Method for producing silicon powder using waste silicon slurry, silicon powder for producing secondary battery negative electrode material, and system for producing silicon powder

Abstract

The present invention relates to a method for preparing a silicon powder using a waste silicon slurry, a silicon powder for preparing a secondary battery negative electrode material, and a system for preparing the silicon powder. The present invention relates to a method for preparing silicon powder, and more specifically, to a method for preparing silicon powder with excellent quality, which can be used as a negative electrode material for an energy storage device, by using waste silicon slurry generated in the solar energy industry and a semiconductor wafer production process as a useful resource and by recycling and reusing the waste silicon slurry to prepare silicon powder, and a silicon powder and a preparation system which can be used for the same.

Description

Technical Field

[0001] The present invention relates to a method for preparing silicon powder using waste silicon sludge, silicon powder for preparing negative electrode materials for secondary batteries, and a system for preparing silicon powder. More specifically, it relates to a method for preparing silicon powder by recycling and reusing waste silicon sludge generated in the solar energy industry and semiconductor wafer production processes as a useful resource so as to effectively prepare high-quality silicon powder that can be used as negative electrode materials for energy storage devices, and silicon powder and a system for preparing the same. Background Art

[0002] Generally, waste silicon slurry generated in the solar industry and semiconductor wafer production process is simply discarded because it cannot find a suitable use. The main known recycling schemes so far include the following methods, that is, chemically treating the metal components contained in the waste silicon slurry to perform drying and prepare low-quality silicon blocks for recycling, or simply drying and using it as a refractory material raw material.

[0003] However, since the waste silicon slurry can be refined to improve its purity, attempts and methods have been proposed to utilize it in the energy storage industry, which is another industry, rather than reusing it in the solar energy industry through screening.

[0004] Korean Patent No. 10-2261429 proposes a method for preparing silicon oxide or silicon / carbon composite by removing cutting oil and performing acid treatment to filter. However, there are limitations that cannot be industrialized due to the complexity of the process and there are limitations that mass production is difficult due to the large amount of waste liquid generated as a by-product of the process.

[0005] The following method is disclosed in Korean Patent Gazette No. 10-2021-0058397, namely, after dispersing silicon slurry in ethanol and performing gravity separation, the active substance for negative electrode material for energy storage is prepared by spray drying by mixing and stirring with a carbon precursor. Korean Authorized Patent No. 10-1650184 discloses a method for recovering silicon particles after preparing silicon agglomerates by ultrasonic treatment, but there is a problem of increased cost of separate processes such as heat treatment.

[0006] On the other hand, since diamond cutters, lubricating oils, and refrigerants are used for waste silicon slurry, a technology for removing organic components remaining after cutting is required. In addition, since the water content of the discharged waste silicon slurry is unstable and the content range is very complex, it is necessary to effectively remove the water.

[0007] Therefore, unlike existing production equipment and process technologies, it is necessary to develop a technology that overcomes the above limitations to enable the reuse of waste silicon slurry to efficiently mass-produce silicon powder that can be used as a negative electrode material for energy storage devices.

[0008] Furthermore, the silicon powder recovered and refined from the waste silicon slurry may shrink, aggregate and coagulate, and may deteriorate in physical properties during long-term storage due to trace amounts of metals and moisture in the silicon powder. Therefore, when the silicon powder recovered and refined from the waste silicon slurry is used in the preparation of secondary battery negative electrode materials, the dispersibility of the silicon powder may decrease, and irreversibility may increase due to problems such as volume expansion.

[0009] Therefore, a new solution is needed that can solve the problem of long-term storage and the problem of degradation of physical properties of silicon powder recovered and refined from waste silicon slurry. Summary of the invention

[0010] Technical issues

[0011] An object of the present invention is to provide a method for preparing silicon powder using waste silicon slurry, which can effectively mass-produce high-purity silicon powder while removing foreign matter such as moisture and organic components, so as to reuse the waste silicon slurry as a negative electrode material for energy storage devices (e.g., secondary batteries).

[0012] Furthermore, another object of the present invention is to provide a novel silicon powder which suppresses shrinkage, aggregation and coagulation of the powder and does not deteriorate in physical properties even when stored for a long period of time.

[0013] Moreover, another object of the present invention is to provide a silicon powder preparation system that can effectively mass-produce high-purity silicon powder while removing foreign matter such as moisture and organic components, so as to reuse waste silicon slurry as a negative electrode material for energy storage devices (e.g., secondary batteries).

[0014] The purpose of the present invention is not limited to the purpose mentioned above. Other purposes and advantages of the present invention that are not mentioned can be understood through the following description and will be more clearly understood through the embodiments of the present invention. In addition, it can be easily known that the purposes and advantages of the present invention can be achieved by the schemes and combinations thereof within the scope of the invention claims.

[0015] Technical Solution

[0016] In order to achieve the above-mentioned purpose, one embodiment of the present invention can provide a method for preparing silicon powder, which comprises: step (a), crushing waste silicon slurry supplied as raw material in an air atmosphere; and step (b), drying in an inert gas atmosphere to remove moisture from the product crushed in the above step (a).

[0017] The average particle size of the waste silicon slurry may be greater than 0 cm and less than or equal to 20 cm. The particle size D of the product crushed in the above step (a) is50 The value may be greater than 0 μm and less than or equal to 50 μm.

[0018] In the above step (a), pulverization and separation of water and hydrocarbon and organic components can be carried out simultaneously.

[0019] The above step (a) may be performed in a fluidized bed pulverizing apparatus.

