Method for purifying silicon powder and purified silicon

Abstract

The invention belongs to the technical field of silicon powder purification, and particularly relates to a silicon powder purification method and purified silicon. The purification method comprises the following steps: (1) mixing silicon powder and a treating agent to obtain a mixture; wherein the treating agent comprises a pickling solution, a dispersing agent and a defoaming agent; (2) stirring the mixture, and separating to obtain purified silicon; wherein the stirring is eccentric stirring. According to the purification method, multi-step acid leaching treatment is not needed, heating is not needed, the process is simple, the cost is low, safety and environment friendliness are achieved, leaching liquid can be recycled, and excessive washing waste liquid cannot be generated; and in addition, most impurities such as Fe, Al, Ca and Ti in the silicon powder can be removed, and the final purity can reach 4N or above from 95%.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon powder purification, and in particular relates to a silicon powder purification method and purified silicon. Background Art

[0002] Crystalline silicon is the basic material for solar cells due to its high stable efficiency, low environmental load and long-lasting performance. The traditional Siemens method for producing polysilicon for solar cells has already encountered problems such as shortage of raw material supply. At the same time, due to the large investment, high production cost and poor safety performance of this technical route, new methods for producing solar-grade polysilicon have been studied at home and abroad.

[0003] For example, Sun Dongya and others invented a method for primary purification of solar-grade silicon materials, which includes: using hydrometallurgical technology, using special metallic silicon as raw material, crushing and grinding, screening out a certain size range as raw silicon powder, and performing three consecutive pickling operations according to different acid combinations and sequences; stirring is maintained during the pickling process, filtering and rinsing with pure water until neutral after pickling, and then drying; for another example, Ma Wenhui and others invented a method for pressurized purification of metallic silicon, which includes: mixing metallic silicon with a purity greater than 98% with a silicon powder; Silicon, sulfuric acid or hydrochloric acid or nitric acid are mixed at a liquid-solid ratio of 0.5:1-20:1 and then pressurized for purification. The temperature of the pressurized purification process is 70℃-350℃, the pressure is 0.1MPa-25MPa, the stirring speed is 250r / min-1200r / min, and the processing time is 0.2h-24h; the silicon material after pressurized purification is finally further treated with hydrofluoric acid with a concentration of 0.5mol / L-8mol / L to obtain high-purity silicon of more than 99.99%. However, the first method mentioned above requires multiple acid washings, complicated steps, and more acid waste; the second method requires a certain temperature and pressure, is more expensive, and heating and pressurization will bring safety issues.

[0004] Therefore, a low-cost, high-efficiency, and environmentally friendly method for purifying metallic silicon is needed. Summary of the invention

[0005] The present invention finds that in the process of pickling for purifying silicon powder (obtained by crushing metallic silicon), most of the impurities such as Fe, Al, Ca, Ti, etc. in the silicon powder can be removed by adopting eccentric stirring. This method does not require multi-step acid leaching treatment, heating and pressurization, and the process is simple; and the final purity can reach above 4N from 95%.

[0006] In order to achieve the above object, the present invention can adopt the following technical solutions:

[0007] On one hand, the present invention provides a method for purifying silicon powder, which comprises: (1) mixing silicon powder with a treatment agent to obtain a mixture; wherein the treatment agent comprises a pickling solution, a dispersant and a defoaming agent; (2) stirring the mixture to separate and obtain purified silicon; wherein the stirring is eccentric stirring.

[0008] Preferably, the purification method can meet one or more of the following conditions: (a) the eccentricity of the eccentric stirring is ...; (b) the rotation speed of the eccentric stirring is 10rpm-400rpm; (c) ultrasonic treatment is performed while stirring.

[0009] Preferably, the ultrasonic treatment in the above purification method satisfies one or more of the following conditions: (a) the ultrasonic power is 100W-400W; (b) the ultrasonic treatment time is 1h-24h.

