. Center tube; 143. Vortex generating cylinder; 144. Diverter cap; 15. Return pipe; 16. Water inlet pipe; 17. Air outlet pipe; 18. Spray chamber; 19. Slow flow chamber; 2. Water spray tower; 21. Demister; 3. Chimney; 4. Spray plate; 41. Interlayer; 42. Nozzle; 43. Air vent; 44. Mixing plate. DETAILED DESCRIPTION

[0027] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0028] like Figure 1 As shown, the method for treating waste gas from a silicone workshop includes the following steps: first, the waste gas is collected through a gas collecting hood and then sent to an inorganic alkali spray tower 1, and the waste gas is sprayed in the inorganic alkali spray tower 1. The liquid used for spraying is a KOH aqueous solution with a mass concentration greater than 20%, CH3SiCl3, CH3SiCl2(OH), and CH3SiCl(OH)2 are hydrolyzed, the hydrochloric acid produced by the hydrolysis is neutralized, and the CH3Si(OH)3 formed after the hydrolysis is dissolved, the mixed liquid produced after the spraying is collected, and the gas after the inorganic alkali spray treatment is sent to a water spray tower 2 for cleaning, and the cleaned gas is sent to a chimney 3 through a centrifugal fan for external discharge; a demister 21 is provided on the top of the water spray tower 2.

[0029] The mass concentration of the KOH aqueous solution is greater than 30%.

[0030] The exhaust gas velocity entering the inorganic alkali spray tower 1 is 1.3m / s to 5.0m / s.

[0031] To treat the monomethyltrichlorosilane waste gas generated in the workshop, two major problems need to be solved: dealing with the acidic hydrogen chloride gas formed when the silicone raw material meets water; and recovering the white or yellow powder crystalline substance formed when it meets water.

[0032] The results of the experiment showed that the generated white or yellow powdery crystalline substance did not dissolve in a KOH solution with a mass concentration of 10%, dissolved in a KOH solution with a mass concentration of 20% after 24 hours, and dissolved in a KOH solution with a mass concentration of 30% or more within 2 hours.

[0033] If an excess KOH solution with a concentration greater than 30% can be used to dissolve the resulting white or yellow powder crystals, while simultaneously neutralizing the generated hydrochloric acid and promoting the absorption of the monomethyl waste gas, the treated wastewater can be discharged to the workshop's wastewater treatment system for subsequent neutralization treatment. This approach can solve both of the above two problems and fully address the wastewater and waste gas treatment and discharge issues.

[0034] Based on the above ideas, the biggest challenge in continuous waste gas treatment is to quickly hydrolyze CH3SiCl3, CH3SiCl2(OH), and CH3SiCl(OH)2. By using a spraying method, monomethyltrichlorosilane gas and its hydrolysis intermediates can be brought into high-frequency and full contact with water, accelerating the hydrolysis while neutralizing hydrochloric acid and dissolving methylsilicic acid. The removal rate of CH3SiCl3 in the waste gas can be achieved within 3 minutes at not less than 98%, and then it can be discharged into the air after further purification by water washing.

