Testing and simulation study of extraction steam heat-supply capacity upstream of the reheater in supercritical units

Abstract This study addresses the practical requirement for steam extraction upstream of the reheater in a 660 MW ultra-supercritical unit to supply industrial steam. A safe test scheme for evaluating the unit’s extraction capacity was developed and implemented. Four representative operating points—minimum dry-load, 50 % BRL, 75 % BRL, and BRL—were tested, yielding the following results: across all load conditions, the extractable steam upstream of the reheater remains approximately 12 % of the boiler’s evaporation rate; the maximum measured extraction reached 215 t/h, corresponding to an external high-pressure steam supply capacity of 250 t/h. An integrated turbine–boiler–heat-supply thermodynamic model was then constructed and simulated to determine the theoretical extraction capacity at various loads. A parametric analysis examined the effects of boiler air flow, main-steam temperature, and reheater spray-water flow on extraction capacity. Based on these findings, an operational optimization combining a slight reduction in main-steam temperature with a moderate decrease in the air–coal ratio was proposed and shown to effectively enhance the unit’s extraction heat-supply capacity upstream of the reheater.