Rheological property and stability of coal-oil mixture fuel

Abstract

Coal-oil Mixture (COM) has been developed with the potential for substitution of fuel oil in the combustion equipment designed for fuel oil. The COM properties are strongly dependent on the characteristics of coal and the medium of suspensions. The rheological properties and stability of COM have been studied using subbituminous and bituminous coals in Thailand, light 1 fuel oil and heavy 6 fuel oil. Variables investigated are coal concentrations (10-50%), coal types, fuel oil types, temperature (40-80°C), particle size distribution (-75, 75-90 and 90-106 microns) and additive types. The COM is classified as a Newtonian fluid at low coal concentration and Bingham plastic model at high coal concentrations and had different yield stress for various types of coal and fuel oil. The COM viscosity is found to increase with coal concentration, increasing fuel oil viscosity, coal fineness: and decreasing temperature. In the study of COM stability using a sedimentation column, sedimentation ratio from the settling behavior of 25 wt% Ban Pu coal with 2 wt% Ethomeen C-20 in LFO and 30 wt% Ban Pu coal with 1 wt% Ethomeen C-20 in HFO are 0.61 and 0.49 respectively. This result led to interpretation of COM stability in terms of network stability rather than classical isolated colloidal particle stability. The screening shows that cationic additives are the most effective additives.