Method for preparing industrial silicon powder

Abstract

The invention provides a method for preparing industrial silicon powder, and relates to the technical field of polycrystalline silicon and organic silicon. The method for preparing the industrial silicon powder comprises the steps of silicon water refining treatment, silicon water heating treatment, water atomization treatment, suction filtration, drying treatment and screening. Water atomization is creatively applied to the technical field of industrial silicon powder preparation, an electromagnetic induction heating coil is additionally arranged on the tundish, and meanwhile, the device structure of an atomizing disc for water atomization is improved, so that the industrial silicon powder can be prepared through direct water atomization of silicon liquid; therefore, the method is high in resource utilization rate, low in production cost, short in process, easy to operate, high in efficiency and beneficial to industrial large-scale production and popularization.

Description

Technical Field

[0001] The invention relates to the technical field of polysilicon and organic silicon, and in particular to a method for preparing industrial silicon powder. Background Art

[0002] With the increasingly severe energy crisis and environmental degradation, governments around the world have made the development of new energy a key development direction, especially crystalline silicon solar cells, which will be the most important type of solar cells for a long time to come. Due to the development of crystalline silicon cells, the market demand for the silicon industry chain continues to increase, and the demand for primary silicon products is increasing year by year.

[0003] Industrial silicon, as an essential raw material for the production of polysilicon, silicone and other fields, must go through processes such as smelting in a submerged arc furnace, refining, casting, crushing, and grinding before it can be used as raw material. The process is complicated and the production cost is high. In addition, varying degrees of impurity elements will be introduced during the casting, crushing, and grinding process, increasing the cost of subsequent processing.

[0004] At present, the mainstream production process of industrial silicon powder is industrial silicon smelting, casting, crushing, finishing, and grinding. There are disadvantages such as complicated process, long process, large silicon loss, and large equipment wear, which leads to high production costs. The casting, finishing, and grinding process often bring in some iron elements, resulting in a decline in product quality and affecting the price of silicon powder.

[0005] There are many processes for industrial silicon grinding, including Raymond method, roller method, disc grinding method, whirling method, mechanochemical method, etc., which are mainly physical and mechanical grinding, which has a long process and high cost; and the mechanochemical method is even more so, not only the grinding time is long, but also the cost of chemical washing and deionized water washing is high, and the impurity removal rate of the obtained powder is low, for example: Chinese patent CN105271238A is such. Or it is carried out by whirling method, such as Chinese patent CN106824475A, which first removes the iron in the silicon block after the silicon raw material is crushed by adsorption through the device structure, and then uses the whirling mill for high-speed pulverization. However, this method has technical defects such as long process, serious air pollution of powder, high cost, and low efficiency.

[0006] There are also some methods that obtain silicon powder by selecting smelting raw materials, casting to obtain ingots, hydrolyzing, pulverizing, and drying, such as Chinese patent CN105108172A. However, hydrolysis and pulverization cannot completely remove aluminum and phosphorus, and the prepared silicon powder still has a high impurity content.

[0007] Although silicon powder is prepared by silicon liquid atomization, the prepared silicon powder is not suitable for polysilicon, organic silicon and other fields.

[0008] For example: Chinese patent CN103043665B discloses a method for preparing silicon powder, which first uses high-temperature slag making to purify polysilicon, and after the slag making reaction is completed, removes the slag liquid; then the silicon liquid is atomized by an atomizer to form low-boron silicon powder. However, due to the disadvantages of long cooling time, large atomization equipment, and large investment in the production of silicon powder by gas atomization, it is not suitable for industrial large-scale production of silicon powder, and gas atomization is easy to form spherical or quasi-spherical particles with stable properties, which is not conducive to the subsequent development and utilization of polysilicon and organosilicon companies. Chinese patent CN103043665A also discloses a method for preparing silicon powder by gas atomizing silicon liquid. The particle size of the obtained silicon powder is not dispersed, and most of them are spherical or quasi-spherical. Although the introduction of slag-making agent can remove the impurity boron, it will introduce other impurities.

[0009] Chinese patent CN117023590A discloses a method for preparing industrial silicon powder, wherein the raw material is silicon dioxide powder, which is heated and reduced in a plasma reactor, and the obtained small silicon particles are melted into small silicon droplets, and then these small silicon droplets collide and fuse to obtain large silicon droplets, which are cooled to obtain silicon powder; obviously, the energy consumption is high, and the different particle sizes of the prepared silicon powder are difficult to effectively control, which is not suitable for industrial production.

