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Vent Gas Recovery

The Vent Recovery Unit accepts the vent gases from the CVD Reactors and separates them into a mixed chlorosilane liquid, recovered HCl gas and recovered hydrogen gas. 
 
The warm vent gases from the reactors are chilled in shell and tube exchangers to condense chlorosilane liquids. The remaining gases are warmed up and fed to the compressors. 
 
The compressors are reciprocating compressors designed to boost the pressure to the required hydrogen return pressure, plus pressure drop needed for the vent recovery unit. 
 
The compressed gases are chilled and fed to the HCl-absorber, where HCl is absorbed in a chilled liquid chlorosilane stream. The rich chlorosilanes are warmed and fed to the HCl distillation, where the HCl is stripped off and recovered as a liquid distillate. HCl is consumed in the Direct Silicon Chlorination step. 
 
The gas from the HCl absorber is sent to carbon adsorber towers where any remaining contaminants are removed. Clean hydrogen is recycled to the CVD reactors. The carbon adsorbers are regenerated by thermal swing. The regeneration purge contains small amounts of H2, HCl and Chlorosilanes that are returned to the suction of the primary compressor suction.