Method for producing Si4210 by 33MVA large submerged arc furnace

Abstract

The invention discloses a method for producing Si4210 through a 33MVA large submerged arc furnace, and belongs to the technical field of metallurgy and energy. According to the method, petroleum coke is added to reduce dependence on charcoal, the petroleum coke is crushed and screened before being used, the particle size is controlled within the range of 1-10 mm, the particle size is reduced, the specific surface area is increased, and reactivity is improved; the used petroleum coke is dried and preheated through a steam pipeline, and the reaction activity is improved by reducing moisture and increasing porosity; the stoking depth is controlled, it is ensured that the material layer structure does not change, and the petroleum coke reacts in the silicon carbide generation area; calcium chloride is added in the mixture, so that the melting point of slag is reduced, the fluidity of the slag is improved, and the stability of a crucible reaction area is ensured. Compared with the method for producing the Si4210 product by using charcoal, the method has the advantages that the used raw materials are relatively common in the market, the selection channel of the raw materials for the high-grade industrial silicon is widened, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and energy, and specifically relates to a method for producing Si4210 in a 33MVA large-scale submerged arc furnace. Background Art

[0002] Industrial silicon production is a process in which silicon ore (effective ingredient SiO2) and a reducing agent (effective ingredient C) undergo a reduction reaction in a submerged arc furnace to produce industrial silicon and gases such as carbon monoxide. Industrial silicon grades are classified according to their chemical composition, with specific grades determined mainly by the content of iron, aluminum, and calcium. Requirements are also set for trace elements according to different uses (polysilicon, organosilicon, and metallurgy).

[0003] At present, the grade of industrial silicon produced by large-scale ore-fired furnaces of about 33MVA in China is generally below Si5210, including Si5510, Si5530, Si6210, 99# silicon, etc. The main reason is that the domestic reserves of high-quality silica are small, and the impurity content of most silica is higher than 0.5%; at the same time, large-scale ore-fired furnaces generally adopt the full coal process, and the reducing agent used is mainly bituminous coal, and the Fe2O3 content is above 0.2%, which makes it difficult to produce high-grade industrial silicon above Si4210. Some small ore-fired furnaces in the south use charcoal to produce Si4210, but the use of charcoal will not only bring in impurities, but also increase production costs, destroy forest resources, and do not meet national and international requirements for carbon emissions. Therefore, it is necessary to develop a full coal process based on coal to produce Si4210. Summary of the invention

[0004] The invention provides a method for producing Si4210 by using a 33MVA large-scale ore-fired furnace, which solves the problem of relying on charcoal to produce Si4210 in the prior art and develops a full-coal process mainly using coal to produce Si4210.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions: A method for producing Si4210 using a 33MVA large-scale ore-fired furnace, comprising the following steps: Treat petroleum coke to reduce moisture, increase macropore porosity above 50nm and specific surface area; The treated petroleum coke is mixed with other raw materials in the mass ratio of silica: petroleum coke: binding coal: non-binding coal: wood chips: calcium chloride = 40:3:6:16:10:1. Mix them thoroughly and evenly, control the ramming depth to be no less than 500mm from the material surface, ensure that the material layer structure of "raw material area - clinker area - SiC generation area - SiC decomposition area - crucible area" does not change, send the mixture to the ore-fired furnace for smelting production, control the material surface temperature not to exceed 500℃, and make the petroleum coke start to react in the silicon carbide generation area.

[0006] In the above steps, by mass percentage, the silicon dioxide content in the silica is more than 99.5%, the iron oxide content is less than 0.07%, the aluminum oxide content is less than 0.3%, and the calcium oxide content is less than 0.2%; the fixed carbon content in the petroleum coke is more than 85%, the iron oxide content is less than 0.05%, the aluminum oxide content is less than 0.1%, and the calcium oxide content is less than 0.1%; the iron oxide content in the caking coal is less than 0.25%, the aluminum oxide content is less than 0.5%, and the calcium oxide content is less than 0.3%; the iron oxide content in the non-caking coal is less than 0.2%, the aluminum oxide content is less than 0.4%, and the calcium oxide content is less than 0.2%; The silica particle size is 50-200mm, the bonding coal particle size is 3-25mm, the non-bonding particle size is 3-20mm, and the wood chip particle size is 10-150mm; The processing process of petroleum coke is as follows: the petroleum coke is crushed and screened, and the particle size is controlled within the range of 1-10mm; then it is dried and preheated through a steam pipeline to reduce the moisture content in the petroleum coke and increase its porosity.

