https://doi.org/10.15255/KUI.2006.001
Published: Kem. Ind. 55 (12) (2006) 511–522
Paper reference number: KUI-01/2006
Paper type: Review
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Importance of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans Emissions from Iron and Steel Production Processes

T. Sofilić, A. Rastovčan-Mioč+ and Z. Šmit

Abstract

Metals and metallic products are fundamental to a large number of modern industries and steel is certainly one of the most significant metallurgical products. Steel and steel castings as universal production material, that provided the grounds for the contemporary industrialization process, will have a continuously irreplaceable role in the future, regardless of the fact that nowadays steel materials are often replaced by other materials (ceramics, polymers, etc.), whenever it is technically required and cost-justified. The development of metallurgy and metallurgical processes is accompanied by pollution of the environment that directly or indirectly endangered the health of humans, certain animal and plant species, water resources systems, and soil. It also lead to increased erosion of material goods and caused many other adverse social and economy-related effects. The integral steelworks concept has, for example, set off a significant increase in the number of emission sources and the increase of harmful substances concentration in the environment. The largest polluters have always been coking plants, iron ore agglomeration facilities, blast furnaces, steel mills, foundries and thermal energy plants. Numerous fundamental scientific research works have proven a series of adverse effects caused by uncontrolled emissions of harmful substances from these plants. Beside the considerable quantities of usual and well-known polluting substances such as sulfur and carbon oxides, fluorides, ammonia, benzene, heavy metals, phenols, cyanides, oil and grease, slag, used refractory material, metallic scrapings, sludge, dust, and scale, there are also relatively small pollutions with long-lasting effects that are hazardous even in their low concentrations and they rarely receive due attention. This polluting substance group consists of persistent organic pollutions represented by polycyclic aromatic hydrocarbon (PAH), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). These compounds are the least explored of all known pollutions generated in the metallurgical processes, in terms of the impact of their emissions to the environment. The paper provides elementary toxicity data for these compounds and a survey of reference data on the currently completed listings of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in the world and in Croatia, illustrating that the metallurgical process account for most of the total emission of these compounds into the environment. Based on the experience of the developed countries that are at the same time the largest iron and steel producers, we calculated an estimate of potential emissions of dibenzo-p-dioxins and polychlorinated dibenzofurans from metallurgical processes in Croatia. The calculation took into account the coking processes, iron ore sintering processes, pig iron production, cast iron, openhearth steel and EAF steel production. The estimated total emission of dibenzo-p-dioxins and polychlorinated dibenzofurans from metallurgical processes to the environment in the time period between 1990 and 2000 in Croatia was m = 3.987 g I-TEQ and annual emission in the same period ranged from QI-TEQ = 1.284 g a–1 in 1990 to QI-TEQ = 0.153 g a–1 in 1995. Emissions of these compounds from metallurgical processes that were active in less recent past were also calculated and the values in the time period between 1960 and 2000 ranged from m = 2.888 g I-TEQ in 1980 to m = 0.153 g I-TEQ in 1995. Based on the data on the existing facilities for steel production in electric arc furnaces we estimated that annual emission of dibenzo-p-dioxins and polychlorinated dibenzofurans could amount to QI-TEQ ~ 0.260 g a–1, whereas the future emission of these compounds from the existing cast iron facilities could be QI-TEQ ~ 0.100 g a–1. In the research follow-up for the impact of metallurgical processes on the overall emission of these compounds to the environment, it is required to measure their emissions from all active metallurgical processes. For the sake of better comprehension of emission flows of dibenzo-p-dioxins and polychlorinated dibenzofurans from metallurgical processes it is necessary to determine the contents of these compounds in all kinds of waste generated in the observed metallurgical processes and to select technical solutions to improve each individual process and to reduce their emissions to the environment.

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Keywords

dioxins, furans, emission, metallurgical processes