Dilution ratio and particle loss performance of a newly developed ejector porous tube diluter compared to a commercial diluter

In this study, a new ejector-porous tube diluter was developed to accurately in situ measure particulate matter at the source, e.g., emissions at coal-fired power plants, and its dilution ratio and particle loss were compared to those of a commercial model. Whereas commercial models supply air to the porous tube diluter (PRD) using a high-pressure compressor, our device replaces the latter with a ring blower, thereby decreasing the power consumption for the same airflow rate. As a demonstration, particle size volume distributions of fly ash at a coal-fired power plant stack were determined for different dilution ratios. PRD flow rates of 10 and 20 L min^-1 for the commercial diluter produced ~2-μm particle volume concentrations of 382 and 572 μm3 cm^-3, respectively, from an initial (undiluted) volume concentration of 756 μm3 cm^-3. However, PRD flow rates of 10 and 30 L min^-1 for the developed device produced ~2-μm particle volume concentrations of 506 and 500 μm3 cm^-3, respectively, from an initial volume concentration of 532 μm3 cm^-3. These particle loss rates were confirmed through field testing.