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Simultaneous determination of collection zone rate constant and froth zone recovery in a mechanical flotation environment
MineralsEngineering,Vol. 12, No. 10, pp. 1163-1176. 1999 © 1999Publishedby ElsevierScienceLtd
Pergamon
0892--6875(99)00103-X
All rights reserved 0892-6875/99/$- see frontmatter
SIMULTANEOUS DETERMINATION OF COLLECTION ZONE RATE CONSTANT AND FROTH ZONE RECOVERY IN A MECHANICAL FLOTATION ENVIRONMENT
M.A. VERA, J.P. FRANZIDIS and E.V. MANLAPIG Julius Kruttschnitt Mineral Research Centre, The University of Queensland, Brisbane, Australia E-mail: M.Vera@ mailbox.uq.edu.au
(Received 6 July 1998; accepted 24 April 1999)
ABSTRACT
This paper presents the results of an investigation in which the new JKMRC Flotation Cell was used to determine the collection zone rate constant and froth zone recovery of a copper rougher ore simultaneously. The determination of these two parameters has been based on the straight line relationship that exists between the overall flotation rate constant and the froth depth [1]. Experimental work was conducted using a copper rougher ore with a P8o of 200 tzm. Operating variables such as airflow rate, impeller speed, feed percent solids, collector and frother dose, and wash water flow rate were investigated. Analysis for copper and iron minerals (chalcopyrite and pyrite, respectively) was carried out. The results indicate that the collection zone rate constant of both copper and iron minerals increased with increasing air flow. Froth zone recovery, on the other hand, decreased as air flow was increased, possibly as a result of increased detachment of particles from bubbles in the froth. Increasing the impeller speed also increased collection zone rate constant and decreased the froth zone recovery of both minerals. Experiments at different wash water flow rates have showed that events occurring in the froth zone do not affect the kinetics of the pulp zone. Moreover, and interestingly, the froth recovery of attached particles (wash water reduced entrainment to a minimum) was non-selective. The froth recovery curves for chalcopyrite and pyrite followed each other very closely in every instance studied. The work has proved that it is possible to measure both the collection zone rate constant and froth zone recovery simultaneously and continuously in a mechanical flotation environment. The results obtained to date are interesting and the work is continuing. © 1999 Published by Elsevier Science Ltd. All rights reserved.
Keywords Sulphide ores; flotation froths; flotation kinetics; froth flotation
1163
1164
M.A. Vera et al. INTRODUCTION
The process of flotation can be divided into two sections: recovery from the collection zone, and recovery from the cleaning (froth) zone. The role of the froth zone in determining flotation performance has been explicitly recognised by many investigators [ 1-6]. Despite this recognition, until recently, flotation modelling has been mainly accomplished by treating the flotation cell as a single rheological system (pulp-based model) or entirely empirically. However, Woodburn et al. [7], acknowledging that the performance factor needed for optimal design is best evaluated on the basis of a kinetic model, proposed a froth-based flotation kinetic modelling approach. The main idea behind this work was to model the kinetics in terms of the froth structure associated parameters. Although all the froth-based model parameters of the work of Woodburn et al. [7] seem to have a physical significance, they were estimated on the basis of very rough assumptions. It goes without saying that the froth structure and all the possible mechanisms occurring in the froth phase are important. Equally important is controlled experimentation on froth, which is very difficult. Model developments on the basis of froth structure might become unreliable when a number o f parameters is just guessed. Consequently, the present study has been conducted looking at the froth through a single parameter, froth zone recovery (Rf). This performance efficiency parameter is defined independently of any mixing regime as the mass rate of particles reporting to the concentrate via true flotation divided by the net mass rate of attached particles at the pulp froth interface. Rf is a number which lumps together the different effects of all possible mechanisms taking place in the froth phase. This paper presents the results of work in which the new JKMRC laboratory flotation cell [8] has been used to study the effects of operating variables, such as wash water flow rate, air flow rate, froth depth, impeller speed, percent solids, and collector and frother doses, on the flotation of copper ore. In particular, the effects of these variables on the collection zone rate constant k~ and froth zone recovery factor R e have been investigated separately, using the technique proposed by Feteris et al. [1], as well as Laplante et al. [2]. It is hoped that splitting the response into that of the pulp zone and froth zone separately will provide a much better understanding of the flotation process and the quantification of froth contribution to it.
