Redesign of tubular inlet geometry to reduce fiber accumulation in UF modules.

Abstract

One of the processes used in the pulp and paper industry is the ultrafiltration (UF) of fiber suspensions using tubular membrane modules to control effluent composition and recover chemical products. Effluent treatment by UF includes bleach effluent treatment, deresining of the pulp wash water, whitewater processing for fiber recovery, and de-inking of effluent. However the behavior of the suspension in the entrance region of a tubular membrane is typically problematic. Modules having tubes with an inside diameter less than one inch are subject to blockage of the inlet tubes due to the accumulation of dewatered fiber within the module header. This study deals with the influence of the inlet geometry on the concentration build-up within a model tubular module. Hence a module was designed to achieve this purpose. The module cell consisted of a header and five impermeable tubes (of equal diameter less than one inch). The inlet geometry of the tubes was varied by changing the inlet angle of a disk lying on top of the tubes. In addition to the influence of the inlet geometry on the concentration build-up in the distribution header, the influence of the inlet flowrate and pumping time was studied. In addition to the transient flow experiments described above, several additional qualitative and quantitative factors were measured. (Abstract shortened by UMI.)