[0010] More preferably, the ultrasonic treatment in the above purification method satisfies one or more of the following conditions: (a) the ultrasonic power is 200W-300W; (b) the ultrasonic treatment time is 8h-16h.

[0011] Preferably, the above purification method can also meet one or more of the following conditions: (a) the mesh size of the silicon powder is 80-200 mesh; (b) the pickling solution is selected from one or more combinations of hydrochloric acid or hydrofluoric acid; (c) the dispersant is selected from one or more combinations of polyester type, polyether type or acrylate; (d) the defoaming agent is selected from one or more combinations of silicone or polyether; (e) the solid-liquid ratio in the mixture is (1:2)-(1:10).

[0012] Preferably, the above purification method satisfies one or more of the following conditions: (a) the mass fraction of hydrochloric acid is 2%-8%, and the mass fraction of hydrofluoric acid is 1%-5%; (b) the mass fraction of the dispersant is 0.1%-3%; (c) the mass fraction of the defoaming agent is 0.5%-5%.

[0013] More preferably, the above purification method satisfies one or more of the following conditions: (a) the mass fraction of hydrochloric acid is 3%-5%, and the mass fraction of hydrofluoric acid is 2%-4%; (b) the mass fraction of the dispersant is 0.2%-0.5%; (c) the mass fraction of the defoaming agent is 1%-2%.

[0014] More preferably, the above purification method satisfies the following conditions: the pickling solution is hydrochloric acid and hydrofluoric acid, the mass fraction of hydrochloric acid is 6%, and the mass fraction of hydrofluoric acid is 3%.

[0015] More preferably, the above purification method satisfies the following conditions: the dispersant is polyether with a mass fraction of 0.5%-0.7%; the defoamer is polyether with a mass fraction of 1%-1.2%; and the solid-liquid ratio in the mixture is (1:3)-(1:4).

[0016] In another aspect, the present invention provides silicon purified by the purification method of the present invention.

[0017] The beneficial effects of the present invention include at least: the silicon powder purification method provided by the present invention does not require multi-step acid leaching treatment, heating and pressurization, has a simple process, low cost, safety and environmental protection, and the leachate can be recycled and reused, and does not generate excessive water washing waste liquid; and most of the impurities such as Fe, Al, Ca, Ti in the silicon powder can be removed, and the final purity can reach more than 4N from 95%. DETAILED DESCRIPTION

[0018] The examples are provided to better illustrate the present invention, but the present invention is not limited to the examples. Therefore, those skilled in the art may make non-essential improvements and adjustments to the implementation scheme according to the above invention content, which still fall within the protection scope of the present invention.

[0019] The terms used herein are only used to describe specific embodiments and are not intended to limit the present disclosure. Unless the context has a significantly different meaning, expressions in the singular include expressions in the plural. As used herein, it should be understood that terms such as "include", "have", "include" are intended to indicate the presence of features, numbers, operations, materials, or combinations. The terms of the present invention are disclosed in the specification, and are not intended to exclude the possibility that one or more other features, numbers, operations, materials, or combinations thereof may exist or may be added. As used herein, " / " may be interpreted as "and" or "or", depending on the circumstances.

[0020] An embodiment of the present invention provides a method for purifying silicon powder, which comprises: (1) mixing silicon powder with a treatment agent to obtain a mixture; wherein the treatment agent comprises a pickling solution, a dispersant and a defoaming agent; (2) stirring the mixture to separate and obtain purified silicon; wherein the stirring is eccentric stirring.

[0021] It should be noted that the present invention has found that using an eccentric stirring device for stirring during the pickling process can remove most of the impurities such as Fe, Al, Ca, Ti, etc. in the silicon powder, and its removal effect is significantly better than the existing centrifugal stirring and mechanical stirring methods.

[0022] It should also be noted that water can be selectively added to the treatment agent in the above-mentioned method to control the mass fraction of the pickling solution, dispersant and defoaming agent in the mixture and the solid-liquid ratio to ensure that the silicon powder can react more fully; of course, it should be understood that if the solid-liquid ratio meets certain requirements, water does not need to be added.

[0023] In some specific examples, the above purification method may meet one or more of the following conditions:

[0024] (a) The eccentricity of the eccentric stirring is 6.67%-20%; for example, 7.23%, 8.25%, 13.33%, 15% or 18%; specifically, the eccentricity of the eccentric stirring in the present invention has an influence on the purification effect; in addition, the calculation formula of the eccentricity is: =E / R, the ratio of the distance E of the stirring shaft away from the center of the tank body to the radius R of the stirring tank;

[0025] (b) the speed of eccentric stirring is 10rpm-400rpm, such as 30rpm-350rpm, 50rpm-380rpm, 80rpm-300rpm, 120rpm-250rpm or 150rpm-250rpm; or 70rpm, 90rpm, 130rpm, 190rpm, 230rpm, 270rpm or 320rpm, etc.; preferably 50rpm-200rpm, such as 80rpm, 110rpm, 150rpm or 180rpm, etc., the purification effect at this speed is better;

[0026] (c) performing ultrasonic treatment while stirring; specifically, performing ultrasonic treatment while stirring during pickling can further reduce the content of impurities such as Fe, Al, Ca, and Ti; wherein ultrasonic treatment is an operation means known in the art and can be treated using a conventional ultrasonic instrument; in addition, the power of the ultrasonic treatment can preferably be 100W-400W, such as 200W, 250W or 300W, etc.; more preferably 200W-300W, such as 220W, 260W or 280W, etc.; in addition, the ultrasonic treatment time can preferably be 1h-24h, such as 5h, 10h, 15h or 20h, etc., more preferably 8h-16h, such as 9h, 13h, or 14h, etc.

[0027] It should be noted that in the above purification method, any one of conditions (a) to condition (c) may be satisfied, or two or more conditions may be satisfied at the same time. It is preferred that the above conditions (a) to condition (c) are satisfied at the same time, and more preferably, the optimal conditions among the above conditions (a) to condition (c) are satisfied at the same time.

[0028] In some specific examples, the above purification method may also meet one or more of the following conditions:

[0029] (a1) The mesh size of the silicon powder is 80-200 meshes. Specifically, in the present invention, if the mesh size of the silicon powder is too small, the silicon powder is too fine and is easily lost; if the mesh size is too large, the reaction area is too small, which is not conducive to the reaction. In addition, the silicon powder can be obtained by crushing metallic silicon.

[0030] (b1) The pickling solution is selected from one or more combinations of hydrochloric acid or hydrofluoric acid; specifically, the pickling solution in the present invention is all pickling solutions used for purifying silicon powder, among which hydrochloric acid or hydrofluoric acid is a commonly used pickling solution, and one or more combinations of hydrochloric acid or hydrofluoric acid are also preferably selected in the present invention, which has a better purification effect;

[0031] In addition, the mass fraction of hydrochloric acid in the pickling solution can be 2%-8%, such as 4%, 6% or 7%, and the mass fraction of hydrofluoric acid can be 1%-5%, such as 2%, 3% or 4%, etc.; more preferably, the mass fraction of hydrochloric acid can be 3%-6%, such as 4%, and the mass fraction of hydrofluoric acid can be 2%-4%, such as 3%; more preferably, the mass fraction of hydrochloric acid can be 6%, and the mass fraction of hydrofluoric acid can be 3%; the pickling effect of the pickling solution of this ratio is better; in addition, it should be understood that hydrochloric acid and hydrofluoric acid can be hydrochloric acid and hydrofluoric acid of any mass concentration diluted to obtain hydrochloric acid with a mass fraction of 2%-8% and hydrofluoric acid with a mass fraction of 1%-5%; for example, the hydrofluoric acid in the present invention is obtained by diluting hydrofluoric acid with a mass fraction of 40%; the hydrochloric acid in the present invention can be obtained by diluting hydrochloric acid with a mass fraction of 36%-38%; in addition, the mass fraction of 2%-8% is the mass fraction of hydrochloric acid in the pickling solution, and similarly, the mass fraction of 1%-5% is the mass fraction of hydrofluoric acid in the pickling solution;

