The EURARE Project: development of a sustainable exploitation scheme for Europe’s Rare Earth Ore Deposits

Numerous European industries are heavily dependent on imported rare earth element (REE) raw materials. This has created a need for the European Union (EU) to ensure a sustainable supply of REE minerals, as well as develop from the ground up the currently non-existent European REE extraction and processing industry. In order to support this, the European Commission, through the Seventh Framework Programme (FP7) scheme, funded the EURARE project which runs from 1st January 2013 to 31st December 2017. Through the EURARE project, selected European REE deposits have been researched and in certain cases identified resources were successfully processed for REE production. Several REE deposits across Europe have been the focus of detailed geological field and laboratory work. Mineral concentrates obtained from the Norra Kärr deposit in Sweden, the Kringlerne deposit in Greenland and the Kvanefjeld deposit in Greenland, Rødberg ore from Norway and bauxite residue from Greece were tested from laboratory to pilot scale by means of conventional and innovative metallurgical processing. The novel technologies developed provide efficiency and selectivity in various steps of the metallurgical processing, from ore beneficiation to metal production. A road map for sustainable REE production in Europe is now being developed, which includes an evaluation of the environmental benefits and risks of the EURARE technologies

Recovery of critical and other raw materials from mining waste and landfills

The transition to a more circular economy is essential to develop a sustainable, low carbon, resource efficient, and competitive economy in the EU. In this context Critical Raw Materials (CRM) are defined as those which are of particularly great importance to the EU economy and at the same time there is a high risk of supply disruptions. First and foremost, improving the circular use of CRM is a key strategy in improving the security of supply and not surprisingly is an objective of various policy documents. This report delivers on action #39 of the Circular Economy Action Plan: "Sharing of best practice for the recovery of critical raw materials from mining waste and landfills". It builds on discussions held during two 2018 workshops and gathers together six examples of existing practices for the recovery of critical, precious, and other materials from extractive waste and landfills, highlighting technological innovation and contributions that have been made to a more comprehensive knowledge-base on raw materials. The report also provides various estimates of potential recovery of certain materials compared to their current demand. Lessons learnt from the practices include awareness that it is very unlikely that recovery processes can target one or just a few specific materials of great interest and disregard other elements or bulk matrixes. Especially in case of very low concentrations, most of the mineral resources and other bulk materials in which they are embedded must be valorised in order to increase economic viability and minimise waste disposal. As recovery processes can be very energy intensive, environmental and land use related aspects are also particularly relevant even though environmental gains may also occur and, moreover, land space can be liberated and reused for new purposes and services. Finally, availability of data and information on secondary materials as well as a harmonized legislative framework within the EU appear to be crucial for the large-scale deployment of recovery practices.JRC.D.3-Land Resource

Development of a new semi-empirical hydration model for the estimation of the thermodynamic properties of aqueous electrolyte solutions

