PM_(10) emissions from industrial coal-fired chain-grate boilers

摘要

Industrial coal-fired boiler is an important air pollutant emission source in China. The chain-grate boiler is the most extensively used type of industrial coal-fired boiler. An electrical low-pressure impactor, and a Dekati® Low Pressure Impactor were applied to determine mass and number size distributions of PM_(10) at the inlet and the outlet of the particulate emission control devices at six coal-fired chain-grate boilers. The mass size distribution of PM_(10) generated from coal-fired chain-grate boilers generally displays a bimodal distribution that contains a submicron mode and a coarse mode. The PM in the submicron mode for burning with raw coal contributes to 33% ± 10 % of PM_(10) emissions, much higher than those for pulverized boilers. And the PM in the submicron mode for burning with briquette contributes up to 86 % of PM_(10) emissions. Multiclones and scrubbers are not efficient for controlling PM_(10) emission. Their average collection efficiencies for sub-micron particle and super-micron particle are 34% and 78%, respectively. Operating conditions of industrial steam boilers have influence on PM generation. Peak of the submicron mode during normal operation period is larger than the start-up period.