Removing 99.99998% of oil aerosols from compressed air and other gases

Abstract

AbstractThe oil and water particulates in compressed air and other gases are present as sprays, mists, fogs, smoke, fumes and vapors. The best method found to date for removing the oil and water contaminants from compressed air is a combination of direct impaction, inertial compaction, diffusion (Brownian motion) and coalescence, the latter being the main method of removing them. Baffles, centrifugal flow and flow directional changes of the air stream are helpful in causing coalescence and impingement. Flowing the air through porous media also is effective. The best way to coalesce liquid particulates from compressed air is to control the air flow and velocity as it passes through a fibrous bed that has predetermined porosity and which has minute strands and permanent electrostatic charges. An element designed with a prefilter with tiny pores in a cloth‐like layer such as silicon‐treated borosilicate enhances coalescing of the liquids. The air passageway between the random microfibers of inert strands located in the next layer through which air travels, and at right angles to the air stream, is very small. he strands must also be very fine (0.5 μ mean diameter). Because of the smaller open area and the smaller diameter of the fibers, this material is more effective as a coalescer of liquid droplets from 5 μ in size down to 0.01 μ in size. This structure also removes small solid particulates by diffusion (Brownian motion) and direct or inertial impaction. As long as air is flowing this design results in an almost continuous film of liquid on the outer layer. Ordinarily excessive air velocities in an element of this kind will cause subdivision of coalesced droplets. An outer cover of a material like a soft plastic, porous foam traps the coalesced film of liquid something like a sponge sleeve would “soak” liquids off a wetted outer cylinder wall. By gravity the liquids migrate down within the foam cover, dropping off the bottom of it and into the sump, out of the gas system.