Modelling and simulation of counter-current and confined jet reactors for hydrothermal synthesis of nano-materials

•CFD and PB modelling for two jet reactors for nanomaterial production is carried out under supercritical conditions.•Predicted temperatures for both reactors are in good agreement with measurements.•Performance of counter-current and confined jet reactors is compared based on nanoparticle size distribution.•Key factors affecting reactor performance are identified as insertion length and tube diameters.•Confined jet reactor offers advantages such as faster mixing and more uniform size distributions.

A confined jet mixer and a counter-current mixer for the continuous hydrothermal flow synthesis of TiO2 nano-materials under supercritical water conditions have been investigated using computational fluid dynamics (CFD). The fluid flow and heat transfer behaviour, including velocity and temperature profiles in both reactor configurations, are studied using the CFD tool ANSYS Fluent. The tracer concentration profiles are also simulated via solving species equations from which the mixing behaviour in the reactors is examined. A combined CFD and population balance model is used to predict the size distribution. The predicted temperature distributions for both reactors were found to be in good agreement with experimentally measured data. Detailed comparison of the hydrodynamic and thermal behaviours, and particle size distributions between the two reactors helped in the identification of key factors that affect the reactor performance, and also provided suggestions for reactor design optimisation and scale-up.