a proposal for a 100% use · 2015-10-29 · a proposal for a 100% use of bauxite residue: the...

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…

Stade, Germany1

1https://en.wikipedia.org/

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

Kolontar, Hungary2

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

Imagine…

Stade, Germany1

2adapted from http://blogs.uni-siegen.de/

1https://en.wikipedia.org/

2

Imagine…

100 % use of BR

Stade, Germany1

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

2

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

Inorganic polymers (IP)

http://www.geopolymer.org/

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


The market is already there …

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


Cu slag1

1http://www.istgrup.com/

Goal

Phase diagrams

BR insoluble in alkaline media

Modificationinto Fe-richprecursor

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

Goal

FeO

SiO2

Al2O3

SiO2

CaO FeO1083 °C

1093 °C

How to increase liquid phase formation?

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

Synthesis of inorganic polymers

High temperatureprocessing

Characterisation of Bauxite Residue

thermodynamic calculations XRD

Overview of work

I

II

III

XRF XRD

SEM strength

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 GoethiteI Ca-Al-Fe-Si-HydroxideP PerovskiteR RutileQ QuartzZ Zincite

HG ICcD I

DICcQ

G

HP

GI IGA

QRC

P

C

CcHH

H

H

Z

Inte

nsity

[a.u

.]

°2ϑCuKα

H ZZ

Z

Z

A GibbsiteC CancriniteCc CalciteD DiasporeH Hematite

XRD

(Internal standard)

High temperature processing

0,4 0,8 1,2 1,6 2,0 2,4

0

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

High temperature processingFactSage calculation 1100 °C – Carbon + silica addition

High temperature processing19 FactSage calculation 1100 °C – Carbon + silica

High temperature processing20 FactSage calculation 1100 °C – Carbon + silica

100BR

98.4BR_1.6C

88.6BR_1.4C_10S

High temperature processingTransformation 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

20 30 40 50 60

M

a)

b)

c)

MN

G

f

NHM

S

HS

SHGc GH H,GG,SZc

c

f

mM

G,cQ

PN,f

Z

N

Z,PZ

Z

Z

S

f

P

P

W

S

G

c,NH,GS

P

S

S

MZ

Z,P

Z

Z

Z

Z

G,S SGG

Z,P

Z

Q G

H,P

PGN,f

IS

W

ZS

SZ

G

Inte

nsity

(a.u

.)

GMG

S

G N,G

G

NP G G,MG

SSMWM

GM

S

S N NG QN NG

MI

°2ϑCuKα

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

20 30 40 50 60

M

a)

b)

c)

MN

G

f

NHM

S

HS

SHGc GH H,GG,SZc

c

f

mM

G,cQ

PN,f

Z

N

Z,PZ

Z

Z

S

f

P

P

W

S

G

c,NH,GS

P

S

S

MZ

Z,P

Z

Z

Z

Z

G,S SGG

Z,P

Z

Q G

H,P

PGN,f

IS

W

ZS

SZ

G

Inte

nsity

(a.u

.)

GMG

S

G N,G

G

NP G G,MG

SSMWM

GM

S

S N NG QN NG

MI

°2ϑCuKα

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)

Synthesis of IP’so K-silicate activation solution, SiO2/K2O = 1.6, H2O/K2O = 16o activation solution/solid ratio = 0.25o Curing: 60 °C, 72 h

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

Steoroscope images

Microstructure – SEM (SE)

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

denser microstructure

less pores, cracks

SEM & strength (3d) of IPs

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

Compressivestrength 13.4 ± 0.4 MPa 19.7 ± 1.1 MPa 43.5 ± 0.5 Mpa

Flexuralstrength 4.2 MPa 5.5 MPa 9.8 MPa

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

Conclusion

BR was transformed into suitable Fe-rich precursormaterial for IP addition of C, SiO2 heat treatment - 1100 °C

Insoluble, dense IPs were sucessfully synthesised dense microstructure strength exceeding 40 MPa

Thank you for your kind attention!

To be continued …

Redmud booth

a proposal for a 100% use · 2015-10-29 · a proposal for a 100% use of bauxite residue: the...

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