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Heat Exchanger Fouling and Cleaning VII
July 1-6, 2007 - Tomar, Portugal
| Editors: |
Hans Müller-Steinhagen, Institute of Technical Thermodynamics, German Aerospace Centre (DLR)
and Institute for Thermodynamics and Thermal Engineering, University of Stuttgart, Germany
M. Reza Malayeri, University of Stuttgart, Germany
A. Paul Watkinson, The University of British Columbia, Canada |
The articles for these proceedings are peer-reviewed.
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FREE ALKALI-INDEX FOR OPTIMIZING THE FUEL MIXTURE IN BIOMASS CO-FIRING
T.E. Blomberg, Kiertomäentie 11 As.1, 01260 Vantaa, Finland
ABSTRACT:
Co-firing biomass with fossil fuels provides a cheap
and efficient reduction of the CO2 emissions in electricity
generation. One of the main challenges in co-firing is the
increased fouling and corrosion rates of the heat transfer
surfaces when biomass is added to the fuel mixture.
Optimization of the fuel mixture from the fouling and
corrosion point of view would be an easier task, if some fuel
properties would provide correlation with the fouling and
corrosion rates. Currently there is no clear understanding of
the most useful fuel indices. The fouling indices used in
coal firing have proved to be less useful in biomass cofiring.
Prediction of the fouling rate from the the (S/Cl)
molar ratio or the (S/available alkali) molar ratio have
shown some success. However, generally accepted
threshold values for these are not available. The newly
developed fouling indices in biomass co-firing are basically
trying to predict the formation of alkali chlorides on the heat
transfer surfaces. Alkali chlorides, especially KCl are
believed to be the substances responsible for the high
fouling and corrosion rates in biomass combustion and cofiring,
whereas the formation of alkali sulfate seems to have
a beneficial effect in the minimization of the fouling and
corrosion rates. However, the mechanism of the formation
of the alkali chlorides and sulfates on the heat transfer
surfaces is not known in detail so the threshold values of the
indices are based on empirical correlations found to fit the
data of a particular experiment. In this paper, a new fouling
index, (x·(Na+K)-2·S)/LHV, is presented. Theoretical
background of the index is described and examples are
given how to use the index in optimization of the fuel
mixture in biomass co-firing. Finally, correlation of the
index with available literature data is presented. Now the
validation of the usefulness of the index requires further
experimental work.
T.E. Blomberg, "FREE ALKALI-INDEX FOR OPTIMIZING THE FUEL MIXTURE IN BIOMASS CO-FIRING" in "Heat Exchanger Fouling and Cleaning VII", Hans Müller-Steinhagen, Institute of Technical Thermodynamics, German Aerospace Centre (DLR)
and Institute for Thermodynamics and Thermal Engineering, University of Stuttgart, Germany
M. Reza Malayeri, University of Stuttgart, Germany
A. Paul Watkinson, The University of British Columbia, Canada
Eds, ECI
Symposium Series, Volume RP5 (2007). http://services.bepress.com/eci/heatexchanger2007/14
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