In filters of the type in which a cake of solids deposited from a liquid slurry thereof on a generally horizontal filter medium is subjected to treatment involving passage of liquid through the cake while on the filter medium, means is provided for increasing the drainage rate of the formed cake by causing the cake to form on the medium from the slurry fed thereto by gravity settling in the liquor of the slurry and by removing liquor of the slurry from above the cake while the liquor still contains unsettled fine particles, such means including means providing a backflushing flow of liquid through the underside of the filter medium and the cake forming thereon into the slurry.
A process is provided for treating brine sludge to render it suitable for ecologically safe disposal by removing therefrom leachable mercury impurities. The process comprises dewatering the sludge and conveying the dewatered sludge through a series of water washings to remove therefrom leachable mercury to render it suitable for land fill disposal.
The present invention features a filtration plate for use in a filter pan comprising a corrugated sheet having a series of alternately upwardly and downwardly opening channels and a reinforcing material bonded to surfaces of the downwardly opening channels. The reinforcing material is effective for strengthening the sheet and retaining heat in a manner effective to slow cooling of the filtration plate during washing and to reduce heat losses from the filtration plate during filtering. According to a preferred aspect of the invention, the corrugated sheet is a monolithic sheet of structural metal having a smooth upper filtration surface. The invention also provides a filter pan configured for use in filtration of a filtrate from solid particles. The filter pan comprises a filtration plate including a corrugated, monolithic sheet of structural metal having a series of alternately upwardly and downwardly opening channels. The filtration plate has an upper filtration surface that is smooth and unbroken by welds or joints, and the upwardly opening channels thereof have a width effective for channeling liquid. The invention also provides a method for making a filtration plate for use in a filter pan, comprising the steps of stamping a sheet of a structural metal to form it into a corrugated sheet having a series of alternately upwardly and downwardly opening channels. The upwardly opening channels have a width effective for channeling a filtrate and the downwardly opening channels include a reinforcing material bonded thereto for strengthening the sheet. The reinforcing material is effective for retaining heat in a manner effective to slow cooling of the filtration plate during washing and for reducing heat losses from the filtration plate during filtering.
A process for the treatment of refinery oily sludges to produce an oily fraction that is reprocessed in the refinery into (i) salable products and (ii) a solid residue meeting environmental regulatory agency requirements for disposal in non-hazardous solid waste landfills. The process includes mixing the refinery oily sludge with a particulate filter aid and preferably a single solvent selected from refinery intermediate and product streams and contacting this mixture with plate filters in a closed filter vessel. A cake residue forms on the filter plates and a filtrate mixture of oil, water and solvent is produced. The filtrate is separated into an oily fraction and a water fraction. The oily fraction is rerouted to refinery operating units for processing into salable products. The water fraction is routed to a refinery water treatment system. When filter cake residue has built to a predetermined level, charge to the filter vessel is discontinued. The filter cake residue is washed with a predetermined quantity of solvent and then steam stripped to remove petroleum hydrocarbons to a desired residual level, e.g. less than about 1,000 ppm or less than 500 ppm. The steam stripped filter cake is then removed from the filter vessel for disposal in an environmentally approved landfill.
