The coal fired thermal power plants plays major role in the power production in the world as they are available in abundance. Many of the existing power plants are based on the subcritical technology which can produce power with the efficiency of around 33%. But the newer plants are built on either supercritical or ultra-supercritical technology whose efficiency can be up to 50%. Main objective of the work is to enhance the efficiency of the existing subcritical power plants to compensate for the increasing demand. For achieving the objective, the statistical modeling of the boiler units such as economizer, drum and the superheater are initially carried out. The effectiveness of the developed models is tested using analysis methods like R2 analysis and ANOVA (Analysis of Variance). The dependability of the process variable (temperature) on different manipulated variables is analyzed in the paper. Validations of the model are provided with their error analysis. Response surface methodology (RSM) supported by DOE (design of experiments) are implemented to optimize the operating parameters. Individual models along with the integrated model are used to study and design the predictive control of the coal-fired thermal power plant.

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The major portion of total captive power comes from thermal power from coal, oil, natural gas, etc., of which coal-fired units contribute 41% of global electricity. The overall efficiency of such power plants is 33% due to variations in power plant design, use of wide fuel ranges, different steam turbines, and lack in modeling and control configurations. To improve this efficiency, knowledge on material and energy flows across subsystems, including fuel handling, boiler, turbine, and air management need to be known properly. In addition, there is a widespread lack in measurement and instrumentation systems in power plants across the fleet and operators. This scenario makes the operational adjustments more difficult. Again, the strictness in environmental compliances (sulfur and nitrogen components) is met at the cost of limiting thermal efficiency. Moreover, to comply with faster load change, less fuel consumption and more efficient supercritical boilers have been studied. Hence, to improve the efficiency level, more research starting from the state-ofthe-art review on modeling, identification, and control methods of coal-fired boilers and the integrated plant is aimed in this work. This will also address the issue of global climate change and reduction in emission of greenhouse gases.

The subcritical coal-fired boilers of thermal power plants consist of a combustion chamber, economizer unit, drum unit (drum, riser, and downcomer), superheater unit (primary superheater, secondary superheater, and final superheater), and reheater unit. The input and output of these units are highly interactive in nature. The efficiency of the subcritical plants is only around 33%. The efficiency needs to be increased to produce more power for the increasing demand, which can be achieved only by implementing supercritical technology or ultra-supercritical technology. However, the conversion of existing subcritical power plants to supercritical power plants is impossible due to the installation cost. So in order to increase the overall efficiency of the existing subcritical power plants, boilers of such units must be examined in order to find safer operational practices. This paper highlights the mathematical modeling of the economizer unit and drum unit of boiler, which can help in enhancing the performance of the boiler system of the power plant. Mass and energy balances for the integrating boiler units have been formulated using first principle laws. The developed model has then been validated with actual plant data obtained from a 210 MW coal-fired thermal power plant. The performance of the open loop responses of the model are analyzed and are included in the results and discussion of the paper. The model provides support for level, pressure, and temperature measurements and predictions. The effect of changes in the parameters of the boiler are studied and discussed in detail.