[0020] Prior to the above step (a), a step (a') of pre-treating and crushing the waste silicon slurry supplied as a raw material may be further included.

[0021] The step (b) may be performed by airflow drying, and the airflow drying may be performed using an inert gas that does not contain oxygen.

[0022] The inert gas may include at least one of argon (Ar) gas and nitrogen (N 2 ) gas.

[0023] Based on 100 weight percent of the total weight of the waste silicon slurry, if the moisture content is greater than or equal to 0 weight percent and less than or equal to 3 weight percent, the step (b) may be performed at a temperature above 20° C. using a low-temperature airflow method.

[0024] Based on 100 weight percent of the total weight of the waste silicon slurry, if the moisture content is greater than 3 weight percent and less than or equal to 80 weight percent, the step (b) can be performed at a temperature above 60° C. using a high-temperature airflow.

[0025] Based on 100 weight percent of the total weight of the silicon powder, the moisture content may be less than or equal to 5 weight percent, and the carbon content may be less than or equal to 10 weight percent.

[0026] According to another embodiment of the present invention, silicon powder prepared by the method for preparing silicon powder according to one embodiment of the present invention may be provided.

[0027] The silicon powder can be used as a negative electrode material for a secondary battery.

[0028] Next, another embodiment of the present invention for achieving the above-mentioned object is silicon powder obtained from waste slurry generated in semiconductor and solar cell manufacturing processes, and has D 50 The value reaches 0.1~2μm, D 90 The particle size distribution reaches a value of 0.5 to 5 μm.

[0029] Preferably, the silicon powder for preparing the negative electrode material of the secondary battery of the present invention has D 10 The value reaches 0.01~0.5μm, D 100 The particle size distribution reaches a value of 1 to 10 μm.

[0030] Moreover, for the silicon powder for preparing the secondary battery negative electrode material of the present invention, based on the total weight of 100 weight percent, the moisture content can be less than 2 weight percent, the total metal content can be less than 2 weight percent, and the carbon content can be less than 5 weight percent.

[0031] Next, the silicon powder preparation system of the present invention for achieving the above-mentioned purpose includes a rotary kiln, which includes: a plurality of shells having a hollow interior and arranged along the length direction; a tube arranged in a manner to penetrate the interior of the plurality of shells and capable of rotating in a horizontal direction; and a heating unit arranged in the interior of at least one of the plurality of shells for heating the tube.

[0032] Among them, the above-mentioned multiple shells may include: a first shell, which is internally configured with a heating unit for heating the above-mentioned tube; and a second shell, which is not configured with a heating unit. The above-mentioned multiple shells may include a third shell, and the above-mentioned third shell is internally configured with a cooling unit for cooling the above-mentioned tube.

[0033] Preferably, the first shell may include: a 1-1 shell, provided with a heating unit for heating the tube to a temperature range of 100 to 200°C; a 1-2 shell, provided with a heating unit for heating the tube to a temperature range of 200 to 500°C; and a 1-3 shell, provided with a heating unit for heating the tube to a temperature range of 500 to 1000°C.

[0034] The rotary kiln may further include a raw material supply device for supplying silicon powder raw material and gas to the interior of the tube, and the raw material supply device may include: a raw material introduction portion for introducing and storing silicon powder raw material; a raw material transfer portion for supplying the silicon powder raw material stored in the raw material introduction portion to the tube; and a gas supply portion for supplying gas to the interior of the tube.

[0035] Preferably, the gas may include an inert gas.

[0036] Furthermore, the tube can be operated in a manner that does not discharge the silicon powder raw material inside by repeatedly performing forward rotation and reverse rotation under any conditions.

[0037] Furthermore, the preparation system of the present invention may further include a drying and crushing device for drying and crushing the waste silicon slurry.

[0038] Among them, the above-mentioned drying and crushing device may include: a dryer for drying the waste silicon slurry; a rotary crusher equipped with rotary blades for crushing the waste silicon slurry; and a fluidized bed crusher, which is provided with a funnel-shaped conduit with a diameter gradually narrowing from the top to the bottom, and the waste silicon slurry is crushed by the collision generated by the fluid flow. Preferably, in the above-mentioned conduit, with the upper part as the reference, the inclination angle of the lower part can be 10°~20°.

[0039] Furthermore, the drying and pulverizing device may further include a cyclone particle separator, a particle collector and a scrubber.

[0040] Effects of the Invention

[0041] In order to solve the problems and limitations of the prior art described above, the method for preparing silicon powder using waste silicon slurry of the present invention can effectively dry waste silicon slurry with different moisture contents, and at the same time remove foreign matter such as organic components, thereby having the advantage of effectively producing high-quality silicon powder that can be used in secondary batteries.

[0042] Furthermore, the silicon powder of the present invention allows the size distribution of the silicon powder for the secondary battery negative electrode material of the present invention to be strictly controlled, thereby suppressing the shrinkage, aggregation and coagulation of the powder.

[0043] Furthermore, the silicon powder for secondary battery negative electrode material of the present invention does not deteriorate in physical properties even when stored for a long period of time.

[0044] Furthermore, the silicon powder for a negative electrode material of a secondary battery of the present invention can have excellent dispersibility when used as a negative electrode material without deteriorating physical properties. Therefore, the silicon powder for a negative electrode material of a secondary battery of the present invention can ensure reliability and reproducibility when used as a negative electrode material.

[0045] Furthermore, in order to solve the problems and limitations of the prior art described above, the silicon powder preparation system of the present invention can effectively dry waste silicon slurry with different moisture contents, and at the same time remove foreign matter such as metal components and organic components, thereby having the advantage of effectively producing high-quality silicon powder that can be used in secondary batteries.

