A carbon dioxide‐recovering high‐efficiency gas‐turbine power‐generation system is proposed in which carbon dioxide (CO2) generated is recovered by adopting the oxygen (O2) combustion method and no thermal nitrogen oxide is generated. In the system, saturated steam produced by utilizing waste heat is adopted as the working fluid of the gas turbine. Thus, the compressing process of the working fluid gas, which is the most energy‐consuming process in generating power by using a gas turbine, is not needed. This makes the system extremely high efficient.
By taking saturated steam of 210°C as an example, the characteristics of the system were simulated. The net exergetic efficiency of the system has been estimated to be 48.4 percent by considering both the exergy of the saturated steam and the electric power required not only to generate high‐pressure oxygen, but also to liquefy the recovered CO2. The value is higher than the exergetic efficiency 37.8 percent of large‐scale thermal power generation plants using the same natural gas, and is 28.0 percent higher than its efficiency of 37.8 percent, the one estimated if the CO2 generated is removed and recovered from the stack gas by using alkanolamine‐based solvent and the recovered CO2 is liquefied.
Two kinds of CO 2 -capturing power generation systems with and without regenerator are proposed which utilize saturated steam produced by making use of waste heat from ironworks, and their thermodynamic and economical characteristics were investigated. As an example of saturated steam, temperature and quantity was assumed to be 200°C and 10 t/h, respectively, by considering use of waste heat from a kiln at a pellet factory in an ironworks. Fundamental characteristics of the two proposed systems are estimated through computer simulation, such as power generation efficiency, energy saving characteristics, amount of CO 2 reduction, and economics. It was shown that the best system is attained for the proposed system without the regenerator when its turbine inlet temperature is set at 350°C. At this condition, the system was estimated to be economically feasible and to have following characteristics: repowering power generation efficiency 97.7 %, annual amount of saved energy 83.3 TJ, annual amount of CO 2 reduction 1 738 t-C, unit cost of generated power 6.42 yen/kWh, annual gross profit 25.4 million yen, and depreciation year 5.70. The proposed system could be adopted in many other waste heat emitting factories owing to its large CO 2 reduction characteristics and its economical profitability.
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