Effects of temperature conditions and heat treatment within a multiple effect evaporator on thin stillage fouling characteristics
Heat transfer fouling is the accumulation and formation of unwanted materials on heat transfer surfaces which leads to a decrease in the overall heat transfer coefficient. Fouling of heat transfer equipment increases energy consumption and maintenance costs and thus decreases processing efficiency. In the fuel ethanol industry, evaporator fouling occurs when thin stillage is concentrated. Fouling affects the efficiency and environmental footprint of more than 200 biorefineries in the US. Thin stillage is the liquid fraction of unfermented materials from fermentation and is composed of carbohydrate, protein, fat and ash. Research on thin stillage fouling has focused on effects of corn oil, pH, Reynolds number, solids concentration and carbohydrates (Singh et al 1999, Wilkins et al 2006ab, Arora et al 2010, Challa et al 2014). However, temperature and heat treatment effects on thin still fouling have not been studied. This study investigated the influence of bulk fluid and initial probe temperatures on thin stillage fouling characteristics. Experiments were conducted using model thin stillage (1% starch solution) and commercial thin stillage with varied temperature conditions. We found that temperature had effects on thin stillage fouling. Increase of initial probe temperature would increase fouling rates and maximum fouling resistance for both commercial thin stillage and model thin stillage. At an initial probe temperature of 120ºC, higher bulk temperature (80ºC) increased fouling rates and reduced induction periods. Effects of evaporator heat treatment were studied by examining fouling behavior among samples from different locations of a multiple effect evaporator. Samples before and after plant cleaning were collected to study effects of plant cleaning. Effects of heat treatment within an evaporator were not detected. Fouling tendencies were reduced after plant cleaning.
Fouling, thin stillage, temperature, evaporator
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign