Industrial & Engineering Chemistry Research, Vol.50, No.10, 6187-6204, 2011
Binary Distillation Column Startup Using Two Temperature Measurements
The problem of designing the startup (SU) control scheme for a binary distillation column with two temperature and two level measurements is addressed. The objective is the quick attainment, with minimum off-spec production and heat consumption, of closed-loop stable operation in continuous regime. The combination of advanced constructive control and conventional distillation dynamics and control tools leads to a variable control structure scheme with: (i) an event controller which, on the basis of the two temperature measurements, decides the duration of an initial open-loop batch operation period at total reflux, and (ii) a set of four (two level and two temperature) linear-decentralized controllers activated in a sequential manner, which steers the column toward its nominal steady-state in a continuous regime, by manipulating the heat duty, reflux, distillate, and bottom flow rates. The proposed SU control scheme is tested through simulations with three high-purity column examples with ideal and nonideal thermodynamics, yielding a behavior that matches or improves the ones obtained in previous studies with detailed model-based schemes.