There are growing needs to produce relatively high purity(99.0% or higher) oxygen at low cost. For small scale production, both pressure swing adsorption(PSA) and membrane process are competitive and less expensive or more convenient than well known cryogenic fractionation technology. A continuous membrane column(CMC) combined with a PSA oxygen generator can be employed to produce high purity oxygen continuously. The oxygen enriched gas generated by a PSA unit, with a concentration of 93~94%, is fed to the CMC that consism of three modules of poly(imide) hollow fibers. Several experiments were conducted by varying parameters, such as feed flow rate, transmembrane pressure drop, stage cut, and feed location in order to obtain a high oxygen concentration above 99.0%. A two-series unit mode was also employed with CMC operation to optimize the given membrane area.

Membrane technology has gained tremendous acceptance by industry in recent years. A long dormant period of laboratory research in academia and industry has evolved into a new era of commercial growth. The total sale of membranes is still modest compared to the major technologies, yet it is one of the fastest growing industries. This can be best illustrated by inspecting the market place. In 1990, the total sales of worldwide membranes was estimated to be approximately 1.6 billion with an annual increase rate of 15%. This means that the estimated total sales of membrane based industry is nearly 5 billion annually. Equally important evidence is an increase in research activities, as demonstrated by the explosion of publications and proliferation of membrane meetings. A number of research centers have sprung up around the world in addition to newly emerging membrane companies and membrane research groups eventually translated into some form of publication. As an example of the rapid growth in membrane research, the number of papers submitted to the Journal of Membrane Science alone was almost 2000 and the number of papers accepted was over 1300 in 1990.The worldwide membrane research expenditure in 1990 was estimated to be around 127 million consisting of 76 million(60%) by industry and 51 million by governments, which can be broken down to 11 million in the U.SA., 20 million in Japan, and 20 million in Europe.