Method for preparing composite reducing agent for industrial silicon by natural fermentation of coffee wastewater and modified petroleum coke
By modifying petroleum coke with coffee wastewater and alkali metal additives, a porous coke carbonaceous reducing agent was prepared, which solved the problem of low reactivity of petroleum coke, improved the efficiency of industrial silicon production and resource utilization, and realized low-carbon and energy-saving industrial silicon smelting.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- KUNMING UNIV OF SCI & TECH
- Filing Date
- 2024-04-12
- Publication Date
- 2026-05-19
AI Technical Summary
The existing petroleum coke reducing agents have low reactivity, resulting in low efficiency in industrial silicon production and insufficient utilization of petroleum coke resources, which also poses environmental pollution problems.
Petroleum coke was modified by co-fermentation with coffee wastewater and alkali metal additives. Through steps such as wet milling, natural fermentation, and microwave roasting, the reactivity and porosity of the petroleum coke were enhanced to prepare a porous whole coke carbonaceous reducing agent.
It improves the reactivity and fixed carbon content of petroleum coke, reduces ash content, decreases slag content, lowers energy consumption and production costs, and improves the smelting efficiency and resource utilization efficiency of industrial silicon, meeting the requirements of low carbon and energy conservation.
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing a composite reducing agent for industrial silicon from petroleum coke through natural fermentation of coffee wastewater, belonging to the field of carbonaceous reducing agent pellet preparation technology. Background Technology
[0002] Raw materials for industrial silicon production include coal, petroleum coke, and charcoal, mixed in any proportion. However, charcoal, derived from trees, is limited in supply and expensive, hindering enterprise development. Petroleum coke, a byproduct of crude oil cracking, has very low ash content, a porosity second only to charcoal, a high fixed carbon content, and certain mechanical strength, making it a viable alternative to charcoal as a reducing agent in industrial silicon production. China's annual petroleum coke production is approximately 25 million tons. Replacing charcoal with petroleum coke as a reducing agent in industrial silicon smelting could broaden its application areas and increase its added value. However, currently, domestic delayed coking plants employ stringent operating conditions to achieve higher liquid product yields and improve economic efficiency. Furthermore, using petroleum coke directly as a full-coke reducing agent has drawbacks such as high conductivity, poor reactivity, low resistivity, low reducing efficiency, and premature crystallization. Much of it does not participate in the reaction, generating highly hazardous silicon carbide, directly affecting silicon quality and hindering industrial silicon production.
[0003] Patent CN103626183A discloses a carbonaceous reducing agent for industrial silicon production, which is composed of petroleum coke and modified petroleum coke particles. This reducing agent has a dry basis fixed carbon content ≥76%, residual ash content ≤1%, volatile matter 10%–16%, and moisture content ≤8%, and can extend the furnace life by approximately double. However, the petroleum coke in this reducing agent has low reactivity.
[0004] Patent CN103626183A discloses a method for preparing a composite carbonaceous reducing agent. The method involves mixing a mixture of prepared petroleum coke, anthracite / bituminous coal, and carbon powder to obtain a mixture. An organic binder, additives, and water are then added to the mixture and stirred until homogeneous. The mixture is then formed into pellets, dried, and the composite reducing agent is obtained. However, this method focuses on the particle size and proportion of the materials and is mainly aimed at the formulation of the reducing agent. The reactivity of the reducing agent is relatively low. Summary of the Invention
[0005] To address the problems in the preparation of petroleum coke reducing agents in existing technologies, this invention proposes a method for preparing a composite reducing agent for industrial silicon from petroleum coke through natural fermentation modification of coffee wastewater. Using petroleum coke as the total coke reducing agent, the method involves wet-milling and fermenting coffee wastewater, petroleum coke, and alkali metal additives. This process allows the organic matter in the coffee wastewater to be modified with affinity for the petroleum coke. Simultaneously, the alkali metals in the coffee wastewater and the K and Na in the alkali metal additives can be adsorbed into the petroleum coke, significantly improving its reactivity. Waste coffee shell powder is then soaked and activated using NaOH solution, modifying the internal organic structure of the coffee shell powder and enhancing its viscosity to prepare a coffee shell binder. This coffee shell binder is used to bind fermented carbon material powder, which is then microwave-calcined to promote cross-linking and rearrangement of the petroleum coke structure. This increases porosity, expands the contact area, and improves reaction efficiency.
