4.4 Thermochemische Reststoffbehandlung und Wertstoffrückgewinnung
Filtern
Dokumenttyp
- Vortrag (95)
- Zeitschriftenartikel (56)
- Beitrag zu einem Tagungsband (15)
- Posterpräsentation (14)
- Buchkapitel (5)
- Tagungsband (Herausgeberschaft für den kompletten Band) (1)
- Dissertation (1)
- Forschungsbericht (1)
Schlagworte
- Recycling (26)
- Phosphor (20)
- Klärschlamm (17)
- Phosphorus (15)
- Phosphorrückgewinnung (14)
- Phosphorus recovery (14)
- Sewage sludge (12)
- Fertilizer (9)
- Klärschlammverordnung (9)
- CFK (8)
- Gichtgasschlamm (7)
- Scandium (7)
- BOFS (6)
- Environmental evaluation (6)
- Fertilzer (6)
- Hydraulic reactivity (6)
- Pyrometallurgy (6)
- Elektroofenstaub (5)
- Gypsum (5)
- Klärschlammasche (5)
- Lichtbogenofen (5)
- Portland Cement (5)
- Pyrometallurgie (5)
- Ressourcenrückgewinnung (5)
- Ringversuch (5)
- Sewage sludge ash (5)
- Tantal (5)
- Wastewater (5)
- XANES spectroscopy (5)
- Zement (5)
- Zink (5)
- Alite (4)
- Cabonfasern (4)
- Carbon Fibers (4)
- Circular economy (4)
- Diffusive Gradients in thin films (DGT) (4)
- Diffusive gradients in thin films (DGT) (4)
- Düngemittel (4)
- Dünger (4)
- Electric arc furnace dust (4)
- LD-Schlacke (4)
- Makronährstoffe (4)
- Nährstoffe (4)
- Phosphat (4)
- Red Mud (4)
- Stahlwerksschlacke (4)
- Steelmaking slag (4)
- Tantalum (4)
- X-ray absorption near-edge structure (XANES) spectroscopy (4)
- Zinc (4)
- Baustoffrecycling (3)
- Bauxite Residue (3)
- Blast furnace sludge (3)
- CDW processing (3)
- Carbonfaser (3)
- DGT (3)
- Electric Arc Furnace (3)
- Gypsum recycling (3)
- Landwirtschaft (3)
- Laser-induced breakdown spectroscopy (3)
- Leichtbau (3)
- Mantelverordnung (3)
- Phosphorus fertilizer (3)
- Recycling fertilizer (3)
- Rotschlamm (3)
- Sekundärrohstoffe (3)
- Selective chlorination (3)
- Soil (3)
- Steelmaking (3)
- Thermochemisch (3)
- X-ray diffraction (3)
- AbfKlärV (2)
- Abwasser (2)
- Abwasserbehandlung (2)
- Agronomic performance (2)
- Agronomische Effizienz (2)
- Alkalien (2)
- Aluminium (2)
- Ammonium (2)
- Analytik (2)
- AshDec (2)
- Ashdec (2)
- Bagasse (2)
- Bassanite (2)
- Building and Construction (2)
- Calcium alkali phosphate (2)
- Calcium silicate (2)
- Calcium sulfate (2)
- Carbide formation (2)
- Carbon feeding (2)
- Carbonfasern (2)
- Chromium (2)
- Clinker substitute (2)
- Combustion Ion Chromatography (2)
- Diffusive gradients in thin-films (DGT) (2)
- Filterstaub (2)
- Gypsum fiberboards and synthetic gypsum (2)
- Heavy metal removal (2)
- Infrared spectroscopy (2)
- Leaching (2)
- Leaching control mechanisms (2)
- Melting experiments (2)
- Monoverbrennung (2)
- Monoverbrennungsanlage (2)
- Nitrification inhibitor (2)
- Nutrient (2)
- P-Recyclingdünger (2)
- Per- and Polyfluoroalkyl substances (PFAS) (2)
- Phopshorus recovery (2)
- Pollutant (2)
- Raman spectroscopy (2)
- Recovery (2)
- Recycling fertiliser (2)
- Recycling fertilisers (2)
- Reduction process (2)
- Reproduzierbarkeit (2)
- SCALE (2)
- Scattering (2)
- Secondary Recources (2)
- Sewage sludge ordinance (2)
- Soil P species (2)
- Struvit (2)
- Struvite (2)
- Thermal treatment (2)
- Thermochemical treatment (2)
- Tricalcium-silicate (2)
- Tricalciumsilikat (2)
- X-ray adsorption near-edge structure (XANES) spectroscopy (2)
- XANES (2)
- Zementersatz (2)
- Zementklinker (2)
- Zinnschlacke (2)
- Zitronensäure (2)
- Abwasserreinigung (1)
- Aerodynamic levitation (1)
- Alit (1)
- Alite hydraulic reactivity (1)
- Ashes (1)
- BESSY (1)
- Bauxite residue (1)
- Bio-P-Kläranlage (1)
- Bioavailability (1)
- Bioceramics (1)
- Blast-furnace sludge (1)
- Bushveld Complex (1)
- CFRP (1)
- CaNaPO4 (1)
- Calcium carbonate (1)
- Carbonbeton (1)
- Chemical extraction (1)
- Chemical extraction methods (1)
- Chemische Löslichkeit (1)
- Chicken manure (1)
- Chicken manure ash (1)
- Chlorination (1)
- Chlorine (1)
- Chromitites (1)
- Clean steel (1)
- Co-combustion (1)
- Combustion and gasification (1)
- Controlled release fertilisers (1)
- Corrosion (1)
- Critical raw materials (1)
- Crystalline phase identification (1)
- DGT-Methode (1)
- Design of experiments (1)
- Diffusive Gradients in Thin-films (DGT) (1)
- EAF slags (1)
- Electric arc furnace (EAF) slags (1)
- Electric arc furnace slags (1)
- Elektrolichtbogenofen (1)
- Elimination (1)
- Entropy (1)
- Extraction (1)
- Extraktion (1)
- Extraktionen (1)
- Extraktionsversuche (1)
- FactSage calculations (1)
- FactSageTM calculations (1)
- Forest soils (1)
- Formation enthalpy (1)
- Forschungsförderung (1)
- Fällmittel (1)
- General Environmental Science (1)
- General Materials Science (1)
- Gesteinskörnungen (1)
- Gipsabfälle (1)
- Gipsrecycling (1)
- Gleichwertigkeit Messverfahren (1)
- Granulat (1)
- Gypsum plasterboards (1)
- Gypsum waste (1)
- Hazardous waste (1)
- Hazenite (1)
- Heat capacity (1)
- Hydration products (1)
- Hydrogen (1)
- ICP-MS (1)
- ICP-OES (1)
- In situ (1)
- In situ synchrotron x-ray diffraction (1)
- In-situ analysis (1)
- Incubated soil/fertilizer mixtures (1)
- Industrial and Manufacturing Engineering (1)
- Industrielles Abwasser (1)
- Interlaboratory comparison (1)
- Iron making (1)
- Klimaneutralität (1)
- Kläranlage (1)
- Klärschlammdüngung (1)
- Kreislaufwirtschaft (1)
- LCA (1)
- Landwirtschaftliche Klärschlammverwertung (1)
- Lead (1)
- Lebensmittelindustrie (1)
- Lightweighting (1)
- MSWI fly ash (1)
- Materials Chemistry (1)
- Mechanische Stabilität (1)
- Metals and Alloys (1)
- Microbially induced carbonate precipitation (MICP) (1)
- Multidisciplinary (1)
- Municipal sewage sludge (1)
- MySpot (1)
- Nachhaltigkeit (1)
- Nano-Fourier-transform infrared spectroscopy (1)
- Neutralammoniumcitrat (1)
