What is an Absorption Tower?

Mary McMahon
Mary McMahon

An absorption tower is an industrial tower used to separate out components of a rising gas with the use of a falling liquid to trap the gas. This equipment is used in a variety of settings for purification, processing of materials, and other activities. The absorption tower usually needs to be custom designed for a specific application to ensure efficient and smooth operation. Like other components of a factory, it needs regular cleaning and maintenance to function properly and can be subject to inspection by regulatory officials.

Man with a drill
Man with a drill

In an absorption tower, the gas is pumped in at the bottom of the tower. It, along with any impurities it contains, begins to float to the top. As it moves toward the top, aerosolized liquid is sprayed into the tower. The droplets catch impurities in the gas and carry them to the bottom of the tower for collection. Some towers can have multiple points where liquid is sprayed out to capture different impurities or maximize the amount of material trapped.

A common use for an absorption tower is as a scrubber. Scrubbers remove material from gases vented from factories to reduce pollution. Air quality standards usually require the use of scrubbers and other safety devices to trap pollutants. In factories using an absorption tower for scrubbing, the waste products captured by the fluid can be safely collected and properly disposed of, or converted into use in other industrial processes. These devices can also be used in settings like refineries to separate out different usable components of gases.

The flow of fluid and gas has to be carefully controlled, as does the temperature, as these factors can have an impact on how much the water can absorb. If conditions in the tower or the factory change, adjustments may need to be made to compensate. Operators can take steps like shutting off components of a factory, using shunts to move waste material to different towers, and so forth to control factory operations and keep conditions as safe and efficient as possible.

For cleaning and maintenance, an absorption tower typically needs to be shut down to allow workers to access it safely. If the tower handles potentially hazardous or toxic substances, special gear may be required to enter it and employees are monitored for signs of exposure. Inspectors can include absorption towers in the list of factory components they examine to confirm compliance with the law and verify claims made by the factory about how it operates.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


Does anybody know how much could it cost? I'm finishing my project just to get my engineer title so I need the price of some equipment and I haven't found anything about the prices of this towers or columns.


How would you determine the efficiency of a gas absorber by only having the hydraulics profile provided by aspen 7? Key components on the separation are hydrogen and ethylacetate.


@Valleyfiah- I can partially answer your question. For the most part, chemicals collected in the gas absorption process are reprocessed into useable materials. From what I understand, there is a lot of research going into reprocessing waste, especially as resources are becoming scarcer. In many cases, reprocessing waste is cheaper and more environmentally friendly than landfill disposal.

Some of the examples of waste reprocessing are as follows. Wet scrubbers collect water-soluble mercury from coal exhaust. The mercury solution is then reprocessed to produce mercury, which is then used for other industrial purposes. Limestone based dry scrubbers in coal plants produce synthetic gypsum. This synthetic gypsum is used in the building supply industry to make drywall. Absorption towers can extract many harmful products and turn them into useable goods.


@Alchemy- What is the difference in a wet absorption column and a dry absorption column? I assume the tower described in the article is a wet column, but how does a dry scrubber column work? What is done with the waste that is collected in wet and dry columns? Do energy and chemical companies reprocess scrubber waste for other industrial purposes or do these companies bury the waste in landfills?


@comparables, A packed bed or packed column is simply a filter medium used to react with acidic gases in an exhaust stack. Think of it as a large filter similar to what you would find in your HVAC filter. The difference being they are much bigger, and can filter out much more harmful pollutants. The packing fits inside of the absorption tower, and works by attracting ionic compounds in the gas.

The packing material must be removed when it is fully saturated. After removal, the packing is disposed of by either extracting the chemicals it traps, or burying them in landfills meant for hazardous waste. Packed bed scrubbers are often considered dry scrubbers because they do not use a liquid to absorb pollutants.


What is a packed bed, and what does it have to do with an absorption tower? My energy professor brought up the term, but I have no clue what he was talking about. It was in the context of an absorption tower and its use in scrubbing pollutants from smokestacks in coal plants.

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