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Die Offshore-Windenergie spielt eine wichtige Rolle beim angestrebten Übergang zu einer emissionsfreien Industrie während der nächsten Jahrzehnte. Allerdings beeinflusst die Gründung der Offshore-Windanlagen den gesamten Installationsprozess. Die Anwendung von Leichtbauprinzipien im Stahlbau, wie beispielsweise die Verwendung von aufgelösten Tragstrukturen, sogenannten Jacket-Fundamenten, bietet ein großes Potenzial zur Reduzierung des Ressourcenverbrauchs, insbesondere im Hinblick auf die benötigte Stahlmenge. Der Vortrag befasst sich daher mit der vollständigen Digitalisierung der schweißtechnischen Fertigungs- und Prüfkette. Ziel ist es, eine vollautomatische Fertigung sowie Qualitätsprüfung von Rohrknoten zu ermöglichen. Diese stellen ein Schlüsselelement von Jacket-Fundamenten dar. Des Weiteren wird der Zusammenhang zwischen der Geometrie der Schweißnaht und der resultierenden Ermüdungsfestigkeit durch numerische Methoden unter Einbeziehung bionischer Prinzipien bewertet. Es wird gezeigt, dass rohrförmige Knoten unter Berücksichtigung von Geometrietoleranzen vollautomatisch geschweißt werden können. Die Schweißnahtform konnte gemäß den numerischen Modellen hergestellt werden, was ein großes Potenzial für eine verlängerte Lebensdauer bietet. Anschließend erfolgt eine Bewertung der Verbesserungen bei der Ressourceneffizienz und der Verringerung des CO2-Fußabdrucks durch ein Life Cycle Assessment.
Life cycle assessment of fusion welding processes considering upstream and downstream process steps
(2023)
In manufacturing, fusion welding processes consume significant resources, presenting a significant opportunity for reducing environmental impact. Although there is a qualitative understanding of the environmental implications of these processes, a quantitative assessment of key parameters remains complex. This study introduces a welding-specific methodology that employs life cycle assessment (LCA) to quantitatively evaluate the environmental footprint of fusion welding technologies. Our approach identifies and analyses the principal parameters affecting the environmental performance of various welding techniques, including traditional joint welding and additive manufacturing via the Direct Energy Deposition-Arc (DED-Arc) process. Real-time resource usage data is integrated to offer an innovative framework for directly deriving environmental impacts. This research contributes to optimising welding processes by providing a precise and quantifiable measure of their ecological impact. This facilitates the advancement of sustainable manufacturing practices.
Im Verbundprojekt R-Rhenania wird eine industrielle Demonstrationsanlage am Standort der Monoverbrennungsanlage Altenstadt der Firma Emter errichtet und im Jahr 2024 den Betrieb aufnehmen. Die vorhandene Rostfeuerung-Monoverbrennung wird so umgebaut, dass ein neues thermochemisches Verfahren integriert werden kann, welches hochwirksame und schadstoffarme Dünger produziert (bis zu 17.000 t/a). Die thermochemischen Produkte werden in Gefäß- und Feldversuchen im ökologischen Landbau auf ihre Düngewirkung getestet. Die Umweltverträglichkeit der Demonstrationsanlage wird untersucht, wie auch die Übertragbarkeit des Verfahrens auf weitere Regionen.
Acetogenic bacteria produce CO2-based chemicals in aqueous media by hydrogenotrophic conversion of CO2, but CO is the preferred carbon and electron source. Consequently, coupling CO2 electrolysis with bacterial fermentation within an integrated bio-electrocatalytical system (BES) is promising, if CO2 reduction catalysts are available for the generation of CO in the complex biotic electrolyte. A standard stirred-tank bioreactor was coupled to a zero-gap PEM electrolysis cell for CO2 conversion, allowing voltage control and separation of the anode in one single cell. The cathodic CO2 reduction and the competing hydrogen evolution enabled in-situ feeding of C. ragsdalei with CO and H2. Proof-of-concept was demonstrated in first batch processes with continuous CO2 gassing, as autotrophic growth and acetate formation was observed in the stirred BES in a voltage range of −2.4 to −3.0 V. The setup is suitable also for other bioelectrocatalytic reactions. Increased currents and lower overvoltages are however required. Atomically-dispersed M−N−C catalysts show promise, if degradation throughout autoclaving can be omitted. The development of selective and autoclavable catalysts resistant to contamination and electrode design for the complex electrolyte will enable efficient bioelectrocatalytic power-to-X systems based on the introduced BES.
