Monday, April 30, 2007

Scale up and reactor design for biological conversion of cellulosic biomass to ethanol featuring enzymatic hydrolysis

Xiongjun Shao1, Lee Lynd*1, Richard LaRoche2, and Charles Wyman3. (1) Thayer School of Engineering at Dartmouth College, 8000 Cummings Hall, Hanover, NH 03755, (2) ANSYS, Inc., 10 Cavendish Ct., Lebanon, NH 03766, (3) Department of Chemical & Environmental Engineering, Center for Environmental Research and Technology, University of California, Riverside, Riverside, CA 92521

Biological conversion of biomass to fuels and chemicals offers recognized benefits.  Important outstanding issues to realizing these benefits include the high current cost of overcoming the recalcitrance of cellulosic biomass together with the absence of systematic scale-up procedures. A reliable scale up strategy could reduce risk, inform process decisions, and reduce cost from pilot and demonstration operations.

This presentation considers the issue of scale-up and fermenter design. In particular, we present a method of analysis which combines kinetic modeling, industrial mixing analysis, and computational fluid dynamics (CFD) simulations. Such an approach enhances the prediction of reactor performance and helps provide guidelines for the analysis and design of large scale fermenters based on bench scale experimentation.

The scale up approach is applied to converting waste paper sludge via simultaneous saccharification and fermentation. Kinetic model parameters specific to converting paper sludge are evaluated based on experimental data and the model is validated by successfully predicting data at different conditions from those used to obtain parameters. Cascade CSTRs is the reactor configuration chosen to achieve high conversion while having feasible mixing requirements. Complete suspension for solids is chosen as the scale up criterion based on bench scale experiments. Industrial mixing analysis coupled with solid-liquid phase CFD simulations is employed to calculate the power requirement and to analyze heat and mass transfer at large scale. Reactor design with emphasis on mixing will also be considered.