Hydrogen is an important commodity in various industrial fields such as ammonium
production, petroleum processing, chemical and petrochemical industries, metallurgical
processing, the electronics industry, town gas, and the aerospace industry. It is normally
manufactured by removing other components or recovering it from gaseous mixtures
generated in various chemical processes. The crude hydrogen-based gases produced
from hydrocarbons by steam reforming or partial oxidation contain various co-products,
by-products, and residual reactants such as carbon dioxide, water vapor, carbon
monoxide, and methane. Moisture and traces of oxygen exist in hydrogen generated by
water electrolysis. Unreacted or by-product hydrogen is obtained in its mixed or fairly
pure state in hydrocracking, hydrotreating, and brine electrolysis processes. Product
hydrogen with a specified purity is prepared from these hydrogen-rich gases through
separation and purification operations.