Why crystalline silicon industry is a highly polluting industry?

People who say that polysilicon is highly polluted are totally ignorant of the actual situation. It is said that the photovoltaic industry is highly polluted, mainly referring to the production of polysilicon. Yes, the production process from silicon material to wafer is essentially a chemical production project. In the process of chemical reaction, substances will inevitably produce some new substances, some of which are toxic substances. These toxic substances, if not recycled, will naturally become pollutants and harm the environment. Such as silicon tetrachloride, a large number of by-products produced in polysilicon production.

the polysilicon production process includes four processes: trichlorosilane hydrogenation synthesis, trichlorosilane purification, polysilicon reduction, tail gas separation and recovery. At present, 8% of polysilicon production in the world adopts the improved Siemens process. After more than 5 years of development, this process has made great progress in energy saving, environmental protection and low-cost production. In view of the special demand of materials in the solar industry, a new polysilicon production process with lower production cost and suitable quality for solar products has been developed, such as silane process.

Three key equipments and technologies in China's polysilicon production technology are imported from Germany, the United States and Japan, and there are 17 core technologies (all with independent knowledge patents) in four processes on the production line. Especially for the core material recovery, the key process is the self-developed chlorohydrogenation technology (which has been patented in China), and has achieved remarkable results. At present, it has been achieved that a large amount of silicon tetrachloride, a by-product produced in the production of polysilicon, can all be converted into trichlorosilane, an intermediate raw material for the production of polysilicon.