Influencing Factors and Optimization of Coal Fines Transportability in Mine Borehole Screen Pipes

This paper establishes a particle flow model to simulate and analyze the coal fines transported through circular and elliptical aperture screen pipes with different parameters based on the discrete element method, which combines experimental research to study the influence of confining pressure, bond strength, and drainage negative pressure on the coal fines transportability. The study shows that: 1) The increase in confining pressure has a nonlinear increasing effect on coal fine particles throughput, and there is a critical threshold. Once this value is exceeded, the particle throughput increases sharply, causing of the screen pipe. When the confining pressure reaches 6 MPa, the screen pipe is filled with coal fines and becomes clogged. 2) The stronger the bonding strength of the coal fine particles, the worse the transportability, and the stronger the anticlogging ability of the screen pipe. 3) Under the condition that the aperture density and the total aperture area are the same, the coal fines throughput of the elliptical aperture screen pipe decreases approximately linearly with the increase in aspect ratio. As particle size increases, the percentage of particles transported through the screen pipe shows an inverted "V" shape, first increasing and then decreasing. 4) Increased aperture density decreases transportability linearly, but the transportability of large-sized particles increases in the case of low density. 5) Under the combined action of confining pressure and drainage negative pressure, the variation law of transportability is basically the same as that under confining pressure, but the throughput is approximately 1.3 times the throughput under confining pressure. 6) The final optimized parameters include elliptical aperture, major axis vertical to the screen axis, aspect ratio 4, and aperture density 35/m.