Use of oxygen in the Outokumpu flash smelting process

CIM Bulletin, Vol. 75, No. 845, 1982

B.ANDERSSON Manager of the Process Technology Department, P. HANNIALA, Process Metallurgist, and S. HARKKI, Manager, Metallurgical Projects, Outokumpu Oy, Engineering Division, Finland

The Outokumpu Flash Smelting Process was put into commercial operation in 1949. The original process was based on the use of preheated air.The adoption of oxygen enrichment of the flash smelting process air in 1971 was a crucial improvement, especially for smelter capacity. Oxygen use according to the Outokumpu method means selection of the most suitable oxygen content for the process air on the basis of the concentrate composition, capacity and matte grade. The furnace is not bound to only one fixed degree of process air oxygen enrichment; the oxygen content may vary from 21%  to 100%.The degree of oxygen enrichment and the matte grade are the most important process parameters in reducing the operating costs of the whole system, including smelting, converting and acid production. Raising the matte grade allows more efficient use of the reaction heat in the smelting stage. Sulphur is recovered in a high-strength, constant-flow gas stream. The blowing time in the converters is reduced considerably.Oxygen enrichment and high matte grade improve the energy efficiency of the plant complex as long as the surplus heat from the system is not wasted. When the operating costs and investment expenditure of the total plant complex are taken into account, a reasonably high degree of oxygen enrichment (35-80%) is the best alternative in practice. Existing operating smelters have achieved single-stream thoughputs of over one million t/yr of concentrates.
Keywords: Pyrometallurgy, Oxygen, Outokumpu, Flash smelting, Harjavalta Works, Smelting, Copper smelting, Nickel smelting, Converting, Sulphur recovery