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Cyclone Dust Collectors
Many industrial processes require dust-size pieces of process material to be collected for
reuse or disposal. Cyclone dust collectors are an efficient and low maintenance means
of removing fine material from an air stream. Unlike filter-based dust collectors, cyclone
dust collectors use the physics of air pressure, mass and momentum to cause particulate
to fall to the bottom of a chamber where it can be collected.
A cyclone dust collector has no moving parts and no filters; instead, it relies on the
design and shape of the dust collector chamber. In cyclone dust collection, the air stream
passes through tubes or around a stationary spinner that direct the air to rotate inside
the chamber. Centrifugal force causes particulate to move to the walls of the chamber
where it strikes the walls of the chamber, losing momentum. Then gravity pulls the
particulate into a hopper at the bottom of the chamber. The particulate-free air (or other
gas) rises through the center of the vortex and is vented at the top of the chamber.

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Top 5 Questions to Ask When Considering a Cyclone Dust Collector
Designing a dust collection system can be quite a daunting task. With so many collector
options and so many application variables to consider, it is difficult to know where to
begin. Cyclones are among the oldest and still most reliable methods of dust collection
available. Because they require very little maintenance, have low up-front cost, and offer
unmatched versatility, cyclone collectors remain a viable solution to many air-handling
challenges. Although heightened environmental regulations and collection efficiency
needs have shifted industry toward the use of filter-media collectors, cyclonic dust
collection still plays a vital role in many air-handling systems. These five questions will
help determine if a cyclone dust collector is right for your application.

1. How big is my dust?
Cyclonic dust collection relies on inertial forces to separate dust particles from an air
stream. The larger and denser the particulate is, the greater its inertia. This is the
reason cyclones have such high collection efficiencies when handling relatively large
dust particles. The forces generated in typical cyclonic dust collectors are not high enough
to achieve effective separation of extremely fine particulate; however some alternative
design cyclones, such as the SplitStream™ Dust Collector from Aerodyne, use a powerful
secondary air stream to create a "counter-cyclonic" action in the collector and raise
efficiencies of fine particulate collection. Another benefit of the secondary air stream is
the ability to use it as a cooler or dryer by drawing the secondary air stream from an
appropriate source.

2. How much dust is too much?
Grain loading or dust loading refers to the amount of dust particulate that is suspended
in a gas stream. This is typically measured in the number of grains per cubic foot of gas.
This is an important number to consider when designing a pollution control system. Not
only will this factor into the size requirement of a dust collector, but it will also determine
the appropriate type of dust collector. The strict air pollution control standards in the
United States often necessitate a "filter-media" dust collector, such as a bag house, for the
final collection stage. Unfortunately, extremely high grain loading conditions can hinder
the proper operation of these collectors, often requiring them to be oversized to
accommodate the large dust volume.
High grain loading can blind filter media, considerably affecting collection efficiencies. As
dust builds up on the filter media, the initial dust cake aids in separation efficiency;
however, extremely high dust loads can block airflow through the filter media. Another
problem high grain loading creates for filter-type collectors is the fast wear of the filter
media due to frequent cleaning.
Installing a cyclone as a pre-filter to a filter bag house or cartridge collector is an effective
way to reduce the load put on the filter media. Placed in-line before a bag house, a
cyclonic dust collector can remove a majority of the larger particulates, thereby reducing
the amount of dust sent to final stage filters.

3. Can I reuse the dust I am collecting?
Dust generated by handling dry bulk materials can be hazardous but also valuable.
Unfortunately, most filter-type dust collection systems are designed for disposal rather
than product reclamation. Filter media collectors such as cartridge filters and bag houses
often do not allow collected particulates to be recovered for reuse due to contamination
or particulate size issues. In many cases, contaminated dust filters in food-grade
applications make product recovery cost-prohibitive. Also, filter collectors receiving a
variety of materials do not lend themselves to product recovery because the materials mix
within the collector. By placing a mechanical collector such as a cyclone in process
before a final filter collector, valuable material can be reclaimed without the threat of
contamination and a cyclone can be placed on the lines handling the most valuable
materials to capture a majority of the particulate.
Unusable fine particulate is another concern involved with reclaiming particulates from a
filter-type dust collector. It is often the case that particulate large enough to be reused is
mixed with very fine, unusable dust. The nature of mechanical separation allows cyclones
sometimes to act as classifiers, collecting the larger particles and sending the fines to a
final filter. A particle size distribution test of the material being collected and a reliable
efficiency curve for a specified cyclone can help to determine if it can be used as a
classifier for a given application.

4. Do I have heat or humidity concerns?
Air handling in manufacturing processes is often a delicate balance with a number of
variables to contend with. Process heat and humidity in the air stream create a difficult
challenge when it comes to dust collection. Collection of red-hot dust particulate is simply
not possible with many bag houses because cotton filters are flammable and flame
retardant filters can be costly. High humidity levels that result in condensation or steam
also pose a problem for these collectors as successful filter cleaning can be inhibited. In
some cases, a cyclonic dust collector can be the solution to these problems. Installed
before a bag house on high heat processes, a cyclone can act as a spark arrestor,
collecting the larger particulates which can retain enough heat to ignite a filter bag. Humid
conditions generally pose less of a problem to cyclones than to filter-type collectors.
Although humidity interferes with the filter cleaning process or completely damages filters,
it can actually improve collection in cyclones. Humidity can saturate dust particulates,
which increases their mass and the inertial force acting on them during cyclonic
separation.

5. How much should I spend?
Perhaps the most important and most difficult question asked when designing a dust
collection system is how much to spend. The simple answer is, it depends. It depends
on what the overall goal of the system should achieve. The best dust collection
systems are those that were designed with several functions in mind: capacity,
operation costs, maintenance costs, and product/material value.
The volume of dust-laden air needing to be moved will dictate the size of collector
required. Simply put, larger collectors cost more to operate.
A cyclonic dust collector placed before a bag house can allow for the use of a smaller
bag house by reducing the amount of dust the bag house receives. Reducing the size
of the bag house not only reduces the operational costs but greatly reduces the
maintenance costs. Fewer bags, cages, cartridges, and retainers mean fewer dollars
spent on replacements.
The value of the product being collected should be considered when it comes to
designing a dust collection system. When dealing with highly valuable material, ease
of product reclamation is extremely important. The cost savings realized by recovering
valuable product should be factored into the cost of a dust collector. If the material
being collected is valuable enough to be reused or repurposed, it may warrant the
inclusion of a cyclone separator in the system. When handling extremely valuable
material, the addition of a cyclonic dust collector can pay for itself in a very short
timeframe.
Although a cyclone dust collector may not be suitable for every application, a wide
range of benefits can be realized from their use. From product reclamation to air
pollution control, cyclone dust collectors remain a valuable tool for many industrial
processes.

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