Process for fluidized-bed catalyst regeneration

A process for the continuous regeneration of catalyst particles by combustion in a fluidized bed of the coke deposited on the catalyst particles in the course of a hydrocarbon-conversion reaction, comprising burning in a first regeneration stage a proportion of about 50 to 90 percent of the coke remaining on stripped catalyst particles received from a hydrocarbon-conversion zone, at a temperature T.sub.1 which does not exceed about 730.degree. C., in a first regeneration zone operated with a dense fluidized bed;

• the catalyst particles to be regenerated being introduced to said first zone essentially countercurrently to an oxygen-containing fluid;
• said first regeneration zone having its own discharge outlet for gaseous effluents containing steam entrained or generated during such combustion, and a CO/CO.sub.2 ratio ranging from 0.3 to 1.5;
• burning the 10 to 50 percent of residual coke from the catalyst particles in a second regeneration stage, in the presence of a fluid containing an excess of oxygen in relation to the stoichiometry of the combustion, at a temperature T.sub.2 greater than T.sub.1 and less than 950.degree. C., in a second regeneration zone distinct from the first one;
• maintaining the temperature T.sub.2 of the regenerated catalyst particles coming from the second regeneration zone and recycled to the conversion-reaction zone at a value predetermined on the basis of the requirements of the conversion-reaction zone by withdrawing a controlled quantity of catalyst from the second zone and cooling it to a temperature level T.sub.3 lower than T.sub.1 ;
• reintroducing the fraction of catalyst so cooled into the fluidized bed of the first regeneration zone;
• increasing the flow rate of the oxidizing fluid supplying the first regeneration zone between 1 and 50 percent of the normal flow rate of that fluid in the absence of the introduction of the cooled catalyst;
• and maintaining the temperature of combustion in the first regeneration zone at substantially the value of T.sub.1 through appropriate adjustment of the quantity of oxygen-containing fluid introduced into that chamber.