A novel diagram-based representation approach is developed to analyze the thermodynamic efficiency and identify quickly the promising energy-use improvement for integrated fractionating and heat exchange processes in delayed coking units. For considering temperature dependence of heat capacity and integrating fractionating and heat exchange processes

an advanced energy level composite curve is constructed by using the simulation results and a stepwise procedure. More accurate results of exergy analysis are obtained and the interaction between different components of the integrated system can be properly revealed in an integrated figure. Then the exergy calculation is performed to validate the performance of processes and to define the targets for improvement. The avoidable exergy destruction is also analyzed by applying the concepts of avoidable and unavoidable exergy destructions for the integrated system. In a case study for a Chinese refinery

the results reveal that the heat exchange between gas oil and deethanization gasoline is the most inefficient process with the highest retrofitting potential

and the lowest exergy efficiency of component in the integration system is only 29.4%. The improvement potential and exergy efficiency for the fractionator are 38.1% and 97.3%

respectively. It is obvious that the fractionator is not the most promising component for improvement.