A kinetic model for the vacuum refining of inductively stirred copper melts
- PDF / 1,741,427 Bytes
- 17 Pages / 603.28 x 783.28 pts Page_size
- 0 Downloads / 207 Views
I.
INTRODUCTION
VACUUM refining is a comparatively new process for the copper pyrometallurgist. However, it has potential with respect to the elimination of more volatile impurities from liquid copper. Among various different types of vacuum refining processes, vacuum induction melting is one possibility for the refining of molten blister or anode copper. Vacuum refining in induction melting units is achieved through evaporation of volatile impurities into the gas phase above the melt. It is known that vacuum induction melting can provide close control of melt composition and temperature while simultaneously preventing undesired contamination by reactive gases such as oxygen. ~ Similarly, through the use of low pressures (below 40 Pascals) and inductive stirring, the rate of refining reactions can be improved and purification processes which would not take place at atmospheric pressures can be carried out. 2-5 The present authors investigated the general feasibility of impurity elimination from blister, anode or cathode type of copper and determined the main factors controlling their elimination. These results were published earlier. In this presentation the kinetics of vacuum induction melting of blister, anode or cathode type of copper at the pilot scale level are reported. A semi-empirical kinetic model was developed and, based on the results of the experimental work, some projections could be made. II. THEORY OF MASS TRANSPORT IN VACUUM A review of the literature 6'7 shows that interest in possible applications of vacuum metallurgy to copper is relatively E. OZBERK, formerly Graduate Student at McGill University, Montreal, PQ, Canada, is Senior Process Specialist, Mining and Metallurgy, The S.N.C. Group, Montreal, PQ, Canada. R. I. L. GUTHRIE is a Professor in the Department of Mining and Metallurgical Engineering, McGill University, Montreal, PQ H3A 2A7, Canada. Manuscript submitted July 9, 1984. METALLURGICALTRANSACTIONS B
new: earliest literature on the subject dates back to the late 1940's, 8 and kinetic studies were only begun in the last twenty years. Nonetheless, the elimination of impurities from various types of copper such as copper matte, crude copper, blister copper, and anode or cathode type of copper have all been investigated during that period. All these studies were laboratory scale experiments and none found industrial application. 6,7
A. Thermodynamics in Relation to Vacuum Metallurgy Any understanding of the kinetics of evaporation of impurities from a liquid metal bath held under vacuum first requires information on the vapor pressures of constituent gas species above the melt. Relatively little data are available on vapor pressures of elements above their dilute solutions in liquid metals. However, vapor pressures of pure elements are more or less precisely known, and a comparison of their values at temperatures of interest can be used as a rough guide in determining those elements which should exhibit preferential evaporation. As a first approximation, dissolved elements with higher v
Data Loading...