[0010] Chinese patent CN113023731A discloses a method for preparing silicon powder, which comprises: spray drying mortar; air flow pulverizing the product obtained by spray drying, thereby obtaining silicon powder; it is obvious that the impurity content in the silicon powder is not effectively controlled, and the silicon powder obtained by spray drying is not suitable for processing and utilization of polysilicon and organic silicon;

[0011] In short, in order to simplify the industrial silicon smelting process, improve production efficiency, and further increase the added value of industrial silicon products, a convenient and efficient method for preparing industrial silicon powder is urgently needed. Summary of the invention

[0012] In order to solve the technical problems in the prior art of silicon powder preparation, such as long physical and mechanical grinding process, high cost, low impurity removal rate of powder, non-green process of swirling method, high impurity content of silicon powder, long cooling time, large atomization equipment, large investment, easy formation of spherical or quasi-spherical particles, high energy consumption, and the prepared silicon powder is not suitable for polysilicon and organosilicon; therefore, the embodiment of the present invention provides a method for preparing industrial silicon powder that can synergistically improve the efficiency of the production process, the impurity removal rate of the powder, reduce production costs, energy consumption, and is suitable for polysilicon and organosilicon. The technical scheme is as follows:

[0013] A method for preparing industrial silicon powder, the method for preparing industrial silicon powder comprises the following steps:

[0014] S1. Silicon water refining treatment: Silica is reduced and smelted to obtain high-temperature silicon water in the silicon bag, and then oxygen is continuously blown into the high-temperature silicon water in the silicon bag for refining to obtain silicon water with low aluminum and calcium impurity content;

[0015] S2, tundish heating treatment: Turn on the tundish heating, heat the tundish to a certain temperature and keep it warm to prevent the silicon water from cooling too quickly and blocking the tundish during the atomization process;

[0016] S3, water atomization treatment: turn on the atomizer, slowly pour the silicon water with low aluminum and low calcium impurity content in S1 into the guide groove of the heated tundish in S2, and the silicon water enters the atomization disk through the guide groove. When entering the atomization disk, high-pressure water flow is used to spray the silicon water to atomize it into silicon powder of different particle sizes. The atomized silicon powder enters the cooling water in the atomization tank to obtain silicon powder-containing cooling water;

[0017] S4, filtration and drying treatment: send the silicon powder-containing cooling water in S3 into the filtration tank, and obtain mixed industrial silicon powder after filtration and drying;

[0018] S5, screening: S4 mixed with industrial silicon powder is vibrated and screened to obtain finished industrial silicon powder of different particle sizes.

[0019] Optionally, the grade of silica in S1 is 98%-99.8%, the oxygen flow rate of oxygen blowing refining is 3-30L / min, the aluminum content in the silicon water with low aluminum and calcium impurity content is less than 0.3%, the calcium content is less than 0.2%, and the temperature of the silicon water is maintained at 1550-1750°C.

[0020] Optionally, an electromagnetic induction heating coil is installed in the tundish of the atomizer in S2 to heat the tundish so that the temperature of the tundish is kept at 1000-1500°C to prevent the silicon water flowing through the tundish from cooling too quickly during atomization, causing blockage.

[0021] Optionally, in S3, the flow rate and pressure of atomized water are adjusted to control the silicon powder of different particle sizes, wherein the atomization flow rate is 50-400 L / min and the atomization pressure is 0.5-50 MPa.

[0022] Optionally, the size of the guide groove in S3 is length × width = 200-1000mm × 10-50mm, the atomizing disk has a square structure with a size of 200-1000mm × 200-1000mm, and multiple atomizing nozzles are evenly distributed on both sides, the aperture of the atomizing nozzle is 0.2-8mm, and the nozzle angle is 20°-60°.

[0023] Optionally, in S3, when the size of the guide groove is 200mm×10mm, there are 12 atomizing nozzles, the aperture of the atomizing nozzle is 2mm, the atomizing water flow rate is 180L / min, the atomizing water pressure is 20MPa, and the height of the cooling water is 1m, the particle size of the silicon powder after atomization is 80-400 mesh.

[0024] Optionally, in S3, when the size of the guide groove is 300 mm × 15 mm, the number of atomizing nozzles is 16, the aperture of the atomizing nozzles is 4 mm, the atomizing water flow rate is 240 L / min, the atomizing water pressure is 10 MPa, and the height of the cooling water is 1 m, the particle size of the silicon powder after atomization is 40-320 mesh.

[0025] Optionally, in S3, when the size of the guide groove is 400mm×20mm, there are 20 atomizing nozzles, the aperture of the atomizing nozzle is 6mm, the atomizing water flow rate is 300L / min, the atomizing water pressure is 5MPa, and the height of the cooling water is 1m, the particle size of the silicon powder after atomization is 20-200 mesh.

[0026] Optionally, the filtration in S4 is performed by a vacuum pump, and the filtration time is 0.5-2h; the drying is performed by utilizing the waste heat generated during the industrial silicon smelting process.

[0027] Optionally, the mixed industrial silicon powder in S4 is irregular particles with a particle size of 8-400 mesh and a total impurity content of less than 0.6%; the price of the finished industrial silicon powder of different particle sizes obtained after vibration screening in S5 can be reduced by 5%-20% compared with the industrial silicon powder prepared by the prior art.

