Reducing CO2 emission and improving exergy based performance of natural gas fired combined cycle power plants by coupling Kalina cycle

Abstract

This paper presents second law analysis of a combined triple power cycle. The Brayton–Rankine combined cycle of a natural gas fired power plant situated in India and the Kalina cycle of Orkuveita Húsavíkur geothermal power plant in Husavik, Iceland were considered. These cycles were simulated in MATLAB and the simulated results were compared with the actual results to validate the simulation. These cycles were then combined and the performance of the resulting triple cycle was evaluated according to Indian atmospheric conditions to investigate the possibility of using Kalina cycle system in India. A significant performance improvement and reduction in CO2 emission was found. With the same fuel consumption, the net power output was found to increase by about 1.27%, the thermal efficiency by 0.54% and the exergy efficiency by 0.51%. To generate the same additional power by the Brayton–Rankine combined cycle alone, an additional 1.24% of natural gas would be burned which would increase the CO2 emission into the atmosphere by 1.24%. The effects of topping cycle pressure ratio, inlet air temperature and relative humidity on the triple cycle performance were also studied and the cycle was optimized with respect to the pressure ratio.