Queensland Alumina Limited (QAL) was commissioned in 1967 with an annual capacity of 3,950,000 tonnes of alumina.
The refinery covers 80 hectares of a 3,050 hectare site on the south-east outskirts of the city of Gladstone. Adjacent to the refinery is a wharf and storage facility on South Trees Island, which is connected to the mainland by a causeway bridge.
QAL produces alumina on behalf of its two shareholders, Rio Tinto Aluminium (80 per cent) and Rusal (20 per cent).
QAL’s bauxite supplies are mined in Weipa in far north Queensland and shipped around Cape York and 2,000 kilometres down to QAL in Gladstone. Here, the alumina is produced through the continuous four-stage “Bayer Process” involving:
- Digestion – dissolving bauxite’s alumina content
Bauxite is finely ground in mills, and then mixed with a recycled caustic soda solution and steam in digester vessels operating at high temperature and pressure. This dissolves the alumina content of the bauxite and the solution is then cooled in a series of flash tanks.
- Clarification – settling out undissolved impurities
The impurities, which remain undissolved, are allowed to settle as a fine mud in thickening tanks. After several washing stages to recover caustic soda, this residue is neutralised with sea water and pumped to storage dams. The solution of alumina in caustic soda is further clarified by filtration.
- Precipitation – forming alumina crystals
Precipitation involves the recovery of alumina crystals from the caustic solution. In open-top tanks, the solution is stirred by mechanical agitation and seeded with previously precipitated alumina to assist crystal growth.
- Calcination – high-temperature drying of alumina
The precipitated material (called hydrate) is washed and calcined at temperatures exceeding 1,000°C. This forms the dry white anhydrous aluminium oxide powder, alumina, which is cooled and conveyed to storage.
Water is essential to QAL’s refinery operations. Since the commissioning of Queensland’s largest water recycling project in 2002, QAL continues to recycle the majority of Gladstone city’s wastewater. In 2011, QAL started construction to source treated effluent from Boyne Island/Tannum Sands for use in the refinery. This work continues in 2013.
QAL’s waste transfer facility allows for the segregation of on-site waste and recycling of materials including metal, cardboard and wood. In 2012, the facility recycled 85 per cent of the 6,060 tonnes of materials brought to the facility.
Land and revegetation
Land revegetation of the plant’s process residue areas continue each year in the buffer zone between QAL and the community. Each year, approximately 2,000 trees are planted by QAL employees and community volunteers. Long-term revegetation work on the former residue disposal area continues to be extremely successful with a large supply of grass for dust control and shelter for native animals.