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The slag samples taken from landfill, which originated from different metallurgical processes, have been characterized in this study. The slags were categorized as electric arc furnace (EAF) slag, argon oxygen decarburization/metal refining process slag and vacuum oxygen decarburization slag based on chromium content and basicity. EAF slags have higher potential in metal recovery than the other two slags due to its higher iron and chromium contents. The size of the iron-chromium-nickel alloy particles varies from a few μm up to several cm. The recoveries of large metal particles and metal-spinel aggregates have potential to make the metal recovery from landfilled slags economically viable.

Metal slags generated from metallurgical processes are a group of promising recyclable sources of metal. Each year, a large amount of copper slag is produced worldwide. Copper slag usually contains a certain quantity of valuable metals, such as copper, nickel, cobalt and iron (Gorai et al., 2003). Therefore, it can be treated as a secondary resource for metal extraction rather than as a waste. Numerous studies have been carried out on metal recovery from copper slag using hydro- and/or pyrometallurgical methods (Altundogan et al., 2004, Banza et al., 2002, González et al., 2005, Das et al., 2010, Kucharski et al., 2014, Yang et al., 2014, Heo et al., 2014). Characterisation of feed material to determine the expected concentrate grade and metal recovery is essential for the design of separation flow sheets and achieving sustainable development in the utilisation of resources (Jan D. Miller et al., 2009). Extensive research has been performed to characterise copper slags in view of metal recovery through various techniques (Li et al., 2009, Das et al., 2010, Cardona et al., 2011). For the sake of metal recovery, the mineralogy and particle size of metal phases are the key metallurgical parameters. Quantification of minerals can be performed by quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN). It is an automated image analysis system using backscattered electron (BSE) and energy dispersive X-ray (EDX) signals from a scanning electron microscope (SEM).QEMSCANhasbeen widely applied inthe studyof mineral properties (Pascoe et al., 2007, Liu et al., 2005, Matjie et al., 2011).X-ray computed tomography (CT) is a non-destructive characterisation technology, which can provide direct volumetric data acquisition and quantitative analysis in three dimensions (3D) with a reasonably short analysis time and limited sample preparation (Jan D. Miller and Lin, 2004). CT scanning has been applied to characterise different properties of rocks and ores (J. D. Miller et al., 2003, Remeysen, 2006, Ghorbani et al., 2011). CT scanning and QEMSCAN are powerful characterisation tools that have not yet been applied in the study of copper slag. In this work, the species and distribution of copper bearing phases were characterized through QEMSCAN. In addition, the distribution of copper bearing grains was studied through CT scanning. Once the mineralogy and distribution of copper bearing particles are understood, the suitable slag processing techniques and conditions can be designed in view of copper recovery. ispartof: Transactions of the Institutions of Mining and Metallurgy, Section C: Mineral Processing and Extractive Metallurgy vol:124 issue:2 pages:83-87 status: published

During gasification of refuse derived fuel (RDF) to produce syngas in a system in which a melt is also produced, the gasified organic fraction of the RDF is in contact with the molten inorganic fraction, i.e. a slag. Examples of such systems are plasma gasifiers, in which crude syngas is further cracked in a plasma converter. Depending on the degree of gas–slag interaction, their compositions may vary and influence the valorisation potential of both resources. To evaluate the influence of this interaction, a pseudo-kinetic model was developed based on local thermodynamic equilibrium between the gas phase and part of the slag phase. The interaction level was accounted for by varying the amount of the slag that equilibrates with the gas. The valorisation potential of the resulting gas and slag phases was evaluated in terms of the heat of combustion and the mineralogy after cooling, respectively. Engineering of the slag composition was made through lime-rich addition. The influence of waste compositi...

