Composite biomass reducing agent for industrial silicon production as well as preparation method and application of composite biomass reducing agent

Abstract

The invention relates to the technical field of industrial silicon production, in particular to a composite biomass reducing agent for industrial silicon production and a preparation method and application thereof. The composite biomass reducing agent consists of the following components in percentage by weight: 40-60% of biomass charcoal, 20-30% of lignin, 10-20% of cellulose and 5-10% of an additive, the biomass charcoal is prepared by pyrolyzing at least one of crop straws, wood wastes and fruit shells, the pyrolysis temperature is 400-600 DEG C, and the pyrolysis time is 1-3 hours; lignin and cellulose are derived from extracts of biomass raw materials; the additive is at least one of calcium carbonate, calcium oxide and calcium hydroxide. According to the novel composite biomass reducing agent provided by the invention, the biomass charcoal is compounded with the lignin, the cellulose and the specific additive, so that the stability, the mechanical strength and the reaction activity of the reducing agent are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial silicon production, and particularly to a composite biomass reducing agent for industrial silicon production, a preparation method thereof, and an application thereof. Background Art

[0002] Industrial silicon (also known as metallic silicon) is an important basic material for high-tech industries such as photovoltaic, semiconductor, and aluminum alloy. Its production mainly adopts the carbothermal reduction method, that is, using silica (SiO2) as raw material and reducing it with carbonaceous reducing agents (such as petroleum coke, coal coke, etc.) in a high-temperature electric furnace.

[0003] However, the traditional carbonaceous reducing agents have the following problems: (1) Fossil fuel reducing agents such as petroleum coke and coal coke will generate a large amount of harmful gases such as carbon dioxide (CO2) and sulfur dioxide (SO2) during the production process, exacerbating the greenhouse effect and air pollution, and not meeting the requirements of green and low-carbon development. (2) Petroleum coke, coal coke, etc. are derived from non-renewable fossil energy, with limited reserves and large price fluctuations. Long-term reliance on these reducing agents is not conducive to the sustainable development of industrial silicon production. (3) The specific surface area and porosity of traditional reducing agents are relatively low, resulting in a limited contact area with silica, low reduction reaction efficiency, and high energy consumption.

[0004] To solve the above problems, in recent years, researchers have begun to explore the application of biomass reducing agents. Biomass is a renewable resource, mainly including crop straws, wood wastes, fruit shells, etc., with wide sources and low costs. The biomass carbon generated by the pyrolysis of biomass reducing agents at high temperatures has a high specific surface area, high porosity, and abundant active sites, which can effectively improve the efficiency of the reduction reaction. In addition, the use of biomass reducing agents can reduce the dependence on fossil energy and lower carbon emissions, meeting the development trend of green manufacturing.

[0005] However, the existing biomass reducing agents still have the following deficiencies in practical applications: The reduction performance of single biomass carbon is greatly affected by the types of raw materials and pyrolysis conditions, and it is difficult to meet the stability requirements of the reducing agent performance for industrial silicon production. Biomass carbon is prone to pulverization at high temperatures, resulting in easy generation of dust when used in an electric furnace, affecting production efficiency and equipment life. The reduction reaction activity of single biomass carbon is relatively low, and it is difficult to achieve efficient reduction at a relatively low temperature. Summary of the Invention

[0006] The present invention proposes a novel composite biomass reducing agent, which significantly improves the stability, mechanical strength, and reaction activity of the reducing agent by compounding biomass carbon with lignin, cellulose, and specific additives.

[0007] The technical solution adopted by the present invention is as follows: A composite biomass reducing agent for industrial silicon production is composed of the following components in percentage by weight: 40-60% of biomass charcoal, 20-30% of lignin, 10-20% of cellulose, and 5-10% of additive;

[0008] The biomass charcoal is prepared by pyrolysis of at least one of crop straws, wood wastes, and fruit shells, the pyrolysis temperature is 400-600 °C, and the pyrolysis time is 1-3 hours; the lignin and cellulose are derived from extracts of biomass raw materials; the additive is at least one of calcium carbonate, calcium oxide, and calcium hydroxide.

[0009] As a further improvement of the present invention, the particle size of the biomass charcoal is 0.1-1 mm, the specific surface area is 200-500 m 2 / g, and the porosity is 60-80%.

[0010] As a further improvement of the present invention, the molecular weight of the lignin is 1000-5000 Da, the cellulose is microcrystalline cellulose, and its particle size is 10-50 μm.

[0011] As a further improvement of the present invention, the additive is calcium carbonate, its particle size is 0.5-5 μm, and the purity ≥ 95%.

