Bioethylene production : from reaction kinetics to plant design

Ethylene production from renewable bioethanol has been commercially proposed in recent years as a sustainable alternative to fossil sources. The possibility to exploit diluted bioethanol as less expensive feedstock was studied both experimentally, using different catalysts at lab-level, and through preliminary process designs. In this work a full-scale plant simulation is presented, built on a detailed reaction kinetics, based on literature data. Rate equations for the primary and side reactions are revised and implemented within the Aspen Plus simulation package, using a range of thermodynamic methods, as best suited to the different process stages. The catalyst loading within the reactor can be effectively distributed according to the underlying kinetics, and the overall plant layout lets foresee the best routes for the material recycling. The detailed reaction modeling and the choice of the thermodynamic models proved essential to obtain reliable predictions. Setting a target yield of 105 tons/year of polymer-grade ethylene, the reactive section must be fed with 76 tons/h of diluted ethanol and operated below 400 °C. The energy input amounts to 17 MWel plus 73 MWth. This newly designed process sets out sustainable ethylene production on a detailed and reassessed computational basis.