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Direct Nickel Flash Smelting

Outotec® Direct Nickel Flash Smelting Process is a continuous Flash Smelting operation for nickel production, eliminating the need for converters. This unique process provides high recovery for valuable metals, while at the same time low operating and capital costs.

The Direct Nickel Flash Smelting Process provides several advantages over the conventional nickel smelting route, such as:

  • Low investment and operating costs for the smelter and acid plant
  • No converting (investment, operating and maintenance) is required
  • No ladle transportation of liquid matte is needed and revert generation is minimal
  • The costs for converter gas treatment and fixation of sulfur in the acid plant are eliminated
  • Simplified flow sheet, only two process steps
  • High recovery of nickel and other valuable metals (copper, cobalt, PGMs).
  • The recovery is improved by the elimination of unnecessary molten material circulation (elimination of the converting step)
  • High sulfur recovery to continuous single stable gas flow, i.e. minimum emissions to the environment and working atmosphere

These features of the state-of-the art Outotec® nickel smelting and refining technology lead to the possibility of optimizing the process concept and the operation mode for the treatment of a wide range of sulfide nickel concentrates. The outcome is low investment and operating costs at the smelter, acid plant and refinery.

In Direct Nickel Flash Smelting technology, high-grade nickel matte with low iron content is produced in the Outotec® Flash Smelting Furnace directly without subsequent converting. The metal values in the smelting slag are recovered in an electric furnace as an iron containing Ni-matte.

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. The concentrate ignites and burns in the turbulent gas/solid suspension resulting in controlled partial oxidation in the reaction shaft. The oxidation process generates a large amount of energy causing the melting of the charge. In the settler, molten particles separate from the gas stream and settle at the bottom of the furnace as distinct matte and slag layers, based on their specific densities. The high-grade matte thus produced is channeled out of the furnace through the launders to water-granulation.  

The slag is tapped along the slag launders directly into the electric Outotec® Slag Cleaning Furnace. Reduction is carried out using lumpy coke as a reducing agent. Reduced metal droplets settle through the slag layer to the bottom of the furnace to form the matte layer with the cleaned slag on top. Injecting concentrate into the melt can be used to increase the sulfur content of the matte and thereby maintain lower operating temperatures. The matte is tapped from the furnace and directed to water-granulation.
 
The high-grade matte and the matte from the Slag Cleaning Furnace are transported to the refinery for further treatment. The waste slag can be stored or used as in landfill.

The rich SO2gas from the Flash Smelting Furnace is conducted through the uptake shaft of the Flash Smelting Furnace to the heat recovery boiler for cooling and partial dust separation. Final dust removal takes place in the electrostatic precipitator and thereafter the gas is conducted to the sulfuric acid plant.

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.