This article was originally published in Engineering News & Mining Weekly’s Tailing & Wastewater Management Feature.
The application of South African minerals processing company Multotec’s technologies on tailings and waste management streams allows for the recovery of resources – such as water, precious metals and by-products – in a way that maximises revenue and the manageability of the process, says product specialist for solid/liquid separation Gerrit du Plessis.
The efficacy and stability of the process, which also removes contaminants that are harmful to the environment, is critical for operations, particularly in South Africa, as it is a water-scarce country.
Operations need to maximise and increase process throughputs, owing to the reduction of quality ore, says Du Plessis, who adds that the metallurgical process requires the use of water and, owing to the national water shortage, “it is important to recover water to the best of the technologies’ abilities”.
He suggests using continuous counter current ion-exchange product, from Multotec’s Australian partner CleanTeQ Water. The product is often used in combination with other technologies such as membrane reverse osmosis (RO) technology.
Multotec’s water-treatment products also include using membrane technology, as well as chemical precipitation, to remove soluble contaminants, recover more precious metals and improve the quality of water for reuse while reducing reagent consumption.
Final product and tailings process streams can be further concentrated using Multotec’s filter press and centrifuge technologies, a trend that has steadily increased, Du Plessis notes, owing to the solutions being used in high-pressure applications, thereby significantly reducing tailings volumes.
However, process equipment used on tailings and waste streams is normally considered a “hard sell”, as operations have a tendency to focus capital on high-value product streams to generate maximum revenue, resulting in waste and tailings streams often being neglected.
“Tailings become more difficult if you consider the decreasing ore grades in some applications. Also, if an operation has a larger volumetric flow of process streams from where the product is recovered, their tailings volumes also increase,” Du Plessis explains, noting that this has often been a deterrent.
However, this is no longer the case, as legislation has stipulated certain controls, and companies have become more aware of the negative impact of environmental pollution, as well as its socioeconomic impact.
Internationally, in some water-scarce areas, tailings dams are prohibited, for which Du Plessis suggests a dewatering-equipment alternative.
“A lot of companies prefer to have a dewatering facility and use that as a backfill into openpit areas, otherwise they won’t be able to execute the project because they are likely to be delayed in receiving a tailings dam licence,” Du Plessis comments.
Using Multotec’s filter press technology makes a tailings dam licence redundant, as the water is retained on site, the recovered water is reused in the plant and allows for waste to be discarded on a smaller footprint or backfilled in a mine pit area, he adds.
To this end, Multotec supplies fully automated filtration technology – such as filter presses – that ensures maximum filter cake moisture is achieved so that the product can be used as dry stacked tailings while “guaranteeing” product discharge from filter chambers.
A filter cloth wash system is then implemented to ensure that the cloths are cleaned regularly to maximise the life span of the filter medium and filter plates, thereby ensuring maximum product use.
“We can also supply turnkey filtration plants to enable end-users to implement a dewatering project cost effectively,” Du Plessis notes.
Multotec’s tailings dam cyclone offering is engineered to ensure an optimum volumetric split between the over- and underflow of the cyclone to match the required rate of rise of the tailings dam.
Other products in the company’s versatile product range include a variety of centrifuges – such as the Conturbex, Pusher and Conthick – as well as the Short Bowl Decanter.
All these products have fit-for-purpose features, are applied in various process streams and are manufactured using special construction materials to resist corrosion and abrasion.
Multotec can supply turnkey filtration plants to enable end-users to implement dewatering project cost effectively
Conturbex centrifuge in operation dewatering and washing recovered salt from a high temperature waste stream, utilised as a chemical reagent in the chemical process
Multotec has partnered with Australian based Clean TeQ Water to provide the African mining market with a continuous counter current ion exchange technology
Multotec’s product range including filter presses and centrifuges offer fit-for-purpose solutions for various process streams