Heat transfer during cooling of bulk distillers dried grains with solubles (DDGS)

Authors: SILIVERU, KALIRAMESH - Kansas State University; Casada, Mark; AMBROSE, R.P. KINGSLY - Purdue University

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2019
Publication Date: 9/5/2019
Citation: Siliveru, K., Casada, M.E., Ambrose, R.P.K. 2019. Heat transfer during cooling of bulk distillers dried grains with solubles (DDGS). Applied Engineering in Agriculture. 35(4):569-577. https://doi.org/10.13031/aea.13158.
DOI: https://doi.org/10.13031/aea.13158

Interpretive Summary: Distillers dried grains with solubles (DDGS) are widely used as animal feed in the U.S. cattle and swine industries. The DDGS have relatively high protein content (approximately 30% dry basis) and fat content (8% to 12% dry basis), which is valuable for animal feed. However, DDGS, including newer, low-oil formulations, are notorious for troublesome flow problems when emptying railcars, leading to railcar damage and disrupting the transportation system. The causes of the handling problems are often initiated during cooling and storage of DDGS in open piles where temperature gradients cause stickiness and subsequent caking and handling problems during transportation. We developed and validated a heat transfer model for predicting the cooling pattern of low-oil DDGS in open piles. Pile temperatures were predicted for winter conditions (average of 43 deg F) and summer conditions (average of 75 deg F). Predicted temperatures were generally within 2 deg F of measured temperatures. The new model can be used by low-oil DDGS producers and handlers to avoid inadequate storage conditions that later lead to flow problems during transportation.

Technical Abstract: Low-oil DDGS is often transported in railcars and trucks from the ethanol plants to livestock facilities. During unloading, DDGS flowability is often reduced due to the hardening of the DDGS bulk from caking. Based on published research, the environmental relative humidity, DDGS glass transition temperature, syrup content, and time of cooling of DDGS piles influence the caking behavior of DDGS. The temperature gradients that develop during cooling of DDGS in piles can cause stickiness and subsequent caking and handling problems during transportation. The objective of this study was to develop and validate a heat transfer model for predicting the cooling pattern of low-oil DDGS piles. A finite volume method approach was used to develop the heat transfer model. Airflow resistance in the porous media of the low-oil DDGS material was implemented using Ergun’s equation. The heat transfer inside the pile was simulated for winter (6 deg C) and summer (24 deg C) ambient conditions. The model agreed well with temperature measurements from three tests with two sizes of experimental piles.