ABSTRACT

This research work aimed at modelling and optimizing the performance parameters of the cracking process for a palm nut cracking machine. The drying temperature of 105°C; five levels of cracking speed (1200, 1400, 1600, 1800 and 2000 rpm); six levels of moisture content (12.4, 14.0, 16.2, 18.1, 20.0 and 27.8% w.b) and five levels of feed rate (360, 400, 450, 514.29, 600kg/h) were selected for the study. Full factorial design was used in the design of the experiment with three independent variables; cracking speed (rpm), moisture content (%) and feed rate (kg/hr), set at five, six, five level factorial respectively. One thousand three hundred and fifty (1350) samples of 1000 g each of fresh palm nuts were used for the experiment, 450 samples were dura, 450 samples tenera and 450 samples were mixed varieties. 150 samples were selected for each experimental run. Three (3) sets of runs were carried out for each variety at the same condition. The samples after drying to specified levels of moisture content, were cracked at 5 different speeds with 5 levels of feed rate. Mean values for each variety was computed and used for statistical analysis. Analysis of variance (ANOVA) and result of the pairwise comparisons for variables in the three varieties of palm nut revealed that the effects of cracking speed, moisture content and feed rate on the performance parameters are statistically significant at 0.05 level of significance. Comparative analysis shows that mixed variety have significant variation of the percentage whole kernel recovery of 48.04 to 97.06% and broken kernel of 1.14 to 47.38%, while tenera variety have significant variation of the cracking time of 0.0021 to 0.0083 h; throughput capacity of 99.23 to 476.19 kg/h; cracking efficiency of 78.30 to 100% and power requirement of 0.09 to 0.73 kW. For dura variety, the highest whole kernel recovery of 90.35% was obtained at the cracking speed of 1600 rpm, moisture content of 18.1% (w.b) and feed rate of 360 kg/h, all at 0.05 level of significance. Models to predict throughput capacity, whole kernel recovery, broken kernel, cracking efficiency and power requirement for dura, tenera and mixed varieties of palm nut cracking machine were developed using the concept of Buckingham Pi theorem. The developed models were verified and validated by fitting them into experimental data. The simulated and experimental results during the cracking process and the best combination for optimum variables for dura, tenera and mixed varieties were obtained. The developed model satisfactorily predicted the performance parameters of the cracking machine during the cracking process with < 5% relative error. This work will help to provide necessary information that will guide in the establishment of optimum condition for this palm nut cracking machine and solving the problem of sorting the nut into various varieties and sizes before cracking, which hitherto poses a greater challenge in palm nut cracking processes.