Oxygen Production via Air Separation
Industrial methods for producing oxygen via air separation primarily include cryogenic distillation, pressure swing adsorption (PSA), and membrane separation.
The cryogenic distillation method begins by purifying the air (removing moisture, CO2, hydrocarbons such as acetylene, dust, etc.). The purified air is then compressed, cooled, and liquefied. Subsequently, leveraging the differing boiling points of oxygen, argon, and nitrogen components within the air (at standard atmospheric pressure: O2 boils at 90.17 K, Ar at 87.29 K, and N2 at 77.35 K), the separation of oxygen, nitrogen, and argon is carried out within a distillation column. Through cryogenic distillation, one can obtain oxygen with a purity of 99.5%, nitrogen with a purity exceeding 99.99%, and argon with a purity exceeding 95%.
The pressure swing adsorption (PSA) method utilizes the differing adsorption characteristics of oxygen and nitrogen on molecular sieve adsorbents to separate these components at ambient temperature, under either low or atmospheric pressure.
Water Electrolysis Method
Under specific conditions, the water electrolysis method employs electrode materials to electrolyze an alkaline solution (such as a 20%–30% KOH solution), thereby yielding hydrogen with a purity of 99.9% and oxygen with a purity ranging from 99.3% to 99.8%. Water electrolysis units are typically configured in one of three structural forms: box-type, atmospheric-pressure filter-press type, or pressurized filter-press type. The process generates 1 m³ of H2 and 0.5 m³ of O2; however, water electrolysis is characterized by relatively high energy consumption.
