ABB announced it is launching an advanced control package embedded within a variable-speed drive. Called SmartMill, it utilizes real-time data for continuous control of individual grinding mills, easing the burden on the operator’s experience and judgment.

Traditionally, according to the company, operators face limited flexibility in optimizing grinding operations; an example is adding balls to the mill load and waiting for load reduction when the mill is overloaded. These adjustments are usually performed with only rudimentary control automation, or none at all. ABB’s SmartMill optimizes the process by adapting the actual mill speed and feed rate to current conditions in real time. The speed is varied according to an advanced control concept that keeps the mill’s solid feed as high as possible, while monitoring signals such as power consumption, motor torque and bearing pressure and mill speed. This automatic selection of optimal set points means that operators can focus on more important tasks.

optiAutomatic selection of optimal set points with SmartMill allows operators to focus on more important tasks.Automatic selection of optimal set points with SmartMill allows operators to focus on more important tasks.

 

Having full control of a mill helps improve the process control strategy. ABB offers advanced process control, which it said increases grinding efficiency, decreases energy consumption and extends equipment lifetime throughout the entire grinding circuit.

SmartMill is a standalone solution for individual mills and incorporates a variable-speed drive system as standard, while accessing all mill operation and maintenance features, such as automatic positioning, creeping speed and the frozen charge protection and remover function.

For inputs, SmartMill uses power, torque and load, which the controller employs to predict future mill behaviors. The outputs can take into account several mill variables, such as feed rate, mill rotation speed, ore hardness and purity, total load and water addition rate. ABB said SmartMill provides full stability to individual mills, without the need for additional controllers or sensors. This leads to increased grinding efficiency, reduced energy consumption, higher throughput, better influence over particle size, fewer shift-to-shift variations and extended liner lifetime.

An APC (Advanced Process Control) approach steers the system trajectory toward optimal operating conditions by continually monitoring and adjusting process parameters.An APC (Advanced Process Control) approach steers the system trajectory toward optimal operating conditions by continually monitoring and adjusting process parameters.

“Normally, there is always a trade-off between particle size, throughput, and recovery,” said Marcelo Perrucci, global product manager, ABB. “SmartMill allows flexible adjustments so that the sweet spot, which will vary from mine to mine, can be readily identified.”

In a recently released ABB white paper, Perrucci noted that “…multivariate control in grinding mills is largely absent—despite the complexity of the grinding process, in which feed rate, mill rotation speed, ore hardness and purity, total load and, in wet mills, water addition rate, all have to be taken into account in order to obtain better productivity and efficiency. Localized PI control loops are found in some operations, but sometimes there is no automated control at all and things are left to the experience and judgment of the operator. This all changes with the introduction of SmartMill.

“SmartMill is a special case of advanced process control (APC)—namely, nonlinear model predictive control (NMPC), where the control algorithms are embedded in the drive system in order to create a standalone solution for the mill. As its name suggests, NMPC tracks multiple important process variables, and the dynamic, and often highly nonlinear, relationships between them, and uses control and optimization algorithms to decide on what actions should be taken to drive the system to an optimal state.”

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