Automatic control of fine coal cleaning circuits has traditionally been limited by a lack of sensors for on-line ash analysis. Although several nuclear-based slurry analyzers are available, none have seen widespread acceptance. In this investigation, image analysis is used for on-line determination of ash content in fine coal slurries. The ash content of a flotation tailings stream is correlated to the mean gray level of the slurry. Calibration data obtained from in-plant testing indicate that the sensor is accurate to ±4% ash over a range from 65 - 90% ash based on a 90% prediction interval. While this result is comparable to existing nuclear-based analyzers, the video-based system is only a fraction of the cost. The sensor is currently installed at the Middle Fork preparation plant owned by Pittston Coal Company where efforts to harden the system for long-term industrial operation are currently underway.
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