Method for producing silicon monoxide for secondary battery anode material

Abstract

The present invention relates to a manufacturing method that allows waste silicon sludge to be mixed with silica sand and vaporized and regenerated into the form of high-purity silicon monoxide, thereby enabling it to be utilized as a raw material for silicon anode materials for secondary batteries. This method is characterized by efficiently removing impurities from the waste silicon sludge and controlling the reaction between silicon and silica sand to produce a lump form in which silicon monoxide is the main component, and by designing the process so that the produced silicon monoxide lump exhibits electrochemical characteristics equivalent to silicon monoxide produced in a conventional process.

Description

Technology Field

[0001] The present invention relates to a method for producing silicon monoxide using waste silicon sludge, and more specifically, to a method for producing silicon monoxide that can be used as a negative electrode material for an energy storage device by recovering and upcycling waste silicon sludge generated in the wafer production process of the solar power industry as a useful resource. Background Technology

[0002] In general, waste silicon sludge generated in the solar power industry is simply discarded because no suitable use can be found. The main recycling methods known to date include chemically treating the metal components contained in the waste silicon sludge to dry it and produce low-quality silicon ingots for recycling, or simply drying it and using it as a raw material for refractory materials.

[0003] However, waste silicon sludge generated in the solar power industry can increase its purity through purification. Accordingly, many attempts and methods are being proposed to utilize waste silicon sludge in other industries rather than recycling it in the solar power industry.

[0004] In addition, back grinding of semiconductor silicon wafers is a process of grinding the back surface of the silicon wafer as part of the wafer operation process. The solid content in the waste silicon sludge generated in this process consists mostly of silicon.

[0005] In the wafer manufacturing process, a method is adopted to produce a large number of wafers at low cost by simultaneously cutting single-crystal and polycrystalline silicon ingots with multiple wire saws. For cutting, a dispersant and a surfactant are mixed with water. When the wire is rotated while injecting the slurry composed as described above, the silicon ingot is pressed and cut, and during this process, cutting debris consisting of fine silicon particles, such as sawdust, is generated and mixed into the water.

[0006] Accordingly, as the demand for silicon has increased explosively due to environmental pollution issues and the high growth of related industries, technologies to recover silicon from waste silicon sludge are being researched.

[0007] As mentioned above, silicon powder is recovered from waste silicon sludge generated in the solar power industry or from waste silicon sludge generated during the manufacturing process of semiconductor silicon wafers and recycled into various other industries.

[0008] However, silicon powders recovered and purified from waste silicon sludge may experience shrinkage, aggregation, and clumping, and their physical properties may deteriorate due to trace amounts of metal and moisture within the silicon powder during long-term storage. Accordingly, when silicon powders recovered and purified from waste silicon sludge are used to manufacture negative electrode materials for secondary batteries, the dispersibility of the silicon powders may be reduced, and irreversibility may increase due to issues such as volume expansion.

[0009] Meanwhile, silicon-based materials are gaining attention as high-capacity anode materials in secondary batteries, particularly lithium-ion batteries. However, pure silicon (Si) has issues with lifespan characteristics due to significant volume expansion during charging and discharging; therefore, SiO₂ is being used as an alternative to mitigate this problem. x Complex oxides of this series are being commercialized. The problem to be solved

[0010] The present invention relates to a silicon anode material for secondary batteries, particularly SiO₂, utilizing waste silicon sludge generated in the solar photovoltaic or semiconductor industries. x The purpose is to provide a technology for recycling as a raw material for cathode materials.

[0011] Specifically, the present invention provides a method for regenerating silicon monoxide by mixing silicon recovered and treated from waste silicon sludge with silica sand, with the aim of contributing to the solution of environmental problems through resource recycling. This method utilizes waste silicon sludge to produce SiO₂ for secondary batteries having high energy density and stability. x We provide technology that enables resource recycling and high value-added production by manufacturing cathode materials and enabling a stable supply of high-performance secondary battery materials.

[0012] The objective of the present invention is to provide a regeneration manufacturing method that mixes waste silicon sludge with silica sand to vaporize it into high-purity silicon monoxide and enables it to be used as a raw material for silicon anode materials for secondary batteries.

[0013] The objective of the present invention is to provide a technology that efficiently removes impurities from waste silicon sludge and induces an appropriate reaction between silicon and silica sand to produce a lump form in which silicon monoxide is the main component.

