Evaluation of the Roles of Absorber and Desorber Catalysts in the Heat Duty and Heat of CO₂ Desorption from Butylethanolamine–2-Amino-2-methyl-1-propanol and Monoethanolamine–Methyldiethanolamine Solvent Blends in a Bench-Scale CO₂ Capture Pilot Plant

Abstract

The performance of a novel bi-blend butylethanolamine (BEA)–2-amino-2-methyl-1-propanol (AMP) solvent developed from an earlier work using a semi-batch method was validated in a bench-scale CO2 capture pilot plant in terms of its CO2 capture performance criteria compared to the benchmark 7 M monoethanolamine (MEA)–methyldiethanolamine (MDEA) solvent blend. Also, the synergistic benefits provided by placement of a solid acid catalyst (HZSM-5) in the desorber column and a solid base catalyst (K/MgO) used for the first time in the CO2 absorber column were evaluated. In addition, a process method was developed to use the pilot plant to determine, for the first time, the intrinsic heat of CO2 desorption from BEA–AMP and MEA–MDEA blends (or any solvent), without making any assumptions and/or reference to the heat of CO2 absorption. The results showed that all of the performance parameters for the novel 4 M BEA–AMP bi-blend were tremendously better than those of the 7 M MEA–MDEA bi-blend for both catalytic and non-catalytic runs, even though the molarity of the 7 M MEA–MDEA bi-blend was much higher, thereby showing the superiority of the BEA–AMP bi-blend solvent. The placement of catalysts in both absorber and desorber columns led to a synergistic benefit in the overall absorption and desorption processes. The heat of desorption has been proven not to be equal to the heat of absorption as a result of their having different conditions of CO2 loading and product species. The results of the heat duty term clearly demonstrate that the desorber catalyst (HZSM-5) worked mainly in reducing the heat of the CO2 desorption component for both solvent systems. This work further demonstrates that the reported results are just the apparent heat of CO2 desorption, which reflects the actual amount of external energy required to make up the theoretical heat of CO2 desorption needed to break the amine–CO2 bonds. Therefore, part of the energy needed for CO2 desorption is provided by HZSM-5 through proton donation. The Lewis base catalyst led to a tremendous improvement in the CO2 absorption process through electron donation during the rate-determining step.

Study of “coordinative effect” within bi‐blended amine MEA + AMP and MEA + BEA at 0.1 + 2–0.5 + 2 mol/L with absorption–desorption parameter analyses

“…The cyclic capacity for MEA + AMP/MEA + BEA solvents at different concentrations was listed in Equation . The α rich was α eq of amine blends, and α lean was 0.30 mol/mol for bench‐scale process of BEA + AMP 7,8 …”

“…The most commonly used energy‐efficient approach is by either solvent improvement, optimization of process intensification, or improvement of packing performance 1,6 . Particularly, adoption and development of improved solvents 7 into a good‐performance structured packing column 8 is a very promising method to reduce heat duty and operation costs 9 …”

“…Later on, the author's group developed a new solvent improvement method: application of “coordinative effects” by blending small amount of MEA with other secondary amines (RR'NH) blends at specific ratios of 0.1–0.5/2. DEA was selected as the first example, and the superior performance amine blends of BEA + AMP 7,8,14,21,22 as second one. From the absorption–desorption parameter studies of single amine, AMP has strong desorption performance with moderate absorption, but BEA has strong absorption performance with moderate desorption 14 .…”

Study of Catalytic CO2 Absorption and Desorption with Tertiary Amine DEEA and 1DMA-2P with the Aid of Solid Acid and Solid Alkaline Chemicals

“…Meanwhile, based on recent studies, the effects of solid base chemicals to MEA (K/MgO, CaCO 3 and MgCO 3 ) [18,19] and DEA (CaCO 3 and MgCO 3 ) [20] on CO 2 absorption have been verified. They accelerate the CO 2 absorption rates.…”

Catalytic solvent regeneration of a CO2‐loaded MEA solution using an acidic catalyst from industrial rough metatitanic acid

“…The characterization results indicated that catalytic activity was affected by specific surface area, acid strength, and the quantity of acid sites on the acidic catalysts. Raphael et al reported that desorption energy consumption could be reduced by 42% with HZSM‐5 catalyst in a full cyclic system . The catalytic desorption kinetics of MEA and MDEA‐MEA with catalysts (HZSM‐5 and γ ‐Al 2 O 3 ) were studied and it was concluded that HZSM‐5 showed faster kinetic and lower activation energy than γ ‐Al 2 O 3 at CO 2 loading range from 0.28 to …”