CRYOGENIC METHOD OPERATING AT NORMAL PRESSURE AND BELOW FOR ENRICHING THE OXYGEN CONTENT IN AIR

摘要

Oxygen and oxygen-enrichment are nowadays produced from air generally by three methods: cryogenic, adsorption and membrane separation. Various methods produce different purities and mass flows of oxygen. Again, the utilization of oxygen-enrichment, i.e. not pure oxygen, is often sufficient in many combustion applications. The process introduced in this paper is a novel cryogenic method producing oxygenenrichment more energy-efficiently than the methods used till now. The mass flow of the produced enrichment may vary with the number of parallel basic modules applied. Due to the low pressures used in the introduced process (at maximum approximately 1.3 bar abs., absolute pressure), the compression work needed is smaller than e.g. in the Linde-Fr?nkl process (the maximum pressure about 6.5 bar abs.), and the process approaches to reversible. Furthermore, the main fraction in mass flow of air, i.e. the nitrogen-enriched fraction, is not liquefied which saves energy compared to the common cryogenic processes that liquefy this fraction. Nevertheless, the achieved low temperature of the nitrogenenriched fraction is efficiently utilized in pre-cooling of the incoming process air. Since the process does not produce pure oxygen, the energy required to separate the last percents of oxygen from nitrogen-enriched fraction is saved. This is noticeable because of the last percents demand proportionately most separation energy.