Mine tailings valorization potential as raw materials for reaction sintered mullite based ceramics

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1 VTT TECHNICAL RESEARCH CENTRE OF FINLAND LTD Mine tailings valorization potential as raw materials for reaction sintered mullite based ceramics Marjaana Karhu VTT Technical Research Centre of Finland Ltd Circular Materials Conference 2018 March , Chalmers Conference Centre, Gothenburg, Sweden

2 Outline Material development for powders at VTT, circular economy and secondary raw materials valorization in powder technology Ongoing research example in CeraTAIL project, valorization of mining waste as raw material asset for refractory ceramics industry The present work has received funding from Academy of Finland (decision # ) for Novel synthesis methods for porous ceramics from mine tailings, CeraTAIL, /03/2018 2

3 Material development for powders at VTT 3

4 VTT Technical Research Centre of Finland Ltd 75 years experience in supporting our clients growth with top-level research and sciencebased results. Learn more: VTT is one of the leading R&D&I organisations in Northern Europe. We provide expert services for our domestic and international customers and partners, both in private and public sectors. * Loikkanen, T. et al. Roles, effectiveness, and impact of VTT. Towards broad-based impact monitoring of a research and technology organisation VTT, Espoo. VTT Technology p. + app. 5 p. Net turnover and other operating income 269 M (VTT Group 2016) Personnel 2,414 (VTT Group 2016) Unique research and testing infrastructure Wide national and international cooperation network 19/03/2018 4

5 ü Material experts team at VTT specialized on powder technology and powder based materials. 19/03/2018 5

6 Circular economy and secondary raw materials R&D service for utilization of industrial by-products and side streams as secondary raw materials in powder technology and in added value industrial materials Evaluate potential and possibilities to utilize side stream and byproducts as raw material on different applications mainly under extreme conditions Demonstration of suitability and performance of secondary raw material based components 6

7 Development steps from waste to value: Secondary raw materials, development steps from powder to product 1 Secondary raw materials and applications Application demands determination of suitable secondary raw material sources from databases Particular side stream suitability mapping of possible applications Processing & modification Processing parameters for test components Design and manufacturing of demo component Side stream modification to convert it to usable secondary raw material Pre-evaluation of technical and economic feasibility against primary raw materials Determination of the most suitable processing routes Design of experiment (DoE) for process parameter mapping Production of test components for characterization and performance testing Design and optimization of component production process Production of components for demonstrations Component performance testing lab and field testing in operation conditions 5 Pi Piloting Piloting of production Tecno-economic evaluation 19/03/2018 7

8 19/03/2018 8

9 CeraTAIL project research example 9

10 Background, motivation for study Mining tailings are a major waste material, comprising the remain generated from ore processing. In current practice, tailings are transported in slurry form and landfilled in storage impoundments [1] Occupation of large areas of land, costly construction and maintenance, and potential environmental and ecological risks, e.g. acid mine drainage. The utilization of mining tailings is a target of growing interest towards circular economy. Mine tailings, currently landfilled waste, to be seen as a raw material asset. [1] 19/03/2018 Kauppila, P. M., Räisänen, M. L. & Myllyoja, S Best Environmental Practices in Metal Ore Mining. Finnish Environment 10 en29/ ISSN (PDF)

11 Background, motivation for study Felsic mining tailings (FMT) are rich in quartz and alkali feldspars and in terms of chemical composition, the dominant oxides are silica (SiO 2 ) followed by alumina (Al 2 O 3 ) [2]. Examples of amounts of FMTs: Mo ore processing mine tailings amount ~1Mt (closed mine) Gold ore processing mine tailings amount ~2.7Mt + increase of 0.44Mt/year Quartz ore mine tailings amount ~0.68Mt + increase of t/year Mullite is one of the most important refractory ceramic material for high-temperature applications, being the only stable crystalline aluminosilicate phase in the SiO 2 Al 2 O 3 binary system. The European refractory industry produces 5.5 million tons of refractory ceramics annually relying on pure raw materials, the main products are: o Magnesia refractories 2.4 million tons o Fireclay refractories 1.2 million tons o High alumina refractories 0.8 million tons. [2] Solismaa, S., Ismailov, A., Karhu, M., Sreenivasan, H.,Lehtonen, M., Kinnunen, P., Illikainen, M., Räisänen, M-L. Valorization of 19/03/2018 Finnish mining tailings for the use of ceramic industry. Bulletin of the Geological Society of Finland, Published online 5 March

12 Research hypothesis, objectives In presented research, the valorization of selected felsic mine tailings (Mo ore tailings, gold ore tailings and quartz ore tailings) as raw material asset for mullite based refractory ceramics is studied. As a research hypothesis, the felsic mining tailings are potential raw materials for reaction sintered mullite based refractory ceramics materials for high-temperature applications by mixture design and by alumina source addition. The aim is to study and increase the understanding of the effect of mine tailings chemical and mineralogical composition to mullite formation; to formed phase and microstructures as well as thermal and mechanical properties of formed ceramic pieces (mechanical strength, bulk density, apparent density, porosity, thermal expansion, ) and compared them to stoichiometric pure 3:2 mullite as a reference in order to establish a direct comparison of performance. 19/03/

