A method for preparing industrial silicon reducing agent from high-ash content bituminous coal by vacuum roasting combined with ultrasonic strengthening purification

Abstract

The present application relates to a kind of vacuum roasting combined with ultrasonic strengthening purification high ash content bituminous coal preparation industrial silicon reducing agent method, belong to the technical field of composite reducing agent for industrial silicon smelting.The high ash content bituminous coal powder, ammonium chloride and potassium carbonate are mixed uniformly to obtain bituminous coal mixture, hydrogen peroxide solution is added to bituminous coal mixture and grinded uniformly to obtain mixture A;Mixture A is vacuum roasting, and furnace cooling is carried out to obtain mixture B;Mixture B is added to acid liquor, and then sodium silicate is added, under the condition of stirring, ultrasonic strengthening acid leaching is carried out, solid-liquid separation is carried out, solid is washed by deionized water until washing liquid is neutral, and drying is carried out to obtain industrial silicon reducing agent.The ash content in the industrial silicon reducing agent of the present application is 0.12-0.23wt%, the ash removal rate is 96-98.5%, the iron content is 0.024-0.035wt%, the aluminum content is 0.011-0.018wt%, the calcium content is 0.0014-0.0019wt%, and the caking index is 23-46.

Description

Technical Field

[0001] This invention relates to a method for preparing industrial silicon reducing agents by vacuum roasting combined with ultrasonic enhancement and purification of high-ash bituminous coal, belonging to the technical field of carbonaceous reducing agent purification for industrial silicon smelting. Background Technology

[0002] Since silicon photovoltaics account for over 95% of the entire photovoltaic industry, industrial silicon is an indispensable raw material. Therefore, the development and application of new low-carbon smelting technologies for industrial silicon are of great significance. Silicon production is an energy-intensive process, and the high emissions caused by using fossil fuels as reducing agents are particularly prominent. Currently, silicon production primarily uses high-coke and high-coal-content coal as reducing agents, inevitably leading to increased coal resource consumption. Based on the distribution and grade characteristics of my country's coal resources, high-quality coal with good reactivity, conductivity, and binding properties suitable for silicon smelting is currently in short supply, increasing the cost of using high-rank coal. Meanwhile, the dominant low-rank coal, due to its high ash content, produces a large amount of ash during high-temperature pyrolysis, affecting the permeability of the furnace charge, resulting in low coal resource utilization, increased slag, and problems such as furnace bottom rise and decreased furnace temperature. This, in turn, increases energy consumption in the smelting process and raises production costs. Therefore, in order to reduce costs and make rational use of coal resources to avoid energy structure imbalance, it is urgent to conduct relevant quality improvement research on ash impurities (especially Fe, Al and Ca impurity elements) in low-rank high-ash bituminous coal and develop new reducing agents to reduce or solve the problems existing in the industrial silicon smelting process. Summary of the Invention

[0003] To address the problem of high impurity content and difficulty in removing impurities from low-rank coal ash, which affects the quality of industrial silicon products and increases production costs, this invention proposes a method for preparing industrial silicon reducing agents from high-ash bituminous coal through vacuum roasting combined with ultrasonic enhancement. Ammonium chloride and potassium carbonate are added to the high-ash bituminous coal powder. The addition of hydrogen peroxide provides a favorable oxidizing environment for the reaction system, facilitating the conversion of various impurities in the ash into oxides. After vacuum heating, the ash impurities react with ammonium chloride more rapidly under the catalysis of potassium ions. Ultrasonic technology is used to enhance the acid leaching of the vacuum roasted product. In the ultrasonic environment, the inclusions of coal ash impurities rupture, and sodium silicate promotes closer contact between the acid and the impurities, further improving the ash removal efficiency.

[0004] A method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic-enhanced purification, the specific steps of which are as follows:

[0005] (1) Vacuum-dried high-ash bituminous coal is pulverized and ground to obtain high-ash bituminous coal powder;

[0006] (2) Mix high-ash bituminous coal powder, ammonium chloride and potassium carbonate evenly to obtain a bituminous coal mixture. Add hydrogen peroxide solution to the bituminous coal mixture and grind and mix evenly to obtain mixture A.

