A device and method for industrial silicon pouring directional solidification

Abstract

A device and method for pouring directional solidification of industrial silicon. The device is a rectangular body as a whole, including an insulating upper cover, an insulating plug, a furnace body, a thermocouple temperature measuring point, and a blower. A graphite funnel, a graphite pad, a cover body device, a funnel moving fixture, a special fixture for silicon ingots to be discharged from the furnace, and a vacuum particle suction machine are used in conjunction. The insulating upper cover is composed of a steel shell and a multilayer ceramic fiberboard. The ceramic fiberboard is placed in the steel shell and is fixedly connected to the shell by fastening bolts passing through the ceramic fiberboard. A hole is reserved in the center of the insulating upper cover for placing a graphite funnel or an insulating plug. Four lifting rings are symmetrically installed on the reinforcing ribs of the top plate of the insulating upper cover for opening and closing with the furnace body. The present invention fully considers the site conditions in front of the industrial silicon ore hot furnace, multiple units are recycled, non-vacuum production, low production energy consumption, simple operation, safety and no environmental protection problems, low overall cost of the device, small maintenance, low consumption of auxiliary materials, and is suitable for large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial silicon purification, and in particular relates to an energy-saving device and method for removing metal impurities by pouring directional solidification of silicon liquid out of an industrial silicon furnace. Background Art

[0002] As a basic material, industrial silicon has been widely used in various industrial fields such as chemical industry, metallurgy, electronic information, machinery manufacturing, aerospace, energy development, etc., becoming a veritable "industrial MSG" and playing a special role in the global economic and social development. However, during the smelting and preparation process of industrial silicon in the carbon thermal reduction reaction of the submerged arc furnace, impurities in the raw silica and carbonaceous reducing agent will partially enter the silicon liquid and affect the product quality of industrial silicon, which has always been a drawback restricting the development of industrial silicon towards high quality. With the development of science and technology, the application field of industrial silicon is constantly expanding, and the improvement of the economic value of subsequent silicon derivatives (organic silicon, silicon-based alloys, polysilicon, etc.) has also put higher and higher requirements on the quality of its raw material industrial silicon. It has become more urgent to develop short-process and low-cost industrial silicon purification technology.

[0003] In order to further improve the quality of industrial silicon, domestic and foreign companies have also adopted different technical measures, such as: selecting the best silica raw materials, modifying carbonaceous reducing agents, refining with oxygen outside the furnace, directional solidification, hydrometallurgy, etc., and have achieved good results in removing various impurities. Among them, directional solidification is a very important technical process. It controls the temperature thermal field to make the silicon ingot grow unidirectionally, and uses the impurity segregation effect to separate the metal elements Fe, Al, Ca, Cr, Ni, Cu, Zn with small segregation coefficients (the segregation coefficients of most metal impurities in silicon are less than 10 -3 ) and other substances are enriched in the final solidified layer to achieve the purpose of removing metal impurities.

[0004] There are also many devices and methods designed according to the process principles of directional solidification technology, such as the Brimann method, heat exchange method, electromagnetic continuous casting method, ingot casting method, etc. However, these methods are all derived from the device and method of obtaining solar polysilicon cell sliced ​​silicon ingots from polycrystalline silicon ingots. The device equipment includes crucibles, thermal insulation thermal fields, heating systems, lifting mechanisms, vacuum systems, temperature measurement systems, computer electronic control systems, etc. The device as a whole is relatively complex and cannot be moved during operation. It cannot be directly used for the device and method of directional solidification of industrial silicon out of the furnace to remove metal impurities. According to the literature, there are few directional solidification technologies by casting method (that is, molten silicon liquid is poured into a set container, and heat preservation or heating is carried out for single-direction crystal growth). There are no fixed product equipment on the market, and various manufacturers are actively exploring and testing. Chinese utility model patent CN200720006080.7 "Simple device for directional solidification of metal silicon" uses several silicon carbon rod heating tubes to continuously heat the top cover of the refractory inner tank and the surrounding insulation heating layer, which has the problems of large energy waste and high production energy consumption; Chinese invention patent CN201610426307.7 "An industrial silicon electric furnace directional solidification reactor and pouring method", although the device has good insulation measures for the upper part and the surrounding of the mold container, the device has no preheating function and does not take into account the effect of the initial room temperature heat capacity of the device itself on the rapid solidification of the poured molten silicon liquid, and cannot form a single direction crystal growth condition for directional solidification, and the solid-liquid interface cannot be kept horizontal and upward, which will greatly affect the purification effect and purification yield; Chinese invention patent CN201110152836.X "An energy-saving device for directional solidification and impurity removal of metallurgical silicon". Although the device is preheated before use, it uses a separate set of resistance heaters. After the preheating is completed, the heater needs to be lifted out of the device in a hot state, which is not conducive to the efficient use of thermal energy. It is also easy to cause the heater to burn and age. In addition, the device uses an open upper cover during the pouring process, which is also not conducive to the efficient use of thermal energy.

