Treatment method of slag slurry generated in cold hydrogenation synthesis process

Abstract

The invention belongs to the technical field of cold hydrogenation synthesis, and particularly relates to a treatment method of slag slurry generated in a cold hydrogenation synthesis process, the slag slurry generated in the cold hydrogenation process is sequentially subjected to primary filtration, secondary diatomite precoating filtration, drying evaporation and rectification purification treatment, so that the recovery rate of chlorosilane (mainly silicon tetrachloride) is up to 99%, and the recovery rate of chlorosilane is up to 99%. Resource waste and environmental pollution are avoided, meanwhile, an alkali washing tank is omitted, the process is simplified, and energy consumption is reduced; in addition, physical separation (filtration, drying and rectification) and solid slag neutralization are adopted in the treatment method, no wastewater is generated, a matched sewage treatment system is not needed, and the environmental protection cost and energy consumption are remarkably reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of cold hydrogenation synthesis, and particularly relates to a treatment method of slag slurry generated in a cold hydrogenation synthesis process. BACKGROUND

[0002] In the polysilicon production field, silicon tetrachloride is a core by-product, and if not properly treated, it will cause serious resource waste and environmental pollution. The cold hydrogenation technology can convert silicon tetrachloride into polysilicon production raw materials, realize resource recycling and cost reduction, and has been widely used in the polysilicon industry.

[0003] However, there are still significant technical pain points in the treatment of slag slurry generated at the outlet of the cold hydrogenation process reactor. The slag slurry is complex in composition, containing unreacted silicon powder, FeCl3, AlCl3 and other metal chloride solid particles, and chlorosilane (containing SiCl4, SiHCl3 and the like) and other liquid substances with recycling value but harmful to the environment.

[0004] In the prior art, the slag slurry discharged in the polysilicon cold hydrogenation production is treated by using the treatment mode of “alkali liquor neutralization + manual salvage of waste slag + waste liquid sent to a sewage treatment station”, and there are three core problems: first, the chlorosilane is not recovered and directly neutralized, causing resource waste and increasing alkali consumption; second, manual salvage of waste slag has operation safety risks, and chlorosilane leakage is easy to cause environmental problems; third, a large amount of wastewater is generated, which needs to be additionally invested in the sewage treatment system, increasing energy consumption and cost. Therefore, there is an urgent need for an efficient, environmentally friendly and low-cost slag slurry treatment method. SUMMARY

[0005] Based on the problems in the background art, the present application provides a treatment method of slag slurry generated in a cold hydrogenation synthesis process.

[0006] The technical scheme of the present application is as follows: The present application provides a treatment method of slag slurry generated in a cold hydrogenation synthesis process, comprising the following steps: (1) The cold hydrogenation slag slurry is injected into a slag slurry stirring tank, and after uniform stirring, it is transported to a slag slurry filter for primary filtration, and the obtained filtrate is discharged into a filtrate recovery tank, and the slag slurry is returned to the slag slurry stirring tank, and when the solid content of the slag slurry in the slag slurry stirring tank reaches a preset value, the filtration is stopped; (2) The filtrate is punched into a diatomite stirring tank, and diatomite is added to the diatomite stirring tank through a diatomite adding tank, and stirred to obtain a pre-coating slurry; the pre-coating slurry is transported to a drum filter for cyclic suction filtration to form a diatomite coating; The slag slurry after primary filtration is sent to the drum filter for secondary filtration, and the obtained clear liquid and exhaust gas are jointly discharged to a gas-liquid separation tank for treatment, and then the liquid is discharged into the filtrate recovery tank or / and punched into the diatomite stirring tank, and the gas is used for suction filtration of the drum filter; (3) The filter cake after secondary filtration is dried in a rake dryer and discharged into a dry residue tank, and the dry residue in the dry residue tank is mixed with lime in a lime tank; (4) When the liquid level of the filtrate recovery tank reaches the first liquid level, the material is fed to the heavy-removal recovery column, and the heavy-removal kettle heater is started to stir, and the material in the heavy-removal recovery column flows to the heavy-removal kettle heater, and when the liquid level of the heavy-removal kettle heater reaches the second liquid level, the material is heated and evaporated; Wherein the high-boiling impurities are discharged from the bottom of the heavy-removal kettle heater and enter the rotary drum overflow tank, and are filtered again from the rotary drum filter; And the steam is condensed by the heavy-removal tower condenser and enters the heavy-removal reflux tank, and if the liquid level of the heavy-removal reflux tank reaches the third liquid level, the reflux operation is performed in the heavy-removal recovery column; when the purity of the product in the heavy-removal reflux tank reaches the preset purity, it is transported to the silicon tetrachloride storage tank area.

[0007] Step (2) The pre-coating slurry is transported to the rotary drum filter, and the diatomite coating is formed by circulating filtration, specifically: The pre-coating slurry is transported to the rotary drum filter, and when the pre-coating slurry in the rotary drum filter reaches the fourth liquid level, the filtration vacuum unit and the circulating water valve on the vacuum cooler are started to perform circulating filtration, and the filtrate is discharged into the gas-liquid separation tank. When the gas-liquid separation tank reaches the fifth liquid level, the reflux pipeline is opened to supplement the liquid level of the filtration liquid in the rotary drum filter, and the remaining filtrate in the gas-liquid separation tank is discharged into the filtrate recovery tank.

[0008] Further, the diatomite coating thickness is controlled to be 50-160 mm.

