Evaluation of a Flowthrough Reactor for Corn Stover Pretreatment Chaogang Liu, Charles E. Wyman Thayer School of Engineering Dartmouth College Hanover, New Hampshire AIChE Annual Meeting Indiana Convention Center Indianapolis, Indiana November 4, 2002 Biomass Refining CAFI

USDA IFAFS Project Overview Multi-institutional effort funded by USDA Initiative for Future Agriculture and Food Systems (IFAFS) Program to develop comparative information on cellulosic biomass pretreatment by leading options with common source of cellulosic biomass –Aqueous ammonia recycle pretreatment - YY Lee, Auburn University –Water only and dilute acid hydrolysis by co-current and flowthrough systems - Charles Wyman, Dartmouth College –Ammonia fiber explosion - Bruce Dale, Michigan State University –Controlled pH pretreatment - Mike Ladisch, Purdue University –Lime pretreatment - Mark Holtzapple, Texas A&M University –Logistical support and economic analysis - Rick Elander/Tim Eggeman, NREL Biomass Refining CAFI

Flowthrough (FT) Pretreatment Flows just hot water or very dilute acid solution through stationary biomass Removes large fraction of hemicellulose and lignin Separates sugars from solids, reducing decomposition Achieves high cellulose digestibility Uses less chemicals than co-current process Provides a less corrosive environment However, high amounts of water are needed, increasing energy for pretreatment and recovery Biomass Refining CAFI

Background on FT Bobleter and his coworkers were pioneers in the study of flowthrough biomass pretreatment Antal, Lee, and Sakaki extended and improved flow treatment with just water Torget et al showed similar performance with very dilute acid concentrations in unique flowthrough configurations Biomass Refining CAFI

How are FT and Batch Different ? Batch FT Xylose yield <90% ~100% Lignin removal 50% Digestion yield <90% ~100% (by SSF) Digestion time 7 days ~2 days (by SSF) Biomass Refining CAFI

Objectives of This Study Evaluate effects of flow rate, temperature, and acid concentration on solubilization of hemicellulose and lignin in a flowthrough reactor Particularly focus on developing detailed time profiles on the fate of major biomass components Investigate how fluid velocity and liquid-solid contact time impact performance Seek to understand reasons for differences between batch and flowthrough systems and gain new insight into hemicellulose hydrolysis mechanisms Provide knowledge from which to develop advanced systems that combine the best features of each while overcoming their limitations Biomass Refining CAFI

Presentation in Context of USDA IFAFS Project Tasks 1.Apply leading pretreatment technologies to prepare biomass for conversion to products 2.Characterize resulting fluid and solid streams 3.Close material and energy balances for each process 4.Determine cellulose digestibility and liquid fraction fermentability 5.Compare performance of pretreatment technologies Biomass Refining CAFI

Corn Stover Composition NREL supplied corn stover to all project participants (source: BioMass AgriProducts, Harlan IA) Stover washed and dried in small commercial operation, knife milled to pass ¼ inch round screen Glucan36.1 % Xylan21.4 % Arabinan3.5 % Mannan1.8 % Galactan2.5 % Lignin17.2 % Protein4.0 % Acetyl3.2 % Ash7.1 % Uronic Acid3.6 % Non-structural Sugars1.2 % Biomass Refining CAFI

Schematic of Flowthrough System Sample Biomass Refining CAFI

Flowthrough Reactors To vary velocity at constant contact time To vary contact time at constant velocity Gasket Filter 1/2-in, O.D. 3/4-in, O.D. 1-in, O.D. 60mm 1/2-in, O.D. 120mm 180mm Biomass Refining CAFI

Effect of Flow Rate and Temperature on Residual Xylose for Water Only Biomass Refining CAFI

Effect of Flow Rate and Temperature on Residual Xylose for Water Only Biomass Refining CAFI

Effect of Flow Rate and Temperature on Residual Xylose for Water Only Biomass Refining CAFI

Effect of Flow Rate and Acid on Residual Xylose at 180 o C Biomass Refining CAFI

Effect of Flow Rate and Acid on Residual Xylose at 180 o C Biomass Refining CAFI

Effect of Flow Rate and Acid on Residual Xylose at 180 o C Biomass Refining CAFI

Effect of Flow Rate on Total Xylose Yield at 180 o C after 16 minutes Biomass Refining CAFI

Xylose Solubilization for Water Only and 0.1wt% Sulfuric Acid at 180 o C and a Flow Rate of 10mL/min Biomass Refining CAFI

Xylose Solubilization for Water Only and 0.1wt% Sulfuric Acid at 180 o C and a Flow Rate of 10mL/min Biomass Refining CAFI

Change in Lignin Removal with Flow Rate for Water Only and Sulfuric Acid after 16 minutes at 180 o C Biomass Refining CAFI

Solubilization of Xylan and Lignin for Water Only Hydrolysis Biomass Refining CAFI

Change in Lignin Removal with Liquid-Solid Contact Time for a Flow Rate of 10mL/min with 0.05wt% Sulfuric Acid at 180 o C Biomass Refining CAFI

Change in Lignin Removal with Fluid Velocity for 0.05wt% Sulfuric Acid Pretreatment at 180 o C and a Flow Rate of 10mL/min Biomass Refining CAFI

Material Balance Slide at 60 FPU/g Biomass Refining CAFI

Material Balance Slide at 15 FPU/g Biomass Refining CAFI

Material Balance Slide for SSF Biomass Refining CAFI

Summary Flow rate acts somewhat like temperature and acid in effect on solubilization of hemicellulose and lignin Increase in xylan removal with flow rate or velocity is inconsistent with traditional first order kinetic models suggesting that simple hydrolysis is not the only factor in hemicellulose removal Data relating lignin and hemicellulose removal and on effects of contact time support idea that lignin reacts and precipitates with time Flow ConditionsHemicellulose Removal Lignin Removal Temperature Acid concentration Flow rate Fluid velocity Liquid-solid contact time Biomass Refining CAFI

Acknowledgements The United States Department of Agriculture Initiative for Future Agricultural and Food Systems Program through Contract for funding our research The United States Department of Energy Biofuels Program and the National Renewable Energy Laboratory Our partners from Auburn University, Michigan State, Purdue, and Texas A&M Universities and the National Renewable Energy Laboratory The Thayer School of Engineering at Dartmouth College Biomass Refining CAFI

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