(8a) Validation of CFD-DEM Simulation of a Continuous Tablet Coating Process

Tablet coating is a widely used unit operation in the pharmaceutical industry. Traditionally, large-scale drum coater systems are loaded with hundreds of kilos of tablets and rotate at relatively low rotation rates (Fr<<1). This leads to several hours of batch processing in order to obtain sufficient coating uniformity. The ConsiGma^TM coater from GEA is a tablet coater which can be integrated into the GEA ConsiGma^TM continuous process line. The ConsiGma^TM Coater operates with low drum loads (3-7 kg) but very high rotation rates (Fr~1) leading to much shorter cycle times in the range of a few minutes. To achieve better coating results the tablets are jetted away from the rotating drum wall by so-called air knives in order to form a stable, gravity-free cascade. This air flow needs to be considered in a simulation model to accurately predict the coating process in the ConsiGma^TM coater. Depending on the desired throughput rates there are three interchangeable sizes of the GEA ConsiGma^TM Coaters.Interchangable means that the drum wheel of the next smaller drum will also fit and operate in the next larger housing (80/160mm or 160/320mm).

In this work we present a model to simulate the coating process in the ConsiGma^TM 160 mm and 320 mm coater using CFD-DEM. The eXtended Particle System (XPS) is used for the DEM simulation and is coupled to AVL Fire® for the CFD¹. The validity of the simulation results, as well as our method for modeling the non-sphericity of the tablets, are shown. The simulations are compared to experimental results, including the quantitative comparisons of the tablet flow and bed shape, as well as coating-related parameters, such as average coating mass on the tablets, standard deviation and coefficient of variation.

This work was funded through the Austrian COMET Program by the Austrian Federal Ministry of Transport, Innovation and Technology (BMVIT), the Austrian Federal Ministry of Economy, Family and Youth (BMWFJ) and by the State of Styria (Styrian Funding Agency SFG).

References

1. Jajcevic D, Siegmann E, Radeke C, Khinast JG. Large-scale CFD–DEM simulations of fluidized granular systems. Chem Eng Sci. 2013;98:298-310. doi:10.1016/j.ces.2013.05.014.