Abstract: Some new ideas for optimal use of LCO for a grassroots refinery were proposed. According to the composition features as well as the complexity of desulfurization of different fractions, LCO is divided into three narrow fractions, i.e. LLCO (light fraction of LCO, < 260 ℃), MLCO (middle fraction of LCO，260-340 ℃) and HLCO (heavy fraction of LCO，>340 ℃). LLCO is pumped to low pressure diesel hydrotreating unit, while MLCO and HLCO, rich in PAHs (polycyclic aromatic hydrocarbons), are processed in hydrocracking unit and residue hydrodesulfurization unit, respectively, to produce reforming and FCC feed. Therefore, the yield of gasoline and aromatic product increases while diesel production decreases. The results show that for optimized scheme, the production of gasoline, PX and benzene increases by 415.6 kt/a, 33.3 kt/a and 14.7 kt/a, respectively, while that of diesel decreases by 774.0 kt/a, and the diesel/gasoline ratio reduces from 1.38 to 1.04. Meanwhile, the refining margins rise by 6.93 Yuan per ton crude, bringing remarkable economic benefit.

Key words: LCO, diesel/gasoline ratio, optimization of overall configuration