TY - CONF A1 - Sichler, Theresa A1 - Herzel, Hannes A1 - Adam, Christian T1 - European Sewage Sludge Ash Monitoring N2 - For the European sewage sludge ash monitoring ash samples from sewage sludge incineration plants were requested from all over Europe. First results of the received samples regarding main and trace element contents were presented at ESPC4. Moreover, a list of all known European facilities for sewage sludge monoincineration was presented. T2 - European Sustainable Phosphorus Conference 4 CY - Vienna, Austria DA - 20.06.2022 KW - Sewage sludge ash KW - Sewage sludge incineration KW - Phosphorus recovery PY - 2022 AN - OPUS4-55145 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Herzel, Hannes T1 - Phase reaction during thermochemical treatment of sewage sludge and biomass ashes with alkali compounds to increase nutrient plant availability N2 - Das Element Phosphor ist für Pflanzen, Tiere und Menschen essenziell. Um die Phosphorversorgung für Pflanzen in der Landwirtschaft zu gewährleisten, werden Phosphordünger eingesetzt. Die Nährstoffe werden hauptsächlich durch Wirtschaftsdünger (Gülle, Jauche, Stallmist) zurückgeführt. Zusätzlich werden in der konventionellen Landwirtschaft mineralische Phosphordünger eingesetzt, die vorwiegend aus dem fossilen Rohstoff Phosphorit gewonnen werden. Um die Abhängigkeit von fossilen Rohstoffen zu reduzieren, sollen nährstoffhaltige Rest- und Abfallstoffe zur Phosphordünger aufbereitet werden. In Abwasserkläranlagen fällt phosphorreicher Klärschlamm als Abfallstoff an. Der größte Anteil des Klärschlammes wird in Steinkohlekraftwerken, Zementwerken oder in Monoklärschlammverbrennungsanlagen verbrannt. Die Klärschlammaschen aus den Monoverbrennungsanlagen enthalten bis zu 12 Gew.-% Phosphor und sind daher für die Düngerherstellung geeignet. Ein geeignetes Verfahren zur Aufbereitung der Klärschlammaschen ist die thermochemische Behandlung im Drehrohrofen. Mit dem sogenannten AshDec®-Prozess, kann ein Phosphordünger hergestellt werden. Aktuell wird eine großtechnische Anlage in Altenstadt (Bayern) geplant, die im Jahr 2023 den Betrieb aufnehmen soll. Der zentrale Bestandteil ist die Phasenumwandlung von schlecht pflanzenverfügbaren Phosphaten in der Klärschlammasche (vorwiegend das Calciumphosphat Whitlockit und Aluminiumphosphat) zu gut pflanzenverfügbaren Calciumalkaliphosphaten im Produkt. Um dies zu erzielen, werden die Aschen mit Natrium- und/oder Kalium-Verbindungen gemischt und einer thermochemischen Behandlung bei 800-1000 °C zugeführt. Um die Pflanzenverfügbarkeit und Düngewirkung von Phosphaten abschätzen zu können, ist die chemische Extraktionsmethode mit neutraler Ammoniumcitratlösung geeignet. In der Dissertation werden die (Phosphor-)Phasenreaktionen und die Prozessbedingungen des thermochemischen Verfahrens untersucht, um das Verfahren gezielt zu modifizieren und die Wirtschaftlichkeit zu steigern. Die Zielphasen der thermochemischen Behandlung sind die Calciumalkaliphosphate CaNaPO4 und CaKPO4, und deren Mischphasen Ca(Na,K)PO4, welche in der Publikation 3.1 synthetisiert wurden. Für diese Calciumalkaliphosphate wurden die thermodynamischen Daten der Standardbildungsenthalpie, Standardentropie, Wärmekapazität und die Wärmemenge der Phasenumwandlung bestimmt (Publikation 3.1). Bei der thermochemischen Behandlung von Klärschlammaschen wurden als Additive Natrium- und Kaliumsulfat bei verschiedenen Temperaturen getestet. Der Einsatz von Kaliumadditiven ist erwünscht, um den Marktwert des Produktes durch die Produktion eines Phosphor-Kalium-Düngers zu erhöhen. Zusätzlich wird eine möglichst geringe Prozesstemperatur angestrebt, bei der die erwünschten Calciumalkaliphosphate gebildet werden. In den Publikationen 3.2 und 3.3 wird gezeigt, dass für Klärschlammaschen eine komplette Phasenumwandlung zu Calciumnatriumphosphaten ab 875 °C in Laborversuchen (Korundtiegel) mit dem Additiv Natriumsulfat erzielt werden kann. Der Einsatz von Kaliumsulfat erforderte notwendige Reaktionstemperaturen von über 1100 °C. Diese unterschiedlichen Reaktionstemperaturen hängen mit den Schmelzpunkten von Natriumsulfat (890 °C) und Kaliumsulfat (1070 °C) zusammen. Um Kaliumsulfat in den Prozess bei niedrigen Temperaturen zu integrieren, wurden Natriumsulfat und Kaliumsulfat vor der Behandlung gemischt. Dies führte zu einer Schmelzpunkterniedrigung und resultierte in Reaktionstemperaturen zwischen 