Cast Shop Technology: Recycling and Sustainability Joint Session: Recycling and Sustainability Joint Session
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Johannes Morscheiser, Novelis Koblenz GmbH
Wednesday 8:30 AM
February 26, 2020
Room: 1B
Location: San Diego Convention Ctr
Session Chair: Mertol Gökelma, NTNU Trondheim
8:30 AM Introductory Comments
8:35 AM
Constellium R&D Approach in Recycling from Lab to Industrial Scale: Anne Pichat1; Alain Vassel1; Pierre-Yves Menet1; Laurent Jouët-Pastre2; 1Constellium Technology Center; 2Constellium Neuf Brisach plant
Tilting Rotating Furnace (TRF) is a widely used technology for aluminium scrap recycling. Although being based on a very simple concept, the optimal operating conditions are not easy to define due to the large number of process parameters and antagonist performance indicators (e.g. productivity, metal recovery, emissions). In order to improve process understanding, a lab TRF has been developed to investigate the effect of key parameters and identify the mechanisms governing the process performance. R&D achievements done for the recycling of Used Beverage Cans (UBC) with this lab furnace are presented together with their implementation at industrial scale. As an example, we quantified the effect of burner settings, salt flux chemistry, scrap contamination on metal recovery. Environmental concerns were also considered in the study. An approach to reduce the emission of Volatile Organic Compounds (VOC) during UBC recycling was developed. Mechanisms are proposed and recommendations were implemented at industrial scale.
8:55 AM
Representative Sampling, Fractionation and Melting of Al-scrap: Stefan Wibner1; Helmut Antrekowitsch1; Barbara Falkensammer2; 1Montanuniversitaet Leoben; 2Hütte Klein-Reichenbach
Production of deoxidation granules for steel metallurgy is done by re-melting aluminum scrap in a two-chamber furnace. In order to determine the amounts of aluminum, non-metals and foreign metals in mixed scrap of an Austrian Al-smelter, the representative sampling of Al-scrap is carried out first. Subsequently, the obtained sample is divided manually into the different fractions. These are on the one hand the fractions of Al and foreign metals like Cu, Fe, Zn and brass, and on the other hand non-metals such as plastics, glass, wood and fines. Accurate characterization of the separated fines is done by TGA, TC, XRF and XRD analysis. Furthermore, melting experiments of the scrap on laboratory scale into a primary aluminum melt are conducted according to the industrial process. The results are of great importance, since the quality of the scrap influences the melting process significantly and the purchasing department can adjust accordingly.
9:15 AM
Recycling of Aluminium Waste from Mixed Household Waste: Sigvart Eggen1; Kurt Sandaunet2; Leiv K Kolbeinsen1; Anne Kvithyld1; 1NTNU; 2SINTEF
Aluminium is used in packaging due to it’s density, strength and preservative capabilities. The paper outlines a methodology to evaluate the recyclability of aluminium waste, where parameters of scrap type, pre-treatment and remelting conditions are alternated with measurements of yield and analysis of metal quality. Aluminium waste from mixed household waste, Cans, will be presented in detail. Cans were decoated at 300C and 550C. The decoated material was then remelted, 4 additions of ∼ 2kg per experiment, by submersion into the molten melt. Porosity, inclusion content and alloy composition was analysed to determine metal quality. The experiments results show that yield of remelting, dross formation relative to melted sample material, and the chemical composition depend on decoating temperature. Cans is recyclable, with good quality and yield, with right treatment. The methodology is hopefully useful for evaluating effects of various process parameters in recycling of aluminium scrap.
9:35 AM
An Assessment of Recyclability of Used Aluminium Coffee Capsules: Mertol Gokelma1; Fabian Diaz2; Ilayda Elif Öner3; Bernd Friedrich2; Gabriella Tranell1; 1Norwegian University of Science and Technology; 2RWTH Aachen University; 3Istanbul Technical University
As a result of increasing demands of aluminum in numerous sectors like construction, automotive, transportation etc., the consumption rate has been sharply rising since decades. Aluminum is also used for many different consumer goods such as food storage materials, drink cans, etc. due to its good formability, density and corrosion resistance. This usage in everyday life leads continuously to new types of scraps such as coffee capsules opening the question of their recyclability due to their multi-component structures. An efficient aluminum recovery in terms of high quality and efficiency is essential with respect to reducing the environmental impact and economic cost. This study focuses on the recyclability of used coffee capsules via direct remelting under a salt flux, avoiding a separate pyrolysis step. Results were evaluated for different aspects such as metal yield, purity/cleanliness as well as gas generation during treatment.
