Breakage of Catalyst Carrier Particles

Principal Investigator: Prof. M. Ghadiri
Co-Investigator(s): Dr C. Couroyer
Sponsor: Institut Français du Pétrole and Rhodia
Status: Completed (Sept. 1996 - 2000)

Abstract

The objective of this project is to investigate the mechanisms of breakage of porous alumina particles used as catalyst carrier beads. These particles often experience mechanical stresses in large scale industrial operations, for example in reactors. The stresses can be sufficiently high to cause fragmentation and surface damage of the catalyst particles. The small fragments and fines which are generated in this way can segregate and accumulate in slow moving regions, causing difficulties in the process operations. For a reliable operation of reactors it is necessary to quantify the extent of breakage, to specify the factors that define the particle strength and to improve the resistance to degradation.

A variety of techniques is used to evaluate particle breakage. These are single particle impact, side crushing, bulk crushing, shear deformation and indentation fracture.

The two pictures in Figure 1 show porous spherical alumina particles and two broken ones after 5 impacts at 908 on a sapphire target at about 10 m s-1. The particle size range of these particles is 1.7 - 2.0 mm.

The production method determines the properties of the beads such as composition and size and volume of their pores. In this work the influence of the production method on the mechanical strength of the particles is under investigation.

The bulk breakage behaviour is analysed by Distinct Element Method using the TRUBAL code developed by Cundall and Strack (1979). The side crushing strength distribution measured experimentally and material properties such as the yield stress, Young's modulus, Poisson's ratio and coefficient of friction are input into the TRUBAL code. The analysis of bulk behaviour provides information on the extent of breakage under different levels of normal loads and on the particle system such as contact forces and strength distribution of the fragmented particles. The predictions of the bulk behaviour are compared with the experimental results obtained by bulk crushing and shearing tests.

The two pictures in Figure 2 show an assembly of 2000 particles before and after applying a pressure of 2 MPa. To visualise the extent of breakage each ball is given a grey density level which is representing the extent of damage of the balls: white for undamaged particles, grey for particles with surface damage, black for broken particles. In this particular test almost all the particles experience surface damage and a few are broken. The broken particles are shown on top of the bed.

Publications

Couroyer, C., Ning, Z. and Ghadiri, M. (1998) "Bulk Crushing Behaviour of Porous Alumina Particles under Compressive Loading". World Congress on Particle Technology 3, Brighton, UK, 7-9 July. paper 61.

Couroyer, C., Ning, Z., Ghadiri, M., Brunard N., Kolenda, K., Bortzmeyer, D. and Laval P. (1998) "Breakage of Macroporous Alumina Beads under Compressive Loading: Simulation and Experimental Validation". European Symposium on Comminution 9, Albi, France, 8-10 September, Vol. 1, pp 89-98.