Synopsis The key aspects of process metallurgy that distinguish platinum group metal (PGM) concentrate smelting from that of other base metal sulphide concentrates are presented. These differences include considerably higher input chrome and magnesia contents that directly raise the slag liquidus temperature and have the potential to increase accumulations of refractory spinels. Most importantly, the higher processing temperature required for PGM smelting and the resulting very high matte superheat lead to considerably more onerous smelting conditions than those typical of other smelting operations. This has presented challenges to furnace design and integrity, especially when coupled with the progressive intensification of smelting, involving doubling, and then redoubling, of furnace power inputs over the past 20 years. These power increases have been enabled by increasingly more advanced furnace cooling and structural technologies. Key technologies include strong constant-force spring-loaded bindings acting in three dimensions to minimize infiltration of superheated matte into brick joints, and robust well-cooled tapholes for reliably tapping the superheated matte. The result has been substantially improved productivity, and reduced smelting capital cost outlay per unit of production. A significant challenge, which was not anticipated, presented itself in the form of insidious corrosion of the furnace lining, and especially high-intensity copper cooling elements. Investigation of corrosion in related industries eventually identified ‘chlorideaccelerated sulphidation’, and this term has been retained as it generically describes the most pertinent aspects of the accelerated low-temperature wear of copper coolers observed in PGM smelting. In addition to discussing the corrosion mechanism, this paper describes a number of solutions that were developed jointly by Anglo American Platinum and Hatch to address the copper corrosion problem. First, new monitoring technologies allowed furnaces to be operated more safely for a longer period of time. Second, a system for replacing corroded coolers from outside the furnace during a fast ‘hot’ shutdown minimized the impact on furnace operating factor and hearth life. Finally, a corrosionresistant graphite-protected cooler design significantly improved furnace campaign life, and heralds a more lasting solution to cooler corrosion in PGM furnaces.
[1]
J. Eksteen.
A mechanistic model to predict matte temperatures during the smelting of UG2-rich blends of platinum group metal concentrates
,
2011
.
[2]
M. Weichert,et al.
Some news about 'Black Spots'
,
2004
.
[3]
A. E. M. Warner,et al.
JOM world nonferrous smelter survey Part IV: Nickel: Sulfide
,
2007
.
[4]
S. Jahanshahi,et al.
CSIRO’s multiphase reaction models and their industrial applications
,
2002
.
[5]
Anglo Platinum Limited.
The smelting operations of Anglo American's platinum business: an update
,
2011
.
[6]
J. Tanzosh,et al.
Estimating effects of chloride on fireside corrosion of furnace walls in coal-fired boilers
,
1988
.
[7]
B. A. Wills.
XVI international mineral processing congress
,
1988
.
[8]
M. Hopf,et al.
New opportunities - exhaustive monitored copper coolers for submerged arc furnaces
,
2006
.
[9]
J. Kapusta.
JOM world nonferrous smelters survey, part I: Copper
,
2004
.
[10]
Patrick Giraudoux,et al.
Proceedings of the International Symposium
,
2014,
Parasite.
[11]
P. Sidky,et al.
Metallic and ceramic coatings : production, high temperature properties and applications
,
1989
.
[12]
G. Irons,et al.
Transport phenomena in electric smelting of nickel matte: Part I. Electric potential distribution
,
1998
.
[13]
R. Hundermark.
The electrical conductivity of melter type slags
,
2003
.
[14]
G. Y. Lai,et al.
High Temperature Corrosion of Engineering Alloys
,
1990
.
[15]
Bruce D. Craig,et al.
Handbook of Corrosion Data
,
1995
.
[16]
Henry Leidheiser,et al.
The Corrosion of Copper, Tin, and Their Alloys
,
1979
.
[17]
J. Nell.
Melting of platinum group metal concentrates in South Africa
,
2004
.
[18]
R. Sullivan,et al.
Hatch Developments in Furnace Design in Conjunction with Smelting Plants in Africa
,
2006
.