Hobbies And Interests
Adsorption
Adsorption is a filtration method used to remove volatile organic chemicals (VOC) from waste gas. The gas flows through a filter that traps the VOC particulates on its surface. Activated carbon is often used in adsorption systems and the EPA reports that 95 to 99 percent of pollutants within waste gas can be removed with activated carbon adsorption systems. Regenerative adsorption systems contain multiple filters and as some filters trap particles, others are treated with steam to remove trapped pollutants which are then shunted out of the system. Non-regenerative absorptive systems are used for low VOC concentrations, trapping particles within disposable filters. Once the filter is saturated, it's discarded and replaced. (Ref. 6)
Biofilters
Biofilters control VOC emissions (Ref. 1) using microorganisms to degrade pollutants. (Ref. 2) Gas flows through a filter that contains a film hosting the microorganisms, which cover the pollutants and oxidize them, producing carbon dioxide and water as a byproduct. (Ref. 3) Biofilters are commonly used to cleanse waste water treatment facility and food processing plant emissions. Their most significant drawback is their bulk, as they require considerable space to install. (Ref. 2)
Reburning
Reburning is used to filter nitrogen oxide emissions from coal-fired boilers. Most U.S. facilities use natural gas as their reburning fuel, but oil or coal can also be used. After primary combustion takes place within the boiler, fuel is directed to a reburning zone above and the fuel molecules convert into hydrocarbons that react with the nitrogen oxide to convert it into nitrogen and water. Additional air is added to a burnout area above the reburning zone to complete combustion. (Ref. 5)
Scrubbers
Scrubbers are used to filter particulate waste and sulfur dioxide emissions, and are most often used to extract soluble pollutants from waste gas. Gas ascends into the scrubber, where it is sprayed with a solvent. The pollutant is trapped within the solution and drained from the system. Cheresources notes that since scrubbers have an efficiency rate of approximately 50 percent, they're typically staggered so that waste gas flows through a series of scrubbers. Semi-dry scrubbers convert waste into a residue by spraying the gas with liquid and evaporating the solution with dryers. Semi-dry scrubbers can achieve a 90 to 95 percent waste removal rate when used with a fabric filter. (Ref. 1)