Experimental Study On Micro-nano Bubbles Strengthening Spray Dust Suppression

Micro-nano bubbles（MNBs）refer to gaseous aggregates of micron and nanometer scale,with diameters generally less than 100μm,that exist at solid-liquid interface or in liquid environment.Micro-nano bubbles technology has a wide range of application prospects in the emerging scientific field of gas-liquid two-phase because of its simple equipment,extremely low production cost,and physical and chemical properties that conventional bubbles do not have.With the progress of science and technology,safety accidents can be controlled,and dust disasters need to be solved.Spraying dust removal is an effective technical means to control the concentration of underground dust.However,due to the different conditions of working face,there are certain limitations,such as low efficiency of respirable dust removal and high water consumption under high pressure.At present,there is a lack of research on micro-nano bubbles in spraying dustfall in China.In this article,therefore,chose the net environmental protection technology co.,LTD.Shanghai micro-nano bubbles generator,by using the method of combination of theory and experiment,explored the micro-nano bubbles size distribution,stability and contrast in raw water adsorption and wettability,and applied to the design of experimental platform for measuring micro-nano bubbles water compared with raw water influence on the efficiency of dust,Finally,the dust removal theory of micro-nano bubbles water spray is discussed.The main conclusions are as follows:（1）The tested device can generate stable micro-nano bubbles,and the bubble content can reach a saturated state.The particle size range of micro-bubbles is mainly distributed in 50μm～70μm,and the existence of nano-level bubbles in the solution is measured,and the particle size peaks are distributed around 80 nm and 160 nm.（2）Micro-nano bubbles can effectively improve the adsorption of dust by raw water.Experimental study shows that Zeta potential and negative oxygen ions of micro-nano bubbles are improved compared with raw water.The potential of the micro-nano bubbles produced by the selected generator is about-15 m V,which enhances the charged property of the raw water.In the spray state of mechanical nozzle and ultrasonic atomizing nozzle,the number of negative oxygen ions in micro-nano bubbles water in the semi-enclosed area is significantly higher than that of raw water,and the environmental wetting degree is improved.（3）The contact angle experiment shows that the micro-nano bubbles water can increase the partial pressure ratio of water vapor in the environment,and the micro-nano bubbles reduces the surface tension of the raw water within a certain period of time,which has a certain impact on the formation of droplets.（4）In the experiment of atomization characteristics of micro-nano bubble water and spray dust removal,the effect of spray dust removal is closely related to the atomization characteristics and wettability of spray medium.The results show that the droplet size of the micro-nano bubbles water from the mechanical nozzle is smaller than that of the original water,and the D₅₀ distribution is between 96 and 153μm.When the air pressure is less than0.4 MPa,the particle size of the bubbles is smaller than that of the original water,and the D₅₀distribution ranges from 59μm to 124μm.In the dust removal efficiency experiment,it is found that both micro and nano bubble water are suitable for two types of nozzle,and the dust removal efficiency of micro-nano bubbles water is higher than that of tap water.For the total dust removal efficiency of x-swirl pressure nozzle,the growth rate is the largest at 2 MPa,which increases by 5.04%.The relative improvement rate reaches 9.73%at 0.5 MPa.The removal efficiency of respirable dust is 50.8%at 2 MPa,and the micro-nano bubbles water can remove respirable dust more effectively.For the dust removal efficiency of ultrasonic atomizing nozzle,the growth rate of total dust and respirable dust increases by 4.5%and4.11%respectively when the gas-liquid pressure is 0.4 MPa.（5）The mechanism of spray dust suppression enhanced by micro and nano bubbles is analyzed.It is concluded that micro-nano bubbles make dust easier to settle through their unique properties and the joint action of various mechanisms.