The granulation of co-products from the dry-grind processing of corn to ethanol

Kyle Vincent Probst, Purdue University

Abstract

In 2008, the dry-grind ethanol industry produced 23 million metric tons of dried distillers grains with solubles (DDGS). Currently DDGS is sold as a feedstock but due to its quality and handling issues, competing with other feed products is challenging. Pellet mills have been used in the past to enhance DDGS handling and prevent particle segregation during transportation. The current drawback to pelleting DDGS is the high capital and maintenance costs. Instead of using expensive pellet mills, the use of wet granulation has been proposed to enhance DDGS densification and handling while minimizing costs. A lab scale drum granulation process was used to manufacture granules of DDGS by adding condensed distillers solubles (CDS) to wet distillers grains (WDG) under varying formulation and process conditions. A full factorial experimental design was used to test all combinations of factor levels which included CDS binder addition (30, 35, and 40% (wt/wt)), CDS solids content (22 and 38%, wet basis), screen size opening (3.175 and 6.35 mm), and residence time (1, 2.5, 5, and 10 min). Measured response variables included mean particle size, bulk density, true density, granule yield (3.35 - 1.68 mm), and porosity. Results from the experiment indicated that as binder addition increased between 30, 35, and 40% mean particle size of the final granules increased to 2.08, 3.15, and 4.45 mm, respectively. As binder solids content increased, the bulk density increased due to the increased amount of dry matter in the final granular product. Porosity decreased as solids content increased mainly due to greater shrinkage of the granules during the drying process. Screen size opening also affected nucleation which influenced the final size and yield of the granules produced. Compression testing of wet granule compacts indicated that increasing CDS binder addition and increasing solids content enhanced granule plasticity. Growth was observed for granules prepared from high binder additions, and low solids content while minimal growth occurred for material prepared from the high solids content CDS. The highest granular yields (~80%) were observed at residence times between 2.5 and 10 minutes with 35% binder addition using the high solids content CDS and the small screen size opening.

Degree

M.S.

Advisors

Ileleji, Purdue University.

Subject Area

Agriculture|Agricultural engineering

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