Abstract: During the second operation period of the deep catalytic cracking-plus(DCC-plus) unit of Dongfang Petrochemical Co., Ltd., the properties of raw materials of the unit changed frequently and the operating conditions was adjusted greatly. Based on the properties of raw materials and catalysts, through regular process accounting and technical analysis, the preheating temperature of raw materials, steam injection, reaction severity and line speed of key parts were regulated, the operation parameters of the slurry system were stabilized, and the equipment management was optimized, etc., which ensure that no unplanned shutdowns occured during the second operation period of the unit. The maintenance period of DCC-plus unit was successfully extended from 3 years to 4 years.

Key words: deep catalytic cracking unit, long-term operation, process checking and analysis, operation