Attrition of granular solids in a shear cell

Bulk particulate solids subjected to compression and shearing may experience attrition and segregation of the debris which can cause amongst others dust hazards, difficulty in material handling and ‘off-specification’ products. This paper presents an experimental investigation on attrition of granular catalyst particles in an annular shear cell. By examining various models of attrition reported in the literature, we find that the model proposed by Neil and Bridgwater unifies our experimental data satisfactorily for the fine debris. The mass fraction of the fines produced can be described by a function of the normal stress, σ, and the shear strain, Γ, in the form of σΓφ, where φ is a power law exponent. However, when the whole attrition products, including fine debris, coarse fragments and non-spherical particles, are considered, the trend of the experimental data does not satisfactorily follow Neil and Bridgwater's model. This implies that the process of particle fragmentation is not adequately described by this model. The experimental results also suggest that, if the normal stress is above a certain level, there exists a period at the initial stage of shearing, during which body fragmentation plays a significant role in particle breaking with the surface damage occurring to a lesser extent in the process. A theoretical analysis of the process has been carried out and will be reported later in another paper, where the two processes of surface damage and particle fragmentation are quantified and decoupled by the use of the distinct element analysis.

[1]  D. M. Walker,et al.  An annular shear cell for granular materials , 1968 .

[2]  J. Novosad,et al.  Studies on granular materials. II. Apparatus for measuring the dynamic angle of internal and external friction of granular materials , 1964 .

[3]  J. Bridgwater,et al.  Attribution of solids—I: Cell Development , 1983 .

[4]  C.E.D. Ouwerkerk,et al.  A micro-mechanical connection between the single-particle strength and the bulk strength of random packings of spherical particles , 1991 .

[5]  J. Bridgwater,et al.  The mixing and segregation of cohesionless particulate materials part II. Microscopic mechanisms for particles differing in size , 1978 .

[6]  P. Laval,et al.  Methodology for Investigating the Mechanical Strength of Reforming Catalyst Beads , 2000 .

[7]  Alexander V. Potapov,et al.  Computer simulation of shear-induced particle attrition , 1997 .

[8]  J. Bridgwater,et al.  A review of attrition and attrition test methods , 1987 .

[9]  J. Bridgwater,et al.  The mixing and segregation of cohesionless particulate materials Part I. Failure zone formation , 1978 .

[10]  J. Bridgwater,et al.  Attrition of solids—II: Material behaviour and kinetics of attrition☆ , 1983 .

[11]  J. Bridgwater,et al.  Attrition of particulate solids under shear , 1994 .

[12]  Brian J. Briscoe,et al.  Tribology in Particulate Technology , 1987 .

[13]  B. Scarlett,et al.  A split ring annular shear cell for the determination of the shear strength of a powder , 1968 .

[14]  P. Cundall,et al.  A discrete numerical model for granular assemblies , 1979 .

[15]  J. E. Gwyn.  On the particle size distribution function and the attrition of cracking catalysts , 1969 .