Techno-economic analysis of pressurized oxy-fuel combustion power cycle for CO₂ capture

Abstract

Growing concerns over greenhouse gas emissions have driven extensive research into new power generation cycles that enable carbon dioxide capture and sequestration. In this regard, oxy-fuel combustion is a promising new technology for capturing carbon dioxide in power generation systems utilizing hydrocarbon fuels. Combustion of a fuel in an environment of oxygen and recycled combustion gases yields flue gases consisting predominantly of carbon dioxide and water. To capture carbon dioxide, water is condensed, and carbon dioxide is purified and compressed beyond its supercritical state. However, conventional atmospheric oxy-fuel combustion systems require substantial parasitic energy in the compression step within the air separation unit, a flue gas recirculation system and carbon dioxide purification and compression units. Moreover, a large amount of flue gas latent enthalpy, which has high water concentration, is wasted. Both lower the overall cycle efficiency. Alternatively, pressurized oxy-fuel combustion power cycles have been investigated. In this thesis, the analysis of an oxy-fuel combustion power cycle that utilizes a pressurized coal combustor is reported. We show that this approach is beneficial in terms of larger flue gas thermal energy recovery and smaller parasitic power requirements. In addition, we find the pressure dependence of the system performance to determine the optimal combustor operating pressure for this cycle.

(cont.) We calculate the energy requirements of each unit and determine the pressure dependence of the water-condensing thermal energy recovery and its relation to the gross power output. Furthermore, a sensitivity analysis is conducted on important operating parameters including combustor temperature, Heat Recovery Steam Generator outlet temperature, oxygen purity and oxygen concentration in the flue gases. A cost analysis of the proposed system is also conducted so as to provide preliminary cost estimates.