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1. Introduction the Biggest Polluters Among Metallurgical Facilities

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1. Introduction the Biggest Polluters Among Metallurgical Facilities ARCHIVESOFMETALLURGYANDMATERIALS Volume 57 2012 Issue 3 DOI: 10.2478/v10172-012-0089-1 T. SOFILIĆ∗, J. JENDRICKOˇ ∗∗, Z. KOVACEVIơ ∗∗∗, M. ĆOSIĆ∗ MEASUREMENT OF POLYCHLORINATED DIBENZO-p-DIOXIN AND DIBENZOFURAN EMISSION FROM EAF STEEL MAKING PROCES BADANIA EMISJI WIELOCHLORKOWYCH DIBENZO-p-DIOKSYN I DIBENZOFURANÓW Z PROCESU WYTWARZANIA STALI W PIECU ŁUKOWYM Electric arc furnace (EAF) steel manufacturing is an important recycling activity which contributes to the recovery of steel resources and steel scrap/waste minimization. Because of the content of plastics, coatings and paintings as well as other nonferrous materials in the charge during melting, a strong emission of pollutants, including polluting substance group consists of persistent organic pollutions (POPs) represented by polycyclic aromatic hydrocarbon (PAH), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) occurs. This study was set out to investigate emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs) from the stack of a new electric-arc furnace-dust treatment plant installed during modernisation of the Melt Shop in CMC SISAK d.o.o., Croatia. Obtained results have been compared with previously obtained results of PCDDs/Fs emission measurements from the old electric-arc furnace dust treatment without dust drop-out box, as well as quenching tower. The total PCDDs/Fs concentration in the stack off gases of both electric arc furnaces EAF A and EAF B were 0.2098 and 0.022603 ng I-TEQ/Nm3 respectively, and these results are close to previous obtained results by other authors. The calculated values of the emission factors for PCDDs/Fs calculated on the basis of measured PCDDs/Fs concentration in the stack off gases in 2008 and 2011 were 1.09 and 0.22 ng I-TEQ/ ton steel, respectively. Keywords: persistent organic pollutions, EAF, PCDDs/Fs, dioxin Produkcja stali w piecu łukowym (EAF) jest ważnym elementem recykling stali co przyczynia się do odbudowy zasobów stali i wykorzystania złomu i odpadów stalowych. Ze względu na zawartość tworzyw sztucznych, powłok i farb, jak również innych materiałów niezależnych we wsadzie, podczas topienia występuje silna emisja zanieczyszczeń, w tym grupy substancji składającej się z trwałych zanieczyszczeń organicznych (POP) takich jak wielopierścieniowe węglowodory aromatyczne (PAH), wielochlorowe bifenyle (PCB), wielochlorowe dibenzo-[1,4]-dioksyny (PCDD) i wielochlorowe dibenzofurany (PCDF). Celem pracy jest zbadanie emisji wielochlorowych dibenzo-[1,4]-dioksyn i dibenzofuranów z nowego układu odpylania zainstalowanego w piecu łukowym w trakcie modernizacji huty CMC Sisak w Chorwacji. Uzyskane wyniki porównano z po- przednio uzyskanymi wynikami pomiarów emisji dioksyn i dibenzofuranów ze starego układu oczyszczania pyłów z pieca łukowego. Całkowite stężenie dioksyn i dibenzofuranów w gazach odlotowych z pieców łukowych A i B wynosi odpowiednio 0,2098 i 0,022603 ng I-TEQ/Nm3, i te wyniki są zbliżone do poprzednich uzyskanych wyników przez innych autorów. Obliczone wartości wskaźników emisji dioksyn i dibenzofuranów na podstawie zmierzonych koncentracji dioksyn i dibenzofuranów w gazach odlotowych w 2008 i 2011 wynosiły odpowiednio 1,09 i 0,22 ng I-TEQ / tonę stali. 1. Introduction lations include significant volumes of gaseous and sol- id polluting substances, such as sulfur and carbon ox- The biggest polluters among metallurgical facilities ide, fluorides, ammonia, benzene, heavy metals, phenols, include coking plants, iron ore sintering and agglomer- cyanides, oil and grease, slag, used refractory material, ation plants, blast furnaces, steel mills, non-ferrous and metallic scrapings, sludge, dust, and scale. There are also light metal production and processing facilities. Emis- relatively small pollutions with long-lasting effects that sions into air and water from these plants and instal- ∗ CMC SISAK D.O.O., BRAĆE KAVURIĆ 12, 44010 SISAK, CROATIA ∗∗ HANIBALA LUCIĆA 5, 44000 SISAK, CROATIA ∗∗∗ METROALFA D.O.O. KARLOVACKAˇ CESTA 4L, 10000 ZAGREB, CROATIA 812 are hazardous, even in their low concentrations, and they (Mazalović et al. [2]). In the late 1970ies, Olie et al. rarely receive due attention. [3] for the first time identified PCDDs/Fs in emissions This polluting substance group consists of persistent from a municipal waste incineration plant. Since that organic pollutions represented by polycyclic aromatic incident, these compounds have ever more frequently hydrocarbon (PAH), polychlorinated biphenyls (PCBs), become the research subject of various environmental polychlorinated dibenzo-p-dioxins (PCDDs), and poly- studies. According to Potykus and Joas [4]; Mc Kay chlorinated dibenzofurans (PCDFs). These compounds [5]; and Pereira [6], elementary physical and chemical are the least explored of all known pollutants generated characteristics of PCDDs/Fs and their extremely adverse in the metallurgical processes, in terms of the impact of impact on human health stimulated the research of their their emissions