A polysilicon lumps drying system

Abstract

The application discloses a kind of polycrystalline silicon block drying system, belong to polycrystalline silicon drying technical field, including in proper order head-to-tail gas lock unit, hot air drying unit, vacuum drying unit, cold air cooling unit, and be located at the front end of system negative pressure water removal unit, each unit is equipped with conveying device for conveying basket. Gas lock unit collects dirty air of previous clean area and is filtered by filter element, prevents pollutant diffusion;Negative pressure water removal unit removes residual water in the inner wall of basket;Hot air drying unit is sealed combined with hot air supply box after basket is lifted, and hot air is blown from top to bottom to dry;Vacuum drying unit uses negative pressure to lower the boiling point of water to completely remove water in small gap on the surface of silicon block;Cold air cooling unit cools silicon block. The application realizes efficient, thorough, clean multistage collaborative drying of polycrystalline silicon block.

Description

Technical Field

[0001] This invention relates to the field of polycrystalline silicon drying technology, and more particularly to a polycrystalline silicon bulk material drying system. Background Technology

[0002] Electronic-grade polysilicon is a core material for the manufacture of integrated circuits and discrete devices, requiring extremely high purity. The content of surface metallic impurities typically needs to be controlled at the ppb (parts per billion) or even ppt (parts per trillion) level. After post-processing steps such as crushing, screening, cleaning, and etching, a large amount of moisture remains on the surface and in the internal crevices of electronic-grade polysilicon blocks. If this residual moisture is not completely removed, it will cause surface oxidation during subsequent packaging, storage, and transportation, leading to a decrease in product purity. Simultaneously, residual moisture can introduce bubbles and impurities during the single-crystal pulling process, severely affecting the quality and yield of downstream single-crystal silicon rods. Therefore, the drying process is a critical step in the post-processing of electronic-grade polysilicon.

[0003] Currently, various polysilicon drying technologies have emerged in the industry, such as hot air circulation drying, cold air cooling, vacuum drying, and microwave heating drying. Among them, hot air drying is one of the most commonly used drying methods in the electronic-grade polysilicon industry. Its core technology lies in using high-temperature clean air forced convection to evaporate and remove moisture from the surface and gaps of the silicon material. However, hot air drying is limited by the thermal conductivity of the silicon material stacking structure. The internal silicon blocks have low thermal conductivity, and the particles are tightly attached to each other, making it difficult for hot air to penetrate into the deep areas between the silicon block layers. This results in uneven drying, and the polysilicon material on the inner side of the stack is often not completely dried. Simple hot air circulation is insufficient to completely remove deep capillary water and adsorbed water.

[0004] Vacuum drying is a drying method that does not require heating the air. Its core advantage lies in utilizing the principle that the boiling point of water decreases and the evaporation rate increases under low pressure, which can achieve rapid evaporation of water at lower temperatures, thereby reducing the risk of high-temperature oxidation. However, simple vacuum drying is limited by the latent heat of phase change of water. The vaporization of a large amount of water requires a large amount of heat energy. Without the assistance of an external heat source, the efficiency of vacuum drying will be severely limited, especially for capillary water in deep layers of stockpiled materials, resulting in a long drying cycle.

[0005] Microwave drying utilizes microwave energy to directly act on water molecules in materials, causing the water molecules to oscillate at high frequency and generate heat, thus achieving rapid evaporation of moisture. However, uneven microwave heating can lead to localized overheating, creating hot spots, increasing the risk of oxidation, and the equipment is also expensive.

[0006] Furthermore, while existing technologies include simple series connections of multiple drying methods, the lack of coordination between drying units and the failure to dynamically adjust drying parameters based on the silicon material's state result in unstable drying performance and high energy consumption. Additionally, after pre-processing steps such as cleaning and etching, moisture remains on the outer and inner walls of the material basket. If this moisture enters subsequent drying units with the basket, it not only reduces drying efficiency but also allows contaminants from the pre-processing steps to diffuse into the drying system, polluting the clean environment and affecting product purity. Existing technologies generally lack effective methods for isolating and removing residual water from the basket itself and contaminated air from the pre-processing steps.

