DIOXIN EMISSIONS FROM COAL COMBUSTION IN DOMESTIC STOVE: FORMATION IN THE CHIMNEY AND COAL CHLORINE CONTENT INFLUENCE

Combustion experiments conducted in domestic stove burning hard coal demonstrated a predominant influence of the coal chlorine content on the PCDD/F emissions, together with a pronounced effect of the flue gas temperature. PCDD/F concentrations of over 100 ng TEQ/m(3), three orders of magnitude higher than in a modern waste incinerator, were measured in the flue gases of a domestic stove when combusting high chlorine coal (0.31%). The PCDD/F concentrations in the flue gases dropped below 0,5 ng TEQ/m3, when low chlorine coal (0.07%) was used. When low chlorine coal was impregnated with NaCl to obtain 0.38% chlorine content, the emission of the PCDD/F increased by two orders of magnitude. Pronounced non-linearity of the PCDD/F concentrations related to chlorine content in the coal was observed. The combustion of the high chlorine coal yielded PCDD/F concentrations in flue gases one order of magnitude lower in a fan cooled chimney when compared to an insulated one, thus indicating formation in the chimney. The influence of flue gas temperature on the PCDD/F emissions was less pronounced when burning low chlorine coal. The predominant pathway of the PCDD/F emissions is via flue gases, 99% of the TEQ in the case of the high chlorine coal for insulated chimney.