| Fully-mechanized mining face exists widely in the coal mine of China. With the devepomet of coal mining and technology, coal mining technology with one-time mining overall height of is widely used. The equipment in this working face is of larger volume and higher power,which leads to an environment with higher dust concentration.Meanwhile the complex mining space induces complex air flow, which makes it difficult to predict the diffusion and pollution of dust with high concentration. This means that it’s difficult to achieve a satisfactory effect of dust removal by directly adopting the dust suppression equipment that is previously applied. The dust especially the respirable dust with high concentration makes a serious threat to the safety production and life safety of underground workers. In view of this, it’s imperative to study the diffusion law and pollution mechanism of respirable dust in fully-mechanized mining face and further optimize efficient coal dust cleaning system. Meanwhile, the study is of very vital significance for scientifically guiding the field dust control, occupational disease prevention, equipment invention and efficient production.Therefore, theoretical analysis, experimental test, numerical simulation and field application was used jointly to study deeply the diffusion and pollution laws of respirable dust at different areas in fully-mechanized mining face from macro to micro dimensions. Basis on the pollution characteristics of the respirable dust and existing dust control measures and methods, an efficient coal dust cleaning system was optimized and designed. After that, the field application of the equipment was studied. Thus, the research project named ’numerical simulation and engineering application on laws of air diffusion and respirable dust pollution at different areas from macro to micro dimensions in fully-mechanized mining face’ was carried out step by step.Firstly, the mathematical model of air - resparable dust was established. A proportional and precise geometric model was established by using the CAD software such as SolidWorks and DesignModeler.Also the mining space was divided into support moving completion area,coal mining area and non-mining area according to the characteristics of dust sources. In accordance with the feature of air and dust diffusion,different areas were made personalized finite element in order to achieve more accurate solution of key pollution area.Secondly, a plurality of sampling points are arranged near the corresponding dust sources to collect the dust particles. Through the analysis of microscopic particle image, the frequency distribution of dust particle size and other related parameters are obtained, results show that the dust whose particle size is ranged from 2 to 4 μm accounted for the largest among respirable dust, which should be regarded as the key object of respirable dust prevention. The analysis data would be used as the scientific basis for dust parameters setting during numerical simulation.Then, air velocity’s influence on respirable dust diffusion and pollution in fully-mechanized mining face is studied by numerical simulation with the Fluent software. Fitting function between respirable dust concentration of breathing zone height and air velocity is obtained.It is found that the optimum air velocity range is 1.5～2.Om/s. The theory of the influence of air velocity on dust diffusion is improved. Meanwhile,combined with the most optimal inlet air velocity for dust removal,nature and cause of maximum velocity zone and high concentration dust group was studied with the airflow streamline and dust trace. Basis on this, the law of respirable dust diffusion & pollution in fully-mechanized mining face is simulated numerically from micro dimensions with the micro particle diffusion condition at the first time. The evolution law of space position, velocity, settlement, diffusion time and other parameters of these three types of dust under time scale was researched from the micro level.At last, a novel coal dust cleaning system was designed according to the respirable dust diffusion & pollution characteristics also and field application was carried out in the 52305-1 fully-mechanized mining face of Daliuta coal mine. After application, the dust concentration in the field was greatly reduced, and the average dust removal rate of full dust and respirable dust was 90.10% and 90.03% respectively, and the dust removal effect was obvious, working environment and labor hygiene conditions was improved to a certain extent. |
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