Deep catalytic cracking process

A method for converting a fluid catalytic cracking system to an improved deep catalytic cracking system comprising the steps of:

• (a) removing a middle section of an existing riser reactor in the fluid catalytic cracking system to produce a lower first narrower catalytic cracking riser reactor section that catalytically cracks a hydrocarbonaceous feedstock in the first carcking zone to produce an intermediate cracked product rich in gasoline, and that has a radius x, a means for feeding said hydrocarbon feedstock, a means for feeding cracking catalyst located in a lower portion thereof, and an upper riser product conduit having connection to a cracked product/spent catalyst separation means;
• and
• (b) replacing said removed middle riser reactor section with a second wider riser catalytic cracking reactor section that cracks said intermediate cracked product in a second cracking zone to produce high yields of C3 and C4 olefins, that has a radius y, wherein the ratio of y:x ranges from about 1.1:1 to about 5.0:1, and that operatively connects the bottom of said second wider catalytic cracking reactor section to the top of said first narrower catalytic cracking riser reactor section by a transition reactor section, and the top of said second wider catalytic cracking reactor section to the bottom of said upper riser product conduit.