Coal Preparation » General
Tramp metal, in particular tungsten carbide pick tips, can cause severe damage to the linings of Dense Medium Cyclones (DMCs). In addition, clay balls recirculating in the cyclones decrease the efficiency of cyclone operation, reducing yields and product quality. This project's aim was to produce a cost-effective monitor that would notify plant operators when these materials were detected in the DMCs.
The use of vibrations or acoustics to "listen" to a Dense Medium Cyclone (DMC) is not new however, systems that were previously developed were expensive and beyond justification to use as a "tramp" monitor. The vibrations (sounds) emitted from a DMC with a circulating pick tip are loud and easily distinguished from the background noise. CSIRO has developed several low-cost accelerometer-based systems for use on screens. This technology was used as the foundation for developing a pick tip and clay ball monitor.
A technically cost effective and straightforward method to detect tramp metal circulating in DMCs was developed, tested in the laboratory and pilot plant, then trialed on three 1.3m DMCs at a site in the Bowen Basin. The system consisted of a single axis MEMs accelerometer glued onto the surface of the DMC, an AD converter, a small mini PC, wireless connectivity, and software specifically written to provide alarm state indications.
A plant trial has confirmed that the system can accurately identify the presence of pick tips in the cyclone, providing an email alarm when the alarm state is activated. While this plant does have clay ball events, they are relatively rare, and therefore, during this trial period to date, no clay balls were confirmed as being present in the three cyclones that were monitored.
A wealth of information is embedded in these vibration spectrums, and the data may include medium to coal ratios, lining wear, flow rates, and feed types. Other properties may emerge with time. It is recommended that further research be undertaken where these spectrums can be matched to plant/cyclone operating conditions.