[0035] like Figure 2-5 As shown, the inorganic alkali spray tower 1 includes a tower body 11, an air inlet pipe 12, a drain pipe 13, a centrifugal cylinder 14, a reflux pipe 15, a water inlet pipe 16 and an air outlet pipe 17. The air inlet pipe 12 is located in the middle of the tower body 11, the centrifugal cylinder 14 is located in the tower body 11 below the air inlet pipe 12, the air outlet pipe 17 is located at the top of the tower body 11, and the air outlet pipe 17 is connected to the inlet of the water spray tower 2. The centrifugal cylinder 14 includes a contraction cone 141, a center pipe 142 and a vortex generating cylinder 143. The air inlet pipe 12 is connected to the eccentric position of the vortex generating cylinder 143. The contraction cone 141 is located below the vortex generating cylinder 143. The two ends of the center pipe 142 are respectively located in the middle and above the vortex generating cylinder 143. The generating tube 143 separates the tower body 11 into a spray chamber 18 and a slow flow chamber 19 from top to bottom. The bottom of the contracting cone 141 is connected to the slow flow chamber 19. The upper end of the central tube 142 is connected to a diverter cap 144. The side wall of the diverter cap 144 is provided with a plurality of exhaust holes communicating with the central tube 142. A plurality of spray plates 4 are arranged horizontally in the spray chamber 18. The spray plate 4 has a closed interlayer 41. The lower surface of the spray plate 4 is provided with a plurality of nozzles 42 identical to the interlayer 41. The spray plate 4 is provided with air vents 43 passing through the upper and lower surfaces of the spray plate 4. The return pipe 15 connects the interlayer 41 with the slow flow chamber 19. The water inlet pipe 16 sends the KOH aqueous solution into the interlayer 41. The inlet of the drain pipe 13 is located at the bottom of the spray chamber 18.

[0036] A plurality of flow mixing sheets 44 are provided in the interlayer 41 .

[0037] In order to further save the amount of stepless alkaline solution and improve the efficiency of waste gas treatment, the structure of the stepless alkali spray tower is designed as above. It has two main purposes. One is to enable the hydrochloric acid mixture to offset the mono-Methyl mixture, slow down the sedimentation rate of the mono-Methyl mixture, make the hydrolysis and dissolution more complete, and the neutralization rate of hydrochloric acid and alkali is faster, so that the gas outlet direction is upward, and the hydrolysis and dissolution of mono-Methyl is slow, so that it sprays downward; on the other hand, before the mono-Methyl is sprayed downward, it is mixed with the alkaline solution to achieve preliminary hydrolysis. The preliminary hydrolysis produces a large amount of gas, which can increase the spraying speed. The water-gas mixture spraying method has a better dispersion effect than the liquid spraying method, and also has the effect of improving the hydrolysis efficiency.

[0038] The centrifugal drum 14 is a tangential entry separator structure that can separate the lighter components of the mixture into the central tube 142. Figure 3 The path shown by the middle dotted line is that the heavy object enters the lower part of the shrinking cone 141. Figure 3 The liquid then enters the slow flow chamber 19. Figure 3 The path shown by the solid thick line, of course, due to the large variety of substances contained in the exhaust gas, this separation does not have a clear boundary. For example, in addition to air and a small amount of hydrochloric acid gas, the gas discharged from the central tube 142 also contains a small amount of monomethane and monomethane hydrolyzate, while the gas discharged from the contraction cone 141 contains not only monomethane and monomethane hydrolyzate, but also air. However, this method can roughly group the exhaust gas. Since the water content of the exhaust gas at this time is extremely low, it will not cause a large amount of adhesion to the inner wall of the return pipe 15 and the centrifugal cylinder 14, and basically will not cause blockage of the channel.

[0039] A monomethyl intermediate is produced in the interlayer 41 of the spray plate 4 due to preliminary hydrolysis, but it will not cause blockage even under the flushing of the alkaline solution.

[0040] Since this solution can improve the waste gas treatment efficiency, it can increase the entry speed of the waste gas. After the entry speed of the waste gas is accelerated, the reflux pipe 15 can achieve unpowered reflux, and the speed at which the stepless alkaline solution enters the spray plate 4 can be appropriately reduced. On the one hand, the dosage is reduced, and on the other hand, the liquid is prevented from interfering with the circulation of the gas in the reflux pipe 15.

[0041] The exhaust gas entering the interlayer 41 through the reflux pipe 15 can provide atomization power for the spraying of the stepless alkaline solution, thereby improving the spraying effect of the inorganic alkaline solution, saving the amount of alkaline solution, and optimizing the effects of hydrolysis, neutralization and dissolution.

