DRI BY ANY OTHER NAME
Posted at Wednesday, 20 July 2005 Last updated on Wednesday, 17 May 2017
By Alan Mitcheson
Operators of bulk fleets will be aware of Direct Reduced Iron (DRI) and of the appropriate precautions that must be taken to ensure its safe carriage by sea. However, we are aware of a number of shippers who are offering a material for bulk shipment that is clearly a DRI product, but is claimed to be safe for bulk carriage by sea without the usual precautions. However, we are also aware of two explosions, and a potential explosion, in the past year that have occurred on vessels that were carrying this cargo.
DRI is produced by passing hot reducing gases such as hydrogen, methane and carbon monoxide over iron ore (oxide), which is usually in the form of pellets or lumps. Although the process is conducted at high temperatures, these temperatures are still substantially below the melting point of iron. This means that the lumps and pellets retain their original shape, but are considerably lighter owing to the removal of oxygen from the ore. Therefore, the pellets and lumps have a hugely porous structure, which makes the material extremely reactive and prone to re-oxidation on contact with air and/or moisture. These oxidation reactions cause self-heating in the stow. Moreover, contact with moisture evolves hydrogen, and several explosions have occurred in ships' holds following its ignition: in one very recent tragic casualty, a vessel was lost completely together with the Master and five of her crew.
DRI is classified as a material that is hazardous only when in bulk (MHB) and is included in the IMO Code of Safe Practice for Solid Bulk Cargoes (the BC Code) as BC015. The normal precautions for the safe transport of DRI require that an inert atmosphere be maintained within the hold for the entire voyage: in practice, and especially for long voyages, this is virtually impossible without carrying portable supplies of nitrogen on deck. Under no circumstances should DRI be loaded wet or allowed to become wet, especially by seawater.
Alternatively, the pellets and lumps can be compressed at temperatures exceeding 650°C to form briquettes. These are commonly referred to as HBI (Hot Briquetted Iron) or hot moulded briquettes, and although still classified as MHB, they pose a lesser hazard than DRI, and have a separate entry in the BC Code (BC016). Significantly, it is not required to maintain an inert atmosphere with the hold.
The process of importing iron ore into the plant, storing and transporting it, then conveying it to and through various screens and furnaces, through the briquetting facility and then to final product storage generates copious quantities of dust. This dust has considerable nuisance value within the factory, and so it is captured and separated from the air in a dust collection facility. Although a waste by-product, this dust still has considerable commercial value and can be utilised in steel making. There is therefore a market for shipping this dust.
However, this material does not have the benefits afforded by compression into large and cohesive briquettes, but rather it retains its porous nature like DRI. Consequently, it will still exhibit self-heating, possibly auto-oxidation, but it will certainly generate hydrogen in sufficient quantities to form explosive atmospheres, even in holds that have been subject to natural ventilation through conventional cargo hold vents. There can be no doubt that this dust, or FINES, has properties that are close to DRI, and it does not merit the relaxation in carriage precautions afforded to HBI.
It is not surprising, then, that shippers have sought to avoid using the term ‘DRI’ to describe this cargo, and there seems to be no bounds on the ingenuity and unscrupulousness employed. The most common device is to call the dust ‘HBI Fines’, or ‘Metallic HBI Fines’ and thereby claim the relaxation in precautions afforded to HBI. We have also seen the same commodity described as ‘Iron Remet Fines’, the term ‘remet’ probably being a shortening of the word ‘remetalised’, signifying that it is metallic, rather then the ore.
In a more sinister vein, we are aware of one manufacturer that stockpiled this material in the open, in the expectation that it would re-oxidise and lose its hazardous properties. Despite being exposed to the elements in a humid climate, where heavy storms were frequent, for up to two years, severe explosions occurred mid voyage in two of the holds of the vessel that was carrying it to Europe, which resulted in the deaths of two crew, with a third severely burnt and paralysed. The cargo was initially described as iron ore in bulk (per Charterparty), and iron oxide fines (per Bill of Lading). Later, it was referred to as re-oxidised fines, re-oxidised DRI fines, and also clarifier fines. Confused? So were we until we received the analysis from 142 samples taken during discharge that showed that almost half of the cargo was fresh DRI.
Despite the foregoing, not all cargoes with ‘DRI’ in the description are hazardous. For example, members have been offered cargoes described as ‘Direct Reduced Iron Ore’. By referring to the typical material composition supplied by the shippers, it could be seen that this was, indeed, iron ore that was destined for the direct reduction process, and therefore a cargo that posed no special hazards. This serves to illustrate the adage, ‘If in doubt, ask!’
Alan Mitcheson, Ilkley Office