Influence of air inlet distance on coal dust pollution characteristics in working environment during tunneling based on CFD method

Abstract

Coal dust is one of the pollutants generated during the coal tunneling process. However, the air inlet distance will increase with the advancement of the working face, resulting in the redistribution of the air flow field, further affecting the pollution characteristics of coal dust. This effect weakens the effectiveness of dust removal equipment. Therefore, transient CFD modeling was used to study the influence of air inlet distance on air flow, dust migration distance, and dust concentration distribution in the breathing zone and achieve the highest dust reduction efficiency. Results showed that the air flow formed two reflows in the tunnel under forced ventilation. When the air inlet distance increased from 6.0 m to 8.4 m, wind flow diffusion distance (along the return side coal wall) Lp and air inlet distance d can be described as Lp = 34.272–7.108d + 0.570d2 . Furthermore, the dust diffusion time to the outlet increased from 35 s to 40 s, and the dust migration distance increased as a power function of air inlet distance. Meanwhile, the dust migration distance in the first 10 s accounted for 45–50% of that for the entire time period. In addition, the dust migration distance decreased only after 25 s, and the dust concentration in the return side breathing zone gradually increased. Finally, air curtains and dust removal fans were recommended for dust control, and the dust in the daily tunneling process can be effectively controlled when da = 15.0 m and de = 8.0 m. The dust reduction efficiency was 85.29–99.90%. The research results provide technical support for the dust outlet installation of dust extraction fans during tunneling and guidance for dust control in the similar working environment.