@conference{
author = "Belošević, Srđan and Sijerčić, Miroslav and Stanković, Branislav and Crnomarković, Nenad and Đekić, Slobodan",
year = "2010",
abstract = "The emission of NOx is of great concern to designers and operators of most industrial furnaces and boilers. The pulverized coal flame in utility scale boilers is also of great importance, affecting the levels and distribution of temperature and heat flux. Numerical studies of combustion and heat transfer processes in energy conversion systems can describe how the fuel chemical energy is converted into thermal energy with high efficiency and acceptable emission. Although there is much technology now available to compute complex flows in energy systems, development of submodels describing individual processes, as well as comprehensive CFD codes are increasing worldwide. A comprehensive 3D differential mathematical model and software were previously developed in-house and validated against experimental data. A practical motivation was to solve operation problems in tangentially-fired furnaces of the power plant Kostolac-B 350 MWe boiler units. The software is aimed for prediction of processes and operation situations in utility boiler pulverized coal-fired furnaces and it is adapted to be used by engineering staff dealing with the process analysis in boiler units. Characteristics of the model are Eulerian-Lagrangian approach to multiphase flow, k-ε turbulence model, particles-to-turbulence interactions modeled by PSI Cell method, diffusion model of particle dispersion, six-flux method for radiation modeling, heterogeneous reactions in kinetic-diffusion regime on the basis of experimentally obtained case-study coal kinetic parameters, within a "shrinking core" concept and with respect to the model of char oxidation, as well as homogeneous reactions controlled by chemical kinetics or turbulent mixing. In addition, submodel describing formation and destruction of thermal and fuel NOx has been developed and validated against available data obtained by monitoring of NOx emission from boiler units. The main motivation for this study was to achieve optimal position of flame with acceptable levels of NOx emission. The flame position depends on many influencing parameters. Selected predictions of pulverized coal flame geometry and position are given in the case-study furnace under different operating conditions, like fuel and air distribution. Even when both the fuel nitrogen content and the combustion temperature are not very high, the emission of NOx may still surpass environmental limits if the combustion process is not managed correctly. It is therefore essential to understand the NOx formation process so that the NOx emission can be controlled. Although post-combustion clean-up is viable, modifying combustion process often controls NOx most economically. In air staging method, e.g., the portion of combustion air is introduced downstream, through special, over-fire-air ports. In this work, the numerical study has been performed to achieve both NOx emission reduction and favorable position of flame in the case-study furnace, by investigating the impact of pulverized coal distribution over the burner tiers, without need for construction changes. The contributions of fuel and thermal NOx are reported as well. The results of the model can help in increasing combustion efficiency, lowering emission of pollution, fuel savings and corresponding economy and enviromental benefits during the facility exploitation.",
publisher = "Istanbul, Turkey : University of Pittsburgh, Swanson school of engineering",
journal = "PCC 2010 : 27th Annual International Pittsburgh Coal Conference : Proceedings",
title = "Modeling and optimization of NOx emission and pulverized coal flame in utility scale furnaces",
volume = "3",
pages = "1968-1989",
url = "https://hdl.handle.net/21.15107/rcub_vinar_12293"
}
