Analysis of Gas Admixing Foam Spray–Drying Process

Abstract

Extensive experiments and critical literature analysis on the foam spray–drying process to estimate the effects of feed foaming on drying kinetics and spray hydrodynamics are presented in the article. The foam spray–drying experiments were carried out in a cocurrent tower equipped with a Sizing Master Shadow (LaVision, Gottingen, Germany) system used to determine particle size distribution, velocity, and shape of particles in the cross section of spray. Local and average drying agent temperature and humidity as well as changes in moisture content and temperature of the discrete phase were measured by a microseparator. A slight effect of feed foaming on the kinetics of the spray-drying process and spray hydrodynamics for all admixed gas flow rates was observed. Experimental results confirmed the effect of feed foaming on final product properties; e.g., an increase of Sauter mean diameter and porosity of the product and decrease of bulk density, tap density, and apparent density at higher foaming gas rates. The study proves that selected physical properties of foam spray–dried products can be controlled as a function of drying conditions and the ratio of foaming gas to drying agent rates.