Silicon Metal With Factory Price

1. Ingredient List

Silicon metal content composition specifications:

2. Related introduction

Silicon metal smelting is a high energy consumption production, China's silicon metal production has been a long time, with the tightening of national energy policy and energy conservation and emission reduction, as well as the promotion of new energy, silicon metal smelting has become a primary product and process, many domestic emerging energy enterprises to build a series of silicon metal, polysilicon, monocrystalline silicon, solar cells and a series of the recycling industry chain, the next few years will inevitably affect China The development of the entire energy sector and the application of new energy.

1、The need to produce silicon for the chemical industry

China's production of silicon metal (silicon content is mainly 98.5%), the original is mainly metallurgical silicon, chemical silicon metal (silicon content is mainly 99.85%) production from the mid-1990s onwards, China's chemical silicon production and export volume growth faster. 1999-2001 China's exports of chemical silicon to Japan have reached 22,000 tons, 30,000 tons, 40,000 tons. From 1999 to 2001, China's exports of chemical silicon to Japan reached 22,000 tons, 30,000 tons, and 40,000 tons respectively, and in 2001, China's exports of chemical silicon to Japan accounted for more than 40% of Japan's chemical silicon imports. China has begun to join the ranks of chemical silicon producers and suppliers, and the number of enterprises producing chemical silicon has been increasing. As a result of the full disclosure of the carbothermal reduction smelting process by Shanghai Guangji Silicon Materials Co., Ltd. in 2002, China's silicon metal production capacity quickly rose from 100,000 tons per year to 1.2 million tons between 2002 and 2004. This resulted in full sanction by the NDRC and the actual production of silicon metal fell back to 700,000 tons in 2006. Total 2006, only Shanghai Guangji Silicon Materials Co., Ltd. Dawu silicon plant in the Xinjiang border construction of a successful 10,000-ton metal silicon plant Jing Xin plant. Other and new silicon plant. Silicon for chemical use refers to the silicon metal used in the production of organic silicon and polysilicon. From a worldwide perspective, the consumption of silicon for metallurgy is more than the consumption of silicon for chemical use, but with the continuous development of science and technology, silicon for chemical use in the production of organic silicon and semiconductors and other fields continue to broaden, widely used in the production of organic silicon monomer and polymer silicone oil, silicone rubber, silicone resin building corrosion, water repellent, etc. They have high-temperature resistance, electrical insulation, radiation resistance, water resistance, and other unique properties. Used in electrical, aviation, machinery, chemical, pharmaceutical, national defense, construction, and other sectors. As the core of integrated circuits, more than 95% of electronic components are made of semiconductor silicon, which is the pillar of the contemporary information industry. "Information superhighway" in a large number of applications in the fiber optic cable fiber, is also produced from silicon metal as raw material. The consumption of chemical silicon in the United States and the European Union has accounted for more than half of the total consumption of silicon metal. Chemical silicon is widely used as a high-tech field and important basic industry, and its consumption is tending to grow steadily. Under normal conditions in the international market, each ton of chemical silicon is priced 300-400 USD higher than metallurgical silicon. Therefore, whether from meeting the export and domestic demand or from improving the economic efficiency of silicon metal enterprises, improving product quality, vigorously developing the production of chemical silicon is necessary.

2, chemical silicon production raw materials in the production of chemical silicon, raw materials is a prerequisite for good operation. Quartz rocks are used as raw materials for the production of chemical silicon metal, and low-ash materials containing carbon are used as reducing agents. The raw materials for the production of chemical silicon by the electric furnace method are mainly silica and carbon raw materials. Carbon raw materials and mainly petroleum coke, there are high-quality anthracite or charcoal, can also be mixed with a part to increase the furnace charge than resistance. The raw materials required to have the necessary purity, have a good reaction capacity to meet the product specifications; a reducing agent with different reaction capacity to be able to react fully with quartzite; furnace charge with different composition, and both different particle sizes to make a good impact on the furnace charge electric furnace through the appropriate fit.

