The separation of the ternary mixture of acetonitrile, methanol and benzene into three high-purity products is complicated by the presence of three binary azeotropes that divide the ternary diagram into three distinct regions. Fortunately the compositions of two of these azeotropes change significantly with pressure. The economic optimum flowsheet has been developed in a recent paper in the literature that uses a process with three columns operating at different pressures. Three high-purity products are produced as bottoms streams from the three columns with the distillate of the third column recycled back to the first column. The plantwide dynamic controllability of this complex, non-ideal interacting process is studied in this paper. An effective control structure is developed that controls one temperature in each column. Pressure compensation in the low-pressure column improves load rejection of both throughput and feed composition disturbances. No on-line composition measurement is required. (C) 2016 Elsevier B.V. All rights reserved.