PCDD/F in flue gas and in bottom ash of lignite domestic combustion and the role of the salt content of the burned briquettes

Lignite briquettes with different salt contents (“normal”-coal: 300 ppm w/w, “salt”-coal: 2000 ppm w/w) were burned in a common type of a house heating facility. The content of polychlorodibenzodioxins and furans (PCDD/F) in the flue gas and in the bottom ash were determined. The values calculated from the homologue sums were significantly higher for the “salt”-coal briquettes regarding their flue gas concentrations and slightly increased in respect to the bottom ashes. Taking in account a wide variety of additional analytical parameters and considering mechanistic aspects, our assumtion was proved that the higher chlorine content of the “salt”-coal briquettes is responsible for these increased values. The evaluation of the homologue profiles and the isomer distribution shows that the mechanism of the formation of PCDD/F in the flue gas is similar for both coal sorts; whereas, however, the formation of these compounds in the bottom ashes occurs under different conditions. Based on the quantitative results, an assessment of lignite domestic heating as source of PCDD/F is given.