JPH07119425B

On-stream catalyst replacement apparatus for countercurrent upstream flow of a gas and hydrocarbon liquid through a downward moving catalyst bed in a reactor vessel. A mixed feed stream of gas and liquid hydrocarbon components enters a reservoir formed between the lower end of the reactor and a conical screen supporting the lower end of a catalyst bed. A wall across the vessel divides the reservoir into a lower surge chamber for receiving the mixed feed and an upper plenum chamber for separating the components into alternate feed rings of gas and hydrocarbon liquid under the conical screen. The mixed feed enters the plenum chamber through a plurality of tubes extending downwardly from the wall to the same depth in the surge chamber that prevents establishing preferential paths for gas to independently enter the plenum chamber. Excessive separation of the gas and liquid components from the mixed feed in the plenum chamber is prevented by use of a plurality of concentric baffles abutting the underside of the conical screen and which are closely spaced apart only sufficient to create adjacent and alternate feed rings of gas and liquid. The depth of the lower end of each baffle is intermediate the depth of the two radially adjacent concentric baffles. Catalyst is continuously or periodically added to, or removed from, the vessel through tubing and a full-bore valve having uniform diameters throughout their lengths to maintain laminar flow of catalyst to or from a pressurizable hopper vessel.