[0007] (3) Mixture A is vacuum roasted and then cooled in the furnace to obtain mixture B;

[0008] (4) Mixture B is added to the acid solution, and sodium silicate is added. The acid leaching is enhanced by ultrasonication under stirring conditions, and the solid and liquid are separated. The solid is washed with deionized water until the washing solution is neutral and then dried to obtain industrial silicon reducing agent.

[0009] The high-ash bituminous coal in step (1) has an ash content of 3-8 wt%, an iron content of 0.3-0.8 wt%, an aluminum content of 0.2-0.6 wt%, a calcium content of 0.5-1.2 wt%, and a caking index of 1-9.

[0010] In terms of mass percentage, the bituminous coal mixture in step (2) contains 3-8% ammonium chloride, 1-4% potassium carbonate, and the remainder is a bituminous coal mixture.

[0011] In step (2), the mass concentration of the hydrogen peroxide solution is 4-10%, and the amount of hydrogen peroxide solution added is 2-6% of the mass of the bituminous coal mixture.

[0012] The vacuum degree of the vacuum calcination in step (3) is 10. -3 ~50 Pa, vacuum calcination temperature is 1000~1300℃, time is 60~120 min.

[0013] The acid solution in step (4) is one or more of hydrochloric acid, sulfuric acid, nitric acid, and oxalic acid, and the acid solution contains H+. + The concentration is 3–8 mol / L.

[0014] In step (4), the liquid-to-solid ratio of acid to mixture B (mL:g) is 6-12:1, and the amount of sodium silicate added is 5-12 g / L.

[0015] In step (4), the ultrasonic power is 150-600W, the ultrasonic-enhanced acid leaching temperature is 30-80℃, and the time is 10-50min.

[0016] The industrial silicon reducing agent of this invention has an ash content of 0.12-0.23 wt%, a deashing rate of 96-98.5%, an iron content of 0.024-0.035 wt%, an aluminum content of 0.011-0.018 wt%, a calcium content of 0.0014-0.0019 wt%, and a bonding index of 23-46.

[0017] The principle of vacuum roasting combined with ultrasonic enhancement for purifying high-ash bituminous coal is as follows: High-ash bituminous coal, sodium chloride, and potassium carbonate are mixed, and an appropriate amount of hydrogen peroxide solution is added to provide an oxidizing environment. Under vacuum roasting conditions, alkali metals promote the diffusion of impurity inclusions within the bituminous coal crystals, accelerating the reaction rate with the chlorinating agent, and allowing the metal chlorine gas to volatilize at a lower temperature. Then, ultrasonic enhancement technology is used to enhance the acid leaching of the vacuum roasted product. The ultrasound generates a cavitation effect in the liquid environment, forming a strong mechanical force that causes the impurity inclusions within the crystals to break down, transforming them into fine impurities. Under the action of sodium silicate surfactant, the solution generates strong adsorption force, further ensuring close contact between the fine impurities and the acid solution, greatly improving the reaction efficiency.

[0018] The beneficial effects of this invention are:

[0019] (1) This invention utilizes vacuum roasting to chlorinate and purify the ash impurities of bituminous coal. The added alkali metal salt can promote the reaction between the impurity inclusions in the microcrystalline structure of bituminous coal and the chlorinating agent, thereby increasing the reactivity and reducing the volatilization temperature of metal chlorides. At the same time, the vacuum environment completely prevents the generated gas from reacting with moisture or oxygen, effectively preventing the generation and emission of toxic gases. This is a clean, efficient and environmentally friendly process.

