Turboexpander Applications in Catalytic Cracking Units

Fluid eatalytie eraeking (FCC) is eonsidered tlie primary eonversion proeess in an integrated refinery. For many refiners, the eat eraeker is tlie key to profitability beeause sueeessful operation of tlie unit ean determine whether or not a refiner stays in business and remains eompetitive. 

The gas oil to a eonventional eraeker is primarily from the atmospherie eolumn, the vaeuum tower, and the delayed eoker unit. Additionally, many refiners blend some atmospherie or vaeuum residue with die eraeker feedstoeks to be proeessed in die FCC unit. 

From die preheater, die feed enters die riser near die base where it eontaets die ineoming regenerated eatalyst. The ratio of eatalyst to oil is normally in the range of 4 1 to 9 1 by weight. 

Effieient eontaeting of the feed and the eatalyst is eritieal for aehieving the desired eraeking reaetions. Steam is eommonly used to atomize the feed beeause feed atomization inereases the availability of feed at the reaetive aeid sites on the eatalyst. Employing a high-aetivity zeolite eatalyst ensures virtually all of the eraeking reaetions 

After exiting tlie riser, tlie catalyst enters the reactor. In modern FCC operations, the reactor serves two basic functions as a disengaging space for the separation of catalyst and vapor, and as the housing for the reactor-internal cyclone. 

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