a fluidized solid process for upgrading or converting a hydrocarbon feedstock wherein carbonaceous deposits accumulate on a particulate fluidized solid and are burned in a regenerator to regenerate the solid , the regenerated solid and entrained combustion products are introduced into a vertical lift pipe , a fluid lift medium is introduced into the lift pipe and the regenerated solid is separated from the lift medium and combustion products to improve the quality of the regenerated solid contacted with the hydrocarbon feedstock .