Thermoeconomic optimization of heat recovery steam generators

The combined cycle power plant (CCPP) is one of the efficient power producing technologies which includes both Brayton (topping) and Rankine (bottoming) cycles. The optimal design of heat recovery steam generator (HRSG) as an important part of a CCPP is a subject of interest. In this paper a thermoeconomic analysis has been applied to optimally design HRSGs in a combined cycle power plant. Two arrangements of heating elements are studied here. The method consists of both developing a simulation program and applying the Genetic Algorithm optimization scheme. The total cost per unit produced steam exergy was introduced as the objective function which included, capital or investment cost, operational cost, and the corresponding cost of the exergy destruction. The objective function per unit of produced steam exergy was minimized while satisfying a group of constraints. The decision variables (or design parameters as well as pinch point temperatures, pressure levels and, mass flow rates) are obtained. The variations of design parameters as well as the exergy efficiency and the total cost with the inlet hot gas enthalpy are shown.