The energy utilization of complex distillation column for multi-component separationwas analyzed. Combining the principle of distillation and the method of pinch analysis, the concept ofcolumn grand composite curve (CGCC) was improved to describe distribution of energy flux in eachtray within the complex column. The concept was further applied to the optimal design of energy uti-lization and heat-integration analysis of the separation system. Analytic method of complex distillatoncolumn was developed. The m...