(320f) Quantification of Degradation of Amine Solvent in CO2 Capture Process.

Extreme weather caused by global warming nowadays is occurring more frequently on a worldwide scale. Global warming resulting from the emission of greenhouse gases has received widespread attention. Among the greenhouse gases, CO₂ is the major contributor to global warming. The primary stationary CO₂ sources are coal-fired and natural gas-fired power plants. Therefore, CCS technologies must be developed to cope with global warming and climate change due to increasing CO₂ emissions. Absorption of CO₂ using amine-based solvents has been considered highly promising because of their high rate and selectivity towards CO₂. However, primary and secondary amine solvents have significant drawbacks, such as high energy consumption during solvent regeneration, high oxidative and thermal degradation of solvent, high equipment corrosion, and low absorption capacity. Solvent degradation is an undesirable operating problem caused by prolonged exposure of amine solvents to CO₂, SOx, and oxygen in the flue gases, resulting in solvent loss and equipment corrosion. Therefore, it very important to quantify the factors influencing the formation of the degradation compounds.

In this work, the CO₂ absorption/desorption performance of aqueous Monoethanolamine (MEA) was studied. The experiments has been conducted in a screening apparatus, which consist of glass round bottom flask, condenser and a temperature control water bath. The 30wt% MEA solution was prepared using deionized water and verified by titration with 1 N standard HCl solution with methyl orange as an indicator. The experiments were conducted with both synthetic flue gases (N₂: CO₂) and (N₂: CO₂: O₂) at a flow rate of 300ml/min. The concentration of CO₂ in the mixed gas stream at the outlet was determined using a CO₂ gas analyzer. The absorption starts when the first bubble of the feed gas emerges into the amine solution. To determine CO₂ loading in amine solution and amine concentration, the liquid sample was taken at regular intervals until the process reached equilibrium. The CO₂ loading and amine concentration were determined using the Chittick apparatus by titration with 1N HCl by neutralization reaction and methyl orange as an indicator. The pH of the solution at regular intervals was also determined using the pH meter. The CO₂-rich amine solution from the absorption experiment was transferred to the desorption flask for the desorption process at 393 K using nitrogen gas for stripping out CO₂. In this work, the applicability of the experiment setup was verified by measuring the equilibrium solubility of CO₂ in 30wt% MEA and pH values, and compared with the literature data. The liquid sample collected at different time interval was further sent for analytical analysis using GC-MS and ICP.

The CO₂ absorption rate, pH values of 30wt% MEA solution at 313 K were measured at different time with a gas mixture flow rate of 300 ml/min and an inlet CO₂ mole fraction of 0.2. The pH of the initial 30wt% amine solution was 11.8 and it decreased to the value of 8 after injecting CO₂. The 30wt% MEA solution achieved the equilibrium CO₂ loading value of 0.55 mol CO₂ per mol amine after six hours of absorption experiment at 313 K, with a gas mixture flow rate of 300 ml/min and an inlet CO₂ mole fraction of 0.2. The above results agree with the literature data (Vega et al., 2018). The presence of degraded products in the solution was confirmed by GC-MS and HPLC. Further, the effect of concentration of O₂ and desorption temperature will be studied and its effect on the CO₂ absorption rate, CO₂ loading and amine degradation rate will be studied.

References

1. Vega, M. Cano, S. Camino, B. Navarrete, J.A. Camino, Evaluation of the absorption performance of amine-based solvents for CO2 capture based on partial oxy-combustion approach, International Journal of Greenhouse Gas Control, Volume 73, 2018, Pages 95-103, ISSN 1750-5836, https://doi.org/10.1016/j.ijggc.2018.04.005.