As production conditions for mineral deposit exploitation are getting tougher and the development of low grade ores comes up to the agenda, the feedstock volume increases and therefore it is very important to increase the efficiency of ore pre-treatment, especially the grinding quality.
Grinding energy makes up more than 5O% of the production cost of iron ore concentrate.
It is well—known that energy-output ratio of the rock is directly proportional to the square of resistance and inversely proportional to elasticity modulus.
We also know that the ultimate compressive strength of the rock is about 7—10 times higher than the ultimate shear resistance.
Thus, while analyzing the physics of fracture process, its important to comply with the following principle of grinding technology - rock failure should be done predominantly through the shear stress.
According to the world’s leading manufacturers over the next 20 years grinding in the drum mills will remain the most efficient way of mineral disintegration.
To date mills (mostly drum mills - ball and SAG type) have reached a certain limit in terms of optimal design, and their further development is possible mainly due to the improved process flow and quality of protective lining.
The lining not only protects the drum against wear-and-tear and dynamic load, but also directly influences the grinding process.
Global experience proved that due to the unique properties (high durability and reliability, high energy dissipation, high wear resistance etc. ) rubber linings have a distinct advantage over metal.
The most popular rubber linings at the market are the linings produced by Valsa GTV (Belaya Tserkov, Ukraine) — “Wave Plate”, “G.M. Wave Plate”, “Lifter Plate”, etc.
In general, the application of pocketed rubber linings ”Wave Plate” in the ball mills of 2nd and 3rd grinding stage have the following benefits compared to the metal linings:
- weight reduction of the complete lining by more than 3—5 times and thus increase of the lifetime of supporting bearings;
- operating cost reduction to replace the worn lining and reduce the risk of accidents;
- noise level reduction by 2-3 times;
- mill efficiency increase by 3—5%;
- required mill capacity achievement at the very first hours of operation;
- reduction of grinding media discharge intensity by 6-10%;
- energy consumption reduction by 7—9% (in general, by 10—12% per process unit);
- lifetime increase by 80-150%;
- run period double increase
Example: Tests performed during 2009 - 2012 (BMC 3.6 x5.5 of the second and third grinding stage at the ore dressing plant of Public JSC “Severny GOK’7.
* As shown above, the specific power consumption in the mills with “Wave plate” rubber lining during the test period compared to a metal lining is lower by 7.1% at the second grinding stage and by 7.46% in the third grinding stage.
Moreover, the application of rubber linings in the ore pre-treatment allows to reduce the specific charge of grinding media by 10% and specific power consumption per process unit by 10—12%.
Thus it is highly efficient to primary select the optimal design of the rubber lining, which can provide the required increment of the final product yield, lower power and balls consumption rather than to rely only on the lining cost itself.
Dyrda V.I -.Dr.-Ing., Professor, Academician, State Prize Laureate, Honoured master of sciences and engineering, Director Research Senior Advisor at Valsa GTV LLC