[0028] Compared with the prior art, the above technical solution has at least the following beneficial effects:

[0029] The above scheme, the present invention proposes a method for preparing industrial silicon powder, which can solve the technical problems existing in the prior art of silicon powder preparation, such as long physical and mechanical grinding process, high cost, low impurity removal rate of powder, swirling method is not a green process, high impurity content of silicon powder, long cooling time, large atomization equipment, large investment, easy formation of spherical or quasi-spherical particles, high energy consumption, and the prepared silicon powder is not suitable for polysilicon, silicone and the like.

[0030] The present invention reduces the aluminum and calcium impurity contents in silicon materials by oxygen blowing refining instead of adding slag-forming agents, and combines industrial silicon with water atomization technology to reduce the introduction of impurity elements and the increase in their contents; the smelted silicon melt is directly water atomized to powder, which reduces the process of silicon remelting and then water atomization to powder, reduces the cost of remelting, and can be directly applied to the subsequent processes of polysilicon and organic silicon.

[0031] The present invention further increases the atomization flow rate and improves the silicon liquid atomization efficiency by improving the structure of the atomizing disk. The electromagnetic induction heating coil installed in the tundish can heat and keep the tundish warm, ensuring that the entire water atomization process is stable and does not block the tundish, which is beneficial to large-scale industrial batch production.

[0032] The present invention applies water atomization to the field of industrial silicon. By adjusting the pressure and flow rate of water atomization and controlling the particle size of silicon powder, the formed silicon powder has an irregular shape rather than a spherical or quasi-spherical shape, thereby meeting the requirements of different downstream manufacturers, replacing traditional ingot mold casting, manual finishing, mechanical grinding and other steps, improving production efficiency and reducing production costs.

[0033] The high-pressure atomized water of the present invention can be recycled and reused, and the drying step can utilize the waste heat generated in the industrial silicon smelting process for drying, thereby realizing the waste heat reuse and saving costs.

[0034] In the process of industrial silicon smelting, the method of the present invention first utilizes oxygen blowing refining to remove impurities, then atomizes the silicon liquid into silicon powder through the atomization effect of water atomization at the temperature of high-temperature silicon liquid, and finally obtains industrial silicon powder of different particle sizes and shapes through water cooling and screening. The method can realize the process of industrial silicon smelting without ingot mold casting, manual crushing, and mechanical grinding, and directly obtain industrial silicon powder.

[0035] In summary, compared with other traditional methods, the method of the present invention creatively applies water atomization to the technical field of industrial silicon powder preparation, and adds an electromagnetic induction heating coil to the tundish, while improving the device structure of the water atomization atomization disk, so that industrial silicon powder can be prepared by direct water atomization of silicon liquid; therefore, the resource utilization rate is high, the production cost is low, the process is short, the operation is easy, the efficiency is high, and it is conducive to large-scale industrial production and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 It is a schematic diagram of the device structure of a method for preparing industrial silicon powder of the present invention;

[0038] Figure 2 It is a schematic diagram of the structure of an atomizing disk in the device structure of a method for preparing industrial silicon powder of the present invention;

[0039] The following are the descriptions of the reference numerals:

[0040] 1. Electromagnetic induction heating coil; 2. Tundish; 3. Guide groove; 4. Atomizing disk; 5. Atomizing tank; 6. Cooling water; 7. Atomizing nozzle. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0042] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0043] In the embodiments of the present invention, "image" and "picture" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they want to express are the same. "of", "corresponding" and "corresponding" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they want to express are the same.

[0044] In the embodiments of the present invention, sometimes a subscript such as W1 may be written as a non-subscript such as W1. When the difference is not emphasized, the meanings to be expressed are the same.

[0045] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0046] A method for preparing industrial silicon powder, the method for preparing industrial silicon powder is combined with Figure 1 and 2 Follow these steps:

[0047] S1. Silicon water refining treatment: Silica is reduced and smelted to obtain high-temperature silicon water in the silicon bag, and then oxygen is continuously blown into the high-temperature silicon water in the silicon bag for refining to obtain silicon water with low aluminum and calcium impurity content;

[0048] S2, tundish heating treatment: Turn on the tundish heating, heat the tundish to a certain temperature and keep it warm to prevent the silicon water from cooling too quickly and blocking the tundish during the atomization process;

[0049] S3, water atomization treatment: turn on the atomizer, slowly pour the silicon water with low aluminum and low calcium impurity content in S1 into the heated tundish in S2, the silicon water enters the atomization disk 4 through the guide groove 3, and is sprayed with high-pressure water flow when entering the atomization disk to atomize the silicon water into silicon powder of different particle sizes. The atomized silicon powder enters the cooling water 6 in the atomization tank 5 to obtain silicon powder-containing cooling water;

[0050] S4, filtration and drying treatment: send the silicon powder-containing cooling water in S3 into the filtration tank, and obtain mixed industrial silicon powder after filtration and drying;

[0051] S5, screening: S4 mixed with industrial silicon powder is vibrated and screened to obtain finished industrial silicon powder of different particle sizes.