[0020] (2) This invention employs ultrasonic vibration-enhanced leaching technology to perform secondary leaching on the product purified by vacuum chlorination. Ultrasonic waves generate strong cavitation in the solution, creating powerful mechanical forces that peel away impurities adhering to the surface of coal crystals, causing difficult-to-remove impurity inclusions to rupture and produce fine cracks. The addition of sodium silicate enhances the activity of the reaction interface, promoting full contact between fine impurities and the acid solution, thereby accelerating the leaching rate and improving efficiency. Simultaneously, the aqueous solution of sodium silicate exhibits water glass properties, increasing the product's adhesion.

[0021] (3) The ash content of the industrial silicon reducing agent of the present invention is 0.12-0.23 wt%, the deashing rate is 96-98.5%, the iron content is 0.024-0.035 wt%, the aluminum content is 0.011-0.018 wt%, the calcium content is 0.0014-0.0019 wt%, and the bonding index is 23-46; it meets the requirements of carbonaceous reducing agents for industrial silicon principles and can be used in industrial applications.

[0022] (4) The process of the present invention is clean and efficient, environmentally friendly, with low investment cost and energy consumption, and strong production safety. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0024] Example 1: The high-ash bituminous coal in this example has an ash content of 5 wt%, an iron content of 0.4 wt%, an aluminum content of 0.3 wt%, a calcium content of 0.8 wt%, and a caking index of 2.

[0025] A method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic-enhanced purification, the specific steps of which are as follows:

[0026] (1) Vacuum-dried high-ash bituminous coal is pulverized and ground to a particle size of less than 0.15 mm to obtain high-ash bituminous coal powder;

[0027] (2) Mix high-ash bituminous coal powder, ammonium chloride and potassium carbonate evenly to obtain a bituminous coal mixture. Add hydrogen peroxide solution to the bituminous coal mixture and grind and mix evenly to obtain mixture A. By mass percentage, the bituminous coal mixture contains 8% ammonium chloride, 1% potassium carbonate, and the remainder is bituminous coal mixture. The mass concentration of the hydrogen peroxide solution is 4%, and the amount of hydrogen peroxide solution added is 6% of the mass of the bituminous coal mixture.

[0028] (3) Mixture A was placed in a vacuum induction furnace and vacuum-calcined for 110 min at a vacuum degree of 10 Pa and a temperature of 1100 °C. Mixture B was obtained by cooling with the furnace.

[0029] (4) Mixture B was added to hydrochloric acid with a concentration of 5 mol / L, and sodium silicate was added. The mixture was subjected to ultrasonic-enhanced acid leaching under stirring conditions. Solid-liquid separation was performed. The solid was washed with deionized water until the washing liquid was neutral and dried to obtain industrial silicon reducing agent (low ash coal). The liquid-solid ratio of hydrochloric acid to mixture B was 7:1 mL:g, and the amount of sodium silicate added was 7 g / L. The ultrasonic power was 200 W, the ultrasonic-enhanced acid leaching temperature was 40 °C, and the time was 10 min.

[0030] In this embodiment, the industrial silicon reducing agent (low-ash coal) has an ash content of 0.12 wt%, a deashing rate of 98.5%, an iron content of 0.024 wt%, an aluminum content of 0.013 wt%, a calcium content of 0.0015 wt%, and a caking index of 32.

[0031] Comparative Example 1: The difference between this comparative example and Example 1 is that it does not contain steps (2) and (3), and the high ash content bituminous coal powder is directly added to hydrochloric acid with a concentration of 5 mol / L, and ultrasonic enhanced acid leaching is carried out without the addition of sodium silicate.

[0032] The ash content of the deashed coal in this comparative example is 1.02 wt%, the deashing rate is 84.6%, the iron content is 0.41 wt%, the aluminum content is 0.19 wt%, the calcium content is 0.078 wt%, and the caking index is 8.

[0033] Example 2: The high-ash bituminous coal in this example has an ash content of 3 wt%, an iron content of 0.3 wt%, an aluminum content of 0.6 wt%, a calcium content of 0.5 wt%, and a caking index of 8.

