Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2010
Publication Date: 12/1/2010
Citation: Wood, C.R., Rosentrater, K.A. 2010. Granular packing influences the bulk density of DDGS. Cereal Chemistry. 87(16):586-596.
Interpretive Summary: DDGS flowability problems can be caused by a number of physical, chemical, and environmental factors. A key property of DDGS which is related to flowability is bulk density. In this study, the effects of uniaxial compression on bulk density were examined. It was found that for all applied loads, resulting strain and compressive stress exhibited curvilinear relationships. Linear relationships existed between applied force and resulting bulk density: the higher the compression, the greater the bulk density. When the applied compressive load was removed, the DDGS regained approximately 50% to 60% of its original bulk volume. These results capture only one-dimensional effects, however, so shear testing should be conducted to fully capture three-dimensional particle interactions. Additionally, interactions among these factors with particle size and shape should also be evaluated.
Technical Abstract: As the quantity of ethanol produced continues to increase, the amount of distillers dried grains with solubles (DDGS), the primary coproduct of ethanol manufacturing, has become more widely available. Currently, the main consumer of DDGS is the livestock industry, but new value added uses are on the horizon. With the increase in the availability of, and demand for DDGS, transportation has become an important issue, since DDGS must increasingly be shipped long distances via railways. Rail transportation is expensive, especially considering the quantities of DDGS which can be loaded onto unit trains. DDGS often has low bulk density and poor flowability characteristics. This study examined compression effects on particle arrangements, as quantified by bulk density and compressibility of the DDGS. Mean loose bulk density was found to be 446.18 kg/m3. A linear relationship (R2 = 0.982 for 50 N applied force, and R2 = 0.959 for 1 kN applied force) was observed between the applied stress (approximately 0.0 to 0.0065 MPa, and 0.0 to 0.13 MPa, respectively) and the resulting packed bulk density (up to 470.21 kg/m3, and 555.03 kg/m3, respectively). Compressive stress increased curvilinearly (R2 = 0.994 for the 50 N load, and R2 = 0.997 for the 1kN load) as the applied strain increased (from appoximately 0.0 to 0.007%, and 0.0 to 24.0%, respectively). As the loading increased, compressibility increased from 5.11% to 19.22%. Bulk restitution after loading was removed was 0.53 to 0.61, respectively. Required storage volume is reduced when the bulk density is increased. But, flowability characteristics should improve as the compressibility, and thus the bulk density, of the product is reduced.