Safe drying device for high-humidity silicon powder

Abstract

The utility model provides a safe drying device for high-humidity silicon powder, which comprises a drying machine and a buffer tank, the drying machine is also provided with a feed port, a gas phase outlet, a jacket layer and a discharge port, the gas phase outlet is used for discharging volatile gas phase chlorosilane, a heating medium is introduced into the jacket layer, the discharge port is connected with the buffer tank through a discharge pipe, the buffer tank is arranged below the drying machine, and the buffer tank is arranged below the drying machine. The buffer tank is a hollow tank body, the bottom of the buffer tank is of a conical structure and is provided with a silicon powder outlet so as to be connected with the packaging mechanism, a plurality of gas inlets are further formed in the periphery of the conical structure of the buffer tank and used for introducing nitrogen, and the buffer tank is further provided with a gas phase outlet used for discharging gas; according to the scheme, the buffer tank is arranged, dried silicon powder is firstly discharged into the buffer tank and then is blown away by nitrogen in the buffer tank, and disilicon in the silicon powder is carried along with the nitrogen to escape, leave the silicon powder and is discharged from the buffer tank, so that the silicon powder discharged from the buffer tank almost does not contain disilicon and has no flash burning danger when being discharged.

Description

Technical Field

[0001] The utility model relates to the technical field of polysilicon byproduct silicon powder processing, in particular to a high-humidity silicon powder safety drying device. Background Art

[0002] In the production process of polysilicon, trichlorosilane is prepared by the reaction of hydrogen chloride gas, hydrogen and silicon powder in the hydrogenation step. After the reaction, a large amount of silicon powder is still not completely reacted and is treated as slurry in the distillation process. The high boiling products after distillation contain a large amount of chlorosilane, silicon powder, and other substances. The clear liquid and waste silicon powder are obtained by preliminary sedimentation separation. In the original waste silicon powder treatment process, the waste silicon powder is dried by a dryer to volatilize and discharge the chlorosilane in it, and the remaining silicon powder is collected.

[0003] In the original processing process, after the drying step, the silicon powder still contains no more than 10% chlorosilane, and the dichlorodisilane in it is a substance that is easy to flash. The ignition point of disilane is only about 40°C. After being dried, the residual temperature of the silicon powder is likely to be higher than 40°C. The moment it is discharged from the dryer, it suddenly comes into contact with air and oxygen, and it is easy to flash. Utility Model Content

[0004] In view of the above defects, the utility model proposes a high-humidity silicon powder safe drying device, including a dryer and a buffer tank. A stirring mechanism is arranged inside the dryer. The dryer is also provided with a feed port, a gas phase outlet, a jacket layer, and a discharge port. The feed port is used to input waste silicon powder to be dried, and the gas phase outlet is used to discharge the volatilized gas phase chlorosilane. A heating medium is introduced into the jacket layer, and the discharge port is connected to the buffer tank through a discharge pipe. The buffer tank is arranged below the dryer. The buffer tank is a hollow tank body. The bottom of the buffer tank is a conical structure, and a silicon powder outlet is arranged to be connected to a packaging mechanism. A plurality of gas inlets are arranged around the conical structure of the buffer tank for introducing nitrogen. The buffer tank is also provided with a gas phase outlet for discharging gas.

[0005] Preferably, the heating medium is superheated steam.

[0006] Preferably, the nitrogen is a room temperature gas.

[0007] Preferably, there are three gas inlets at the bottom of the buffer tank, and the three gas inlets are evenly distributed on the outer wall around the bottom of the buffer tank, and the gas inlets are arranged in an inclined upward direction.

[0008] Preferably, a primary sieve plate and a secondary sieve plate are also provided inside the buffer tank, the primary sieve plate is provided at the position where the cylinder and the cone of the buffer tank are connected, the secondary sieve plate is provided below the primary sieve plate, and the mesh of the secondary sieve plate is larger than the mesh of the primary sieve plate, two gas inlets are provided on the side wall between the secondary sieve plate and the primary sieve plate, the opening directions of the two gas inlets are inclined, and the inclination directions are consistent, the opening directions of the two gas inlets are provided along the tangential direction of the side wall of the cone, the other gas inlet is provided on the side wall below the secondary sieve plate, and the orientation of the one gas inlet is vertically provided along the side wall of the cone.