BACKGROUND Figure 1 shows a diagram of the two phase flotation model. The collection zone and froth zone are clearly depicted. In this paper, the methodology described by Feteris et al. [1] has been used to quantify froth zone performance. Two important assumptions are involved in this methodology: (1) that the transfer of particles from the body of pulp to the pulp/froth interface depends only on events occurring in the pulp zone, and (2) that the transfer of particles from the froth to the concentrate depends only on events occurring in the froth zone. Sample collection at different froth depths provides the procedure for simultaneous determination of froth zone recovery and collection zone rate constant. The froth zone recovery efficiency equation is presented in equation 1, in which froth zone performance is defined as the total rate of transfer from the pulp to the concentrate divided by the rate of transfer from the pulp to the froth phase. Rf = k / k~
(1)
k, the overall flotation rate constant, is calculated from the overall recovery by considering the system as a perfect mixer: k = R / {~ (1 - R)} where R is experimental overall recovery and z is mean residence time.
(2)
Collection zone rate constant and froth zone recovery in mechanical flotation environment
1165
Concentrate
Froth
k
::ll:l:::l:lllll;llll;:lll:l::li:li::l:lllzl::ll:ll;:l;t:llllli:l
!:.-.:i!i!iiiigiiiigigigiii~!~i~i!iig~!!i!!!!iii~i!iiiiiiii~iiiiig~i!g!!ii!!~ i!i~i!~iiiiiiiiiiiiiiiiiiiiiiii~i!!!!!!i!iiiiiiiiiiii~iiiiiiiiii
k/k
Feed v
Pulp
Fig.1 Two-phase model description of flotation after [1]. The flotation rate constant at zero froth depth is the collection rate of the pulp zone (1%), which is independent of the froth depth. Thus, at zero froth depth, R~ by definition is equal to 100%. At all froth depths greater than zero, froth zone recovery will be less than or equal to 100%. Equation 1 may be developed further by incorporating a relationship between flotation rate constant (k) and froth depth (FD). The existence of a linear relationship with negative slope between flotation rate constant and froth depth has been reported by several researchers [ 1, 2, 9]. Such a relationship is plotted in Figure 2. Note that Figure 2 shows flotation rate constant as a function of froth depth for Run 4 (see Tables 1 and 2 below). Figure 2 depicts two repeatability tests for Run 4, which clearly suggest the same trend. These experimental results once more confirm the linear relationship between flotation rate constant and froth depth. Hence, the relationship can be expressed as follows: k = a - b (FD)
<3)
Now, when froth depth is zero, 1% may be determined by extrapolation as shown in Figure 2. Hence a = 1%. Next, let (FD)k= 0 be the intercept of the straight line (equation 3) with the X-axis, i. e. when k = 0 (this is equivalent to having a very deep froth, so that no material is transferred from the froth to the concentrate). Hence, b = kJ(FD)k=_ 0. Hence 1%= b * (FD)k=o. Substitution for a and b into equation 3 leads to: k = 1% { 1 - ( F D ) / ( F D ) k = o
}
(4)
which, when substituted into equation 1, yields: Rf = { 1 - (FD)/(FD)k=O }
(5)
This says that froth recovery per unit froth depth is constant. And, as indicated by Feteris et al. [1], for a given size range of mineral, the probability of drainage per unit froth depth is also constant.
1166
M.A. Vera et al.
In this p a p e r t h e a b o v e p r o c e d u r e is u s e d to d e t e r m i n e kc a n d Rf f r o m c o n t i n u o u s flotation tests w h i c h w e r e c o n d u c t e d u n d e r b u b b l e s u r f a c e a r e a flux levels e q u i v a l e n t to t h o s e o b t a i n e d in f u l l - s c a l e o p e r a t i o n .
3.5 ~Collection
z o n e rate c o n s t a n t k c
3.0
.-"~
"~~O.
2.0
-
o
0.5 [
oRUN 4--1=.1
0.0 [
~ R U ? rep. 2
0
3
~ ,
,
/ =x,~ r
6 9 Froth D e p t h (cm)
12
15
F i g . 2 F l o t a t i o n z o n e rate c o n s t a n t (k) as a f u n c t i o n o f f r o t h d e p t h (FD). TABLE RUN
PARAMETER
AFR
VARIED
(L/min)
1 Experimental
% SOLIDS
IMPELLER
WASH
COLLECTOR
FROTHER
SPEED
WATER
DOSE
DOSE
.........................................................................................................................
