How does a fluid catalytic cracking unit regenerate its catalyst?

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In a fluid catalytic cracking unit, the catalyst is regenerated through a continuous process designed to remove carbon deposits that impair its efficiency.1

The regeneration process follows these steps:

Separation and Stripping: As cracking reactions occur, carbon deposits on the catalyst particles. The spent catalyst is separated from the reactor product vapors using cyclone separators and dropped into a stripper section. There, steam is used to remove any remaining hydrocarbons from the catalyst.1
Combustion: The stripped catalyst is transferred through a standpipe to a regenerator vessel. In this vessel, the carbon deposits are burned off by a current of air.1
Heat Recovery: The regeneration process occurs at high temperatures (675–785 °C, or 1,250–1,450 °F). This intense heat serves a dual purpose: it cleans the catalyst and raises its temperature, providing the necessary heat to sustain the cracking reaction when the catalyst is recontacted with fresh feed.1

To maintain consistent activity, a small portion of the catalyst is periodically withdrawn and replaced with fresh material.1