For removal and elimination of pollutants from an air stream, manufacturers and industrial operators have many types of air pollution control at their disposal. One such control is a type of air scrubber, called a wet scrubber. Wet scrubbers reduce or eliminate pollutants by dissolving or absorbing them in a liquid solution. They can remove both particulates and gaseous impurities, but these require different absorption techniques or chemical reactions, so, to achieve optimal operating conditions, wet scrubbers are usually configured for the cleanup of either one or the other. The correct configuration ensures removal efficiency rates up to 95%.
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Applications of Wet Scrubbers
Wet scrubbers are often used in applications like paper and pulp, steelworks, fertilizing, energy and power generation, construction, manufacturing, and propane and natural-gas related processes. Processes and environments like these rampantly produce dangerous impurities like solvent fumes, hydrocarbon, volatile organic compounds (VOCs), and hazardous air pollutants (HAPs). Such air impurities can wreak havoc on both the environment and human health.
For example, they can cause the rise of carbon emissions and the occurrence of acid rain, smog, and overall climate change, as well as both mild and severe allergies, asthma, and a host of health problems that may not emerge until later in life. Because of the seriousness of the potential problems caused by industrial air pollution, government and private agencies alike have enacted air purity requirements and recommend or require the use of emission control systems like wet scrubbers.
Wet Scrubber Design and Customization
Once upon a time, wet scrubbers consistently came in industrial, permanently-mounted designs. Now, they are more commonly constructed as relatively small devices that range from semi-portable to mobilized. This design allows them to clean localized areas more quickly and easily. The basic configurations of all wet scrubbers are fairly similar. They consist of duct work and a fan or pump system, a collection area or chamber, and another pump.
To increase efficiency, extra filters may be added both before and after scrubbing. Pre-filters are also used to boost efficiency. They work by gathering larger pollutants so that the scrubber can devote more attention to smaller particles. To enhance efficiency even more, final filters may be used at a wet scrubber’s exhaust end. In the same way that a solution may be reused, scrubbed air can be returned to circulation within the machine. However, it is generally just cast into the atmosphere instead.
How Wet Scrubbers Work
The duct work and fan or pump system draws in or pushes polluted air or gas toward the collection area or chamber, where it is deposited, then pressurized by the second pump. Depending on the specific contaminant and gas combination, wet scrubbers pressurize and remove pollutants either through a high pressure liquid spray or a pool of scrubbing solution. To put it another way, wet scrubbers remove pollutants by catching them in liquid droplets, collecting the liquid droplets, and then absorbing or dissolving the pollutants in the droplets.
Notable Types of Wet Scrubbers
The two most common wet scrubber types are spray scrubbers and pool scrubbers. Spray scrubbers spray a pressurized cleaning solution into a moving gas/air stream. This attracts heavier particulates, which, in turn, uncouple from the gas and instead stick to the liquid. Used liquid that has been gathered in a chamber is cleaned and put through the system again. Pool scrubbers, on the other hand, force a gas stream through a saturation chamber (or pool) of scrubber solution. Here, the solution collects and binds contaminants as a cleaned air stream passes through. If it is deemed necessary, chemical solutions may be substituted or added in to help destroy or reconfigure harmful pollutants.
In addition, wet scrubbers can be further categorized by pressure drop. Wet scrubbers grouped by this measure fall into one of three categories: low-energy scrubbers, medium-energy scrubbers, and high-energy scrubbers. Low-energy scrubbers have pressure drops of less than five inches of water, while medium-energy scrubbers have pressure drops between five inches and fifteen inches of water, and high-energy scrubbers have pressure drops greater than fifteen inches of water. However, because wet scrubbers tend to function over such a wide range of pressure drops, this form of categorization can be impractical.
Benefits of Using Wet Scrubbers
Wet scrubbers can operate successfully at a variety of temperature points and with numerous moisture contents, which makes it possible for them to decontaminate process streams in many different environments. Wet scrubbers are also popular because they can neutralize corrosive gases, process both gases and particulates, and take up less space. In addition, they do not contain secondary dust sources, so there is no risk of particulates escaping during transport or via a hopper. Because they use water, wet scrubbers also pose a lower risk of fires or explosions.