Liquid Atomization Experiment on Pulse Combustion Spray Drying

Based on the discussing of atomizing mechanism, liquid atomization experiments were carried out in the tailpipe of a Helmholtz-type pulse combustor. An optical analyzer was used for measuring the mean diameters of atomized droplets and their distribution. The effects of liquid viscosity on atomized droplet size and size distribution were investigated and analyzed. The results indicated that the droplet-size distribution is approximately a normal distribution. The range of the droplets' Sauter mean diameter is between 53 and 76 μm. The pulsating gas flow from the pulse combustor can be used to atomize liquid or slurry without a nozzle, and the atomizing effect can meet the spray drying requirements.

I. Introduction

Aimed at nozzle clogging and damage of spray dryer, a pulse combustor was employed in the spray drying system offers a new approach for liquid atomization and drying. The pulse combustion spray dryer can atomize and dry liquid material using the unstable high temperature gas stream, which was generated by a pulse combustor. For the pulse combustion spray dryer, there is no need for any form of nozzle dispersion, and its atomization mechanisms differ from those of conventional atomizers, such as rotary atomizers, pressure and pneumatic nozzles. The unstable high temperature gas stream is characterized by oscillations with transient velocities of about ±100 m/s and frequencies from 20 to 150 Hz[1]. The enhanced mixing and transport processes lead to a high efficient moisture evaporation rate during pulsating spray drying. It has many advantages, such as efficient use of energy, a high heat and mass transfer rate, and simple structure of equipment[2].