[0014] The objective of the present invention is to provide a process design that enables the manufactured silicon monoxide lumps to have electrochemical properties similar to silicon monoxide manufactured in a conventional process. means of solving the problem

[0015] According to one embodiment of the present invention, a method for manufacturing silicon monoxide using waste silicon sludge comprises: (S1) mixing and molding silicon powder and silica sand powder and then drying; (S2) heating under vacuum or an inert atmosphere to remove an oxide film on the surface of the silicon powder and obtaining silicon powder from which the oxide film has been removed; and (S3) reacting the silicon powder from which the oxide film has been removed with the silica sand to generate silicon monoxide gas and depositing the generated silicon monoxide to obtain a silicon monoxide deposit.

[0016] According to one embodiment of the present invention, a method for producing silicon monoxide using waste silicon sludge can be provided, characterized in that the oxygen content of the silicon powder in step (S1) is 10 wt% or less.

[0017] According to one aspect of the present invention, in step (S1), D of the silicon powder 50 A method for producing silicon monoxide using waste silicon sludge characterized by having a thickness of 100㎛ or less can be provided.

[0018] According to one embodiment of the present invention, a method for producing silicon monoxide using waste silicon sludge is provided, characterized by mixing silicon powder and silica powder in step (S1) such that the ratio is 30:70 to 40:60 in terms of weight ratio (wt%).

[0019] According to one embodiment of the present invention, a method for producing silicon monoxide using waste silicon sludge can be provided, characterized in that the heating temperature of step (S2) is 1,100°C to 1,200°C.

[0020] According to one embodiment of the present invention, a method for producing silicon monoxide using waste silicon sludge can be provided, characterized in that the reaction of step (S3) is performed at a temperature of 1,200°C to 1,400°C.

[0021] According to one embodiment of the present invention, a method for producing silicon monoxide using waste silicon sludge can be provided, characterized in that the reaction of step (S3) is performed at a pressure of 1,000 Pa or less.

[0022] According to one embodiment of the present invention, a method for producing silicon monoxide using waste silicon sludge can be provided, characterized in that the deposition rate of the silicon monoxide deposit is 60% or more, the oxygen content of the silicon monoxide deposit is 32 wt% to 38 wt%, and the aluminum content of the silicon monoxide deposit is 130 ppm or less. Effects of the invention

[0023] By converting waste silicon sludge into high-value-added cathode material precursors, cost reduction and resource recycling can be achieved.

[0024] The manufactured silicon monoxide lumps can possess excellent electrochemical performance (cycle stability and capacity retention rate) through a microporous structure and a stable composition ratio.

[0025] In addition to the effects described above, the specific effects of the present invention are described together with the specific details for implementing the invention below. Brief explanation of the drawing

[0026] Figure 1 shows a flowchart of a method for manufacturing silicon monoxide using waste silicon sludge. Figure 2 shows a schematic diagram of a manufacturing apparatus used to produce silicon monoxide using waste silicon sludge. Figure 3 is an SEM image of the waste silicon sludge powder used in the present invention. Figure 4 is an SEM image of the silica powder used in the present invention. Figure 5 is an SEM image of a silicon monoxide deposit produced by the present invention. Specific details for implementing the invention

[0027] The aforementioned objectives, features, and advantages are described in detail below, and accordingly, a person skilled in the art to which the present invention pertains will be able to easily implement the technical concept of the present invention.

[0028] In describing the present invention, detailed descriptions of known technologies related to the present invention are omitted if it is determined that such descriptions could unnecessarily obscure the essence of the invention.

[0029] Details not described in this specification that can be sufficiently technically inferred by a person skilled in the art are to be omitted.

[0030] As used in this specification, singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising,” “containing,” and “having” should not be interpreted as necessarily including all of the various components described in the specification, and should be interpreted as meaning that some of the components may not be included or that additional components may be included.

[0031] As used in this specification, O refers to elemental oxygen, Al refers to elemental aluminum, Si refers to elemental silicon, SiO refers to silicon monoxide, SiO2 refers to silicon dioxide, and SiO x represents silicon dioxide, where x is 0 < x ≤ 2.

[0032] According to one embodiment of the present invention, a method for manufacturing silicon monoxide using waste silicon sludge comprises: (S1) mixing and molding silicon powder and silica sand powder and then drying; (S2) heating under vacuum or an inert atmosphere to remove an oxide film on the surface of the silicon powder and obtaining silicon powder from which the oxide film has been removed; and (S3) reacting the silicon powder from which the oxide film has been removed with the silica sand to generate silicon monoxide gas, and depositing the generated silicon monoxide gas to obtain a silicon monoxide deposit.