- Neutralammoniumnitrat (1)
- Niobium (1)
- Nitrate (1)
- Nitrogen (1)
- On-Line Analyse (1)
- On-line analysis (1)
- Oxide melts (1)
- P sink method (1)
- P speciation (1)
- P-Recyclate (1)
- P-Rückgewinnung (1)
- P-Senken (1)
- P-efficiency (1)
- P-recovery (1)
- Passive sampling (1)
- Permeat (1)
- Perowskit (1)
- Pflanzenverfügbarkeit (1)
- Pflanzenwurzel (1)
- Phase formation (1)
- Phase transformation (1)
- Phoshpor availability (1)
- Phosphate dynamics (1)
- Phosphate extractability and availability (1)
- Phosphor-Rückgewinnung (1)
- Phosphorbestimmung (1)
- Phosphorus availability (1)
- Phosphorus elimination (1)
- Phosphorus plant-availability (1)
- Phosphorus recycling (1)
- Phosphous recovery (1)
- Photometric P determination (1)
- Plant Experiment (1)
- Plant availability (1)
- Plant growth test (1)
- Plant-availability (1)
- Plasma (1)
- Platinum (1)
- Pot experiment (1)
- Pot experiments (1)
- Process Metallurgy (1)
- Process control (1)
- Process upscaling (1)
- Push-out Test (1)
- Raman (1)
- Recovery potential (1)
- Recycled gypsum (1)
- Recycled sources (1)
- Recyclingdüngemittel (1)
- Red mud (1)
- Reduction (1)
- Reduktionsprozess (1)
- Relative agronomische Effizienz (RAE) (1)
- Renewable Energy, Sustainability and the Environment (1)
- Resource Recovery (1)
- Ressourceneffizienz (1)
- Ressourcenschonung (1)
- Retentat (1)
- Rhenanite (1)
- Ringversuch P-Gehalt in Klärschlamm (1)
- Rückgewinnung (1)
- Sc recovery (1)
- Scattering-type scanning near-field optical microscopy (s-SNOM) (1)
- Schlacke (1)
- Secondary P-fertilizer (1)
- Sekundärgipse (1)
- Sekundärrohstoff (1)
- Selective Chlorination (1)
- Sewage Sludge (1)
- Sewage Sludge Ashes (1)
- Sewage sludge ash (SSA) (1)
- Sewage sludge disposal (1)
- Sewage sludge incineration (1)
- Silicate (1)
- Silicon carbide (1)
- Spectroscopy (1)
- Stalwerksschlacke (1)
- Steelmaking residues (1)
- Strategy and Management (1)
- Sugar cane bagasse (1)
- Sugarcane bagasse (1)
- Sustainability (1)
- Synchrotron (1)
- Synchrotron radiation (1)
- Technologietransfer (1)
- Thermal analysis (1)
- Thermochemische Prozesse (1)
- Upscaling (1)
- Ureolytic bacteria (1)
- Vegetationsversuche (1)
- Versuchskampagne (1)
- Wasserstoffplasma (1)
- Waste (1)
- Waste water (1)
- Waste water treatment (1)
- Wiederholbarkeit (1)
- Wiederverwertung (1)
- Wood ash (1)
- X-ray diffraction (XRD) (1)
- X-ray spectroscopy (1)
- Zentrat (1)
- Zinc chloride (1)
- Zinnschlacken (1)
- fertilizer (1)
- infrared spectroscopy (1)
- microspectroscopy (1)
- multi scale testing (1)
- soil (1)
- thermochemische Behandlung (1)
- x-ray diffraction (1)
- Ökobilanz (1)
Organisationseinheit der BAM
- 4.4 Thermochemische Reststoffbehandlung und Wertstoffrückgewinnung (188) (entfernen)
Paper des Monats
- ja (3)
Despite its contribution to tackling climate change by lightweight design, growing CFRP production also results in a global waste generation of 62 kt/a. Accordingly, the energy-intensive production process of carbon fibers (CF) necessitates sustainable recycling solutions.
Herein we will give an overview of current recycling processes, discuss their limitations and present a novel approach for safe treatment of CF unsuitable for material recovery . Our project CF Pyro examines feedstock recycling in pyrometallurgical processes, focusing on reactivity of CF, process stability and prevention of hazardous WHO fiber release. Besides fundamental experimental breakthroughs, their broader impact on circular economy will be presented.
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.
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.
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.
Basic oxygen furnace slag (BOFS) is a by-product of the steelmaking process, of which about 10.4 Mt are produced annually in the European Union. Besides its predominant use in road construction, earthwork, and hydraulic engineering, it is also possible to use BOFS as a source material for Portland cement clinker.
The main difference in the chemical composition of BOFS from the chemical composition of Portland cement clinker is its high content of iron oxides (7-50 wt.%). In recent decades, many researchers have investigated the production of both Portland cement clinker and crude iron from BOFS via thermochemical reductive treatment. Carbothermal treatment of liquid BOFS causes reduction of iron oxides to metallic iron, which separates from the mineral phase due to its higher density.
In this study, German BOFS was reduced in a small-scale electric arc furnace using petrol coke as reducing agent. The produced low-iron mineral product was chemically similar to Portland cement clinker and contained the most important Portland cement mineral alite (Ca3SiO5) as main component. Besides alite, the mineral product contained other Portland cement clinker constituents such as belite (β-Ca2SiO4) and tricalcium aluminate (Ca3Al2O6).
The production of Portland cement clinker and crude iron from BOFS has economic and ecological benefits for both the cement and steel industry. Cement clinker from reduced BOFS may be used as a substitute for cement clinker from conventional cement production, thereby CO2 emissions will be reduced. The steel industry benefits from a high-value application for its by-products that avoids cost expensive landfilling and may even bring economic advantages. However, reductive treatment requires high temperatures and, for economic reasons, has to be carried out immediately after casting of the liquid BOFS, which is a logistical challenge for most steel plants. A cost-benefit analysis is therefore essential.
