Modern Mining August 2019

Spiral test rig solves separation challenges

Responding to industry’s need to re-treat chrome dumps, Multotec has been adapting its versatile spiral test rig to upgrade ultra-fine chrome. The full-scale test rig is part of a range of dedicated facilities employed by Multotec’s Technology Division to optimise mineral sepa- ration and concentration methodologies for customers. Located at the company’s headquar- ters in Spartan, Gauteng, the rig allows eight to 10 different spirals to be erected at a time. “With the drive to process tailings in the chrome sector, we have been running tests on a more compressed spiral with a reduced pitch,” says Jeantelle Rust, R&D engineer at Multotec Process Equipment. “This reduces the velocity of the very fine particles.” This configuration works particularly well when dealing with fine material, hence its application in tailings, says Rust. The spiral could offer a cost-efficient way of separating ultra-fine chrome material and recovering valu- able product. “Such a solution presents an attractive com- mercial proposition to industry, and will also address environmental concerns presented by tailings dumps,” she says. Using a mouth-organ product box, the material being tested on the spiral rig is split into eight product fractions, not just the usual three for product, middlings and tailings. This helps optimise the mass balance for reporting purposes. The spiral test rig has also been used to evolve designs that are able to handle coarser material. Customers were looking for a solu- tion to the ‘beaching’ of coarse coal product

on the spiral’s surface, for instance. “We were able to modify the angles and diameter of the trough to address this chal- lenge,” she says. “Our ability to make small adjustments to the equipment, and to test material repeatedly at full scale, is the key to finding practical solutions.” Multotec has also conducted research for producers of mineral sands – or heavy minerals – where head grades were steadily dropping. This necessitated the treatment of larger ton- nages, requiring higher capacity spirals. “Space constraints on the customer’s site meant that adding spirals to their process was not an option,” says Rust. “Wider spirals were thus tested for higher throughput, with different angles to minimise losses.” While the spiral appears to be a relatively simple piece of equipment, she highlights that the variety of forces at play makes it impos- sible to accurately model a spiral’s action and results. The kind of testing conducted by Multotec is therefore vital to achieve optimal separation efficiencies. Multotec, website: www.multotec.com Multotec spiral modifications include reducing the spiral pitch for fine chrome separation. at-height and confined-space rescue service. “After the silo had been emptied, a consider- able quantity of coal build-up was revealed, so we rigged a system to allow for it to be removed safely and quickly,” Zinn adds. “The specialised services we offer to the petrochemical and power generation indus- tries are highly applicable to the mining industry. The traditional means of carrying out maintenance of this kind is to erect scaf- folding, which is time-consuming and costly. With rope access, the necessary work can commence straightaway, making the most of the tight timeframe of the shutdown,” Zinn elaborates. Skyriders, website: www.ropeaccess.co.za

Skyriders’ skills on display at coal mine The mining industry’s requirement for tight schedules and limited downtime when it comes to routine maintenance has allowed Skyriders Access Specialists to showcase the benefits of rope access for a project at a major coal-mining company in Mpumalanga.

Sub-contracted to Enprotec of Middelburg, the scope of work for Skyriders was twofold, explains Marketing Manager Mike Zinn. The first task was to rig and install a system to give access to an inverted cone within a dis- card-coal silo, in order to carry out cutting and welding work. The second major requirement was rigging the old inverted cone that was being replaced. In addition, Skyriders provided a standby work-

August 2019  MODERN MINING  43