A method for effectively recovering metallic silicon from industrial silicon slag

Abstract

This invention relates to the field of metallurgical technology, specifically to a method for effectively recovering metallic silicon from industrial silicon slag. The method involves first crushing the silicon slag, adding plasma water for slurry preparation, obtaining a silicon slag slurry, then adding a modifier, inhibitor, trapping agent, and frother to generate bubbles. The slurry is then refined using electromagnetic slag-forming in a medium-frequency induction furnace, and finally poured into a mold for cooling to obtain metallic silicon. The modifier is quicklime powder, the inhibitor and trapping agent are a mixture of various components, the frother is No. 4 flotation oil, the slag-forming agent is a mixture of base materials and auxiliary materials, and the gas is a mixture of argon, chlorine, and other gases. This method can solve the problems of high impurity and complex chemical composition in industrial silicon slag, improving the purity of the recovered metallic silicon.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method for effectively recovering metallic silicon from industrial silicon slag. Background Technology

[0002] With the rapid development of metallurgical refining of metallic silicon, the amount of industrial silicon slag being dumped is gradually increasing. Due to its low price, industrial silicon slag has long been treated as solid waste, occupying vast amounts of land resources and causing serious environmental pollution. Furthermore, this inefficient disposal method results in the loss of significant amounts of silicon resources due to ineffective recycling. Currently, the photovoltaic industry is developing rapidly, and the price of industrial silicon is constantly rising. Recycling and reusing the metallic silicon in silicon slag could bring considerable economic benefits and effectively solve the environmental pollution problems it causes, promoting the development of the silicon industry. However, due to the high impurity level and complex chemical composition of silicon slag, effective recycling is difficult. Therefore, an effective method for recycling metallic silicon from industrial silicon slag is needed. Summary of the Invention

[0003] In view of this, the purpose of this invention is to propose an effective method for recovering metallic silicon from industrial silicon slag, so as to solve the problem that the high impurity and complex chemical composition of industrial silicon slag makes it difficult to effectively recover.

[0004] To achieve the above objectives, this invention provides a method for effectively recovering metallic silicon from industrial silicon slag, the specific steps of which are as follows:

[0005] (1) Crush the silicon slag, then add plasma water to slurry to obtain silicon slag slurry;

[0006] (2) Add the modifier to the slag slurry and stir for 3-5 minutes to mix thoroughly so that the pH of the silicon slag slurry is 7-9. Then add the inhibitor and stir for 2-4 minutes. Then add the capture agent and stir for 2-7 minutes. Then add the foaming agent and stir for 1-5 minutes. Then open the aeration valve to generate bubbles. Then scrape the bubbles for 8-15 minutes. Finally, rinse with plasma water until neutral and then filter and dry to obtain selected silicon slag.

[0007] (3) The selected silicon slag and slag-forming agent are added to a mixer for thorough mixing, and then placed in a medium-frequency induction furnace for electromagnetic slag-forming refining. The refining temperature is 1450-1600℃, and the refining time is 1-2.5h. Gas blowing refining is also carried out, with the pressure of the introduced gas being 1-20MPa and the flow rate being 0.5-10m³. 3 / h, the ventilation time is 0.1-0.5h, after the blowing refining is completed, the temperature is maintained for 0.2-1h, the slag liquid is removed, and the refined silicon liquid is obtained;

[0008] (4) Pour the refined silicon liquid into a mold and cool it to obtain metallic silicon.

[0009] Preferably, the particle size of the crushed silicon slag in step (1) is no greater than 50 mesh.

[0010] Preferably, the concentration of the silica slag slurry in step (1) is 10wt%-35wt%.

[0011] Preferably, the modifier in step (2) is quicklime powder or magnesium oxide.

[0012] Preferably, the inhibitor in step (2) is one or a mixture of several of lactic acid, citric acid, ammonium salicylate, diethylenetriamine, triethylenetetramine, oxalic acid, sodium hexametaphosphate, and water glass, and the amount added is 50-100 g / t based on the weight of the slag slurry.

[0013] Preferably, the scavenging agent in step (2) is one of butyl xanthate and kerosene, and the amount added is 20-30 g / t based on the weight of the slag slurry.

[0014] Preferably, the foaming agent in step (2) is No. 4 flotation oil, and the amount added is 10-15g / t based on the weight of the slag slurry.

[0015] Preferably, in step (3), the slag-forming agent comprises 90wt%-95wt% of base material and 5wt%-10wt% of auxiliary material, wherein the base material consists of CaO, SiO2, CaF2, MgO, Na2CO3, Li2O, and Al2O3, with CaO comprising 1wt%-100wt% of the base material and CaF2 comprising 1wt%-30wt% of the base material. ， The auxiliary material is one or a mixture of several of MgCl2, NaCl, and CaCl2.

