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Thesis - University Access Only
Master of Science (MS)
Agricultural and Biosystems Engineering
Distillers Dried Grains with Solubles (DDGS) is one of the non-fermentable corn residues obtained from dry grind ethanol processing. It is rich in proteins, fat, vitamins, and minerals. It is an excellent source of digestible protein for ruminants and non-ruminants. It is a valuable feed ingredient for livestock ration, improves the palatability and also reduces the feed cost. To utilize it efficiently, it has to be transported greater distances and alas DDGS flowability is often problematic due to caking and bridging during storage and transportation. This is a major issue faced by the ethanol producers and farmers and needs to be addressed.
To address the flow problem, the key factors affecting the flowability of DDGS should be determined first. As an initial step, the flow properties of Distillers Dried Grains (DDG) with varying soluble levels and moisture contents were studied. In most of the ethanol industries, the addition of condensed distillers solubles (CDS) to distillers wet grains (DWG) is often an inconsistent process which leads to variations in processing conditions and final nutrient levels. A calibration method was developed to determine the soluble contents in dry grind ethanol co-product streams. DDG with varying soluble levels and moisture contents were prepared using the developed method. The effect of soluble levels and moisture contents on the flow properties and chemical properties of DDGS were investigated using Carr test. It was found that the higher levels of solubles and moisture content had a negative impact on the flow properties of DDGS.
Anti caking agents are used in powder industries to prevent the agglomeration of particles. Keeping this in mind, a common flow agent was added to the DDGS with varying soluble levels and moisture contents at different inclusion rates and the flow properties ofDDGS were studied using the same Carr test. The results showed that the addition of flow agent did not significantly improve the flowability of DDGS.
EMC isotherms for DDGS at various relative humidity and temperatures are essential to optimize its storage and transportation conditions. DDGS showed a type III isotherm behavior, which is common in high sugar foods. Nine traditional isotherm models were evaluated for DDGS sorption isotherm data. A new model, termed as "GMR (Ganesan-Muthu-Rosentrater)" model, was developed incorporating soluble effect along with the effect of temperature and moisture content. This model was ranked first in terms of performance with fairly random residuals and thus recommended for DDGS sorption isotherm analysis.
Dynamic adsorption data of DDGS with four soluble levels were also collected along with the EMC isotherm data at various temperatures and humidity levels. Three commonly used models were used to fit the adsorption data of DDGS. A new model was developed by incorporating soluble, temperature, and relative humidity effect along with time and moisture content effect. This model has been termed as "GRM (Ganesan- Rosentrater-Muthu)" model, which proved to perform well. The proposed GRM model could be used by ethanol producers to plausibly predict water adsorption of DDGS at any given time, specific temperature, and relative humidity conditions.
Jenike instantaneous shear tests were performed on DDGS with various soluble levels and moisture contents, as it is the standard method used for determining bulk material's cohesiveness and wall friction properties. The results showed that DDGS with higher soluble level was the one with most strength, greatest ability to support obstructions to flow and hence the least free-flowing one. DDGS with higher soluble and moisture content was likely to have cohesive arching problems and was classified as cohesive and more compressible.
The flow properties obtained from Carr and Jenike tests were meticulously analyzed using exploratory data analysis techniques. A comprehensive model (R =0.93; SE=0.12) was developed, by combining the important flow properties obtained from both Carr and Jenike tests using response surface modeling, to predict the flowability of DDGS with varying soluble levels and moisture contents. The model developed in this study was solely based on the DDGS obtained from one ethanol plant (Dakota Ethanol LLC., Wentworth, SD). As composition of DDG and syrup varies between plants, the flow properties of DDGS would also be different among the plants. So it is recommended to determine the flow properties (Carr and Jenike) of DDGS obtained from each ethanol plant and develop a similar model to predict the flowability of DDGS from any hatch of interest.
The results obtained from this study shown that DDGS has flow problem at higher levels of solubles and flow agent addition did not show any improvement in the flowability. At above certain moisture content, the moisture content was acting as a lubricant easing the flow of DDGS. DDGS is likely to have more cohesive, arching problems at higher soluble and consolidation levels. This often inhibits the free flow of DDGS out of railcars or trucks or storage structures. So, a comprehensive model was developed by combining both Carr and Jenike flow properties to predict the flowability of DDGS. Currently, there is no literature available on DDGS flowability. This sequentially obtained information about DDGS flow properties, and the factors affecting its flow are very crucial for DDGS processing, and handling operations. This study is thus an initial step taken towards the effective handling and utilization of DDGS and other ethanol co-product streams.
Library of Congress Subject Headings
bulk solids flow
Includes bibliographical references (235-254)
Number of Pages
South Dakota State University
Copyright © 2007 Vykundeshwari Ganesan. All rights reserved
Ganesan, Vykundeshwari, "Experimental and Modeling the Flow Properties of Distillers Dried Grains (DDG) with Varying Soluble Levels and Moisture Contents" (2007). Theses and Dissertations. 616.