[0052] In particular, the grade of silica in S1 is 98%-99.8%, the oxygen flow rate of oxygen blowing refining is 3-30L / min, the aluminum content in the silicon water with low aluminum and calcium impurities is less than 0.3%, the calcium content is less than 0.2%, and the temperature of the silicon water is maintained at 1550-1750℃.

[0053] In particular, the tundish 2 of the atomizer in S2 is equipped with an electromagnetic induction heating coil 1 to heat the tundish so that the temperature of the tundish is kept at 1000-1500°C to prevent the silicon water flowing through the tundish from cooling too quickly during atomization, causing blockage.

[0054] In particular, in S3, the flow rate and pressure of atomized water are adjusted to control the silicon powder of different particle sizes, wherein the atomization flow rate is 50-400 L / min and the atomization pressure is 0.5-50 MPa.

[0055] In particular, the size of the guide groove 3 in S3 is length × width = 200-1000mm × 10-50mm, the atomizing disk 4 has a square structure with a size of 200-1000mm × 200-1000mm, and multiple atomizing nozzles 7 are evenly distributed on both sides, the aperture of the atomizing nozzle 7 is 0.2-8mm, and the nozzle angle is 20°-60°.

[0056] In particular, in S3, when the size of the guide groove 3 is 200mm×10mm, the number of the atomizing nozzles 7 is 12, the aperture of the atomizing nozzles 7 is 2mm, the atomizing water flow rate is 180L / min, the atomizing water pressure is 20MPa, and the height of the cooling water 6 is 1m, the particle size of the silicon powder after atomization is 80-400 mesh.

[0057] In particular, in S3, when the size of the guide groove 3 is 300 mm × 15 mm, the number of the atomizing nozzles 7 is 16, the aperture of the atomizing nozzles 7 is 4 mm, the atomizing water flow rate is 240 L / min, the atomizing water pressure is 10 MPa, and the height of the cooling water 6 is 1 m, the particle size of the silicon powder after atomization is 40-320 mesh.

[0058] In particular, in S3, when the size of the guide groove 3 is 400mm×20mm, the number of the atomizing nozzles 7 is 20, the aperture of the atomizing nozzles 7 is 6mm, the atomizing water flow rate is 300L / min, the atomizing water pressure is 5MPa, and the height of the cooling water 6 is 1m, the particle size of the silicon powder after atomization is 20-200 mesh.

[0059] In particular, the filtration in S4 is carried out by a vacuum pump, and the filtration time is 0.5-2h; the drying is carried out by utilizing the waste heat generated during the industrial silicon smelting process.

[0060] In particular, the mixed industrial silicon powder in S4 is irregular particles with a particle size of 8-400 mesh and a total impurity content of less than 0.6%; the price of the finished industrial silicon powder of different particle sizes obtained after S5 vibration screening can be reduced by 5%-20% compared with the industrial silicon powder prepared by the prior art.

[0061] Example 1

[0062] A method for preparing industrial silicon powder, the method for preparing industrial silicon powder comprises the following steps:

[0063] S1. Silicon water refining treatment: Silica is reduced and smelted to obtain high-temperature silicon water in the silicon bag. The grade of silica is 98% and the temperature of the high-temperature silicon water is 1600℃. Then, oxygen is continuously blown into the high-temperature silicon water in the silicon bag for refining. The oxygen flow rate of oxygen blowing refining is 15L / min and the refining temperature is 1580℃ to obtain silicon water with low aluminum and calcium impurity content. The aluminum content of the silicon water with low aluminum and calcium impurity content is 0.3%, the calcium content is 0.2%, and the content of other impurities is 0.4%;

[0064] S2, tundish heating treatment: Turn on tundish 2 for heating, and keep tundish 2 at 1200℃ to prevent the silicon water from cooling too quickly and blocking the tundish during the atomization process;

[0065] S3, water atomization treatment: turn on the atomizer, slowly pour the silicon water with low aluminum and low calcium impurity content in S1 into the heated tundish 2 in S2, the silicon water enters the atomizing disk 4 through the guide groove 3, and is sprayed with high-pressure water flow when entering the atomizing disk to atomize the silicon water into silicon powder of different particle sizes, and the atomized silicon powder enters the cooling water in the atomizing tank 5 to obtain silicon powder-containing cooling water 6; wherein: the size of the guide groove is 200mm×10mm, there are 12 atomizing nozzles, the aperture of the atomizing nozzle is 2mm, the atomizing water flow rate is 180L / min, the atomizing water pressure is 20MPa, and the height of the cooling water is 1m, the particle size of the atomized silicon powder is 80-400 mesh; the cooling water in the atomizing tank is cooling circulating water,