[0046] Along with the above-mentioned effects, specific effects of the present invention will be described in the course of explaining specific matters for implementing the invention below. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The flowchart briefly shows a method for preparing silicon powder using waste silicon slurry according to one embodiment of the present invention.

[0048] Figure 2 The flowchart briefly shows a method for preparing silicon powder using waste silicon slurry according to another embodiment of the present invention.

[0049] Figure 3 The cross-sectional view briefly shows a rotary kiln included in a silicon powder preparation system according to an embodiment of the present invention.

[0050] Figure 4 The figure briefly shows a drying and pulverizing device included in a silicon powder preparation system according to an embodiment of the present invention.

[0051] Figure 5 The schematic diagram briefly shows the silicon powder preparation system of the present invention. DETAILED DESCRIPTION

[0052] The above objects, features and advantages will be described in detail in the following content so that ordinary technicians in the technical field to which the present invention belongs can easily implement the technical ideas of the present invention.

[0053] In the process of describing the present invention, if it is determined that a detailed description of a known technology related to the present invention may make the gist of the present invention unnecessarily obscure, the detailed description will be omitted.

[0054] For the contents not described in this specification, the description will be omitted as long as a person skilled in the art can fully implement the technical derivation.

[0055] Unless otherwise clearly indicated in the context, the singular expressions used in this specification include the plural expressions. In this specification, the terms "include", "comprise", "have", "have" and the like should not be interpreted as necessarily including all the multiple structural elements described in the specification, but may not include some of the structural elements, or may also include other structural elements.

[0056] <Method for preparing silicon powder>

[0057] First, a method for preparing silicon powder using waste silicon slurry according to an embodiment of the present invention is described in detail.

[0058] Reference Figure 1 The present invention can provide a method for preparing silicon powder using waste silicon slurry, which comprises: step (a), crushing the waste silicon slurry supplied as a raw material in an air atmosphere; and step (b), drying in an inert gas atmosphere to remove moisture from the product crushed in the above step (a).

[0059] Step (a)

[0060] Waste silicon sludge is agglomerated and mixed in a so-called filter cake state to form aggregates of various sizes. In addition, the waste silicon sludge is placed outside and exists in a state containing water. If the water is not removed, there is a problem that a silicon dioxide (SiO2) oxide film may be formed on the silicon surface. In addition, metal component blades of diamond cutters used in silicon wafer cutting, lubricating oil used for cutting, hydrocarbon organic substances such as refrigerants, etc. will remain in the waste silicon sludge, so foreign matter containing metal components and carbon organic components will remain in the waste silicon sludge.

[0061] Therefore, in step (a), a pulverization process may be performed so that agglomerated particles of the waste silicon slurry supplied as a raw material are separated and silicon slurry particles, which are already relatively small particles, are also chopped finer.

[0062] For example, the average particle size of the waste silicon slurry used as the raw material can reach a range greater than 0 cm and less than or equal to 20 cm, for example, a range greater than 0 cm and less than or equal to 15 cm, for example, a range greater than 0 cm and less than or equal to 10 cm, but is not limited to this. In practice, it can be mixed with a variety of particle sizes and can exist in a coagulated state.

[0063] The particle size D of the product pulverized in the above step (a) is 50 The value may be in the range of greater than 0 μm and less than or equal to 50 μm, for example, in the range of greater than 0 μm and less than or equal to 30 μm, for example, in the range of greater than 0 μm and less than or equal to 10 μm, but is not limited thereto. As described above, the crushed powder can suppress shrinkage, agglomeration and condensation, and can also suppress the degradation of physical properties caused by oxidation, etc., caused by trace amounts of hydrocarbons, water, etc. remaining in the silicon powder during long-term storage.

[0064] Above D 50 The value means the particle size (size) value that occupies 50% in the order of the smallest particle size (size) in the particle distribution of the entire powder. In the present invention, D 50 The value is based on the value measured as follows: based on 100 weight percent, 10 to 20 weight percent of the sample to be measured is added to an isopropyl alcohol (IPA) solvent, followed by ultrasonic treatment for 10 to 30 minutes, and then analyzed using a particle size analyzer (CILAS laser particle size analyzer).

[0065] The pulverizing device used in the above step (a) is not particularly limited as long as the average particle size of the product after the above pulverization is satisfied, but preferably, the above pulverization and the foreign matter separation process of hydrocarbon and organic components including water can be performed simultaneously.

[0066] For example, in the above step (a), a fluidized bed pulverizer may be preferably used, and more specifically, a cyclone separation device may be used. Specifically, the waste silicon slurry supplied in the above step (a) may be pulverized very finely by the collision process between particles in the fluidized bed pulverizer along with high-speed gas. In this case, hydrocarbon organic components, water, etc. attached to the silicon slurry fall off in the form of fine particles, and finally the advantage of separating the above foreign matter while the silicon slurry is pulverized is achieved.

[0067] Alternatively, if the silicon slurry particles as the supplied raw material have a very excessive amount of water, a high-temperature airflow (eg, about 400° C. or less) may be supplied to the pulverizing device to remove part of the water in the pulverizing process as step (a).

[0068] Referring to an example of the present invention Figure 2 In order to more effectively carry out the pulverizing process in the above step (a), if the waste silicon slurry supplied as the raw material has excessive agglomeration or there is a large amount of slurry with large particle size, a step (a') of pre-treating and pulverizing the waste silicon slurry may be further included before step (a). As described above, the pre-treating and pulverizing step (a') and the pulverizing step (a) may be included to perform a total of two steps of pulverization, or the pulverizing step (a) may be performed alone, which can be selected according to the particle agglomeration state and particle size state of the waste silicon slurry provided as the raw material.

