Mathematical model of the stack region of a commercial lead blast furnace
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INTRODUCTION
INVESTIGATIONS of the chemical conditions and associated energy effects H-a] within the lead blast furnace of Brunswick Mining and Smelting Ltd. (BMS), New Brunswick, Canada, have been summarized by Hussain and Morris. tSj Within the furnace, a large thermodynamic driving force prevails for the reduction of PbO to lead metal. This large driving force is perforce maintained in order to reduce Fem in the sinter feed to Fe H for incorporation in the slag. Despite the large driving force, the reduction reactions are essentially confined to a region of about 2.5 m depth above the tuyeres. The principal lead bearing phase in the sinter feed was found to be a complex lead calcium silicate, Pb3Ca2Si3Oll. Kinetic studies by Hussain and Morris tSj upon the reduction of lead minerals by CO/CO2 gas mixtures established that this material was substantially less reactive than pure PbO. The temperature for initiation of the reduction of Pb3 Ca2Si30, ( - 7 5 0 ~ is much greater than that of PbO ( - 2 6 0 ~ and the activation energy for reduction of the silicate ( - 1 6 0 kJ/mol) is larger than that for PbO ( - 1 0 0 kJ/mol). The low conversions noted in the upper reaches of the furnace were thus attributed to the low reactivity of the sinter and also to the low porosity ( - 3 pct) and large size of the material (1 to 15 cm). Hussain and Morris also observed that with mixtures of Fe203 and lead calcium silicate, the overall conversion was limited by the rate of reduction of the silicate and hence for prediction purposes, the reduction rate of commercial sinter could be regarded as identical to the reduction rate of lead calcium silicate. The grain model introduced by Sohn and Szekely 16'71was found to describe the gas-solid reactions satisfactorily. In particular, the conversion of lead calcium silicate was found to be strongly influenced by the structural parameters of the solid in accord with the grain model as well as the temperature noted above. MANSOOR M. HUSSAIN, Postdoctoral Fellow, and DAVID R. MORRIS, Professor, are with the Department of Chemical Engineering, University of New Brunswick, Fredericton, NB E3B 5A3, Canada. Manuscript submitted January 25, 1988. METALLURGICAL TRANSACTIONS B
The processes occurring in a blast furnace are complex. This is due to the strong interactions between the state variables and the distributed nature of the various phases involved in the process. Mathematical simulation offers the most convenient tool for investigating the physical and chemical states of a blast furnace. Mathematical simulation can also serve to examine changes in design and operation and be used for process control. This tool has been extensively used in respect to the iron blast furnace, t81but there is only one model of a lead blast furnace reported in the literature.tgl This model has only limited applicability since it depends on an assumed sinter composition and an assumed reaction rate equation. In this paper, the stack region of the furnace has been simulated using experimentally measured kineti
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