[0007] Therefore, there is an urgent need for a drying system for polycrystalline silicon blocks that can perform multi-stage synergistic drying, has high drying efficiency and good drying effect, and can effectively isolate previous contaminants and ensure the cleanliness of the drying system. Summary of the Invention

[0008] The purpose of this invention is to provide a polycrystalline silicon bulk material drying system to solve the problems of uneven drying, difficulty in completely removing deep moisture, and easy diffusion and pollution of previous dirty air in the prior art.

[0009] This invention is implemented by the following technical solution: a polycrystalline silicon block drying system, comprising an airlock unit, a hot air drying unit, a vacuum drying unit, a cold air cooling unit, a negative pressure water driving unit, and a material basket. Each of the airlock unit, hot air drying unit, vacuum drying unit, and cold air cooling unit is equipped with a conveying device, which are connected sequentially end-to-end. The conveying device includes a conveying trough, rollers, wheels, and a drive motor. The conveying trough is arranged along the moving direction of the material basket. Several rollers are arranged side-by-side and rotating on the conveying trough, with both ends of the rollers extending out of the conveying trough. The rollers are connected by a synchronous belt drive. A drive motor is provided on the conveying trough, and the output shaft of the drive motor is connected to the rollers via a drive connection. The material basket is movably mounted on the conveying device, with an opening at the top. The material basket includes a bottom plate and side plates. Drainage holes are provided on the bottom plate, and side plates are arranged around the bottom plate.

[0010] Furthermore, the airlock unit includes an airlock unit frame, a filter box, an air filter element, and an air collection hood, which are used to collect dirty air from the preceding clean area and filter it through the air filter element to prevent the spread of pollutants.

[0011] Furthermore, the hot air drying unit includes a hot air drying unit frame, a hot air supply box, a return air duct, a first telescopic joint, and a return air box. The material basket is raised and sealed with the hot air supply box by a first lifting cylinder, and hot air is blown in from top to bottom for drying. Multiple hot air drying units are provided to thoroughly dry the silicon blocks in the material basket.

[0012] Furthermore, the vacuum drying unit includes a vacuum drying unit frame, an upper vacuum chamber, a lower vacuum chamber, a slide rail, a slider, a support beam, and a lifting cylinder. After the material basket is in place, the lower vacuum chamber rises and seals with the upper vacuum chamber before evacuating air. The negative pressure is used to lower the boiling point of water and thoroughly remove water from the tiny gaps on the surface of the silicon block.

[0013] Furthermore, the cold air cooling unit includes a cold air cooling unit bracket, a cold air return box, a second telescopic joint, and a cold air supply box. Cold air is introduced into the material basket from the cold air supply box at the bottom and then sent out from the cold air return box to cool the silicon block.

[0014] Furthermore, the negative pressure water-driving unit includes a negative pressure water-absorbing device and an air knife. The negative pressure water-absorbing device sucks away the water from the top and outer sidewalls of the basket, while the air knife cleans the water from the inner wall of the basket.

[0015] Advantages of this invention: 1. This invention utilizes a multi-stage synergy of an airlock unit, a hot air drying unit, a vacuum drying unit, a cold air cooling unit, and a negative pressure water driving unit to employ the most suitable drying mechanism for different forms of moisture, resulting in high drying efficiency and good drying effect. 2. The airlock unit can collect dirty air from the preceding clean area and filter it through the air filter to prevent pollutants from spreading to the subsequent drying unit and ensure the cleanliness of the drying system. 3. The vacuum drying unit uses negative pressure to lower the boiling point of water, thoroughly removing moisture from the tiny crevices on the surface of the silicon block, resulting in thorough and uniform drying; 4. It has a simple structure and a high degree of automation. The units are automatically connected by a conveyor system, resulting in high production efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0017] Figure 2 This is a structural cross-sectional view of the material basket and conveying device.

[0018] Figure 3 This is a schematic diagram of the airlock unit.

[0019] Figure 4 This is a schematic diagram of the hot air drying unit.

[0020] Figure 5 This is a schematic diagram of the vacuum drying unit.

[0021] Figure 6 This is a schematic diagram of the cold air cooling unit.

[0022] Figure 7 This is a schematic diagram of the negative pressure water drive unit.

