Computational fluid dynamic modelling of a 550 MW tangentially-fired furnace under different operating conditions

In the present paper, a computational fluid dynamics (CFD) modelling study was performed for the combustion of the brown coal in a large-scale tangentially-fired furnace (550 MW) under different operating conditions. The AVL Fire CFD code has been used to model the furnace. The mathematical models of coal combustion with the appropriate kinetic parameters were written and added to the code as user defined functions. It consists of pulverised coal (PC) devolatilization, char burnout, heat and mass transfer, and nitric oxide formation. The simulation of the PC combustion was carried out using multi-step reaction chemistry schemes. The level of confidence of this numerical model was based on the previous validations of the lignite combustion in a lab-scale furnace, as well as the validation parameters of the present furnace at the standard existing conditions in terms of temperature values and species concentrations. Performance of the boiler under different operating conditions was investigated, from which the effects of air and coal mass flow rates were considered at full load with different operating schemes of coal mills (out-of-service operations). The validated model was used to perform the following investigation parameters: furnace gas temperatures, species concentrations (CO and CO2), and velocity distributions. This study provides good information to optimize the operations of the utility tangentially-fired boiler with less emissions production. (C) 2013 The authors, Published by Elsevier Ltd.