(82c) Chemical Modeling of Biomass Gasification

The gasification of biomass produces a syngas that can be used for the production of renewable transportation fuels, but often requires cleaning and conditioning. Of particular importance is the formation of tars, or condensable organic compounds. These compounds can be removed by catalytic steam reforming, but this adds considerable cost and complexity. An understanding of the chemical mechanisms and kinetics of gasification allows design and optimization for minimized tar formation, thus reducing the demand on the steam reforming step. Of particular interest to gasification are Polynuclear Aromatic Hydrocarbons (PAHs), which are formed at typical gasification temperatures (700°C to 950°C) and are refractory. We have studied the pyrolysis of model compounds, biopolymers and biomass and have developed chemical models to describe the kinetics of PAH formation. Model compounds were pyrolyzed using a hyperthermal nozzle and products, including radicals, were measured with laser photoionization mass spectrometery and matrix isolation infrared spectroscopy. Biopolymers and biomass were studied in a Laminar Entrained Flow Reactor (LEFR) and tars were detected with a Molecular Beam Mass Spectrometer (MBMS). Kinetic models are being used in Computational Fluid Dynamics (CFD) modeling to develop comprehensive and predictive tools for gasifier performance. These tools will ultimately aid in improved gasifier design and operation for more cost effective fuel production.