Method for smelting industrial silicon by high-calorific-value pulverized coal side-blown reinforced submerged arc furnace

Abstract

The invention relates to a method for smelting industrial silicon by a high-calorific-value pulverized coal side-blown reinforced submerged arc furnace, and belongs to the technical field of silicon smelting. According to the invention, mixed gas dust formed by mixing fine-particle pulverized coal and air is fed into the molten pool through side blowing to form strong stirring and combustion effects, so that the carbothermal reduction reaction of silica is strengthened. According to the method, the high-calorific-value pulverized coal is selected as a main reducing agent to replace part of traditional petroleum coke, so that the smelting efficiency is improved, the production cost is reduced, the stability and the environmental protection performance of the furnace condition are improved, meanwhile, the technology developed by the invention can also relax the requirements on the petroleum coke, and the purity and / or the yield of the obtained product also have certain substitutes. The invention provides an efficient, energy-saving and environment-friendly new technical approach for the industrial silicon smelting industry.

Description

Technical Field

[0001] The invention relates to the technical field of silicon smelting, in particular to an enhanced smelting method in a process of smelting industrial silicon in a submerged arc furnace, and proposes a new technology for side-blowing enhancement using high calorific value pulverized coal. Background Art

[0002] Industrial silicon is an important raw material for many industries such as metallurgy, chemical industry, and electronics. Industrial silicon is generally prepared by carbon thermal reduction. The current production and smelting of industrial silicon uses a mixed carbonaceous reducing agent of petroleum coke, coal, and charcoal. However, due to the high ash content, the impurity content of the generated industrial silicon is high, and it is difficult to reach chemical grade and chemical grade. At the same time, for environmental protection, the proportion of wood blocks and coal has gradually decreased. The traditional method of smelting industrial silicon in a submerged arc furnace mainly relies on petroleum coke and other reducing agents, but there are problems such as low thermal efficiency, difficulty in controlling furnace conditions, and high cost. With the adjustment of energy structure and the advancement of smelting technology, finding efficient, energy-saving, and environmentally friendly smelting methods has become an urgent need in the industry.

[0003] Patent CN202211532606.0 involves a method for preparing industrial silicon by smelting silica by pulverized coal injection, which comprises the following steps: Step 1, respectively weighing silica, petroleum coke and coal, and crushing each of them to form silica powder, petroleum coke powder, pulverized coal and fine-particle pulverized coal, wherein the particle size distribution of the crushed silica is below 80 mm, the particle size of the pulverized coal is not more than 20 mm, and the particle size of the fine-particle pulverized coal is not more than 3 mm, the silicon dioxide content in the silica is greater than 99wt%, and the mass ratio of the silica, petroleum coke and pulverized coal is 2.6-2.7:1.6-1.8:3.7-4.0; the particle size of the petroleum coke is The diameter is not more than 20mm; the ash content of petroleum coke is not more than 1wt%, the solid carbon content is more than 85wt%, the volatile matter is 8-12%, and the moisture content is not more than 2%; the mass of the fine-particle pulverized coal is 5-15% of the mass of the pulverized coal; the pulverized coal is bituminous coal or anthracite, the bituminous coal has a fixed carbon content of more than 50%, a volatile matter of 25-35%, an ash content of no more than 3%, and a moisture content of 2-5%; the anthracite has a fixed carbon content of more than 80%, a volatile matter of 8-12%, a moisture content of less than 2%, and an ash content of less than 3%. Step 2, add the loosening agent, petroleum coke, pulverized coal and silica powder into the ore-fired furnace from the top charging port; the fine-particle pulverized coal is mixed with air to form a mixed gas dust, which is sent into the molten pool through the injection system through the top spray gun, forming a strong stirring in the molten pool, strengthening the occurrence of the reduction reaction, and finally producing silicon water; the mixed gas dust is sprayed to the slag liquid layer of the hot ore furnace; the loosening agent is biomass / wood chips, and the amount of loosening agent added is 5-15% of the mass of silica powder; Step 3, after the smelting is completed, the silicon water is poured into the mold and crushed into industrial silicon products of corresponding particle size. After optimization, the patent can achieve a silicon yield of 38.1% and a silicon purity of 99.6wt%. Summary of the invention

[0004] Based on CN202211532606.0, in order to further improve the silicon yield and / or improve the purity of the product and reduce the requirements for petroleum coke as much as possible, the present invention attempts for the first time a method for smelting industrial silicon in an in-smelting furnace using high calorific value pulverized coal to be strengthened by side blowing. The high calorific value pulverized coal is efficiently introduced into the in-smelting furnace by side blowing, and a high calorific value gas-dust mixture of air and pulverized coal is sprayed into the in-smelting furnace by side blowing to form an outside-in combustion system. At the same time, it can also prevent metal from sticking to the furnace wall, make the temperature distribution more uniform, strengthen the carbon thermal reduction reaction of silica, improve smelting efficiency, reduce production costs, and improve furnace condition stability. In addition, the quality and yield of the resulting product can be improved to a certain extent.

