Inter-stage attemperation system and method

Abstract

Systems and methods for controlling exhaust steam temperatures from a finishing superheater are provided. In certain embodiments, the system includes a controller which includes control logic for predicting an exhaust temperature of steam from the finishing superheater using model-based predictive techniques (e.g., based on empirical data or thermodynamic calculations). Based on the predicted exhaust temperature of steam, the control logic may use feed-forward control techniques to control the operation of an inter-stage attemperation system upstream of the finishing superheater. The control logic may determine if attemperation is required based on whether the predicted exhaust temperature of steam from the finishing superheater exceeds a set point temperature as well as whether the inlet temperature of steam into the finishing superheater drops below a set point temperature of steam. The attemperation system may include a characterizing function to linearize the valve operation controlled by the control logic to inject cooled, high-pressure feedwater into the steam upstream of the finishing superheater, which may, in turn, control the exhaust temperature of steam from the finishing superheater. The disclosed embodiments may also be applied to any systems where an outlet temperature of a fluid from a heat transfer device may be controlled.