SAG mill installations are the main workhorse in the majority of comminution circuits across the world. But with ever declining head grades, the need for higher throughput circuits has become evident.
To help miners address some of the challenges faced by SAG-based mills, FLSmidth has released a composite rubber and ceramic discharge head pulp lifter that increases SAG mill operating capacity with minimal CAPEX. The solution is designed to increase throughput, minimize downtime and extend the wear life of components.
“It represents a significant advance on traditional cast steel chrome moly pulp lifters,” explains Jack Meegan, FLSmidth’s Product Line Manager for Liners and Wear Parts. “Instead of cast steel, they are made of a combination of cut and fabricated structural steel, rubber and a ceramic matrix used for its exceptional sliding abrasion properties.”
Half the numbers of parts – half the weight
Fabricated materials weigh less than cast steel, and in some cases, FLSmidth has been able to reduce total lifter weight by 50%. Lower weight allows for the use of larger parts, which has reduced the number of parts that make up the discharge arrangement of the SAG mill by more than 60%. Fewer parts mean fewer liner handler movements during relining, reduced downtime and of course, cost savings.
The redesigned solution not only improves liner performance, but also increases wear life and lowers total replacement costs. The new design is also more robust and allows for effective operation under a wider range of operating conditions without risk of overloading the SAG mill.
With detailed analysis of the processing environment and an understanding of the specific wear mechanisms on the pulp lifters, Meegan explains how his team was able to propose an alternative design: "To increase the slurry rate we had to challenge geometric and operating restrictions. By evaluating mill diameter, head length, rotation, angle of discharge, length and height of pulp directors, grate open area and recirculation of the mills, we were able to simulate a number of alternative designs. We selected and quantified the benefits of each modification made to the existing design and incorporated them into a new mill discharge arrangement. This detailed analysis enabled us to adjust the shape and form of the pulp lifters and center cones for optimized flow and the lowest possible re-circulation of slurry in the assembly."
For Meegan, the most interesting improvement comes from the optimized geometrical design features: "This was critical to the support we provided to a copper customer in Chile with a 40 foot diameter SAG installation. The mill pulp lifter processed more than 28 million tons while improving slurry throughput by 6%. Our customer reached break-even at half of the parts' lifetime and a throughput benefit to the order of seven digits USD in 12 months."