[0005] To achieve the above technical purpose, the present invention provides a method for smelting industrial silicon using a high calorific value pulverized coal side-blowing enhanced ore-fired furnace, comprising the following steps: Step 1, according to the mass ratio of silica: petroleum coke: high calorific value pulverized coal = 2.5-2.8:1.5-1.9:3.5-4.0, silica, petroleum coke, high calorific value pulverized coal are prepared, the calorific value of the high calorific value pulverized coal is not less than 6500 kcal / kg; its particle size is less than or equal to 20 mm; a loosening agent is prepared according to 5-14% of the mass of silica powder; the loosening agent includes biomass; Step 2, adding the bulking agent, petroleum coke, high calorific value pulverized coal and silica powder prepared in proportion into the submerged arc furnace through the charging port on the furnace top; the fine-grained pulverized coal is mixed with air to form a mixed gas dust, which is sent into the molten pool through the injection system through the spray gun on the furnace wall side to produce silicon water; the mixed gas dust is sprayed to the slag liquid layer in the upper part of the molten pool of the submerged arc furnace; the fine-grained pulverized coal is a mixture of bituminous coal and / or anthracite, and its particle size is less than 6mm, and more preferably less than or equal to 3mm, and the particle size of the fine-grained pulverized coal is smaller than that of the high calorific value pulverized coal; the content of fine-grained pulverized coal in the mixed gas dust is 10-15g / L, and before being sent into the molten pool, the temperature of the mixed gas dust is greater than 150°C, the flow rate of the gas-dust mixture is Am / s, and the value of A is 3-5.

[0006] Step 3: After the smelting is completed, the silicon water is poured into the mold and crushed into industrial silicon products of corresponding particle size.

[0007] The present invention selects high calorific value pulverized coal as the main reducing agent, the calorific value of which is not less than 6500 kcal / kg, and the particle size is controlled within 20 mm to ensure good combustion and reaction efficiency.

[0008] The particle size distribution of the silica powder used in the present invention is less than 80 mm, the particle size distribution of the petroleum coke is less than 20 mm, the silicon dioxide in the silica is greater than 99 wt%, and the mass ratio of the silica, petroleum coke and high calorific value pulverized coal is 2.5-2.8:1.5-1.9:3.5-4.0; the ash content of the petroleum coke is less than 2 wt%, the fixed carbon is greater than 80 wt%, the volatile matter is less than 10%, and the moisture content is less than 5%; the high calorific value pulverized coal is bituminous coal or anthracite, the bituminous coal has a fixed carbon content greater than 50%, a volatile matter of 25-35%, an ash content less than 5%, and a moisture content less than 5%; the anthracite has a fixed carbon content greater than 80%, a volatile matter of 5-10%, an ash content less than 5%, and a moisture content less than 2%.

[0009] The present invention adds a loosening agent, petroleum coke, high calorific value pulverized coal and silica powder into a submerged arc furnace from a furnace top charging port; fine-particle pulverized coal is mixed with air to form a mixed gas dust, which is sent into a molten pool through a spray gun on the furnace wall side through a spray system, forming a strong stirring in the molten pool, promoting the occurrence of redox reaction, and finally producing silicon water; the mixed gas dust is sprayed to the slag liquid layer in the middle and upper part of the molten pool of the submerged arc furnace; the loosening agent can be biomass waste slag, and the amount of the loosening agent added is 5-14% of the mass of the silica powder; the fine-particle pulverized coal is a mixture of bituminous coal and / or anthracite, and its particle size is less than 6mm, and more preferably less than or equal to 3mm, and the particle size of the fine-particle pulverized coal is smaller than the particle size of the high calorific value pulverized coal; the content of fine-particle pulverized coal in the mixed gas dust is 10-15g / L, and before being sent into the molten pool, the temperature of the mixed gas dust is greater than 150°C, the flow rate of the gas-dust mixture is Am / s, and the value of A is 3-5.

[0010] Furthermore, in step 2, the loosening agent, petroleum coke, high calorific value pulverized coal and silica powder are added to the submerged arc furnace through a quantitative feeder and a feed pipe from the top feed port of the furnace; the fine-particle pulverized coal is mixed with air to form a mixed gas dust, which is sent into the molten pool through a spray gun on the side of the furnace through a spray system, forming a strong stirring in the molten pool, promoting the occurrence of redox reaction, and finally producing silicon water; the mixed gas dust is sprayed to the middle and upper part of the molten pool of the submerged arc furnace. During smelting, the molten pool temperature is 2500-2600℃. In industrial applications, when the temperature in the molten pool is lower than the normal smelting temperature (i.e., lower than 2500-2600℃), the mixed gas intake is increased (such as the flow rate of the mixed gas is increased to A+ (0.5~1.5) m / s), and when the temperature is too high, the mixed gas intake is reduced (such as controlling the flow rate of the mixed gas at A- (0.5~1) m / s).

