Dual cascade control design for binary distillation columns

In this paper, a linear cascade scheme to control both effluent purities in binary distillation columns with temperature and delayed composition measurements is presented. First, the column input-output behavior is modeled as a set of linear integrators, driven by control inputs and reconstruction load disturbances. This control model yields a linear cascade control scheme with: (i) a purely integral decentralized primary component that, driven by delayed composition measurements, yields the temperature setpoints, (ii) a PI secondary controller that, driven by the temperatures measurements, tracks the temperature setpoints, and (iii) simple tuning guidelines. The methodology only requires six easily-obtainable steady-state parameters with physical meaning. The proposed methodology is applied to a representative example through simulations, yielding smaller quality deviations and faster regulation times than the ones yielded by previous two-point cascade schemes