Impact attrition of spray-dried burkeite particles

Abstract

Particle attrition in manufacturing plants handling particulate solids could cause processing as well as environmental problems, and lead to the degradation of product quality. Spray-dried powders are particularly prone to attrition because of their porous and often weak structure. Spray-dried burkeite particles are a good example and have been used as a model porous powder to investigate the effect of structure on their breakage propensity. The particles are subjected to well-defined stresses due to impact, and the change in the particle size distribution is determined by particle size analysis based on sieving. It is found that impact breakage of burkeite is affected by the structure, and some unexpected trends for breakage are observed; for a given impact velocity some smaller particle sizes break to a greater extent as compared with larger particles. This is attributed to uncontrollable variations of porosity (and hence particle envelope density) as a function of size. To study the effect of porosity on attrition of the spray-dried powders, structure visualisation and analysis have been carried out by Scanning Electron Microscope (SEM) and X-ray microtomography (XRT). SEM images show three levels of structure in a single particle of spray-dried burkeite. Based on the XRT results, the particle envelope density increases as particle size increases, and the variation of envelope density influences the impact breakage. Once the relevant values of the envelope density are taken into account, then the trend of impact breakage data becomes as expected, and the material mechanical properties of the particles can be inferred from the breakage results.

Impact breakage of acicular crystals

“…They observed that a unification of breakage data could be obtained when the relative change in the surface area was expressed as a function of particle size, density and velocity. Using the extent of breakage obtained from a single particle impact test, Bonakdar et al [27] had a similar observation for burkeite particles.…”

Coupling of abrasion attrition theory with mechanical characteristics for particle attrition in a fluidized bed reactor

“…The difference in experimental results is arisen from discrepancies in the particle structure among inconsistency size, giving rise in turn to variations in the physical properties. 4 It is concluded that increasing the circulation flow rate increased the tendency of particle attrition. With increasing circulation flow rate, the kinetic energy increases and hence is more likely to exceed the critical inherent strength of the particle.…”

“…In addition, the large amount of fine debris produced by attrition process will, fouling equipment, lead to reduced process efficiency. 4 Not only that, but the attrition also has harmful effects on the process operating conditions of crystallizer or reactor because of the changes in particle mechanical properties such as particle size distribution, roughness, hardness, and shape. 5 It would reduce the fractured strength of particle and induce more irrecoverable deformation.…”

“…For example, attrition can cause many problems such as cumulative mass losses of debris, which significantly effects the product quality. In addition, the large amount of fine debris produced by attrition process will, fouling equipment, lead to reduced process efficiency 4 . Not only that, but the attrition also has harmful effects on the process operating conditions of crystallizer or reactor because of the changes in particle mechanical properties such as particle size distribution, roughness, hardness, and shape 5 .…”

Effect of Structure on Strength of Agglomerates using Distinct Element Method

“…Agglomerates may be formed in various ways and their mechanical strength depends on many factors due to the degree of freedom afforded by the primary particles. Weak agglomerates formed for example by spray-drying are prone to attrition, which has adverse effects on product quality, ability to process, dust formation and explosion hazards [1]. Therefore it is highly desirable to develop predictive ability for agglomerate breakage.…”