Method for preparing composite reducing agent for industrial silicon by using different caking coals and grinding medium

Abstract

The present application relates to a kind of methods for preparing composite reducing agent for industrial silicon by using grinding medium to strengthen different caking coal, and belongs to the technical field of preparing composite reducing agent for industrial silicon.The present application uniformly mixes high-viscosity coal powder and non-viscosity coal powder to obtain coal powder mixture A, coffee wastewater is added to the coal powder mixture A and grinding is carried out to obtain coal powder mixture B;the coal powder mixture B is pressed to form a cylindrical blank;the cylindrical blank is placed in an argon atmosphere and subjected to microwave calcination, and is cooled to room temperature with the furnace to obtain a composite reducing agent pellet for industrial silicon.The present application adds coffee wastewater to the mixed coal powder, so that the coffee wastewater penetrates into the pores of the mixed coal powder, increases the contact area between different caking coals, and further increases the reaction rate of the mixed coal in smelting by microwave heating, promotes the crosslinking rearrangement of the structure of the mixed coal, and reduces the reaction activation energy.

Description

Technical Field

[0001] This invention relates to a method for preparing composite reducing agents for industrial silicon using grinding media to enhance the bonding of coals with different bonding properties, and belongs to the technical field of composite reducing agent preparation for industrial silicon. Background Technology

[0002] Currently, industrial silicon production primarily involves smelting silica and carbonaceous reducing agents in an electric arc furnace. To improve smelting efficiency, various carbonaceous reducing agents (petroleum coke, charcoal, coal, etc.) are rationally mixed and proportioned in actual production to ensure the full combustion and utilization of different materials. Among the reducing agents selected for industrial silicon smelting, coal with a certain degree of caking properties accounts for a large proportion, mainly because caking coal has a high resistivity, a suitable caking index, low price, and is not easily graphitized. Low-rank non-caking coal is a low-value resource in industrial silicon smelting, with extremely low utilization rates, while high-rank caking coal has high usage costs. Therefore, researching how to more effectively apply low-rank non-caking coal in industrial silicon smelting is of great significance in reducing the usage cost of high-rank caking coal.

[0003] Coffee wastewater is an acidic waste liquid containing a high concentration of organic matter. Its rich nutrient content can easily lead to eutrophication of water bodies and harm human health. To alleviate the increased pressure on the ecological environment caused by the discharge of coffee wastewater, its rational application in relevant fields can achieve the efficient and clean utilization of organic wastewater resources. Summary of the Invention

[0004] To address the issues of high cost of high-rank caking coal and limited practical application value of low-rank non-caking coal used in industrial silicon smelting, this invention proposes a method for preparing composite reducing agents for industrial silicon by strengthening different caking coals with grinding media. This involves adding coffee wastewater to mixed coal powder, allowing it to penetrate the pores of the mixed coal powder, increasing the contact area between different caking coals, and then using microwave heating to further enhance the reaction rate of the mixed coal in smelting by the organic components and alkali metals in the coffee wastewater, promoting cross-linking and rearrangement of the mixed coal structure, and reducing the activation energy of the reaction.

[0005] A method for preparing composite reducing agents for industrial silicon using grinding media to enhance the bonding of coals with different caking properties, the specific steps of which are as follows:

[0006] (1) Vacuum-dried high-viscosity coal and non-viscosity coal are crushed and ground to a particle size of less than 0.2 mm and a particle size of 0.1 mm to 0.2 mm accounts for 20% to 35% to obtain high-viscosity coal powder and non-viscosity coal powder;

[0007] (2) Mix high-viscosity coal powder and non-viscosity coal powder evenly to obtain coal powder mixture A. Add coffee wastewater to coal powder mixture A and grind it to obtain coal powder mixture B.

[0008] (3) The coal powder mixture B is pressed into a cylindrical blank;

[0009] (4) The cylindrical blank is placed in an argon atmosphere for microwave calcination and then cooled to room temperature in the furnace to obtain composite reducing agent pellets for industrial silicon.

[0010] In step (1), the caking index of high-viscosity coal powder is 90~95, and the caking index of non-viscosity coal is 0~8.

[0011] Based on the mass of coal powder mixture A, in step (2), the high-viscosity coal powder accounts for 75-90% and the non-viscosity coal powder accounts for 10-25%; the amount of coffee wastewater added is 8-12% of the mass of coal powder mixture A.

