CFD Model of Particle Agglomeration in Spray Drying

Abstract

A 3D CFD model of the agglomeration of droplets and particles in a counter-current spray drying process was developed and verified. An original discrete phase model was elaborated, with an agglomeration module taking into account hydrodynamic segregation of particles, droplet coalescence and droplet shrinkage, for accurate calculations of mass balance of the discrete phase. The characteristic drying curves were applied to the model of particle moisture evaporation, which included the coupling of particle agglomeration with heat, mass and momentum transfer between the discrete and continuous phases. Two agglomeration zones were observed in the tower: wet particle agglomeration in the atomization zone, and "dry agglomeration" above the air inlets, due to the intensive mixing of particle streams. A comparison of the calculated particle size distributions and experimental data obtained from particle dynamics analysis (PDA) measurements proves the accuracy of the developed methodology. The elaborated model allows the final PSD of the powder in the spray towers to be predicted.

CFD modeling of a pilot-scale countercurrent spray drying tower for the manufacture of detergent powder

“…Jaskulski et al [34] carried out experimental and three-dimensional, steady-state CFD study of spray drying of maltodentrin solution (50% wt/wt) in a pilot-scale counter-current tower having a height of 8 m and diameter of 0.5 m. Experiments were carried out at different gas to feed ratios to assess the influence of operating conditions on the level of agglomeration and the gas temperature profile. The Reynolds stress turbulence (RST) model for was used.…”

“…Although in a few studies [31,34] these processes were modelled using the stochastic approach of Sommerfeld [36] , the predicted particle size distribution in this approach is sensitive to the number of parcels used in particle tracking as well as the CFD mesh size.…”

“…A review of these studies carried out until 2010 can be found in [29]. In contrast, comprehensive CFD modeling studies of spray drying in counter-current towers, which is the subject of this paper, are scarce despite many industrial applications [8,[30][31][32][33][34] . It is a poorly understood process compared with that in co-current towers [35] .…”

Three-dimensional computational fluid dynamics (CFD) study of the gas–particle circulation pattern within a fluidized bed granulator: By full factorial design of fluidization velocity and particle size

“…Recently, computational fluid dynamics (CFD) has emerged as an effective tool for investigating gas-particle fluidized bed hydrodynamics. In literature, CFD has been widely applied for modeling multiphase flow of wet granulation process to reduce 6 the design time and cost [26][27][28][29][30][31][32][33][34][35]. In general, two different approaches of CFD modelling are used to model a gas-solid fluizied bed: the Eulerian-Eulerian approach, in which all phases are considered as interpenetrating continua and the Eulerian-Lagrangian approach in which at least one phase is considered as a discrete phase interacting with the other phases [30,[36][37][38][39][40][41][42][43].…”

CFD model-supported design of monodisperse co-current spray dryers

“…In some production processes full control of the size of particles in the dried powder is required. For this reason CFD simulations are used to identify theoretically regions where agglomeration can take place [6] or to predict final particle size distribution in the product [7]. In food industry, like skimmed milk powder production, it is also necessary to take into account influence of process parameters on product quality.…”