Assessment of Threshold Wind Velocities of Industrial Granular Materials: A Comparative Evaluation of Experimental Methods

To maintain a high standard of environmental quality, industrial plants must be able to foresee and control the impacts resulting from their activities. One of the most challenging issues for the metallurgical and mining industry when it comes to protecting the environment is the measurement of particulate matter emissions generated by the wind action over the erodible surfaces of stockpiles of granular materials. It is known that the emissive phenomenon starts from a specific threshold friction velocity, which is an inherent characteristic of each material. This parameter can be derived from relationships available in the scientific and technical literature, which, however, only provide qualitative estimations. Therefore, the threshold friction velocity of the specific materials under investigation must be assessed through laboratory tests. This article discusses the results obtained for nine raw materials sampled in a metallurgical plant by applying three different procedures, (1) the sieve-based analysis suggested by U.S. EPA; (2) the laboratory tests performed with an Environmental Wind Tunnel; and (3) the PI-SWERL tests (i.e., tests performed with a Portable In-Situ Wind ERosion Lab), and presents a comparative analysis of the three methods. Findings indicate that the EPA methodology tends to be less accurate than the wind tunnel and PI-SWERL tests, though its accuracy can be slightly improved by adding an additional sieve size for materials with finer aggregates. The wind tunnel and PI-SWERL provided comparable results, with PI-SWERL offering practical advantages due to its portability and an effective synchronization between its data acquisition systems.