Task 2.10 - Advanced Sampling and Analysis of Fine Particulates

The objectives of this study are to develop a sampling method to capture the fine particulate and classiyi the particulate according to their size and chemistry. When developing the sampling method, two criteria need to be met: 1) the particulate are randomly dispersed on the sampling media and 2) the sampling media can be put directly into a scanning electron microscope (SEM) for analysis to prevent any alteration of the particulate. Several methods for the sampling and analysis of fine particulate are to be tested. Each sampling test will be analyzed using the FPT technique for collecting the size, shape, and chemical composition of 1500 to 2000 individual fine particulate. The FPT data will be classified using cluster analysis and principal component analysis to provide a classification system for these particles. As reported previously, particulate samples were collected using the advanced hybrid particulate collector (AHPC) on the inlet port of the particulate test combustor (PTC) when the Absaloka coal was burned in early April. The samples were collected at the inlet rather than the outlet port because of the loading that was expected and the temperature at which the PTC was run. Samples at the inlet were expected to see a much greater particulate loading than at the outlet because of the efficiency of the particulate collection device on the PTC. Also, polycarbonate filters cannot withstand temperatures above 230oC for long periods of time; therefore, a quick loading time was required. The samples were briefly scanned and photographed using the SEM to determine the best particulate loading time. The particulate were too close together on the 20- and 30-second polycarbonate filters to be able to analyze individual particles. The particle dispersion on the vitreous carbon substrate appeared to be the best of the four samples. Aerosols were produced from pure 1.0 M aqueous solutions of NaCl, Na2S04, (NHq)2SOo, NHqNO~, and K20 (KOH) using a Tri-Jet Model 3460 aerosol generator and collected by direct impingement on a vitreous carbon substrate. Because NaCl is the normal aerosol produced with the generator, it was briefly examined using SEM to determine the degree of dispersion. Good dispersion with nearly all particulate size below 2 pm and the majority in the O.1-pm range was achieved with a substrate collection time of 2-3 minutes. The brief examination also demonstrated that the sample could be introduced directly into the SEM for analysis with no prior carbon coating or other preparation and that charging of the sample was minimal