Modeling, Simulation and Experimental Validation of a New Rigorous Desorber Model for Low Temperature Catalytic Desorption of CO2-Loaded Amine Solvents over Solid Acid Catalysts

Abstract

Carbon Capture and Storage (CCS) have gained tremendous attention amongst policy makers, researchers and engineers in response to the increasing fears for climate change which is caused by increased amounts of greenhouse gases (GHGs) being emitted into the atmosphere. This is in an effort to decarbonize fossil fuels, especially coal, in order to make them environmentally sustainable while allowing these fuels to contribute to the global energy mix. Due to its maturity, post-combustion capture by chemical absorption, has been the technology focus to capture carbon dioxide (CO2) from combustion flue gases emanating from fossil fuel-based power plants. In this work, a numerical model for catalyst-aided CO2 desorption from CO2-loaded aqueous amines solution has been developed. The model includes a hot water-heater and considers phase separation at the top of the desorption column. The model was validated with experimental data obtained from an integrated post-combustion CO2 capture pilot plant which used 5 M monoethanolamine (MEA), and 5 M MEA mixed with 2 M N-Methyldiethanolamine (MDEA) solutions with two industrial catalysts, namely, HZSM-5 and γ-Al2O3. The model considers the presence of electrolytes and multi-component mass transfer as well as both the physical and chemical contribution of the catalyst in aiding the process. The data obtained from model simulation were in good agreement with the experimental data in terms of CO2 production rates with an absolute average deviation of approximately ±8.9 % for MEA and ±7.7 % for MDEA. The simulation slightly over-predicted the CO2 production rate at the low temperature regime (75 °C) and under-predicted the CO2 production rate at the high temperature regime (95 °C) in both cases. Also, the temperature profiles predicted by the model was in close agreement with the experimental temperature profiles even though it under-predicted them. Based on the simulation as well as the experimental data, HZSM-5 was seen to have greater effect in aiding CO2 desorption than γ-Al2O3 for both solvents. However, the extent of aiding desorption of CO2 from loaded MEA was higher than that of MEA-MDEA. Also, the concentration of CO2 in the gas phase was seen to be quite high and can greatly decrease the driving force for mass transfer. Furthermore, it was interesting to observe that that the presence of maldistribution in the column be shown based on the simulation results.