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Heat Exchanger Fouling and Cleaning: Fundamentals and Applications
May 18-22, 2003 - Santa Fe, New Mexico, USA
| Editors: |
Paul Watkinson, University of British Columbia, Canada
Hans Müller-Steinhagen, German Aerospace Centre (DLR) and University of Stuttgart
M. Reza Malayeri, German Aerospace Centre (DLR) |
The articles for these proceedings are peer-reviewed.
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Bayer Process Heat Exchangers Cleaning Efficiency: Optimizing the Acid Dissolution of Sodalite Scale
Sébastien Fortin , Alcan International Limited
Raymond Breault, Alcan International Limited
ABSTRACT:
Aluminum metal is produced by the electrolytic reduction of aluminum oxide
(Al2O3), mainly extracted from bauxite ore digested in a hot caustic soda solution. This solution is supersaturated with respect to sodium aluminate and silicate, which react together to form sodalite
(3[Na2O·Al2O3·2SiO2 ·2H2O]
·Na2CO3) at high temperatures. Heat exchanger tubes are
scaled with this compound, which seriously reduces heat transfer coefficient,
thus increasing energy costs.
Heat exchanger tubes are cleaned periodically with a sulfuric acid solution that
contains a corrosion inhibitor. An investigation was undertaken in order to study
the parameters affecting sodalite scale dissolution by sulfuric acid: temperature,
solution concentration, flow rate, etc. A custom-made set-up was used, simulating a
heater cleaning operation, using scaled tube sections as test specimens.
It was found that by increasing the temperature, the flow rate and the acid concentration,
the scale dissolution rate increases. However, it was also determined that the presence
of a corrosion inhibitor reduces the efficiency of the cleaning operation at high
temperatures. This result was further investigated by adding organic compounds
to the sulfuric acid solution.
Sébastien Fortin and Raymond Breault, "Bayer Process Heat Exchangers Cleaning Efficiency: Optimizing the Acid Dissolution of Sodalite Scale" in "Heat Exchanger Fouling and Cleaning: Fundamentals and Applications", Paul Watkinson, Hans Müller-Steinhagen, and M. Reza Malayeri Eds, ECI
Symposium Series, Volume RP1 (2003). http://services.bepress.com/eci/heatexchanger/10
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