Multi-objective optimal design of gas-fired heater based on modified design model of fired heater taking into account exergy, economic and environmental factors

Abstract

Heaters are one of the central parts of natural gas reduction stations using turboexpanders to prevent the formation of hydrate and corrosion failure. This study intends to design a fired heater by applying a combustion sub-model to derive an optimal model for this kind of application. This model is developed to accurately consider all subsections of the fired heater namely radiation, convection, and shield sections, as well as flue gas composition, and its volume. Within this context, a multi-objective optimization is employed to identify the optimal design of the gas-fired heater in the natural gas reduction station for the Ramin power plant case study. The total economic and environmental costs, together with modified exergy efficiency, are selected as objective functions. Multi-criteria-decisionmaking-method is employed on Pareto frontiers optimal curve to suggest the optimal solution. Results show that the developed model can outperform previous models in thermal efficiency with relatively similar costs. Besides, the optimal point in Pareto suggested by the decision-making-method accounts for a higher modified exergy efficiency (1.3%) than the counterpart, which thermal efficiency is regarded as an objective function. At the same time, its total cost remained almost constant. The effects of changes in each of the design parameters on the objective functions are also evaluated.