Modification and evaluation of a groundnut cracker for cracking Jatropha Curcas seeds

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Jatropha curcas L. is a multipurpose drought-resistant plant with numerous attributes and considerable potentials. The most valuable aspect of the plant is the oil content of its seed kernel. In the extraction of the oil, the seeds are either cracked to obtain the kernels or used without cracking. Using uncracked nuts produce oil at low recovery and quality, whiles cracking manually involves so much labour and time. The objective of the study was to modify an existing motorised Groundnut Cracker with a winnower for cracking Jatropha curcas seeds and to evaluate its performance. The physical dimensions of seeds and kernels were determined for the design of the sieve of the cracker. The cracker was evaluated using 3 kg seed samples at cracking drum speeds of 140, 150, 160, 170 and 180 rpm and feed gate openings of 32, 48 and 64 mm. Chemical extraction of Jatropha curcas oil for kernel samples with 0 %, 20 %, 40 %, and 100 % husk contents was done. A sieve with hole diameter 10 mm was selected and designed for the cracker. At 140 rpm and 48 mm feed gate opening, the cracker had a capacity of 1037.90 kg/h, blower loss of 2.76 %, cleanliness of 88.65 %, uncracked seeds of 3.32 %, kernel recovery of 48.57 %, cracking efficiency of 96.68 % and machine efficiency of 90.84 %. Chemical oil extraction gave the lowest oil yield from the sample with 100 % husk at 66.7 % of oil extraction and highest oil yield from the sample with 0 % husk content at 93.5 % of oil extraction, an increase of 40.1 % in oil yield due to seed cracking.
A thesis submitted to the Department of Agricultural Engineering, Kwame Nkrumah University of Science and Technology in partial fulfilment of requirements for the degree of Master of Science in Agricultural Machinery Engineering, 2012