The Millstar Advanced Control System has a comprehensive suite of control strategies that can be applied to provide an innovative control solution for almost any milling circuit configuration. The modularised approach allows clients to select a combination of modules best suited to their plant problems and objectives and build on it with time
- Maximises throughput.
- 1-4% increased throughput due to stability
- More consistent feed to downstream processes, thereby increasing recovery.
- Optimal usage of mills.
- Improved control of mill feed rate.
- Better management of fine and coarse material, thereby preventing mill overloads.
- Prevents violation of constraints, making daily operation easier.
- Robust control solutions for effectively handling instrumentation failures.
MILL FEED CONTROL
There are a host of difficulties related to the controlling of the feed to the mill, such as long time delays between feeders and weightometers, and variable ore. MillStar’s feed controllers have been specifically designed to compensate for long time delays and handling changes in the process dynamics due to variable ore and/or changes in the feeders responses.
MILL THROUGHPUT OPTIMISATION
Obtaining optimum power usage from a mill is highly process-dependent. MillStar’s Power Optimiser dynamically determines the optimum operating point for the mill and controls the mill to maintain the power. A number of safety checks are also present to substantially reduce the number of mill overloads.
By operating at the optimum power and minimising the overloads, the throughput is also maximised. Additionally, by optimising the recirculating load in a milling circuit it is possible to maximise the possible throughput of the milling circuit.
MILL DISCHARGE PRODUCT CONTROL
Typically, the mill discharge section is controlled using many separate single-input single-output control loops; however, the system is multivariable. MillStar’s Model Predictive Controller (MPC) provides a superior multi-input, multi-output control solution by minimising all variable errors from setpoint simultaneously while taking both control variable and controlled variable constraints into account.
This module takes into account multivariable interactions between input and output mill discharge variables and controls the sump level and cyclone overflow product size and/or density.
CYCLONE SWITCHING CONTROL
Clusters of cyclones are often used for mill discharge classification. By controlling the number of open cyclones, the pressure within the cluster can be controlled. Stabilising the pressure improves the stability of the cyclone overflow particle size and density, which improves the consistency of the feed to the flotation.
When thickeners are located between unit operations, such as between milling and leaching, they present an opportunity to be used in an integrated control strategy. It is possible to significantly stabilise individual thickeners as well as downstream circuit operation by employing an effective thickener control and optimisation solution.
The LeachStar Thickener Controller is aimed at providing the following benefits:
- Reduction in flocculent consumption.
- Improving the clarity of the thickener overflow water.
- Ensuring stable thickener operation by minimising bed slides or high rake torque scenarios.
- Stabilising the flow rate and density of the underflow, thereby improving the performance of downstream processes.
Mill Discharge Density Estimator
The Mill Discharge Density Estimator uses two distinct algorithms, based on first-principle models, as well as signals from plant instruments, which can include thermocouple temperature readings, to provide an estimate of the mill discharge density and flow rate.
Particle Size Estimator
The Particle Size Estimator (PSE) is a soft-sensor capable of accurately predicting the particle size of the hydrocyclone overflow product on a closed loop milling circuit. It is based on an empirical model, identified from extensive plant test work. The PSE can be used to:
- Estimate the cyclone overflow particle size on plants without a physical measurement.
- Act as an intelligent filter, a backup sensor, or be used in a fault detector on plants that do have a physical measurement of the cyclone overflow size.
- Intelligently interpolate readings when a physical measurement instrument is multiplexed between different streams.
The accurate measurement of the power consumption of a mill is very important in industry, as this measurement is used to control feed rates, mill loading and other control parameters. A reliable measurement is, however, difficult to obtain, as the power drawn fluctuates over the period of rotation and is subject to process noise. The MillStar Power Filter is capable of removing the noise to obtain a true reflection of the base power consumption of the mill for use in control systems.