The Benefits Of Continuous Mining
By Chris Pearson
May 2, 2020 - Whilst the mining industry focuses increasingly on sustainability and safety, open-pit mines are constantly struggling to pass-match trucks and shovels. The answer lies in innovative technology that can deliver the benefits of continuous mining using existing truck fleets, without the need to install capital-intensive conventional conveyers.
Shovels represent considerable CAPEX and OPEX costs, yet the efficiency of a shovel seldomly sustains 60% of its capacity. Industry expert MMD recognized that it could design a machine that harnessed the capability of the shovel and vastly improved the speed of loading trucks.
The machine in question is a fully mobile surge loader (FMSL) – purpose-designed to bring continuous production to open-pit mines. This innovative solution draws upon MMD’s experience in Colombia some 16 years ago as well as a more recent in-pit sizing & conveying (IPSC) installation in China.
There is a lot of room for improvement in accuracy and efficiency here. Trucks rarely achieve 90% of their fill factor and most large electric rope shovels rarely load above 6,000 tons per hour (tph), when they should be loading at 10,000 because they are waiting on trucks.
Transforming Mining & Accuracy in Colombia and China
In Colombia, MMD installed a heavy duty apron plate feeder in a coal mine, which could receive material directly from a dragline. The mine was unable to invest in a shovel, as it would take too long to get the machinery onsite and into production. The new working method saw trucks queuing under a controlled feeder unit; the result was that trucks were filled almost three times faster, taking just 75 seconds. Accuracy was also considerably increased, sometimes with a 98% fill factor, and the need for trucks to reverse into the loading position was eliminated.
Meanwhile in China, MMD’s fully mobile sizer was directly partnered with the shovel, allowing material to be continuously loaded into the receiving hopper before being sized and discharged onto a face conveyer. Since the hopper capacity of the station exceeds the cycle time of the shovel, the shovel operator is unable to overwhelm the system, ensuring that it performs smoothly and consistently.
Consequently, MMD regularly observed the shovel operator loading the hopper easily and continuously. When working optimally, the sizer achieved a throughput of between 9,000 and 12,000tph before the equipment had to be repositioned – a significant increase on conventional truck loading.
Increasing Shovel Utilization
Drawing upon both these experiences, MMD created the FMSL – a turnkey system for loading trucks in mines where conveyors are impractical or costly to implement. Operating between the shovel and trucks, the FMSL decouples the truck and shovel loading operations, and given its manoeuvrability can easily be repositioned wherever the shovel goes.
This new approach enables shovel utilization to be increased to almost 95%, thus reducing the number of trucks needed and eliminating shovel waiting time. Automated start/stop delivery means that the truckload is constantly monitored and can signal to the feeder at optimum payload, which not only eliminates the underfilling of trucks but also prevents overfilling and associated spillage and haulage road maintenance. Equally importantly, with a full hopper on the surge loader, the shovel can reposition without holding up the trucks.
At the same time, the working environment for truck drivers is considerably enhanced and made safer as they are physically separated from the swinging shovel bucket and direct loading impact of oversize lumps. Instead, the operator monitors the loader from the shovel’s control cabin, overseeing a system that is automated, repetitious and highly efficient.
This step forward was achieved through sophisticated production modelling that compared the loading process with conventional techniques. MMD talked to miners to get as much input as possible. Then it developed software to define benchmarks for truck and shovel operations and compare these against actual production run rates. This software demonstrated precisely what would occur. Harnessing this information, the team generated a simulation of trucks loaded in a traditional fashion and compared it with the same operations using the FMSL. It was immediately clear that the new solution represented a major improvement in terms of performance.
Taking Open-Cast Mines To The Next Level
Based on data simulations, MMD believes that the FMSL can deliver between 20% and 40% production gains with the shovel loading at maximum capacity, compared with existing truck-and-shovel techniques with a standard cycle of three to four shovel passes per truck.
Using greater numbers of the loaders within a mine can increase the benefits substantially – for instance not only can the number of trucks for a mine be reduced, there can also be a reduction in the number of shovels in the new system.
Large open-pit mines could deploy multiple units to facilitate mining on multiple benches, with the fully mobile sizer and surge loader for ore processing and individual surge loaders accompanying each shovel to manage overburden.
The FMSL can prove particularly effective in mining operations that have switched – or are in the process of switching – to autonomous truck mining. Integrating seamlessly into the operation, it can greatly boost the transition to autonomy by simplifying truck movements. In turn, this makes the mine much safer for the shovel operator.
MMD’s priorities were to increase production, reduce ongoing CAPEX and OPEX and decrease truck wear and spotting time, whilst enhancing mine safety. Its experiences in Colombia and China have demonstrated that investing in tomorrow’s technology can transform the efficiency and safety of open-cast mines today.