Earl D Brennan

US Patent:

43098789, Jan 12, 1982

Filed:

Aug 22, 1980

Appl. No.:

6/180308

Inventors:

Earl D. Brennan - Monroeville PA

Assignee:

Koppers Company, Inc. - Pittsburgh PA

International Classification:

B01D 902

US Classification:

62542

Abstract:

An apparatus and process for purifying and separating a crystalline compound from its impurities in a slurry containing same, said process comprising introducing said slurry under pressure into a cylindrical pressurized filter-washer having a substantially constant inside diameter which is substantially free of protrusions, said filter-washer having a filter means with a screen contiguous with an internal surface of the cylinder, said screen having a smooth surface sufficient to provide minimum friction so as to allow a moving bed of crystals to move past it and withdraw a filtrate without blinding, filtering the crystals, withdrawing the filtrate, and moving the crystal bed past the filter screen, applying a controlled restraining force on the crystal bed so as to prevent relaxation and channeling and over-compacting of said bed by means of a compression and harvest means substantially contiguous with said inside diameter and located between said filter means and an exit means, said compression and harvest means comprising a rotatable plate with cutting edges for removing crystals from said bed and perforations for receiving crystals to be passed through said plate to a melting zone, rotating said plate to pass crystals through said perforations, melting the harvested crystals in said melting zone and withdrawing a portion of said melted crystals as purified product from said exit means located in said melting zone, passing the blance of said melted crystals in a countercurrent manner through the perforations in said compression and harvest means and through the moving crystal bed between said compression and harvest means and said filter means, thereby effecting purification by displacing the liquid medium and impurities from the interstices between the crystals.