Technique to measure surface-fouling tendencies of steepwater from corn wet milling

Surface-fouling tendencies of raw light steepwater (LSW) and membrane-filtered light steepwater (FSW) from corn wet-milling were studied using an annular fouling probe. The probe contained a heated surface to simulate the surface temperature of an evaporator. The heated region caused a fraction of solids in the steepwater to adhere to the surface, thus fouling the probe over time. FSW samples were prepared by filtering LSW using a microfiltration membrane with a nominal pore size of 0.1 mum. Fouling tendencies of both samples were established at an initial probe wall temperature of 99degreesC. Batches (30 L) were circulated through the fouling probe until the inner surface temperature of the probe reached 200degreesC. Temperature and power supplied to the probe were measured over time and used to calculate fouling resistance and rate of fouling. Measurement of maximum fouling resistance and fouling rate had a coefficient of variation (COV) of 5.1 and 7.4%, respectively. Maximum fouling resistances attained over a 12-hr period were 0.36 and 0.049 m(2) degreesC/kW for LSW and FSW, respectively. Average rates of fouling were 4.53 x 10(-4) and 0.82 x 10(-4) m(2) degreesC/kW/min for LSW and FSW, respectively, showing an 80% decrease in fouling rate using microfiltration to, remove 19% of solids.