Distillation Startup of Fully Thermally Coupled Distillation Columns: Theoretical Examinations

The fully thermally coupled distillation column offers an alternative to conventional distillation towers, with the possibility of savings in both energy and capital costs. This innovative and promising alternative provides the opportunity to separate a multicomponent mixture into fractions with high purities merely in one column. A lack of knowledge still exists when dealing with the startup of this process. The startup of continuous distillation columns is a challenging control problem due to permanent changes in the process variables combined with highly nonlinear behaviour due to complex heat and mass transfer operation. The rigorous model presented in this contribution allows for a detailed analysis implying the startup behaviour of a distillation column from ambient and empty state to the steady state operating point. The model considers the influence of the heat accumulation of the column wall and internals and allows for a detailed analysis of variables with hydraulic and thermodynamic significance. Beside this first time startup analysis of dividing-wall columns the designed model allows the solution of a wide variety of problems, from operability studies to process control.