Some fundamental aspects of spray drying

Abstract

Abstract Equations are proposed to predict the three‐dimensional motion of droplets in a spray dryer, based on a knowledge of the characteristics of the atomizing device and of the gas flow patterns in the drying chamber. If the droplet size distribution produced by the atomizing device is known or can be assumed, the trajectories of the droplets can be calculated throughout the drying process and hence the evaporative capacity and thermal efficiency of the spray dryer can be predicted. Experimental verification of this theoretical approach was obtained from a study of the drying of calcium lignosulfonate solutions of various concentrations in a 122‐cm diam. × 183‐cm high laboratory circular concurrent chamber with a conical bottom where the drying air was introduced tangentially near the top. An experimental study of the effects of a number of operating variables on the capacity and the efficiency of the spray dryer was also carried out. These effects were interpreted in terms of the droplet trajectories obtained in each case.