Shape Characteristics of Non-Spherical Black Liquor Droplets, 2004 International Chemical Recovery Conference

The size and shape of droplets sprayed into the furnace of a recovery boiler have a paramount effect on the combustion and flight-path characteristics of black liquor droplets. This study presents a method to analyze black liquor particle shapes and experimental data obtained with industrial scale splashplate nozzles. A large number of particle shape characteristics were studied and a few were chosen for detailed study. From the view point of heat and mass transfer connected to drying and combustion, the most relevant droplet characteristic is the ratio of volume and surface. Sauter mean diameter is the most important property of the overall spray in this context. Depending on the spraying practice the Sauter mean diameter was between 3.6 mm and 7.7 mm. From the view point of droplet trajectory the aspect ratio and sphericity were found to be the most important factors. The average value of aspect ratio in nine test cases varied between 3.3 and 4.0. Average sphericity was almost constant, from 0.85 to 0.89.