[0012] A preparation method of a composite biomass reducing agent for industrial silicon production includes the following steps:

[0013] Step 1: Pyrolyze at least one of crop straws, wood wastes, and fruit shells at 400-600 °C for 1-3 hours to obtain biomass charcoal;

[0014] Step 2: Alkaline-treat the biomass raw material to extract lignin and cellulose;

[0015] Step 3: Mix the biomass charcoal, lignin, cellulose, and additive in proportion and stir evenly;

[0016] Step 4: Dry the mixture at 100-150 °C for 2-4 hours to obtain the composite biomass reducing agent.

[0017] As a further improvement of the present invention, the alkaline treatment uses a sodium hydroxide solution with a concentration of 5-10%, a treatment temperature of 60-80 °C, and a treatment time of 2-4 hours.

[0018] As a further improvement of the present invention, in the mixing step, the stirring speed is 200-500 rpm, and the stirring time is 30-60 minutes.

[0019] As a further improvement of the present invention, in the drying step, hot air drying is adopted, and the wind speed is 1-3 m / s.

[0020] Application of a composite biomass reducing agent for industrial silicon production. The composite biomass reducing agent and silica are mixed at a mass ratio of 1:2 - 1:4, and reduced in an electric furnace at 1600 - 1800 °C for 2 - 4 hours to obtain industrial silicon.

[0021] As a further improvement of the present invention, the electric furnace is one of an arc furnace and an induction furnace. An inert gas is introduced for protection during the reaction. The inert gas is nitrogen or argon, and the flow rate is 10 - 20 L / min.

[0022] Beneficial effects of the present invention: (1) The present invention uses biomass charcoal as the main reducing agent, replacing traditional fossil fuel reducing agents such as petroleum coke and coal coke, significantly reducing the emissions of harmful gases such as carbon dioxide (CO2) and sulfur dioxide (SO2), meeting the requirements of green and low-carbon development; at the same time, biomass charcoal is derived from renewable resources (such as crop straws, wood wastes, fruit shells, etc.), effectively reducing the dependence on non-renewable fossil energy and realizing the sustainable utilization of resources.

[0023] (2) By compounding biomass charcoal with lignin, cellulose and specific additives, the present invention significantly increases the specific surface area, porosity and reaction activity of the reducing agent, enhancing its contact area and reaction efficiency with silica; in addition, the introduction of additives further improves the mechanical strength and high-temperature stability of the reducing agent, reduces dust generation, increases the service life and production efficiency of the electric furnace, thereby reducing energy consumption and production costs.

[0024] (3) The preparation method provided by the present invention has a simple process, convenient operation, wide raw material sources and low costs, and is suitable for large-scale industrial production; at the same time, the application conditions of the composite biomass reducing agent in industrial silicon production are compatible with traditional processes, and there is no need to carry out large-scale transformation of existing equipment, having high economic efficiency and popularization value. Specific embodiments

[0025] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0026] The present invention provides a composite biomass reducing agent for industrial silicon production, which is composed of the following components by weight percentage: 40 - 60% of biomass charcoal, 20 - 30% of lignin, 10 - 20% of cellulose, and 5 - 10% of additives; the biomass charcoal is prepared by pyrolysis of at least one of crop straws, wood wastes or fruit shells, the pyrolysis temperature is 400 - 600 °C, and the pyrolysis time is 1 - 3 hours; the lignin and cellulose are derived from extracts of biomass raw materials; the additives are at least one of calcium carbonate, calcium oxide and calcium hydroxide.

[0027] In the present invention, the particle size of the biochar is 0.1 - 1 mm, the specific surface area is 200 - 500 m 2 / g, and the porosity is 60 - 80%. The molecular weight of lignin is 1000 - 5000 Da, and the cellulose is microcrystalline cellulose with a particle size of 10 - 50 μm. The additive is calcium carbonate with a particle size of 0.5 - 5 μm and a purity ≥ 95%.

[0028] A preparation method of a composite biomass reducing agent for industrial silicon production, comprising the following steps:

[0029] Step 1: Pyrolyze at least one of crop straws, wood wastes, and fruit shells at 400 - 600 °C for 1 - 3 hours to obtain biochar;

[0030] Step 2: Alkaline-treat the biomass raw material to extract lignin and cellulose. The alkaline treatment uses a sodium hydroxide solution with a concentration of 5 - 10%, a treatment temperature of 60 - 80 °C, and a treatment time of 2 - 4 hours;

[0031] Step 3: Mix the biochar, lignin, cellulose, and additive in proportion and stir evenly. In the mixing step, the stirring speed is 200 - 500 rpm and the stirring time is 30 - 60 minutes;

[0032] Step 4: Dry the mixture at 100 - 150 °C for 2 - 4 hours to obtain the composite biomass reducing agent. In the drying step, hot air drying is used with a wind speed of 1 - 3 m / s.

