Dustiness test of fine and nanoscale powders using a standard rotating drum with a modified sampling train

• Main Authors: Ming-Long Leu, 呂銘龍
• Other Authors: Chuen-Jinn Tsai
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/38140881293121954864

碩士 === 國立交通大學 === 環境工程系所 === 96 === Dustiness is defined as the propensity of a material to become airborne when handled. In order to quantify and determine the dustiness of fine and nanopowders, the standard rotating drum tester was used to determine the dustiness of two nanopowders: nano-TiO2 and fine ZnO, in the standard 1-min tests. Then the sampling train was modified to determine the number and mass distributions of the generated particles in the respirable size range using a SMPS (Scanning Mobility Particle Sizer), an APS (Aerodynamic Particle Sizer) and a MOUDI (Multi-orifice Uniform Deposit Impactor) in the 30-min tests. In the standard test, it was found that the dustiness of nanopowder was much higher than submicro-powder. The average inhalable, thoracic and respirable dustiness mass fraction in mg/kg and the dustiness level of TiO2 nanopowder were 6713±546 (high), 576±37 (moderate) and 15±2 (low), respectively, and were 142±20 (very low), 73±6 (low) and 11±0.3 (low) for ZnO submicro-powder. In the modified test, it was found that very few particles below 100 nm were generated from both powders as measured by the SMPS. The average total particle concentrations below 100 nm are only 1.87 and 1.74 #/cm3, which correspond to 7.84×10-5 (assuming TiO2 bulk density is 0.13 g/cm3) and 3.72×10-4 (assuming ZnO bulk density is 0.60 g/cm3) μg/kg-min, for TiO2 and ZnO, respectively. The released rate of particles decreased with increasing rotation time for both nanopowders in the 30-min tests as measured by the SMPS and APS. The shape of the distribution function does not change very much with the NMD (number median diameter) of 356-391 nm and the GSD (geometric standard distribution) of 1.7-1.88 for the SMPS data, and the mode changes slightly from 898 to 835 nm, about 7 %, for the APS data during the 30-min test. The MOUDI data show that nanoparticle emission from the nanoscale and fine powders are negligibly low, which confirms the nearly zero nanoparticle mass concentrations converted from SMPS data. Due to the fluffy structure of the released TiO2 agglomerated particles, the mass distributions measured by the MOUDI showed large differences with those determined by the APS assuming the bulk densities of the powders. The differences were small for the ZnO agglomerates which were more compact than the TiO2 agglomerates.