(718a) Pilot-Plant Testing of a Novel Phase-Change Solvent for CO2 Capture
AIChE Annual Meeting
Wednesday, November 17, 2021 - 8:00am to 8:25am
A new type of solvents called phase-change solvents (PCSs), promise up to 50% reduction of capture costs with experimentally recorded regeneration energies of 2.3-2.5 GJ/ ton CO2 . This is achieved through a liquid-liquid phase split, triggered by reaction with CO2 and/or temperature increase , that replaces part of the energy intensive treatment in the desorber by mechanical separation of the liquid phases and direct recycle of one of them to the absorber. While several PCSs have been proposed in published literature and undergone lab-scale characterization , there are very few PCSs that have been tested at pilot plant scale (i.e., DMCA/MCA/AMP , DEEA/MAPA , DMX  and 3H ). Pilot plant testing is a critical step in the course of process upscaling as the validity of the lab-scale results is tested and issues that may not appear at lab-scale are uncovered. Recently, Papadopoulos et al.  proposed the novel PCS mixture S1N (N1-Cyclohexylpropane-1,3-diamine)/ DMCA (N,N-Dimethylcyclohexylamine) which was tested experimentally and exhibited regeneration energy of 2.3 GJ/ton-CO2, and vapor losses and viscosity lower by 10% and 70% than those of other solvents.
In this work, we investigate for the first time the performance of S1N/DMCA in a pilot plant. We perform baseline experiments with 30 wt.% MEA and we test S1N/DMCA at 2M and 3M concentrations. Absorption and stripping are performed at atmospheric pressure, while critical operating parameter data, such as temperature, pressure, pressure drop, liquid levels, gas-liquid flows and gas concentrations are monitored online and registered. Liquid samples are collected periodically for off-line analysis (CO2-loading and amine content titrations). Several KPIs are estimated and monitored for the comparative evaluation of solvent and process performance, such as cyclic capacity, CO2 removal rate, and regeneration energy, under different L/G ratios (mass solvent flow rate/mass flue gas flow).
The results from MEA experiments indicate reliable pilot plant operation, which is in line with literature data [13,14], with an absorber temperature profile in the range of 32-45 °C. MEA further exhibited a maximum cyclic capacity of 0.312 mol CO2/kg solvent, whereas the attained rich loading at steady-state was 11.5% lower than loadings attained from lab-scale equilibrium experiments. This is a clear indication of the satisfactory operation of the pilot plant. For S1N/DMCA, the absorber and stripper columns operated in a range of 31.9-41.7 °C and 84-90 °C, respectively. These results are in-line with the results of Zhang , who also performed pilot tests of cyclic amines of similar chemical structures. Both the 2M and 3M solvent mixtures were observed to readily separate into two liquid phases at the phase-separator, placed after the absorber. The CO2 rich phase formed in the 2M solvent mixture case was found to contain lower amounts of CO2 than the 3M case. Therefore, the 3M S1N/DMCA case was selected to proceed in further investigation. At such an amine concentration, the CO2-lean phase had a total amine content of approximately 85 wt.% and enabled approximately a 35% lower solvent flow to the desorber enabling a drastic reduction in the heat of regeneration. Figure 1 further illustrates the cyclic capacity of S1N/DMCA and MEA at different L/G ratios. It is observed that the cyclic capacity of S1N/DMCA may be up to 3 times higher than that of MEA, while it was further observed that its regeneration energy was up to 59% lower than that of MEA. Additional investigations at different operating conditions will be performed and reported in the conference.
Figure 1. Cyclic capacity depending on L/G ratio for 3M S1N/DMCA and MEA.
This research has been co-financed by the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call ResearchâCreateâ Innovate, Project Î¤2ÎÎÎ-01911. This work has received funding from the European Unionâs Horizon 2020 research and innovation program under the grant agreement 727503 - ROLINCAP â H2020-LCE-2016-2017/H2020-LCE-2016-RES-CCS-RIA
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