Though a cross pairing has previously been utilized in the control of a fully thermally coupled distillation column, the details of the experiment have not been examined yet. Investigated here is the employment and evaluation of a three-loop PI control with a cross pairing using a FTCDC as a control for a practical hexane process; how the pairing works is also investigated. HYSYS simulations of the process, with several different control configurations, are conducted to compare their control performances and to show that the proposed cross pairing gives a satisfactory specification control of three products in the distillation column.