Experimental investigation of transport processes and fouling in biofuel process streams

The increasing popularity of sweet sorghum as a bioenergy feedstock for ethanol production via liquid or solid-state fermentation is motivated by easily accessible sugars, low inputs for crop growth, simple process set-up for bioethanol production, and a potential for complete crop utilization. Total solids content in sweet sorghum fermented liquid is approximately 3wt%. The movement of these solids through the system can have a significant downstream impact in terms of fouling particularly on heat exchange equipment. Experiments to quantify sweet sorghum fermented juice fouling were thus undertaken-the primary objective was determining fouling resistance of fermented sweet sorghum liquid. Resistance to heat transfer value of fermented sweet sorghum was found to be approximately 9.25 × 10^-5 m² °C/W and fouling intensity is equivalent to that of tap water. Fermented sweet sorghum and water's R_f values were found to be in the same order of magnitude, one tenth of corn and maize ethanol thin stillage fouling resistance. This has been established using two independent experiments. The induction period for fermented sweet sorghum fouling was more than 5 hours. We expect low levels of fouling at bioethanol facilities will use fermented sweet sorghum for ethanol production.