[0032] (c1) the dispersant is selected from one or more combinations of polyester, polyether or acrylate; specifically, the dispersant in the present invention can be all dispersants known in the art, preferably one or more combinations of polyester, polyether or acrylate, which have better dispersion effect and thus better purification effect in the present invention; wherein polyester, polyether and acrylate belong to conventional concepts in the art, for example, polyester can include polyethylene terephthalate, polybutylene terephthalate, polycarbonate, unsaturated polyester resin or polylactic acid; polyether can include polyethylene glycol, polypropylene glycol, polyether polyol or polyether amine; acrylate can include methyl methacrylate, methyl ethyl acrylate, butyl acrylate, ethyl acrylate or 2-ethylhexyl acrylate;

[0033] In addition, the mass fraction of the dispersant can be 0.1%-3%, such as 0.5%, 1%, 1.5%, 2% or 2.5, etc.; more preferably 0.2%-0.5%, such as 0.3%, 0.35% or 0.4%, etc.; the preferred mass fraction has a better dispersing effect, can make the reaction proceed better, and improve the purification efficiency;

[0034] (d1) the defoamer is selected from one or more combinations of silicone or polyether; specifically, the defoamer in the present invention can be selected from defoamers known in the art, preferably one or more combinations of silicone or polyether; wherein the silicone defoamer can include silicone oil defoamer, diatomaceous earth defoamer, polysiloxane defoamer or polydimethylsiloxane defoamer, etc.; the polyether type can include polyethylene glycol, polypropylene glycol, polyether polyol or polyether amine, etc.; the acrylate can include methyl methacrylate, methyl ethyl acrylate, butyl acrylate, ethyl acrylate or 2-ethylhexyl acrylate, etc.;

[0035] In addition, the mass fraction of the defoaming agent is 0.5%-5%, such as 1%, 2%, 3% or 4%, etc.; more preferably 1%-2%, such as 1.2%, 1.5%, 1.7% or 1.9%, etc.; the effect of the preferred mass fraction is better than other mass fractions, and the purification effect is better.

[0036] (e1) The solid-liquid ratio in the mixture is (1:2)-(1:10); specifically, as mentioned above, the solid-liquid ratio in the mixture will affect the acidification effect of the silicon powder, and then affect the purification effect. In the present invention, the solid-liquid ratio can be (1:2)-(1:10), such as 1:4, 1:6, 1:8 or 1:9, etc., and preferably (1:3)-(1:4), such as 1:3 and 1:4, which have a better purification effect.

[0037] It should be noted that in the above purification method, conditions (a1) to (e1) may satisfy any one of the conditions, or may satisfy two or more conditions at the same time. Preferably, the above conditions (a1) to (e1) are satisfied at the same time, and more preferably, the optimal conditions among the above conditions (a1) to (e1) are satisfied at the same time. For example, the above purification method satisfies the following conditions: the mesh size of the silicon powder is 80-200 mesh; the pickling solution is hydrochloric acid and hydrofluoric acid, the mass fraction of hydrochloric acid is 6%, and the mass fraction of hydrofluoric acid is 3%; the dispersant is polyether, the mass fraction is 0.5%-0.7%; the defoaming agent is polyether, the mass fraction is 1%-1.2%; the solid-liquid ratio in the mixture is (1:3)-(1:4).

