Why the crystalline silicon industry is a highly polluting industry 10

Say polysilicon. People with high pollution do not understand the actual situation at all, and the photovoltaic industry is rumored in society.

High pollution, mainly refers to the production of polysilicon. Yes, the production process from silicon to wafer is essentially a chemical production process. In the process of chemical reaction, some new substances will inevitably be produced, some of which are toxic substances.

These toxic substances, if not **, will naturally become pollutants and harm the environment. For example, silicon tetrachloride, a large by-product produced in the production process of polysilicon.

The polysilicon production process includes trichlorosilane.

Hydrogenation synthesis, trichlorosilane purification, reduction of polysilicon, tail gas separation and other four processes. At present, 80% of the world's polysilicon production adopts the modified Siemens process, which has been developed for more than 50 years, and has made great progress in energy-saving, environmentally friendly and low-cost production.

A new process for the production of lower-quality, high-quality polysilicon that is suitable for solar products.

Polysilicon production technology in China.

There are three key equipment and technologies imported from Germany, the United States and Japan, and there are four processes on the production line, with a total of 17 core technologies (all with independent knowledge patents) put into use. Especially the core material, the key process is the self-developed hydrochloride technology (which has been declared a Chinese patent), which has achieved remarkable results. At present, a large number of by-products produced by polysilicon, silicon tetrachloride, can be converted into trichlorosilane, an intermediate raw material for the production of polysilicon.

In order to save operating costs, the company does not make great efforts in the treatment of emissions and harmful substances, resulting in environmental pollution.

It will cause damage to the air.

1) The high-crystalline silicon project shall comply with the national industrial policy, land use policy and industry development plan, and the minimum capital ratio in the investment of new construction, reconstruction and expansion projects shall not be less than 30%. Strictly control the construction of new polysilicon projects in areas with energy shortages and high electricity prices, and refuse to approve or record polysilicon projects that lack comprehensive support, safety, health and environmental protection standards.

2) Within 1,000 meters of areas with high environmental requirements such as basic farmland protection areas, nature reserves, scenic spots, drinking water source protection areas, residential concentration areas, recuperation areas, food production sites, etc., established in accordance with the law, or within sensitive areas of key ecological function areas planned by the state or local governments, no new high-crystalline silicon projects and belts shall be built. The high-crystalline silicon projects that have been put into operation in the above-mentioned areas shall be gradually withdrawn through relocation, transfer and suspension of production in accordance with the relevant plans of the region.

Waste gas: mainly the exhaust gas of the waste gas treatment process during normal production, the acid waste gas of the product post-treatment and the silicon core preparation process, etc., and the main waste gas pollutants are HCL, NOX, chlorosilane, HF, etc.

Wastewater: It is mainly the washing wastewater of the product post-treatment and silicon core preparation process during normal production, the washing water of the equipment floor in the equipment area, and the putative clean sewage discharged from the circulating water and desalinated water system. The main wastewater pollutants are SS, COD, salt, etc.

Solid waste: The main solid wastes are silica powder generated by the raw material preparation and SiHCl3 synthesis process, NaCl and SiO2 solid waste generated by the process waste treatment process, and Ca(NO3)2 CaF2 solid waste generated by the pickling waste liquid treatment process.

Noise: The main noise-producing equipment is pumps, compressors and vent pipes.

The overall process of high-purity crystalline silicon production is harmless or rarely harmful to the human body, and I have a relative who has worked in the production workshop all his life until he retires normally.

The production process of monocrystalline silicon wafers.

Monocrystalline silicon is purified and manufactured from nature's abundant silicon raw materialsPolysilicon, and then through the zone melting or Zhizopull method to produce zone melt single crystal or Zhizopull single crystalline silicon, further form silicon wafers, polished wafers, epitaxial wafers, etc. Monocrystalline silicon grown by the Zorghy method is used in the production of low-power integrated circuit components.

Zone melting process: The monocrystalline silicon grown is mainly used in high-power electronic components.

Straight-pull processing technology: feeding, melting, neck reduction, shoulder growth, equal diameter growth, tail growth, and the finished crystal rod is lifted to the upper furnace chamber for cooling for a period of time and then taken out, that is, a growth cycle is completed.

Suspension zone melting process: rod polycrystalline ingots are accurately fixed vertically with fixtures from the top and bottom axes. An area is melted by electronic bombardment, high-frequency induction, or optical focusing, so that the liquid is supported by surface tension without falling.

Moving the sample or heater moves the melt zone. This method does not use a crucible, which can avoid crucible contamination, so it can prepare very pure single crystals, and can also be used for zone melting.

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