Control Strategy Of The Steam Temperature For Ultra Supercritical Units Over 600℃ Class

The control strategy of the steam temperature for the 600 class ℃ultra supercritical units is proposed, with special focus on the start-up and shut-down process to reduce the risk of over temperature failure because the operation temperature is close to the upper temperature limits of the metal of the boiler and heat exchangers. Over temperature is a serious concern for the safe operation of the utility boiler. The traditional control strategy of the steam temperature does not work well for those utility boilers over 600 class. It may lead to ℃ the creep of the boiler heating metal material surface or the creep of the steam pipe speeding, and therefore threaten the safety of the units. For this reason, the improved steam temperature control strategy is especially focused upon to avoid over temperature during start-up and shut-down. At the same time, in the normal operation of the units, advanced control strategy such as internal model control, coordination control, decoupling control, model predictive control and fuzzy control is studied to better control the superheated steam temperature and the reheat steam temperature. It is beneficial not only for reducing the probability of unit over temperature, but also for maintaining the safe and stable operation of the unit with the improvement of the ability of the energy-saving and the emission reduction. The advanced control strategies have been tested in several 600 class ultra supercritical units.℃...