How PRISM® Membrane Dryers Work

Membrane dryers can be described as “molecular filters” where water travels across the membrane faster than other gas molecules.  The permeation of gases is driven by the difference in partial pressure across a thin polymeric separating layer supported on a spongy porous substrate which makes up the core of the membrane. Gases permeate across the separating layer at a rate that is proportional to the driving force and the permeation coefficient. As wet feed gas flows along the high-pressure side (or “feed” side) of a membrane dryer, water permeates across the membrane to the low-pressure side (or “permeate” side). The water vapor content of the feed gas becomes progressively lower as it flows along the length of the membrane dryer, leading to less driving force for permeation. Dry air is injected to aid in driving water permeation. This low-pressure purge gas can then exit the membrane, while the high-pressure, dry product gas continues through the membrane, and exits the bores of the hollow fibers at the end.