| Due to the high seam thickness in the coal mining process,fully mechanized top coal caving method is often used.With the improvement of mechanization of coal mines,large-scale and more efficient coal mining equipment is adopted at the fully mechanized caving face,resulting in high dust concentration at the coal mine site.There are many equipments in the fully mechanized caving face,the layout is complex,and the flow rule of the airflow in working face is complex.It makes it difficult to predict the laws of dust migration and diffusion,which result in difficulty to achieve the desired effect of the dust-removal equipment used in the fully mechanized caving face and seriously threatens the safety of coal mines production and health of workers.For the particle size of respirable dust is more smaller,it is more harmful to the workers' bodies and mechanical equipment.Therefore,studying the rule of respirable dust diffusion in the fully mechanized caving face is significative for scientifically guiding coal dust control at mine site,occupational disease prevention and the research and development of dust-removal equipment.In this paper,theoretical analysis,numerical simulation and field measurement are combined to study the migration and diffusion rule of respirable dust in time and space of fully mechanized caving face,and we have obtained the changes in concentration and migration speed of the respirable dust during the individual operation and overall operation of every processes in the working face.Aiming at the dust production characteristics of every processes in the fully mechanized caving face,the selective preference and application of nozzles were conducted,which greatly reduced the dust concentration in the working face.Firstly,the mathematical model of airflow-respirable dust two-phase flow in fully mechanized caving face was established.A one-to-one proportional physical model that was in line with the site was established by three-dimensional modeling software of SolidWorks.Then the ANSYS-ICEM meshing software was employed to divide unstructured meshes of physical models.The meshes were optimized and the poor quality meshes were removed so that the meshes' quality can meet the requirements of numerical simulation.Through the refinement of the local meshes,the local exact solution of the physical model in the numerical simulation process is achieved.Through ANSYS-fluent numerical simulation software,the flow of airflow-respirable dust in the fully mechanized caving face was numerically simulated.The trend of the airflow in the whole working face was obtained through numerical simulation.The trend of wind velocity decreases first,then increases and last decreases.Combined with the flow rules of airflow,the migration and diffusion rule of the respirable dust in time and space was simulated for the individual operation and overall operation of every processes in the fully mechanized caving face.And it is found that the the respirable dust concentration under the overall operation was more higher than the individual operation of every processes.The respirable dust migrates by the carrying effect of airflow.Combined with flowing condition of the airflow,the movement speed of respirable dust during individual operation and overall operation of every processes was analyzed,and finally obtained the temporal and spatial evolution of respirable dust in fully mechanized caving face.Through nozzle atomization experiments,the nozzles were selective preference.Aiming at the proportion of particles size of respirable dust generated from every processes and based on the numerical simulation,the nozzles used in each process were determined and installed on the site.After the site applying,the dust concentration of fully mechanized caving face has been greatly reduced.The average dust reduction rate of total dust and respirable dust is 89.3%and 89.5%,respectively.The effect of dust reduction is good,which greatly improves the working environment for the workers in the fully mechanized caving face. |
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