Effect of compression speed on energy requirement and oil yield of Jatropha curcas L. bulk seeds under linear compression

• Deformation energy and oil yield decreased significantly (p < 0.05) at higher speed.
• The increase in oil point force at higher speed was statistically significant.
• Oil point deformation at higher speed increased significantly (p < 0.05).
• Oil point deformation energy statistically increased along with higher speed.
• Higher speed did not cause any serration effect on the force–deformation curves.

The influence of pressing speed on energy demand and percentage oil yield of Jatropha curcas L. bulk seeds was examined in compression loading test using Universal Testing Machine and vessel diameter of 60 mm. Maximum force of 100 kN and speed between 1 and 50 mm min−1 were applied on jatropha bulk seeds of initial moisture content 8.61% ± 1.14% (w. b.) at pressing height of 60 mm. The mechanical behaviour and deformation characteristic curves of jatropha bulk seeds were also assessed in relation to speed. Based on the statistical analysis of results, deformation energy decreased significantly (p < 0.05) with increasing speed from 0.43 ± 0.01 to 0.41 ± 0.01 kJ and oil yield from 19.05 ± 1.16 to 11.66 ± 0.82 (%) while slight decreases in maximum deformation from 45.02 ± 0.29 to 43.38 ± 2.63 (mm) were not statistically significant (p > 0.05). In contrast, oil point force increased with increasing compression speed from 17.03 ± 2.33 to 59.27 ± 30.81 kN, oil point deformation from 38.22 ± 0.49 to 41.99 ± 1.40 mm and oil point energy from 0.15 ± 0.01 to 0.31 ± 0.09 kJ, all significant at p < 0.05. The dependency between force and deformation curves of jatropha bulk seeds as function of speed did not exhibit any serration effect. The present study provides preliminary result that can support the incorporation of the speed variable into the already published tangent curve mathematical model, which can represent mechanical and deformation behaviour of bulk oilseeds under compression loading.