Abstract: A catalytic reaction chamber for contacting a reactant stream with catalyst particles which are disposed as an annular-form bed and are downwardly movable therethrough via gravity-flow. The annular bed is spaced between a catalyst-retaining screen and a perforated centerpipe. A plurality of vertically-positioned catalyst-transfer, or withdrawal, conduits are circumferentially-disposed substantially adjacent the outer surface of the centerpipe and extend the entire length of the catalyst bed. These contain a first plurality of apertures which face into the bed of catalyst particles and which are sized to permit catalyst particles to flow therethrough. A second plurality of apertures is disposed substantially 180.degree. opposite the first plurality of apertures, and sized to inhibit the flow of catalyst particles therethrough.

Abstract: A catalytic reaction chamber for contacting a reactant stream with catalyst particles which are disposed as an annular-form bed and are downwardly movable therethrough via gravity-flow. The annular bed is formed between a catalyst-retaining screen and a perforated center-pipe. A plurality of vertically-positioned catalyst-transfer, or withdrawal, conduits are circumferentially-disposed substantially adjacent the outer surface of the centerpipe and extend the entire length of the catalyst bed. These contain a plurality of apertures which face into the bed of catalyst particles and which are sized to permit catalyst particles to flow therethrough. The use of these perforated catalyst-transfer conduits serves to alleviate the problems associated with the occurrence of stagnant catalyst areas which result from catalyst particles being "pinned" against the perforated centerpipe within the reaction zone, and unable to assume a downward flow pattern.