ABB says advanced process control (APC) using a straightforward design and deployment of model predictive control (MPC) with its System 800xA DCS can enable higher levels of automation and optimisation in a grinding and flotation circuit.

In a typical grinding circuit, ore is fed into the mills where abrasion, attrition and impact reduce its size, ABB says. Usually, the grinding circuit contains at least two interconnected mills with material classifiers (eg cyclones) separating the fine material from the coarse (that then goes for regrinding).

“The process is energy intensive with power consumption of roughly 20 MW to 30 MW and feed throughputs of 2,500 t/h to 3,000 t/hr,” ABB says. “Process variables are mill loads, motor torque and power, plus pressures and flow rates. The ground product is specified in terms of fineness.”

The introduction of an APC controller can lead to increased throughput, homogeneous product quality, reduced consumables and lower maintenance costs, according to ABB.

Further, APC can be advantageously deployed in the flotation plant, where the ground ore, now in slurry form, is washed to separate valuable minerals from waste. The goal is maximum production or maximum yield at a given concentrate quality.

APC performs timely adjustments to froth levels, air flows and reagents leading to process stabilisation, minimised reagents and increased recovery, according to ABB.