[0009] Preferably, a nitrogen main pipe and a gas distribution pipe connected to the nitrogen main pipe are also provided, and the gas distribution pipe is connected to three gas inlets of the buffer tank to introduce nitrogen into the buffer tank.

[0010] Preferably, a first backflush pipe, a second backflush pipe, and a third backflush pipe respectively connected to the nitrogen main pipe are also provided. The nitrogen main pipe is used to introduce nitrogen. The first backflush pipe is connected to the gas phase outlet pipeline of the dryer and is used to backflush the silicon powder carried by the gas phase outlet and is easy to clog the pipeline. The second backflush pipe is connected to the discharge pipe and is used to backflush the silicon powder in the storage tank. The third backflush pipe is connected to the pipeline of the silicon powder outlet of the buffer tank and is used to backflush the silicon powder in the silicon powder outlet pipeline.

[0011] This solution sets up a buffer tank, into which the dried silicon powder is first discharged, and then blown away by the nitrogen in the buffer tank, so that the disilicon therein is carried away with the nitrogen, leaves the silicon powder, and is discharged from the buffer tank, so that the silicon powder discharged from the buffer tank contains almost no disilicon, and there is no risk of flash fire during discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the structure of this scheme.

[0013] Figure 2 A schematic diagram of another embodiment of a buffer tank.

[0014] Figure 3 Schematic diagram of the internal structure of the buffer tank from a top view.

[0015] In the figure: a dryer 10, a stirring mechanism 11, a gas phase outlet 12, a jacket layer 13, a discharge port 14, a buffer tank 20, a silicon powder outlet 21, a gas inlet 22, a primary sieve plate 23, a secondary sieve plate 24, a nitrogen main pipe 30, a first backflush pipe 31, a second backflush pipe 32, a third backflush pipe 33, and a gas distribution pipe 40. DETAILED DESCRIPTION

[0016] See also Figure 1-3A high-humidity silicon powder safety drying device includes a dryer 10 and a buffer tank 20. A stirring mechanism 11 is arranged inside the dryer 10. The dryer 10 is also provided with a feed port, a gas phase outlet 12, a jacket layer 13, and a discharge port 14. The feed port is used to input waste silicon powder to be dried, and the gas phase outlet 12 is used to discharge the volatilized gas phase chlorosilane. A heating medium is introduced into the jacket layer 13. The discharge port 14 is connected to the buffer tank 20 through a discharge pipe. The buffer tank 20 is arranged below the dryer 10. The buffer tank 20 is a hollow tank body. The bottom of the buffer tank 20 is a conical structure, and a silicon powder outlet 21 is arranged to be connected to a packaging mechanism. A plurality of gas inlets 22 are arranged around the conical structure of the buffer tank 20 for introducing nitrogen. The buffer tank 20 is also provided with a gas phase outlet for discharging gas.

[0017] This solution utilizes the introduced flowing nitrogen to increase the exposed surface area of ​​chlorosilane in silicon powder and the flow rate of chlorosilane, thereby achieving gasification of chlorosilane, which is simultaneously carried out by nitrogen.

[0018] Furthermore, the heating medium is superheated steam, and the temperature of the superheated steam is controlled so that the internal temperature of the dryer 10 reaches above 140° C., thereby volatilizing and evaporating the chlorosilane.

[0019] Furthermore, the nitrogen is a room temperature gas. For example, the temperature is room temperature or lower than room temperature. The silicon powder discharged from the dryer 10 has residual heat. If the seal is poor or air leaks, the disiloxane therein will flash when in contact with the air. The introduction of nitrogen in this scheme not only stirs the silicon powder and carries away the chlorosilane, but also reduces the temperature of the silicon powder by controlling the low temperature of the nitrogen; it also reduces the temperature of the environment in which the disiloxane is located and the surrounding silicon powder, thereby reducing the temperature of the disiloxane. Even if there is leakage, contact with air, or when it is discharged, the flash of the disiloxane can be avoided; thirdly, the introduction of nitrogen also plays a role in stirring and breaking up the silicon powder, so that the silicon powder has good fluidity, and the material is discharged smoothly without blockage. This solution is different from the prior art. In order to accelerate the volatilization of chlorosilane, it is easy to think of introducing heated nitrogen to accelerate the volatilization of chlorosilane through heat and quickly escape from the silicon powder. This is not applicable in this solution. Since the silicon powder in this solution must be discharged for packaging or storage after drying, if there is residual disilcontinuity, or even disilcontinuity with a certain temperature carried by high-temperature nitrogen, it is more likely to flash when it is discharged due to the temperature reaching above the flash point and contacting the air at the same time. Therefore, this solution uses low-temperature gas. Although it cannot accelerate the volatilization of chlorosilane through heat and mass transfer, it can also accelerate the rapid evaporation and escape of liquid chlorosilane remaining in the silicon powder by controlling the gas flow rate, and it will not increase the temperature of disilcontinuity.