[0023] Figure 8 This is a schematic diagram of a partial structure at the air knife.

[0024] In the diagram: 1. Airlock unit; 2. Hot air drying unit; 3. Vacuum drying unit; 4. Cold air cooling unit; 5. Negative pressure water driving unit; 6. Conveying device; 7. Material basket; 101. Airlock unit frame; 102. Filter box; 103. Air filter element; 104. Air collection hood; 201. Hot air drying unit frame; 202. Hot air supply box; 203. Return air duct; 204. First expansion joint; 205. Return air box; 206. Hot air valve; 207. First lifting cylinder; 208. Seal; 209. Guide plate; 301. Vacuum drying Unit frame; 302, upper vacuum chamber; 303, lower vacuum chamber; 304, slide rail; 305, slider; 306, support beam; 307, lifting cylinder; 401, cold air cooling unit bracket; 402, cold air return box; 403, second telescopic joint; 404, cold air supply box; 405, second lifting cylinder; 501, negative pressure water suction device; 502, air knife; 5011, water suction trough; 601, conveying trough; 602, roller; 603, roller; 604, drive motor; 605, synchronous belt; 701, base plate; 702, side plate. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] like Figure 1 As shown, a polycrystalline silicon ingot drying system includes an airlock unit 1, a hot air drying unit 2, a vacuum drying unit 3, a cold air cooling unit 4, a negative pressure water-driving unit 5, and a material basket 7. Each of the airlock unit 1, hot air drying unit 2, vacuum drying unit 3, and cold air cooling unit 4 is equipped with a conveying device 6. The conveying devices 6 on the airlock unit 1, hot air drying unit 2, vacuum drying unit 3, and cold air cooling unit 4 are connected end-to-end in sequence to transport the material basket 7 carrying the polycrystalline silicon ingot to each unit for corresponding processing.

[0027] like Figure 2As shown, the conveying device 6 includes a conveying trough 601, rollers 602, wheels 603, and a drive motor 604. The conveying trough 601 is arranged along the moving direction of the material basket. Several rollers 602 are arranged side by side and rotate on the conveying trough 601. The two ends of the rollers 602 extend out of the conveying trough 601, and the rollers 602 are connected to each other by a synchronous belt 605. The drive motor 604 is provided on the conveying trough 601, and the output shaft of the drive motor 604 is connected to the rollers 602. The material basket 7 is movably arranged on the conveying device 6. The top of the material basket 7 is open. The material basket 7 includes a bottom plate 701 and side plates 702. The bottom plate 701 has drainage holes, and the side plates 702 are arranged around the bottom plate 701.

[0028] like Figure 3 As shown, the airlock unit 1 is located at the very front of the entire drying system. When the material basket 7 is fed in, the airlock unit 1 is responsible for collecting the dirty air from the preceding clean area, filtering it through the filter element to prevent the spread of pollutants, thereby increasing the cleanliness level as the material basket 7 enters the drying system and ensuring a clean environment in subsequent drying units. Specifically, the airlock unit 1 includes an airlock unit frame 101, a filter box 102, an air filter element 103, and an air collection hood 104. A conveying device 6 is fixedly installed on the airlock unit frame 101. The filter box 102 is fixedly installed on the top of the airlock unit frame 101, above the conveying device 6. An air inlet is opened at the bottom of the filter box 102. The top of the filter box 102 is connected to the system return air fan duct. An air filter element 103 is installed at the air inlet inside the filter box 102. An air collection hood 104 is provided around the air inlet of the filter box 102, with the bottom edge of the air collection hood 104 15-50mm away from the top of the side plate 702 of the material basket 7. During operation, the system's return air fan draws air through the filter box 102. The air carrying dirt from the preceding clean area is collected by the air collection hood 104 as it passes through the material basket 7, and then discharged after being filtered by the air filter element 103. This isolates and filters the dirty air, preventing it from spreading to subsequent units and improving the cleanliness level.

