(447d) Calibration of a CFD-DEM Fluidised Bed Simulation for Plastic Recycling Using Positron Emission Particle Tracking

Industrial-scale plastic recycling using pyrolysis in fluidised beds is an emerging technology aiming to address the ever growing plastic waste crisis. Whilst we developed a basic understanding of fluidised beds with a single solid phase, such as the fluid catalytic cracking in modern oil-refineries which have been used for decades, binary systems which introduce a non-identical second solid species often lead to difficulties in reactor design. Uneven particle distributions, segregation and hot-spots lead to not only product issues but also safety issues which need to be understood and removed.

The Discrete Element Method (DEM) does, when calibrated properly, reproduce the behaviour of moving granular material very well. Coupled with the well developed computational fluid dynamics (CFD) it provides a powerful tool in predicting the behaviour of a fluidised granular system such as fluidised beds.
These systems however need to be calibrated and even though the conventional techniques of calibration for DEM models such as shear cells or angle of repose measurements can lead to quantitative granular properties, the characterisation and calibration of the fluid phase is currently much less precise.

We use positron emission particle tracking, a Lagrangian particle tracking technique, to directly compare coupled DEM-CFD simulations of fluidised beds with real world fluidised beds. The rich, high-resolution data yielded by PEPT allows us to fine tune drag models and particle parameters in a significantly more precise manner than is possible using conventional measurements such as pressure drop alone.