Two-stage riser catalytic cracking process

Abstract

This invention relates to a new two-stage riser catalytic cracking process, particularly to an improvement of the conventional riser reactor and reaction-regeneration system by application of a two-stage riser reactor to fulfill the aims of the concatenation of oil-vapor, catalyst in relays as result in shortening reaction time and increasing average performance of the catalyst.

What is claimed is:  
     
         1 . A catalytic cracking process, comprising the steps of: 
 (a) high temperature catalyst coming from a regenerator entering into the bottom of the first stage riser ( 6 ) to contact with the feedstock ( 15 ), which then is vaporized and begins to react;    (b) separating the partially coked catalyst, which is to be regenerated, from oil-vapor in an intermediate separator ( 4 );    (c) recycling the partially coked catalyst to a regenerator ( 2 ) to complete the first cycle after the catalyst is stripped in a striping section ( 5 ) in which the entrained oil-vapor is separate;    (d) oil-vapor from the intermediate separator ( 4 ) entering the second stage riser ( 7 ) to contact with the hot catalyst coming from an external heat absorber ( 3 );    (e) oil-vapor carrying the catalyst flowing upwards and performing catalytic cracking reactions continuously; and    (f) then, the mixture of oil-vapor and catalyst entering a settler ( 1 ) to separate, and the oil-vapor out of the settler ( 1 ) going into a fractionation system while the catalyst returns to the regenerator ( 2 ) after being stripped, which completes the second cycle of the catalyst.    
     
     
         2 . The catalytic cracking process according to  claim 1 , wherein oil-vapor coming from the first stage of riser ( 6 ) also can be separated through the intermediate separator ( 4 ) and the other separators into gasoline, diesel oil, liquefied petroleum gas and heavy oil; then one or several of them will enter the second stage of riser to perform reactions.