Alumina (aluminium oxide) is a major dry bulk cargo, with global seaborne trade of approximately 30 to 40 million tonnes per year, principally moving from refineries in Australia, Brazil, the Caribbean, and West Africa to aluminium smelters in the Middle East, China, Iceland, Russia, and elsewhere. Alumina is the intermediate product between bauxite and aluminium metal: bauxite is refined to alumina at refineries adjacent to mining operations or at large industrial sites, and the alumina is shipped to smelters where it is electrolysed to aluminium. The IMSBC Code regulates alumina shipments and provides separate schedule entries for the principal commercial grades.
Schedule structure
The IMSBC Code includes the following alumina-related schedule entries:
- Alumina (calcined): the principal smelter-grade product, a fine white powder of calcined aluminium oxide. Group C (not liquefiable, no chemical hazard).
- Alumina silica: a related material with higher silica content used in selected refractory and chemical applications. Group A in some forms (liquefaction risk).
- Alumina hydrate: an intermediate calcination product used as a chemical feedstock. Group C.
Most seaborne alumina trade is calcined smelter-grade alumina, classified Group C, and handled under standard bulk cargo procedures.
Smelter-grade and chemical-grade alumina
Smelter-grade alumina (SGA) is the dominant product, comprising approximately 90 per cent of seaborne alumina trade. It is a fine white powder of calcined aluminium oxide produced at temperatures of 1,000 to 1,200 degrees Celsius. The product has a particle size distribution centred around 80 to 120 micrometres with a small fraction below 20 micrometres. The bulk density is approximately 1.0 tonne per cubic metre as loaded.
Chemical-grade alumina (CGA) is a broader category including reactive aluminas, fused aluminas, and tabular aluminas used in refractories, ceramics, abrasives, polishing, catalyst supports, and water treatment. CGA grades are generally higher value, finer particle size, and shipped in smaller quantities.
Cargo properties
Alumina is non-toxic and non-flammable. It is hygroscopic and absorbs moisture from humid air, increasing in weight by a few per cent over a long voyage in tropical conditions. The principal handling concerns are:
- Dust generation: alumina dust is fine, abrasive, and a respiratory hazard. Loading and discharge operations require dust suppression at the shiploader, conveyor transfer points, and grab discharge.
- Free flow and self-trimming: alumina is highly flowable and self-trims during loading. No mechanical trimming is generally required. The cargo can also flow rapidly through small openings, making hatch and seal integrity critical.
- Compatibility with steel surfaces: dry alumina is benign to steel; moist alumina can promote corrosion in poorly drained bilges and tank-top steelwork over time.
Major routes
Alumina seaborne trade flows include:
- Western Australia (Wagerup, Pinjarra, Worsley refineries) to Middle East smelters (Bahrain, UAE, Qatar) and Chinese smelters.
- Queensland (Yarwun, Gladstone refineries) to China and other Asian markets.
- Brazil (Alunorte, Pará) to North American and European smelters.
- Jamaica and Suriname to North American Atlantic-coast smelters and European refineries.
- Guinea (Friguia, Compagnie des Bauxites de Guinée alumina) to European markets.
Receiving ports for alumina are typically dedicated smelter terminals with covered conveyor systems and silos for dust-controlled handling.
Loading and discharge
Alumina is loaded by enclosed shiploaders with dust filtration to minimise emissions at the loading point. The cargo is highly flowable and fills the hold uniformly with little intervention. Hatch covers should be closed promptly after loading to prevent rain ingress and cross-contamination from other dust sources. Bilge wells should be inspected and cleared before loading.
During the voyage no specific handling is required. The cargo is stable, non-self-heating, and non-reactive. Hold ventilation is generally not necessary and may be counterproductive by introducing moisture.
Discharge is by grab-fitted shore cranes (less common, since the dust generation is significant) or by pneumatic or vacuum unloaders that draw the alumina out through suction pipes into shore silos. Pneumatic unloaders are increasingly favoured at modern smelter terminals because they minimise dust emissions and allow continuous direct delivery into the smelter feed system.
Comparable bulk cargoes
Alumina is one of several Group C white-powder bulk cargoes that includes cement, phosphate rock concentrate, and certain barium compounds. From a handling perspective alumina is most similar to cement: high flowability, dust generation, and pneumatic unloading at receiving terminals. The difference is that cement is moisture-sensitive (it begins to hydrate on moisture exposure), whereas alumina is moisture-tolerant though hygroscopic.