Analysis of a cordierite (MAS) recuperator from a molybdenum heat-treating furnace
Recuperators which can transfer waste heat from industrial furnaces to the combustion air can result in fuel conservation. Available alloys cannot currently satisfy the demand for higher thermodynamic efficiencies from higher temperature recuperated combustion air because of their properties at high temperatures. Therefore, selected ceramic materials are principal candidates for use in waste-heat recovery devices for flue gas temperatures of 1100 to 1650/sup 0/C. A leading configuration now under investigation is the cross-flow fixed-boundary extended-surface ceramic honeycomb heat exchanger. The need for a material that has both low thermal expansion and high thermal shock resistance and is also fabricable and relatively inexpensive has led to the development of cordierite (magnesium aluminosilicate - MAS). A cordierite honeycomb recuperator was exposed for about 2200 h to representative process temperatures from 1100 to 1550/sup 0/C in a molybdenum and tungsten reheating furnace. This recuperator performed satisfactorily for test and exhaust inlet temperatures of 1100 to 1400/sup 0/C. Electron microprobe and ceramographic examination demonstrated that molybdenum and tungsten carryover in the waste gas stream significantly penetrated the cordierite at temperatures as low as 675/sup 0/C. The leading edges of the exhaust inlet section showed significant microstructural modification. A subsequent accidental overfiring to 1560/sup 0/C resulted in slumping of this modified material. Exhaust-to-air channel leakage caused deposits in air channels and modified the microstructure in bonding lines between layers in the honeycomb. Cracking also occurred in the air outlet section. Significant microstructural modification, including coarsening within the walls and glass formation on the air-channel wall surfaces, was observed.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 6067948
- Report Number(s):
- ORNL/TM-6794
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
320304* -- Energy Conservation
Consumption
& Utilization-- Industrial & Agricultural Processes-- Waste Heat Recovery & Utilization
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CERAMICS
CRYSTAL STRUCTURE
DESIGN
ELEMENTS
ENERGY
ENERGY CONSERVATION
ENERGY RECOVERY
ENERGY SOURCES
EQUIPMENT
FLUE GAS
FURNACES
GASEOUS WASTES
HEAT
HEAT RECOVERY
HEAT RECOVERY EQUIPMENT
HEAT TREATMENTS
INDUSTRY
MAGNESIUM COMPOUNDS
MATERIALS
METAL INDUSTRY
METALS
MICROSTRUCTURE
MOLYBDENUM
OXYGEN COMPOUNDS
PERFORMANCE
PERFORMANCE TESTING
RECOVERY
REFRACTORY METALS
SILICATES
SILICON COMPOUNDS
TESTING
TRANSITION ELEMENTS
TUNGSTEN
VERY HIGH TEMPERATURE
WASTE HEAT
WASTES