Influence of site arrangement and green belt on industrial wind erosion, a case study of storage piles and surrounding areas in open yards

摘要

Industrial units, such as steel production sites, have several diffuse sources of atmospheric pollutants. This is the case of open storage yards of granular materials subject to wind erosion. In these units, the industrial infrastructure (conveyor belts, blast furnaces, tanks, chimneys and administrative buildings) and vegetation barriers work as obstacles to the atmospheric flow. A vegetation barrier is, in fact, an efficient control technology to limit dust emission. Recently, the monitoring of dust emissions from storage piles shifted towards mathematical modelling instead of field measurements. In this sense, Computational Fluid Dynamics (CFD) is a very useful tool to evaluate the emission of pollutants on a local scale, since they can represent at detail level the obstacles effect to contaminants dispersion. Thus, the main objective of this work 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. Based on this, it was evaluated the configuration of a typical granular material storage yard to identify and to obtain the precise location, geometry and dimensional information of sources of and main obstacles in their surroundings. 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 friction velocity on each source. In addition to CFD simulations, we propose to quantify stockpiles dust emissions using a modified version of the USEPA model that explicitly include the effects of the amount of non-erodible particles. The emission estimation discussed in this work took into account the effects of surface treatment with a polymer solution. The surface treatment causes the increase of the threshold friction velocity of each granular material and consequently reduces the global emissions. The presence of vegetation barriers is included in the present CFD simulations through the set-up of a porous region that decreases the velocity profile on the sources. 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. In addition, the presence of vegetation barriers significantly attenuated fluid flow.