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Control System Retrofits to Improve Plant Efficiency.pdf

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Babcock Wilcox 1 Control System Retrofits to Improve Plant Efficiency T. Leung Babcock Wilcox Cambridge, Ontario, Canada J. Peet Babcock Wilcox Cambridge, Ontario, Canada Presented to: Canadian Electrical Association Thermal Generating Station Construction and Commissioning Session March 1995 Vancouver, British Columbia, Canada BR-1589 Summary The availability of powerful first principles type models designed for PC-based computer hardware pro- vides a simple and effective tool for the study of tran- sients within power plants. All of the essential compo- nents of the plant including the controls can be modelled and the behavior of the plant to various transients can be evaluated. This paper will address the use of such a dynamic model to design an improved control strategy for pulverized coal fired drum type boilers connected to single reheat type turbine generators. Comparisons with the current techniques will be used to quantify the ben- efits and demonstrate the simplicity of the control meth- odology. Introduction Utilities in North America are faced with a declining margin between installed capacity and electrical demand. Consequently, a greater proportion of units are required to participate in middle load and peaking duty. This ap- plies to the larger, more efficient plant and older, smaller units which previously were base loaded. A utility’s abil- ity to meet the system demand in the most cost effective manner will be, to some degree, dependent on the load range and maneuverability of the individual units. The unit efficiency under cycling duty will depend on the degree to which boiler and turbine efficiencies can be maintained over the operating load range. The parameters which can affect the unit efficiency during cycling operation or limit the unit’s capability to cycle are: 1. Pressure and temperature control to the turbine 2. Extent of overfiring/underfiring in the boiler 3. Excess air and exhaust gas temperature leaving the boiler The paper w
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