Date of Award
Master of Science (MS)
The Aerodynamic Particle Sizer (APS) is a near real time laser particle sizer that counts and sizes particles in the range of 0.5 /xm to 3 0 /xm, which makes it ideal for measuring the particle size distribution of fly ash from coal combustion. While the APS has proven to be a valuable instrument for measuring particle size distribution from flue gas streams, data indicate that the APS may not be providing an accurate particle size distribution over the entire range of 0.5 /xm to 30 /xm.
The primary objective of this study was to determine the ability of the APS to obtain an accurate particle size distribution and mass concentration of dusts such as suspended coal fly ash. A secondary objective was to compare the relative merits of the APS with an impactor and a multicyclone. A third objective was to develop an improved correction curve to allow the APS to give a more accurate mass particle size distribution and total mass concentration over the entire range of 0.5 /xm to 30 /xm.
The experimental effort consisted of design and assembly of a bench-scale aerosol generation and sampling system to disperse dry powders into an air stream where they could be sampled by four different methods. The four methods were: 1) APS, 2) Pollution Control Systems Inc. Mark 3 impactor, 3) Flow Sensor 6-stage multicyclone, and 4) modified EPA Method 5 dust loading. Tests were conducted with four different dusts including BCR67 and BCR70 dusts with certified known particle size distributions, and two fly ashes produced from pulverized coal combustion.
Measured mass median diameters with the APS were lower than the certified values for the test dusts, the greater error occurring for the larger particles. Both impactor and multicyclone measured particle size distributions were in good agreement with the certified distributions. A new efficiency curve was generated which enables the APS to provide the correct particle size distribution for the certified test dusts. The ability of the APS to provide an accurate particle size distribution over the entire range from 0.5 /xm to 30 fim is limited by high concentrations of small particles and low count efficiency for particles from 15 nm to 3 0 fim.
Miller, Stanley J., "Evaluation of an Aerodynamic Particle Sizer With Certified Polydisperse Test Dusts" (1990). Theses and Dissertations. 985.