Computational Study of Pulverized Coal Combustion in Boiler—Unit 7 of TPP Kakanj

Abstract

Computational simulations and mathematical modelling have become an indispensable tool for analysis, solution, prediction and optimization of processes in various industries. We report on the simulation of combustion of dust-coal in a boiler Unit 7 (230 MWe) of Thermal Power Plant (TPP) Kakanj, BiH. This boiler was chosen for the study because of the high temperature corrosion detected on its side membrane walls in the furnace diffuser, suspected to be caused due to non-optimal distributions of velocity, temperature and composition of flue gases, especially of oxygen, in the wall-adjacent regions. The numerical simulation were carried out using Ansys Fluent CFD software with the comprehensive combustion model based on the RANS approach for two-phase flow of dispersed coal particles in multi-component gaseous medium, with standard chemical kinetics and radiation models. In order to obtain realistic boundary and input conditions for the simulation of combustion in the boiler, the precursor simulations were performed, first for flow of pulverized coal in a double-swirl burner, and the results interpolated to 24 burner exits into the boiler. Although computationally much more demanding, imposing the inlet data from the precursor simulations led to improved, more realistic mixing of coal dust and oxidant, and consequently to the combustion conditions closer to the real ones. The simulations confirmed the occurrence of adverse conditions prone to cause the corrosion. The results of both simulations are presented and discussed.