Characterization of Biomass Ignition, Combustion, and Upgrading of Bio-char Coproducts

An increasing demand for sustainable biofuels has led to increasing interest for biomass production and utilization for advanced biorefineries. A biorefinery using a fast pyrolysis thermochemical process will aim to convert various types of biomass into high yielding bio-oil (a precursor to drop-in biofuels), bio-char (charcoal co-product), and synthesis gas (syngas). This study focuses on characterizing fire risks during harvesting operations in the biomass feedstock supply chain as well as upgrading the co-product, bio-char, into a higher value added activated carbon and subsequent use as adsorbents. South Dakota consistently ranks as a top producer of sunflower crops, which could be used as potential feedstocks for future biorefineries. The South Dakota Oilseeds Council identified combine harvester fires as a major limiting factor for sunflower production. Ignition and combustion properties of sunflowers and corn stover were investigated and related to their composition, surface and internal properties to identify the dust source and overall combustion mechanism. A prototype system was invented to isolate the hot components of the combine harvester’s exhaust manifold and turbocharger system from exposure to combustible organic dust. This system has been successfully tested on one combine, Case International Harvester Model 8120, during the 2012 sunflower harvest season in central South Dakota. No fires occurred during the entire season while harvesting several thousand acres of sunflowers. Overall, the results suggest the prototype can prevent exposure of dust to the hot exhaust manifold and simultaneously reduce the temperature of exposed areas well below the sunflower dust ignition point. Bio-char was upgraded using several different types of physical activation methods to develop advanced porosity characteristics and increase surface area. These activated carbon materials have pore characteristics and BET surface area that are comparable to previously reported conventional activated carbon materials. This value added activated carbon co-product, which could be used for water purification, improves the economic potential of thermochemical conversion pathways for producing renewable transportation fuels. These products can be produced more economically using a synergistic combination of thermochemical, physical activation, and heat recovery processes