Performance Evaluation of Chinese Mini Combine Rice Mill cum Grind Machine
Authors: Shailendra Khatri
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Rice is the most important food grain crop in Nepal along with maize and wheat. Post harvest handling is one of the important processes after harvesting rice. Milling and grinding are main post harvest operations for using rice as food. Traditional milling and grinding practices such as water mill (PaaniGhatta), and mortar and pestle(Jhantos, Okhal and Dhikis) are very slow, tedious, drudgerious, labour- intensive and time-consuming and low output practices. Therefore, there is a need of a low cost rice milling machine having multiple function (milling and grinding).Hence, a study was conducted to evaluate the performance of Chinese mini combine rice mill cum flour grind machine powered by a 3HP electric motor. Combine mill performance was evaluated in terms of percentage of broken rice, milling efficiency, head rice recovery, machine efficiency, machine capacity, unmilled grain, milling losses, grinding efficiency and grinding rate at moisture content of 13.5 %. Based on this study, result showed that the combine mill has a milling capacity of 87kg/hr rough rice or paddy at 13.4% moisture content. Similarly, it has a grain grinding capacity of 119.87 kg/hr. The milling efficiency or recovery of 69.63% was obtained for Khumal-4 paddy variety.The head rice recovery based on total milled rice, unmilled grain percentages, broken grain and grain in husk from the combine mill were 82.47%, 2.29%,15.24%, and 2.11%, respectively. Additionally, a grinding efficiency of 88.82% was achieved from the grinding compartment of combine mill.
Considering economic perspectives, the combine mill becomes profitable only after 393.5 h of annual machine use which is equivalent to 236.14 quintal of rice output at a machine output capacity of 59.67 kg/hr with respect to investment cost of NRs 40,000 andmilling charge at NRs 2 per kg. The benefit cost ratio (B/C ratio) was found out to be 1.18. The internal rate of return (IRR) turned out to be 46.2 percent. The Payback period (PBP) was calculated to be 1.85 years. As B/C ratio is greater than 1, IRR is greater than the rate of interest (15 percent) and PBP is of less duration, the investment in mini combine mill is economicallyviable. Overall, finding of this evaluation study can be used to compare any other rice mill in future. It can be concluded that combine mill has possibility of becoming a one of the suitable milling and grinding technology for hilly and mountainous areas of Nepal.