Behavior of dioxins in the sintering process of iron ores

The new "law concerning special measures against dioxins" is promulgated in January, 2000 in Japan and the emission control of dioxins has been enforced to the iron ore sintering plants and some other plants/processes for metals recycling. In 1997, a collaborative research project was formed by the researchers and engineers of Japanese integrated steel makers and universities, in order to investigate the behaviors of dioxins and relating substances in the sintering process of iron ores and to search for new technological principles for suppression of the emissions rather than waste gas treatments. The project has carried out the examination of previous literatures and data, several plant measurements and tests, experiments using process simulators (sinter-pots) and fundamental researches. The present paper reports a part of the results of the measurements and analyses of a sintering plant equipped with several waste gas treatment processes. Characteristics of behaviors and flows of dioxins in the sintering bed windboxes and gas treatment processes are discussed. Further, the effect of additives to raw materials, especially chlorine-hearing materials, on the discharged amount of dioxins in exhaust gas is examined based on the results of sinter-pot tests.