377342 CO2 Capture from Fossil Fuel Power Plant Flue Gas Using Aqueous Solution of Renewably Prepared Alkanolamine
The continuous emission of CO2 from coal-fired power plants, cement manufacturing, refineries, etc., is considered as one of the major reasons for the greenhouse effect and global warming. The utilization of fossil fuels contribute to 64% of greenhouse gas emission worldwide and fossil fuel based power generation currently accounts for over one third of global annual CO2 emissions. The concentration of CO2 in environment has reached upto 392 ppm by volume as of 2011, which was 280 ppm in pre-industrial times and if this trend continues, by 2050 CO2 concentration is expected to raise upto 550 ppm. Due to the adverse effects of CO2 discharge on the global environment, as well as the world’s immense dependence on fossil fuels, the development of strategies for the reduction of CO2 emissions has become increasingly important. With this viewpoint, considerable efforts are underway towards the development of CO2 capture technologies. Because of its higher efficiency and lower complexity, amine based closed loop chemical absorption/desorption technology (CADT) is preferred industrially as an effective gas sweetening process for CO2 removal from process gas streams. In previous investigations, several amine based solvents e.g., monoethanolamine, diethanolamine, etc. were tested towards CADT. However, the various limitations associated with each solvent system such as severe degradation in presence of O2 and CO2, inferior CO2 loading capacity, lower CO2 absorption rates, etc. induces the quest to find a new solvent system which will overcome these limitations. Among the several newly developed amines, ethylaminoethanol (EAE) represents one of the possible candidates for the bulk removal of CO2 from power plant flue gas. The major raw material for the manufacturing of EAE is ethanol which, in turn, can be prepared from agricultural products and/or residues; hence EAE represents a promising absorbent as it can be prepared from renewable resources. In EAE, the hydrogen atom is replaced by an ethyl group which further enhances its basicity and hindrance around the nitrogen atom. Additionally, it also possesses a number of advantages over MEA such as less volatility, lower thermal energy requirement during CO2 stripping and higher pKa value.
In this contribution, we examined the potential of aqueous EAE towards capturing CO2 from power plant flue gas. The solvent stability in terms of degradation in presence of O2 was studied at different experimental conditions by performing accelerated degradation experiments using a high-temperature high-pressure subcritical reactor and the samples obtained after performing the degradation reactions were analyzed via gas chromatography (GC). The reaction kinetics of oxidative degradation of aqueous EAE was investigated. Influence of various operating parameters such as stirring speed, initial amine concentration, O2 concentration, and degradation temperature on kinetics of oxidative degradation of aqueous EAE was assessed and multiple regression analysis was performed to estimate the kinetic parameters.
In addition to the degradation study, the kinetics of absorption of CO2 in the aqueous EAE was also investigated in detail by using stirred cell reactor. A novel fall in pressure technique was employed for the absorption study and fall in the CO2 pressure during the absorption experiments was determined by using pressure transducer coupled with a data acquisition system. Effects of various process parameters such as stirring speed, amine concentration, and reaction temperature on absorption kinetics were examined in detail. The results obtained indicate that the aqueous EAE possess relatively high CO2 absorption capacity and faster absorption kinetics as compared to previously investigated amine based solvent systems. The experimental set-ups and procedures and results obtained during this investigation will be presented in detail.
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