BHP Billiton subsidiary QNI operates a nickel refinery at Yabulu, 25 kilometres north of Townsville in Queensland, Australia. Three projects, part of an all-encompassing Yabulu Optimisation Initiative, have specifically targeted energy and water use efficiencies, with significant results.
QNI refines over 3.5 million wet tonnes of imported nickel laterite ores each year, using a complex hydrometallurgical process to produce high-quality nickel and cobalt products for sale into world markets.
Celebrating 30 years of operation on the north Queensland coast this year, QNI’s Yabulu Refinery has been working for many years on improving the efficiency of its operations. The impetus is a major expansion project now approved and being readied for commencement in 2005.
Yabulu Optimisation Initiative
The strategy to improve efficiencies, known as the Yabulu Optimisation Initiative, provides the operation with a sustainable future through increased cobalt and nickel recoveries, increased throughput and decreased unit costs. The optimisation projects commenced with employee workshops aimed at identifying viable projects. Some 550 projects were proposed, with further study reducing this number to 33.
QNI undertook a step-by-step process to identify and prioritise projects that offer potential environmental and economic benefits. Three projects from this initiative, specifically aimed at energy and water reuse with the added benefit of increased cobalt recovery, were effectively commissioned in 2003. Many more are on the way.
The three projects are:
- the Boiler Feed Water Preheat Project
- the Green Water Re-Use Project
- the Cobalt Plant Water Re-Use Project.
Positive results from these projects, including water and energy usage efficiencies together with greenhouse gas reductions per tonne of product, have so far justified the extensive efforts expended. The initiatives also represent a breakthrough in engineering design and implementation and an outstanding achievement in the refinery’s quest for a more sustainable minerals processing operation.
The projects are already contributing efficiencies in direct water and coal savings and increased product sales, with a total value of over AUD$3.8 million per year.
The Boiler Feed Water Preheat Project has resulted in a new boiler feedwater system that utilises heat energy available from distillation columns in the area to preheat water prior to it being fed to the powerhouse turbines. Utilising the available heat energy reduces the requirement to consume steam in the powerhouse to preheat the water. The significant benefits from this project are energy savings and increased production.
The Green Water Re-Use Project recovers water, nickel and heat energy from 85˚C basic nickel carbonate slurry. The old process resulted in a loss of nickel and valuable hot water to the tailings dam. The reuse of water from this project has a direct impact on the quantity of new water used in the plant. Approximately one million litres of water per day is saved as a result of this process, together with increased nickel recoveries.
The Cobalt Plant Water Re-Use Project recovers heat and water, saving over 350 000 litres of new water every day together with energy savings.
In combination, these projects have reduced the quantity of new water used in the production process from 206 kilolitres per tonne of final product to 185.7 kilolitres per tonne of final product, a saving of 20.3 kilolitres per tonne. The quantity of energy used per tonne of final product has been reduced from 583 gigajoules per tonne to 567 gigajoules per tonne. Greenhouse gas emissions from the plant have been reduced from 46.5 tonnes of carbon dioxide per tonne of final product
to 45.5 tonnes.
Specifically, these projects have reduced materials and energy intensity in two ways. Firstly, by increasing cobalt recovery, they have increased the quantity of product produced per tonne of ore processed in the plant. One of the projects also reduces the amount of nickel lost to tailings, thereby increasing the amount of nickel product obtained from the ore. Secondly, the projects have reduced the amount of new water and energy (coal) used to produce the final products.
These successes at Yabulu Refinery confirm, once again, that projects that benefit the environment can also return a sound economic benefit.
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