[0029] like Figure 4 , Figure 7 and Figure 8As shown, the negative pressure water driving unit 5 is mainly set at the front end of the system and is used to remove the water adhering to the outside and inner wall of the material basket 7 after it has been etched and cleaned. The negative pressure water-driving unit 5 includes a negative pressure water-absorbing device 501 and an air knife 502. The negative pressure water-absorbing device 501 is installed at the position of the two conveying devices 6 adjacent to each other between the airlock unit 1 and the hot air drying unit 2. The air knife 502 is installed on the side of the hot air drying unit frame 201 of the hot air drying unit 2 where the material is discharged. The air knife 502 is made of polytetrafluoroethylene and has a strip-shaped air outlet. The air knife 502 is connected to a compressed air pipeline. High-pressure air enters the chamber of the air knife 502 and is then sent out from the strip-shaped air outlet. The high-pressure air is sprayed into the material basket 7 in a laminar flow manner through the air duct designed at the air knife outlet. The air outlet direction of the air knife 502 is opposite to the moving direction of the material basket 7 and the angle with the horizontal is 30°-60°. The high-speed air sprayed from the air outlet of the air knife 502 is injected into the interior of the material basket 7. As the material basket 7 moves, the water in the material basket 7 is blown downward from top to bottom and then discharged from the drain hole at the bottom of the material basket. The negative pressure water absorption device 501 primarily removes water from the top and outer sidewalls of the material basket 7, while the air knife 502 cleans the water from the inner wall of the material basket 7. The negative pressure water absorption device 501 has a 5-10mm wide water absorption groove 5011 on the side facing the material basket. The water absorption groove 5011 is connected to the cavity of the negative pressure water absorption device 501, which is connected to a vacuum system. Through the cooperation of the negative pressure water absorption device 501 and the air knife 502, residual water on the top, outer sidewalls, and inner wall of the material basket 7 is removed, preventing the material basket 7 from carrying moisture from the previous drying process into subsequent drying units and improving overall drying efficiency.

[0030] like Figure 4As shown, the function of the hot air drying unit 2 is to dry the silicon blocks in the material basket 7 with hot air. Two units are provided; in addition to this embodiment, the number of hot air drying units 2 can be adjusted according to the overall production cycle to thoroughly dry the silicon blocks in the material basket 7. Specifically, the hot air drying unit 2 includes a hot air drying unit frame 201, a hot air supply box 202, a return air duct 203, a first telescopic joint 204, and a return air box 205. A conveying device 6 is vertically mounted on the hot air drying unit frame 201. The hot air supply box 202 is fixedly mounted on the hot air drying unit frame 201 above the conveying device 6. A hot air valve 206 is installed on the top of the hot air supply box 202, and the hot air valve 206 is connected to a hot air fan duct. An air outlet is opened at the bottom of the hot air supply box 202, through which hot air is supplied. The bottom air outlet of the air box 202 is movably and sealed to the top of the material basket 7; a first lifting cylinder 207 is fixedly installed on the frame 201 of the hot air drying unit, and the telescopic end of the first lifting cylinder 207 is connected to the bottom of the conveying device 6; a return air trough 203 is provided at the bottom of the conveying device 6, and a first telescopic joint 204 is connected to the bottom of the return air trough 203. The lower end of the first telescopic joint 204 is connected to the return air box 205, the return air box 205 is fixedly connected to the frame 201 of the hot air drying unit, and the return air box 205 is connected to the hot air return air duct. Figure 2 As shown, during operation, after the conveying device 6 delivers the basket 7 to its position, the first lifting cylinder 207 actuates, raising the conveying device 6 and the basket 7 it supports, sealing the top of the basket 7 with the bottom of the hot air supply box 202 above it. Then, the hot air valve 206 is opened, and hot air generated by the hot air blower is blown from above into the basket 7 through the hot air supply box 202. The hot air passes through the silicon blocks inside the basket 7, carrying away moisture from the surface and crevices of the silicon blocks, and then returns to the hot air return duct through the return air trough 203 at the bottom of the basket 7 and the first expansion joint 204. By setting multiple hot air drying units 2, the silicon blocks in the basket 7 are continuously and repeatedly dried with hot air, ensuring that the silicon blocks in the basket 7 are thoroughly dried. Furthermore, a sealing element 208 is provided around the edge of the bottom air outlet of the hot air supply box 202 and the top of the side plate 702 of the material basket 7 to ensure a sealed connection between the hot air supply box 202 and the material basket 7 and to prevent hot air leakage; several guide plates 209 are provided on both sides of the bottom air outlet of the hot air supply box 202 to guide the hot air into the material basket 7 evenly.