[0012] The coffee wastewater refers to the organic wastewater obtained during the wet preliminary pulping and washing process of green coffee. The coffee wastewater contains a large amount of organic matter such as caffeic acid, caffeine and pectin, with an organic matter content of 35~50wt%. The coffee wastewater mainly contains alkali metals such as K and Na, with an alkali metal content of 5~9wt%.

[0013] The diameter of the cylindrical blank in step (3) is 40~45mm and the height is 40~45mm.

[0014] In step (4), the microwave roasting temperature is 400~550℃, the time is 0.5~2h, and the microwave power is 1~5kW.

[0015] The industrial silicon composite reducing agent pellets in step (4) have a bonding index of 65-83, an activation energy of 16-18 KJ / mol, and a resistivity of 3.2 × 10⁻⁶. 5 ~5.6×10 5 μΩ·m, with a strength of 10~14MPa.

[0016] The organic components and alkali metals in coffee wastewater promote the cross-linking and rearrangement of the mixed coal structure, thereby reducing the activation energy of the reaction.

[0017] Coffee wastewater contains a large amount of organic matter such as caffeine, caffeic acid, and pectin. Pectin, with its strong viscosity, helps improve the cohesiveness of the mixed sample. After grinding and heating, the carbon chain structure in the organic matter of coffee wastewater undergoes varying degrees of breakage and recombination, making the internal structure of the mixed sample more stable. At the same time, the cross-linking and rearrangement of the organic carbon structure generates small molecule gases (CH4, CO2, and H2O, etc.), further creating a large number of pores within the sample. This allows alkali metals to migrate more quickly and effectively into these pores, accelerating the chemical reaction rate and promoting a reduction in the activation energy of the reaction.

[0018] The beneficial effects of this invention are:

[0019] (1) The present invention mixes low-rank non-caking coal with high-caking coal with low application value to prepare a reducing agent for silicon smelting. By controlling the amount of non-caking coal added, the bonding index of the composite reducing agent can be effectively controlled, so that the reactants in silicon smelting can be fully contacted and the smelting efficiency can be improved.

[0020] (2) In the grinding process, coffee wastewater is used as the grinding medium. During the stirring process, coffee wastewater can effectively penetrate into the pores of the mixed coal, so that different bonding coals can contact each other better. After microwave heating, the organic components and alkali metals in the coffee wastewater will promote the cross-linking and rearrangement of the mixed coal structure, reduce the reaction activation energy, and increase the rate of silicon smelting carbothermic reduction reaction, thereby realizing the efficient and clean utilization of organic wastewater.

[0021] (3) Under the condition of grinding with coffee wastewater, the present invention uses low-rank non-sticky coal as a reducing agent for silicon smelting to prepare industrial silicon composite reducing agent pellets. The pellets have a bonding index of more than 60, an activation energy of less than 20 KJ / mol, a resistivity much greater than 3500 μΩ·m, and a pellet strength greater than 10 MPa, which meets the requirements of carbonaceous reducing agents for industrial silicon smelting. Detailed Implementation

[0022] 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.

[0023] In this embodiment of the invention, the coffee wastewater is derived from the organic wastewater obtained during the wet preliminary pulping and washing process of green coffee. The coffee wastewater contains a large amount of organic matter such as caffeic acid, caffeine and pectin, with an organic matter content of 35-50 wt%. The coffee wastewater mainly contains alkali metals such as K and Na, with an alkali metal content of 5-9 wt%.

[0024] Example 1: A method for preparing composite reducing agents for industrial silicon using grinding media to enhance the bonding of coals with different caking properties. The specific steps are as follows:

[0025] (1) High-viscosity coal and non-viscosity coal that have been vacuum dried (vacuum dried at 110℃ for 12h) are crushed and ground to a particle size of less than 0.2mm and a particle size of 0.1mm~0.2mm accounts for 25% to obtain high-viscosity coal powder and non-viscosity coal powder; the caking index of the high-viscosity coal powder is 92 and the caking index of the non-viscosity coal is 0.

[0026] (2) High-viscosity coal powder and non-viscosity coal powder are mixed evenly to obtain coal powder mixture A. Coffee wastewater is added to coal powder mixture A and the mixture is ground to obtain coal powder mixture B. Based on the mass of coal powder mixture A, the high-viscosity coal powder accounts for 90% and the non-viscosity coal powder accounts for 10%. The amount of coffee wastewater added is 9% of the mass of coal powder mixture A.

[0027] (3) The coal powder mixture B is pressed into a cylindrical blank by a pressure of 20MPa; the diameter of the cylindrical blank is 40mm and the height is 40mm.

