High-temperature gases environments

It has been established that salts can deposit or form on metals during gas-metal reactions. Molten layers could then develop at high operating temperatures. Consequently, the laboratory testing of corrosion resistance in molten salts could yield valuable results for evaluating resistance to some high-temperature gaseous environments. 

A probe for the measurement of salt condensation in high temperature gaseous environments has been designed and is being developed by Jenkins [1994]. Fig. 17.26 is a simplified sketch of the probe assembly. The probe is inserted into the flue gas stream to be tested, and hot gas is drawn through an annular space... 

High-temperature gas phase oxidation-corrosion data have been obtained for two exposures in the CONOCO COAL plant and one exposure in the HYGAS plant. Table VI summarizes the operating environments and in-plant times for these exposures. Since the pilot plants operate at variable temperatures, pressures, and gas compositions, weighted average values are given for the plant exposures. 

S. A. Jansson and E. A. Gulbransen, Thermochemical considerations of high temperature gas-solid reactions. In High Temperature Gas-didetal Reactions in Mixed Environments, ed. S. A. Jansson and Z. A. Foroulis, New York, American Institute of Mining, Metallurgical, and Petroleum Engineerings, 1973, p. 2. 

R. L. McCarron and. J. W. Shulz, The etfects of water vapour on the oxidation behavior of some heat resistant alloys. Proceedings Symposium on High Temperature Gas-Metal Reactions in Mixed Environments, New York, AIME, 1973, p. 360. 

In addition to loss of the platinum, the carlxm support that anchors the platinum crystallites and provides electrical coimectivity to the gas-diffusion media and bipolar plates is also subject to degradation. In phosphoric acid fuel cell, graphitized carbons are the standard because of the need for corrosion resistance in high-temperature acid environments [129], but PEM fuel cells have not employed fully graphitized carbons in the catalyst layers, due in large part to the belief that the extra cost could be avoided. Electrochemical corrosion of carbon materials as catalyst supports will cause electrical isolation of the catalyst particles as they are separated from the support or lead to aggregation of catalyst particles, both of which result in a decrease in the electrochemical active surface area of the catalyst and an increase in the hydrophUicity of the surface, which can, in turn, result in a decrease in gas permeability as the pores become more likely to be filled with liquid water films that can hinder gas transport. 

In a beyond-design-basis accident, it is assumed that the air-cooled passive decay-heat-cooling system has failed and that significant structural failures (vessel failure, etc.) have occurred. Decay heat continues to heat the reactor core but decreases with time. To avoid the potential for catastrophic accidents (accidents with significant release of radionuclides), the temperature of the fuel must be kept below that of fuel failure by (1) absorption of decay heat in the reactor and silo structure and (2) transfer of decay heat through the silo walls to the environment. For the modular high-temperature gas-cooled reactor (MHTGR), the maximum size of reactor that can withstand this accident without major fuel failure is -600 MW(t). 

Chemical stability for corrosive attack in acidic and basic environments Having inert nature and with standing most organic solvents Stability toward sintering and high-temperature gas reactions Being conductive... 

We showed above that wide-bandgap semiconductors are promising for the development of high temperature gas sensors such as FET, Schottky, and MOS-based devices aimed at operation in corrosive environments. However, there are fields of gas sensing where semiconductors with much smaller band gap and lower chemical stability can be applied. Thermoelectric gas sensors are applicable in this... 

Because of their hardness and their ability to withstand high-temperature oxidizing environments, ceramics would be the ideal material of choice for many applications, but imtil recently, their usefulness had been limited because of their lack of toughness. For example, gas turbine engines could operate several hundred degrees higher at much greater efficiency if their superalloy blades were replaced with ceramic blades. 

Cladding oxidation in the high-temperature steam environment began at 11,040 s and gradually increased as the core uncovered. Uncovery was completed at 11,360 s. The exothermic oxidation reaction increased core temperatures, which led to fuel rod gas pressurization and the first clad rupture at 13,230 s. Clad rupture allowed double-sided oxidation, which produced an abrupt increase in core temperatures. Molten materials from the highest temperature... 

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