High Emissions of PCDD/Fs from Coal Fired Stoves: Indications of the Formation in the Chimney

Emissions from solid fuels fired heating appliances in residential sector are considered to have a significant share in total PCDD/F emissions into the air, especially in some countries, where such appliances are widely used. In the year 2000 the dioxin emission inventory for the European Union attributed 21% of the total PCDD/F emissions to the residential combustion of wood and 8% to the residential combustion of coal. However, the emission factors for residential combustion of coal and wood are highly uncertain. Very high emissions of PCDD/Fs up to 660 μg TEQ/ton for coal combustion in stoves were reported for the first time by the Austrian Federal Environment Agency when sampling emissions from combustion of hard coal of Polish origin. The experiments latter performed by the North Rhine-Westphalia State Environment Agency gave values up to 133 μg TEQ/ton for coal combustion in stoves. The conditions and mechanisms that could lead to high emissions from residential coal combustion are not yet entirely understood. Besides the uncertainty in the PCDD/Fs emission inventories this also prevents the conception and implementation of abatement measures. The gap in knowledge was already identified within the “Community Strategy for Dioxins, Furans and PCBs”, which has attributed the highest research priority to the domestic combustion of wood and coal. The conventional coal fired stoves have very low energy efficiency due to the incomplete combustion and heat losses through the chimney. Temperatures of the flue gases at the stove exit in excess of 500° C, together with residence times of some seconds in the chimney at temperatures above 300° C suggests PCDD/F formation. Therefore an experimental program was prepared to investigate the effects of the temperature profile in the chimney on PCDD/Fs emissions. The experimental programme was designed to address also the possible memory effects when changing the operational parameters.JRC.H.5-Rural, water and ecosystem resource