Experimental investigation of the effect of rotor speed of a horizontal shaft centrifugal palm nut cracker on optimum whole kernel production and shell particle size

Abstract

The study was conducted to investigate the effect of rotor/cracking speed of a horizontal shaft centrifugal palm nuts cracker on kernel production and to determine the rotor speed that would give optimum whole kernel production in relation to smaller fragments of shell particle size. Samples of mixed varieties of palm nuts at 7.82% moisture content (wet basis) was obtained, the samples were subjected to cracking through a centrifugal nutcracker operating at a rated speed of 1450 rpm using a rotor with ten (10) exit channels of 50 × 50 mm which was available for the study. Fifteen (15) rotor speeds of 1600, 1680, 1760, 1891, 2068, 2175, 2250, 2450, 2650, 2800, 2962, 3150, 3300, 3450, and 3550 rpm were selected. Data obtained on the quantity of uncracked nuts, whole kernels, broken kernels and particle size analysis of shells, were used in the computation of the palm nut cracking characteristics and ANOVA was used at 0.05 significant level to check the effect of rotor/cracking speed on whole kernel production and shell particle size. Results showed that increase in rotor speed result in increase in percentage of whole kernel production and decrease in size of shell particles, but a decrease in whole kernel production which led to intolerable increase in broken kernels at a certain speed of the rotor (2962 rpm). The optimum cracking/rotor speeds for palm nuts that gave high percentage production of whole kernels of 90% and above, low percentage of broken kernels of less than 10% and reduced particle size of shells of 6.34 to 8.31 mm compared to that of the kernels of 10.97–12.33 mm is in the range of 2650–3150 rpm. However, results of this study are viable parameters for the development of a mechanical palm kernel/shell separator. Keywords: Rotor speed, Horizontal shaft, Centrifugal nut cracker, Palm nut, Whole kernel production, Shell particle size, Geometric mean diameter