Synthesis of Heat Exchanger Network Subject to Fouling and Ageing with the Cleaning Schedule Optimized

In order to reduce extra capital and energy cost caused by fouling and ageing, this paper presents a new methodology for synthesizing heat exchanger network (HEN) with the cleaning schedule optimized. Two cleaning methods with different cleaning efficiency are used to remove fouling and ageing, so the cleaning mode has to be selected along with an optimal cleaning schedule. The process is implemented in three steps. First the original HEN is obtained by means of pseudo-temperature enthalpy diagram approach (PTHDA). Then the structure of the HEN is simplified through loop-breaking and small size units eliminating methods. Finally a mixed integer nonlinear programming (MINLP) is formulated to optimize heat transfer area and the cleaning schedule. An example is provided to demonstrate the application and effectiveness of this approach.