Dividing wall column for industrial multi purpose use

Dividing wall columns (DWC) for the distillation of multicomponent mixtures have received much attention in the past 15 years and have experienced a booming development. Since DWC demand higher efforts in equipment design and process control they are predominantly used in continuously operated dedicated production plants and spread only over a limited number of chemical companies. No open literature can be found where DWC are used in multi-purpose plants. The distillation equipment in those plants, typically batch wise operated, has to show a high degree of flexibility – an attribute that hardly seems to fit for dividing wall columns. Lonza set up the worldwide first multi-purpose DWC on the production site in Visp that fully meets the demands of a steadily changing production environment characterized by several different production campaigns, processes and products produced in the same plant throughout a year.This paper reports on the equipment design and the specific technical solutions that had to be implemented in order to satisfy the harsh specifications of multi-purpose production. Particular attention is put on the modelling and simulation of the column and the control scheme that has been applied. The paper contributes a new approach for setting up a flowsheet simulation that overcomes the frequently occurring problems in convergence and enhances robustness of the simulation.Since the launch of the column several different processes were successfully operated in this equipment. In each single case we directly transferred the process concept from simulation to the plant without piloting. The launch and operation of the column are explained in detail and finally the simulation results are compared to real operation data from the production.