Sentry Scrubber 2000
Fume scrubbers remove contaminates from an airstream by intimate contact between
a scrubbing liquid, which is dispersed to provide a large surface area, and a turbulently
flowing gas stream. For contaminates which are soluble in the scrubbing liquid,
the removal takes place by absorption of the contaminate. Spray chambers, Venturi
scrubbers, and packed towers can be used to accomplish this absorption.
Gas/liquid interfacial surface area can be produced by use of spray nozzles that
disperse the liquid. The size, and therefore the surface area, of the liquid droplets
formed depend on the flow rate, pressure drop, and design of the spray nozzles.
The arrangement and size of the spray nozzles also determine the interfacial area
available per cubic foot of scrubber volume. Tests conducted by an independent,
international research organization have demonstrated that uniform gas/liquid contact
could be achieved only by use of a double-overlapping spray pattern. Therefore,
the usual configurations of sprays are not recommended for mass transfer operations.
In addition, the number of transfer units developed does not increase in direct
proportion to the height of a spray column (Perry's Chemical Engineers Handbook).
This presents a problem for scale-up.
Venturi scrubbers can rely on the gas-phase energy to produce interfacial area for
gas/liquid contact. Thus, generation of a large liquid surface area requires
a high pressure drop in the gas stream. Alternately, jet scrubbers can aspirate
the gas phase by use of a high liquid flow delivered at high pressure. The
performance of such units is unique for each size and design. With either
type of scrubber, there is a large power requirement. Since the gas/liquid
contact time is short, the number of transfer units achieved by these devices is
limited (Perry's Chemical Engineers Handbook).
Packed towers are the most common device for pollution control applications ("Handbook,
Control Technologies for Hazardous Air Pollutants", U.S. EPA). Packed
towers provide a large wetted surface area for absorption. All of the surface
area of the packing is available as long as the minimum liquid flow needed is uniformly
applied to the packed bed. Further, the mass transfer efficiency of packed
beds can be predicted reliably from technology developed over more than 50 years.
Also, packed scrubbers have low power requirements and are adaptable easily to corrosion-resistant
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