Recognizing the need to reduce waste at the source, limit fugitive emissions of hazardous VOC's within a process system, decrease disposal costs and the affiliated cradle to grave responsibility, filter manufacturers are aggressively pursuing self-cleaning filter designs which will greatly contribute to the environmental goals of plant engineers in their quest to accomplish a much safer, environmentally friendly, working atmosphere.
Unlike conventional bag and cartridge disposable media filters, and open screen vibrating filters, self-cleaning filters offer the plant engineer the ability to "close" the process loop and obtain consistently higher capacity filtrate. As bag and cartridge filters remove debris the differential pressure across the filter rises, this increase in differential pressure reduces the capacity of a centrifugal pump as it trails left on the curve. The potential of collapsing the media when using a positive displacement pump exists as by its nature a positive displacement pump will continue to build pressure as solids loading increases. Burst bags and collapsed cartridges are rarely identified until the completion of a batch or process when replacement is required thus jeopardizing end product integrity.
As with many process applications the risk of upset conditions always exists. While some self-cleaning filter manufacturers utilize perforated media it must be realized their ability to handle relatively high differential pressure is limited, and may result in collapse. Durable wedge wire slotted elements seem to be the preferred construction. By incorporating innovative welding techniques, slotted elements appear to withstand extremely high differentials, and by design; when handling shear sensitive products, prohibit extrusion.
In a self-cleaning filtration system media regeneration occurs at low or nonexistent differential pressures. Pending on cleaning initiation an control sophistication cleaning is accomplished on time, and independent of pressure, which offers the "clean" rated capacity of existing bag and cartridge filter designs throughout the entire batch or process.
1. Process fluid is pumped into the top of one or more filter stations through a tapered inlet header.
2. The fluid then passes through a screen, leaving debris deposited on the inside.
3. Clean filtrate exits the side outlet of the filter(s) through the outlet header.
4. Debris retained on the screen is removed by a cleaning disc that is moved up and down the screen.
5. This combined action of the disc and process flow physically moves the debris to a chamber at the bottom of the housing.
6. The concentrated debris is periodically purged through an automated valve into a purge header and out of the process loop.
The concentrated purged fluid can be recycled into another batch, directed into a waste stream, or reintroduced into the current process once the large solids have been removed via a salvage system. Once the process or batch has been completed; pending on the filter design, little viable product remains in the self-cleaning filter itself. Higher yields are accomplished as there are no fluid laden bags or cartridges to be removed, disposed, and replaced.
Self-cleaning filtration systems offer the design diversity and control flexibility to meet many process filtration requirements while addressing the obvious environmental concerns of today's plant and process engineering professionals.
RPA Process Technologies
9151 Shaver Road
Portage, MI 49024
Toll Free (US only):
1-800-656-3344
Voice: +1 269 323-1313
Fax: +1 269 323-0065
www.RPAprocess.com
info@RPAprocess.com
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