When a pump feeding a crude column through the heater stops, should the evaporation of the residual liquid in the heater due to the residial heat in the heater refractory be considered for the relief case (e.g. total power failure case)? Or is it normally ignored due to limited inventory of liquid in the heater?
Answers
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29/11/2013
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Alan Goelzer, Jacobs Consultancy, alan.goelzer@jacobs.com
Crude Heaters and Vacuum Heaters should be designed to be "de-inventoried" upon failure of the feed pumps for any reason. Best way to do this is via injection of emergency steam upon failure to convection inlets or via routine velocity steam injection to coil inlets. Steam MUST BE superheated for this service. Evaporation of crude will continue for finite time period after flow stops and burners are tripped to pilots and then electively to full off. Question on power failure relief load are heat sink inventory of the tower and continuing heat sink potentials of pump-arounds and P/A air coolers and overhead air coolers.
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29/11/2013
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Yes. It is called "tube boil-out", and is also considered when there is a fired reboiler.
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