Dust Control Handbook for Industrial Minerals Mining and Processing

CostsThe total structure ventilation design has proven to be one of the most cost-effective systems tolower respirable dust concentrations throughout an entire closed mineral processing structure.Not only is the initial cost of this technique inexpensive when compared to other engineeringcontrols, but its operation and maintenance are also minimal. Operations can install all thecomponents for this system in-house to reduce their costs.OPEN STRUCTURE DESIGNThe outside ambient environment can be an effective source of ventilation to dilute and carryaway dust generated and liberated within a structure. Therefore, in some cases, an openstructuredesign can be used as an optimal way to provide for whole structure ventilation. Theopen design is similar to the total structure ventilation design in that it has the potential to be aglobal approach to lower dust levels throughout an entire building or structure. In the openstructuredesign, the natural environment acts as an effective method of diluting and carryingaway dust liberated during operations in mineral processing structures. No dust plume shouldever be visible with an open-structure design. As with the total structure ventilation system, thefirst goal is to capture the major dust sources at their point of origin, before they are allowed toescape out into the plant and contaminate the work environment. The open-structure design is asecondary technique to control the residual dust not captured at the source.In a study that compared three different building types: masonry, an open-structure design, and asteel-sided design, respirable dust concentrations were significantly lower in the open-structurebuilding [Cecala et al. 2007; USBM 2006]. Figure 8.8 shows a conceptual drawing of a typicalopen-structure design with a roof in comparison with an identical sized walled processingfacility. Obviously, a roof provides a little more protection from the natural elements than atotally open design. If an open-structure design is considered for an operation, a number ofissues need to be addressed:Product residue that becomes airborne from plant vibration or high-wind events canaccumulate on walls, beams, and other equipment.An open-structure design must be considered a secondary design. Engineering controlsare needed to eliminate the major dust sources at their point of origin before beingliberated into the plant and contaminating the work environment.A great effort must be made to provide safety railings and guards to minimize thepotential for any personnel falling from the structure.Equipment and personnel must be protected from environmental elements such as rain,snow, sleet, and hail. One possibility to minimize this concern would be to design astructure with a roof and sufficient overhang. In addition, equipment freeze-up problemscan happen when low outside air temperatures occur.Controls for Secondary Sources 213