Study of atomization characteristics and dust suppression effect of micro-nano bubble enhanced ultrasonic dry fog in excavation working face

To optimize spray-based dust capture efficiency at coal mine working face, a novel micro-nano bubble enhanced ultrasonic dry fog dust suppression approach was developed. The characteristics of micro nano bubbles water were studied through wettability experiments and the dust suppression effect of micro nano bubbles water and tap water was compared by using the custom-designed spray dust suppression experimental platform. Experimental results indicate that micro-nano bubble water increases the concentration of negative ions around the spray area compared to tap water. Additionally, the surface tension of micro-nano bubble water is 9.3 mN/m lower than that of tap water and the contact angle of micro-nano bubble water with coal particles is 5.76° smaller than that of tap water. Application findings of tunnel working face confirm that the micro-nano bubble ultrasonic dry fog purification system achieving average suppression efficiencies of 60.43 % for total dust and 44.84 % for respirable dust, representing a relative improvement of over 30 % compared to the conventional purification system. Moreover, the micro-nano airflow dry fog purification system consumes water at an average rate of 5.13 L/min, which is 2.43 L/min lower than the conventional water curtain purification system, indicating a relative reduction in water usage by more than 30 %. Evidently, the micro-nano bubble ultrasonic dry fog purification system delivers effective dust control and reduce water consumption.