Energy requirements of size reduction of some selected cereals using attrition mill

Maize, sorghum and millet are economic crops. Primary processing methods of these foods in either dry or wet state require size reduction, an energy driven unit operation. Hence, energy pattern during size reduction of these crops using attrition mill was studied. Maize, sorghum and millet (1, 2, 3, 4 and 5 kg/min) of two different moisture content levels (12.0, 32.0% wb) were separately milled using attrition mill. Temperature of product and machine parts, duration of operation, and quantity of fuel (diesel) consumed was recorded. Standard equations were adopted to quantify energy, energy intensity, exergy and exergy losses. Energy intensity of reducing dry (12.0 % wb) maize, sorghum and millet using attrition mill were 5.5 MJ/kg, 5.2 MJ/kg and 5.0 MJ/kg respectively. While 1.2 MJ/kg, 1.1MJ/kg and 0.8 MJ/kg were energy intensity for wet (32.0% wb) milling maize, sorghum and millet respectively. Exergy efficiency of grinding dry maize, sorghum and millet using attrition mill were 64.7, 64.9 and 66.8% respectively while 71.2, 71.4 and 71.9% were recorded for wet milling maize, sorghum and millet respectively. Energy and exergy utilization were significantly (p 0.05) different between dry and wet milling. Smaller magnitudes of energy (14 – 30%) were destroy exergy while loss exergy accounts for the balance. Attrition mill is more appropriate for wet milling.