Coke drum and blowdown system overpressure protection design-Part 2

摘要

The blowdown(BD)system in delayed coking units(DCUs)receives waste streams generated during the coke drum(CD)decoking process to recover valuable hydrocarbons and water.In recent DCU designs,the CD pressure-relief valves(PRVs)also discharge to this system and then to the flare system via the BD PRVs.Having two overpressure protection devices in series imposes some challenges in the design.The aim of this article is to identify the main characteristics and difficulties for designing CD and BD relief systems for this configuration.Part 1,published in the April issue of Hydrocarbon Processing,provided details on different destinations for CD relief;identification of the main relief contingencies involved in the design;and PRV set pressure definition,sizing and selection.The following will detail the critical elements and key considerations in the BD system and flare hydraulics.