[0069] For example, the above-mentioned pretreatment crushing step (a') can be performed in an ordinary crushing device. For example, the average particle size of the pretreatment crushed product can reach a range greater than 0 cm and less than or equal to 15 cm, for example, can reach a range greater than 0 cm and less than or equal to 3 cm, for example, can reach a range greater than 0 cm and less than or equal to 1 cm, but is not limited to this.

[0070] The pulverizing device that can be used in the above step (a') is not particularly limited, and for example, a ball mill, a bead mill, a blade mill, an air mill, a jet mill, a rod mill, a roller mill, a jaw crusher, an impact crusher, a wheeler mill, a hammer mill, etc. can be used.

[0071] Step (b)

[0072] Step (b) is a drying process performed under an inert gas atmosphere in order to more effectively remove moisture from the product of step (a).

[0073] According to an example of the present invention, in order to quickly dry the water, the above step (b) can be performed by a hot air flow drying method that uses a high-speed flow of high-temperature gas to vaporize and remove the water. In order to prevent oxidation, the gas supplied in the above air flow drying method can use an inert gas that has been deoxygenated. In the present invention, since an inert gas is used in the air flow drying method, the drying method can be performed in an inert gas atmosphere.

[0074] According to an example of the present invention, the inert gas in the step (b) may include one or more of argon (Ar) gas and nitrogen (N 2 ) gas. For example, nitrogen gas may be used to perform airflow drying.

[0075] The waste silicon slurry is placed outside and exists in a state of containing water. Since the waste silicon slurry discharged from various solar energy industries and a plurality of factories is used, the water content contained in the waste silicon slurry is not constant.

[0076] On the other hand, since heat energy needs to be applied together with airflow drying in the drying process for removing moisture, in order to maximize energy efficiency which has become a major issue recently, it is preferred to adjust to different temperatures during drying according to the moisture content of the waste silicon slurry.

[0077] According to an example of the present invention, based on 100 weight percent of the total weight of the waste silicon slurry, if the water content is greater than or equal to 0 weight percent and less than or equal to 3 weight percent, the above step (b) can be performed in a low-temperature airflow mode, for example, a temperature of 20°C or above, for example, a temperature of 40°C or above, for example, a temperature of 60°C or above, but not limited thereto. In addition, since it is a process of removing moisture, the upper limit of the temperature condition of the low-temperature airflow mode is not particularly limited, but from the perspective of energy efficiency, in order not to use an excessively large heat source, for example, a temperature of 200°C or below, for example, a temperature of 150°C or below, for example, a temperature of 120°C or below, but not limited thereto, can be achieved.

[0078] According to an example of the present invention, based on 100 weight percent of the total weight of the waste silicon slurry, if the water content is greater than 3 weight percent and less than or equal to 80 weight percent, the above step (b) can be performed in a high-temperature airflow mode, for example, a temperature of 80°C or above, for example, a temperature of 100°C or above, for example, a temperature of 200°C or above, for example, a temperature of 300°C or above, but not limited thereto. In addition, since it is a process of removing moisture, the upper limit of the temperature condition of the high-temperature airflow mode is not particularly limited, but from the perspective of energy efficiency, in order not to use an excessively large heat source, for example, a temperature of 500°C or below, for example, a temperature of 400°C or below, for example, a temperature of 350°C or below, but not limited thereto, can be achieved.

[0079] In the above-mentioned step (b), the gas may be supplied under atmospheric pressure, and the flow rate of the supplied gas may be adjusted according to the selected equipment.

[0080] Additionally, the method for producing silicon powder of the present invention can further improve the quality of the produced silicon powder by introducing the dry powder into a hydrogen reduction furnace for hydrogen reduction, thereby removing the silicon oxide film present on the surface of the silicon powder.

[0081] The silicon powder preparation method of the present invention can also be performed in a device capable of continuously performing the above-mentioned steps (a) and (b) according to the silicon powder preparation device. For example, it can also be designed to simultaneously perform the crushing and drying steps or sequentially perform the crushing step and the drying step in a device in which a crushing device is attached to the upper end of a cyclone separation device.

[0082] In the silicon powder obtained through the above steps (a) and (b) according to the preparation method of the present invention, based on 100 weight percent of the total weight of the silicon powder, the moisture content can reach the following level, for example, less than or equal to 5 weight percent, for example, less than or equal to 3 weight percent, for example, less than or equal to 2 weight percent, and the carbon content can reach the following level, for example, less than or equal to 10 weight percent, for example, less than or equal to 8 weight percent, for example, less than or equal to 5 weight percent, thereby showing excellent quality.

[0083] The silicon powder of the present invention can be used as a material for an energy storage device, for example, can be used as a negative electrode material for a secondary battery.

[0084] <Silica powder>

[0085] Next, the silicon powder according to another embodiment of the present invention is described in detail. Preferably, the silicon powder according to another embodiment of the present invention can be used as a negative electrode material for a secondary battery.

[0086] The silicon powder for the negative electrode material of the secondary battery of the present invention is silicon powder obtained from waste slurry generated in the semiconductor and solar cell manufacturing process, and has D 50 The value is 0.1~2μm, D 90 The particle size distribution is 0.5 to 5 μm.

