Iron ore concentrate is a major dry bulk cargo distinct from natural iron ore in that it is the product of beneficiation: crushing, grinding, magnetic or flotation separation, and dewatering of lower-grade iron ore to produce a higher-grade concentrate suitable for steel-making. The cargo is regulated under the International Maritime Solid Bulk Cargoes Code (IMSBC) under a dedicated Group A schedule entry separate from natural iron ore. Iron ore concentrate is among the most liquefaction-prone bulk cargoes because of its uniform fine particle size and characteristic moisture content from the dewatering process.
Schedule structure
The IMSBC Code includes a separate schedule for iron ore concentrate distinct from the iron ore (Group C) and iron ore fines (Group A) schedules:
- Iron ore concentrate (Group A): cargoes of beneficiated iron ore with characteristic fine particle size (typically more than 90 per cent below 1 millimetre and significant fraction below 100 micrometres) and moisture content of 5 to 12 per cent at loading. Liquefiable, subject to TML and MC certification.
The Group A classification triggers all the pre-loading testing and certification requirements that apply to other Group A cargoes.
Cargo properties
Iron ore concentrate is produced principally from magnetite and hematite ores by:
- Crushing and grinding to liberate iron-bearing minerals from gangue.
- Magnetic separation (for magnetite) or flotation (for hematite) to concentrate the iron content.
- Filtration and partial dewatering to reduce moisture for transport.
- Pelletisation in some cases (producing iron ore pellets, which are a separate cargo with different properties).
The resulting concentrate is a fine, uniform, dense powder. Iron content typically exceeds 65 per cent Fe by mass, compared with 60 to 65 per cent for direct shipping iron ore. Bulk density is approximately 2.5 to 3.0 tonnes per cubic metre, with stowage factor of approximately 0.33 to 0.40 cubic metres per tonne. The combination of high density, fine particle size, and high moisture means iron ore concentrate is one of the most heeling-prone cargoes if liquefaction occurs.
Liquefaction risk
Iron ore concentrate is highly liquefaction-prone for several reasons:
- Uniform fine particle size with a high fraction below 100 micrometres provides ideal conditions for pore-water development under ship motion.
- High moisture content from the dewatering process, typically 7 to 11 per cent, is often close to the transportable moisture limit.
- High bulk density means small volumetric shifts produce large heeling moments.
The Proctor-Fagerberg test is the recommended method for determining TML on iron ore concentrate cargoes. Pre-loading certification typically reports MC in the range of 6 to 10 per cent and TML in the range of 8 to 12 per cent. The IMSBC requirement is that MC be no more than 90 per cent of TML at loading.
Major routes
Iron ore concentrate seaborne trade flows include:
- Brazil (Vale’s Carajás S11D operation produces iron ore concentrate alongside direct-shipping ore; exported through Ponta da Madeira and Tubarão).
- Chile (Compañía Minera del Pacífico magnetite concentrate from the Atacama region).
- Peru (Marcona iron concentrate from Shougang Hierro Peru and Marcobre).
- Mexico (Pacific coast magnetite concentrate exports to Asian steelmakers).
- Iran (Bandar Abbas, Persian Gulf exports of magnetite concentrate).
- Russia (Murmansk and Eastern Siberia concentrate exports).
- Ukraine (until 2022, significant Black Sea exports; reduced post-invasion).
Receiving ports are principally Chinese steelmaker terminals at Qingdao, Bayuquan, Caofeidian, and others, supplemented by Japanese and South Korean steelmaker imports.
Pre-loading testing and procedures
Iron ore concentrate consignments require:
- Sampling per the IMSBC Section 4 protocol.
- Laboratory determination of TML by the Proctor-Fagerberg method (the modified version validated for fine cargoes).
- Laboratory determination of moisture content (no more than seven days before loading).
- Cargo declaration including TML, MC, transport-related properties, and shipper certification.
- Master’s review of the certification before loading commences.
The “can test” can be performed shipside as a rapid screening tool but is not a substitute for laboratory certification.
Cargo handling onboard
Loading is by shore conveyor and shiploader. The cargo self-trims and no mechanical trimming is generally required. Pre-loading hold preparation includes inspection of bilge wells, drainage paths, hatch cover integrity, and ventilation closures.
During the voyage, the cargo is generally not ventilated. Continuous bilge well monitoring detects any moisture migration, which is an early warning of potential liquefaction. Some operators install vibration sensors or motion-monitoring systems on bulk carriers carrying liquefaction-prone cargoes; sudden changes in roll behaviour or in cargo compaction can indicate developing liquefaction.
Discharge
Discharge is by grab-fitted shore cranes or, at modern dedicated steelmaker terminals, by continuous unloaders with bucket elevators. Discharge proceeds at controlled rates with attention to dust suppression. Iron ore concentrate is highly abrasive and grab and conveyor wear is significant.