[0011] The loosening agent is selected from one or more of straw, coconut shell, bagasse and corn cob, and the amount of the loosening agent added is 8-12% of the mass of silica powder, and more preferably 9-11%. When used in industry, it can be fed into the molten pool through the Clyde pulverized coal injection system via the furnace side spray gun.

[0012] Before being fed into the molten pool, the temperature of the mixed gas and dust is preferably 150~250℃.

[0013] As a further preference, the fine-particle pulverized coal is composed of bituminous coal and anthracite in a mass ratio of bituminous coal: anthracite = 2-4:8-6, which of course includes a solution of a mass ratio of bituminous coal: anthracite = 3:7.

[0014] Furthermore, the loosening agent, petroleum coke, high calorific value pulverized coal, silica powder, and binder are mixed evenly in proportion to form a loose charge, which is added to the submerged arc furnace from the top charging port; the binder is a silane coupling agent; the amount of the silane coupling agent added is 5-10% of the mass of the silica powder, preferably 8-10%. This scheme uses petroleum coke, high calorific value pulverized coal, silica powder, and binder in appropriate proportions to fully mix to form a uniform dispersion system. At the same time, the addition of the loosening agent can increase the porous dispersion structure around the silica powder, petroleum coke, and pulverized coal to form an excellent oxygen flow path. The silane coupling agent can fix the porous dispersion structure to ensure the stability of the structure. Even with the consumption of petroleum coke, pulverized coal, and loosening agent, the entire porous structure still maintains a framework structure, and the pores of the porous structure are enlarged to improve the oxygen transport capacity.

[0015] Preferably, the molten pool temperature is 2540-2600°C.

[0016] Preferably, the present invention provides a method for preparing industrial silicon by smelting silica by pulverized coal injection, comprising the following steps: Step 1, weighing silica, petroleum coke and coal respectively, and crushing each of them to form silica powder, petroleum coke powder, high calorific value pulverized coal and fine pulverized coal, wherein the particle size distribution of the crushed silica is below 80 mm, the particle size of the high calorific value pulverized coal is not more than 20 mm, the particle size of the fine pulverized coal is not more than 3 mm, and the particle size of the fine pulverized coal is smaller than the particle size of the high calorific value pulverized coal; the silicon dioxide content in the silica is greater than 99wt%, and the mass ratio of the silica, petroleum coke and pulverized coal is 2. 66:1.7:3.8; the particle size of the petroleum coke is not more than 20mm; the ash content of the petroleum coke is 2wt%, the fixed carbon content is 88wt%, the volatile matter is 9%, and the moisture content is 1%; the high calorific value pulverized coal is composed of bituminous coal and anthracite in a mass ratio of bituminous coal: anthracite = 3:7, bituminous coal has 58% fixed carbon, 35% volatile matter, 3% ash, and 4% moisture, anthracite has 90% fixed carbon, 7% volatile matter, 2% ash, and 1% moisture, and the calorific value is 7875 kcal / kg. Fine particle pulverized coal is composed of bituminous coal and anthracite in a mass ratio of bituminous coal: anthracite = 3:7, wherein bituminous coal has 58% fixed carbon, 35% volatile matter, 3% ash, and 4% moisture, anthracite has 90% fixed carbon, 7% volatile matter, 2% ash, and 1% moisture.

[0017] Step 2, after the loosening agent, petroleum coke, high calorific value pulverized coal, silica powder and binder are mixed evenly, they are added into the submerged arc furnace through a quantitative feeder and a belt conveyor from a furnace top feeding port; the fine pulverized coal is mixed with air to form a mixed gas-dust, the concentration of the fine pulverized coal in the mixed gas is 15g / L, and the mixed gas is fed into the molten pool through a Clyde pulverized coal injection system through a furnace side spray gun to form stirring in the molten pool, the flow rate of the gas-dust mixture is 4.0m / s, and the temperature of the gas-dust mixture before being fed into the molten pool is 150~ 190°C, more preferably 170-190°C, promotes the occurrence of redox reaction, and finally produces silicon water; the loosening agent uses biomass waste residue, specifically sugarcane bagasse, and the amount of the loosening agent added is 10% of the mass of silica powder; the loosening agent, petroleum coke and silica powder are mixed to form a loose charge, and the charge uses silane coupling agent as a binder, and the amount of the silane coupling agent added is 8% of the mass of silica powder; the mixed gas dust is sprayed to the slag liquid layer in the middle and upper part of the ore furnace molten pool; Step 3, the mixed gas is provided by the Clyde injection system. When the temperature in the molten pool is lower than the normal smelting temperature, the mixed gas intake is increased. When the temperature is sufficient to maintain the molten pool temperature, the mixed gas intake is reduced. The molten pool temperature is 2550°C. Step 4: After the smelting is completed, the silicon liquid is poured into a mold and crushed into industrial silicon products of corresponding particle size.

