Technische Universität Bergakademie Freiberg: Qucosa
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Implementation of Carbonates and CO2 into the T-dependent Pitzer Model of Oceanic Systems. I. System NaOH – Mg(OH)2 – Ca(OH)2 – CO2 – H2O
Full text linkThe THEREDA model has been extended by phases and species formed within the title system. A temperature range of 0 °C to 100 °C is considered. Most of the solubility products, Pitzer parameters and association constants were adapted from the model of Königsberger et al. (Königsberger, E., Königsberger, L.-C., Gamsjäger, H.: Low-temperature thermodynamic model for the system Na2CO3−MgCO3−CaCO3−H2O. Geochim. Cosmochim. Acta, 63, (1999), pp. 3105–3119, DOI 10.1016/S0016-7037(99)00238-0). Literature on solubility data of carbonates of magnesium and calcium is critically evaluated. As far as experimental solubility data were available, they were compared with model calculations. The data comprise the minerals magnesite (MgCO3), nesquehonite (MgCO3∙3H2O), lansfordite (MgCO3∙5H2O), hydromagnesite (4MgCO3∙Mg(OH)2∙4H2O), dypingite (4MgCO3∙Mg(OH)2∙5H2O), calcite (CaCO3), aragonite (CaCO3), vaterite (CaCO3), ikaite (CaCO3∙6H2O), dolomite (MgCO3∙CaCO3), huntite (3MgCO3∙CaCO3), magnesian calcite (solid solution between CaCO3 and MgCO3), eitelite (Na2CO3·MgCO3), pirssonite (Na2CO3·CaCO3·2H2O), gaylussite (Na2CO3·CaCO3·5H2O), natrite (Na2CO3), thermonatrite (Na2CO3·H2O), Na2CO3·7H2O, natron (Na2CO3·10H2O), nahcolite (NaHCO3), wegscheiderite (Na2CO3·3NaHCO3) and trona (Na2CO3·NaHCO3·2H2O). There are minerals known as artinite (MgCO3∙Mg(OH)2∙3H2O) or barringtonite (MgCO3·2H2O), for which no solubility data exist. The literature survey also covers geochemical observations on the existence of carbonate minerals, laboratory investigations on the decomposition, formation and conversion as well as spectral and XRD characterization of carbonate phases.
For important minerals, such as magnesite or hydromagnesite, the uncertainty of the solubility constants is large.
The added Pitzer parameters, concern the binary cation - carbonate, cation - hydrogen carbonate and the ternary interactions, including mixing parameters of the anions HCO3-, CO32- and OH-. Mixing parameters of these anions with chloride or sulfate are not considered in this work. From the data situation and the modelling results, conclusions are drawn with respect to future experimental work to obtain more reliable equilibrium data
Field Studies on the Effect of Bioaugmentation with Bacillus amyloliquefaciens FZB42 on Plant Accumulation of Rare Earth Elements and Selected Trace Elements
Full text linkThis study is an investigation of the effect of soil bioaugmentation (inoculation) on a field scale with the commercially available product RhizoVital®42, containing Bacillus amyloliquefaciens FZB4, on element bioavailability, plant biomass production, as well as accumulation of rare earth elements (REEs), germanium, and selected trace elements. Zea mays and Helianthus annuus were selected as test plants. Post-harvest, results showed inoculation increased biomass production of Z. mays and H. annuus by 24% and 26%, albeit insignificant at p ≤ 0.05. Bioaugmentation enhanced Z. mays shoot content of P, Cd, and Ge by percentages between 73% and 80% (significant only for Ge) and decreased shoot content of REET, Pb, and Cu by 28%, 35%, and 59%, respectively. For H. annuus grown on bioaugmented soil, shoot content of Ca, Cu, Ge, REET, and Pb increased by over 40%, with a negligible decrease observed for Cd. Summarily, results suggest that bioaugmentation with Bacillus amyloliquefaciens FZB42 could enhance biomass production, increase soil element bioavailability enhance, and increase or reduce plant accumulation of target elements. Additionally, differences in P use efficiency could influence bioaugmentation effects on P accumulation
