Design Considerations for Fossil-Fired Steam Generators in Favor of the Once-Through System

Utility power plants are more and more faced with cycling needs. Fossil fired steam generators for large units developed from circulation to once through technique. Nowadays primary energy needs led to supercritical design pressures. Advantages and disadvantages are discussed.This paper handles the aspects of steam generation at different pressure levels, compares the criteria for application of the well known systems and describes design principles for heat transfer in furnace and heat exchanger elements.