Fluidized bed regeneration of carbon-contaminated catalysts using gas discharge nozzles of specific dimensions

摘要

In fluidized bed regeneration of carbon-contaminated catalysts, such as cracking catalysts, wherein at least a portion of the oxygen- containing gas required for fluidization and burn-off of carbon deposits is introduced as a separate stream into the dense phase of the fluidized catalyst, contained in the regeneration chamber, by means of a plurality of gas discharge nozzles, affixed to at least one manifold member substantially horizontally disposed at the lower end of the regeneration chamber, catalyst attrition is reduced and backflow of catalyst particles into the nozzles is minimized by utilizing gas discharges which are restricted in internal cross-sectional area in their upstream portion connected to the manifold member and expanded in the internal cross- sectional area of their downstream portion such that (a) the numerical ratio of the difference between diameter of the downstream portion and the diameter of the upstream portion divided by the length of the downstream portion taken in the direction of gas flow does not exceed 0. 18 and (b) the ratio of the diameter of the upstream portion to its length taken in direction of gas flow does not exceed 1.67.