Objective The mole fraction of carbon monoxide in rectisol off gas is reduced below 0.20% in order to meet the design index.

Methods The reasons for the high carbon monoxide content in rectisol off gas were analyzed, and the system was optimized. Furthermore, the stripping hydrogen was designed in the secondary intermediate pressure flash distillation section of the rectisol and the amount adjustment was optimized. Apart from that, technical transformation was carried out to address the problem of unbalanced and insufficient cooling capacity recovery and utilization in the system.

Results After optimization, the mole fraction of carbon monoxide in rectisol off gas decreased to 0.19%, which meets the design index requirements and realizes the purpose of energy saving and consumption reduction.

Conclusions The system optimization operation, the design and optimization adjustment of stripping hydrogen and the technical transformation can effectively reduce the content of the carbon monoxide in the off gas to reach the design index.