7
solids content. The highest floated concentrate P2O5 grade
was achieved at the middle level feed slurry solids con-
tent 17.5%, below or above which the floated concentrate
P2O5 grade drops slightly. This is because the entrained
gangue minerals were reduced when the feed slurry per-
cent solids decreased from high level 25% to middle level
17.5%. However, the further decreasing of the feed slurry
solids content from middle level 17.5% to low level 10%
will increase the feed water recovered in froth product,
which is generally proportional to hydraulic gangue min-
erals entrainment. Another possible reason, the amount
of relatively coarse high P2O5 grade phosphate particles
were more easily lost to nonfloated tailings at the low-level
feed solids slurry, which decreased the floated concentrate
P2O5 grade.
Figure 11 depicts the effects of wash water flow rate
and feed slurry solids content on the floated concentrate
P2O5 recovery. The results given in Figure 11 show that the
highest floated concentrate P2O5 recovery was achieved at
the middle-level feed percent solids 17.5% and the low-
level wash water rate. The flotation P2O5 recovery slightly
decreases with the increasing of the flotation feed slurry
solids content from middle-level 17.5% to high-level 25%,
and the decreasing of the flotation feed slurry solids content
from middle-level 17.5% to low-level 10%. The increase in
wash water rate to minimize the unwanted gangue mineral
particles entrainment can reject some unliberated phos-
phate/gangue middling particles and thus slightly decrease
the flotation recovery. Therefore, the optimized process
operation conditions are to control the balance between a
high recovery of the desired P2O5 and a high-grade P2O5
value of the phosphate concentrate.
Figure 12 shows the effects of feed slurry solids con-
tent and flotation feed particle size (P80) on the floated
concentrate P2O5 recovery. The floated concentrate P2O5
recovery increases when the flotation feed particle size (P80)
decreases from 53 microns to 38 microns and 20 microns.
The floated concentrate P2O5 recovery drops more sharply
for coarser flotation feed than finer feed when the flota-
tion feed percent solids increases from middle-level 17.5%
to 25%.
Laboratory Column and Mechanical Cell Flotation
Following the completion of benchtop mechanical cell
and laboratory column optimization testing, benchtop
mechanical cell flotation under optimized conditions and
column flotation were conducted on various ultrafine phos-
phate slime samples.
Figure 13 is offered to summarize the P2O5 grade and
recovery relationships for the optimal bench-top mechani-
cal cell and column flotation results realized from treat-
ment of a 38x0 micron ultrafine phosphate slime. The
® Software
y(%)
ts above predicted value
ts below predicted value
ater(L/Min)
olids(%)
P80 =37
0
200
400
600
800 10
14
18
21
25
86
88
91
93
95
A: Washwater(L/Min)
C: Feed Solids(%)
Figure 11. Floated concentrate P
2 O
5 recovery vs wash water
rate and feed slurry solids content
Design-Expert® Software
P2O5 Recovery(%)
Design points above predicted value
Design points below predicted value
95.4625
86.3567
X1 =B: Particle Size P80
X2 =C: Feed Solids(%)
Actual Factor
A: Washwater(L/Min) =400
20
28
37
45
53 10
14
18
21
25
87
88
90
91
92
B: Particle Size P80
C: Feed Solids(%)
Figure 12. Floated concentrate P
2 O
5 recovery vs feed
particle size and feed slurry solids content
0
20
40
60
80
100
10 15 20 25 30 35
P
2 O
5 Grade(%)
Quartz/muscovite gangue minerals 38x0 microns feed
column rougher
Quartz/muscovite gangue minerals 38x0 microns feed
column rougher-cleaner
Quartz/muscovite gangue minerals 38x0 microns feed
benchtop rougher and 5-stage cleaners
Figure 13. Flotation column vs benchtop mechanical cell
P2O5
Recovery(%)
P2O5
Recovery(%)
PO
2
5
Recovery
(%)