Wet Scrubbers

A wet scrubber is a device that is used to control air pollution. It removes some of the harmful particles or gases from industrial exhaust systems. This term is used because a liquid removes unwanted materials from a gas stream, and the liquid washes the particles away. The most common liquid used to do this is water. Exhaust gases caused by combustion may contain materials that are dangerous to the environment, but the wet scrubber will clean flue gas or other dust particles and pollutants in various gases.  Exhaust gases, such as hydrogen chloride or ammonia can be removed by a wet scrubber. It is very important that wet scrubbers be thoroughly cleaned after use because they can transmit bacteria. In 2005 in Norway, 10 people died from Legionnaires’ disease that was caused by only a few infected scrubbers.

Wet scrubbers are sometimes used in plants that manufacture acids, fertilizer, asphalt, and in steel mills or in large power plants. Wet scrubbers are often used in petroleum production plants. They have the ability to absorb odors, gases, and vapors as they collect particulates, and they also clean and cool the exhaust. Since businesses are mandated by the Federal Environmental Protection Agency to control harmful pollutants, many companies rely on wet scrubbers to continue their businesses. Without them, they would be forced to close down by the government due to anti-pollution laws. The cost of these scrubbers is a business expense that cannot be avoided by these companies.

Wet scrubbers remove particulates better than fabric filters or electrostatic precipitators that are also used to remove pollutants. The benefits of these scrubbers over some other pollution control devices are that they are able to remove gases as well as particulate materials, and they are also able to handle moisture and high temperatures. In addition, they can neutralize gases that can be corrosive. Wet scrubbers do not require a lot of space in order to operate. Their smaller size makes them economical for businesses to use. The disadvantages of wet scrubbers are that disposing of water may be difficult due to waste-water regulations, and also that the scrubber may need to have a settling pond or sludge clarifier to meet these regulations. Also, operating costs of scrubbers can be very expensive because of the high power requirements. There may also be corrosion problems that result from dissolved pollutants and water that may be dangerous acidic solutions. Product recovery is also difficult if a business want to access the dust particles to use in future products.

The main parts of a wet scrubber are usually a scrubbing container, mist eliminator, ductwork, pumping system, used liquid treatment, and an exhaust system. The system is controlled with technology that monitors it and makes any adjustments that may be necessary. The scrubber is the tower where the gas is washed or cleaned.

There are many types of wet scrubbers that are manufactured for specific purposes. One of the most popular is the Venturi scrubber that removes particulate from exhaust air streams. The scrubber passes particulate affected air through a Venturi tube. Water is used to control and remove the dust. This scrubber works by flooding water over the wet dust particles with a great amount of turbulence. The particles are then moved to a chevron style separator or to a cyclone separator.

The pressure drop of a scrubber is the usual way for scrubbers to be categorized. There are low-energy scrubbers, medium-energy scrubbers, and high-energy scrubbers. They use between five inches of water and 15 inches of water to remove pollutants. Scrubbers may also be classified according to how a company uses them. This is often based on how they collect particulates or gaseous pollutants.