[0009] After the clear liquid obtained in step (2) is discharged together with the exhaust gas to the gas-liquid separation tank for treatment, the liquid is discharged into the filtrate recovery tank or / and is punched into the diatomite stirring tank, and the gas is used for filtration in the rotary drum filter, specifically: The obtained clear liquid and exhaust gas are discharged together into the gas-liquid separation tank for gas-liquid phase separation, and the gas phase material is discharged from the upper gas phase outlet of the gas-liquid separation tank to the air inlet of the filtration vacuum unit for air extraction; in the air discharged from the filtration vacuum unit, the gas with a proportion not less than a first preset proportion is cooled by the vacuum cooler and then returned to the rotary drum filter for recycling; and the remaining proportion of gas is sequentially discharged to the primary recovery condenser and the secondary recovery condenser for treatment, and finally discharged into the waste gas treatment system when the gas pressure outside the rotary drum shell of the rotary drum filter exceeds the preset pressure. In the clear liquid separated from the gas-liquid separation tank, a second preset proportion of the clear liquid is punched into the diatomite stirring tank, and the remaining proportion of the clear liquid is discharged into the filtrate recovery tank.

[0010] In addition, it also includes: When the slurry level in the slurry stirring tank is lower than the sixth level, the discharging is stopped; the drum filter and the gas-liquid separation tank keep the filtration cycle operation to keep the liquid level in the drum filter stable; and the drum filter stops feeding the rake dryer.

[0011] The filter cake after the secondary filtration in step (3) is sent to the rake dryer, and after drying, is discharged into the dry residue tank, specifically: The rake dryer, the drying filter and the drying exhaust fan are started, and the micro-negative pressure value in the rake dryer is kept within the preset negative pressure value; the steam heating of the rake dryer is started to dry the filter cake after the secondary filtration in the rake dryer; After the rake dryer runs for about 10-90 min, the silicon tetrachloride content in the dry residue is detected, and if the silicon tetrachloride content is less than the preset content, the dry residue is discharged into the dry residue tank.

[0012] Further, the filter cake after the secondary filtration is subjected to steam heating in the rake dryer, and the gas phase material is discharged from the gas phase outlet of the rake dryer, and is sequentially subjected to the drying filter and the drying exhaust fan treatment, and is discharged into the waste gas treatment system.

[0013] The dry residue in the dry residue tank in step (3) is mixed with the lime in the lime tank, specifically: After the ton bag packaging machine for the dry residue is installed, the neutralization screw is started, the lime tank discharges the lime according to the detection result of the dry residue, and the dry residue discharged from the dry residue tank is mixed with the lime in the neutralization screw, and when the ton bag reaches the specified value, the dry residue tank, the lime tank and the neutralization screw are automatically turned off, the packaging is completed, and the ton bag is replaced.

[0014] The application also provides a treatment system for the slurry generated in the cold hydrogenation synthesis process, which comprises a primary filtration unit, a secondary filtration unit, a dry residue treatment unit, a purification unit and a gas-liquid circulation unit. The primary filtration unit comprises a slurry stirring tank and a slurry filter connected in sequence, the filtrate outlet of the slurry filter is communicated with a filtrate recovery tank, and the slurry backflow port of the slurry filter is communicated with the feeding port of the slurry stirring tank. The secondary filtration unit comprises a drum filter, a diatomite stirring tank and a diatomite adding tank, the discharging port of the diatomite adding tank is communicated with the feeding port of the diatomite stirring tank, the liquid inlet of the diatomite stirring tank is communicated with the liquid outlet of the gas-liquid separation tank, the discharging port of the diatomite stirring tank is communicated with the feeding port of the drum filter, and the slurry inlet of the drum filter is communicated with the slurry outlet of the slurry stirring tank. The dry residue treatment unit comprises a rake dryer, a dry residue tank and a neutralization screw connected in sequence, the feeding port of the rake dryer is communicated with the filter cake outlet of the drum filter, and the feeding port of the neutralization screw is further connected with a lime tank. The purification unit comprises a heavy-removal recovery column, a heavy-removal kettle heater, a heavy-removal column condenser and a heavy-removal reflux tank, the feed inlet of the heavy-removal recovery column is communicated with the discharge outlet of the filtrate recovery tank, the discharge outlet at the bottom of the heavy-removal recovery column is communicated with the feed inlet of the heavy-removal kettle heater, the gas phase outlet of the heavy-removal kettle heater is communicated with the bottom gas phase return port of the heavy-removal recovery column, the top gas phase outlet of the heavy-removal recovery column is communicated with the gas inlet of the heavy-removal column condenser, the condensate outlet of the heavy-removal column condenser is communicated with the feed inlet of the heavy-removal reflux tank, the reflux port of the heavy-removal reflux tank is communicated with the top reflux port of the heavy-removal recovery column, and the discharge outlet of the heavy-removal reflux tank is communicated with the silicon tetrachloride storage tank area; The gas-liquid circulation unit comprises a gas-liquid separation tank, the gas-liquid outlet of the drum filter is communicated with the feed inlet of the gas-liquid separation tank, the gas phase outlet of the gas-liquid separation tank is communicated with the circulation gas return port of the drum filter, and the liquid phase outlet of the gas-liquid separation tank is communicated with the feed inlet of the filtrate recovery tank.

[0015] The gas-liquid circulation unit further comprises a suction filtration vacuum unit and a vacuum cooler, the gas phase outlet of the gas-liquid separation tank is communicated with the gas inlet of the suction filtration vacuum unit, the gas outlet of the suction filtration vacuum unit is communicated with the gas inlet of the vacuum cooler, and the gas outlet of the vacuum cooler is communicated with the circulation gas return port of the drum filter; the liquid phase outlet of the gas-liquid separation tank is provided in two ways, one way is communicated with the liquid inlet of the diatomite stirring tank to supplement the suction filtration liquid level, and the other way is communicated with the feed inlet of the filtrate recovery tank to recover the clear liquid.