Die Klinkerphasenbildung durch Sinterung in Drehrohröfen bei der Herstellung von Portlandzementklinker (PZK) ist gründlich erforscht und optimiert. Im Hinblick auf mög-liche ökonomische und ökologische Vorteile befassen sich aktuelle Forschungsvorha-ben darüber hinaus mit der Herstellung von Klinkermineralen aus Stahlwerksschla-cken, die eine vergleichbare chemische Zusammensetzung aufweisen.
Neuste Untersuchungen zeigen, dass nach der reduzierenden Behandlung schmelz-flüssiger Linz-Donawitz-(LD)-Schlacken und Abscheidung des gebildeten metallischen Eisens eine mineralische Schlacke entsteht, die unabhängig von ihren Abkühlbedin-gungen ca. 50–60 Gew.% des wichtigsten Klinkerminerals Alit (C3S) enthält und eine hohe hydraulische Reaktivität aufweist.
Die Stabilität des Alits auch nach langsamer Abkühlung deutet auf eine Stabilisierung des Minerals durch Nebenelemente aus den LD-Schlacken hin. Ein sinkender Anteil an LD-Schlacke durch Zusatz synthetischer Schlackemischung, die sich hinsichtlich ihrer Hauptkomponenten wie eine ausreduzierte LD-Schlacke zusammensetzt, führt zu einem Rückgang des Alitgehaltes und dem Zerfall der Schlacke beim Erstarren.
Steelmaking slag is a by-product of steel production of which 4.5 Mt were produced in 2020 in Germany alone. It is mainly used in road construction, earthwork and hydraulic engineering. A smaller part is returned to the metallurgical circle, used as fertilizer or landfilled.
With this use, iron oxides still contained in steelmaking slag are lost. In addition, the possibility of producing higher-grade products from steelmaking slag is foregone. In recent decades, many researchers have investigated the production of Portland cement clinker and crude iron from basic oxygen furnace slags (BOFS) via a reductive treatment. Carbothermal treatment of liquid BOFS causes a reduction of iron oxides to metallic iron, which separates from the mineral phase due to its higher density. Simultaneously, the chemical composition of the reduced slag is adapted to that of the Portland cement clinker.
In this study, German BOFS was reduced in a small-scale electric arc furnace using petrol coke as a reducing agent. The resulting low-iron mineral product had a similar chemical composition to Portland cement clinker and was rich in the tricalcium silicate solid solution alite (Ca3SiO5). Based on its chemical and mineralogical composition, similar to that of Portland cement clinker, the reduced BOFS has the potential to react comparably. In our study, the reduced BOFS produced less heat of hydration compared to OPC and its hydraulic reaction was delayed. However, adding gypsum has been shown to accelerate the hydration rate of the reduced BOFS compared to that known from the calcium silicates of Portland cement clinker.
Further research to improve the hydraulic properties of the reduced slag is essential. If successful, producing a hydraulic binder and crude iron from BOFS could have economic and ecological benefits for both the cement and steel industry.
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 the production of both Portland cement clinker and crude iron from BOFS via a thermochemical reductive treatment. The reductive treatment of liquid BOFS causes a reduction of iron oxides to metallic iron, which separates from the mineral phase due to its higher density and can be recovered. An advantage of this process is that simultaneously the chemical composition of the reduced BOFS is adapted to that of Portland cement clinker and the hydraulic reactive mineral alite (Ca3SiO5) is formed.
In this study, German BOFS was reduced in a small-scale electric arc furnace and a low-iron mineral product rich in alite was produced. 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, adding gypsum accelerated the hydration rate of the reduced BOFS.
Further research to improve the hydraulic properties of the reduced BOFS is essential. If successful, the production of a hydraulic material and crude iron from BOFS could have economic and ecological benefits for both the cement and steel industry.
Basic oxygen furnace slags (BOFS) are by-products of the steelmaking process. Several researchers have studied the production of Portland cement clinker and metallic iron from BOFS via a reductive treatment.
In this study, we applied a carbothermal reduction of BOFS in a technical-scale electric arc furnace and characterised the clinker-like products. Those clinker-like non-metallic products (NMPs) had a chemical and mineralogical composition comparable to clinker for ordinary Portland cement (OPC) and contained large elongated alite crystals as major component. The pure NMPs reacted more slowly and achieved a lower degree of hydration compared with commercial OPC.
If the reactivity of the products can be further increased by employing specific adaptations, it can be used as a full clinker substitute for OPC. Nevertheless, it is also an option to use the material without further modifications as a cement component or concrete addition, which contributes to the strength development in both cases.
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.
Die Klinkerphasenbildung durch Sinterung in Drehrohröfen bei der Herstellung von Portlandzementklinker (PZK) ist gründlich erforscht und optimiert. Im Hinblick auf mögliche ökonomische und ökologische Vorteile befassen sich aktuelle Forschungsvorhaben darüber hinaus mit der Herstellung von Klinkermineralen aus Stahlwerksschlacken, die eine vergleichbare chemische Zusammensetzung aufweisen.
Neuste Untersuchungen zeigen, dass nach der reduzierenden Behandlung schmelzflüssiger Linz-Donawitz-(LD)-Schlacken und Abscheidung des gebildeten metallischen Eisens eine mineralische Schlacke entsteht, die unabhängig von ihren Abkühlbedingungen ca. 50–60 Gew.% des wichtigsten Klinkerminerals Alit (C3S) enthält und eine hohe hydraulische Reaktivität aufweist.
Die Stabilität des Alits auch nach langsamer Abkühlung deutet auf eine Stabilisierung des Minerals durch Nebenelemente aus den LD-Schlacken hin. Ein sinkender Anteil an LD-Schlacke durch Zusatz synthetischer Schlackemischung, die sich hinsichtlich ihrer Hauptkomponenten wie eine ausreduzierte LD-Schlacke zusammensetzt, führt zu einem Rückgang des Alitgehaltes und dem Zerfall der Schlacke beim Erstarren.
Tricalcium-silicate (C3S) or Alite is the most important mineral in Portland cement. Since pure tricalcium-silicate is only stable above temperatures of 1250 °C, its decomposition has to be prevented technically by fast cooling after the sintering process. At room temperature, the decomposition velocity is very slow so that metastable tricalcium-silicate is obtained.
Although the mechanisms of clinker phase formation during burning process of Portland cement in a rotary kiln were solved and improved over the years, in view of possible economic and ecological benefits current projects aim to produce clinker phases from metallurgical slags. Recent studies discovered that the mineral phase which remained after a reducing treatment and separation of formed metallic iron from molten Linz-Donawitz (LD-) slags contained about 60 wt.% Alite despite it was cooled slowly. Because the results could be verified using slags from different origins and varying cooling velocities a chemical stabilisation of the Alite can be assumed. First tests in mortars indicate that workability, hardening and solid state properties are comparable with an ordinary Portland cement. An application of the observed phenomenon in cement production requires enhanced knowledge about formation and stabilisation conditions of Alite during crystallisation from melts in contrast to the sintering reactions in conventional Portland cement production. Therefore, this study focuses on the stabilisation mechanisms of Alite in consolidating melts. Samples from different melting experiments are analysed to determine stabilising factors.
