Abstract: In view of a series problems in a 2.8 Mt/a catalytic cracking(FCC) unit, including low cetane number of FCC diesel and unsatisfactory product distribution (low yield of FCC gasoline and insufficient yield of liquefied petroleum gas), a petrochemical company has implemented a new process that recycles light cycle oil (LCO) to the bottom nozzle of the riser via a cross-line modification, and the product distribution was optimized. The average diesel yield decreased from 20.3% to 15.7%, generating significant economic benefits.During the trial operation, the chemical composition and reaction mechanisms of LCO were analyzed to evaluate recycling parameters and effectiveness. The optimal recycling rate was determined to balance product distribution and economic efficiency.

Key words: catalytic cracking, light cycle oil, recycling, product distribution, economic analysis