Doniambo nickel smelting plant - November 2000
Metallurgical production
The first nickel smelter was built in 1877 at "Pointe Chaleix", Noumea.
Currently, the SLN Doniambo smelting plant in Nouméa has an output of about 60 000 tonnes of nickel per year through electrical smelting. Nickel metal produced is contained in "ferronickels" for about 4/5 of the output, and in nickel mattes (nickel sulfide) for the balance. SLN was incorporated in 1880!
Ores exports
Nickel ores are exported by the so called "petit mineurs" (small miners). About 1.6 million tonnes of garnieritic ore (saprolite) are sold to Japan each year. They contain about 30 000 t of nickel metal. Since 1988 nickeliferous limonite is mined and exported to Australia. Yearly ores exports are about 2 Mt containing nearly 20 000 t of nickel and 2000 t of cobalt. Overall it is about 50 000 t of nickel and 2 000 t of cobalt which are exported each year in the ores.
Nickel production history
Since the begining of nickel mining in New Caledonia about 2,5 millions tonnes of nickel metal contained in exported nickel ores were exported. Meanwhile some 2,5 Mt of nickel métal were produced in metallurgical products smelted in New Caledonia. Nickel output as metallurgical products is therefore historically equivalent to nickel exported in ores. Since year 2000 exported nickel tonnage in metallurgical products tends to be higher than nickel tonnage exported in ores (see graph).
Valorisation
In metallurgical products nickel is valorised three to four times the value of nickel in exported ores.
Since the origin of nickel mining in New Caledonia about 2.5 Mt of Ni have been exported in nickel ores and an equivalent quantity of metals exported in metallurgical products. Historically the metal tonnage produced by smelting is therefore equivalent to the metal tonnage exported in ores. However the nickel exported in ores has been historically paid at 23% of the metal value in average. More precisely the metals sold in ores were paid at 30% of the value of the metals sold in metallurgical products.
From 2000 to 2006 value of exported metallurgical products was 50 billion Francs CFP per annum in average (420 M€) against 13 billion CFP (110 M€) for the exported ores.
Two metallurgical technologies for lateritic nickel ores
According to the ores nature there are two different technologies.
Garnierite (saprolite) is processed by smelting in electric furnaces. This is pyrometallurgy ( SLN Doniambo plant).
Laterite (limonite) is processed by chemical agents (sulfuric acid or ammoniac) which dissolve nickel and cobalt from the ore. This is hydrometallurgy.
Projects to built one and even two new metallurgical plants are underway.
One of them located in the South at Goro, will produce nickel and cobalt from limonite. Construction started in 2002. It was halted in 2003 but resumed end of 2004 and was completed in 2009. The selected hydrometallurgical process uses sulfuric acid leaching in autoclaves at a temperature of 270° under 60 hp pressure. Nickel and cobalt are then separately extracted using organic solvents. Finished products is nickel oxide and cobalt carbonate. Annual output capacity will be 60 000 t of nickel and 5 000 t of cobalt contained in the finished products. Production is being ramped up since 2010 but nominal output has not yet been reached
A second project is being built in the North based on the Koniambo massif saprolitic nickel resource. Infrastructure works and plant construction are in progress. Process to be used will be electric smelting. The metallurgical plant is currently under construction. Smelting is planned to start in the second half of 2012 progressively ramping up then to the full capacity of 60 000 tonnes par year of contained nickel in the metallurgical products.