Oxygen production routes assessment for oxy-fuel combustion

Abstract

Oxyfuel combustion is a promising alternative to decarbonize the power sector. However, the main barrier to the commercial deployment of the technology is the high energy consumption associated with oxygen production (~200-300 kWh per ton of O2), which penalizes the thermal-to-electric efficiency 7-12% compared to traditional air-combustion plants. Typically, oxygen is obtained from a cryogenic air separation process. Nevertheless, other technologies have been gaining momentum in recent years, such as membrane technologies, chemical looping air separation, and renewable-driven electrolysis. The present work evaluates all these options for O2 production to retrofit a 550 MWe coal-fired power plant with oxyfuel combustion. A techno-economic assessment is carried out to estimate the energy penalty, the O2 production cost (€/ton) and the Levelized Cost of Electricity. The best results are obtained for a combination of oxygen transport membranes and electrolysis, halving the energy penalty compared with cryogenic air separation, obtaining 7.56% versus 8.88% respectively. Besides, oxygen transport membrane presents the lowest Levelized Cost of Electricity of retrofitting cases as 51.48 $/MWh with a 98.56 kWh/ton O2 produced, while conventional cryogenic distillation shows 52.7 $/MWh and 242.24 kWh/ton O2 produced.