Impact of physical properties of coal slurry droplets on their interaction with coal particles

The use of alternative slurry fuels is a well-known approach to reducing hazardous emissions during combustion without a significant decrease in efficiency. Very little is currently known about the behavior of fuel droplets colliding with wall and with each other. It is important to understand these collisions to predict the processes characteristics during the spraying and subsequent combustion of a slurry fuel in a boiler furnace. Experiments into the collisions characteristics of coal-water slurry droplets were conducted, when varying the viscosity, density and surface tension of the slurry containing different sizes solid coal particles. The rheological characteristics of the slurry were varied by using such additives as transformer oil, neonol, emulsifier D_cD, Tween-20 and Tween-80. The use of surfactants was found to reduce the critical resultant velocity of a droplet sufficient for its breakup. The obtained data were compared with earlier findings. It was established that the fuel compositions are non-Newtonian fluids that demonstrate different secondary atomization characteristics. Nevertheless, droplet-particle interaction regimes tended to be very similar, which is accounted for by inhomogeneity of liquids. A chart was also produced to illustrate the use of identified specific aspects of interaction of slurry droplets with solid particles in thermal engineering applications.