[0031] like Figure 5As shown, the function of the vacuum drying unit 3 is to dry the silicon block, which still has residual heat after being dried by hot air, under vacuum negative pressure. The negative pressure is used to lower the boiling point of water and thoroughly remove water from the tiny crevices on the surface of the silicon block. Specifically, the vacuum drying unit 3 includes a vacuum drying unit frame 301, an upper vacuum chamber 302, a lower vacuum chamber 303, slide rails 304, sliders 305, a support beam 306, and a lifting cylinder 307. The upper vacuum chamber 302 is fixedly installed on the top of the vacuum drying unit frame 301, and the lower vacuum chamber 303 is installed below the upper vacuum chamber 302, moving up and down. The upper vacuum chamber 302 and the lower vacuum chamber 303 are movably and sealed together. Several slide rails 304 are vertically installed on the vacuum drying unit frame 301, and sliders 305 are installed on the slide rails 304. A support beam 306 is installed between two sliders 305, and the support beam 306 is fixedly connected to the lower vacuum chamber 303. A conveying device 6 is installed in the lower vacuum chamber 303. The lifting cylinder 307 is hinged to the lower vacuum chamber 303 and the vacuum drying unit frame 301. The telescopic end of the lifting cylinder 307 is connected to the bottom of the lower vacuum chamber 303. The upper vacuum chamber 302 is connected to the vacuum system, and the upper vacuum chamber 302 and the lower vacuum chamber 303 are sealed together by a sealing gasket. During operation, the material basket 7 is fed into the lower vacuum chamber 303 by the conveying device 6. The lifting cylinder 307 pushes the lower vacuum chamber 303 to rise along the slide rail 304. The slider 305 and the support beam 306 play a guiding and bearing role, so that the lower vacuum chamber 303 and the upper vacuum chamber 302 are sealed together to form a closed vacuum chamber. Then the vacuum system evacuates the air, so that a negative pressure is formed in the chamber. Utilizing the principle that the boiling point of water decreases under negative pressure, the moisture in the tiny gaps on the surface of the silicon block is rapidly vaporized and evaporated at a lower temperature and is drawn away by the vacuum system. After the evacuation is completed, the pressure is maintained for a period of time to allow the moisture to evaporate fully, and then the pressure is released to complete the vacuum negative pressure drying, and the moisture in the tiny gaps on the surface of the silicon block is completely removed.

[0032] like Figure 6As shown, the function of the cold air cooling unit 4 is to cool down the silicon blocks after they have been dried by hot air and vacuum in the previous steps, so that the temperature of the silicon blocks when they are discharged is reduced to a level suitable for packaging. Specifically, the cold air cooling unit 4 includes a cold air cooling unit bracket 401, a cold air return box 402, a second telescopic joint 403, and a cold air supply box 404. A conveying device 6 is mounted on the cold air cooling unit bracket 401. The cold air return box 402 is mounted on the cold air cooling unit bracket 401 and above the conveying device 6. The top of the cold air return box 402 is connected to the system cooling return air, and the bottom of the cold air return box 402 has an air intake. The air intake at the bottom of the cold air return box 402 is movably and sealingly connected to the top of the material basket 7. The second telescopic joint 403 is located at the bottom of the conveying device 6. The lower end of the second telescopic joint 403 is connected to the cold air supply box 404, which is connected to the system cooling air duct. A second lifting cylinder 405 is fixedly installed on the cold air cooling unit bracket 401, and the telescopic end of the second lifting cylinder 405 is connected to the conveying device 6. During operation, after the material basket 7 is conveyed to the cold air cooling unit 4, the second lifting cylinder 405 is activated to lift the conveying device 6 and the material basket 7, which are then sealed together with the cold air return box 402. Cold air is introduced into the material basket 7 from the bottom cold air supply box 404 through the second telescopic joint 403. The cold air passes through the silicon block and carries away the heat, and is then sent out from the cold air return box 402 to cool the silicon block in the material basket 7.