2.1, silicon oxide minerals smelting silicon metal is a slag-free process, chemical silicon smelting of silica selection is more stringent, not only the content of impurities to be less, but also requires high mechanical strength, sufficient thermal stability, suitable particle size composition. Silicon smelting for chemical use is best done with silica. The natural form of silicon oxide exists either as a separate quartz mineral, or as rock silica, which is almost entirely accumulated from silicon oxide, or as sandstone in the form of silica. The impurities and adhesions in the minerals containing silicon oxide used in the production of chemical silica are either completely reduced or partially reduced during the melting process, or they enter the product silicon in the form of compounds or generate slag. This not only increases energy consumption and reduces product quality, but also causes difficulties in the melting process. Therefore, the chemical composition of the silicon oxide minerals used for chemical smelting is strict. Requirements SiO2 greater than 99%, Fe2O3 less than 0.15%, Al2O3 not more than 0.2%, CaO not more than 0.1%, the sum of impurities is not more than 0.6%. The silica used must be washed before melting and the surface is clean.

The silica used in the furnace is required to have a certain particle size. The particle size of silica is an important process factor in smelting. The suitable particle size of silica is influenced by various factors such as the type of silica, electric furnace, capacity, operating conditions, and the type and particle size of the reducing agent, and is determined by the specific smelting conditions. In general, the 6300KVA three-phase electric furnace (built-in 1983 at Dawu Silicon Plant) requires a silica particle size of 8-100mm, and the 3200KVA three-phase electric furnace requires silica particle size of 8-80mm, and the proportion of intermediate particle size composition should be larger. When the particle size is too large, because it can not and mash furnace viscous and reaction speed, easy to make the unreacted silica into the liquid silicon, resulting in an increase in the amount of slag, out of the furnace difficulties, silicon recovery rate is reduced, energy consumption increases, and even cause the bottom of the furnace rise, affecting normal production. The particle size is too small, although it can increase the contact surface of the reducing agent, which is conducive to the reduction reaction, but the gas produced in the reaction process can not be smoothly discharged and will slow down the reaction speed. The particle size is too small. Impurities brought in will increase, affecting product quality. Production of silica less than 5 mm is generally not suitable.

2.2 carbon-reducing agent chemical silicon smelting used in the main reducing agent are petroleum coke, bituminous coal, charcoal. To increase the resistivity of the charge, increase chemical activity, but also with gas coal coke, silica coke, blue carbon, semi-coke, low-temperature coke, woodblocks. In the chemical composition of a carbonaceous reductant, the main consideration should be fixed carbon, ash, volatile matter, and moisture. The general requirement is that the fixed carbon should be high, the total amount of reductant required is reduced, thus the ash brings in fewer impurities, the amount of slag is reduced accordingly, the power consumption is reduced, and the impurity content in chemical silicon is reduced. The resistivity of the carbonaceous reducing agent should be high and the porosity should be high. Charge resistivity depends mainly on the carbonaceous reductant. Carbonaceous reductants have high resistivity, good chemical activity, and high recovery of silicon.

Petroleum coke is the lowest ash content among the reductants used for silicon metal production, containing 0.17-0.6% ash, 90-95% fixed carbon, and no more than 3.5%-13% volatile fraction. Chemical silicon smelting uses petroleum coke as a reducing agent, which is because of its low ash content and is conducive to improving product quality. However, due to the small resistivity of petroleum coke, poor reactivity, easy graphitization at high temperature, when the dosage is large, resulting in poor control of the furnace conditions, resulting in non-sintering of the charge, serious stabbing fire, high electricity consumption, and difficulties in discharging the furnace.

Wood charcoal has high specific resistance and reactivity, and the content of impurities is low, so it is a more ideal reducing agent for smelting silicon for industrial chemistry, but the properties of charcoal are made from different wood and different methods are very different. The ash content of peeled charcoal is usually one-half to one-third lower than that of peeled charcoal, and the bark has a great influence on the ash content of charcoal. The main component of charcoal is carbon, and the ash content is low, generally less than 10%. The electrical resistivity is large and the chemical activity is good. Years of production practice have proved that charcoal is an important carbonaceous raw material to meet the needs of smelting chemical silicon, but the source of charcoal is restricted, and charcoal reducers can no longer be used.

From the situation abroad, the majority of countries no longer use charcoal. Many domestic manufacturers have also done a lot of work in seeking and using charcoal substitutes. It has been proved that among various carbon-reducing agents, bituminous coal is another ideal reducing agent other than charcoal in terms of reactivity and specific resistance.