Phase formation and evolution was investigated in the CaO–SiO2 system in the range of 70–80 mol% CaO. The samples were container-less processed in an aerodynamic levitation system and crystallization was followed in situ by synchrotron x-ray diffraction at the beamline P21.1 at the German electron synchrotron (DESY). Modification changes of di- and tricalcium silicate were observed and occurred at lower temperatures than under equilibrium conditions. Despite deep sample undercooling, no metastable phase formation was observed within the measurement timescale of 1 s. For the given cooling rates ranging from 300 K s−1 to about 1 K s−1, no decomposition of tricalcium silicate was observed. No differences in phase evolution were observed between reducing and oxidizing conditions imposed by the levitation gas (Ar and Ar + O2). We demonstrate that this setup has great potential to follow crystallization in refractory oxide liquids in situ. For sub-second primary phase formation faster detection and for polymorph detection adjustments in resolution have to be implemented.
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.
Analyseverfahren und Messhäufigkeit zur Bestimmung des Phosphorgehalts im Klärschlamm nach AbfKlärV
(2022)
Auf dem Betreiberforum der DWA-Plattform P-Rück wurden die Empfehlungen für den Vollzug der Phosphorrückgewinnungspflicht aus Klärschlamm vorgestellt. Diese Empfehlungen behandeln die Häufigkeit der Phosphoruntersuchungen im Klärschlamm, wo ein Jahresgang empfohlen wird und eine Empfehlung der Phosphorbestimmung über Aufschluss der Probe in der Mikrowelle und Messung mit ICP-OES. Untermauert wurden die Empfehlungen mit den Ergebnissen von Klärschlamm-Monitoring, Ringversuch und Analytikvergleich aus dem Vorhaben extraWERT.
Der Vortrag liefert eine Zusammenfassung der wichtigsten Ergebnisse des extraWERT-Vorhabens mit Schwerpunkt auf den Umsetzungsfragen zur Klärschlammverordnung. Bei diesen Punkten handelt es sich um die Untersuchung von monatlichen Phosphorschwankungen in kommunalem Klärschlamm und die Gleichwertigkeit verschiedener Verfahren zur Phosphorbestimmung in Klärschlamm.
In Deutschland ist ab 2029 eine Phosphorrückgewinnung aus Klärschlamm verpflichtend. Ausgenommen sind Klärschlämme mit weniger als 20 g P/kg TM. Für die Phosphorbestimmung sind verschiedene Methoden nach Klärschlammverordnung als gleichwertig zugelassen: Der Königswasseraufschluss in der Mikrowelle und am Rückfluss sowie die Messung an ICP-OES, ICP-MS und die photometrische Bestimmung mittels Ammoniummolybdaten. An der BAM wurden die unterschiedlichen Methodenkombinationen aus Aufschluss- und Messmethode an 15 Klärschlämmen überprüft und in einem Ringversuch mit einem Klärschlamm getestet. Die Ergebnisse werden in diesem Vortrag zusammengefasst. Als Folge der Untersuchungen wird für die Phosphorbestimmung in Klärschlamm die ICP-OES-Messung nach Königswasseraufschluss in der Mikrowelle empfohlen.
Agricultural sewage sludge utilization becomes less important in Germany. In 2017, new fertilizer and waste laws caused the agricultural sewage sludge utilization to collapse by more than a quarter. From 2029, in German wastewater treatment plants (WWTPs) phosphorus (P) must be recovered from sewage sludge ifit contains more than 2 wt % P. Agricultural utilization will be prohibited for large WWTPs > 100,000 population equivalents (pe) from 2029 and > 50,000 pe from 2032. In Germany, each federal state must annually report amounts and quality of agriculturally utilized sewage sludge which was 17 % of the total disposal in 2019. The reports of 10 States were evaluated for 2016 and 2017 representing approx. 60 % ofthe total agriculturallyused sludge volume. Whereas phosphorus recovery is mandatory this does not apply to other nutrients. However, many P recovery processes recover other nutrients, too. Considering three differentscenariosfor future German sewage sludge disposal shows that 70 - 77 % ofthe P load in sewage sludge will probably be recovered in the future. At the same time, this applies for about 0 - 16 % of nitrogen, 36 - 52 % of calcium, 31-53 % of potassium, and 40 - 52 % of magnesium. However, these recovered nut rient loads can substitute only 1 % or less ofthe commercial fertilizer demand except from phosphorus which is about 45 % ofthe demand.
Die Ergebnisse des extraWERT-Vorhabens wurden Vertreter*innen des Umweltministeriums von Bund und Ländern vorgestellt und im Zusammenhang mit dem Vollzug der AbfKlärV diskutiert. Es ging um die Phosphorschwankungen in kommunalem Klärschlamm und eine Empfehlung der Untersuchungshäufigkeit, um den Phosphorgehalt rechtssicher festzustellen. Des weiteren wurde die Performance verschiedener nach Verordnung gleichwertiger Analyseverfahren für Phosphor in Klärschlamm diskutiert anhand von Ringversuchsergebnissen und Eigenuntersuchungen an 15 Klärschlammproben.
Gleichwertigkeit der nach AbfKlärV zulässigen Verfahren zur Phosphorbestimmung in Klärschlamm
(2021)
In dem Meeting wurde den Notifizierern und Ausrichtern des jährlichen länderübergreifenden Ringversuchs Klärschlamm die Ergebnisse zu Untersuchungen hinsichtlich der Gleichwertigkeit verschiedener nach AbfKlärV zulässiger Verfahren zur Phosphorbestimmung in Klärschlamm vorgestellt. Die Untersuchungen an 15 Klärschlammproben ergaben die höchsten Ergebnisse für das Messverfahren ICP-OES und das Aufschlussverfahren in der Mikrowelle. Diese Ergebnisse wurden im Ringversuch bestätigt.
Die landwirtschaftliche Klärschlammverwertung ist in der Bundesrepublik Deutschland seit Jahren rückläufig. Neben den Risiken durch Schadstoffeinträge gibt es in Deutschland Regionen mit einem stark erhöhten Nährstoffüberschuss. Um die Grundwasserbelastung zu verhindern wurde u.a. das Düngerecht verschärft, was die Flächenkonkurrenz zwischen Klärschlamm und Wirtschaftsdünger vergrößern wird.
Es ist davon auszugehen, dass sich die neuen Regelungen im Düngerecht und der Klärschlammverordnung massiv auf die landwirtschaftliche Verwertung von Klärschlamm und damit auf die Kreislaufwirtschaft verschiedener Nährstoffe auswirken werden. In diesem Beitrag werden erste Ergebnisse des Projekts extraWERT vorgestellt.
