Abstract: An improved vessel design is provided for contact of gas or vapour with particulate solid material, for example for adsorption systems such as air drying and solvent recovery systems, in which a plurality of trays for containing the particulate material are supported by a pillar structure within the shell of the vessel, the shell serving merely as an envelope which does not provide support for the trays thereby enabling a considerable reduction in material costs for the shell and greater design flexibility for the site where the vessel is to be installed. The pillar preferably forms a manifold for conveying gas or vapour streams to or from each of the trays and deflecting baffles for the gas or vapour streams are also provided. A sparge pipe may also extend along the duct to introduce steam or other purge gas for regeneration of an adsorbent in situ.