Investigation On Diffusion Mode Of Fugitive Heavy Particle And Its Application

As one of the most representative pollutant, particulate pollution is not only serious harmful to public health, but also increasingly becoming the key factor restricting the improvement of the urban environmental quality in China. Compared with organized particulate pollution, researches on dust emissions released from open sources develop slowly and many urgent problems are needed to be solved. Nowadays, fugitive dust emissions generated by stockpiles in the open storage yards of mineral and industrial sites, construction locations and habour areas, etc, are becoming the dominant portions of air pollution, and subsequent atmospheric dust dispersion has brought about many ecological and economical problems.This paper, taking open stockpiles as an example, integrates theoretical analysis, numerical method and experiment approach, to study particle behavior. Then diffusion mode for heavy particle is put forward. Firstly, as a fundamental basic parameter of particulate pollution, quanlitative estimation of dust emissions has been always focused. Therefore, the further investigation is carried out in the present study. Pickup velocities of particle and dust emissions are measured in wind tunnel. Empirical relationship for dust emissions has been established based on experimental data. Non-dimensional parameters expressing the pickup velocity are obtained, and Reynolds and Archimedes numbers are selected to adequately describe the pariticle lift-off phenomenon.Secondly, aerodynamics method, based on US EPA mode, is used to estimate dust emissions in open storage yards. The calculation procedure is adjusted and friction wind velocities, the most effective variable, are predicted. Meanwhile, the simulated values over exposed subareas are validated against EPA results and flow patterns over the stockpiles are satisfiedly achived. From this view, the present study has provided a new method for friction wind velocity, which plays a dominant role in the assessment of dust emissions. This actual aerodynamical way provides easier accessibility than US EPA standards to obtaining the quantification of dust lift from exposed surfaces. It enables to estimate the dust eroded with higher preciseness.Then, regarding to the art computational fluid dynamics (CFD) method, force analysis of single particle is discussed. DPM dust diffusion model is proposed. The results are compared with experimental data tested in wind tunnel to valid the model. Taking Gaussian model as a constract, the error analysis is performed. This mode favours to predict heavy particles uptake from stockpiles storing in open areas.Finally, with the help of the diffusion mode, a simulation based on the actual port is undertaken. Dust emissions are determined and the concentration of particulate dispersion is evaluated. A clear understanding of the influence of wind erosion is obtained and feasible solutions are also provided. The present paper has demonstrated a quantitative measurement for dust emissions of inorganized source in the open yards.