Q & A > Question Details
What are the effects of continuous usage of FCCU direct fires air heater during normal operation to support Regenerator base temperature especially at a condition of limited fresh catalyst availability?
02/05/2017 A: Eric Hennings, Technip Stone & Webster, EHennings@technip.com
Continuous operation of direct fired air preheater (DFAH) has been practiced successfully for many years. Operation of DFAH enhances the heat balance challenge on feeds with low carbon precursors or very high conversion to olefins. The air distributor must be designed for the higher temperature as well as lower air density.
The main issue with this operation occurs when the DFAH is shut down under emergency conditions. During such a shutdown, the air distributor is rapidly cooled from operating to MAB discharge temperature. The air distributor must be designed to accommodate this rapid cooling.
A modern DFAH with appropriate instrumentation can be expected to run continuously. Many of the older DFAH's lack dependability are only designed for brief "startup" conditions.