Scientific Events

Besides their ubiquitous use in load-bearing structures, metals also possess qualities of energetic materials. Lithium, for example, is a common fuel in batteries, while aluminum is frequently added to solid rocket propellants and used in pyrotechnics. At high temperatures, metal powders can be burned in air in a similar way to hydrocarbon fuels, releasing chemically stored energy as sensible heat. Contrary to hydrocarbon combustion, however, the main reaction products are solid oxide particles that can, in principle, be retrieved from the exhaust fumes. This amenability to oxide sequestration has stimulated the idea of harnessing metal powders as recyclable energy carriers which are burned, retrieved and, subsequently, recharged by a reduction process based on clean primary energy. Conceptually, the metal powders are akin to high-temperature batteries, serving as a means to buffer the large spatial and temporal intermittency associated with renewable energy sources. Motivated by the potential use of metal powders as recyclable fuels, we qualitatively discuss the physical and chemical processes involved in the combustion of a single metal particle and of metal dusts, respectively. Subsequently, a population balance model for predicting the size distribution of the oxide smoke precipitating in the vicinity of a single burning aluminum particle is presented. Here, we specifically focus on the kinetic rates that control the phase transitions and smoke dynamics, integrating recently developed detailed kinetics for gas phase and heterogeneous surface reactions. The population balance equation governing the oxide size distribution is solved with the aid of a tailored adaptive grid method. An alternative, potentially more economical solution approach we propose is based on an embedded reduced order representation of the particle size distribution that is informed by a training step. The accuracy and convergence properties of this method are investigated for a simplified test case involving particle growth and dispersion in a laminar plane jet. In the final part of the seminar, the physical description, from an Eulerian viewpoint, of metal powders is discussed with a particular emphasis on the ramifications of carrier flow turbulence. In order to account for the small-scale interactions between dispersed particles and the ambient gas phase, the population balance equation governing the metal powder or oxide smoke is integrated into a probabilistic description that naturally accounts for the variability among independent realizations of a turbulent, particle-laden flow. Owing to the high dimensionality of the resulting transport equations, a stochastic solution approach based on Eulerian stochastic fields is proposed for which we show preliminary accuracy and convergence analyses.

Abstract: Many layered materials of interest for electrochemical energy storage and conversion applications are flexible hosts whose interlayers can be expanded to accommodate not just ions but also solvents, organic molecules, polymers, and organometallics. When these “hybrid” materials are placed into an electrochemical environment, the distinction between surface and bulk becomes blurred since the electrochemical interface can now be viewed to extend into the interlayer. During this seminar, I will discuss fundamental aspects of charge storage at electrochemical interfaces and how interfacial charge storage and reactivity change under confinement. I will also describe synthesis of hybrid layered materials and the use of in situ and operando characterization to understand the relationships between structure and composition and the resulting electrochemical reactivity. [more]

Metal powder has superior energy density compared to fossil fuels and hydrogen. Therefore, metal powders have gained interest as a material for energy storage. The main benefits of metal fuels are that they do not produce CO2 emissions during combustion, they have the potential to be retrofitted in existing coal power plants and they can fit into the existing fuel transportation infrastructure. Furthermore, this enables the production of sustainable energy since metal fuels can be regenerated from metal oxides, using hydrogen from renewable sources. In this presentation, the main characteristics of metal fuels are presented with a final focus on clean combustion. A series of burners has been developed: - single particle or fuel jet in a micro burner to study single particle combustion and particle-particle interaction - Bunsen-type burner for stabilizing laminar and weakly turbulent premixed flames - Tornado-swirl burner First numerical studies are also started for comparison. Furthermore, a 100 KW demonstrator set-up is developed to demonstrate clean combustion to produce steam (placed at Swinkels brewery and Metalot centre). Studies to scale up are also conducted. The main objective of this practical systems is the development of an integrated flexible metal fuel burner with a capacity of 100 KW (TRL5). This is an essential step towards implementation of this sustainable technology. This project forms the basis to further develop full scale burners with a capacity of 10 MWth. The development of the prototype burner is executed by a consortium which covers the entire supply chain. This includes the production of metal powder, fuel preparation, burner and combusted product handling. The industrial partners have broad experience in metal powder supply, dense energy carriers and operating coal fired power plants. Furthermore, techno-economic analyses and the assessment of retrofit potential to existing assets will be carried out. Status-quo will be presented [more]

