Optimise your thickener efficiency for maximum profitability

Su-Anne Willemse, Endress + Hauser

 

Published in:

Electricity+Control, January 2016

Enquiries: Suanne.Willemse@za.endress.com

 

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 A key step in most ore refining operations is the physical separation of process water from the useful extract or tailings. The optimisation of this process is critical for several reasons:

• The availability of large volumes of process quality water in South Africa is always limited and expensive, making the use of recycled water attractive
• Energy and flocculants costs are major contributors to process costs
• In many cases, tailings can be re-processed to extract fine traces of precious metals. However, for this to be economically viable the water content of the tailings needs to be minimised reducing the energy and chemicals needed for extraction to an absolute minimum
• Impure waste water can leach into ground water and waterways polluting water supplies; South African regulations determine acceptable levels of impurities that can be discharged

Large tanks, known as thickeners, are used to separate fine suspended mineral particles from the process water, producing a stream of clarified water from the top of the thickener overflow and a thick sludge of settled solids (underflow) from the bottom. Flocculants are mixed with the solid – liquid suspension in the entry feedwell of the thickener. The flocculants aggregate the fine particles, which speeds up settling of the solids.

 

Take note

  • In modern mining, every small improvement reflects on the bottom line.
  • Thickening tanks play a crucial role in separation of fine mineral particles and process water.
  • Outflow density and volumetric flow can – and must – be measured accurately and reliably to optimise process efficiency.