A vessel for contacting a plurality of objects with a fluid. An upwardly directed stream of fluid and a portion of the objects are confined in a conduit such that the fluid stream causes the objects to flow upward from a moving bed thereof to a disengaging position from where they fall onto a distribution shield and move downward to a feed position. The vessel may be used for treating electrically conductive objects wherein the fluid is an electrolyte, an electrode is positioned to contact the moving bed, and a counterelectrode is positioned in spaced relation to the moving bed. The vessel may be fixed or portable.