Scheduling control of a deaerator plant

The deaerator of a pourer plant may experience severe two-phase steam/water problems especially during restart of the power plant following a unit tri p. Unless suitable control strategies are adopted, cavitation in the suctio n area and choking in the deaerator can occur. Cavitation can cause expensi ve damage to the feedwater pumps, while choking will interrupt the operatio n of the deaerator. These all lead to failure of the restart. Some models a nd control schemes have been developed in recent years to study cavitation. A model that can predict the transient behaviour of the deaerator plant fo r possible cavitation and choking has been developed. In this paper, a sche duling control for deaerator operation based on this model is proposed. Thi s scheme utilises operational status and process variables to predict possi ble cavitation or choking, and then takes the necessary action to avoid the loss of head in the suction area and high velocity of steam in the deaerat or equalisers. The simulation results show that the control scheme will ens ure safe operation, even during restart of the power plant. (C) 1998 Elsevi er Science Ltd. All rights reserved.