[0038] It should also be noted that the conditions of the purification method in the present invention can meet any one of the above conditions (a) to (c) and (a1) to (e1), preferably meet two or more of the above conditions at the same time, more preferably meet all of the above conditions, and even more preferably, meet the most preferred condition of all of the above conditions at the same time; for example, the purification method in the present invention meets the following conditions: the eccentricity of the eccentric stirring is 13.3%, and the rotation speed is 60rpm; ultrasonic treatment is carried out while stirring, the power of the ultrasonic treatment is 250W, and the treatment time is 12h; the silicon powder is 80-200 mesh silicon powder; the pickling solution includes hydrochloric acid and hydrofluoric acid, the mass fraction of hydrochloric acid is 6%, and the mass fraction of hydrofluoric acid is 3%; the dispersant is a polyester dispersant with a mass fraction of 0.7%; the defoamer is a polyether defoamer; the solid-liquid ratio is 1:3; the purity of the silicon purified under these conditions is better than that of the silicon purified under other conditions, and its purity can reach more than 4N from 95%.

[0039] An embodiment of the present invention also provides silicon purified by the purification method of the present invention.

[0040] It should be noted that the purity of silicon purified by the purification method of the present invention can reach above 4N, and it can be applied in industrial fields such as photovoltaic cell manufacturing, aerospace, shipbuilding or machinery manufacturing.

[0041] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with specific examples, but the content of the present invention is not limited to the following examples.

[0042] 1. Sample preparation

[0043] In the following examples, the contents of impurities Fe, Al, Ca, and Ti in the refined metallic silicon (ICP test (inductively coupled plasma test)) are shown in Table 1 below.

[0044] Table 1 Impurity content of metallic silicon after refining

[0045] Impurities Fe Al Ca Ti Content (ppm) 14339 5053 2079 1301

[0046] Example 1

[0047] (1) Refined metallic silicon is used as raw material, and 80-200 mesh silicon powder is obtained by crushing, mixing and screening;

[0048] (2) mixing silicon powder with 4% HCl, 2% HF, 0.5% polyethylene glycol and 1% polysiloxane, and then adding deionized water to a solid-liquid ratio of 1:3 to obtain a first mixture;

[0049] (3) stirring the first mixed solution by an eccentric stirrer with an eccentricity of 13.3% and a rotation speed of 200 rpm; performing ultrasonic treatment while stirring at an ultrasonic power of 250 W; and treating for 12 hours to obtain a second mixture;

[0050] (4) The second mixture is separated, the leaching solution is recovered, washed with pure water until neutral, and dried at 85° C. to obtain purified silicon powder.

[0051] Example 2

[0052] (1) Refined metallic silicon is used as raw material, and 80-200 mesh silicon powder is obtained by crushing, mixing and screening;

[0053] (2) mixing silicon powder with 4% HCl, 2% HF, 0.5% polyethylene glycol and 1% polysiloxane, and then adding deionized water to a solid-liquid ratio of 1:3 to obtain a first mixture;

[0054] (3) stirring the first mixed solution by an eccentric stirrer at a speed of 200 rpm for 12 h to obtain a second mixture;

[0055] (4) The second mixture is separated, the leaching solution is recovered, washed with pure water until neutral, and dried at 85° C. to obtain purified silicon powder.

[0056] Example 3

[0057] (1) Refined metallic silicon is used as raw material, and 80-200 mesh silicon powder is obtained by crushing, mixing and screening;

[0058] (2) mixing silicon powder with 4% HCl, 2% HF, 0.5% polyethylene glycol and 1% polysiloxane, and then adding deionized water to a solid-liquid ratio of 1:3 to obtain a first mixture;

[0059] (3) stirring the first mixed solution by an eccentric stirrer with an eccentricity of 6.67% and a rotation speed of 200 rpm; performing ultrasonic treatment while stirring at an ultrasonic power of 250 W; and treating for 12 hours to obtain a second mixture;

[0060] (4) The second mixture is separated, the leaching solution is recovered, washed with pure water until neutral, and dried at 85° C. to obtain purified silicon powder.