Es wurden erste Ergebnisse des Projekts extraWERT vorgestellt. Im Projekt werden monatlich Klärschlammproben von 10 kommunalen Kläranlagen untersucht, deren P-Gehalt im Grenzbereich der AbfKlärV liegt zwischen 1,7 und 2,3%. Die ersten Ergebnisse lagen zu fünf Kläranlagen vor, es wurden Daten zum TS-Gehalt, zur oTS und zu den Nährstoffgehalten präsentiert.
New developments in legislation and technology development for P-recovery were presented with focus on the situation in Germany.
Im Projekt extraWERT geht es um die Ermittlung von Nährstoffpotenzialen in Abwasser und Klärschlamm. Neben kommunalen Kläranlagen soll auch die Industrie als Quelle für nährstoffreiche Abfallströme betrachtet werden. Mit dem Vortrag sollten Mitglieder des MIV zu einer Projektbeteiligung bewegt werden. Es sollen rohes und gereinigtes Abwasser von direkt einleitenden Betrieben auf Makronährstoffe untersucht werden, neue Erkenntnisse werden insbesondere für die Nährstoffe Calcium und Magnesium erwartet.
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.
Agricultural sewage sludge utilization becomes less important in Germany. In 2017, new fertilizer and waste laws caused the agricultural sewage sludge utilization to collapse by more than a quarter. From 2029, in German wastewater treatment plants (WWTPs) phosphorus (P) must be recovered from sewage sludge ifit contains more than 2 wt % P. Agricultural utilization will be prohibited for large WWTPs > 100,000 population equivalents (pe) from 2029 and > 50,000 pe from 2032. In Germany, each federal state must annually report amounts and quality of agriculturally utilized sewage sludge which was 17 % of the total disposal in 2019. The reports of 10 States were evaluated for 2016 and 2017 representing approx. 60 % ofthe total agriculturally used sludge volume. Whereas phosphorus recovery is mandatory this does not apply to other nutrients. However, many P recovery processes recover other nutrients, too.
Considering three differentscenariosfor future German sewage sludge disposal Shows that 70 - 77 % ofthe P load in sewage sludge will probably be recovered in the future.
At the same time, this applies for about 0 - 16 % of nitrogen, 36 - 52 % of calcium, 31-53 % of potassium, and 40 - 52 % of magnesium. However, these recovered nutrient loads can substitute only 1 % or less ofthe commercial fertilizer demand except from phosphorus which is about 45 % ofthe demand.
Die landwirtschaftliche Klärschlammverwertung ist in der Bundesrepublik Deutschland seit Jahren rückläufig, hatte im Jahr 2017 jedoch noch einen Anteil von rund 18 % [20]. Diese Art der Verwertung wird kontrovers diskutiert, da der Klärschlamm im Rahmen der Abwasserreinigung eine Schadstoffsenke darstellt. In vergangenen Jahrzehnten wurden insbesondere die hohen Gehalte an Schwermetallen im Klärschlamm als kritisch für eine landwirtschaftliche Verwertung eingestuft. Diese Belastung konnte allerdings durch Absenkung der Einträge von Schmermetallen in das Abwasser signifikant gesenkt werden. Neben Schwermetallen kamen jedoch auch organische Schadstoffe wie Pharmazeutika, Kosmetika und Haushaltschemikalien in den Fokus der Diskussion über den Einsatz von Klärschlamm auf Agrarflächen. Heute geraten zunehmend weitere Inhaltsstoffe in den Fokus, deren Auswirkungen noch nicht abschließend geklärt sind, weshalb eine einheitliche Bewertung über Grenzwerte nicht darstellbar ist. Beispiele für diese neuen Stoffgruppen sind Mikroplastik, Nanopartikel, Antibiotikaresistenzen und persistente organische Spurenstoffe. Neben den angesprochenen Risiken gibt es in Deutschland Regionen mit einem stark erhöhten Nährstoffüberschuss. In der Kritik steht vor allem eine nicht ordnungsgemäße Düngung mit Stickstoff, welche mit Nitratauswaschungen in das Grundwasser einhergeht. Um diese Grundwasserbelastung zu verhindern wurde u.a. das Düngerecht erneut verschärft, was die Flächenkonkurrenz zwischen Klärschlamm und Wirtschaftsdünger weiter vergrößern wird. Auf Druck der EU-Kommission stehen zudem weitere Anpassungen im Düngerecht bevor, da die beschlossenen Änderungen aus Kommissionssicht nicht ausreichen, um die Nitratrichtlinie einzuhalten. Vor dem Hintergrund der angeführten Probleme wurde im Koalitionsvertrag der 18. Legislaturperiode (2013) festgeschrieben, „die Klärschlammausbringung zu Düngezwecken [zu] beenden und Phosphor und andere Nährstoffe zurück[zu]gewinnen“ [5]. Die novellierte AbfKlärV beinhaltet allerdings kein grundsätzliches Aufbringungsverbot und eine Rückgewinnungspflicht besteht lediglich für den Nährstoff Phosphor. Es ist davon auszugehen, dass sich die neuen Regelungen im Düngerecht und der Klärschlammverordnung massiv auf die landwirtschaftliche Verwertung von Klärschlamm und damit auf die Kreislaufwirtschaft verschiedener Nährstoffe auswirken werden. Zur Ermittlung dieser Auswirkungen wird seit Oktober 2018 im Auftrag des Umweltbundesamtes das REFOPLAN-Projekt „extraWERT“ (FKZ 3718 26 330 0) von der Bundesanstalt für Materialforschung und -prüfung (BAM) in Kooperation mit dem Institut für Siedlungswasserwirtschaft (ISA) der RWTH Aachen durchgeführt. In diesem Beitrag werden erste Ergebnisse dieses Projekts vorgestellt.
Ab 2029 gilt für alle Kläranlagen in Deutschland eine Pflicht zur Rückgewinnung von Phosphor (P) aus Klärschlamm. Ausgenommen sind nur Anlagen mit Schlämmen mit weniger als 20 g P/kg bezogen auf die Trockenmasse (TM). Für eine Überprüfung der Phosphorschwankungen im Klärschlamm wurden neun verschiedene Kläranlagen ausgewählt mit Phosphorgehalten nahe der "Rückgewinnungsgrenze" von 20 g/kg TM. Der entwässerte Klärschlamm dieser Anlagen wurde monatlich beprobt und auf seinen Phosphorgehalt geprüft. Die Phosphorschwankungen betrugen je nach Anlage zwischen 4 % und 13 % (relative Standardabweichung), im Mittel rund 7 %.
Phosphorus (P) recovery is obligatory for all sewage sludges with more than 20 g P/kg dry matter (DM) from 2029 in Germany. Nine wastewater treatment plants (WWTPs) were chosen to investigate variations of phosphorus contents and other parameters in sewage sludge over the year. Monthly sewage sludge samples from each WWTP were analyzed for phosphorus and other matrix elements (C, N, H, Ca, Fe, Al, etc.), for several trace elements (As, Cr, Mo, Ni, Pb, Sn) and loss of ignition. Among the nine WWTPs, there are four which have phosphorus contents both above and below the recovery limit of 20 g/kg DM along the year. Considering the average phosphorus content over the year, only one of them is below the limit. Compared to other matrix elements and parameters, phosphorus fuctuations are low with an average of 7% over all nine WWTPs. In total, only hydrogen and carbon are more constant in the sludge.
