Anyone involved in the transportation and storage of coal will likely know about the hazards associated with the dust generated by this process and recognize it should be given special consideration. Dust collectors are commonly used during the transport of coal to control and minimize the amount of loose dust present in the handling facility. Managing coal dust is important due to the high level of combustion and associated fire risk; the development of a strategy for keeping a facility clean and operational is crucial.
Handling and transporting coal can create combustible dust situations that should be thoroughly researched to determine the best control methodology for a facility. Just as there are many different types of coal – from Pittsburgh to Powder River Basin – there are many dust collectors and filter media technologies available and a dust control solution can be tailored to meet specific needs.
It is easier to include effective dust collection in the initial design stage of a new facility, but it is also possible to retrofit existing facilities. Initial things to consider are the local regulations and/or guidelines for the processes occurring at a facility. Does the type of coal being processed have any special guidelines? It is easier to include effective dust collection in the initial design stage of a new facility, but it is also possible to retrofit existing facilities. A good understanding of the regulations is required in order to develop a dust control strategy.
Choosing the Right Design to Meet a Coal Operator's Needs
Dust collection technologies have greatly expanded and improved over the years. There are now a variety of designs that may be beneficial for an operator’s application depending on their requirements and/or limitations. Dust collector configurations consist of point-of-use localized collectors or remote centralized collectors, while overall collector size can vary from large to compact. Filtration media is available in bag, cartridge or filter-pack styles and filter media can be cleaned by compressed or reverse air. Start collector selection by asking a few initial questions to set up a framework from which dust collector styles can be compared and to determine which one best meets the requirements:
- Consider where coal dust is generated in the facility. Is there only one dusty location or is it generated at multiple points throughout the facility? Can the dust from multiple points mix in one large dust collector or does the dust need to be kept separated due to different disposal requirements?
- Is there space for dust collection equipment or does it need to be inserted around an existing process line? If space is at a premium, can a smaller dust collector be inserted on the transport line? Newer style dust collectors allow for a point-of-use concept to be applied directly on transport lines, minimizing the amount of space required.
- What are the local weather conditions for the facility? Are there any concerns with an outdoor dust collector location? For example, would an indoor dust collector be preferred due to freezing temperatures?
- Is compressed air available at the dust collector location? Does it already exist in the facility or would it need to be added if the dust collector required it?
Dust collected during material transport can either be returned to the process at the point it was generated (point-of-use collection) or sent to a centralized dust collector located away from the process. To limit the total number of dust collectors in a facility, a centralized dust collector will typically be considered first. But is there space available for a large dust collector near the dust generation points? If not, the dust collector may need to be located a long distance away from the collection point to accommodate the size of the dust collector. When dust collectors are located further from the dust generation point, they require a good duct system design to prevent dust from settling out in the ducts. The distances involved can increase the amount of duct maintenance needed to ensure the duct is in good condition and can increase the fan size and operational horsepower requirements.
When selecting between point-of-use use or centralized dust collectors, consider the benefits of each type and determine which would be the best fit to the required application.
Point-Of-Use Dust Collectors
Benefits from a point-of-use dust collector strategy include smaller equipment footprints, reduction or elimination of waste streams, reduction or elimination of duct runs and associated maintenance, as well as simplified and easier installation.
Newer point of use dust collectors have very small footprints and use small filter packs. The latest design in point of use dust collector technology, the Torit® PowerCore® CPV from Donaldson (Figure 1) can squeeze into the tight paces in existing facilities due to its compact design as compared to older, larger baghouse technology.
This collector can often be placed directly on enclosed transport conveyor belts depending on the facility requirements. This style of dust collector has been used to retrofit existing facilities that did not have dust collection initially and needed to add it due to a process change but were limited by available space (Figure 2).
They have also been used on new facility designs to minimize the space needed for dust collection and provide faster, easier maintenance, as the small filter packs are replaced from the clean side of the dust collector and do not require confined space entry.
A point-of-use dust collector can return the filtered coal dust back to the process stream instead of removing and disposing of it as a separate waste stream. Newer point-of-use dust collectors have filter packs with vertically positioned flutes to minimize the amount of dust that stays in the filters. As a consequence, more dust is cleaned back out of the filter during each cleaning pulse therefore there will be less dust remaining in the filter during the last cleaning cycle. Also, the collector can be configured without a collector hopper in a ‘bin vented style’ point-of-use dust collector and therefore there is no final hopper dump at the end of the cycle. Overall cleanup time is minimized and disposal costs are reduced.
Another benefit of using smaller, compact point-of-use dust collectors is that they can operate independently so the entire dust collection system is not down if maintenance needs to be performed. This feature also allows a tailored percentage of dust control to be operated on an as-needed basis, rather than running continuously as in a centralized collector approach.
This saves on fan horsepower and operational costs. Smaller point-of-use collectors can also be placed indoors and that may be preferred in a cold climate. Indoor dust collectors avoid condensation issues on the interior surfaces of collectors and allow maintenance work to be completed inside, away from harsh weather environments which is a benefit for your employees.
If a bag filter is preferred – but there is a need to incorporate some of the benefits from a point-of-use solution – a few existing baghouse technologies have been redesigned and reduced in size to allow them to be located on or near the process.
This style of bin vent filter bag dust collector provides the benefit of a smaller design and can be installed indoors or outside, but still uses filter bag technology, which includes a wide variety of filter media options (Figure 3).
Centralized Dust Collectors
Centralized dust collectors filter the coal dust from multiple points in the process stream and often handle large quantities of air. Since the collector is typically located away from the process, the resulting larger size of the collector usually does not create concerns. Many significant technology improvements have been made to these types of dust collectors, providing a wider range of options and benefits.
New centralized dust collector designs have been optimized to include some of the same benefits realized from point-of-use collectors. For example, DonaldsonTorit® PowerCore® VH collectors use updated filter technology that is specially designed for abrasive applications. This may be the best solution for a facility as it still uses a centralized dust collection approach, but has a much smaller footprint than a traditional baghouse dust collector (Figure 4), allowing it to be used indoors or outdoors.
One situation where a traditional centralized dust collector may be the best solution is in the absence of a reliable compressed air supply.
Compressed air is required for reverse pulse cleaning in most of the dust collectors previously discussed. If compressedair is not available or is not easily accessible to the dust collector location, this maybe a key consideration in the selection process. Because some traditional centralized dust collectors use medium pressure reverse flow air for cleaning and do not require compressed air, they may be the best selection foflow air for cleaning and do not require compressed air, they may be the best selection for a facility.
Choosing the Right Dust Collection Technology
How does one pick the right dust collector solution for their facility? First, consider what type of coal dust is to be collected, as well as the existing guidelines and regulations for the industry and facility. Then review the different options available to determine what features would be most beneficial to the facility. Ask: is it more important to minimize dust collector footprint, have an easy filter change-out, maintain only one dust collector, optimize fan operational hours, reduce compressed air dependence or reduce product disposal? Is there a particular dust collection method that can get most – if not all – of what an operator needs?
For help answering these questions, it is best to work with a reputable dust collection technology provider that offers a full range of products and has the expertise to discuss each possible solution to ensure the operator gets exactly what they need for their facility.
