Coke drum hot spots can be difficult, if not impossible, to predict but there are operating practices that can help minimize the occurrence of coke drum hot spots/blowouts.
We are currently constructing two new delayed coker heaters at our El Dorado, Kansas facility. As part of this project, we have performed both a process hazard analysis (PHA) and a safety integrity level (SIL) evaluation.
After a Coke drum is taken offline, it is steam stripped with ‘little’ steam @ 2.5 t/hr for 30 minutes (28 ft drum) to main fractionator to recover volatile hydrocarbon material.
Standard laboratory tests include salt, BS&W, gravity, viscosity, and filterable solids. The amount, and type of filterable solids can be the greatest factor to consider for interface emulsion resolution and predicting performance.
We have worked with several refining organizations that process heavy Canadian crude oils to find the optimum desalter operating temperature. In general, raising temperature reduces the crude oil viscosity, which is desirable from a Stokes’ Law stand point as it makes breaking the emulsion easier.
On some occasions more frequent, or continuous mudwash may help dilute effluent water, thus reducing high concentrations of solids slugging the effluent water exchangers during the mudwash cycle.
We have extensive experience removing calcium and other metals from crude oils, with over 20 successful applications removing contaminants spanning the last 8 years.
Along the lines of Ron’s last point on secondary treatment of brine, some refineries have installed diversion tanks to receive the effluent water when the mud wash is being used.