Structural approaches to synthesizing the control system are gaining popularity. At the early stages of the process design, information on process control systems is available only in the structural form involving qualitative information on relationships between the process variables, so that a structural approach is the most appropriate option for control system design at this stage. A thermally integrated distillation sequence was studied for the design of control structures during the early process design stage. A new structural approach is used to synthesize automatically the best control structure.