[0018] In the present invention, the silicon yield = 1t / silica unit consumption*100%.

[0019] By adopting the process of the present invention, the silicon yield is greater than 37.5% and the purity of the obtained industrial silicon is greater than or equal to 99.45%.

[0020] After optimization, the silicon yield was 38.5% and the silicon purity was 99.8wt%.

[0021] It can be seen from the above description that the present invention has the following advantages: 1. The present invention solves the defects of the existing process and attempts for the first time to use the method of blowing to spray air and pulverized coal into the ore-fired furnace through the furnace wall, thereby forming a combustion system from the outside to the inside. At the same time, it can also prevent metal from sticking to the furnace wall, making the temperature distribution more uniform. It not only solves the problem of pipeline blockage under the action of the blowing wind, but also gives the pulverized coal a certain combustion space to achieve the effect of full release. More importantly, it can also reduce the quality requirements for petroleum coke.

[0022] 2. The present invention releases heat from the combustion of the slag liquid layer, reduces heat loss, and achieves the goal of increasing the overall furnace temperature when the amount of petroleum coke used is low and the quality is average, providing favorable conditions for subsequently reducing the slag content.

[0023] 3. The present invention utilizes pulverized coal injection to form a composite reduction system with petroleum coke, which effectively improves the production efficiency of industrial silicon and obtains industrial silicon with Si≥99.5wt%.

[0024] 4. The present invention utilizes the difference in particle size between pulverized coal, petroleum coke and silica to form a staggered structure, thereby increasing the contact area between pulverized coal, petroleum coke and silica. At the same time, the low particle size of fine pulverized coal is directly side-blown into the molten pool, which can greatly improve the reaction efficiency.

[0025] 5. The stirring effect brought by the side blowing of the present invention helps to maintain the uniform distribution of temperature and composition in the furnace, and can also reduce the adhesion of metal to the furnace wall, improve the stability of the furnace condition and avoid the formation of eddies. At the same time, since the furnace wall is far away from the heat source, fine-particle pulverized coal is blown in by side blowing to provide a close heat source. In addition, the gas-dust mixture blown in has a certain flow rate that can drive the flow rate of the melt at the furnace wall, which is beneficial to heat transfer. The fine-particle pulverized coal has a small particle size, which can increase the contact area and strengthen the reaction in the upper part of the molten pool, and the flow rate is moderate to avoid the formation of eddies. At the same time, the side blowing of fine-particle pulverized coal is conducive to forming a combustion system from the inside to the outside from the edge of the furnace, thereby increasing heat transfer.

[0026] 6. The present invention utilizes the side blowing enhancement of high calorific value pulverized coal to significantly increase the carbon thermal reduction reaction rate of silica and shorten the smelting cycle; at the same time, the full utilization of high calorific value pulverized coal reduces carbon emissions, which is in line with the development trend of green smelting. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 .A flow chart of a specific implementation of the present invention. DETAILED DESCRIPTION

[0028] Example 1

[0029] A method for strengthening industrial silicon in a submerged arc furnace by side blowing of high calorific value pulverized coal, such as Figure 1 As shown, including: Step 1, respectively weigh silica (SiO2: 99.38%, Fe2O3: 0.13%, Al2O3: 0.12%, CaO: 0.01%), petroleum coke and coal, and crush them into silica powder, petroleum coke powder, high calorific value pulverized coal and fine pulverized coal, wherein the particle size of the crushed silica is below 80 mm, the particle size of the high calorific value pulverized coal is not more than 20 mm, the particle size of the fine pulverized coal is not more than 3 mm, and the particle size of the fine pulverized coal is smaller than that of the high calorific value pulverized coal, and the calorific value of the high calorific value pulverized coal is 6500 kcal / kg, so as to ensure good combustion and reaction efficiency. The particle size distribution of the crushed silica is less than 80 mm, the particle size distribution of the petroleum coke is less than 20 mm, the silicon dioxide in the silica is greater than 99 wt%, and the mass ratio of the silica, petroleum coke and high calorific value pulverized coal is 2.55:1.8:4.0; the ash content of the petroleum coke is 2 wt%, the fixed carbon is 84 wt%, the volatile matter is 9%, and the moisture content is 5%; the fine particle pulverized coal is bituminous coal, which has 58% fixed carbon, 35% volatile matter, 3% ash and 4% moisture.

