Dust Control Handbook for Industrial Minerals Mining and Processing

Dry DrillingDry drilling is accomplished without the use of water for dust control. Dust control isaccomplished using a dust collection system mounted on the drill. These systems have theability to operate in various climates, i.e., they are not subject to freezing at lower temperaturesas with the use of water, and they can be up to 99 percent efficient if properly maintained[USBM 1987]. There are different types of dust collector configurations used which aredependent upon the size of the drill.Medium- to Large-Diameter Drill Dust Collection SystemsFigure 3.4 shows a typical dry dust collection system on a medium- to large-diameter drill. Drilldust is generated by the bailing air, which is compressed air that is forced through the drill steelout the end of the drill bit and used to flush the cuttings from the hole (Figure 3.2 depicts asimilar scenario, but includes water). In a properly operating collection system, these cuttingsare contained by the drill deck and shroud located over the drilling area. This dusty air fromunderneath the shrouded drill deck is removed by the dust collector system. The collector iscomposed of an exhaust fan and filters which filter the air from underneath the shroud area. It isgenerally self-cleaning, using compressed air to pulse through the filters at timed intervals toclean them and prevent clogging. The filtered fine-sized material then drops out the bottom ofthe collector to the collector dump.Figure 3.4. A basic dry dust collection system on a drill.Sources of Dust Emissions from Collection SystemsDamaged, nonfunctional, or missing dust collector filters are generally the root cause of dustyexhaust air from the collector. Other emission sources in the collection system can be caused bydamaged or worn collector system enclosure components or operational conditions impeding theenclosure components from containing and capturing dust.84 Drilling and Blasting