A proposal for a 100% use of bauxite residue: The process, results - PowerPoint PPT Presentation

A proposal for a 100% use of bauxite residue: The process, results on the novel Fe-rich binder and how this can take place within the alumina refinery T. Hertel, L. Arnout, A. Peys, L. Pandelaers, B. Blanpain, Y. Pontikes 06/10/2015

The dirty by-product of the Bayer process… Kolontar, Hungary 2 Stade, Germany 1  production: > 140 Mt of BR/yr  landfilled: > 2.7 Bt 1 https://en.wikipedia.org/ 2 http://i.dailymail.co.uk/

Imagine… 2 Stade, Germany 1 1 https://en.wikipedia.org/ 2 adapted from http://blogs.uni-siegen.de/

Imagine… 2 Stade, Germany 1 100 % use of BR 1 adapted from ttps://en.wikipedia.org/ 2 adapted from http://blogs.uni-siegen.de/

Inorganic polymers (IP) • Al- and Si-rich cementitious amorphous binder • polymerisation of an alkali activated precursor • alternative to OPC http://www.geopolymer.org/

Inorganic polymers (IP) • Al- and Si-rich cementitious amorphous binder • polymerisation of an alkali activated precursor • alternative to OPC http://www.geopolymer.org/

Inorganic polymers (IP) • Al- and Si-rich cementitious amorphous binder • polymerisation of an alkali activated precursor • alternative to OPC http://www.geopolymer.org/

Inorganic polymers (IP) • Al- and Si-rich cementitious amorphous binder • polymerisation of an alkali activated precursor • alternative to OPC The market is already there …

Inorganic polymers (IP) • Fe-rich precursors such as copper, lead, ferro-nickel slags • Partially vitrified • Iron in oxidation state +II Cu slag 1 1 http://www.istgrup.com/

Inspiration by Fe-rich precursors Goal • Partially vitrified • Iron in oxidation state +II BR insoluble in alkaline media Modification into Fe-rich precursor Reduction of iron: Fe +III  Fe +II  Support formation of liquid phase Thermal treatment Phase diagrams

SiO 2 Goal How to increase liquid phase formation? SiO 2 1093 °C CaO FeO 1083 °C FeO Al 2 O 3

SiO 2 Goal How to increase liquid phase formation? SiO 2 1093 °C CaO FeO 1083 °C FeO Al 2 O 3

Aim of present work Development of near zero-waste process for the synthesis of IP BR High temperature partially vitrified processing Fe-rich precursor Synthesis IP

Overview of work Characterisation of Bauxite Residue  XRF  XRD I High temperature  thermodynamic calculations processing  XRD II Synthesis of inorganic polymers  SEM  strength III

Characterisation of BR Oxides wt.% A Gibbsite Z G Goethite C Cancrinite I Ca-Al-Fe-Si-Hydroxide Fe 2 O 3 47.9 Cc Calcite P Perovskite H D Diaspore R Rutile P H Hematite Al 2 O 3 18.9 H Intensity [a.u.] Q Quartz Z Z Zincite CaO 11.0 (Internal standard) Z Cc SiO 2 9.6 Z H Z H H C H D Q I TiO 2 6.5 R I A D C G G Cc I I Cc G I H G Q P Na 2 O 4.0 20 30 40 50 60 °2 ϑ CuK α XRF XRD

High temperature processing FactSage calculation 1100 ° C – Carbon addition 100 Ca(Al,Fe) 6 O 10 90 Ca 2 (Al,Fe) 8 SiO 16 80 Corundum 70 Fe FeO 60 Mellilite wt.% 50 NaAlO 2 Nepheline 40 Perovskite 30 Liquid phase Spinel 20 Gas 10 Ti-Spinel 0 0,4 0,8 1,2 1,6 2,0 2,4 wt.% C

High temperature processing FactSage calculation 1100 ° C – Carbon addition 100 Ca(Al,Fe) 6 O 10 90 Ca 2 (Al,Fe) 8 SiO 16 80 Corundum 70 Fe FeO 60 Mellilite wt.% 50 NaAlO 2 Nepheline 40 Perovskite 30 Liquid phase Spinel 20 Gas 10 Ti-Spinel 0 0,4 0,8 1,2 1,6 2,0 2,4 wt.% C

High temperature processing FactSage calculation 1100 ° C – Carbon + silica addition

