In recent years, the greenhouse effect of carbon dioxide in combustion exhaust gas generated upon combustion of fossil fuels has been one of major causes of global warming. Each country addresses reductions of greenhouse gas emissions based on Kyoto Protocol to the United Nations Frameworks Convention on Climate Change to solve the problem.
Under such a circumstance, the study has been in progress on a carbon dioxide capture system that prevents the release into the air of carbon dioxide contained in combustion exhaust gas generated upon the combustion of a fossil fuel at thermal plants or other facilities where a large amount of the fossil fuel is consumed. Such a carbon dioxide capture system, after bringing the combustion exhaust gas into contact with an amine absorbing liquid, separates the carbon dioxide from the combustion exhaust gas and captures the separated carbon dioxide.
Specifically, the carbon dioxide capture system includes an absorber and a stripper. The absorber causes the carbon dioxide contained in the combustion exhaust gas to be absorbed in the amine absorbing liquid. The stripper heats the absorbing liquid (rich liquid) containing the absorbed carbon dioxide and supplied from the absorber, causes the carbon dioxide to be released from the rich liquid, and regenerates the absorbing liquid. The stripper is coupled to a reboiler configured to supply a heating source, and the rich liquid is heated within the stripper. The absorbing liquid (lean liquid) regenerated in the stripper is supplied to the absorber. The absorbing liquid circulates within the system.
In the carbon dioxide capture system, however, the combustion exhaust gas (decarbonated combustion exhaust gas) from which the carbon dioxide is absorbed in the amine absorbing liquid in the absorber is released together with amine into the air. Since a large amount of the combustion exhaust gas is discharged from the thermal plant or other facilities, a large amount of an amino group-containing component (amine) may be released together with the decarbonated combustion exhaust gas. Thus, when the carbon dioxide capture system is used in the thermal plant, it is desirable to efficiently reduce the amount of the amine to be released with the decarbonated combustion exhaust gas in the absorber into the air.