[0033] The present invention comprises a step of crushing a waste silicon sludge cake or pellet to mix the crushed waste silicon powder with silica sand in a wet-dry manner, and a step of drying a molded silicon and silica sand composite, and a process including a step of placing the silicon and silica sand composite into a reactor and vaporizing it into silicon monoxide gas in a heating section to deposit it in a deposition section.

[0034] According to one embodiment of the present invention, a method for producing silicon monoxide using waste silicon sludge can be provided, characterized in that the oxygen content of the silicon powder is 10 wt% or less.

[0035] According to one aspect of the present invention, D of the silicon powder 50 A method for producing silicon monoxide using waste silicon sludge characterized by having a thickness of 3㎛ or less can be provided.

[0036] According to one embodiment of the present invention, a method for producing silicon monoxide using waste silicon sludge can be provided, characterized in that the mixing ratio of silicon powder and silica powder in step (S1) is 30:70 to 40:60 based on the weight ratio (wt%) of silicon powder to silica powder.

[0037] Waste silicon sludge crushing stage

[0038] Silicon wafer manufacturers provide silicon sludge in the form of cakes or pellets after passing through processes such as filter presses, as the discharge of liquid sludge due to the large amount of water used during the diamond saw cutting process increases transportation costs. At this time, the average particle size of the waste silicon sludge cakes or pellets supplied as raw materials is 20 cm or less, and when ground in an air atmosphere, they pass through fin mills, disc mills, etc. D 50 The value may be 500㎛ or less. More preferably, D 50 It is recommended to grind the waste silicon to a particle size of 50㎛. The size of a single waste silicon particle may be 100㎛ or less.

[0039] Wet and dry mixing and molding steps of waste silicone and silica sand

[0040] When mixing the ground silicon powder and silica sand, the weight specific gravity is mixed at 30 to 40 wt% for silicon and 60 to 70 wt% for silica sand. At this time, the dimensions of the silica sand may exceed 1 µm and be 100 µm or less, and the purity must be 98 wt% or higher. When mixing dry, a high-speed mixer may be mainly used, and it does not matter whether equipment such as a ribbon mixer, V-mixer, cone mixer, or planetary mixer is used. When mixing wet, moisture may be added up to 0 to 50%, and likewise, a high-speed mixer may be mainly used, and it does not matter whether equipment such as a ribbon mixer, V-mixer, cone mixer, or planetary mixer is used. The above high-speed mixer may mix for 5 to 30 minutes at a speed between 500 and 3,000 RPM.

[0041] A mixture of silicon and silica sand containing moisture can be placed in a mold and pressurized to increase the contact area between the silicon and the silica sand, and the diameter of the molded body can be 0.5 cm to 30 cm. However, it is preferable that the thickness of the molded body not exceed 10 cm. For example, when making a molded body with a diameter of 30 cm, through holes, etc., can be formed to maintain the thickness at 10 cm or less. This is to ensure that silicon monoxide gas generated by the reaction between the silicon powder and the silica sand powder is discharged consistently in all molded bodies.

[0042] Drying step of waste silicone and silica sand composite molded body

[0043] A moisture-containing silicone and silica sand composite molded body is loaded into a suitable tray and placed in a dryer. At this time, air is supplied and exhausted while the temperature of the dryer is raised in the range of 0 to less than 150°C, and once 150°C is reached, nitrogen is supplied and exhausted to dry the body for 2 hours to prevent oxidation. To dry the moisture in stages, the temperature is maintained at 190°C for 2 hours, 230°C for 2 hours, and 280°C for 3 hours, respectively, and the heating rate for each stage may be within 10°C per minute. Detailed temperature conditions can be controlled according to the moisture content, and the moisture content of the final molded body is preferably less than 1 wt%.

[0044] According to one embodiment of the present invention, a method for producing silicon monoxide using waste silicon sludge can be provided, characterized in that the heating temperature of step (S2) is 1,100°C to 1,200°C.

[0045] Oxide film removal step for waste silicon

[0046] In a typical silicon monoxide manufacturing process, when silicon with a low oxygen content is used, metallic silicon and silica sand react normally. However, when waste silicon with a high oxygen content is used, the reaction with silica sand proceeds only restrictively due to the thick oxide film formed on the surface.

