Injection phenomena in nonferrous processes
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I.
INTRODUCTION
THEsubmerged injection of gas into molten baths has been practiced in both the ferrous and nonferrous industries for a century. Two nonferrous processes in which this technique is applied are the converting o fmattes and zinc slag fuming. In both cases cold air is injected horizontally at relatively low pressure (50 to 100 kPag) into a bath at 1150 to 1250 °C through a large number of closely spaced tuyeres having a diameter o f 30 to 60 ram. In slag fuming a reductant, pulverized coal, is also injected through the tuyeres into the bath. Although both processes have been operated successfully worldwide for a long time,there is considerable scope for improvement. In converting operations the tuyeres become plugged periodically with accretions which must be removed by forcing a punching bar through individual tuyeres. The punching action, possibly in combination with local bath motion, causes severe refractory wear at the tuyere line which ultimately limits the duration of a converter campaign. Moreover, the gradual blockage of a given tuyere causes a reduction in the air flow through it which concomitantly may reduce converter productivity. Thus, prevention of tuyere plugging could result in an increase in the life of the refractory lining, removal o f tuyere punching equipment, and an increase in converter productivity.l Tuyere blockage is not a problem in zinc fuming, but a recent study 2 has shown that the fuming kinetics are limited by the fraction of injected coal that penetrates into the slag bath; the remainder combusts with the injected air or passes unreacted through the bath. With current practices only about 35 pet of the coal enters the bath as reductant, according to model predictions based on numerous in-plant fuming trials. If this fraction were increased, the productivity of a fuming A.A. BUSTOS, Graduate Student, G.G. RICHARDS, formerly Graduate Student, now Assistant Professor, and J.K. BRIMACOMBE, Stelco Professor of Process Metallurgy, are all with the Department of Metallurgical Engineering, T h e University of British Columbia, Vancouver, British Columbia V6T 1W5, Canada. N.B. GRAY is Senior Lecturer, Department of Chemical Engineering, T h e University of Melbourne, Parkville, Victoria 3052, Australia. Manuscript submitted April 2 9 , 1983. METALLURGICAL
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furnace could be improved markedly and perhaps lead to continuous fuming. It is obvious that the performance of these processes, as described above, is related to the dynamic behavior o f the two fluids--air and bath. Therefore, the present study was initiated to investigate the injection dynamics and related accretion build-up in the tuyeres of an operating copper converter and slag fuming furnace as a function of operating conditions. II.
PREVIOUS WORK
Injection dynamics and tuyere blockage have been the subjects o fseveral studies, but relatively little work has been done directly on the copper (or nickel) converter and nothing has been reported, to the authors' knowledge, on the fuming furnace. Hoefele
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