[0028] (4) The cylindrical blank is placed in an argon atmosphere (argon flow rate is 1.5L / min) for microwave calcination, and then cooled to room temperature with the furnace to obtain composite reducing agent pellets for industrial silicon; wherein the microwave calcination temperature is 450℃, the time is 1h, and the microwave power is 3kW.

[0029] In this embodiment, the composite reducing agent pellets for industrial silicon have a bonding index of 78, an activation energy of 17.5 KJ / mol, and a resistivity of 4.3 × 10⁻⁶. 5 μΩ·m, and the pellet strength is 11MPa.

[0030] Comparative Example 1: The difference between this comparative example and Example 1 is that no coffee wastewater is added;

[0031] The comparative example of industrial silicon composite reducing agent pellets has a bonding index of 43, an activation energy of 26 kJ / mol, and a resistivity of 2.5 × 10⁻⁶. 3 μΩ·m, and the pellet strength is 8MPa.

[0032] Example 2: A method for preparing composite reducing agents for industrial silicon using grinding media to enhance the bonding of coals with different caking properties. The specific steps are as follows:

[0033] (1) High-viscosity coal and non-viscosity coal that have been vacuum dried (vacuum dried at 115℃ for 18h) are crushed and ground to a particle size of less than 0.2mm and a particle size of 0.1mm~0.2mm accounts for 30% to obtain high-viscosity coal powder and non-viscosity coal powder; the caking index of the high-viscosity coal powder is 93 and the caking index of the non-viscosity coal is 3.

[0034] (2) High-viscosity coal powder and non-viscosity coal powder are mixed evenly to obtain coal powder mixture A. Coffee wastewater is added to coal powder mixture A and the mixture is ground to obtain coal powder mixture B. Based on the mass of coal powder mixture A, high-viscosity coal powder accounts for 80% and non-viscosity coal powder accounts for 20%. The amount of coffee wastewater added is 11% of the mass of coal powder mixture A.

[0035] (3) The coal powder mixture B is pressed into a cylindrical blank by a pressure of 20MPa; the diameter of the cylindrical blank is 42mm and the height is 41mm;

[0036] (4) The cylindrical blank is placed in an argon atmosphere (argon flow rate is 1L / min) for microwave calcination, and then cooled to room temperature with the furnace to obtain composite reducing agent pellets for industrial silicon; wherein the microwave calcination temperature is 470℃, the time is 1.5h, and the microwave power is 4kW.

[0037] In this embodiment, the composite reducing agent pellets for industrial silicon have a bonding index of 83, an activation energy of 16.2 kJ / mol, and a resistivity of 5.6 × 10⁻⁶. 5 μΩ·m, and the pellet strength is 13MPa.

[0038] Comparative Example 2: The difference between this comparative example and Example 2 is that no coffee wastewater is added;

[0039] The binder index of the industrial silicon composite reducing agent pellets in this comparative example is 32, the activation energy is 23.9 kJ / mol, and the resistivity is 3.5 × 10⁻⁶. 3 μΩ·m, and the pellet strength is 6MPa.

[0040] Example 3: A method for preparing composite reducing agents for industrial silicon using grinding media to enhance the bonding of coals with different bonding characteristics. The specific steps are as follows:

[0041] (1) High-viscosity coal and non-viscosity coal that have been vacuum dried (vacuum dried at 100℃ for 24h) are crushed and ground to a particle size of less than 0.2mm and a particle size of 0.1mm~0.2mm accounts for 20% to obtain high-viscosity coal powder and non-viscosity coal powder; the caking index of the high-viscosity coal powder is 90 and the caking index of the non-viscosity coal is 1.

[0042] (2) High-viscosity coal powder and non-viscosity coal powder are mixed evenly to obtain coal powder mixture A. Coffee wastewater is added to coal powder mixture A and the mixture is ground to obtain coal powder mixture B. Based on the mass of coal powder mixture A, high-viscosity coal powder accounts for 75% and non-viscosity coal powder accounts for 25%. The amount of coffee wastewater added is 12% of the mass of coal powder mixture A.

[0043] (3) The coal powder mixture B is pressed into a cylindrical blank by a pressure of 20MPa; the diameter of the cylindrical blank is 44mm and the height is 45mm;

[0044] (4) The cylindrical blank is placed in an argon atmosphere (argon flow rate is 1.2L / min) for microwave calcination, and then cooled to room temperature with the furnace to obtain composite reducing agent pellets for industrial silicon; wherein the microwave calcination temperature is 400℃, the time is 2h, and the microwave power is 2kW.