Bituminous coal is characterized by high resistance and high reactivity, and low-ash bituminous coal is obtained after washing. The ash content can reach about 3%, Fe2O3 content up to 0.2-0.3%, and Al2O3 content less than 1%. The ash content of our reductant bituminous coal is mostly above 3%, while the ash content of foreign reductant bituminous coal is mostly around 1%. The chemical method of selected bituminous coal used in the USSR can get the fine coal with iron oxide content less than 0.1%. The role of the woodblock is to increase the resistance of the material layer, the size of the dosage has an impact on the furnace conditions. The amount of woodblock is too large, the material layer is loose, the furnace condition becomes bad, electricity consumption increases, woodblock because of the ignition point, the carbon content is low, the actual reducing agent is minimal.

Impurities in the carbon raw material are mainly ash, all composed of oxides. In chemical production, the oxide in the ash is also to be reduced, both to consume electricity and carbon, and the reduced impurities are still mixed into the silicon liquid, reducing the strength of silicon. In production practice, for every 1% increase in ash in the furnace charge, it consumes 100 degrees-120 degrees more electricity, therefore, the less ash content in the raw material of carbon, the better.

2.3 Electrode Electrode is one of the main consumable materials in chemical silicon production. Chemical silicon smelting electrodes, generally using graphite electrodes and carbon electrodes, are the main domestic use of graphite electrodes.

In the silicon smelting furnace, the electrode is the heart, an important part of the conductive system. Current is fed into the furnace through the electrode to produce an electric arc for chemical silicon smelting. Requirements for electrode materials: (1) Good electrical conductivity and low resistivity to reduce electrical energy loss. (2) high melting point, low coefficient of thermal expansion, not easy to deformation; (3) sufficient mechanical strength at high temperature and low impurity content. Graphite electrode has low ash content, better electrical conductivity, heat resistance, and corrosion resistance, and is the best choice for silicon smelting for chemical use.

3、Smelting process of silicon for the chemical industry

The process of silicon for the chemical industry includes furnace charge preparation, electric furnace melting, silicon refining, and casting, and crushing to remove slag inclusions. Before the preparation of the furnace charge, all raw materials are subjected to the necessary treatment. The silica is crushed in a jaw crusher to a size of no more than 100 mm, screened out to remove pieces smaller than 5 mm, and rinsed with water. The crushed pieces are melted in the upper part of the furnace, which reduces the permeability of the charge and makes it difficult to carry out the production process. Petroleum coke has a high conductivity coefficient, and it is necessary to crush it to a size of not more than 10mm and to control the amount of petroleum coke powder. Because of its direct combustion on the mouth of the furnace, it will cause insufficient reducing agent.

In chemical silicon production, bituminous coal can completely replace charcoal, such as Hunan Zhuzhou fine washed bituminous coal, with 77.19% fixed carbon, 19.4% volatility, 3.41% ash content, 0.22% Fe2O3 content, 0.99% Al2O3 content, and 0.17% CaO content. After production practice, it is feasible to use such bituminous coal for smelting chemical silicon.

The woodblocks and chips used for the production of chemical silicon are processed by a wood chipper and wood chipper. The carbon-reducing agent in the furnace charge is mainly petroleum coke and bituminous coal, and the amount of wood and wood chips depends on the furnace conditions. Instead of using wood in production, the product quality is more stable. The ratio of the furnace charge is determined according to the required product level. The ratio of petroleum coke and bituminous coal is determined by the amount of carbon required for each batch of ore silicon. The ratio of petroleum coke to bituminous coal has a large impact on the working resistance of the charge.

After each component of the charge is weighed, the charge is mixed evenly, and after the furnace is pounded, the well-mixed charge is added to the furnace centrally. Maintain a certain height of the charged surface and add the charge evenly.