In several WWTPs with chemical phosphorus elimination, phosphorus fuctuations showed similar courses like iron and/or aluminum. WWTPs with chamber flter presses rather showed dilution efects of calcium dosage. As result of this study, monthly phosphorus measurement is highly recommended to determine whether a WWTP is below the
20 g/kg DM limit.
Phosphorus recycling from sewage sludge will be obligatory in Germany from 2029. Phosphorus content determination in sewage sludge is crucial to assess the prescribed recycling rates. Currently, German law regards sample preparation using aqua regia digestion in a microwave or under reflux conditions as well as instrumental phosphorus determination by ICP-OES, ICP-MS, or photometric determination with ammonium molybdate as equivalent. However, it is questionable whether these methods are indeed equivalent regarding phosphorus quantification in sludges near the limit of 20 g/kg for mandatory recycling. To answer this question, 15 sewage sludges of 11 different wastewater treatment plants were investigated with all permitted method (digestion and measurement) combinations. Moreover, one sewage sludge was also examined in an interlaboratory comparison (ILC) with 28 participants. This study shows that the above-mentioned methods differ in some cases significantly but across all method combinations and sludges, phosphorus recovery was between 80 and 121% after normalization to the grand mean (average of 15 sludges between 85 and 111%). The ILC and the examination of 15 sludges produced largely similar results. There is a tendency to higher phosphorus recovery after microwave digestion compared to reflux digestion and ICP-OES measurements determine higher phosphorus contents than ICP-MS and photometric phosphorus determination. As a result, the authors recommend ICP-OES determination of phosphorus in sewage sludge after microwave digestion.
Future nutrient recovery from sewage sludge regarding three different scenarios - German case study
(2022)
Agricultural sewage sludge utilization becomes less important in Germany. In 2017, new fertilizer and waste laws caused the agricultural sewage sludge utilization to collapse by more than a quarter. From 2029, German wastewater treatment plants (WWTPs) must recover phosphorus (P) from sewage sludge if it contains more than 2 wt % P. Agricultural utilization will be prohibited for large WWTPs >100,000 population equivalents (pe) from 2029 and >50,000 pe from 2032. In Germany, each federal state must annually report amounts and quality of agriculturally utilized sewage sludge which was 16% of the total disposal in 2019. The reports of 10 states were evaluated for 2016 and 2017 representing approx. 60% of the total agriculturally used sludge volume. In 2016, 60% of the WWTPs’ sludges exceeded the recovery limit of 2 wt % P which is 70% of the amount of sludge and 85% of the phosphorus load. Other nutrients are not affected by the recovery obligation. However, many P recovery processes recover other nutrients, too. Considering three different scenarios for future German sewage sludge disposal shows that 70–77% of the P load in sewage sludge will probably be recovered in the future. At the same time, this applies for about 0–16% nitrogen, 36–52% of calcium, 31–53% of potassium, and 40–52% of magnesium. However, these recovered nutrients loads can substitute only 1% or less of the commercial fertilizer demand except from phosphorus which is up to 43% of the demand.
The present work demonstrates a sustainable approach of using relatively coarser iron ore particles for ironmaking. The motivation is to reduce the energy consumption in the milling of the iron ore by utilizing coarser iron ore particles (+0.05 mm) and to select a suitable binder for improving pellet properties. Iron ore fines in the range of 0.05–0.25 mm was selected and classified into three size ranges. Fluxed iron ore pellets were prepared using lime as a binder for the basicity of 0, 1, and 2. Reduction of these pellets with a packed bed of coal fines was performed in the temperature range of 900–1200 °C for a duration of 30–120 min. The direct reduction kinetics of the iron ore pellets were studied by employing diffusion and chemical reaction control models to the experimental data. The results show that pellets made with coarser iron ore particles have improved reduction behavior and kinetics. The reduction reaction is found to be a mixed control. The activation energy for the reduction reaction varies from 44.3 to 74.76 kJ mol−1 as iron ore particle size decreases from 0.25 to 0.05 mm and basicity increases from 0 to 2.
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.
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.
More sustainable waste management practices are an important element in the Transformation towards a circular economy (CE). Activities in this area should be dedicated to all groups of waste, including those generated in the water and sewage sector. This paper presents the characteristics of sewage sludge ash (SSA) coming from Polish municipal waste incineration plants. Due to the high content of nutrients such as phosphorus (8.01% P2O5), calcium (5.11% CaO) and magnesium (2.75% MgO), the analyzed SSA may constitute a valuable source of raw materials for the fertilizer industry.
Despite the good fertilizing properties of the SSA, in some cases the presence of heavy metals such as cadmium (0.74–1.4 mg/kg dry matter), lead (49.8–99 mg/kg dry matter), mercury (3.93 mg/kg dry matter) and arsenic (4.23–4.43 mg/kg dry matter) and poor bioavailability of P from SSA disqualifies this waste from direct use as a fertilizer. Therefore, it is necessary to look for methods that will allow the municipal SSA to be processed, for example, technologies for the extraction of phosphorus and the production of phosphate fertilizer. This way of SSA management is in the line with the CE assumptions, in which waste becomes a valuable source of secondary raw materials. Fertilizer produced from waste meeting quality, safety and labelling requirements and limits of organic, microbiological and physical contaminants will be able to be traded freely within the European Union (EU) and receive the CE marking. The idea of use of SSA for fertilizer purposes is consistent not only with the objectives of the CE but also with the Polish National Waste Management Plan 2022 and the Municipal Sewage Sludge Strategy 2019–2022, which emphasizes the necessity to maximize the use of biogenic substances contained in wastewater. Therefore, sustainable management of SSA, in particular its storage in a way enabling the recovery of phosphorus, should be promoted.
Popioły pochodzące z instalacji do spalania komunalnych osadów ściekowych, znajdującej się na terytorium Polski, poddano procesom termochemicznego przekształcania, dzięki czemu otrzymano produkty nawozowe spełniające kryteria dopuszczające je do obrotu jako nawozy mineralne. Ponadto dokonano analizy możliwości wykorzystania popiołów na cele nawozowe zgodnie z obecnie przyjętymi dokumentami strategicznymi i planistycznymi dotyczącymi gospodarki odpadami na poziomie krajowym i europejskim.
