Applying different optimization approaches to achieve optimal configuration of a dual pressure heat recovery steam generator

The optimal design for heat recovery steam generator (HRSG) should be chosen based on technical and economic considerations. Therefore, parameters that are related to thermodynamic and economic aspects should be considered in optimization approaches. It is worth mentioning that one of the significant issues in the HRSG design is the diversity of arrangements between various components (economizer, evaporator, and superheater), which absolutely affect the HRSG performance. According to these facts, in the present article, different arrangements of a dual pressure HRSG are analyzed, and the economizer at the high-pressure level is divided into two parts; these arrangements are optimized by applying different optimization approaches to achieve the optimal configuration. These approaches include the reduction of gas pressure drop, the reduction of generated steam cost and the consideration of both approaches as the third approach. These three approaches are also considered to perform economic and thermodynamic optimization. With regard to the limitations of optimization such as the pinch and approach point, seven different configurations are considered. First, a comprehensive model is developed for calculating thermodynamic, heat transfer, and pressure loss. To perform a thorough optimization, both thermodynamic and geometric variables as well as diversity of various arrangements is considered using genetic algorithm. The results of the optimization study show that the best arrangement is not unique, and each arrangement has different characteristics. Hence, the best arrangement for the HRSG is chosen according to the importance of the objective functions. Copyright (c) 2012 John Wiley & Sons, Ltd.