Study on Supercharging and Dust Suppression Technology of Supersonic Spray Fortress at Coal Transfer Point of Belt Conveyor

To address coal dust emissions at the feeding and discharging ports of belt conveyor transfer points, this study proposes a pressure-enhanced dust suppression system based on a supersonic spray fortress. A coupled numerical and physical model of the transfer point was established, incorporating assumptions of coal flow-induced airflow, tangential distribution of induced effects, and incompressible fluid behavior. The multiphase gas-particle-spray flow was characterized using the Stokes equation for particle motion and the standard k-epsilon turbulence model. The supersonic spray fortress was designed as an irregular hexahedral metal structure integrating gas-liquid pipelines and equipped with three supersonic atomizing nozzles arranged at composite angles (45 degrees horizontal spacing and 45 degrees downward inclination). A geometric model of the coal conveying system was constructed, and mesh independence verification was conducted to ensure the reliability of numerical simulations. Spray characteristics were experimentally investigated using a Winner319 laser particle size analyzer and a three-dimensional particle image velocimetry (3D-PIV) system, enabling measurement of droplet size parameters (SMD, V50, N50) and velocity under pressures ranging from 0.2 to 0.4 MPa. Field experiments were performed at a coal mine transfer point to monitor dust concentrations before and after system implementation. The results indicate that spray characteristics are highly sensitive to operating pressure. As pressure increases from 0.2 to 0.4 MPa, droplet SMD decreases from 65-70 mu m to 30-45 mu m, while initial velocity increases from 12 to 20 m/s; droplet size shows minimal variation with distance. The spray fortress significantly regulates the airflow field, reducing peak airflow velocity by more than 60% (from >10 to <= 4.8 m/s) and decreasing the proportion of high-velocity regions (>5 m/s) from 35% to <= 8%. In terms of dust behavior, peak dust velocity decreases by over 70% (from >20 to <= 6 m/s), accompanied by a substantial reduction in coarse particles (>10 mu m). Field application results show that within a range of -10 to 15 m, the total dust removal efficiency reaches 51.4-93.4%, while respirable dust removal efficiency is 44.6-87.9%. The dust particle size distribution shifts toward finer fractions (0-2.5 mu m), primarily due to the effective capture of medium and coarse particles by spray droplets. The supersonic spray fortress achieves synergistic regulation of airflow and dust transport through mechanisms such as momentum offset, spatial coverage, and collision capture. With optimized spray parameter configuration and strategic placement at the upper and lower ports of the chute, a full-process dust control system is established, providing a reliable and effective solution for dust mitigation at belt conveyor transfer points.