900 °C bis 1000 °C für die untersuchten Mischungen von Natrium- und Kaliumsulfat (Publikation 3.3). Die Zusammensetzung der Calciumalkaliphosphate Ca(Na,K)PO4 war anders als erwartet. Bei der Phasenanalytik stellte sich heraus, dass bei geringem und mittlerem Anteil von Kaliumsulfat im Alkali-Additiv nur Calciumnatriumphosphate mit sehr geringen Kaliumgehalten gebildet wurden. Erst bei einem hohen Anteil von Kaliumsulfat in der Mischung der Alkalisulfate konnten kaliumhaltige Calciumalkaliphosphate nachgewiesen werden (u.a. (Ca0.9Mg0.1)(Na0.6K0.4)PO4). Dieser geringere Einbau von Kalium in die Calciumalkaliphosphate hängt mit den zusätzlich stattfindenden Reaktionen zwischen den Alkalien und den Silikaten zusammen. Es ist bekannt, dass die zugegebenen Alkalisulfate zuerst mit Silikaten und anschließend mit den Phosphaten reagieren. Silikate bauen bevorzugt Kalium ein, deswegen konnten erst kaliumhaltige Phosphate gebildet werden, wenn die Reaktion mit den Silikaten abgeschlossen war. Dies führte zu einem geringeren Kaliumanteil in den gebildeten Phosphaten im Vergleich zum Kaliumanteil der verwendeten Alkaliadditive. Das in Silikaten gebundene Kalium ist wahrscheinlich schlecht für die Pflanzen verfügbar. Dies könnte den Einsatz der produzierten Phosphor-Kalium-Dünger einschränken. Der bevorzugte Kaliumeinbau in Silikaten konnte auch in Kalkulationen mit den thermodynamischen Daten aus der Publikation 3.1 gezeigt werden. Mittels Phasenanalytik vor und nach der chemischen Extraktion, konnte die Zugehörigkeit zu verschiedenen Modifikationen der Calciumalkaliphosphaten sicher bestimmt werden und eine ungefähre Zusammensetzung dieser Calciumalkaliphosphate abgeschätzt werden. So konnte nachgewiesen werden, dass die Modifikation vom CaNaPO4 ungefähr 10 % Magnesium einbauen kann. Wenn mehr Magnesium eingebaut wird, bildet sich die Phase (Ca,Mg)NaPO4, die eine vergleichbare Struktur wie die bekannte Phase (Ca0.72Mg0.28)NaPO4 aufweist. Dieses magnesiumreiche Calciumnatriumphosphat entstand vermutlich, wenn entweder erhöhte Anteile an Kalium eingebaut wurden (Ca0.8Mg0.2)(Na0.85K0.15)PO4 (Publikation 3.3) oder die Phasenumwandlung vom Calciumphosphat Whitlockit zum Calciumalkaliphosphat CaNaPO4 noch nicht abgeschlossen war (Publikation 3.2). Wenn mehr Kalium eingebaut wird, dann entsteht eine Phase (u.a. (Ca0.9Mg0.1)(Na0.6K0.4)PO4) ähnlich zu den Mischphasen aus der Publikation 3.1. In den Publikationen 3.4 und 3.5 wurden keine Klärschlammaschen untersucht, sondern Biokohlen aus Modellklärschlämmen (Publikation 3.5) und Biomasseaschen (Publikation 3.4) aus der Vergasung oder Verbrennung einer Mischung aus Zuckerrohrbagasse und Hühnertrockenkot. Die thermochemischen Produkte der Biokohlen bzw. Biomasseaschen enthielten das gewünschte CaNaPO4 und hatten eine hohe Düngewirkung in Pflanzenwachstumsversuchen mit Sojapflanzen bzw. Gräsern. KW - AshDec KW - Recycling fertilizer KW - Calcium alkali phosphate PY - 2020 SP - 1 EP - 186 CY - Jena AN - OPUS4-54724 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Herzel, Hannes A1 - Adam, Christian A1 - Schaaf, T. A1 - Künstler, J. T1 - Thermochemical P recycling from ash by AshDec ® process N2 - Klärschlammaschen können eine hohe Phosphatkonzentration aufweisen und stellen damit einen geeigneten Sekundärrohstoff für die Produktion von Phosphatdüngemitteln dar. Bisher wird dieses Potential der Klärschlammaschen für die Phosphor-Rückgewinnung jedoch kaum genutzt, da die in den Aschen enthaltenen Phosphate für Pflanzen kaum verfügbar und die Aschen teilweise mit toxischen Schwermetallen belastet sind. Im AshDec®-Verfahren wird die Klärschlammaschen im Drehrohrofen im Temperaturbereich 800-1000°C unter Zugabe von Alkali-Additiven (bsp. Na2CO3) thermochemisch behandelt, um ein wirksames und schadstoffarmes Phosphatdüngemittel herzustellen. Aktuell bereitet die Firma Emter GmbH den Bau der ersten großtechnischen AshDec®-Anlage mit einer Kapazität von 30.000 Jahrestonnen Klärschlammasche am Standort ihrer Klärschlammverbrennungsanlage (Altenstadt / Oberbayern) vor. Die erste Ausbaustufe dieser Anlage wird durch das BMBF-Projekt R-Rhenania im Rahmen der Förderinitiative RePhoR begleitet. T2 - Wastewater, Water and Resource Recovery (Workshop) CY - Online meeting DA - 11.04.2022 KW - Phosphorus recovery KW - Heavy metal removal KW - Ashdec PY - 2022 AN - OPUS4-54727 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schraut, Katharina