1
AFR
conditions
C ~ m ) . .............. L . . ~ . . . . ~
.................. .(S(..t)................. . ( ~ . . - . ~ . ~ L
25.5
20.0
1070
290
240
8
2
42.5
20.0
1070
290
240
8
3
44.7
20.0
1070
290
240
8
...... 4 * ................................................... 5 2 : o
5
% SOLIDS
................ ..2.0:0 ...................... 1 . 0 2 0 ................... 2..9.9 . ....................... 2 . 4 . 0 ............................ ..s................
52.0
11.0
1070
290
240
8
52.0
20.0
1070
290
240
8
7
52.0
23.0
1070
290
240
8
8
52.0
27.0
1070
290
240
8
6*
9
IMPELLER
52.0
20.0
800
290
240
8
10*
SPEED
52.0
20.0
I070
290
240
8
....... 1 . ! ................................................... 5 . 2 : 0 . ................ 2 0 : 0 . ..................... ! 4 ~
12"
WASH
....... 1.3. ................
52.0
20.0
1070
.W..A..~R ................ 52:0 ................ .2..0:,9. ..................... .1.070.
.................... 2.9.o. ....................... 2 4 . 0 ............................. ..s...............
290
240
8
................... 5 . ~ ....................... 2 4 0 ............................. 8 ..............
14#
COLLECTOR
52.0
20.0
1070
290
80
8
15 ~
DOSE
52.0
20.0
1070
290
160
8
52.0 52.0
20.0 20.0
1070 1070
290 290
240 320
8 8
16~ 17 ~ 18~
FROTHER
52.0
20.0
1070
290
240
0
19#
DOSE
52.0
20.0
1070
290,
240
4
52.0 52.0
20.0 20.0
1070 1070
290 290
240 240
8 16
20 # 21 #
* same test: included as runs for ease of comparison # Tests conducted six months later.
Collection zone rate constant and froth zone recovery in mechanical flotation environment
TABLE
2a Testwork
Run Feed Grade (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
Cu
Fe
4.10
9.18
4.06
8.42
4 . 1 1 9.42
4.07
3.80
4.07
4.23
3.98
4.23
4.07
4.07
4.07
3.85
9.00
9.07
9.00
9.23
9.09
9.23
9.00
9.00
9.00
8.87
on the new JKMRC
f l o t a t i o n cell: S u m m a r y
1167
table of results
FD
Conc.Grade
Overall
k,
Rf
(cm)
(%)
Recovery (%)
(!/rain)
(%)
G-Cu G-Fe
R - C u R-Fe
CPY
PY
CPY
1.5
22.90 33.70 56.76 39.81
0.30
0.16
94.94
91.65
5.0
22.80 33.50 54.00 35.49
80.12
72.20
7.0
23.10 33.50 49.19 29.25
72.17
61.08
1.5
1 2 . 6 0 22.30 65.22 69.14
94.00
92.69
1.36
0.49
PY
5.0
1 8 . 8 0 30.00 63.03 61.59
80.25
75.62
7.0
20.20 31.50 82.57 61.22
72.35
65.87
1.5
1 6 . 0 0 29.70 65.25 63.57
5.0
20.10 32.90 64.15 62.09
74.69
82.63
7.0
21.30 33.30 80.50 57.38
64.57
75.68
1.5
1 2 . 6 0 24.00 92.56 80.81
88.63
56.20
5.0
1 8 . 5 0 32.00 90.33 72.55
62.76
60.65
7.0
1 8 . 7 0 31.90 68.01 57.03
47.65
44.91
1.5
1 7 . 5 0 31.70 56.32 61.42
0.35 88.64
91.48
5.0
1 9 . 2 0 33.90 79.17 53.31
62.14
71.59
7.0
20.70 33.50 76.51 50.59
47.00
60.23
1.47
3.01
1.41
3.01
0.40
0.98
92.41 94.79
1.5
1 2 . 5 0 24.00 92.68 80.81
56.63
56.20
5.0
1 8 . 5 0 32,00 90.33 72.55
62.76
50.65
7.0
1 8 . 7 0 31,90 86.01 57.03
47.68
44.91
1.5
1 4 . 1 0 25,50 91.04 73.88
90.79
91.74
5.0
1 7 . 5 0 31.60 87.93 68.45
7.0
1 8 . 6 0 32.00 56.04 64.50
1.5
1 7 . 3 0 31,30 87.97 68.79
92.50
91.27
5.0
1 8 . 8 0 32.10 65.07 60.72
74.99
70.90
7.0
1 9 . 1 0 32.20 63.30 56.37
64.99
59.25
1.5
1 7 . 4 0 29,50 68.77 69.15
94.15
95.48
5.0
20.50 32.90 84.36 65.37
80.50
84.68
7.0
21.20 33,10 63.25 64.71