[0006] A method for preparing a composite reducing agent for industrial silicon from petroleum coke through natural fermentation of coffee wastewater includes the following specific steps:
[0007] (1) Coffee wastewater, alkali metal additives and petroleum coke are mixed and then wet-milled to obtain mixture A;
[0008] (2) Mixture A is placed in a closed environment at a temperature of 20-35℃ and fermented naturally for 7-28 days to obtain fermented carbon material B. Fermented carbon material B is dried and ground to obtain fermented carbon material powder.
[0009] (3) The coffee shell powder was added to NaOH solution for soaking and activation treatment, and the solid and liquid were separated to obtain the coffee shell binder; the fermented carbon material powder, coffee shell binder and water were mixed to obtain the fermented carbon material mixture;
[0010] (4) The mixture of fermented carbon materials is cold-pressed and dried to obtain a cylindrical blank;
[0011] (5) 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.
[0012] The alkali metal additive in step (1) is one or more of K2CO3, Na2CO3, NaOH, NaHCO3, KOH, NaCl and KCl, the fixed carbon content of petroleum coke is 84-96 wt.%, and the petroleum coke particle size is less than 0.15 mm and not greater than 0.063 mm, accounting for 40-50 wt.%.
[0013] In step (1), the mixture A contains 10-35 wt.% coffee wastewater, 3-8 wt.% alkali metal additives, and 60-80 wt.% petroleum coke.
[0014] In step (2), the carbon material powder fermented in the process contains 30-40 wt.% particles with a diameter not exceeding 0.063 mm.
[0015] In step (3), the particle size of the coffee shell powder is less than 0.15 mm; the mass concentration of the NaOH solution is 4-8%, and the soaking and activation treatment time is 20-60 min.
[0016] By mass percentage, the coffee shell binder accounts for 3-5% of the fermented carbon material mixture in step (3), water accounts for 6-12%, and the remainder is fermented carbon material powder.
[0017] The cold pressing pressure in step (4) is 10-20 MPa, the diameter of the cylindrical blank is 50-60 mm, and the height is 60-100 mm.
[0018] The microwave roasting temperature in step (5) is 450-600℃, the time is 1.5-3h, and the microwave power is 2-5kW.
[0019] The fixed carbon content of the composite reducing agent pellets for industrial silicon in step (4) is greater than 80%, the ash content is less than 3%, the reactivity is greater than 90%, and the cold strength of the pellets is greater than 8000N.
[0020] The coffee wastewater is a residual liquid generated during the coffee making process. It contains high levels of organic matter (such as COD and BOD) and polyphenols (such as tannins, caffeic acid, and caffeine). The coffee wastewater also contains alkali metals such as K, Ca, and Na, with K, Ca, and Na concentrations of 60–100 mg / L, 10–20 mg / L, and 6–15 mg / L, respectively.
[0021] The industrial silicon composite reducing agent pellets have a fixed carbon content greater than 80%, an ash content less than 3%, a reactivity greater than 90%, and a cold strength greater than 8000N.
[0022] The principle of co-fermentation modification of petroleum coke with coffee wastewater and alkali metal additives: Wet milling ensures sufficient contact between petroleum coke and coffee wastewater, allowing the wastewater to better penetrate the pores of the petroleum coke and increasing the reaction contact area. In a closed environment, the organic matter in the coffee wastewater produces highly selective biocatalytic enzymes during natural fermentation. These enzymes adhere to the surface and pores of the petroleum coke particles, while the alkali metal additives have good migration characteristics, allowing the additives and the potassium in the coffee wastewater to react. + Ca 2+ Na +Cations migrate to the active sites of these catalytic enzyme molecules, altering the carbon material structure and graphitization characteristics. After microwave roasting, the macromolecular structure and oxygen-containing functional groups in the fermentation carbon material decompose and become more easily detached. The carbon skeleton sheds a large number of methylene and methyl groups, and hydrogen bonds break, generating a large number of active hydrogen molecules. These active hydrogen molecules migrate outward to the surface and pores of petroleum coke particles and react with the organic matter attached to coffee wastewater, further catalyzing and promoting pyrolysis, thus increasing the reactivity of the petroleum coke. Furthermore, as the temperature increases, more CH4 and H2 are produced, and the gaseous products escape outward, causing numerous micropores to form on the surface of the petroleum coke particles. Simultaneously, molten or gaseous alkali metal molecules such as K, Ca, and Na continue to diffuse inward, further promoting the cracking of fixed carbon in the petroleum coke, lowering the activation energy required for the cracking reaction, and improving the reactivity of the petroleum coke.