[0007] Beneficial effects: The present invention provides a method for producing Si4210 in a 33MVA large-scale submerged arc furnace, which solves the problems existing in the prior art of producing industrial silicon in a large-scale submerged arc furnace of about 33MVA by adding petroleum coke and improving the production process; calcium chloride is added to the mixture of the present invention, and calcium carbonate can also be used instead, so as to reduce the melting point of the slag, improve the fluidity of the slag, and ensure the stability of the crucible reaction area; the petroleum coke is crushed and screened before use, and the particle size is controlled in the range of 1-10mm, so as to reduce the particle size, increase the specific surface area, and improve the reactivity; and the petroleum coke is dried and preheated through a steam pipeline, so as to reduce moisture and increase porosity, thereby improving the reaction activity. ; By improving the angle of the tamping rod of the tamping car, the tamping rod is inserted to a depth of more than 500 mm below the material surface, ensuring that the material layer structure of "raw material area-clinker area-SiC generation area-SiC decomposition area-crucible area" does not change, and controlling the material surface temperature not to exceed 500°C, so that the petroleum coke reacts in the silicon carbide generation area; the present invention uses a small amount of petroleum coke, most of which is bituminous coal, and does not use charcoal. A small amount of wood chips is used as a loosening agent. Compared with the prior art of using charcoal to produce Si4210 products, the raw materials used in the present invention are more common in the market, which broadens the selection channels for raw materials used for high-grade industrial silicon, while reducing production costs and protecting forest resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 ] is a reaction flow chart in an embodiment of the present invention. DETAILED DESCRIPTION

[0009] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments: Example 1

[0010] like Figure 1 As shown, a method for producing Si421 in a 33MVA large-scale ore-fired furnace comprises the following steps: The petroleum coke is crushed and screened, and the particle size is controlled at 1-10mm. Reducing the particle size increases the specific surface area and improves the reactivity. Then it is dried and preheated through the steam pipeline to reduce the moisture and increase the macropore porosity above 50nm. The ratio of raw materials used is silica: silica: petroleum coke: caking coal: non-caking coal: wood chips: calcium chloride = 200kg: 15kg: 30kg: 80kg: 50kg: 5kg. After being fully mixed, the mixture is sent to the submerged arc furnace for smelting production by a conveyor belt. The ramming depth is controlled to be no less than 500mm from the material surface to ensure that the material layer structure of "raw material area-clinker area-SiC generation area-SiC decomposition area-crucible area" does not change. The mixture is sent to the submerged arc furnace for smelting production. Current is introduced into the furnace through three-phase electrodes. The arc heat generated by the arc at the end of the electrode and the resistance heat generated by the current passing through the charge provide the required temperature for the reaction between the raw materials. The pores between the charges ensure the efficiency of gas participation in the reaction during the reaction. The surface temperature is controlled not to exceed 500°C, so that the petroleum coke starts to react in the silicon carbide generation area. By mass percentage, the silica content of the used silica is 99.54%, the content of ferric oxide is 0.064%, the content of aluminum oxide is 0.25%, and the content of calcium oxide is 0.15%; the fixed carbon content of the used petroleum coke is 85.13%, the content of ferric oxide is 0.03%, the content of aluminum oxide is 0.05%, and the content of calcium oxide is 0.06%; the content of ferric oxide in the used binding coal is 0.18%, the content of aluminum oxide is 0.25%, and the content of calcium oxide is 0.22%; the content of ferric oxide in the used non-binding coal is 0.14%, the content of aluminum oxide is 0.38%, and the content of calcium oxide is 0.16%; The particle size of silica used is 50-200mm, the particle size of petroleum coke used is 1-10mm, the particle size of bonding coal used is 3-25mm, the particle size of non-bonding used is 3-20mm, and the particle size of wood chips used is 10-150mm.

[0011] During the implementation of the method in this embodiment, the average daily output of a single furnace is more than 58 tons, and the silicon recovery rate is more than 85%, which is much higher than the same type of furnace in the same industry; Si4210 accounts for the highest proportion of 100% of the products produced. Example 2

