The heat exchange among the stages in the rectifying and stripping sections increases the possibility of energy conservation for a distillation column. From that point of view, an internal heat integrated distillation column called HIDiC was proposed. In the conventional HIDiC structure, as the stripping section and the pressurized rectifying section are provided in parallel, it is difficult to supply and remove the heat to and from the stages so that those are similar to the case of the reversible distillation. We showed in the previous paper that by executing the heat exchanges among the appropriately selected stages in the rectifying and stripping sections in discrete manner, the amount of enthalpy change to the composition change that is similar to the ideal form can be obtained. We also proposed a design methodology to achieve it, and demonstrated that the process designed by using the proposed methodology showed high energy conservation performance by process simulation studies. Here, such HIDiC is called "discretely heat integrated distillation column" (D-HIDiC). The D-HIDiC designed by the proposed methodology was applied to a commercial purpose distillation column as the world first commercial application of HIDiC technology. It was successfully operated at excellent energy conservation with zero reboiler duty in the stable operation. In this research, the details of design results and the operating conditions of that commercial plant are explained. Then, the energy conservation performance of the proposed D-HIDiC is verified through the comparison of the energy consumption among the proposed D-HIDiC, the conventional distillation column and the conventional HIDiC. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.