A1 - Adamczyk, Burkart A1 - Simon, Sebastian A1 - von Werder, Julia A1 - Meng, Birgit A1 - Stephan, Dietmar A1 - Adam, Christian T1 - Formation and hydraulic reactivity of an alite rich material from post treated basic oxygen furnace slag N2 - Basic oxygen furnace slag (BOFS) is a by-product of steelmaking of which about 10.4 Mt are produced annually in the EU. BOFS is mostly used in road construction, earthwork and hydraulic engineering. However, in this use, the iron bound in BOFS is lost and the opportunity to produce higher value products from BOFS is forgone. In recent decades, many researchers have investigated a thermochemical process to reduce iron oxides to metallic iron in molten BOFS. The metallic iron formed separates from the reduced slag due to its higher density and can be recovered. An advantage of this process is that simultaneously the chemical composition of the reduced slag is adapted to that of the Portland cement clinker and the hydraulic reactive mineral alite is formed. In this study, BOFS was reduced in a small-scale electric arc furnace using petrol coke as reducing agent, and the hydraulic properties of the reduced, low-iron BOFS were investigated. Despite a chemical and mineralogical composition similar to that of Portland cement clinker, the reduced BOFS produced less heat of hydration, and its reaction was delayed compared to Portland cement. However, the addition of gypsum, as is also done in cement production from Portland cement clinker, has been found to accelerate the hydration rate of reduced BOFS. Further research to improve the hydraulic properties of the reduced slag is essential. If successful, the production of a hydraulic binder and crude iron from BOFS could have economic and ecological benefits for both the cement and steel industry. T2 - GeoMin Köln 2022 CY - Cologne, Germany DA - 11.09.2022 KW - BOFS KW - Portland Cement KW - Hydraulic reactivity PY - 2022 AN - OPUS4-56080 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schraut, Katharina A1 - Adamczyk, Burkart A1 - Adam, Christian T1 - Reductive treatment of steel making slags to produce a hydraulic binder and crude iron N2 - Steelmaking slags are a by-product of steel production, that are currently used primarily in road construction, earthwork, and hydraulic engineering. In this use, the iron bound in the steelmaking slags (< 30 wt.%) is lost. Recovery of iron from steelmaking slags is possible by thermochemical reductive treatment. The reductive treatment of liquid steelmaking slags causes iron oxides to be reduced to metallic iron, which separates from the mineral phase due to its higher density. The chemical composition of the mineral phase is thus adapted to that of the Portland cement clinker and the mineral alite, the most important component of Portland cement, is formed. This way, crude iron can be recovered, and at the same time a hydraulic binder can be produced. This process, however, is uneconomical due to the high temperatures required (~1800 °C). In the current project, the process is to be adapted so that the reduction of liquid steelmaking slag can be carried out at ~1600 °C. The chemical composition is to be modified in such a way that the melting temperature of the slags as well as their viscosity are in a technically suitable range and still a product with good cementitious properties is obtained. T2 - LithiumDays CY - Online meeting DA - 06.12.2021 KW - BOFS KW - Portland Cement KW - Hydraulic reactivity PY - 2021 AN - OPUS4-56081 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Vogel, Christian T1 - Microspectroscopy reveals dust-derived apatite grains in highly-weathered soils from the Kohala climosequence on Hawaii N2 - Dust deposition is an important source of phosphorus (P) to many ecosystems. However, there is little evidence of dust-derived P-containing minerals in soils. Here we studied P forms along a well-described climatic gradient on Hawaii, which is also a dust deposition gradient. Soil mineralogy and soil P forms from six sites along the climatic gradient were analyzed with bulk (X-ray diffraction and P K-edge X-ray absorption near edge structure) and microscale (X-ray fluorescence, P K-edge X-ray absorption near edge structure, and Raman) analysis methods. In the wettest soils, apatite grains ranging from 5 to 30 μm in size were co-located at the micro-scale