4. Demonstrating flexible operation of the Technology Centre Mongstad (TCM) CO₂ capture plant (2019)

Mai Bui^a,b, Nina E. Flø^c, Thomas de Cazenove^c, Niall Mac Dowell^a,b,*

^aCentre for Process Systems Engineering, Imperial College London, South Kensington, London SW7 2AZ UK ^bCentre for Environmental Policy, Imperial College London, South Kensington, London SW7 1NA UK ^cTechnology Centre Mongstad (TCM), 5954 Mongstad Norway ^*Corresponding author

Abstract 

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This study demonstrates the feasibility of flexible operation of CO₂ capture plants with dynamic modelling and experimental testing at the Technology Centre Mongstad (TCM) CO₂ capture facility in Norway. This paper presents three flexible operation scenarios: (i) effect of steam flow rate, (ii) time-varying solvent regeneration,  and (iii) variable ramp rate. The dynamic model of the TCM CO₂ capture plant developed in gCCS provides further insights into the process dynamics. As the steam flow rate decreases, lean CO₂ loading increases, thereby reducing CO₂ capture rate and decreasing absorber temperature. The time-varying solvent regeneration scenario  is demonstrated successfully. During “off-peak” mode (periods of low electricity price), solvent is regenerated, reducing lean CO₂ loading to 0.16 mol_CO2/mol_MEA and increasing CO₂ capture rate to 89–97%. The “peak” mode (period of high electricity price) stores CO₂ within the solvent by reducing the reboiler heat supply and increasing solvent flow rate.

During peak mode, lean CO₂ loading increases to 0.48 mol_CO2/mol_MEA, reducing CO₂ capture rate to 14.5%, which in turn decreases the absorber temperature profile. The variable ramp rate scenario demonstrates that different ramp rates can be applied successively to a CO₂ capture plant. By maintaining constant liquid-to-gas (L/G) ratio during the changes, the CO₂ capture performance will remain the same, i.e., constant lean CO₂ loading (0.14–0.16 mol_CO2/mol_MEA) and CO₂ capture rate (87–89%).

We show that flexible operation in a demonstration scale absorption CO₂ capture process is technically feasible. The deviation between the gCCS model and dynamic experimental data demonstrates further research is needed to improve existing dynamic modelling software. Continual development in our understanding of process dynamics during flexible operation of CO₂ capture plants will be essential. This paper provides additional value by presenting a comprehensive dynamic experimental dataset, which will enable others to build upon this work.

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