Distillation is one of the most widely used separation units that consumes the largest amount of energy in chemical and petrochemical industries. Heat integration of thermally coupled distillation column is one of the methods to reduce energy-consumption. This paper provides a comparison between two simple columns with direct configuration and thermally coupled distillation column with direct sequence backward integration arrangement for separation of a ternary mixture based on energy-consumption. The influence of changing numbers of first and second column trays on heating and cooling rate of each column are investigated based on a developed mathematical model using conservation law of mass and energy and bubble-point method. The average relative error between calculated and industrial temperatures in some trays is about 0.74%. The condenser duty of high pressure column is about 9.73×109 kJ/h to provide heating of low pressure column. According to the simulation results, the thermally coupled construction saves energy about 50% more.