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Mineralogical Influence on Leaching Behaviour of Steelmaking Slags Steelmaking Behaviourof Leaching on Influence Mineralogical Engström Fredrik

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Mineralogical Influence on Leaching Behaviour of Steelmaking Slags Steelmaking Behaviourof Leaching on Influence Mineralogical Engström Fredrik ISSN: 1402-1544 ISBN 978-91-7439-XXX-X Se i listan och fyll i siffror där kryssen är DOCTORAL T H E SI S Fredrik Engström Mineralogical Influence on Leaching of Behaviour Steelmaking Slags Department of Chemical Engineering and Geoscience Division of Minerals and Metallurgical Engineering Mineralogical Influence on Leaching ISSN: 1402-1544 ISBN 978-91-7439-197-8 Luleå University of Technology 2010 Behaviour of Steelmaking Slags A Laboratory Investigation Fredrik Engström A Laboratory Investigation Mineralogical influence on leaching behaviour of steelmaking slags A Laboratory Investigation by Fredrik Engström Doctoral Thesis Luleå University of Technology Department of Chemical Engineering and Geoscience Division of Minerals and Metallurgical Engineering SE-97187 Luleå Sweden 2010 Printed by Universitetstryckeriet, Luleå 2010 ISSN: 1402-1544 ISBN 978-91-7439-197-8 Luleå 2010 www.ltu.se LIST OF PAPERS This thesis is based on the following papers: I. Dirk Durinck, Fredrik Engström, Sander Arnout, Jeroen Heulens, Peter Tom Jones, Bo Björkman, Bart Blanpain and Patrick Wollants: Hot stage processing of metallurgical slags. Resources, Conservation and Recycling (2008), Vol 52, No 10, p 1121-1131. II. Mia Tossavainen, Fredrik Engström, Qixing Yang, Nourreddine Menad, Margareta Lidström Larsson and Bo Björkman: Characteristics of steel slag under different cooling conditions. Waste Management (2007), Vol 27, No 10, p 1335-1344. III. Fredrik Engström, Daniel Adolfsson, Qixing Yang, Caisa Samuelsson and Bo Björkman: Crystallization behaviour of some steelmaking slags. Steel Research International (2010), Vol 81, No 5, p 362-371. IV. Fredrik Engström, Margareta Lidström Larsson, Caisa Samuelsson, Åke Sandström, Ryan Robinson and Bo Björkman: Leaching behaviour of aged steel slags. Submitted (Resources, Conservation and Recycling) 2010. V. Fredrik Engström, Daniel Adolfsson, Caisa Samuelsson, Åke Sandström and Bo Björkman: A study of the solubility of pure slag minerals. Submitted (Minerals Engineering) 2010. I VI. Sina Mostaghel, Fredrik Engström, Caisa Samuelsson and Bo Björkman: Stability of spinels in a high basicity EAF slag. Proceedings of 6th European Slag Conference, October 20-22, 2010, Madrid, Spain. F. Engström’s contribution to the papers: • Practical experiments. • Responsible for characterization of materials obtained during experimental work using XRD, SEM and leaching. • Interpretation of leaching data and correlation to mineralogical phases. • Thermodynamic calculations. • Responsible for writing Papers II-V and parts of Paper I. • Supervising and contributing to the discussion of Paper VI. II Related publications not included in this thesis: VII. Mia Tossavainen, Fredrik Engström, Nourreddine Menad and Qixing Yang: Stability of modified steel slags. Proceedings of 4th European Slag Conference, June 20-21, 2005, Oulu, Finland. VIII. Qixing Yang, Fredrik Engström, Mia Tossavainen and Daniel Adolfsson: Treatments of AOD slag to enhance recycling and resource conservation. Proceeding of Securing the Future, International Conference on Mining and the Environment, Metals and Energy Recovery, June 27-July 1, 2005, Skellefteå, Sweden. IX. Qixing Yang, Fredrik Engström, Mia Tossavainen and Mingzhao He: AOD slag treatment to recover metal and to prevent slag dusting. Proceeding of the 7th Nordic-Japan Symposium on Science and Technology of Process Metallurgy, Jernkontoret, September 15-16, 2005, Stockholm, Sweden. X. Qixing Yang, Lotta Nedar, Fredrik Engström and Mingzhao He: Treatments of AOD slag to produce aggregates for road construction. Proceeding of AISTech 2006, May 1-4, 2006, Cleveland, USA, Vol. 1, p 573-583. XI. Qixing Yang, Björn Haase, Fredrik Engström and Anita Wedholm: Stabilization of EAF slag for use as construction material. Proceedings of REWAS 2008, Global Symposium on Recycling, III Waste Treatment. Minerals, Metals & Materials Society, October 12- 15, 2008, Cancun, Mexico, p 49-54. XII. Fredrik Engström, Margareta Lidström Larsson, Caisa Samuelsson and Bo Björkman: Ageing investigation of steel slags from electric arc furnace processes. Proceedings of REWAS 2008, Global Symposium on Recycling, Waste Treatment. Minerals, Metals & Materials Society, October 12-15, 2008, Cancun, Mexico, p 353- 358. XIII. Qixing Yang, Fredrik Engström, Bo Björkman and Daniel Adolfsson: Modification study of a steel slag to prevent the slag disintegration after metal recovery and to enhance slag utilization. Proceedings of the VIII international conference on molten slags, fluxes and salts, January 18-21, 2009, Santiago, Chile, p 33-41. XIV. Fredrik