Operation Analysis of Self Reflux Demethanizer in Ethylene Plant
Since the start of operation in September 2020,the ethylene plant of Sinochem Quanzhou Petrochemical has experienced multiple operating conditions such as excessive ethylene heavy fraction at the top of the demethanizer tower/full liquid level in the reflux tank at the top of the tower,and the first start-up process of the per cooling and demethanizer units takes a long time.During the first shutdown and maintenance period in 2022,the inlet filter screen of the overhead condenser of the self reflux demethanizer was removed.After start-up,the ethylene content in the high-pressure exhaust gas at the top of the demethanizer tower under full load conditions did not exceed 0.03%,and the liquid level in the overhead reflux tank remained stable at 10%～12%.And by analyzing the previous start-up processes of the demethanizer in this device,the nodes of C3 washing oil injection,liquid phase methane delivery coke valve injection,ethylene refrigerant control method during start-up,demethanizer pressure selection,and abnormal changes in the process adjustment direction of the top heavy component are analyzed,providing start-up experience for similar deep cooling distillation units.
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