COWARD ENVIRONMENTAL SYSTEMS, INC.
500 Birchfield Drive,Suite 501, Mt. Laurel, NJ 08054
856-727-4400 -fax 856-727-4344
e-mail: cesi@cowardenvironmental.com

Fume Hood & Process Exhaust
Low Capacity Scrubbing

Employee Safety, EPA Pressure and the Clean Air Act of 1990: These motivational forces are rapidly causing industry to pay greater attention to the control of polluted air streams. Fume hoods and process exhausts are typical sources of such pollution. What is the best method of control? No one method can claim universal usage. Each application must be reviewed on its own merits and the method of control that best suits the applicable criteria be chosen with all disciplines involved contributing to the final decision.

Low capacity systems sometimes offer the greatest design challenge. Removal efficiency, space, sound, identification of the contaminant; these are but a few of the criteria requiring consideration. If used for low capacities such as exhausting a single fume hood or small process hood, standard packed tower scrubbers sometimes are unable to meet the criteria. For example, the scrubber may meet the removal efficiency but its internal resistance (2" - 6" w.g.) may require the use of a noisy fan. It also may not satisfy space restrictions.

Harrington Environmental Engineering, Inc. has designed and engineered an eductor venturi scrubber (Model HPEV) primarily for removal of particulate and nuisance gases from process tanks and gas streams. The HPEV does not require an exhaust fan, it satisfies tight space requirements and it can meet most performance requirements. The HPEV line of scrubbers (eleven sizes) has an exhaust capacity range of 5 CFM to 75,000 CFM. Each scrubber is manufactured from high corrosive resistant fiberglass reinforced (FRP) plastic.

The HPEV Scrubber operates by passing a scrubbing liquid under pressure through a spray nozzle which provides both motive force and droplet size most suitable for maximum entrainment and scrubbing efficiency. The passage of the liquid spray through the venturi throat creates a suction at the HPEV inlet.

This causes polluted gases to be drawn into the venturi throat where violent, turbulent contact between the scrubbing liquid and gas stream creates the desired scrubbing action. The resulting liquid/gas stream then passes into a sump tank or separator chamber where the noncondensable cleaned gases are separated from the liquid and vented to the atmosphere. Single stage gas and vapor absorption efficiencies of 80% to 90% can be achieved depending upon the type of contaminant, the type of scrubber liquid and the pressure at the spray nozzle. Single stage particulate collection efficiencies can approach 98% to 99% down to 3.0 micron particle size. Higher spray nozzle pressures or multiple staging can improve the performance if required.

Harrington normally supplies the venturi, the sump tank, the high pressure pump and the interconnecting piping as part of their scrubber package.

Remember, the proper selection of a fume scrubber is the responsibility of the end user, the sales representative, the factory and the consulting engineer. All parties must work together to improve the quality of our environment. Sharing of acceptable information and utilizing accepted ventilation and engineered principles will help this goal become achievable. The HPEV scrubber manufactured by Harrington creates the opportunity to serve one segment of the swiftly growing air pollution control market.

Coward-Environmental Systems, Inc. has applied over 60 fume scrubbers since first representing Harrington and our engineers are prepared to discuss your specific needs.

By:

Dan Herber

Harrington Environmental Engineering