Process and apparatus for separating valuable or harmful liquids from slurries

A filtration process for recovering Process Liquid that is at least partially miscible with water from a feed slurry that predominantly comprises a mixture of the Process Liquid and solid particles, the process including the steps of:

• (a) introducing the feed slurry into a reservoir above a substantially horizontal Filter Medium therein and wherein the Filter Medium allows liquids to flow through it while blocking the passage of more than 50 wt % of the solid particles in the feed slurry through the Filter Medium, and;
• (b) introducing into the reservoir above the Filter Medium a Sweep Liquid that is less dense than and not miscible with water, and less dense than and non-miscible with the Process Liquid to create a lower layer of liquid that is in contact with the upstream surface of the Filter Medium and predominantly comprises Process Liquid and an upper layer of liquid that predominantly comprises Sweep Liquid and an interface between the two liquid layers, and;
• (c) applying a pressure differential across the Filter Medium, wherein said pressure differential causes liquid to flow through the Filter Medium as filtrate, and;
• (d) preventing an excessive accumulation of solid particles on the upstream surface of the Filter Medium by agitating at least a portion of the slurry that is in close proximity to the Filter Medium and;
• (e) allowing the flow of liquid through the Filter Medium in step (c) and the prevention of excessive accumulation of solid particles onto the surface of the Filter Medium in step (d) to continue until at least a portion of the Process Liquid has been displaced out of the slurry through the Filter Medium thereby forming a depleted slurry above the Filter Medium that comprises solid particles and Sweep Liquid and is depleted of Process Liquid, and;
• (f) recovering at least a portion of the filtrate from the reservoir.