RHEOLOGICAL STUDIES ON A SLURRY BIOFUEL TO AID IN EVALUATING ITS SUITABILITY AS A FUEL

Biomass is an often abundant, renewable, low ash and low sulfur fuel. Due to these properties, biofuels are promising alternatives for tradi tional petroleum-based fuel applications; however, traditional biofuel s for internal combustion engines are not cost competitive with gasoli ne, diesel or fuel oils. One method to reduce the cost of biofuels is to use slurry fuels which have a potential lower cost than liquid biof uels due to high conversion efficiencies. Slurry biofuels, such as a m ixture of corn and water, could provide a biofuel alternative for dies el engines, pressurized gasifiers and heating oil applications such as burners or gas turbines. Use of these biomass slurries poses importan t questions about their stability and suitability for practical applic ations in internal combustion engines and combustors. This work report s rheology data for stable corn-starch water slurries (CSWS) which use d a polyacrylic acid thickener to eliminate settling of the slurry and to provide desirable shear-thinning behavior for most of the composit ions evaluated. The effect of shear rate on the viscosity of the CSWS was studied using a BOHLIN-controlled stress (CS) rheometer. The well- known Ostwald-de Waele power law and Sisko models for viscosity fit th e data. The effect of corn starch content, thickener content and tempe rature on the viscosity of CSWS was also studied. The favorable shear thinning properties were observed for starch contents up to 45% starch and should aid pumping, injection and spraying. The lower heating val ues of the slurries, however, are undesirably low. (C) 1997 Elsevier S cience Ltd.