SUMMARY 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 © 2012 John Wiley & Sons, Ltd.

The heat recovery steam generator (HRSG) and duct burner are parts of a combined cycle which have considerable effect on the steam generation. The effect of the gas turbine, duct burner and HRSG on power generation is investigated to reduce exergy destruction and power loss in the gas turbine. The results show that with an increase in duct burner flow rate, pressure loss in the recovery boiler increases, steam generation increases on the HP side while it decreases on the LP side. With a reduction in the HP pinch point, thermal recovery increases while the LP pinch point does not have a significant effect. Then, power loss due to pressure drop in the gas turbine and the electricity cost are considered as two objective functions for optimization. Finally, the sensitivity analysis on ambient temperature, compressor pressure ratio, fuel lower heating value, duct burner fuel rate, condenser pressure and main pressure are performed and results are reported. It is concluded that with an increment in compressor pressure ratio, the duct burner flow rate and consequently steam generation increases while electricity cost decrease.

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This paper investigates the simulation of a hybrid desalination system composed of multi-effect evaporation with thermal vapour compression desalination (METVC) and reverse osmosis (RO) plant. The hybrid desalination system is also integrated with a gas turbine power plant through a heat recovery steam generator (HRSG). First, a comprehensive Thermodynamic model for HRSG, METVC, and RO are developed for predicting thermal behaviour of hybrid desalination system. Depending on the interconnection between input and output streams of METVC and RO, six configurations are proposed, and their results are compared in two different scenarios. In the first scenario, METVC desalination production is fixed at its maximum capacity of 70000 m 3 /day. The heat potential of power plants is fully extracted at maximum capacity of production of METVC. In the second scenario, METVC desalination production is not fixed. The limitation on the total production of the desalination plant (METVC+RO) is imposed as a constraint to the optimization problem. The results show that, regardless of the scenario under consideration, cconfiguration 1(the outlet water of the cooling system in METVC has been used for the feed water of the RO system) has the minimum energy consumption as well as maximum exergy efficiency.