72.70
78.63
1.5
1 2 . 5 0 24,00 92.68 80.81
68.83
88.20
5.0
1 8 . 5 0 32,00 93.33 72.65
62.76
60.65
7.0
1 8 . 7 0 31.90 86.01 67.03
47.68
44.91
1.5
1 1 . 1 0 21,80 93.25 50.49
56.69
87.48
5.0
1 7 . 1 0 30,70 88.68 71.48
55.64
55.25
7.0
1 8 . 5 0 3t.60
37.90
41.59
1.5
1 2 . 6 0 24.00 92.56 80.81
88.63
56.20
5.0
1 8 . 5 0 32.00 90.33 72.55
62.76
60.65
7.0
1 8 . 7 0 31.90 56.01 67.03
47.56
44.91
2.24
0.98
0.62
59.31 72.45 57.03 1.62
1.40
3.01
3.27
0.49
0.47
0.98
0.97
65.10 64.81 3.01
3.05
0.98
61.43
1.5
1 7 . 2 0 31.60 92.61 78.97
1.00 85.63
63.28
5.0
1 9 . 3 0 33.20 87.28 64.74
52.10
44.25
7.0
20.00 33.70 82.22 56.72
32.94
21.95
M. A. Vera et
1168
al.
T A B L E 2b S u m m a r y table o f results (cont.) Run
Feed Grade
FD
..................... .(~.~ ............... ~).
14#
15#
16#
17#
18#
19#
20#
21#
Cu
Fe
5.22
9.89
5.27
5.64
3.23
3.63
3.38
3.34
3.67
10.30
11.10
9.93
10.30
9.87
9.73
10.20
Conc. Grade ................ (.~). ............
G-Cu
G-Fe
Overall
k=
.R.e~ve.~.(.~) . . . . . . . . . . . . . R-Cu
Rf
~!/.m'....). . . . . . . . . . . . . . . . . . . . . . . ~ ) .
...........
R-Fe
CPY
PY
CPY
PY
80.92 42.51
1.25
0.21
91.72
90.03
1.5
17.30 25.30
5.0
18.80
26.40
70.76
33.62
49.56
56.38
7.0
20.10
26.90
63.50
26.82
38.31
40.21
1.5
16.30 25.30
82.53
46.46
65.79
87.98
5.0
20.40 3t.20 78.35 43.54
63.01
69.49
7.0
21.00
31.90
33.70
43.92
1.5
15.40
26.00 90.87 63.80
91.25
93.46
5.0
19.60
30.50 87.35 54.44
76.03
68.23
7.0
20.60
31.80
82.61
59.15
59.33
1.5
11.80
27.40
89.14 57.65
93.73
93.14
5.0
13.60
29,40
87.08
52.38
79.09
77.12
7.0
14.70 30.80
86.19
50.01
70.72
67.97
81.38
83.55
5.0
20.50 34.30 65.31
32.32
37.95
45.16
7.0
21,20
34.90
45.90
19.67
t3.13
23.23
1.5
18.70 33.90
70.98
31.48
84.79
84.92
5.0
18.70
49.31
49.73
7.0
19.30 33.60
52.87
21.66
29.03
29.92
1.5
18.00
34.20
75.97
36.90
89.23
90.90
5.0
18.60 34.00
70.95
32.82
64.10
71.81
7.0
19.20
34.70
63.03
27.42
49.74
60.63
1.5
16.10 34.30
79.19
47.88
93.85
90.24
5.0
16.20
33.90
75.93
36.59
79.51
67.46
7.0
17.60
34.60
74.22
27.16
71.32
54.44
75.46
1.50
0.23
41.31 1.65
0.31
50.77
1.5
1.71
0.80
0.76
0.28
0.17
0.10
33.60 61.67 28.21
0.71
0.79
0.13
0.19
# Tests c o n d u c t e d six m o n t h s latex
EXPERIMENTAL The high S b Flotation Cell [8] developed at the J K M R C was used in the experiments. The new J K M R C cell was designed to mimic industrial flotation conditions, i. e. to achieve superficial gas velocities equivalent to those produced at the industrial level. This generates bubble surface area flux values similar to those which have been measured in full-scale flotation cells. The new J K M R C cell is a 16-1itre mechanical flotation cell, which is operated continuously. The cell is rectangular with a cross-sectional area of 600 cm 2, and fitted with a bottom driven impeller. Tailings discharge and pulp level control are achieved by means of a weir. An adjustable porous ceramic plate is used to ensure a well-defined froth zone and to eliminate (or at least minimise) entrainment via wash water addition through it. A i r hold-up determination, which is required for calculation of the kinetic rate constant, is by means o f a conductivity technique [10].
