Various processes based on phase change, absorption, adsorption, permeation through
membranes, and chemical reactions are available for separation, recovery and
purification of hydrogen. Some of these processes are employed in practical operations
according to operating conditions, specifications, and end uses for removed and
recovered components. The prime technology is the pressure swing adsorption
processes, which have several advantages over the other methods. Technical progress
for improvement of hydrogen recovery and energy consumption can be made mainly by