Liquid atomization is a largely widespread unit operation. The disintegration of a liquid into droplets depends on the nature of the nozzle, on the process parameters as well as physicochemical characteristics of the fluid. The aim of this work is to study the contribution of the process (liquid outlet speed and air pressure) and physicochemical (viscosity and surface tension) factors on the size distribution of droplets generated by single- and two-fluid flat spray nozzles. The obtained droplet median diameters which range between 77 and 594 mu m for the single-fluid nozzle and between 11 and 599 mu m for the two-fluid nozzle, are discussed in relation with operating conditions of atomization process. Dimensional analysis was performed as a modeling approach. Despite energy input for the droplet formation is known to be influenced by different origins according to single and two-fluid nozzles, it is shown that a unique correlation, with specific values of parameters for each nozzle type, gathers all the parameters affecting droplet size. In the range of process and formulation parameters tested, this correlation is validated and gives satisfactory agreement for the single- and two-fluid nozzles

Carcel Carrión, JA.; Dumoulin, E. (2013). Milk powder agglomerate growth and properties in fluidized bed agglomeration. Dairy Science and Technology. 93(4-5):523-535. doi:10.1007/s13594-013-0132-7.Milk powder agglomerate growth and properties in fluidized bed agglomerationAbstract Fluidized bed agglomeration is used to produce large and porous dry agglomerates with improved instant properties. Water (or binder solution) is sprayed in the fluidized bed of particles to render their surface sticky. The agglomerate growth results from the repetition of different steps (wetting of the particle surface, particles collision and bridging, and drying) and depends on the processing conditions and product properties. In this work, skim and whole milk powders were fluidized in hot air and agglomerated by spraying water in a bench-scale batch fluidized bed. The aim was to study the impact of the sprayed water flow rate (0-5.5 g.min − 1 ), particle load (300-400 g), initial particle size (200-350 μm), and composition (skim-whole milk) on the growth mechanisms and on the properties of the agglomerates obtained. Powder samples were regularly taken in the fluidized bed during agglomeration and characterized for the size, size distribution, and water content. Whatever the conditions tested, the size increase and the evolution of the particle size distribution during agglomeration were found to mainly depend on the relative amount of water sprayed in the particle bed. Agglomeration occurred in two stages, with first the rapid association of initial particles into intermediate structures, and second, the progressive growth of porous agglomerates. In any case, agglomeration allowed improving instant properties of the milk powder.

No abstract