Heating fcc feed in a backmix cooler

Abstract

A process for the fluidized catalytic cracking of an FCC feedstock uses a backmix catalyst cooler to heat FCC feed and control tube wall temperatures to avoid coking and thermal cracking. Heated FCC feed contacts the catalyst in a reactor riser to convert the feedstock. Prior heating of the feed raises its temperature so that it is more easily vaporized and better distributed throughout the riser. Using FCC catalyst to heat the feed maintains the heat balance between the reactor and the regenerator so that the catalyst circulation to the riser can remain unchanged. The backmix type cooler has heat exchange tubes located in a separate vessel. Catalyst from the dense bed of a regeneration zone is circulated to a section of the cooler located above the heat exchange tubes. One form of the invention uses two conduits to transfer catalyst to the section of the cooler above the exchange tubes and thereby control the temperature of the catalyst above the heat exchange tubes. Heat exchange and tube wall temperatures are controlled by the addition of fluidizing gas.