[0005] Based on this, the currently known casting method directional solidification purification technology and equipment for industrial silicon are difficult to balance energy consumption cost and purification efficiency, which restricts its large-scale application in actual production fields. Summary of the invention

[0006] The purpose of the present invention is to address the shortcomings of the above-mentioned existing industrial silicon casting method directional solidification technology, and to provide an energy-saving device and method for removing metal impurities by directional solidification of industrial silicon liquid out of the furnace. The device has the characteristics of large single furnace production capacity, simple and easy process, good impurity removal effect, low operating energy consumption, and low auxiliary material consumption, and is suitable for large-scale production.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] A device for pouring directional solidification of industrial silicon, which adopts the principle of directional solidification combining pouring and heat exchange. In order to meet the conditions of intermittent discharge of silicon liquid from industrial silicon ore-fired furnace (one bag of silicon liquid is discharged every 2 to 4 hours) and the space restrictions in front of the ore-fired furnace, the device needs to adopt a track circulation movement method, and multiple devices are configured for circulation according to the actual working conditions and production capacity. The device is a rectangular body as a whole, including an insulation cover, an insulation plug, a furnace body, a thermocouple temperature measuring point, and a blower. It is used in conjunction with graphite funnels, graphite pads, cover equipment, funnel moving fixtures, silicon ingot discharge fixtures, and vacuum particle suction machines and other tooling and facilities.

[0009] The insulation cover is mainly composed of a steel shell and a multilayer ceramic fiberboard. The ceramic fiberboard is placed in the steel shell and is fixedly connected to the shell by fastening bolts that penetrate the ceramic fiberboard at intervals. A hole is reserved in the center of the insulation cover for placing a graphite funnel or insulation plug. Four lifting rings are symmetrically installed on the reinforcement ribs of the top plate of the insulation cover steel shell for opening and closing with the furnace body.

[0010] Furthermore, the multi-layer ceramic fiber board has a single layer thickness of 50 mm and a number of layers of ≥ 5.

[0011] The insulation plug is similar in structure to the insulation upper cover and is composed of a steel plug body and multiple layers of ceramic fiberboard.

[0012] The furnace body is composed of assembled graphite container, alumina ceramic hollow balls, 2 layers of standard T3 high-alumina refractory bricks (power auxiliary preheating resistance wire is embedded in the inner layer of refractory bricks), a single layer of 50mm thick ceramic fiberboard, and side vertical plates of the furnace body steel shell. The alumina ceramic hollow balls are used to keep warm and fill the insulation layer between the assembled graphite container and the refractory bricks, and play a role in supporting the assembled graphite container. The power auxiliary preheating resistance wire embedded in the refractory brick plays a role in heating and preheating the device before pouring silicon liquid, and the power interface is connected with an industrial quick-connect connector.

[0013] Furthermore, the volume of the assembled graphite container should meet the requirement of being greater than or equal to the molten volume of 2000 kg of industrial silicon + the volume increased by about 10% after solidification, and the inner diameter height of the assembled graphite container volume is about 600-700 mm.

[0014] Furthermore, before the silicon liquid is poured into the assembled graphite container, a layer of water-based silicon nitride or silicon dioxide release agent is pre-coated on the inner surface.

