Application of Liquidus Projections in SiO2-Al2O3-CaO Systems with Fe2O3 and V2O5 to Study the Dissolution of Alumina Crucibles in Gasification Slags Containing Vanadium.

Entrained flow gasification occurring above 1400 °C is a technique to convert petroleum coke, a byproduct of petroleum refining, into synthesis gas. The molten ash/slag formed in the process has a high amount of V and Ni compounds, which are corrosive to the reactor walls. Slag viscosity is an important parameter that must be controlled to tap the slag from the gasifier. The viscosity of the slags is measured in high-temperature viscometers. Alumina crucibles, used in viscosity measurements, were severely corroded by high V/Ni slags in several in-house experiments. To study the chemistry of these dissolutions, saturation solubilities of alumina crucibles in the slags (at 1500 °C) and precipitated primary phases were determined from liquidus projections prepared in Factsage. The 10 slags considered in this study were composed of SiO2 (<50.2 wt %), Al2O3 (<29.2 wt %), Fe2O3 (<41.4 wt %), CaO (<16.6 wt %), NiO (<20.4 wt %), and V2O5 (<20.5 wt %). The precipitated primary phases were corundum (solid solution), spinel (solid solution), V_spinel (solid solution), mullite (solid solution), and anorthite. Experiments were performed with ash placed on alumina discs in a reducing atmosphere. The ash compositions were based on previous in-house viscosity and ash melting experiments. Saturation solubilities were above 30 wt % in multiple tests with perforated and intact crucibles. In two such cases, hercynite, which can inhibit slag penetration into a crucible, was predicted as a primary phase. In another test with an intact crucible, anorthite, which leads to indirect dissolution, was predicted as a primary phase and was also identified in the X-ray diffraction (XRD) results of the slag-crucible interface. Here, saturation solubility was 8.9 wt %. It was concluded that determination of saturation solubilities and primary phases would lead to successfully measuring the viscosity of slags containing V and Ni in alumina crucibles.

Switchable Explosives: Performance Tuning of Fluid-Activated High Explosive Architectures.

We present our discovery of switchable high explosives (HEs) as a new class of energetic material that cannot detonate unless filled with a fluid. The performance of fluid-filled additive-manufactured HE lattices is herein evaluated by analysis of detonation velocity and Gurney energy. The Gurney energy of the unfilled lattice was 98% lower than that of the equivalent water-filled lattice and changing the fluid mechanical properties allowed tuning of the Gurney energy and detonation velocity by 8.5% and 13.4%, respectively. These results provide, for the first time since the development of HEs, a method to completely remove the hazard of unplanned detonations during storage and transport.

Circular economy priorities for photovoltaics in the energy transition.

Among the many ambitious decarbonization goals globally, the US intends grid decarbonization by 2035, requiring 1 TW of installed photovoltaics (PV), up from ~110 GW in 2021. This unprecedented global scale-up will stress existing PV supply chains with increased material and energy demands. By 2050, 1.75 TW of PV in the US cumulatively demands 97 million metric tonnes of virgin material and creates 8 million metric tonnes of life cycle waste. This analysis leverages the PV in Circular Economy tool (PV ICE) to evaluate two circular economy approaches, lifetime extension and closed-loop recycling, on their ability to reduce virgin material demands and life cycle wastes while meeting capacity goals. Modules with 50-year lifetimes can reduce virgin material demand by 3% through reduced deployment. Modules with 15-year lifetimes require an additional 1.2 TW of replacement modules to maintain capacity, increasing virgin material demand and waste unless >90% of module mass is closed-loop recycled. Currently, no PV technology is more than 90% closed-loop recycled. Glass, the majority of mass in all PV technologies and an energy intensive component with a problematic supply chain, should be targeted for a circular redesign. Our work contributes data-backed insights prioritizing circular PV strategies for a sustainable energy transition.

Nano-mechanical properties of Fe-Mn-Al-C lightweight steels.

