Maksym Dosta

Influence of Feed Composition and Drying Parameters on the Surface Composition of a Spray-Dried Multicomponent Particle

Surface properties of multicomponent particles produced in spray drying can be controlled by selective accumulation of specific components, which are present in the liquid feed, on the particle surface. Such modification of the surface composition can take place only before a solid shell forms on the particle surface. In this contribution, the influence of the concentration of surface active component on modifications of the surface composition is discussed. Based on results of single-droplet drying simulations, changes in the concentration of the surface active component at the solution-air interface are related to the composition of spray-dried particles.

Development of a multi-compartment population balance model for high-shear wet granulation with discrete element method

Abstract This paper presents a multi-compartment population balance model for wet granulation coupled with DEM (discrete element method) simulations. Methodologies are developed to extract relevant data from the DEM simulations to inform the population balance model. First, compartmental residence times are calculated for the population balance model from DEM. Then, a suitable collision kernel is chosen for the population balance model based on particle–particle collision frequencies extracted from DEM. It is found that the population balance model is able to predict the trends exhibited by the experimental size and porosity distributions by utilising the information provided by the DEM simulations.

Identification of micro parameters for discrete element simulation of agglomerates

The mechanical behaviour of solid particles like agglomerates, granules or crystals strongly depends on their micro structure, e.g. structural defects and porosity. In order to model the mechanical behaviour of these inhomogeneous media the discrete element method has been proven to be an appropriate tool. The model parameters used are typically micro parameters like bond stiffness, particle-particle contact stiffness, strength of the bonds. Due to the lack of general methods for a direct micro parameter determination, normally laborious parameter adaptation has to be done in order to fit experiment and simulation. In this contribution a systematic and automatic way for parameter adaptation using real experiments is proposed. Due to the fact, that discrete element models are typically systems of differential equations of very high order, gradient based methods are not suitable. Hence, the focus will be on derivative free methods.

Numerical estimation of the restitution coefficient for dry and wet agglomerates

In this contribution a novel simulation tool, which is able to predict the agglomerate deformation and breakage during different loading conditions, was developed. This simulation system is based on the Discrete Element Method (DEM). For a better understanding of the soft, non-elastic deformation behaviour of wet and dry agglomerates, the models of liquid and solid bridges have been implemented in the DEM to perform a detailed simulation. As a result, the dependency of the restitution coefficient on the viscosity of the binder, impact velocity and agglomerate size and shape were obtained.

Photonic glass for high contrast structural color

Non-iridescent structural colors based on disordered arrangement of monodisperse spherical particles, also called photonic glass, show low color saturation due to gradual transition in the reflectivity spectrum. No significant improvement is usually expected from particles optimization, as Mie resonances are broad for small dielectric particles with moderate refractive index. Moreover, the short range order of a photonic glass alone is also insufficient to cause sharp spectral features. We show here, that the combination of a well-chosen particle geometry with the short range order of a photonic glass has strong synergetic effects. Using a first-order approximation and an Ewald sphere construction the reflectivity of such structures can be related to the Fourier transform of the permittivity distribution. The Fourier transform required for a highly saturated color can be achieved by tailoring the substructure of the motif. We show that this can be obtained by choosing core-shell particles with a non-monotonous refractive index distribution from the center of the particle through the shell and into the background material. The first-order theoretical predictions are confirmed by numerical simulations.

Copula-based approximation of particle breakage as link between DEM and PBM

Abstract In process engineering, the breakage behavior of particles is needed for the modeling and optimization of comminution processes. A popular tool to describe (dynamic) processes is population balance modeling (PBM), which captures the statistical distribution of particle properties and their evolution over time. It has been suggested previously to split up the description of breakage into a machine function (modeling of loading conditions) and a material function (modeling of particle response to mechanical stress). Based on this idea, we present a mathematical formulation of machine and material functions and a general approach to compute them. Both functions are modeled using multivariate probability distributions, where in particular so-called copulas are helpful. These can be fitted to data obtained by the discrete element method (DEM). In this paper, we describe the proposed copula-based breakage model, and we construct such a model for an artificial dataset that allows to evaluate the prediction quality.

Novel multiscale simulation environment for modeling of fluidized bed granulation

In this contribution the architecture of a novel simulation environment, which has been developedfor the multiscale modeling of fluidized bed spray granulation, is presented. The novel environment describes the granulation process on four different time and length scales. On the one hand, it allows to predict dynamics of the global production process, whereby, on the other hand, material properties can be considered.

Energetic Aspects of Granule Impact: Influence of the Liquid Layers

The influence of the thickness (40 μm–1 mm) and the viscosity (1–300 mPa⋅s) of the liquid layer at the contact as well as impact velocity (1–2.4 m/s) on the energy dissipation during the normal impact of spherical granules was investigated. Using a free‐fall device the restitution coefficients of γ‐Al2O3 granules impacted on a steel wall with a liquid layer were measured. With increasing liquid viscosity the restitution coefficient and the critical thickness of liquid layer at which the granule sticks decreased. With decreasing impact velocity the restitution coefficient greatly decreases. A rational explanation of obtained effects was given by results of numerically solved force and energy balances.