By: Dr. Mohamed Ismail and Dr. Maqbool Ahmed
ERI – RC Environmental Consultant, Jubail.
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Understanding Three Major Industrial Wastes
(Red Mud, Phosphogypsum and Gypsum)
Waste Characterization
Current Status of Waste Handling
Disposal methods (Worldwide)
Recovery/Uses (Worldwide)
Conclusions
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1. RED MUD from Alumina Refinery, RIC
Expected Generation : 2.65 Million Tons/Year
2. PHOSPHOGYPSUM from Phosphate Plant, RIC
Expected Generation : 6.11 Million Tons/Year
3. GYPSUM from FGD process in JIC and RIC
Expected Generation : 0.42 Million Tons/Year
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Bayer process (invented in 1887, by Austrian scientist Carl
Josef Bayer) involves digestion of bauxite (an aluminumcontaining ore) with sodium hydroxide (NaOH) at
temperatures from 140 to 260 °C under high pressure
(around 35 atm.) to produce Alumina (Al2O3). This process
generates a highly alkaline (>13 pH) waste, called Bauxite
Residue or Red Mud.
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Red mud after
water evaporation
Red mud in “as it is” state,
solid concentration ~400g/l
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Typical Chemical Analysis of Bauxite Ore
Component
%
Aluminium Trioxide (Al2O3)
45-60
Iron Trioxide (Fe2O3)
2-9
Titanium Dioxide (TiO2)
3.5 (max)
Silicon Dioxide (SiO2)
2-9
Loss on Ignition (LOI)
27-30
Free Moisture
12 (max)
Source: ATKINS FEED Report of RIC, 2012.
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Typical Chemical Analysis of Red Mud
Component
%
Component
%
Al2O3
14-20
V2O5
0-0.15
SiO2
10-12
ZnO
0-0.03
Fe2O3
45-60
MgO
0-0.06
TiO2
2-6
MnO
0-0.2
CaO
2-4
K2O
0-0.07
Na2O
5-8
LOI
7-12
P2O5
0.1-0.3
Source: ATKINS FEED Report of RIC, 2012.
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In general, depending on the quality of Bauxite ore used, Red
Mud generation varies from 0.3 tons/ton Alumina for high
quality ore to 2.5 tons/ton Alumina for the lowest quality.
Red Mud will be generated in RIC as follows:
Bauxite Ore
4 to 9 Million
Tons/Year
Alumina
Production
1.8 to 2.4 Million
Tons/Year
Expected RED
MUD Generation
~ 2.65 Million
Tons/Year
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Typical Red Mud slurry contains 70-80% of water which
is sent to settling or drying ponds which is a dominant
practice until now. The free caustic soda left in waste
stream needs to be neutralized before material in
settling ponds can be removed for final disposal or
reuse.
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Factors to be considered for disposal techniques of Red Mud
(containing 70 to 80% water):
Reducing waste volume by dewatering
Neutralizing the mud
Assessing the potential reuse of dried residue
Minimizing the environmental impact.
In China, most of the Red Mud (RM) disposal is in landfill (Fei
Peng et al).
In Japan, majority of RM is deposited into the ocean after
neutralization.
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Based on Master Plan study for RIC, an onsite storage for Red
Mud (termed “residue”) has been recommended. Accordingly,
facility has designated a Red Mud storage area of approx. 800
Hectares which will be stored by “dry stacking” method.
At RIC, the red mud is first washed to remove as much
alkaline materials as possible. After the residue is thickened
to reduce water content, it is sent to the residue storage
areas which act as drying beds to further reduce water
content and reduce risks from leachate generation.
The current cells constructed for storage of Red Mud in RIC
are fully lined by 1.5mm HDPE double liner by using
International Best Practice design.
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Improving sandy (acidic) soils and add moisture holding
capacity
Improve capacity to retain nutrients within soils to
enhance agricultural capacities
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Neutralizing acidic mine waste and gases
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Base material for road and embankment construction
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Paving slab and building materials
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Recovering metal for further processing (iron, titanium,
rare earths)
As a soil enhancing fertilizer to develop green spaces for
existing or new agricultural land.
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Studies conducted on Red Mud (RM) reported several uses:
As a pH modifier in the heap leaching of gold ores (R.E.
Browner, 1992)
As a pigment in anticorrosive marine paints (T. Skoulikidis et
al, 1992)
In India, about 2.5 million tons were absorbed by the cement
industry in 1998-99 (Hind et al).
In China, approximately 10% of RM produced is recycled for
further metal extraction or utilized as a raw material for brick
production (Fei Peng et al, Chemosphere).
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Neutralized red mud has been tested as a road base material
in Kaiser Corporation in USA, China and Greece, and the
compacted material showed resistance to erosion and proved
to be stable under heavy roads.
In Australia the coarse portion of bauxite residue (“red sand”)
is used as a road base for new road construction.
Chinese research shown silicate cement made from Red Mud
is strong, sulfate and frost resistant, and a low cost
alternative to Ordinary Portland Cement (OPC).
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Ras Al Khair will become one
of the largest sites in world for
production of phosphoric acid and
phosphate fertilizers.
Phosphoric acid is produced by wet process, which involves
digestion of phosphate rock in sulfuric acid.
