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

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

May 12, 2023 8 likes •324 views

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

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A proposal for a 100% use

  • f 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

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The dirty by-product of the Bayer process…

Stade, Germany1

1https://en.wikipedia.org/

  • production: > 140 Mt of BR/yr
  • landfilled: > 2.7 Bt

Kolontar, Hungary2

2http://i.dailymail.co.uk/

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Imagine…

Stade, Germany1

2adapted from http://blogs.uni-siegen.de/ 1https://en.wikipedia.org/

2

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Imagine…

100 % use of BR

Stade, Germany1

1adapted from ttps://en.wikipedia.org/ 2adapted from http://blogs.uni-siegen.de/

2

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  • Al- and Si-rich cementitious amorphous binder
  • polymerisation of an alkali activated precursor
  • alternative to OPC

Inorganic polymers (IP)

http://www.geopolymer.org/

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  • Al- and Si-rich cementitious amorphous binder
  • polymerisation of an alkali activated precursor
  • alternative to OPC

Inorganic polymers (IP)

http://www.geopolymer.org/

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  • Al- and Si-rich cementitious amorphous binder
  • polymerisation of an alkali activated precursor
  • alternative to OPC

Inorganic polymers (IP)

http://www.geopolymer.org/

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  • Al- and Si-rich cementitious amorphous binder
  • polymerisation of an alkali activated precursor
  • alternative to OPC

Inorganic polymers (IP)

The market is already there …

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  • Fe-rich precursors such as copper, lead, ferro-nickel slags
  • Partially vitrified
  • Iron in oxidation state +II

Inorganic polymers (IP)

Cu slag1

1http://www.istgrup.com/

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Goal

Phase diagrams BR insoluble in alkaline media

Modification into Fe-rich precursor

Reduction of iron: Fe+III  Fe+II  Support formation of liquid phase

Inspiration by Fe-rich precursors

  • Partially vitrified
  • Iron in oxidation state +II

Thermal treatment

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Goal

FeO SiO2 Al2O3 SiO2 CaO FeO

1083 °C 1093 °C

How to increase liquid phase formation?

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Goal

FeO SiO2 Al2O3 SiO2 CaO FeO

1083 °C 1093 °C

How to increase liquid phase formation?

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Aim of present work

IP BR

Development of near zero-waste process for the synthesis of IP

partially vitrified Fe-rich precursor Synthesis High temperature processing

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Synthesis of inorganic polymers High temperature processing Characterisation of Bauxite Residue

 thermodynamic calculations  XRD

Overview of work

I II III

 XRF  XRD  SEM  strength

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XRF

Characterisation of BR

Oxides wt.% Fe2O3 47.9 Al2O3 18.9 CaO 11.0 SiO2 9.6 TiO2 6.5 Na2O 4.0

20 30 40 50 60 G Goethite I Ca-Al-Fe-Si-Hydroxide P Perovskite R Rutile Q Quartz Z Zincite H G I Cc D I D I Cc Q G H P G I I G A Q R C P C Cc H H H H Z

Intensity [a.u.] °2ϑ CuKα

H Z Z Z Z A Gibbsite C Cancrinite Cc Calcite D Diaspore H Hematite

XRD

(Internal standard)

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High temperature processing

0,4 0,8 1,2 1,6 2,0 2,4 10 20 30 40 50 60 70 80 90 100

wt.% wt.% C

FactSage calculation 1100 °C – Carbon addition

Ti-Spinel Ca(Al,Fe)6O10 Ca2(Al,Fe)8SiO16 Corundum Fe FeO Mellilite NaAlO2 Nepheline Perovskite Liquid phase Spinel Gas

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High temperature processing

0,4 0,8 1,2 1,6 2,0 2,4 10 20 30 40 50 60 70 80 90 100

wt.% wt.% C

FactSage calculation 1100 °C – Carbon addition

Ti-Spinel Ca(Al,Fe)6O10 Ca2(Al,Fe)8SiO16 Corundum Fe FeO Mellilite NaAlO2 Nepheline Perovskite Liquid phase Spinel Gas

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High temperature processing

FactSage calculation 1100 °C – Carbon + silica addition

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High temperature processing

19 FactSage calculation 1100 °C – Carbon + silica

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High temperature processing

20 FactSage calculation 1100 °C – Carbon + silica

100BR 98.4BR_1.6C 88.6BR_1.4C_10S

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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

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20 30 40 50 60

M

a) b) c)

M N G f N H MS H S S H G c G H H,G G,S Zc c f m M G,c Q P N,f Z N Z,P Z Z Z S f P P W S G c,N H,G S P S S M Z Z,P Z Z Z Z G,S S G G Z,P Z Q G H,P PG N,f I S W Z S S Z G

Intensity (a.u.)

