Method for withdrawing a particulate solid from a packed, fluidized bed

A method is disclosed for withdrawing particulate spent catalyst particles from a packed, non-fluidized bed of such particles in contact with a liquid medium within a vessel having a withdrawal conduit or pipe which has an inlet that opens within the bottom of the bed and faces generally downwardly so that a first section extends upwardly from the inlet, and a second section extends downwardly, and the spent catalyst particles exits the packed bed through a uniform and continuous flow path opening into a solids recovery vessel whose pressure is controlled to regulate flow of such spent catalyst from the reaction vessel independent of the rate of flow through the withdrawal conduit.