Background to the Study

Research, development, demonstration, and deployment of advanced solvents is at the forefront of decarbonising the fossil fuel combustion sectors with the aim of making CO₂ capture more competitive in a net zero economy.  Considering the extensive research in solvent design and development, a rapid and reliable screening protocol is imperative for new solvents and process configurations to be ranked against existing systems. 

The primary goal of the study is to review prospective prime solvents and process designs to accelerate the deployment of CO2 capture technologies. IEAGHG commissioned Khalifa University, United Arab Emirates (UAE) to conduct a comprehensive assessment of promising aqueous and water-lean PCC solvents. This study identifies and characterises prime solvent candidates for the next generation of post-combustion carbon capture (PCC) technology. The solvent comparison was carried out against a benchmark 30 wt.% monoethanolamine (MEA) aqueous solution and the IEAGHG benchmark system (IEAGHG 2019/09).
 

Key messages

·        Based on the collected data and their detailed analysis, no single amine was identified to have an overriding superior performance in terms of capital and operating costs.  Most of the amines spanned between slightly better and poorer performance compared with MEA in terms of both capital and operating expenditures.  The most promising amines were found to be 2-(isopropylamino) ethanol (IPAE), aminoethylethanolamine (AEEA), 2-methyl piperazine (2-MPZ), 2-(ethylamino) ethanol (2EAE), 2-amino-1,3-propandiol (2APD), 3-(methylamino) propylamine (MAPA), piperazine/2-amino-2-methyl-1-propanol (PZ/AMP) and monoethanolamine/ethylene glycol (MEA/EG).

·        The solvent properties that have the most influence on the capital cost are the absorption capacity, reaction rate, absorption enthalpy (heat of absorption) and the liquid viscosity.

·        In terms of process configurations, the most promising modifications include absorber inter-cooling, rich solvent split, stripper overhead compression, split flow, and lean vapour compression as per the reduction in the specific reboiler duty.

·        The sensitivity analysis has shown that the CO₂ gas concentration is a predominant determinant of the cost of capture.  Therefore, it is cheaper to capture CO₂ from higher concentration sources.  The cost of capture increases linearly (slight slope) for capture rate of about 85%, but exponentially increases for capture rates of > 95% on a conventional process.

·        A solvent database has been developed in this study, codenamed CO₂SOLV which hosts a large number of the most relevant solvents for PCC.  An equilibrium-based process model that is integrated with the CO₂SOLV database has been developed.  This model serves to analyse the data and deduce conclusions in terms of technical and economic performance of the solvents and process configurations.

·        As more solvents are being proposed for the application of PCC, rapid screening of solvents becomes a necessity.  A decision tool has been developed that offers high throughput screening of solvents inclusive of technical and economic indicators.  Further, solvents can be assessed on a comparable basis under the same operating conditions.

This report is available to download.