Dextrose filtration using microfiltration membranes

The technical and economic feasibility of microfiltration for clarification of dextrose syrups were studied using a tubular ceramic membrane made of cc-alumina with a pore size of 0.2 mu m. Clarified syrup (permeate) had low color and no suspended solids at all concentration factors up to 100. Fouling of the membranes was a function of operating parameters. High pressures increased the rate of initial fouling. Flux increased with increased crossflow velocity for all transmembrane pressures and feed concentrations of dextrose syrup. An asymptotic flux was reached at a pressure of about 207 kPa, indicating that microfiltration performance was limited by concentration polarization. A microfiltration membrane plant was designed for clarification of 500 gallons per minute (113.6 m(3)/hour) of dextrose syrup based on the process data and various capital and operating costs. The optimum membrane plant would have two feed-and-bleed stages with a total area of 883.2 m(2), both stages having equal area. Operating costs of the membrane plant is $517,408/year. In contrast, operating costs for rotary vacuum precoat filtration, which uses diatomaceous earth as a filter aid, would be $1.8 million per year.