The accumulation of uncollected fly ash from flue gas in post-combustion CO2capture processes is a significant concern in current coal-fired power plants due to its potential impact on the performance of CO2absorbent and absorption towers. In order to determine the effect of fly ash on the mass transfer performance of CO2absorption into monoethanolamine (MEA) and diethanolamine (DEA) aqueous solutions, experimental studies were carried out using a small-sized packed tower equipped with θ-ring random packing. These studies were conducted under various operating parameters, including solution temperature, liquid/gas ratio (L/G), packing height, and fly ash concentration. The results show that the effect of fly ash on the outlet CO2concentration was primarily observed during the initial stages of the experimental process. Moreover, the presence of fly ash leads to a reduction in the volumetric overall mass transfer coefficient (KGav) when using MEA and DEA solution, and increasing the fly ash concentration further exacerbates this negative impact. However, the effect of fly ash on the reduction inKGavis not significantly related to its chemical composition but rather depends on the operational parameters. With increasing solution temperature, liquid/gas ratio (L/G), and packing height, theKGavvalues for different solutions exhibit an upward trend. The negative effect of fly ash onKGavremains relatively stable for MEA as solution temperature and packing height increase. Compared to MEA, fly ash has a greater negative effect on DEA solution under the same experimental conditions. The analysis reveals that the detrimental effect of fly ash onKGavprimarily stems from its ability to alter the distribution state of the absorption liquid within the packed tower.
In this paper, by means of thermo-gravimetric analysis(TGA), the desorption kinetics of CO 2 absorbed in two kinds of rich amine solutions, MDEA (3.25mol/L) and MDEA+DEA(3.25mol/L-0.3mol/L), were investigated under different heating rates(2.5℃/min, 5℃/min, 10℃/min and 20℃/min). The thermal analysis kinetics was applied to analyze the TG-DTG curves of two rich amine solutions so as to research CO 2 desorption kinetics. In addition, the CO 2 desorption kinetics parameters have been calculated with model-free method Flynn-Wall-Ozawa (FWO) and model-fitting method Coats-Redfern (CR). The results indicated that CO 2 desorption process could be divided into two stages. The CO 2 and H 2 O were released with non-uniform speed in the first stage and MDEA or DEA with higher boiling points were evaporated in the second stage. For MDEA solution the average activation energy E was 50.36kJ/mol, the pre-exponential factor A was 1.68×10 7 , and the most probable integral mechanism function was G α = α 3 / 2 . For MDEA+DEA solution the average activation energy E was 59.68kJ/mol, the pre-exponential factor A was 2.22×10 7 , and the most probable integral mechanism function was G α = [ ( 1 + α ) 1 / 3 − 1 ] 2 . The technical feasibility of CO 2 desorption performance in rich amine solutions with thermo-gravimetric analysis method was demonstrated.
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