End products
The main product of the HIsmelt process is hot metal, which can be used as direct charge to steelmaking processes or cast into pig iron. Slag is produced as a by-product.
The hot metal product is continuously tapped from the Smelt Reduction Vessel (SRV) via a foreheath. As slag is batch tapped through a slag notch (similar to mini blast furnaces) the hot metal is slag free.
If required, the hot metal can be treated in a hot metal desulphurisation plant to remove sulphur. The slag can be used as a valuable raw material in a variety of applications.
Comparison of hot metal quality produced by HIsmelt and blast furnace
| Typical analysis | Blast furnace | HIsmelt |
| Carbon | 4.5% | 4.4 +/- 0.15% |
| Silicon | 0.5 +/- 0.3% | <0.01% |
| Manganese | 0.4 +/- 0.2% | <0.02% |
| Phosphorus | 0.09 +/- 0.02% * | 0.02 +/- 0.01% ** |
| Sulphur | 0.04 +/- 0.02% | 0.1 +- 0.05% # |
| Temperature | 1430 - 1500°C | 1420°C |
*Whilst using high phosphorus ore; # After hot metal desulphurisation
Slag by-product
Slag is produced in the smelting process due to the reaction between the flux, the gangue in the ore and the ash in the coal.
Slag can be granulated or directed into pits for further processing. It can then be used as a raw material for a variety of purposes such as cement manufacture, road base and soil conditioning.
If titano-magnetite ore is used, the slag becomes a valuable co-product if its content in titania is rich enough (typically above 50 per cent) to be considered as pigment feed stock.