[0033] When the drying system of the present invention is working, the basket 7 carrying polycrystalline silicon blocks passes sequentially through the airlock unit 1, the negative pressure water-driving unit 5, the hot air drying unit 2, the vacuum drying unit 3, and the cold air cooling unit 4: First, the airlock unit 1 collects and filters the dirty air in the preceding clean area to prevent the diffusion of pollutants and improve the cleanliness level; then, the negative pressure water suction device 501 and the air knife 502 of the negative pressure water-driving unit 5 remove residual water from the top, outer sidewall, and inner wall of the basket 7, respectively, wherein the blowing pressure of the air knife 502 is 0.2-0.6 MPa and the blowing time is 30-90 s. Then, two hot air drying units 2 heat the silicon blocks in the basket 7 to about 120°C and hold for 80 seconds to remove most of the moisture from the surface and crevices of the silicon blocks. Next, the vacuum drying unit 3 uses negative pressure drying to thoroughly remove water from the tiny crevices on the surface of the silicon blocks, evacuating to below 50Pa and assisting in heating to 40-60°C and holding the pressure for 5-15 minutes. Finally, the cold air cooling unit 4 introduces clean cold air at 20-30°C into the basket 7 to cool the silicon blocks, reducing the outlet temperature to below 35°C for easier subsequent packaging. All units are connected end-to-end by the conveyor device 6, working in coordination to achieve efficient, thorough, and clean drying of the polycrystalline silicon blocks.

[0034] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "front," "rear," "top," "bottom," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

Claims

1. A polycrystalline silicon bulk material drying system, characterized in that, The unit includes an airlock unit (1), a hot air drying unit (2), a vacuum drying unit (3), a cold air cooling unit (4), a negative pressure water-driving unit (5), and a material basket (7). Each of the airlock unit (1), the hot air drying unit (2), the vacuum drying unit (3), and the cold air cooling unit (4) is equipped with a conveying device (6). The conveying devices (6) on the airlock unit (1), the hot air drying unit (2), the vacuum drying unit (3), and the cold air cooling unit (4) are connected end to end in sequence. The conveying device (6) includes a conveying trough (601), a roller (602), a roller (603), and a drive motor (604). The conveying trough (601) moves along the material basket. The direction of movement is set, and several rollers (602) are arranged side by side rotating on the conveying trough (601). The two ends of the rollers (602) pass through the conveying trough (601). The rollers (602) are connected to each other by a synchronous belt (605). A drive motor (604) is provided on the conveying trough (601). The output shaft of the drive motor (604) is connected to the rollers (602) for transmission. The material basket (7) is moved and set on the conveying device (6). The top of the material basket (7) is set with an opening. The material basket (7) includes a bottom plate (701) and a side plate (702). The bottom plate (701) is provided with a drain hole. The side plate (702) is provided around the bottom plate (701).

2. The polycrystalline silicon bulk material drying system according to claim 1, characterized in that, The airlock unit (1) includes an airlock unit frame (101), a filter box (102), an air filter element (103), and an air collection hood (104). A conveying device (6) is fixedly installed on the airlock unit frame (101). A filter box (102) is fixedly installed on the top of the airlock unit frame (101) and above the conveying device (6). An air inlet is opened at the bottom of the filter box (102). The top of the filter box (102) is connected to the system return air fan duct. An air filter element (103) is installed at the air inlet inside the filter box (102). An air collection hood (104) is provided below the air inlet of the filter box (102) along the four sides. The bottom edge of the air collection hood (104) is 15-50mm away from the top of the side plate (702) of the material basket (7).

3. The polycrystalline silicon bulk material drying system according to claim 1, characterized in that, The hot air drying unit (2) includes a hot air drying unit frame (201), a hot air supply box (202), a return air duct (203), a first telescopic section (204), and a return air box (205). A conveying device (6) is installed on the hot air drying unit frame (201). A hot air supply box (202) is fixedly installed on the hot air drying unit frame (201) above the conveying device (6). A hot air valve (206) is installed on the top of the hot air supply box (202). The hot air valve (206) is connected to the hot air fan pipe. An air outlet is opened at the bottom of the hot air supply box (202) for hot air supply. The bottom air outlet of the box (202) is connected to the top of the material basket (7) in a movable and sealed manner. A first lifting cylinder (207) is fixedly installed on the frame (201) of the hot air drying unit. The telescopic end of the first lifting cylinder (207) is connected to the bottom of the conveying device (6). A return air trough (203) is provided at the bottom of the conveying device (6). A first telescopic joint (204) is connected to the bottom of the return air trough (203). The lower end of the first telescopic joint (204) is connected to the return air box (205). The return air box (205) is fixedly connected to the frame (201) of the hot air drying unit. The return air box (205) is connected to the hot air return air pipe.