The novel concepts Enhanced Waste Management (EWM) and Enhanced Landfill Mining (ELFM) intend to place landfilling of waste in a sustainable context. The state of the technology is an important factor in determining the most suitable moment to valorize – either as materials (Waste-to-Product, WtP) or as energy (Waste-to-Energy, WtE) – certain landfill waste streams. The present paper reviews thermochemical technologies (incineration, gasification, pyrolysis, plasma technologies, combinations) for energetic valorization of calorific waste streams, with focus on municipal solid waste (MSW), possibly processed into refuse derived fuel (RDF). The potential and suitability of these thermochemical technologies for ELFM applications are discussed. From this review it is clear that process and waste have to be closely matched, and that some thermochemical processes succeed in recovering both materials and energy from waste. Plasma gasification/vitrification is a viable candidate for combined energy and material valorization, its technical feasibility for MSW/RDF applications (including excavated waste) has been proven on installations ranging from pilot to full scale. The continued advances that are being made in process control and process efficiency are expected to improve the commercial viability of these advanced thermochemical conversion technologies in the near future. ispartof: Journal of Cleaner Production vol:55 pages:10-23 status: published

The main objective of “Enhanced landfill mining” is the valorization of the excavated waste materials that have been stored in the landfill. Previous landfill mining projects have shown that each landfill site has its own potential with regard to landfill mining. Factors such as the age of the landfill, type of landfill and the country or region where the landfill is located might have an impact on the type of materials stored in the landfill and their valorization potential. In the present article, the valorization options for the materials stored at the REMO site in Houthalen (Belgium) are assessed based on excavation tests done at locations containing either municipal solid waste (MSW) or industrial waste (IW). The results reveal differences in the composition and the characteristics of the waste materials with regard to type of waste (MSW versus IW) and the period during which the waste was stored. Based on the characteristics of the different fractions, an initial assessment was made with regard to their valorization potential. For the plastics, paper/cardboard, wood and textile recovered in this study, waste-to-energy is the most suitable valorization route since the level of contamination was too high to allow high quality material recycling. For metals, glass/ceramics, stones and other inerts in the waste, material valorization might be possible when the materials can adequately be separated. The amount of combustible in the excavated waste varied between 23 and 50% (w/w) with a calorific value of around 18 MJ kg−1 dw and confirm the large potential of waste-to-energy for landfill mining. All waste samples recovered from the landfill contained a large amount (40–60% (w/w)) of a fine grained (

a b s t r a c t In a circular economy material loops are closed by recycling of pre-consumer manufacturing scrap/ residues, urban mining of End-of-Life products and land !ll mining of historic (and future) urban waste streams. However, in the past land !ll mining was not performed with a focus on resource recovery. This paper addresses this gap by introducing the concept of Enhanced Land !ll Mining, de !ned as the safe conditioning, excavation and integrated valorization of land !lled waste streams as both materials and energy, using innovative transformation technologies and respecting the most stringent social and ecological criteria. The feasibility of ELFM is studied by synthesizing the research on the Closing the Circle project, the !rst ELFM project targeting the 18 million metric ton land !ll in Houthalen-Helchteren in the East of Belgium. It is argued that Environmental Impact Assessments of ELFM projects should be wide in scope and time. Embedded in a broad resource management perspective, the worldwide potential of ELFM is highlighted, in terms of climate gains, materials and energy utilization, job creation and land reclamation. The potential is quanti !ed for the EU-27 with its 150,000 e500,000 land !lls. However, for ELFM to reach its full potential, strategic policy decisions and tailored support systems, including combined incentives for material recycling, energy utilization and nature restoration, are required.

