4 Material und Umwelt
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- 4.4 Thermochemische Reststoffbehandlung und Wertstoffrückgewinnung (34) (entfernen)
Eingeladener Vortrag
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Ausgehend von der aktuellen Situation in Deutschland werden die Themen Baustoffaufbereitung, Ressourceneffizienz vorgestellt und Möglichkeiten zur Verbesserung der Baustoffqualität von Baurestmassen vorgestellt. Zielkonflikte und Beispiele dazu aus dem Baubereich (z.B. Mantelverordnung) werden benannt.
Conventional fertilisers have their disadvantages as nutrient release is not synchronised with the demand of plants. Several approaches of "next generation fertilisers" are aiming at controlled nutrient release. Recycling fertilisers are often not soluble in water but fully plant available. They are suitable raw materials for the production of new types of controlled release fertilisers.
Vorstellung des REFOPLAN-Projekts extraWERT Erhebung zusätzlicher Wertstoffpotenziale in Klärschlamm
(2019)
Auf dem Regionalgruppentreffen wurden erste Projektergebnisse vorgestellt und die Probenahmestrategie diskutiert. Vorgestellt wurde eine Rückberechnung der mittleren Wertstoffgehalte aus dem Klärschlamm-Monitoring 2014 (Krüger und Adam) und erste Auswertungen der Klärschlammbericht-Rohdaten aus NRW und Hessen.
Carbonfasern sind äußerst stabil und werden auch in Anlagen zur Verbrennung von Sondermüll kaum zerstört. Beim Handling carbonfaserhaltiger Abfälle können Gesundheitsrisken auftreten (Abgabe von WHO-Fasern). Es werden Methoden der Verwertung carbonfaserhaltiger Reststoffe in der Pyrometallurgie diskutiert.
In the transition to the Circular Economy (CE) model, where the added value of products is kept as long as possible and waste is eliminated, the sustainable management of raw materials plays a key role. In above CE model, especial attention is paid to CRMs which are economically and strategically important for the European economy, but have a high-risk associated with their supply.
One of the most important element which can not be replaced and is an essential element for human nutrition, yet limited resource is phosphorus (P). An importance of issues related to sustainable P management results from EU legislation, which indicated P as a Critical Raw Material (CRM).
The sustainable management of P-resources is especially important for the Baltic region. A consequence of waterborne loads passing into the sea, mainly as wastewater with a high P content is the eutrophication of the Baltic Sea environment. Due to the largest inputs of P (37%) into the Baltic Sea originate from Poland, the development of sustainable solutions aimed at more rational P management for this country is externally important.
Blast furnace (BF) sludge and electric arc furnace (EAF) dust are typical wastes that incur from iron and steel production. In addition to iron, calcium, carbon, and silicon they usually contain high concentrations of heavy metals such as zinc, lead, and cadmium that are potentially hazardous to the environment, rendering disposal in landfills ecologically problematic and costly. Consequently, pyrometallurgical, hydrometallurgical, and hybrid methods for selective elimination of non-ferrous heavy metals from BF sludge and EAF dust have been conceived, of which only the carbothermic reduction route taken in the so-called Waelz rotary kiln process has been proven to be economically successful. However, this process has several drawbacks regarding efficiency of heavy-metal removal and recovery of iron, and it does not allow processing of BF sludge. In this study, we investigated the efficiency and feasibility of selective chlorination and evaporation of non-ferrous heavy metals, particularly zinc and lead, in both BF sludge and EAF dust as an alternative, thermochemical processing route. To this end, hydrochloric acid and iron(II) chloride solution have been used as chlorinating agents, and the process of heavy-metal chlorination and evaporation has been investigated under inert operating conditions, at variable chlorine concentrations, and at temperatures between 500 and 1200 °C.
High zinc and lead removal efficiencies of > 99.5 % were achieved with both chlorinating agents, but iron(II) chloride turned out to be overall more efficient for removal of zinc and lead from BF sludge and EAF dust. Interestingly, and in contrast to previous studies, the iron was completely retained in the processed solid residue, therefore rendering the processed residues virtually zinc- and lead-free raw materials that may either be used internally (e.g., feeding processed BF sludge and EAF dust back into the respective furnaces) or externally (e.g., for cement production).