Thermoschock- und korrosionsbeständige wärmedämmende Werkstoffverbunde auf Basis von nachwachsenden Rohstoffen für den Einsatz im Stahluntergussverfahren: Abschlussbericht
Full text linkGegenstand des Projektes war die Erforschung eines innovativen Werkstoffkonzeptes für feuerfeste Steine, wie Rohr- und Kanalsteine, die im Stahluntergussverfahren eingesetzt werden. Durch die Kombination eines feuerfesten, wärmedämmenden Werkstoffs auf der Basis von Reisschalenasche (RSA) mit einer Aluminiumoxid- oder aluminiumoxidreichen, über Flammspritzen erzeugten Beschichtung sollten sowohl exzellente wärmedämmende Eigenschaften als auch eine hohe Beständigkeit gegenüber chemischen Wechselwirkungen mit der Stahlschmelze erreicht werden. Für RSA-Substrate wurde eine ausreichende Feuerfestigkeit mit einer starken nicht-linearen Dehnung festgestellt. Flammgespritzte Schichten auf Basis von Aluminiumoxid wurden umfangreich charakterisiert. Die hergestellten Werkstoffverbunde zeigten eine gute Hochtemperaturstabilität sowie Thermoschockbeständigkeit. In Kooperation mit dem Industriepartner wurden mittels Flammspritzen funktionalisierte Kanalrohrstein-Prototypen erfolgreich mit Stahlschmelze beaufschlagt. Die erstarrten Stahlblöcke wurden hinsichtlich ihrer Population nicht-metallischer Einschlüsse mit Hilfe einer neu entwickelten Routine (automatisierter Rasterelektronenmikroskopie) inkl. umfassender detaillierter und statistischer Auswertung charakterisiert. Die Ergebnisse der Abgussversuche zeigten sogar eine leicht geringere Einschlusspopulation im Stahl nach Kontakt mit dem neuentwickelten Werkstoffverbund im Vergleich zum Schamotte-basierten Referenzmaterial.
Das Projekt wurde von 2021 bis 2024 an der Technischen Universität Bergakademie Freiberg von der Deutschen Forschungsgemeinschaft (DFG) gefördert (Projektnummer 456277449) und erfolgreich beendet.:1 Allgemeine Angaben 1
2 Zusammenfassung / Summary 1
3 Wissenschaftlicher Arbeits- und Ergebnisbericht 3
3.1 Ausgangsfragen und Zielsetzung des Projektes 3
3.2 Beschreibung der projektspezifischen Ergebnisse und Erkenntnisse 3
4 Veröffentlichte Projektergebnisse 10
4.1 Publikationen mit wissenschaftlicher Qualitätssicherung 10
4.2 Weitere Publikationen und öffentlich gemachte Ergebnisse 10
4.3 Patente 11The aim of the project was to investigate an innovative material concept for refractory bricks, such as runner bricks, which are used in the steel ingot casting process. By combining a refractory, heat-insulating material based on rice husk ash (RSA) with an alumina or alumina-rich coating produced by flame spraying, both excellent heat-insulating properties and high resistance to chemical interactions with the molten steel were expected. For RSA substrates, sufficient refractoriness with strong non-linear elongation was found. Flame-sprayed coatings based on alumina were extensively characterized. The material composites produced exhibited good high-temperature stability and thermal shock resistance. In cooperation with the industrial partner, functionalized runner brick prototypes by means of flame spraying were successfully exposed to molten steel. The solidified steel blocks were characterized with regard to their population of non-metallic inclusions using a newly developed routine (automated scanning electron microscopy), including comprehensive detailed and statistical evaluation. The results of the casting tests even showed a slightly lower population of inclusions in the steel after contact with the newly developed composite material compared to the fireclay-based reference material.
