Abstract: In order to reduce the olefin content of stable gasoline, FCC naphtha was used as quench oil in riser in a 4.8 Mt/a FCC unit of CNOOC Huizhou Petrochemical Company. It was found that the recycle of FCC naphtha into riser as quench oil had influence on product property and distribution, pressure distribution of oil and gas pipeline as well as energy consumption. The results showed that the volume fraction of olefins in the stable gasoline decreased by 1.3 percentage points when the quench oil naphtha was 15 t/h. Compared with that before the recycle of FCC naphtha, FCC conversion rate increased from 76.07% to 76.12%, the yield of coke increased from 7.29% to 7.74%, and total liquid recovery decreased slightly; the ratio of benzene to aromatics in gasoline decreased from 4.07% to 3.93%, sulfur transfer coefficient decreased from 2.89% to 2.28%; density of light diesel (20 ℃) increased from 948 kg/m³ to 951 kg/m³; the energy consumption increased by more than 90 MJ/t; the pressure drop from the outside of VQS to the inlet of air compressor increased by 2.5 kPa. The problem of salt deposition in the top tray and top circulation system of the fractionator was alleviated by the recycle of FCC naphtha.

Key words: catalytic cracking, naphtha, quench oil, recycle, olefins, energy consumption