Influence of water vapor and slag environments on corrosion and mechanical properties of ceramic materials Page: 4 of 14
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INFLUENCE OF WATER VAPOR AND SLAG ENVIRONMENTS ON CORROSION
AND MECHANICAL PROPERTIES OF CERAMIC MATERIALS*
K. Natesan and M. Thiele
Energy Technology Division
Argonne National Laboratory
Argonne, IL 60439
Conceptual designs of advanced combustion systems that utilize coal as a feedstock require high-
temperature furnaces and heat transfer surfaces that can operate at temperatures much higher than those
prevalent in current coal-fired power plants. The combination of elevated temperatures and hostile
combustion environments requires the development and application of advanced ceramic materials in these
designs. The objectives of the present program are to evaluate the corrosion behavior of candidate ceramic
and metallic materials in air and slag environments and evaluate the residual mechanical properties of the
materials after corrosion. The program emphasizes temperatures in the range of 1000-1400*C for ceramic
materials and 600-1000*C for metallic alloys. Coal/ash chemistries based on thermodynamic/kinetic
calculations and slags from actual combustors are used in the program. The materials being evaluated
include monolithic silicon carbide from several sources, silicon carbide in a silicon matrix, silicon carbide in
alumina composites, silicon carbide fibers in a silicon carbide-matrix composite, and some advanced nickel-
base alloys. This paper presents results from an ongoing study of the corrosion performance of candidate
ceramic materials exposed to dry air, air with water vapor, and slag environments and the effects of these
environments on the flexural strength and energy absorbed during fracture of these materials.
Coal is a complex and relatively dirty fuel that contains varying amounts of sulfur and a substantial
fraction of noncombustible mineral constituents, commonly called ash. Conceptual designs of high-
performance power systems (HIPPS) that utilize coal as a feedstock require high-temperature furnaces and
heat transfer surfaces capable of operating at higher temperatures than those used in conventional coal-
fired power plants. The combination of elevated temperatures and hostile combustion environments requires
the use of ceramic materials in at least the first few passes of the heat exchangers in these designs.
In addition to conventional steam turbines, HIPPS would employ a combined cycle that uses a gas
turbine driven by a working fluid (air) that is separately heated in a high-temperature advanced furnace.1 The
ultimate goal is to produce electricity from coal with an overall thermal efficiency of 47% or greater
(compared with =35% for current systems) and to reduce CO2 emissions by 25-30%. The pulverized-coal
high-temperature advanced furnace (HITAF) in the HIPPS concept will heat air to an intermediate temperature
of =1000*C and burn supplemental clean fuel to boost the temperature of air to a turbine inlet temperature of
21300*C. Use of supplemental fuel can be reduced as the HITAF technology evolves to permit the heating of
air to higher temperatures in the furnace. The HITAF represents a major departure from conventional
pulverized-coal-fired boilers in which only steam is raised to a maximum of 530-620*C. The purpose of the
HITAF is to heat the clean working fluid, air, to the required turbine inlet temperatures. At the elevated
temperatures of the HITAF, transfer of heat from the combustion gases to the working fluid will be
dominated by radiative heat transfer, and the design of the heat transfer surface will be critical for the success
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Natesan, K. & Thiele, M. Influence of water vapor and slag environments on corrosion and mechanical properties of ceramic materials, article, March 1, 1997; Illinois. (digital.library.unt.edu/ark:/67531/metadc689734/m1/4/: accessed September 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.