Kinetics of the zinc slag-Fuming process: Part i. industrial measurements
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I.
INTRODUCTION
S L A G processing is emerging as an important unit operation in the evolving technology for the extraction of nonferrous metals. Slag reduction is a vital part of both the QSL and flash-smelting processes for lead concentrates. Developments in the smelting of tin also rely on improved methods of slag treatment; and in the extraction of copper and nickel the trend toward the use of higher matte grades requires a separate slag-treatment step rather than simple slag recycle. Traditionally slag processing has been only a "slag cleaning' step, a secondary operation outside the mainstream of the primary smelting circuit. In copper and copper-nickel extraction, electric-arc furnace treatment, with or without a coke addition, or milling and flotation have become the standard processes. In lead-zinc and copper-zinc smelting, slag fuming has normally been practiced. These slagtreatment processes were developed on an empirical basis and have evolved in a similar manner to their present state. As a result our understanding of slag processing is rudimentary and difficult to apply in process design. Moreover, fundamental work on slag thermodynamics, slag physicochemical properties, and reaction kinetics is not yet sufficiently comprehensive to provide a basis for rigorous process analysis. Knowledge of process kinetics is also very limited and hence process development is hindered. As a consequence the potential role of slag processing in nonferrous extractive metallurgy is being realized only slowly. The benefits of an improved understanding could be considerable. G.G. RICHARDS, formerly Graduate Student, now Assistant Professor, and J. K. BRIMACOMBE, Stelco Professor of Process Metallurgy, are with The Centre for Metallurgical Process Engineering, Department of Metallurgical Engineering, The Universtty of British Columbia. Vancouver, BC V6T 1W5, Canada. G. W TOOl', Technical Development Superintendent, is with Cornmco Ltd., Trad, BC V1R 4L8, Canada. Manuscnpt submitted July 11, 1984 METALLURGICALTRANSACTIONS B
The overall purpose of this work, therefore, has been to develop a more complete understanding of the kinetics of one particular slag treatment process--zinc slag fuming. Because at this stage our knowledge of the process is so incomplete, the approach taken has been a direct analysis of the industrial process itself rather than an intensive study of some particular aspect. Before describing the study, it is worthwhile to review briefly the major features of slag fuming. II.
ZINC SLAG FUMING
Zinc slag fuming was developed to remove and recover zinc from lead blast-furnace slag. The earliest experimental work on the problem was conducted in Australia by the Sulphide Corporation at Cockle Creek between 1906 and 1920.t Commercial development of the process, however, was made by the Anaconda Copper Mining Co. and the Consolidated Mining and Smelting Co. in the 1920's. 2'3 The first furnace was blown in at the Anaconda Smelter, East Helena, Montana in December 1927. Little change in the process has been
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