Fluid cracking regeneration period

The most dominant catalytic process in the United States is the fluid catalytic cracking process. In this process, partially vaporized medium-cut petroleum fractions called gas oils are brought in contact with a hot, moving, freshly regenerated catalyst stream for a short period of time at process conditions noted above. Spent catalyst moves continuously into a regenerator where deposited coke on the catalyst is burnt off. The hot, freshly regenerated catalyst moves back to the reactor to contact the hot gas oil (see Catalysts, regeneration). 

Catalyst residence time or process period). Catalyst residence time in a moving-bed or fluid unit, or process period in a fixed-bed unit, is the length of time a catalyst particle is used to crack oil in each cycle before it is regenerated. Catalyst residence time is equal to the ratio of the amount of catalyst in the reactor to the catalyst-circulation rate. In moving-bed units, it is essentially the same for all catalyst particles, whereas in fluid units there is a variation, as already discussed. 

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