4.4 Thermochemische Reststoffbehandlung und Wertstoffrückgewinnung
Filtern
Erscheinungsjahr
- 2020 (17) (entfernen)
Dokumenttyp
- Zeitschriftenartikel (11)
- Vortrag (4)
- Dissertation (1)
- Posterpräsentation (1)
Sprache
- Englisch (17) (entfernen)
Schlagworte
- Phosphorus (3)
- Phosphorus fertilizer (3)
- Circular economy (2)
- Fertilizer (2)
- Leaching control mechanisms (2)
- Melting experiments (2)
- Phosphorus recovery (2)
- Sewage sludge (2)
- XANES spectroscopy (2)
- Ammonium (1)
- AshDec (1)
- Bauxite Residue (1)
- Bioceramics (1)
- Calcium alkali phosphate (1)
- Carbon Fibers (1)
- Chemical extraction (1)
- Chicken manure ash (1)
- Critical raw materials (1)
- Diffusive Gradients in Thin-films (DGT) (1)
- Diffusive Gradients in thin films (DGT) (1)
- Diffusive gradients in thin films (DGT) (1)
- EAF slags (1)
- Electric Arc Furnace (1)
- Electric arc furnace (EAF) slags (1)
- Electric arc furnace slags (1)
- Entropy (1)
- Extraction (1)
- FactSage calculations (1)
- FactSageTM calculations (1)
- Fertilzer (1)
- Formation enthalpy (1)
- Gypsum recycling (1)
- Heat capacity (1)
- LCA (1)
- Municipal sewage sludge (1)
- Nitrification inhibitor (1)
- Nutrient (1)
- P-recovery (1)
- Phase transformation (1)
- Phopshorus recovery (1)
- Plant availability (1)
- Recovery potential (1)
- Recycling fertiliser (1)
- Recycling fertilizer (1)
- Red Mud (1)
- Scandium (1)
- Secondary Recources (1)
- Sewage Sludge (1)
- Sewage Sludge Ashes (1)
- Sewage sludge ash (1)
- Sewage sludge ash (SSA) (1)
- Sewage sludge ordinance (1)
- Steelmaking (1)
- Sugar cane bagasse (1)
- Sustainability (1)
- Thermochemical treatment (1)
- Waste water (1)
- Waste water treatment (1)
- Wastewater (1)
- X-ray absorption near-edge structure (XANES) spectroscopy (1)
Organisationseinheit der BAM
- 4 Material und Umwelt (17) (entfernen)
Paper des Monats
- ja (1)
Eingeladener Vortrag
- nein (4)
Based on recently published research on leaching control mechanisms in electric arc furnace (EAF) slags, it is assumed that a FeO/SiO2 ratio of around one leads to low leached V and Cr concentrations. This ratio influences the mineral phase composition of the slag toward higher amounts of spinel and a lower solubility of calcium silicate phases by suppressing the formation of magnesiowuestite and highly soluble calcium silicate phases. To evaluate this hypothesis, laboratory and scaled up tests in an EAF pilot plant were performed on slag samples characterized by elevated V and Cr leaching and a high FeO/SiO2 ratio. Prior to the melting experiments, the optimum FeO/SiO2 ratio was calculated via FactSageTM. In the melting experiments, the ratio was adjusted by adding quartz sand, which also decreased the basicity (CaO/SiO2) of the slag. As a reference, remelting experiments without quartz sand addition were conducted and additionally, the influence of the cooling rate of the slag was examined. The remelted (without quartz sand) and the remelted modified slags (with quartz sand) were analyzed chemically and mineralogically and the leaching behavior was investigated. The modification of the slags yielded a minimized release of V and Cr, supporting the hypothesis that the FeO/SiO2 ratio influences the mineralogy and the leaching behavior.
Uranium and thorium species in phosphate rock and sewage sludge ash based phosphorus fertilizers
(2020)
Phosphorus (P) is an essential element for all forms of life and is thus often applied as phosphate rock-based P-fertilizers in agriculture to enable continuous farming. However, these P-fertilizers contain also hazardous uranium (U) and thorium (Th), up to 660 and 220 mg/kg, respectively. On the contrary, novel P-fertilizers made from sewage sludge (ash) contain only low mass fractions of U and Th. In addition to the total amount of U and Th in P-fertilizers, their mobility and bioavailability is important, which depends to a large extent on their chemical state, especially oxidation state and chemical bonding. Thus, we analyzed their chemical state in various P-fertilizers by U and Th L3-edge HERFD-XANES spectroscopy. Phosphate rocks and sewage sludge-based P-fertilizers contain mainly U(IV) compounds which have only a low bioavailability. In contrast, acidic treatment of phosphate rock to produce super phosphates lead to an oxidation to U(VI) compounds (including formation of uranium phosphates) with a strongly increased bioavailability. On the contrary, all analyzed P-fertilizers contain Th in form of strongly insoluble phosphates and oxides with a low bioavailability. Additionally performed water extractions and Diffusive Gradients in Thin-films (DGT) experiments support these findings.
In recent times, as the need for new high-tech materials is growing steadily to fulfil future sustainability goals, more and more looks turn towards industrial waste streams as potential sources of valuable metals. Bauxite residue (BR), accumulating during alumina production, is one of the major waste streams in the metal industry. Suitable re-use possibilities for BR are intensively investigated including approaches for the recovery of scandium (Sc). This transition metal, even though rarely recognized by the broader audience yet, has recently gained the interest of e.g. aerospace industries and SOFC-producers since its use is strongly improving the performance and durability of the respective materials.