Treatment and reusing of hazardous wastes have become significant issues of modern societies. Blast furnace sludge (BFS) and electric arc furnace dust (EAFD) are such typical wastes, because they usually contain high amounts of undesirable elements such as zinc (Zn) and lead (Pb).
These elements can cause operational problems in reusing of BFS and EAFD. In this study, the Ferro Duo GmbH and the Federal Institute for Materials Research and Testing have investigated a novel approach for eliminating and/or recovering Zn and Pb from both wastes. Applied was a selective chlorination and volatilization of Zn and Pb as chlorides at temperatures between 500 °C and 1100 °C. Both product obtained, Zn and Pb in the form of ZnCl2 and PbCl2 and the purified solid mineral compound are attractive materials for further use. Hydrochloric acid and iron(II) chloride were used as chlorination agents. Exceptionally high Zn and Pb removal efficiencies of >99.5 % could be achieved with both chlorination agents, whereby iron(II) chloride exhibited better performance.
Since the recycling of tantalum bearing post-consumer waste is practically not existent, metallurgical residues are the most important feed for the tantalum recycling. Most tin ores naturally contain significant quantities of refractory metals. During the smelting process in primary tin production these elements are enriched in the slag phase. This slag is a highly valuable raw material for tantalum production due to its considerable concentration of tantalum and its functioning as an additional slag former in further pyrometallurgical treatment.
In this paper the first process stage of an existing pyrometallurgical process for tantalum recovery, mainly from low grade pyrometallurgical residues, is discussed. Smelting trials were carried out in a pilot-scale electric arc furnace to analyse the effect of feeding on the activity of carbon as a reducing agent. Therefore, blowing petroleum coke through an iron lance and the manual adding of coke into the melting bath were tested. During the pyrometallurgical treatment elements with a high affinity to carbon were reduced to their carbide form and enriched in the molten iron-based metal phase. The objective of the process was to reduce the oxidic tantalum completely and to enrich it into the metal phase. Furthermore, the transfer of unwanted elements such as titanium into the metal phase was aimed to be avoided.
Spoon test specimens were taken from the liquid mineral melt to follow the evolution of the reduction process. The cooled down solidified melting bath was investigated by using the XRD and EDX method to characterise the slag system and to identify relevant mineral phases.
Since the recycling of tantalum bearing post-consumer waste is practically not existent, metallurgical residues are the most important feed for the tantalum recycling. Most tin ores naturally contain significant quantities of refractory metals. During the smelting process in primary tin production these elements are enriched in the slag phase. This slag is a highly valuable raw material for tantalum production due to its considerable concentration of tantalum and its functioning as an additional slag former in further pyrometallurgical treatment.
In this paper the first process stage of an existing pyrometallurgical process for tantalum recovery, mainly from low grade pyrometallurgical residues, is discussed. Smelting trials were carried out in a pilot-scale electric arc furnace to analyse the effect of feeding on the activity of carbon as a reducing agent. Therefore, blowing petroleum coke through an iron lance and the manual adding of coke into the melting bath were tested. During the pyrometallurgical treatment elements with a high affinity to carbon were reduced to their carbide form and enriched in the molten iron-based metal phase. The objective of the process was to reduce the oxidic tantalum completely and to enrich it into the metal phase. Furthermore, the transfer of unwanted elements such as titanium into the metal phase was aimed to be avoided.
Spoon test specimens were taken from the liquid mineral melt to follow the evolution of the reduction process. The cooled down solidified melting bath was investigated by using the XRD and EDX method to characterise the slag system and to identify relevant mineral phases.
Previous research shows that analytical methods based on Diffusive Gradients in Thin films (DGT) provide very good correlations to the amount of bioavailable nutrients and pollutants in the environmental samples. However, these DGT results do not identify which compound of the specific element has the high bioavailability. Using various spectroscopic techniques (infrared, XANES and NMR spectroscopy) to analyze the dried DGT binding layers after deployment could allow us to determine the specific elements or compounds. Nutrients such as phosphorus and nitrogen are often, together with other elements, present as molecules in the environment. These ions are detectable and distinguishable by infrared and NMR spectroscopy, respectively. In addition, XANES spectroscopy allows for the specification of nutrients and pollutants (e.g. chromium) on the DGT binding layer. Furthermore, microspectroscopic techniques make it also possible to analyze compounds on the DGT binding layer with a lateral resolution down to 5 µm2. Therefore, species of elements and compounds of e.g. a spatial soil segment can be mapped and analyzed, providing valuable insight to understand the dynamics of nutrients and pollutants in the environment. Here we will present the advantages and limitations of this novel combination of techniques.
