DOI: 10.1094/CC-83-0311 |  VIEW ARTICLE

Effect of pH on Fouling Characteristics and Deposit Compositions in Dry-Grind Thin Stillage.

M. R. Wilkins (1), V. Singh (2), R. L. Belyea (3), P. Buriak (2), M. A. Wallig (4), M. E. Tumbleson (2), and K. D. Rausch (2,5). (1) Biosystems and Agricultural Engineering, Oklahoma State University, Stillwater, OK 74078. (2) Agricultural and Biological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801. (3) Animal Sciences, University of Missouri-Columbia, Columbia, MO 65211. (4) Veterinary Pathobiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801. (5) Corresponding author. Phone: 217-265-0697. Fax: 217-244-0323. E-mail: <krausch@uiuc.edu> Cereal Chem. 83(3):311-314. Accepted January 26, 2006. Copyright 2006 AACC International, Inc.

Dry-grind corn processing facilities produce ethanol, carbon dioxide, and distillers dried grains with solubles (DDGS). To produce DDGS, dry-grind corn processors concentrate thin stillage in multieffect evaporators. Concentration of thin stillage uses large amounts of energy, and efficient operation is important for long-term economic stability of the industry. Little data are available on fouling of evaporators during thin stillage concentration. We evaluated how thin stillage pH and acid type used during pH adjustment affected fouling as measured by induction period, fouling rate, and deposit composition. Using an annular fouling appa­ratus, fouling tests were conducted at pH 3.5, 4.0, and 4.5. In a second experiment, we used two types of acid, HCl or H(2)SO(4), to adjust thin stillage to pH 3.5. Induction periods were shorter at pH 3.5 than at pH 4.0 or 4.5. As pH increased, fouling deposit protein decreased and ash increased. Concentrations of most elements, including P, Ca, Mg, Mn, and K, increased with an increase in pH. Phosphorus was the most abundant mineral element in fouling deposits. Induction periods were similar for the two acids. Thin stillage pH has an influence on deposit concentration, fouling rate, and induction period.