Phosphate Rock + Sulfuric Acid
Phosphoric Acid(Primary Product) + Phosphogypsum(By
Product)
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For every ton of phosphoric acid produced, up to 5 tons of
Phosphogypsum waste may be created. (EU Commission, BAT
document)
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Mass Fraction
w(component)/
%
CEIRussia
South
AfricaPhalaborwa
MoroccoKhouribga
USA
Florida
Senegal
KSA
(Hazm Al
Jalamid)
P2O5
38.9
36.8
33.4
34.3
36.7
29.35
CaO
50.5
52.1
50.6
49.8
50
51.78
SiO2
1.1
2.6
1.9
3.7
5.0
3.71
F
3.3
2.2
4.0
3.9
3.7
3.37
CO2
0.2
3.5
4.5
3.1
1.8
8.29
Al2O3
0.4
0.2
0.4
1.1
1.1
0.115
Fe2O3
0.3
0.3
0.2
1.1
0.9
0.074
MgO
0.1
1.1
0.3
0.3
0.1
0.279
Na2O
0.4
0.1
0.7
0.5
0.3
0.20
K2O
0.5
0.1
0.1
0.1
0.1
0.02
SO3
0.1
0.2
1.6
0.1
-
1.165
Cl
-
-
0.1
-
-
0.053
SrO
2.9
0.3
0.1
-
-
-
Ref: 1. N. Frankovic Mihelj et al., Waste Phosphogypsum
– Toward Sustainable, Chem. Biochem. Eng. Q.27 (2013)
2. Phosphate Rock Analysis Data, Phosphate Plant, RIC 17
Mass fraction
W(component)/ %
PG1
(July 2010)
PG 2
(RIC, KSA)
Total P2O5
0.48
0.44
CaO
33.64
28.53
SO3
53.46
53.99
MgO
0.002
0.0185
SiO2
1.09
1.88
Ref: 1. N. Frankovic Mihelj et al., Waste Phosphogypsum
– Toward Sustainable, Chem. Biochem. Eng. Q.27 (2013)
2. Phosphogypsum Analysis Data, Phosphate Plant, RIC.
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About 6.11 Million TPY of Phosphogypsum (PG) is
expected from a facility in RIC.
The selected storage/disposal method is by Dry stacking
along with leak-proof liner system, with stack height of
50m.
Facility has designated an area of approx. 650 Hectares
for PG storage.
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River Discharge
China (Yangtse)
France (Seine)
Romania (Danube)
Estuary Discharge
Netherland (mouth of Rhine, Rotterdam)
Spain (Confluence of the Tinto and Odiel Rivers, Huelva)
Sea Discharge
Tampa Bay, Florida (with little tidal movement)
Mediterranean Sea (Sfax, Tunisia, Tripoli, Lebanon)
North Sea (Immingham, UK)
Ocean
North Atlantic (Safi and Jorf Lasfar, Morrocco)
Source: ATKINS FEED Report of RIC, 2012.
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Currently, above practice of discharge to water bodies is in
rapid decline, due to following International Regulations
which prohibits such activities:
London Convention of International Maritime Organization
(IMO)
European Union Regulations
Currently, new plants around the world are designed not to
discharge slurry material but operate closed loop production
system contained on-site.
Source: ATKINS FEED Report of RIC, 2012.
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Three common methods used to store PG are:
1.
Dry Stacking (21 to 74m stack height in Florida, USA)
2.
Wet Stacking (Brazil, China, Finland, USA, Spain, South
Africa)
3.
Back-fill to the mine
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Agriculture
As a fertilizer and soil conditioner for more than 50 crops including
rice, wheat, fruits and vegetables.
Housing and Construction
As a raw material for cement, plasterboard, bricks, blocks, tiles and
artificial stones.
Roads
All weather and paved roads, embankment and fills.
Coastal and Marine
For building artificial reefs by using mixture of PG, fly ash & cement.
Source: ATKINS FEED Report of RIC, 2012.
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Practice in USA
Mainly PG is kept stored by stacking method and has been
allowed a limited use for agricultural purpose.
Practice in Europe
In Europe, PG is used as a fertilizer, soil amendment,
construction, wallboards and cement.
Other Countries
Brazil, China, India and South Africa are also recognizing the
value of PG as a resource.
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Treatment of bauxite residue – a possible beneficial activity at
RIC
Treatment of coal mine waste to remove barium and radium
Fertilizer binder
Filler for plastic lumber
Additive to red drilling mud to improve qualities
Treatment of metal finishing wastes
Removal of color and organics from textile waste
Combination of red mud to enhance phosphate retention in
sandy soils
De-icing additive
Source: ATKINS FEED Report of RIC, 2012.
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FGD gypsum is a principal residue from steam
generation units fitted with flue gas desulphurization
(FGD) equipment. This is the product of the reaction
between SO2 in the flue gases and hydrated lime used to
separate it from the flue gases.
Approximately 0.42 Million TPY of gypsum is expected to
be generated by Flue Gas Desulfurization process in the
Steam generation units from Jubail and Ras Al Khair.
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Location
Ras Al Khair
Jubail
Chemical Composition
CaSO4
CaSO3
CaCO3
Fly Ash
MgCO3
91.93%
0.34%
2.58%
4.53%
0.63%
Calcium Sulphate
Free Moisture
Sodium Salts
Calcium Sulphite
>90% dry
<10%
<0.06%
0.5%
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Construction works
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Sealing material
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Cement manufacturing
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Fill for landscaping / land reclamation
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Fertilizer in agriculturee and forestry
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Raw material for aggregates, bricks and cement
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It is noted that Red Mud has various uses including
brick manufacturing, as a pH modifier and in
cement industries, etc.
For Phosphogypsum, there is a potential to use it
for several purpose such as roads, construction
works, agriculture, etc.
Regarding Gypsum, it is a valuable material to be
used mainly for cement industries.
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Since, there is a great potential to reuse the
above waste materials, we encourage the
Investors to come forward to utilize the
major waste materials produced in Ras Al
Khair and Jubail namely Red Mud,
Phosphogypsum, Gypsum and Fly Ash.
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