The same common themes for energy-efficient circuits have been discussed in countless papers. "Crush more, grind less!" "Don't overgrind!" And, of course, a popular topic is the energy savings offered by going to an HPGR circuit instead of primary grinding. These general concepts are all valid, but they are just pieces of the bigger puzzle; there is further room for improvement.
Designing plants for maximum profit
With diminishing ore grades and rising energy costs, ensuring that a plant has the lowest total cost of ownership is vital. One way to achieve this is to reduce the number of lines in the comminution circuit with as few moving components as possible – a strategy that has been employed in SAG mill circuits for some time. From a CAPEX perspective, the single unit equipment typically has a lower installed cost than multiple smaller units. Cost savings come from a smaller footprint, a reduction in installation costs, a reduction in ancillary equipment, and shorter commissioning time, which results in quicker realization of production targets. By having a single-line circuit, equipment availability is increased as there is less equipment that needs regular maintenance and that can break down. Moreover, larger machines tend to have similar maintenance intervals as smaller machines; but with less machines to maintain, the overall plant availability can be increased.
Metso MP®2500, HRC™3000 and VTM-4500-C – industry-leading equipment for industry-leading mines
The MP®2500 cone crusher, the HRC™3000 HPGR, and the VERTIMILL® VTM-4500-C are the largest equipment of their kind. With these machines, single line/single equipment crushing circuits up to 95,000 tpd are now achievable. However, these machines are not just known for their sheer size. They offer significant improvements over the traditional versions available to the market. Metso's MP cone crushers are the industry standard when it comes to large cone crushing and are known for processing more ore than any competitive unit at the same reduction ratio or product size. And now, the MP®2500 offers the largest available feed opening on the market, which potentially reduces the load on the primary crusher and could allow for smaller or a lower quantity of primary crushers.
Metso's HRC™3000 features the patented Arch-frame and a flanged roll design, which provides increased machine capacity, improved energy efficiency, and increased roll life compared to traditional HPGRs on the market. In closed-circuit testing, the Arch-frame and flanges were shown to increase the circuit capacity by over 20% and decrease specific energy by over 10%. The Arch-frame also provides alignment that is critical for larger HPGR sizes, such as the HRC™3000.
Finally, the VERTIMILL® VTM-4500-C is the world's largest gravity-induced stirred mill and the only stirred mill on the market that is practical to use in a high-capacity secondary grinding application. This means that an HRC™ HPGR can directly feed a VERTIMILL® grinding mill. In one operating installation, two VTM-4500-C mills are in a closed circuit with multiple stages of high-frequency screens, and are accepting a feed of 90% passing 3 mm and grinding to a specification of 85% passing 74 microns at 400 mtph. Additionally, with the VTM-7000-C model now available, operators are able to further reduce the number of lines while taking advantage of the energy efficiency and footprint benefits of the VERTIMILL®.
Putting it all together
Regardless of how efficient any piece of equipment is, in order to have the most profitable operation, the total comminution circuit must be designed to maximize the overall plant efficiency while providing the required liberation for the downstream processes. Every plant has different needs, and our expertise extends beyond the supply of a single piece of equipment. Our experts can help provide a total flowsheet solution that fits the unique needs of your plant.
Want to learn more?
Product Manager, HRC™ High Pressure Grinding Rolls, Mining