[0015] Furthermore, the diameter of the alumina ceramic hollow sphere is 5 to 8 mm, and the thickness of the thermal insulation layer is greater than 200 mm.

[0016] Furthermore, the power-assisted preheating resistance wire is made of high-temperature-resistant and oxidation-resistant iron-chromium-aluminum alloy, and is evenly arranged around the assembled graphite container in 3 to 4 upper and lower rows, and the maximum heating temperature can reach 1200°C.

[0017] The furnace body is vertically composed of a layer of alumina ceramic hollow balls, a graphite baffle ring, an assembled graphite container, a graphite powder bonding layer, an air-cooling heat dissipation pipeline, a layer of standard T3 high-aluminum refractory bricks, a furnace body steel shell bottom plate, and four track wheels from top to bottom. The air-cooling heat dissipation pipeline is horizontally pre-buried in the graphite powder bonding layer, and its air inlet is connected to the blower for uniform heat dissipation at the bottom of the assembled graphite container.

[0018] Furthermore, the graphite powder bonding layer is a mixture of graphite powder and organic adhesives such as starch and dextrin, stirred into a muddy state, leveled after pre-buried air-cooled heat dissipation pipes, and air-dried or baked to form a good heat transfer lining layer.

[0019] There are two thermocouple temperature measuring points, which are respectively set in the refractory bricks near the power auxiliary preheating resistance wire on the side facade of the furnace body ① and the lower center of the assembled graphite container bottom plate, ② for measuring the temperature inside the furnace body to provide information feedback on the crystallization directional solidification growth state of the silicon liquid in the assembled graphite container.

[0020] The present invention also discloses a process method for an industrial silicon casting type directional solidification device, which is characterized by comprising the following steps:

[0021] Step 1, assembly: first assemble the assembled graphite container into a topless box shape, fill the alumina ceramic hollow balls around the graphite container with the help of a cover device, and after it is firmly supported, use a vacuum particle suction machine to clean the inside of the assembled graphite container, and spray or brush a layer of water-based silicon nitride or silicon dioxide release agent; then assemble the assembled graphite container top plate and graphite baffle ring, fill a layer of alumina ceramic hollow ball insulation layer on the outside of the graphite baffle ring, cover the device insulation cover, place the middle insulation plug, and move it to the preheating station.

[0022] Step 2, preheating: Connect the power cord with the quick-plug industrial connector, turn on the power switch, and preheat the device with electrical heating. The preheating temperature is controlled within the range of 1100-1200℃, and is regulated by the thermocouple temperature measuring point ①. After preheating, cut off the power supply and move to the pouring station.

[0023] Step 3, pouring: open the lifting and removing insulation plug, place the graphite funnel, and quantitatively pour the molten industrial silicon liquid into the assembled graphite container of the device through the graphite funnel. The temperature of the molten industrial silicon liquid must be greater than 1600℃; after the silicon liquid is poured, quickly clamp and remove the graphite funnel, and seal the center hole of the assembled graphite container top plate with a graphite pad, pour in an appropriate amount of alumina ceramic hollow balls flush with the upper edge of the graphite retaining ring, and cover the insulation plug. The device is pushed to the directional solidification station.

[0024] Step 4, directional solidification: connect the blower and the thermocouple temperature measuring point power plug, turn on the blower switch, ensure that the inlet and outlet pipes are unobstructed, the bottom of the assembled graphite container dissipates heat evenly, and the silicon liquid undergoes directional solidification and crystal growth. The total solidification time is controlled within 60 to 72 hours. After the solidification and cooling is completed, the device is moved to the furnace discharge station.

[0025] Step 5, taking out of the furnace: When the thermocouple temperature measurement points ① and ② are both below 300℃, the insulation cover can be opened to accelerate the cooling of the device to room temperature. The alumina ceramic hollow balls are sucked and collected into a fixed container by a vacuum particle suction machine, and the graphite retaining ring and graphite pad are removed, and the top plate of the assembled graphite container is lifted off, and the side plate of the assembled graphite container is pried apart from the silicon ingot, and the silicon ingot is lifted out of the furnace with a special fixture for silicon ingots.

