(46a) Changes in Characteristic Parameters of Co-Fired Biomass and Coal Particles Exposed to Oxy-Fired and High Pressure Conditions

Many single particle reaction models exist for biomass and/or coal under air-fired, atmospheric conditions, while models for non-conventional conditions remain sparse. The overall aim of the present work is to develop a single particle reaction model for biomass/coal blends under oxy-fired, high pressure conditions. Creation of such a model necessitates the inclusion of fuel/char particle structural characteristics from before and after exposure to such non-conventional combustion conditions. The focus of this paper is the characterization of several fundamental, structurally-dependent parameters of biomass/coal fuels and how they change under oxy-fired, high pressure conditions compared with traditional air-fired, atmospheric pressure conditions.

Several solid fuel/char parameters are analyzed before and after 1) pyrolysis under nitrogen conditions and 2) oxidation under oxy-fired conditions - both at pressures up to 2 MPa. Data is collected for different pure fuels (both coals and biomasses) and their blends. Various instrumentation methods are employed for determining these structurally-dependent parameters. Pyrolysis and oxidation along with mass change measurements are conducted using a high pressure TGA. The blending ratio used for the various coals and biomass materials is 15% biomass to 85% coal weight ratio. Biomass materials are preprocessed by means of torrefaction up to a temperature of 400 ˚C. The relationship of the characteristic parameters to the mechanism and rate model development of fuel pyrolysis and char oxidation for biomass/coal blends under oxy-fired, high pressure conditions is explored.