[0016] Advantages The present application sequentially performs first-stage filtration, second-stage diatomite pre-coating filtration, drying evaporation and rectification purification treatment on the slurry generated in the cold hydrogenation process, so that the recovery rate of chlorosilane (mainly silicon tetrachloride) is as high as 99%, resource waste and environmental pollution are avoided, the alkali washing tank is cancelled, the process is simplified and the energy consumption is reduced; in addition, the treatment method adopts physical separation (filtration, drying and rectification) and solid residue neutralization, no wastewater is generated, no supporting wastewater treatment system is needed, and the environmental protection cost and energy consumption are significantly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a structural schematic view of a treatment system for slurry generated in a cold hydrogenation synthesis process.

[0018] The reference signs are as follows: 1-Slurry mixing tank, 2-Slurry filter, 3-Drum filter, 4-Drum overflow tank, 5-Rake dryer, 6-Drying filter, 7-Drying exhaust fan, 8-Dry slag tank, 9-Lime tank, 10-Neutralization spiral, 11-Dry slag ton bag packaging machine, 12-Vacuum cooler, 13-Vacuum filtration unit, 14-Gas-liquid separator, 15-Filtrate recovery tank, 16-Primary recovery condenser, 17-Secondary recovery condenser, 18-Deweight recovery tower, 19-Deweight reactor heater, 20-Deweight tower condenser, 21-Deweight reflux tank, 22-Diatomaceous earth mixing tank, 23-Diatomaceous earth addition tank. Detailed Implementation

[0019] The following examples are intended to illustrate the present invention, and not to further limit the invention.

[0020] Example 1 This embodiment provides a method for treating the slurry generated in a cold hydrogenation synthesis process, including the following steps: (1) The cold hydrogenated slurry is injected into the slurry mixing tank 1 and stirred evenly. Then it is transported to the slurry filter 2 for primary filtration. The filtrate is discharged into the filtrate recovery tank 15, and the slurry is returned to the slurry mixing tank 1. When the solid content of the slurry in the slurry mixing tank 1 reaches the preset value of 5~10%, filtration is stopped. If the solid content of the slurry in the slurry mixing tank 1 does not reach the preset value, filtration continues.

[0021] In the specific implementation process, the temperature of the slurry mixing tank 1 is controlled between 40 and 120°C, the pressure is controlled between 0.01 and 0.12 MPaG, the liquid level is controlled between 20 and 80%, and the weight is controlled between 3000 and 15000 kg. The temperature of the slurry filter 2 is controlled between 40 and 80°C, and the pressure is controlled between 0.20 and 0.50 MPaG. The filtration accuracy of slurry filter 2 is controlled below 1μm.

[0022] When the slurry filter 2 is running, the opening of the bottom valve needs to be controlled in order to meet the pressure required for filtration.

[0023] In this invention, the slurry mixture exiting the slurry mixing tank 1 is first filtered through the slurry filter 2 to separate solids such as silicon powder, FeCl3, and AlCl3 metal chlorides from the chlorosilane liquid (mainly silicon tetrachloride). When the solids concentration in the slurry is below 5%, primary filtration is performed. The filtered chlorosilane liquid enters the filtrate recovery tank 15, increasing the solids content and decreasing the chlorosilane content in the slurry, thus improving the efficiency of subsequent slurry treatment. The filtered chlorosilane is a clear liquid without solids, reducing pressure on subsequent pipelines and preventing pipe blockage during venting. Filtration is stopped when the solids content of the slurry in the slurry filter 2 is between 5% and 10%, and the filtered slurry is discharged into the rotary drum filter 3. At this point, the initial recovery of chlorosilanes from the slurry mixture is completed.

[0024] In existing technologies, the initial solids concentration in slurry from other processes is between 20% and 50%, or even higher. High solids concentrations are associated with high temperatures and pressures, placing greater demands on the system and increasing its load capacity. This invention directly controls the solids concentration in the slurry for primary filtration, using physical methods to remove chlorosilanes from the supernatant, further increasing the solids concentration in the slurry to 5% to 10%, facilitating subsequent slurry treatment.

[0025] (2) Filtrate is pumped into diatomaceous earth mixing tank 22, and diatomaceous earth is added to diatomaceous earth mixing tank 22 through diatomaceous earth adding tank 23. The mixture is stirred to obtain pre-coated slurry. The pre-coated slurry is transported to drum filter 3 for circulation filtration to form diatomaceous earth coating. The slurry after primary filtration is fed into the rotary drum filter 3 for secondary filtration. The resulting clear liquid and exhaust gas are discharged together to the gas-liquid separator 14 for further processing. The liquid is discharged into the filtrate recovery tank 15, and the gas is used for vacuum filtration in the rotary drum filter 3.

[0026] Before the slurry is fed into the rotary drum filter 3, the rotary drum filter 3 first performs a pre-coating of the diatomaceous earth filter layer. The process is as follows: First, open the diatomaceous earth addition tank 23 and add a specified amount of diatomaceous earth into the tank for later use.

[0027] A specified amount of filtrate, primarily silicon tetrachloride, is pumped into the diatomaceous earth mixing tank 22 and stirred. All the diatomaceous earth in the diatomaceous earth adding tank 23 is then transferred into the mixing tank 22. During this process, nitrogen gas can be used to purge the diatomaceous earth in the adding tank 23 to prevent residue. After completion, the diatomaceous earth adding valve is closed. The mixing tank 22 is stirred for a specified time until fully mixed, yielding the pre-coating slurry.

[0028] Next, the pre-coated slurry is conveyed to the rotary drum filter 3 for circulating filtration to form a diatomaceous earth coating, specifically: The pre-coated slurry is transported to the drum filter 3. When the pre-coated slurry in the drum filter 3 reaches the fourth liquid level, the circulating water valve on the vacuum unit 13 and the vacuum cooler 12 is opened to perform circulating filtration. The filtrate enters the gas-liquid separator 14. When the gas-liquid separator 14 reaches the fifth liquid level, the return pipeline is opened to replenish the liquid level of the filtrate in the drum filter 3, and the remaining filtrate in the gas-liquid separator 14 is collected into the filtrate recovery tank 15.

