Dynamic behavior of superheated steam and ways of control

Abstract

A simple way of calculating the dynamic behavior of a superheater is presented. A comparison of the measured data with the calculated result verifies the accuracy of this simple method. It is the first time that a phase compensation for real roots, i.e., the twin lead/lag loop which is facile for engineering applications, is used in superheated steam temperature control. Numerous simulation results show that both the response time lapse and maximal dynamic deviation are greatly reduced. Moreover, a formula to calculate the setting parameters is presented, together with a practical example of its engineering application in superheated steam temperature control with single-stage attemperation in a power plant boiler. This method can remarkably improve the control performance of superheated steam temperature and makes it possible for one stage attemperation to be sufficient for the superheater of power plant boilers, thus simplifying the superheater system and reducing investment. Because the control performance is remarkably raised, the set values of the steam temperature control system can be raised above rated values and also the operational economy, without impairing the operation safety.

Keywords

automatic control, superheater, steam temperature, dynamic behaviour, twin lead/lag