[0033] An application of a composite biomass reducing agent for industrial silicon production. Mix the composite biomass reducing agent and silica in a mass ratio of 1:2 - 1:4, and carry out a reduction reaction in an electric furnace at 1600 - 1800 °C for 2 - 4 hours to obtain industrial silicon. The electric furnace is one of an arc furnace and an induction furnace. An inert gas is introduced for protection during the reaction. The inert gas is nitrogen or argon with a flow rate of 10 - 20 L / min.

[0034] Example 1:

[0035] (I) Raw material preparation

[0036] Biomass raw material: Corn straw is selected as the biomass raw material. Additive: Calcium carbonate with a particle size of 1 μm and a purity of 95%.

[0037] (II) Preparation steps

[0038] Step 1: Pyrolyze the corn straw at 500 °C for 2 hours to obtain biochar. The particle size of the biochar is 0.5 mm, the specific surface area is 300 m 2 / g, and the porosity is 70%.

[0039] Step 2: Treat the corn straw with 8% sodium hydroxide solution at 70 °C for 3 hours to extract lignin and cellulose. The molecular weight of lignin is 3000 Da, and the cellulose is microcrystalline cellulose with a particle size of 30 μm.

[0040] Step 3: Mix biomass charcoal (50%), lignin (25%), cellulose (15%) and calcium carbonate (10%) in proportion, with a stirring speed of 300 rpm and a stirring time of 45 minutes.

[0041] Step 4: Dry the mixture at 120 °C for 3 hours using hot air drying with a wind speed of 2 m / s to obtain the composite biomass reducing agent.

[0042] (III) Application test

[0043] Mix the composite biomass reducing agent and silica in a mass ratio of 1:3, and carry out a reduction reaction in an electric arc furnace at 1700 °C for 3 hours, with nitrogen introduced for protection at a flow rate of 15 L / min.

[0044] Test results: The yield of industrial silicon is 92%, the consumption of the reducing agent is 1.2 tons per ton of silicon, and the dust generation amount is 0.5 kg per ton of silicon.

[0045] Example 2:

[0046] (I) Raw material preparation

[0047] Biomass raw material: Select wood waste as the biomass raw material. Additive: Calcium oxide, with a particle size of 3 μm and a purity of 96%.

[0048] (II) Preparation steps

[0049] Step 1: Pyrolyze the wood waste at 450 °C for 2.5 hours to obtain biomass charcoal. The particle size of the biomass charcoal is 0.8 mm, the specific surface area is 400 m 2 / g, and the porosity is 65%.

[0050] Step 2: Treat the wood waste with 6% sodium hydroxide solution at 65 °C for 2.5 hours to extract lignin and cellulose. The molecular weight of lignin is 2000 Da, and the cellulose is microcrystalline cellulose with a particle size of 20 μm.

[0051] Step 3: Mix biomass charcoal (55%), lignin (20%), cellulose (15%) and calcium oxide (10%) in proportion, with a stirring speed of 400 rpm and a stirring time of 50 minutes.

[0052] Step 4: Dry the mixture at 130 °C for 2.5 hours using hot air drying with a wind speed of 1.5 m / s to obtain the composite biomass reducing agent.

[0053] (3) Application test

[0054] Mix the composite biomass reducing agent and silica in a mass ratio of 1:2.5, and carry out a reduction reaction in an induction furnace at 1650 °C for 2.5 hours, while introducing argon for protection with a flow rate of 12 L / min.

[0055] Test results: The yield of metallurgical grade silicon is 90%, the consumption of the reducing agent is 1.3 tons per ton of silicon, and the dust generation amount is 0.6 kg per ton of silicon.

[0056] Example 3:

[0057] (1) Raw material preparation

[0058] Biomass raw material: Select fruit shells (such as walnut shells) as the biomass raw material. Additive: Calcium hydroxide, with a particle size of 2 μm and a purity of 97%.

[0059] (2) Preparation steps

[0060] Step 1: Pyrolyze the walnut shells at 550 °C for 1.5 hours to obtain biomass carbon. The particle size of the biomass carbon is 0.3 mm, the specific surface area is 450 m 2 / g, and the porosity is 75%.

[0061] Step 2: Treat the walnut shells with a 10% sodium hydroxide solution at 75 °C for 4 hours to extract lignin and cellulose. The molecular weight of lignin is 4000 Da, and the cellulose is microcrystalline cellulose with a particle size of 40 μm.

[0062] Step 3: Mix biomass carbon (45%), lignin (30%), cellulose (15%) and calcium hydroxide (10%) in proportion, with a stirring speed of 250 rpm and a stirring time of 40 minutes.