[0047] Therefore, a pretreatment step is required to remove the surface oxide film of waste silicon particles by first reacting the surface oxide film of the waste silicon with the internal metallic silicon to generate silicon monoxide gas. During this process, the temperature is maintained at approximately 1,100°C to 1,600°C, and the internal pressure is 1 x 10⁻⁶ -1 The reaction takes place at 100,000 Pa, more preferably at 1,100°C to 1,200°C, 1x10 -1 The waste silicon surface oxide film can be removed under conditions of up to 1,000 Pa.

[0048] According to one embodiment of the present invention, a method for producing silicon monoxide using waste silicon sludge can be provided, characterized in that the reaction of step (S3) is performed at a temperature of 1,200°C to 1,400°C.

[0049] According to one embodiment of the present invention, a method for producing silicon monoxide using waste silicon sludge can be provided, characterized in that the reaction of step (S3) is performed at a pressure of 1,000 Pa or less.

[0050] According to one embodiment of the present invention, a method for producing silicon monoxide using waste silicon sludge can be provided, characterized in that the deposition rate of the silicon monoxide deposit is 60% or more, the oxygen content of the silicon monoxide deposit is 32 wt% to 38 wt%, and the aluminum content of the silicon monoxide deposit is 130 ppm or less.

[0051] Reaction step between waste silicon with oxide film removed and silica sand

[0052] When the oxide film is removed and the silicon metal inside the waste silicon is exposed, the surface free energy increases, reacting with nearby silica sand to generate silicon monoxide gas. At this time, the temperature is maintained at approximately 1,100°C to 1,600°C, and the vacuum level (internal pressure) is 1 x 10⁻⁶ -1 The reaction takes place at 100,000 Pa and is more preferably maintained at 1,100°C to 1,400°C, so that 1x10 -1The reaction takes place at 1,000 Pa. The reaction time may increase or decrease in proportion to the input amount and the applied thermal energy.

[0053] The silicon monoxide gas generated through this process can be deposited on an unheated deposition area and recovered. The configuration of the device in more detail is as follows.

[0055] Reactor (10)

[0056] As a space encompassing the entire system of the facility, which houses the charging section, heating section, vacuum and inert gas supply section, and deposition section, the interior is maintained under vacuum or inert gas. The reactor is protected by a double jacket through which cooling water is introduced.

[0057] Loading part (20)

[0058] The charging section is composed of a graphite crucible, etc., and is installed inside the reactor to hold a composite molded body made of waste silicon and silica sand. The charging section serves as a space where the composite molded body reacts by thermal energy applied from the heating section.

[0059] Heating part (30)

[0060] The charging section is heated to a constant temperature using electric resistance heating, induction heating, etc. The temperature is precisely controlled through temperature sensors and control devices to maximize reaction efficiency.

[0061] Vacuum and inert gas supply unit (40-1, 40-2)

[0062] The pressure inside the reactor is controlled via a vacuum pump, and if necessary, an inert gas such as argon (Ar) can be injected to support oxidation prevention and accelerated cooling.

[0063] deposition part (50)

[0064] Silicon monoxide gas generated through the reaction between silicon and silica sand can be deposited on an unheated deposition area and recovered, and the deposition area is composed of stainless steel (Steel Use Stainless, SUS) that does not react with silicon monoxide gas.

[0066] The structure and operation of the present invention will be described in more detail below through preferred embodiments. However, these are presented as preferred examples of the present invention and should not be interpreted in any way as limiting the present invention.

[0068] Experimental group 1

[0069] An experiment was conducted to investigate how the deposition rate of silicon monoxide is affected by the oxygen content of the silicon sludge used as a raw material. Oxygen in the silicon sludge raw material exists in the form of silicon dioxide on the silicon surface. The temperature was raised from room temperature to 800°C and waited for 1 hour, then raised again to 1,100°C and waited for 3 hours, then raised again to 1,200°C and waited for 3 hours, and finally raised once more to 1,370°C and waited for 50 hours. During the above heating process, the temperature was increased at a rate of 3°C per minute. These heating conditions in Experimental Group 1 were established as the basic heating conditions for Experimental Group 1. The deposition rates according to the oxygen content of the silicon sludge raw material are shown in Table 1 below.

