Experimental and numerical investigation of flameless pulverised coal combustion
type: CreativeWork
description: Aim of this work was to investigate the applicability of flameless combustion technology principles to pulverised coal combustion. Lab-scale experiments showed, that it is highly beneficial in terms of NOx reduction to use N2 as coal carrier instead of air. The finding has been supported by OH* chemiluminescence imaging which revealed a suppression of ignition in the coal jet when N2 is used. With the investigated settings, NOx emissions are always above the legislative limit of 200 mg/m3 (stp). However, emissions close to the limit can be achieved with a variety of settings of the thermal load, inlet velocity, wall temperature, burner air ratio, and primary combustion zone volume. The inlet velocity has no significant influence on NOx emissions whereas an increase of the wall temperature also increases NOx emissions. The parameters thermal load and primary combustion zone volume are interrelated by the residence time in the primary combustion zone. As long as the residence time is above a certain threshold, NOx emissions are low and constant for almost all settings. These high residence times have only been achieved with the burner air ratio below 0.8. Predictions of NOx emissions based on NO models from literature are not reliable for mainly one reason. The oxidation of intermediates (such as HCN and NH3) in the primary substoichiometric combustion zone is insufficient for burner air ratios below 1.0. With conventional models, intermediates are only oxidised by O2. However, O2 is consumed by other reactions as well so that its concentration approaches [O2]=0 mol/m3 in the substoichiometric zone and the intermediates are retained unto the injection of burnout air where they are quickly oxidised to NO. Thus, NO predictions with conventional models usually turn out too high. With a model which is based on intermediate oxidation by OH, predictions for stoichiometric conditions in the primary combustion zone are poor. In this work the concept of oxidation by OH has bee…
abstract: Aim of this work was to investigate the applicability of flameless combustion technology principles to pulverised coal combustion. Lab-scale experiments showed, that it is highly beneficial in terms of NOx reduction to use N2 as coal carrier instead of air. The finding has been supported by OH* chemiluminescence imaging which revealed a suppression of ignition in the coal jet when N2 is used. With the investigated settings, NOx emissions are always above the legislative limit of 200 mg/m3 (stp). However, emissions close to the limit can be achieved with a variety of settings of the thermal load, inlet velocity, wall temperature, burner air ratio, and primary combustion zone volume. The inlet velocity has no significant influence on NOx emissions whereas an increase of the wall temperature also increases NOx emissions. The parameters thermal load and primary combustion zone volume are interrelated by the residence time in the primary combustion zone. As long as the residence time is above a certain threshold, NOx emissions are low and constant for almost all settings. These high residence times have only been achieved with the burner air ratio below 0.8. Predictions of NOx emissions based on NO models from literature are not reliable for mainly one reason. The oxidation of intermediates (such as HCN and NH3) in the primary substoichiometric combustion zone is insufficient for burner air ratios below 1.0. With conventional models, intermediates are only oxidised by O2. However, O2 is consumed by other reactions as well so that its concentration approaches [O2]=0 mol/m3 in the substoichiometric zone and the intermediates are retained unto the injection of burnout air where they are quickly oxidised to NO. Thus, NO predictions with conventional models usually turn out too high. With a model which is based on intermediate oxidation by OH, predictions for stoichiometric conditions in the primary combustion zone are poor. In this work the concept of oxidation by OH has bee…
author: Stadler, Hannes Alexander
language: eng
keywords: info:eu-repo/classification/ddc/620, Experiment, Kohlefeuerung, Kohlekraftwerk, Stickstoffoxidemission, Flammenlose Verbrennung, Numerische Strömungssimulation, Ingenieurwissenschaften, flameless combustion, computational fluid dynamics, nitrogen oxide emission, coal combustion
date published: 2010
date modified: 2026-07-30T19:43:35Z
provider: RWTH Aachen University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Publikationsserver der RWTH Aachen University