Device and method for recycling silicon sludge with high additional value

Abstract

The invention discloses a high-added-value silicon sludge recovery device and a method thereof. The high-added-value silicon sludge recovery device comprises a furnace body, the pretreated silicon sludge feeding system comprises a material collecting bin and a discharging pipe which is communicated with the furnace body and the material collecting bin; the smelting storage system comprises a straight-through type ceramic crucible; the electromagnetic heating system comprises a graphite heater and an induction coil sleeved outside the graphite heater; the silicon monoxide collecting system comprises a collecting barrel; the high-purity silicon drawing and collecting system comprises a graphite plug positioned at the bottom of the straight-through type ceramic crucible and a driving mechanism for driving the graphite plug to move up and down in the straight-through type ceramic crucible; and the vacuum system comprises a mechanical pump communicated with the hearth of the furnace body. According to the method, the pretreated silicon sludge is directly subjected to electromagnetic induction heating in the vacuum environment, silicon in the silicon sludge reacts with silicon oxide on the surface layer to prepare silicon monoxide, meanwhile, high-purity silicon is prepared through directional solidification of redundant silicon in the silicon sludge, and then high-added-value recovery of the silicon sludge is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of pyrometallurgy, and in particular to a device and method for recovering silicon mud with high added value. Background Art

[0002] Currently, in the solar cell silicon wafer cutting process, silicon wafers are cut from single-crystal silicon rods or multi-crystal silicon ingots using multi-wire sawing. Based on current industry trends, diamond wire sawing technology is the mainstream method for multi-wire sawing of silicon wafers. During the diamond wire sawing process for both single-crystal silicon rods and multi-crystal silicon ingots, silicon powder and other impurities are deposited into the cutting slurry, forming silicon sludge. Clearly, the large amount of unused high-purity silicon in this silicon sludge represents a valuable recyclable resource. However, if this sludge is not properly recycled, not only will it be a waste of resources, but the large amount of silicon sludge generated by the photovoltaic industry (over 500,000 tons per year) will accumulate and cause serious environmental pollution.

[0003] Currently, the traditional recycling method involves directly producing industrial silicon from silicon sludge through medium-frequency induction melting. Because the silicon powder in silicon sludge is extremely fine and has a thin film of silicon oxide (SiO2) on its surface, this undoubtedly increases the difficulty of smelting and recovery. This also results in the low purity of the recovered industrial silicon. Furthermore, the silicon oxide layer enters the slag and is removed, resulting in resource waste. Improving the recovery value of silicon sludge has become an urgent issue in silicon sludge recycling.

[0004] Silicon dioxide (SiO) has the ability to reversibly insert / extract lithium, and its theoretical specific capacity is as high as 2400mAh.g -1 , and its volume expansion rate, rate characteristics, and cycle performance are all superior to those of silicon. Therefore, as an ideal negative electrode material for lithium-ion batteries, it has attracted widespread attention in recent years and has developed rapidly. Currently, the preparation principle of silicon oxide is Si + SiO2 → SiO↑. This involves mixing fine silicon powder with silicon dioxide powder in a 1:1 molar ratio, then heating them to 1300-1400°C in a corundum tube under vacuum conditions for a solid-solid reaction, followed by desublimation and collection. Given the fact that the silicon powder in silica sludge is essentially a thin layer of silicon oxide coated on the surface of silicon, and in conjunction with the aforementioned principle of silicon oxide preparation (Si + SiO2 → SiO↑), the present invention proposes to smelt the pretreated silica sludge, which has undergone cleaning (to remove organic matter from the raw silica sludge), granulation, and drying, under vacuum conditions. This process utilizes the rapid reaction between silicon and the surface silicon oxide (due to the extremely small silicon powder particle size in the silica sludge, the contact and reaction area between the silicon and the surface silicon oxide is large) to produce silicon oxide, which is then collected through desublimation. Simultaneously, because the molar ratio of silicon to silicon oxide in the silica sludge is greater than 1:1, the silicon water obtained by melting the remaining silicon after the reaction is directionally solidified, thereby producing high-purity silicon. It should be noted that the cleaning, granulation, and drying processes of silica sludge have been extensively reported and are not part of the present invention. The raw material used in this invention is the pretreated silica sludge that has undergone these treatments.

