Vale has added a second site to its Sustainable Sand efforts, having started industrial-scale production of the by-product at its Viga mine in Congonhas, Minas Gerais, Brazil.
The operation has the capacity to process 200,000 t/y of sand, with 80,000 t slated for 2022 and 185,000 t in 2023.
Obtained from the treatment of iron ore tailings, Sustainable Sand is one of the company’s initiatives to reduce the use of dams in its operations in Minas Gerais. The material can replace natural sand, extracted from river beds, with a wide application in the civil construction market.
Jean Menezes, Operations Manager of the Viga mine plant, said: “Due to the geological characteristics of the mine and the mineral processing technology applied, we developed a coarser sand, with low presence of fine particles in the material, and high purity content, having in its composition between 89% and 98% silica and less than 7% iron.”
The company is already conducting tests of the material with concrete and mortar producers in the Southeast Region, with the Sustainable Sand flowing between the production site and the clients by rail, taking advantage of the existing logistics at the site.
The Viga mine is Vale’s second unit to manufacture Sustainable Sand on an industrial scale, following the same quality controls as for iron ore production. The first was the Brucutu mine, in São Gonçalo do Rio Abaixo, Minas Gerais, which processed 250,000 t of the material last year. The company’s projection is to produce 1 Mt of Sustainable Sand this year, before doubling the volume in 2023.
Each tonne of sand produced represents one tonne less of tailings being placed in piles or dams, Vale says.
Another initiative adopted by Vale to reduce its dependence on dams, and which also favours the production of Sustainable Sand at the mines, is the tailings filtration system. The technology reduces the moisture of the tailings, enabling both dry stacking of the material and the manufacture of sand for the market. Four tailings filtration plants have been implemented in Minas Gerais – one in the Vargem Grande Complex (in 2021), two in the Itabira Complex (between 2021 and 2022) and one in the Brucutu Mine (in 2022).
Vale has already invested more than BRL50 million ($9.7 million) and established partnerships with more than 40 organisations, including universities, research centres and domestic and foreign companies to study applications for material from iron ore processing. The objective is to make Vale’s operations safer and more sustainable, promoting the circular economy and benefiting society.
In March this year, the first road in Brazil to use Vale’s Sustainable Sand in all four layers of pavement was inaugurated. The 425-m-long track at Cauê mine, in Itabira, will be monitored for two years with 96 pressure, temperature, deformation and humidity sensors. Tests carried out during five years in the laboratory indicated that the increase in useful life is of the order of 50% and the cost reduction is 20% when compared with materials more commonly used for road construction, such as sand extracted from the environment. In addition, each kilometer of pavement can consume up to 7,000 t of tailings.
In April 2022, a study released by the University of Queensland (UQ), through its Sustainable Minerals Institute (SMI), the University of Geneva (Unige) and the United Nations Environment Program (UNEP) pointed out that the sand from the iron ore production process, called “ore-sand”, can contribute to solve two important environmental issues by reducing both the extraction of natural sand from the environment and the generation of mining waste.