with quartz, a known continental dust indicator suggesting recent atmospheric deposition. In addition to colocation with quartz, further evidence of dust-derived P included backward trajectory modeling indicating that dust particles could be brought to Hawaii from the major global dust-loading areas in central Asia and northern Africa. Although it is not certain whether the individual observed apatite grains were derived from long-distance transport of dust, or from local dust sources such as volcanic ash or windblown fertilizer, these observations offer direct evidence that P-containing minerals have reached surface layers of highly-weathered grassland soils through atmospheric deposition. T2 - BESSY Science Seminar CY - Online meeting DA - 01.04.2022 KW - Phosphorus KW - Soil KW - X-ray diffraction KW - X-ray absorption near-edge structure (XANES) spectroscopy KW - Fertilizer KW - Raman spectroscopy KW - infrared spectroscopy PY - 2022 AN - OPUS4-54584 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Vogel, Christian A1 - Huang, L. T1 - Ammonium and nitrate in agricultural soils analyzed with the Diffusive Gradients in Thin-films technique N2 - The aim of this study was to investigate the passive sampler method Diffusive Gradients in Thin-films (DGT) for ammonium and nitrate in amended soils. Therefore, we used soils from a pot experiment with maize where nitrogen (N) was supplied as ammonium sulfate nitrate (ASN), without and with a nitrification inhibitor (NI). The additional use of a NI can delay the nitrification in the soil and making the ammonium available for a longer period in the soil solution after its application. Homogenized soil samples were collected directly from each pot after one week of incubation before sowing and after harvesting the maize. Nitrate and ammonium in these soil samples were extracted using DGT devices equipped with a Putolite A520E (for nitrate) and Microlite PrCH (for ammonium) binding layer. Ammonium DGT which determined the mobile and labile ammonium forms based on diffusion and the resupplies from the solid soil phase, only showed a significantly higher amount of extractable ammonium with NI compared to that without NI for some samples. However, significantly lower values were found for nitrate of treatments with NI compared to without NI after harvest. Thus, the lower nitrate amounts for treatments with NI compared to the treatments without NI after harvest indicated the delay of the nitrification process by the NI. Furthermore, we compared also the ammonium and nitrate DGT results to chemical extraction with KCl solutions. The results demonstrated that the trends of DGT results and chemical extraction were complimentary through all the treatments. T2 - International Passive Sampling Workshop (IPSW) 2021 virtual CY - Online meeting DA - 04.11.2021 KW - Phosphorus KW - Diffusive gradients in thin-films (DGT) KW - Ammonium KW - Nitrate PY - 2021 AN - OPUS4-53698 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Vogel, Christian A1 - Krüger, O. A1 - Gentzmann, Marie A1 - Adam, Christian T1 - Can we use passive samplers for the determination of chromium(VI) in phosphorus fertilizers? N2 - Phosphorus (P) fertilizers from secondary resources became increasingly important in the last years. However, these novel P-fertilizers can also contain toxic pollutants. Chromium in its hexavalent state (Cr(VI)) is regulated with low limit values for agricultural products due to its high toxicity, but the determination of Cr(VI) in these novel fertilizer matrices can be hampered by redox processes that lead to false results. Thus, we applied the passive sampler technique Diffusive Gradients in Thin-films (DGT) for the determination of Cr(VI) in fertilizers and compared the results with the standard wet chemical extraction method (German norm DIN EN 15192) and Cr K-edge X-ray absorption near-edge structure (XANES) spectroscopy. We determined an overall good correlation between the wet chemical extraction and the DGT method. DGT was very sensitive and in most cases selective for the analysis of Cr(VI) in P-fertilizers. However, hardly soluble Cr(VI) compounds cannot be detected with the DGT method since only mobile Cr(VI) is analyzed. Furthermore, Cr K-edge XANES spectroscopy showed that the DGT binding layer also adsorbs small amounts of mobile Cr(III) compounds which leads to overestimated Cr(VI) values. The