High Al Low-density steels could have a transformative effect on the light-weighting of steel structures for transportation. They can achieve the desired properties with the minimum amount of Ni, and thus are of great interest from an economic perspective. In this study, the mechanical properties of two duplex low-density steels, Fe-15Mn-10Al-0.8C-5Ni and Fe-15Mn-10Al-0.8 C (wt.%) were investigated through nano-indentation and simulation through utilization of ab-initio formalisms in Density Functional Theory (DFT) in order to establish the hardness resulting from two critical structural features (κ-carbides and B2 intermetallic) as a function of annealing temperature (500-1050 °C) and the addition of Ni. In the Ni-free sample, the calculated elastic properties of κ-carbides were compared with those of the B2 intermetallic Fe3Al-L12 and the role of Mn in the κ structure and its elastic properties were studied. The Ni-containing samples were found to have a higher hardness due to the B2 phase composition being NiAl rather than FeAl, with Ni-Al bonds reported to be stronger than the Fe-Al bonds. In both samples, at temperatures of 900 °C and above, the ferrite phase contained nano-sized discs of B2 phase, wherein the Ni-containing samples exhibited higher hardness, attributed again to the stronger Ni-Al bonds in the B2 phase. At 700 °C and below, the nano-sized B2 discs were replaced by micrometre sized needles of κ in the Ni-free sample resulting in a lowering of the hardness. In the Ni-containing sample, the entire α phase was replaced by B2 stringers, which had a lower hardness than the Ni-Al nano-discs due to a lower Ni content in B2 stringer bands formed at 700 °C and below. In addition, the hardness of needle-like κ-carbides formed in α phase was found to be a function of Mn content. Although it was impossible to measure the hardness of cuboid κ particles in γ phase because of their nano-size, the hardness value of composite phases, e.g. γ + κ was measured and reported. All the hardness values were compared and rationalized by bonding energy between different atoms.

Quantifying the Pathway and Predicting Spontaneous Emulsification during Material Exchange in a Two Phase Liquid System.

Kinetic restriction of a thermodynamically favourable equilibrium is a common theme in materials processing. The interfacial instability in systems where rate of material exchange is far greater than the mass transfer through respective bulk phases is of specific interest when tracking the transient interfacial area, a parameter integral to short processing times for productivity streamlining in all manufacturing where interfacial reaction occurs. This is even more pertinent in high-temperature systems for energy and cost savings. Here the quantified physical pathway of interfacial area change due to material exchange in liquid metal-molten oxide systems is presented. In addition the predicted growth regime and emulsification behaviour in relation to interfacial tension as modelled using phase-field methodology is shown. The observed in-situ emulsification behaviour links quantitatively the geometry of perturbations as a validation method for the development of simulating the phenomena. Thus a method is presented to both predict and engineer the formation of micro emulsions to a desired specification.

Spontaneous Emulsification as a Function of Material Exchange.

Direct visualization at 1873 K of 0% to 8% molten FeAl droplets suspended in a SiO2 enriched oxide medium was carried out to image the evolution of droplet morphology during reaction between Al and SiO2. Phenomena such as perturbation growth, necking and budding of offspring droplets from a bulk body are observed. The observations are used to discuss and inform a new approach to the nature of interfacial tension and the impact this has on concepts used to define interfacial tension for a two phase system with material exchange across the interface. The mapping of global interfacial tension coupled with free energy dissipation has been used to give an energetic reasoning as to the behaviour seen with respect to aluminium content in the metal phase.

A Fe-C-Ca big cycle in modern carbon-intensive industries: toward emission reduction and resource utilization.

Herein a big Fe-C-Ca cycle, clarifying the basic element flows and energy flows in modern carbon-intensive industries including the metallurgical industry and the cement industry, was proposed for the first time in the contexts of emission reduction and iron ore degradation nowadays. This big cycle was focused on three industrial elements of Fe, C and Ca and thus it mainly comprised three interdependent loops, i.e., a C-cycle, a Fe-cycle and a Ca-path. As exemplified, we started from the integrated disposal of hot steel slags, a man-made iron resource via char gasification and the employment of hematite, a natural iron resource greatly extended the application area of this idea. Accordingly, based on this concept, the theoretical potentials for energy saving, emission reduction and Fe resource recovery achieved in modern industry are estimated up to 7.66 Mt of standard coal, 63.9 Mt of CO2 and 25.2 Mt of pig iron, respectively.

Integration of coal gasification and waste heat recovery from high temperature steel slags: an emerging strategy to emission reduction.

With the continuous urbanization and industrialization in the world, energy saving and greenhouse gas (GHG) emission reduction have been serious issues to be addressed, for which heat recovery from traditional energy-intensive industries makes up a significant strategy. Here we report a novel approach to extract the waste heat and iron from high temperature steel slags (1450-1650 (o)C) produced in the steel industry, i.e., integration of coal gasification and steel slag treatment. Both the thermodynamics and kinetics of the pertinent reactions were identified. It was clarified that the kinetic mechanism for gasification varied from A2 model to A4 model (Avrami-Erofeev) in the presence of slags. Most importantly, the steel slags acted not only as good heat carriers but also as effective catalysts where the apparent activation energy for char gasification got remarkably reduced from 95.7 kJ/mol to 12.1 kJ/mol (A2 model). Furthermore, the FeO in the slags was found to be oxidized into Fe3O4, with an extra energy release, which offered a potential for magnetic separation. Moreover, based on the present research results, an emerging concept, composed of multiple industrial sectors, was proposed, which could serve as an important route to deal with the severe environmental problems in modern society.