Collection zone rate constant and froth zone recovery in mechanical flotation environment
1169
The experimental set-up is shown in Figure 3. Slurry was made up in a 120-1itre sump provided with a pneumatic mixer for good particle suspension. A centrifugal pump was used to re-circulate the solids and assist with particle suspension. Slurry was withdrawn from the sump with a peristaltic pump (feed pump), at a point located at the base of the conic section of the sump. Collector was added on-line continuously. Air addition was carried out using an in-line mixer [8]. This device was placed between the feed pump and the inlet to the flotation cell (underneath the impeller). In this configuration bubble formation takes place independently of the impeller mechanism, which means that bubbles are originated outside of the flotation cell. Froth depth was varied by moving the lip of the cell up and down and adjusting the height of the ceramic porous plate. In this way, froth depth was varied without changing the pulp volume. This plate located on the top of the cell was also used as a wash water distributor, and wash water addition was quantified by a well calibrated pump. Likewise, launder water was accurately measured.
M~,'alle flamticacell lip 1< froth del~ <8(era) W a s h w pump 0~- 11/mln We~
I
-~iii:.iii:.i:.i:.ii::i::ii:.iii:i:iiiiii~
\
Pmmnmlc~
!
Ceramic porousplate 1Jmd~ waler pump 1-2 l/nin
Collector a/klti/m
I
~m
i~
~ivm hnpaer
750< I m ~ ( i ~ d
Sum~w~ol
Tin~
< 1400
I
disdm'~.~[_..___J
Feed inlet
b 0.3-1 ~
Slalicin-line
Pressulised l ~ - , ~ r a ~ , ~ , ~ , a n i ~ pump
IIo~ta"
gauge
Air irmmre
40- 50L/rain
Fig.3 Schematic diagram of the new JKMRC flotation cell rig. The flotation testwork was conducted at Mount Isa Mines Ltd. (Copper Concentrator) over two periods, six months apart. The sample used was copper rougher feed which was floated at chemical conditions similar to those in the actual industrial circuit. The test procedure consisted of making up the slurry in the 120 litre sump at the required solids percent. Then, frother was added (8 ppm MIBC). Collector addition was carried out continuously with a peristaltic
1170
M.A. Vera et
al.
pump (240 g/t). Slurry ready to be floated was fed into the JKMRC cell by the peristaltic pump (3.5 1/min). Sample collection was conducted when steady-state was reached (approx. 2 mean residence times, 8 min). It should be noted that, in this system, the total tailings stream is made up of the tailings overflow and purge streams (Figure 3). For each run conducted, concentrate and tailings were collected at three different froth depths (1.5, 5, and 7 cm). The experimental conditions used in this study are given in Table 1. The parameters varied were air flow rate (AFR), solids percent, impeller speed (IS), wash water flow rate (WW), collector dose, and frother dose. Numerous tests were conducted to determine the reproducibility of the experimental technique, which was found to be good (see Figure 2). All the samples were weighed (wet and dry), and assayed for copper and iron to provide complete mass balances. The copper and iron assays were converted into chalcopyrite and pyrite using the following conversion factors: % CPY (chalcopyrite) = % Cu / 0.34624 % Fecpv = % CPY * 0.30423 % Fepv = % FeTot~ -- % Fecpv % PY (pyrite) = (% Ferot,~ - % CPY * 0.30423) / 0.4655
RESULTS AND DISCUSSION The feed grade, concentrate grade, overall recovery, collection zone rate constant (1%) and froth zone recovery (Rf) determined experimentally for both copper and iron minerals are shown in Table 2. As can be seen, there was a very small fluctuation of copper and iron content in the feed (average 4.05% Cu and 9.04% Fe) during the first period of testwork. However, during the experimental work conducted six months later, there was a much greater fluctuation in the Cu and Fe grades. Table 2 shows that concentrate grade increased in all cases as froth depth increased. On the other hand, overall recovery decreased in all cases as froth depth increased. These results were as expected. It is interesting to note that in general very good recoveries were achieved even though the mean residence time in the cell was less than 5 minutes. Table 2 also shows the effect of operating conditions on 1% and Rf. Runs 1 through 4 were c a m e d out at different aeration rates with all other conditions kept constant. These results indicate that as air flow rate increased, k~ increased for both copper and iron minerals, with the effect on chalcopyrite being much greater than the effect on pyrite. Rf, however, underwent a different behaviour. It increased slightly up to a point where it decreased drastically as air flow rate increased. This may be the result of an increase in detachment in the froth as the air flow rate was increased. It is worth mentioning that air injection took place through a static in-line mixer (see Figure 3), which broke down air into small bubbles independently of the impeller mechanism. It is believed that this device is responsible for the Rf behaviour. This is because of the compromise between superficial gas velocity and bubble diameter. These two quantities (Jg and db) or the combination of them (bubble surface area flux, Sb) have an effect on the stability of the pulp-froth interface, which will affect froth zone recovery. Figure 4 illustrates these effects graphically at 5 cm froth depth 1.