[0029] Afterwards, the slurry after primary filtration is filtered in a rotary drum filter 3. During rotation, the filtered solids are scraped off by an internal scraper and fall into a rake dryer 5. The resulting clear liquid and exhaust gas are discharged together to a gas-liquid separator 14 for further processing. The liquid is then discharged into a filtrate recovery tank 15 and / or pumped into a diatomaceous earth mixing tank 22, while the gas is used for filtration in the rotary drum filter 3. Specifically: The obtained clear liquid and exhaust gas are discharged together into the gas-liquid separator 14 for gas-liquid phase separation. The gas phase material is discharged from the upper gas phase outlet of the gas-liquid separator 14 and then pumped into the air inlet of the vacuum filtration unit 13. Most of the gas discharged from the vacuum filtration unit 13 is cooled by the vacuum cooler 12 and then returned to the circulating gas return port of the drum filter 3 for recycling. A small portion of the gas is discharged sequentially to the primary recovery condenser 16 and the secondary recovery condenser 17 for treatment before finally being discharged into the waste gas treatment system if the gas pressure on the drum shell of the drum filter 3 exceeds the preset pressure. The clear liquid separated by the gas-liquid separator 14 is partially returned to the diatomaceous earth mixing tank 22 to replenish the liquid level of the filtrate in the drum filter 3, while the remaining clear liquid is collected into the filtrate recovery tank 15.

[0030] Also includes: When the slurry level in the slurry mixing tank 1 is below 20% (sixth level), the discharge is stopped; the rotary drum filter 3 and the gas-liquid separator 14 maintain a vacuum filtration cycle to keep the liquid level in the rotary drum filter 3 stable; and the rotary drum filter 3 stops feeding into the rake dryer 5.

[0031] In specific operation, the temperature of the diatomaceous earth addition tank 23 is controlled between 20 and 40°C, the pressure is controlled between 0.01 and 0.50 MPaG, and the amount of diatomaceous earth added is 500 to 1500 kg / time. The temperature of the diatomaceous earth mixing tank 22 is controlled between 20 and 40°C, the pressure is controlled between 0.01 and 0.50 MPaG, the feed rate of diatomaceous earth is controlled between 500 and 1500 kg / batch, the feed rate of silicon tetrachloride is controlled between 2000 and 12000 kg / batch, and the concentration of the pre-coating slurry is controlled between 5 and 20%. The temperature of the rotary drum filter 3 is controlled between 20 and 50°C, the external pressure of the drum is controlled between 5 and 40 kPaG, the vacuum degree inside the drum is controlled between -40 and -100 kPaG, and the coating thickness of the diatomaceous earth is controlled between 50 and 160 mm. The liquid level of the rotary drum filter 3 is controlled between high and low levels, where the high level is 1 / 2 of the drum diameter and the low level is 1 / 3 of the drum diameter. The temperature of the gas-liquid separator 14 is controlled between 20 and 50°C, the vacuum degree is controlled between -40 and -100 kPaG, and the liquid level inside the tank is controlled between 30 and 70%. The steam temperature of the rake dryer 5 is controlled between 70~120℃, the steam pressure is controlled between 0.01~0.50MPaG, the steam consumption is 200~600kg / batch, the drying temperature is controlled between 70~120℃, the drying pressure is controlled between 50~-60kPaG, the oil level in the grease tank is controlled between 20~80%, and the drying capacity is 1000~5000kg / batch. The temperature (inlet and outlet) of the vacuum unit 13 is controlled between 20 and 50°C, the vacuum degree is controlled between -40 and -100 kPaG, and the pumping volume is controlled between 500 and 2000 Nm³. 3 The exhaust pressure is controlled between 10 and 50 kPaG, and the liquid level in the tank is controlled between 30 and 70%; the cooling water flow rate is controlled between 15 and 35 L / min. The inlet temperature of the medium in the vacuum cooler 12 is controlled between 20 and 50°C, the inlet pressure is controlled between 10 and 80 kPaG, the inlet temperature of the circulating water is 32°C, the outlet temperature is 38°C, and the pumping speed is controlled between 500 and 2000 Nm³. 3 The exhaust pressure is controlled between 10 and 50 kPaG, and the liquid level in the tank is controlled between 30 and 70%; the cooling water flow rate is controlled between 15 and 35 L / min. The inlet temperature of the primary recovery condenser 16 is controlled between 50~120℃, the outlet temperature is controlled between 45~50℃, and the inlet / outlet pressure is controlled between 0.01~0.50MPaG. The inlet temperature of the circulating water is 32℃, the outlet temperature is 38℃, the inlet pressure of the circulating water is controlled between 0.10~0.50MPaG, and the outlet pressure is controlled between 0.10~0.50MPaG. The inlet temperature of the secondary recovery condenser 17 is controlled between 20~60℃, the outlet temperature is controlled between -30~-45℃, and the inlet / outlet pressure is controlled between 0.01~0.50MPaG. Refrigerant is used, the refrigeration evaporation temperature is controlled at -45℃, and the refrigeration evaporation pressure is controlled between 0.001~0.10MPaG. The temperature of the filtrate recovery tank 15 is controlled between 25 and 60°C, the pressure is controlled between 0.01 and 0.20 MPaG, and the liquid level inside the tank is controlled between 30 and 70%.

[0032] Compared to a single-stage filtration method that purifies the filtrate, this invention further filters the slurry from the slurry filter 2 into a rotary drum filter 3, separating the solids and chlorosilanes in the slurry again. The rotary drum filter 3 has its own filter cloth with a filtration precision of 100-120 ppm, which can further filter the solids in the slurry. Moreover, the pre-coated slurry from the diatomaceous earth mixing tank 22 can form a special filter coating on the filter cloth, forming a denser filter cake. The diatomaceous earth has a mesh size of 200-250 mesh, which is smaller and has a better filtration effect, removing solids such as silica powder, FeCl3, and AlCl3. After filtration through the diatomaceous earth coating, the chlorosilane content of the slurry is further reduced, and the chlorosilane content in the solids is reduced to about 0.5%. After vacuum filtration, the main component of the filter cake formed is the solids of the slurry.

