Steam Turbine Design Considerations for Ultrasupercritical Cycles

Abstract

The current coal-fired power generation market requires higher cycle efficiencies not only for economic reasons, but also as a means of reducing plant carbon footprint. To achieve these goals, the plant must operate at higher pressures and temperatures in the supercritical (SC) and ultrasupercritical (USC) domains. This paper describes Bechtel’s experience and challenges in regard to the conceptual design and integration of large steam turbines operating under these severe conditions. Several examples of projects are described wherein Bechtel applied this neutral but proactive technical approach in the development or design phase to achieve the best and most cost-effective solution for its customers. The topics presented also relate to steam cycle optimization in terms of plant output, steam conditions, number of reheat circuits, and type and number of heaters. The impact on balance of plant systems, including water treatment, availability, and redundancy criteria, is also addressed.