A highly-integrated nonlinear dynamic model of the KDA process has been used in the past for control structure selection studies. The original model consists of many unit operations including three distillation columns. These columns were originally modelled by Brognaux (1992) using the Shortcut Library models available within SpeedUp. In this work, the HDA case study is revisited but the nonlinear model has been revised to include modified models for the distillation columns and other unit operations; The modelling issues associated with the development of this more rigorous HDA model are discussed in the context of its use for control structure selection.