An apparatus includes a vessel and a radial adsorption bed within the vessel and either an axial adsorption bed for a storage tank within the inner diameter of the radial adsorption bed. In one example, the radial adsorption bed surrounds an axial adsorption bed. A process that can be conducted in the vessel includes directing a gas mixture across the radial adsorption bed, thereby causing adsorption of at least a portion of a gas component present in the gas mixture and producing partially purified product. The partially purified gas is directed through the axial adsorption bed, thereby causing further purification of the partially purified gas and producing product gas. In another example, the radial adsorption bed surrounds a storage tank. The storage tank can be employed to store a gas generated or used in a separation process conducted in the radial adsorption bed. For instance, the storage tank can be employed to store product gas or void gas generated in a vacuum/pressure swing adsorption process.