13 Mineralogical and chemical composition The three felsic mine tailings were selected for investigation, their mineralogical and chemical composition analysis. Table 1. Mineralogical composition of tailings samples. Sample code Sample code Quartz Alkali feldspars K-micas Mg-Fe silicates Carbonate minerals Mo ore tailings[ 3 ] FMT <0.5 non Gold ore tailings[ 4 ] FMT Quartz ore tailings[ 5 ] FMT < <0.5 non Table 2. Chemical composition of tailings samples. Sample code SiO2 Al2O3 Si/Al molar Fe2O3 MgO CaO K2O Na2O ratio FMT FMT FMT [3] Haapala, I., & Rämö, O. Mineral deposits related to granitic rocks. In: W. D. Maier, R. Lahtinen, & H. O Brien (Eds.) Mineral Deposits of Finland (2015) Amsterdam: Elsevier Scientific Publ. Co. DOI: /B [4] Sorjonen-Ward, P. Hartikainen, A., Nurmi, P. Rasilainen, K., Scaubs, P., Zhang, Y. & Liikanen, J. Exploration Targeting and Geological Context of Gold Mineralization in the Neoarchean Ilomantsi Greenstone Belt in Eastern Finland. In: W. D. Maier, R. Lahtinen, & H. O Brien (Eds). Mineral Deposits of Finland (2015) Elsevier Inc. 19/03/ [5] Lehtinen, M. Industrial Minerals and Rocks. In: Maier, W., Lahtinen, R., O Brien, H. (Eds). Mineral deposits of Finland (2015) Elsevier Inc.

14 Experimental procedure Recipes for reaction sintering experiments were formulated aiming to composition of 3:2 mullite (3Al 2 O 3 2SiO 2 ) and Al:Si ratio was balanced with commercial aluminum oxide hydroxide (boehmite, AlO(OH)) powder addition. Mixtures were prepared by ball milling and before mixing, mine tailings were grounded by jet milling aiming to under 10 µm particle size in order to increase the reactivity. Grounded mine tailings and milled mixtures were then uniaxially compressed to green pellets of the size 20*3 mm using approximately 25 MPa pressure. Heat-treatment of green pellets of grounded pure mine tailings and reaction sintering of the mixture pellets were performed in air chamber furnace in air atmosphere, and in ambient air pressure. The heating rate was 3.3 C/min up to 1300 C and temperature was kept for 3 hours. Fig 1. Compressed pellets in green state (FMT1 + mixtures). Fig2. Heat-treated FMT1 and reaction sintered mixtures. 19/03/

15 Microstructure analysis Fig (a)-(c). SEM images of reaction sintered pieces of mixtures of (a) FMT1 (b) FMT2 and (c) FMT3 balanced with boehmite. After heat-treatment at 1300 C for 3 hours, the compressed pellets of pure FMT1 and FMT2 were completely melted loosing their shape, on the other hand, the mixtures balanced with boehmite remained their shape during reaction sintering. Formed microstructure consisted of needle shape crystals surrounded by amorphous glass phase. Crystalline phases have different morphologies which most probably resulted differences in tailings mineralogical compositions. The reaction sintered mixture from FMT3 showed more spherical crystal grains, also visible cracks in the structure. 19/03/

16 Phase structure analysis Fig. XRD patterns of Mo ore tailings (FMT1) and reaction sintered mixtures. XRD combined to EDS analysis identified the crystalline needle network as mullite phase in reaction sintered FMT3 mixtures. The peaks related to quartz, muscovite and albite have been disappeared, indicating mullite crystallization via solid solution. 19/03/

17 Conclusions This research work reported valorization potential of selected felsic, quartz feldspar rich mine tailings as raw material asset for mullite based refractory ceramics with reaction sintering experiments. High alkali-feldspar contents caused Mo ore tailings and gold ore tailings melting far below 1300 C not suitable for high temperature resistant refractory applications as such. However, the achieved results suggested that by mixture design and by alumina addition it is possible to prepare novel type of aluminosilicate ceramics by utilizing felsic mine tailings. Mullite is crystallized via solid solution, forming crystalline mullite net structure surrounded by amorphous glass phase. Enabling higher temperature resistance (>1300 C), showing capability for refractory ceramic applications. In forthcoming research work, the properties of these mineral-based ceramics are studied more detailed and compared to pure 3:2 mullite as a reference in order to establish a direct comparison of performance. In addition, the research is ongoing to substitute industrial grade alumina source with lowcost Al-rich waste based material showing promising results. 19/03/

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