Evaluation of CO2-capturing power generation systems utilizing waste heat from ironworks

Two kinds of CO2-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 200degreesC 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 CO2 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 350degreesC. 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 CO2 reduction 1 738t-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 CO2 reduction characteristics and its economical profitability.