Dust Removal Gets A Rethink

Total cost of ownership is becoming a key factor in selecting equipment.

By Seán Ottewell, Editor at Large

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The Compact filters (Figure 2) reportedly provide two-to-three times more filtration than similarly dimensioned bag (pocket) filters. In-line pulse jet cleaning maintains a low pressure drop; filter efficiencies of 99.999% for 0.5-micron and larger particles are said to be typical.

Seven filter media are available, including options for oleophobic, high temperature and anti-static applications. Filter change-out is fast, tool-free and carried out from the clean air plenum side, notes the company. It's never necessary to enter the dirty air plenum side for servicing, which eliminates concerns about employee exposure to hazardous dusts.

"Thanks to filter service life that is three-to-five times longer than conventional filters, [the TCO] is surprisingly low with Tri-Flow Compact — with no compromise of filtration performance," says Doneff. "The new filters are used to best advantage in mixing operations, transfer points, bag loading, storage silos and batch areas — essentially wherever cartridges and bags would have been used in the past. Higher efficiency probably tops the list of which benefit most appeals to chemical operating companies. But longer filter life, higher product recovery and safety are also very important to these buyers."

Tri-Mer is developing new media options but won't divulge exactly what these might be or which applications they target.

MikroPul, Charlotte, N.C., is focusing on low-cost operation, longer maintenance-free operation and space-saving design to ensure a good TCO.

The Mikro-Pulsaire K/LP is based on the company's Mikro-Pulsaire collector technology that reportedly can increase air-to-cloth ratios by 12–32%, decrease pressure drop by 29–57% and improve dust discharge by 50–75%.

The K/LP lowers operating costs by using a patented Expandiffuse two-stage inlet with diffusers at right angles to each other. The final housing inlet occupies nearly one full side of the housing. This large opening reduces velocities by over 90%. Combined with low pressure (less than 30 psi) cleaning, this new design reportedly provides a number of benefits: less dust reaching the bags because of dropout to the hopper and virtual elimination of dust re-entrainment; lower pressure drop; fewer cleaning pulses; and reduced compressed air consumption.

Meanwhile, GEA Wiegand, Ettlingen, Germany, has opened up a new field of application — dust removal — for its liquid jet pumps. Traditionally, the pumps generate and maintain a vacuum of up to 50 mbar, depending on the temperature of the motive fluid. Now, the company is promoting their use, not only to produce a vacuum, but also to scrub gas to remove dust (Figure 3). In initial tests, exhaust air containing HCl was extracted from a tumbling dryer and scrubbed until the exhaust air met TA Luft-acceptable standards — with the simultaneous generation of a vacuum of 50 mbar. Dust collection tests continue.

The compact unit includes a jet pump made of conductive polypropylene with glass fiber reinforcement, a polypropylene separator, perfluoroalkoxy (PFA) motive fluid pumps and titanium plate heat exchangers. The jet pumps don't have any moving parts and therefore are nearly maintenance-free, says the company, which adds their simple design makes them insensitive to dirt and provides a long service life.

Seán Ottewell is Chemical Processing's Editor at Large. You can e-mail him at sottewell@putman.net.


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