Abstract: In order to solve the environmental problem of high content of volatile organic compounds（VOCs） in coke cooling hot water tank caused by oil entrainment of coke cooling water during overflow coke cooling process of 1.2 Mt/a delayed coking unit in a petrochemical company,the overflow coke cooling process was transformed into coke soaking coke cooling process.By adding a steam extractor on the evaporator line at the top of the reflux tank of the contact cooling drum, the steam and oil gas generated in the coke cooling process of the coke drum were pumped to the fractionation system, and the heat in the coke layer was removed by utilizing the vaporization latent heat of the coke cooling water, so as to achieve coke soaking and coke cooling in the coke drum. The coke cooling time of the coke drum could reach the water discharging condition within 12 h after the process of coke soaking coke cooling was completed and put into operation, which had no impact on the production cycle of the unit. During coke cooling, the mass concentration of VOCs in the top of hot water tankdecreased from 352.8 mg/m³ to 1.6 mg/m³，the mass concentration of oil in the coke cooling water decreased from 20-70mg/L to 1-10mg/L.The decrease of 30 m³/d in the waste oil tank indicated that more oil and gas in the coke process were recovered to the fractionation system, thus reducing the oil and gas carried out with the cold coke water. The steam energy consumption of 1.0MPa steam increased by 4.13 MJ/t, the electrical energy consumption decreased by 2.04 MJ/t, and the total energy consumption increased by 2.09 MJ/t, which had little impact on the energy consumption of the unit. The volatile of petroleum coke increased slightly, which could meet the index requirements. The problemof environmental protection existing in the original overflow coke cooling process was solved, and the environmental operation of the unit was realized after the coke soaking coke cooling process was adopted in the coke drum.

Key words: delayed coking, coke cooling water, coke soaking coke cooling, volatile organic compounds