Direct Reduced Iron: A general description covering lumps, pellets, cold and hot-moulded briquettes, formed by a manufacturing process in which, as for sponge iron, iron oxide is reduced at temperatures below the fusion point of iron. Cold-moulded briquettes are produced at a temperature below 650°C and have a density of under 5.0, whilst hot-moulded briquettes have a density greater than 5.0 and are manufactured at a temperature in excess of 650°C.
No Direct-Reduced Iron should be loaded if its temperature upon shipment exceeds 65°C and lumps, pellets and cold-moulded briquettes should not be carried unless previously treated with a satisfactory oxidation and corrosion inhibiting process to protect against dangerous reaction with sea-water or with air. Nevertheless, it is held that the only proven method of safely carrying direct-reduced iron pellets, lumps and cold-moulded briquettes is in cargo holds maintaining an inert atmosphere, whilst the most effective method of providing such an atmosphere, is to inject inert gas at the bottom of the cargo stow, thus forcing out air contained in the cargo – as is the practice for the export of direct-reduced iron-pellets from Canada.
Such an inert atmosphere should contain less than 5% oxygen and less than 1% of hydrogen, and monitoring equipment used on board to check that the cargo-hold’s oxygen and hydrogen contents are being so maintained, as well as reporting the cargo temperature. Very few dry-cargo ships have such equipment, or the facility to maintain inert conditions in these circumstances.
Hot-moulded briquettes do not require inert gas filled holds. On the contrary, adequate surface ventilation should be provided and, although forced ventilation may not be necessary, oxygen introduced into cargo compartments may become depleted, and caution should thus be exercised before entering cargo spaces.
Holds should be clean and dry prior to loading hot-moulded briquettes and hatch-covers should be watertight to prevent the ingress of water onto cargo.
Loading can only be conducted in dry weather and stopped immediately if rain occurs. There should be no wooden fittings in cargo spaces and no heated areas such as warm bulkheads.
Upon completion of loading hatchcovers are closed and the vessel thoroughly washed with high pressure freshwater spray to remove fines. Following this it may be necessary to reopen hatches for one or two days to aid the evaporation of any cargo moisture. If the briquettes remain too moist it is not uncommon for them to heat up to between 60 and 80°C during the voyage, although the cargo temperature will return to normal as the moisture dries out.
- Bulk Direct – Reduced Iron (Cold) Stowage Factor 15/17
- Bulk Direct – Reduced Iron (Hot) Stowage Factor 12/13