This article examines the procedures involved in implementing the divided-wall column technology for processing petrochemical cuts. Special simulation tools have been developed for the design of the overall column configuration and an evolutionary algorithm is used to find the optimum column design based on the total annual costs. Practical operation is verified on a laboratory scale with a special set of divided-wall column elements designed as a variable unit construction kit. The positive experiences and the clear economical advantages have led to industrial realisations of the new concepts in numerous commercial plants. The columns meet all expectations regarding energy consumption, product yield and purity. (C) 2003 Elsevier B.V. All rights reserved.