[0066] S4, filtration and drying treatment: send the cooling water containing silicon powder in S3 into the filtration tank, filter and dry to obtain mixed industrial silicon powder; wherein: the filtration is carried out by a vacuum pump, and the filtration time is 1h; the drying is carried out by using the waste heat generated during the industrial silicon smelting process;

[0067] S5. Screening: The S4 mixed industrial silicon powder is vibrated and screened to obtain 40% qualified industrial silicon powder; the mixed industrial silicon powder is irregular particles with an average particle size of 50um and an impurity content of less than 0.4%. The price of finished industrial silicon powder of different particle sizes can be reduced by 5% compared with the industrial silicon powder prepared by the prior art.

[0068] Example 2

[0069] A method for preparing industrial silicon powder, the method for preparing industrial silicon powder comprises the following steps:

[0070] S1. Silicon water refining treatment: Silica is reduced and smelted to obtain high-temperature silicon water in the silicon bag. The grade of silica is 99.5%, and the temperature of the high-temperature silicon water is 1620℃. Then, oxygen is continuously blown into the high-temperature silicon water in the silicon bag for refining. The oxygen flow rate of oxygen blowing refining is 12L / min, and the refining temperature is 1600℃ to obtain silicon water with low aluminum and calcium impurity content. The aluminum content of the silicon water with low aluminum and calcium impurity content is 0.2%, the calcium content is 0.2%, and the content of other impurities is 0.3%;

[0071] S2, tundish heating treatment: Turn on tundish 2 for heating, and keep the tundish at 1200℃ to prevent the silicon water from cooling too quickly and blocking the tundish during the atomization process;

[0072] S3, water atomization treatment: turn on the atomizer, slowly pour the silicon water with low aluminum and low calcium impurity content in S1 into the heated tundish in S2, the silicon water enters the atomizing disk 4 through the guide groove 3, and is sprayed with high-pressure water flow when entering the atomizing disk 4 to atomize the silicon water into silicon powder of different particle sizes, and the atomized silicon powder enters the cooling water in the atomizing tank 5 to obtain silicon powder-containing cooling water 6; wherein: the size of the guide groove is 300mm×15mm, the number of atomizing nozzles 7 is 16, the aperture of the atomizing nozzle is 4mm, the atomizing water flow rate is 240L / min, the atomizing water pressure is 10MPa, and the height of the cooling water is 1m, the particle size of the silicon powder after atomization is 40-320 mesh; the cooling water in the atomizing tank is normal temperature cooling circulating water.

[0073] S4, filtration and drying treatment: send the cooling water containing silicon powder in S3 into the filtration tank, filter and dry to obtain mixed industrial silicon powder; wherein: the filtration is carried out by a vacuum pump, and the filtration time is 1h; the drying is carried out by using the waste heat generated during the industrial silicon smelting process;

[0074] S5. Screening: The S4 mixed industrial silicon powder is vibrated and screened to obtain 50% qualified industrial silicon powder; the mixed industrial silicon powder is irregular particles with an average particle size of 70um and an impurity content of 0.35%; the price of finished industrial silicon powder of different particle sizes can be reduced by 10% compared with the industrial silicon powder prepared by the existing technology.

[0075] Example 3

[0076] A method for preparing industrial silicon powder, the method for preparing industrial silicon powder comprises the following steps:

[0077] S1. Silicon water refining treatment: Silica is reduced and smelted to obtain high-temperature silicon water in the silicon bag. The grade of silica is 99.8%, and the temperature of the high-temperature silicon water is 1650℃. Then, oxygen is continuously blown into the high-temperature silicon water in the silicon bag for refining. The oxygen flow rate of oxygen blowing refining is 8L / min, and the refining temperature is 1620℃ to obtain silicon water with low aluminum and calcium impurity content. The aluminum content of the silicon water with low aluminum and calcium impurity content is 0.15%, the calcium content is 0.1%, and the content of other impurities is 0.2%;

[0078] S2, tundish heating treatment: Turn on tundish 2 for heating, and keep the tundish at 1150°C to prevent the silicon water from cooling too quickly and blocking the tundish during the atomization process;

[0079] S3, water atomization treatment: turn on the atomizer, slowly pour the silicon water with low aluminum and low calcium impurity content in S1 into the heated tundish in S2, the silicon water enters the atomizing disk 4 through the guide groove 3, and uses high-pressure water jet when entering the atomizing disk to atomize the silicon water into silicon powder of different particle sizes, and the atomized silicon powder enters the cooling water 6 in the atomizing tank 5 to obtain silicon powder-containing cooling water; wherein: the guide groove size is 400mm×20mm, the number of atomizing nozzles 7 is 20, the aperture of the atomizing nozzle is 6mm, the atomizing water flow rate is 300L / min, the atomizing water pressure is 5MPa, and the height of the cooling water is 1m, the particle size of the atomized silicon powder is 20-200 mesh. The cooling water in the atomizing tank is cooling circulating water,