[0005] Compared with the traditional method of preparing industrial silicon by recovering silicon mud through induction melting, the method proposed in the present invention can not only improve the quality of the obtained silicon (i.e., obtain high-purity silicon), but also avoid waste of silicon oxide. By utilizing the reaction between silicon and surface silicon oxide, high-value silicon iodide that can be used as negative electrode material for lithium-ion batteries is obtained. Summary of the Invention

[0006] The purpose of the present invention is to overcome the technical deficiencies of traditional induction melting to recover silicon mud, propose a high-value-added silicon mud recovery device and method, and solve the problems of low purity of industrial silicon prepared and low silicon mud utilization rate in the prior art.

[0007] In order to achieve the above technical objectives, the present invention proposes a high value-added silicon sludge recovery device, comprising: furnace body; The pre-treated silicon mud feeding system includes a collection bin for storing the pre-treated silicon mud raw materials and a feed pipe connecting the furnace body and the collection bin; A smelting storage system includes a straight-through ceramic crucible located inside the furnace body and used to convert silicon mud into silicon oxide; The electromagnetic heating system includes a graphite heater disposed outside the straight-through ceramic crucible to heat the silicon mud inside the crucible and generate silicon dioxide gas, and an induction coil sheathed outside the graphite heater; A silicon oxide collection system, comprising a collection barrel connected to the straight-through ceramic crucible and used for condensing and collecting silicon oxide gas; A high-purity silicon extraction and collection system includes a graphite plug located at the bottom of a straight-through ceramic crucible and a drive mechanism for driving the graphite plug to move up and down inside the straight-through ceramic crucible; The vacuum system includes a mechanical pump connected to the furnace body and furnace.

[0008] Preferably, the smelting storage system further comprises a thermal insulation ceramic and a slotted water-cooled crystallizer sequentially located below the straight-through ceramic crucible; The slotted water-cooled crystallizer is placed at the bottom of the straight-through ceramic crucible to prevent the silicon water from leaking during the directional solidification and collection process. The heat-insulating ceramic is placed between the straight-through ceramic crucible and the slotted water-cooled crystallizer to prevent the ceramic crucible from cracking due to the quenching of the slotted water-cooled crystallizer.

[0009] Preferably, the pre-treated silicon mud feeding system further comprises a discharge valve and a vacuum valve installed on the discharge pipe; The top of the material collecting bin is provided with an openable hatch cover, which is equipped with a vacuum pipe to vacuum the material collecting bin; The top of the feed pipe is connected to the collecting bin, and the bottom is connected to the furnace, serving as a silicon mud feeding channel; The discharge valve is installed on the upper half of the discharge pipe, and the feeding and stopping of silicon mud raw materials are realized by opening and closing the discharge pipe channel; The vacuum valve is installed at the lower half of the discharge pipe, and realizes the connection and isolation between the collection bin and the furnace by opening and closing, thereby realizing the vacuum control of the collection bin and the furnace separately.

[0010] Preferably, the electromagnetic heating system further comprises a medium frequency induction heating power supply and a thermal insulation layer; The induction coil is connected to the output electrode of the medium frequency induction heating power supply to generate an alternating electromagnetic field for heating the material; The graphite heater adopts a slotted structure and is located outside the straight-through ceramic crucible and the slotted water-cooled crystallizer, and is used for preheating and melting silicon mud; The heat-insulating layer is located outside the graphite heater and is used to keep the graphite heater warm and reduce energy consumption.

[0011] Preferably, the silicon oxide collection system further comprises a collection pipe and an air suction device; The two ends of the collection pipe are respectively connected to the straight-through ceramic crucible and the collection bucket, serving as a silicon oxide collection channel; The collection barrel is cooled by circulating water and is used for condensing silicon dioxide gas and collecting powder; The suction device is connected to the collection barrel and is used to maintain the negative pressure of the collection barrel and absorb the silicon dioxide gas volatilized by the reaction in the straight-through ceramic crucible into the collection barrel. A filter is installed at the inlet of the suction pipe of the suction device.

[0012] Preferably, the driving mechanism comprises a draw rod and a servo motor; The pulling rod is installed on the furnace body, and the two ends of the pulling rod are respectively connected to the graphite plug and the servo motor. Driven by the servo motor, the pulling rod moves downward continuously, thereby directionally solidifying the silicon water in the crucible in the form of continuous ingot casting and realizing the collection of high-purity silicon.

