Influence of particle attrition on erosive wear of bends in dilute phase pneumatic conveying

Bulk materials like sand particle/alumina, which do not possess good air retention properties or high permeability are generally conveyed in the dilute phase, suspension flow in conventional pneumatic conveying systems. High inlet conveying air velocity is thus necessary to successfully convey such materials. As a result of high air velocity, the particles impact on the bend surface and cause erosion of bends and attrition of particles. The study of bend erosion has been a subject of research for a long time and the influence of various operating parameters has been widely investigated. The authors have carried out an extensive experimental plan to study the influence of recirculation of material on the erosion of bends and attrition of particles. It is expected that the severity of erosion may go down as the particles lose sharp edges due to the recirculation of material. Silica sand having a mean particle size of 435 mu m was conveyed in the pneumatic conveying pilot plant. The pipeline test loop is 48 m long and 67 mm bore. The bends were placed in horizontal-horizontal orientation with R/d ratio of 4.0. The solid particle erosion behavior of three test bends (B1, B2 and B3) and particle attrition have been analyzed. A 300 kg batch of sand was recirculated 29 times through the test pipeline, thus conveying a total of 8.7 tonnes. The mass loss and bend wall thickness were regularly monitored. Material sample during each run was collected to assess the extent of particle attrition and changes in the particle morphology. This paper presents the experimental results of a comprehensive analysis of the erosion and particle degradation with a change in particle morphology. A correlation has been developed between the extent of material recirculated through the test pipeline and its influence on the erosion of bends and degradation of particles.