Process for minimizing afterburn in a FCC regenerator

Abstract

The invention relates to a process and apparatus for controlling afterburning in the regenerator of a FCC unit. The process and apparatus inject steam into the dilute phase within a regenerator to promote combustion of carbon monoxide before it enters the regenerator cyclones, plenum, or flue gas transfer lines.

What is claimed is:  
     
         1 . A process for regenerating spent catalyst from the reaction zone of a fluidized catalytic cracking reactor comprising the steps of: 
 (a) passing spent catalyst from the reaction zone of a fluid catalytic cracking reactor to a regenerator, said regenerator having therein a fluidized catalyst bed and a dilute phase zone above said catalyst bed, said dilute phase zone comprising the gases carbon monoxide and oxygen;    (b) contacting the spent catalyst with a gas comprising oxygen to produce a regenerated catalyst;    (c) passing said regenerated catalyst to the reaction zone; and,    (d) injecting an effective amount of steam to mix the gases present in the dilute phase zone so that a substantial portion of the carbon monoxide present in the dilute phase zone combusts.    
     
     
         2 . The process according to  claim 1  wherein said secondary gas is radially injected into said dilute phase.  
     
     
         3 . The process according to  claim 1  wherein said secondary gas is tangentially injected into said dilute phase.  
     
     
         4 . The process according to  claim 1  wherein an oxygen-containing gas is also injected into said dilute phase along with said steam.  
     
     
         5 . The process according to  claim 1  wherein said steam is injected into said first zone, said second zone, or both.  
     
     
         6 . The process according to  claim 1  wherein said steam is injected into said dilute phase at a position at least about 3 feet above an upper level of said catalyst bed.  
     
     
         7 . The process according to  claim 1  wherein said steam is injected into said dilute phase at a position between about 3 and about 9 feet above the upper level of said catalyst bed.  
     
     
         8 . The process according to  claim 1  wherein at least about 50 mole % of the carbon monoxide combusts before passing through the inlet to the solid-gas separator.  
     
     
         9 . The process according to  claim 1  wherein at least about 90 mole % of the carbon monoxide combusts before passing through the inlet to the solid-gas separator.