All the Figures depicting experimental results have been plotted for the 5 cm froth depth case only, so as not to clutter the Figures with data points. Similar trends were observed at 1.5 and 7 cm froth depths.
Collection zone rate constant and froth zone recovery in mechanical
_~
4
. . . . . :
t ;
. . . .
I ;
. . . .
i :
. . . .
i :
. . . .
-t ~"
2.s
"6 0
i..............
-I
1
i .............
i ..............
-
::..............
!.............
.
.
.
0
Py,
.
i
.
.
kc (l/min)
.
.
t0
.
I
I'"'"
.
.
.
.
20
..........
.
I
.
.
i--, ........
-
i
.
30
.
.
e0
:.,o
" ............
.
1171
100
. . . .
Cpy,ke(l/min)Ii . . . . . . . . . . . . . . . ~
'
0
i : ......
- ............
1.5
flotation environment
.
.
40
..........
:
.
i
,o '
50
-
0
60
Air F l o w R a t e (I/min)
Fig.4
Collection zone rate constant and froth zone recovery versus air flow rate. (%Sol = 20, IS = 1070 RPM, W W F R = 290 cm3/min, Collector dose = 240 g/t, and Frother dose = 8 ppm).
Figure 5 depicts the effect of percent solids on 1% and Rf at 5 cm froth depth (Runs 5 through 8). Varying percent solids affected both k c and Rf. The former went through a maximum value at 20--23 % solids. This may be related to the bubble carrying process, which indicates an optimum bubble loading to transfer particles from pulp to the froth; curves like these have been reported for column flotation tests [11]. R r increased slightly with increase in solids, which is an indication of bubble overloading. This is observed for copper minerals. The behaviour of pyrite is unclear, although the R~ values are very similar to those obtained for chalcopyrite. It is believed that these findings are also related to the static in-line mixer. This is operated with feed slurry, which will affect the performance of the in-line mixer (bubble size distribution) as its density (percent solids) changes.
8
---
'l .....
..I 6
!5 e, •
O~
4 3
''
"~-
cpy,
Rf(%)
I>".P"~..............
.............
' 'a . . . . . . . | .........
,I
:.... ..::__: i o
! ....
i ..............
i ............
i.............. [
.............
:. . . . . . . . . . . . . .
.............
' ...........................................
I
. . . . .
............
! ....
~-'-:-"
--
- - - .~
.;~:_ ...........
; .............
cpy, ke O/min) I . . . i . . . . . . . . . . ~
~
100
........
-: -
:::.............
so
; ............
........... i ............
40
2O
............. - ............. .:............. : ~ ; . - . . - ; ~ , ~ , ~ ........ ~............ O
0
....
'
:
5
10
i ....
~'7
.....--
":.
. . . . . .
-
15
:
i,,,,i
20
B--4
-'El
....
25
~.
o 30
% Solids
Fig.5
Collection zone rate constant and froth zone recovery versus percent solids (AFR 52 L/min, IS = 1070 RPM, W W F R = 290 cm3/min, Collector dose = 240 g/t, and Frother dose = 8 ppm).
