Effect Of Windbreak On The Diffusion Law Of Dust In Open-yard Stockpile In Local Area

Atmospheric pollution is one of the most noticeable environmental problems in the world at present.The large amount of dust generated by large-scale open-yard stockpiles under wind-induced effect is one of the major causes for the occurrence of air pollution such as haze.The research on the effect of windbreak on the diffusion law of dust in open-yard stockpile in local area is significant prerequisites for preventing and controlling air pollution such as dust pollution and even haze.In this paper,the open-air alkali slag pile was sampled on site,and the density and particle size distribution of the bulk of the pile were tested.Based on this,the particulate matter displacement was calculated.The physical model of the windbreak and the pile was established according to a certain proportion,and the wind tunnel blow test was carried out to obtain the flow field distribution under different wind speeds.The three-dimensional pile reactor and windbreak numerical model corresponding to the wind tunnel test model was established.The discrete-phase model was loaded on the basis of the gas-phase flow field simulation,and the gas-solid two-phase simulation was carried out to study the diffusion characteristics of particulate matter in the area around the stack under the conditions of different wind speed,particle size and windbreak setting condition.The research indicates:(1)The windbreak can effectively reduce the incoming wind speed and reduce the dusting amount of the open-air pile,thereby reducing the diffusion of particulate matter.However,the flow field behind the material pile becomes chaotic due to the installation of the windbreak,and generating a larger vortex which drives the particles to diffuse to the height.Before the windbreak is installed: when the incoming wind speed is 0.87 m/s,the particulate matter is concentrated on the leeward slope of the pile;when the incoming wind speed is 3.91 m/s,the high-concentration area of the particulate matter is the area of 1 ~ 4 in the X direction;When the incoming wind speed is 7.22 m/s,the high concentration region of the particulate matter is the region of 2 ~ 6 in the X direction.After the windbreak is installed: when the incoming wind speed is 3.91 m/s,the high concentration area of the particulate matter is the area of 11~ 28 in the X direction;when the incoming wind speed is 7.22 m/s,the highconcentration area of the particulate matter is the area of 20 ~ 34 in the X direction.(2)Under the same particle size,with the increase of wind speed,the dusting amount of the open-air pile increases correspondingly,the concentration of particulate matter at each height position increases obviously,and the high-concentration area of particulate matter diffusion increases and is far away from the direction of the pile;under the same inflow wind speed condition,with the increase of the particle size of particulate matter,the particle diffusion concentration in the flow field behind the open-air pile first increases and then decreases,and the particle concentration near the ground is higher and higher.In addition,the higher concentration area is closer to the material pile.(3)A windbreak provided before and behind the pile can better reduce the amount of dust generated by the pile and control the diffusion of particulate matter.If only one windbreak is provided,arranged in front of the pile rather than in the rear of the pile can reduce the amount of dust caused by wind erosion in the open air material pile.