Let’s all discuss the technical maturity of domestic polysilicon manufacturers at present

In 2006, China’s production of solar-grade polysilicon was just over 80 tons, while the domestic demand was 4,000 tons, of which 2,691 tons were required by the solar industry; as a result, the vast majority of polysilicon had to be imported. Insufficient supply and high costs of silicon raw materials have become bottlenecks restricting the development of China’s photovoltaic industry. At present, only seven or eight manufacturers in countries such as Germany and Japan have the capability to produce solar-grade polysilicon.

Luoyang Zhongsi is considered quite advanced in China

There is a silicon manufacturing company in Guangdong; its technology is said to be excellent, ranking among the best in the world.

How come I haven’t heard about it? Do you know what that company’s name is? What exactly does it do?

The table above provides a comparative analysis of the technical characteristics, advantages, disadvantages, as well as relevant manufacturers for several of the current main production technologies for high-purity semiconductor-grade polycrystalline silicon and solar-grade polycrystalline silicon, including the Siemens process, the silane method (the modified Siemens process should be used instead), the fluidized bed method, the direct solidification and purification technique using metallurgical silicon, and the thermal carbon reduction method. Among these, the production capacity of polycrystalline silicon manufactured using the modified Siemens process accounts for approximately 80% of the world’s total production capacity, and the situation of technological monopoly in this field is not expected to change in the short term. Polysilicon is a form of elemental silicon. When molten elemental silicon solidifies under supercooled conditions, silicon atoms arrange themselves in a diamond lattice to form numerous nuclei. If these nuclei grow into grains with different crystal plane orientations, then these grains combine together to form polycrystalline silicon. Polysilicon can be used as a raw material for producing single-crystalline silicon, and the difference between polysilicon and single-crystalline silicon lies mainly in their physical properties. For example, in terms of the anisotropy of its mechanical, optical, and thermal properties, it is far less pronounced than single-crystalline silicon ； In terms of electrical properties, the conductivity of polycrystalline silicon crystals is also far less significant than that of single-crystalline silicon, to the point where it is practically non-conductive. In terms of chemical reactivity, the difference between the two is minimal. Polycrystalline silicon and single-crystalline silicon can be distinguished by their appearance, but true identification requires analyzing factors such as the crystal plane orientation, conductivity type, and resistivity. Siemens process: Crushed metallurgical-grade silicon is mixed with HCI gas in a sulfurized bed reactor and reacts to produce trichlorosilane and hydrogen, Si + 3HCI → SiHCl3 + H2. Since SiHC13 is a liquid below 30°C, it can be easily separated from hydrogen. Next, SiHCl3 is separated from other chlorides through distillation; the impurity level in the SiHCl3 obtained through distillation can be below the 10-10% requirement for electronic-grade silicon. The purified SiHCl3 is used to produce polycrystalline silicon ingots through the CVD process. Improved Siemens method – closed-loop hydrogen reduction of trichlorosilane. The modified Siemens process involves synthesizing hydrogen chloride using chlorine and hydrogen (or by using purchased hydrogen chloride). Hydrogen chloride is then combined with industrial silicon powder at a certain temperature to produce trichlorosilane, which is subsequently separated and purified through distillation. The purified trichlorosilane is used in a hydrogen reduction furnace to carry out a CVD reaction in order to produce high-purity polycrystalline silicon. The vast majority of existing polysilicon plants at home and abroad use this method to produce electronic-grade and solar-grade polysilicon. The raw materials and auxiliary materials used in this method to produce polysilicon are silicon trichloride hydride, hydrogen chloride, hydrogen, calcium oxide, hydrofluoric acid, nitric acid, and sodium hydroxide. Silane method – thermal decomposition of silanes. Silane (SiH4) is produced by methods such as the hydrogenation of silicon tetrachloride, the decomposition of silicon alloys, hydride reduction, and the direct hydrogenation of silicon. The resulting silane is then purified and used in a thermal decomposition furnace to produce rod-shaped polysilicon of high purity. Its auxiliary raw materials also include liquid ammonia, ammonium chloride (provided by ammonia fertilizer plants), metallic magnesium, etc. In the fluidized bed process, silicon tetrachloride, hydrogen, hydrogen chloride, and industrial silicon are used as raw materials to produce trichlorosilane under high temperature and pressure in a fluidized bed (boiling bed). Trichlorosilane is then subjected to further disproportionation and hydrogenation reactions to yield dichlorodihydrosilane, which subsequently produces silane gas. The resulting silane gas is fed into a fluidized bed reactor containing fine silicon powder to undergo a continuous thermal decomposition reaction, thereby producing granular polycrystalline silicon products. Because the silicon involved in the reaction in the fluidized bed reactor has a large surface area, it enables high production efficiency, low power consumption, and low costs, making it suitable for the large-scale production of solar-grade polysilicon. The only drawback is poor security and high risk. Secondly, the purity of the product is not high, but it is generally sufficient for use in solar cell production. The ELKEM method is a solidification and purification technique for metallurgical silicon. The main method currently used to produce solar-grade silicon involves using refined metallurgical-grade silicon; phosphorus impurities are removed through electron beam heating in a vacuum environment, followed by solidification. Afterwards, boron and carbon are removed using plasma oxidation, and solidification occurs once again. Crown plasma mixed with water vapor can reduce the boron content to 0.1 ppm, and the metal impurity content in the re-solidified silicon can be reduced to the ppb level. The highest efficiency of conventional process diodes made from this solar-grade silicon can reach 14%, while those produced using high-efficiency processes can achieve a maximum efficiency of 16%. This solar-grade silicon has entered the pilot production stage with an annual output of 60 tons. Polysilicon purification is an energy-intensive industry, and it is also a highly polluting industry if strict environmental controls are not in place. As mentioned earlier, during crystal growth using the Siemens method, a high temperature of around 1100°C must be maintained, which requires a large amount of electricity. It is no wonder then that the United States produces over 50% of the world’s polysilicon, as it has an abundant supply of electricity and relatively low electricity costs in its developed regions. The production of 1,000 tons of polysilicon generates 3,500 tons of trichlorosilane and 4,500 tons of silicon tetrachloride waste liquid. Trichlorosilane and silicon tetrachloride that are not treated or recycled are toxic liquids that cause severe environmental pollution. The polysilicon purification plants built by developed countries all include systems for recovering toxic gases and liquids. Given China’s current environmental standards and enforcement level, the consequences of blindly developing polysilicon projects are truly concerning.