Even though many sources classify Sc as one of the REE, there are many aspects, such as its ionic radius, which significantly differentiate Sc from the REE and cause its behaviour to be distinct as well. The large ionic potential (radius/charge) causes Sc to be incompatible in most rock forming minerals, which results in generally low concentrations in the earth’s crust and rare occurrences of natural Sc-deposits.
The general occurrence of enriched concentrations of Sc in some BRs compared to the earth’s crust is known for some time now and has especially been investigated for Greek materials. However, the (geo)chemical and mineralogical behaviour, the Sc speciation, the association and the variation of Sc occurrences in BRs of different origin is still not fully understood. This study aims to gain better knowledge on the different kinds of Sc-occurrences and their possible impact on future recovery schemes. We therefore apply a diverse set of analytical methods including novel measurement techniques such as X-ray absorption near edge structure (XANES) spectroscopy as well as standard techniques such as electron microprobe analyses, and Raman spectroscopy on BRs from Germany, Hungary and Greece. Information on the local distribution of Sc is determined by high-resolution laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) mappings.
Sc in Greek BR seems to have an affinity towards Fe-Phases such as Goethite and Hematite. However, whereas some of these phases show distinct enrichment of Sc, others are particularly barren, which might be a result of the different input materials. By means of XANES measurements it was possible to show that Sc in the Greek samples occurs adsorbed on the surface of those Fe-Phases, likely in the form of amorphous Sc-hydroxide or -oxyhydroxide or can be incorporated into the crystal lattice as well. The general affinity of Sc to those kinds of phases has been reported for natural rocks such as laterites before, where similar investigations were made using the XANES method [8]. Likewise, the Fe-association has been observed for Greek BR by Vind et al. [7]. Hungarian BRs show similar results as the Greek samples and LA-ICP-MS mappings show distinct Sc enrichment rims surrounding mineral particles. In German BR, Fe as well as Ti-phases occur to be partially enriched in Sc. Depending on the original primary bauxite, the source rock of the bauxite and the bauxite processing route, it is likely that many different parameters influence the occurrence and species of Sc in the BR. Theoretically, it either can therefore remain within its original carrier or can be partially or fully redistributed within the BR. Since the processing of the bauxite involves elevated temperatures, pressure and dissolving reagents, it is however very likely that some of the Sc will be redistributed and adsorb on mineral surfaces of smaller and larger particles, making beneficiation steps rather ineffective.
The study shows that there is no general rule defining how Sc is associated mineralogically or chemically within BRs. Therefore, the effective development of a recovery method needs a case specific background knowledge on the Sc-species present in the BR of interest. This research has received funding from the European Community’s Horizon 2020 Programme SCALE (H2020/2014-2020) under grant agreement n° 730105.
New developments in legislation and technology development for P-recovery were presented with focus on the situation in Germany.
Gypsum (calcium sulfate dihydrate) has excellent building material properties and has been widely used in constructions in the last decades in many countries. Accordingly, an increase of waste gypsum in C&D waste is expected in the upcoming years. On one hand, sulfates are unwanted in other secondary building materials (particularly in recycled concrete aggregates) and should be minimized for quality reasons. On the other hand, used gypsum from CDW can also be used in gypsum production if the high quality requirements for the recycled gypsum – especially regarding the sorting accuracy - are met.
A large percentage of the gypsum from buildings was installed as gypsum plasterboards in interior fittings so far. Gypsum plasterboards are comparatively simple to remove and to separate during selective dismantling. Therefore, a high sorting purity can be achieved. In addition, techniques for the recycling of gypsum plasterboards already exist and high quality standards can be achieved. Also, the reuse in gypsum production has been improved in the last decade. Furthermore, an environmental evaluation of the whole process of gypsum plasterboard recycling and reuse showed that this approach can be environmentally advantageous. Therefore, a closed-loop recycling of gypsum plasterboards is feasible.
This poster will show the development of gypsum consumption in different countries as well as a prognosis for the upcoming of gypsum in CDW in the future decades in Germany. Furthermore, a simplified scheme of the recycling process and selected results from an environmental evaluation will be presented.
As one of the most energy and carbon consuming industries, steelmakers have an intrinsic interest in the development of technologies, reducing their carbon footprint as well as their carbon input. Besides generating new feedstocks from biomass or waste polymers, the valorization of carbon fiber reinforced polymer (CFRP) waste streams seems to be extremely promising based on the high carbon content of carbon fibers (CF), chars from CFRP and even unprocessed CFRP waste of >92%, 98% and 79%, respectively. Although, reduction of environmental impact from those high-performance materials was achieved by the development of smart recycling solutions, the continuous truncation by mechanical treatment of CF over multiple cycles, analogous to paper fibers, and the large global CFRP waste stream of 62 kt/a demand for a sustainable management of end-of-life (EOL) CFRP. Recently it was demonstrated that CF can be used safely as reductant in pyrometallurgical processes in a downhole electric furnace without significant WHO fiber emission. Therefore we anticipate a huge potential of CF based materials as sustainable reductant for steelmaking in an electric arc furnace (EAF). To facilitate the applicability of EOL CFRP in steelmaking, we investigated the interaction between CF based materials and liquid metal phases, appearing during the process, on different scales. Particularly, we examined the reactivity, wettability and dissolution behavior of CF and CFRP concerning liquid slag and steel. The presented results indicate that understanding the impact of the microstructure of CF on their behavior is crucial for their application in EAF steelmaking without risking potential hazards by WHO fiber emission. Besides the detailed elucidation of structure reactivity relationships of CF, the broader impact on circular economy will be presented.