[0013] The present invention also proposes a method for recovering silicon sludge based on the above-mentioned high value-added device, comprising the following steps: S1: A certain amount of granular pretreated silicon mud is loaded into the collecting bin of the pretreated silicon mud feeding system, and a portion of granular pretreated silicon mud is pre-placed in the straight-through ceramic crucible of the smelting storage system; S2: Close the furnace door and the cover of the aggregate bin, and start the mechanical pump to extract the vacuum; S3: Turn on the electromagnetic heating system to heat the pre-placed silicon mud in the straight-through ceramic crucible, and at the same time turn on the suction device of the silicon oxide collection system to absorb the silicon oxide gas generated by the reaction in the straight-through ceramic crucible and realize its desublimation collection in the collection bucket; S4: After all the silicon mud in the straight-through ceramic crucible is melted into silicon water and the reaction is complete, the pre-treated silicon mud feeding system is started to add silicon mud to the straight-through ceramic crucible to a first preset height; S5: When the liquid level of the molten silicon water in the straight-through ceramic crucible rises to a certain height, the servo motor of the high-purity silicon pulling and collecting system is turned on to drive the pulling rod downward, thereby performing directional solidification of the silicon water and collecting the high-purity silicon. At the same time, when the liquid level of the silicon water in the straight-through ceramic crucible drops to a certain position, the downward movement of the pulling rod is stopped; S6: Continue to start the pre-treated silicon mud feeding system to add silicon mud to the straight-through ceramic crucible to a second preset height, repeat S5, and repeat this cycle to achieve continuous high-value-added recovery of pre-treated silicon mud to prepare silicon oxide and high-purity silicon.

[0014] Preferably, in step S1, the granular pretreated silicon mud is cleaned to remove organic matter, granulated and dried, and the diameter of the granulated granular silicon mud is 5~15 mm; the top surface of the granular pretreated silicon mud loaded in the collecting bin is 100~200 mm away from the lower edge of the upper vacuum pipe; the top surface of the granular pretreated silicon mud pre-placed in the straight-through ceramic crucible is 100~200 mm away from the lower edge of the collection pipe of the silicon dioxide collection system; after the silicon mud is replenished in step S4, the top surface of the silicon mud in the straight-through ceramic crucible is 150~200 mm away from the lower edge of the collection pipe of the silicon dioxide collection system.

[0015] Preferably, in step S5, the height to which the silicon water in the straight-through ceramic crucible rises is controlled to be 100-150 mm above the bottom surface of the straight-through crucible; after the pulling is started, the lowest height to which the silicon water level in the straight-through ceramic crucible drops is controlled to be 10-30 mm above the upper end surface of the slit-type water-cooled crystallizer; and the downward movement speed of the pulling rod is controlled to be 0.5-1.5 mm / min.

[0016] Preferably, the first preset height and the second preset height are equal.

[0017] The high value-added silicon sludge recovery device proposed in the present invention has the following beneficial effects: 1. By setting up a straight-through ceramic crucible to maximize the contact reaction area between silicon in ultrafine silicon powder and surface silicon oxide in silicon mud, a rapid reaction between silicon and surface silicon oxide is achieved under vacuum and high temperature conditions in the furnace body to generate silicon dioxide gas, and the silicon dioxide gas generated by the reaction is condensed and collected by a silicon dioxide collection system, thereby obtaining a silicon dioxide product that can be used as a negative electrode material for lithium-ion batteries. This is conducive to reducing the waste of silicon oxide resources in the silicon mud recovery process, improving the silicon mud recovery rate and recovery value, and solving the problems of low purity of industrial silicon prepared in the existing technology and low silicon mud utilization rate; 2. Use directional solidification of silicon water to remove impurities, improve the purity of silicon materials obtained from recycled silicon mud, and further increase the value of silicon mud recovery; 3. The device has a compact structure, is safe and reliable, and occupies a small area. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic structural diagram of a device for recovering silicon sludge with high added value according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a graphite heater in the device for recovering silicon mud with high added value of the present invention; Figure 3 This is a schematic diagram of the structure of a slotted water-cooled crystallizer in the device for recovering high-value-added silicon mud of the present invention.

