Ceramic particles are pelletized and fired to produce high porosity catalyst pellets of complex shapes.
These pellets fill cylindrical reactor columns with particulate packing structures that are key to the in-service performance, but will suffer breakages, which impact on catalyst performance.
The combined Finite-Discrete Element Method (FEMDEM) is ideally suited to capturing both the multi-body pellet interactions and pellet fracture and fragmentation.
A mechanical characterization of prismatic and cylindrical ceramic specimens has been undertaken.
Each set of specimens has been characterised by means of micro- and nano-indentations, ultrasonic and strength tests – i.e. three-point bending tests (bars) and Brazilian tests (cylinders). Standard laboratory rigs are generally too compliable for capturing the deformations of stiff and tiny ceramic specimens. For this reason, a novel digital image correlation methodology has been developed to obtain both strength and stiffness from three-point bending tests on alumina bars which would have been otherwise impossible.
FEMDEM numerical results have been compared to the corresponding experimental results (i.e. loading curves and displacements from digital image correlation analyses) to investigate the code capability to describe fracture in highly stiff and brittle porous media.
Consequently the code has been used to evaluate the pre- and post-fragmentation behaviour of complex shaped catalyst supports.
The FEMDEM code has been also used to simulate the deposition of cylindrical catalyst supports and other complex-shaped bodies in a cylindrical container. A post processing tool has been implemented to extrapolate the packing density profiles, packing structure, bulk porosity and orientation distributions of the resulting bodies making up the pack of pellets. The numerical results have then been compared with the corresponding experimental packing density profiles and orientation distributions published in the literature.