This paper presents an inventory of sewage sludge ashes (SSA) generated in the mono-incineration plants for municipal sewage sludge in Poland. This research focused on the detailed study of mass flows, chemical composition, and phosphorus recovery potential. There are currently 11 sludge mono-incineration plants operated with a total capacity of 160,300 Mg dry weight (d.w.) of sludge annually. Recently, a significant increase in the amount of SSA generated in these plants has been observed, reaching 26,756 Mg in 2018. Chemical composition of SSA showed significant amounts of the main nutrients: calcium (~14%), phosphorus (~13%), magnesium (~3%), and potassium (~1%). Additional main elements were iron (~14.5%), silicon (~13%), and aluminium (~6%). The main trace elements in the SSA were zinc (~3750 mg/kg) and copper (~899 mg/kg). Pollutants, according to fertilizer regulations of different countries, present in Polish SSA were chromium(~703 mg/kg), nickel (~260 mg/kg), lead (~94 mg/kg), and Cadmium (~9 mg/kg). The radionuclides, uranium, and thorium often present in higher amounts in commercial phosphate rock-based fertilizers, were only detected in SSA t low levels of 4–9 mg/kg and 2–3 mg/kg, respectively. Theoretical phosphorus recovery potential from the SSA (from plants in Cracow, Lodz, Gdansk, Gdynia, Szczecin, and Kielce) was estimated at 1613.8 Mg, of which 33.9% is bioavailable. Currently, in Poland, the recommended approach is the production of fertilizers as a result of the extraction of phosphorus from the SSA with its use in the production of secondary mineral fertilizers.
Further research in this area is required considering Polish conditions and legislation.
Phosphorus (P) recovery from sewage sludge ash (SSA) is one of the most promising approaches of phosphate rock substitution in mineral fertilizers and might be a sustainable way to secure supply of this raw material in the future. In the current investigation, the process of thermochemical treatment of SSA was applied to SSA coming from selected mono-incineration plants of municipal sewage sludge in Poland (Cracow, Gdansk, Gdynia, Lodz, Kielce and Szczecin).
The Polish SSA was thermochemically converted in the presence of sodium (Na) additives and a reducing agent (dried sewage sludge) to obtain secondary raw materials for the production of marketable P fertilizers. The process had a positive impact on the bioavailability of phosphorus and reduced the content of heavy metals in the obtained products. The P solubility in neutral Ammonium citrate, an indicator of its bioavailability, was significantly raised from 19.7–45.7% in the raw ashes and 76.5–100% in the thermochemically treated SSA. The content of nutrients in the recyclates was in the range of 15.7–19.2% P2O5, 10.8–14.2% CaO, 3.5–5.4% Na2O, 2.6–3.6% MgO and 0.9–1.3% K2O. The produced fertilizer raw materials meet the Polish norms for trace elements covered by the legislation: the content of lead was in the range 10.2–73.1 mg/kg, arsenic 4.8–22.7 mg/kg, Cadmium 0.9–2.8 mg/kg and mercury <0.05 mg/kg. Thus, these products could be potentially directly used for fertilizer production. This work also includes an analysis of the possibilities of using ashes for fertilizer purposes in Poland, based on the assumptions indicated in the adopted strategic and planning documents regarding waste management and fertilizer production.
One of the key elements in the transformation towards a circular economy (CE) is providing more sustainable practices for resources and waste management. Improvement actions focused on transformation towards a CE should be targeted at all groups of materials and waste. As water is essential for human survival and well-being and plays a significant role in sustainable development (SD), the actions related to the reuse of water and the recovery of raw materials from wastewater and other water-based waste should be taken. The paper presents a proposition for a new CE model framework in the water and wastewater sector, which includes the six following actions: reduction—prevent wastewater generation in the first place by the reduction of water usage and pollution reduction at source; reclamation (removal)—an application of effective Technologies for the removal of pollutants from water and wastewater; reuse—reuse of wastewater as an alternative source of water supply (non-potable usage), recycling—recovery of water from wastewater for potable usage; recovery—recovery of resources such as nutrients and energy from water-based waste, and rethink—rethinking how to use resources to create a sustainable economy, which is `free` of waste and emissions. The novelty of the proposed CE model framework is that it presents possible ways of implementing CE principles in the water and wastewater sector, with a strong emphasis not only technological but also organisational and societal changes. Application of the proposed model may help to further transform the European economy to the CE model. Moreover, the indicated model can be significant tool supporting an assessment of local or regional progress towards CE in the water and wastewater sector and further environmental management and planning.
Hydrogen plasma treatment of iron ores or iron oxide containing wastes can be an efficient option to produce green iron e.g. for steel production. This way iron oxide is reduced to metallic iron in the liquid form by the highly reactive species that are formed in a hydrogen plasma. Hydrogen plasma can be used at the same time to remove undesired gangue elements. The presentation shows the experimental setup, shows first results of iron ore reduction by hydrogen plasma and gives an outlook for industrial application of the technology.
The challenge of the project ASHES is focused on the recycling of nutrients from residues of thermochemical processing of by-products of sugar cane industry (bagasse/straw) in Brazil to increase the energy efficiency of thermal conversion and to enable the recycling of process ashes as fertilisers. Dry lignocellulosic biomass (straw, bagasse) are combusted, gasified and subsequently combined with post-thermochemical treatment in the AshDec process to increase the plant availability of phosphorus. Different fertilizer formulations are granulated/pelletized and tested regarding their storage/handling characteristics.
Jährlich entstehen in Brasilien ca. 2 bis 10 Millionen Tonnen Aschen aus der Verbrennung von Zuckerrohrbagasse. Die Aschen enthalten schwankende Zusammensetzungen an mineralischen Nährelementen und könnten daher zu Düngezwecken verwendet werden.
Allerdings ist (i) die Nährstoffverfügbarkeit gering, (ii), die entsprechende Nährstoffzusammensetzung nicht optimal für die Nutzung der Aschen als Düngemittel für die Hauptanbaukulturen in Brasilien und (iii) weisen die Aschen aufgrund häufig schlechter Verbrennungsqualitäten hohe organische Kohlenstoffgehalte auf. Im Rahmen des Forschungsprojekts ASHES („Rückführung von Nährstoffen aus Aschen von thermochemischen Prozessen mit Bagasse bzw. Zuckerrohrstroh“), arbeiten 7 deutsche und 4 brasilianische Partner an der Optimierung der thermochemischen Verwertung von Rückständen aus der Zuckerproduktion in Brasilien, inklusive der Formulierung von optimierten Düngemischungen auf Basis der generierten Aschen. In dieser Veröffentlichung wird die Verarbeitung dieser optimierten Mischungen zu Pellets und Granulaten unter Verwendung verfügbarer regionaler Reststoffe wie Filterkuchen (Vinasse-Presskuchen) sowie Hühnertrockenkot beschrieben. Zur Untersuchung der Handlingeigenschaften wurden die produzierten Pellets und Granulate hinsichtlich ihrer mechanischen Stabilität und des Wasseraufnahmevermögens untersucht. Dafür wurden geeignete Prüfverfahren angepasst und entsprechende Versuche durchgeführt.
Calcium sulfate hemihydrate (CaSO4ᐧ0.5H2O), also known as bassanite, has been used as a precursor to produce gypsum (dihydrate, CaSO4ᐧ2H2O) for various construction and decorative purposes since prehistoric times. The main route to obtain hemihydrate is a thermal treatment of gypsum at temperatures typically between 150 °C and 200 °C to remove some of the structural water.
