The true role of the adsorption column in exhaust gas recovery
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Many people in the polysilicon industry believe that installing an adsorption system in the off-gas recovery process serves to further purify the hydrogen gas coming out of the absorption tower, by removing any remaining chlorosilanes and hydrogen chloride. In fact, the real purpose of the adsorption columns is not to eliminate the small amounts of chlorosilanes and hydrogen chloride present in the recovered hydrogen; rather, their aim is to remove impurities such as boron, phosphorus, and iron from that hydrogen. Because, before entering the reduction furnace, hydrogen first mixes with trichlorosilane before going into the furnace. During the deposition of silicon, a large amount of hydrogen chloride is generated; the silicon deposition process takes place in an environment containing high levels of hydrogen chloride. The chlorosilanes contained in hydrogen are mainly dichlorodihydrosilane and trichlorosilane, with dichlorodihydrosilane being beneficial for the deposition reaction of polycrystalline silicon, while trichlorosilane itself is a raw material used for the deposition of polycrystalline silicon. Therefore, I believe the main purpose of adsorption is to remove the boron and phosphorus impurities contained in the recovered hydrogen. Our factory once tried to feed recycled hydrogen, after adsorption, directly into the reduction furnace for use in reactions; as a result, the polycrystalline silicon produced had excessive levels of impurities, mainly boron and phosphorus.
I’m not sure; let’s check what others have discussed
Symbols, learn *a bit about them. Wait for experts to make the judgment.
The adsorption column is used to absorb impurities; any impurity will be absorbed, including chlorosilanes, HCL, boron, phosphorus, iron, and so on.
Waiting for experts :victory::time:
The adsorption column is primarily used to remove impurities such as HCL, chlorosilanes, boron, and phosphorus. The adsorption of impurities like boron and phosphorus by activated carbon is a chemical adsorption process that is irreversible; however, relying on activated carbon for boron removal is not very effective. At certain levels of purity, the concentration of boron impurities can actually increase
It is simply assumed that adsorption may be able to remove B\P, but this needs to be supported by experimental and analytical data……
Waiting for the expert’s analysis! Hope to see an analysis with specific data
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