Design of Combined Heat and Power Plant using MINLP optimization model

This paper presents a mixed integer nonlinear programming (MINLP) mathematical model to simultaneously optimize the configuration of a combined cycle power plant (CCPP), the geometric design and operating conditions as well. The whole process is modelled by considering detailed energy and mass balances. Physical and chemical properties of air, flue gases and water (working fluid for power cycle), overall heat transfer coefficients are computed using nonlinear correlations. On the other hand, discrete decisions (integer variables) are employed to model the tube number, diameters and widths of tubes in each equipment section as well as the number of fins per unit length of tube among others. Continuous variables are related to the pressures, temperatures and flow-rates of gases and working fluid streams. GAMS (General Algebraic Modelling System) is used to implement and to solve the mathematical model. Once the proposed MINLP model was successfully validated with literature, it was solved for three objective functions. The obtained results are presented and discussed in detail.