At present, polysilicon production faces four major problems: reducing energy consumption, reducing pollution, improving quality, and expanding production. At present, the vast majority of China's solar silicon materials industry relies on imports, so it is necessary to improve the technological change subject to the people's situation.
The solar photovoltaic industry chain includes crystalline silicon raw material production, silicon rod and wafer production, solar cell manufacturing, component packaging, photovoltaic product production and photovoltaic power generation systems. Among them, silicon raw material is the most important production link, and there has been a saying that “silicon is the king†in the industry. At present, more than 90% of solar photovoltaic cells in the world are produced from monocrystalline or polycrystalline silicon. At present, there are four major problems that need to be addressed in polysilicon production: reducing energy consumption, reducing pollution, improving quality, and expanding production. The vast majority of China's solar silicon materials industry is currently dependent on imports, so it is necessary to improve the technological change subject to the situation of the people.
Technology is still lacking China's solar silicon is mainly dependent on imports in the global photovoltaic industry chain, high-purity silicon material not only requires the purity of silicon as high as 7-9, and the impurities such as boron and phosphorus are limited to dozens of ppt. One-hundred millionth, which is the core raw material for photovoltaic companies to produce solar cells. Therefore, the synthesis, purification, purification, and production of high-purity silicon materials have become the most upstream industries in the photovoltaic industry cluster. At present, although China's silicon raw mineral reserves account for 25% of the world's total reserves, most of the raw materials needed by domestic solar cell manufacturers (such as Suntech, Tianwei Yingli, etc.) need to be imported from abroad. This is because the silicon material used for the production of solar cells is mainly single crystal silicon and polycrystalline silicon that are extracted from silicon raw materials through different refining methods. In China, the existing production technology of high-purity silicon raw materials has insufficient deficiencies in terms of output and energy consumption compared with Western developed countries. As a result, this not only greatly increases the production cost of the company, but also becomes a “bottleneck†that restricts the current development of China's photovoltaic industry to the upstream links, enabling our country to sell high-energy, high-polluted raw materials at a very low price. At the same time, high-purity silicon materials are purchased at extremely high prices.
It is understood that although China's silicon material industry started earlier (in the 1950s), due to the small scale of production, backward technology, serious environmental pollution, high consumption, and high costs, most companies have successively stopped production or converted production due to losses. Until 2004, only Emei Semiconductor Material Factory and Luoyang Monocrystalline Silicon Co., Ltd. were left in China. Their production capacity was only 100 tons/year, and the actual output of silicon materials that could meet the needs of solar cell production was only 80 tons. Experts predict that the demand for silicon materials for solar cell production in China will reach 4,365 tons in 2010 and 16,200 tons in 2015. If we do not change the production status of domestic polysilicon by independent intellectual property rights, the state of China's silicon material industry subject to the international market will not be changed, which will jeopardize the further development of China's photovoltaic industry.
Distillation energy-saving technologies Reduce energy consumption Comprehensive utilization Reduce pollution Modern processes pay great attention to energy conservation. A large amount of human and material resources are invested in foreign countries to develop energy-saving technologies. New energy-saving technologies, new processes, new measures, and new methods continue to emerge. China's polysilicon production, after adopting advanced technologies that have matured in the chemical industry, will no longer be a "high energy consumption, high pollution" industry, but a "green sunshine business." The polysilicon distillation process is studied, and energy analysis technology is used to analyze the polysilicon distillation process. Energy conservation can be achieved from the following aspects:
First, implement multi-effect distillation to make full use of energy. Multi-effect distillation is to divide the raw materials into roughly equal N feeds, which are fed into the N rectification towers, where the pressures are successively increasing. The operating temperatures of the N towers are also successively increased. The steam at the top of the higher pressure and temperature tower provides heat to the bottom boiler reboiler of the lower tower and is itself condensed, and so on. This saves the energy consumption of the low pressure column reboiler and the high pressure tower condenser. The water consumption. In this system, only the first highest pressure tower is heated, the system can work, and the required energy is about 1/N of the energy consumption of a single tower. For example, three towers can be used together to produce three-way distillation. Technology, its energy consumption is only 1/3 of the original, energy-saving rate of 67%, the energy-saving effect is very obvious.
In the production of polysilicon, many towers are installed for the purpose of purifying polysilicon, and can be matched with reasonable energy and temperature difference to realize multi-effect distillation and achieve the purpose of significant energy saving and emission reduction.
