US Program on Materials Technology for Ultrasupercritical Coal-Fired Boilers

One of the pathways for achieving the goal of utilizing the available large quantities of indigenous coal, at the same time reducing emissions, is by increasing the efficiency of power plants by utilizing much higher steam conditions. The US Ultra-Supercritical Steam (USC) Project funded by US Department of Energy (DOE) and the Ohio Coal Development Office (OCDO) promises to increase the efficiency of pulverized coal-fired power plants by as much as nine percentage points, with an associated reduction of CO2 emissions by about 22% compared to current subcritical steam power plants, by increasing the operating temperature and pressure to 760 degrees C (1400 degrees F) and 35 MPa (5000 psi), respectively. Preliminary analysis has shown such a plant to be economically viable. The current project primarily focuses on developing the materials technology needed to achieve these conditions in the boiler. The scope of the materials evaluation includes mechanical properties, steam-side oxidation and fireside corrosion studies, weldability and fabricability evaluations, and review of applicable design codes and standards. These evaluations are nearly completed, and have provided the confidence that currently-available materials can meet the challenge. While this paper deals with boiler materials, parallel work on turbine materials is also in progress. These results are not presented here in the interest of brevity.