Mining Mirror November 2018 | Page 26

Mining in focus it comprises a number of additional flotation steps to upgrade the ore in order to achieve the desired product. “The first stage is known as rougher flotation; after that, the ore goes through a further six stages of cleaner flotation. The re-cleaner tailings are reground and re-floated. This product joins the mainstream acidspar circuit. The re-float tails and first cleaner tails are processed and forms the product known as Metspar, a lower-grade fluorspar product. The acidspar at Nokeng has a grade of 97.2% calcium fluorite. This is filtered to contain less than 10% moisture, and the premium product, which is our acid spar, is then transported to the port and sold to international clients,” says Brits. Most of Nokeng’s clients are based in the United States and Europe, but there are other buyers from other countries around the world. Metspar contains more than 80% calcium fluorite, and is used in the pyrometallurgical metallurgical industry, mostly for smelting, as it reduces the temperature at which smelting takes place and therefore reduces energy consumption. Local and international offtake partners for the product are in place or is in the process of being negotiated. Unique flotation The unique flotation process includes a conditioning step that requires the temperature of the mixture to be increased to more than 60 degrees Celsius. Therefore, boilers had to be installed. The increased temperature significantly improves the separation of the fluorspar from the gangue (unwanted minerals). In Nokeng’s case, the gangue is mainly iron oxide, which is hematite, and silica. “To increase the temperature, several methods can be used, but all involve energy input. Electricity springs to mind immediately, but electricity is only economical in small amounts. The most efficient and the most economical way to satisfy the heat requirements is with coal-fired boilers. To generate enough steam, we require low-pressure boilers,” says Brits. Brits adds that Nokeng has not signed coal contracts yet, but are looking at outsourcing the boiler operation and maintenance to ensure optimal performance of these units. The mine has installed four boilers. Each of the boilers produce about 10 tonnes per hour of steam. The plan is to have three boilers operating at any one time and then have a fourth boiler on standby. In addition to the mine and processing facility near Rust de Winter, SepFluor also plans to construct a chemical plant in Bronkhorstspruit, which will beneficiate the product produced at the mine. Construction of the chemical plant is expected to start within the next two years. Nokeng’s premium product will be acidspar. Acidspar is the key ingredient in the manufacture of hydrofluoric acid (a solution of hydrogen fluoride in water) and is a precursor to almost all fluorine compounds, including pharmaceuticals such as fluoxetine, diverse materials such as PTFE, and elemental fluorine itself. “Our plan is to develop the beneficiation of fluorspar by means of installing a chemicals plant that is currently in a bankable feasibility stage, to establish the financial and the technical requirements. We would then take the fluorspar produced at the mine and process it by using other intermediate products like sulphuric acid with fluorspar in certain process Teichmann was awarded the contract to build the tailings dam. [24] MINING MIRROR NOVEMBER 2018 www.miningmirror.co.za