Pyrometallurgical Processes

Intensive process development is going on in the copper smelting processes. One emerging flash smelting process is the Kivset process, which is in use in Kazak­stan. The Noranda-Mitsubishi continuous smelter will start in 1999. In this proc­ess the plant has been retrofitted by combining the Noranda reactor with a con­tinuous Mitsubishi type converting furnace. It makes possible a practically contin­uous operation from concentrate to blister smelting. The operation of the smelter and the emission values obtainable will be seen in the future.

Researchers already have some vision of the copper smelter of tomorrow. It goes further than today’s concept of flash smelting-flash converting. The smelter will have only one single furnace which produces directly blister copper, discard slag and has only one continuous off-gas stream. It could be as follows:

• The flash smelting furnace has two reaction shafts, one for smelting concen­trates to matte and one for smelting matte and high grade concentrates to blister. Due to SO₂ recirculation it is possible to use pure oxygen in smelting.

• The slag from the blister copper smelting part runs into a smelting settler and is reduced.

• The matte from the primary smelting part is continuously tapped and gran­ulated. The copper content of the slag is reduced in the slag cleaning unit located at the other end of the furnace so that the continuously skimmed slag can be discarded.

The low dust-containing process gas passes through a gas cooling unit and through dust separation to a new generation acid plant, which is able to pro­duce sulphuric acid without dilution of the high strength process gas. Sepa­rated dust is treated so that impurities are bled off in concentrated saleable or inert form. Residue from the treatment unit is then circulated back into the primary smelting unit.

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