(204a) Heat Exchanger Network Synthesis and Optimization With Consideration for Variation in Process Streams' Properties

A mathematical modeling approach was employed to investigate the influence of variation of process parameters on the retrofit of heat exchanger network in a process plant. The two cases studied were the base case when the process stream parameters were assumed constant within the specified supply and target temperature bounds, and changing phase case when the process streams parameters were considered constant within the temperatures intervals bounds defined by the bubble and dew points. Themathematicalmodelsdescribing the process were developed with appropriate constraints, and the solver DICOPT included in the General Algebraic Modeling System (GAMS) software was used for the solution of the mathematical model problems, to generate heat exchanger network and cost total annual cost (TAC) optimization results.The optimization results showed that the hot utility demand increased from 96.85MW in the base case to 123.85 MW in the changing phase and cold utility demand increased from 88.38 MW in the base case to 115.39MW in the changing phase. The heater area requirements were 151 m² and 181.31 m² for base case and changing, respectively and cooler areas requirements were 1830.85 m² to 2222.64m², respectively for base case and changing phase, respectively. The study concluded that heat exchanger network synthesis with assumption based on negligible sensible heat due to phase change could not give a correct representation of the process thermal behavior.