Analytical Formulation of the Performance of the Allam Power Cycle

Thermal power plants operating on fossil fuels emit a considerable amount of polluting gases like carbon dioxide and nitrogen oxides. Several technologies have been developed or under development to avoid the emissions of, mainly, CO₂ that is formed as a result of air fuel combustion. While post-combustion capture methods are viable solution for reduction of CO₂ in the existing power plants, implementation of the concept of oxyfuel combustion in future power cycles appears to be a promising technique for clean power generation from fossil fuels. A novel power cycle that employs oxyfuel combustion method has been developed by NET Power. A 50 MWth demonstration plant has been built in Texas. The main components of the cycle include a turbine, an air separation unit (ASU), a combustor, a recuperator, multi-stage CO₂ compression with intercooling, two CO₂ pumps, and a condenser. The mixture of the combustion products consists of CO₂ and steam which are separated at a high-pressure condenser. The captured CO₂ is pressurized to around 300 bar. Over 90% of the supercritical CO₂ flow is recycled back to the cycle as the working fluid, and the rest is sent for further processing and storage. The present paper reports thermodynamic analysis of a 300 MWe NET Power cycle. The effects of the highest temperature and pressure of the cycle as well as the turbine pressure ratio on the overall efficiency of the cycle have been examined. The study aims to identify the areas which have improvement potential in order to boost the cycle efficiency. Compared to the combined cycle power plants, the NET Power cycle offers design simplicity with relatively high power generation efficiency without emitting polluting gases. A successful commercialization of the cycle is expected to have a dramatic impact on future power generation.