[0019] Explanation of the accompanying symbols: 11-straight-through ceramic crucible; 12-slit water-cooled crystallizer; 13-insulating ceramic; 14-pre-treated silicon mud pre-placed in the ceramic crucible; 21-aggregate bin; 22-hatch cover; 23-aggregate bin vacuum pipe; 24-discharge pipe; 25-unloading valve; 26-vacuum valve; 27-pre-treated silicon mud raw material in the aggregate bin; 31-medium frequency induction heating power supply; 32-electrode; 33-graphite heater; 34-induction coil; 35-insulation layer; 41-collecting pipe; 42-collecting barrel; 43-suction device; 44-front end filter of the suction pipe; 51-graphite plug; 52-pull rod; 53-servo motor; 61-furnace body; 62-furnace chamber; 63-observation window; 64-furnace chamber vacuum pipe; 65-mechanical pump.

[0020] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] In order to overcome the technical deficiencies of traditional induction melting to recover silicon mud, the present invention provides a high-value-added device and method for recovering silicon mud, so as to solve the problems existing in the prior art such as low purity of industrial silicon, waste of surface silicon oxide resources, low silicon mud utilization rate, and low production efficiency.

[0023] The present invention provides a device for recovering silicon mud with high added value.

[0024] In this preferred embodiment, refer to Figure 1 , a high value-added silicon mud recovery device includes: furnace body; The pre-treated silicon mud feeding system includes a collection bin 21 for storing the pre-treated silicon mud raw material and a feed pipe 24 connecting the furnace body and the collection bin; The smelting material storage system includes a straight-through ceramic crucible 11 located inside the furnace body and used to convert silicon mud into silicon oxide; An electromagnetic heating system includes a graphite heater 33 disposed outside the through-type ceramic crucible to heat it and an induction coil 34 sheathed outside the graphite heater; A silicon oxide collection system, comprising a collection barrel 42 connected to the straight-through ceramic crucible and used for condensing and collecting silicon oxide gas; A high-purity silicon extraction and collection system includes a graphite plug 51 located at the bottom of a straight-through ceramic crucible and a driving mechanism for driving the graphite plug 51 to move up and down inside the straight-through ceramic crucible; The vacuum system includes a mechanical pump 65 connected to the furnace body and the furnace chamber.

[0025] In order to achieve the purpose of containing the materials, in this embodiment, the smelting storage system includes a straight-through ceramic crucible 11, a slotted water-cooled crystallizer 12, and a heat-insulating ceramic 13. The straight-through ceramic crucible 11 is placed on the upper part of the slotted water-cooled crystallizer 12 to contain the materials being heated (such as pre-pretreated silicon mud 14); the slotted water-cooled crystallizer 12 is placed on the lower part of the straight-through ceramic crucible 11 to prevent the silicon water from leaking during the directional solidification and collection process. Figure 2 The slit-type water-cooled crystallizer 12 adopts a structure with an open slit at the top and a closed loop at the bottom, which helps to form the axial temperature gradient required for the directional solidification of silicon water while being partially magnetically permeable; in addition, the slit-type water-cooled crystallizer 12 is made of red copper, and the slit is filled with insulating refractory materials such as mica to prevent leakage of silicon water; the insulating ceramic 13 is placed between the straight-through ceramic crucible 11 and the slit-type water-cooled crystallizer 12 to prevent the ceramic crucible 11 from cracking due to the rapid cooling of the slit-type water-cooled crystallizer 12.

[0026] In order to realize the storage and feeding of the pre-treated silicon mud raw material, in this embodiment, the pre-treated silicon mud feeding system includes a collecting bin 21 , a discharge pipe 24 , a discharge valve 25 and a vacuum valve 26 . The collecting bin 21 is used to store pre-treated silicon mud raw materials 27. Its top hatch 22 can be opened and is vacuum-sealed. There is a vacuum pipe 23 for vacuuming on the upper part, and the bottom is connected to the discharge pipe 24; the other end of the vacuum pipe 23 is connected to the mechanical pump 65 for extracting the vacuum from the collecting bin 21; the top of the discharge pipe 24 is connected to the collecting bin 21, and the lower part is connected to the furnace 62, which is used as a feeding channel for silicon mud 27; the unloading valve 25 is installed in the upper half of the discharge pipe 24, and the feeding and stopping of silicon mud raw materials 27 are realized by opening and closing the discharge pipe channel; the vacuum valve 26 is installed in the lower half of the discharge pipe 24, and the communication and isolation between the collecting bin 21 and the furnace 62 are realized by opening and closing, thereby realizing that the collecting bin 21 and the furnace 62 can be vacuum controlled separately.