G M G S G N,G G N P G G,M G S S M W M G M S S N NG QN N G M I

°2ϑ CuKα

XRD of precursor

c Calcium Iron Oxide, f Iron Calcium Silicate, G Gehlenite, H Hematite, I Iron, M Magnetite, m Maghemite, N Nepheline, P Perovskite, Q Quartz, S Spinel, W Wüstite, Z Zincite (internal standard)

100BR 98.4BR_1.6C 88.6BR_1.4C_10S

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20 30 40 50 60

M

a) b) c)

M N G f N H MS H S S H G c G H H,G G,S Zc c f m M G,c Q P N,f Z N Z,P Z Z Z S f P P W S G c,N H,G S P S S M Z Z,P Z Z Z Z G,S S G G Z,P Z Q G H,P PG N,f I S W Z S S Z G

Intensity (a.u.)

G M G S G N,G G N P G G,M G S S M W M G M S S N NG QN N G M I

°2ϑ CuKα

XRD of precursor

100BR 98.4BR_1.6C 88.6BR_1.4C_10S

c Calcium Iron Oxide, f Iron Calcium Silicate, G Gehlenite, H Hematite, I Iron, M Magnetite, m Maghemite, N Nepheline, P Perovskite, Q Quartz, S Spinel, W Wüstite, Z Zincite (internal standard)

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20 30 40 50 60

M

a) b) c)

M N G f N H MS H S S H G c G H H,G G,S Zc c f m M G,c Q P N,f Z N Z,P Z Z Z S f P P W S G c,N H,G S P S S M Z Z,P Z Z Z Z G,S S G G Z,P Z Q G H,P PG N,f I S W Z S S Z G

Intensity (a.u.)

G M G S G N,G G N P G G,M G S S M W M G M S S N NG QN N G M I

°2ϑ CuKα

XRD of precursor

100BR 98.4BR_1.6C 88.6BR_1.4C_10S

c Calcium Iron Oxide, f Iron Calcium Silicate, G Gehlenite, H Hematite, I Iron, M Magnetite, m Maghemite, N Nepheline, P Perovskite, Q Quartz, S Spinel, W Wüstite, Z Zincite (internal standard)

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Synthesis of IP’s

  • K-silicate activation solution, SiO2/K2O= 1.6, H2O/K2O = 16
  • activation solution/solid ratio = 0.25
  • Curing: 60 °C, 72 h

100BR 98.4BR_1.6C 88.6BR_1.4C_10S Steoroscope images

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Microstructure – SEM (SE)

100BR 98.4BR_1.6C 88.6BR_1.4C_10S

denser microstructure less pores, cracks

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SEM & strength (3d) of IPs

100BR 98.4BR_1.6C 88.6BR_1.4C_10S Compressive strength 13.4 ± 0.4 MPa 19.7 ± 1.1 MPa 43.5 ± 0.5 Mpa Flexural strength 4.2 MPa 5.5 MPa 9.8 MPa

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Process within alumina refinery

Bayer process BR slurry C mixing filter press BR cake alkaline liquor

alkalis waterglass

firing precursor

Fe, Fe3O4

IP

SiO2

H2O

1http://img.tradeindia.com/ 2https://encrypted-tbn1.gstatic.com

1 2

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Conclusion

  • BR was transformed into suitable Fe-rich precursor

material for IP

  • addition of C, SiO2
  • heat treatment - 1100 °C
  • Insoluble, dense IPs were sucessfully synthesised
  • dense microstructure
  • strength exceeding 40 MPa
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Thank you for your kind attention!

To be continued …

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