Abstract:
Heat integration and HEN synthesis, which is a heuristic approach to utilize energy efficiently and economically, has been widely used either in the petroleum or petrochemical industries. Therefore, there are many innovations, and a lot of research effort to develop the models to optimize the energy usage with the cost reduction. In this work, we present a new heat exchanger network model consisting of an extension of the stage-wise superstructure approach that was first proposed by Yee and Grossmann (1990). Motivated by systems where splitting of large FCP stream is needed to match with several smaller FCP streams (like crude fraction units), we add several matches per branch. Given the non-convex nature of the resulting MINLP and the associated difficulties to solve it without good initial points especially in the General Algebraic Modelling System (GAMS) and the DICOPT solver, we propose a new initialization strategy for generating feasible starting points using sequential technique to solve the MINLP problem and develop bounding condition to obtain the best solution. The successful application of our approach using examples from literature and real industrial process presented here showed that our new stage-wise superstructure model and initialization strategy can be applied to the complex MINLP problem which provides a more profitable network than others in literature.
