Solubilities of Chlorine in CaO-SiO 2 -Al 2 O 3 -MgO Slags: Correlation Between Sulfide and Chloride Capacities
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0 0:75 TðKÞ
whereas chloride capacities were formulated as the function of temperature and optical basicity in the following equation: 54; 600 60; 200 2 log CCl ¼ 43:6 K þ 39:2 þ 0:5: TðKÞ TðKÞ
DOI: 10.1007/s11663-010-9465-2 Ó The Minerals, Metals & Materials Society and ASM International 2010
I.
INTRODUCTION
OUR daily life would depend a great deal on various types of ‘‘new’’ materials. On such ‘‘new’’ materials are discarded as wastes, however, we often encounter numerous serious social problems. Plastic products are a typical example of such wastes. In 1999, the volume of plastic disposed as waste in Japan was about 8 million tons, 40 pct (3.2 million tons) of which was disposed of by landfill, 35 pct (2.8 million tons) was disposed of by incineration, and the remaining 25 pct (2.0 million tons) was recycled for reutilization.[1] An impetus for more recycling was proposed by national legislation that went into effect in April 2000. The law for recycling plastic used as containers and packaging has increased the need for commercialized processes. To meet such requirements, the Japanese steelmaking industry has developed innovative technology for recycling various wastes at their iron and steelmaking complexes. For example, Wakimoto et al.[2] pioneered the injection of waste plastic into blast furnaces through the tuyere system. Facilities for injecting waste plastic now have been installed at a number of blast furnaces in Japan. Waste plastic, M. OKEDA, Graduate Student, M. HASEGAWA, Associate Professor, and M. IWASE, Professor, are with the Thermochemistry Research Group, Department of Energy Science and Technology, Kyoto University, Kyoto 606-8501, Japan. Contact e-mail: iwase@ namihei.mtl.kyoto-u.ac.jp Manuscript submitted August 31, 2010. Article published online December 23, 2010. METALLURGICAL AND MATERIALS TRANSACTIONS B
however, often contains polyethylene vinyl chloride (PVC). When injected into blast furnace, PVC would decompose and generate HCl, which eventually reacts with liquid slag. From the previous comments, it would be evident that a strong incentive exists to understand the behavior of chlorine in liquid slag. By using a gas equilibrium technique incorporating Ar + HCl + H2O + H2 mixtures, the authors[3] investigated the reaction between gaseous HCl and CaO-SiO2-Al2O3 slags, which would be formulated as follows: ð1=2ÞfCaOgslag þðHClÞ ¼ Ca1=2 Cl slag þð1=2ÞðH2 OÞ ½1 where { } and (), respectively, denote liquid and gas phases,[4] and the subscripts to brackets correspond to the solvents. The equilibrium constant for reaction [1] is expressed as follows: " # 1=2 fCa1=2 Cl ð%ClÞPH2 O ½2 log Kð1Þ ¼ log 1=2 PHCl aCaO where fCa1=2 Cl and (%Cl), respectively, are the activity coefficient and chlorine concentration in weight pct and other symbols have the usual meanings. In the present study, the work has been extended to CaO-SiO2-Al2O3MgO slags with fixed Al2O3 contents of 30 and 35 wt pct, respectively, to derive a correlation between sulfide and chloride capacities through our own
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