Pelletization by Agglomeration of Wet Distillers Grains during Rotary Drum Granulation and Drying

Abstract

The process of producing spherical pellets that are free flowing by promoting agglomeration of particulate solids is referred to as pelletization. Unlike pelletization by extrusion which applies a mechanical force to feed particulate solids through a die, pelletization by agglomeration promotes the use of the natural forces of particle attraction and bonding to form spherical pellets or granules. In rotary drum drying of dried distillers grains with solubles (DDGS), which is a common practice in the industry, the process of agglomeration can be induced to produce spherical pellets of DDGS. This study was a preliminary investigation of pelletization of DDGS by agglomeration in a rotary drum. Five batches of experimental trials of DDGS agglomeration were conducted using a bench-scale rotary drum. Wet distillers grain (WDG) was blended with 20% by weight of condensed distillers solubles (CDS) used as a binder and spherical granules (pellets) formed were dried to about 4 to 10% (w.b.). For comparison purposes, a control sample of DDGS was produced without the binder to show the initial characteristics before agglomeration. Granules were produced to the desired size range of 1.7 mm to 3.4 mm. They were spherical in shape and may likely possess a better flow property, even though this was not measured. A bulk density of 566 kg/m3 was measured for the smaller sized granule (1.7 mm), indicating that agglomeration may be a method of increasing the bulk density and potentially flow property of DDGS.