[0033] During rotation, the residue is scraped off by a scraper and enters the rake dryer 5. The rake dryer 5 uses low-temperature drying, with the temperature controlled between 70 and 120°C, to evaporate and recover residual chlorosilanes. Simultaneously, it prevents the sublimation and precipitation of metal chlorides such as FeCl3 and AlCl3. The filter cake contains only silicon powder, FeCl3, AlCl3, and other metal chlorides, while chlorosilanes are almost undetectable. Therefore, not only is the purity of the filtrate improved, but the chlorosilanes in the slurry solids are also recovered, maximizing resource recovery.

[0034] In addition, diatomaceous earth is chosen for pre-coating treatment for two reasons: firstly, it is an environmentally friendly material, being a green filter material; secondly, its smaller mesh size allows for further filtration of solids such as silica powder, FeCl3, and AlCl3 in the slurry.

[0035] (3) The filter cake after secondary filtration is dried in rake dryer 5 and then discharged into dry residue tank 8. The dry residue in dry residue tank 8 is mixed with lime in lime tank 9. Specifically: Turn on the rake dryer 5, the dryer filter 6 and the dryer exhaust fan 7 to maintain the slight negative pressure value inside the rake dryer 5 within the preset negative pressure value; turn on the steam heating of the rake dryer 5 to dry the filter cake after secondary filtration inside the rake dryer 5. After the rake dryer 5 has been running for about 10 to 90 minutes, the silicon tetrachloride content in the dried residue is detected. If the silicon tetrachloride content is less than the preset content, the dried residue is discharged into the dried residue tank 8.

[0036] After the dry residue ton bag packaging machine 11 has installed the ton bag, the neutralization screw 10 is turned on. The lime tank 9 discharges material according to the dry residue test results, and mixes it with the dry residue discharged from the dry residue tank 8 in the neutralization screw 10. The pH of the dry residue after lime neutralization is controlled between 6 and 9. When the ton bag reaches the specified value, the dry residue tank 8, lime tank 9 and neutralization screw 10 are automatically shut off to complete the packaging and replace the ton bag.

[0037] The filter cake after secondary filtration is heated by steam in the rake dryer 5. The gaseous material is discharged from the gas outlet of the rake dryer 5 and then enters the dryer filter 6 and the dryer exhaust fan 7 for treatment before being discharged into the waste gas treatment system.

[0038] In other words, the filter cake formed by pre-coating diatomaceous earth in this invention enters the subsequent drying and neutralization stages along with the slurry after filtration, without the need for separate treatment, and is compatible with slurry treatment processes; and the waste gas generated from drying and filtration is sent to the waste gas treatment system after two-stage condensation to recover chlorosilanes, without secondary pollution.

[0039] In practice, the temperature of the filtered gas in the dryer filter 6 is controlled between 70 and 120°C, and the pressure of the filtered gas is controlled between 0.01 and 0.10 MPaG. The inlet temperature of the dryer exhaust fan 7 is controlled between 50 and 120°C, the outlet temperature of the precooler is controlled between 30 and 60°C, the exhaust pressure is controlled between 30 and 100 kPaG, and the exhaust temperature is controlled between 50 and 120°C. The temperature of the dry residue ton bag packaging machine 11 is controlled between 20~40℃, the pressure is controlled at atmospheric pressure (101kPaG), and the weight of the ton bag is controlled between 500~2000kg / bag; The temperature of neutralization spiral 10 is controlled between 50 and 90°C, and the pressure is controlled at 101 kPaG. The conveying capacity of the neutralizing screw 10 is controlled between 1000 and 3000 kg / h; The temperature of lime silo 9 is controlled between 20 and 40°C, the pressure is controlled between 0.01 and 0.09 MPaG, the weight inside the silo is controlled between 1000 and 3000 kg, and the material level inside the silo is controlled below 80%. The temperature of the dry slag hopper 8 is controlled between 70 and 120°C, the pressure is controlled between 0.01 and 0.09 MPaG, the weight inside the hopper is controlled between 1000 and 3000 kg, and the material level inside the hopper is controlled below 80%.

[0040] The present invention feeds the dried residue from the rake dryer 5 into the dried residue tank 8. The dried residue in the dried residue tank 8 is mixed with the lime in the lime tank 9 to further adjust the acidity and alkalinity of the solid contents of the dried residue. In addition, the lime reacts with any trace amounts of chlorosilane that may be present in the dried residue to completely remove the chlorosilane from the solid contents, ensuring safety and environmental protection.

[0041] (4) When the liquid level of the filtrate recovery tank 15 reaches the first liquid level, the material is fed into the de-weight recovery tower 18, and the de-weight kettle heater 19 is turned on to stir. The material in the de-weight recovery tower 18 flows to the de-weight kettle heater 19. When the liquid level of the de-weight kettle heater 19 reaches the second liquid level, the material is heated and evaporated. High-boiling-point impurities are discharged from the bottom of the de-weighing kettle heater 19 and enter the drum overflow tank 4, then return from the drum overflow tank 4 to the drum filter 3 for filtration. Furthermore, to facilitate the pump filtration of high-boiling-point impurities, dilution is required, and silicon tetrachloride is then pumped from the gas-liquid separator 14 into the drum overflow tank 4. When the liquid level in the drum filter 3 exceeds the high limit, it overflows into the drum overflow tank 4 through the overflow line.