Second, improve the separation efficiency, reduce the reflux ratio, and further achieve energy saving. During the separation process, the improvement of separation efficiency can greatly reduce energy consumption, improve product quality, reduce emissions, increase recovery rate, and increase corporate profits. In the polysilicon distillation process, new separation equipment such as highly efficient guided sieve plates and new types of fillers can improve the separation efficiency and reduce the operation reflux ratio of the rectification tower. Since the energy consumption and reflux ratio of the rectification tower are linear, such It reduces the energy consumption proportionally. Increasing the separation efficiency is also the most effective way to increase the quality of polysilicon products and reduce the emissions of silicon tetrachloride.
Third, to optimize the process and achieve energy conservation. The company will conduct comprehensive material balance and energy balance on polysilicon production stocks, examine the rationality of its energy consumption, adopt thermal integration technology, optimize the process, and maximize energy conservation and consumption reduction. Through energy-saving and clean production throughout the production line, and closed-loop clean production in the production process, energy consumption and consumption of Si (silicon), H2 (hydrogen), Cl2 (chlorine) and other raw materials can be reduced, and the cost can be reduced. International competitiveness, quality meets current and future requirements for VLSI and solar cells.
In addition, a large amount of chlorosilane by-products such as SiCl 4 (SiCl 4 ), SiH 2 Cl 2 (SiCl 2 ), and SiHCl 3 (Trichlorosilane) are generated during the polysilicon production process, which results in high production costs and partial chlorosilanes. The introduction of hydrogen chloride into the tail gas discharge system not only increases the cost of tail gas treatment, but also increases the discharge of pollutants. The concentration of chlorine ions in the waste water reaches 1700-2500 mg/L. How to effectively solve the outlet of chlorosilane by-products is the key to reducing the production cost of polysilicon and achieving energy-saving and emission reduction, and it is also a major technical problem facing polysilicon production companies.
The comprehensive utilization of exhaust gas, by-products, and waste heat recovery can reduce the pollution of polysilicon projects to the environment and further achieve the goal of energy conservation and emission reduction. Most polysilicon companies in foreign countries set up factories, which are mostly combined with chemical companies. They operate under the umbrella of the “chemical group.†It is easy to realize the “circular economy†within the group, and waste can be “zero emissionâ€. For example, German company WACKER has realized the closed-loop production of polysilicon. The annual sales of silicon materials are more than 3 billion euros, of which 1 billion euros is obtained from the organosilicon products that are processed further by polysilicon byproducts. In addition to the hydrogenation of silicon tetrachloride to trichlorosilane, it is also possible to use silicon tetrachloride, hydrogen chloride, etc. to make fumed silica, ethyl silicate, silicone products, synthetic quartz, etc., which are currently in demand on the market. material. Improving photoelectric conversion efficiency and reducing production costs Increasing the conversion efficiency of photovoltaic materials and reducing the manufacturing cost of solar cells are two goals pursued by the photovoltaic industry. Polysilicon wafers are the core part of solar photovoltaic cells. The quality of silicon wafers plays a crucial role in the photoelectric conversion rate of solar energy. Under normal circumstances, the photoelectric conversion rate of ordinary solar photovoltaic cells is 10% to 14%, and the conversion rate of high-purity silicon solar photovoltaic cells can reach 16% or even higher, so for the production process of solar cells, The production of polysilicon is even more crucial.
There are two main methods for producing semiconductor grade polysilicon from metallurgical grade silicon: the modified Siemens method and the silane method. In its production process, multi-stage distillation technology and its equipment are crucial. Through the new chemical distillation equipment and related distillation technology, the quality of the final product ultra-pure silicon can be improved.
We have noticed that in recent years, due to the support of governments in various countries, the downstream PV industry has grown rapidly. However, due to the large-scale investment and time constraints in the expansion of production in the upper reaches, the supply of polysilicon has been significantly insufficient. As a result, the supply and demand imbalance has caused the polysilicon prices to continue to rise.
Polysilicon material is the highest part of the total cost of photovoltaic power generation. In most domestic photovoltaic companies, the cost of silicon materials accounts for more than 56.2% of the total solar cell production costs, and accounts for about 30% of the cost of grid-connected photovoltaic power generation systems.
Therefore, further reducing costs and increasing the market competitiveness of polysilicon materials will play an important role in promoting the development of the entire photovoltaic industry chain. The main countermeasures are: First, the introduction of a new type of separation and mass transfer equipment, such as the efficient guided sieve towers and packed towers of the Beijing University of Chemical Technology, have a great role in accelerating the integration of the polysilicon production distillation process and achieving closed-loop cleaner production; Second, the introduction of new distillation equipment to increase the production of polysilicon, to achieve the large-scale production of polysilicon; Third, the development and application of large-scale synthesis furnace and reduction furnace.
