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
research and development of separation media such as absorbents, adsorbents, polymer
membranes and hydrogen storage alloys to achieve superior performances in selectivity,
rate-capability, capacity, and durability.
Addition of hydrogen to natural gas is a possible way to enlarge the use of hydrogen
into energy fields. For this purpose, a beneficial effect in terms of improving
combustion properties and reducing polluting emissions can be obtained for burner
combustion of town gas and lean-burn operation of internal combustion engines.