Abstract:

1. Modeling of Biomass to Determine Proximate Compositions Gavin George Dr. Larry Baxter Dept. of Chemical Engineering, Brigham Young University, Provo, Utah • Abstract: • Estimated percentages of cellulose, hemi-cellulose, lignin, and other minor proximate components in biomass materials. • Analyzed by elemental ratios and experimental heating values. • Analysis: • Visual basic program to calculate the percentages of cellulose, lignin, protein, and other extractives. • Biobank database3 of elementary analysis supplied the needed elemental data. • Cellulose and lignin percentages were determined using the areas formed on the hydrogen/carbon vs. oxygen/carbon graph by lines drawn from the biomass to the points for cellulose, lignin, and a third compound. • Third compound was taken as a lipid or protein because a large portion of the unknown extractives were expected to have a similar composition. Results: Introduction: • Previous research limited to lengthy laboratory techniques. • A simpler approach; using heating values and molecular group contributions. • Basis for the computer code is a geometric relationship of elemental ratios plotted graphically. • Gross calorific values checked the validity of the findings by multiplying heats of combustion by mass percentages. • Predicted GCVs were then compared with experimentally determined gross calorific values. • The user interface of the program: • Majority of biomass material falls in the area between the lignin and cellulose points. • Deviation from the line connecting lignin and cellulose results from other compounds in the sample. • Different structures of lignin exist, represented by the cluster of three lignin points on the graph. • Used the relative amounts of hetero atoms in a sample to estimate the percentage of certain more complex components. • Percentage protein was determined by the established formula: • Mass% Nitrogen * 6.25 = Mass% Protein1 • Conclusions: • The type of analysis provides more accurate estimates for those biomass materials with smaller amounts of exotic compounds and those with limited degradation of proximate compounds. • This program could prove to be an effective method to screen large numbers of biomass materials for a desired proximate composition. This could be followed by a more exact laboratory analysis. • Hemicellulose and cellulose concentrations differentiated by the following estimates: • Hardwood/Grasses: 63% Cellulose, 37% Hemicellulose4 • Softwood : 53% Cellulose, 47% Hemicellulose4 • Basic components such as cellulose, hemi-cellulose and lignin have distinct heating values, which determined a total heating value. • Hf Cellulose: 976 kJ/kmol2 Hf Lignin: 1593 kJ/kmol2 • Hf Hemi-Cellulose: 762 kJ/kmol2 • Acknowledgements: • US DOE/EE Biopower Program • National Renewable Energy Laboratory 1 - U.S Department of Energy, Office of Transportation Technologies, Biofuels, http://www.ott.doe.gov/biofuels/glossary.html#P 2 - Development of an ASPEN Plus Physical Properties Data base for Biofuels Components, Robert J. Wooley Victoria Putsche, National Renewable Energy Laboratory, http://www.afdc.doe.gov/pdfs/3955.pdf 3 - BioBank version 2.4, BIOS consulting, Graz, Austria 4 - Emissions of Rural Wood-Burning Cooking Devices, Grant Ballard-Tremeer, Appendix D Wood combustion, http://www.energy.demon.nl/thesis/AppdxD.htm 1.   5 - “Bioenergy Feedstock Characteristics”, Jonathan Scurlock, Oak Ridge National Laboratory, Bioenergy Feedstock Development Programs, http://bioenergy.ornl.gov/papers/misc/biochar_factsheet.htmlz