[0034] A method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic-enhanced purification, the specific steps of which are as follows:

[0035] (1) Vacuum-dried high-ash bituminous coal is pulverized and ground to a particle size of less than 0.15 mm to obtain high-ash bituminous coal powder;

[0036] (2) Mix high-ash bituminous coal powder, ammonium chloride and potassium carbonate evenly to obtain a bituminous coal mixture. Add hydrogen peroxide solution to the bituminous coal mixture and grind and mix evenly to obtain mixture A. By mass percentage, the bituminous coal mixture contains 7% ammonium chloride, 3% potassium carbonate, and the remainder is bituminous coal mixture. The mass concentration of the hydrogen peroxide solution is 8%, and the amount of hydrogen peroxide solution added is 5% of the mass of the bituminous coal mixture.

[0037] (3) Mixture A is placed in a vacuum induction furnace at a vacuum degree of 10. -3 The mixture was calcined under vacuum at 1000℃ for 120 min and then cooled in the furnace to obtain mixture B.

[0038] (4) Mixture B was added to hydrochloric acid with a concentration of 3 mol / L, and sodium silicate was added. The mixture was subjected to ultrasonic-enhanced acid leaching under stirring conditions. Solid-liquid separation was performed. The solid was washed with deionized water until the washing liquid was neutral and dried to obtain industrial silicon reducing agent (low ash coal). The liquid-solid ratio of hydrochloric acid to mixture B was 6:1 mL:g, and the amount of sodium silicate added was 8 g / L. The ultrasonic power was 350 W, the ultrasonic-enhanced acid leaching temperature was 50 °C, and the time was 30 min.

[0039] In this embodiment, the industrial silicon reducing agent (low-ash coal) has an ash content of 0.18 wt%, a deashing rate of 97.6%, an iron content of 0.031 wt%, an aluminum content of 0.018 wt%, a calcium content of 0.0018 wt%, and a caking index of 28.

[0040] Comparative Example 2: The difference between this comparative example and Example 2 is that it does not contain steps (2) and (3), and the high ash content bituminous coal powder is directly added to hydrochloric acid with a concentration of 3 mol / L, and ultrasonic enhanced acid leaching is carried out without the addition of sodium silicate.

[0041] The ash content of the deashed coal in this comparative example is 1.39 wt%, the deashing rate is 80.6%, the iron content is 0.47 wt%, the aluminum content is 0.22 wt%, the calcium content is 0.081 wt%, and the caking index is 7.

[0042] Example 3: The high-ash bituminous coal in this example has an ash content of 6 wt%, an iron content of 0.8 wt%, an aluminum content of 0.2 wt%, a calcium content of 0.7 wt%, and a caking index of 1.

[0043] A method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic-enhanced purification, the specific steps of which are as follows:

[0044] (1) Vacuum-dried high-ash bituminous coal is pulverized and ground to a particle size of less than 0.15 mm to obtain high-ash bituminous coal powder;

[0045] (2) Mix high-ash bituminous coal powder, ammonium chloride and potassium carbonate evenly to obtain a bituminous coal mixture. Add hydrogen peroxide solution to the bituminous coal mixture and grind and mix evenly to obtain mixture A. By mass percentage, the bituminous coal mixture contains 3% ammonium chloride, 1% potassium carbonate, and the remainder is bituminous coal mixture. The mass concentration of the hydrogen peroxide solution is 5%, and the amount of hydrogen peroxide solution added is 6% of the mass of the bituminous coal mixture.

[0046] (3) Mixture A was placed in a vacuum induction furnace and vacuum-calcined for 60 min at a vacuum degree of 20 Pa and a temperature of 1200 °C. Mixture B was obtained by cooling the furnace.

