Study of limestone particle impact attrition

Impact attrition of limestone particles was investigated at temperatures from 25 to 580∘C and 1 atm pressure. Impacts changed the particle size distribution and mean particle diameter significantly for conveying gas velocities of 20–100 m/s. With increasing temperature less attrition occurred due to a decrease in particle impact velocity and an increase in the threshold particle impact velocity. The activation energy for impact attrition was (-5.1)–(-5.4)kJ/mol. The mean limestone particle diameter decreased with increasing number of impacts and increasing impact velocity. Two empirical equations give good agreement with the experiments. Based on the experimental observations and correlations, an impact mechanism is suggested, where the area of new surface generated is proportional to the total kinetic energy consumed, to the number of impact cycles and an exponential decrease with temperature. When particles break, each particle generally splits into 2–3 daughter particles. The threshold particle velocities for breaking limestone particles were found to be ∼8.5–13.5m/s at 25–580∘C, similar to the reported literature values.