Drum Agglomeration of Corn Stover and Corn Co-products from Bioprocessing

Yi Li, Purdue University

Abstract

Crop residues have high availability and low prices. As the largest single source of residue, corn stover had a total production estimated between 170 and 256 million dry tons in 2005. Since corn stover has a low bulk density, handling and storage of corn stover in industry is always difficult and costly. Corn steep liquor (CSL) and corn molasses (CM) are common condensed fermented corn extractives from wet-milling ethanol plant. The high nutrient content makes the two coproducts a good choice for animal feed. However, transportation and handling of the liquid coproducts are also difficult. Ruminants are also unable to utilize liquid feed efficiently. The primary goal of this study was to investigate the granulation of corn stover and liquid coproducts, CSL and CM from corn bioprocessing. A factorial experimental design was employed to test the combinations of key factor levels hammer mill screen size (6.4 and 12.8 mm), the amount of coproduct (1:4, 1:5 and 1:6 by wt.) and residence time (0.5 and 1 min) on corn stover granules. The measured response variables of stover granules were loose bulk density, tapped bulk density, particle density, yield of desirable granules (1.78 < size < 7.87 mm), granule size and porosity. Results from the experiment unveiled some general rules of granulation of corn stover particles. Granulation with screen size of 6.4 mm, coproduct level of 1:4, and a short residence time (both 0.5 and 1.0 min) produced desirable sized granules with the highest yield. In granulation of CM, an increase in particle size, particle density and yield of desirable granules was observed with increasing coproduct level and residence time, and the smaller particle size screened through 6.4 mm. Also, granule yield increased with 1.4 stover to coproduct ratio and large screen size (12.8 mm). Statistical analysis indicated that the particle size of corn stover on density, granule size and yield of desirable granules was significant. The amount of coproduct significantly influenced density of granules, granule size and the yield of desirable granules. Residence time significantly increased density of granules and decreased yield of desirable granules. However, because of the small sample size used for density measurements, the density results are not conclusive. Overall, the study demonstrated that it was possible to produce uniform sized granules using two very difficult to handle feedstocks.

Degree

M.S.E.

Advisors

Ileleji, Purdue University.

Subject Area

Agricultural engineering

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