In this contribution, we introduce (Fig. 1) a more efficient and sustainable method (T < 100 °C) that enables the direct, rapid, and reversibly conversion of gypsum to bassanite using reusable high salinity aqueous solutions (brines with c[NaCl] > 4 M). The optimum conditions for the efficientproduction 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 typical behaviour of the bassanite phase in low salt environments.
Traditionally, hemihydrate is obtained through a solid state thermal treatment because bassanite is considered to be metastable with respect to gypsum and anhydrite in aqueous solutions, and therefore gypsum-to-bassanite conversion should not occur in water. 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 is 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 structure for many hours before reverting into gypsum. This property is extremely advantageous for practical processing and efficient crystal extraction in industrial scenarios.
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.
In the near future, phosphorus (P) recycling will gain importance in terms of decreasing primary resources. Sewage sludge (SSL) is an adequate secondary P-resource for P-fertilizer production but it is also a sink for heavy metals and organic pollutants. The present study is an investigation on thermochemical P-recycling of SSL. Various temperatures and amendments were tested regarding their performance to remove heavy metals and polycyclic aromatic hydrocarbons (PAH) and simultaneous increase of the plant-availability of P. The investigations were carried out on two types of SSL originating from wastewater treatment plants with chemical P-precipitation and enhanced biological P-removal, respectively. The results show that thermochemical treatment with chlorine donors is suitable to remove the majority of heavy metals and that a combination of a gaseous chlorine donor (HCl) and sodium additives leads to both high heavy metal removal and high plant availability of P. Furthermore, plant experiments Show that almost all investigated thermochemical treatments can significantly reduce the bioavailability and plant uptake of heavy metals. Furthermore, PAHs are secondarily formed during low-temperature treatments (400–500 ° ), but can be significantly reduced by using sodium carbonate as an additive.
Phosphorus (P) resource availability and quality is declining and recycling P-fertilizers from waste materials are becoming increasingly important. One important secondary P resource is sewage sludge (SSL) where P is often bound as aluminum phosphate (Al-P), iron phosphate (Fe-P) and polyphosphate (poly-P), respectively. Thermal treatment in different ways is a promising way in P recycling to produce highly plant-available P-fertilizers. To investigate mechanisms behind transformation of hardly available P-species toward plant-available P forms we treated a model SSL containing different kinds of defined P sources by low-temperature conversion (LTC) at 500 °C and subsequent thermochemical treatment of the LTC product with Na additives (TCT) at 950 °C, respectively. Pot experiments with ryegrass were carried out to determine the plant availability of P of the different treatments. The poly-P (here pyrophosphates) based fertilizers had a very high plant availability after both thermal treatments. During LTC treatment the plant availability of the Fe-P and Al-P variants increased because of the Formation of Fe(II) phosphates and/or pyro-/polyphosphates. Especially the formation of Al-polyphosphate shows a high plant availability. The subsequent TCT further increased strongly the plant availability of the Fe-P variants because of the formation of highly plant-available CaNaPO4. Thus, a direct TCT without prior LTC probably also produce CaNaPO4 and is recommended for Fe-P based SSL. However, a molar Ca/P ratio of 1 in the fertilizer is favorable for CaNaPO4 formation. Thus, the knowledge on the source of primary P in SSL is essential for choosing the accurate thermal treatment method to produce highly plant-available P-fertilizers from SSL.
Phosphorus (P) recycling from sewage sludge for agricultural needs has to meet requirements for agricultural implementation, such as short and long-term P-plant-availability under field conditions. Field experiments often bring no evaluable results, because agricultural soils got a high potential of P-supply even if they are classified as low in P-supply according to the CAL extraction method. The present study presents a possible way to investigate the P-plant-availability of P-recycling-fertilizers under field-like conditions. The plant experiments are firstly performed in small Mitscherlich pots in growth chambers and subsequently in containers with a high soil volume of 170 kg under greenhouse conditions, in which plants can grow until ripening. The tested P-recycling fertilizers were produced from sewage sludge in a large-scale thermal process. It was a two-step treatment process performed with a pyrolysis of sewage sludge at 550°C (SSC-550) and a subsequent thermochemical post-treatment at 950°C with Na2SO4 (SSA-Na) and HCl + Na2SO4 (SSA-HCl/Na) as additives. The results show, that the P-recycling-products from pyrolysis got an adequate long-term but a 65% lower short-term P-plant-availability compared to triple superphosphate. SSA-Na and SSA-HCl/Na show both a high short and longterm P-plant-availability comparable to triple-superphosphate. This can be explained by their highly plant-available P-compound CaNaPO4.
Optimierung eines pyrometallurgischen Tantal- und Niob- Recyclingprozesses mithilfe von On-Line LIBS
(2018)
Die Entwicklung von Hochleistungselektronik zu immer kleineren Bauformen ohne Leistungseinbußen ist ohne den Einsatz von Technologiemetallen wie Niob und Tantal heute praktisch nicht mehr realisierbar. Besonders in technischen Geräten wie Smartphones und Tablets sind Tantal- und Niobkondensatoren aufgrund ihrer hohen Leistungsdichten bereits unverzichtbar geworden. Für die nachhaltige Produktion von Elektronik stellt jedoch vor allem das Tantalerz Coltan als sogenanntes „conflict mineral” ein großes Problem dar.
Um den Wirtschaftsstandort Europa unabhängiger von Primärrohstoffimporten aus Krisenregionen zu machen, ist die Entwicklung von effizienten Recyclingverfahren heute wichtiger denn je. An der Bundesanstalt für Materialforschung und -prüfung (BAM) findet daher zurzeit die Optimierung eines pyrometallurgischen Industrieprozesses zur Niob- und Tantalrückgewinnung statt, welchem hauptsächlich niedrigkonzentrierte metallurgische Rückstände aus der Tantal- und Niob- bzw. der Zinngewinnung als Einsatzstoffe dienen.
Zu diesem Zweck werden im kleintechnischen Lichtbogenofen der BAM (480 kVA, max. Materialdurchsatz ca. 150 kg/h) Versuche mit einem neuen innovativen Messgerät durchgeführt, welches eine On-Line Analyse von Hochtemperaturprozessen ermöglicht. Der eingesetzte Prototyp nutzt das Verfahren der laserinduzierten Plasmaspektroskopie (LIBS), um die chemische Zusammensetzung der Schlackephase noch im Schmelzbad und während eines Schlackeabgusses zu bestimmen. Nach einer Kalibrierung auf das vorliegende Stoffsystem ermöglicht dieser On-Line-LIBS Prototyp der BAM daher eine in-situ Bestimmung der Elementverteilung in der Schmelze. Die hier gewonnenen Daten sollen helfen, die aktuelle Prozessführung zu verbessern und die Tantal- und Niobausbeute noch weiter zu erhöhen.