Patent ID: 10456728

Abstract:
A process for recovering valuables from vent gas in polyolefin production is disclosed. The process includes a compression cooling separation step, a heavy hydrocarbon separation step, a light hydrocarbon separation step, a N2 purification step, and a turbo expansion step in sequence. The N2 purification step comprises a membrane separation procedure. The light hydrocarbon separation step comprises at least one gas-liquid separation procedure. A first gas, which is obtained by the gas-liquid separation procedure and is heated through heat exchange with multiple streams in the light hydrocarbon separation step, enters the heavy hydrocarbon separation step and is further heated; the heated first gas then enters the N2 purification step; a first generated gas, which is obtained by the membrane separation procedure of the N2 purification step, enters the heavy hydrocarbon separation step and the light hydrocarbon separation step in sequence, and is cooled through heat exchange with multiple streams in the heavy hydrocarbon separation step and the light hydrocarbon separation step; and then the cooled first generated gas enters the turbo expansion step. The energy consumption of a compressor can be greatly reduced. An external cooling medium with a temperature lower than an ambient temperature is not needed. The purity and recovery of N2 and hydrocarbons can be improved, which can facilitate reduction of energy consumption of a whole system, an investment, and a material consumption.