In the distillation columns

feed composition and temperature always affect the mass exchange and energy utilization

and improper feed-location can cause bad behavior of the separation and energy. To solve the feed position problem of the multi-feed distillation column

a method that identifies improper feed locations is proposed. By defining the conception of the heat transfer temperature driving force and heat transfer rate

mass transfer driving force and mass transfer rate of the tray

the method using the heat/mass transfer composite curve for the bottleneck identification is presented and applied to identify bottlenecks of the multi-feed demethanizer. The strategy that adjusts the feed locations for the process reengineering can achieve the goal of the debottlenecking for the distillation. Process simulation and bottleneck analysis show that the proposed method can identify the feed bottleneck of the demethanizer and the process reengineering can realize the debottlenecking operation. The heat and mass transfer characteristics of the whole tower become better with saving more cold energy.