Innovations in industrial air filtration
Innovations in industrial air filtration
The two most common forms of air or gas filter are the cylindrical cartridge or ‘bag' filter, and the 'flat' panel filter, mounted in a dividing wall or plenum chamber. The flat panel systems tend to be used in heating, ventilation and air conditioning (HVAC) systems in commercial and industrial applications.
Bag filters are commonly used in larger scale industrial air filtration systems. The cylindrical cartridge or bag is located in a cylindrical housing, a series of which form a ‘baghouse' system. The air flow is through the bag from outside to in, so that separated solids accumulate on the outside, from which they can be blown by a reverse pulse of compressed air. Although generally giving way to nonwoven media, woven fabrics still have an important role in baghouses because of their ability to flex during the reverse pulse. Hence, they can break the accumulated dust cake, allowing it to fall away from the bag.
Donaldson, a leading worldwide provider of filtration systems and replacement parts, has recently introduced Synteq XP® compressed air filter media, which the company claims increases efficiency considerably whilst reducing energy consumption due to a much lower media delta pressure, achieving energy savings of up to 40% (see Figure 2). The new filter medium combines a unique fibre blend and a new manufacturing technique that does not require a binder.
Donaldson claims that end users can save a ‘three-to-four digit Euro sum' on energy costs per annum. Furthermore, assembly and servicing have been simplified through specially designed filter housings. The advantages were confirmed by examination of performance data in line with the ISO 12500-1 standard, which showed that at a flow rate of 1,100 m3/h more than €1,500 per annum could be saved. This was well in excess of the costs of the filter, even allowing for the cost of the filter housing.
This savings potential is also demonstrated by PowerCore® dust collection technology, which Donaldson says is superior to conventional bag filter units and leads to substantial reductions in operating costs. The Donaldson units using this new technology are up to 70% smaller than conventional dust collectors. For example, a dust collection unit previously equipped with 81 bag filters of 2.40 m in length, has been replaced by only 12 PowerCore filter packs. Ten minutes was required for replacing a traditional bag filter, compared to two minutes to replace the fewer PowerCore filters. The replacement of the filter packs is a remarkably clean process and therefore very service-friendly.
Donaldson was able to transfer experience of air intake filter design for heavy duty vehicles to the development of the company's dust collection technology. PowerCore filter packs combine advanced filter manufacturing techniques with patented Ultra-Web® nanofibre technology. The filter media, shaped similarly to intake filters, is formed into fluted channels and layered so a rugged structure is produced. This allows a higher dust load to collect on the surface of the media flutes than would be possible with conventional filter fibres, with a depth loading of 540 g/m2 for standard polyester. This high surface filtration performance combined with a patented pulse cleaning technology leads to the performance increase.
For years, the filtration industry has been looking for a synthetic alternative to glass mat media that offers better filter performance with lower energy costs. To solve this challenge, Hollingsworth & Vose Company designed and developed NanoWave™, an environmentally-friendly all-synthetic extended surface, high-loft material (see Figure 3). Developed for the ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers) -certified HVAC bag filter media market, the material has three times the dirt holding capacity of conventional media.
NanoWave is the only synthetic media that equals or exceeds the performance of glass mat after discharge. Unlike conventional synthetic media, which rely on electrostatic charge, NanoWave is a mechanical filter that meets the same efficiency at half the resistance in a discharged condition with no performance decay throughout filter life. Where extra high efficiency and low pressure drop are required, NanoWave media can be electrostatically charged. The significantly lower pressure drop for a given efficiency results in lower energy consumption for air handling equipment.
Hollingsworth & Vose's innovative NanoWave synthetic media also improves filter manufacturing, installation productivity and clean disposal compared to traditional synthetics. Designed specifically to meet ASHRAE bag standards, NanoWave media can be converted into filters using conventional ASHRAE bag manufacturing equipment, such as conventional sewn and ultrasonics, eliminating capital expenses for switching plant equipment.
NanoWave media provides glass mat levels of performance without the concerns for fibre shedding during filter processing, installation, and use that is associated with glass media. NanoWave media's high stiffness allows proper bag opening, and it retains its shape in variable HVAC systems, reducing set-up time and increasing productivity. The media's design also allows for incineration and low impact disposal leading to reduced pressure on the environment. These benefits increase the product value from filter production through filter installation to final replacement.