Abstract: Industrial site arrangement, meteorological conditions, emission control technologies and the wide range of materials and specific conditions that compose storage piles on industrial sites may strongly affect the wind erosion and particles take-off. Due to the potential environmental impacts to nearby communities, it is essential the monitoring and accurate quantification of these emissions. It can be carried out by field measurements or by mathematical models using emission factors as recommended by the United States Environmental Protection Agency (USEPA) in AP-42 documentation. However, field campaigns may be prohibitive as a high number of factors influence the emissions and it changes several times during an operational day. The Computational Fluid Dynamics (CFD) is an important tool to address this outcome and to predict the flow field on the stockpiles. In the present work, numerical simulations of a full scale steel plant site were carried out to predict the emitted mass from stockpiles considering simultaneously the influence of: wind direction, wind magnitude (gust), existence of natural (green belts) and artificial (wind fences) barriers, porosity of the barriers, dust suppressants (water and polymer solution aspersion) and stored material characteristics (for instance, density and particle size distribution which affects the threshold friction velocity). Preliminary results indicate that the direction and magnitude of the wind gust influence the velocity distribution in the entire yard and may increase erosion levels on certain locations. The presence of green belts reduces the overall velocity distribution within the industrial site. The insertion of wind fences in areas already protected by green belts can cause an additional protection of the diffuse sources. Their efficiency is strongly dependent on the case. The effects of reducing or increasing emissions in a real industrial yard, considering all the factors already mentioned, are very heterogeneous. Therefore, the present results allow the analysis and selection of the possible scenarios in industrial yards looking for the most suitable combination leading to the optimization of yard management and environmental controls to reduce the emissions and their impact more efficiently in the environment and in the human health. In this sense, Computational Fluid Dynamics is a particularly useful tool to evaluate the emission of pollutants on a local scale, since they can represent at detail level the obstacles effect. Thus, the main objective of this report was to perform CFD simulations of the turbulent atmospheric flow incident to stockpiles and surrounding areas of a full industrial unit to obtain the distribution of the friction velocity for eight prevailing wind directions. The most widely used mathematical model to estimate atmospheric emissions from storage piles (proposed by the United States Environmental Protection Agency – USEPA) requires, as the main input data of the model, the distribution of near wall velocity to estimate the friction velocity on each source. Both friction velocity distribution and emission estimation showed the protective effects of vegetation barriers and surface treatment. However, it was clear during the work that even if it is reached an emission reduction about 99%, the residual emission rate may be negative to the environment if a given source presents a high frequency of disturbance. The main results of the CFD simulations for the full industrial site evidence that its arrangement presents important effects on the flow structure over the site. There are critical wind flow directions for which the friction velocity increases on the stockpiles and on the ground surrounding it, which increases the emissions and resuspension of deposited particle on the ground surrounding the piles. For instance, the piles arrangement inside the yard categorizes several regions of low, medium, and high erosion. Piles with small particle size should be placed at low eroded zones and coarse particles piles can be moved to high eroded zones. The estimation through the USEPA model is highly dependent on the number of disturbances whose estimation becomes difficult without access to the dynamics of the storage yards. In the present report, the emission rate estimation was calculated hourly, and number of disturbances was considered uniform along the working day. However, soon it is expected that through data provided by the company, it is possible to understand and parameterize the storage dynamics and material recovery from stockpiles.

Keywords: diffuse sources, emission estimation, CFD, wind barriers, granular materials.