Engström, Caisa Samuelsson and Bo Björkman: Mineralogical influence of different cooling conditions on leaching behaviour of steelmaking slags. Proceedings of the 1st International Slag Valorisation Symposium, 6-7 April, 2009, Leuven, Belgium, p 67-80. XV. Charlotte Andersson, Bo Björkman, Fredrik Engström, Sina Mostaghel and Caisa Samuelsson: The need for fundamental measurements for a sustainable extraction of metals. Seetharaman – Seminar 2010. IV XVI. Daniel Adolfsson, Fredrik Engström, Ryan Robinson and Bo Björkman: Cementitious phases in ladle slag. Accepted for publication in Steel Research International, November 2010. XVII. Daniel Adolfsson, Fredrik Engström, Ryan Robinson and Bo Björkman: Hydraulic properties of ladle slag. Submitted to Cement and Concrete Research, September 2010. XVIII. Daniel Adolfsson, Ryan Robinson, Fredrik Engström and Bo Björkman: Hydraulic properties of mayenite. Submitted to Cement and Concrete Research, September 2010. XIX. Chandra Sekhar Gahan, Jan-Eric Sundkvist, Fredrik Engström and Åke Sandström: Utilization of steel slags as neutralizing agents in biooxidation of a refractory gold concentrate and their influence on the subsequent cyanidation. Submitted to Resources, Conservation and Recycling, September 2010. XX. Chandra Sekhar Gahan, Jan-Eric Sundkvist, Fredrik Engström and Åke Sandström: Comparative assessment of Industrial oxidic by- products as neutralising agents in biooxidation and their influence on gold recovery in subsequent cyanidation. Proceedings of the 11th International Seminar on Mineral Processing Technology MPT- 2010, December 15-17, 2010, Jamshedpur, India. V VI ABSTRACT The Swedish steelmaking industry produces large amounts of by-products. In 2008, the total amount of slag produced reached approximately 1,300,000 metric tons, of which 20% was deposited. Due to its strength, durability and chemistry, steel slag is of interest in the field of construction, since it has similar or better qualities than ordinary ballast stone, which makes it a competitive construction material. However, some steel slags face an array of quality concerns that might hinder their use. These concerns generally involve the following physical and chemical properties: • Volume expansion • Disintegration • Leaching of metals By controlling and modifying process parameters during slag handling in liquid state, the physical and chemical properties of steel slags can be adequately modified to obtain a high-quality product for external application. The present work was undertaken as a research project within the Minerals and Metals Recycling Research Centre, MiMeR. The major goal of this work has been to investigate how different treatment methods including hot stage processing, cooling rates, ageing time and chemical composition influence the final properties of the slag. Analysis techniques used in this investigation include: thermodynamic calculations using FactsageTM, X-ray diffraction analyses (XRD), scanning electron microscopy (SEM), leaching tests (EN12457-2/3) and thermo-gravimetric analyses (TG). VII The results from this study show that it is possible to control/change the properties of the final product by additions to the liquid slag, thereby changing the chemical composition, as well as by varying the rate and method of cooling. The mineralogical composition, the size of the crystals and the composition of some solid solutions are affected by the cooling rate. The solubility of elements such as chromium and molybdenum varies, probably due to their presence in different minerals. The reactivity of the investigated slag samples increases as the cooling rate increases. When steel slags are aged, the leaching properties of the materials are changed. The total leachability and the pH decrease for all the investigated samples. All elements except magnesium decrease in leachability. As the slags are aged CaCO3 is formed on the slag surfaces. The degree of carbonation differs between different slags, due to the presence of different calcium-rich minerals in the slag. In order to form CaCO3, the calcium-containing mineral must be dissolved. This means that the solubility of the calcium-containing mineral will affect the outcome of the carbonation. The rate of dissolution for six typical slag minerals was investigated in order to distinguish the difference in solubility between the different minerals. Acidic to alkaline pHs (4, 7 and 10) were selected to investigate the solubility of the minerals under conditions comparable to those prevailing in newly produced slags and the potential future pH values obtained under acid conditions. It can be concluded that all six minerals behave differently when dissolving and that the rate of dissolution is generally slower at higher pH. At pH 10, the solubility of merwinite, akermanite and gehlenite is considered slow. The dissolution of -Ca2SiO4 is not affected in the same way as the other minerals when the
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