[0027] In order to heat the material, in this embodiment, the electromagnetic heating system includes a medium frequency induction heating power supply 31, an induction coil 34, a graphite heater 33 and a thermal insulation layer 35; the induction coil 34 is located outside the graphite heater 33 and is connected to the output electrode 32 of the medium frequency induction heating power supply 31 to generate an alternating electromagnetic field for heating the material; Figure 3 The graphite heater 33 adopts a slotted structure and is located outside the straight-through ceramic crucible 11 and the slotted water-cooled crystallizer 12. It is used to preheat and melt the silicon mud 14 inside the straight-through ceramic crucible 11. At the same time, the slotted structure can facilitate the electromagnetic field to penetrate into the straight-through ceramic crucible 11, thereby improving the material heating efficiency; the insulation layer 35 is located between the graphite heater 33 and the induction coil 34, which is used for heat preservation and reducing energy consumption.

[0028] To condense and collect the silicon oxide produced by the reaction, in this embodiment, the silicon oxide collection system includes a collection pipe 41, a collection barrel 42, and an air suction device 43. The ends of the collection pipe 41 are connected to the straight-through ceramic crucible 11 and the collection barrel 42, respectively, serving as a silicon oxide collection channel. The outer wall of the collection barrel 42 is cooled with circulating water, so that the silicon oxide gas condenses when it cools, allowing it to be collected. The air suction device 43 can be located at the end of the collection barrel 42 to maintain negative pressure in the collection barrel 42 and to draw silicon oxide gas volatilized from the reaction in the straight-through ceramic crucible 11 into the collection barrel 42. In addition, to prevent silicon oxide gas from entering the air suction device 43, a filter 44 is installed at the inlet of the air suction pipe of the air suction device 43.

[0029] To achieve directional solidification of silicon water and collection of high-purity silicon, in this embodiment, the high-purity silicon extraction and collection system includes a graphite plug 51 and a drive mechanism; the drive mechanism includes a pull rod and a servo motor. The graphite plug 51 is installed at the top of the pull rod 52 to block the material in the straight-through ceramic crucible 11 to prevent it from leaking. At the same time, it can also partially preheat the silicon mud inside the straight-through ceramic crucible 11 during the initial heating period. The two ends of the pull rod 52 are respectively connected to the graphite plug 51 and the servo motor 53. Driven by the servo motor, it moves downward continuously, and then directionally solidifies the silicon water in the crucible and realizes the collection of high-purity silicon in the form of continuous ingot casting. At the same time, circulating cooling water is used for cooling in the pull rod 52 to establish the axial temperature gradient required for directional solidification of silicon water.

[0030] To achieve the vacuum environment required for high-value silicon sludge recovery, in this embodiment, the vacuum system 6 includes a vacuum pipe 64 and a mechanical pump 65. In addition to housing the components of the high-value silicon sludge recovery apparatus of the present invention, the furnace body 61 primarily forms a furnace chamber 62. Furnace chamber 62 houses the entire smelting system and serves as a reaction chamber. It is also equipped with an observation window 63 and a front-hinged door. A vacuum pipe 64 connects furnace chamber 62 to a mechanical pump 65, which is used to extract the vacuum from furnace chamber 62 and the collection bin 21.

