Alcoa Brasil’s Filtro Prensa project will create new ways to manage bauxite residue

Work on Alcoa Brasil's Filtro Prensa project began in August 2021 at the company's Poços de Caldas alumina refinery, which is fed by a captive adjacent bauxite mine. It is R$310 million (US$55 million) investment that will fully transform the waste disposal system at the Minas Gerais facility. The construction was projected to take 15 months and employ roughly 500 people at its peak, with an opening date set for November 2022.

The project took approximately seven years to complete. A new bauxite residue filtering plant will change how the refinery manages bauxite residue, which is mostly made up of red mud and coarse sand and is a byproduct of the alumina refining process. The coarse sand fraction (red sand) makes up about 40% of the residual, whereas the fine silt fraction makes up about 60%. (red mud).

It will produce a dry residue with just 30% moisture, which is similar to natural soil moisture, and will route the water extracted to the manufacturing process, where it will be reused, through a closed circuit. Trucks will transport the dry material, which will be emptied and compacted in a new waste disposal location. This is the third Alcoa plant to use the technology, with the other two being in Australia. It's also the first in Brazil. Because the water can now be recycled in a closed-loop system, the method saves a lot of water.

Diemme Filtration, situated in Lugo, Italy, and part of the Aqseptence Group, is supplying the filter press technology. Filtro Prensa will employ two GHT25000P overhead beam filter presses with Alcoa-specific features (such as valves, electricals and components). They each contain 100 plates, but they may be expanded to 130. Similar filter presses were also delivered by Diemme to Alcoa's Australian alumina refinery plants at Kwinana and Pinjarra, both in Western Australia. Alcoa was Australia's first significant alumina production to employ residual filtering.

Filter press technology has several benefits that make it particularly well suited to the treatment of bauxite residues. Filter presses, in comparison to other technologies, produce drier residue (with a residual moisture content of less than 30% w/w). As a result, according to Diemme, the material handling properties of the cake created by utilising filter presses are significantly superior to those acquired by other methods.

Alcoa has three manufacturing facilities in Brazil, located in Poços de Caldas (MG), So Lus (MA), and Juruti (PA), as well as offices in So Paulo (SP), Poços de Caldas (MG), and Braslia (DF), as well as a significant stake in bauxite miner Mineraço Rio do Norte (MRN) and four hydroelectric plants, Machadinho, Barra Grande, Serra do Fac

“Re-defining what it means to be the most sustainable upstream aluminum company requires a deep commitment to continuously improving our footprint and a relentless pursuit of innovation that will help us progress,” said John Slaven, Alcoa Executive Vice President and Chief Operations Officer last year.

“By continuing to roll out this bauxite residue filtration technology across more of our refineries, we continue to set new benchmarks in regard to resource management while making progress on goals aligned with our Advance Sustainably strategic priority,” added John Slaven.