The thermally coupled distillation sequence (TCDS) has attracted increasing interest in a range of chemical processes because of its potential energy and capital cost savings in multicomponent separations. In addition, the TCDS has attracted particular attention in retrofit projects because of its lower energy requirements compared to the existing conventional column sequence, easy design; and small modification. This, however, can create a bottleneck in the column. The main aim of this study was to identify bottlenecks in a retrofitted TCDS systematically using a hydraulic performance indicator and fractional utilization of area (FUA), and to propose a novel strategy for the use of a side reboiler or a side condenser for debottlenecking of the column. A practical method using the response surface methodology (RSM) is proposed for TCDS design and optimization. The optimum TCDS structure can be observed in a practical manner while minimizing the simulation runs. The use of a side reboiler or a side condenser in a retrofitted TCDS could debottleneck the column and increase the process capacity. This can reduce the temperature difference between the top and side reboiler location, or between the bottom and side condenser location, which has potential use as a heat pump by utilizing the heat from the top vapor stream or side vapor stream, respectively. The column grand composite curve (CGCC) was used to indicate the thermodynamic feasibility of the implementation of the heat pump system into the TCDS. The results showed that the operating cost could be reduced dramatically through novel combinations of internal and external heat integration, such as TCDS using a top vapor recompression heat pump.