Abstract: Method and apparatus for separating gases, especially for removing water or from a gas such as air. This invention uses a short-cycle process which produces reduction in dewpoint (for dehydrating gas separation processes) or change in gas concentration (for non-dehydrating gas separation processes) at high pressure, and which includes adding a short burst of heat during the beginning of the reactivation cycle to boost desorption and complete it typically in about thirty minutes or less time. An easily desorbed desiccant (or other adsorbent material for non-dehydrating applications) and the short low-temperature burst of heat serve to reactivate a significant portion of the desiccant bed (or adsorbent bed), and the cooler purge fluid that follows cools that portion of the bed in preparation for the next drying (or adsorbing) cycle.