(170g) Dust Dispersion Particle Breakage: Classification Based on Brittleness Index

Dust explosions are a frequent problem in the process industries causing loss of life and property. Standards such as ASTM, ISO etc. provide guidelines for determining the explosion parameters P_max and K_St, (the maximum pressure and rate of pressure rise, respectively) in a dust explosion. These parameters are found in standard 20-L or 1-m³ devices and are used to perform explosion risk assessments and mitigation. In these devices, it is assumed the particle size distribution of the dispersed dust remains constant throughout the testing procedure. Recent studies show a significant particle size reduction can result from dispersion in the standard 20-L apparatus, which can affect the explosion parameters. The reduction in particle size due to the dispersion process depends on the dust and the explosion apparatus. Therefore, it is necessary to quantify the particle size reduction of different dusts due to dispersion in various explosion apparatuses (20-L, 36-L and 1-m³) and correlate it to the dust properties that influence particle breakage.

This research studied particle size reduction for a range of materials in the 20-L, 36-L and 1-m³ dust explosion apparatus. The dispersion-induced particle breakage was correlated to the properties of the dusts, which were measured using Nanoindentation. Based on the particle breakage, dusts were categorized into three categories, with a brittleness index range associated with each category. In addition, the effect of dust concentration on particle breakage and behavior of nanomaterial was examined.

Dispersion results show the 20-L and 36-L dust explosion apparatus cause significantly more particle breakage than the 1-m³ apparatus. It also shows that not all materials undergo particle breakage. In addition, the 1-m³ apparatus caused particle breakage only in material with high brittleness index. The results show that the brittleness index correlates directly to the particle breakage trend. Also, results indicate particle breakage is inversely related to dust concentration. Nanomaterial dispersion result shows particle breakage followed by subsequent re-agglomeration post-dispersion.

This research will help process industries identify dusts that are susceptible to breakage based on their brittleness index and prone to give misleading explosion results during standard dust explosion testing, permitting a proper dust explosion risk assessment.