[0042] The steam is condensed by the heavy removal tower condenser 20 and then enters the heavy removal reflux tank 21. If the liquid level in the heavy removal reflux tank 21 reaches the third level, it is refluxed into the heavy removal recovery tower 18. The exhaust valve at the top of the heavy removal recovery tower 18 automatically exhausts the gas and controls the pressure at the top of the tower. After the operation is stable, the components in the heavy removal reflux tank 21 are sampled and analyzed. When the purity of the product in the heavy removal reflux tank 21 reaches the preset purity, it is transported to the silicon tetrachloride storage area for storage and use in the cold hydrogenation unit.

[0043] The filtrate collected in the filtrate recovery tank 15 includes liquid recovered from the primary recovery condenser 16 and the secondary recovery condenser 17.

[0044] Considering that the filtrate collected in the filtrate recovery tank 15 is a clear liquid without solid particles, but the clear liquid still contains some high-boiling impurities such as FeCl3 and AlCl3, if the cold hydrogenation unit directly reuses it, the cold hydrogenation unit will accumulate heavy components such as FeCl3 and AlCl3, which will affect the stable operation of the system and the quality of subsequent products. Therefore, the filtrate is purified again through step (4) to remove heavy components and impurities before it can be reused.

[0045] In practical implementation, the top temperature of the deweight recovery tower 18 is controlled between 40 and 60°C, the bottom temperature is controlled between 80 and 100°C, the top pressure is controlled between 0.10 and 0.30 MPaG, the feed flow rate is controlled between 200 and 600 kg / h, the reflux flow rate at the top of the tower is controlled between 700 and 1200 kg / h, and the reflux ratio is controlled between 1.0 and 2.0. The medium temperature of the de-weighing kettle heater 19 is controlled between 80~100℃, the medium pressure is controlled between 0.10~0.50MPaG, the heating steam temperature is controlled between 70~120℃, the steam pressure is controlled between 0.20~1.00MPaG, and the bottom discharge rate is controlled between 20~80kg / h. The temperature of the drum overflow tank 4 is controlled between 30 and 70°C, the pressure between 10 and 50 kPaG, and the liquid level inside the tank is controlled between 30% and 70%. Furthermore, the drum overflow tank 4 and the drum filter 3 form a linkage loop: during startup, the drum overflow tank 4 maintains the liquid level inside the drum filter 3 through the loop, increasing the filtration area and improving the filtration effect. During shutdown, the drum overflow tank 4 forms a backflow loop with the drum filter 3, preventing the sedimentation and accumulation of solid particles in the slurry.

[0046] The medium inlet temperature of the de-weighting tower condenser 20 is controlled between 20~50℃, and the medium inlet pressure is controlled between 0.10~0.50MPaG. The circulating water inlet temperature is 32℃, the outlet temperature is 38℃, the inlet pressure is controlled between 0.10~0.50MPaG, and the outlet pressure is controlled between 0.10~0.50MPaG. The circulating water flow rate is controlled between 5~30m³. 3 Between / h; The temperature of the deweight reflux tank 21 is controlled between 30 and 50°C, the pressure is controlled between 0.10 and 0.50 MPaG, and the liquid level in the tank is controlled between 30 and 70%.

[0047] In summary, this invention sequentially processes the slurry generated from the cold hydrogenation process through primary filtration, secondary diatomaceous earth pre-coating filtration, drying and evaporation, and distillation purification. This achieves a chlorosilane (mainly silicon tetrachloride) recovery rate of up to 99%, avoiding resource waste and environmental pollution. Simultaneously, it eliminates the need for an alkaline washing tank, simplifying the process and reducing energy consumption. Furthermore, this treatment method employs physical separation (filtration, drying, and distillation) and solid residue neutralization, generating no wastewater and eliminating the need for a supporting wastewater treatment system, significantly reducing environmental costs and energy consumption.

[0048] Example 2 To adapt to Example 1, this example provides a slurry treatment system for the cold hydrogenation synthesis process, including a primary filtration unit, a secondary filtration unit, a dry slag treatment unit, a purification unit, and a gas-liquid circulation unit, such as... Figure 1 As shown: The primary filtration unit includes a slurry mixing tank 1 and a slurry filter 2 connected in sequence. The filtrate outlet of the slurry filter 2 is connected to the filtrate recovery tank 15, and the slurry return port of the slurry filter 2 is connected to the feed port of the slurry mixing tank.

[0049] The secondary filtration unit includes a rotary drum filter 3, a diatomaceous earth mixing tank 22, and a diatomaceous earth adding tank 23. The outlet of the diatomaceous earth adding tank 23 is connected to the inlet of the diatomaceous earth mixing tank 22. The liquid inlet of the diatomaceous earth mixing tank 22 is connected to the liquid outlet of the gas-liquid separator 14. The outlet of the diatomaceous earth mixing tank 22 is connected to the inlet of the rotary drum filter 3. The slurry inlet of the rotary drum filter 3 is connected to the slurry outlet of the slurry mixing tank 1.

[0050] The dry residue processing unit includes a rake dryer 5, a dry residue tank 8, and a neutralization spiral 10 connected in sequence. The feed inlet of the rake dryer 5 is connected to the filter cake outlet of the rotary drum filter 3. The feed inlet of the neutralization spiral 10 is also connected to a lime tank 9, and the discharge outlet of the neutralization spiral 10 is connected to a dry residue ton bag packaging machine 11. In addition, the gas phase outlet of the rake dryer 5 is connected to the primary recovery condenser 16 via the dryer filter 6 and the dryer exhaust fan 7. The gas outlet of the primary recovery condenser 16 is connected to the secondary recovery condenser 17. The gas outlet of the secondary recovery condenser 17 is connected to the external waste gas treatment system through a pipeline.

