Process Dryers

Common impurities that can be removed from a gas stream include water, carbon dioxide, carbon monoxide, mercaptan, ammonia, methyl alcohol, ethyl alcohol, hydrogen sulphide, oxygenates, acetylenes, nitrous oxide, nitrogen dioxide, propyne and butyne. Some of these can be removed with the same adsorbent used for dehydration. For some, a separate adsorbent that can be regenerated, is filled in the same bed. Some of the impurities cannot be removed by regenerable adsorbents. Here a separate bed with "sacrificial" adsorbent is used (Guard Bed) and operated upto complete equilibrium.
With a two bed system, the entire wet gas flows through the adsorption bed. Simultaneously, the bed in regeneration is being reactivated by flowing hot gases from various sources for a specific period of time. This is followed by a cooling phase. Depending on the flow rate, multiple beds are also used to keep adsorber size within manufacturing limits. The flow for adsorption is divided in two or more beds and one bed is regenerated. A single bed is taken into adsorption after regeneration and the time for adsorption per bed is determined by the regeneration time and the total number of installed beds.