[0026] The device is reassembled according to step 1 and recycled. The silicon ingot is polished and cleaned around the sides and bottom, and the last solidified impurity-rich layer on the top is cut off by a diamond band saw or wire saw. The removal amount is 10-15% of the total height of the silicon ingot, and the side and bottom surfaces with a thickness of 10mm are cut off to obtain high-quality 4N grade industrial silicon.

[0027] The positive effects of the present invention are as follows:

[0028] 1. A pouring directional solidification device for silicon liquid out of the furnace for industrial silicon, which adopts the directional solidification principle combining pouring and heat exchange method, and uses alumina ceramic hollow balls, ceramic fiberboard, high-alumina refractory bricks and other insulation materials to form top and surrounding insulation, with only the bottom dissipating heat in a single direction, to achieve the directional solidification and crystallization conditions of silicon liquid, and through crystal growth, cutting and separation, most of the metal impurities with low segregation coefficient in industrial silicon can be efficiently removed.

[0029] 2. The industrial silicon out of the furnace silicon liquid pouring directional solidification device of the present invention reasonably and efficiently utilizes the heat energy of the industrial silicon out of the furnace silicon liquid, assists in the preheating energy of a small amount of power supply, and stably improves the quality of industrial silicon products. It has significant advantages in comprehensive and efficient utilization of heat energy, quality improvement and consumption reduction, and has obvious economic benefits and market competitiveness.

[0030] 3. The single furnace capacity of the device of the present invention is large. A single furnace can carry out directional solidification purification treatment on at least 2000 kg of industrial silicon. The larger the processing capacity of a single furnace is designed to be, the smaller the unit energy consumption of auxiliary heating is.

[0031] 4. The device of the present invention fully considers the site conditions in front of the industrial silicon ore-fired furnace, multiple units are used in a circular manner, non-vacuum production, low production energy consumption, simple operation, safety and no environmental problems, low overall cost of the device, small maintenance volume, and low consumption of auxiliary materials. It is suitable for large-scale production, and is also suitable for the upgrade, promotion and application of existing industrial silicon production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 is a schematic structural diagram of an industrial silicon pouring directional solidification device according to the present invention.

[0033] FIG. 2 is a schematic diagram of the device of the present invention in a state of directional solidification and crystal growth of silicon liquid.

[0034] Figure 3 It is a schematic diagram of the three-dimensional cross-section structure of the assembled graphite container in the device of the present invention.

[0035] Figure 4 It is a schematic diagram of the structure of the air-cooling heat dissipation pipeline in the device of the present invention.

[0036] like Figure 1 As shown: 1-lifting ring 2-fastening bolt 3-upper cover steel shell 4-multilayer ceramic fiberboard 5-galvanic temperature measuring point ① 6-furnace steel shell 7-single-layer ceramic fiberboard 8-power auxiliary preheating resistance wire 9-standard T3 high-alumina refractory brick 10-alumina ceramic hollow ball 11-assembled graphite container 12-track wheel 13-graphite powder bonding layer 14-air cooling heat dissipation duct 15-galvanic temperature measuring point ② 16-blower 17-graphite baffle ring 18-graphite funnel 19-graphite pad 20-insulation plug

[0037] Note: The thermal insulation cover is composed of parts numbered 1 to 4; the furnace body is composed of parts numbered 6 to 14. DETAILED DESCRIPTION

[0038] The following examples are used to illustrate and verify the effects of the present invention, but the technical scope of the present invention is not limited by the examples.

[0039] The specific implementation methods of the present invention are as follows:

[0040] like Figure 1 , Figure 2 As shown, the device of the present invention is a rectangular body, which can be moved as a whole on the rails through track wheels. The device includes a heat-insulating upper cover, a heat-insulating plug (20), a furnace body, thermocouple temperature measuring points ①② (5, 15), a blower (16), and is used in conjunction with a graphite funnel (18), a graphite pad (19), a cover body device, a funnel moving fixture, a special fixture for silicon ingot unloading, and a vacuum particle suction machine.

