Effect of Deposit Types, Mine Development and Industry …
511
• Fe in sphalerite—the level of Fe in sphalerites can vary considerably by deposit.
Some zinc mines have very low iron in sphalerite (e.g. Century, Tennessee), which
allows production of high Zn grade concentrates and low residue formation in
smelters. Other deposits have much higher iron in sphalerite such as Broken Hill
(which contains a high iron form of sphalerite called marmatite) and Dugald River.
• Mn in sphalerite—Dugald River also has elevated levels of Mn in sphalerite. This
affects concentrate quality and marketability. Mn causes operational challenges in
the cell houses of electrolytic zinc refineries (Mn mud build up).
• Fine grained silica—some SEDEX deposits (e.g. Century, McArthur River) have
fine grained silica intergrowths with sphalerite that results in elevated silica in concentrate. This can affect the settling properties of residues in the smelter. Smelters
can apply penalties for silica above 4%.
• Organic carbon, which can be present.
• Fluorine—which is present in Cannington ore can cause problems with corrosion
in the gas handling system of smelters. An acid leach using aluminium sulphate
is used to leach fluorine minerals from lead and zinc concentrates.
• Dolomite (MgO, CaO)—Irish mines (e.g. Tara, Galmoy) have sometimes leached
concentrates with sulphuric acid to improve concentrate grades [4]. Applicable to
Irish/MVT type deposits.
Smelting
Sinclair [5] estimated that in 2003, 89% of primary zinc smelter production was
from the electrolytic process. Most of the remaining capacity was from plants using
the Imperial Smelting Process (ISP). Major changes in lead and zinc smelting by
country have also occurred since 2000. There has been a major increase in lead and
zinc smelting in China. In the meantime, smelters in North America, Europe and
Australia have closed (Table 3). Many of these closures were hastened by tightening environmental standards for lead, particularly those plants using sinter plant
flowsheets (Cockle Creek, Herculaneum, Avonmouth and Duisburg). In addition,
Glencore closed the Portovesme ISP plant in Italy, focusing instead on improving its
electrolytic zinc smelter, Kivcet lead smelter and zinc solvent extraction plant. The
decline in ISP plants has made it more difficult for mines producing zinc concentrates with elevated lead to market their concentrates. This has affected McArthur
River (MIM/Xstrata/Glencore), which produces a low-grade zinc concentrate with
significant lead.
511
• Fe in sphalerite—the level of Fe in sphalerites can vary considerably by deposit.
Some zinc mines have very low iron in sphalerite (e.g. Century, Tennessee), which
allows production of high Zn grade concentrates and low residue formation in
smelters. Other deposits have much higher iron in sphalerite such as Broken Hill
(which contains a high iron form of sphalerite called marmatite) and Dugald River.
• Mn in sphalerite—Dugald River also has elevated levels of Mn in sphalerite. This
affects concentrate quality and marketability. Mn causes operational challenges in
the cell houses of electrolytic zinc refineries (Mn mud build up).
• Fine grained silica—some SEDEX deposits (e.g. Century, McArthur River) have
fine grained silica intergrowths with sphalerite that results in elevated silica in concentrate. This can affect the settling properties of residues in the smelter. Smelters
can apply penalties for silica above 4%.
• Organic carbon, which can be present.
• Fluorine—which is present in Cannington ore can cause problems with corrosion
in the gas handling system of smelters. An acid leach using aluminium sulphate
is used to leach fluorine minerals from lead and zinc concentrates.
• Dolomite (MgO, CaO)—Irish mines (e.g. Tara, Galmoy) have sometimes leached
concentrates with sulphuric acid to improve concentrate grades [4]. Applicable to
Irish/MVT type deposits.
Smelting
Sinclair [5] estimated that in 2003, 89% of primary zinc smelter production was
from the electrolytic process. Most of the remaining capacity was from plants using
the Imperial Smelting Process (ISP). Major changes in lead and zinc smelting by
country have also occurred since 2000. There has been a major increase in lead and
zinc smelting in China. In the meantime, smelters in North America, Europe and
Australia have closed (Table 3). Many of these closures were hastened by tightening environmental standards for lead, particularly those plants using sinter plant
flowsheets (Cockle Creek, Herculaneum, Avonmouth and Duisburg). In addition,
Glencore closed the Portovesme ISP plant in Italy, focusing instead on improving its
electrolytic zinc smelter, Kivcet lead smelter and zinc solvent extraction plant. The
decline in ISP plants has made it more difficult for mines producing zinc concentrates with elevated lead to market their concentrates. This has affected McArthur
River (MIM/Xstrata/Glencore), which produces a low-grade zinc concentrate with
significant lead.