Rate-based model development, validation and analysis of chilled ammonia process as an alternative CO2 capture technology for coal-fired power plants

• Alternative chemical solvents are necessary to reduce the efficiency penalty.
• Closed-loop rate-based model for chilled ammonia process was developed.
• Two absorbers and one stripper were needed to decarbonise 580 MWel coal-fired power plant.
• Lean loading and ammonia concentration had a major impact on process performance.
• The optimal equivalent work was found at moderate stripper pressures.

Due to recent concerns about climate change, which has been triggered by greenhouse gas emissions, the European Union has recommended the decarbonisation of the power sector by 2050 in order to meet its emission reduction target. As a large share of the power generation is currently based on fossil fuels, mainly coal, with this trend expected to continue, clean coal technologies need to be developed. Carbon capture and storage using chemical solvents has been identified to be the most suitable option for coal-fired power plants. The technology which is closest to market commercialisation uses amines, such as monoethanolamine, as a solvent. However, high degradation rates due to impurities present in the flue gas and a considerable heat requirement for solvent regeneration make the application of alternative solvents necessary. In this study, a rate-based aqueous ammonia process model was developed, validated and then modified to a chilled ammonia process model. The model was then scaled up to process flue gas from a 580 MWel supercritical coal-fired power plant. A sensitivity study revealed that the lowest parasitic load occurs for the lean solvent characterised by 12.5%wt NH3 concentration and 0.29 loading, with the stripper operated between 12.5 and 17.5 bar. The equivalent work requirement for a CAP plant operated at such conditions was found to be up to 15.7% lower than the reference amine scrubbing plant.