Alternative solvents for post combustion carbon capture

CATEGORY: CARBON CAPTURE
International Journal of Energy & Environment. 2013, Vol. 4 Issue 3, p441-448
Alternative solvents for post combustion carbon capture
Arachchige, Udara S. P. R. (1) (udara.s.p.arachchige@hit.no)
Melaaen, Morten C. (1), (2) (Morten.C.Melaaen@hit.no)
1 Telemark University College, Porsgrunn, Norway.
2 Tel-Tek, Porsgrunn, Norway.
Abstract:
The process model of post combustion chemical absorption is developed in Aspen Plus for both coal and gas fired power plant flue gas treating. The re-boiler energy requirement is considered as the most important factor to be optimized. Two types of solvents, mono-ethylamine (MEA) and di-ethylamine (DEA), are used to implement the model for three different efficiencies. The re-boiler energy requirement for regeneration process is calculated. Temperature and concentration profiles in absorption column are analyzed to understand the model behavior. Re-boiler energy requirement is considerably lower for DEA than MEA as well as impact of corrosion also less in DEA. Therefore, DEA can be recommended as a better solvent for post combustion process for carbon capture plants in fossil fuel fired power industries.
Introduction
Global climate change has rapidly become the most prominent environmental issue in the present day. It is a well-known fact that the main contributor for the issue is the fossil fuel based energy generation. It can be solved either by shifting to renewable energy sources (clean energy sources) or eliminating the emission of available plants with emission reduction technologies. However, green house gas emission free technologies will not be practical solution in near future. Therefore, most possible alternative is carbon capture and sequestration as it can be applied in existing power plants and industries without major modifications. The most well-established method for carbon dioxide (CO2) capture is post combustion chemical absorption method with alkanolamine solvents. Weak base amines are reacted with CO2 and other acid gases to form weak chemical bonds. Alkanolamine can be mainly categorized as, primary (monoethanolamine-MEA, diglycolamine-DGA), secondary (diethanolamine-DEA) and tertiary (methyldiethanolamine-MDEA, triethanolamine-TEA) amines. However, the most applicable amine among them is MEA, due to the low partial pressure of CO2 in the flue gas of fossil fuel fired power plant. The most important parameter when designing a carbon capture plant is operating cost, which is related to the energy requirement in regeneration process. Even though MEA is widely use amine for CO2 capture, regeneration energy requirement is high for that process. Therefore, alternative solvents should be analyzed to perform the post combustion capture process with fewer energy requirements.
Both MEA and DEA are considered as highly reactive amines for gas absorption process. However, secondary amines are less corrosive as well as required less heat of regeneration, due to an additional ethanol group. The objective of this research was to compare the possible solvents that can be used for post combustion CO2 capture with lower energy requirement. In this study, MEA and DEA solvents are selected to optimize the CO2 capture process. Operating conditions are selected to avoid the main drawback of alkanolamine, which is large energy requirement. The physical properties of both amines are summarized in Table 1.
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