DIRECT REDUCED IRON (A) – Hot moulded briquettes
This product is included in the IMO Code of Safe Practice for Solid Bulk Cargoes as a material hazardous in bulk (MHB) and Group B a cargo which possesses a chemical hazard which could give rise to a dangerous situation on a ship.
In a recent case which resulted in the cargo heating and giving off hydrogen the description of the cargo given to the ship was found to be suspect which gives serious concern re cargoes loaded from this port.
The Cargo Declaration:
‘Name of the cargo’ stated: - Briquettes of Iron Ore (Briquettes, Hot-Moulded).
However in the same document under the title, ‘Cargo information’
The cargo’s name under the B.C.Code (IMO) is stated as: Direct Reduced Iron (A) Briquettes Hot Moulded Length 110 mm, Width 50mm, Thickness 35mm, Fines under 4mm, not more than 5%.
It is unusual for a cargo of DRI (A) to heat to a dangerous level or produce dangerous levels of hydrogen.
The vessel loaded 47,000 mt of cargo in Nos.1, 3 and 5 Holds in Novorossiysk. The temperature of the cargo as loaded during the period 11/13-2-2009 was reported to be within the range of 10C to 21C. The vessel sailed for Xingang on 14-2-2009 and on that day the temperatures of the cargo had increased to within the range of 20 C to 54 C.
On 17-2-2009 the temperature of the cargo in Nos.3 and 5 Holds had risen to 77 C and 64 C respectively. The temperature in No.3 Hold rose to 95 C on 18-2-2009 and increased to 100C on 20-2-2009. It was then learned that the hydrogen content in Nos.3 and 5 Holds was in excess of 2%. The lower flammable limit of hydrogen in air is 4% thus immediate ventilation of the hold spaces was advised.
The voyage continued with daily ventilation of the cargo holds through the ventilation windows on the hatch covers and the hatch accesses at the fore and after ends of the cargo holds. However heavy weather around 7-3-2009 prevented ventilation of the hold spaces and the hydrogen level increased from 0.16% to 0.95% vol. Weather conditions improved the following day which allowed ventilation of the holds and clearance of the hydrogen again. In view of this continued hydrogen generation and the possibility of further heavy weather preventing hold ventilation it was suggested that inerting of the holds in a suitable location should be considered.
Favourable weather conditions were forecast for the planned route and the voyage continued with good weather and conditions which permitted continuous ventilation of the cargo spaces and no build up of hydrogen concentrations to flammable or explosive concentrations occurred. However a further short spell of inclement weather, with seas over the deck, forced closure of the ventilation system once more with the resultant increase of hydrogen in the cargo holds.
Direct Reduced Iron, hot moulded briquettes are normally considered a relatively safe cargo to ship. The iron is in a densely moulded form, moulded at a temperature of 650C and has a limited surface area exposed to oxidation and water reaction. However when the briquettes are broken there is an increase in surface area of reactive iron exposed to oxidation to evolve heat and react with water to release hydrogen.