A method for treating chlorosilane slurry

Abstract

The present invention discloses a method for treating chlorosilane slurry, which comprises first sending impurity-containing chlorosilane into a settling tank for sedimentation, then sending the obtained slurry into a slurry flash tank, flashing under the condition of passing hot nitrogen, and then flowing the flashed slurry into the slurry settling tank for secondary sedimentation. The slurry after secondary sedimentation is sent to a thin film evaporator for evaporation, and then dried in a slurry dryer and sent to a hydrolysis tank for hydrolysis reaction to finally obtain solid silicon dioxide and silicon micropowder; and the steam generated in the process is collected in a clear liquid buffer tank after condensation, and then sent to a clear liquid distillation tower for distillation, and the light component distilled is condensed and flowed into an STC buffer tank for collection, and the heavy component is recovered separately. The method of the present invention can effectively recover by-products such as silicon powder generated in the chlorosilane production process, and realize the harmless treatment of chlorosilane slurry, with good application prospects and environmental benefits.

Description

Technical Field

[0001] The present invention particularly relates to a method for treating chlorosilane slurry. Background Art

[0002] During the chlorosilane production process, due to the reaction characteristics and catalytic conversion efficiency, byproducts such as silicon powder are produced. These byproducts are difficult to directly recycle, and direct discharge can have serious impacts on the environment and personnel safety due to the special properties of the materials. Furthermore, higher byproduct content can negatively impact subsequent reactions. However, some byproducts can be reusable, and recycling them can reduce material costs. Summary of the Invention

[0003] The present invention aims to provide a method for treating chlorosilane slurry. This method reduces material consumption by gradually purifying reusable products and recycling them back into or participating in the main reaction. Furthermore, the treated slurry can be decontaminated by treatment (such as hydrolysis or distillation) to convert the chlorosilanes contained in it into harmless solid wastes such as silica and silica powder, making them easier to dispose of.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for treating chlorosilane slurry comprises the following steps:

[0006] 1) The chlorosilane containing impurities generated after the reaction is discharged from the reactor and sent to a settling tank for sedimentation;

[0007] 2) The upper gas phase obtained after sedimentation is sent to a scrubber for washing and dust removal, and the lower slurry is sent to a slurry flash tank for flash evaporation;

[0008] 3) During flash evaporation, hot nitrogen is introduced into the slurry flash tank to strip the volatile substances in the slurry. The stripped slurry is further concentrated, and the volatile substances flow into the clear liquid buffer tank after condensation with the hot nitrogen. The nitrogen can be reheated and used through the return line, and the slurry after flash evaporation flows into the slurry settling tank for secondary settling;

[0009] 4) The upper clear liquid obtained after the secondary sedimentation is filtered through a slurry clear liquid filter and then flows into a clear liquid buffer tank. The lower slurry is sent to a thin film evaporator for evaporation to evaporate the residual chlorosilane in the slurry, which is then condensed and flows into a clear liquid buffer tank. The lower slurry is sent to a slurry dryer to dry the residual liquid phase.

[0010] 5) The gas generated during the drying process is condensed and sent to the clear liquid buffer tank. The dried solid is sent to the hydrolysis tank, where the residual chlorosilane in the solid is hydrolyzed with water. The generated gas is sent to the tail gas scrubber for harmless treatment. The water used in the tail gas scrubber can be recycled to the hydrolysis tank to spray hydrolyze the slurry solids. The hydrolysis products produced are solid substances such as solid silicon dioxide and silicon powder.

[0011] 6) The liquid collected in the clear liquid buffer tank is distilled through the clear liquid distillation tower. The light components distilled out are condensed and flow into the STC buffer tank for collection, and then recycled to the slurry sedimentation tank for washing, dissolution and extraction; the heavy components are collected and subjected to high-boiling cracking treatment. The trichlorosilane and dichlorosilane obtained after treatment can be recovered and introduced into the back-end process of the production line for purification and use.

[0012] Furthermore, in step 1), the temperature in the settling tank is 100-200° C., and the pressure is 1.5-3 MPa.