[0041] The thermal insulation cover is mainly composed of a steel shell (3) and a multi-layer ceramic fiber board (4). The multi-layer ceramic fiber board (4) is connected and fixed by fastening bolts (2), and the ceramic fiber board (4) is placed in the steel shell (3). A hole is reserved in the center of the thermal insulation cover for placing a graphite funnel (18) or a thermal insulation plug (20). Four lifting rings (1) are symmetrically installed on the top plate reinforcement rib of the steel shell (3).

[0042] The thermal insulation plug (20) is similar in structure to the thermal insulation upper cover and is composed of a steel plug body and multiple layers of ceramic fiberboard.

[0043] The furnace body is composed of an assembled graphite container (11), alumina ceramic hollow balls (10), two layers of standard T3 high-alumina refractory bricks (9) [the inner layer of refractory bricks is embedded with a power auxiliary preheating resistance wire (8)], a single layer of ceramic fiberboard (7), a furnace body steel shell (6) and side panels. The furnace body is composed of a layer of alumina ceramic hollow balls (10), a graphite retaining ring (17), an assembled graphite container (11), a graphite powder bonding layer (13), an air-cooled heat dissipation pipeline (14), a layer of standard T3 high-alumina refractory bricks (9), a furnace body steel shell (6), a bottom plate, and four track wheels (12) from top to bottom.

[0044] The volume of the assembled graphite container (11) is specifically 1200×1200×650 mm, which meets the volume requirement of directional solidification of 2000 kg of molten industrial silicon. Before the silicon liquid is poured, the inner surface of the assembled graphite container (11) is pre-coated with a layer of water-based silicon nitride or silicon dioxide release agent.

[0045] The diameter of the alumina ceramic hollow sphere (10) is 5 to 8 mm, and the thickness of the thermal insulation layer is 210 mm.

[0046] The power auxiliary preheating resistance wire (8) is made of high temperature resistant and oxidation resistant iron-chromium-aluminum alloy, and is evenly arranged around the assembled graphite container (11) in four upper and lower rows. The maximum temperature can reach 1200° C. The power connection interface uses an industrial quick-connect connector.

[0047] There are two thermocouple temperature measuring points, which are respectively arranged in the refractory brick near the power auxiliary preheating resistance wire on the side facade of the furnace body ① (5) and the lower center of the bottom plate of the assembled graphite container ② (15), for measuring the temperature inside the furnace body so as to provide information feedback on the crystallization directional solidification growth state of the silicon liquid in the assembled graphite container.

[0048] When using the device of the present invention, in order to achieve the purpose and effect of directional solidification impurity removal, the process method of the present invention has the following specific operating steps:

[0049] Step 1, assembly: first assemble the assembled graphite container (11) into a topless box shape, use a cover device (thin-walled pointed top cover that can cover the container) to fill the alumina ceramic hollow balls (10) around the graphite container, and after the support is stable, use a vacuum particle suction machine to clean the inside of the assembled graphite container (11), and spray or brush a layer of water-based silicon nitride or silicon dioxide release agent; then assemble the top plate and graphite retaining ring (17) of the assembled graphite container (11), fill a layer of alumina ceramic hollow balls (10) insulation layer on the outside of the graphite retaining ring (17), cover the device insulation cover, place the middle insulation plug (20), and move it to the preheating station.

[0050] Step 2, preheating: Connect the power cord with the quick-plug industrial connector, turn on the power switch, and preheat the entire device with electrical heating. The preheating temperature is controlled within the range of 1100-1200℃ and regulated by the thermocouple temperature measuring point ① (5). After preheating is completed, cut off the power supply and move to the pouring station.

[0051] Step 3, pouring: open the lifting and removing insulation plug (20), place the graphite funnel (18), and quantitatively pour the molten industrial silicon liquid into the assembled graphite container (20) of the device through the graphite funnel (18). The temperature of the molten industrial silicon liquid must be greater than 1600°C. After the silicon liquid is poured, quickly clamp and remove the graphite funnel (18), and seal the center hole of the top plate of the assembled graphite container (11) with a graphite pad (19), pour in an appropriate amount of alumina ceramic hollow balls (10) flush with the upper edge of the graphite retaining ring (17), and cover the insulation plug (20). The device is moved to the directional solidification station.