[0016] Preferably, in step (3), the weight ratio of selected silicon slag and slag-forming agent is 10:1-20.

[0017] Preferably, the gas in step (3) is one or a mixture of several of the following: argon, chlorine, water vapor, CO, and CO2.

[0018] The beneficial effects of this invention are:

[0019] Simple process: This method is simple to operate, and the reagents and equipment used are relatively common, making it easy to produce and implement on-site.

[0020] High production efficiency: The process flow of this method is reasonable and the production process is well controllable, which can greatly improve production efficiency and reduce production costs.

[0021] High product quality: High-purity metallic silicon can be prepared from industrial silicon slag by combining electromagnetic-slag-forming refining with air blowing refining and using slag-forming agents. The purity can reach more than 99.5%.

[0022] In summary, this invention provides an effective method for recovering metallic silicon from industrial silicon slag, realizing the recycling of solid waste, fully embodying the development model of a circular economy, realizing the concept of turning waste into treasure, and saving natural resources. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0024] Example 1

[0025] A method for effectively recovering metallic silicon from industrial silicon slag, comprising the following specific steps:

[0026] (1) The silicon slag was provided by Suzhou Chuanmao Metal Materials Co., Ltd. The silicon slag was crushed, and the particle size after crushing was no more than 30 mesh. Then, plasma water was added for slurrying to obtain a silicon slag slurry with a concentration of 25wt%.

[0027] (2) Add quicklime powder to 10t slag slurry and stir for 3 minutes to mix thoroughly so that the pH of the silica slag slurry is 8. Then add 70g oxalic acid and stir for 4 minutes. Then add 20g kerosene and stir for 6 minutes. Then add 15g foaming agent and stir for 2 minutes. Then open the air valve to generate bubbles and scrape the bubbles for 14 minutes. Finally, rinse with plasma water until neutral and then filter and dry to obtain selected silica slag.

[0028] (3) 10t of selected silicon slag, 2.25t of CaO, 1.5t of SiO2, 0.5t of CaF2, 0.25t of Al2O3, and 0.5t of NaCl were added to a mixer for thorough mixing. Then, the mixture was placed in a medium-frequency induction furnace for electromagnetic slag-forming refining at a temperature of 1450℃ for 2.5 hours. Argon gas was introduced during the refining process at a pressure of 20MPa and a flow rate of 1.5m³. 3 / h, the ventilation time is 0.5h, after the blowing refining is completed, the temperature is maintained for 1h, the slag liquid is removed, and the refined silicon liquid is obtained;

[0029] (4) Pour the refined silicon liquid into a mold and cool it to obtain metallic silicon with a purity of 99.8% and impurities of 0.05% Fe, 0.04% Al, 0.01% Ca, 0.01% Mg and the balance being other.

[0030] Example 2

[0031] A method for effectively recovering metallic silicon from industrial silicon slag, comprising the following specific steps:

[0032] (1) The silicon slag was provided by Suzhou Chuanmao Metal Materials Co., Ltd. The silicon slag was crushed, and the particle size after crushing was no more than 20 mesh. Then, plasma water was added for slurrying to obtain a silicon slag slurry with a concentration of 30wt%.

[0033] (2) Add quicklime powder to 10t slag slurry and stir for 4 minutes to mix thoroughly so that the pH of the silica slag slurry is 7.5. Then add 50g citric acid and stir for 2 minutes. Then add 20g butyl xanthate and stir for 2-7 minutes. Then add 10g foaming agent and stir for 2 minutes. Then open the air valve to generate bubbles and scrape the bubbles for 10 minutes. Finally, rinse with plasma water until neutral and then filter and dry to obtain selected silica slag.

[0034] (3) 10t of selected silicon slag, 7t of CaO, 0.3t of CaF2, 0.3t of Al2O3, and 0.4t of NaCl2 were added to a mixer and thoroughly mixed. Then, the mixture was placed in a medium-frequency induction furnace for electromagnetic slag-forming refining at a temperature of 1600℃ for 2 hours. Gas blowing refining was performed, with steam introduced at a pressure of 18MPa and a flow rate of 2m³ / h. 3 / h, the ventilation time is 0.3h, after the blowing refining is completed, the temperature is maintained for 0.7h, the slag liquid is removed, and the refined silicon liquid is obtained;

[0035] (4) Pour the refined silicon liquid into a mold and cool it to obtain metallic silicon with a purity of 99.5% and impurities of 0.06% Fe, 0.05% Al, 0.01% Ca, 0.01% Mg and the balance being other.

[0036] Example 3

[0037] A method for effectively recovering metallic silicon from industrial silicon slag, comprising the following specific steps:

[0038] (1) The silicon slag was provided by Suzhou Chuanmao Metal Materials Co., Ltd. The silicon slag was crushed, and the particle size after crushing was no more than 30 mesh. Then, plasma water was added for slurrying to obtain a silicon slag slurry with a concentration of 25wt%.