9:55 AM Break
10:10 AM
Fractional Solidification for Purification of Recycled Aluminium Alloys: Susanna Venditti1; Dmitry Eskin1; Alain Jacot1; 1Bcast Brunel University
Recycling Al is an up-to-date topic nowadays due to the economic benefit and sustainability, in fact recycled Al employs only 5% percent of the energy necessary for its extraction from bauxite ore, saving 9 ton of CO2 per 1 ton of Al recycled. In this research project the principles of fractional solidification have been applied to reduce the amount of impurities in model recycled Al alloys. A set-up based on isothermal squeezing of a semi-solid alloys has been developed and tested. The ultrasonic vibration applied to the semi-solid material has proven to enhance the purification achievable, up to 65% of reduction in the concentration. A number of potential impurities such as Fe, Si, Ni, Cu have been tested. The role of solute partitioning during the process has been evaluated and characterized through the use of CT scanning and modelling.
10:30 AM
A Rapid Method of Determining Salt Flux Melting Point and Composition: Ray Peterson1; 1Real Alloy
Salt fluxes are commonly used in the recycling of dirty aluminum scraps and drosses. The salt fluxes perform many functions such as stripping away the oxide films and promoting droplet coalescence, but to be effective they must be in a molten state. The most common class of salt fluxes used in aluminum recycling contain a mixture of sodium chloride (NaCl) and potassium chloride (KCl), and often minor amounts of a fluoride compound such as cryolite. Fluxes are specified to certain chemical compositions to produce a defined melting point of the flux. The NaCl – KCl phase diagram is a simple eutectic system. By measuring the liquidus temperature of the mixture it is possible to accurately back calculate the composition of the blend and verify that the delivered flux matches the desired specifications. This paper describes a practical method for measuring the liquidus temperature and then inferring the flux composition.
10:50 AM
Automatic Skimming Procedure for Reducing Aluminium Losses and Maintaining the Uniform Quality of the Molten Metal: Varuzan Kevorkijan1; Uroš Kovačec2; Sandi Žist1; Matjaz Godec3; 1Impol R in R d.o.o.; 2Impol LLT d.o.o.; 3Institute of Metals and Technology
Among the parameters involved in the production of aluminium alloys, a particularly demanding in terms of regulation are those involved in dross skimming. To reduce aluminium losses and maintain the uniform quality of skimming, the skimming depth (dross removal) should be limited, as much as possible, to near the interface between the dross layer and the molten metal. The purpose of this work was the development of an automatic skimming procedure. The position of the skimming spoon was guided by a continuous measurement of the temperature gradient across the dross layer, with thermocouples positioned on its bottom edge. The efficiency of this novel procedure was validated by continuous tracing of the specific amount of skimmed dross (SASD), recognized as a valuable quantitative indicator of the quality and the efficiency of the melting procedure as well as of the quality of the molten metal produced.
11:10 AM
Evaluation of the Effect of CO2 Cover Gas on the Rate of Oxidation of an AlMgSi Alloy: Cathrine Solem1; Kai Erik Ekstrĝm1; Gabriella Tranell1; Ragnhild Aune1; 1Norwegian University of Science and Technology (NTNU)
Additions of small amounts (>2ppm) of Be to AlMg alloys have proven to decrease their rate of oxidation. As Be can cause respiratory health issues, it is desirable to evaluate other parameters that may have the same inhibiting effect. In the present study six aluminium alloys, i.e. Al5Mg, Al5Mg5Si, Al1Mg1Si, Al5Mg1Si, Al1Si5Mg and Al5Si, have been investigated by Thermogravimetric Analysis (TGA) monitoring the mass change as a function time and temperature in atmospheres of Ar, synthetic air and an atmospheric mixture of synthetic air, Ar and CO2 (<5%) at 750°C for 7h. The TGA results revealed a two-step mass gain in synthetic air for all AlMg alloys, and the microscopic analysis showed that both MgO and MgAl2O4 were present in the oxide films. For the atmospheric mixture, the mass gain was significantly lower confirming that CO2 has an inhibiting effect on the overall rate of oxidation of these alloys.