The project was funded by the German Research Foundation (DFG) from 2021 to 2024 at the Technische Universität Bergakademie Freiberg (project number 456277449) and was successfully completed.:1 Allgemeine Angaben 1
2 Zusammenfassung / Summary 1
3 Wissenschaftlicher Arbeits- und Ergebnisbericht 3
3.1 Ausgangsfragen und Zielsetzung des Projektes 3
3.2 Beschreibung der projektspezifischen Ergebnisse und Erkenntnisse 3
4 Veröffentlichte Projektergebnisse 10
4.1 Publikationen mit wissenschaftlicher Qualitätssicherung 10
4.2 Weitere Publikationen und öffentlich gemachte Ergebnisse 10
4.3 Patente 1
Two polymorphs of N,N′-diphenyl-2-[1-(propylamino)ethylidene]propanediamide
No full textTwo polymorphs of the title compound, C20H23N3O2, have been isolated. Polymorph (I) crystallizes in the monoclinic space group P21/n and polymorph (II) in the tetragonal space group I41/a. The main difference between the two polymorphs on the molecular level is the orientation of the n-propyl group. This group is antiperiplanar in (I) and synclinal in (II). The core of the molecule consists of two carbamoyl units bound to an enamine unit. The most prominent features are intramolecular N—H⋯O hydrogen bonds in both polymorphs. Both polymorphs form dimers with graph set R22(12) via intermolecular N—H⋯O hydrogen bonds. Adjacent dimers of (I) are connected via a weak C—H⋯O interaction, resulting in a chain parallel to the crystallographic a-axis. The dimers of (II) are connected by weak C—H⋯π interactions, forming intermolecular chains along the c-axis direction
Synthesis and crystal structure of an ionic phenyltin(iv) complex of N-salicylidene-valine
No full textTriethylammonium dichloro[N-[(2-oxyphenyl)methylidene]valinato]-phenyl-tin(iv) was prepared and characterized by spectroscopic methods and single crystal X-ray crystallography. The compound consists of a triethylammonium cation and a tin complex as anion. The tin complex is composed of a tridentate O,N,O-Schiff base ligand coordinated to a SnCl2Ph unit. The tin atom is in distorted octahedral coordination geometry. NMR spectroscopic studies have shown that the unusual hexa-coordinated tin complex was formed as a kinetically controlled product. Storage of the solid product for several years led to a transformation into a thermodynamically stable penta-coordinated tin complex
Solid-liquid equilibria of Sorel phases and Mg (OH)2 in the system Na-Mg-Cl-OH-H2O. Part I: experimental determination of OH− and H+ equilibrium concentrations and solubility constants at 25°C, 40°C, and 60°C
No full textSorel phases are the binder phases of the magnesia building material (Sorel cement/concrete) and of special concern for the construction of long-term stable geotechnical barriers in repositories for radioactive waste in rock salt, as potentially occurring brines are expected to contain MgCl2. Sorel phases, in addition to Mg(OH)2, are equally important as pH buffers to minimize solubility and potential mobilization of radionuclides in brine systems. In order to obtain a detailed database of the relevant solid-liquid equilibria and the related pHm values of the equilibrium solutions, extensive experimental investigations were carried out. Solid phase formation was studied by suspending MgO and Mg(OH)2 in NaCl saturated MgCl2-solutions at 25°C. Mg(OH)2 and the 3-1-8 Sorel phase were identified as the stable solid phases, while the 5-1-8 Sorel phase is metastable. Equilibration at 40°C did not lead to any solid phase changes. Both OH− and H+ equilibrium concentrations were analyzed as a function of MgCl2 concentration at 25°C and 40°C. In addition to our already published solid-liquid equilibria for the ternary system Mg-Cl-OH-H2O (25°C–120°C), the equilibrium H+ concentrations (pHm) determined at 25°C, 40°C and 60°C are now reported. Analyzing these data together with known ion-interaction Pitzer coefficients, the solubility constants for Mg(OH)2 and the 3-1-8 phase at these three temperatures, for the metastable 5-1-8 phase at 25°C and for the 2-1-4 phase at 60°C have been consistently calculated
Optimising mine planning by integrating geospatial modelling into system dynamics
No full textIn an era of mineral-driven energy transition, the largely untapped mineral reserves in Africa are gaining global attention. Kenya, presently featuring Africa's most modern mining law, has set a high target to increase the mining sector's contribution to the GDP from barely 1% currently to 10% by 2030. Despite regulatory reforms and advances in Earth observation and geospatial technologies, gaps in mining sector governance have persisted with the lack of spatially enabled decision support models for strategic mine planning at regional scales involving multiple projects, interconnected sectors, and diverse stakeholders, including local communities. Motivated by the urgent need to address the gaps using an applied case study of Taita Taveta, a mineral-rich region in Kenya, this thesis developed a system dynamics model that integrates spatial metrics and simulates scenarios from 1969 to 2029, with the aim of informing long-term strategy, policy, and planning in the mining sector. Branded the Taita-Taveta Integrated Mine Planning Model (TIMPM), this scalable prototype incorporated 40 variables into 7 model sectors representing 75 mining areas, protected areas, and spatial planning