Oxygen reheat furnace atmosphere

Oxidation of iron and steel in reheat furnace atmospheres initially follows the linear rate law. The initial period can be very long when the free oxygen concentration is low or absent. 

Oxidation in reheat furnace atmospheres follows the linear law initially and may become parabolic at the later stage if the furnace atmosphere contains a sufficient amount of free oxygen. 

In the presence of free oxygen, the dominant oxidizing species in the reheat furnace atmosphere is oxygen. 

Table 5-4 summarizes the types of high-temperature corrosion which occur in various industrial processes (Lai et al., 1985). As can be inferred from this table, many high-temperature processes involve atmospheres which contain oxidants in addition to O2, H2O, or CO2 the most prevalent of these are sulfur, carbon, nitrogen, and chlorine. The corrosive effects of these additional oxidants depend on the oxygen potential in the atmosphere, which is measured by the equilibrium Pq. In relatively high- multi-oxidant atmospheres, such as those resulting from the combustion of hydrocarbon fuels with excess air, the corrosive effects tend to be minimal or even beneficial. An example of a beneficial effect is that of traces of sulfur in the combustion environment of a reheat furnace which acts to slow the oxidation rate of steel as a result of a surface-poisoning effect (Lee, 1997). 

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