Minimization of CO2 capture energy penalty in second generation oxy-fuel power plants

Abstract

Oxy-combustion is one of the most promising technologies to reduce CO2 emissions from coal-fired power plants. Nevertheless, as CO2 capture system there is an important energy penalty and efficiency of the overall power plant substantially decreases. It is well accepted that the application of first generation post-combustion and oxy-fuel combustion technologies reduce the power plant efficiency in 10–12 efficiency points.Air separation unit (ASU) and compression and purification unit (CPU) are the main energy consumers in the oxy-fuel process. Moreover, the oxidant flow, which is a mixture of O2 and recirculated flue gases (RFG), requires a high heating demand in order to preheat it before the boiler inlet.This paper presents a methodology for the minimization of the energy penalty in oxy-fuel power plants that also includes ASU and CPU optimized designs with lower energy consumption, a boiler working with a high oxygen concentration (up to 40%v) in oxidant and waste energy integrated with a new designed steam cycle. Results show an important increase in power plant net efficiency (36.42%, LHV basis) regarding oxy-fuel reference power plant (32.91%). As a consequence, energy penalty can be reduced from original 10.5 points to 7.3 points.