De-watering, disposal and utilization of red mud: state ... - Redmud.org

Components,
(%)
Gibbsite
Hematite
Goethite
SAHS
Illite
Boehmite
Diaspore
Ca-Al-silicate
CaTiO 3
Calcite
Quartz
Anatase
Rutile
Na-titanates
Magnetite
Chamosite
Ilmenite
Others
Table 2. Mineralogical composition of different digestion residues
Weipa Trombetas South
Manchester
33.0
-
33.0
3.5 38.0 3.5
18.0 19.0 10.0
27.0 27.0 27.0
2.0
-
-
2.0
0.6
2.0
-
1.2
2.0
-
-
-
-
1.5
-
0.5
1.4
-
6.0
2.2
0.5
2.0
2.5
6.0
6.0
0.8
2.0
-
-
6.0
-
-
-
-
-
-
-
-
-
-
5.8
-
Darling
Range
5.6
14.5
14.5
5.4
4.7
3.5
2.5
1.7
-
2.3
37.1
1.0
-
0.6
1.3
-
1.0
3.4
Iszka Parnasse
Fig. 1 Typical particle size distribution for fine and coarse fractions of bauxite residue
As can be seen, about 80% of the particles in red mud are less than 10µm, therefore the
settling rate is expected to be extremely low. However, flocculation helps in speeding up
settling; over the last few decades synthetic flocculants have been developed and these have
replaced the outdated starch-based settling aids.
Red mud containing more than 28% moisture is thixotropic in nature, i.e. viscosity greatly
decreases when it is submitted to mechanical effects, namely shear stress. It has a tendency to
develop fissures and cracks on drying, thereby leading to dust problems during drying in
windy weather conditons. If the filter cake is disposed of as it is, virtually no dusting of the
-
33.0
6.0
32.0
-
0.8
0.7
12.5
7.0
3.0
-
-
-
-
-
-
-
5.0
-
38.0
1.0
26.0
-
0.6
0.6
10.0
10.5
3.6
-
-
-
-
-
6.0
-
3.7
3