Comprehensive Investigation of Wet Powder Blending

Subject area
Powder technology; coating technology Keywords
Mixing; liquid distribution; wet powders; simulation Staff
Univ.-Prof. Dipl.-Ing. Dr.techn. Johannes Khinast
Ass.Prof. Dr.techn. Dipl.-Ing. Stefan Radl
MSc Bhageshvar Mohan
MSc Mingqiu Wu Duration
01. May 2012 - 30. April 2015

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Distribution of liquid on the surface of particles in a simple shear flow for two shearing speeds (dimensionless shear rate).

Description

Flow of highly saturated wet granular matter is encountered in a wide range of engineering applications, including chemical, pharmaceutical, and mechanical engineering, food processing and petroleum engineering. However, the detailed understanding, modeling and simulation of the effects stemming from the liquid bridges in these materials still pose significant challenges. The objective of the proposed work is the development of a new method to investigate wet granular flows in great detail. Specifically, we plan to (i) develop a numerical strategy to directly simulate wet agglomerates, even at high liquid saturation levels, (ii) build up an innovative experimental setup to validate our simulations, (iii) apply the developed methodology to relevant systems, and (iv) couple the results of our direct simulations with a relatively new method, i.e., the Discrete Element Method (DEM). In the first part of the proposed work we will adapt a state-of-the-art numerical strategy initially developed for gas-liquid multiphase flow. Our work will include the modeling of the solid-phase geometry, the accurate treatment of the dynamic contact angle and wetting dynamics, a detailed contact detection between solid particles and finally the modeling of the forces between particles in contact. With this adapted numerical method we will be able - for the first time - to simulate the flow of a liquid and a gaseous phase in moving complex granular matter. This will, for example, enable us to look at the details of the liquid distribution in sheared granular matter, which is essential for, e.g., granulation processes. In the second part we will construct an innovative experimental setup to investigate static as well as dynamic forces in a particle bed. Exact control of the relative distance and motion between the particles will be achieved using ultra-precise micromanipulators. The novelty of this setup is that we will be able to measure the forces between multiple particles, up to high saturation levels and under defined relative velocity. Also, we will use a shear cell to validate our simulation results for a large bed of particles. Furthermore, we will apply our method to study topics associated with wet granular matter, including the microscale simulation of granules, consolidation and liquefaction effects, mixing problems associated with wet granular matter, as well as the dissolution of tablets. Finally, we will connect our knowledge obtained from the detailed simulations with other simulation tools already in use by academia and industry. Specifically, it is our goal to develop models for the Discrete Element Method that predict the distribution of liquid bridges, as well as dynamic and static forces at high saturation levels. The results of the proposed work are expected to have significant impact on the use of simulations in many branches of science, like pharmaceutical engineering, geomechanics or petroleum engineering. Furthermore, significant fundamental knowledge will be gained during the application of the methodology in the area of granulation and drying, as well as tablet dissolution. This will be an important factor for the rational (opposed to the currently applied trial-and-error based) development of new drug delivery systems. FWF Project Number: P23617 Sponsored By
Austrian Science Foundation (FWF, www.fwf.ac.at)