[0087] Among them, D 50 Value, D 90 The values ​​mean the particle size (size) values ​​that account for 50% and 90% of the distribution of all powders in the order of the smallest particle size (size). 50 Value and D 90 The value can be determined by Cilas equipment.

[0088] The silicon powder for the negative electrode material of the secondary battery of the present invention is obtained by recovering and refining the waste slurry generated in the semiconductor and solar cell manufacturing process, and the particle size distribution is particularly controlled.

[0089] The silicon powder for the negative electrode material of the secondary battery of the present invention is D 50 The value is controlled to 0.1~2μm, D 90 The value is controlled to 0.5 to 5 μm, which inhibits the shrinkage, aggregation and coagulation of the powder, and can also inhibit the degradation of physical properties caused by trace metals and moisture in the silicon powder during long-term storage. In addition, the silicon powder for secondary battery negative electrode material with particle size controlled in the above manner can ensure reliability and reproducibility when used as a secondary battery negative electrode material.

[0090] The silicon powder for the negative electrode material of the secondary battery of the present invention is D 50 The value can be controlled to be 0.1 to 2 μm, preferably 0.3 to 1 μm, and more preferably 0.5 to 0.9 μm.

[0091] Moreover, the D of the silicon powder for the negative electrode material of the secondary battery of the present invention is 90 The value can be controlled to be 0.5 to 5 μm, preferably 0.8 to 4 μm, and more preferably 1 to 3.5 μm.

[0092] The silicon powder for secondary battery negative electrode material whose size distribution is controlled in the above manner can suppress the shrinkage, agglomeration and coagulation of the powder, and can also suppress the degradation of physical properties caused by trace metals and moisture in the silicon powder during long-term storage. In addition, the silicon powder for secondary battery negative electrode material whose particle size is controlled in the above manner can ensure reliability and reproducibility when used as a secondary battery negative electrode material.

[0093] Furthermore, preferably, the silicon powder for the negative electrode material of the secondary battery of the present invention may have D 10 The value is 0.01~0.5μm, D 100 The particle size distribution is 1 to 10 μm.

[0094] Furthermore, as described above, the silicon powder for negative electrode material of secondary battery of the present invention is obtained from waste slurry generated in the process of manufacturing semiconductors and solar cells, impurities and water contained in the raw material are removed.

[0095] Therefore, through the moisture removal process, the silicon powder for secondary battery negative electrode material of the present invention preferably has a moisture content of less than 2 weight percent based on a total weight of 100 weight percent, and more preferably has a moisture content of less than 1 weight percent.

[0096] Moreover, the silicon powder for secondary battery negative electrode material of the present invention contains metals such as aluminum (Al), iron (Fe), copper (Cu) in trace amounts in ppm. The silicon powder for secondary battery negative electrode material of the present invention contains less than 2 weight percent of the metal components as described above, and more preferably less than 1 weight percent.

[0097] Preferably, the silicon powder of the present invention can be prepared by the method for preparing silicon powder of an embodiment of the present invention.

[0098] <Silicon powder preparation system>

[0099] Next, a system for preparing silicon powder according to another embodiment of the present invention is described in detail.

[0100] Rotary kiln

[0101] Reference Figure 3 The silicon powder preparation system of the present invention includes a rotary kiln 100. First, the rotary kiln 100 included in the preparation system of the present invention is described in detail.

[0102] Reference Figure 3 The silicon powder preparation system of the present invention includes a rotary kiln 100, which includes: a plurality of shells 10, each having a hollow portion formed therein and arranged along a length direction; a tube 20, which is arranged to penetrate the interior of the plurality of shells 10 and can rotate in a horizontal direction; and a heating unit H, which is arranged inside at least one of the plurality of shells 10 and is used to heat the tube 20.

[0103] Reference Figure 3 The above-mentioned multiple shells 10 are hollow inside and are respectively arranged along the length direction, in other words, respectively arranged along the horizontal direction.

[0104] Figure 3 In the figure, the plurality of shells 10 are shown in a box shape, but the shape of the shell 10 is not particularly limited as long as it is a structure surrounding the tube 20.

[0105] A heating unit H for heating the tube 20 is disposed inside at least one of the plurality of shells 10. Although not limited thereto, Figure 3 As shown, the heating unit H may be formed in a coil shape surrounding the tube.

[0106] like Figure 3 As shown, the plurality of shells 10 are arranged along the length direction, and can respectively apply heat in different temperature ranges to the tube 20. Therefore, the plurality of shells 10 can apply a temperature gradient along the length direction of the tube 20.

[0107] Preferably, the plurality of shells 10 may include: a first shell 11 in which a heating unit H for heating the tube 20 is disposed; and a second shell 30 in which no heating unit is disposed.

[0108] Among them, the above-mentioned first shell 11 may include: a 1-1 shell 12, equipped with a heating unit H for heating the above-mentioned tube 20 to a temperature range of 100 to 200°C; a 1-2 shell 13, equipped with a heating unit H for heating the above-mentioned tube 20 to a temperature range of 200 to 500°C; and a 1-3 shell 14, equipped with a heating unit H for heating the above-mentioned tube 20 to a temperature range of 500 to 1000°C.

[0109] Therefore, the plurality of shells 10 may apply temperature gradients in various temperature ranges to the tube 20 .

[0110] Furthermore, the plurality of shells 10 may further include a third shell (not shown), in which a cooling unit (not shown) for cooling the tube is disposed. The cooling unit may be a cooling module or the like.

[0111] Next, refer to Figure 3 The rotary kiln 100 of the present invention includes a pipe 20, which is arranged to penetrate the interior of the plurality of shells 10 and can rotate in a horizontal direction.

