Dynamic Modeling and Process Simulation of Steam Bottoming Cycle
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In this work, a flexible combined heat and power plant with a steam Rankine bottoming cycleis proposed as a suitable alternative for the power generation system of an oil and gas offshore facility. The power system should be able to produce simultaneously 58 MW of power and 52 MW of heat at 150 C, and to respond rapidly to the sudden changes of load that may be expected. The nominal operating conditions and the sizes of the components integrating the thermal power plant were obtained from a multi-objective optimization where maximum efficiency and minimum weight were the objective variables. A dynamic model of the combined heat and power plant was developed in the Modelica language by means of the software Dymola and the specialized library ThermoPower. Specific components were expressly programmed for this purpose due to the special requirements of the power system in terms of heat and power demand. This model was validated with both design and o-design steady state data generated by the software Thermofex. Dynamic simulations were carried out in order to test the correct performance of the developed models and their ability to predict the dynamic behavior of a thermal power plant. Preliminary results of the transient performance of the proposed combined heat and power plant for a sudden gas turbine change of load were obtained, both in open-loop and with a control structure implemented. It was found that the power plant model was able to predict the dynamic behavior that could be expected for a reduction in the gas turbine load, proving the feasibility of the developed models to be utilized in a deeper assessment of the transient performance of thermal power generation systems.