A review of coal gangue identification research-application to China's top coal release process

Top coal caving is a process for the rational extraction of large amounts of coal resources. However, this process readily causes release of excessive amounts of gangue during the coal release process. The conventional technique, which involves visual inspection, is not only labor-intensive but also can introduce inaccuracies. Coal and gangue identification methods used during the top coal caving process are reviewed herein. The methods developed and studied over the last 20 years, such as gamma identification, acoustic identification, radar detection, vibration technology, image identification, and infrared positioning, are described separately, and their principles for use are explained. The advantages and disadvantages of these methods are analyzed, and an evaluation index for coal gangue identification methods is established by using hierarchical analysis (AHP). The results indicate that the γ-ray method is optimal to use under the current system. A future gangue identification method is conceived and proposed, which has reference value for the research and applications of gangue identification technology.