Chemical silicon production is continuous. The conditions inside the furnace are not constant. Chemical silicon production in an electric furnace is a process in which electrical energy is converted into thermal energy, and then the thermal energy is used to directly heat the material and produce a chemical reaction. Therefore, the electrical characteristics of the furnace are very important. The melting is operated in a closed arc to maintain a high-temperature furnace, improve thermal efficiency, and increase the utilization rate of the electric furnace, using a capacity of 3200KVA and 6300KVA silicon metal furnace each in the study. Melting is carried out using a certain time of stewing and regular centralized charging operation. Under normal conditions, it is difficult for the charge to sink automatically, and it is generally necessary to force the charge to sink. The furnace condition is easy to fluctuate and difficult to control. Therefore, it is necessary to judge correctly and deal with it in time during production. Every 4 hours out of the furnace, refining and casting, crushing and picking slag finishing into storage.

4, electric furnace operation chemical silicon melting is carried out in the submerged arc state. To produce a constant homogeneous silicon metal, the best furnace operation needs to be implemented in the melting process. The main source of heat is electrical energy. Therefore, the distribution of the current flow path route and the electric flow of each route in the furnace has an important influence on the temperature distribution in each zone of the furnace and the entire melting process. Attention should be paid to maintaining the load balance of the three phases of electric energy so that the output can be increased, the quality ensured and the electric power consumption reduced.

4.1 Charging and pounding furnace to make the silicon melting furnace to achieve the purpose of high quality and high yield, in addition to the requirements of good electric furnace parameters, fine raw materials, a reasonable ratio, the operation method is very important factors. A reasonable charging method plays a leading role in the structure of the material layer, the stability of the electrode in the furnace, and the full utilization of thermal energy. In production, charging and furnace tamping are combined. According to the different conditions and characteristics of the melting process, the charging and furnace pounding operations should be completed promptly. To maintain a good permeability of the furnace, it is necessary to carry out an eyelet and pounding furnace. A small pounding furnace according to the furnace conditions, the large pounding furnace is generally carried out every hour or so, pounding furnace to be about to penetrate, pounding furnace pounding out of the block of material pushed to the center of the furnace, pounding furnace process can not be pounding furnace while adding new material. An electrode area for pounding furnace operation is not desirable, must be concentrated unified pounding furnace, unified charging, to maintain a high melting temperature. The most important factor for stable furnace operation is to maintain a constant temperature distribution in the charge layer. If the temperature distribution in the furnace chamber is [disrupted, the furnace operation will be seriously disturbed. The particle size and homogeneity of the charge in production, the charging and discharging of the furnace as well as the handling of the charged surface of the furnace chamber affect the electrode movement. Too much electrode movement and too strong pounding of the furnace can make the furnace operation unstable.

4.2 Closed-arc operation

Closed-arc operation is to properly bury the electrode into the furnace charge and use the semi-molten charge as the impedance body to generate an arc between the electrode and the molten charge. To do the closed-arc operation, the first thing to consider is the feeding method. The feeding method has a feeding method, split feeding method, multiple feeding method. Except for one feeding method is open arc operation, all other methods can do closed arc operation. In the production of chemical silicon, we use the split feeding method, the material layer structure is stable, low electricity consumption, and long furnace age. There are several issues to be dealt with in the operation: First, we must choose the suitable electrical parameters so that the electrode can be inserted into the charge layer with proper depth; second, we must find a way to control the specific resistance of the charge; third, the size of the charge has an important influence on the smelting of silicon, and the size is too large and too small for the furnace condition. The advantages of closed-arc operation are: ① the structure of the charge layer in the furnace can form a complete system, and the charge sinks in turn; ② the arc light is not exposed, the radiation heat loss on the charged surface is greatly reduced, maintaining high furnace temperature and improving thermal efficiency, thus increasing production, improving product quality and reducing power consumption. ③Can make the electrode consumption reach balance and stability, avoid the occurrence of miss fracture accident. ④The temperature of the material surface is lower so that the equipment on the material surface is subject to lighter thermal corrosion, which prolongs the life of the equipment and improves the utilization rate of the electric furnace equipment. ⑤ Less dust can make the furnace surface operation has a better operating environment. Furnace regardless of size, as long as the appropriate measures are taken, you can achieve closed-arc operation and obtain the desired production results.

4.3 Distribution technology electric arc furnace is a device that uses the heat generated by the electric arc for heating. In the chemical silicon smelting process, the physical and chemical changes are closely linked to the electrical regime. The power distribution operation of the

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