Research on the distribution law of spatio-temporal permeability screening and adaptation characteristics of banana-type equal-thickness classification of coal gangues

Screening is an important technological challenge to alleviate environmental contamination and resource waste and enhance the large-scale synthesis of coal gangue solid waste resources. Single inclination vibrating screen for coal gangue grading process can easily cause concentrated accumulation of materials at the infeed end, loosening and stratification difficulties, and deterioration of grading effect. A single inclination screen surface is replaced by a variable inclination (banana-type) for coal gangues classification and separation. High-speed camera testing and IPP image analysis system was used to study the spatio-temporal permeability distribution characteristics of material groups on the screen surface with variable and single inclination. It is found that the difference in displacement and motion velocity amplitudes between the feeding end and the discharging end of the variable inclination is greater than that of single inclination. The integrated optical density (IOD) of gangue on the screen surface with variable inclination is 1.5 times that of single inclination, and the gangue under the screen with variable inclination is 2.5 times that of single inclination. It indicates that the inclined screen surface is more conducive to the loosening and stratification of the coal gangue, where the material distribution is more uniform. Multi-stage sampling and multi-layer classification method was adopted to analyze the screened products. It shows that the penetration position of particles on single and variable inclination screen surfaces are both located in the middle, while the penetration amount of the latter is more significant. The dominant particle sizes of the undersized products are 6−3 mm and −3 mm, and the order of the proportion of coal gangue of −3mm in the product yield during the single and variable inclination screening processes is II>I>III>IV>V and II>III>I>IV>V, and the penetration rate are both II>III>I>IV>V. Moreover, the screening efficiency and the whole misplaced content are increased by 2.24% and 1.74% compared with the single inclination, respectively. At the same time, the distribution size is closer to 6 mm. Besides, the gangue and screen inclination angle adaptation characteristics are studied. When the coal gangue >6 mm accounts for 55%, a smaller screen inclination gradient should be selected, such as 3° and 4°, matching the productivity of 18 t/h, achieving the best screening performance and processing capacity. This study will improve the classification effect of coal gangue and the comprehensive utilization rate of solid waste resources, providing new ways and technical support for the directional transformation of coal gangue and the high value-added comprehensive utilization of solid waste resources.