Design of a Compact Dilution Sampler for Stationary Combustion Sources

Abstract

The dilution sampling method simulates the rapid cooling and dilution processes after hot flue gas have left the stack. This allows gases or vapors to nucleate both homogeneously and heterogeneously, and to condense on preexisting particles in processes analogous to those that occur in the ambient environment. Using this method the authors can collect filterable particulate matter (PM) and condensible PM, that is, primary PM, simultaneously. In order to make this method more suitable for field investigation, a compact dilution sampler was developed. The sampler enhances mixing of dilution air with the stack gas, and thus shortens the length of the mixing section. The design decreases the nominal flow rate through the aging section, and accordingly reduces the size of the residence chamber. The decreased size of the sampler is suitable for field test. Sampling gas is pressured into the residence chamber, and air pressure in the chamber is micro-positive. Uncollected redundant gas is automatically discharged through unused sampling ports, which keeps the unit stable. Performance evaluation tests demonstrate that the design is reasonable. The sampler has been applied to characterize PM emissions from various combustion sources in China. IMPLICATIONS Particulate matter (PM) emitted from stationary combustion sources is an important contributor to urban ambient PM, especially for PM2.5 (PM ≤2.5 μm in aerodynamic diameter). Characterizing PM emissions from various combustion sources and providing reliable emission data are important for identifying their contributions to urban ambient PM and for designing corresponding control measures. This research developed a compact dilution sampler, which is a reliable tool for characterizing PM emissions from stationary combustion sources in China. The data obtained by the field measurements using the dilution sampler will be helpful for source apportionment and emission inventory development. © 2011 Air and Waste Management Association.