[0030] Step 2, the loosening agent, petroleum coke, high calorific value pulverized coal, silica powder and binder are mixed evenly and then added to the submerged arc furnace through a quantitative feeder and a material pipe from the furnace top feeding port; the fine pulverized coal is mixed with air to form a mixed gas and dust, the concentration of the fine pulverized coal in the mixed gas is 10g / L, and the mixed gas is sent into the molten pool through the Clyde pulverized coal injection system through the furnace wall side spray gun to form stirring in the molten pool (the flow rate of the gas-dust mixture is 4.5m / s, and the gas-dust mixture is stirred before being sent into the molten pool). The temperature of the mixture is 150-160°C), which promotes the occurrence of redox reaction and finally produces silicon water; the loosening agent is straw, and the amount of the loosening agent added is 5% of the mass of silica powder; the loosening agent, petroleum coke and silica powder are mixed to form a loose charge, and the charge uses silane coupling agent as a binder, and the amount of the silane coupling agent (KH792) added is 5% of the mass of silica powder; the mixed gas dust is sprayed to the upper middle part of the molten pool of the ore-fired furnace.

[0031] Step 3, the mixed gas is provided by the Clyde injection system. When the temperature in the molten pool is lower than the normal smelting temperature, the mixed gas intake is increased. When the temperature is sufficient to maintain the molten pool temperature, the mixed gas intake is reduced. The molten pool temperature is 2560°C. Step 4: After the smelting is completed, the silicon water is poured into a mold and crushed into industrial silicon products of corresponding particle size. The silicon yield is 37.8% and the silicon purity is 99.3wt%.

[0032] Example 2 A method for strengthening industrial silicon in a submerged arc furnace by side blowing of high calorific value pulverized coal, such as Figure 1 As shown, including: Step 1, respectively weighing silica (SiO2: 99.38%, Fe2O3: 0.13%, Al2O3: 0.12%, CaO: 0.01%), petroleum coke and high calorific value pulverized coal, and crushing them into silica powder, petroleum coke powder, high calorific value pulverized coal, and fine pulverized coal, wherein the particle size of the crushed silica is less than 80 mm, the particle size of the high calorific value pulverized coal is not more than 20 mm, the particle size of the fine pulverized coal is not more than 3 mm, and the particle size of the fine pulverized coal is less than 10 mm. The particle size of high calorific value pulverized coal is 20mm; the silicon dioxide content in the silica is greater than 99wt%, the mass ratio of the silica, petroleum coke and high calorific value pulverized coal is 2.6:1.7:3.5; the particle size of the petroleum coke is not greater than 20mm; the ash content of the petroleum coke is 2wt%, the fixed carbon content is 87wt%, the volatile matter is 9%, and the moisture content is 2%; the high calorific value pulverized coal is anthracite, anthracite has 90% fixed carbon, 7% volatile matter, 2% ash, 1% moisture, and 8450 kcal / kg of heat. The fine particle pulverized coal is anthracite, with a fixed carbon content of 90wt%, 7% volatile matter, and 1% moisture.

[0033] Step 2, the loosening agent, petroleum coke, high calorific value pulverized coal, silica powder and binder are mixed evenly and then added to the submerged arc furnace through a quantitative feeder and a feed pipe from the furnace top feeding port; the fine pulverized coal is mixed with air to form a mixed gas, the concentration of the fine pulverized coal in the mixed gas is 20g / L, and the mixed gas is fed into the molten pool through a Clyde pulverized coal injection system through a furnace wall side spray gun to form stirring in the molten pool (the flow rate of the gas-dust mixture is 3.5m / s, and the gas-dust mixture is heated before being fed into the molten pool). The temperature is 180-200°C), which promotes the occurrence of redox reaction and finally produces silicon water; the loosening agent is rice husk, and the amount of the loosening agent added is 15% of the mass of silica powder; the loosening agent, petroleum coke and silica powder are mixed to form a loose charge, and the charge uses silane coupling agent as a binder, and the amount of the silane coupling agent (KH792) added is 10% of the mass of silica powder; the mixed gas dust is sprayed to the slag liquid layer in the upper part of the molten pool of the ore-fired furnace.

[0034] Step 3, the mixed gas is provided by the Clyde injection system. When the temperature in the molten pool is lower than the normal smelting temperature, the mixed gas intake is increased. When the temperature is sufficient to maintain the molten pool temperature, the mixed gas intake is reduced. The molten pool temperature is 2590°C. Step 4: After the smelting is completed, the silicon water is poured into a mold and crushed into industrial silicon products of corresponding particle size. The silicon yield is 38.1% and the silicon purity is 99.6wt%.