[0023] The beneficial effects of this invention are:
[0024] (1) This invention uses petroleum coke as a coke reducing agent. The porous coke carbonaceous reducing agent prepared by adding coffee wastewater for natural fermentation has a high fixed carbon content, good reactivity, and low ash content. When applied to industrial silicon smelting, it can improve the silica reduction rate, reduce the slag content, increase the industrial silicon output, reduce the raw material cost of industrial silicon smelting, and effectively solve the problem of excessive energy consumption.
[0025] (2) This invention utilizes coffee wastewater and alkali metal additives to co-ferment and modify petroleum coke. The porous coke carbonaceous reducing agent prepared in this way has high chemical reactivity. During use, it can significantly reduce the power consumption per ton of silicon, increase active power, reduce carbon emissions, and reduce production costs, which is in line with the background of dual carbon and low carbon energy saving.
[0026] (3) In this invention, coffee wastewater is mixed with alkali metal additives and petroleum coke for wet grinding. During the grinding process, coffee wastewater can effectively penetrate and promote the combination of petroleum coke and alkali metal additives, increase the contact area and improve the porosity, so that the mixed carbon material has high reactivity and improves the reaction efficiency of industrial silicon smelting.
[0027] (4) The coffee shell binder used in the preparation of industrial silicon composite reducing agent pellets by naturally fermenting and modifying petroleum coke using coffee wastewater will heat the carbon material to the sintering temperature during microwave roasting to achieve densification and thus improve the strength of the pellets.
[0028] (5) After the coffee shells are soaked in NaOH solution, -OH penetrates into the crystalline region of the coffee shell fibers, weakening the hydrogen bonds between cellulose and hemicellulose and the saponification of ester bonds between xylan hemicellulose and other components, causing the organic components to swell, increasing the porosity, and forming a hydrogel. With coffee shell adhesive as the adhesive, the alkali metal in the coffee shell can effectively enhance the reaction activity of the pellets in silicon smelting and accelerate the reaction rate.
[0029] (6) This invention enables high-quality and efficient recycling and comprehensive utilization of coffee wastewater, improves the economic value of waste resources, solves the environmental and treatment cost problems caused by coffee wastewater, and further reduces the cost of raw materials for industrial silicon smelting. Detailed Implementation
[0030] 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.
[0031] In this embodiment of the invention, coffee wastewater is a residual liquid generated during the coffee making process. Coffee wastewater contains high levels of organic matter (such as COD and BOD) and polyphenols (such as tannins, caffeic acid, and caffeine). Coffee wastewater also contains alkali metals such as K, Ca, and Na, with K, Ca, and Na contents of 84.5 mg / L, 13.2 mg / L, and 7.3 mg / L, respectively.
[0032] Example 1: A method for preparing a composite reducing agent for industrial silicon from petroleum coke through natural fermentation modification of coffee wastewater, the specific steps of which are as follows:
[0033] (1) Coffee wastewater, alkali metal additive (Na2CO3) and petroleum coke are mixed and then wet-milled to obtain mixture A; the fixed carbon content of the petroleum coke is 86%, and the petroleum coke particles with a diameter of less than 0.15 mm and a diameter of no more than 0.063 mm account for 50%; based on the total mass of mixture A as 100%, the content of coffee wastewater in mixture A is 25 wt%, the content of alkali metal additive (Na2CO3) is 5 wt%, and the content of petroleum coke is 70 wt%;
[0034] (2) Mixture A was placed in a closed environment at 20°C and allowed to ferment naturally for 7 days to obtain fermented carbon material B. Fermented carbon material B was placed in a drying oven at 100°C and dried for 12 hours before being ground to obtain fermented carbon material powder. The fermented carbon material powder contained 40 wt.% of particles with a diameter not greater than 0.063 mm.
[0035] (3) Coffee shell powder (particle size less than 0.15 mm) was added to a 6 wt.% NaOH solution and soaked for 30 min to activate it. The solid and liquid were separated to obtain coffee shell binder. Fermented carbon material powder, coffee shell binder and water were mixed to obtain fermented carbon material mixture. Based on the mass of fermented carbon material mixture as 100%, coffee shell binder accounted for 4%, water accounted for 8%, and the remainder was fermented carbon material powder.