[0031] The high value-added silicon sludge recovery device proposed in the present invention has the following beneficial effects: 1. By providing a straight-through ceramic crucible 11, a large contact reaction area is created between the silicon in the ultrafine silicon powder of the silicon mud and the surface silicon oxide. Under vacuum and high temperature conditions in the furnace body, a rapid reaction between the silicon and the surface silicon oxide is achieved to generate silicon dioxide gas. The silicon dioxide gas generated by the reaction is condensed and collected by a silicon dioxide collection system, thereby obtaining a silicon dioxide product that can be used as a negative electrode material for lithium-ion batteries. This is beneficial to reducing the waste of silicon dioxide resources in the silicon mud recovery process, improving the silicon mud recovery rate and recovery value, and solving the problems of low purity of industrial silicon prepared in the prior art and low silicon mud utilization rate. 2. Use directional solidification of silicon water to remove impurities, improve the purity of silicon materials obtained from recycled silicon mud, and further increase the value of silicon mud recovery; 3. The device has a compact structure, is safe and reliable, and occupies a small area.

[0032] The present invention further provides a method for recovering silicon sludge with high added value.

[0033] In this preferred embodiment, a method for recovering silicon sludge based on the above-mentioned high value-added device comprises the following steps: S1: The smelting storage system 1, the pre-treated silicon mud feeding system 2, the electromagnetic heating system 3, the silicon oxide collection system 4, the high-purity silicon extraction and collection system 5 and the vacuum system 6 are connected according to Figure 1 After the assembly relationship shown is assembled, a certain amount of granular pretreated silicon mud 27 is loaded into the collecting bin 21 of the pretreated silicon mud feeding system 2, and a portion of granular pretreated silicon mud 14 is pre-placed in the straight-through ceramic crucible 11 of the smelting storage system 1; Preferably, in this embodiment, the diameter of the granular silicon mud that has been cleaned, granulated and dried is 5~15mm; the top surface of the granular pretreated silicon mud 27 loaded into the collecting bin 21 is 100~200mm away from the lower edge of the upper vacuum pipe 23; the top surface of the granular pretreated silicon mud 14 pre-placed in the straight-through ceramic crucible 11 is 100~200mm away from the lower edge of the collection pipe 41 of the silicon dioxide collection system 4.

[0034] S2: Close the furnace door and the cover 22 of the collecting bin, and start the mechanical pump 65 to draw a vacuum; S3: Turn on the electromagnetic heating system 3 to heat the pre-placed silicon mud 14 in the straight-through ceramic crucible 11, and at the same time turn on the suction device 43 of the silicon oxide collection system 4 to absorb the silicon oxide gas generated by the reaction in the straight-through ceramic crucible 11 and realize its desublimation collection in the collection bucket 42; S4: After the silicon mud 14 in the straight-through ceramic crucible 11 is completely melted into silicon water and the reaction is complete (no more silicon dioxide gas is produced), the pre-treated silicon mud feeding system 2 is started to add silicon mud to a certain height in the straight-through ceramic crucible 11; Preferably, after the silicon mud is replenished, the top surface of the silicon mud in the straight-through ceramic crucible 11 is 150-200 mm away from the lower edge of the collecting pipe 41 of the silicon monoxide collecting system 4 .

[0035] S5: When the liquid level of the molten silicon water in the through-type ceramic crucible 11 rises to a certain height, the servo motor 53 of the high-purity silicon extraction and collection system 5 is turned on to drive the extraction rod 52 to move downward, thereby performing directional solidification of the silicon water and collecting the high-purity silicon. At the same time, when the liquid level of the silicon water in the through-type ceramic crucible 11 drops to a certain position, the downward movement of the extraction rod 52 is stopped; Preferably, the upper height to which the silicon water in the straight-through ceramic crucible 11 rises is controlled to be 100-150 mm above the bottom surface of the straight-through ceramic crucible 11; after the pulling is started, the lowest height to which the silicon water level in the straight-through ceramic crucible 11 drops is controlled to be 10-30 mm above the upper end surface of the slit-type water-cooled crystallizer 12; and the downward movement speed of the pulling rod 52 is controlled to be 0.5-1.5 mm / min.

[0036] S6: Continue to start the pre-treated silicon mud feeding system 2 to add silicon mud to a certain height in the straight-through ceramic crucible 11, repeat S5, and repeat this cycle to achieve continuous high-value-added recovery of pre-treated silicon mud to prepare silicon oxide and high-purity silicon.

[0037] The reciprocating process in step S6 includes intermittent feeding and withdrawing processes of "feed-stop-feed" and "stop-withdraw-stop," which are performed alternately. The silicon oxide collection system is always in operation during the entire process. The first preset height and the second preset height are equal.

