Diffusion Law Analysis And Emission Assessments Optimization Of PM_2.5 In Dust From Piles

One of the most significant environmental issues in the present-day world is atmospheric pollution.Open piles of material generate a lot of dust due to wind,which contains particles of different particle sizes.Among them,PM_2.5 particles are more harmful to people,which will seriously harm the environment around the piles and people’s physical and mental health.At present,the installation of storm nets is an extremely effective method.Therefore,it is an important step to study the influence of different working conditions and different wind speeds on the diffusion law of PM_2.5 in the dust of the open pit.Firstly,sampling and measuring the material pile on site,constructing a corresponding scale physical model,and conducting wind tunnel tests to obtain the flow field change law under different wind speed conditions.The installation of windscreens can effectively reduce the velocity of incoming wind,especially butterfly-shaped windscreens,which have a more significant wind reduction effect.However,the installation of windscreens will cause turbulence in the flow field behind the pile,which will generate vortices in different areas of the flow field and bring the particulate matter to a higher position.Secondly,based on the wind tunnel test results,a corresponding numerical model is established and numerical calculations are carried out for the gas-solid two-phase to analyze the distribution law of PM_2.5 under different working conditions and different wind speed conditions.Under the same wind speed,the particulate matter will spread to the far side at twice the height of the pile without a net,the diffusion distance will be longer and the concentration will remain higher;when a flat windbreak net is set,the dust will appear in the area of high concentration at the leeward slope and produce a large vortex;when a butterfly windbreak net is set,the area of high concentration of particulate matter will not appear at the leeward slope,but will form a large vortex of high concentration at a distance behind the pile.As wind speed increases,PM_2.5concentrations at various heights decrease significantly,and the range of high levels tends to narrow,showing a negative correlation between PM_2.5 particulate matter intensity and changes in ambient wind speed.The diffusion concentration of PM_2.5particulate matter behind the pile is significantly reduced after the installation of the planar windscreen.With the butterfly windscreen,no high particulate concentration zones occur at any of the three wind speeds.Finally,a new method for evaluating the PM_2.5 emission reduction effect of windscreens is proposed based on the recommended formula of the Code for Environmental Impact Assessment of Port Construction Projects,combined with numerical simulations,and the PM_2.5 reduction effect of three working conditions,namely no windscreen,flat windscreen,and butterfly windscreen,is simulated and evaluated by this method.The results of the PM_2.5 emission assessment were compared and it was found that the reduction of PM_2.5 emissions with a butterfly windbreak was more significant.