[0042] The degree of hydrolysis of the waste gas before treatment is generally low, and the amount of stepless alkaline solution, the concentration of the stepless alkaline solution and the number of spray plates 4 can be controlled according to actual conditions; since the upward airflow is diverted and slowed down, the residence time of the waste gas in the inorganic alkali spray tower 1 is prolonged and the discharge is slowed down, and the same is true in the water spray tower 2; in order to increase the cleaning intensity of the interlayer inside the spray plate, a fan can be set on the return pipe to increase the flow rate of the airflow entering the spray plate.

[0043] The waste water outputted from the drain pipe 13 is collected and the methyl silicon and hydrochloric acid therein are separated out to complete the continuous cleaning of the waste gas.

[0044] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. A method for treating waste gas from an organosilicon workshop, characterized in that: The method comprises the following steps: firstly collecting the waste gas through a gas collecting hood and then sending it into an inorganic alkali spray tower (1); spraying the waste gas in the inorganic alkali spray tower (1); the liquid used for spraying is a KOH aqueous solution with a mass concentration greater than 20%; CH3SiCl3, CH3SiCl2(OH), and CH3SiCl(OH)2 are hydrolyzed; the hydrochloric acid generated by the hydrolysis is neutralized; and CH3Si(OH)3 formed after the hydrolysis is dissolved; the mixed liquid generated after the spraying is collected; the gas after the inorganic alkali spraying treatment is sent to a water spray tower (2) for cleaning; and the cleaned gas is sent to a chimney (3) through a centrifugal fan for external discharge; The mass concentration of the KOH aqueous solution is greater than 30%; The exhaust gas velocity entering the inorganic alkali spray tower (1) is 1.3m / s~5.0m / s; The inorganic alkali spray tower (1) comprises a tower body (11), an air inlet pipe (12), a drain pipe (13), a centrifugal cylinder (14), a reflux pipe (15), a water inlet pipe (16) and an air outlet pipe (17), wherein the air inlet pipe (12) is located in the middle of the tower body (11), the centrifugal cylinder (14) is located in the tower body (11) below the air inlet pipe (12), the air outlet pipe (17) is located at the top of the tower body (11), and the air outlet pipe (17) is connected to the water spray tower. (2) is connected to the inlet, the centrifugal cylinder (14) includes a contraction cone cylinder (141), a central tube (142) and a vortex generating cylinder (143), the air inlet pipe (12) is connected to the eccentric position of the vortex generating cylinder (143), the contraction cone cylinder (141) is located below the vortex generating cylinder (143), the two ends of the central tube (142) are respectively located in the middle of the vortex generating cylinder (143) and above the vortex generating cylinder (143), and the vortex generating cylinder (143) The tower body (11) is divided into a spray chamber (18) and a slow flow chamber (19) at the top and bottom. The bottom of the contraction cone (141) is connected to the slow flow chamber (19). The upper end of the central tube (142) is connected to a diversion cap (144). The side wall of the diversion cap (144) is provided with a plurality of exhaust holes communicating with the central tube (142). A plurality of spray plates (4) are arranged horizontally in the spray chamber (18). The spray plates (4) have A closed interlayer (41), a plurality of nozzles (42) identical to those of the interlayer (41) are provided on the lower surface of the spray plate (4), a vent hole (43) penetrating the upper and lower surfaces of the spray plate (4) is provided on the spray plate (4), a return pipe (15) connects the interlayer (41) and the slow flow cavity (19), a water inlet pipe (16) delivers a KOH aqueous solution into the interlayer (41), and an inlet of the drain pipe (13) is located at the bottom of the spray cavity (18).

2. The method for treating waste gas from an organosilicon workshop according to claim 1, characterized in that: A plurality of flow mixing sheets (44) are provided in the interlayer (41).

3. The method for treating waste gas from an organosilicon workshop according to claim 1, characterized in that: A demister (21) is provided on the top of the water spray tower (2).

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