[0036] (4) The fermented carbon material mixture is cold-pressed at 15MPa and dried to obtain a cylindrical blank; the cylindrical blank has a diameter of 60mm and a height of 80mm;
[0037] (5) The cylindrical blank is placed in an argon atmosphere (argon flow rate is 2L / min) for microwave calcination, and then cooled to room temperature in the furnace to obtain a porous whole coke industrial silicon composite reducing agent; wherein the microwave calcination temperature is 500℃, the time is 2h, and the microwave power is 3kW.
[0038] The porous coke industrial silicon composite reducing agent of this embodiment has a fixed carbon content of 81.3 wt.%, an ash content of 2.8 wt.%, a reactivity of 92.7%, and a pellet cold strength of 8243 N.
[0039] 20g of silica (99.5% SiO2, 0.05% Al2O3, 0.03% Fe2O3, 0.05% CaO) was crushed into blocks with a particle size of 25-100mm. After washing and sieving, it was mixed evenly with 10.2g of the above-mentioned composite carbonaceous reducing agent and added to a submerged arc furnace for smelting. After smelting, 8.7g of industrial silicon product was obtained. The composition of the industrial silicon product obtained after smelting was Si>99.6Wt.%, Fe≤0.19Wt.%, Al≤0.09Wt.%, Ca≤0.05Wt.%.
[0040] Example 2: A method for preparing a composite reducing agent for industrial silicon from petroleum coke through natural fermentation modification of coffee wastewater, the specific steps of which are as follows:
[0041] (1) Coffee wastewater, alkali metal additive (K2CO3) and petroleum coke are mixed and then wet-milled to obtain mixture A; the fixed carbon content of the petroleum coke is 89%, and the petroleum coke particles with a diameter of less than 0.15 mm and a diameter of no more than 0.063 mm account for 45%; based on the total mass of mixture A as 100%, the content of coffee wastewater in mixture A is 30 wt%, the content of alkali metal additive (K2CO3) is 6 wt%, and the content of petroleum coke is 64 wt%;
[0042] (2) Mixture A was placed in a closed environment at 30°C and allowed to ferment naturally for 18 days to obtain fermented carbon material B. Fermented carbon material B was placed in a drying oven at 100°C and dried for 10 hours before being ground to obtain fermented carbon material powder. The fermented carbon material powder contained 37 wt.% of particles with a diameter not greater than 0.063 mm.
[0043] (3) Coffee shell powder (particle size less than 0.15 mm) was added to a 4 wt.% NaOH solution and soaked for 50 min to activate it. The solid and liquid were separated to obtain coffee shell binder. Fermented carbon material powder, coffee shell binder and water were mixed to obtain fermented carbon material mixture. Based on the mass of fermented carbon material mixture as 100%, coffee shell binder accounted for 5%, water accounted for 9%, and the remainder was fermented carbon material powder.
[0044] (4) The fermented carbon material mixture is cold-pressed at 15MPa and dried to obtain a cylindrical blank; the cylindrical blank has a diameter of 58mm and a height of 85mm;
[0045] (5) The cylindrical blank is placed in an argon atmosphere (argon flow rate is 3L / min) for microwave calcination, and then cooled to room temperature in the furnace to obtain a porous whole coke industrial silicon composite reducing agent; wherein the microwave calcination temperature is 550℃, the time is 2.5h, and the microwave power is 4kW.
[0046] The porous coke industrial silicon composite reducing agent of this embodiment has a fixed carbon content of 81.3 wt.%, an ash content of 2.8 wt.%, a reactivity of 94.1%, and a pellet cold strength of 8216 N.
[0047] 20g of silica (99.5% SiO2, 0.05% Al2O3, 0.03% Fe2O3, 0.05% CaO) was crushed into blocks with a particle size of 25-100mm. After washing and sieving, it was mixed evenly with 9.9g of the above-mentioned composite carbonaceous reducing agent and added to a submerged arc furnace for smelting. After smelting, 8.4g of industrial silicon product was obtained. The composition of the industrial silicon product obtained after smelting was Si>99.6Wt.%, Fe≤0.19Wt.%, Al≤0.09Wt.%, Ca≤0.05Wt.%.