results of certain types of P-fertilizers containing mobile Cr(III) or partly immobile Cr(VI), showed that optimization of the DGT method is required to avoid over- or underestimation of Cr(VI). T2 - International Passive Sampling Workshop (IPSW) 2021 virtual CY - Online meeting DA - 04.11.2021 KW - Phosphorus KW - Sewage sludge KW - Chromium KW - Fertilizer PY - 2021 AN - OPUS4-53699 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Adam, Christian A1 - Schaaf, T. A1 - Kugler, Stefan A1 - Ulbrich, J. A1 - Schmidt, S. A1 - Pavinato, P. A1 - Burkhardt, J. A1 - Arnold, U. A1 - Conzelmann, L. A1 - Kraus, F. T1 - Cloop - Closing the global nutrient loop N2 - Recycled fertilizers produced using processes for the recovery of phosphate from residual materials such as wastewater, sewage sludge and sewage sludge ashes show very good bioavailability, but it is still a product largely unknown to the market. The aim of CLOOP is therefore to document the properties and effects of such fertilizers through chemical, mineralogical and ecological analyses as well as analytical method development and pot and field plant growth trials. Outotec focused on 3 points in CLOOP: Experimental campaigns, process simulations as well as economic analyses with focus on the AshDec process, respectively the design of a large-scale AshDec plant for phosphorus recovery. The laboratory scale trials as well as the semi-industrial scale campaign provided valuable insights into the operating parameters of the process and the plant. As a result, for example, the temperature range could be significantly lowered, and the additive addition reduced by approx. 20 %. They have further shown that the AshDec process is not susceptible to operating fluctuations and that the product can be consistently produced at high quality. With the selection of suitable operating parameters, heavy metals (As, Pb, Cd, (Zn)) can be removed. Within the campaign, about 1.5 t of fertilizer for the plant trials in CLOOP could be produced. An AshDec plant process was digitally created in simulation software, allowing valuable process parameters to be simulated at various operating parameters. On this basis, a full-scale plant was designed. The data obtained in the project were used for a detailed economic analysis including a sensitivity analysis. It was possible to show under which conditions this plant can be operated economically. At BAM, the AshDec fertilizer was synthesized with different additives and then applied to plant experiments at Uni Bonn. The goal hereby was to check differences in plant uptake. Because of the promising results of AshDec synthesized with sodium-carbonate and because this AshDec version does not require special off gas treatment for sulfur recovery (compared to AshDec synthesized with sodium-sulfate), all project partners agreed on continuing working with this AshDec variation. It was then used as a raw P-source for formulating it into NPK-fertilizers, by granulation with ammonium-sulfate and straw ash as potassium source. These recycling fertilizers were applied to plant- and field experiments by project partners in Brazil (University of Sao Paulo) and Australia (University of Queensland). Furthermore, in leaching experiments, the solubility of phosphorus in AshDec was compared to triple super phosphate. The experiments were carried out on soils with a varying phosphorus buffering index. Results show, that the phosphorus form in AshDec is way less soluble in water. This indicates that AshDec has the potential for a so-called next generation fertilizer – a fertilizer which’s nutrients remain in the soil and supply the plant according to its needs. At the moment, this behavior gets examined more in depth in lysimeter experiments in cooperation with University of Technology Berlin. The focus of KWB is the Life Cycle Assessment (LCA) of different NextGen fertilizers to evaluate the entire process chain from recovery to fertilizer application. The NextGen fertilizer is credited by the amount of plant available nutrients in the product, which replace nutrients from conventional fertilizer. The LCA covers N-struvite precipitation from municipal wastewater, K-struvite precipitation from industrial wastewater and the AshDec-product from sewage sludge. The LCA task is almost complete. It could be shown that struvite precipitation has comprehensive environmental