Model-based measurement and control of fluidised bed spray granulation processes

Magdeburg, Univ., Fak. für Verfahrens- und Systemtechnik, Diss., 2012von Andreas Büc

Conservative Finite Volume Schemes for Multidimensional Fragmentation Problems

In this article, a new numerical scheme for the solution of the multidimensional fragmentation problem is presented. It is the first that uses the conservative form of the multidimensional problem. The idea to apply the finite volume scheme for solving one-dimensional linear fragmentation problems is extended over a generalized multidimensional setup. The derivation is given in detail for two-dimensional and three-dimensional problems; an outline for the extension to higher dimensions is also presented. Additionally, the existing one-dimensional finite volume scheme for solving conservative one-dimensional multi-fragmentation equation is extended to solve multidimensional problems. The accuracy and efficiency of both proposed schemes is analyzed for several test problems

Multi-zone & multi-compartment model for dynamic simulation of horizontal fluidized bed granulator

[EN] Due to the ongoing development and implementation of process control and observation techniques in production processes of particulate products, the research on complexly designed process apparatuses has become of great interest. The work presented in this paper is focused on a model-based study on a multi-chamber horizontal fluidized bed apparatus for fluidized bed layering granulation. The model for the solid phase is extended by a new drying model. Because of the great variety of parameters that influence this complex system a preliminary model-based study on a simplified setup shall show which construction or process parameters influence the product quality.Financial support for this research from German Research Foundation (DFG) as part of the SPP project DynSim 1679 is gratefully acknowledged.Mielke, L.; Bück, A.; Tsotsas, E. (2018). Multi-zone & multi-compartment model for dynamic simulation of horizontal fluidized bed granulator. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 123-130. https://doi.org/10.4995/IDS2018.2018.7474OCS12313

Microwave drying of wet clay with intermittent heating

In this article, we study an alternative process for the conservative drying of wet clay based on combined microwave heating and convective drying. The study is founded on an experimental analysis of the processes that control drying of porous matter in presence of temperature gradients. We show and discuss that process control cannot be reliably based on temperature alone because mass transfer phenomena associated with microwave heating dictate drying kinetics. Essentially, the occurrence of pressure build up and liquid expulsion, dominating mass transfer if microwave heating is uncontrolled or with high power, vitally depend on the moisture content of the clay. As a consequence, the deterioration of clay is problematic if internal evaporation rates are high, thus at the start of drying when also the moisture content is high. Following this, we propose intermittent microwave heating in combination with convective drying periods with the aim to reduce overall drying time (compared to conventional convective drying) and to improve product quality by reduced material shrinkage. Drying experiments indicate that the overall drying time reduction and product quality depend on the frequency and duration of the two subsequent periods of intermittent heating and convective drying. The observations can be explained with the evolution of the pore-scale distribution of liquid and vapor during drying

Robust feedback control of continuously operated convective dryers for particulate materials

[EN] Convective drying is a common process for the treatment of particulate solids also operated in continuous mode. Continuous operation is characterised by operation in steady-state with constant product throughput and constant product quality. Due to external influences, i.e. seasonal or local variations in the properties of the initial wet material, deviations in the product quality can result, for example over- or under-drying, or on-set of unwanted reaction. In this contribution a new feedback control concept is developed that is robust with respect to variations and uncertainties in the drying kinetics of the material and can reject and attenuate process disturbances.Seidel, C.; Neugebauer, C.; Dürr, R.; Bück, A. (2018). Robust feedback control of continuously operated convective dryers for particulate materials. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 83-90. https://doi.org/10.4995/IDS2018.2018.7245OCS839

Modeling of Particle Behavior in a Wurster Fluidized Bed: Coupling CFD-DEM with Monte Carlo

