COMMINUTION AND CRUSHING
for SAG and ball mills in 2010, ME Elecmetal has grown to be a leading supplier of high quality grinding media solutions world-wide, expanding on its reputation as the premier supplier of cast grinding mill liners, crusher products and solutions in the mining industry.”
The ME Elecmetal SuperSAG ® ball was developed in response to the need for SAG mill balls that did not spall and break, causing production, maintenance and consumption problems. The design of the new ball used high quality‘ clean steel’ bars made from virgin steel, instead of melted steel scrap, as raw material, and saw attention to advanced forging techniques, and uniform, precision heat treatment. The result was a ball with improved‘ toughness’ to resist spalling and breakage from the high impacts in modern SAG mills, and improved resistance to abrasion wear because of increased‘ hardness.’
The company states:“ The improved performance of this SuperSAG ball led to a paradigm shift in the SAG milling community, from accepting breakage and spalling as normal and desirable to expecting SAG balls to remain competent and spherical from the time they are introduced into the mill until they are worn enough to pass through the slots in the discharge grates of the SAG mill. Maintaining the round shape for the complete life cycle of the ball is important for SAG mill productivity. Balls that break prematurely or wear into ovoid shapes in SAG mills clog grate slots, creating significant reduction in throughput and increased downtime, resulting in revenue loss. When balls maintain the round shape they more successfully pass through slot openings allowing designed throughput to be more easily achieved.”
In several instances, primary grinding( SAG) balls that maintain roundness are used to supplement ball charging in secondary ball mills, saving a portion of the costs of new balls. SAG balls that do not break maintain maximum size during their lifetime in the mill, thereby bring maximum crushing force to bear on the ore. The result is often higher productivity.
“ The same principles used in developing the SAG mill ball line was used in developing the ME Ultragrind ® ball mill balls. These balls range in size from 40 to 100 mm. They have proven to be highly effective in ball mill circuits around the world, and are often bundled with SuperSAG ® media products to provide comprehensive grinding media solutions in many of the world’ s leading mining ventures.”
ME Elecmetal’ s modern grinding media production facility opened in China in 2012, with present full production capacity approaching 400,000 t annually of forged grinding balls used for SAG, ball and regrind mill applications. Recently the company has also noted a demand
ME Elecmetal points out that balls that break prematurely or wear into ovoid shapes in SAG mills clog grate slots, creating significant reduction in throughput and increased downtime, resulting in revenue loss. When balls maintain the round shape they more successfully pass through slot openings allowing designed throughput to be more easily achieved
for high quality media in Africa, and the construction of one more manufacturing facility is presently underway in Zambia. The ball production facility is Quality Management System certified ISO 9001:2008, Environmental Management System certified ISO 14001, and Occupational Health and Safety Management Systems certified OHSAS 18001.
Overall, the range of ME Elecmetal grinding media spans from 22 mm to 160 mm, with surface, volumetric and centre hardness characteristics exceeding those of the competition.
“ Each batch of the media produced is subject to the rigorous testing procedure that includes chemistry composition verification, a hardness test and a drop test.”
The ME Grinding Media Application Team is also an integral part of the ME FIT System, which stands for Fully Integrated Technology.“ ME Elecmetal is the first company to offer this integral system which brings together our array of products and services. The ME FIT System is an optimised mill liner and grinding media system integrating consulting, products and services, people, logistics, and manufacturing all into one. Our approach is to provide concrete, measurable results that help our customers improve their revenue.”
Collahuasi is a mine with three open-pit ore deposits located in Chile. Collahuasi has been working with ME Elecmetal’ s FIT System for several years.“ Operationally, we have made huge progress working with ME Elecmetal, and not just because we have improved our grinding efficiency. Formerly, grate plugging events occurred frequently and were difficult to troubleshoot since there were two vendors involved, one for liners and another for the media. By implementing the FIT System, we were able to control one of the key variables, which is the grinding media”, explains Claudio Muñoz, Superintendent of Process Engineering at Doña Inés de Collahuasi mining company. Regarding grinding media consumption, Collahuasi has also had a positive development.“ We achieved a 22 % reduction in the wear rate of grinding balls in the 40 ft SAG mill and just finished the analysis on another of our mills with a 24 % reduction in terms of reduced wear rate. So, there is a net economic advancement”, says Muñoz.
Outotec’ s GrindForce- back to basics
Stirred milling and attrition type grinding, Outotec says,“ has overtaken traditional tumbling mills and impact grinding to become the comminution benchmark for regrinding circuits in flotation plants and fine grinding in leaching operations, due largely to energy efficiency gains.”
This major shift towards stirred milling has predominately been driven by the decreasing mineral particle liberation sizes of today’ s mined ore deposits, where finer grinding requires significantly more comminution power. In addition, ore head grades are decreasing, resulting in the need to crush and grind more rock to produce the same amount of valuable metal.
“ With the current drop in commodity prices, the mining industry requires innovative technologies and solutions that can reduce operating costs and a key area for improvement is energy savings. Outside the mining sector, there are technologies that can have valuable crossover applications. Of particular note are opportunities for technology and know-how crossover arising from the similarities between the hard rock mining and industrial minerals industries.” One such crossover technology from industrial minerals is the Outotec HIGmill™, which was developed over many years with the primary design motivation being significant energy savings for the grinding of fine particles.
The HIGmill itself is a vertical, fine grinding, stirred mill comprising a drive train attached to a rotating shaft within a stationary grinding chamber shell. Attached to the shaft are GrindForce rotating grinding rotors, not flat discs like in traditional stirred mills. These grinding rotors agitate and mix the bed of fine( 2 to 6 mm) ceramic grinding media producing a highly
62 International Mining | MARCH 2017