General Uncertainty Analysis B.2 Uncertainty in F B.3 Uncertainty in W C (t ss) B.4 Uncertainty in R e (t ss) B.5 Sample Uncertainty Calculations I also thank my family. I thank my immediate family: Karen my wife and our three daughters Ana, Sarah, and Katy. They are precious gifts which shower me with love, prayers, understanding, sacrifice, and support. I am also indebted to our extended family of parents and siblings for their prayers and encouragement. And to our church family at Trinity Christian Reformed Church in Ames for their friendship, love, prayers, and acts of kindness. They opened themselves to us and treated us like family, transforming a bearable situation into a blessing. I owe much to Dr. Robert Brown and to his colleague Jerod Smeenk. I value their friendship and the opportunity to share in their accumulated wisdom. Dr. Brown unselfishly committed himself to me and my situation. He faithfully and insightfully guided me along a direct path toward successful conclusion of this project. Jerod's patient, day-today instruction and organized and well maintained laboratory environment enabled me to complete my work in a timely fashion. My work also benefitted from diligent, competent, and responsible help in the laboratory. Fellow graduate student Nathan Nelson and laboratory associate Nicholas Sikes were always willing to help tackle equipment problems. Undergraduate assistants Karl Broer, Harrison Bucy, Mark Wright, and Nick Howard were assets in the lab, investing themselves in my research and success beyond what their wage required.

This study focuses on the fate of carbon in the char generated by devolatilization of biomass during fluidized bed gasification. A carbon balance model was developed to distinguish between char transformed to carbon-bearing gases and its comminution and elutriation as fine char during gasification. The model accurately predicts the transient accumulation of char carbon in the reactor. Experiments revealed steady state reactor char carbon loadings were achieved after multiple hours of gasification. The model formed the basis of an experimental methodology that assesses the transformation of char carbon based on collection of elutriated solids from the reactor and assessment of the steady state char carbon loading in the reactor. Experiments were performed to distinguish the relative contributions of chemical reaction and physical comminution toward conversion of char to gaseous and solid products. The effects of equivalence ratio, gasification temperature, superficial gas velocity, biomass particle size, and the addition of steam on the partitioning of char carbon between gaseous and solid products during gasification of ground seed corn in a bubbling fluidized bed were investigated. This study revealed that char conversion during gasification of biomass was limited by elutriation of fine char particles arising from fragmentation or attrition of primary char product. Additionally, increased chemical reaction of char to form gases was usually accompanied by increased elutriation of fine char, which suggests that chemical reaction increased the porosity of the char and its susceptibility to fragmentation and attrition. Finally, decreasing superficial gas velocity, increasing equivalence ratio, and decreasing particle size led to increased carbon conversion, while increasing temperature and steam concentration in the reactor had negligible effect.