Size distribution analysis of wheat, maize and soybeans and energy efficiency using different methods for coarse grinding

M. Thomas, W.H. Hendriks, A.F.B. van der Poel

This research investigated three grinding technologies to reduce the size of maize, wheat and full
fat soybeans to a course particle. To correct for the different mechanisms of particle size re-
duction between the different mills, the relationship between specific mechanical energy (SME)
and its resulting mean particle size was expressed per ton of ground product. Analysis of co-
variance was used to estimate differences between the treatment means after correction for en-
ergy consumption.
Experimental results, obtained under pilot scale grinding tests, showed that type and condi-
tions used for the three mill types affected size reduction ratios for maize, soybeans and wheat.
The RR of particles was smallest for the roller mill and multicracker device and largest for the
hammer mill for all feed materials studied and varied between 1.60 (roller mill, wheat) and 5.95
(hammer mill, maize). The mean particle size was smallest when grinding using a hammer mill
with a 5 mm screen.
The efficiency of energy use was calculated as effective SME (kJ/kg). Total energy use was
shown to be the highest for the hammer mill. Soybeans required the largest amount of energy for
grinding, with maize the smallest. The constant for Kick’s law (C k values, kJ/kg) per grinding
device was calculated to relate particle sizes and energy demand: both roller mill and multi-
cracker device showed lower C k values, indicating a better grinding efficiency of these devices.
For coarse grinding, the roller mill was shown to be the most energy efficient device followed
by the multicracker device and the hammer mill was the least efficient. For feed manufacturers it
is important to use/combine these devices to ensure an efficient milling operation and to match
the grinding device with its specific grinding objective (fine, coarse or with a specific particle size
distribution). Tasks are different per animal species and were discussed.

Animal Feed Science and Technology

Volume 240, 21 March 2018, Pages 11–21

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