[0048] Example 3: A method for preparing a composite reducing agent for industrial silicon from petroleum coke through natural fermentation modification of coffee wastewater, the specific steps of which are as follows:
[0049] (1) Coffee wastewater, alkali metal additive (KOH) and petroleum coke are mixed and then wet-milled to obtain mixture A; the fixed carbon content of the petroleum coke is 94%, and the petroleum coke particles with a diameter of less than 0.15 mm and a diameter of no more than 0.063 mm account for 48%; based on the total mass of mixture A as 100%, the content of coffee wastewater in mixture A is 32 wt%, the content of alkali metal additive (KOH) is 8 wt%, and the content of petroleum coke is 60 wt%;
[0050] (2) Mixture A was placed in a closed environment at 32°C and allowed to ferment naturally for 21 days to obtain fermented carbon material B. Fermented carbon material B was placed in a drying oven at 105°C and dried for 12 hours before being ground to obtain fermented carbon material powder. The fermented carbon material powder contained 40 wt.% of particles with a diameter not greater than 0.063 mm.
[0051] (3) Coffee shell powder (particle size less than 0.15 mm) was added to an 8 wt.% NaOH solution and soaked for 20 min to activate it. The solid and liquid were separated to obtain coffee shell binder. Fermented carbon material powder, coffee shell binder and water were mixed to obtain fermented carbon material mixture. Based on the mass of fermented carbon material mixture as 100%, coffee shell binder accounted for 4%, water accounted for 10%, and the remainder was fermented carbon material powder.
[0052] (4) The fermented carbon material mixture is cold-pressed at 20MPa and dried to obtain a cylindrical blank; the cylindrical blank has a diameter of 55mm and a height of 85mm;
[0053] (5) The cylindrical blank is placed in an argon atmosphere (argon flow rate of 2.5L / min) for microwave calcination and cooled to room temperature in the furnace to obtain a porous whole coke industrial silicon composite reducing agent; wherein the microwave calcination temperature is 600℃, the time is 3h, and the microwave power is 5kW.
[0054] The porous coke industrial silicon composite reducing agent of this embodiment has a fixed carbon content of 92.3 wt.%, an ash content of 2.1 wt.%, a reactivity of 95.4%, and a pellet cold strength of 8469 N.
[0055] 20g of silica (99.5% SiO2, 0.05% Al2O3, 0.03% Fe2O3, 0.05% CaO) was crushed into blocks with a particle size of 25-100mm. After washing and sieving, it was mixed evenly with 10.0g of the above-mentioned composite carbonaceous reducing agent and added to a submerged arc furnace for smelting. After smelting, 8.8g of industrial silicon product was obtained. The composition of the industrial silicon product obtained after smelting was Si>99.6Wt.%, Fe≤0.19Wt.%, Al≤0.09Wt.%, Ca≤0.05Wt.%.
[0056] Example 4: A method for preparing a composite reducing agent for industrial silicon from petroleum coke through natural fermentation modification of coffee wastewater, the specific steps of which are as follows:
[0057] (1) Coffee wastewater, alkali metal additive (NaOH) and petroleum coke are mixed and then wet-milled to obtain mixture A; the fixed carbon content of the petroleum coke is 92%, and the petroleum coke particles with a diameter of less than 0.15 mm and a diameter of no more than 0.063 mm account for 46%; based on the total mass of mixture A as 100%, the content of coffee wastewater in mixture A is 20 wt%, the content of alkali metal additive (NaOH) is 5 wt%, and the content of petroleum coke is 75 wt%;
[0058] (2) Mixture A was placed in a closed environment at 25°C and allowed to ferment naturally for 15 days to obtain fermented carbon material B. Fermented carbon material B was placed in a drying oven at 100°C and dried for 12 hours before being ground to obtain fermented carbon material powder. The fermented carbon material powder contained 38 wt.% of particles with a diameter not greater than 0.063 mm.
[0059] (3) Coffee shell powder (particle size less than 0.15 mm) was added to a 5 wt.% NaOH solution and soaked for 40 min to activate it. The solid and liquid were separated to obtain coffee shell binder. Fermented carbon material powder, coffee shell binder and water were mixed to obtain fermented carbon material mixture. Based on the mass of fermented carbon material mixture as 100%, coffee shell binder accounted for 5%, water accounted for 12%, and the remainder was fermented carbon material powder.
