Part-Load Operation of a Novel Calcium Looping System for Flexible CO2Capture in Coal-Fired Power Plants

Abstract

The increasing share of renewable energy supply is forcing fossil-fueled power plants to undergo flexible operation, with large load changes during the day and even periods of complete shutdown. Dual circulating fluidized bed (DCFB) calcium looping (CaL) has rapidly emerged as a viable option for efficient post-combustion CO2 capture in baseload coal-fired power stations. However, DCFBs might be unsuitable for flexible carbon capture at very low power plant capacity factors, beyond which the solid entrainment rate becomes insufficient. This work introduces a CaL system featuring the unique option of decoupling the solid circulation from the carbonator flue gas load with a carbonator bottom interlink. The concept has been successfully demonstrated with high CO2 capture efficiency (Hornberger et al. Fuel Process. Technol., 2020, 106557), but not yet regarding its load flexibility behavior. The carbonator performance has been assessed at partial loads as low as 40%, identifying a minimum active space time of 41 s as a basis to achieve an equilibrium normalized capture efficiency of 90%. In addition, the calciner performance has been evaluated for a variety of oxy-fuel cases (31-55 vol %db) and calcination temperatures (850-940 °C). The obtained results endorse the suggested novel CaL system's suitability for the flexible decarbonization of load-following power plants.