FROM BAUXITE RESIDUE TO A NOVEL BINDER: Options for the Alumina Refinery Tobias Hertel, Lukas Arnout, Silviana Onisei, David Ariño Montoya, Bart Blanpain, Yiannis Pontikes 2nd Bauxite Residue Valorisation and Best Practices Conference, Athens, 2018 May 7, 2018

OXIDES Motivation The secondary resource: Bauxite Residue (BR) Only 1 – 3 % (by mass) is industrially valorised

Why? Motivation Effective valorisation with large-volume applications LEGISLATIVE BARRIER strict waste legislations, complicated licensing to use BR  barrier for some industrial sectors to reuse BR; landfilling often more economical and easy solution  policy actions needed TECHNICAL BARRIER availability of well-established raw materials at low price - robust and simple valorisation processes needed - economic benefit Effective valorisation with large-volume applications Construction materials as promising route

Geopolymer/Inorganic Polymer Performance of BR as a binder material Motivation Geopolymer/Inorganic Polymer Cement water Ca-Si-Hydrates Ca(OH)2 Alkali (silicate) solution Inorganic Polymer cement (hydraulic phases) (ferro)aluminosilicate source (mainly amorphous, glassy phase) water Alkali (silicate) solution BR No hydraulic phases (exception BR from sinter process) No reactive glass phase

Performance of BR as a binder material Motivation Mechanical properties

Technology readiness level Aim of the present work Presentation of selected processes to transform BR into novel binders (where BR actively participates to the properties of the final building material) INDUSTRIAL SCALE PILOT PLANT SCALE Proposals, flowsheet LABORATORY SCALE demonstrated TRL Technology readiness level

[Ordinary Portland Cement] Use of BR in raw meal of clinker production [Ordinary Portland Cement] Addition of BR limited to about 5 wt% Firing at 1450 °C Ariño Montoya et al. 5th International Slag Valorisation Symposium; 2017.​ Low additions of BR

[Calciumferrosulfoaluminate cements] Use of BR in raw meal of clinker production [Calciumferrosulfoaluminate cements] Addition of BR of about 40 wt% Compressive Strength of 40 MPa Firing at 1200 – 1300 °C -> formation of hydraulic phases CSFA clinker + Gypsum MPa CSFA cement + Water, Sand CSFA mortars Onisei et al. Slag Valorisation Symposium Leuven 2017, Leuven 3-5 April 2017

[Aluminoferrite and ferrobelitic clinkers cements] Use of BR in raw meal of clinker production [Aluminoferrite and ferrobelitic clinkers cements] Tuesday, 8th – 14:40 David Ariño Montoya et al. Bauxite Residue as a main raw material in the production of calcium sulfo ferroaluminate clinker Firing at 1250 °C CSFA cement + Water, Sand CSFA mortars

> 40 MPa Transformation of BR into precursor for inorganic polymers BR slag as reactive component in binder Trivial additions Firing at 1100 - 1200 °C -> formation of reactive glass phase Water quenching BR slag + alkaline activator Compressive Strength > 40 MPa Inorganic Polymer

Compressive strength up to 55 MPa Transformation of BR into precursor for inorganic polymers integrated, near-zero-waste processes → metal recovery → building materials Firing at 1250 °C Compressive strength up to 55 MPa Water quenching BR slag Fe MPa + alkaline activator + sand Inorganic Polymer Mortar

Transformation of BR into supplementary cement. material Firing at 1200 °C Water quenching Tuesday, 8th – 16:20 – Poster SIVAKUMAR et al. Modified bauxite residue as an alternative supplementary cementitous material BR slag supplementary cement. material

Alternative heat treatment technologies microwave assisted furnace C as microwave energy absorber Firing at 1100 - 1200 °C Water quenching BR slag Options to reduce overall environmental footprint Use of established, robust processes Reduction of risks, cost, complexity Tuesday, 8th – 16:20 – Poster HERTEL & Cardenia et al. Microwave treatment of bauxite residue for the production of inorganic polymers + alkaline activator pressing Inorganic Polymer Binder

Alternative heat treatment technologies sinter-pot furnace (pilot plant scale) (conventionally used for iron ore sintering) Firing at 1100 - 1200 °C Water quenching BR slag Tuesday, 8th – 15:40 ARNOUT et al. Increasing the reactivity of bauxite residue for the use as building material: an alternative activation treatment + alkaline activator pressing Inorganic Polymer Binder

> 50 MPa Reducing the overall environmental footprint Firing at 1100 - 1200 °C Water quenching BR slag Compressive Strength > 50 MPa + alkaline activator 84 % of BR in binder Less BR needs to be fired pressing Inorganic Polymer Binder

Use of BR slurry in hybrid binders (cement / reactive slag) less BR is treated towards slag valorisation of BR slurry in as-it-is state No additional alkaline activator needed L/S = 0.75 liquid content: 43 % Compressive Strength of 45 MPa with > 80 wt% BR (BR in BR slag + BR slurry) curing MPa Hybrid Binder Mortar

Alkali silicate solution Binder from BR – flowsheet – options for the alumina industry BR slurry filter press alkaline solution water B2O3 SO3 SiO2 CaO C cake alkalis soluble SiO2 autoclave SiO2 Alkali silicate solution

Binder from BR – flowsheet – options for the alumina industry Thermal treatment furnace rotary kiln top rotary blown converter microwave sintering furnace

Ordinary Portland cement Binder from BR – flowsheet – options for the alumina industry 1100 – 1200 °C 1200 - 1250 ° 1250 - 1300 °C > 1300 °C granulation equipment Calciumsulfo- aluminate -ferrite clinker Portland cement clinker BR slag BR slag SO3 milling equipment milling equipment magnetic separator milling equipment CSFA cement magnetic non- magnetic Fe Ordinary Portland cement BR slag precursor

BR slag precursor casting pressing CSFA cement Ordinary Portland cement BR slag precursor Alkali silicate solution H2O H2O BR slurry mixer BR Soluble silicates shaping casting pressing BR in disposal area curing chamber Farming amphiroll Inorganic polymers Hybrid binder Calciumsulfoferroaluminate cement Ordinary Portland cement Pozzolanic cement densified, storable aggregate Building products Aggregates, cements, bricks, blocks, tiles, porous materials, fire resistant materials

Conclusions crucial for a sustainable management of the residue towards novel binders indispensable factors to convince industrial partners Industrial implementation Focus on technical feasibility on real-life conditions and economic and environmental aspects currently investigated in a pilot plant scale in the framework of the EIT KIC RECOVER and in the upcoming H2020 RemovAl project Possibilities of various binder formation from mainly BR derived materials are proven in a laboratory scale

Thank you for your kind attention Acknowledgements Thank you for your kind attention FROM BAUXITE RESIDUE TO A NOVEL BINDER: Options for the Alumina Refinery Tobias Hertel, Lukas Arnout, Silviana Onisei, David Ariño Montoya, Bart Blanpain, Yiannis Pontikes The research leading to these results has received funding from the European Community’s Horizon 2020 Programme ([H2020/2014–2019]) under Grant Agreement no. 636876 (MSCA-ETN REDMUD). This publication reflects only the authors’ view, exempting the Community from any liability. Project website: http://www.etn.redmud.org. This work has received funding from EIT RawMaterials, a European Institute of Innovation and Technology (EIT) Knowledge and Innovation Community (KIC) under the Project Agreement No. 16365 (RECOVER). Project website: https://recover.technology. Further thank goes to (alphabetic order): Chiara Cardenia, CRM Group/Liège, Theodoros Karachalios, Pithchai Pandian Sivakumar, who contributed to this work