[0047] (4) Mixture B was added to hydrochloric acid with a concentration of 6 mol / L, and sodium silicate was added. The mixture was subjected to ultrasonic-enhanced acid leaching under stirring conditions. Solid-liquid separation was performed. The solid was washed with deionized water until the washing liquid was neutral and dried to obtain industrial silicon reducing agent (low ash coal). The liquid-solid ratio of hydrochloric acid to mixture B was 10:1 mL:g, and the amount of sodium silicate added was 7 g / L. The ultrasonic power was 500 W, the ultrasonic-enhanced acid leaching temperature was 30 °C, and the time was 40 min.

[0048] In this embodiment, the industrial silicon reducing agent (low-ash coal) has an ash content of 0.23 wt%, a deashing rate of 96%, an iron content of 0.027 wt%, an aluminum content of 0.016 wt%, a calcium content of 0.0017 wt%, and a caking index of 37.

[0049] Comparative Example 3: The difference between this comparative example and Example 3 is that it does not contain steps (2) and (3), and the high ash content bituminous coal powder is directly added to hydrochloric acid with a concentration of 6 mol / L, and ultrasonic enhanced acid leaching is carried out without the addition of sodium silicate.

[0050] The ash content of the deashed coal in this comparative example is 1.15 wt%, the deashing rate is 82.3%, the iron content is 0.38 wt%, the aluminum content is 0.23 wt%, the calcium content is 0.09 wt%, and the caking index is 10.

[0051] Example 4: The high-ash bituminous coal in this example has an ash content of 8 wt%, an iron content of 0.5 wt%, an aluminum content of 0.4 wt%, a calcium content of 1.2 wt%, and a caking index of 5.

[0052] A method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic-enhanced purification, the specific steps of which are as follows:

[0053] (1) Vacuum-dried high-ash bituminous coal is pulverized and ground to a particle size of less than 0.15 mm to obtain high-ash bituminous coal powder;

[0054] (2) Mix high-ash bituminous coal powder, ammonium chloride and potassium carbonate evenly to obtain a bituminous coal mixture. Add hydrogen peroxide solution to the bituminous coal mixture and grind and mix evenly to obtain mixture A. By mass percentage, the bituminous coal mixture contains 7% ammonium chloride, 4% potassium carbonate, and the remainder is bituminous coal mixture. The mass concentration of the hydrogen peroxide solution is 10%, and the amount of hydrogen peroxide solution added is 2% of the mass of the bituminous coal mixture.

[0055] (3) Mixture A was placed in a vacuum induction furnace and vacuum-calcined for 80 minutes at a vacuum degree of 50 Pa and a temperature of 1300 °C. Mixture B was obtained by cooling the furnace.

[0056] (4) Mixture B was added to hydrochloric acid with a concentration of 8 mol / L, and sodium silicate was added. The mixture was subjected to ultrasonic-enhanced acid leaching under stirring conditions, and solid-liquid separation was performed. The solid was washed with deionized water until the washing liquid was neutral and dried to obtain industrial silicon reducing agent (low ash coal). The liquid-solid ratio of hydrochloric acid to mixture B was 8:1 mL:g, and the amount of sodium silicate added was 12 g / L. The ultrasonic power was 150 W, the ultrasonic-enhanced acid leaching temperature was 60 °C, and the time was 35 min.

[0057] In this embodiment, the industrial silicon reducing agent (low-ash coal) has an ash content of 0.21 wt%, a deashing rate of 97.1%, an iron content of 0.026 wt%, an aluminum content of 0.015 wt%, a calcium content of 0.0019 wt%, and a caking index of 46.

[0058] Comparative Example 4: The difference between this comparative example and Example 4 is that it does not contain steps (2) and (3), and the high ash content bituminous coal powder is directly added to hydrochloric acid with a concentration of 8 mol / L, and ultrasonic enhanced acid leaching is carried out without the addition of sodium silicate.

[0059] The ash content of the deashed coal in this comparative example is 1.21 wt%, the deashing rate is 81.8%, the iron content is 0.41 wt%, the aluminum content is 0.24 wt%, the calcium content is 0.073 wt%, and the caking index is 8.

