Mixing in Chemical Reactors

Mixing is at the core of many industrial processes that require the contact of reactants for chemical reactions or the homogenisation of solutions or emulsification of two-phases. The research objectives of this area range from theoretical fundamental studies to the development of robust strategies for the scale-up of chemical reactors and the conception of new mixing technologies. Advanced modelling tools such as Computational Fluid Dynamics (CFD) and network modelling, along with experimental techniques such as Planar Laser-Induced Fluorescence (PLIF), Particle Image Velocimetry (PIV), shadowgraphy, and micromixing test systems, are used to optimize mixing processes for enhanced efficiency and effectiveness across diverse industrial applications.

Two principal mixing technologies have been developed and studied: NETMIX, a novel patented static micro/meso-structured mixer and reactor based on a network of chambers connected by channels, permitting efficient and reproducible control of a fluid mixture, particularly suited for the continuous production of nanomaterials; and CIJs - Confined Impinging Jets mixers with high throughputs and robust operation for mixing of fluids with very dissimilar flow rates and viscosities.

NETmix is being used in industrial processes and has been adopted by other research groups to enhance their technologies, overcoming mass and heat transfer limitations, and increasing technology readiness levels. Recent advancements in NETmix include studies in multiphase flow based on CFD and experimental fluid mechanics techniques. Multiphase NETmix applications include hydrate production and water ozonation, as well as electrochemical reactions, notably in hydrogen production—an essential field for Portugal's Energy Transition Agenda, integrated within the country's Recuperation and Resilience Plan.

CIJs have addressed the challenge of mixing dissimilar fluids at stoichiometric flow rate ratios in Reaction Injection Moulding (RIM) processes through the introduction of a general design equation for injectors, revolutionizing Polymer Engineering research and extending CIJs applications to continuous fast emulsification processes. Margarida Brito's PhD research in this topic earned her the Young Research Award in Mixing from EFCE.

Research and development of these mixing technologies have led to advances in mixing science, including new codes for Lagrangian Mixing Simulation, fundamental studies on flow via Proper Orthogonal Decomposition (POD) and its applicability, and innovative experimental methods for micromixing visualization through Reactive Planar Laser-Induced Fluorescence (PLIF). The concept of 2D laminar mixing has been pioneered, resulting in technologies with optimized scales that achieve faster, and more efficient mixing compared to traditional stirred mixers or micro-scaled mixers.

The transition from traditional stirred mixers to advanced technologies with higher performance, overcoming the throughput limitations of micro devices, embodies the main contribution of our group's research. The two cornerstone technologies are being exploited by spin-off companies Fluidinova ( and MICE-molds ( Additionally, NETmix is the core technology of CoLAB NET4CO2, affiliated with Petrogal, Portugal's leading oil company.

Major projects in this research area include: