MINERAL PROCESSING (2)

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RECYCLING OF IRON FROM RED MUD BY MAGNETIC SEPARATION AFTER CO-ROASTING

WITH PYRITE

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GROUP MEMBER: M .ANUS 14MN36(G.L)IMRAN 14MN06TANVEER AHMEED 14MN20KHALID HUSSAIN 14MN29TAHIR ALI 14MN60

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OBJECTIVES

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OBJECTIVE

Recycling of Iron from Alumina’s tailing

Make Toxic Red Mud environment friendly

To make the Tailing Profitable

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INTRODUCTION

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WHAT IS RED MUD ? Red mud is a toxic iron rich residue

of Industrial process of Bauxite

Highly Basic pH 10-13

Effects the air,land and water environment of surrounding area

At present,77 Million Tones of red mud is generated annually worldwide

Contain Gibbsite ,Boehmite, Goethite, Hematite (α-Fe203), Anatase and Clay Minerals

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What is RED MUD ? Red mud contain 10-30% hematite

Hematite is being recovered by ‘RED MUD’

Hematite in red mud being transformed into ‘MAGNETITE ’(the highest gade iron ore) with the help of Pyrite

Remaining 2-3% Iron used as ‘REFRACTORY’

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Flow-sheet diagram of recycling of Iron from red mud

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XRD (X-Ray diffraction): for mineralogy & crystallography

XRF (X-Ray Fluorescence): for elemental analysis

TGA (Thermogravimetric Analysis): thermo-analytic technique,works on increasing temprature (heating rate)

TERMINOLOGY

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DTA (Differential Thermal Analysis): thermo-analytic technique,records temprature difference between Sample & Reference

Anaerobic roasting: heated below melting point in absence of air

TERMINOLOGY

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Experiment

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Red mud samples dried at 110 ◦ C for 4 h before testing

30 g of red mud contain the mole ratio of FeS2 to Fe2 O3 was 1:4 or 1:8 roasted at 600 ◦ C for 30 min under N2 atmosphere.

The thermogravimetric analysis (TG) and differential thermal analysis (DTA) of the samples were performed on a thermal analyzer

SAMPLING

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In Fig. the (a)TG-(b)DTA curves showing three weight-loss stages in the range of 500–750 ᵒc

23% of weight-loss

Desulfurization of pyrite at 280ᵒC

Thermo-chemical behavior of pyrite

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TGA-DTA Curves at different mole ratios

The XRD patterns of (a) the anaerobic decomposed residue of pyrite at 700 ◦ C; and (b) the co-roasting product of the above residue with hematite at 600 ◦ C.a=mole ratio of 1:1

b=mole ratio of 1:5c=mole ratio of 1:10d=mole ratio of 1:20

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a= from a Alumina plant in Shanxi,China.b= from a Alumina plant in Henan,China.

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Production process

Red mud samples

Al2O3(%)

SiO2(%)

Fe2O3(%)

TiO2(%)

CaO(%)

Na2O(%)

Sintering Process

1a2b

5.5112.20

4.5920.37

9.78.8

3.813.74

42.3938.00

0.615.76

Bayer’s Process

3a4b

23.2022.36

22.0919.05

13.219.4

6.245.13

18.4013.31

5.648.24

The main chemical compositions of the collected red mud samples

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Co-roasting of Pyrite and Hematite The mixture of hematite and pyrite with

different mole ratios are heated at 500ᵒC for 1h (pyrite decomposes into iron monosulphide FeS)

When the temprature reaches from 525-600ᵒC hematite could be transformed into roasted Magnetite

FeS2 + 4Fe2O3 = 3Fe3O4 + 2S 2S + 12Fe2O3 = 8Fe3O4 + 2SO2

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a=mole ratio of pyrite to hematite in red mud is 1:4

b=mole ratio of pyrite to hematite in red mud is 1:8

Red mud sample no.

Pyrite mixed with 30g red mud

Magnetic part Mass (g)

Magnetic partFe (%)

Non-magnetic partMass (g)

Non-magnetic partFe(%)

11234

0.55a0.28b0.51a0.74a1.10a

3.32.73.04.56.2

36.433.835.236.938.7

24.326.225.022.520.0

1.072.041.190.611.65

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INDUSTRIAL APPLICATION

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1 ton red mud (Fe 15%)+40 kg pyrite is needed to get 232 kg Fe3 O4 upon magnetic separation.

At least 10 kg pyrite is needed to guarantee the transformation, but 167 mol SO2 might be released.

INDUSTRIAL APPLICATION

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CONCLUSION

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Hematite can be transformed into magnetite at 525 ◦ C

The released SO2 used for sulfuric acid production

This method is expected to be applied in industry only if the amount of the pyrite is calculated based on the content of Fe2 O3 in red mud.

CONCLUSIONS

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THANKS FOR YOUR TIME