Development of a new dilution system for continuous measurement of particle concentration in the exhaust from a coal-fired power plant

We developed an ejector-porous tube diluter to suppress particle nucleation and minimize particle loss. To measure fine particles in a stack continuously, clean air was periodically supplied at high pressure in the diluter. The particle concentrations in the exhaust from a coal-fired power plant in South Korea were measured and compared with results obtained using an existing commercial diluter. The newly developed diluter successfully suppressed the particle nucleation of volatile compositions, which commonly happens at cold dilutions of hot gases by maintaining the preheater temperature above 200 °C. The PM_2.5/PM₁₀ ratio obtained using the diluter was approximately 0.88, which was lower than the ratio (0.98) obtained using the commercial diluter. Thus, the commercial diluter showed significant particle losses in the PM_2.5–10 size range. The inside of the developed diluter was kept free of contamination over 24 h by periodically suppling clean air to allow continuous measurement of the PM₁₀ and PM_2.5 from a coal-fired power plant stack. Therefore, it is advantageous to use the developed diluter to measure PM₁₀ and PM_2.5 accurately over the long term.