Fcc dual elevation riser feed distributors for gasoline and light olefin modes of operation

Abstract

A fluid catalytic cracking process includes feeding hydrocarbon into a riser in the presence of a catalyst, cracking the hydrocarbon in the riser in the presence of the catalyst to form a cracked stream, and separating the catalyst from the cracked stream. When in a gasoline mode, the hydrocarbon is fed through a first distributor into the riser, and when in a light olefin mode, the hydrocarbon is fed through a second distributor into the riser. The second distributor is positioned at a higher elevation than the first distributor.

Description

[0001]This application is a continuation-in-part of application number Ser. No. 11 / 365,715, filed on Mar. 1, 2006.BACKGROUND OF THE INVENTION[0002]This invention relates generally to a process for catalytic cracking of hydrocarbons.DESCRIPTION OF THE PRIOR ART[0003]Fluid catalytic cracking (FCC) is a catalytic conversion process for cracking, heavy hydrocarbons into lighter hydrocarbons accomplished by contacting the heavy hydrocarbons in a fluidized reaction zone with a catalyst composed of finely divided particulate material. Most FCC units use zeolite-containing catalyst having high activity and selectivity. As the cracking reaction proceeds, substantial amounts of highly carbonaceous material referred to as coke are deposited on the catalyst, forming spent catalyst. High temperature regeneration burns coke from the spent catalyst. The regenerated catalyst may be cooled before being returned to the reaction zone. Spent catalyst is continually removed from the reaction zone and re...

AI Technical Summary

Benefits of technology

[0007]An FCC process which may include a dual elevation riser feed distributor and may vary the residence time requirement for multiple modes of operation. One aspect of the invention may be the ability to shift operation for the unit to different modes of operation without shutting down the unit. In accordance with the invention, an FCC process may utilize a dual elevation riser feed distributor rather than a single elevation feed distributor. The dual elevation riser feed distributor may enable the refiner to operate the unit in one mode of operation, such as a gasoline mode, with a first elevation feed distributor or in a second mode of operation, such as a light olefin mode, with a second, higher, elevation feed distributor. In a preferred embodiment, both sets of feed distributors may be generally identical except for their positions vertically with respect to each other within the riser, and they may have generally the same number, size, and arrangement of nozzles, or the equivalents thereof, in order to provide the refiner with additional flexibility and options for running the new and improved FCC process.

Problems solved by technology

A problem presented by the prior art is that changing operation of an FCC unit, such as from olefin production mode to gasoline production mode, by substantially changing riser residence time may require the unit be shut down for equipment changes to be made.

Shutting down an FCC process stops the production of the valuable products and disrupts the desired steady state of operations.

Therefore, changing modes of operation in this way may be undesirable for several reasons, including effects on productivity, efficiency and cost.

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