Improving comminution productivity through extending mill liner life in SAG mills
Mill liner systems can be one of the largest maintenance costs for minerals processing plants. Quality grinding media comes at a high price and is in short supply. Mills are getting bigger, which means more time is needed for relining. This, in turn, can mean significant lost production tonnage. And whilst managers and shareholders are always looking for ways to do better, it’s not only mill targets that continue to climb—escalating energy and equipment/system costs show no sign of slowing down.
Motivated by these challenges of rising costs and lost production, SAG mill operators are looking for innovative ways to improve productivity and satisfy growing targets. They are continually in need of improved equipment protection, increased energy efficiency and reduced operational costs.
To help address these mill challenges, FLSmidth automation experts developed the new generation Impactmeter and ECS/ProcessExpert® system, which can either be used as complimentary solutions or as stand-alone systems.
Advantages of installing the Impactmeter and ECS/ProcessExpert system on SAG mills include:
- The milling equipment is better protected because undesirable impacts caused by mill charge can be prevented
- Higher production is achieved thanks to increased energy efficiency from maximum impact energy being converted to ore reduction
- Operational costs are reduced due to the increased life of liner systems and a lower consumption of grinding media
“We use the Impactmeter to protect our SAG mill liners, allowing us to extend the operation of the mill and at the same time maximize uniform production,” said Ramon Sandoval, General Manager of Process Control at Toromocho, Minera Chinalco Peru.
A positive impact on mill performance
The new generation Impactmeter was released by FLSmidth in June 2015. It’s a mill performance instrument that monitors the charge dynamics inside SAG mills and promotes equipment protection, increased milling efficiency and decreased operational costs. This innovative sensory system, with an advanced design human machine interface (HMI), has already proven its capability in mining settings to identify undesirable impacts that result from mill charge.
The Impactmeter makes use of acoustic sensors positioned on a determined arc surrounding the mill shell. These sensors are enclosed in specially designed, environmentally secure enclosures that are suited to the extreme conditions of a milling operation. Eight acoustic sensors are installed for bi-directional mill operation and four are installed for mono-directional mills.
The sensors provide acoustical information to a processing unit. Proprietary software and algorithms isolate high-energy impacts inside the mill from low-energy impacts and other charge noise. The operational principle is based on the fact that the sound generated by the mill can be interpreted as a continuous signal, superimposed by the sound of the impacts of the biggest mass components of the mill load. The Impactmeter detects and analyzes those impacts, grouping them into two types:
- Critical Impacts: undesirable impacts that occur mostly by direct strikes on the liners
- Standard Impacts: impacts of lower energy, mostly related to the load tumbling
A data acquisition system processes the analog sound signals received from the acoustic sensors, converting them to digital signals, that are delivered to the redesigned HMI. The HMI is based on FLSmidth's proprietary Expert Control and Supervision (ECSTM) solution, a platform designed for mining industries. The communication protocols to integrate the Impactmeter with other process control systems, including OPC, Modbus RTU/TCP and several native PLC drivers, are built as part of the solution.
An advanced process control solution
The ECS/ProcessExpert system is a modern, advanced process control solution used to stabilize and then optimize key minerals processes. It balances equipment loads; manages and corrects process disruptions; and minimizes wear on the plant’s equipment—all by drastically reducing or eliminating manual involvement from mill operators—to ensure optimum plant performance and achieve maximum efficiency and higher profitability.
With an ability to combine multiple process control technologies, such as model predictive control and fuzzy logic, and the intelligence to select which technology is applied based on the problem being solved, this next-generation, process-oriented solution for grinding circuits has proven its worth.
Intelligent process objects integrate process and control engineering knowledge into proven standardized applications that are easier to maintain. A dynamic strategic decision tree shows operators exactly what actions the advanced process control system is taking, allowing them to easily understand the intentions of the system and the reasoning behind them. The strategic decision tree is closely integrated with the standard operating procedures at the mine.
The ECS/ProcessExpert solution also enables a minerals plant to develop a uniform operation strategy that outlines the best way to run the plant. Once this strategy has been established, training new operators becomes much easier.
The Impactmeter and ECS/ProcessExpert system can both individually improve mill operations. But when combined together, they can have an even greater effect. FLSmidth has successfully proven that critical impacts can be reduced more than 40% by combining the Impactmeter and the ECS/ProcessExpert system. Undesirable impacts caused by steel balls striking the mill liners are minimized, which prolongs liner life, reduces media degradation and extends production time between mill relining campaigns.
“Las Bambas knows the importance of the Impactmeter and ProcessExpert to preserve the operation of SAG mills and optimize the operation, so we are in the process of implementing such systems," said Julio Palomino Calle, Superintendent of Process Control, Minera Las Bambas, Peru. "We expect to extend the life of our SAG mill liners and improve the productivity of our grinding circuits by using both solutions.”
He has already witnessed the benefits of the combined systems at other Peruvian plants.
When operating as a stand-alone system, the Impactmeter allows an operator to manually react to the impact conditions. The instrument provides valuable impact data that can be used to improve mill performance, but does not control the mill. Instead, mill function continues to be managed by the mill control system.
When installed to operate in conjunction with the ECS/ProcessExpert system, the Impactmeter provides additional flexibility to the milling operation. When integrated in this way, the acoustic signals provided by the Impactmeter allow the advanced process control system to make small and frequent adjustments to mill operational conditions that improve ore reduction and energy efficiency. At the same time, the elimination of ball-on-liner impacts helps to prolong liner life and extend production between mill relining campaigns, further adding to mill availability and reducing operational costs.
Meeting the challenges head on
The challenges that minerals plants face today—along with the ongoing push to do better and reach new targets—will always remain. But the new-generation Impactmeter, when applied alone or combined with the advanced technology of the ECS/ProcessExpert system, can help tackle these challenges head-on.
With the Impactmeter monitoring the charge dynamics within SAG mills, equipment is better protected. With the ECS/ProcessExpert system managing and correcting process disruptions, plants can achieve maximum efficiency. Extended mill liner life and increased operational efficiency lead to the ideal outcome: improved comminution productivity and higher profitability.
The results are already speaking for themselves.
CONTACT: King Becerra