Table 2 also shows (Runs 9 through 11) that 1%increased and Rf decreased as the impeller speed increased. This operating condition is responsible for the degree of particle suspension, as well as the level of turbulence in the cell. k c increases because pulp-froth transfer is promoted as a consequence of more energy being available. R r decreases probably because of a higher level of instability in the lower regions of the
1172
M . A . Vera et al.
froth, caused by the increased turbulence in the upper regions of the pulp zone (at the higher rpm values, the pulp-froth interface became very mobile and wavy). This additional energy in the froth would increase particle detachment all across the froth and promote drainage. Figure 6 shows 1% and Rf as a function of impeller speed at 5 cm froth depth. Of particular interest is the similarity of the Rf values for chalcopyrite and pyrite at each impeller speed. This finding suggests drop-back for both minerals without any selectivity in their rates of drainage. 8
' '
'
I
.... I
.=
6
•a
s
qP
E
3
....
! '
'
'
I ' '
' '
~-c,,..,(~)! --x--
,
:
:
i
i
i ..........
! ..........
........
py, Rf(%)
................... t
1
l
:, ....... !
::..........
I
0
~,"
:
i
~
:
i,,, 200
1100
:
i,,,
..i
....
i
:::~;~
400
600
":'i
.........
6o
~,
~..... i !..........i..........i..........1 ,o :
i
:
.........
! .... ::;"-~
,,,
--,
.......... ! .......... i......... -t '°
!~':
:
Impeller
Fig.6
' ! . . . . . . . . .
Cpy, kcO/min) I ..... ~
-.--P.,.c(~,m,n)
,..,,,
! ' '
i ..........
i .......... i .......... t
'
'
...... ~ ......... i .......... .......... ; ......... t
I
p-I
' I
'
- '
,~:,
,i" . . . . . .
800
1000
Speed
~ ........ 1 .o
;,,
1200
1400
--
,t o 1600
(rpm)
Collection zone rate constant and froth zone recovery versus impeller speed. (AFR 52 L/min, %Sol = 20, WWFR = 290 cm3/min, Collector dose = 240 g/t, and Frother dose = 8 ppm).
In Runs 12 and 13 the effect of wash water flow rate on 1% and Rf was investigated. Figure 7 shows that the kinetic process (pulp--froth transfer) was not affected by this variable, i. e. 1% remained unaltered for chalcopyrite and pyrite when wash water rate was increased from 290 to 600 cm3/min. This result is a validation of the first assumption of this methodology (see Background above), i. e. that only events or actions taking place in the pulp will affect iL On the other hand, Rf decreased as the water flow increased. This indicates that the drainage of weakly attached particles and a much better cleaning action in the froth was promoted as a result of increasing the wash water rate. (Note that wash water was added through the ceramic porous plate in all the experiments conducted. Consequently, reported results are believed to be mainly for attached particles, i. e. particles recovered by true flotation).
8
~
=
. . . .
,
. . . .
,
. . . .
7
Cpy, kc (llmin)
6
- ~ - ~,, ko (I,,,,) .........
5
i
i, ~ . . ~ . . . ]
; ........
.
~ .
i
i
i :
3
.........
' ...............
3=
o
2
..........
i. . . . . . . . . .
] ..........
~- -
1
.........
i ..........
" ........ l~-
o
0
.... 0
I . . . . . . . . 100
200
. . . .
I
. . . .
.
. .......... .
'
--o-
.
:. . . . . . . . . . .
.
.
.
I
: ..........
.
~ .........
flow
500
so
..
60
;o
i :
400
100
. . . .
C p y , R I (%)
"'-:~
i . . . . . . . . . . . .
water
. . . .
i..l --~*-" ~" Rf(~)
i ............................... :
300 Wash
'
...... i . . . . . . . . . . i-
~ ..........
.
. . . .
I .................
E
0
Fig.7
i
.................
o
~
~. . . . . . . . . .
: .........
l~ .........
: .........
I . . . . . . . . 600
700
,< t"D,
40
@,
20
""
0 800
rate (ml/mln)
Collection zone rate constant and froth zone recovery versus wash water flow rate. (AFR 52 L/min, IS = 1070 RPM, %Sol = 20, Collector dose = 240 g/t, and Frother dose = 8 ppm).
Collection zone rate constant and froth zone recovery in m e c h a n i c a l flotation e n v i r o n m e n t
1173
Runs 14 through 17 explored 1%and Rf at different collector concentrations. Table 2 shows that feed grade was not the same for each experiment, however an optimum collector dose does appear to exist, i. e. concentrate grade increased and then decreased. Overall recovery decreased as froth depth increased for each collector dose; at constant froth depth, it increased as collector dose increased, levelling off. By increasing collector concentration, kc for both chalcopyrite and pyrite increased, as did Rf for both minerals (Figure 8). A plausible explanation for this finding could be that viscosity increased in the froth zone owing to the large number of particles transported from the pulp to the froth [12]. Because of this, drainage rate (dropback) would be made difficult resulting in an increase of froth zone recovery.
