Research And Application Of Air-water Atomization Annular Envelope Dust Control Device For Roadheader

With the progress of technology and the continuous improvement of mining efficiency,the dust concentration at the working face is always high.The accumulation of highly concentrated dust can lead to dust explosion accidents,and the long-term exposure of miners to highly concentrated dust can also cause pneumoconiosis,which seriously threatens underground safety and workers’ health.The performance of the nozzle used in the external spraying device is the core component that determines the dust reduction effect.At the present stage,the external spraying device of underground digging machine in China mostly has such shortcomings as low dust reduction efficiency and large water consumption,which is mainly due to the unreasonable choice of nozzle and the lack of technical data related to nozzle structure design,atomization characteristics and dust reduction efficiency.The main reason is the unreasonable selection of nozzles and the lack of technical data on nozzle structure design,atomization characteristics,dust reduction efficiency and so on.In order to solve the above problems,an air-water atomization annular envelope dust control device is designed by using the internal mixing air-assisted atomization nozzle in the background of a comprehensive excavation working face in Sima coal mine of Shanxi Lu’an Chemical Group.The main conclusions of the study are as follows.(1)The optimal structure parameters of the internal mixing air-assisted atomization nozzle were obtained.Considering the nozzle atomization parameters and dust reduction efficiency,it is reasonable to obtain the highest dust reduction efficiency when the diameter of water injection hole is 1.5 mm,the diameter of air cap outlet is 2.0 mm and the number of air injection holes is 4 for the studied air-assisted atomization nozzle.(2)Four different nozzle arrangements were designed and simulated.The results showed that Option D formed a complete water mist barrier around the head of the roadheader,completely shielding the dust generated by the roadheader from spreading and achieving a good dust suppression effect by spraying.(3)The variation law of spray field of air-water atomized annular envelope dust control device under different working parameters was studied.The results show that when the air supply pressure is constant,the droplet size in the atomization field of the air-water atomization ring envelope dust control device increases significantly and shows more uniform distribution as the water supply pressure increases,and the distribution is most uniform when the spraying pressure is 0.7 MPa;under the condition that the water supply pressure is certain,as the air supply pressure increases,the air-water When the supply pressure is lower than 0.5 MPa,the droplet velocity in the spray field increases with the increase of the supply pressure;if the supply pressure continues to increase,the peak droplet velocity decreases instead of increasing.(4)The results of physical and chemical characteristics of dust,wind flow movement and dust distribution law at the site of the heaving workface were obtained through a combination of field sampling analysis and numerical calculation.It was found that the overall particle size of the dust generated during the excavation of the heaving face was small and the respiratory dust accounted for about 20%.The minimum dust concentration was 159.4 mg/m3 and the maximum dust concentration was 420.7 mg/m3 at the section of 1.6 m height,both of which far exceeded the allowable dust concentration of the national regulations for header workings and seriously affected the physical and mental health of miners.(5)After the structure and working parameters of the air-water atomization ring envelope dust control device were adjusted to the optimized data,the device was applied on site in a comprehensive excavation workface of Sima coal mine of Shanxi Lu’an Chemical Group,and the dust concentration and dust reduction efficiency before and after dust reduction were sampled.The results show that the air-water atomized annular envelope dust control device can effectively reduce the dust concentration at the header face,with the dust reduction efficiency of 90.9% and 77.1% for full dust and dust extraction respectively.