Thermodynamic Analysis of Semi-Closed Cycles with Oxy-Fuel Combustion and Carbon Dioxide-Steam Working Fluid

Abstract

Reducing emissions of harmful substances during the production of electricity at thermal power plants is possible by the transition to semi-closed gas turbine cycles with oxy-fuel combustion and carbon dioxide-steam working fluid. Their main advantages compared with closed Rankine cycles with water vapor and open Brayton cycles with combustion products of the air-fuel mixture are the absence of the toxic substances formation danger and the effective separation of working fluid components based on the thermodynamic principle, which allows to subsequently dispose of high-purity carbon dioxide. This paper presents the results of the energy performance thermodynamic analysis of the most known oxy-fuel combustion power cycles with a carbon dioxide-steam working fluid. A technique for modeling thermal schemes of promising power units is described in detail, taking into account losses for cooling high-temperature carbon dioxide turbines, energy costs for the production and compression of oxygen, as well as compression of carbon dioxide before disposal. Based on the results of mathematical modeling, it was found that the net electrical efficiency for the semi-closed combined cycle with oxy-fuel combustion can reach 44.5% at a gas turbine inlet temperature of 1400°C, and 43.2% for the Allam cycle at 1100°C.