(567bd) Analysis of Heat Transfer Fouling Characteristics During Evaporation of Clarified Pine Wood Hydrolysate to Concentrate Sugars

Gurram, R. N., South Dakota School of Mines and Technology
Menkhaus, T., South Dakota School of Mines and Technology
Gilcrease, P. C., South Dakota School of Mines & Technology
Christopher, L. P., South Dakota School of Mines & Technology

Lignocellulosic feedstocks such as pine wood waste are becoming viable biomass sources for ethanol production. Within the ethanol production process, concentrating the sugar-rich hydrolysate stream by evaporation prior to fermentation can enhance the fermentation productivity and reduce downstream distillation costs. However, fouling of the evaporator surface by soluble and suspended solids within the hydrolysate can become problematic. This can reduce the heat transfer rate and ultimately increase energy consumption of the process. In this study we analyzed fouling characteristics of (polyelectrolyte) clarified pine wood hydrolysate using an annular fouling probe containing a heated surface to mimic a continuous evaporator operation. The heated region of the probe caused solids in the hydrolysate to adhere to the surface, thus fouling the probe over time. 500 mL batches of hydrolysate were circulated through the annulus of the fouling probe while temperatures and power supplied to the probe were measured over time and used to calculate fouling resistance, rate of fouling and induction period. Hydrolysate pH and Reynolds number (in both the laminar and turbulent regions) were analyzed for their effects on fouling rate, induction period and fouling deposit ash concentration and composition (as measured by inductively coupled plasma ? ICP ? spectroscopy). It is shown that by optimizing these variables the evaporation operation can lead to significantly higher concentrations of sugars and concomitantly increase the fermentation productivity and decrease the overall cost of lignocellulosic ethanol production.