[0038] The present invention proposes a high-value-added method for recovering silicon sludge, which has the following beneficial effects: (1) Utilizing the large contact reaction area between the silicon in the ultrafine silicon powder of silicon mud and the surface silicon oxide, a rapid reaction between the silicon and the surface silicon oxide is achieved under vacuum and high temperature conditions to generate silicon dioxide gas, which is then condensed and collected by a silicon dioxide collection system to obtain silicon dioxide products that can be used as negative electrode materials for lithium-ion batteries. Obviously, this is conducive to reducing the waste of silicon dioxide resources in the silicon mud recovery process and improving the recovery rate and recovery value of silicon mud; (2) Using directional solidification of silicon water to remove impurities, improve the purity of silicon material obtained from recycled silicon mud, and further increase the value of silicon mud recovery; (3) The entire recycling process can achieve semi-continuous recycling of pretreated silicon sludge through intermittent feeding and intermittent pulling of "feeding-stopping-feeding" and "stopping-pulling-stopping", which is undoubtedly conducive to improving the production efficiency of silicon sludge recycling; (4) This method is highly operational and economical.

[0039] It should be noted that the orientations or positional relationships indicated by terms such as "upper" and "lower" in the descriptions of this application are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this application and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be interpreted broadly. For example, they can be fixed, removable, or integral; mechanical or electrical; directly or indirectly through an intermediary; or internally connected between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances. Relational terms such as "first" and "second" are used solely to distinguish one entity or operation from another and do not necessarily require or imply any actual relationship or order between these entities or operations. The terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0040] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A device for recovering silicon mud with high added value, characterized in that: include: furnace body; The pre-treated silicon mud feeding system includes a collection bin for storing the pre-treated silicon mud raw materials and a feed pipe connecting the furnace body and the collection bin; A smelting storage system includes a straight-through ceramic crucible located inside the furnace body and used to convert silicon mud into silicon oxide; The electromagnetic heating system includes a graphite heater disposed outside the straight-through ceramic crucible to heat the silicon mud inside the crucible and generate silicon dioxide gas, and an induction coil sheathed outside the graphite heater; A silicon oxide collection system, comprising a collection barrel connected to the straight-through ceramic crucible and used for condensing and collecting silicon oxide gas; A high-purity silicon extraction and collection system includes a graphite plug located at the bottom of a straight-through ceramic crucible and a drive mechanism for driving the graphite plug to move up and down inside the straight-through ceramic crucible; The vacuum system includes a mechanical pump connected to the furnace body and furnace.

2. The device for recovering high value-added silicon mud according to claim 1, characterized in that: The smelting material storage system also includes a heat-insulating ceramic and a slotted water-cooled crystallizer sequentially located below the straight-through ceramic crucible; The slotted water-cooled crystallizer is placed at the bottom of the straight-through ceramic crucible to prevent the silicon water from leaking during the directional solidification and collection process. The heat-insulating ceramic is placed between the straight-through ceramic crucible and the slotted water-cooled crystallizer to prevent the ceramic crucible from cracking due to the quenching of the slotted water-cooled crystallizer.

3. The high value-added silicon mud recovery device according to claim 1, characterized in that: The pre-treated silicon mud feeding system also includes a discharge valve and a vacuum valve installed on the discharge pipe; The top of the material collecting bin is provided with an openable hatch cover, which is equipped with a vacuum pipe to vacuum the material collecting bin; The top of the feed pipe is connected to the collecting bin, and the bottom is connected to the furnace, serving as a silicon mud feeding channel; The discharge valve is installed on the upper half of the discharge pipe, and the feeding and stopping of silicon mud raw materials are realized by opening and closing the discharge pipe channel; The vacuum valve is installed in the lower half of the discharge pipe, and realizes the connection and isolation between the collection bin and the furnace by opening and closing, thereby realizing the vacuum control of the collection bin and the furnace separately.

4. The device for recovering high value-added silicon mud according to claim 1, characterized in that: The electromagnetic heating system also includes a medium frequency induction heating power supply and a thermal insulation layer; The induction coil is connected to the output electrode of the medium frequency induction heating power supply to generate an alternating electromagnetic field for heating the material; The graphite heater adopts a slotted structure and is located outside the straight-through ceramic crucible and the slotted water-cooled crystallizer, and is used for preheating and melting silicon mud; The heat-insulating layer is located outside the graphite heater and is used to keep the graphite heater warm and reduce energy consumption.

5. The high value-added silicon mud recovery device according to claim 1, characterized in that: The silicon oxide collection system also includes a collection pipe and an air suction device; The two ends of the collection pipe are respectively connected to the straight-through ceramic crucible and the collection bucket, serving as a silicon oxide collection channel; The collection barrel is cooled by circulating water and is used for condensing silicon dioxide gas and collecting powder; The suction device is connected to the collection barrel and is used to maintain the negative pressure of the collection barrel and absorb the silicon dioxide gas volatilized by the reaction in the straight-through ceramic crucible into the collection barrel. A filter is installed at the inlet of the suction pipe of the suction device.

6. The high value-added silicon mud recovery device according to claim 1, characterized in that: The driving mechanism includes a draw rod and a servo motor; The pulling rod is installed on the furnace body, and the two ends of the pulling rod are respectively connected to the graphite plug and the servo motor. Driven by the servo motor, the pulling rod moves downward continuously, thereby directionally solidifying the silicon water in the crucible in the form of continuous ingot casting and realizing the collection of high-purity silicon.

7. A method for recovering silicon sludge based on the device for recovering silicon sludge with high added value according to any one of claims 1 to 6, characterized in that: The steps include: S1: A certain amount of granular pretreated silicon mud is loaded into the collecting bin of the pretreated silicon mud feeding system, and a portion of granular pretreated silicon mud is pre-placed in the straight-through ceramic crucible of the smelting storage system; S2: Close the furnace door and the cover of the aggregate bin, and start the mechanical pump to extract the vacuum; S3: Turn on the electromagnetic heating system to heat the pre-placed silicon mud in the straight-through ceramic crucible, and at the same time turn on the suction device of the silicon oxide collection system to absorb the silicon oxide gas generated by the reaction in the straight-through ceramic crucible and realize its desublimation collection in the collection bucket; S4: After all the silicon mud in the straight-through ceramic crucible is melted into silicon water and the reaction is complete, the pre-treated silicon mud feeding system is started to add silicon mud to the straight-through ceramic crucible to a first preset height; S5: When the liquid level of the molten silicon water in the straight-through ceramic crucible rises to a certain height, the servo motor of the high-purity silicon pulling and collecting system is turned on to drive the pulling rod downward, thereby performing directional solidification of the silicon water and collecting the high-purity silicon. At the same time, when the liquid level of the silicon water in the straight-through ceramic crucible drops to a certain position, the downward movement of the pulling rod is stopped; S6: Continue to start the pre-treated silicon mud feeding system to add silicon mud to the straight-through ceramic crucible to a second preset height, repeat S5, and repeat this cycle to achieve continuous high-value-added recovery of pre-treated silicon mud to prepare silicon oxide and high-purity silicon.

8. The method for recovering high value-added silicon mud according to claim 7, characterized in that: In step S1, the granular pretreated silicon mud is cleaned to remove organic matter, granulated and dried, and the diameter of the granulated granular silicon mud is 5~15 mm; the top surface of the granular pretreated silicon mud loaded in the collecting bin is 100~200 mm away from the lower edge of the upper vacuum pipe; the top surface of the granular pretreated silicon mud pre-placed in the straight-through ceramic crucible is 100~200 mm away from the lower edge of the collection pipe of the silicon oxide collection system; in step S4, after the silicon mud is replenished, the top surface of the silicon mud in the straight-through ceramic crucible is 150~200 mm away from the lower edge of the collection pipe of the silicon oxide collection system.

9. The method for recovering high value-added silicon mud according to claim 7, characterized in that: In step S5, the height to which the silicon water in the straight-through ceramic crucible rises is controlled to be 100-150 mm above the bottom surface of the straight-through crucible; after the pulling is started, the lowest height to which the silicon water level in the straight-through ceramic crucible drops is controlled to be 10-30 mm above the upper end surface of the slit-type water-cooled crystallizer; and the downward movement speed of the pulling rod is controlled to be 0.5-1.5 mm / min.

10. The method for recovering high value-added silicon mud according to claim 7, characterized in that: The first preset height and the second preset height are equal.

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