Dynamic behavior of coke drum process safety valves during blocked outlet condition in the refinery delayed coking unit

The design of Delayed Coking Unit of a refinery is a challenging project. This study highlights some of the design considerations in the delayed coking unit with an emphasis on process point of view and more specifically on the relief conditions of coke drums operating under an upset event which results in overpressure of coke drums.The results provided a practical and useful approach to control release of hot and heavy hydrocarbons to minimize their environmental impact. Blocked outlet conditions of normally open path of coke drum to the main fractionator is a critical issue in a refinery. Pressure safety valves calculations were carried out to address their dynamic behavior. It was assumed that the operating team will recognize the problem with sudden abnormal pressure fluctuations and intervene the upset condition in less than 15 min. A HYSYS simulation helped us to analyze the problem in more details.

► Dynamic behavior of coke drums in a refinery Delayed Coking Unit upon upset conditions was analyzed.
► The analysis used numerical calculations and HYSYS simulation.
► Process safety valves were designed to control blocking of Coke drum lines to the main fractionator.
► Hydraulics of piping when flow into the Blowdown section is suddenly increased was analyzed.
► Recommendations for the flare network ware given to prevent or ensure safe release of hot materials.