AbstractFluid dynamics and its influence on heat and mass transport rates in gas–liquid reactors is, in general, an important starting point for development of a process design. Improvements in the understanding of these aspects can be particularly fruitful in the case of urea reactors where the fluid‐dynamic patterns are complicated by the co‐current flow of two phases and the bubbling mode of the vapors. The analysis of such systems highlighted the non‐optimal design of existing reactors and led to the conception of new reactor internals. Several industrial applications demonstrate the ability of the new configuration to improve reactor efficiency. Both energy‐saving and production increases were obtained. This is a further demonstration that even mature technologies can be improved, leading not only to economic advantages, but also to a reduction in their environmental impact.© 2003 Society of Chemical Industry