[0112] The tube 20 may be formed of a hollow cylindrical tube. However, the cross section of the tube 20 is not limited to a circle, and may be formed in various shapes such as a triangle, a quadrangle, and a hexagon.

[0113] The raw material of silicon powder will move along the length direction inside the tube 20. The silicon powder can move along the length direction inside the tube 20 by rotating the tube 20. To this end, a spiral wall can be formed inside the tube 20 to allow the silicon powder to move. In addition, the tube 20 can also be tilted to facilitate the movement of the silicon powder.

[0114] The tube 20 is arranged to penetrate the interior of the plurality of shells 10. As described above, the plurality of shells 10 can apply temperature gradients in various temperature ranges to the tube 20. Therefore, the silicon powder moving along the length direction inside the tube 20 can be heat-treated in various temperature ranges by heat supplied from the plurality of shells.

[0115] Moreover, refer to Figure 3 The rotary kiln 100 may further include a raw material supply device for supplying silicon powder raw materials and gas into the interior of the tube 20 .

[0116] Preferably, the raw material supply device may include: a raw material introduction portion 41 for introducing and storing silicon powder raw material; a raw material transfer portion 42 for supplying the silicon powder raw material stored in the raw material introduction portion 41 to the tube 20; and a gas supply portion 43 for supplying gas to the inside of the tube.

[0117] The gas may include an inert gas, and the inert gas may include one or more of argon (Ar) gas and nitrogen (N 2 ) gas. For example, nitrogen gas may be used.

[0118] Reference Figure 3 The silicon powder raw material passing through the pipe 20 may be discharged from the discharge port 60 , and the remaining gas may be separated by the residual gas separator 50 .

[0119] Furthermore, the rotary kiln 100 of the present invention can be operated without discharging the silicon powder raw material inside by repeatedly rotating the tube 20 forward and reverse under arbitrary conditions.

[0120] For example, the above-mentioned arbitrary condition may be a condition for generating a fault signal of the above-mentioned rotary kiln 100 .

[0121] The operation of the tube 20 as described above may be controlled by a control device (not shown) for controlling the rotary kiln 100 .

[0122] Drying and crushing equipment

[0123] Next, refer to Figure 4 The silicon powder preparation system of the present invention may further include a drying and crushing device 200 for drying and crushing the waste silicon slurry.

[0124] The drying and pulverizing device 200 is a device capable of drying and pulverizing waste silicon slurry.

[0125] Reference Figure 4The drying and crushing device 200 may include: a dryer for drying the waste silicon slurry; a rotary crusher equipped with rotary blades for crushing the waste silicon slurry; and a fluidized bed crusher, which is provided with a funnel-shaped conduit with a diameter gradually narrowing from the top to the bottom, and crushes the waste silicon slurry through collisions generated by fluid flow.

[0126] In the above-mentioned conduit, it is preferred that the lower portion has an inclination of 10° to 20° based on the upper portion.

[0127] Furthermore, the drying and pulverizing device 200 may further include a cyclone particle separator, a particle collector, and a scrubber.

[0128] First, waste silicon slurry is put into a dryer, and the dryer dries the waste silicon slurry with hot air at 200-250°C.

[0129] Next, the dried waste silicon slurry is pulverized by the rotary pulverizer and the fluidized bed pulverizer. As described above, the waste silicon slurry is first pulverized by the rotary blades of the rotary pulverizer, and then the waste silicon slurry is pulverized by the fluidized bed pulverizer. In this case, a high-temperature, high-speed fluid can be supplied to the fluidized bed pulverizer at a speed of 25 to 30 m3 / hr, and nitrogen gas can be used as the high-temperature, high-speed fluid.

[0130] The silicon powder discharged from the fluidized bed pulverizer may pass through the cyclone particle separator, the particle collector and the scrubber in sequence.

[0131] As described above, the silicon powder discharged from the fluidized bed mill can be separated by the cyclone particle separator and moved to the particulate collector. Fine particles that are difficult to be captured by the cyclone particle separator will eventually be collected by a bag filter (not shown), and ultrafine particles that pass through the bag filter will eventually be collected and discharged by a scrubber.

[0132] In this case, in order to achieve smooth airflow guidance and silicon particle crushing, the lower part is preferably inclined at an angle of 10° to 20° based on the upper part, for example, it can have an inclination of about 15°. The bulk silicon and the airflow of the high-temperature nitrogen gas move together toward the upper part of the funnel-shaped tube as described above and fall to the lower part. The funnel-shaped tube compresses part of the volume of the gas and reaches the lower part. The speed of the gas increases by at most 20% or more than the inflow speed, thereby playing the role of the driving force for the high-speed rotation and wear of the bulk silicon.

[0133] The lower part of the fluidized bed mill is composed of a slow funnel-shaped bottom with an inclination based on the ground, so that large pieces of silicon gather in the middle. The pieces falling from the top can naturally collide and crush with the pieces gathered in the middle.

[0134] On the other hand, the unseparated silicon filter cake in block form will continue to rotate in the lower part of the fluidized bed mill and go through the drying, rotating, collision and separation processes until the final dry separation is achieved.

[0135] However, if too many silicon particles are supplied, there is a problem that the rotation stops and the particles accumulate at the bottom, thereby preventing the flow. Taking these points into consideration, it is preferred that the supply rate of the silicon raw material used for drying reaches, for example, about 70 to 120 kg / hr. If the supply rate of the silicon raw material is greater than 120 kg / hr, there is a problem that the drying quality may deteriorate and the decomposition and crushing of the silicon blocks may not be smooth. On the other hand, if the supply rate of the raw material is less than 70 kg / hr, the production yield becomes low, which may lead to poor mass productivity.

