Flexibility in Gas Separation

The flexibility (also called easy of expansion) is the ability to operate under variable feed quality conditions, either on a short-term or long-term basis (Miller and Stöcker 1989; Brunetti et al. 2010). The changes in feed composition occur very often in refinery applications, particularly when the source of the feed is a catalytic process or when the feedstock to the upstream unit changes as well as in flue gas streams.

In membrane processes, the increase in feed impurity concentrations tend to cause a decrease in product purity, which, however, can be maintained for small feed composition changes by adjusting the feed-to-permeate pressure ratio. In most refinery membrane applications, however, the major product impurity is methane and this can be allowed to increase slightly in the product without major downstream impact. The flue gas stream contains an amount of CO₂ranging from 5 % to 35 % depending on the process, the rest being mainly nitrogen and few percentage of oxygen....