[0012] A method for producing Si421 using a 33MVA large-scale ore-fired furnace comprises the following steps: The petroleum coke is crushed and screened, and the particle size is controlled at 1-10mm. Reducing the particle size increases the specific surface area and improves the reactivity. Then it is dried and preheated through the steam pipeline to reduce moisture and increase porosity. The raw material ratio is silica: silica: petroleum coke: caking coal: non-caking coal: wood chips: calcium chloride = 200kg: 15kg: 30kg: 80kg: 50kg: 5kg. After being fully mixed, the mixture is sent to the submerged arc furnace for smelting production by a conveyor belt. The ramming depth is controlled to be not less than 500mm from the material surface to ensure that the material layer structure of "raw material area-clinker area-SiC generation area-SiC decomposition area-crucible area" does not change. The mixture is sent to the submerged arc furnace for smelting production. Current is introduced into the furnace through three-phase electrodes. The arc heat generated by the arc at the end of the electrode and the resistance heat generated by the current passing through the charge provide the required temperature for the reaction between the raw materials. The pores between the charges ensure the efficiency of the gas participating in the reaction during the reaction. The surface temperature is controlled not to exceed 500°C, so that the petroleum coke starts to react in the silicon carbide generation area. By mass percentage, the silica content of the used silica is 99.7%, the iron dioxide content is 0.05%, the aluminum oxide content is 0.08%, and the calcium oxide content is 0.05%; the fixed carbon content of the used petroleum coke is 86.7%, the iron oxide content is 0.02%, the aluminum oxide content is 0.02%, and the calcium oxide content is 0.04%; the iron oxide content of the used binding coal is 0.22%, the aluminum oxide content is 0.45%, and the calcium oxide content is 0.23%; the iron oxide content of the used non-binding coal is 0.18%, the aluminum oxide content is 0.23%, and the calcium oxide content is 0.08%; The particle size of silica used is 50-200mm, the particle size of petroleum coke used is 1-10mm, the particle size of bonding coal used is 3-25mm, the particle size of non-bonding used is 3-20mm, and the particle size of wood chips used is 10-150mm.

[0013] During the implementation of this embodiment, the average daily output of a single furnace is more than 60 tons, and the silicon recovery rate is more than 87%, which is much higher than the output of the same furnace type in the same industry; among the products produced, Si4210 accounts for the highest proportion of 92%.

[0014] The above are only preferred embodiments of the present invention, which cannot limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical ideas proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for producing Si4210 using a 33MVA large-scale submerged arc furnace, characterized in that: The following steps are involved: Pre-treating petroleum coke; The treated petroleum coke is mixed with other raw materials in the mass ratio of silica: petroleum coke: binding coal: non-binding coal: wood chips: calcium chloride = 40:3:6:16:10:

1. After being fully mixed, it is sent to the submerged arc furnace for smelting production. The ramming depth is controlled to be no less than 500mm from the material surface to ensure that the material layer structure of "raw material area-clinker area-SiC generation area-SiC decomposition area-crucible area" does not change. The material surface temperature is controlled not to exceed 500℃, so that the petroleum coke begins to react in the silicon carbide generation area.

2. The method for producing Si4210 by a 33MVA large-scale submerged arc furnace according to claim 1, characterized in that: The silica contains more than 99.5% silicon dioxide, less than 0.07% iron oxide, less than 0.3% aluminum oxide and less than 0.2% calcium oxide.

3. The method for producing Si4210 by a 33MVA large-scale submerged arc furnace according to claim 1, characterized in that: The petroleum coke has a fixed carbon content of more than 85%, a ferric oxide content of less than 0.05%, an aluminum oxide content of less than 0.1%, and a calcium oxide content of less than 0.1%.

4. The method for producing Si4210 by a 33MVA large-scale submerged arc furnace according to claim 1, characterized in that: The caking coal has a ferric oxide content of less than 0.25%, an aluminum oxide content of less than 0.5%, and a calcium oxide content of less than 0.3%.

5. The method for producing Si4210 by a 33MVA large-scale ore-fired furnace according to claim 1, characterized in that: The caking-free coal has a ferric oxide content of less than 0.2%, an aluminum oxide content of less than 0.4%, and a calcium oxide content of less than 0.2%.

6. The method for producing Si4210 by a 33MVA large-scale submerged arc furnace according to claim 1 or 3, characterized in that: The pretreatment process of petroleum coke is as follows: the petroleum coke is crushed and screened to control the particle size within the range of 1-10mm; then it is dried and preheated through a steam pipeline to reduce the moisture content in the petroleum coke and increase the macropore porosity above 50nm.

7. The method for producing Si4210 by a 33MVA large-scale submerged arc furnace according to claim 1 or 2, characterized in that: The silica particle size is 50-200 mm.

8. The method for producing Si4210 by a 33MVA large-scale submerged arc furnace according to claim 1 or 4, characterized in that: The bonding coal has a particle size of 3-25 mm.

9. The method for producing Si4210 by a 33MVA large-scale submerged arc furnace according to claim 1 or 5, characterized in that: The non-bonded particle size is 3-20 mm.

10. The method for producing Si4210 by a 33MVA large-scale submerged arc furnace according to claim 1, characterized in that: The wood chips have a particle size of 10-150 mm.

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