“Bulk Handling Today” attended FLSmidth’s open day at Mintek recently. We were there to hear about the in’s and out’s of the company’s Reflux Classifier (RC) technology.
Global product manager, Taavi Orupold, took us through the basics of the equipment and technology. “The RC can be used as a volumetric gravity separator to treat fines generally less than 2.0mm, and a size classifier which, although efficient may not be cost-effective.”
The classifier is able to treat -2.0mm + 0.038 microns.Current applications are working between 38 microns to 1mm and coal applications are working between 75 microns to 2mm.
Importantly the feed to the units must be sized correctly with a top to bottom size ratio of 4:1 being ideal for minerals and as much as 8:1 for coal applications. It is suited to be the primary fines treatment unit after desliming; and for tailings and fine reject retreatment.
The RC is a combination of a lamella settler, autogenous dense medium separator and a fluidised bed separator. The operation draws together the best elements of these different systems resulting in a powerful density-based separation developing within the inclined channels. This forces low density particles to overflow but retains high density particles.
Fine high density particles form an autogenous dense medium (the fluidised bed). This zone then sends smaller and low density particles towards the inclined channels, and then to overflow.
Modular and portable
RC’s are commercially used in coal, iron ore, mineral sands, chromite, manganese, potash and spodumene (lithium) applications. But in fact, they can be used in all gravity separation applications such as barite, silica sands and PGM rougher tailings.
“Perhaps the biggest advantage of the RC is that it is entirely transportable. It can be moved with ease from the factory to site and when broken down into two major components and units up to RC 2000 size can be fitted into a standard 20’ open top container,” says Taavi.
After tea, Nick Boonzaaier, previous senior process development engineer at the Grootgeluk coal mine; now employed by FLSmidth, gave an honest and forthright take on what it’s actually like to run this RC first-hand. His advice? “It’s preferable to get in on the ground-floor with the RC design or there will be much time spent ‘tweaking’ because many aspects have to be changed to get the most out of the system.
“Overall RC is invaluable, in my opinion, but it requires a considerable amount of time in training and preparing staff for this new technology. Computerised control is not enough. You need people on the floor, daily inspections and weekly washes are non-negotiable. There is also no substitute for comprehensive training in this technology.”
Having had a good hard look at a RC100 test unit running at Mintek, we weren’t sure why there weren’t more takers? It’s true that nobody wants to be first, and everybody wants to be second, but especially given the state of the economy at present, the payback on a RC can be counted in months.