Dieser Vortrag beschreibt die Entwicklung eines neuen chemischen Verfahrens, das in einem Kooperationsprojekt zwischen der Bundesanstalt für Materialforschung und -prüfung (BAM) und der Ferro Duo GmbH entwickelt wird. Mit dem entwickelten Verfahren soll es ermöglicht werden, schwermetallhaltige Filterstäube und -schlämme, die als Abfälle während der Produktion von Roheisen und Rohstahl anfallen und die derzeit größtenteils deponiert werden, zu recyceln und die darin enthaltenen Wertstoffe (v.a. Eisen, Kohlenstoff und Zink) wieder in den Rohstoffkreislauf zurückzugeben. Dies wird durch eine Chlorierung der in den Filterstäuben und -schlämmen enthaltenen Schwermetalloxiden erreicht, die bei Temperaturen zwischen 650 und 1100 °C in Form von Schwermetallchloriden verdampft und so selektiv separiert werden. Erste experimentelle Ergebnisse zeigen, dass die Gehalte an Schwermetallen wie Zink, Blei und Cadmium um bis zu 99,7% reduziert werden können und die thermochemisch behandelten Filterstäube und -schlämme durch das Verfahren in sekundäre Rohstoffe für die Roheisenproduktion umgewandelt werden können.
Dieser Beitrag beschreibt die Entwicklung eines neuen chemischen Verfahrens, das in einem Kooperationsprojekt zwischen der Bundesanstalt für Materialforschung und -prüfung (BAM) und der Ferro Duo GmbH entwickelt wird. Mit dem entwickelten Verfahren soll es ermöglicht werden, schwermetallhaltige Filterstäube und -schlämme wie Gichtgasschlämme oder Elektroofenstäube, die als Abfälle während der Produktion von Roheisen und Rohstahl anfallen und die derzeit größtenteils deponiert werden, zu recyceln und die darin enthaltenen Wertstoffe (v.a. Eisen, Kohlenstoff und Zink) wieder in den Rohstoffkreislauf zurückzugeben. Das Verfahren basiert auf dem Prinzip der Chlorierung der in den Filterstäuben und -schlämmen enthaltenen Schwermetalloxide nach Zugabe eines flüssigen Chlordonators wie Eisen(II)-chlorid-Lösung oder Salzsäure. Die so chlorierten Schwermetalloxide werden bei Temperaturen zwischen 650 und 1100 °C in Form von Schwermetallchloriden verdampft und so selektiv vom behandelten Feststoff separiert. Erste experimentelle Ergebnisse zeigen, dass die Gehalte an Schwermetallen wie Zink, Blei und Cadmium um bis zu 99,7% reduziert werden können und die thermochemisch behandelten Filterstäube und -schlämme durch das Verfahren in sekundäre, im Wesentlichen aus Eisenoxiden bestehenden Rohstoffe für die Roheisenproduktion umgewandelt werden können. Da die chlorhaltigen Lösungen selbst Abfallstoffe aus anderen Industriezweigen sind (z.B. aus der Titandioxidproduktion oder der Stahlbeize), vereint das hier entwickelte Verfahren auf elegante Weise zwei Abfallstoffströme und wandelt diese in sekundäre Rohstoffe – einem mineralischen Rohstoff für die Roheisenproduktion sowie Zinkchlorid – um.
Due to the vital importance of phosphorus (P) and its increasing scarcity as a natural resource, phosphorus recovery has recently gained significant scientific and technical interest. An interesting sources of phosphorus are sewage sludge (SS) and sewage sludge ash (SSA) due to the major part of the phosphate from P rich wastewater is transferred to the sludge (approx. 90%). Despite the fact that the raw materials base is large (PURE report indicates that in 2020 the amount of sewage sludge generated in Poland will reach 180% of the dry matter of sewage sludge produced in 2010), at present recycling of phosphorus is not a commonly used practice in Poland.
