Revamping Atmospheric Crude Heaters
SUMMARY
The revamp of an atmospheric crude unit heater, which was suffering from coking caused by asphaltene precipitation and poor burner stability, resulting in a significantly increased heater run length.
TEXT
Refinery atmospheric crude heaters can experience rapid increases in tube metal temperature (TMT), requiring unplanned shutdowns for decoking. In the case of the Navajo Refining Company facility in Artesia, New Mexico, USA, rapid increase in the atmospheric crude heater’s TMT resulted in a shutdown every three to six months. In this case, as well as others observed in the industry, coke formation was initiated by asphaltene precipitation from unstable crudes.
Industry-wide, atmospheric crude heater coking is an unusual problem, with some heaters operating reliably at an average radiant section heat flux of 13-14,000 Btu/hr-ft2 or higher. However, some crude oils, including those produced from North American fields in West Texas, New Mexico, Ohio/Pennyslvania and Alberta are known to be unstable when there is asphaltene precipitation in certain areas of the crude unit. The equipment in these areas includes preheat exchangers, fired heaters, and atmospheric column flash zone and stripped section internals.
The Artesia refinery was experiencing chronic coking in its atmospheric column heater, with periodic shutdowns to remove coke at intervals as short as 90 days…