Techno-economic comparison of CO2 capture technology options to retrofit a 500 MWe subcritical coal power plant in India

CO2 emissions from the existing coal power plant fleet in India (which is dominated by old and inefficient subcritical units) is one of the major contributors to the national GHG inventory. The use of CO2 capture (CC) technologies is one of the promising ways of reducing CO2 emissions from these subcritical plants. As the CC technologies are yet to be commercially deployed at coal power plants in India, use of techniques such as techno-economic analysis could give an idea about the feasibility of different CC technologies. The current study aims to compare two post-combustion CC technologies viz. calcium looping and MEA (monoethanolamine) based scrubbing, which can be retrofitted to an existing 500 MWe subcritical coal power plant in India. A thermodynamic analysis of the 500 MWe subcritical plant retrofitted with various pollution control equipment and these two CC technologies is performed using an indigenously developed Aspen Plus model whereas the economic analysis is performed using actual plant cost data and the exponent scaling function method. The techno-economic analysis is performed for the use of Indian high ash (HA) coal considering an average plant capacity factor of 85% and CO2 capture efficiency of 90%. Regeneration of the sorbent/solvent is also possible using renewable energy sources such as biomass and solar thermal. For the integrated system (i.e. existing coal power plant + CC system) using Indian HA coal, the subcritical plant retrofitted with calcium looping technology has a better performance as compared to MEA scrubbing technology in terms of all the performance and cost parameters such as net power output (669.5 MWe vs 326.8 MWe), net electric efficiency (27.5 % vs 25.3 %), SPECCA (4.1 GJHHV/tCO2 vs 5.7 GJHHV/tCO2), LCOE (92.5 $/MWhnet vs 98.2 $/MWhnet) and cost of CO2 avoided (52.4 $/tCO2 vs 61.5 $/tCO2). Thus, the use of calcium looping technology is recommended for existing subcritical plants in India as it has a better performance in terms of efficiency and cost and it not only helps in reducing CO2 emissions but also helps in increasing the electricity generation capacity of the existing plants. Given the urgency to reduce CO2 emissions and to stop addition of new coal fired capacity, use of calcium looping technology could address the twin issues of environmental protection as well as energy security.