Kalbar Conversations Column

Improving environmental outcomes with centrifuges

   Wednesday 31st March, 2021

To minimise the environmental impact of the Fingerboards project, Kalbar Operations will utilise centrifuge equipment as part of the mineral sands mining process.

This article addresses key questions regarding centrifuge equipment, how centrifuges work, and why centrifuges will provide improved environmental outcomes for the project.

What is a centrifuge? How does it work?

A centrifuge is a machine that houses a rotating cylinder in which substances of different densities can be separated through rotational speed. A simple example of a centrifuge is your washing machine - the drum containing your laundry items spins rapidly to separate, or spin dry, water (which is lighter) from the (heavier) laundry items.

There are different types of centrifuges. The specific type that Kalbar proposes to use is called a solid bowl decanter centrifuge (SBC). Like all centrifuges, they simply separate the water and denser solid particles in a liquid “mud” by spinning it very fast inside the centrifuge, causing the dense solid particles to separate from the lighter water particles, just like the spin cycle of a washing machine.

What will the centrifuge be used for?

Centrifuges will extract water from fine sand tailings to produce a solid cake and the extracted water will be re-used and recycled, with the remaining soil returned to the site as backfill as part of the rehabilitation process.

Are centrifuges safe to use?

Yes - centrifuges are a widely used safe and mature technology. A centrifuge is operated wet and does not use any flammable or volatile chemicals.

Centrifuges use a flocculant to improve the separation of very fine clays. This flocculant is the same type that is widely used in agriculture as a soil conditioner, in land management to reduce sediment run-off, and in potable water treatment across Gippsland to increase drinking water clarity. The flocculant breaks down fast in contact with UV light and oxygen and is not hazardous to aquatic and other animals.

Are centrifuges noisy?

SBC centrifuges produce roughly the same sound (90dBA) as standing three metres away from an average petrol lawnmower. On the Fingerboards project, they will be housed inside an enclosed building with sound cladding which will reduce audible noise even further.

Why have you introduced centrifuges into the mining process for the Fingerboards project?

Because the fine tailings are dewatered to a solid cake, there is no need to construct any tailings dams. The use of a dry cake in the backfill process will accelerate the commencement of the rehabilitation process, reduce the extent of disturbed area, and reduce water consumption.

Will the use of centrifuge technology require more water than what is indicated in the Fingerboards Project Environmental Effects Statement (EES)?

No - the use of centrifuge technology greatly improves water recovery by “increasing gravity” and because it takes place inside a closed system, there are no evaporation or infiltration losses that occur - resulting in higher water re-use.

Which other industries or mines use centrifuges?

Centrifuges are commonly used in industries such as dairy (cream separators), food processing (oat, almond and rice milks are made with a SBC), beer brewing (to remove yeast and other solids), sludge dewatering in wastewater treatment, and various other industrial and mining processes.

In mining projects, SBCs are widely used throughout Australia to dewater tailings.

For additional details regarding centrifuge equipment or any other aspect of the Fingerboards project, contact us at contactus@kalbaroperations.com.au.

John Francisco - Project Director