Dust Control in Specific Areas
The following is a list of some of the typical areas at mines and quarries generating dust that can be controlled by dust collection equipment:
- Rail or truck dumps
- Conveyor belt transfer points
- Silos or bin filling
- Rail, barge or truck loading
Guidelines to Practical Dust Collection
Years of experience in mining and quarry dust control has highlighted a number of significant points:
Good Design and Equipment Selection Is Essential
Anything marginal in either design or selection results in immediate or short term inadequacies in collector performance. The difference in selections between an effective and ineffective dust collector is often much narrower than in many other industries.
Everywhere That Material Is Supposed to Drop Through Air, Dust Is Generated
The most obvious dust generation points may seem to be conveyor transfer points and feed points from screens and crushers. But often, oversized feed-outs from screens or transfer of large product into bins will generate significant dust.
Budgetary constraints are important, so it is generally better to do some parts right than a lot of parts wrong.
Dust Collectors Philosophy: Source or Central
Two basic strategies exist for applying dust control to mines and quarries; source collection (putting the dust collector at the source of the dust emission so collected dust can be deposited directly back into the process stream) or centralized collection (putting the collector in a central location where dusty air is ducted to the collector and discharged as a separate process stream).
Source Collection Operational Advantages Include:
- Lower capital costs as less ducts, and fewer hoppers, screw conveyors or rotary valves are typically required.
- Fewer maintenance problems as fewer ducts or hoppers are being used that can block or bridge. In addition, since there are fewer hoppers, there are fewer hopper discharge devices that need to be maintained.
- A shutdown of one unit may result in temporary increased emissions in a single area, but will be unlikely to necessitate a complete plant shutdown.
Dust Collection Considerations
The following points need to be considered in the selection of central dust collectors for mining and quarrying applications:
- Mine and quarry dust is often abrasive and particle impact against filter media needs to be considered to avoid possible filter damage. This requires consideration of incoming air velocity, dust distribution, and air patterns within the collector.
- Dust removal and disposal requires careful consideration to avoid blockages, equipment abrasion, secondary dust emissions, and higher costs for maintenance and materials handling.
Source collection systems may be easier to deal with since hoppers and ducting are often not used. But when using source collection, the following should be considered:
- Since collectors are often much closer to the source of dust generation, be aware of any water or oil in the dust as this could create problems with filter medias.
- Filter abrasion typically is not an issue, however, if the source collector is being used as a bin vent, place the collector as far from the inlet as possible to avoid abrasion and/or unnecessarily high dust loading.