Application problem
The customer had multiple coal types that they processed through the coal prep plant. Some of the coal types had different settling characteristics.
This affected the tailings thickener efficiency and the ‘Clearometer’ instrument that tested settling rates in the incoming feed well, failed from time to time, which meant that the floccing rate changed and the suspended solids increased, decreasing the quality of the return water back to the prep plant.
Solution
Hawk provided a high powered, three-crystal sonar transducer with automatic scum cleaning impact plate. The two outputs of the sonar system provided:
1. BED Level (Heavy density compacted interface). This heavier ‘BED’ level output, was used as one of the input loops, to control the underflow pump, guaranteeing an optimised density being pumped to the tailings dam.
2. Hindered/fluffy layer (low density interface). The hindered/fluffy layer was used to monitor the deviation distance between it and the heavier compact bed. As the deviation moved greater than a set distance flocculent dosing increased. As the deviation decreased flocculent dosing decreased.
The high powered, three-crystal array transducer penetrated the suspended solids, even under poor settling conditions. The hindered/fluffy layer output could also be used, in the floc dosing control loop to automate this function if the ‘Clearometer’ failed.