Abstract: A filtration system suitable for recovering base stock from used lubricating oil and other applications passes feedstock over nano-filtration membranes in a serpentine flow. Pressure boosters installed in the openings separating consecutive stacks serve to restore lost pressure of the feedstock. As pretreatment a “knocking” non-blinding filter separates particulates from a feedstock by a knocking action that dislodges particulate matter which has come to rest on the screen. Further pretreatment includes a vacuum evaporator for flash evaporation of volatile components from a liquid and effecting the extraction of water and glycol from used engine lubricating oil. The liquid is heated or cooled when flowing over some of the surfaces to adjust for heat lost or acquired during exposure of the liquid surface to a gas or vacuum. Liquid moves on the surface of the discs under centrifugal force or a wiper blade guides the liquid as it moves over the support surface.

Abstract: A filtration system suitable for recovering base stock from used lubricating oil and other applications pass feedstock over nano-filtration membranes assembled as a stack of membranes all experiencing parallel flow. On exiting a first stack of membranes the feedstock passes through an opening in a pressure-sustaining separator plate to flow in the reverse direction past a second stack of membranes and subsequently establish a serpentine flow of feedstock through multiple stacks of membranes. The stacks of membranes all share a common pressure containment vessel. Pressure boosters installed in the flow-through openings of separator plates separating consecutive stacks can serve to restore lost pressure of the feedstock and maintain effective permeation of permeate through the membranes. A pressure control valve at the outlet to the permeate-receiving cavities of a stack can be used to adjust the trans-membrane pressure.