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Nickel Flash Smelting

Outotec® Nickel Flash Smelting Process was first developed and implemented in Harjavalta, Finland in 1959. Efficiency and improved environmental and in-plant hygiene have been the guiding principles in the development of Outotec processes. Today, Outotec® Flash Smelting has become a benchmark nickel-smelting method and a clear global leader in the world’s primary nickel production from sulfide raw materials.

Outotec® Nickel Flash Smelting Process has several advantages:

  • High recovery of nickel and other valuable metals (copper, cobalt, PGMs)
  • Low investment and operating costs for the smelter and acid plant
  • Capability to treat different qualities of sulfide raw materials with variable feed rates
  • High sulfur recovery, continuous high-strength SO2 stream from Flash Furnace to the acid plant
  • Improved in-plant hygiene due to compact equipment 

In Nickel Flash Smelting technology, sulfide nickel concentrate is processed in the Outotec® Flash Smelting Furnace to produce nickel matte and slag. The matte is transported to the Peirce-Smith converters where it is blown to high-grade matte. The metal values in the smelting and converting slags are recovered in the electric furnace as nickel matte. The matte is circulated to the Peirce-Smith converters.

The dried feed mixture, oxygen-enriched process air and distribution air are mixed in the concentrate burner to assure an even distribution of the feed in the reaction shaft suspension. As the dried charge flows downwards in the reaction shaft, the concentrate particles dissociate, ignite and undergo controlled partial oxidation generating a large amount of heat, which results in the melting of the material into fine droplets. In the settler, the immiscible slag and matte phases separate and form two layers according to their specific densities.

The process gas flows upward through the uptake shaft and then to a heat recovery boiler for cooling. Part of the flue dust is separated from the gas stream in the boiler. The gas flows onward to an electrostatic precipitator where the remaining fine dust is recovered. The dust collected under the boiler and precipitator is returned back to the furnace.

The produced slag is tapped from the Flash Furnace and directed along with the converter slag into an electric slag cleaning furnace before being granulated and discarded. Reduction is carried out batch-wise using coke as a reducing agent.  During the settling period, reduced metal droplets and mechanically trapped matte droplets are settled through the slag layer to the bottom of the electric furnace to form the matte layer. Immiscible slag components with a much lower density stay at the top of the bath and form the cleaned slag layer.

The mattes obtained from the flash smelting furnace and from the electric Outotec® Slag Cleaning Furnace are converted in Peirce-Smith converters with oxygen-enriched air, which is blown through tuyeres into the converter. For slag forming purposes, some silica flux is added. The produced high-grade matte is granulated and further treated in the refinery. The waste slag is also granulated and transferred to the slag disposal area.

Outotec provides complete tailored process solutions for customers’ needs. Decades of experience in the supply of Flash Smelting plants have resulted in extensive metallurgical know-how that ensures the most profitable process choice and its optimal performance. Outotec’s life-cycle technology partnership with the customer spans from the early stages of the process solution design all through the supply and commissioning of the entire process chain with integrated process control and holistic service and support concept. Continuous research and development ensure that the customer is provided with the latest advancements in process and equipment solutions.