[0039] (2) Add magnesium oxide to 10t slag slurry and stir for 3 minutes to mix thoroughly so that the pH of the silica slag slurry is 8. Then add 60g oxalic acid and stir for 4 minutes. Then add 25g kerosene and stir for 6 minutes. Then add 12g foaming agent and stir for 2 minutes. Then open the aeration valve to generate bubbles and scrape the bubbles for 14 minutes. Finally, rinse with plasma water until neutral and then filter and dry to obtain selected silica slag.

[0040] (3) 10t of selected silicon slag, 5t of CaO, 2t of CaF2, 1t of Na2CO3, 1t of Al2O3, and 1t of CaCl2 were added to a mixer and thoroughly mixed. Then, the mixture was placed in a medium-frequency induction furnace for electromagnetic slag-forming refining at a temperature of 1500℃ for 2 hours. Gas blowing refining was also performed, with chlorine gas introduced at a pressure of 15MPa and a flow rate of 0.5m³. 3 / h, the ventilation time is 0.1h, after the blowing refining is completed, the temperature is maintained for 0.4h, the slag liquid is removed, and the refined silicon liquid is obtained;

[0041] (4) Pour the refined silicon liquid into a mold and cool it to obtain metallic silicon with a purity of 99.9% and impurities of 0.02% Fe, 0.01% Al, 0.01% Ca, 0.01% Mg and the balance being other.

[0042] Example 4

[0043] A method for effectively recovering metallic silicon from industrial silicon slag, comprising the following specific steps:

[0044] (1) The silicon slag was provided by Suzhou Chuanmao Metal Materials Co., Ltd. The silicon slag was crushed, and the particle size after crushing was no more than 40 mesh. Then, plasma water was added for slurrying to obtain a silicon slag slurry with a concentration of 20wt%.

[0045] (2) Add quicklime powder to 10t slag slurry and stir for 3 minutes to mix thoroughly so that the pH of the silica slag slurry is 8.5. Then add 100g citric acid and stir for 3 minutes. Then add 30g kerosene and stir for 7 minutes. Then add 10g foaming agent and stir for 4 minutes. Then open the air valve to generate bubbles and scrape the bubbles for 12 minutes. Finally, rinse with plasma water until neutral and then filter and dry to obtain selected silica slag.

[0046] (3) 10t of selected silicon slag, 4.5t of CaO, 4.5t of SiO2, 2.25t of CaF2, 1.5t of MgO, 0.75t of Li2O, and 0.75t of MgCl2 were added to a mixer and thoroughly mixed. Then, the mixture was placed in a medium-frequency induction furnace for electromagnetic slag-forming refining at a temperature of 1450℃ for 1.5 hours. Gas blowing refining was performed, introducing a mixture of argon and steam at a pressure of 10MPa and a flow rate of 2m³ / h. 3 / h, the ventilation time is 0.1h, after the blowing refining is completed, the temperature is maintained for 0.9h, the slag liquid is removed, and the refined silicon liquid is obtained;

[0047] (4) Pour the refined silicon liquid into a mold and cool it to obtain metallic silicon with a purity of 99.6% and impurities of 0.04% Fe, 0.03% Al, 0.01% Ca, 0.01% Mg and the balance being other.

[0048] Example 5

[0049] A method for effectively recovering metallic silicon from industrial silicon slag, comprising the following specific steps:

[0050] (1) The silicon slag was provided by Suzhou Chuanmao Metal Materials Co., Ltd. The silicon slag was crushed, and the particle size after crushing was no more than 50 mesh. Then, plasma water was added for slurrying to obtain a silicon slag slurry with a concentration of 10wt%.

[0051] (2) Add quicklime powder to 10t slag slurry and stir for 4 minutes to mix thoroughly so that the pH of the silica slag slurry is 9. Then add 75g water glass and stir for 4 minutes. Then add 25g butyl xanthate and stir for 4 minutes. Then add 14g foaming agent and stir for 5 minutes. Then open the air valve to generate bubbles and scrape the bubbles for 15 minutes. Finally, rinse with plasma water until neutral and then filter and dry to obtain selected silica slag.

[0052] (3) 10t of selected silicon slag, 6t of CaO, 6t of SiO2, 1t of CaF2, 3t of Na2CO3, 2t of Li2O, and 2t of MgCl2 are added to a mixer for thorough mixing. Then, the mixture is placed in a medium-frequency induction furnace for electromagnetic slag-forming refining at a temperature of 1450℃ for 1 hour. Gas blowing refining is performed by introducing a mixture of steam and CO2 at a pressure of 8MPa and a flow rate of 4m³ / h. 3 / h, the ventilation time is 0.3h, after the blowing refining is completed, the temperature is maintained for 0.2h, the slag liquid is removed, and the refined silicon liquid is obtained;

[0053] (4) Pour the refined silicon liquid into a mold and cool it to obtain metallic silicon with a purity of 99.9% and impurities of 0.01% Fe, 0.01% Al, 0.01% Ca, 0.01% Mg and the balance being other.

