Different from those used to electronics and solar cells, monocrystalline silicon, is also different from amorphous silicon thin-film devices and solar cells, polysilicon is made up of tiny silicon materials. Major polysilicon producer Hemlock Semiconductor, OCI, WACKER (Wacker Chemie), GCL-poly energy, and REC, LDK Solar, MEMC, and some smaller producers.
Polysilicon industry is developing rapidly, and levels above 1000t polysilicon production plant were built. However, polysilicon production process, hydrogen, chlorine, trichlorosilane and silicon and other harmful substances, and there are fire, explosion, poisoning, suffocation, electric shock injuries and many other risk factors.
Harmful substances produced in the polysilicon production process of chlorine gas, hydrogen, Silicon, hydrogen chloride, trichlorosilane, main risk characteristics are:
1. hydrogen gas: mix can form explosive mixtures with air, heat or open flame or explosion. Gas is lighter than air, when indoors use and storage, leakage increased stranded roof difficult to discharge, when Mars will cause an explosion. Halogens such as fluorine, chlorine, bromine and hydrogen will react violently.
2. oxygen, combustible materials, combustible matter combustion and explosion of one of the essential elements and oxidation of most active substances. And combustible (such as acetylene and methane) forms explosive mixtures.
3. chlorine: a pungent odor and can be generated with a number of chemical explosions or explosive material. Almost all metallic and non-metallic corrosion. Are highly toxic. Is a strong irritant gases.
4. hydrogen chloride: anhydrous hydrogen chloride is non corrosive, but when in contact with water, are corrosive. Can react with reactive metal powders, releasing hydrogen gas. Cyanide can produce highly toxic hydrogen cyanide gas.
5. three hydrogen Silicon chlorine: open flame burning strongly. Subject to high thermal decomposition may produce toxic chlorine gas. Reacts with oxidants, are a fire hazard. Very volatile and fumes in the air, in contact with water or water vapour can generate heat and toxic corrosive smoke. Combustion (decomposition) products: hydrogen chloride, silica.
6. Silicon tetrachloride: heating or hot water liberation, release toxic corrosive smoke.
7. hydrofluoric acid: corrosive, very strong. H vesicant immediately burned. Can react with bare metal and releases hydrogen with air to form an explosive mixture.
8. a nitric acid: strong oxidizing. And combustible (such as benzene) and organic matter (such as sugar, cellulose) exposure will react violently, even cause fire. With alkali metals react violently. Has strong corrosion resistance.
9. the nitrogen: in case of high fever, increased pressure within the container. Cracking and danger of explosion.
10. hydrogen fluoride: highly corrosive. In case of high fever, increased pressure within the container, is in danger of cracking and exploding.
11. sodium hydroxide solution: this product is non-combustible, with strong strong corrosive, irritant can cause the human body burns.
Second, electric shock, other risk factors such as mechanical damage
Fire, explosion, poisoning is polysilicon projects in major danger and harmful factors in production, in addition, there is electric shock, mechanical damage, corrosion, dust and other hazardous and harmful factors. Are:
1. preparation of hydrogen: electrolyzer, hydrogen, and oxygen tanks, fire and explosion, electric shock and mechanical damage.
2. hydrogen chloride synthesis: synthesis furnace of hydrogen chloride, chlorine and hydrogen gas buffer tanks, fire and explosion, poisoning, electrocution.
3. the three Silicon-hydrogen chloride synthesis: three Silicon-hydrogen chloride synthesis furnace, synthesis gas scrubbers, feeding machine, fire and explosion, electric shock, poisoning, corrosion, mechanical damage and dust.
4. the synthesis gas separation: mixed gas scrubber, hydrogen chloride absorption tower, Tower, the mixed gas compressor hydrogen chloride resolved, fire and explosion, electric shock, poisoning, corrosion, mechanical damage.
5. separation of chlorosilanes: distillation, reboiler, condenser air, fire and explosion, electric shock, poisoning, corrosion, mechanical damage.
6. the three hydrogen Silicon chlorine reduction: three hydrogen Silicon chlorine carburetor, reduction furnace, reduction furnace cooling water circulation pumps, fire and explosion, electric shock, poisoning, corrosion, mechanical damage.
7. restore gas separation: mixed gas scrubber, gas compressors, hydrogen chloride absorption towers, fire and explosion, electric shock, poisoning, corrosion, mechanical damage.
8. hydrogen-Silicon tetrachloride: Silicon tetrachloride carburetor, hydrogen furnace, fire and explosion, electric shock, poisoning, corrosion, mechanical damage.
Based on the above analysis, it is the main potential risks of fire and explosion, chemical poisoning, harmful factors in terms of technology, equipment, facilities and protection problems and defects, is very likely to occur, it should be for reasons that may occur and take preventive measures to actively exclude.
Primary prevention measures are: automatic control system for production use, and improve the standard of control; in chlorine, hydrogen chloride, trichlorosilane Silicon Silicon chloride, hydrochloric acid, easy to leak part of fresh air and sets flammable and toxic gas detection and alarm system; personnel issued qualified for the job for antivirus, dust-proof and burns and other protective equipment to avoid risks of polysilicon.
