Feed injection system for catalytic cracking process

Abstract

A catalytic cracker riser reactor is connected to a regenerator standpipe through which hot, regenerated catalyst enters the riser bottom region. A hydrocarbon feed, such as gas oil, and dispersing gases, such as steam, are introduced through a single bottom entry nozzle assembly. The nozzle assembly comprises three concentrically arranged conduits. An inner conduit provides a passageway for a first dispersing gas and terminates in a first cap having at least one outlet passage for discharging the first dispersing gas in a generally radially outward and upward direction. The first conduit and first cap are enclosed by a second conduit and second cap, the annulus formed thereby providing a passageway for a liquid hydrocarbon feed. The second cap also has at least one outlet passage for discharging the mixture of hydrocarbon feed and first dispersing gas into the riser reactor in a radially outward and upward direction. A first dispersing gas enters the inner conduit and proceeds to the first cap into a mixing zone located in the vicinity of the discharge passage between the first and second caps. Hydrocarbon feed enters the second conduit, continues through an annulus to the second cap and is mixed with the first dispersing gas in the mixing zone, resulting in the formation of a fine two-phase mixture of small dispersed bubbles in heavy petroleum hydrocarbon liquid. As the fine two-phase mixture passes through the outlet passage into the riser reactor to contact with regenerator catalyst, the two-phase mixture suddenly expands, forming a fine atomization of heavy petroleum hydrocarbon feed with narrow droplet size evenly distributed across the riser reactor.