[0052] Step 4, directional solidification: connect the power plugs of the blower (16) and the thermocouple temperature measuring points (5, 15), turn on the blower (16), ensure that the air inlet and outlet pipes are unobstructed, assemble the graphite container (11) to evenly dissipate heat at the bottom, and the silicon liquid is directional solidified and crystallized. The total solidification time is controlled within 60 to 72 hours. After the solidification and cooling is completed, the device is moved to the furnace discharge station.

[0053] Step 5, taking out of the furnace: When the thermocouple temperature measurement points ① (5) and ② (15) are both below 300°C, the heat preservation cover can be opened to accelerate the cooling of the device to room temperature. The alumina ceramic hollow balls (10) are sucked and collected into a fixed container by a vacuum particle suction machine, and the graphite retaining ring (17) and the graphite pad (19) are removed and lifted off the top plate of the assembled graphite container (11), and the side plate of the assembled graphite container 11 is pried apart from the silicon ingot, and the silicon ingot is lifted out of the furnace using a special clamp for the silicon ingot.

[0054] The device is reassembled according to step 1 and recycled. The silicon ingot is polished and cleaned around the sides and bottom, and the last solidified impurity-enriched layer on the top is cut off by a diamond band saw or wire saw. The removal amount is 10-15% of the total height of the silicon ingot, and the 10mm thick side and bottom are cut off to obtain purified high-quality industrial silicon. After testing and analysis, it reaches 4N grade purity, that is, the sum of metal impurities such as Fe, Al, Ca, Cr, Ni, Cu, and Zn is less than 100ppmw.

Claims

1. A device for industrial silicon casting directional solidification, characterized in that: The device is a rectangular body, including an insulation cover, an insulation plug, a furnace body, a thermocouple temperature measuring point, and a blower. It is used in conjunction with a graphite funnel, a graphite pad, a cover device, a funnel moving fixture, a special fixture for silicon ingots to be discharged from the furnace, and a vacuum particle suction machine. The thermal insulation cover is mainly composed of a steel shell and multiple layers of ceramic fiberboard. The ceramic fiberboard is placed in the steel shell and is fixedly connected to the steel shell by fastening bolts passing through the ceramic fiberboard at intervals. A hole is reserved in the center of the thermal insulation cover for placing a graphite funnel or a thermal insulation plug. Four lifting rings are symmetrically installed on the reinforcing ribs of the top plate of the thermal insulation cover steel shell for opening and closing with the furnace body. The thermal insulation plug has a similar structure to the thermal insulation cover and is composed of a steel plug body and multiple layers of ceramic fiberboard. The furnace body is horizontally composed of assembled graphite containers, alumina ceramic hollow balls, and 2 layers of standard T3 high-aluminum refractory bricks from the inside to the outside, and the inner layer of refractory bricks is embedded with a power supply auxiliary preheating resistance wire, a single layer of 50mm thick ceramic fiberboard, and a side vertical plate of the furnace body steel shell; the power supply auxiliary preheating resistance wire embedded in the refractory brick plays a role in heating and preheating the device before pouring silicon liquid, and an industrial quick-plug connector is used to connect the power interface.

2. The industrial silicon pouring directional solidification device according to claim 1, characterized in that: The multi-layer ceramic fiberboard has a single-layer thickness of 50 mm and a number of layers of ≥ 5.

3. The industrial silicon pouring directional solidification device according to claim 1, characterized in that: The volume of the assembled graphite container should meet the requirement of being greater than or equal to the molten volume of 2000 kg of industrial silicon + the volume increased by about 10% after solidification. The inner diameter height of the assembled graphite container is between 600 and 700 mm.

4. The industrial silicon casting directional solidification device according to claim 1 or 3, characterized in that: Before the silicon liquid is poured into the assembled graphite container, a layer of water-based silicon nitride or silicon dioxide release agent is pre-coated on the inner surface.