[0045] In this embodiment, the composite reducing agent pellets for industrial silicon have a bonding index of 80, an activation energy of 17.9 kJ / mol, and a resistivity of 3.2 × 10⁻⁶. 5 μΩ·m, and the pellet strength is 14MPa.

[0046] Comparative Example 3: The difference between this comparative example and Example 3 is that no coffee wastewater is added;

[0047] The binder index of the industrial silicon composite reducing agent pellets in this comparative example is 46, the activation energy is 31.1 kJ / mol, and the resistivity is 3.3 × 10⁻⁶. 3 μΩ·m, and the pellet strength is 7MPa.

[0048] Example 4: A method for preparing composite reducing agents for industrial silicon using grinding media to enhance the bonding of coals with different caking properties. The specific steps are as follows:

[0049] (1) High-viscosity coal and non-viscosity coal that have been vacuum dried (vacuum dried at 120℃ for 12h) are crushed and ground to a particle size of less than 0.2mm and a particle size of 0.1mm~0.2mm accounts for 35% to obtain high-viscosity coal powder and non-viscosity coal powder; the caking index of the high-viscosity coal powder is 95 and the caking index of the non-viscosity coal is 8.

[0050] (2) High-viscosity coal powder and non-viscosity coal powder are mixed evenly to obtain coal powder mixture A. Coffee wastewater is added to coal powder mixture A and the mixture is ground to obtain coal powder mixture B. Based on the mass of coal powder mixture A, high-viscosity coal powder accounts for 75% and non-viscosity coal powder accounts for 25%. The amount of coffee wastewater added is 8% of the mass of coal powder mixture A.

[0051] (3) The coal powder mixture B is pressed into a cylindrical blank by a pressure of 20MPa; the diameter of the cylindrical blank is 45mm and the height is 42mm;

[0052] (4) The cylindrical blank is placed in an argon atmosphere (argon flow rate is 1.4L / min) for microwave calcination, and then cooled to room temperature with the furnace to obtain composite reducing agent pellets for industrial silicon; wherein the microwave calcination temperature is 550℃, the time is 0.5h, and the microwave power is 1kW.

[0053] In this embodiment, the composite reducing agent pellets for industrial silicon have a bonding index of 65, an activation energy of 17.3 kJ / mol, and a resistivity of 3.8 × 10⁻⁶. 5 μΩ·m, and the pellet strength is 10MPa.

[0054] Comparative Example 4: The difference between this comparative example and Example 4 is that no coffee wastewater is added;

[0055] The binder index of the industrial silicon composite reducing agent pellets in this comparative example is 26, the activation energy is 28.7 kJ / mol, and the resistivity is 3.6 × 10⁻⁶. 3 μΩ·m, and the pellet strength is 4MPa.

[0056] Example 5: A method for preparing composite reducing agents for industrial silicon using grinding media to enhance the bonding of coals with different caking properties. The specific steps are as follows:

[0057] (1) High-viscosity coal and non-viscosity coal that have been vacuum dried (vacuum dried at 110℃ for 20h) are crushed and ground to a particle size of less than 0.2mm and a particle size of 0.1mm~0.2mm accounts for 22% to obtain high-viscosity coal powder and non-viscosity coal powder; the caking index of the high-viscosity coal powder is 91 and the caking index of the non-viscosity coal is 6.

[0058] (2) High-viscosity coal powder and non-viscosity coal powder are mixed evenly to obtain coal powder mixture A. Coffee wastewater is added to coal powder mixture A and the mixture is ground to obtain coal powder mixture B. Based on the mass of coal powder mixture A, high-viscosity coal powder accounts for 85% and non-viscosity coal powder accounts for 15%. The amount of coffee wastewater added is 11% of the mass of coal powder mixture A.

[0059] (3) The coal powder mixture B is pressed into a cylindrical blank by a pressure of 20 MPa; the diameter of the cylindrical blank is 41 mm and the height is 43 mm.

[0060] (4) The cylindrical blank was placed in an argon atmosphere (argon flow rate of 1.2L / min) for microwave calcination and cooled to room temperature with the furnace to obtain composite reducing agent pellets for industrial silicon; wherein the microwave calcination temperature was 430℃, the time was 1.5h, and the microwave power was 4kW.

[0061] In this embodiment, the composite reducing agent pellets for industrial silicon have a bonding index of 77, an activation energy of 16.8 kJ / mol, and a resistivity of 5.2 × 10⁻⁶. 5 μΩ·m, and the pellet strength is 12MPa.