[0051] The purification unit includes a deweight recovery tower 18, a deweight reactor heater 19, a deweight tower condenser 20, and a deweight reflux tank 21. The inlet of the deweight recovery tower 18 is connected to the outlet of the filtrate recovery tank 15. The bottom outlet of the deweight recovery tower 18 is connected to the inlet of the deweight reactor heater 19. The gas phase outlet of the deweight reactor heater 19 is connected to the bottom gas phase return outlet of the deweight recovery tower 18. The top gas phase outlet of the deweight recovery tower 18 is connected to the gas inlet of the deweight tower condenser 20. The condensate outlet of the deweight tower condenser 20 is connected to the inlet of the deweight reflux tank 21. The reflux outlet of the deweight reflux tank 21 is connected to the top reflux outlet of the deweight recovery tower 18. The outlet of the deweight reflux tank 21 is connected to the silicon tetrachloride storage tank area. In addition, the bottom outlet of the de-weighing kettle heater 19 is connected to the inlet of the drum overflow tank 4, and the outlet of the drum overflow tank 4 is connected to the slurry inlet of the drum filter 3. Together with the slurry after primary filtration, they participate in secondary filtration to achieve the re-recovery of residual chlorosilanes in high-boiling impurities and the centralized filtration and separation of solid impurities.

[0052] The gas-liquid circulation unit includes a gas-liquid separator 14. The gas-liquid outlet of the rotary drum filter 3 is connected to the feed inlet of the gas-liquid separator 14. The gas phase outlet of the gas-liquid separator 14 is connected to the circulating gas return port of the rotary drum filter 3. The liquid phase outlet of the gas-liquid separator 14 is connected to the feed inlet of the filtrate recovery tank 15.

[0053] Furthermore, the gas-liquid circulation unit also includes a vacuum filtration unit 13 and a vacuum cooler 12. The gas phase outlet of the gas-liquid separator 14 is connected to the air inlet of the vacuum filtration unit 13, the air outlet of the vacuum filtration unit 13 is connected to the air inlet of the vacuum cooler 12, and the air outlet of the vacuum cooler 12 is connected to the circulating gas return port of the rotary drum filter 3. The liquid phase outlet of the gas-liquid separator 14 is divided into two paths: one path is connected to the liquid inlet of the diatomaceous earth mixing tank 22 to replenish the filtration liquid level, and the other path is connected to the feed inlet of the filtrate recovery tank 15 to recover the clear liquid.

[0054] The processing system provided by this invention consists of processing units that cooperate with each other and do not operate independently. Instead, it is a highly efficient and complete cyclic operation system that can ensure a high recovery rate of chlorosilanes (mainly silicon tetrachloride) and can also process solid dry residue. The system is simple to operate and saves resources.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for treating slurry generated in a cold hydrogenation synthesis process, characterized in that, Includes the following steps: (1) The cold hydrogenated slurry is injected into the slurry mixing tank, stirred evenly, and then transported to the slurry filter for primary filtration. The obtained filtrate is discharged into the filtrate recovery tank, and the slurry is returned to the slurry mixing tank. When the solid content of the slurry in the slurry mixing tank reaches the preset value, the filtration is stopped. (2) Filtrate is pumped into the diatomaceous earth mixing tank, and diatomaceous earth is added to the diatomaceous earth mixing tank through the diatomaceous earth adding tank. The mixture is stirred to obtain a pre-coated slurry. The pre-coated slurry is then transported to a rotary drum filter for circulation filtration to form a diatomaceous earth coating. The slurry after primary filtration is sent to a rotary drum filter for secondary filtration. The resulting clear liquid and exhaust gas are discharged together to a gas-liquid separator for further processing. The liquid is discharged into a filtrate recovery tank and / or injected into a diatomaceous earth mixing tank, while the gas is used for filtration in the rotary drum filter. (3) The filter cake after secondary filtration is dried in a rake dryer and then discharged into a dry residue tank. The dry residue in the dry residue tank is mixed with the lime in the lime tank. (4) When the liquid level in the filtrate recovery tank reaches the first liquid level, feed the material into the de-weight recovery tower and simultaneously turn on the de-weight kettle heater to stir. The material in the de-weight recovery tower flows to the de-weight kettle heater. When the liquid level in the de-weight kettle heater reaches the second liquid level, heat and evaporate the material. High-boiling-point impurities are discharged from the bottom of the de-weighing kettle heater and enter the drum overflow tank, and then return from the drum overflow tank to the drum filter for filtration. The steam is condensed by the condenser of the deweight removal tower and then enters the deweight removal reflux tank. If the liquid level in the deweight removal reflux tank reaches the third level, it will be refluxed into the deweight removal recovery tower. When the purity of the product in the deweight removal reflux tank reaches the preset purity, it will be transported to the silicon tetrachloride storage tank area.

2. The method for treating the slurry generated in the cold hydrogenation synthesis process according to claim 1, characterized in that, Step (2) involves conveying the pre-coated slurry to a rotary drum filter for circulating filtration to form a diatomaceous earth coating. Specifically: The pre-coated slurry is transported to the rotary drum filter. When the pre-coated slurry in the rotary drum filter reaches the fourth liquid level, the circulating water valve on the vacuum filtration unit and vacuum cooler is opened to perform circulating filtration. The filtrate enters the gas-liquid separator. When the gas-liquid separator reaches the fifth liquid level, the return pipeline is opened to replenish the liquid level of the filtrate in the drum filter. The remaining filtrate in the gas-liquid separator is then collected into the filtrate recovery tank.

3. The method for treating the slurry generated in the cold hydrogenation synthesis process according to claim 2, characterized in that, The thickness of the diatomaceous earth coating should be controlled between 50 and 160 mm.