[0060] (4) The fermented carbon material mixture is cold-pressed at 10MPa and dried to obtain a cylindrical blank; the cylindrical blank has a diameter of 53mm and a height of 70mm;
[0061] (5) The cylindrical blank is placed in an argon atmosphere (argon flow rate of 2.5L / min) for microwave calcination and cooled to room temperature in the furnace to obtain a porous whole coke industrial silicon composite reducing agent; wherein the microwave calcination temperature is 500℃, the time is 2h, and the microwave power is 4kW.
[0062] The porous coke industrial silicon composite reducing agent of this embodiment has a fixed carbon content of 86.7 wt.%, an ash content of 2.8 wt.%, a reactivity of 93.8%, and a pellet cold strength of 8375 N;
[0063] 20g of silica (99.5% SiO2, 0.05% Al2O3, 0.03% Fe2O3, 0.05% CaO) was crushed into blocks with a particle size of 25-100mm. After washing and sieving, it was mixed evenly with 9.9g of the above-mentioned composite carbonaceous reducing agent and added to a submerged arc furnace for smelting. After smelting, 8.8g of industrial silicon product was obtained. The composition of the industrial silicon product obtained after smelting was Si>99.6Wt.%, Fe≤0.19Wt.%, Al≤0.09Wt.%, Ca≤0.05Wt.%.
[0064] Example 5: A method for preparing a composite reducing agent for industrial silicon from petroleum coke through natural fermentation modification of coffee wastewater, the specific steps of which are as follows:
[0065] (1) Coffee wastewater, alkali metal additive (K2CO3) and petroleum coke are mixed and then wet-milled to obtain mixture A; the fixed carbon content of the petroleum coke is 95%, and the petroleum coke particles with a diameter of less than 0.15 mm and a diameter of no more than 0.063 mm account for 40%; based on the total mass of mixture A as 100%, the content of coffee wastewater in mixture A is 34 wt%, the content of alkali metal additive (K2CO3) is 6 wt%, and the content of petroleum coke is 60 wt%;
[0066] (2) Mixture A was placed in a closed environment at 35°C and allowed to ferment naturally for 28 days to obtain fermented carbon material B. Fermented carbon material B was placed in a drying oven at 100°C and dried for 12 hours before being ground to obtain fermented carbon material powder. The fermented carbon material powder contained 32 wt.% of particles with a diameter not greater than 0.063 mm.
[0067] (3) Coffee shell powder (particle size less than 0.15 mm) was added to a 7 wt.% NaOH solution and soaked for 60 min to activate it. The solid and liquid were separated to obtain coffee shell binder. Fermented carbon material powder, coffee shell binder and water were mixed to obtain fermented carbon material mixture. Based on the mass of fermented carbon material mixture as 100%, coffee shell binder accounted for 4%, water accounted for 10%, and the remainder was fermented carbon material powder.
[0068] (4) The fermented carbon material mixture is cold-pressed at 20MPa and dried to obtain a cylindrical blank; the cylindrical blank has a diameter of 60mm and a height of 90mm;
[0069] (5) The cylindrical blank is placed in an argon atmosphere (argon flow rate is 3L / min) for microwave calcination, and then cooled to room temperature in the furnace to obtain a porous whole coke industrial silicon composite reducing agent; wherein the microwave calcination temperature is 600℃, the time is 3h, and the microwave power is 5kW.
[0070] The porous coke industrial silicon composite reducing agent of this embodiment has a fixed carbon content of 92.1 wt.%, an ash content of 2.2 wt.%, a reactivity of 96.3%, and a pellet cold strength of 8574 N.
[0071] 20g of silica (99.5% SiO2, 0.05% Al2O3, 0.03% Fe2O3, 0.05% CaO) was crushed into blocks with a particle size of 25-100mm. After washing and sieving, it was mixed evenly with 10.1g of the above-mentioned composite carbonaceous reducing agent and added to a submerged arc furnace for smelting. After smelting, 9.2g of industrial silicon product was obtained. The composition of the industrial silicon product obtained after smelting was Si>99.6Wt.%, Fe≤0.19Wt.%, Al≤0.09Wt.%, Ca≤0.05Wt.%.
