Thermodynamic analysis of high-ash coal-fired power plant with carbon dioxide capture

Abstract

SUMMARY A thermodynamic analysis of a 500-MWe subcritical power plant using high-ash Indian coal (base plant) is carried out to determine the effects of carbon dioxide (CO2) capture on plant energy and exergy efficiencies. An imported (South African) low-ash coal is also considered to compare the performance of the integrated plant (base plant with CO2 capture plant). Chemical absorption technique using monoethanolamine as an absorbent is adopted in the CO2 capture plant. The flow sheet computer program “Aspen Plus” is used for the parametric study of the CO2 capture plant to determine the minimum energy requirement for absorbent regeneration at optimum absorber–stripper configuration. Energy and exergy analysis for the integrated plant is carried out using the power plant simulation software “Cycle-Tempo”. The study also involves determining the effects of various steam extraction techniques from the turbine cycle (intermediate-pressure–low-pressure crossover pipe) for monoethanolamine regeneration. It is found that the minimum reboiler heat duty is 373 MWth (equivalent to 3.77 MJ of heat energy per kg of CO2 captured), resulting in a drop of plant energy efficiency by approximately 8.3% to 11.2% points. The study reveals that the maximum energy and exergy losses occur in the reboiler and the combustor, respectively, accounting for 29% and 33% of the fuel energy and exergy. Among the various options for preprocessing steam that is extracted from turbine cycle for reboiler use, “addition of new auxiliary turbine” is found to be the best option. Copyright © 2011 John Wiley & Sons, Ltd.