on the environment. origin and distribution in the environment. PCDDs and PCDFs, or as they are commonly re- At first, due to the fact that there was no unique ferred to, PCDDs/Fs, fall into the group of persistent technology and no sufficient information needed for tox- organic pollutants (POPs) and impose a great risk for icity assessment of PCDDs/Fs, and since Potykus and the living environment (Fig. 1). These compounds are Joas [4], a number of different methods were developed not produced as standard chemicals, except for very at national levels. The purpose of adopting a unique in- small quantities for research purposes or as chemically ternational factor of equivalent toxicity (I-TEF) was to pure substances, but are generated in various chemical achieve a higher level of uniformity and comparability processes in the manufacture of chlorine compounds, of results defining PCDDs/Fs content in samples of dif- pulp and paper mills, or processes that require high tem- ferent materials of different origin. Today, the analysis peratures (waste incineration, metallurgical processes in of PCDDs/Fs in various samples commonly includes 17 iron and steel and light metal industry, cement manufac- compounds (7 PCDDs and 10 PCDFs) and their level in ture, etc.). The generation of these compounds requires the sample is described as toxic equivalent (I-TEQ) in carbon, oxygen and chlorine, as well as metallic cata- correlation to 2,3,7,8-tetrachlorinated dibenzo-p-dioxin lysts and adequate temperature. The optimal temperature (2,3,7,8-TCDD). range for pyrosynthesis of these compounds is between Due to the great risk of PCDDs/Fs accumulation 400 and 700◦C. in the natural environment, and in an attempt to prevent environmental pollution with these compounds from var- ious emitters, many countries have made an inventory of industrial sources [7-11] and their emission to the environment in order to achieve better understanding of how individual sources participate in the total emission of PCDDs/Fs and to develop a strategy of reduction of these emissions. Municipal solid waste incinerators and iron and steel plants represent major sources of atmospheric pollution by PCDDs/Fs [9-14]. With the progressive abatement of emissions from municipal solid waste incinerators, the iron and steel industries are now becoming ma- jor contributors to the global atmospheric pollution by PCDDs/Fs [7, 15]. The most significant source of PCDDs/Fs among metallurgical processes is definitely sintering of iron ore intended for pig iron production in blast furnaces. If the sintering process is the largest source of PCDDs/Fs among iron and steel making processes, then the pig Fig. 1. Structural formula of PCDD and PCDF iron production process in blast furnaces is the smallest source. Using such pig iron as converter in steel produc- PCDDs/Fs as environment pollutants aroused inter- tion continues the series of technological processes for est of scientists during the mid-60ies of the past cen- production of finished steel products that are increasingly tury when they were identified as the cause of Kanemi demanded on the world market, burdening the environ- Yusho disease in Japan [1], and in the mid-70ies when ment further with toxic dioxins and furans. they emerged as undesirable by-products in a misguid- As opposed to this steel making process, PCDDs/Fs ed production process for 2,4,5-trichlorinephenols, caus- emissions are more significantly generated in the EAF ing an environmental pollution incident in Seveso, Italy 813 steel making processes using steel scrap as charge (of- off-gases in quenching tower to avoid the ’de novo’ syn- ten as much as 100%), which is almost always pollut- thesis of PCDDs/Fs. The cooled and treated primary off ed with various inorganic and organic substances. Due gas is then mixed with secondary off gas, after which it to the presence of organic pollution, EAF and its dust passes through a fabric filter where the fine particles are treatment plant, as well as stack gas drainage system, removed. under specific thermodynamic conditions become a very The present work was initially motivated by the in- complex reactor where pyrolysis and pyrosynthesis oc- stallation of a new EAF dust treatment plant developed cur, generating dioxins, furans, and other organic com- by TECOAER - StG Group S.p.A., Italy. The paper dis- pounds. Inside this “reactor“ many PCDDs/Fs molecules cusses the PCDDs/Fs emission concentration in off gases occur and/or decompose during melting and refinement from old electric arc furnace (EAF A) dedusting plant processes but many of them also leave the reactor and without off gases pretreatment as well as the newly in- pollute the environment and the human impact of these stalled electric arc furnace (EAF B) dedusting plant with pollutants is still of concern because of their ability to off-gases pretreatment i.e. with a dust drop-out box and bio-accumulate in the food chain and then in human fat quenching tower installed between the EAF and bag fil- tissue. ters. EAF steel manufacturing is a batch process which can result in fluctuating emissions during heating of the charge and from heat to heat.
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