In a rapidly evolving world, the demand on raw materials is increasing steadily and many technologies are dependent on a secure supply of hi-tech metals. Recently, scandium (Sc) has attracted attention since its use in high strength Al-alloys and solid-oxide-fuel-cells strongly improves the performance of those materials.
The element Sc is not exceptionally rare but quite resistant to geochemical enrichment processes, it is scarcely found enriched to high concentrations and is recovered as a by-product. Since Sc enrichment in Greek bauxite residues was shown by Ochsenkühn-Petropoulou et. al (1994), intensive research on this material and development of efficient Sc-recovery methods is ongoing.
This study investigates Sc-bearing species in bauxite residues from alumina production. It aims to provide direct evidence about the Sc-speciation’s in those secondary resources and tries to find the link to speciation’s in primary resources, e.g. bauxites and laterites.
Therefore, Sc K edge XANES (X-ray absorption near edge structure) spectroscopy is performed using synchrotron radiation to determine the presence of certain Sc-components and distinguish between adsorbed and chemically bonded Sc as was shown for lateritic deposits in Australia by Chassé et al. 2016. For comparison, reference standards of Sc-bearing and Sc-adsorbed species are synthesized. Indirect inferences from leaching behavior of bauxites, in cases supported by analyses with LA-ICP-MS, suggest Sc to be associated with either iron- or aluminum phases (Vind et al. 2017); (Suss et al.). It remains unclear how different primary materials influence Sc-speciation in the bauxite residue. Therefore, a comparison between different European bauxite residues is made in this study. The investigations should help to understand Sc chemistry and
behavior in different primary and secondary materials and provide fundamentals for metallurgical processing. The research is incorporated in the SCALE project (GA No. 730105) funded by EU Horizon 2020 research and innovation program.
An existing pyrometallurgical process for tantalum and niobium recovery, mainly from low grade pyrometallurgical residues, was investigated. Series of melting experiments were carried out in a pilot-scale electric arc furnace to study how the amount, the grain size and the way of feeding affect the activity of carbon as a reducing agent. During the pyrometallurgical treatment refractory metals such as tantalum and niobium are reduced to their carbide form and enriched in the molten iron-based metal phase. The cooled down slag and metal phase were analysed to investigate thermodynamic and kinetic conditions of the carbide formation. FACT Sage simulations were also used to investigate the material system in state of thermodynamic equilibrium. Results show that mass transfer and kinetics may play an important role if compared to equilibrium analyses using FACT Sage.
An existing pyrometallurgical process for tantalum and niobium recovery, mainly from low grade pyrometallurgical residues, was investigated. Series of melting experiments were carried out in a pilot-scale electric arc furnace to study how the amount, the grain size and the way of feeding affect the activity of carbon as a reducing agent. During the pyrometallurgical treatment refractory metals such as tantalum and niobium are reduced to their carbide form and enriched in the molten iron-based metal phase. The cooled down slag and metal phase were analysed to investigate thermodynamic and kinetic conditions of the carbide formation. FACT Sage simulations were also used to investigate the material system in state of thermodynamic equilibrium. Results show that mass transfer and kinetics may play an important role if compared to equilibrium analyses using FACT Sage.
The use of secondary building materials can meet the requirements of sustainability in several ways: the extended time availability of primary raw materials and, thereby, the protection of natural ressources as well as the conservation of landfill sites. Regarding the predicted decrease of gypsum supply in Germany, particularly the recycling of gypsum (calcium sulfate) is of growing importance. Currently, the gypsum demand is fulfilled (at least 60%) by gypsum as side product from coal-fired power plants (FGD Gypsum). Germany’s natural gypsum deposits fulfil the remaining gypsum demand. Due to national climate protection goals the gypsum supply from coal power plants will decrease significantly in the future.
In addition, the content of sulfates in other secondary building materials, in particular in recycled concrete aggregates, should be minimized for quality reasons. Separated gypsum can be used in gypsum production if the high quality requirements for recycled gypsum are met. Accordingly, there have been significant advancements in the processing of gypsum residues in the last years. Since almost all processing steps in the recycling process are associated with environmental impacts, an evironmental evaluation of the use of recycled gypsum as a substitute in gypsum production has to be carefully conducted.
The presentation focusses on the techniques for generating recycled gypsum from gypsum plaster boards, the related quality requirements and a comprehensive environmental evaluation of the complete process.