Numerical prediction of NOx emissions in a full-scale furnace

A Mokhtardidouche,H Naji,A Benarous,L Loukarfi

doi:10.5755/j01.mech.20.1.3904

A Mokhtardidouche, H Naji + Show 2 more

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https://doi.org/10.5755/j01.mech.20.1.3904

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Abstract

The present paper deals with a numerical predic-tion of the thermal level and emission rate of nitrogen ox-ides within an industrial furnace. Favre averaged forms of the governing equations accounting for radiative heat losses are solved via a finite volume formulation. Turbu-lent fluxes are closed using a model for which a limited Pope correction is performed. The relaxation model of Magnussen is used to describe the two-step chemis-try/turbulence interaction for the non-premixed flame. The effect of the swirl number has been also investigated. The predicted static temperature as well as NO emission rate at the furnace exit show good agreement with in-situ meas-urements. In addition, the numerical computation shows that the depression is about 28% for the rate of NO, which it is obtained by adopting a moderate swirl at the primary-air entrance. DOI: http://dx.doi.org/10.5755/j01.mech.20.1.3904

Highlights

Nowadays, national and international current legislations incite industrialists to optimize their processes to strongly reduce pollutants emissions
The main topic of this study has been to carry out a numerical investigation of flow characteristics and NO emissions in a full-scale furnace designed for cement production
To deepen our understanding of the thermal and dynamic fields, as well as emissions of NO, the radiative transfer equation has been included in the energy equation using the discrete ordinates model

Summary

Introduction

National and international current legislations incite industrialists to optimize their processes to strongly reduce pollutants emissions. This is true for cement production units, where substantial quantities of nitrogen oxides (NOx) and carbon dioxides (CO2) are produced due to high temperatures required for clinkering [1]. The first way consists in a better and direct control of the combustion process to limit the production of the primary pollutants. In this context, air or fuel combustion staging can be used to reduce NOx emissions but the performance is limited because a high temperature zone is required to sinter the clinker. There have been some successes in using low primary air burners for rotary kilns, in which the non-premixed flame is diluted by hot products [4]

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