6
rate increases from 0 liter/minute to 400 liter/minute and
800 liter/minutes, respectively. The addition of wash water
to flotation column froth zone can minimize the unwanted
gangue mineral particles entrained. The floated concentrate
P2O5 grade slightly increases when the flotation feed par-
ticle size (P80) increases from 20 microns to 38 microns and
53 microns. This is because the entrained gangue minerals
particles decrease as the increasing of flotation feed particle
size (P80).
Figure 10 displays the effects of feed slurry solids con-
tent and wash water flow rate on the floated concentrate
P2O5 grade. As shown in Figure 10, the wash water rate
has a far more significant effect on the improvement of
the floated concentrate P2O5 grade than the flotation feed
Without wash water
With wash water
Flotation bubbles with particles attached
50 µm
Figure 8. Microscopic observations of froth without wash
water and with wash water. Entrained silica reduced by wash
water
Table 3. Three-factor three-level central composite design
flotation results
Feed Concentrate Tailings Mass P2O5
Run P2O5 P2O5 P2O5 Yield Recovery
(%)(%)(%)(%)(%)
1 9.8 28.80 1.2 31.16 91.57
2 10.8 19.28 1.4 52.57 93.85
3 8.8 22.20 1.5 35.27 88.97
4 9.8 28.90 1.2 31.05 91.56
5 10.8 26.80 1.4 37.01 91.83
6 9.8 29.20 1.2 30.71 91.52
7 9.8 30.10 1.86 28.12 86.36
8 9.8 29.10 1.2 30.82 91.53
9 10.8 31.60 1.5 30.90 90.40
10 9.8 15.70 1.74 57.74 92.50
11 10.8 25.30 2.04 37.66 88.22
12 9.8 30.70 1.3 28.91 90.57
13 8.8 15.10 0.9 55.63 95.46
14 9.8 29.00 1.2 30.94 91.54
15 9.8 16.80 1.3 54.84 94.01
16 8.8 20.50 1.56 38.23 89.05
17 8.8 28.90 1.02 27.91 91.64
Design-Expert® Software
P2O5 Grade(%)
Design points above predicted value
Design points below predicted value
31.6
15.1
X1 =A: Washwater(L/Min)
X2 =C: Feed Solids(%)
Actual Factor
B: Particle Size P80 =37
0
200
400
600
800
10
14
18 21
25
15
19.5
24
28.5
33
A: Washwater(L/Min) C: Feed Solids(%)
Figure 10. Floated concentrate P
2 O
5 grade vs wash water
rate and feed slurry solids content
Design-Expert® Software
P2O5 Grade(%)
31.6
15.1
X1 =A: Washwater(L/Min)
X2 =B: Particle Size P80
Actual Factor
C: Feed Solids(%) =20
0
200
400
600
800
20
28
37
45
53
13
18
23
28
33
A: Washwater(L/Min) B: Particle Size P80
Figure 9. Concentrate P
2 O
5 grade vs wash water rate and
feed particle size P
80
P2O5
Grade(%)
P2O5
Grade(%)
rate increases from 0 liter/minute to 400 liter/minute and
800 liter/minutes, respectively. The addition of wash water
to flotation column froth zone can minimize the unwanted
gangue mineral particles entrained. The floated concentrate
P2O5 grade slightly increases when the flotation feed par-
ticle size (P80) increases from 20 microns to 38 microns and
53 microns. This is because the entrained gangue minerals
particles decrease as the increasing of flotation feed particle
size (P80).
Figure 10 displays the effects of feed slurry solids con-
tent and wash water flow rate on the floated concentrate
P2O5 grade. As shown in Figure 10, the wash water rate
has a far more significant effect on the improvement of
the floated concentrate P2O5 grade than the flotation feed
Without wash water
With wash water
Flotation bubbles with particles attached
50 µm
Figure 8. Microscopic observations of froth without wash
water and with wash water. Entrained silica reduced by wash
water
Table 3. Three-factor three-level central composite design
flotation results
Feed Concentrate Tailings Mass P2O5
Run P2O5 P2O5 P2O5 Yield Recovery
(%)(%)(%)(%)(%)
1 9.8 28.80 1.2 31.16 91.57
2 10.8 19.28 1.4 52.57 93.85
3 8.8 22.20 1.5 35.27 88.97
4 9.8 28.90 1.2 31.05 91.56
5 10.8 26.80 1.4 37.01 91.83
6 9.8 29.20 1.2 30.71 91.52
7 9.8 30.10 1.86 28.12 86.36
8 9.8 29.10 1.2 30.82 91.53
9 10.8 31.60 1.5 30.90 90.40
10 9.8 15.70 1.74 57.74 92.50
11 10.8 25.30 2.04 37.66 88.22
12 9.8 30.70 1.3 28.91 90.57
13 8.8 15.10 0.9 55.63 95.46
14 9.8 29.00 1.2 30.94 91.54
15 9.8 16.80 1.3 54.84 94.01
16 8.8 20.50 1.56 38.23 89.05
17 8.8 28.90 1.02 27.91 91.64
Design-Expert® Software
P2O5 Grade(%)
Design points above predicted value
Design points below predicted value
31.6
15.1
X1 =A: Washwater(L/Min)
X2 =C: Feed Solids(%)
Actual Factor
B: Particle Size P80 =37
0
200
400
600
800
10
14
18 21
25
15
19.5
24
28.5
33
A: Washwater(L/Min) C: Feed Solids(%)
Figure 10. Floated concentrate P
2 O
5 grade vs wash water
rate and feed slurry solids content
Design-Expert® Software
P2O5 Grade(%)
31.6
15.1
X1 =A: Washwater(L/Min)
X2 =B: Particle Size P80
Actual Factor
C: Feed Solids(%) =20
0
200
400
600
800
20
28
37
45
53
13
18
23
28
33
A: Washwater(L/Min) B: Particle Size P80
Figure 9. Concentrate P
2 O
5 grade vs wash water rate and
feed particle size P
80
P2O5
Grade(%)
P2O5
Grade(%)