Abstract: The circulating screw compressor in the C₄ full hydrogenation unit plays a vital role in the reliable operation of the unit. It can effectively improve the material utilization efficiency and reduce the losses of C₄ components and hydrogen in the purge gas. The compressor may shut down due to faults existing in the oil circuit system, liquid injection system, instrument system or sealing system. This paper analyzes the causes of the compressor failure, puts forward corresponding countermeasures, and thoroughly investigates the impacts of different switching conditions on material loss and product quality after shutdown. The conclusions are drawn as follows: both the scheme of interrupting hydrogen make-up by the circulating compressor and the scheme of interrupting hydrogen make-up while halting the recovery of the first-stage purge gas will markedly raise hydrogen consumption and purge gas loss. Although recovering the first-stage hydrogenation purge gas by lowering operating pressure can reduce material consumption to a certain extent, the mitigation effect is limited and the improvement is insignificant. All the above schemes can maintain the stable operation of the unit. During design, the operational requirement of controlling the switching time within 0.5 hours should be considered to ensure that the second-stage full hydrogenation system can maintain normal circulation while ensuring product quality unaffected.

Key words: C₄ full hydrogenation, screw compressor, compressor failure, purge gas, hydrogen consumption