Energy and exergy-based thermodynamic assessment and optimization of a reheat Brayton–regenerative Kalina cycle hybrid system

There has always been a concerted effort to enhance the efficiency of power generation systems, which has significantly rationalized the modern power plants. Taking a leaf out of these works, an endeavour is made to investigate a novel hybrid system of Reheat Brayton and Regenerative Kalina cycles. The assessment protocol involved the framing of molar, energy, and exergy equations for the devices and solving them in the MATLAB environment. Thermodynamic evaluation from both first and second law perspectives using Coke Oven gas (COG) as fuel is the crux of this research. Furthermore, this work includes an optimization study and comparison of the fuels COG, Synthesis gas (SG), and methane in terms of air–fuel ratios, dissociation effects, and greenhouse gas emissions. The Brayton-Kalina power ratio was found to vary from 0.154 to 0.679 at a minimum pressure ratio (r_p) of 4 for a temperature range of 400 ℃ to 600 ℃. However, with an increase in the pressure ratio, the power ratio also increased appreciably, hovering in the range of 3.57–5.63 at its maximum value. The existence of a temperature-dependent optimum pressure ratio in the range of 8 to 15, wherein the total exergy destruction attains a minimum, is a noteworthy observation. The optimal values of Exergy efficiency, Ecological coefficient of performance, and Air rate are 26.43%, 0.359, and 0.146, respectively. A comparison of fuels revealed that specific carbon emissions were maximum for SG and minimum for methane. The dissociation effects were minimal in SG and the highest in methane gas.