Evaluation of tubular ceramic heat-exchanger materials in residual-oil-combustion environment
Fourteen different structural ceramic tubes were exposed to a residual oil combustion environment at 1200/sup 0/C for 500 h with a total of six thermal cycles. Silicon carbide and alumina ceramics survived the exposure. Best candidates for heat exchanger use in residual oil combustion environments include siliconized silicon carbide, pressureless sintered silicon carbide, and high-purity alumina. Cordierite, mullite, and zirconia-mullite cracked extensively. Molten nodules or deposits of cristobalite, tridymite, and silicate glass containing fuel oil impurities such as Na, Al, Ca, V, Fe, and Ni formed on the upstream side of the SiC-based specimens. Active oxidation proceeds with the release of CO and CO/sub 2/ at the interface of the nodules or deposits formed on the SiC. Fuel oil impurities including Fe and Ni reacted with the free Si in siliconzed SiC to form low-melting alloys. Surface roughness and grain growth were observed in pressureless sintered SiC as a result of reactions. Microcracks were observed in chemically vapor deposited (CVD) SiC and CVD SiC on SiC. A thin layer of iron-nickel aluminate formed on the outer surfaces of aluminum oxide tubes. Significant grain growth was observed in the upstream side of the high-purity alumina tubes. The test exposure increased helium permeability of siliconized SiC, pressureless sintered SiC, high-purity alumina, and CVD SiC, but it decreased the air permeability of relatively permeable, porous materials. The room temperature C-ring fracture strength of pressureless sintered SiC and high-purity alumina decreased significantly during the exposure but that of siliconized SiC increased slightly. The thermal expansion of pressureless sintered SiC increased while the thermal expansion of siliconized SiC and high-purity alumina remained constant.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- OSTI ID:
- 6589735
- Report Number(s):
- ORNL/TM-7578
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
02 PETROLEUM
36 MATERIALS SCIENCE
ALUMINIUM OXIDES
CORROSION RESISTANCE
CERAMICS
HEAT EXCHANGERS
MATERIALS TESTING
SILICON CARBIDES
WASTE HEAT UTILIZATION
COMBUSTION PRODUCTS
FRACTURE PROPERTIES
FUEL OILS
IMPURITIES
PERMEABILITY
RESIDUAL FUELS
TENSILE PROPERTIES
THERMAL EXPANSION
VERY HIGH TEMPERATURE
ALUMINIUM COMPOUNDS
CARBIDES
CARBON COMPOUNDS
CHALCOGENIDES
EXPANSION
FUELS
LIQUID FUELS
MECHANICAL PROPERTIES
OILS
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PETROLEUM PRODUCTS
SILICON COMPOUNDS
TESTING
WASTE PRODUCT UTILIZATION
320304* - Energy Conservation
Consumption
& Utilization- Industrial & Agricultural Processes- Waste Heat Recovery & Utilization
025000 - Petroleum- Combustion
360205 - Ceramics
Cermets
& Refractories- Corrosion & Erosion