High temperature corrosion problems in coal based power plant and possible solutions

High temperature corrosion problems in coal-based power plant have been matters of concern since the very early days of using the combustion of coal to raise steam to generate electricity. The early problems could be separated into water-wall corrosion, typically at temperatures in the range 350 - 450 degrees C; and superheater and reheater corrosion, typically at metal temperatures in the range 500 - 650 degrees C. These issues have changed in the last few years for a number of reasons, including demands for higher efficiency, procedures adopted to reduce NOx emissions, and cost pressures to use lower-grade fuels. Solutions to high-temperature corrosion problems include the selection of more corrosion-resistant materials of construction; the use of protective coatings and claddings; and modification of the process or the design to reduce the aggressiveness of the conditions experienced by the components at risk In addition, it is increasingly necessary to develop instrumentation capable of measuring the extent of corrosion, preferably in a non-intrusive way that can be applied to plant in service; and 'lifing models' that will allow the planning of maintenance outages, help with run-repair-replace decisions, and allow the penalties associated with performance different from the original design conditions to be quantitatively assessed.