Materials Technology for Coal-Conversion Processes Quarterly Report: October-Decemeber 1978 Page: 28
xiii, 65 p. : charts, tablesView a full description of this report.
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various locations in the fluidized-bed and freeboard sections of the com-
bustor. The temperature along the length of the air-cooled probes was re-
corded at three locations, i.e., at the two end specimens and the center
specimen. The temperature differential between the cooling air inlet and
outlet for the air-cooled probes was approximately 100*C.
Three 360-ks (100-h) corrosion tests have been completed in the
atmospheric-pressure fluidized-bed combustor. The experimental conditions
for these tests are given in Table IX. In tests CT-2 and CT-3, NaCl or
CaC12 salt was introduced in the fluidized bed by treating the limestone
in salt solution and drying. The materials, specimen location, and tem-
perature of the corrosion specimens for the three runs are given in Tables X-
XII.
c. Results
The top and bottom view of the air-cooled probes and coupon holders
from the three corrosion tests are shown in Figs. 18-23. The surfaces of the
corrosion coupons are shown in Figs. 24-26. The air-cooled tubular specimens
and the flat coupons, which were placed inside the fluidized bed, had thin
oxide scales and 20- to 30-mm-thick surface deposits from the bed material.
Some of the surface scale spalled during cooling. The corrosion specimens
that were placed in the freeboard section of the combustor had a fine
powdery deposit on the bottom surfaces and a loose particulate deposit on
the top surfaces. The deposits from the various corrosion specimens are
being identified by x-ray diffraction and electron microprobe analysis.
The corrosion specimens are being examined metallographically to
evaluate the extent of corrosion as a function of temperature and location
in the combustor. Metallographic examination of the corrosion coupons
placed inside the fluidized bed has been completed for the three test runs.
The corrosion behavior of these specimens was evaluated by measuring the
average thickness of the surface scale and the average depth of internal
corrosive penetration at the side surfaces and the top and bottom edges of
the specimens. Values for the thickness of the surface scale and internal
corrosive penetration for specimens from the three corrosion tests are given
in Tables XII-XV. The average temperature of the specimens in these tests
was ti 845*C.
All the corrosion specimens that were examined had a 2- to 3-um-thick
oxide scale on the surface. The internal corrosive penetration consisted
primarily of internal oxidation along the grain boundaries and carbide
particles and patches of sulfides ahead of the oxidation front. Internal
corrosion along the top and bottom edges of the nickel-base alloys was
generally greater than that along the side surfaces. This difference in the
corrosion behavior is due to the position of the corrosion coupons in the
fluidized bed, viz., the side surfaces are parallel and the top/bottom edges
are perpendicular to the flow of the fluidizing gas and bed material.
The average thickness of surface scale and internal corrosive
penetration measured on the side surfaces of the specimens are shown in
Figs. 27 and 28 for specimens located 102 and 610 mm above the fluidizing-
gas distributor plate, respectively. In the absence of salt, the total28
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Argonne National Laboratory. Materials Science Division. Materials Technology for Coal-Conversion Processes Quarterly Report: October-Decemeber 1978, report, 1979?; Argonne, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc283206/m1/42/: accessed July 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.