In this presentation the formation of spinel (MgAl₂O₄) by reaction between periclase (MgO) and corundum (Al₂O₃) is addressed. The reaction MgO + Al₂O₃ => MgAl₂O₄ may be regarded as a model case for diffusive phase transformations in oxide systems. All phases involved are moderately to highly refractory and have applications in ceramics. Above about 800°C, periclase and corundum react to form a layer of polycrystalline spinel at their interface. A pronounced dichotomy of the internal microstructure and texture of the spinel layer reveals the original position of the periclase-corundum interface. This reflects the direction and extent of the necessary Mg²⁺ and Al³⁺ transfer across the spinel layer and allows to quantify the underlying diffusion process. Systematic deviations of the Mg/Al ratio of the spinel from local equilibrium values at the spinel-periclase and the spinel-corundum interface are due to a finite mobility of the two reaction interfaces. The resistance against interface motion arises from dislocation climb at the periclase-spinel interface, which is complemented by the formation of Schottky defects in the reactant periclase. In contrast, the corundum-spinel interface moves by the glide of partial dislocations. This is energetically less expensive than the dislocation climb at the periclase-spinel interface and allows for comparatively rapid approximation of local equilibrium. [more]

The extraction and processing of resources are directly linked to 50% of all human-induced climate impacts and 90% of biodiversity losses (Bruno Oberle et al., 2019). Promoting resource efficiency is therefore recognised worldwide as a solution approach to counteract this rapid development. The circular economy (CE) approach brings new dynamism to the discussion of the well-known concept of resource efficiency (van Ewijk, 2018; Weizsäcker et al., 1997). Both approaches aim to reduce resource use and thus prevent tremendous environmental impacts. For example, the CE is thought to be crucial for reaching climate neutrality by 2050 as well as decoupling of economic growth and resource use (European Commission, 2020). Studies estimate that eco-design, waste prevention and reuse may result in up to EUR 600 billions of savings for businesses in Europe (Kalmykova et al., 2018). The metal industry is of high importance in this discussion as metal production is responsible for 8% of the global energy expenditure (UNEP 2013). Steel production alone is responsible for a quarter of all industrial GHG emissions (Allwood et al., 2011; Ito et al., 2020). However, the metal industry and especially the steel industry can look back on a long history of recycling as a core principle of the CE resulting in great resource savings. Nevertheless, there are major doubts as to whether future steel production can be covered entirely by secondary material. This is due to the dependency of the recycling infrastructure on primary metallurgy, the limits of recycling and the low degree of circularity of steel (Haas et al., 2015; Pauliuk, Wang, et al., 2013; Steger et al., 2018; Xylia et al., 2018). In the presentation, the challenges of resource use in general as well as the possible strategies of the Circular Economy are presented and their applicability for the field of metals, in particular steel, is discussed. To illustrate this, project examples will be presented in which, on the one hand, the CE strategies of re-purposing/re-manufacturing and, on the other hand, a technical approach of sorting by specific type for recyling will be illustrated. [more]

Natural materials are multifunctional. Consider the simple shell of a gastropod: it evolved to achieve balance during locomotion, protection against predation and dehydration, storage of mineral, anchoring structure for muscles… And what is fascinating is that all this is realised using 95% of calcium carbonate. As a comparison, the engineered equivalent of a mollusc shell would be chalk, a material with very low functionalities… The key difference between natural and most engineered materials is the intricate microstructures in which the building blocks (calcium carbonate in our example) are arranged. Developing the tools to translate these microstructures into engineered materials would allow us to better understand microstructure-properties relationships. Ultimately, this could create new sets of materials with unique combinations of properties.In this seminar, I will present the latest progress from our group on the fabrication of bioinspired microstructures for engineering and discuss the potential of those materials. [more]

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