Abstract
Particle size is a key quality parameter of a powder detergent as it determines its performance, the bulk density and the look and feel of the product. Consequently, it is essential that particle size is controlled to ensure the consistency of performance when comparing new formulations. The majority of study reported in the literature relating to particle size control, focuses on the spray produced by the atomisation technique. One approach advocated to achieve particle size control is the manipulation of the ratio of the mass slurry rate and mass flow rate of gas used for atomisation. Within this study, ratio control was compared with an automatic cascade loop approach using online measurements of the powder particle size on a small-scale pilot plant. It was concluded that cascade control of the mean particle size, based on manipulating the mass flow rate of gas, resulted in tighter, more responsive control. The effect of a ratio change varied with different formulations and different slurry rates. Furthermore, changes in slurry rate caused complications, as the impact on particle size growth in the dryer is non-linear and difficult to predict. The cascade loop enables further study into the effect of particle size on detergent performance.
Highlights
In the manufacture of detergents, spray drying provides a rapid method to disperse slurry into liquid droplets and produce a dried powdered product
The drying efficiency, packing and porosity of the powder are dependent on the particle size distribution (PSD) making it a key quality parameter of the powder detergent
Following on from this research carried out with two-fluid nozzle configurations, the research in this paper considers the most appropriate methodology to control the PSD from a spray dryer for complex detergent slurries
Summary
In the manufacture of detergents, spray drying provides a rapid method to disperse slurry into liquid droplets and produce a dried powdered product. To understand the spray drying process, knowledge of a number of fundamental aspects of chemical engineering is required including fluid mechanics, mass and heat transfer, reactor engineering, particle technology and material sciences [1]. The particle size distribution (PSD) plays a critical role in all aspects of the drying process, with the distribution determining the contact surface area for heat and mass transfer, and the settling velocity helping determine the residence time and the level of solid–liquid separation in the droplets [2]. The drying efficiency, packing and porosity of the powder are dependent on the PSD making it a key quality parameter of the powder detergent
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