Abstract
Ferritic T23 steel and austenitic TP347HFG steel have been studied with an emphasis on understanding the impact of specimen geometry on their steam oxidation behaviour. The selected materials were tested over a wide range of temperatures from 600 to 750°C. The tests were carried out in 100% steam conditions for 1000 hours. The tests indicated that the ‘curved-shaped’ specimens show slower mass gain, scale ticking and void nucleation rates than ‘bridge-shaped’ specimens (with flat and convex surfaces combined). Furthermore, a bridge TP347HFG sample showed the formation of lower amount of flaky oxide at 750°C.
Highlights
Steam oxidation is matter of growing interest as research aimed at the improvement of power plant efficiency indicates the needs for higher temperatures and pressures
The scale formed at 600 and 650°C starts to exfoliate on the T23 ferritic steel due to the surface cracking through the outer oxide layers (Fig. 8a and g)
Results of the tests in this study show that steam oxidation in a temperature range 600–750°C shows parabolic rate dependence (750°C) and the oxidation rate follows
Summary
Steam oxidation is matter of growing interest as research aimed at the improvement of power plant efficiency indicates the needs for higher temperatures and pressures. Each 1% increase in overall efficiency can result in as much as 3% reduction in CO2 emissions.[1] steam temperature in conventional power plants is expected to rise from 50 to 100°C by 2030 in order to reduce CO2 emissions further. Most of the coal-fired power plants operate at temperatures between 520 and 565°C and with pressures up to 180 bar achieving efficiencies of 38–40%. In the new design units, the efficiency of energy generation is above 40% due to higher steam conditions (600–620°C). The most efficient power plants, currently designed and tested, are expected to have 44–46% efficiencies, with steam temperatures between 700 and 720°C and 360 bar pressure
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