Collector-assisted efficient coal/gangue recognition based on liquid intervention in longwall top coal caving

Efficient coal/gangue recognition is vital to improve the top coal recovery in thick seam mining with the longwall top coal caving method. Gangue is a gray-black rock mixed into the top coal flow during the drawing process. Liquid intervention is a new approach to distinguish coal and gangue based on their temperature difference through infrared thermal imaging. This study employs three common flotation collectors, kerosene, hydrocarbon oil, and activated slime collectors, with different concentrations for efficient coal/gangue recognition based on liquid intervention compared with that based on traditional liquid (clean water). The results show that all three collectors have a stronger ability to improve the temperature variation value of coal/gangue and expand the temperature difference between coal and gangue. In general, kerosene exhibits the best effect, and the activated slime and hydrocarbon oil collectors have a better effect when the concentration is low. The analyses of temperature dropping mechanisms verify that the recognition efficiency significantly improves with different collector-assisted interventions, while different collectors need different concentrations to achieve the best improving effect. This research provides a foundation to find an economical and efficient intervening liquid with a better recognition efficiency.