By: Thomas Boakye

When CO2 is considered gas of interest, flue gas from natural gas or coal-fired power plants, cement, and iron and steel industries mostly comprises of pollutants including NOx, O2, SOx, and flue dust which can potentially affect the performance of the amine blend in the presence of oxygen. Flue dust comes from a variety of industrial sources and is made up of tiny inorganic oxide particles including Al2O3, Fe2O3, ZnO, CuO, MgO, MnO and SiO2.Understanding how these impurities dissolve and interact with the blend is crucial for designing more robust and efficient CO2 capture processes.

Regardless of the effectiveness of electrostatic precipitators which remove most of the dust particles from flue gases before CO2 capture, traces of these dust particles can escape and accumulate in a downstream absorber overtime, hence clogging packings, pipelines and heat exchangers. This can reduce the efficiency of the equipment. The most detrimental impact of these dust particles is their ability to catalyze the rate of degradation of an amine solvent. This leads to the formation of degradation products which can decrease the performance of the solvent through foaming, fouling and corrosion. This easily primes to amine losses hence the need for reclaiming and to replace with fresh amine which can incur a lot of operating cost.

Another direct impact is the release of toxic compounds due to the degradation of the amine which pose a threat to the environment. These inorganic oxides serve as catalysts in a typical oxidative amine degradation. Oxidative degradation occurs in the presence of oxygen and other oxidants in flue gas. Upon dissolution with the amine, these metal oxides release their metal ions which reacts with the amine with a direct electron transfer redox reaction. The dissolved metal serves as a Lewis acid by accepting electron from the amine which leads to the formation of an amine radical hence the release of ammonia as a predominant emission from amine degradation.  The reduced metal is further oxidized by the dissolved oxygen and this becomes an alternating procedure till the complete degradation of the amine solvent.

The research involves conducting comprehensive laboratory experiments, carefully simulating the conditions encountered in an actual CO2 absorption system. The effects of these flue gas impurities on the amine blend’s stability will be critically analyzed to determine the degradation rates. Based on these rates, a model will be developed to predict the stability of any new solvent when exposed to different flue gas concentration scenarios. This information can be used to optimize the capture process and ensure that it is as efficient as possible. By studying these interactions, potential challenges will be identified and effective mitigation strategies proposed.