[0070] Si:SiO2 weight ratio Si Oxygen Content (wt%) Charge amount (kg) Deposition amount (kg) Deposition rate (%) Example 1 37:63 3 801 703 88 Example 2 37:63 5 800 656 82 Example 3 37:63 9 801 542 68 Comparative Example 1 37:63 15 801 381 48 Comparative Example 2 37:63 24 801 140 18

[0072] The meaning of each term in Table 1 is as follows.

[0073] Si:SiO2 weight ratio : weight ratio of silicon powder and silica powder

[0074] Si Oxygen Content (%) : Oxygen content of silicon sludge

[0075] Charge Amount (kg): Charge amount of mixed silicon sludge and silica sand

[0076] Deposited amount (kg): Amount of vaporized silicon monoxide deposited

[0077] Deposition Rate (%) : Ratio of deposited amount to loaded amount

[0079] It can be observed that the reactivity of the mixed silicon sludge and silica sand differs depending on the oxygen content of the silicon sludge raw material. Oxygen on the surface of the metallic silicon sludge exists in the form of an oxide film of silicon dioxide and can be removed in the form of silicon monoxide gas in the 1,100–1,200°C range. However, it was confirmed that under the same process conditions, differences in the amount of vaporization occurred depending on the initial oxygen content present on the surface of the metallic silicon, and a high deposition rate was observed when the oxygen content was 10% or less, preferably 5% or less, and more preferably 3% or less. When the Si oxygen content was within 10%, the deposition rate was high at over 60%, and when the Si oxygen content was 3%, a very high deposition rate of 88% was observed.

[0081] Experimental group 2

[0082] It was confirmed that the deposition rate varied depending on the particle size of the metallic silicon included in the silicon sludge. The results are listed in Table 2 below.

[0083] Si:SiO2 weight ratio D 50 (㎛) Charge amount (kg) Deposition amount (kg) Deposition rate (%) Example 4 37:63 0.6 801 703 88 Example 5 37:63 2.2 800 489 61 Comparative Example 3 37:63 5.4 801 271 34 Comparative Example 4 37:63 8.0 800 0 0

[0084] The meaning of each term in Table 2 is as follows.

[0085] Si:SiO2 weight ratio : weight ratio of silicon powder and silica powder

[0086] D 50 (㎛): Particle size of silicon particles in silicon sludge

[0087] Charge Amount (kg): Charge amount of mixed silicon sludge and silica sand

[0088] Deposited amount (kg): Amount of vaporized silicon monoxide deposited

[0089] Deposition Rate (%) : Ratio of deposited amount to loaded amount

[0091] The silicon sludge raw material used in the present invention is typically generated during the process of cutting polysilicon ingots for solar cells with a diamond saw, and is approximately D 50It has a particle size of =0.6±0.3㎛. On the other hand, by grinding high-purity polysilicon ingots, D 50 Productivity was compared with metallic silicon raw materials having a particle size of =8±0.5㎛. It was confirmed that silicon raw materials produced from the same source exhibit different vaporization reactions depending on particle size under identical conditions. Therefore, the optimal particle size of the silicon raw material is D 50 It can be confirmed that a standard of 3㎛ or less is desirable, and more specifically, 1㎛ or less is desirable. In experimental group 2, the heating conditions are the same as the basic heating conditions of experimental group 1.

[0093] Experimental group 3

[0094] It was confirmed that the deposition rate varied depending on the Si:SiO2 weight ratio (wt%) of silicon sludge and silica sand. The results are listed in Table 3 below.

[0095] Si:SiO2 weight ratio Si Oxygen Content (wt%) Charge amount (kg) Deposition amount (kg) Deposition rate (%) Comparative Example 5 27:73 5 800 296 37 Example 6 32:68 5 800 512 64 Example 7 37:63 5 800 652 81 Example 8 39:61 5 800 488 61 Comparative Example 7 45:54 5 800 384 48

[0096] The meaning of each term in Table 3 is as follows.

[0097] Si:SiO2 weight ratio : weight ratio of silicon powder and silica powder

[0098] Si Oxygen Content (%) : Oxygen content of silicon sludge

[0099] Charge Amount (kg): Charge amount of mixed silicon sludge and silica sand

[0100] Deposited amount (kg): Amount of vaporized silicon monoxide deposited

[0101] Deposition Rate (%) : Ratio of deposited amount to loaded amount

[0103] It was found that the reactivity varied depending on the mixing weight ratio of silicon sludge raw material and silica sand. Theoretically, 1 mole of silicon reacts with 1 mole of silicon dioxide to vaporize and deposit silicon monoxide gas. At this time, the reaction occurs within a range where silicon is 32 to 39 wt% and silica sand is 68 to 61 wt%, and it was confirmed that the most desirable mixing ratio of silicon and silicon dioxide (Si:SiO2) is required to be 36 wt%:64 wt% to 38 wt%:62 wt%. In particular, as shown in the results in Table 3, an excellent deposition rate was observed at a ratio of 37 wt%:63 wt%. The heating conditions for experimental group 3 are the same as the basic heating conditions for experimental group 1.

