Regenerative adsorption gas dryer

A regenerative adsorption gas dryer having a wet gas inlet and a first drying tower and a second drying tower and a dried gas outlet in which the wet gas inlet and the first and second drying towers and the dried gas outlet are arranged such that a flow of purge gas regenerates an off-stream in one of said first and second drying towers and in which a stream of wet gas from the wet gas inlet enters an on-stream in one of the first and second drying towers so as to exit the tower as a stream of dried gas so as to continue to the dried gas outlet, the towers for the off-stream and the on-stream being reversible, the regenerative adsorption gas dryer further comprising:

• a first check valve suitable for controlling the stream of dried gas between the first drying tower and the dried gas outlet;
• a second check valve suitable for controlling the stream of dried gas between the second drying tower and the dried gas outlet, said first and second check valves being arranged such that a pressure of the stream of dried gas exiting the tower with the on-stream opens the check valve of the tower so as to allow the stream of dried gas to continue to the dried gas outlet and such that a pressure of the stream of dried gas from the tower with the on-stream closes the check valve of the tower with the off-stream;
• a first bypass to the said first check valve;
• and a second bypass to said second check valve, each of said first and second bypasses allowing a restricted flow of gas to be extracted from the stream of dried gas from the tower having the on-stream so as to form the flow of purge gas for the tower having the off-stream, each of the first and second drying towers having a replaceable desiccant cartridge, said desiccant cartridge suitable for drying the stream of wet gas into the towers, said first and second check valves and said first and second bypasses being respectively incorporated into the desiccant cartridge and are replaceable therewith.