Influence of physical properties of Jatropha curcas L. seeds on shellingperformance using a modified disc mill

Publication Type

Journal contribution (peer reviewed)

Authors

Romuli, S; Karaj, S; Müller, J

Year of publication

2015

Published in

Industrial Crops and Products

Editor

Elsevier

Band/Volume

77/

DOI

10.1016/j.indcrop.2015.10.014

Page (from - to)

1053-1062

Keywords

Jatropha, Non-removable shells, Physic nut, Seed geometry, Specific energy, Terminal velocity, Winnowing

The objective of this study was to investigate the effect of physical characteristics of different size classesof J. curcas seeds on shelling performance using a modified disc mill. The seeds were grouped into foursize classes using sieves with hole diameters of 8, 9, 10 and 12 mm. Length, breadth, width, arithmeticand geometric diameter, bulk and solid density, and surface area were significantly different at p ≤ 0.01.No significant differences were found in terms of sphericity and moisture content. Smaller seed sizelead to higher porosity and percentage of shells. Rupture force was examined along length (L), width(W), and breadth (B) axes. A prototype of a disc mill was re-engineered and optimized. The preferentialorientation of the seeds passing the mill was in the vertical direction. Optimum setting of rotational speedand aperture between the discs of the mill were strongly related to seed breadth. As the output fractions,dust, shells, fragmented kernels and full kernels could be separated pneumatically. Meanwhile, partially-shelled and unshelled seeds could only be separated manually by visual inspection. Under optimumconditions, the shelling efficiency for the four size classes was determined as 81.0, 83.5, 83.7, and 84.6%,respectively. Compared with results from unsorted seeds, pre-sorting the seeds significantly reduced theamount of partially-shelled and unshelled seeds at p ≤ 0.01. The maximum capacity of the machine wasestimated as 131.5 kg/h which resulted in the lowest energy consumption of 0.002 kWh/kg.