The solar photovoltaic industry chain includes crystalline silicon raw material production, silicon rod and wafer production, solar cell manufacturing, component packaging, photovoltaic product production and photovoltaic power generation systems. Among them, silicon raw material is the most important production link, and there has been a saying that “silicon is the king†in the industry. At present, more than 90% of solar photovoltaic cells in the world are produced from monocrystalline or polycrystalline silicon. At present, there are four major problems that need to be addressed in polysilicon production: reducing energy consumption, reducing pollution, improving quality, and expanding production. The vast majority of China's solar silicon materials industry is currently dependent on imports, so it is necessary to improve the technological change subject to the situation of the people.
Technology is still lacking China's solar silicon is mainly dependent on imports in the global photovoltaic industry chain, high-purity silicon material not only requires the purity of silicon as high as 7-9, and the impurities such as boron and phosphorus are limited to dozens of ppt. One-hundred millionth, which is the core raw material for photovoltaic companies to produce solar cells. Therefore, the synthesis, purification, purification, and production of high-purity silicon materials have become the most upstream industries in the photovoltaic industry cluster. At present, although China's silicon raw mineral reserves account for 25% of the world's total reserves, most of the raw materials needed by domestic solar cell manufacturers (such as Suntech, Tianwei Yingli, etc.) need to be imported from abroad. This is because the silicon material used for the production of solar cells is mainly single crystal silicon and polycrystalline silicon that are extracted from silicon raw materials through different refining methods. In China, the existing production technology of high-purity silicon raw materials has insufficient deficiencies in terms of output and energy consumption compared with Western developed countries. As a result, this not only greatly increases the production cost of the company, but also becomes a “bottleneck†that restricts the current development of China's photovoltaic industry to the upstream links, enabling our country to sell high-energy, high-polluted raw materials at a very low price. At the same time, high-purity silicon materials are purchased at extremely high prices.
It is understood that although China's silicon material industry started earlier (in the 1950s), due to the small scale of production, backward technology, serious environmental pollution, high consumption, and high costs, most companies have successively stopped production or converted production due to losses. Until 2004, only Emei Semiconductor Material Factory and Luoyang Monocrystalline Silicon Co., Ltd. were left in China. Their production capacity was only 100 tons/year, and the actual output of silicon materials that could meet the needs of solar cell production was only 80 tons. Experts predict that the demand for silicon materials for solar cell production in China will reach 4,365 tons in 2010 and 16,200 tons in 2015. If we do not change the production status of domestic polysilicon by independent intellectual property rights, the state of China's silicon material industry subject to the international market will not be changed, which will jeopardize the further development of China's photovoltaic industry.
Distillation energy-saving technologies Reduce energy consumption Comprehensive utilization Reduce pollution Modern processes pay great attention to energy conservation. A large amount of human and material resources are invested in foreign countries to develop energy-saving technologies. New energy-saving technologies, new processes, new measures, and new methods continue to emerge. China's polysilicon production, after adopting advanced technologies that have matured in the chemical industry, will no longer be a "high energy consumption, high pollution" industry, but a "green sunshine business." The polysilicon distillation process is studied, and energy analysis technology is used to analyze the polysilicon distillation process. Energy conservation can be achieved from the following aspects:
First, implement multi-effect distillation to make full use of energy. Multi-effect distillation is to divide the raw materials into roughly equal N feeds, which are fed into the N rectification towers, where the pressures are successively increasing. The operating temperatures of the N towers are also successively increased. The steam at the top of the higher pressure and temperature tower provides heat to the bottom boiler reboiler of the lower tower and is itself condensed, and so on. This saves the energy consumption of the low pressure column reboiler and the high pressure tower condenser. The water consumption. In this system, only the first highest pressure tower is heated, the system can work, and the required energy is about 1/N of the energy consumption of a single tower. For example, three towers can be used together to produce three-way distillation. Technology, its energy consumption is only 1/3 of the original, energy-saving rate of 67%, the energy-saving effect is very obvious.
In the production of polysilicon, many towers are installed for the purpose of purifying polysilicon, and can be matched with reasonable energy and temperature difference to realize multi-effect distillation and achieve the purpose of significant energy saving and emission reduction.
