An experimental study on the improvement of coal and gangue identification efficiency by liquid intervention

Coal / gangue intelligent recognition is one of the basic technologies for the realization of unmanned intelli⁃ gent mining of deep resources. This paper proposes a new way to improve the efficiency of coal / gangue recognition by using liquid intervention and infrared detection. The experiments on different liquid intervention coal / gangue recogni⁃ tion were conducted. The expansion effect of liquid intervention on the difference of infrared image of coal / gangue was analyzed from the infrared image characteristics，temperature changes of coal / gangue，and temperature difference be⁃ tween coal and gangue. The mechanism of liquid intervention to improve the efficiency of coal / gangue recognition is revealed from the view of macro⁃reaction and micro⁃structure. The research results show that the surface of the coal/gangue sample has different extent of temperature drop after liquid intervention，which effectively expands the difference between coal and gangue in infrared images，and can significantly improve the efficiency of coal / gangue recognition. Different liquids have different intervention effects. Compared with the air controlled group in hydrochloric acid，sodium hydroxide lye，and water，the degree of temperature difference of coal/gangue is enlarged as follows: water>sodium hydroxide lye>dilute hydrochloric acid>air. The temperature difference between gangues can reach 1.5 °C after the intervention of water for 3 s，the maximum temperature difference in the whole process of the test can reach 2.7 °C ，indicating that the intervention of clean water can significantly improve the efficiency of coal / gangue rec⁃ ognition in a short time，and it is a potential candidate liquid. The identification test of coal/gangue mixed samples shows that the intervention of water on coal and gangue mixed sample also has a better distinguishing effect. The sig⁃ nificant temperature drop caused by the coal / gangue after liquid intervention is the result of the combined effect of liq⁃ uid volatilization and slow chemical reaction，of which volatilization is the dominant effect. The alcohol intervention test results confirm this too. The difference in the surface microstructure of coal and gangue leads to the accumulation of droplets on the surface of coal samples，which is the internal reason for the expansion of the temperature difference between coal and gangue caused by liquid intervention.