article i nfo Slags from non-ferrous metallurgy are Fe rich, with Si as a minor constituent, and with low levels of Al. Due to variations in the slag cooling practice, they can exist as semi-amorphous or as crystalline solids. Considering that both higher Al in the slag and a higher cooling rate during solidification would have an impact on the availability of Al and ultimately on the formation of linkages in the inorganic polymer, we study the micro- structure and reactivity of a Fe and Al rich slag cooled in different ways. Results show that high cooling rates lead to a predominantly amorphous material. For lower cooling rates the content of amorphous phase varies from 52 wt.% to 12 wt.%. Spinel is the primary phase precipitating, whereas, for the lowest cooling rate investigated, pyroxenes form as well. Dissolution tests in a 10 M NaOH solution for 96 h reveal that approx. 54 wt.% of Al and 33 wt.% of Si of the total content become available for the highly amorphous slag. On the contrary, the dissolved Al and Si are below 5 wt.% when slag pot cooling is applied. The above strongly influence the resulting inorganic polymers with the ones originating from the amorphous slag being superior in mechanical properties.

article i nfo This work aims to assess the possibility of using ladle metallurgy and argon oxygen decarburization stainless steel slag as a hydraulic binder after mechanical activation. Prolonged milling in ethanol suspension resulted in 10-fold increase of the surface area and increase of the amorphous phase. Calorimetric analysis of slags mixed with water indicated the occurrence of exothermic reactions. XRD results revealed that periclase, merwinite, γ-C2S and bredigite, decreased with hydration time. Thermogravimetric analyses indicated that the main hydration products are most probably C-S-H, CH and MH. The hydrated products in both slags were similar to C-S-H gel. WDS analysis demonstrated Ca and Si to be widespread in the structure. Formation of M-S-H gel or incorporation of Mg in the C-S-H gel remains uncertain. The 90 days compressive strength of mortars prepared from slags reached approximately 20% for LM and 10% for AOD of the compressive strength of mortars prepared from OPC.

Options to Prevent Dicalcium Silicate-Driven Disintegration of Stainless Steel SlagsIn this paper, a short overview is given on the strategy for high dicalcium silicate stainless steel slags stabilisation along with some results from work done and currently being performed at the K.U. Leuven.

Ferroalloys are added during secondary steelmaking to impart special properties to the steel. Depending upon the ferroalloy quality this may lead to the formation of inclusions. The present knowledge lacks in the exact content of the individual elements and the nature of inclusions dispersed in the ferroalloys. In order to broaden the knowledge concerning ferroalloy quality, eight different ferroalloys (i.e. FeMo, FeNb, HCFeMn, LCFeMn, FeTi70, FeTi35, FeSi75 and FeP) were characterised for their impurity content. The samples were investigated for chemical analysis (inductively coupled plasma atomic emission spectroscopy and Leco combustion technique) and microstructural analysis (SEM energy dispersive spectroscopy). These impurities are linked to the ferroalloy manufacturing route. The inclusions observed in the microstructure are in good agreement with the inclusions extracted by the dissolution technique. In the present manuscript, the possible influence of ferroalloy quality over steel cleanli...

This paper covers the Flemish legislative tools concerning the management of bottom ash, fly ash and APC residue from municipal waste incinerators, with respect to their contamination with heavy metals. The situation in Flanders is compared to the one in the Walloon region, The Netherlands, Germany and France. Waste management in the countries considered differs on the level of available management options, of leaching tests and of limit values. To make an indicative comparison of leaching tests and limit values in the different countries, leaching tests were carried out on bottom ash and fly ash, and the results are compared to the relevant limit values for recycling and landfilling of the different countries. The comparison of legislations as well as the leaching results show that discrepancies in waste management between the different regions and countries exist. Recently, European limit values for landfilling became available. European legislation on recycling, however, has not been developed and urgently needs to be considered and drafted as the market for recycling can be expanding rapidly.

