Improving the understanding of a novel complex azeotropic distillation process using a simplified graphical model and simulation

Sasol Technology and Linde AG have developed an innovative azeotropic distillation process. A light-boiling binary entrainer (ethanol and water) is used to recover hydrocarbons from a process stream that also contains oxygenated species. Conventional distillation cannot be used because of low-boiling azeotropes that exist between the hydrocarbons and oxygenates. The use of a binary entrainer is crucial to the success of the process concept. Each entrainer component on its own could not achieve the desired separation of octene and oxygenates. Extensive use has been made of graphical conceptualising techniques and steady-state simulations to aid process development and process synthesis. A single ternary diagram does not provide sufficient insight into the system. Hence, a paper pyramid model was constructed, by joining ternary diagrams to better visualise vapour–liquid equilibrium relationships of the four key components in this system.