The modeling of aqueous electrolyte solutions is a field of intense scientific research. The presence of charged particles in a polar solvent, like water, causes significant deviations from the ideal behavior. Dense electrolyte solutions can only be described through the use of semi-empirical ionic activity models. Semi - empirical are the models which are based on a theory for the description of ionic activity, but at the same time use regression parameters. A large number of such semi-empirical activity models already exists and this thesis attempts to categorize and present most of them. Most semi-empirical models focus in strong electrolyte solutions, without taking into account ion-pairing or ionic hydration phenomena. So while there are many models capable of describing strong electrolyte solutions, very few of them can be successfully applied in complex hydrometallurgical solutions. The large variety of ionic complexes found in this systems, sets as primary criterion for the selection of a semi-empirical model the model’s capability to be easily applied to the system and not the model’s predictive accuracy. In practice single parameter models (Bromley equation, SIT theory), which are easily applied, are often preferred to the multi-parameter models (Pitzer equation, Electrolyte - NRTL theory), which are more reliable but more complex as well. The present doctoral thesis proposes a new Semi Empirical Hydration Model (SEHM) capable of application in complex electrolyte solutions. The SEHM model is a single parameter model, which describes in a semi-empirical fashion the ion hydration and ion pairing phenomena. The theoretical basis of the SEHM model presents it with clear advantages compared to the other single parameter models, as it is able to fit the ionic activity coefficients and at the same time predict thermodynamic properties of the solution, like the osmotic coefficient and the mole fraction of the free solvent. On the other side, the mathematical model of the SEHM, when compared to the other single parameter model is more complex. This mathematical complicity is comparable to the multi-parameter models and in this sense the SEHM model is placed somewhere in between the two categories. The greatest advantage and novelty of the SEHM model is the physical meaning of its parameters which can provide indications of the extent of ionic hydration and ionic complex formation in the solutionΗ μοντελοποίηση των ηλεκτρολυτικών διαλυμάτων αποτελεί τομέα έντονης επιστημονικής έρευνας. Η παρουσία ηλεκτρικού φορτίου σε έναν πολικό διαλύτη, όπως το νερό, προκαλεί έντονες αποκλίσεις από την ιδανική συμπεριφορά του διαλύματος. Σε πυκνά ηλεκτρολυτικά διαλύματα, η πρόβλεψη της κατάστασης της θερμοδυναμικής τους ισορροπίας είναι εφικτή μόνο με τη χρήση ημι-εμπειρικών μοντέλων περιγραφής της μη-ιδανικότητας. Ως ημι-εμπειρικά χαρακτηρίζονται τα μοντέλα εκείνα, τα οποία βασίζονται σε κάποιο θεωρητικό μοντέλο περιγραφής της μη-ιδανικότητας των διαλυμάτων, αλλά ταυτόχρονα περιέχουν και παραμέτρους προσαρμογής σε πειραματικά δεδομένα του εξεταζόμενου συστήματος. Στη βιβλιογραφία προτείνεται μεγάλο πλήθος τέτοιων ημι-εμπειρικών μοντέλων, το οποίο η παρούσα διατριβή επιχειρεί να καταγράψει και να παρουσιάσει. Τα ημι-εμπειρικά μοντέλα της βιβλιογραφίας εστιάζονται κυρίως σε διαλύματα ισχυρών ηλεκτρολυτών, χωρίς να λαμβάνουν υπόψη τους φαινόμενα συμπλοκοποίησης ή υδρόλυσης. Η μεγάλη ποικιλία ιοντικών συμπλόκων που συναντιούνται σε βιομηχανικά διαλύματα, θέτει ως πρώτο κριτήριο για την επιλογή ενός μοντέλου την ευκολία με την οποία αυτό μπορεί να χρησιμοποιηθεί στο συγκεκριμένο σύστημα. Στην πράξη επιλέγονται συχνότερα μονοπαραμετρικά μοντέλα (εξίσωση Bromley, θεωρία SIT), τα οποία σε σχέση με τα πολυπαραμετρικά μοντέλα (Pitzer, NRTL) έχουν μικρότερη ακρίβεια στις προβλέψεις τους, αλλά πλεονεκτούν στην ευκολία της εφαρμογής τους στα συγκεκριμένα συστήματα. Η παρούσα διατριβή προτείνει ένα νέο ημι-εμπειρικό μοντέλο ενυδάτωσης (SEHM), ικανό να εφαρμοστεί στα σύνθετα διαλύματα της υδρομεταλλουργίας. Το μοντέλο SEHM είναι ένα μονοπαραμετρικό μοντέλο, το οποίο περιγράφει με ημι-εμπειρικό τρόπο τα φαινόμενα ιοντικής ενυδάτωσης και σύζευξης, πλεονεκτώντας απέναντι στα άλλα μονοπαραμετρικά μοντέλα, καθώς έχει την ικανότητα να προβλέπει άμεσα φυσικά μεγέθη του διαλύματος, όπως τα γραμμομοριακό κλάσμα του διαλύτη και συντελεστή ωσμωτικής πίεσης. Στον αντίποδα αυτών των πλεονεκτημάτων, το μαθηματικό μοντέλο του SEHM είναι σαφώς πιο περίπλοκο από τα αντίστοιχα μονοπαραμετρικά μοντέλα. Η μαθηματική πολυπλοκότητα του είναι συγκρίσιμη με αυτήν των πολυπαραμετρικών μοντέλων πλεονεκτώντας απέναντί τους τόσο στον αριθμό των παραμέτρων προσαρμογής, όσο και στη φυσική σημασία των μεγεθών του SEHM. Το γραμμομοριακό κλάσμα του διαλύτη και η μέση ιοντική ακτίνα των ενυδατωμένων ιόντων είναι μεγέθη τα οποία παρέχουν ενδείξεις για την έκταση της ιοντικής ενυδάτωσης -σύζευξης στο διάλυμ

Exploitation of Kaolin as an Alternative Source in Alumina Production

The extensive consumption of aluminum, combined with the shortage of the existing raw materials, and particularly bauxite, necessitates the exploitation of alternative raw materials for the production of alumina. The present paper focuses on the possible use of kaolin, as an abundant, cheap and high-aluminum content raw material, in alumina production, via the application of the Aranda-Mastin technology in the leaching step. From this point of view, leaching experiments were conducted on untreated kaolin and thermally treated, metakaolin, applying atmospheric pressure, temperature of 90 °C and with an aqueous solution of a low HCl concentration as the leaching agent. Leaching, in the aforementioned conditions, is an industrially applied process, characterized by highly efficient aluminum dissolution in the case of metakaolin with low silicon dissolution at a short retention time, but with respectively lower achieved results for untreated kaolin. In order to raise the aluminum dissolution rate from untreated material, temporal and subsequently chemical intensification was applied. The analysis indicated a higher aluminum dissolution rate, up to 70%, with the application of a high acid concentration of leaching agent, performed for a long retention time that could be further improved