[0061] Example 4

[0062] (1) Refined metallic silicon is used as raw material, and 80-200 mesh silicon powder is obtained by crushing, mixing and screening;

[0063] (2) mixing silicon powder with 4% HCl, 2% HF, 0.5% polyethylene glycol and 1% polysiloxane, and then adding deionized water to a solid-liquid ratio of 1:3 to obtain a first mixture;

[0064] (3) stirring the first mixed solution by an eccentric stirrer with an eccentricity of 20% and a rotation speed of 200 rpm; performing ultrasonic treatment while stirring at an ultrasonic power of 250 W; and treating for 12 hours to obtain a second mixture;

[0065] (4) The second mixture is separated, the leaching solution is recovered, washed with pure water until neutral, and dried at 85° C. to obtain purified silicon powder.

[0066] Example 5

[0067] (1) Refined metallic silicon is used as raw material, and 80-200 mesh silicon powder is obtained by crushing, mixing and screening;

[0068] (2) mixing silicon powder with 4% HCl, 2% HF, 0.5% polyethylene glycol and 1% polysiloxane, and then adding deionized water to a solid-liquid ratio of 1:3 to obtain a first mixture;

[0069] (3) stirring the first mixed solution by an eccentric stirrer with an eccentricity of 13.3% and a rotation speed of 200 rpm; performing ultrasonic treatment while stirring at an ultrasonic power of 100 W; and treating for 12 hours to obtain a second mixture;

[0070] (4) The second mixture is separated, the leaching solution is recovered, washed with pure water until neutral, and dried at 85° C. to obtain purified silicon powder.

[0071] Example 6

[0072] (1) Refined metallic silicon is used as raw material, and 80-200 mesh silicon powder is obtained by crushing, mixing and screening;

[0073] (2) mixing silicon powder with 4% HCl, 2% HF, 0.5% polyethylene glycol and 1% polysiloxane, and then adding deionized water to a solid-liquid ratio of 1:3 to obtain a first mixture;

[0074] (3) stirring the first mixed solution by an eccentric stirrer with an eccentricity of 13.3% and a rotation speed of 200 rpm; performing ultrasonic treatment while stirring at an ultrasonic power of 400 W; and treating for 12 hours to obtain a second mixture;

[0075] (4) The second mixture is separated, the leaching solution is recovered, washed with pure water until neutral, and dried at 85° C. to obtain purified silicon powder.

[0076] Example 7

[0077] (1) Refined metallic silicon is used as raw material, and 80-200 mesh silicon powder is obtained by crushing, mixing and screening;

[0078] (2) mixing silicon powder with 6% HCl, 3% HF, 0.5% polyether polyol and 1% polysiloxane, and then adding deionized water to a solid-liquid ratio of 1:4 to obtain a first mixture;

[0079] (3) stirring the first mixed solution by an eccentric stirrer at a speed of 60 rpm; performing ultrasonic treatment while stirring at an ultrasonic power of 250 W; treating for 12 h to obtain a second mixture;

[0080] (4) The second mixture is separated, the leaching solution is recovered, washed with pure water until neutral, and dried at 85° C. to obtain purified silicon powder.

[0081] Example 8

[0082] (1) Refined metallic silicon is used as raw material, and 80-200 mesh silicon powder is obtained by crushing, mixing and screening;

[0083] (2) mixing silicon powder with 6% HCl, 3% HF, 0.7% polyether polyol and 1.2% polysiloxane, and then adding deionized water to a solid-liquid ratio of 1:3 to obtain a first mixture;

[0084] (3) stirring the first mixed solution by an eccentric stirrer at a speed of 60 rpm; performing ultrasonic treatment while stirring at an ultrasonic power of 250 W; treating for 12 h to obtain a second mixture;

[0085] (4) The second mixture is separated, the leaching solution is recovered, washed with pure water until neutral, and dried at 85° C. to obtain purified silicon powder.