benefits, mainly since positive side effects occur in sewage sludge treatment (e.g. reduced sludge volume). In principle, the energetic and ecological profile of the AshDec process compared to direct use of sewage sludge ash cannot be assessed as being generally beneficial or negative. Regarding the global warming potential, the Ashdec process shows that the expenses (e.g. energy, chemicals) cannot be covered by the P fertilizer credit. In contrast, the impact categories “terrestrial acidification potential”, and “freshwater eutrophication potential” show positive results as the credits for conventional fertilizer are higher than the burdens for the process. At University Bonn, the standardized pot experiments were conducted with several AshDec variations, using ryegrass, soybean, and spinach on a slightly acidic sandy soil and an organic-free standard substrate. P-uptake and biomass production of different AshDec variations were generally like those of triple super phosphate and struvite, and clearly outperformed untreated sewage sludge ash and rock phosphate. Field trials in Australia and Brazil with sugarcane on acidic soils are still ongoing and results are expected by the end of 2021. T2 - PLANT 2030 Status Seminar 2021 (BMBF) CY - Online meeting DA - 10.03.2021 KW - Recycling fertiliser KW - Phosphorus recovery PY - 2021 AN - OPUS4-52251 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schraut, Katharina A1 - Adamczyk, Burkart A1 - Simon, Sebastian A1 - von Werder, Julia A1 - Meng, Birgit A1 - Stephan, Dietmar A1 - Adam, Christian T1 - Hydraulic reactivity of alite rich material from post-treated basic oxygen furnace slags N2 - Basic oxygen furnace slags (BOFS) are a by-product of steel production. In 2016, 10.4 Mt of BOFS were produced in the European Union (EU). The main part of BOFS is used in road construction, earthwork and hydraulic engineering. A smaller part is returned to the metallurgical circle, used as fertilizer or landfilled. However, it is also possible to produce higher value products from BOFS. For example, many researchers have investigated the possibility of producing Portland cement clinker and crude iron from BOFS by a carbothermal post-treatment. In this study, German BOFS was reduced in a small-scale electric arc furnace using petrol coke as reducing agent. The carbothermal treatment reduces the iron oxides in the BOFS to metallic iron, which accumulates at the bottom of the furnace by density separation. In addition to metallic iron, the process generates a mineral product rich in the tricalcium silicate solid solution alite. As the main constituent of Portland cement clinker, the hydraulic reactive mineral alite is of high economic importance. In previous studies, the hydraulic reactivity of the mineral product was investigated by testing the compressive strength of blends with 70 wt.% ordinary Portland cement (OPC). Recent investigations focused on the hydraulic properties of the pure mineral product from the reduced BOFS. The heat of hydration of the mineral product was measured by isothermal calorimetry and compared with the heat of hydration of a synthetic low-iron slag and OPC. In addition, the formation of hydration products was investigated with differential scanning calorimetry (DSC) and x-ray diffraction analysis (XRD) on freeze-dried samples after defined curing times. The results of the calorimetric measurements indicate that the mineral product produced less heat of hydration and its reaction was delayed compared to the synthetic low-iron slag and OPC. Hydration products such as portlandite and calcium silicate hydrates (C-S-H) formed later and in lower amounts. The production of a hydraulic material from BOFS by reductive treatment is of great interest to both the cement and steel industries. The substitution of cement clinker in OPC with a hydraulic material such as reduced BOFS leads to a reduction in greenhouse gas emissions from cement production. The steel industry benefits from an application for its by-products that avoids cost expensive landfilling and may even bring economic advantages. Furthermore, it may be possible to return the recovered crude iron to production. T2 - 3rd European Mineralogical Conference CY - Cracow, Poland DA - 30.08.2021 KW - BOFS KW - Calcium silicate KW - Hydraulic reactivity PY - 2021 AN - OPUS4-53473 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -