The role of turbulence promoters in hyperfiltration plant optimization

Abstract

Numerical calculations were performed to obtain process parameters for hyperfiltration with membranes having characteristics similar to cellulose acetate. The concentration polarization and friction loss equations used in the calculation were modified to include provision for a wide range of turbulence promoter characteristics. The characteristics of the turbulence promoters were based on potential performance curves derived from an extensive literature survey. The presence of turbulence promoters causes marked reduction of optimum entrance velocity and tube length. As a result, the channel pressure drop for tubes with turbulence promoters is always less under optimum conditions than the value for tubes with no promoters provided the friction factor with promoters is less than 100 times the value with no promoters. While none of these affect costs greatly, there is direct cost advantage for turbulence promoters which minimize fouling, thereby giving higher average fluxes for longer periods of time. Only where the membrane is strained to produce water of required quality is there a direct effect of turbulence promoters on product water cost because of this beneficial effect on concentration polarization.