A pneumatic rice polishing system has been developed to minimize broken content (BP) and maximize the degree of polishing (DP). This rice polisher consists of a metallic cyclone coated with hard abrasive material, a blower, a collection system.
Brown rice is feed vertically at the rate of 1.5 kg/min that flows towards the abrasive cyclone through horizontal air flow at 72.2 m/s. Experiments were carried out at different moisture content (M) and grit size of abrasive material (E) at fixed number of passes. Degree of polishing and broken content varied with both M and E. System showed DP from 4.224 ± 0.02% (13% M and 60 E) to 13.250 ± 0.56% (12% M and 36 E) whereas BP from 2.146 ± 0.14% (10% M and 60 E) to 49.717 ± 2.64% (13% M and 36 E). Effect of M and E and their square were found significant (p < 0.05 and p < 0.01) on DP and BP. Optimum values of DP and BP were achieved at 100 E and 11.70% M (wet basis) respectively with a value of 10.359% and 0.476%.
Tray type separator had more percentage of paddy (76.03%) and brown rice (99.89%) compared to compartment type paddy separator with 28.32% and 99.5% of percentage of paddy and brown rice, respectively. Furthermore, rice breakage of tray type separator (18.34%) was significantly less than that of compartment type (21.75%).