[0105] Experimental group 4

[0106] It was confirmed that the deposition rate varied depending on the reaction temperature. The aluminum content of the silicon sludge used was 50 ppm, and the aluminum content of the silica sand was 250 ppm. The experimental results are shown in Table 4.

[0107] Reaction temperature (°C) Si:SiO2 weight ratio Si Oxygen Content (wt%) Charge amount (kg) Deposition amount (kg) Deposition rate (%) SiO - ICP results Al(ppm) Comparative Example 8 1100 37:63 5 800 384 48 1 Example 9 1200 37:63 5 800 520 65 1 Example 10 1310 37:63 5 800 560 70 5 Example 11 1330 37:63 5 800 592 74 21 Example 12 1370 37:63 5 800 654 82 55 Example 13 1390 37:63 5 800 676 85 110 Example 14 1400 37:63 5 800 676 85 110 Comparative Example 9 1410 37:63 5 800 735 92 134 Comparative Example 10 1430 37:63 5 800 756 94 136

[0108] The meaning of each term in Table 4 is as follows.

[0109] Reaction Temperature (°C): The temperature maintained during the reaction between silicon sludge raw material and silica sand

[0110] Si:SiO2 weight ratio : weight ratio of silicon powder and silica powder

[0111] Si Oxygen Content (%) : Oxygen content of silicon sludge

[0112] Charge Amount (kg): Charge amount of mixed silicon sludge and silica sand

[0113] Deposited amount (kg): Amount of vaporized silicon monoxide deposited

[0114] Deposition Rate (%) : Ratio of deposited amount to loaded amount

[0115] SiO - ICP Results: Inductively Coupled Plasma (ICP) Results for Deposited Silicon Monoxide

[0116] It was found that the deposition rate and the amount of vaporization of specific metallic foreign substances varied depending on the reaction temperature between the silicon sludge raw material and the silica sand. In particular, it is presumed that aluminum contamination occurs due to the alumina lining performed to prevent metallic foreign substance contamination during the process of crushing the silica sand rock at the silica sand raw material stage.

[0117] It is presumed that silicon atoms diffuse into the alumina during a high-temperature vacuum to form an Al-O-Si phase, and vaporization begins at a specific temperature, and the condition that simultaneously satisfies metal impurities (quality) and deposition rate (productivity) was found to be best at 1,350°C to 1,400°C. More specifically, conditions of 1,360°C to 1,380°C, for example, 1,370°C is preferred. After raising the temperature from room temperature to 800°C, wait for 1 hour, then raise the temperature again to 1,100°C and wait for 3 hours, then raise the temperature again to 1,200°C and wait for 3 hours, and finally maintain at 1,200°C as indicated in Table 4, or raise the temperature once more to 1,310°C, 1,330°C, 1,370°C, 1,390°C, 1,410°C, or 1,430°C and wait for 50 hours. The above heating process raised the temperature at a heating rate of 3℃ per minute.

[0118] As shown in Table 4, the deposition rate tended to increase as the reaction temperature increased. However, looking at the SiO₂-ICP results, the aluminum content also increased. Since an undesirable increase in aluminum content is undesirable, the results of measuring the aluminum content while varying the operating conditions are shown in Table 4. It was found that the aluminum content was 130 ppm or less at a reaction temperature of 1,400℃ or lower, and it was confirmed that the aluminum content decreased to a minimum of 1 ppm depending on the reaction temperature.

[0120] Experimental group 5

[0121] It was confirmed that the deposition rate varied depending on the vacuum (pressure) and reaction temperature. The experimental results are shown in Table 5.