[0080] S4, filtration and drying treatment: send the cooling water containing silicon powder in S3 into the filtration tank, filter and dry to obtain mixed industrial silicon powder; wherein: the filtration is carried out by a vacuum pump, and the filtration time is 0.5h; the drying is carried out by using the waste heat generated during the industrial silicon smelting process;

[0081] S5. Screening: The S4 mixed industrial silicon powder is vibrated and screened to obtain 70% finished industrial silicon powder; the mixed industrial silicon powder is irregular particles with an average particle size of 89um and an impurity content of 0.3%; the price of finished industrial silicon powder of different particle sizes can be reduced by 12% compared with industrial silicon powder prepared by existing technology.

[0082] Example 4

[0083] A method for preparing industrial silicon powder, the method for preparing industrial silicon powder comprises the following steps:

[0084] S1. Silicon water refining treatment: Silica is reduced and smelted to obtain high-temperature silicon water in the silicon bag. The grade of silica is 99.8%, and the temperature of the high-temperature silicon water is 1650℃. Then, oxygen is continuously blown into the high-temperature silicon water in the silicon bag for refining. The oxygen flow rate of oxygen blowing refining is 8L / min, and the refining temperature is 1630℃ to obtain silicon water with low aluminum and calcium impurity content. The aluminum content of the silicon water with low aluminum and calcium impurity content is 0.15%, the calcium content is 0.1%, and the content of other impurities is 0.2%;

[0085] S2, tundish heating treatment: Turn on tundish 2 for heating, and keep the tundish at 1200℃ to prevent the silicon water from cooling too quickly and blocking the tundish during the atomization process;

[0086] S3, water atomization treatment: turn on the atomizer, slowly pour the silicon water with low aluminum and low calcium impurity content in S1 into the heated tundish 2 in S2, the silicon water enters the atomizing disk 4 through the guide groove 3, and is sprayed with high-pressure water flow when entering the atomizing disk to atomize the silicon water into silicon powder of different particle sizes, and the atomized silicon powder enters the cooling water 6 in the atomizing tank 5 to obtain silicon powder-containing cooling water 6; wherein: the size of the guide groove is 400mm×20mm, the number of atomizing nozzles 7 is 20, the aperture of the atomizing nozzle is 8mm, the atomizing water flow rate is 360L / min, the atomizing water pressure is 3MPa, and the height of the cooling water is 1m, the particle size of the silicon powder after atomization is 20-160 mesh; the cooling water in the atomizing tank is cooling circulating water

[0087] S4, filtration and drying treatment: send the cooling water containing silicon powder in S3 into the filtration tank, filter and dry to obtain mixed industrial silicon powder; wherein: the filtration is carried out by a vacuum pump, and the filtration time is 0.5h; the drying is carried out by using the waste heat generated during the industrial silicon smelting process;

[0088] S5. Screening: The S4 mixed industrial silicon powder is vibrated and screened to obtain 85% qualified industrial silicon powder; the mixed industrial silicon powder is irregular particles with an average particle size of 120um and an impurity content of 0.3%; the price of finished industrial silicon powder of different particle sizes can be reduced by 15% compared with the industrial silicon powder prepared by the existing technology.

[0089] Example 5

[0090] A method for preparing industrial silicon powder, the method for preparing industrial silicon powder comprises the following steps:

[0091] S1. Silicon water refining treatment: Silica is reduced and smelted to obtain high-temperature silicon water in the silicon bag. The grade of silica is 99.8%, and the temperature of the high-temperature silicon water is 1650℃. Then, oxygen is continuously blown into the high-temperature silicon water in the silicon bag for refining. The oxygen flow rate of oxygen blowing refining is 10L / min, and the refining temperature is 1620℃ to obtain silicon water with low aluminum and calcium impurity content. The aluminum content of the silicon water with low aluminum and calcium impurity content is 0.1%, the calcium content is 0.1%, and the content of other impurities is 0.2%;

[0092] S2, tundish heating treatment: Turn on tundish 2 for heating, and keep the tundish at 1200℃ to prevent the silicon water from cooling too quickly and blocking the tundish during the atomization process;

[0093] S3, water atomization treatment: turn on the atomizer, slowly pour the silicon water with low aluminum and low calcium impurity content in S1 into the heated tundish in S2, the silicon water enters the atomizing disk 4 through the guide groove 3, and is sprayed with high-pressure water flow when entering the atomizing disk 4 to atomize the silicon water into silicon powder of different particle sizes, and the atomized silicon powder enters the cooling water in the atomizing tank to obtain silicon powder-containing cooling water; wherein: the size of the guide groove is 400mm×20mm, the number of atomizing nozzles 7 is 20, the aperture of the atomizing nozzle 7 is 8mm, the atomizing water flow rate is 240L / min, the atomizing water pressure is 1MPa, and the height of the cooling water is 1m, the particle size of the atomized silicon powder is 8-120 mesh; the cooling water in the atomizing tank is cooling circulating water,

