Fluid particle backmixed cooling process

A process for the controlled cooling of hot fluidized catalysts which comprises:

• (a) passing spent catalyst having coke deposited thereon, and oxygen-containing regeneration gas to the lowermost portion of a catalytic combustion chamber containing a relatively dense bed of fluidized catalyst to oxidize said coke;
• (b) passing said oxidized catalyst upward through said combustion chamber to an uppermost section of said combustion chamber containing catalyst in a relatively dilute phase;
• (c) passing said oxidized catalyst through said uppermost section of said combustion chamber to a surmounted disengagement chamber having a relatively dense phase of catalyst collecting in the lowermost portion of said disengagement chamber;
• (d) passing said catalyst from said lowermost portion of said disengagement chamber to a heat removal zone extrinsic from said combustion and disengagement chamber;
• (e) cooling said catalyst in said extrinsic heat removal zone by indirect heat exchange against a cooling fluid entered and removed from said extrinsic heat removal zone;
• (f) fluidizing said catalyst in said heat removal zone by passage of a fluidizing gas in direct contact with said catalyst being cooled and wherein said catalyst is continuously mixed;
• (g) passing said cooled catalyst back to said lowermost portion of said disengagement chamber, wherein the extent of fluidization in step (f) is controlled by
• (i) sensing the quantity of said cooling fluid being removed from said indirect heat exchange means in step (e);
• (ii) comparing that sensed quantity with a predetermined set point to generate a controller output signal;
• and,
• (iii) transmitting said controller output signal to a flow regulation means which regulates the quantity of fluidized gas passed in step (f) to said extrinsic heat removal zone.