[EN] CFD-DEM approach is applied to investigate circulation motion of particles in a mono-disperse system under both dry and wetting conditions. Good agreement between simulation results and measurement data is observed, in terms of cycle time and residence time in dry condition. The deposition of droplets on the particle surface is modeled by a Monte Carlo approach. The influence of cohesion forces on the macroscopic particle circulation is discussed. In addition, information about coating coverage, the layer thickness and particle size distribution can be predicted by this integrating approach.The authors gratefully acknowledge the funding of this work by the German Federal Ministry of Science and Education (BMBF) as a part of the InnoProfileTransfer project NaWiTec (03IPT701X).Jiang, Z.; Rieck, C.; Bück, A.; Tsotsas, E. (2018). Modeling of Particle Behavior in a Wurster Fluidized Bed: Coupling CFD-DEM with Monte Carlo. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 205-212. https://doi.org/10.4995/IDS2018.2018.7239OCS20521

Drying of sugarcane bagasse in a partially filled horizontal drum

[EN] One-phase model have been reported to describing the simultaneous heat and mass transfer in a horizontal drum partially filled by sugarcane bagasse with attention to the loss of water promoted by the increase of temperature. Mass and energy balances were written in MatLab language and solved by finite difference method. Predicted temporal and spatial profiles of moisture content and temperature are shown. Experimental tests were carried out in a horizontal drum and the temporal profiles were obtained. Great adjustments between experimental and predicted data were observed, indicating that the model is able to describe the transport phenomena in this system.Tada, É.; Bück, A.; Casciatori, F.; Thoméo, J. (2018). Drying of sugarcane bagasse in a partially filled horizontal drum. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 497-504. https://doi.org/10.4995/IDS2018.2018.7827OCS49750

The Effect of the Presence of Very Cohesive Geldart C Ultra-Fine Particles on the Fluidization of Geldart A Fine Particle Beds

The effect of the presence of ultra-fines (d < 10 μm) on the fluidization of a bed containing fine particles (d < 100 μm), is the subject of this paper. Practically, it can happen due to breakage or surface abrasion of the fine particles in some processes which totally changes the size distribution and also fluidization behaviour. The materials used in this study are both ground calcium carbonate (GCC); fine is CALCIT MVT 100 (Geldart’s group A) and ultra-fine is CALCIT MX 10 (group C). The experimental results for different binary mixtures of these materials (ultra-fines have 30%, 50%, or 68% of the total mixture weight) show that the physical properties of the mixtures are close to those of pure ultra-fine powders. Using mean values of the bed pressure drop calculated from several independent repetitions, the fluidization behaviour of different mixtures are compared and discussed. The fluidization behaviour of the mixtures is non-reproducible and includes cracking, channelling and agglomeration (like for pure ultra-fine powders). Increasing the portion of ultra-fine materials in the mixture causes a delay in starting partial fluidization, an increase in the bed pressure drop as well as a delay in reaching the peak point

Eulerian Multiphase Simulation of the Particle Dynamics in a Fluidized Bed Opposed Gas Jet Mill

The compressible and turbulent gas–solid multiphase flow inside a fluidized bed opposed jet mill was systematically investigated through numerical simulations using the Euler–Euler approach along with the kinetic theory of granular flow and frictional models. The solid holdup and nozzle inlet air velocity effects on the gas–solid dynamics were assessed through a detailed analysis of the time-averaged volume fraction, the time-averaged velocity, the time-averaged streamlines, and the time-averaged vector field distributions of both phases. The simulated results were compared with the experimental observations available in the literature. The numerical simulations contributed to a better understanding of the particle–flow dynamics in a fluidized bed opposed gas jet mill which are of fundamental importance for the milling process performance

Spray Printing of Porous Substrates from Nanosuspensions

In this work, we present and characterise an experimental setup that allows the generation of porous packings from nanosuspensions. By defined positioning and drying of solid-containing droplets, large-scale porous structures can be generated. Examples of such structures are shown and characterised. Operational challenges are presented, and it is discussed how they can be overcome to allow the maximum degree of freedom in packing generation