Reactive gas-liquid two-phase porous media flows are common in industrial processes as well as nature. Examples, are geological flows and particle impregnation. In this proposed research we will focus on reactive flows in trickle-beds. Trickle-beds are columns packed with catalytically active particles with a co-current downflow of a gas-liquid mixture. They are an important reactor type often applied in chemical industry for, e.g., hydrogenation reactions. Upscaling of trickle-beds from lab-scale to industrial scale is problematic due to the complex gas-liquid hydrodynamics (with possibly incomplete wetting), mass and heat transfer, and reactions taking place inside the catalytic particles. To obtain a better qualitative understanding of the complex interplay of transport phenomena and reactions we propose a combined computational and experimental approach. Three PhD students will collaborate to get a quantitative understanding of the relevant phenomena at a particle-resolved level. The first PhD will focus on the liquid-gas hydrodynamics outside the particles. A massively parallel particle-resolved model with thousands of particles will be developed that implements a combined volume-of-fluid and immersed-boundary method. This student will also be in charge of implementing (external) mass and heat transfer. Because of the high Schmidt/Prandtl number in the liquid phase thin mass/temperature boundary layers are expected. To tackle this an adaptive-mesh-resolution approach will be used for this scalar transport. This first PhD student has a computational/numerical signature. PhD 2 will focus on modeling the transport phenomena and reaction inside the particles. The transport through the porous material will be described by a Dusty-Gas type model that includes diffusive as well as convective transport. The transport of reactants and products will be combined with advanced modeling of the catalytic reaction kinetics. We propose to implement micro-kinetic models through the use of lookup tables. The 3rd PhD student focusses on experimental validation using MRI. First, a cold-flow setup will be used to characterize the gas-liquid hydrodynamics. Liquid hold-up, (partial) wetting as well as liquid velocities will be measured with a particle-resolved accuracy. Last, reactive flows will be investigated using the model reaction of hydrogenation of α-methylstyrene to cumene. A unique feature of the proposal is the close collaboration of the three subprojects. After the initial phase of method development the scopes of the projects will be widened through this collaboration. When the cold-flow setup and the hydrodynamic code is developed PhD 3 and PhD 1 will collaborate in a validation study. A one-to-one comparison between particle-resolved simulations and MRI measurements will be the result. PhD 1 and 2 will collaborate to merge the hydrodynamic code and the particle modeling into one model that included mass and heat transfer inside and outside the particles. This code will make it possible to investigate the interplay of transport phenomena and reaction for systems of thousands of particles (still particle-resolved). PhD 2 and 1 will also collaborate on more detailed particle modelling, say, for 1 or a few particles. For (partially) wetted particles there will be both liquid and gas present in the particles. Convective flow in macro pores will be relevant. The liquid-gas porous media flow was developed by PhD 1 can be applied to investigate this. This will show in detail how the two-phase flow inside a single pellet interacts with reaction, heat creation, and phase change (due to evaporation). The interplay of flow, transport and reaction at both the bed level and for single particles determined in the simulation and measured in the reactive MRI setup will be compared. This will be the final piece-de-resistance of this project: a detailed one-to-one comparison of particle-resolved simulations and MRI experiments for hydrogenation α-methylstyrene to cumene in a trickle bed.

This is a continuation proposal for CPU time on the national supercomputer Snellius for the group Multi-scale Modelling of Multi-phase Flows of the Chemical Engineering and Chemistry Department at the TU Eindhoven. The computational research on this group deals with modelling of flow, heat and mass transfer in multi-phase reactors. We focus on gas-solid systems (e.g. fluidized beds and porous materials), gas-liquid (e.g. bubbly flows) and gas-liquid-solid (e.g. trickle beds). Simulations are either highly resolved or more coarse-grained. The usage of super computers such as Snellius is essential for this research.

Iron powder is a new promising high-energy density, CO2-free energy carrier. When iron particles are combusted, heat and power are generated. The combustion products, iron oxides, are recovered and converted back into iron using green hydrogen. Contrary to other storage and conversion concepts, iron powders are simple to store at large scale, safe to handle and transportable. CIRCL focuses on dedicated experiments and advanced numerical simulations of the regeneration of the iron oxides back to iron in a fluidized bed using green hydrogen. This will enable future scale-up to industrial size applications of the metal energy storage and conversion system.

Efficient processes for converting renewable electrical energy into hydrogen are crucial for achieving the energy transition. Large-scale production of hydrogen is possible by splitting water into hydrogen and oxygen by electrolysis. However, electrolysis has a low efficiency that is closely related to the flow and transport phenomena near electrodes, especially around the hydrogen bubbles formed. In this project, researchers study the formation of hydrogen bubbles, the transport of chemicals near the bubbles and electrodes, and the interaction between bubbles. The insights from the research can be used by the industrial companies involved to make their electrolysis processes much more efficient.