[0060] Example 5: The high-ash bituminous coal in this example has an ash content of 4 wt%, an iron content of 0.6 wt%, an aluminum content of 0.5 wt%, a calcium content of 0.6 wt%, and a caking index of 9.

[0061] A method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic-enhanced purification, the specific steps of which are as follows:

[0062] (1) Vacuum-dried high-ash bituminous coal is pulverized and ground to a particle size of less than 0.15 mm to obtain high-ash bituminous coal powder;

[0063] (2) Mix high-ash bituminous coal powder, ammonium chloride and potassium carbonate evenly to obtain a bituminous coal mixture. Add hydrogen peroxide solution to the bituminous coal mixture and grind and mix evenly to obtain mixture A. By mass percentage, the bituminous coal mixture contains 5% ammonium chloride, 2% potassium carbonate, and the remainder is bituminous coal mixture. The mass concentration of the hydrogen peroxide solution is 7%, and the amount of hydrogen peroxide solution added is 4% of the mass of the bituminous coal mixture.

[0064] (3) Mixture A was placed in a vacuum induction furnace and calcined for 100 min at a vacuum degree of 30 Pa and a temperature of 1150 °C. Mixture B was obtained by cooling the furnace.

[0065] (4) Mixture B was added to hydrochloric acid with a concentration of 7 mol / L, and sodium silicate was added. The mixture was subjected to ultrasonic-enhanced acid leaching under stirring conditions, and solid-liquid separation was performed. The solid was washed with deionized water until the washing liquid was neutral and dried to obtain industrial silicon reducing agent (low ash coal). The liquid-solid ratio of hydrochloric acid to mixture B was 12:1 mL:g, and the amount of sodium silicate added was 6 g / L. The ultrasonic power was 400 W, the ultrasonic-enhanced acid leaching temperature was 80 °C, and the time was 50 min.

[0066] In this embodiment, the industrial silicon reducing agent (low-ash coal) has an ash content of 0.13 wt%, a deashing rate of 98.2%, an iron content of 0.033 wt%, an aluminum content of 0.011 wt%, a calcium content of 0.0014 wt%, and a caking index of 23.

[0067] Comparative Example 5: The difference between this comparative example and Example 5 is that it does not contain steps (2) and (3), and the high ash content bituminous coal powder is directly added to hydrochloric acid with a concentration of 7 mol / L, and ultrasonic enhanced acid leaching is carried out without the addition of sodium silicate.

[0068] The ash content of the deashed coal in this comparative example is 1.28 wt%, the deashing rate is 81.1%, the iron content is 0.39 wt%, the aluminum content is 0.21 wt%, the calcium content is 0.083 wt%, and the caking index is 6.

[0069] Example 6: The high-ash bituminous coal in this example has an ash content of 7 wt%, an iron content of 0.7 wt%, an aluminum content of 0.3 wt%, a calcium content of 1 wt%, and a caking index of 4;

[0070] A method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic-enhanced purification, the specific steps of which are as follows:

[0071] (1) Vacuum-dried high-ash bituminous coal is pulverized and ground to a particle size of less than 0.15 mm to obtain high-ash bituminous coal powder;

[0072] (2) Mix high-ash bituminous coal powder, ammonium chloride and potassium carbonate evenly to obtain a bituminous coal mixture. Add hydrogen peroxide solution to the bituminous coal mixture and grind and mix evenly to obtain mixture A. By mass percentage, ammonium chloride accounts for 6% of the bituminous coal mixture, potassium carbonate accounts for 3% of the bituminous coal mixture, and the remainder is the bituminous coal mixture. The mass concentration of the hydrogen peroxide solution is 6%, and the amount of hydrogen peroxide solution added is 3% of the mass of the bituminous coal mixture.

[0073] (3) Mixture A was placed in a vacuum induction furnace and vacuum-calcined for 90 min at a vacuum degree of 40 Pa and a temperature of 1250 °C. Mixture B was obtained by cooling in the furnace.