[0054] Comparative Example 1

[0055] The difference between Comparative Example 1 and Example 1 is that NaCl in step (3) is replaced with Na2CO3.

[0056] Comparative Example 2

[0057] The difference between Comparative Example 2 and Example 1 is that the blowing refining step in step (3) is deleted.

[0058] Comparative Example 3

[0059] The difference between Comparative Example 3 and Example 1 is that the refining temperature in step (3) is changed to 1700℃.

[0060] Table 1. Purity and impurity content of metallic silicon prepared in the examples and comparative examples.

[0061]

[0062] Data Analysis: As can be seen from Examples 1-5, the metallic silicon prepared by the method of the present invention for effectively recovering metallic silicon from industrial silicon slag has a purity of over 99.5%, and the contents of Fe, Al, Ca, and Mg in the impurities are low. As can be seen from Examples 1 and Comparative Examples 1 and 3, the chloride in the slag-forming agent has a significant impact on the purity of metallic silicon, while the increase in refining temperature has a smaller impact on the purity of metallic silicon. However, for Fe impurities, the introduction of chloride and refining at lower temperatures greatly reduce the content of Fe impurities. This may be because chloride has the effect of removing iron in silicon slag at appropriate temperatures. As can be seen from Examples 1 and Comparative Example 2, air blowing refining helps to improve the purity of metallic silicon and comprehensively reduce the contents of Fe, Al, Ca, and Mg in the impurities.

[0063] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in the details for the sake of brevity.

[0064] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for effectively recovering metallic silicon from industrial silicon slag, characterized in that, The specific steps are as follows: (1) The silicon slag is crushed and then plasma water is added for slurry preparation to obtain silicon slag slurry; (2) Add the modifier to the slag slurry and stir for 3-5 minutes to mix thoroughly so that the pH of the silicon slag slurry is 7-9. Then add the inhibitor and stir for 2-4 minutes. Then add the capture agent and stir for 2-7 minutes. Then add the foaming agent and stir for 1-5 minutes. Then open the aeration valve to generate bubbles. Then scrape the bubbles for 8-15 minutes. Finally, rinse with plasma water until neutral and then filter and dry to obtain selected silicon slag. (3) The selected silicon slag and slag-forming agent are added to the mixer for thorough mixing, and then placed in a medium-frequency induction furnace for electromagnetic slag-forming refining. The refining temperature is 1400-1500℃, the refining time is 1-2.5h, and gas blowing refining is carried out. The pressure of the gas is 1-20MPa, and the flow rate is 0.5-10m³. 3 / h, the ventilation time is 0.1-0.5h, after the blowing refining is completed, the temperature is maintained for 0.2-1h, the slag liquid is removed, and the refined silicon liquid is obtained; (4) Pour the refined silicon liquid into a mold and cool it to obtain metallic silicon; The modifier in step (2) is quicklime powder or magnesium oxide; The inhibitor in step (2) is one or a mixture of several of the following: lactic acid, citric acid, ammonium salicylate, diethylenetriamine, triethylenetetramine, oxalic acid, sodium hexametaphosphate, and water glass. The amount added is 50-100 g / t based on the weight of the slag slurry. In step (2), the scavenging agent is either butyl xanthate or kerosene, and the amount added is 20-30 g / t based on the weight of the slag slurry. In step (2), the foaming agent is No. 4 flotation oil, and the amount added is 10-15g / t based on the weight of the slag slurry. In step (3), the slag-forming agent consists of 90wt%-95wt% base material and 5wt%-10wt% auxiliary material. The base material is CaO, SiO2, CaF2, MgO, Na2CO3, Li2O and Al2O3. CaO is 1wt%~100wt% of the base material, CaF2 is 1wt%~30wt% of the base material, and the auxiliary material is one or a mixture of several of MgCl2, NaCl and CaCl2.

2. The method for effectively recovering metallic silicon from industrial silicon slag according to claim 1, characterized in that, In step (1), the particle size of the crushed silicon slag is no greater than 50 mesh.

3. The method for effectively recovering metallic silicon from industrial silicon slag according to claim 1, characterized in that, The concentration of the silica slag slurry in step (1) is 10wt%-35wt%.

4. The method for effectively recovering metallic silicon from industrial silicon slag according to claim 1, characterized in that, In step (3), the weight ratio of selected silicon slag and slag-forming agent is 10:1-20.

5. The method for effectively recovering metallic silicon from industrial silicon slag according to claim 1, characterized in that, The gas in step (3) is one or a mixture of several of the following: argon, chlorine, water vapor, CO, and CO2.

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