5. The industrial silicon pouring directional solidification device according to claim 1, characterized in that: The diameter of the alumina ceramic hollow ball is 5-8 mm, and the thickness of the heat preservation filling insulation layer is greater than 200 mm.

6. The industrial silicon pouring directional solidification device according to claim 1, characterized in that: The power-assisted preheating resistance wire is made of high-temperature-resistant and oxidation-resistant iron-chromium-aluminum alloy, and is evenly arranged around the assembled graphite container in 3 to 4 upper and lower rows, and the maximum heating temperature can reach 1200°C.

7. The industrial silicon pouring directional solidification device according to claim 1, characterized in that: The furnace body is vertically composed of a layer of alumina ceramic hollow balls, a graphite baffle ring, an assembled graphite container, a graphite powder bonding layer, an air-cooled heat dissipation pipeline, a layer of standard T3 high-aluminum refractory bricks, a furnace body steel shell bottom plate, and 4 track wheels from top to bottom; the air-cooled heat dissipation pipeline is horizontally pre-buried in the graphite powder bonding layer, and its air inlet is connected to the blower for uniform heat dissipation at the bottom of the assembled graphite container.

8. A method for an industrial silicon casting directional solidification device, characterized in that: The steps include: Step 1, assembly: first assemble the assembled graphite container into a topless box shape, fill the alumina ceramic hollow balls around the graphite container with the help of a cover device, and after the support is stable, use a vacuum particle suction machine to clean the inside of the assembled graphite container, and spray or brush a layer of water-based silicon nitride or silicon dioxide release agent; then assemble the top plate and graphite baffle ring of the assembled graphite container, fill a layer of alumina ceramic hollow ball insulation layer on the outside of the graphite baffle ring, cover the device insulation cover, place the middle insulation plug, and move it to the preheating station; Step 2, preheating: Connect the power cord with the quick-insert industrial connector, turn on the power switch, and preheat the device as a whole with electric heating. The preheating temperature is controlled within the range of 1100-1200°C, and is regulated by the thermocouple temperature measuring point ①. After the preheating is completed, cut off the power supply and move to the pouring station; Step 3, pouring: open the lifting and removing insulation plug, place the graphite funnel, and quantitatively pour the molten industrial silicon liquid into the assembled graphite container of the device through the graphite funnel. The temperature of the molten industrial silicon liquid must be greater than 1600°C; after the silicon liquid is poured, quickly clamp and remove the graphite funnel, and seal the center hole of the top plate of the assembled graphite container with a graphite pad, pour in an appropriate amount of alumina ceramic hollow balls flush with the upper edge of the graphite retaining ring, cover the insulation plug again, and move the device to the directional solidification station; Step 4, directional solidification: connect the blower and the thermocouple temperature measuring point power plug, turn on the blower switch, ensure that the inlet and outlet air pipes are unobstructed, and the bottom of the assembled graphite container dissipates heat evenly. The silicon liquid performs directional solidification and crystal growth. The total solidification time is controlled within 60 to 72 hours. After the solidification and cooling is completed, the device is moved to the furnace discharge station; Step 5, taking out of the furnace: when the temperature measuring points ① and ② of the thermocouple are both below 300°C, the insulation cover can be opened, the acceleration device is cooled to room temperature, the alumina ceramic hollow balls are sucked and collected into a fixed container by a vacuum particle suction machine, the graphite retaining ring and the graphite pad are removed, the top plate of the assembled graphite container is lifted off, the side plate of the assembled graphite container is pried apart from the silicon ingot, and the silicon ingot is lifted out of the furnace with a special fixture for silicon ingots; The device is reassembled according to step 1 and recycled. The silicon ingot is polished and cleaned on all sides and the bottom. The last solidified impurity-enriched layer on the top is cut off with a diamond band saw or wire saw. The removal amount is 10-15% of the total height of the silicon ingot, and the side and bottom with a thickness of 10mm are cut off to obtain high-quality 4N grade industrial silicon.

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