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What Is Post-Combustion Capture?

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  • Written By: Alex Newth
  • Edited By: Angela B.
  • Last Modified Date: 10 December 2014
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Many businesses, especially power plants and industries using petrochemicals, produces a large amount of carbon dioxide from combusting hydrocarbons, and that carbon dioxide must be captured in a process called post-combustion capture so it does not affect the environment. The most common method for post-combustion capture is to pass the carbon through a solvent that absorbs the excess carbon. The capture unit itself is relatively simple. This process is one of the most popular for capturing carbon and has been used since the 1940s, in part because it can fit into most industries. The problem with using this process is that it has high running costs, and plants use from 10 percent to 30 percent more energy just to capture the carbon.

When a business combusts petrochemicals, carbon dioxide is released in large amounts. To cut down the amount of carbon released into the atmosphere, post-combustion capture is used. The flue gas is passed through a capturing unit, which combines the carbon gas with a solvent. Commonly, amine solvents — or those based off nitrogen — are used. The amine solvent absorbs and captures the carbon from the flue gas, so the carbon can be transported and stored later.

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The post-combustion capture unit is rather simple, and it usually integrates with the combustion chamber itself. Air and hydrocarbons are pumped into an area where, under high temperature, they combust and create energy. The exhaust gas is pumped into an amine tower, where it is instantly mixed with nitrogen and pushed below for storage.

Post-combustion capture has been used since the 1940s, and part of the reason it is so popular is that scientists and industry workers have a lot of experience using this system. Another reason is that the capture unit can be easily retrofitted, or added to an existing plant. The capture unit is so simple and well known that repairs are easier than with other systems.

While post-combustion capture is popular, there are some downsides to using this system. There are high operating costs, because the business will need to buy a steady stream of amine solvent to keep the capture unit working. Capture units also are best for small to medium operations; large-scale operations are usually beyond the scope of this unit. Plants also need to use from 10 percent to 30 percent more energy, depending on the solvent used, to capture the carbon; these costs are usually pushed onto the business's customers.

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