Proper grind control has been limited by the inability to track the particle sizes in the overflow in real-time and on an individual cyclone basis. Instruments based on older technology, such as those using ultrasonics, laser diffraction, or mechanical calipers, do not perform real-time measurements, having typical update rates of three to nine minutes. In addition, they require samplers, typically have low uptime rates, and cannot cost effectively monitor individual cyclones. These limitations have been overcome with the advent of a new technology, acoustic impact based particle size tracking (PST). This new measurement has enabled higher level control of the particle size through control of the grind circuit and individual cyclones.

The first commercial implementation of acoustic impact based particle size tracking has resulted in a system that monitors the overflow of every cyclone in a cluster with real-time four-second updates. This paper details the calibration and resulting accuracy of this technology under different cyclone overflow pipe orientations, different ore types, particularly with varying specific gravities, and different size fractions. The results from seven different concentrators will be presented. The dry solids specific gravities ranged from 2.7 to 4.1. The overflow pipe orientations ranged from vertical to horizontal. The size fractions varied from a P80 of 75 to 200 μm. The measurement accuracies obtained were within five percentage points for one standard deviation under plant operating conditions as referenced to samples obtained from the overflow pipes and sieved using both wet and dry sieving procedures.