[0035] Example 3 A method for preparing industrial silicon by smelting silica using pulverized coal injection, comprising: Step 1, respectively weighing silica (SiO2: 99.38%, Fe2O3: 0.13%, Al2O3: 0.12%, CaO: 0.01%), petroleum coke and coal, and crushing each of them to form silica powder, petroleum coke powder, high calorific value pulverized coal and fine pulverized coal, wherein the particle size distribution of the crushed silica is below 80 mm, the particle size of the high calorific value pulverized coal is not more than 20 mm, the particle size of the fine pulverized coal is not more than 3 mm, and the particle size of the fine pulverized coal is smaller than the particle size of the high calorific value pulverized coal; the silicon dioxide content in the silica is greater than 9 9wt%, the mass ratio of silica, petroleum coke and pulverized coal is 2.66:1.7:3.8; the particle size of the petroleum coke is not more than 20mm; the ash content of petroleum coke is 2wt%, the solid carbon content is 88wt%, the volatile matter is 9%, and the moisture content is 1%; the high calorific value pulverized coal is composed of bituminous coal and anthracite in a mass ratio of bituminous coal: anthracite = 3:7, bituminous coal has 58% fixed carbon, 35% volatile matter, 3% ash, 4% moisture, anthracite has 90% fixed carbon, 7% volatile matter, 2% ash, 1% moisture, and a calorific value of 7875 kcal / kg. Fine particle pulverized coal is composed of bituminous coal and anthracite in a mass ratio of bituminous coal: anthracite = 3:7, wherein bituminous coal has 58% fixed carbon, 35% volatile matter, 3% ash, 4% moisture, anthracite has 90% fixed carbon, 7% volatile matter, 2% ash, 1% moisture, and a calorific value of 7875 kcal / kg.

[0036] Step 2, the loosening agent, petroleum coke, high calorific value pulverized coal, silica powder and binder are mixed evenly and then added to the submerged arc furnace through a quantitative feeder and a belt conveyor from the furnace top feeding port; the fine pulverized coal is mixed with air to form a mixed gas and dust, the concentration of the fine pulverized coal in the mixed gas is 15g / L, and the mixed gas is fed into the molten pool through the Clyde pulverized coal injection system through the furnace side spray gun to form stirring in the molten pool (the flow rate of the gas-dust mixture is 4.0m / s, and the temperature of the gas-dust mixture before being fed into the molten pool is 4.0m / s). The temperature is 150-160°C), promoting the occurrence of redox reaction, and finally producing silicon water; the loosening agent uses biomass waste residue, specifically sugarcane bagasse, and the amount of the loosening agent added is 10% of the mass of silica powder; the loosening agent, petroleum coke and silica powder are mixed to form a loose charge, and the charge uses silane coupling agent as a binder, and the amount of the silane coupling agent (KH792) added is 8% of the mass of silica powder; the mixed gas dust is sprayed to the slag liquid layer in the upper part of the molten pool of the ore-fired furnace; Step 3, the mixed gas is provided by the Clyde injection system. When the temperature in the molten pool is lower than the normal smelting temperature, the mixed gas intake is increased. When the temperature is sufficient to maintain the molten pool temperature, the mixed gas intake is reduced. The molten pool temperature is 2550°C. Step 4: After the smelting is completed, the silicon water is poured into a mold and crushed into industrial silicon products of corresponding particle size. The silicon yield is 38.3% and the silicon purity is 99.6wt%.

[0037] Example 4 A method for strengthening industrial silicon in a submerged arc furnace by side blowing of high calorific value pulverized coal, such as Figure 1 As shown, including: Step 1, respectively weighing silica (SiO2: 99.38%, Fe2O3: 0.13%, Al2O3: 0.12%, CaO: 0.01%), petroleum coke and coal, and crushing each of them to form silica powder, petroleum coke powder, high calorific value pulverized coal and fine pulverized coal, wherein the particle size distribution of the crushed silica is below 80 mm, the particle size of the high calorific value pulverized coal is not more than 20 mm, the particle size of the fine pulverized coal is not more than 3 mm, and the particle size of the fine pulverized coal is smaller than the particle size of the high calorific value pulverized coal; the silicon dioxide content in the silica is greater than 9 9wt%, the mass ratio of silica, petroleum coke and pulverized coal is 2.66:1.7:3.8; the particle size of the petroleum coke is not more than 20mm; the ash content of petroleum coke is 2wt%, the solid carbon content is 88wt%, the volatile matter is 9%, and the moisture content is 1%; the high calorific value pulverized coal is composed of bituminous coal and anthracite in a mass ratio of bituminous coal: anthracite = 3:7, bituminous coal fixed carbon 58%, volatile matter 35%, ash 3%, moisture 4%, anthracite fixed carbon 90%, volatile matter 7%, ash 2%, moisture 1%, and calorific value is 7875 kcal / kg. Fine particle pulverized coal is bituminous coal: anthracite = 3:7, bituminous coal fixed carbon 58%, volatile matter 35%, ash 3%, moisture 4%, anthracite fixed carbon 90%, volatile matter 7%, ash 2%, moisture 1%, and calorific value is 7875 kcal / kg.

