Dust suppression in iron ore processing plants

Abstract

Handling taconite pellets produces dust. As the pellets are transported, they abrade and produce a fine material that represents a concern for airborne dust. Pellet-breakdown studies revealed that as much as 43% (by weight) of the fine particles were 10 μm in diameter and smaller (material regulated by the U.S. Environmental Protection Agency). This is a significant amount of material that represents a concern for dust emissions; therefore, a dust suppressant is needed. Water is the most common dust suppressant used to prevent fines from becoming airborne. To effectively suppress dust, the material must wet well and must remain wet. Surfactants, hygroscopic materials and binders are additives that address at least one of these concerns. Evaluating the wetting behavior of the iron ore revealed that the pellets were highly hydrophilic (contact angles less than 30°). The wetting kinetics of fine particles were increased 99% using acetyletic glycol surfactants, which demonstrated that these surfactants greatly improved wettability. However, in dust-suppression studies using a drop tower that simulated dust generation in a plant, surfactants did not reduce airborne dust. This indicated that ease of wetting was not the primary problem in suppressing taconite dust. In contrast, hygroscopic materials (that prevent moisture from evaporating) and tall oil pitch (a nonhygroscopic binder) reduced airborne dust by as much as 58%.