Title: Numerical modelling of MILD combustion for coal

Authors: Ju Pyo Kim, U. Schnell, G. Scheffknecht, A.C. Benim

Addresses: Institute of Process Engineering and Power Plant Technology (IVD), University of Stuttgart, Pfaffenwaldring 23, 70569 Stuttgart, Germany. ' Institute of Process Engineering and Power Plant Technology (IVD), University of Stuttgart, Pfaffenwaldring 23, 70569 Stuttgart, Germany. ' Institute of Process Engineering and Power Plant Technology (IVD), University of Stuttgart, Pfaffenwaldring 23, 70569 Stuttgart, Germany. ' Department of Mechanical and Process Engineering, Dusseldorf University of Applied Sciences, Josef-Gockeln-Str. 9, 40474 Dusseldorf, Germany

Abstract: Emissions of nitrogen oxides from coal combustion are a major environmental problem because they have been shown to contribute to the formation of acid rain and photochemical smog. Moderate and Intensive Low oxygen Dilution (MILD) combustion is a promising technology for decreasing pollutant emissions and improving combustion efficiency. A combination of air preheating and fuel dilution with combustion products of low oxygen concentration are the main features of this technique. In the MILD combustion mode, preheated air and fuel are gradually mixed with large amounts of recirculated exhaust gas. The objective of the present work is to investigate the capability of present fuel NO mechanisms for pulverised coal combustion to predict the observed nitrogen oxide levels in MILD combustion mode. For this purpose, knowledge of the fate of coal nitrogen during the combustion process is vital. The interaction between turbulence and chemistry is modelled by an advanced Eddy Dissipation Concept (EDC). The NOx model is used to predict NO profiles that are compared to measurements obtained from semi-industrial scale experiments.

Keywords: MILD combustion; coal combustion; NO emissions; nitrogen oxide; CFD; computational fluid dynamics; modelling; low oxygen concentration; acid rain; photochemical smog; environmental pollution; combustion efficiency; air preheating; fuel dilution; turbulence modelling; eddy dissipation concept.

DOI: 10.1504/PCFD.2007.014683

Progress in Computational Fluid Dynamics, An International Journal, 2007 Vol.7 No.6, pp.337 - 346

Published online: 25 Jul 2007 *

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