[0013] Furthermore, the flash evaporation treatment in step 2) is to reduce the system pressure from 1.5-3 MPa to 0.01-0.5 MPa, so that the liquid phase in the tank is quickly vaporized.

[0014] Furthermore, the temperature of the hot nitrogen in step 3) is 100-150°C.

[0015] Furthermore, the evaporation temperature in step 4) is 70-120° C., and the pressure is controlled at 0.01-0.15 MPa.

[0016] Furthermore, in step 4), the slag slurry dryer adopts electric heating or steam heating, and its temperature is controlled at 120-150° C. and its pressure is controlled at 0.01-0.15 MPa.

[0017] Furthermore, the distillation temperature in step 6) is 100-150°C.

[0018] Furthermore, the light fraction collected in the STC buffer tank in step 6) can be recycled to flush the slurry settling tank, thereby dissolving high-boiling substances in the slurry and reducing the pressure in the subsequent evaporator and dryer. It can also be introduced into the reactor to re-participate in the reaction.

[0019] The significant advantages of the present invention are:

[0020] (1) Compared with the traditional method, the present invention reduces the number of slurry stirring tanks and increases the hot nitrogen stripping operation. The hot nitrogen is used to stir and tumble the materials in the slurry flash tank, which can improve the recovery rate of chlorosilane and silane in the slurry. At the same time, nitrogen is an inert gas and will not react with the slurry. It can avoid the problem of overheating and overpressure caused by the continuous production of chlorosilane by hydrogen when hydrogen reacts with the slurry. In addition, the silane / chlorosilane stripped out flows into the clear liquid buffer tank after condensation, and the nitrogen can be recycled and reheated using waste heat, with basically no loss.

[0021] (2) Compared with the traditional method, the present invention adds a thin film evaporator to evenly increase the temperature of the slurry, and then further dries the slurry. This can avoid the situation where the outer layer of the slurry is dried due to high temperature when entering the slurry dryer, and the internal chlorosilane cannot be effectively evaporated, thereby improving the recovery rate of chlorosilane in the slurry.

[0022] (3) The present invention adds an STC flushing pipeline to the slurry settling tank, which can use STC to dissolve and extract the slurry, thereby improving the recovery rate of chlorosilane in the slurry and extending the service life of the equipment. DETAILED DESCRIPTION

[0023] In order to make the contents of the present invention easier to understand, the technical solutions of the present invention are further described below in conjunction with specific implementation methods, but the present invention is not limited thereto. Example

[0024] A method for treating chlorosilane slurry comprises the following steps:

[0025] 1) The chlorosilane containing impurities generated after the reaction is discharged from the reactor and sent to a sedimentation tank for sedimentation at 100-200°C and a pressure of 1.5-3 MPa;

[0026] 2) The upper gas phase obtained after sedimentation is sent to a scrubber for washing and dust removal, and the lower slurry is sent to a slurry flash tank. By reducing the system pressure from 1.5-3 MPa to 0.01-0.5 MPa, the liquid phase in the tank is quickly vaporized and flash evaporated;

[0027] 3) During the flash evaporation, hot nitrogen at 100-150℃ is introduced into the slurry flash tank to strip the volatile substances in the slurry. The stripped slurry is further concentrated, and the volatile substances flow into the clear liquid buffer tank after condensation with the hot nitrogen. The nitrogen can be reheated and used through the return line, and the slurry after flash evaporation flows into the slurry settling tank for secondary settling;

[0028] 4) The upper clear liquid obtained after the secondary sedimentation is filtered through a slurry clear liquid filter and then flows into a clear liquid buffer tank. The lower slurry is sent to a thin film evaporator and evaporated at 70-120°C and a pressure of 0.01-0.15 MPa to evaporate the residual chlorosilane in the slurry. The chlorosilane is condensed and flows into the clear liquid buffer tank. The lower slurry is sent to an electric heating or steam heating slurry dryer and dried at 120-150°C and a pressure of 0.01-0.15 MPa.