[0020] Furthermore, there are three gas inlets 22 at the bottom of the buffer tank 20, and the three gas inlets 22 are evenly distributed on the outer wall around the bottom of the buffer tank 20, and the gas inlets 22 are arranged in an inclined upward direction. The setting of the inclined angle makes the flow direction of the nitrogen gas introduced almost opposite to the direction of the silicon powder falling, increasing the contact area, so that the falling silicon powder is inevitably blown and dispersed by the nitrogen gas.

[0021] Furthermore, a primary sieve plate 23 and a secondary sieve plate 24 are arranged inside the buffer tank. The primary sieve plate is arranged at the position where the cylinder and the cone of the buffer tank are connected, and the secondary sieve plate is arranged below the primary sieve plate, and the mesh of the secondary sieve plate is larger than the mesh of the primary sieve plate. Two gas inlets are arranged on the side wall between the secondary sieve plate and the primary sieve plate, and the opening directions of the two gas inlets are inclined, and the inclination directions are consistent. The opening directions of the two gas inlets are arranged along the tangential direction of the side wall of the cone, and the other gas inlet is arranged on the side wall below the secondary sieve plate, and the orientation of the one gas inlet is vertically arranged along the side wall of the cone.

[0022] For example, a gas inlet is arranged vertically along the side wall of the cone, which can be nearly parallel to the axial direction of the cone, and the inlet position is close to the silicon powder outlet 21. The arrangement of this scheme firstly receives the dried silicon powder through two sieve plates to prevent the silicon powder from accumulating inside the tank body and deteriorating the contact with nitrogen. The two gas inlets arranged tangentially and in the same inclination direction can make the nitrogen enter the tank body in a swirl manner, and form a vortex inside the cone after entering, driving the silicon powder vortex to turn, increasing the surface area and contact opportunity with nitrogen. After passing through the secondary sieve plate, the secondary sieve plate can play a role in evenly distributing the nitrogen in the third gas inlet. At the same time, in order to affect the speed and flow rate of the silicon powder falling, in order to match the primary sieve plate, the mesh of the secondary sieve plate is set larger than the mesh of the primary sieve plate, close to the third gas inlet arranged vertically, so that the silicon powder falling from the secondary sieve plate is blown up and dispersed again, and will not accumulate at the silicon powder outlet 21. The two silicon in the silicon powder is contacted with nitrogen again by the secondary blowing and taken away, which also increases the fluidity of the silicon powder at the silicon powder outlet 21.

[0023] Compared with the hollow structure inside the buffer tank, the two-stage sieve plate can not only buffer the fall of silicon powder, but also the nitrogen inlet is located below the sieve plate. The sieve plate can slow down and evenly distribute the force of the gas blowing away the silicon powder. Moreover, through the partition of the first sieve plate and the nitrogen inlet located below it, the silicon powder can be prevented from flying seriously inside the tank body, which would cause the gas to be drawn in and carry too much silicon powder when it is discharged.

[0024] Furthermore, a nitrogen main pipe 30 and a gas distribution pipe 40 connected to the nitrogen main pipe 30 are provided. The gas distribution pipe 40 is connected to three gas inlets 22 of the buffer tank 20 to allow nitrogen to flow into the buffer tank 20 .

[0025] After the implementation of this solution, the waste silicon powder after sedimentation will discharge the clear liquid, and the remaining waste silicon powder will be in the state of flowing slurry, which will be pumped into the dryer 10 naturally through a pump group or by setting a sedimentation tank above the dryer 10. The humidity content of the silicon powder discharged into the buffer tank 20 after drying is less than 2%, indicating that the chlorosilane content in the silicon powder is less than 2%, and the disilconium content is very small, almost less than 0.1%, and the temperature is relatively low, so when it is discharged from the buffer tank 20 into the packaging mechanism, will there be a flash fire problem? In horizontal comparison, in the original design, the humidity content of the silicon powder detector discharged from the dryer 10 is about 9-10%, the humidity is still relatively high, and the residual temperature is also relatively high, and the risk of flash fire is very high.

