Improved dust capture methods for crushing plant

Abstract

The use of compressive crushing equipment such as gyratory crushers within minerals processing plants can potentially generate large quantities of dust. Remedies to this problem include the retrofitting of shrouds, enclosures, local exhaust ventilation (LEV) systems and water suppression systems. The single or combined application of these systems must be optimised to ensure they operate efficiently. It is desirable that the future design planning of such facilities include integrated dust suppression and/or removal systems to ensure material delivery rates are maintained and the welfare of the workforce is protected. The tipping of mineral ore into the crusher feed bin is investigated by the construction and solution of computational fluid dynamic (CFD) models validated by data obtained from scale experiments. A 3D computational model was constructed using the Fluent™ CFD software to represent the background ventilation regime within an underground crushing installation. The falling ore is represented as a continuum granular fluid falling under gravity from the raised bed of the dump truck. Transient path lines are computed to simulate the updraft airflow generated by the tipping process and indicate the dispersion path of any entrained dust. The relationships between the falling ore material, the displaced air and the shear induced flow are determined by an analysis of the computed volume/mass flow rates predicted across the crusher opening. A parametric study has been performed on the model of the tipping process to investigate the influence on dust dispersion of; the orientation of the dump truck, the surrounding ventilation characteristics and the material tipping rate, volume and initial fill level of the crusher bin. The operation of LEV systems has also been simulated to identify the influence of such systems on the airflow characteristics in and around the crusher feed bin. An analysis of the airflow patterns predicted by the CFD simulation models indicates strong shear flows induced between the tipped material and the surrounding airflow in the vicinity of the crusher during tipping, and a strong influence of the background ventilation regime on the path taken by this shear flow. Scale experimental studies were conducted to characterise the induced shear flow and visualise the potential entrainment and transport of dust. An analysis of these preliminary experiments is presented.