4. The method for treating the slurry generated in the cold hydrogenation synthesis process according to claim 1, characterized in that, The clarified liquid obtained in step (2) is discharged together with the exhaust gas to a gas-liquid separator for processing. The liquid is then discharged into a filtrate recovery tank and / or injected into a diatomaceous earth mixing tank, while the gas is used for filtration in a rotary drum filter. Specifically: The obtained clear liquid and exhaust gas are discharged together into a gas-liquid separator for gas-liquid phase separation. The gas phase material is discharged from the upper gas phase outlet of the gas-liquid separator and then pumped into the air inlet of the vacuum filtration unit. Among the exhaust gas from the vacuum filtration unit, the gas with a proportion not less than the first preset ratio is cooled by the vacuum cooler and returned to the circulating gas return port of the drum filter for recycling. The remaining gas, when the gas pressure on the drum shell of the drum filter exceeds the preset pressure, is sequentially discharged to the primary recovery condenser and the secondary recovery condenser for treatment, and finally discharged into the waste gas treatment system. Of the clear liquid separated by the gas-liquid separator, the second preset proportion of clear liquid is returned to the diatomaceous earth mixing tank, while the remaining proportion of clear liquid is collected into the filtrate recovery tank.

5. The method for treating the slurry generated in the cold hydrogenation synthesis process according to claim 4, characterized in that, Also includes: When the slurry level in the mixing tank is lower than the sixth level, discharge is stopped; the drum filter and the gas-liquid separator maintain a continuous filtration cycle to keep the liquid level in the drum filter stable; and the drum filter stops feeding material into the rake dryer.

6. The method for treating the slurry generated in the cold hydrogenation synthesis process according to claim 1, characterized in that, The filter cake after secondary filtration in step (3) is fed into a rake dryer, dried, and then discharged into a dry residue tank. Specifically: Turn on the rake dryer, dryer filter and dryer exhaust fan, and keep the slight negative pressure value inside the rake dryer within the preset negative pressure value; turn on the steam heating of the rake dryer to dry the filter cake after secondary filtration inside the rake dryer. After the rake dryer has been running for about 10 to 90 minutes, the silicon tetrachloride content in the dried residue is tested. If the silicon tetrachloride content is less than the preset content, the dried residue is discharged into the dried residue tank.

7. The method for treating the slurry generated in the cold hydrogenation synthesis process according to claim 6, characterized in that, The filter cake after secondary filtration is heated by steam in a rake dryer. The gaseous material is discharged from the gas outlet of the rake dryer and then enters the dryer filter and the dryer exhaust fan for treatment before being discharged into the waste gas treatment system.

8. The method for treating the slurry generated in the cold hydrogenation synthesis process according to claim 1, characterized in that, Step (3) involves mixing the dry residue in the dry residue container with the lime in the lime container, specifically as follows: After the dry residue ton bag packaging machine is installed with the ton bag, the neutralization screw is turned on. The lime tank discharges material according to the dry residue detection results and mixes with the dry residue discharged from the dry residue tank in the neutralization screw. When the ton bag reaches the specified value, the dry residue tank, lime tank and neutralization screw are automatically turned off to complete the packaging and replace the ton bag.

9. A system for treating slurry generated in a cold hydrogenation synthesis process, characterized in that, It includes a primary filtration unit, a secondary filtration unit, a dry residue treatment unit, a purification unit, and a gas-liquid circulation unit; The primary filtration unit includes a slurry mixing tank and a slurry filter connected in sequence. The filtrate outlet of the slurry filter is connected to a filtrate recovery tank, and the slurry return port of the slurry filter is connected to the feed port of the slurry mixing tank. The secondary filtration unit includes a rotary drum filter, a diatomaceous earth mixing tank, and a diatomaceous earth adding tank. The outlet of the diatomaceous earth adding tank is connected to the inlet of the diatomaceous earth mixing tank. The liquid inlet of the diatomaceous earth mixing tank is connected to the liquid outlet of the gas-liquid separator. The outlet of the diatomaceous earth mixing tank is connected to the inlet of the rotary drum filter. The slurry inlet of the rotary drum filter is connected to the slurry outlet of the slurry mixing tank. The dry slag processing unit includes a rake dryer, a dry slag tank, and a neutralization spiral connected in sequence. The feed inlet of the rake dryer is connected to the filter cake outlet of the rotary drum filter, and the feed inlet of the neutralization spiral is also connected to a lime tank. The purification unit includes a heavy removal and recovery tower, a heavy removal kettle heater, a heavy removal tower condenser, and a heavy removal reflux tank. The inlet of the heavy removal and recovery tower is connected to the outlet of the filtrate recovery tank. The bottom outlet of the heavy removal and recovery tower is connected to the inlet of the heavy removal kettle heater. The gas phase outlet of the heavy removal kettle heater is connected to the bottom gas phase return outlet of the heavy removal and recovery tower. The top gas phase outlet of the heavy removal and recovery tower is connected to the gas inlet of the heavy removal tower condenser. The condensate outlet of the heavy removal tower condenser is connected to the inlet of the heavy removal reflux tank. The reflux outlet of the heavy removal reflux tank is connected to the top reflux outlet of the heavy removal and recovery tower. The outlet of the heavy removal reflux tank is connected to the silicon tetrachloride storage tank area. The gas-liquid circulation unit includes a gas-liquid separator, the gas-liquid outlet of the rotary drum filter is connected to the feed inlet of the gas-liquid separator, the gas phase outlet of the gas-liquid separator is connected to the circulating gas return port of the rotary drum filter, and the liquid phase outlet of the gas-liquid separator is connected to the feed inlet of the filtrate recovery tank.

10. The slurry treatment system generated in the cold hydrogenation synthesis process according to claim 9, characterized in that, The gas-liquid circulation unit also includes a vacuum filtration unit and a vacuum cooler. The gas phase outlet of the gas-liquid separator is connected to the air inlet of the vacuum filtration unit, the air outlet of the vacuum filtration unit is connected to the air inlet of the vacuum cooler, and the air outlet of the vacuum cooler is connected to the circulating gas return port of the rotary drum filter. The liquid phase outlet of the gas-liquid separator is set in two ways: one is connected to the liquid inlet of the diatomaceous earth mixing tank, and the other is connected to the feed inlet of the filtrate recovery tank to recover the clear liquid.

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