SEM evaluation of advanced refractory failures in slagging gasifiers Page: 1 of 2
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1582 Microsc Microanal 11(Suppl 2), 2005
DOI: 10.1017/S1431927605509942 Copyright 2005 Microscopy Society of America
SEM Evaluation of Advanced Refractory Failures
W. K. Collins,* C. L. Dahlin,* J. P. Bennett*, K.S. Kwon,* and J. C. Rawers*
*US Department of Energy, Albany Research Center, Albany, OR 97321
The SEM is an invaluable tool in the evaluation of advanced refractories and their failure. A reaction
vessel's refractory liner, at minimum, must protect the reaction vessel from elevated temperatures,
corrosive slag and thermal cycling. To understand the failure mechanisms ARC staff had first to
determine how an advanced chrome rich refractory was attacked by various components that make
up a slag. Refractory cups were made from the refractory of interest and various compounds that can
be found in a slag such as CaO, Si02, Fe203, NaCl were placed into the test cups and fired for 24
hours at the required temperature with the desired atmosphere. Fig 1.
The cups are prepared for examination by embedding in epoxy and cross sectioning. SEM
examination revealed how various slag compositions attacked and penetrated the refractory. The
slag could corrode, free refractory grains or react with the refractory and from a new compound. Fig.
2. It was found that the only way to measure slag component penetration was with multiple
elemental X-ray maps. Si02 penetrated deeply and in many instances moved through the cup. Fig 3.
The knowledge of slag refractory interactions gather during cup testing was applied to actual spent
refractory from reaction vessels. Obtaining samples from the reaction vessel itself proved difficult
due to time constraints imposed in relining. Samples were selected based on spent brick shape, color
or location in the heap of spent refractory Fig. 4. Sample preparation affected the results dry, water
or oil coolant during cutting may dissolve reaction products. The complex reactions between the
slag and refractory made for very interesting and time consuming evaluation. Elemental X-ray maps
at low and high magnification combined with point analysis aided in locating regions of interest.
Crystals were found growing in voids and appear to be from vapor deposition Fig. 5. Other crystal
structures are from the slag refractory interaction. Knowledge gathered from this and other
supporting research resulted in a new patented refractory composition that resists slag penetration.
References
[1] W. K Collins et al., Microsc. Microanal. 6 (Suppl. 2) (2000) 426.
[2] J. P. Bennet et al, US DOE Albany Research Center Annual Report, Low Chrome/Chrome
Free Refractories for Slagging Gasifiers, (2004)
[3] J. P. Bennet et al, US DOE Albany Research Center Annual Report, Advanced Refractories for
Slagging Gasifiers, (2004)
[4] C. L. Dahlin, US DOE Albany Research Center internal report, Instructions for Forensic
Analysis of Gasifier Refractory Materials, (2003)
[5] K. Kwong et al, United States Patent, 6,815,386 (2004)
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Collins, W.Keith; Dahlin, Cheryl L.; Bennett, James P.; Kwong, Kyei-Sing & Rawers, James C. SEM evaluation of advanced refractory failures in slagging gasifiers, article, August 1, 2005; (https://digital.library.unt.edu/ark:/67531/metadc886710/m1/1/: accessed April 20, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.