4. The polycrystalline silicon bulk material drying system according to claim 3, characterized in that, A sealing element (208) is provided between the edge of the bottom air outlet of the hot air supply box (202) and the top of the side plate (702) of the material basket (7), and several guide plates (209) are provided on both sides of the bottom air outlet of the hot air supply box (202).

5. The polycrystalline silicon bulk material drying system according to claim 4, characterized in that, The hot air drying unit (2) is provided with multiple units.

6. The polycrystalline silicon bulk material drying system according to claim 1, characterized in that, The vacuum drying unit (3) includes a vacuum drying unit frame (301), an upper vacuum chamber (302), a lower vacuum chamber (303), a slide rail (304), a slider (305), a support beam (306), and a lifting cylinder (307). The upper vacuum chamber (302) is fixedly provided on the top of the vacuum drying unit frame (301), and the lower vacuum chamber (303) is provided vertically below the upper vacuum chamber (302). The upper vacuum chamber (302) and the lower vacuum chamber (303) are movably and sealedly connected. The frame (301) is vertically provided with several slide rails (304), and a slider (305) is provided on the slide rails (304). A support beam (306) is provided between two sliders (305). The support beam (306) is fixedly connected to the lower vacuum chamber (303). A conveying device (6) is provided in the lower vacuum chamber (303). A lifting cylinder (307) is hinged to the lower vacuum chamber (303) and the frame (301) of the vacuum drying unit. The extension end of the lifting cylinder (307) is connected to the bottom of the lower vacuum chamber (303).

7. A polycrystalline silicon bulk material drying system according to claim 6, characterized in that, The upper vacuum chamber (302) is connected to the vacuum system, and the upper vacuum chamber (302) and the lower vacuum chamber (303) are sealed together by a sealing gasket.

8. The polycrystalline silicon bulk material drying system according to claim 1, characterized in that, The cooling unit (4) includes a cooling unit bracket (401), a cooling return air box (402), a second telescopic section (403), and a cooling air supply box (404). A conveying device (6) is mounted on the cooling unit bracket (401). The cooling return air box (402) is mounted on the cooling unit bracket (401) above the conveying device (6). The top of the cooling return air box (402) is connected to the system cooling return air, and the bottom of the cooling return air box (402) has an opening. The air intake at the bottom of the cold air return box (402) is connected to the top of the material basket (7) in a movable and sealed manner. A second telescopic joint (403) is provided at the bottom of the conveying device (6). The lower end of the second telescopic joint (403) is connected to the cold air supply box (404), which is connected to the system cooling air duct. A second lifting cylinder (405) is fixedly installed on the cold air cooling unit bracket (401), and the telescopic end of the second lifting cylinder (405) is connected to the conveying device (6).

9. A polycrystalline silicon bulk material drying system according to any one of claims 1 to 8, characterized in that, The negative pressure water-driving unit (5) includes a negative pressure water-absorbing device (501) and an air knife (502). Between the airlock unit (1) and the hot air drying unit (2), the two conveying devices (6) are adjacent to each other. An air knife (502) is installed on the side of the hot air drying unit frame (201) of the hot air drying unit (2) where the material is discharged. The air discharge direction of the air knife (502) is opposite to the moving direction of the material basket (7) and the angle with the horizontal is 30°-60°. The negative pressure water-absorbing device (501) has a water-absorbing groove (5011) with a width of 5-10mm on the side facing the material basket. The water-absorbing groove (5011) is connected to the cavity of the negative pressure water-absorbing device (501). The cavity of the negative pressure water-absorbing device (501) is connected to the vacuum system.

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