[0094] S4, filtration and drying treatment: send the cooling water containing silicon powder in S3 into the filtration tank, filter and dry to obtain mixed industrial silicon powder; wherein: the filtration is carried out by a vacuum pump, and the filtration time is 20 minutes; the drying is carried out by using the waste heat generated during the industrial silicon smelting process;

[0095] S5. Screening: The S4 mixed industrial silicon powder is vibrated and screened to obtain 95% qualified industrial silicon powder; the mixed industrial silicon powder is irregular particles with an average particle size of 150um and an impurity content of 0.4%; the price of finished industrial silicon powder of different particle sizes can be reduced by 20% compared with the industrial silicon powder prepared by the existing technology.

[0096] Comparative Example 1

[0097] After reduction smelting, silica is used to obtain high-temperature silicon water in the silicon bag. The grade of silica is 99.8%, and the temperature of the high-temperature silicon water is 1650℃. Then, oxygen is continuously blown into the high-temperature silicon water in the silicon bag for refining. The oxygen flow rate of oxygen blowing refining is 8L / min, and the refining temperature is 1630℃ to obtain silicon water with low aluminum and calcium impurity content. The aluminum content of silicon water with low aluminum and calcium impurity content is 0.2%, the calcium content is 0.1%, and the content of other impurities is 0.2%. The impurity content increases by 0.1% after ingot mold casting and manual finishing. Mechanical grinding increases other impurity elements by 0.2%, and 10% of unqualified fine powder below 200 mesh is produced during mechanical grinding.

[0098] In summary, by comparing the embodiment with the comparative example, it can be found that the atomized silicon powder process of the embodiment basically does not introduce impurities, the obtained silicon powder has higher purity, and the production process is shortened. The silicon powder yield in the production process is high, which can reach 95%, saving 5-20% of the production cost; the comparative example undergoes traditional casting, finishing, and grinding processes, and the process flow is long, the silicon powder loss is large, the loss rate is about 10%, and 0.3% impurity elements are introduced, especially the iron element is increased a lot, which has a greater impact on subsequent downstream production.

[0099] The above scheme, the present invention proposes a method for preparing industrial silicon powder, which can solve the technical problems existing in the prior art of silicon powder preparation, such as long physical and mechanical grinding process, high cost, low impurity removal rate of powder, swirling method is not a green process, high impurity content of silicon powder, long cooling time, large atomization equipment, large investment, easy formation of spherical or quasi-spherical particles, high energy consumption, and the prepared silicon powder is not suitable for polysilicon, silicone and the like.

[0100] The present invention reduces the aluminum and calcium impurity contents in silicon materials by oxygen blowing refining instead of adding slag-forming agents, and combines industrial silicon with water atomization technology to reduce the introduction of impurity elements and the increase in their contents; the smelted silicon melt is directly water atomized to powder, which reduces the process of silicon remelting and then water atomization to powder, reduces the cost of remelting, and can be directly applied to the subsequent processes of polysilicon and organic silicon.

[0101] The present invention further increases the atomization flow rate and improves the silicon liquid atomization efficiency by improving the structure of the atomizing disk. The electromagnetic induction heating coil installed in the tundish can heat and keep the tundish warm, ensuring that the entire water atomization process is stable and does not block the tundish, which is beneficial to large-scale industrial batch production.

[0102] The present invention applies water atomization to the field of industrial silicon. By adjusting the pressure and flow rate of water atomization and controlling the particle size of silicon powder, the formed silicon powder has an irregular shape rather than a spherical or quasi-spherical shape, thereby meeting the requirements of different downstream manufacturers, replacing traditional ingot mold casting, manual finishing, mechanical grinding and other steps, improving production efficiency and reducing production costs.

[0103] The high-pressure atomized water of the present invention can be recycled and reused, and the drying step can utilize the waste heat generated in the industrial silicon smelting process for drying, thereby realizing the waste heat reuse and saving costs.

[0104] In the process of industrial silicon smelting, the method of the present invention first utilizes oxygen blowing refining to remove impurities, then atomizes the silicon liquid into silicon powder through the atomization effect of water atomization at the temperature of high-temperature silicon liquid, and finally obtains industrial silicon powder of different particle sizes and shapes through water cooling and screening. The method can realize the process of industrial silicon smelting without ingot mold casting, manual crushing, and mechanical grinding, and directly obtain industrial silicon powder.

[0105] In summary, compared with other traditional methods, the method of the present invention creatively applies water atomization to the technical field of industrial silicon powder preparation, and adds an electromagnetic induction heating coil to the tundish, while improving the device structure of the water atomization atomization disk, so that industrial silicon powder can be prepared by direct water atomization of silicon liquid; therefore, the resource utilization rate is high, the production cost is low, the process is short, the operation is easy, the efficiency is high, and it is conducive to large-scale industrial production and promotion.