parameters. The model projected Taita Taveta population to exceed 427000 by 2029 with an annual water demand of 31 million cubic metres. From GIS analysis, 16% of the mapped mines were located within a kilometre of the water bodies, with most human-induced degradation taking place 3-35 m from the Voi River. TIMPM's flexible structure supports multi-stakeholder participation and spatio-temporal simulations of divergent mining and land-use scenarios with policies for long-term sustainability, transparency, and accountability in mining sector governance. The findings reinforce the superiority of machine learning in geospatial analysis for precise parameterisation of decision support models. The outlook projects a growing need for a participatory, geodata-driven systems approach to developing integrated decision support systems for sustainable mineral resource governance
The effect of the intermediate principal stress for dimensioning in room and pillar mining:
No full textDas Pfeiler- und Säulenbergbauverfahren ist eine weit verbreitete Bergbautechnologie, die Stabilität und geringe Umweltauswirkungen gewährleistet. Bestehende Methoden zur Bemessung von Pfeilern und Stollen beruhen auf klassischen Versagenskriterien, die die mittlere Hauptspannungskomponente nicht berücksichtigen. Auf der Grundlage einer detaillierten Analyse bestehender echter triaxialer Versagenskriterien wird ein erweitertes Hoek-Brown-Kriterium (EHB genannt) als fortschrittliche Alternative für die Bemessung von Stollen und Pfeilern vorgeschlagen. Das EHB-Modell wurde in den expliziten Finite-Differenzen-Code FLAC3D implementiert und es wurden mehrere beispielhafte Pfeiler- und Stollenmodelle erstellt. Die entsprechenden numerischen Simulationen, in denen die Ergebnisse des EHB-Modells mit denen des klassischen HB-Modells verglichen werden, zeigen, dass die mittlere Hauptspannungskomponente die Pfeilerfestigkeit, den Sicherheitsfaktor, das Ausziehungsverhältnis, den Spannungskonzentrationsfaktor und das Volumen (Ausmaß) der gestörten Aushubzone erheblich beeinflusst. Diese Ergebnisse führen zu verbesserten Vorhersagen von Versagensmechanismen und bieten einen zuverlässigen und effizienten Rahmen für die Planung von Bergwerken.The room and pillar mining method is widely used mining technology to ensure stability and low environmental impact. Existing pillar and drift design methods are based on classical failure criteria, which do not consider the intermediate principal stress component. Based on the detailed analysis of existing true triaxial failure criteria, an extended Hoek-Brown criterion (called EHB) is proposed as an advanced alternative for drift and pillar design. The EHB model is implemented into the explicit finite difference code FLAC3D and several exemplary mine pillar and drift models were created. The corresponding numerical simulations comparing EHB and classical HB model results show that the intermediate principal stress component significantly influences pillar strength, factor-of-safety, extraction ratio, stress concentration factor, and volume (extent) of the excavation disturbed zone. These results lead to improved predictions of failure mechanisms and provide a reliable and efficient framework for mine design
Crystal structures of methyl 3,5-dimethylbenzoate, 3,5-bis(bromomethyl)phenyl acetate and 5-hydroxybenzene-1,3-dicarbaldehyde
No full textThe crystal structures of the title compounds, methyl 3,5-dimethylbenzoate (C10H12O2; 1), 3,5-bis(bromomethyl)phenyl acetate (C10H10Br2O2; 2) and 5-hydroxybenzene-1,3-dicarbaldehyde (C8H6O3; 3) were determined by single-crystal X-ray analysis. The crystals of 1 are composed of strands of C—H⋯O=C bonded molecules, which are further arranged into layers. As a result of the presence of two bromomethyl substituents in compound 2, molecular dimers formed by crystallographically non-equivalent molecules are connected to structurally different two-dimensional aggregates in which the bromine atoms participate in Br⋯Br bonds of type I and type II. In the case of compound 3, which possesses three donor/acceptor substituents, the molecular association in the crystal creates a close three-dimensional network comprising Caryl—H⋯Ohydroxy, Cformyl—H⋯Oformyl and O—H⋯Oformyl bonds
CFD-gestützte Untersuchung und verbesserte Auswertung von Hochtemperaturexperimenten
No full textDie vorliegende Dissertationsschrift widmet sich der CFD-gestützten Untersuchung von Hochtemperaturversuchen, die für das Verständnis der Wärme- und Stoffübertragung im Labormaßstab von entscheidender Bedeutung sind. Mithilfe der CFD-Modellierung werden komplexe Temperatur- und Stoffverteilungen in Versuchsanlagen detailliert analysiert. Dies umfasst ein Modell zur Abbildung des Wärme- und Stoffübergangs im HITECOM-Reaktor und damit zur Identifizierung kritischer Betriebsbedingungen, ein Modell zur Analyse der Partikelbewegung im KIVAN-Reaktor unter inhomogenen Temperatur- und Strömungsbedingungen sowie die modellgestützte Analyse der Stofftransportlimitierungen in einer DMT-Thermowaage. Die Kombination von CFD-Modellierung und experimentellen Daten unterstützt die Entwicklung präziser kinetischer Modelle und verbessert die Vorhersage des Stoffumsatzes. Diese Ergebnisse tragen wesentlich zur Weiterentwicklung und Optimierung von Hochtemperaturprozessen in verschiedenen Industriezweigen bei