Exploitation of Kaolin as an Alternative Source in Alumina Production

The extensive consumption of aluminum, combined with the shortage of the existing raw materials, and particularly bauxite, necessitates the exploitation of alternative raw materials for the production of alumina. The present paper focuses on the possible use of kaolin, as an abundant, cheap and high-aluminum content raw material, in alumina production, via the application of the Aranda-Mastin technology in the leaching step. From this point of view, leaching experiments were conducted on untreated kaolin and thermally treated, metakaolin, applying atmospheric pressure, temperature of 90 °C and with an aqueous solution of a low HCl concentration as the leaching agent. Leaching, in the aforementioned conditions, is an industrially applied process, characterized by highly efficient aluminum dissolution in the case of metakaolin with low silicon dissolution at a short retention time, but with respectively lower achieved results for untreated kaolin. In order to raise the aluminum dissolution rate from untreated material, temporal and subsequently chemical intensification was applied. The analysis indicated a higher aluminum dissolution rate, up to 70%, with the application of a high acid concentration of leaching agent, performed for a long retention time that could be further improved

On the Direct Reduction Phenomena of Bauxite Ore Using H2 Gas in a Fixed Bed Reactor

The Bayer Process is the dominant industrial method to produce alumina from bauxite ore. Due to the generation of large amounts of Bauxite Residue (red mud), an alternative method, called the Pedersen Process, is of our interest. This process makes use of a combination of pyrometallurgical and hydrometallurgical techniques in order to prevent the Bauxite Residue generation. In the conventional Pedersen Process, iron in the bauxite is separated in the form of pig iron through a carbothermic smelting-reduction step which has a CO2 emission similar to that during conventional iron production. In order to eliminate the CO2 emission of this step, the focus of the present work is to reduce the iron oxides of bauxite ore by hydrogen gas (H2) prior to smelting and minimizing the use of solid carbon materials for the reduction. The thermochemistry and the kinetics of reactions during calcination and direct reduction of a bauxite ore were studied by a thermogravimetric technique and in situ analysis of the gaseous products. The onset temperatures for the decomposition of bauxite components during calcination were determined. The kinetics of the reduction of hematite to metallic iron was studied and it is shown that the reduction of iron oxides to metallic iron starts at temperatures below 560 °C and it accelerates at higher temperatures. Moreover, it is indicated that the formation of hercynite (FeAl2O4) phase retards the complete reduction at temperatures higher than 760 °C.publishedVersio

ΣIDERWIN—A New Route for Iron Production

Iron and steel production contributes to ~10% of global CO2 emissions. In recent decades, different scenarios and low-emission pathways have been taken up by steelmaking industries with the collaboration of universities and research institutes to tackle this problem. One of the most promising novel methods to replace the current steelmaking process is the low-temperature electrolysis of iron oxide. This technology is currently being developed under the H2020 ΣIDERWIN project, a European project led by ArcelorMittal, the world’s leading steel and mining company. The ΣIDERWIN project aims at developing an innovative electrochemical process to transform iron oxide into steel metal plates. This process produces steel by electrolysis without direct CO2 emissions. In this operation, electrical energy and iron oxide are converted into chemical energy consisting of separated iron metal from the oxygen gas. It is a disruptive innovation that entirely shifts the way steel is presently produced. One of the advantages of this process is the fact that, in addition to iron oxide (hematite), it is possible to feed this process with other iron-containing raw materials. An alternative raw material which is being studied to be used in this process is bauxite residue (BR), the waste material from the Bayer process for alumina production. The iron oxide of the conversion of bauxite residue to metallic iron is under investigation, and insights are showing that it could follow up the electrochemical route for sustainable iron production. This research deals with the effect of the current density and temperature on current efficiency comparing two different raw materials, pure iron oxide–hematite and bauxite residue

Mud2metal: Lessons learned on the path for complete utilization of bauxite residue through industrial symbiosis

A new concept for a holistic exploitation of the bauxite residue (BR) is presented, where a multitude of niche and bulk application products are produced, leading to a near zero-waste, financially viable, and environmentally benign process. Based on the combination of recent research results, the ‘‘Mud2Metal’’ conceptual flow sheet was developed in order to produce added value products rationalizing BR sustainable valorization. The Mud2Metal flow sheet is analyzed technologically, environmentally, and economically, addressing the challenges and the effects of each processing step, for the case of the Greek BR. The Mud2Metal flow sheet is focused on the selective removal of rare earth elements, the subsequent production of pig iron for the iron and steel industry, and the valorization of the residual slag’s engineered mineral matrix into a variety of building materials. Based on further technological innovation and flow sheet integration/optimization, the plant operation could become economically profitable for the alumina industry, environmentally benign, and socially acceptable; in one word: sustainable.status: publishe