[0086] Comparative Example 1

[0087] (1) Refined metallic silicon is used as raw material, and 80-200 mesh silicon powder is obtained by crushing, mixing and screening;

[0088] (2) mixing silicon powder with 4% HCl, 2% HF, 0.5% polyether polyol and 1% polysiloxane, and then adding deionized water to a solid-liquid ratio of 1:3 to obtain a first mixture;

[0089] (3) The first mixed solution was stirred by a centrifugal stirrer (Miqi ZQM-4L model) at a speed of 200 rpm; while stirring, ultrasonic treatment was performed at an ultrasonic power of 250 W; the treatment was performed for 12 h to obtain a second mixture;

[0090] (4) The second mixture is separated, the leaching solution is recovered, washed with pure water until neutral, and dried at 85° C. to obtain purified silicon powder.

[0091] Comparative Example 2

[0092] (1) Refined metallic silicon is used as raw material, and 80-200 mesh silicon powder is obtained by crushing, mixing and screening;

[0093] (2) mixing silicon powder with 4% HCl, 2% HF, 0.5% polyether polyol and 1% polysiloxane, and then adding deionized water to a solid-liquid ratio of 1:3 to obtain a first mixture;

[0094] (3) The first mixed solution was stirred by a mechanical stirrer (Lichen LC-OES-120) at a speed of 200 rpm; ultrasonic treatment was performed while stirring at an ultrasonic power of 250 W; the treatment was performed for 12 h to obtain a second mixture;

[0095] (4) The second mixture is separated, the leaching solution is recovered, washed with pure water until neutral, and dried at 85° C. to obtain purified silicon powder.

[0096] Comparative Example 3

[0097] The purity after purification according to the method of the existing patent CN102757050A and the changes in the content of impurities Fe, Al, Ca, and Ti.

[0098] Comparative Example 4

[0099] The purity after purification according to the method of the existing patent CN101293654A and the changes in the content of impurities Fe, Al, Ca, and Ti.

[0100] 2. Sample testing

[0101] By using the ICP test method (the concentration values ​​of 259.94 nm for iron, 309.152 nm for aluminum, 396 nm for calcium and 323 nm for titanium), the contents of impurities Fe, Al, Ca and Ti in the purified silicon powders in Examples 1 to 8 and Comparative Examples 1 to 2 were tested respectively, and the results are shown in Table 2 below.

[0102] Table 2 Impurity content of purified silicon powder in Examples 1 to 8 and Comparative Examples 1 to 2

[0103]

[0104]

[0105] It can be seen from Table 2 that Examples 1 to 8 and Comparative Examples 1 to 2 all reduce the contents of impurities Fe, Al, Ca, and Ti in the refined metallic silicon, among which Example 7 has the best purification effect; in addition:

[0106] By comparing Example 1 with Comparative Example 1, it can be seen that under the same conditions, the purification effect of eccentric stirring (Example 1) is better than that of centrifugal stirring (Comparative Example 1);

[0107] By comparing Example 1 and Comparative Example 2, it can be seen that under the same conditions, the purification effect of eccentric stirring (Example 1) is better than that of mechanical stirring (Comparative Example 2);

[0108] By comparing Example 1 and Example 2, it can be seen that under the same conditions, the purification effect of acid washing + ultrasound (Example 1) is better than that of single acid washing (Example 2);

[0109] By comparing Example 1, Example 3 and Example 4, it can be seen that different eccentricities have an impact on the purification effect; different eccentricities have different purification effects on different impurities;

[0110] By comparing Example 1, Example 5 and Example 6, it can be seen that different ultrasonic powers have an impact on the purification effect; different ultrasonic powers have different purification effects on different impurities;

[0111] Comparing Example 1 with Example 7, the amount of acid, the type of defoaming agent, the solid-liquid ratio and the rotation speed were adjusted, and the purification effect was improved. The purification effect of Example 7 was better than that of Example 1.