[0029] 5) The gas generated during the drying process is condensed and sent to the clear liquid buffer tank. The dried solid is sent to the hydrolysis tank, where the residual chlorosilane in the solid is hydrolyzed with water. The generated gas is sent to the tail gas scrubber for harmless treatment. The water used in the tail gas scrubber can be recycled to the hydrolysis tank to spray hydrolyze the slurry solids. The hydrolysis products produced are solid substances such as solid silicon dioxide and silicon powder.

[0030] 6) The liquid collected in the clear liquid buffer tank is passed into the clear liquid distillation tower and distilled at 100-150°C. The light components distilled out are condensed and flow into the STC buffer tank for collection. They are then circulated through the STC flushing pipeline to the slurry settling tank for flushing, dissolution and extraction. The heavy components are collected and subjected to high-boiling cracking treatment. The trichlorosilane and dichlorosilane obtained after treatment are recovered and introduced into the back-end process of the production line for purification before use.

[0031] Comparative Example 1

[0032] In step 3) of this example, a comparative example was performed without the introduction of hot nitrogen. Testing showed that the recovery rate of chlorosilane after flash evaporation with hot nitrogen reached 34%, significantly better than the 25% recovery rate obtained by flash evaporation alone.

[0033] Comparative Example 2

[0034] In step 4) of this example, a thin-film evaporator was not used. Instead, the lower slurry obtained after secondary sedimentation was directly fed to a slurry dryer for drying before proceeding to subsequent operations. Testing showed that the recovery rate of chlorosilane obtained by thin-film evaporation in this example reached 95%, significantly higher than the 80% recovery rate obtained without thin-film evaporation.

[0035] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for treating chlorosilane slurry, characterized in that: The following steps are involved: 1) The chlorosilane containing impurities generated after the reaction is discharged from the reactor and sent to a settling tank for sedimentation; 2) The upper gas phase obtained after sedimentation is sent to a scrubber for washing and dust removal, and the lower slurry is sent to a slurry flash tank for flash evaporation; 3) During flash evaporation, hot nitrogen is introduced into the slurry flash tank. The resulting steam is condensed and flows into the clear liquid buffer tank, while the slurry after flash evaporation flows into the slurry settling tank for secondary settling; 4) The upper clear liquid obtained after the secondary sedimentation is filtered through the slurry clear liquid filter and then flows into the clear liquid buffer tank. The lower slurry is sent to the thin film evaporator for evaporation. The gas generated during the evaporation process is condensed and flows into the clear liquid buffer tank, while the lower slurry is sent to the slurry dryer for drying. 5) The gas generated during the drying process is condensed and sent to the clear liquid buffer tank. The dried solid is sent to the hydrolysis tank, where the residual chlorosilane in the solid is hydrolyzed with water. The generated gas is sent to the tail gas scrubber for harmless treatment. The hydrolysis products produced are solid silicon dioxide and silicon powder. 6) The liquid collected in the clear liquid buffer tank is distilled through the clear liquid distillation tower. The light components distilled out are condensed and flow into the STC buffer tank. The heavy components are collected and subjected to high-boiling cracking treatment. The cracking products are recovered and introduced into the back-end process of the production line for purification before use.

2. The method for treating chlorosilane slurry according to claim 1, wherein: In step 1), the temperature in the settling tank is 100-200° C. and the pressure is 1.5-3 MPa.

3. The method for treating chlorosilane slurry according to claim 1, wherein: The flash evaporation treatment in step 2) is to reduce the system pressure from 1.5-3 MPa to 0.01-0.5 MPa, so that the liquid phase in the tank is quickly vaporized.

4. The method for treating chlorosilane slurry according to claim 1, wherein: The temperature of the hot nitrogen in step 3) is 100-150°C.

5. The method for treating chlorosilane slurry according to claim 1, characterized in that: The evaporation temperature in step 4) is 70-120° C., and the pressure is controlled at 0.01-0.15 MPa.

6. The method for treating chlorosilane slurry according to claim 1, characterized in that: The slag slurry dryer in step 4) adopts electric heating or steam heating, and its temperature is controlled at 120-150° C. and the pressure is controlled at 0.01-0.15 MPa.

7. The method for treating chlorosilane slurry according to claim 1, characterized in that: The distillation temperature in step 6) is 100-150°C.