Technical Development

QAL is installing three new Seawater Condensers to assist with condensing odorous compounds in the Digestion section of the plant.

Seawater currently used to transport the waste red mud to the Residue Management Area (RMA), will be rediverted to the seawater condensers to interact with waste steam and condense odorous compounds present.

The large dilution effect of the seawater and the interaction with the red mud reduces the odour threshold below detection of the human nose, hence greatly removing odour discharged to the environment.

Looking like a supercharged stick blender, SWIRLFLOW sits at the top of the mixing tank and generates a tornado-like swirl throughout the fluid and was invented to overcome production losses caused by scale build-up.

The movement created by SWIRLFLOW picks up solids from the base of the tank and lifts them to the upper regions, where the solids continue to spiral downward along the tank wall en-route back to the base, to be lifted again. The swirling motion also creates a cleansing effect against the tank walls, reducing scale.

Many mineral processing procedures rely on keeping solids in suspension in large tanks. Inefficient processing through uneven mixing and build-up of solids (scale) around the tank wall can reduce the amount of metal extracted, cause frequent downtime for equipment maintenance, and increase energy consumption.

In order to improve the quality of water discharged into the South Trees Inlet, a number of treatment methods were investigated. This included using Moving Bed Biofilm Reactors (MBBR), Trickle Filters (TF) and Facultative Ponds (FP). All methods involved the use of “bugs” to help remove organic matter and were monitored by measuring their performance as BOD (Biological Oxygen Demand in mg/L) consumed. As bugs consume the BOD, the level of Dissolved Oxygen (DO) decreases. This means that high levels of BOD are detrimental if released into the surrounding environment. Low levels of DO reflect the inability to treat high levels of BOD (oxygen demanding microbes- bugs) in the water being discharged. The lower the BOD output, the better the performance and the better the discharged water quality.

Evaluation of results from the three different pilot treatment methods focussed on the performance of the facultative ponds and their ability to remove BOD to low levels. From the pilot scale work, implementation proceeded to the building of Cell 1 – a 21 hectare facultative pond with the aim to reduce BOD levels. Data is currently being collected to assess the full scale pond and to determine its maximum capabilities and its minimum limitations. Based on the results from Cell 1, a second pond, Cell 2 is also being constructed.