Dilution Ratio and Particle Loss Performance of a Newly Developed Ejector Porous Tube Diluter Compared to a Commercial Diluter

ABSTRACT In this study, a new ejector porous-tube diluter was developed for accurate in-situ particulate matter measurements at emission sources such as coal-fired power plants. The dilution ratio and particle loss of the developed diluter were compared to that of a commercial porous-tube ejector diluter. In commercial diluters, air is supplied to the porous-tube by a compressor. In contrast, the developed diluter uses a ring blower for this purpose instead. The use of a ring blower instead of a high-pressure compressor to supply air to the porous-tube diluter (PRD) resulted in less power consumption with an equal airflow supply. For demonstration purposes, fly ash particle size volume distributions were determined at different dilution ratios. When the PRD flow rate to the commercial diluter was 10 and 20 L/min, the volume concentrations of approximately 2 μm particles were 382 and 572 μm3/cm3 respectively, at which point the initial (undiluted) volume concentration was 756 μm3/cm3. When the PRD flow rate to the developed diluter was 10 and 30 L/min, the volume concentrations of approximately 2 µm particles were 506 and 500 μm3/cm3 respectively, at which point the initial volume concentration was 532 μm3/cm3. This particle loss rate was confirmed through field tests in the coal-fired power plant stack. In conclusion, the newly developed diluter had relatively little large particle losses and required lower dilution air flow rates. Therefore, the newly developed diluter was confirmed to be a promising means to measure particle size distributions in flue-gas stacks.