Evaluating and optimizing the performance of single and blended amines based on their chemical structures for carbon dioxide capture from industrial gas streams

Abstract

With the well-known fact on negatively impact of the human activities and the tremendously growth of industrial sectors and the increase in the global energy demand, the increase of the Green House Gas (GHG) including CO2 is very central because almost all fossil fuel activities lead to generation of this environmentally harmful GHG which found to cause increasing on the average global temperature which causing several major issues such as extreme weather conditions, heat waves, sea level rise, wild fires, health problems and many more. Actions are required immediately to reduce the emission such as using alternative energy source with less GHG emission and use Carbon Capture and Sequestration (CCS). Post combustion capture by using a liquid absorbent solution is successful method specially the ability to regenerate the solution which makes this method cost sufficient for industrial applications. The scientists are still looking for perfect fit solution in both performance and management’s levels. This research is focused on finding a good solution that has high absorption-desorption performance and has lower corrosion rate, foaming and degradation. The relation between the performance and the chemical structure, finding the optimum condition of the single amine solutions and the blend ratio for best performance were also studied. However, two sets of amines studied mono amines and diamines. In the diamine set, the ethanol was added to the nitrogen atom in the structure while in the monoamine, the alkyl group was added to the structure. The desorption and absorption parameters criteria were used for selecting components of amine blend. The concentration and the ratio of the blend components varied in order to find the optimum ratio and concentration. The optimum blend and its single components were then studied for corrosion, foaming and degradation. The results of screening of 4AB and 4A2MB showed that adding methyl group to the straight chain enhance the absorption and the desorption performance while reduce the heat duty. The study of the diamines 22AEE and BMEM showed adding 3 methyl group sto the nitrogen atoms in the structure reduced the absorption and desorption performance and increased the heat duty, while in 22AEE and EDA; adding the -OH group to EDA as seen in 22AEE increased the rich loading, desorption rate and cyclic capacity while absorption rate, pKa, and heat duty reduced by adding the ethanol group to the structure. Considering –OH group in the structure increases the solubility of the amine and makes it less volatile which is preferred. However, the mass transfer limitations on all amines in this research had no impact on the performance at the concentrations used in the research. On the other hand, increasing the number of amine groups from mono to diamine caused to generate larger amounts of bicarbonate ions which lead to higher CO2 desorption rates and cyclic capacity, but lower heat duty. Also, the higher alkyl group found to have high viscosity. Adding ethanol groups to the diamine increased the viscosity in general but it had no impact on the performance. The developed criteria of blend selection of the diamine in terms of absorption parameter was based on taking the average pKa1 and pKa2 which resulted at the end in selection of the best performance fit of 22AEE:EDA (3:1) of overall 1M blend after screening several ratios and concentration. This had an outstanding desorption characteristics/heat duty as well as very good absorption characteristics. 22AEE to EDA 3:1 blend, implying that it is a good potential solvent for post combustion CO2 capture. Then, carried 3:1 blend for further management testing like (corrosion, foaming and degradation/emission). 22AEE found to have lower foaming than EDA and thus due to the existing three hydrophilic groups and higher surface tension compared to two groups in EDA structure. Corrosion found to be higher in EDA than 22AEE. The degradation rate found higher in 22AEE while the accumulated emission found higher in EDA.