SPECIALIST EQUIPMENT
binders over vast distances. In most cases, the cost of the binder is the main driving factor with average binder prices at approximately US$200 per ton. Such prices may be double depending on how remote the location is. Backfi ll plants and systems rely on the
preparation of the fi ll, transportation and placing of it. In essence there is a limit to the capabilities of such plant that use only water, binder and tailings as they are limited by the properties of the materials themsevles (PSD, density, mineralogy, binder type, water chemistry and conditions as temperature) and limitations of the plants and pipes. Certain chemicals can increase the solids content and fl owability, at the same time reducing binder content, maintaining the same fl ow and UCS. In certain operation, some can also decrease wear of the system (paddles of the mixer and pipe wear). In addition it is possible to reduce the amount of the water needed for the paste preparation and also increase the amount of the tailings in the paste, whilst decreasing the amount of tailings sent to the pond (surface disposal) .
Off -the-shelf or customer-specifi c solution? Is there a standard product and/or dosage best suited for your mine backfi ll? T e answer is, unfortunately, no. Each mine by its very nature is unique. T e mineralogy of the orebody, the processing method(s), the tailings management method(s), and the water properties are all unique and all have infl uences and aff ect the properties of mine backfi ll. As the mine develops the mineral processing systems may be adjusted to improve recovery rates and hence there may be some variation in chemical properties of the tailings from case to case. T is will require a study for each project to determine the best-suited chemistry. It should also be noted that besides material properties, conditions and requirements from the mine can play a major role in selection of most suitable technology or blend of the technologies currently available. T e only way to obtain an eff ective understanding of how the mine backfi ll can be optimised is by small-scale laboratory testing followed by site testing and trials. A regular
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testing regime is recommended to ensure consistent production of mine backfi ll with the desired properties such as fl ow ability (viscosity), solids content and fi nal compressive strength for the lowest price and maximum benefi t.
The search for the holy grail of cost optimisation
Cost optimisation is a continuous process linked to the cost and availability of the required binders, which in some cases is linked to the amount of available tailings left over from the mineral extraction process. In the search for cost optimisation there has
to be certain element of trust between the mine operator and the chemical supplier. T e mine operator needs to divulge the costs per cubic metre and the key elements to be optimised. Note that in some cases further optimisation on an economic scale is simply unfeasible. Chemicals have the ability to increase/extend the operating range of backfi ll plants so should be viewed as a complementary element, though the cost benefi t, if any, is the ultimate deciding factor. So be wary of anybody claiming that they
have the single ingredient to solve all your mine backfi ll challenges with no testing. If this was the case, then our job would be replaced by a web page and you would order the required product online.
For more information at
www.engineerlive.com/ime
Martijn-K Mannot-Russell & Zlatko Martic are with BASF Construction Chemicals.
www.ugc.basf.com
Graph illustrating chemical eff ect by drop in pumping pressure
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