By Joe Kiolbasa, Donaldson Torit Product Manager
Most dust control content focuses on advances in industrial dust collector filters and industrial dust control maintenance with the majority focusing in on dust collectors using cartridge filters. While collectors with cartridges offer many advantages, there are thousands of facilities in North America still buying and operating baghouses. This article addresses the filtration needs of baghouse owners and operators.
Baghouse filters can be made of a wide variety of materials. If the airstream going into the collector is above 275°F, then you can use P84, Aramid, Ryton and other materials. If there is high moisture content in the airstream from dryers, or if high acid or alkali conditions exist in the air stream, polypropylene should be strongly considered. But, each of these applications is special, requiring bags made of special materials that address your specific needs.
In most instances and applications, standard polyester has been the filter media of choice in baghouse filters because it does a good job of filtering air, it lasts an acceptable amount of time, and the first installed cost is economical. Another type of polyester bag filter that can provide better baghouse performance, and do it economically, are filter bags made of hydroentangled polyester.
Dura-Life™ Polyester Fabric Collector Bags are used for general purpose applications to improve baghouse performance. These bags deliver cleaner air and longer filter life than conventional polyester media through the unique hydroentanglement manufacturing process which requires no needling, which plagues traditional media with large pores that embed dust, inhibit cleaning and shorten filter life. Dura-Life polyester bag filters can improve the performance of most popular brands of baghouse collectors.
The following points provide an overview of the benefits of spunlace polyester filters which will help you unlock your baghouse performance for your application:
1. More uniform filter media
Most standard polyester bag filters are made of a felt manufactured via a needling process. In this process, a large set of needles with barbs rapidly moves up and down through a bed of media fibers to entangle the polyester fibers together to create the felt.
In 1976, DuPont introduced a new process where micro-fine water jets were used to entangle the fibers together. This process of hydroentangling, or spunlacing, provides a stronger, more uniform material with smaller pores than common needled felt polyester.
2. Longer Filter Life
When dust is filtered in a baghouse using hydroentangled spunlace bag filters, a much larger percentage of the dust is captured on the outer surface of the bag than is captured on the outer surface of the common polyester bag filter. This phenomenon is known as surface-loading. When it comes time to pulse the dust off the bag via a reverse pulse of air inside the bag, the surface-loaded dust pulses off the bag easily and drops into the baghouse hopper. The more effective the pulse and filter cleaning, the better the airflow (less pressure drop) through the bag. Proper airflow means the baghouse continues to adequately filter dust from the air.
Conversely, filters made with common needled felts are not as uniform in pore size or structure as hydroentangled polyester bags. They are likely to have many larger pores, and because of this, dust collected on these bags tends to imbed deeper into the fabric. This is known as depth-loading, and when it comes time to clean these bag filters it’s far more difficult to pulse the dust out of them. This results in dirtier bags where airflow is restricted, and a higher pressure drop that rises more quickly.
Lab and field results have consistently shown hydroentangled bags last longer due to better surface-loading and pulse cleaning. In fact, hydroentangled bags have been known to last two to three times longer than common polyester bag filters.
3. Reduced Emissions
Looking at the previous pressure drop chart, one might assume that it is easier for air to pass through the hydroentangled bags and, therefore, more dust must be getting through these bags too. But that is not the case. Hydroentangled bag filters actually emit up to 30% fewer particle emissions than common needled felt bag filters on particles 2.5 microns and smaller. Again, this is due to hydroentangled polyester’s smaller pores and more uniform material. This can be a big benefit to plant managers using baghouses to keep their facilities clean and to meet EPA emissions standards.
4. Reduced Energy Costs
Another benefit of the surface-loading and lower pressure drop of hydroentangled bags is the reduced fan energy used to draw air through the baghouse. Fans will not have to work as hard because there is less restriction in the bag filters. Further, if fans are equipped with an EISA-compliant motor and use a variable frequency drive, the annual energy savings can be quite dramatic. The example below shows energy consumption reduced by over US$6,000 per year using hydroentangled bags on one collector with 484 bags. Obviously, the more collectors a facility has, the greater the potential energy savings.
Needled Polyester Bag Clean Air Side (300x)
Hydroentangled Polyester Bag Clean Side (300x)
5. Reduced Maintenance Costs
One of the least favorite jobs a plant employee has to do is replace bag filters in a baghouse. It’s a dusty, dirty job, and it might need to be done in extremely hot or cold weather conditions depending on location and time of year. In addition to being unpleasant, it can be costly to the company that owns the baghouse. Often times this work has to be done when the plant is not running since the baghouse needs to be turned off while the bag filters get replaced. This can result in weekend or holiday labor rates, which can increase project costs.
Field experiences have shown hydroentangled bag filters can last two to three times longer than needled felt polyester bags when replacement is due to excessively high pressure drop. Assuming hydroentangled bags last twice as long as needled felt bags and factoring in labor and bag costs, a plant could save more than US$3,500 each time its employees replace hydroentangled bags in a 484 bag baghouse. Once again, if a facility has multiple baghouses, the savings can add up quickly.
Many companies still use baghouses to keep their facilities clean. By asking for hydroentangled felt baghouse bags, like the Dura-Life polyester bag filters, plant managers can keep their facilities cleaner while reducing their energy and maintenance costs.
