AACC International - 2009 Meeting Abstract - Heat transfer surface fouling: Implications on bioprocessing

Meeting Abstract - Poster Presentation

Heat transfer surface fouling: Implications on bioprocessing
K. D. RAUSCH (1), A. Arora (1), M. R. Wilkins (2), R. M. Agbisit (3), V. Singh (1), M. E. Tumbleson (1)
(1) University of Illinois, Urbana, IL, U.S.A.; (2) Oklahoma State University, Stillwater, OK, U.S.A.; (3) Kansas State University, Manhattan, KS, U.S.A.
Cereal Foods World 54:A62

During processing of cereal and other agricultural crops into food and industrial products, evaporators are used to remove water. Heated surfaces become coated with deposits; this results in increased energy use. Future bioprocesses likely will use water to produce biofuels and food products; evaporation will remain a method for water removal in these processes. In the corn dry grind process, 6 to 7 L thin stillage are produced per 1 L ethanol. In corn wet milling, 1 to 2 L water per kg corn are needed for starch production; this water passes through steepwater evaporators. As emphasis on renewable fuels continues, cellulosic feedstocks are to be used to produce fuel ethanol. For cellulosic ethanol, it is anticipated that water use will increase 2 to 3 times over that required for conventional ethanol processes; a large percentage will need to be removed from ethanol and coproduct streams. Despite its importance in economic operation, heat transfer surface fouling is not well understood. A probe was used to quantify fouling tendencies of fluids passing over heated surfaces. Microfiltration reduced fouling tendencies of steepwater by 5 fold, although solids content was reduced by only 19%. Thin stillage from dry grind fouled more rapidly than thin stillage from wet milling. The observed effect of pH was counter to industry experience; flow rate (Reynolds number) affected fouling rate. Solids content alone did not explain decreased fouling tendencies in microfiltered stillage. Additional work is needed to understand causes of fouling and to determine constituents associated with accelerated fouling. This understanding could be used to avoid increased energy consumption and reduced process efficiencies.