DRI by any other name is jDRI by any other name is just as dangerousust as dangerous

Operators of bulk fleets will be aware of Direct Reduced Iron (DRI) and of the precautions that must be taken to ensure its safe carriage by sea. However, the Association is aware of a number of shippers who are offering a material for bulk shipment that clearly a DRI product, but is claimed to be safe for bulk carriage by sea without the usual precautions. In the past year two explosions and a potential explosion, have occurred on vessels carrying this cargo. This article by Alan Mitcheson of Burgoynes highlights some of the problems with the carriage of DRI.

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 temperature, this is still substantially below the melting point of iron. This means that the limps 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 very porous structure, which makes the material extremely reactive and prone to re-oxidation on contract with air and/ or moisture.

Creative explosive hydrogen on contract with moisture

Oxidation reactions of DRI cargoes result in self-heating of the stow. Moreover, contract with moisture evolves hydrogen, and several explosions have occurred in ship's holds following its ignition: in one recent tragic casualty, a vessel was lost completely together with its master and five crewmembers.

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 voyage, this is virtually impossible without carrying portable supplies of nitrogen on desk. Under no circumstances should DRI be loaded wet or allow to become wet, especially by seawater.

Briquettes may be less hazardous

Alternatively, the pellets and lumps can be compressed at temperature exceeding 650C to form briquettes. These are commonly referred to as hot briquetted iron (HBI) 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 within the hold.

"Fines" similar to DRI but often not described as such

The process of importing iron ore into a 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 or 'fine'. This has considerable nuisance value within the factory and so it is captured and separated from the air in a dust-collection facility. It also has considerable commercial value for steel making and so there is a market for shipping it.

Fines are not normally compressed into large cohesive briquettes and remain porous like DRI. Consequently they can exhibit self-heating and possibly auto-oxidation. They will also 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 fines have properties close to DRI and they do 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 fines. Indeed there seem 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. Fines have also been described as 'Iron Remet Fines', the term 'remet' probably being a shortening of the word 'remetalised', signifying it is metallic rather than the ore.

Fatal consequences of misleading description

The Association is aware of one manufacturer that stockpiled the material in the open in the expectation it would re-oxidise and lose its hazardous properties. Despite being exposed to the elements in a humid, stormy climate for up to two years, severe explosions occurred mid-voyage in two holds of a vessel carrying it to Europe. Two crewmembers died and a third was severely burnt and paralysed.

The cargo was initially described as 'iron ore in bulk' in the charterparty and 'iron oxide fines' in the bill of lading. Later, it was referred to as 're-oxised fines'. An analysis from 142 samples taken during discharge showed that almost half of the cargo was fresh DRI.

Not all 'DRI' cargoes hazardous

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".

The Association is very grateful to Dr Alan Mitcheson, Principal Members, Burgounes, for writing this article.

Source : Signals
01 Jan 2005

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