Coupled heat transfer model for the combustion and steam characteristics of coal-fired boilers

Abstract

This paper presents a coupled heat transfer model for coal-fired boilers that integrates boiler's fire side computational fluid dynamics (CFD) solution with the boiler's steam cycle, and thus, can predict the boiler steam temperatures subject to different boiler design and operation conditions. In this coupled model, the heat transfer submodels describing the gas-steam heat exchange for each part of boiler heating surfaces are integrated by exchanging the steam temperatures iteratively. This coupled heat transfer model is self-consistent since it ensures the fire side heat transfer solution to always coincide with the steam temperature changes across each boiler heating surface. This model is specifically designed to provide efficient computational solutions to engineering boiler problems in which the changes of boiler steam temperatures subject to different boiler design and operation conditions are of the major concerns. This model is applied to a 320 MW subcritical boiler to evaluate the impacts of coal switching and boiler operation adjustment on boiler's heat transfer distributions and steam temperatures. The simulation results demonstrate that this model can effectively capture the complex coupled heat transfer behavior between the fire and steam sides of boiler and serve as an efficient predictive tool for engineering boiler problems.