Improved Filtration Analysis Applied to Filter Press Separations

Improved Filtration Analysis Applied to Filter Press Separations

Raymond Collins, Engineering and Process Sciences, The Dow Chemical Co., Midland, MI

A non-traditional model describing the separation of solid particles from a liquid suspension by pressure-driven flow through a permeable barrier has been successfully applied to the design of several filter press applications.  This flow model was derived by applying fundamental physical principles to the unsteady, mixed-phase system represented by cake filtration with a filter cloth.  The analysis has proven suitable for operating modes employing both constant applied pressure and constant feed flow rate.  The design procedure uses small-scale experiments to determine a governing permeability function with a reproducible dependence on the collected volume of filtrate that is characteristic of the properties of the solids, liquid and filter cloth.  The experimental method and various lab-scale test filters will be described, and the utility of this method will be demonstrated for a few common, large-scale applications in chemical processing.   These include the removal of polymer fines and metal hydroxides from wastewater, the deliquoring of biomass from a concentrated sediment of fermentation broth, and the isolation and washing of micron-sized solids used to manufacture energy materials.