[0026] Furthermore, a first backflush pipe 31, a second backflush pipe 32, and a third backflush pipe 33 are provided, which are respectively connected to the nitrogen main pipe 30. The nitrogen main pipe 30 is used to introduce nitrogen. The first backflush pipe 31 is connected to the gas phase outlet 12 pipeline of the dryer 10, and is used to backflush the silicon powder carried by the gas phase outlet 12, which is easy to block the pipeline. The second backflush pipe 32 is connected to the discharge pipe, and is used to backflush the silicon powder in the storage tank. The third backflush pipe 33 is connected to the pipeline of the silicon powder outlet 21 of the buffer tank 20, and is used to backflush the silicon powder in the pipeline of the silicon powder outlet 21. The purpose of setting up multiple backflush pipes is to backflush the silicon powder that may remain in the pipeline to avoid pipeline blockage.

[0027] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of this patent.

Claims

1. A high-humidity silicon powder safe drying device, characterized in that: The invention comprises a dryer and a buffer tank. A stirring mechanism is arranged inside the dryer. The dryer is also provided with a feed port, a gas phase outlet, a jacket layer and a discharge port. The feed port is used to input waste silicon powder to be dried. The gas phase outlet is used to discharge volatilized gas phase chlorosilane. A heating medium is introduced into the jacket layer. The discharge port is connected with the buffer tank through a discharge pipe. The buffer tank is arranged below the dryer. The buffer tank is a hollow tank body. The bottom of the buffer tank is a conical structure and a silicon powder outlet is arranged to be connected with the packaging mechanism. A plurality of gas inlets are arranged around the conical structure of the buffer tank for introducing nitrogen. The buffer tank is also provided with a gas phase outlet for discharging gas.

2. The high-humidity silicon powder safety drying device according to claim 1, characterized in that: The heating medium is superheated steam.

3. The high-humidity silicon powder safe drying device according to claim 1, characterized in that: The nitrogen is a gas at room temperature.

4. The high-humidity silicon powder safety drying device according to claim 1, characterized in that: The number of gas inlets at the bottom of the buffer tank is three, and the three gas inlets are distributed on the outer wall around the bottom of the buffer tank, and the gas inlets are arranged in an inclined upward direction.

5. The high-humidity silicon powder safety drying device according to claim 4, characterized in that: A primary sieve plate and a secondary sieve plate are also arranged inside the buffer tank. The primary sieve plate is arranged at the position where the cylinder and the cone of the buffer tank are connected. The secondary sieve plate is arranged below the primary sieve plate, and the mesh of the secondary sieve plate is larger than the mesh of the primary sieve plate. Two gas inlets are arranged on the side wall between the secondary sieve plate and the primary sieve plate. The opening directions of the two gas inlets are inclined, and the inclination directions are consistent. The opening directions of the two gas inlets are arranged along the tangential direction of the side wall of the cone. The other gas inlet is arranged on the side wall below the secondary sieve plate, and the direction of the one gas inlet is vertically arranged along the side wall of the cone.

6. The high-humidity silicon powder safety drying device according to claim 4, characterized in that: A nitrogen main pipe and a gas distribution pipe connected to the nitrogen main pipe are also provided. The gas distribution pipe is connected to three gas inlets of the buffer tank to introduce nitrogen into the buffer tank.

7. The high-humidity silicon powder safety drying device according to claim 5, characterized in that: A first backflush pipe, a second backflush pipe, and a third backflush pipe respectively connected to the nitrogen main pipe are also provided. The nitrogen main pipe is used to introduce nitrogen. The first backflush pipe is connected to the gas phase outlet pipeline of the dryer and is used to backflush the silicon powder carried by the gas phase outlet and is easy to clog the pipeline. The second backflush pipe is connected to the discharge pipe and is used to backflush the silicon powder in the storage tank. The third backflush pipe is connected to the pipeline of the silicon powder outlet of the buffer tank and is used to backflush the silicon powder in the silicon powder outlet pipeline.

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