Here, we show that calcium sulfate dihydrate (gypsum) can be directly, rapidly and reversibly converted to calcium sulfate hemihydrate (bassanite) in high salinity solutions (brines). The optimum conditions for the efficient production of bassanite in a short time (<5 min) involve the use of brines with c(NaCl) > 4 M and maintaining a temperature, T > 80 °C. When the solution containing bassanite crystals is cooled down to around room temperature, eventually gypsum is formed. When the temperature is raised again to T > 80 °C, bassanite is rapidly re-precipitated. This contrasts with the better-known behaviour of the bassanite phase in low-salt environments. In low-salinity aqueous solutions, bassanite is considered to be metastable with respect to gypsum and anhydrite, and therefore gypsum-to-bassanite conversion does not occur in pure water. Interestingly, the high-salinity transformation of gypsum-to-bassanite has been reported by many authors and used in practice for several decades, although its very occurrence actually contradicts numerical thermodynamic predictions regarding solubility of calcium sulfate phases. By following the evolution of crystalline phases with in situ and time-resolved X-ray diffraction/scattering and Raman spectroscopy, we demonstrated that the phase stability in brines at elevated temperatures was inaccurately represented in the thermodynamic databases. Most notably for c(NaCl) > 4 M, and T > 80 °C gypsum becomes readily more soluble than bassanite, which induces the direct precipitation of the latter from gypsum. The fact that these transformations are controlled by the solution provides extensive opportunities for precise manipulation of crystal formation. Our experiments confirmed that bassanite remained the sole crystalline phase for many hours before reverting into gypsum. This property is extremely advantageous for practical processing and efficient crystal extraction in industrial scenarios.
AbstractRed mud is the waste of bauxite refinement into alumina, the feedstock for aluminium production1. With about 180 million tonnes produced per year1, red mud has amassed to one of the largest environmentally hazardous waste products, with the staggering amount of 4 billion tonnes accumulated on a global scale1. Here we present how this red mud can be turned into valuable and sustainable feedstock for ironmaking using fossil-free hydrogen-plasma-based reduction, thus mitigating a part of the steel-related carbon dioxide emissions by making it available for the production of several hundred million tonnes of green steel. The process proceeds through rapid liquid-state reduction, chemical partitioning, as well as density-driven and viscosity-driven separation between metal and oxides. We show the underlying chemical reactions, pH-neutralization processes and phase transformations during this surprisingly simple and fast reduction method. The approach establishes a sustainable toxic-waste treatment from aluminium production through using red mud as feedstock to mitigate greenhouse gas emissions from steelmaking.
Im Verbundforschungsprojekt REALight wurden Leichtgranulate aus gemischtem Mauerwerkbruch in einem thermischen Blähverfahren im Pilotmaßstab hergestellt. Im Teilprojekt der BAM stand die Charakterisierung dieser Leichtgranulate und ihre Anwendung in gebundenen Systemen im Vordergrund. Im Rahmen des Abschlussvortrags wurden Ergebnisse zur Entwicklung von Steinergänzungsmörteln sowie Infraleichtbeton vorgestellt.
Fused cement clinker can be produced from molten basic oxygen furnace slag (BOFS) by way of a reductive thermochemical treatment. During the thermochemical treatment, oxidic iron is reduced to metallic iron and separated. The resulting low-iron slag has a chemical and mineralogical composition similar to ordinary Portland cement (OPC) clinker. In this study, the hydraulic reactivity of the fused clinker from BOFS with and without gypsum was investigated using isothermal calorimetry, differential scanning calorimetry, in situ X-ray diffraction and powder X-ray diffraction. Furthermore, a synthetic fused clinker without foreign ions and fused clinker produced by a mixture of both materials was studied. The hydraulic reaction of the fused clinker from BOFS was considerably slower than that of OPC. However, the reaction can be accelerated by adding gypsum as a sulfate carrier. Furthermore, the results showed an increased reaction rate with decreasing content of foreign ions such as Fe, P or Mn.