[0038] Step 2, the loosening agent, petroleum coke, high calorific value pulverized coal, silica powder and binder are mixed evenly and then added to the submerged arc furnace through a quantitative feeder and a belt conveyor from the furnace top feeding port; the fine pulverized coal is mixed with air to form a mixed gas-dust, the concentration of the fine pulverized coal in the mixed gas is 15g / L, and the mixed gas is fed into the molten pool through the Clyde pulverized coal injection system through the furnace side spray gun to form stirring in the molten pool (the flow rate of the gas-dust mixture is 4.0m / s, and the temperature of the gas-dust mixture before feeding into the molten pool is 4.0m / s). The temperature is 170-190°C), promoting the occurrence of redox reaction, and finally producing silicon water; the loosening agent uses biomass waste residue, specifically sugarcane bagasse, and the amount of the loosening agent added is 10% of the mass of silica powder; the loosening agent, petroleum coke and silica powder are mixed to form a loose furnace charge, and the furnace charge uses silane coupling agent as a binder, and the amount of the silane coupling agent (KH792) added is 8% of the mass of silica powder; the mixed gas dust is sprayed to the middle and upper part of the molten pool of the ore-fired furnace; Step 3, the mixed gas is provided by the Clyde injection system. When the temperature in the molten pool is lower than the normal smelting temperature, the mixed gas intake is increased. When the temperature is sufficient to maintain the molten pool temperature, the mixed gas intake is reduced. The molten pool temperature is 2550°C. Step 4: After the smelting is completed, the silicon water is poured into a mold and crushed into industrial silicon products of corresponding particle size. The silicon yield is 38.5% and the silicon purity is 99.8wt%.

[0039] Example 5 The conditions are the same as those in Example 4, except that no silane coupling agent is added.

[0040] The silicon yield of this embodiment is 38.0%, and the silicon purity is 98.45wt%.

[0041] Comparative Example 1 The difference between Comparative Example 1 and Example 4 is that high calorific value pulverized coal and fine-particle pulverized coal are not added, and the mass ratio of silica to petroleum coke is 2.66:5.5. The leavening agent, petroleum coke, silica powder and adhesive are evenly stirred to form loose particles, which are put into the furnace and smelted at 2500°C in the electric arc furnace. Finally, silicon water is poured into the mold and crushed into industrial silicon products of corresponding particle size. The silicon yield is 35.8% and the silicon purity is 99.45wt%. The difference between Comparative Example 1 and Example 4 is that Example 4 uses fine-particle pulverized coal, which is preheated in advance and has a certain speed to accelerate heat transfer in the furnace, while Example 4 uses pulverized coal to obtain an industrial silicon product with improved silicon purity.

[0042] In comparison, the product purity of Example 3 is better than that of Comparative Example 1, that is, the side-blowing treatment can effectively improve the purity of industrial silicon. It also shows that the use of pulverized coal can also improve the purity of industrial silicon.

[0043] Comparative Example 2 The difference between Comparative Example 2 and Example 4 is that before being fed into the molten pool, the temperature of the gas-dust mixture is 80-90°C, the mass ratio of silica, petroleum coke and pulverized coal is 2.7:1.5:3.8, and then the charge is placed in a submerged arc furnace for smelting treatment at 2500°C. Finally, the silicon water is poured into a mold and crushed into industrial silicon products of corresponding particle size, with a silicon yield of 36.3% and a silicon purity of 99.45wt%. The product purity and silicon yield of Example 4 are better than those of Comparative Example 2, that is, effective preheating of fine-particle pulverized coal can improve the purity and silicon yield of industrial silicon.

[0044] Comparative Example 3 The difference between Comparative Example 3 and Example 4 is that the flow rate of the fine-particle pulverized coal gas dust mixture is 6.5 m / s. Finally, silicon water is poured into the mold and crushed into industrial silicon products of corresponding particle size. The silicon yield is 35.1% and the silicon purity is 99.5 wt%. In comparison, the product purity and silicon yield of Example 4 are better than those of Comparative Example 3, that is, the flow rate of the fine-particle pulverized coal gas dust mixture should not be too high to effectively improve the purity and silicon yield of industrial silicon.

[0045] Comparative Example 4 The difference between Comparative Example 4 and Example 3 is that the leavening agent, petroleum coke, silica powder, high calorific value pulverized coal, fine-particle pulverized coal, and adhesive are evenly stirred to form a loose charge; the charge is then placed into a submerged arc furnace through the furnace top for smelting treatment at 2500°C; finally, silicon water is poured into a mold and crushed into industrial silicon products of corresponding particle size, with a silicon yield of 37.5% and a silicon purity of 99.5wt%; and the difference between Comparative Example 4 and Example 3 is that Example 4 uses side-blown spray gas dust containing pulverized coal, which can ensure a loose state in the charge and ensure stable coverage of the combustion gas, thereby obtaining an industrial silicon product with improved silicon purity.

[0046] In comparison, the product purity and silicon yield of Example 4 are better than those of Comparative Example 3.

[0047] Comparative Example 5 The difference between Comparative Example 5 and Example 3 is that the amount of the leavening agent added is 15% of the mass of the silica powder.

[0048] The silicon yield of this comparative example is 38.1% and the silicon purity is 99.45wt%.

[0049] The present invention proposes a method for smelting industrial silicon in a high calorific value pulverized coal side-blowing enhanced ore-fired furnace. Through innovative side-blowing technology and the use of high calorific value pulverized coal, the smelting efficiency is significantly improved, the production cost is reduced, and the furnace stability and environmental protection performance are improved. This provides a new idea and direction for the development of industrial silicon smelting technology.

