Local Spray Closure Dedust Technique Of Coal Dust Sources In Fully-mechanized Mining Face

The coal dust production in fully mechanized coal face accounts for about 45%?80%of the total production in mine,of which coal cutting and support movement processes are the main dust sources.With the popularization of fully-mechanized and full-seam nining method and the increasing mining intensity of coal seam,the existing theory and control technology of coal dust pollution is not enough to meet the actual demand.For this reason,theoretical analysis,numerical simulation,experiment and field application are combined to study local spray closure dedust technique and equipment in fully-mechanized mining face.In the research on coal dust pollution in fully-mechanized mining face,the effect of turbulent airflow from coal cutting on coal dust dispersion is often ignored,so that the research conclusion cannot reflect the actual situation of coal dust pollution on site.Therefore,the coal dust pollution characteristics in fully-mechanized mining face before and after turbulent airflow from coal cutting disturbance were simulated and compared to analyze the influence of turbulent airflow from coal cutting on coal dust dispersion.The turbulent airflow from coal cutting was fairly stable and the deviated migration airflow under turbulent airflow from coal cutting disturbance was the main reason for the lateral dispersion of coal dust and the pollution of footway area,Under turbulent airflow from coal cutting disturbance,the pollution region in the respiratory zone by coal dust noved forward by 11.3 m along the direction of ventilation along mining face,and the pollution region was prolonged by approximately 7.2 m and the peak coal dust concentration along the footway space was approximately doubled.The particle size and velocity of drop were the main factors influencing the efficiency of dust collection by drop and the closure effect of fog flow,and it should also be the main basis for selecting the nozzle for spray dedust.The atomization characteristic experiment of 15 nozzles in 5 categories were carried out,not only the macroscopic atomization parameters such as the atomization Angle,effective range and flow rate of the nozzles were measured,but also the microscopic atomization parameters such as the particle size and velocity of droplets were measured under the wind disturbance and the distribution law of the particle size and velocity of droplets under the wind disturbance was obtained.According to the experimental results,the hybrid solid-cone wide-angle nozzle with an X-shaped diversion core and a spray orifice diameter of 2.4 mm was selected for intenlal spray in shearer,the direct fan nozzle with a jet stabilizer and a spray orifice diameter of 2.0 mm was selected for external spray in shearer,and the hybrid solid-cone wide-angle nozzle with an X-shaped diversion core and a spray orifice diameter of 2.0 mm was selected for spray between hydraulic support and arrangement was optimized and improved.Based on the coal dust pollution characteristics under turbulent airflow from coal cutting disturbance and the atomization characteristics of different types of nozzles,the local spray closure dedust technique was put forward,and the corresponding Venturi negative-pressure secondary dedust device and shear scrubber were developed.Under the spray pressure of 6 MPa,the average diameter of spray droplets by Venturi negative-pressure secondary dedust device was 50.59 ?m,and its negative pressure suction flow rate was 11.57 m3/min.The spray group in shear scrubber consists of 10 nozzles,and the spray coverage size under spray pressure of 4 MPa can completely cover the drum.In additon,in order to meet different field application conditions,shear scrubbers driven by motor and hydraulic motor was developed.Its flow rate was 190 m3/min and 220 m3/min,respectively.In order to investigate the dust removal effect of this dedust technique,the field applications were respectively carried out in the No.1001 and No.1007 fully-mechanized mining face of Fucun Coal Mine and the No.905 fully-mechanized mining face of Jiangzhuang Coal Mine owned by Shandong Energy Zaozhuang Mining Group Co.,Ltd.The results show that the complete application of local spray closure dedust technique can effectively alleviate the coal dust pollution in the fully-mechanized mining face:the average dust removal rate of each sampling point in the No.905 mining face of jiangzhuang coal mine was about 53.0%,among which the concentration of coal dust in the location where support moving worker,TG drum driver and MG drum driver operated were 73.7,80.3 and 85.2 mg/m3 respectively,and,the dust removal rate increased by 36.7%on average compared with the original spray dust removal facilities.