COMMINUTION AND CRUSHING units and an abundance of surplus kinetic energy are already proven to process sustained tonnage rates exceeding 14,000 t / h , whilst maintaining an impressive 400 mm x 400 mm maximum product size – even when the feed approaches a 10:1 crushing ratio . At the same time , the TRC 25.37 is able to develop an impressive 11 % increase in the surface area of the product , significantly assisting the oil recovery process .”
The company adds : “ In the redesign of the oil sands Primary Crushing Plant , none of the components were ignored in the New Generation plant . Not just functionality and reliability being key areas of focus , but of equal importance were considerations for maintainability and reduction of downtime , during both planned and unplanned maintenance outages . The net result is the most effortlessly maintainable , cleanest and powerful primary crushing plant , which now fulfils both the immediate and future needs for mining oil sands .”
The TRC 25.37 is designed for a sustained 17,000 t / h throughput capacity in all oil sands materials and the most frigid ambient conditions . The two units which commenced production in 2016 are detuned to the contracted 14,000 t / h capacity but can be fully realised with a simple change to the ratio of the apron feeder . “ For those mines not immediately requiring the implementation of a complete new crushing plant , the upgrade to the powerful New Generation TAKRAF TRC 25.34 DRC has proven to be an economically effective means to increase production through elimination of stalls and reduced maintenance downtime ; as well as increased recovery through achieving a high crushing ratio , even in the most extreme winter conditions .”
This type of primary crusher upgrade typically requires a shutdown period of 22 to 30 days . Economically , the payback period is less than two winter seasons , says TAKRAF . Finally , TAKRAF is also working on solutions for copper ore , iron ore and bauxite mines , together with mines with difficult overburden ; which will culminate in a New Generation range of Extreme Class machines for their hard ore types .
Increasing mill capacity through HydroFloat
The HydroFloat™ from the Eriez Flotation Division is an innovative fluidised-bed flotation cell that can substantially increase the upper particle size that can be successfully treated by flotation . An IMPC 2016 paper by Mankosa et al outlined recent studies that were conducted using laboratory , bench-scale and pilot-scale equipment , that indicate that this technology can be used to float coarse sulphide middlings that cannot be recovered by conventional flotation machines . Recent data collected from pilot-scale tests conducted at a base metal concentrator indicate that this technology can float middlings particles as large as 850 microns in diameter containing as little as 1 % exposed hydrophobic mineral . As such , the crossover of this technology into the base metals industry has the potential to substantially reduce grinding costs and increase concentrator recovery / capacity through the use of split-feed circuitry . The split-feed concept , which is often used for upgrading industrial minerals , involves segregation of the feed into more than one size class followed by subsequent upgrading using mills / separators / reagents specifically optimised for each size class . An example split-feed circuit was developed that utilises two stages of classifying cyclones in conjunction with the HydroFloat separator . The circuit is designed to recover , recycle and regrind coarse middlings containing small amounts of valuable mineral while simultaneously rejecting coarse wellliberated siliceous gangue so that mill throughput can be increased . Coarse tailings also maximise water recovery from impoundments while reducing overall impoundment size . Simulation data conducted using well-known process models suggest that this approach can increase existing primary mill capacity by up to 25 % with only modest investments in new classifying and flotation equipment .
The shown simplified flowsheet includes a primary grinding mill , primary classifying cyclones , rougher-scavenger flotation banks , cleaner flotation columns and a middlings regrind mill . The availability of the HydroFloat technology allows the circuit to be modified as shown . In this case , the primary classifying cyclones are reconfigured to provide a substantially coarser size cut ( eg D80 increased from 150 to 300 microns ). This layout allows the underflow to be passed back to the primary mill , while the overflow is passed to a secondary set of classifying cyclones . The secondary cyclone bank produces a fine ( eg minus 200 micron ) overflow that is sufficiently liberated to be upgraded by the downstream conventional / column flotation circuit and a coarse ( eg nominal 150 x 300 micron ) underflow that is passed to the HydroFloat circuit . In this case , feed to the HydroFloat is reclassified using a CrossFlow separator to ensure near-complete removal of fines . The HydroFloat is then used as a highly efficient flotation separator to ensure that all particles containing valuable sulphide mineral report to the overflow concentrate , which is recycled back to the primary grinding mill for further size reduction and liberation . The HydroFlow at the underflow , which consists of coarse liberated gangue , is rejected as a throw-away product that is essentially free of valuable mineral . As such , the siliceous gangue tonnage rejected by the HydroFloat makes room for new feed tonnage in the primary grinding mill . IM
Examples of ( a ) the simplified baseline flowsheet and ( b ) modified split-feed flowsheet incorporating the HydroFloat technology
MARCH 2017 | International Mining