[0050] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for smelting industrial silicon using a high calorific value pulverized coal side-blowing enhanced ore-fired furnace, characterized in that: The method comprises the following steps: Step 1, according to the mass ratio of silica: petroleum coke: high calorific value pulverized coal = 2.5-2.8:1.5-1.9:3.5-4.0, silica, petroleum coke, high calorific value pulverized coal are prepared, the calorific value of the high calorific value pulverized coal is not less than 6500 kcal / kg; its particle size is less than or equal to 20 mm; a loosening agent is prepared according to 5-14% of the mass of silica powder; the loosening agent includes biomass; Step 2, adding a bulking agent, petroleum coke, high calorific value pulverized coal and silica powder prepared in proportion into the ore-fired furnace from the furnace top charging port; fine-particle pulverized coal is mixed with air to form a mixed gas dust, which is sent into the molten pool through a spray gun on the furnace wall through a spray system to produce silicon water; the mixed gas dust is sprayed onto the slag liquid layer of the hot ore furnace; the fine-particle pulverized coal is a mixture of bituminous coal and / or anthracite, and its particle size is less than 6 mm, more preferably less than or equal to 3 mm, and the particle size of the fine-particle pulverized coal is smaller than that of the high calorific value pulverized coal; the content of fine-particle pulverized coal in the mixed gas dust is 10-15 g / L, and before being sent into the molten pool, the temperature of the mixed gas dust is greater than 150°C, the flow rate of the gas-dust mixture is Am / s, and the value of A is 3-5; Step 3: After the smelting is completed, the silicon water is poured into the mold and crushed into industrial silicon products of corresponding particle size.

2. The method for smelting industrial silicon by using a high calorific value pulverized coal side-blowing enhanced ore-fired furnace according to claim 1, characterized in that: The diameter distribution of silica powder is less than 80 mm, the particle size distribution of petroleum coke is less than 20 mm, the silicon dioxide in the silica is greater than 99 wt%, the ash content of the petroleum coke is less than 2 wt%, the fixed carbon is greater than 80 wt%, the volatile matter is less than 10%, and the moisture content is less than 5%; High calorific value pulverized coal is bituminous coal or anthracite. The fixed carbon content of bituminous coal is greater than 50%, the volatile matter is 25~35%, the ash content is not more than 5%, and the moisture content is not more than 5%; the fixed carbon content of anthracite is greater than 80%, the volatile matter is 5~10%, the ash content is not more than 5%, and the moisture content is not more than 2%.

3. The method for smelting industrial silicon by side-blowing enhanced ore-fired furnace with high calorific value pulverized coal according to claim 1, characterized in that: During smelting, the molten pool temperature is 2500-2600°C.

4. The method for smelting industrial silicon by side-blowing enhanced ore-fired furnace with high calorific value pulverized coal according to claim 1, characterized in that: When the temperature in the molten pool is lower than 2500-2600℃, increase the intake volume of the mixed gas. When the temperature is too high, reduce the intake volume of the mixed gas.

5. The method for smelting industrial silicon by side-blowing enhanced ore-fired furnace with high calorific value pulverized coal according to claim 1, characterized in that: The loosening agent is selected from one or more of straw, coconut shell, bagasse and corn cob, and the amount of the loosening agent added is 8-12% of the mass of the silica powder, and more preferably 9-11%.

6. The method for smelting industrial silicon by side-blowing enhanced ore-fired furnace with high calorific value pulverized coal according to claim 1, characterized in that: The pulverized coal is injected into the molten pool through the furnace side lance via the Clyde pulverized coal injection system.

7. The method for smelting industrial silicon by side-blowing enhanced ore-fired furnace with high calorific value pulverized coal according to claim 1, characterized in that: Before being fed into the molten pool, the temperature of the mixed gas and dust is preferably 150~250℃.

8. The method for smelting industrial silicon by side-blowing enhanced ore-fired furnace with high calorific value pulverized coal according to claim 1, characterized in that: The fine-particle pulverized coal is composed of bituminous coal and anthracite in a mass ratio of bituminous coal: anthracite = 2-4:8-6.

9. The method for smelting industrial silicon by side-blowing enhanced ore-fired furnace with high calorific value pulverized coal according to claim 1, characterized in that: The molten pool temperature is 2540-2600°C.

10. The method for smelting industrial silicon by side-blowing enhanced ore-fired furnace with high calorific value pulverized coal according to claim 1, characterized in that: After the loosening agent, petroleum coke, high calorific value pulverized coal, silica powder and binder are uniformly mixed according to the proportion, a loose charge is formed, and the loose charge is added into the submerged arc furnace from the charging port on the furnace top; the binder is a silane coupling agent; the amount of the silane coupling agent added is 5-10% of the mass of the silica powder.

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