Experimental study of the temperature distribution and water evaporation in an axial dual-zone vortex chamber spray dryer

Abstract

The use of an axial dual-zone vortex chamber for spray drying applications is experimentally studied, focusing on water spray evaporation. In the hot zone of the vortex chamber, hot air (maximum 300 °C) is fed; in the cold zone, mild temperature (80 °C) air. The spray nozzle is installed in the hot feed air zone, in the cylindrical wall of the vortex chamber and injects the water radially toward the center line of the chamber. In spray drying applications, the generated flow and temperature field should allow a fast initial drying of the droplets in the hot zone, followed by rapid evacuation of the particles that are formed to the cold zone where final drying takes place and particles can be evacuated. A slightly different design of the hot and cold zone vortex chambers aims at intensifying the axial motion. Experiments with detailed temperature measurements during dry operation and with injection of a water spray are combined to gain insight in the spray penetration and deflection, the motion of the hot and cold air in the vortex chamber and the resulting temperature profile, and water evaporation and its effect on the temperature profile. A two-fluid nozzle is used and the influence of the hot air inlet temperature, the air flow rate, the water flow rate and the droplet size studied, as well on the temperature profile as on the evaporation capacity. The experimental data allow a first evaluation of the concept.