Modeling and control of a supercritical coal fired boiler
Paranjape, Rohit Damodar
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A boiler or a steam generating unit is an integral part of any electric utility plant. It requires a source of heat at a sufficient temperature level to produce steam. The fossil fuels are burnt in the furnace of the boiler for this purpose. The type of steam generating unit considered in this project was a coal fired unit. An advantage of using supercritical conditions is reduction in physical size of the boiler and steam piping for the same heat carrying capacity and a greater overall efficiency of the unit. The steam is superheated and reheated in order to generate electric power with a turbogenerator. The heat of superheat is all recoverable in the turbine. A variation in the steam temperature and pressure, etc., may cause an unequal expansion and contractions in the turbine parts. Rapid and excessive changes can result in damage to the turbine. Moreover, such variations also cause a change in the unit electric generation. In the electric utility plants, the objectives are to produce required units of electricity continuously and make load changes as and when required and as quickly as possible. Thus, control of steam temperature, pressure, etc., or control of boiler-turbine system is a very important and challenging problem in electric utility plants. A dynamic simulator for the supercritical coal fired unit was developed as a first part of this project. It was based on the Cromby 2 model developed by McDonald, Kwatny and Spare of the Philadelphia Electric Company. This simulator was benchmarked against plant data provided by Texas Utilities Electric on a steady state basis.