Advanced Exergoeconomic Evaluation of Large-Scale Coal-Fired Power Plant

Abstract

Conventional exergy-based analysis can only identify the location and magnitude of thermodynamic inefficiencies (exergy destruction), while an advanced analysis can further reveal their source and avoidability by splitting each inefficiency into endogenous/exogenous and avoidable/unavoidable parts and their combinations. In this paper, a framework and implementation for a comprehensive evaluation of energy systems via conventional and advanced exergoeconomic analyses are summarized and performed to a state-of-the-art pulverized-coal power plant. An easy-to-implement procedure was proposed to calculate the endogenous exergy destruction. Different from the previous analyses of such plants, the boiler subsystem of the considered plant is simulated in detail with coal combustor and a series of (radiation- or convection-dominating) heat surfaces. The exergoeconomic performances (exergy dissipation as well as the related costs) of each component and the whole system are evaluated first. Then, the splitting of all exergy destructions and costs is performed for the insights of their sources and avoidability to suggest improvement measures. The results show that large parts of the exergy destructions within most of the components are endogenous; particularly, over half of the avoidable thermodynamic inefficiencies within most of the components are endogenous with the share of the avoidable part varying significantly among different components. Most costs related to either investment or exergy destruction are endogenous, and only nearly 10% of the costs of the whole system could be avoided for such a modern power plant. Moving convection-dominating heating surfaces into the furnace and increasing air-preheating temperature are suggested for performance enhancement.