Corrosion of HR3C heat exchanger alloy in a biomass fired PF utility boiler
✍ Scribed by C. Liu; J. A. Little; P. J. Henderson; P. Ljung
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- German
- Weight
- 539 KB
- Volume
- 51
- Category
- Article
- ISSN
- 0947-5117
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✦ Synopsis
Detailed microscopic examinations have been conducted on two, temperature-regulated probes (commercial HR3C heat exchanger alloy) after being exposed to biomass flue gas inside a PF boiler for 3770 h at 600 8C and 650 8C respectively. Corrosion of the tube proceeds via scale formation and internal element depletion. Three characteristic types of internal corrosion have been identified depending on their position relative to the flue gas passage and deposit/flue gas chemistry. Severe, mainly internal corrosion occurs at down-stream locations where higher potassium chloride content exists within the deposit. Corrosion mechanisms corresponding to each type of internal corrosion have been proposed based on further laboratory tests and thermodynamic analysis. The increased temperature (650 8C) causes slightly higher material wastage for the alloy.
Detaillierte mikroskopische Untersuchungen wurden an zwei, temperatur-regulierten Proben (kommerzielle Wa Èrmetauscherlegierung HR3C) nach 3770 h Auslagerung in Biomassenabgas in einem PF-Kessel bei 600 bzw. 650 8C durchgefu Èhrt. Die Korrosion des Rohres erfolgt u Èber Zunderbildung und innere Elementverarmung. In Abha Èngigkeit von der relativen Position zum Abgasdurchtritt und von der Ablagerungs-/Abgas-Chemie wurden drei Typen von innerer Korrosion identifiziert. Starke, im wesentlichen innere Korrosion tritt an den stromabwa Èrtsgerichteten Stellen auf, wo hohe Kaliumchloridgehalte in den Ablagerungen vorhanden sind. Aufbauend auf weiteren Laborversuchen sowie thermodynamischer Analyse sind entsprechend den einzelnen Typen der inneren Korrosion Korrosionsmechanismen vorgeschlagen worden. Die erho Èhte Temperatur (650 8C) verursacht einen etwas ho Èheren Materialverlust fu Èr die Legierung.
2 Results
Ash deposit and corrosion products cover the two as-received probes. The deposit that survives handling (involving retrieving and cutting, etc.) to this stage is relatively well sintered and is likely to be a small fraction of the original deposit collected on the probe surface inside the boiler. It is this densely sintered deposit layer that is attached to the scale/substrate interface and therefore directly responsible for tube corrosion. The up-stream (fire-side) deposit on the probes ap-Materials and Corrosion 51, 765±773 (2000) Corrosion of heat exchanger alloy 765