Protecting mineral slurries in the Amazon rain forest of Brazil is akin to a James Bond mission. The terrain is rugged, the locations are remote. Among the scarlet macaws and tree frogs, prowling jaguars and slithering anacondas live in the 1,100 different tree species with 2.5 million different insect species crawling about.
Simply getting to the mining sites can take up to a day of travel and the challenges of piping slurries hundreds of miles means protection against aerobic bacteria contamination, slime formation and interior erosion is difficult at best. But the mission is not impossible.
With the 5th largest bauxite reserve in the world and a vast array of minerals - from Kaolin, copper and iron ore to gold and diamonds - Brazil’s mining industry has grown over the last decade. So, too, have concerns about protecting the rainforest as well as the minerals and people living near mining sites. But the introduction of piping rather than traditional delivery methods, has helped.
“Slurring and pumping [minerals] through a pipeline is a viable option. This is especially true in rugged terrain where rail and conveyor construction can become expensive and time consuming. Furthermore, a pipeline can offer the benefits of being unobtrusive, more environmentally friendly and less subject to interference from local populations,” Mauricio Franzim, Technology Manager, Brazil, Biocides said.
While there are many positives to piping minerals, protecting the slurries is full of challenges. It is a lengthy process that involves many stages. For example, mining kaolin in Monte Dourado takes 25 steps from mine to customer - the first is simply the mining itself, but before it’s shipped it is blended, degritted, screened, leached and stored several times. And during each of these steps, protecting the mineral is crucial.
“Preservation from bacteria contamination is costly for kaolin and bauxite processes. Spoilage occurs when aerobic bacteria deplete the oxygen content and the slurries become anaerobic. Then facultative anaerobes, like sulfate-reducing bacteria, form hydrogen sulfide which imparts a foul smell to the clay and eventually forms iron sulfide that turns the clay gray to black. This increases corrosion of the pipelines and causes viscosity and rheology problems,” Craig Waldron, Global Market Manager, Building Products, explains.
With facilities located in southeast Brazil, Lonza has been working to provide commercial solutions for mineral slurry protection for years. But finding the right ones have been time consuming.
“Significant thought goes into determining the best biocide. Is it chemically compatible with customer formulation? Is it effective against a broad spectrum of microorganisms? How long does it reside in the product? What are the chemical breakdown products? What is the impact in the rheology of the slurry?” Waldron says.
Based on lab and plant trials, Lonza created the blends Proxel™ BZ Plus, Proxel™ DCB and Proxel™ BN, using Benzisothiazolinone (BIT) which have proven safe and effective. In addition to biocides, Lonza performs plant hygiene audits, monitors tank storage for microorganisms, conducts audits during vessel loading, provides microorganism tests and analytical evaluations (the latter to determine the level of Lonza actives in formulations).
Lonza is currently working on a project with Brazil’s Instituto Nacional de Tecnologia to combine biocide and corrosion inhibitors for bauxite slurries. It is in the early test phase, but the mission to protect mineral slurries continues.