Evaluation of efficiency improvements and performance of coal-fired power plants with post-combustion CO2 capture

摘要

The power sector needs to be decarbonised by 2050 to meet the global targetfor greenhouse gas emission reduction and prevent climate change. With fossilfuels expected to play a vital role in the future energy portfolio and highefficiency penalties related to mature CO2 capture technologies, this researchaimed at evaluating the efficiency improvements and alternate operating modesof the coal-fired power plants (CFPP) retrofitted with post-combustion CO2capture. To meet this aim, process models of the CFPPs, chilled ammoniaprocess (CAP) and calcium looping (CaL) were developed in Aspen Plus® andbenchmarked against data available in the literature. Also, the process model ofchemical solvent scrubbing using monoethanolamine (MEA) was adapted fromprevious studies. Base-load analysis of the 580 MWel CFPP retrofits revealedthat if novel CAP retrofit configurations were employed, in which a new auxiliarysteam turbine was coupled with the boiler feedwater pump for extracted steampressure control, the net efficiency penalty was 8.7–8.8% points. This was closeto the 9.5% points in the MEA retrofit scenario. Conversely, CaL retrofit resultedin a net efficiency penalty of 6.7–7.9% points, depending on the fuel used inthe calciner. Importantly, when the optimised supercritical CO2 cycle was usedinstead of the steam cycle for heat recovery, this figure was reduced to 5.8%points. Considering part-load operation of the 660 MWel CFPP and uncertaintyin the process model inputs, the most probable net efficiency penalties ofthe CaL and MEA retrofits were 9.5% and 11.5% points, respectively.Importantly, in the CaL retrofit scenarios, the net power output was found to bearound 40% higher than that of the CFPP without CO2 capture and double thanthat for the MEA retrofit scenario. Such performance of the CaL retrofit scenarioled to higher profit than that of the 660 MWel CFPP without CO2 capture,especially if its inherent energy storage capability was utilised. Hence, this studyrevealed that CaL has the potential to significantly reduce the efficiency andeconomic penalties associated with mature CO2 capture technologies.