[0122] Vacuum level (Pa) Reaction temperature (°C) Charge amount (kg) Deposition amount (kg) Deposition rate (%) Example 15 10 1,200 800 520 65 Example 16 10 1,370 800 654 82 Example 17 10 1,400 800 676 85 Example 18 100 1,200 800 481 60 Example 19 100 1,370 800 648 81 Example 20 100 1,400 800 656 82 Example 21 1,000 1,200 800 480 60 Example 22 1,000 1,370 800 536 67 Example 23 1,000 1,400 800 544 68 Comparative Example 11 10,000 1,200 800 168 21 Comparative Example 12 10,000 1,370 800 232 29 Comparative Example 13 10,000 1,400 800 256 32

[0123] The meaning of each term in Table 5 is as follows.

[0124] Vacuum (Pa): The vacuum (pressure) maintained during the reaction between silicon sludge raw material and silica sand

[0125] Reaction temperature (°C): The temperature maintained during the reaction between silicon sludge raw material and silica sand

[0126] Charge Amount (kg): Charge amount of mixed silicon sludge and silica sand

[0127] Deposited amount (kg): Amount of vaporized silicon monoxide deposited

[0128] Deposition Rate (%) : Ratio of deposited amount to loaded amount

[0130] The reaction temperature conditions were established by raising the temperature from room temperature to 800°C and waiting for 1 hour, raising it again to 1,100°C and waiting for 3 hours, raising it again to 1,200°C and waiting for 3 hours, and finally maintaining it at 1,200°C as indicated in Table 5, or raising it once more to 1,370°C or 1,400°C and waiting for 50 hours. During the above heating process, the temperature was raised at a rate of 3°C per minute. At each reaction temperature, the vacuum (pressure) was maintained at 10, 100, 1,000, or 10,000 Pa. It was confirmed that the deposition rate was approximately 60% or higher under vacuum conditions of 1,000 Pa or less and reaction temperature conditions of 1,200 to 1,400°C.

[0132] Although the experimental groups, examples, and comparative examples of this specification have been described in more detail with reference to the attached drawings, this specification is not necessarily limited to these experimental groups, examples, and comparative examples, and may be modified in various ways within the scope of the technical concept of this specification. Accordingly, the experimental groups, examples, and comparative examples disclosed in this specification are intended to explain, not limit, the technical concept of this specification, and the scope of the technical concept of this specification is not limited by these examples. Therefore, the experimental groups, examples, and comparative examples described above should be understood as illustrative in all respects and not restrictive. The scope of protection of this specification shall be interpreted by the claims, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of this specification.

Claims

Claim 1 A method for manufacturing silicon monoxide using waste silicon sludge comprises: (S1) a step of mixing and molding silicon powder and silica sand powder and then drying; (S2) a step of heating under vacuum or an inert atmosphere to first react the oxide film on the surface of the silicon powder with internal metallic silicon to generate silicon monoxide gas, thereby removing the oxide film and obtaining silicon powder from which the oxide film has been removed; and (S3) a step of reacting the silicon powder from which the oxide film has been removed with the silica sand to generate silicon monoxide gas, and depositing the generated silicon monoxide gas to obtain a silicon monoxide deposit; wherein the heating temperature of step (S2) is 1,100℃ to 1,200℃. Claim 2 A method for producing silicon monoxide using waste silicon sludge, characterized in that, in claim 1, the oxygen content of the silicon powder in step (S1) is 10 wt% or less. Claim 3 In claim 1, the silicon powder D in step (S1) above. 50 A method for producing silicon monoxide using waste silicon sludge characterized by having a thickness of 100㎛ or less. Claim 4 A method for producing silicon monoxide using waste silicon sludge, characterized in that, in claim 1, the mixing ratio of silicon powder and silica powder in step (S1) is 30:70 to 40:60 based on the weight ratio (wt%) of silicon powder to silica powder. Claim 5 delete Claim 6 A method for producing silicon monoxide using waste silicon sludge, characterized in that, in claim 1, the reaction of step (S3) is performed at a reaction temperature of 1,200℃ to 1,400℃. Claim 7 A method for producing silicon monoxide using waste silicon sludge according to claim 1, characterized in that the reaction in step (S3) is performed at a vacuum of 1,000 Pa or less. Claim 8 A method for producing silicon monoxide using waste silicon sludge according to claim 1, wherein the deposition rate of the silicon monoxide deposit is 60% or more, the oxygen content of the silicon monoxide deposit is 32 wt% to 38 wt%, the aluminum content of the silicon monoxide deposit is 130 ppm or less based on the total mass ratio of the deposit, and the deposition rate (%) is the ratio of the deposited amount (kg) of the obtained silicon monoxide to the charged amount (kg) of the silicon powder and silica sand powder.

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