Products - Wet Collectors

Anagha Fume Scrubber:

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Wet Collectors
Fume (gas) scrubbers may be categorized by pressure drop as follows:
  • Low-energy scrubbers (0.5 to 2.5 inches water gauge - 124.4 to 621.9 Pa)
  • Low- to medium-energy scrubbers (2.5 to 6 inches water gauge - 0.622 to 1.493 kPa)
  • Medium- to high-energy scrubbers (6 to 15 inches water gauge - 1.493 to 3.731 kPa)
  • High-energy scrubbers (greater than 15 inches water gauge - greater than 3.731 kPa)
Due to the large number of commercial scrubbers available, it is not possible to describe each individual type here. However, the following sections provide examples of typical scrubbers in each category.

Low-energy scrubbers:
In the simple, gravity-spray-tower scrubber, liquid droplets formed by liquid atomized in spray nozzles fall through rising exhaust gases. Dirty water is drained at the bottom.
These scrubbers operated at pressure drops of 1 to 2 in. water gauge ( to kPa) and are approximately 70% efficient on 10 m particles. Their efficiency is poor below 10 m. However, they are capable of treating relatively high dust concentrations without becoming plugged.

Low- to medium-energy scrubbers:
Wet cyclones use centrifugal force to spin the dust particles (similar to a cyclone), and throw the particulates upon the collector's wetted walls. Water introduced from the top to wet the cyclone walls carries these particles away. The wetted walls also prevent dust reentrainment. Pressure drops for these collectors range from 2 to 8 in. water ( to 2 kPa), and the collection efficiency is good for 5 m particles and above.

Medium- to high-energy scrubbers co-current-flow scrubber:
Packed-bed scrubbers consist of beds of packing elements, such as coke, broken rock, rings, saddles, or other manufactured elements. The packing breaks down the liquid flow into a high-surface-area film so that the dusty gas streams passing through the bed achieve maximum contact with the liquid film and become deposited on the surfaces of the packing elements. These scrubbers have a good collection efficiency for respirable dust.

Three types of packed-bed scrubbers are:
  • Cross-flow scrubbers
  • Co-current flow scrubbers
  • Counter-current flow scrubbers
Efficiency can be greatly increased by minimizing target size, i.e., using 0.003 in. (7.62 mm) diameter stainless steel wire and increasing gas velocity to more than 1,800 ft/min (9.14 m/s)

High-energy scrubbers:
Venturi scrubbers consist of a venturi-shaped inlet and separator. The dust-laden gases venturi scrubber enter through the venturi and are accelerated to speeds between 12,000 and 36,000 ft/min (60.97-182.83 m/s). These high-gas velocities immediately atomize the coarse water spray, which is injected radially into the venturi throat, into fine droplets. High energy and extreme turbulence promote collision between water droplets and dust particulates in the throat. The agglomeration process between particle and droplet continues in the diverging section of the venturi. The large agglomerates formed in the venturi are then removed by an inertial separator.

Venturi scrubbers achieve very high collection efficiencies for respirable dust. Since efficiency of a venturi scrubber depends on pressure drop, some manufacturers supply a variable-throat venturi to maintain pressure drop with varying gas flows.

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