[0112] Comparing Example 1 with Example 8, the amount of acid, the type of defoamer, the solid-liquid ratio and the rotation speed were adjusted, and the purification effect was improved. The purification effect of Example 8 was better than that of Example 1.

[0113] Comparing Example 7 and Example 8, Example 8 increases the content of dispersant and defoamer and reduces the solid-liquid ratio compared with Example 7, and its purification effect is slightly lower than that of Example 7;

[0114] By comparing Example 7 with Comparative Example 3, it can be seen that the purity after purification by the method of the existing patent CN102757050A is lower than that of Example 7;

[0115] By comparing Example 7 with Comparative Example 4, it can be seen that the purity after purification by the method of existing patent CN101293654A is lower than that of Example 7.

[0116] In summary, the present invention adopts ultrasound combined with one-step pickling and eccentric stirring to significantly reduce the content of impurities Fe, Al, Ca, and Ti in silicon powder and improve the purity of silicon.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be covered by the scope of the claims of the present invention.

Claims

1. A method for purifying silicon powder, characterized in that: include: (1) mixing silicon powder with a treatment agent to obtain a mixture; wherein the treatment agent includes a pickling liquid, a dispersant and a defoaming agent; (2) Stirring the mixture to separate purified silicon; wherein the stirring is eccentric stirring.

2. The method for purifying silicon powder according to claim 1, characterized in that: The stirring method meets one or more of the following conditions: (a) The eccentricity of eccentric stirring is 6.67%-20%; (b) the speed of eccentric stirring is 10 rpm-400 rpm; (c) Ultrasonic treatment is performed while stirring.

3. The method for purifying silicon powder according to claim 2, characterized in that: Ultrasonic treatment meets one or more of the following conditions: (a) The power of ultrasound is 100W-400W; (b) The ultrasonic treatment time is 1h-24h.

4. The method for purifying silicon powder according to claim 3, characterized in that: Ultrasonic treatment meets one or more of the following conditions: (a) The power of ultrasound is 200W-300W; (b) The ultrasonic treatment time is 8h-16h.

5. The method for purifying silicon powder according to any one of claims 1 to 4, characterized in that: The purification method meets one or more of the following conditions: (a) The mesh size of silica powder is 80-200 mesh. (b) the pickling solution is selected from one or more combinations of hydrochloric acid or hydrofluoric acid; (c) the dispersant is selected from one or more combinations of polyester, polyether or acrylate; (d) the defoaming agent is selected from one or more combinations of silicone or polyether; (e) The solid-to-liquid ratio in the mixture is (1:2)-(1:10).

6. The method for purifying silicon powder according to claim 5, characterized in that: The purification method meets one or more of the following conditions: (a) The mass fraction of hydrochloric acid is 2%-8%, and the mass fraction of hydrofluoric acid is 1%-5%; (b) the mass fraction of the dispersant is 0.1%-3%; (c) The mass fraction of the defoaming agent is 0.5%-5%.

7. The method for purifying silicon powder according to claim 6, characterized in that: The purification method meets one or more of the following conditions: (a) The mass fraction of hydrochloric acid is 3%-5%, and the mass fraction of hydrofluoric acid is 2%-4%; (b) the mass fraction of the dispersant is 0.2%-0.5%; (c) The mass fraction of the defoaming agent is 1%-2%.

8. The method for purifying silicon powder according to claim 7, characterized in that: The pickling liquid is hydrochloric acid and hydrofluoric acid, the mass fraction of hydrochloric acid is 6%, and the mass fraction of hydrofluoric acid is 3%.

9. The method for purifying silicon powder according to claim 8, characterized in that: The dispersant is polyether with a mass fraction of 0.5%-0.7%; the defoamer is polyether with a mass fraction of 1%-1.2%; and the solid-liquid ratio in the mixture is (1:3)-(1:4).

10. Silicon purified by the purification method according to any one of claims 1 to 9.

Images