[0106] It should be understood that the term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship, but it may also indicate an "and / or" relationship. Please refer to the context for specific understanding.

[0107] In the present invention, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, or c can be represented by: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0108] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0109] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing industrial silicon powder, characterized in that: The method for preparing the industrial silicon powder comprises the following steps: S1. Silicon water refining treatment: Silica is reduced and smelted to obtain high-temperature silicon water in the silicon bag, and then oxygen is continuously blown into the high-temperature silicon water in the silicon bag for refining to obtain silicon water with low aluminum and calcium impurity content; S2, tundish heating treatment: Turn on the tundish heating, heat the tundish to a certain temperature and keep it warm to prevent the silicon water from cooling too quickly and blocking the tundish during the atomization process; S3, water atomization treatment: turn on the atomizer, slowly pour the silicon water with low aluminum and low calcium impurity content in S1 into the guide groove of the heated tundish in S2, and the silicon water enters the atomization disk through the guide groove. When entering the atomization disk, high-pressure water flow is used to spray the silicon water to atomize it into silicon powder of different particle sizes. The atomized silicon powder enters the cooling water in the atomization tank to obtain silicon powder-containing cooling water; S4, filtration and drying treatment: send the silicon powder-containing cooling water in S3 into the filtration tank, and obtain mixed industrial silicon powder after filtration and drying; S5, screening: S4 mixed with industrial silicon powder is vibrated and screened to obtain finished industrial silicon powder of different particle sizes.

2. The method for preparing industrial silicon powder according to claim 1, characterized in that: The grade of silica in S1 is 98%-99.8%, the oxygen flow rate of oxygen blowing refining is 3-30L / min, the aluminum content in the silicon water with low aluminum and calcium impurities is less than 0.3%, the calcium content is less than 0.2%, and the temperature of the silicon water is maintained at 1550-1750℃.

3. The method for preparing industrial silicon powder according to claim 1, characterized in that: An electromagnetic induction heating coil is installed in the tundish of the atomizer in S2 to heat the tundish so that the temperature of the tundish is kept at 1000-1500℃ to prevent the silicon water from cooling too quickly when flowing through the tundish during atomization, causing blockage.

4. The method for preparing industrial silicon powder according to claim 1, characterized in that: In S3, the flow rate and pressure of atomized water are adjusted to control the silicon powder of different particle sizes, wherein the atomization flow rate is 50-400 L / min and the atomization pressure is 0.5-50 MPa.

5. The method for preparing industrial silicon powder according to claim 1, characterized in that: The size of the guide groove in S3 is length × width = 200-1000mm × 10-50mm, the structure of the atomizing disk is square, the size is 200-1000mm × 200-1000mm, and multiple atomizing nozzles are evenly distributed on both sides. The aperture of the atomizing nozzle is 0.2-8mm, and the nozzle angle is 20°-60°.

6. The method for preparing industrial silicon powder according to claim 5, characterized in that: In S3, when the size of the guide groove is 200mm×10mm, there are 12 atomizing nozzles, the aperture of the atomizing nozzle is 2mm, the atomizing water flow rate is 180L / min, the atomizing water pressure is 20MPa, and the height of the cooling water is 1m, the particle size of the silicon powder after atomization is 80-400 mesh.

7. The method for preparing industrial silicon powder according to claim 5, characterized in that: In S3, when the size of the guide groove is 300mm×15mm, there are 16 atomizing nozzles, the aperture of the atomizing nozzle is 4mm, the atomizing water flow rate is 240L / min, the atomizing water pressure is 10MPa, and the height of the cooling water is 1m, the particle size of the silicon powder after atomization is 40-320 mesh.

8. The method for preparing industrial silicon powder according to claim 5, characterized in that: In S3, when the size of the guide groove is 400mm×20mm, there are 20 atomizing nozzles, the aperture of the atomizing nozzle is 6mm, the atomizing water flow rate is 300L / min, the atomizing water pressure is 5MPa, and the height of the cooling water is 1m, the particle size of the silicon powder after atomization is 20-200 mesh.

9. The method for preparing industrial silicon powder according to claim 1, characterized in that: The filtration in S4 is carried out by a vacuum pump, and the filtration time is 0.5-2h; the drying is carried out by utilizing the waste heat generated during the industrial silicon smelting process.

10. The method for preparing industrial silicon powder according to claim 1, characterized in that: The mixed industrial silicon powder in S4 is irregular particles with a particle size of 8-400 mesh and a total impurity content of less than 0.6%; the price of the finished industrial silicon powder of different particle sizes obtained after S5 vibration screening can be reduced by 5%-20% compared with the industrial silicon powder prepared by the existing technology.

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