Combustion dynamics of droplets of aqueous slurries based on coal slime and waste oil

Abstract

This paper shows the analysis of burnout characteristics of droplets of the following slurry fuels: (i) based on coal slime with or without the addition of waste turbine oil; (ii) based on coal dust with or without the addition of waste turbine oil. The oil share in the mixtures varied from 0% to 15%. The solid component share varied in the range of 40–60%. Single droplets with an initial size of 1–5 mm were burned in a tubular muffle furnace at temperatures of 700–900 °C. The inertia of gas-phase and heterogeneous ignition and the combustion time of mixtures were estimated. Based on experimental data, the values of the linear and mass burnout rates of fuel droplets were calculated. At a furnace temperature of less than 800 °C, the characteristics of ignition and burnout of droplets of water-containing fuel mixtures and solid particles deteriorated significantly. The most preferred is the combustion of coal slime in the composition of aqueous slurry with the addition of high-reactive components (for example, waste oil of petroleum origin or vegetable oils). To intensify ignition and combustion, it is recommended to use no more than 50% of the solid component in the mixture. The maximum linear burnout rate was typical for droplets about 3 mm in size and reached values of 0.5–0.6 mm2/s. The mass burnout rates of droplets of the investigated fuels with a size of 5 mm varied in the range of 0.0005–0.0018 g/s.