[0062] Comparative Example 5: The difference between this comparative example and Example 5 is that no coffee wastewater is added;

[0063] The comparative example of industrial silicon composite reducing agent pellets has a bonding index of 56, an activation energy of 23.8 kJ / mol, and a resistivity of 4.8 × 10⁻⁶. 3 μΩ·m, and the pellet strength is 9MPa.

[0064] Example 6: A method for preparing composite reducing agents for industrial silicon using grinding media to enhance the bonding of coals with different caking properties. The specific steps are as follows:

[0065] (1) High-viscosity coal and non-viscosity coal that have been vacuum dried (vacuum dried at 120℃ for 15h) are crushed and ground to a particle size of less than 0.2mm and a particle size of 0.1mm~0.2mm accounts for 26% to obtain high-viscosity coal powder and non-viscosity coal powder; the caking index of the high-viscosity coal powder is 92 and the caking index of the non-viscosity coal is 5.

[0066] (2) High-viscosity coal powder and non-viscosity coal powder are mixed evenly to obtain coal powder mixture A. Coffee wastewater is added to coal powder mixture A and the mixture is ground to obtain coal powder mixture B. Based on the mass of coal powder mixture A, high-viscosity coal powder accounts for 82% and non-viscosity coal powder accounts for 18%. The amount of coffee wastewater added is 10% of the mass of coal powder mixture A.

[0067] (3) The coal powder mixture B is pressed into a cylindrical blank by a pressure of 20MPa; the diameter of the cylindrical blank is 42mm and the height is 40mm;

[0068] (4) The cylindrical blank is placed in an argon atmosphere (argon flow rate is 1.3L / min) for microwave calcination, and then cooled to room temperature with the furnace to obtain composite reducing agent pellets for industrial silicon; wherein the microwave calcination temperature is 480℃, the time is 1h, and the microwave power is 5kW.

[0069] In this embodiment, the composite reducing agent pellets for industrial silicon have a bonding index of 70, an activation energy of 17.5 kJ / mol, and a resistivity of 4.4 × 10⁻⁶. 5 μΩ·m, and the pellet strength is 12MPa.

[0070] Comparative Example 6: The difference between this comparative example and Example 6 is that no coffee wastewater is added;

[0071] The binder index of the industrial silicon composite reducing agent pellets in this comparative example is 48, the activation energy is 21.4 kJ / mol, and the resistivity is 4.5 × 10⁻⁶. 3 μΩ·m, and the pellet strength is 7MPa.

[0072] 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 composite reducing agents for industrial silicon using grinding media to enhance the bonding of coals with different caking properties, characterized in that, The specific steps are as follows: (1) Vacuum-dried high-viscosity coal and non-viscosity coal are crushed and ground to a particle size of less than 0.2 mm and a particle size of 0.1 mm to 0.2 mm accounts for 20% to 35% to obtain high-viscosity coal powder and non-viscosity coal powder; the caking index of the high-viscosity coal powder is 90 to 95 and the caking index of the non-viscosity coal is 0 to 8. (2) Mix high-viscosity coal powder and non-viscosity coal powder evenly to obtain coal powder mixture A. Add coffee wastewater to coal powder mixture A and grind it to obtain coal powder mixture B. Based on the mass of coal powder mixture A, high-viscosity coal powder accounts for 75-90% and non-viscosity coal powder accounts for 10-25%. The amount of coffee wastewater added is 8-12% of the mass of coal powder mixture A. The coffee wastewater refers to the organic wastewater obtained in the wet preliminary pulping and washing process of green coffee. (3) The coal powder mixture B is pressed into a cylindrical blank; (4) The cylindrical blank is placed in an argon atmosphere for microwave calcination and cooled to room temperature in the furnace to obtain composite reducing agent pellets for industrial silicon; the microwave calcination temperature is 400~550℃, the time is 0.5~2h, and the microwave power is 1~5kW.

2. The method for preparing composite reducing agents for industrial silicon using grinding media to enhance the bonding of different types of coal, as described in claim 1, is characterized in that: Step (3) The diameter of the cylindrical blank is 40~45mm and the height is 40~45mm.

3. The method for preparing composite reducing agents for industrial silicon using grinding media to enhance the bonding of different types of coal, as described in claim 1, is characterized in that: Step (4) The bonding index of the composite reducing agent pellets for industrial silicon is 65~83, the activation energy is 16~18 KJ / mol, and the resistivity is 3.2×10⁻⁶. 5 ~5.6×10 5 μΩ·m, with a strength of 10~14MPa.