Improved steam plant efficiency via elevated temperature and pressure levels can be justified if it is more than compensated by the return on investment and other benefits like reduced emissions. The balance is a moving target with simultaneous shifts in relative cost, availability and acceptability of fuels, process development, regulation and operating modes, but technical limits are partly set by the performance of materials in some critical high temperature components of the plant. For optimal material solutions, one limiting factor is the water side oxidation resistance at highest operating temperatures and pressures that extend to the supercritical (SC) range. In this paper, selected materials and modelling options are compared for components where waterside oxidation can contribute by limiting the service life. The implications are discussed for future service thermal plants that increasingly need to accommodate cyclic service, fast ramping and reduced minimum loads. The results from recent materials development programs have not been able to circumvent all consequences from counteracting features in materials properties, so that the overall progress towards higher maximum temperatures has been slow, and the improvements in oxidation or corrosion resistance tend to be associated with significant direct and indirect alloying cost. The constraints from fluctuating demand in plant operation are likely to grow in importance, and the design codes and other guidelines include only partial solutions and tools to account for such trend. For example, the life-limiting contributions of high temperature oxidation and corrosion via lost load-bearing wall thickness is more easily accommodated than impact from increased growth rates of cracks and defects. The solutions are however likely to be only partly directly related to the materials that define the life-limiting boundaries for a given component and its process environment.
|Conference||7th International Symposium on Supercritical Water-Cooled Reactors, ISSCWR-7|
|Period||15/03/15 → 18/03/15|