Effect of Dryer Parameters on Drying Rate and Quality of Spent Brewers' Grain

Abstract

The effect of four operational parameters (shape of flight, number of flights, vapour extraction rate and drum temperature) of a conductive rotary dryer on the drying rate and quality of spent brewers' grain was investigated in this study, with the aim of mechanizing the drying of spent brewers' grain for animal feed production. The Taguchi statistical method was used to determine the optimum levels of the parameters, at which drying rate was highest. Drying rate of 0.0746 kg/min was attained at the optimum parameter levels of curved flight shape, 2 flights, vapour extraction rate of 0.03 m³/s and drum temperature of 190 ⁰C. The four parameters contributed 1.72, 0.59, 1.45 and 89.36 % to the drying rate respectively. Drum temperature had the most significant effect with signal-to-noise-ratio difference of 2.39 andF value of 12.99.Moisture content of the spent brewers' grain decreased from 78.27 to 8.16 % and the crude fibre and crude protein contents increased from 2.4 and 7.87 % to 8.94 and 25.38 % respectively. Dehydration of the spent brewers' grain was achieved in 2.5 hours as against 72 hours of sun-drying. Deterioration and fermentation of the spent grain were totally prevented and the mechanically dried product was successfully stored for over 26 months. Considering the time spent for dehydration, the conductive rotary dryer performed better than traditional sun-drying method.