Problems in contacting cooling system in DCU and countermeasures

In the contacting cooling system of a 1.0MM TPY delayed coking unit adopting closed cooling tower technology,a series of problems occurred in the operation,such as large amount of oil slurry withdraw,large flare emission because of non-condensable gas release and serious fouling in heat exchangers in sour water stripper because of high oil in tower overhead waste water.At the same time,the delayed coking unit was required to recycle plant waste oil as the quench oil of coke towers.To solve these problems,the contacting cooling system was revamped in a scheduled shut-down for maintenance.The revamping mainly includes adding blow-down tower bottom heater and quench oil pipeline to the top of coke towers,installing demulsifier injection system and providing ways for recovery of non-condensable gas.After revamping,the self-produced waste oil and plant waste oil were recycled as quench oil,the venting tower overhead acidic water quality was improved to meet the requirements of the sour water stripping unit and about 2 000 tons of non-condensable gas were recycled.Both environmental and economic benefits have been achieved.