Red mud processing and utilization

KISHAN KUMAR MAHILANGE16MS06013MATERIAL SCIENCE & ENGINEERINGIIT BHUBANESWAR

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CONTENTSIntroduction to red mudComposition of red mudEnvironmental problems associated with

disposal of red mudStorage and disposal of red mudNeutralization of red mudUtilization of red mudConclusionReferences

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INTRODUCTION Red mud or red sludge is a

high alkaline waste product that is generated in the production of alumina from bauxite in the Bayer process.

Depending on the raw material processed, 1–2.5 tons of red mud is generated per ton of alumina produced..

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What does Red mud consist of?

Red mud from alumina production(70% NaOH solution+ 30% BR)

Disposed and settled red mud Dry bauxite residue(>65% solid content)

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Bayer’s process of alumina production 5

Typical composition of red mud:- Composition Percentage

Fe2O3 30-60%

Al2O3 10-20%

SiO2 10-20%

Na2O 2-10%

CaO 2-8%

TiO2 trace-25%

Company Al2O3 (%)

Fe2O3 (%)

SiO2

(%) TiO2 (%)

Na2O (%)

CaO (%)

BALCO, Korba 18.10-21.0 35.0-37.0 6.0-6.5 17.0-19.0 5.2-5.5 1.7-2.2

HINDALCO, Renukoot

17.5-19.0 35.5-36.2 7.0-8.5 16.3-14.5 5.0-6.0 3.2-4.5

HINDALCO, Muri

19.0-20.5 44.0-46.0 5.5-6.5 17.0-18.9 3.3-3.8 1.5-2.0

HINDALCO, Belgaum

17.8-20.1 44.0-47.0 7.5-8.5 8.2-10.4 3.5-4.6 1.0-3.0

MALCO, Metturdam

18.0-22.0 40.0-26.0 12.0-16.0 2.5-3.5 4.0-4.5 1.5-2.5

NALCO, Damanjodi

17.7-19.8 48.2-53.8 4.8-5.7 3.6-4.1 3.8-4.6 0.8-1.2

Chemical composition of Indian red mud:-

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Environmental problems of red mud:- Disposal of red mud is typically problematic for most alumina refineries.

Red mud is disposed as dry or semi dry material in red mud pond or bauxite mines. Untreated red mud has such high pH (typically 11-13) that plant growth is impossible and this posses a very serious and alarming environmental problem.

The environmental problems associated with the disposal of red mud are:

• Its high pH

• Alkali seepage into underground water

• Safety storage problem

• Alkaline airborne dust emissions

• Vast area of land required for disposal.

• Minor and trace amounts of heavy metals and radionuclides seepage into ground water.

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Red mud spill/disaster in Hungary drew world attention in 2010 - Ajka Alumina plant accident,Hungary

In October 2010, approximately one million cubic meter of red mud from an alumina plant near ‘Kolontar’ in ‘Hungary’ was accidently released into the surrounding contryside and flooding several nearby localities, including the village of Kolontár and the town of Devecser. Known as big “red mud disaster" claimed 10 lives, 150 were seriously injured.

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STORAGE AND DISPOSAL OF RED MUD Most of the bauxite residue produced is stored on land for future

rehabilitation or use called red mud ponds/stacks or bauxite residue disposal areas (BRDAs).

Disposal methods:• CCD- closed cycle disposal (traditional method)• MCCD- Modified closed cycle disposal Current methods:• Sea water discharge• Lagooning• Dry stacking method• Dry disposal

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Traditional method-CCD

Modified-MCCD

Red mud disposal lake in the vicinity of Kashipur region of Orissa,India 

The pond of NALCO factory in Damandjodi (India)

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Dry disposal:• Dry filtered cake

• Solid content:>65%• Transported by trucks

• minimizes the land area required for storage

• Minimizes the risk of leakage to groundwater

Dry stacking:• Paste like, thixotropic

• Solid content:>48-55%

• Pumped via pipeline

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Sea water discharge:• From the mud washing circuit• Solid content: 30-40%• Via pipeline or ships• reduce caustic soda levels

Lagooning:• From the mud washing circuit• Solid content: 30-40%• Via pipeline or ships

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Acid neutralization: :

Carbon dioxide treatment :

14NEUTRALIZATION OF RED MUD

UTILIZATION OF RED MUD Building and chemical industries:• Building materials, engineering constructions

• Paving blocks

• As a feedstock for manufacturing Adsorbents and catalyst supports

• Ceramics, glasses, paints, polymers, coatings

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Continued…. Waste water treatment:• For removal of toxic heavy metal and metalloid ions,

inorganic anions such as nitrate, fluoride, and phosphate, as well as organics including dyes, phenolic compounds and bacteria.

Metallurgy:• Steel making, additives for slags

• Selection of main components (Fe, Al)

• Selection of other metals (Ti, V, RM)

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Recovery of metals Two main approaches which have been generally

investigated to recover iron values are based on :

a) Solid state reduction of red mud followed by magnetic separation to recover iron; and

b) Reduction smelting in a blast/electric/low shaft furnace (with or without pre reduction) to produce pig iron.

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Continued… National Metallurgical Laboratory (NML), Jamshedpur

has evaluated technical feasibility of Al2O3 extraction, along with Vanadium oxide, from Muri red mud by Soda-Lime sinter process.

Prasad and co-workers have explored the production of ferrotitanium to utilize both iron and titanium values of Indian red muds.

Recovery of Fe, Al2O3,V and Cr from red mud has been developed by Regional Research Laboratory (RRL), Bhubaneswar.

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CONCLUSION Red mud has wide range of application from building material to

metal recovery. Developments in dry disposal methods will lead to better

management of residue but neutralization of red mud will be an essential ingredient of any permanent solution.

Continuous research is required by studying residue neutralization technologies to reduce alkalinity of red mud which is the most important barrier for its reuse and disposal management.

Red mud ponds can be rehabilitated by growing suitable flora and fauna on it.

Depending on mud characteristics, a systematic strategy should be taken up by each alumina plant and a zero waste alumina refinery may be realized by developing a universal technique of disposal, management and full utilization of red mud.

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References

Current Status of an Industrial Waste: Red Mud an Overview by Sucharita Patel, B.K. Pal, Nit Rourkela, Orissa

Neutralization and Utilization of red mud for its better waste management by Suchita Rai, Kailas L. Wasewar , Changkyoo Yoo.

Agrawal, A., Sahu, K.K.., Pandey, B.D., (2004). Solid waste management in non-ferrous industries in India. Resources, Conservation and Recycling 42 99–120. (http://www.sciencedirect.com/science/article/pii/S092134490300168X).

U.S. Geological Survey, Mineral Commodity Summaries (2015). (http://minerals.usgs.gov/minerals/pubs/mcs/2015/mcs2015.pdf)

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Waste is waste if you waste it. Otherwise it is

a resource.21

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