​The ISASMELT™ reactor is an upright cylinder and the key feature of the process is the ISASMELT™ lance, which enters through the top of the furnace with the tip submerged in the molten slag bath. Feed falls in through the top of the furnace and is reacted within the bath with the air and the oxygen injected down the lance. The injection of the air and the oxygen into the bath creates a highly turbulent bath facilitates rapid reactions and heat transfer.

The lance located centrally in the furnace injects air, oxygen and fuel into the molten bath. The lance height is positioned so that its tip is located just under the surface of the molten slag in the furnace. The blast of air, oxygen, and fuel down the lance violently stirs the liquid. This stirring ensures very intimate contact between the feed and the oxygen. A frozen layer of slag on the outside of the lance protects it from the aggressive environment in the furnace. The off-gases from reactions in the furnace pass up through the freeboard of the furnace into a waste heat boiler where the contained heat is captured to make steam and the cooled gases pass through to an electrostatic precipitator for the removal of the dust before the gases enter to an acid plant.

The submerged lance exhibits all the thermodynamic advantages of a tuyere with none of its engineering disadvantages. During the smelting process the liquid level in the furnace can rise and fall. Unlike a tuyere, the lance can be raised and lowered automatically or manually so that its tip is always where it is required.

The products of the smelting ISASMELT™ process are tapped from the bottom of the furnace through a water-cooled taphole.

Tapping of the furnace is by semi-automated machinery. The furnace can be tapped intermittently or continuously.

The products flow into a settling furnace, where the matte or metal separates from the slag.