High temperature processing 19 FactSage calculation 1100 ° C – Carbon + silica

High temperature processing 20 FactSage calculation 1100 ° C – Carbon + silica 98.4BR_1.6C 88.6BR_1.4C_10S 100BR

High temperature processing Transformation of BR • Induction furnace: 1100 ± 10 ° C – 1 hour • closed iron crucible, gas inlet/outlet • inert atmosphere – Argon 99.995 % Aim: semi-vitrified material  precursor for IP

XRD of precursor Z 100BR m S a ) Z M Z Z,P c H,P Z Q MS f N c Calcium Iron Oxide, Zc M N,f f S M H c G H P H,G G,c H,G G f Iron Calcium Silicate, P H G c,N H G,S S N S G Gehlenite, H Hematite, Z b) 98.4BR_1.6C I Iron, Intensity (a.u.) Z W S W M Magnetite, Z S P G Z,P Z m Maghemite, f N N,f S N Nepheline, Q S PG G G S G,S I P G G G S P Perovskite, Q Quartz, Z c ) S S Spinel, 88.6BR_1.4C_10S M Z W Wüstite, Z Z S Z Zincite (internal standard) G M M Z,P S I N G G M M W M G N NG QN G S P G G,M S N,G S N G 20 30 40 50 60 °2 ϑ CuK α

XRD of precursor Z 100BR m S a ) Z M Z Z,P c H,P Z Q MS f N c Calcium Iron Oxide, Zc M N,f f S M H c G H P H,G G,c H,G G f Iron Calcium Silicate, P H G c,N H G,S S N S G Gehlenite, H Hematite, Z b) 98.4BR_1.6C I Iron, Intensity (a.u.) Z W S W M Magnetite, Z S P G Z,P Z m Maghemite, f N N,f S N Nepheline, Q S PG G G S G,S I P G G G S P Perovskite, Q Quartz, Z c ) S S Spinel, 88.6BR_1.4C_10S M Z W Wüstite, Z Z S Z Zincite (internal standard) G M M Z,P S I N G G M M W M G N NG QN G S P G G,M S N,G S N G 20 30 40 50 60 °2 ϑ CuK α

XRD of precursor Z 100BR m S a ) Z M Z Z,P c H,P Z Q MS f N c Calcium Iron Oxide, Zc M N,f f S M H c G H P H,G G,c H,G G f Iron Calcium Silicate, P H G c,N H G,S S N S G Gehlenite, H Hematite, Z b) 98.4BR_1.6C I Iron, Intensity (a.u.) Z W S W M Magnetite, Z S P G Z,P Z m Maghemite, f N N,f S N Nepheline, Q S PG G G S G,S I P G G G S P Perovskite, Q Quartz, Z c ) S S Spinel, 88.6BR_1.4C_10S M Z W Wüstite, Z Z S Z Zincite (internal standard) G M M Z,P S I N G G M M W M G N NG QN G S P G G,M S N,G S N G 20 30 40 50 60 °2 ϑ CuK α

Synthesis of IP’s K-silicate activation solution, SiO 2 /K 2 O= 1.6, H 2 O/K 2 O = 16 o activation solution/solid ratio = 0.25 o Curing: 60 ° C, 72 h o Steoroscope images 100BR 98.4BR_1.6C 88.6BR_1.4C_10S

Microstructure – SEM (SE) 98.4BR_1.6C 88.6BR_1.4C_10S 100BR denser microstructure less pores, cracks

SEM & strength (3d) of IPs 98.4BR_1.6C 88.6BR_1.4C_10S 100BR Compressive 13.4 ± 0.4 MPa 19.7 ± 1.1 MPa 43.5 ± 0.5 Mpa strength Flexural 4.2 MPa 5.5 MPa 9.8 MPa strength

Process within alumina refinery C BR slurry SiO 2 2 Bayer process mixing firing Fe, Fe 3 O 4 BR cake filter press H 2 O precursor 1 alkaline liquor IP alkalis waterglass 1 http://img.tradeindia.com/ 2 https://encrypted-tbn1.gstatic.com

Conclusion  BR was transformed into suitable Fe-rich precursor material for IP  addition of C, SiO 2  heat treatment - 1100 °C  Insoluble, dense IPs were sucessfully synthesised  dense microstructure  strength exceeding 40 MPa

 Redmud booth To be continued … Thank you for your kind attention!