Influence of dust catchers on PM₁₀ emission characteristics of power plants

Influence of dust catchers on PM₁₀ emission characteristics was determined experimentally at the inlet and outlet of dust catchers at five different power plants. Electrical low pressure impactor(ELPI) with a sampling system, which consisted of an isokinetic sampler probe, pre-cut cyclone, two-stage dilution system and sample line to the instruments, was used to measure in situ. Size distribution is measured on the range from 0.03μm to 10μm in aerodynamic diameter. The results show that the testing system can be used widely for sampling of particulate matters from stationary sources. Before and after all the dust catchers, the particle number size distributions display the bimodal distribution which contained the submicron mode and the coarse mode with a peak around 0.07~0.12μm and 0.76~ 1.23μm, respectively. The minimum collection efficiencies of the ESP and the bag-house both appear in the particle size range of 0.1 ~ lμm. In this size range, bag-house collection efficiency is higher than that of ESP. The ESP collection efficiencies of PM₁ and PM_2.5 based on the number concentration are also lower than that of PM₁₀.The mass concentration of PM₁₀ is mainly dominated by the particles which are larger than 1 μm, while the number concentration is dominated by the particles which are smaller than 0.1μm. Mass and number size distributions measured after ESP can be seen and the mass and number concentration of PMi₁₀ will increase obviously by rapping the last electric field. Furthermore, the ESP collection efficiencies based on the number concentration and mass concentration were both decreased by ESP rapping with different degrees; and the maximum drop degree appeared in PM₁.