Effects of Adherence in the Drying of Brewer’s Spent Grain with Rotating Equipment

Abstract

Brewer's spent grain (BSG) is a biomass with a high lignocellulosic content that can be reused in thermal processes, however it has high moisture content, which avoids it from being used in these processes. Pretreatment by drying rotating equipment turns out to be a suitable alternative. This work studied the rotational drying of BSG analyzing the effects of adhesion of solids. To do this, a standard pan combined with an external blower was chosen as a rotary dryer due to the easy access to the bed and the inner surface of the dryer. In addition, this type of dryer made possible to determine the relationship between BSG moisture and adhesion force. Under the operating conditions of the experiments, the moisture content of BSG decreased from 80 to 8.6% (wb), making it possible for the biomass to be utilized in thermal processes. Moisture ratios higher than 0.6 led to greater adherence and consequent agglomeration of solids, reducing their mobility and heat transfer with the internal surface of the dryer. At the start of drying, the bed's rotational speed rate of BSG was approximately 14 rpm, half of the maximum rate of 28 rpm, also the temperatures of the BSG and the inner wall of the tray were in equilibrium, showing that changes in biomass adhesion would take non-uniform drying. Novelty StatementUnderstanding of the drying of spent grain with focus on adhesion and cohesion mechanisms allows adequate strategies to reduce negative effects of agglomeration, allowing the reuse of this biomass.