Cement as agent for immobilising Pb from air pollution control residues is compared with the use of different silica-containing materials. The DIN 38414-S4 leaching test was used to control Pb leachability and to compare obtained Pb leachate concentrations with the landfill limit of 2 mg/l for Pb. Firstly, one scrubber residues was treated with cement and micro-silica. With cement, the Pb leachability could be reduced with a factor ranging from 3 to 50 depending on the type and amount of cement used and depending on the curing time. The landfill limit of 2 mg/l was, however, never attained. From all tested silica-containing additives, aerosil could reduce the initial Pb leaching (101.3 mg/l) to below the detection limit at a dosage of 0.13 g aerosil/g residue. Second best and an economically preferable silica-containing additive was micro-silica: a reduction from 101.3 to 0.7 mg/l was observed at a dosage of 0.4 g micro-silica/g residue. The formation of Ca-silicates was found to be responsible for the decreased Pb leachability. To generalise the findings, the Pb leachability of five cement-treated and five micro-silica-treated air pollution control residues were compared. For three scrubber residues, 2–20 times lower Pb leachate concentrations were measured for micro-silica-treated samples (cured for 5 weeks) than cement-treated samples. For a fly ash and a boiler ash the difference was, respectively, 48 and 17 times. pH-dependent leaching tests showed that at pH=2.5, Pb leaching is 250 times lower for the micro-silica-treated residue than for the cement-treated residue and almost seven times lower at pH 12.4.

The contribution of the emission of PCBs by a municipal waste incinerator in Wilrijk, a relatively industrialized district in the largest city of Flanders, to the total emission to air and to the total human intake was estimated. Therefore it was compared to the emission of PCBs by evaporation from PCB containing applications (transformers, capacitors, paint, ink, etc.) and to the intake of PCBs with food. As there was a lack of PCB data from the incinerator, the PCB emission concentration was estimated using three different approaches. A PCB measurement of the incinerator emission, performed later on, fell within the predicted range of 0.0004-0.005 ng TEQ/Nm3. Emission of PCBs from PCB containing applications and intake from food were deduced from information available on Flemish and European level. The results indicate a PCB contribution from the incinerator to local emissions between 0.3% and 3% of the emission from PCB containing applications and a contribution to human intake less than 6 x 10(-4)% of the intake from food.

Superior to the homogeneous catalyst or physisorbed catalyst system is a system with the ansa-metallocene catalyst [{C2 H4 (1-ind)2 }Zr(CH3 )] on a support formed by covalently anchoring methylalumoxane (MAO) on the internal pore walls of MCM-41. This system is a highly active and shape-selective mesoporous host in the co-oligomerization [shown schematically in Equation (a)] of ethene and propene with ansa-metallocenes. TMA=trimethylaluminum, ind=indenyl.

The anchoring of alumoxane, synthesized by the in situ hydrolysis of trimethylaluminum, on the internal pore walls of a mesoporous MCM-41 support generates a highly active and selective host for bis(cyclopentadienyl)zirconium dimethyl (Cp2Zr(CH3)2) in the oligomerization of propene. The regioselective preference of the immobilized metallocene is preserved and a typical Flory–Schulz distribution for the propene oligomers is obtained.

The flue gas cleaning system of a MSW incinerator with a capacity of 350 kt/year was changed to improve the HCl elimination efficiency. Instead of the semi-wet operating spray reactor and subsequent baghouse, a two-step wet flue gas cleaning was added behind the baghouse. Elemental composition, X-ray powder diffraction patterns and TGA measurements showed that the resulting APC residue was totally different from the former residue. As a consequence, leaching characteristics of both residues also differed and another treatment was required prior to disposal. For the former residue, mainly leaching of Pb (>100 mg/l), necessitated treatment prior to landfilling. The lower alkalinity of the new residue resulted in a leachate pH of 9.7 and a Pb concentration of 0.8 mg/l. The leachate pH of the former residue was 12.4. The leaching of Pb and Zn increased above 100 mg/l when immobilising the new residue with cement. Better results were obtained when immobilising with micro silica. The high CaCl 2 ·2H 2 O content of the new residue brought along clogging of the bag filter system. Adding 1.4% of CaO (or 1.9% of Ca(OH) 2 ) to the residue already improved these inconveniences but again significantly changed the leaching behaviour of the residue.