Second, improve the separation efficiency, reduce the reflux ratio, and further achieve energy saving. During the separation process, the improvement of separation efficiency can greatly reduce energy consumption, improve product quality, reduce emissions, increase recovery rate, and increase corporate profits. In the polysilicon distillation process, new separation equipment such as highly efficient guided sieve plates and new types of fillers can improve the separation efficiency and reduce the operation reflux ratio of the rectification tower. Since the energy consumption and reflux ratio of the rectification tower are linear, such It reduces the energy consumption proportionally. Increasing the separation efficiency is also the most effective way to increase the quality of polysilicon products and reduce the emissions of silicon tetrachloride.
Third, to optimize the process and achieve energy conservation. The company will conduct comprehensive material balance and energy balance on polysilicon production stocks, examine the rationality of its energy consumption, adopt thermal integration technology, optimize the process, and maximize energy conservation and consumption reduction. Through energy-saving and clean production throughout the production line, and closed-loop clean production in the production process, energy consumption and consumption of Si (silicon), H2 (hydrogen), Cl2 (chlorine) and other raw materials can be reduced, and the cost can be reduced. International competitiveness, quality meets current and future requirements for VLSI and solar cells.
In addition, a large amount of chlorosilane by-products such as SiCl 4 (SiCl 4 ), SiH 2 Cl 2 (SiCl 2 ), and SiHCl 3 (Trichlorosilane) are generated during the polysilicon production process, which results in high production costs and partial chlorosilanes. The introduction of hydrogen chloride into the tail gas discharge system not only increases the cost of tail gas treatment, but also increases the discharge of pollutants. The concentration of chlorine ions in the waste water reaches 1700-2500 mg/L. How to effectively solve the outlet of chlorosilane by-products is the key to reducing the production cost of polysilicon and achieving energy-saving and emission reduction, and it is also a major technical problem facing polysilicon production companies.
The comprehensive utilization of exhaust gas, by-products, and waste heat recovery can reduce the pollution of polysilicon projects to the environment and further achieve the goal of energy conservation and emission reduction. Most polysilicon companies in foreign countries set up factories, which are mostly combined with chemical companies. They operate under the umbrella of the “chemical group.†It is easy to realize the “circular economy†within the group, and waste can be “zero emissionâ€. For example, German company WACKER has realized the closed-loop production of polysilicon. The annual sales of silicon materials are more than 3 billion euros, of which 1 billion euros is obtained from the organosilicon products that are processed further by polysilicon byproducts. In addition to the hydrogenation of silicon tetrachloride to trichlorosilane, it is also possible to use silicon tetrachloride, hydrogen chloride, etc. to make fumed silica, ethyl silicate, silicone products, synthetic quartz, etc., which are currently in demand on the market. material. Improving photoelectric conversion efficiency and reducing production costs Increasing the conversion efficiency of photovoltaic materials and reducing the manufacturing cost of solar cells are two goals pursued by the photovoltaic industry. Polysilicon wafers are the core part of solar photovoltaic cells. The quality of silicon wafers plays a crucial role in the photoelectric conversion rate of solar energy. Under normal circumstances, the photoelectric conversion rate of ordinary solar photovoltaic cells is 10% to 14%, and the conversion rate of high-purity silicon solar photovoltaic cells can reach 16% or even higher, so for the production process of solar cells, The production of polysilicon is even more crucial.
There are two main methods for producing semiconductor grade polysilicon from metallurgical grade silicon: the modified Siemens method and the silane method. In its production process, multi-stage distillation technology and its equipment are crucial. Through the new chemical distillation equipment and related distillation technology, the quality of the final product ultra-pure silicon can be improved.
We have noticed that in recent years, due to the support of governments in various countries, the downstream PV industry has grown rapidly. However, due to the large-scale investment and time constraints in the expansion of production in the upper reaches, the supply of polysilicon has been significantly insufficient. As a result, the supply and demand imbalance has caused the polysilicon prices to continue to rise.
Polysilicon material is the highest part of the total cost of photovoltaic power generation. In most domestic photovoltaic companies, the cost of silicon materials accounts for more than 56.2% of the total solar cell production costs, and accounts for about 30% of the cost of grid-connected photovoltaic power generation systems.
Therefore, further reducing costs and increasing the market competitiveness of polysilicon materials will play an important role in promoting the development of the entire photovoltaic industry chain. The main countermeasures are: First, the introduction of a new type of separation and mass transfer equipment, such as the efficient guided sieve towers and packed towers of the Beijing University of Chemical Technology, have a great role in accelerating the integration of the polysilicon production distillation process and achieving closed-loop cleaner production; Second, the introduction of new distillation equipment to increase the production of polysilicon, to achieve the large-scale production of polysilicon; Third, the development and application of large-scale synthesis furnace and reduction furnace.
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