Application of Oil-free Screw Compressor in Hydrogen Chloride Mixed Gas Compression

Aiming at the difficult to recover hydrogen chloride mixed tail gas generated during the production of lithium bis(fluorosulfonyl)imide (LiFSI), the PRO II process simulation software was adopted to optimize the parameters of the compression condensation recovery process in this paper. Considering equipment investment, operating energy consumption and anti corrosion risks comprehensively, the optimal process parameters were determined, with the final compressor pressure of 2.0MPaG and condensation recovery temperature of 0°C. By comparing the advantages and disadvantages of reciprocating compressors and oil injected screw compressors, a two stage series oil free screw compressor was selected as the pressurization equipment. High temperature corrosion caused by acidic gas was inhibited by upgrading the compressor casing and rotor to 2205 duplex steel material and using thionyl chloride as the special internal liquid spraying medium. A three stage composite sealing structure consisting of front labyrinth, double end dry gas and isolation comb tooth seals was designed to achieve zero leakage of process gas. The industrial operation results of the LG58/0.0 2.0 unit show that under working conditions with wide fluctuations of inlet pressure (0–0.01MPaG) and inlet temperature (−10–10°C), the discharge pressure of the unit remains stable, the outlet temperature can be steadily controlled within 70–75°C, no medium leakage or oil contamination occurs, and the purity of recovered hydrogen chloride products meets process requirements. This complete oil free screw compression solution can provide engineering references for pressurization recovery and equipment selection of strongly corrosive mixed gas in the lithium battery and fluorine chemical industries.