If you are involved in the manufacturing or wastewater treatment industry and work as a plant manager, a process engineer, or a purchasing or Environmental Health and Safety (EHS) professional, then you may be looking for a solution to remove harmful pollutants and odors from your process exhaust streams before they are released into the atmosphere and contaminate the outside air. Industrial scrubbers are a technology that can fulfill these needs.
In order to remove gas pollutants and odors from exhaust streams, industrial scrubbers serve as pollution filtration systems that use solids (in “dry scrubbers”) or water or other liquids (in “wet scrubbers”). A few advantages of industrial scrubbers include low-risk processing of incendiary gases, its ability to handle high-temperature, high-humidity gas streams without temperature limit or condensation problems, no secondary dust sources, and its ability to neutralize corrosive gases and absorb gas and solid particulate matter with the use of a single device. Furthermore, small spaces can accommodate industrial scrubbers which ensures lower capital costs and site placement flexibility. The Kem-Group is proud to manufacture the most critical component of an industrial scrubber the random packing. Kem-Group manufactures plastic random packing in a variety of styles and thermoplastics. Some of the styles of plastic random packing manufactured by Kem-Group include Tri-Pack, Pall Ring, Saddle and Kemflake. These random packing styles are available in resins such as Polypropylene, CPVC, PVC, PVDF, Tefzel and more.
Dry Vs. Wet Scrubbers
Industrial scrubbers can be classified as “wet” or “dry.” Although dry scrubbers typically are unable to remove pollutants to the same extent as wet scrubbers, they are ideal for use in facilities without the necessary infrastructure to handle released wastewater.
Without use of liquids, dry scrubbers remove contaminants from exhaust gases. Alternatively, they make use of a dry reaction material (a “sorbent”), such as alkaline slurry, and are generally used to remove acid from gases by passing the gas through the sorbent “dust” to enhance binding.
Unlike dry scrubbers, wet scrubbers pass contaminated gas through a liquid that is intended to remove pollutants. More than 99 percent of airborne particulate matter may be removed using wet scrubbers, which are a flexible and affordable pollution control device.
How Wet Scrubbers Work
The most frequently used solvent for removing inorganic pollutants is water. In the most fundamental configuration, contaminated gas is sent through water that is enclosed in a metal or composite container. The water then absorbs the contaminants, and clean gas exits the scrubber.
Other liquids, in addition to water, can be used as absorbing solutions capable of removing various contaminants. The chemical composition of the absorbing solutions can be altered to change the overall charge. Since the charge of pollutants varies, wet scrubbers are filled with the liquid that will bind the most effectively to remove the contaminate from the gas. The most common scrubbing liquid used for acid-gas control (e.g., HCl, SO2, or both) is caustic solution (sodium hydroxide, NaOH), though sodium carbonate (Na2CO3) and calcium hydroxide (slaked lime, Ca [OH]2) can also be used.
Wet Scrubbing of Particulate Matter
By trapping them in liquid droplets, wet scrubbers may remove particle debris. Following the collection of the droplets, the polluting gases are dissolved or absorbed by the liquid. A mist eliminator must be used to separate any droplets from the outlet gas stream that are present in the scrubber’s incoming gas. Additionally, the produced scrubbing liquid needs to be cleaned before it can be released into the environment or used again in the plant.
The amount of power applied to a wet scrubber determines how well it can capture particulate matter. To achieve high removal efficiency, a mist eliminator that is correctly constructed and kept is also crucial.
Wet scrubbers are typically the only single air pollution management technology that can eliminate both pollutants when the gas stream contains gases and particle matter.
Packed-Bed Wet Scrubbers
Absorbers are wet scrubbers used to remove gaseous pollutants. High removal efficiencies in absorbers require good gas-to-liquid contact. A bed of plastic random packing is utilized to provide the gas-to liquid contact. To remove gaseous pollutants, various wet-scrubber designs are used, with one of the most popular sub-categories of wet scrubber known as Packed-Bed, Packed-Tower, or “acid gas” (when they are used to control inorganic gases).
Even though they can also accumulate solid particles, packed bed scrubbers are often used for the treatment of gas. In the chemical, aluminum, coke and ferroalloy, food and agricultural, and chromium electroplating sectors, as well as in acid plants, fertilizer plants, steel mills, and asphalt plants, packed-bed scrubbers are often employed.
Applicable Pollutants for Packed-Bed Wet Scrubbers
Packed-Bed wet scrubbers are used to control inorganic fumes, vapors, and gases, Volatile Organic Compounds (VOC) as well as Particulate Matter (PM) and Hazardous Air Pollutants (HAP) in particulate form (PMHAP)
How Packed-Bed Scrubbers Operate
Through inertial or diffusional impaction, interaction with a sorbent or reagent slurry, or absorption into liquid solvent, packed-bed scrubbers effectively eliminate air contaminants.
Packed-bed scrubbers have a chamber with layers of random packing media such as the Tri-Pack packing style to create a large surface area for liquid-particle contact. The effectiveness of the low gas-phase pressure drop and gas-liquid contact is influenced by the packing’s shape, weight, surface area, and price. A plate towards the bottom of the scrubber serves as support for the packing.
Waste gas is forced into the scrubber’s chamber and flows vertically or horizontally through the packing, while scrubbing liquid is used above the packing. This permits the liquid to flow down through the bed to coat the plastic random packing thus creating a layer of film. The gas stream flows up the chamber (“counter-current” to the liquid) in vertical designs (packed towers). Some packed beds, on the other hand, are designed horizontally to allow gas flow across the packing (“cross-current”).
The waste produced falls to the bottom of the chamber as the cleaned gas is then channeled through a mist eliminator incorporated into the structure’s top.
Advantages of Packed-Bed Wet Scrubbers
The advantages of Packed-Bed wet scrubbers include relatively low pressure drop, its use of Fiberglass-reinforced plastic (FRP) construction, its capability of achieving relatively high mass-transfer efficiencies, its relatively low capital cost and small space requirements, its ability to collect Particulate Matter (PM) as well as gases and the opportunity to change the height and/or type of scrubber packing media.
For more information on Kem-Group’s plastic random packing styles such as the Tri-Pack, Pall Ring, Saddle or Kemflake please visit our website at www.kempac-packing.com .