[0136] Reference Figure 5 , Figure 5 The schematic diagram of the silicon powder preparation system of the present invention is shown. The silicon powder preparation system of the present invention comprises the rotary kiln 100 described above, and preferably, may comprise a drying and pulverizing device 200 for drying and pulverizing the silicon powder raw material.

[0137] The silicon powder raw material passing through the drying and pulverizing device 200 is heat-treated by moving to the rotary kiln 100. The silicon powder raw material heat-treated by the rotary kiln 100 may be finally refined into a material that can be used as a negative electrode material of an energy storage device (eg, a secondary battery).

[0138] Moreover, preferably, the system for preparing silicon powder of the present invention can be used in the above-mentioned preparation method of the present invention, and can be used for preparing the above-mentioned silicon powder of the present invention.

[0139] The following describes the structure and function of the present invention in more detail through the preferred embodiments of the present invention. However, this is only a preferred example of the present invention and is not to be construed as limiting the present invention in any aspect.

[0140] <Example>

[0141] 1. Preparation of silicon powder

[0142] (1) Embodiment 1

[0143] 100 kg of filter cake of silicon powder with a moisture content of 45 weight percent was prepared as a supply raw material, and was crushed at a speed of 30 to 60 Hz / bead and a supply rate of 3 to 10 kg / min at room temperature (23 to 25°C) using a roller crushing device (manufacturer: Innoxecom) equipped with a 2-axis crushing shaft (wet type) and a 1-axis channel crushing shaft (wet type).

[0144] The pulverized silicon powder was placed in a cyclone separator (manufacturer: Innoxecom), and the drying temperature of the dryer was set to 60° C., and hot air nitrogen flow drying was performed for less than 5 minutes using nitrogen gas.

[0145] Table 1 shows the properties of the silicon powder of Example 1 prepared as above.

[0146] (2) Examples 2 to 3, Comparative Examples 1 to 3

[0147] Silicon powders were prepared in the same manner as in Example 1, and silicon powders of Example 2, Example 3, and Comparative Examples 1 to 3 having the particle size distribution shown in Table 1 were prepared.

[0148] [Table 1]

[0149]

[0150] The particle size distribution of the silicon powder described in Table 1 above was measured using a Cilas device.

[0151] In addition, the moisture content of the silicon powder was analyzed by measuring the weight change of the sample in a drying oven. The metal content was measured by using an ICP-OES device, and the carbon content was measured by using a carbon analyzer CS995.

[0152] 2. Physical property evaluation

[0153] The dispersion stability of the silicon powders of the above-described examples and comparative examples was evaluated.

[0154] The silicon powders of Examples 1 to 3 and Comparative Examples 1 to 3 were used to prepare respective silicon slurries.

[0155] Specifically, a slurry prepared by mixing various silicon powders and N-methylpyrrolidone (NMP) in a manner such that the silicon content reaches 10 weight percent was treated in a continuous cycle with 500 Watt of electricity and 20 kHz of ultrasound for 30 minutes, thereby preparing silicon slurries using silicon powder of Examples 1 to 3 and silicon slurries using silicon powder of Comparative Examples 1 to 3.

[0156] In order to evaluate the dispersion stability of the silicon slurry, each silicon slurry was stored in a cylinder marked with scale lines, and it was observed whether stratification occurred over time, and the height excluding the clear upper layer liquid stratified to the upper layer was measured as a percentage (%) of the initial height. In addition, Table 2 records the results of measuring and calculating the height excluding the clear upper layer liquid stratified to the upper layer as a percentage (%) of the initial height.

[0157] [Table 2]

[0158]

[0159] As shown in the above experimental results, it was confirmed that the examples of the present invention were superior in long-term storage safety compared to the comparative examples.

[0160] Therefore, since the silicon powder of the present invention has excellent long-term storage stability, it can prevent the degradation of physical properties and can be used to prepare negative electrode materials with excellent reversibility.

[0161] The present invention has been described above, but the present invention is not limited to the embodiments disclosed in this specification, and it is self-evident that a variety of modifications can be implemented by ordinary technicians within the scope of the technical concept of the present invention. Moreover, even if the effects of the structure of the present invention are not clearly disclosed in the process of describing the embodiments of the present invention, the effects that can be predicted by the corresponding structure should also be recognized.

[0162] [Explanation of Reference Numerals]

[0163] 100: Rotary kiln

[0164] 10: Shell

[0165] 11: First shell

[0166] 12: Shell 1-1

[0167] 13: Shell 1-2

[0168] 14: Shells 1-3

[0169] 20: Tube

[0170] 30: Second shell

[0171] 41: Raw material feeding section

[0172] 42: Raw material transfer department

[0173] 43: Gas supply unit

[0174] 50: Residual gas separator

[0175] 60: Exhaust port

[0176] 200: Drying and crushing device.

Claims

1. A method for preparing silicon powder, characterized in that: include: Step (a), crushing waste silicon slurry supplied as a raw material under an air atmosphere; as well as Step (b) is drying under an inert gas atmosphere to remove moisture from the product pulverized in the above step (a).

2. The method for preparing silicon powder according to claim 1, characterized in that: The average particle size of the waste silicon slurry is greater than 0 cm and less than or equal to 20 cm. The particle size D of the product pulverized in the above step (a) is 50 The value is greater than 0 μm and less than or equal to 50 μm.