[0063] Step 4: Dry the mixture at 140 °C for 2 hours using hot air drying with a wind speed of 2.5 m / s to obtain the composite biomass reducing agent.

[0064] (3) Application test

[0065] Mix the composite biomass reducing agent and silica in a mass ratio of 1:3.5, and carry out a reduction reaction in an electric arc furnace at 1750 °C for 3.5 hours, while introducing nitrogen for protection with a flow rate of 18 L / min.

[0066] Test results: The yield of metallurgical grade silicon is 94%, the consumption of the reducing agent is 1.1 tons per ton of silicon, and the dust generation amount is 0.4 kg per ton of silicon.

[0067] The implementation and test data of the above Examples 1 - 3 are shown in the following table.

[0068]

[0069]

[0070] As can be seen from the above table, the composite biomass reducing agent provided by the present invention exhibits excellent reduction efficiency, low energy consumption, and low dust generation amount in the production of metallurgical silicon. At the same time, it has the advantages of environmental friendliness and sustainable resource utilization, and is suitable for large-scale industrial applications.

[0071] In summary, the composite biomass reducing agent for the production of metallurgical silicon, its preparation method and application of the present invention not only solve the problems existing when using single biomass carbon as a reducing agent, but also significantly improve the production efficiency and product quality of metallurgical silicon by optimizing the components and preparation process. The application of this composite biomass reducing agent marks the development of the metallurgical silicon production field towards a more environmentally friendly, efficient and sustainable direction, providing strong technical support for the green transformation of the industry. In the future, with the continuous maturity of technology and the further reduction of costs, this composite biomass reducing agent is expected to be more widely applied and promoted in the production of metallurgical silicon, making greater contributions to the goal of achieving green and low-carbon development.

[0072] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite biomass reducing agent for industrial silicon production, characterized in that: The invention is composed of the following components in weight percentage: 40-60% biochar, 20-30% lignin, 10-20% cellulose, and 5-10% additives; The biomass charcoal is prepared by pyrolysis of at least one of crop straw, wood waste, and fruit shells, the pyrolysis temperature is 400-600° C., and the pyrolysis time is 1-3 hours; the lignin and cellulose are derived from extracts of biomass raw materials; and the additive is at least one of calcium carbonate, calcium oxide, and calcium hydroxide.

2. The composite biomass reducing agent for industrial silicon production according to claim 1, characterized in that: The particle size of the biochar is 0.1-1 mm, and the specific surface area is 200-500 m 2 / g, porosity is 60-80%.

3. The composite biomass reducing agent for industrial silicon production according to claim 1, characterized in that: The molecular weight of the lignin is 1000-5000Da, and the cellulose is microcrystalline cellulose with a particle size of 10-50 μm.

4. The composite biomass reducing agent for industrial silicon production according to claim 1, characterized in that: The additive is calcium carbonate with a particle size of 0.5-5 μm and a purity of ≥95%.

5. A method for preparing a composite biomass reducing agent for industrial silicon production, characterized in that: The following steps are involved: Step 1: pyrolyzing at least one of crop straw, wood waste, and fruit shell at 400-600° C. for 1-3 hours to obtain biochar; Step 2: treating the biomass raw materials with alkali to extract lignin and cellulose; Step 3: Mix the biochar, lignin, cellulose and additives in proportion and stir evenly; Step 4: Dry the mixture at 100-150° C. for 2-4 hours to obtain a composite biomass reducing agent.

6. The method for preparing a composite biomass reducing agent for industrial silicon production according to claim 5, characterized in that: The alkali treatment uses a sodium hydroxide solution with a concentration of 5-10%, a treatment temperature of 60-80° C., and a treatment time of 2-4 hours.

7. The method for preparing a composite biomass reducing agent for industrial silicon production according to claim 5, characterized in that: In the mixing step, the stirring speed is 200-500 rpm and the stirring time is 30-60 minutes.

8. The method for preparing a composite biomass reducing agent for industrial silicon production according to claim 5, characterized in that: In the drying step, hot air drying is adopted, and the wind speed is 1-3m / s.

9. An application of a composite biomass reducing agent for industrial silicon production, characterized in that: The composite biomass reducing agent is mixed with silica in a mass ratio of 1:2-1:4, and subjected to reduction reaction at 1600-1800° C. in an electric furnace for 2-4 hours to obtain industrial silicon.

10. The method for preparing a composite biomass reducing agent for industrial silicon production according to claim 9, characterized in that: The electric furnace is one of an electric arc furnace and an induction furnace. Inert gas protection is introduced during the reaction process. The inert gas is nitrogen or argon with a flow rate of 10-20 L / min.

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