[0074] (4) Mixture B was added to hydrochloric acid with a concentration of 4 mol / L, and sodium silicate was added. The mixture was subjected to ultrasonic-enhanced acid leaching under stirring conditions. Solid-liquid separation was performed. The solid was washed with deionized water until the washing liquid was neutral and dried to obtain industrial silicon reducing agent (low ash coal). The liquid-solid ratio of hydrochloric acid to mixture B was 9:1 mL:g, and the amount of sodium silicate added was 11 g / L. The ultrasonic power was 600 W, the ultrasonic-enhanced acid leaching temperature was 70 °C, and the time was 20 min.

[0075] In this embodiment, the industrial silicon reducing agent (low-ash coal) has an ash content of 0.15 wt%, a deashing rate of 97.9%, an iron content of 0.035 wt%, an aluminum content of 0.017 wt%, a calcium content of 0.0016 wt%, and a caking index of 41.

[0076] Comparative Example 6: The difference between this comparative example and Example 6 is that it does not contain steps (2) and (3), and the high ash content bituminous coal powder is directly added to hydrochloric acid with a concentration of 4 mol / L, and ultrasonic enhanced acid leaching is carried out without the addition of sodium silicate.

[0077] The ash content of the deashed coal in this comparative example is 1.32 wt%, the deashing rate is 80.8%, the iron content is 0.43 wt%, the aluminum content is 0.26 wt%, the calcium content is 0.079 wt%, and the caking index is 5.

[0078] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic-enhanced purification, characterized in that, The specific steps are as follows: (1) Vacuum-dried high-ash bituminous coal is pulverized and ground to obtain high-ash bituminous coal powder; (2) Mix high-ash bituminous coal powder, ammonium chloride and potassium carbonate evenly to obtain a bituminous coal mixture. Add hydrogen peroxide solution to the bituminous coal mixture and grind and mix evenly to obtain mixture A. (3) Mixture A is vacuum roasted and then cooled in the furnace to obtain mixture B; (4) Mixture B is added to the acid solution, and sodium silicate is added. The acid leaching is enhanced by ultrasonication under stirring conditions, and the solid and liquid are separated. The solid is washed with deionized water until the washing solution is neutral and then dried to obtain industrial silicon reducing agent.

2. The method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic enhancement purification according to claim 1, characterized in that: The high-ash bituminous coal in step (1) has an ash content of 3-8 wt%, an iron content of 0.3-0.8 wt%, an aluminum content of 0.2-0.6 wt%, a calcium content of 0.5-1.2 wt%, and a caking index of 1-9.

3. The method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic enhancement purification according to claim 1, characterized in that: In terms of mass percentage, the bituminous coal mixture in step (2) contains 3-8% ammonium chloride, 1-4% potassium carbonate, and the remainder is a bituminous coal mixture.

4. The method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic enhancement purification according to claim 3, characterized in that: In step (2), the mass concentration of the hydrogen peroxide solution is 4-10%, and the amount of hydrogen peroxide solution added is 2-6% of the mass of the bituminous coal mixture.

5. The method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic-enhanced purification according to claim 1, characterized in that: The vacuum degree of step (3) vacuum calcination is 10. -3 ~50 Pa, vacuum calcination temperature is 1000~1300℃, time is 60~120 min.

6. The method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic enhancement purification according to claim 1, characterized in that: Step (4) The acid solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, and oxalic acid. The acid solution contains H+. + The concentration is 3–8 mol / L.

7. The method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic-enhanced purification according to claim 1, characterized in that: In step (4), the liquid-solid ratio of acid solution to mixture B (mL:g) is 6-12:1, and the amount of sodium silicate added is 5-12 g / L.

8. The method for preparing industrial silicon reducing agent from high-ash bituminous coal by vacuum roasting combined with ultrasonic enhancement purification according to claim 1, characterized in that: Step (4) The ultrasonic power is 150-600W, the ultrasonic enhanced acid immersion temperature is 30-80℃, and the time is 10-50min.