The immobilization of MSWI-scrubber residues with soluble PO4(3-) was studied and compared to the immobilization using cement. The DIN 38414-S4 leaching protocol and pH dependent leaching were used to evaluate the leaching of Pb and Zn. Four different scrubber residues from MSW combustion (Pb concentration: 2.8-4.8 mg/g; Zn concentration: 3.0-12.3 mg/g) were mixed with water and cement or Na2HPO4 as source of soluble PO4(3-) at dosages of at least 0, 0.1, 0.2, 0.3 and 0.4 g per g residue. With cement as well as with PO4(3-) a reduction in Pb and Zn leaching was observed. With 0.4 g cement per g residue, the Pb leaching was reduced by a factor ranging from 70 to 100, but still exceeded the Pb landfill limit of 2 mg/l. With PO4(3-) the Pb leaching was reduced with a factor of 100-300 to below 2 mg/l. The Zn landfill limit (10 mg/l) was only exceeded by one untreated residue. Adding 0.2 g cement or 0.1 g PO4(3-) per g of that residue was enough to reduce leaching below 10 mg/l. However, when 0.6 g Na2HPO4 per g residue was added to a lime based scrubber residue, an increase in Zn leaching up to 12.5 mg/l was observed due to an increase in pH of up to 13.0. When using NaH2PO4 and H3PO4 no such increase in Zn leaching was observed. pH dependent leaching performed on one of the four residues showed that in the pH range of 2.5-6, Pb leaching was 100-50 times lower with Na2HPO4 treatment than with cement. In the pH range from 7-11, almost equal results were obtained for cement treated and Na2HPO4 treated residue. Above a pH of 12, Pb leaching was three times lower for the PO(4)(3-)-treated residue than for the cement treated residue. With soluble PO4(3-), Pb leaching below 2 mg/l could be attained at a dosage of 0.27 g PO4(3-)/g residue. With cement, Pb leaching was never below 2 mg/l.

When a fly ash waste material from a copper refining process containing large amounts of As2O3 is solidified using cement and lime, the arsenic concentration in the leachate can be lowered to ca. 5 mg/l in a saturated solution of Ca(OH)2. It is shown that the decrease of the concentration in the leachate, mainly of As(III), is due to the formation of insoluble CaHAsO3 in the leachate in the presence of Ca(OH)2. This method is compared with a method whereby use is made of oxidation of the waste before solidification to oxidise As(III) to As(V) using H2O2. The arsenic concentration in the leachate of the extraction test of an oxidised S/S sample was lowered to ca. 0.5 mg/l, a factor of 10 below the one for a non-oxidised sample. It is shown that the decrease of the concentration in the leachate mainly of As(V) is due to the formation of insoluble Ca3(AsO4)2 in the presence of Ca(OH)2. Extensive use was made of the speciation program MINTEQA2, to clarify the immobilisation of arsenic.

TMS has forged cooperative agreements with several carefully selected organizations that actively work to benefit the materials science community. In this occasional series, JOM will provide an update on the activities of these organizations. This installment features the Center for Resource Recovery & Recycling (CR3), a research center established by Worcester Polytechnic Institute, Colorado School of Mines, and K.U. Leuven

Copper slag can be treated as a secondary resource since it usually contains a substantial amount of copper and other valuable metals. Characterization of the slags to determine the expected metal recovery is essential for the design of separation flow sheets. In this study, the chemical and mineralogical composition of a copper slag from El Teniente, Chile were characterized. The copper content of the fayalite based slag is around 0.87 wt% which is higher than for certain copper ores. Copper exists as sulfides in the form of droplets in the slag. The content and particle size distribution of the major sulfide phases (bornite, chalcopyrite and chalcocite) were quantified using analytical scanning electron microscopy (QEMSCAN). The copper bearing particles have a wide particle size distribution from a few microns up to mm level. Large copper bearing particles (> 100 µm) are composed mainly of bornite and chalcocite and tend to accumulate in the lower part of the slag layer. As characterized with X-ray computed tomography (CT), around 70 volume% of copper value exist in these large copper bearing particles.