Study on coupling diffusion of composite dust and cloud-mist dedust technology in fully mechanized driving face of mixed coal-rock roadway

Aiming at addressing the problem of coal dust and rock dust mixed pollution in mixed coal-rock roadways, this study conducted a CFD numerical simulation on the coupling migration and pollution of coal dust and rock dust in the fully mechanized driving face of mixed coal-rock roadway (i.e., roadway section with both coal seam and rock stratum). Research findings: Small coal dust particles mainly migrate backward along the upper space of the roadway, while large coal dust particles mostly diffuse backward along the bottom of the air return side and settle evidently, with the concentration being higher than 1,000 mg/m3. The concentration of rock dust starts to decline significantly to about 350–800 mg/m3 in the middle and rear of the roadway. The concentration of coal dust is relatively high (200–500 mg/m3) in the front of the roadway, and it decreases gradually to around 175 mg/m3 in the middle and rear sections. With the increase of diffusion time T of rock dust and coal dust, the diffusion distance LD shows a linear increasing trend. Both rock dust and coal dust conform to the linear equation LD = 0.82 T + 11. After the application of the cloud-mist dedust technology, all the measuring points in the mixed coal-rock roadway witnessed a dust removal efficiency of above 75 %, which is a mark of effectiveness of the technology in improving the underground working environment.