3. The method for preparing silicon powder according to claim 1, characterized in that: In the above step (a), pulverization and separation of water and hydrocarbon and organic components are carried out simultaneously.

4. The method for preparing silicon powder according to claim 1, characterized in that: The above step (a) is performed in a fluidized bed pulverizing apparatus.

5. The method for preparing silicon powder according to claim 1, characterized in that: Prior to the above step (a), the method further comprises a step (a') of pre-treating and crushing the waste silicon slurry supplied as a raw material.

6. The method for preparing silicon powder according to claim 1, characterized in that: The step (b) is performed by air flow drying. The above-mentioned air flow drying method is performed using an inert gas that does not include oxygen.

7. The method for preparing silicon powder according to claim 6, characterized in that: The inert gas includes at least one of argon gas and nitrogen gas.

8. The method for preparing silicon powder according to claim 1, characterized in that: Based on 100 weight percent of the total weight of the waste silicon slurry, if the moisture content is greater than or equal to 0 weight percent and less than or equal to 3 weight percent, the step (b) is performed at a temperature above 20° C. using a low-temperature airflow method.

9. The method for preparing silicon powder according to claim 1, characterized in that: Based on 100 weight percent of the total weight of the waste silicon slurry, if the moisture content is greater than 3 weight percent and less than or equal to 80 weight percent, the step (b) is performed at a temperature above 60° C. using a high-temperature airflow.

10. The method for preparing silicon powder according to claim 1, characterized in that: Based on 100 weight percent of the total weight of the silicon powder, the moisture content is less than or equal to 5 weight percent, and the carbon content is less than or equal to 10 weight percent.

11. A silicon powder for preparing anode material of a secondary battery, characterized in that: Silicon powder obtained from waste slurry generated in the semiconductor and solar cell manufacturing process has D 50 The value reaches 0.1~2μm, D 90 The particle size distribution reaches a value of 0.5 to 5 μm.

12. The silicon powder for preparing negative electrode material for secondary battery according to claim 11, characterized in that: The above silicon powder has D 10 The value reaches 0.01~0.5μm, D 100 The particle size distribution reaches a value of 1 to 10 μm.

13. The silicon powder for preparing negative electrode material for secondary battery according to claim 11, characterized in that: Based on the total weight of 100 weight percent, the moisture content is less than 2 weight percent.

14. The silicon powder for preparing negative electrode material for secondary battery according to claim 11, characterized in that: Based on 100 weight percent of the total weight, the content of total metals included is less than 2 weight percent.

15. The silicon powder for preparing negative electrode material for secondary battery according to claim 11, characterized in that: Based on 100 weight percent of the total weight, the carbon content is less than 5 weight percent.

16. A system for preparing silicon powder, characterized in that: Including a rotary kiln, the rotary kiln comprises: A plurality of shells are provided with a hollow space inside and are arranged along the length direction; a tube, which is arranged to penetrate the interiors of the plurality of shells and is rotatable in a horizontal direction; and The heating unit is disposed inside at least one of the plurality of shells and is used to heat the tube.

17. The silicon powder preparation system according to claim 16, characterized in that: The multiple shells include: A first shell having a heating unit disposed therein for heating the tube; and The second shell is not equipped with a heating unit.

18. The silicon powder preparation system according to claim 17, characterized in that: The plurality of shells include a third shell, and a cooling unit for cooling the tube is disposed inside the third shell.

19. The silicon powder preparation system according to claim 17, characterized in that: The first housing comprises: The 1-1 shell includes a heating unit for heating the tube to a temperature in the range of 100 to 200° C.; The 1-2 shell includes a heating unit for heating the tube to a temperature in the range of 200 to 500° C.; and The 1-3 shell includes a heating unit for heating the tube to a temperature in the range of 500 to 1000°C.

20. The silicon powder preparation system according to claim 16, characterized in that: The heating unit is formed in a coil shape surrounding the tube.

21. The silicon powder preparation system according to claim 16, characterized in that: The rotary kiln further comprises a raw material supply device for supplying silicon powder raw material and gas into the interior of the tube. The above-mentioned raw material supply device comprises: The raw material placing part is used to place and store silicon powder raw materials; a raw material transfer unit for supplying the silicon powder raw material stored in the raw material introduction unit to the tube; and The gas supply unit is used to supply gas to the inside of the tube.

22. The silicon powder preparation system according to claim 21, characterized in that: The above-mentioned gas includes an inert gas.

23. The silicon powder preparation system according to claim 16, characterized in that: The pipe is operated so as not to discharge the silicon powder raw material inside by repeatedly performing forward rotation and reverse rotation under arbitrary conditions.

24. The silicon powder preparation system according to claim 16, characterized in that: It also includes a drying and crushing device for drying and crushing the waste silicon slurry.

25. The silicon powder preparation system according to claim 24, characterized in that: The above drying and crushing device comprises: A dryer, used for drying the waste silicon slurry; a rotary pulverizer having rotary blades for pulverizing waste silicon slurry; and The fluidized bed pulverizer is provided with a funnel-shaped conduit whose diameter gradually narrows from the top to the bottom, and pulverizes the waste silicon slurry through the collision generated by the fluid flow.

26. The silicon powder preparation system according to claim 25, characterized in that: In the above-mentioned conduit, the inclination angle of the lower portion is 10° to 20° based on the upper portion.

27. The silicon powder preparation system according to claim 25, characterized in that: The drying and pulverizing device further comprises a cyclone particle separator, a particle collector and a scrubber.

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