I ask you again, what is the name of that company in Guangdong? What silicon is being produced? Please reply after seeing this, thank you!

:'( :'( :'( Why isn’t it popular anymore? Are there very few people who know about it? Is it still because of technical restrictions that disclosure is not allowed?

Since its establishment, Jiake Company has been dedicated to the production and sales of metallurgical silicon, and it is one of the industry leaders that was among the first to overcome the shortage of solar silicon materials through innovative technologies. Jiakē solar silicon is also the only silicon material in China that has been successfully mass-produced on a commercial scale using metallurgical purification methods. We aim to provide low-cost, high-performance, and energy-efficient green silicon materials to support the rapid development of the PV industry, and to create a peaceful, healthy, and harmonious society. http://www.solarsi.com/cn/company.asp

It seems that the technology of the American company CDI is mostly used; I’m not quite sure about the specific methods

CDI Company’s technology relates only to the dry recovery step in polysilicon production, which is also essential for large-scale polysilicon production

1. Polysilicon technology is not yet mature. 2. The industry is overheated. 3. The owners of the polysilicon production projects under construction assume that having the raw materials is sufficient to produce qualified products; many of them have underestimated the technical challenges involved. 4. A few years later, many of these projects end up in the red once they are operational. 5. They strive to go public, using the guise of high-tech to attract investors’ money

It’s still the same old problem as before: how to deal with silicon tetrachloride. The more of it is used, the more silicon tetrachloride is generated, and sooner or later the environmental protection authorities will come after us

It’s a highly promising industry; as far as I know, many people are interested in getting involved in it.

Excuse me, on the 14th floor: what is the hydrogenation conversion rate you can achieve there, and how low can the energy consumption be?

Polysilicon has now essentially established itself in our country; as far as I know, three companies have already started work on their second and third phases of production, while some are preparing to start work on their fourth phase. The returns from this industry are very good, and several more companies are currently in the process of starting such projects. If you don’t believe it, everything will become clear next year. The polysilicon produced annually in quantities of thousands of tons these days is mostly manufactured using the reverse Siemens process; for smaller quantities, new processes are employed. As this involves technical confidentiality, I won’t go into further detail.