[0072] Example 6: A method for preparing a composite reducing agent for industrial silicon from petroleum coke through natural fermentation modification of coffee wastewater, the specific steps of which are as follows:
[0073] (1) Coffee wastewater, alkali metal additives (NaOH and NaCl in a mass ratio of 1:1) and petroleum coke are mixed and then wet-milled to obtain mixture A. The petroleum coke has a fixed carbon content of 85%, and 42% of the petroleum coke particles are less than 0.15 mm and have a particle size of no more than 0.063 mm. Based on the total mass of mixture A as 100%, the content of coffee wastewater in mixture A is 15 wt%, the content of alkali metal additives is 5 wt%, and the content of petroleum coke is 80 wt%.
[0074] (2) Mixture A was placed in a closed environment at 20°C and allowed to ferment naturally for 10 days to obtain fermented carbon material B. Fermented carbon material B was placed in a drying oven at 100°C and dried for 12 hours before being ground to obtain fermented carbon material powder. The fermented carbon material powder contained 34 wt.% of particles with a diameter not greater than 0.063 mm.
[0075] (3) Coffee shell powder (particle size less than 0.15 mm) was added to a 6 wt.% NaOH solution and soaked for 40 min to activate it. The solid and liquid were separated to obtain coffee shell binder. Fermented carbon material powder, coffee shell binder and water were mixed to obtain fermented carbon material mixture. Based on the mass of fermented carbon material mixture as 100%, coffee shell binder accounted for 5%, water accounted for 6%, and the remainder was fermented carbon material powder.
[0076] (4) The fermented carbon material mixture is cold-pressed at 10MPa and dried to obtain a cylindrical blank; the cylindrical blank has a diameter of 50mm and a height of 65mm;
[0077] (5) The cylindrical blank is placed in an argon atmosphere (argon flow rate is 2L / min) for microwave calcination, and then cooled to room temperature in the furnace to obtain a porous whole coke industrial silicon composite reducing agent; wherein the microwave calcination temperature is 450℃, the time is 1.5h, and the microwave power is 3kW.
[0078] The porous coke industrial silicon composite reducing agent of this embodiment has a fixed carbon content of 81.1 wt.%, an ash content of 2.9 wt.%, a reactivity of 92.1%, and a pellet cold strength of 8194 N.
[0079] 20g of silica (99.5% SiO2, 0.05% Al2O3, 0.03% Fe2O3, 0.05% CaO) was crushed into blocks with a particle size of 25-100mm. After washing and sieving, it was mixed evenly with 10.0g of the above-mentioned composite carbonaceous reducing agent and added to a submerged arc furnace for smelting. After smelting, 8.2g of industrial silicon product was obtained. The composition of the industrial silicon product obtained after smelting was Si>99.6Wt.%, Fe≤0.19Wt.%, Al≤0.09Wt.%, Ca≤0.05Wt.%.
[0080] Example 7: A method for preparing a composite reducing agent for industrial silicon from petroleum coke through natural fermentation modification of coffee wastewater, the specific steps of which are as follows:
[0081] (1) Coffee wastewater, alkali metal additives (KOH and K2CO3 in a mass ratio of 1:1) and petroleum coke are mixed and then wet-milled to obtain mixture A. The petroleum coke has a fixed carbon content of 94%, and 50% of the petroleum coke particles are less than 0.15 mm and have a particle size of no more than 0.063 mm. Based on the total mass of mixture A as 100%, the content of coffee wastewater in mixture A is 28 wt%, the content of alkali metal additives is 7 wt%, and the content of petroleum coke is 65 wt%.
[0082] (2) Mixture A was placed in a closed environment at 33°C and allowed to ferment naturally for 24 days to obtain fermented carbon material B. Fermented carbon material B was placed in a drying oven at 100°C and dried for 12 hours before being ground to obtain fermented carbon material powder. The fermented carbon material powder contained 40 wt.% of particles with a diameter not greater than 0.063 mm.
[0083] (3) Coffee shell powder (particle size less than 0.15 mm) was added to a 6 wt.% NaOH solution and soaked for 35 min to activate it. The solid and liquid were separated to obtain coffee shell binder. Fermented carbon material powder, coffee shell binder and water were mixed to obtain fermented carbon material mixture. Based on the mass of fermented carbon material mixture as 100%, coffee shell binder accounted for 4%, water accounted for 9%, and the remainder was fermented carbon material powder.
[0084] (4) The fermented carbon material mixture is cold-pressed at 15MPa and dried to obtain a cylindrical blank; the cylindrical blank has a diameter of 59mm and a height of 95mm;
[0085] (5) The cylindrical blank is placed in an argon atmosphere (argon flow rate of 2.5L / min) for microwave calcination and cooled to room temperature in the furnace to obtain a porous whole coke industrial silicon composite reducing agent; wherein the microwave calcination temperature is 550℃, the time is 2.5h, and the microwave power is 4kW.
