Study of a directly heated oxy-fuel supercritical power generation system.

摘要

The Directly heated supercritical oxy-fuel gas turbines have the potential to become an important addition to current power generation systems. They provide a higher thermal efficiency and more effective carbon capture techniques than existing gas turbines. Due to the higher density of the working fluids, the turbomachinery size in these systems can be reduced significantly; this will facilitate to minimize the operational cost. To achieve supercritical working fluid at the turbine inlet combustion needs to be conducted under enormous amounts of pressure; these values are is about 10 times those found in the present gas turbines. Additionally, existing material operational constraints limits the maximum temperature that can be produced during the oxy-combustion process. Therefore, designing a directly heated supercritical gas turbine poses an immense amount of challenge. Motivated by the advantages of a supercritical power generation system, this study focuses on development of the conceptual layout of a ?300 MW supercritical power generation system. The investigation has been performed incorporating two different types of combustor feed system: Gaseous and Liquid. The thermodynamic cycle analysis has been performed using ASPEN HYSYSRTM simulation package based on the proposed conceptual design. Furthermore, the entropy generation during the combustion process has been estimated numerically. The investigation contains the analysis of the net plant efficiency as well as the development of the P-v diagram and T-s for the gas turbines of the power generation systems. The study reveal that, although the gaseous feed system driven gas turbine generates more entropy than the liquid feed system driven gas turbine; more net work can be extracted while using the liquid feed system. Finally, the study is performed incorporating carbon dioxide recirculation into the combustor to keep the combustion temperature within the material operation range. The carbon dioxide recirculation case has been studied only for the liquid feed system driven gas turbines. While conducting the analysis incorporating carbon dioxide recirculation, both gaseous CO2 and liquid CO2 recirculation circumstance has been investigated for the performance comparison purposes. The analysis exhibits that, the net plant efficiency while recirculating gaseous carbon dioxide is ≈56. 7 % where as for the liquid carbon dioxide is ≈44.5 %. This is due to the fact that, the condensation and pumping process of the carbon dioxide requires significantly more energy than the gaseous carbon dioxide compression process.