Research On The Characteristics Of Dust Migration And Distribution During Coal Cutting Operations In High Mining Faces In The Northern Shaanxi Mining Area

The Northern Shaanxi mining area,as one of the major coal production regions in China,primarily adopts the mining method of high fully-mechanized mining with a mining height exceeding 3.5 meters.The dust generated from coal cutting operations in these mining faces is characterized by high output and wide distribution.Currently,dust control in high mining faces faces the challenge of high investment with low effectiveness.The key to coal mine dust control lies in understanding the distribution characteristics of dust in the roadway.Given the insufficient research on the distribution of dust migration in high mining faces,this study focuses on the dust generated from coal cutting operations in the high mining faces of the Northern Shaanxi mining area.A combined approach of field measurements,theoretical analysis,similarity experiments,and numerical simulations is employed to thoroughly investigate the dust migration distribution characteristics resulting from coal cutting operations.The main research findings are as follows:The dust pollution level in the walkway area between supports after coal cutting operations in high mining faces in the Northern Shaanxi mining area is high,with dust concentrations far exceeding regulatory limits.The highest dust concentration is found within 6 meters behind the shearer,and the quantity of dust changes in line with the trend of concentration changes.Based on the characteristics of dust generation during coal cutting operations,the initial motion state of dust is divided into six modes,and the force acting on dust in different directions is determined by its initial motion mode.The dust migration time is the time required for dust to settle to the floor in the vertical direction,and the smaller the particle size,the longer the time required for dust deposition.Particle size has a small impact on the time it takes for dust to reach its final velocity,but it significantly changes the final velocity value.Based on the gas-solid two-phase flow,the dimensional analysis approach establishes the similarity criteria for dust migration experiments.Taking the l high mining face of the Honglilin mine as a prototype,a dust migration experimental platform with a geometric ratio of 5:1 is constructed.The platform consists of roadway models,mining equipment models,dust sources and dust generation devices,ventilation systems,and dust removal devices,which can stably complete various dust migration simulation experiments.Under the conditions of extraction ventilation,the flow field distribution characteristics in the confined space of high mining faces are obvious.There are multiple high-speed zones and vortex zones inside the roadway due to sudden expansions,contractions,and the obstruction of mining equipment to the airflow.The obstruction of the shearer in the coal cutting area in front of the support weakens the flow field around it rapidly,while the flow field behind the drum gradually strengthens and remains stable.The airflow in the walkway area between supports gradually weakens,and the overall flow field intensity is lower than that in the coal cutting area.The distribution of suspended dust concentration and deposition rate follows an exponential function after coal cutting operations in the areas in front of and between supports.The suspended dust concentration in all roadway cross-sections in front of the supports is higher than that between supports.Influenced by the change in airflow field,the dust concentration in front of the supports decreases more slowly.The fastest deposition of dust occurs within 10 meters behind the shearer,followed by a slow decrease in deposition rate,with the deposition rate of dust in front of the supports slightly higher than that between supports.After coal cutting operations,the average particle size distribution of suspended dust and deposited dust in front of and between supports follows a power function with distance.The average particle size of suspended dust between supports is slightly smaller than that in front of the supports,and the trends of particle size variation are consistent in both areas.As the distance from the dust source increases,the average particle size of suspended dust and deposited dust in front of and between supports becomes closer,but overall,the average particle size of deposited dust in front of the supports is larger than that between supports.The suspended dust concentration in front of the supports is inversely proportional to the extraction volume and the particle size of dust from the dust source,and directly proportional to the dust production.In the areas between supports,the suspended dust concentration is directly proportional to the extraction volume and dust production,and inversely proportional to the particle size of dust from the dust source.The deposition rate of dust in front of and between supports is influenced by different factors,and the trends are consistent.The deposition rate of dust is directly proportional to the extraction volume and dust production.The particle size distribution of suspended dust and deposited dust is directly proportional to the extraction volume and particle size of dust from the dust source,and inversely proportional to the dust production.In addition,the particle size distribution of suspended dust and deposited dust in the areas between supports is more susceptible to disturbances.The research findings of this paper deepen the understanding of the characteristics of dust migration and distribution during coal cutting operations,and provide a basis for the optimization of ventilation systems and the design of dust removal measures in high mining faces.Furthermore,it will be beneficial for reducing miners’ inhalation of dust.Figure [84] Table [25] References [165]...