[0086] The porous coke industrial silicon composite reducing agent of this embodiment has a fixed carbon content of 92.7 wt.%, an ash content of 2.4 wt.%, a reactivity of 95.8%, and a pellet cold strength of 8423 N;
[0087] 20g of silica (99.5% SiO2, 0.05% Al2O3, 0.03% Fe2O3, 0.05% CaO) was crushed into blocks with a particle size of 25-100mm. After washing and sieving, it was mixed evenly with 10.1g of the above-mentioned composite carbonaceous reducing agent and added to a submerged arc furnace for smelting. After smelting, 9.1g of industrial silicon product was obtained. The composition of the industrial silicon product obtained after smelting was Si>99.6Wt.%, Fe≤0.19Wt.%, Al≤0.09Wt.%, Ca≤0.05Wt.%.
[0088] 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 a composite reducing agent for industrial silicon from petroleum coke through natural fermentation modification of coffee wastewater, characterized in that, The specific steps are as follows: (1) Coffee wastewater, alkali metal additives and petroleum coke are mixed and then wet-milled to obtain mixture A; the alkali metal additives are one or more of K2CO3, Na2CO3, NaOH, NaHCO3, KOH, NaCl and KCl; in mixture A, coffee wastewater accounts for 10~35 wt.%, alkali metal additives account for 3~8 wt.%, and petroleum coke accounts for 60~80 wt.%; (2) Mixture A is placed in a closed environment at a temperature of 20~35℃ and fermented naturally for 7~28 days to obtain fermented carbon material B. Fermented carbon material B is dried and ground to obtain fermented carbon material powder. (3) The coffee shell powder is added to NaOH solution for soaking and activation treatment, and the solid and liquid are separated to obtain coffee shell binder; the fermentation carbon material powder, coffee shell binder and water are mixed to obtain fermentation carbon material mixture; the mass concentration of NaOH solution is 4~8%, and the soaking and activation treatment time is 20~60min; (4) The mixture of fermented carbon materials is cold-pressed and dried to obtain a cylindrical blank; (5) 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.
2. The method for preparing a composite reducing agent for industrial silicon from petroleum coke through natural fermentation modification of coffee wastewater according to claim 1, characterized in that: Step (1) The fixed carbon content of petroleum coke is 84~96 wt., and the petroleum coke particles with a diameter less than 0.15 mm and a diameter not greater than 0.063 mm account for 40~50 wt.
3. The method for preparing a composite reducing agent for industrial silicon from petroleum coke through natural fermentation modification of coffee wastewater according to claim 1, characterized in that: In step (2), the particle size of the fermented carbon material powder is no greater than 0.063 mm, accounting for 30~40 wt.%.
4. The method for preparing a composite reducing agent for industrial silicon from petroleum coke through natural fermentation modification of coffee wastewater according to claim 1, characterized in that: Step (3) The particle size of the coffee shell powder is less than 0.15 mm.
5. The method for preparing a composite reducing agent for industrial silicon from petroleum coke by natural fermentation modification of coffee wastewater according to claim 1, characterized in that: By mass percentage, in step (3) the coffee shell binder accounts for 3-5%, water accounts for 6-12%, and the remainder is fermented carbon material powder.
6. The method for preparing a composite reducing agent for industrial silicon from petroleum coke by natural fermentation modification of coffee wastewater according to claim 1, characterized in that: Step (4) The cold pressing pressure is 10~20MPa, the diameter of the cylindrical blank is 50~60mm, and the height is 60~100mm.
7. The method for preparing a composite reducing agent for industrial silicon from petroleum coke by natural fermentation modification of coffee wastewater according to claim 1, characterized in that: Step (5) The microwave roasting temperature is 450~600℃, the time is 1.5~3h, and the microwave power is 2~5kW.
8. The method for preparing a composite reducing agent for industrial silicon from petroleum coke by natural fermentation modification of coffee wastewater according to claim 1, characterized in that: Step (4) The fixed carbon content of the composite reducing agent pellets for industrial silicon is greater than 80%, the ash content is less than 3%, the reactivity is greater than 90%, and the cold strength of the pellets is greater than 8000N.