~.
2
. . . . . . . .
= . . . . . . . .
I . . . . . . . .
~v
i ....
-.
...................
100
...
~,
tll i
0 u
........
1
;~o:
~
.......
~
...........
:
:
-o--Cpy,
:............
::........
Rf(%)l-I
>,--Py,
60
~="
I-t
b
._o _~
Cpy, 0.5
-
kc (l/min)
...
Py, kc (l/min)
| ...........
! ...........
~. . . . . . . . . . . . . . . . . . . . . .
-1
o ....
0
i ....
0
Fig.8
50
i ....
i ....
100
i ....
150
200
Collector
Dose
i . . . . . . . . 250
300
*~
=oi
o
350
(g/t)
Collection zone rate constant and froth zone recovery versus collector concentration. (AFR 52 L/min, IS = 1070 RPM, WWFR = 290 cm3/min, %Sol =20, and Frother dose = 8 ppm).
Figure 9 shows 1%and Rf as a function of frother concentration (Runs 18 through 21), at 5 cm froth depth. The results indicate that 1% was unchanged for both minerals as frother dose was varied. This finding suggests that frother did not contribute in any significant way to controlling bubble size distribution in the pulp zone (probably as a result of the external air injection by means of the in-line mixer). At the same time, Rf increased equally for both minerals as frother dose increased. These findings show that selectivity is achieved in the pulp zone, and again support the assumption that events in the pulp zone are unaffected by changes in the froth performance.
"11 60
1/ in) ~
~,
o=
~....................
_ "6 o
: : : : : : . . . . . . . . . : . . . . . . . . . . : . . . . . . . . . . :. . . . . . . . . . : . . . . . . . . . . : . . . . . . . . . . i. . . . . . . . . . : . . . . . . . . . ---'--'e-'~ --El: • ~ '
0.5 0 0
Fig.9
40
Py, kc ( l / m i n )
2
i .... l
4
l---i , ..........
6
8
10
Frother
Dose (ppm)
=r
12
!. ........
14
-~ 20
0 16
Collection zone rate constant and froth zone recovery versus frother concentration. (AFR 52 L/min, IS = 1070 RPM, WWFR = 290 cm3/min, Collector dose = 240 g/t, %Sol = 20).
1174
M.A. Vera et
al.
To sum up the findings of Figures 8 and 9, flotation requires the formation of a stable bubble-particle aggregate, which enables the particle to be carried over from the pulp to the froth. Two conditions are required to achieved this: (1) a good level of hydrophobicity (collector addition), and (2) an appropriate level of surface tension (frother dosage). The concept of the critical surface tension of wetting in the pulp has proved to be important for selective flotation [13]. This helps us understand that selectivity in the flotation process is taking place in the pulp, and that the froth zone is a hurdle to the efficient transport of particles to the concentrate as has been shown in this paper. Finally, one common observation of all the results obtained so far is that Rf appears to be non-selective for attached particles. This can be seen by simply correlating froth zone recovery values for pyrite and chalcopyrite. Figure 10 illustrates clearly that pyrite and chalcopyrite are related by a 45 ° straight-line, which is a good indication of the non-selective behaviour of attached particles throughout the froth zone. This finding has also been observed by Savassi et al. [14], who were not able to observe any significant upgrading of attached particles in the froth. This suggests that the froth zone only acts to reject the entrained particles, selectively, and not attached particles. This result merits further investigation.
8o
Y = 0.9964x
80
~
50
~
40
~
30 20 lO o
0
10
20
30
40
50
60
70
80
90
100
Froth Zone Recovery of Chalcopyrite (%)
Fig.10 Pyrite-Rf versus chalcopyrite-Rf, the non-selective graph.
CONCLUSIONS The new JKMRC high S b flotation cell has been used for the simultaneous determination of collection zone rate constant and froth zone recovery allowing the flotation process to be studied considering the two phases, viz. froth zone and pulp zone, independently. This determination was carried out continuously. As expected, collection zone rate constant showed a strong dependence on aeration rate, which once again proves the importance of this parameter on flotation. Froth zone recovery was found to be strongly affected by impeller speed, air flow rate, wash water addition, and frother dose. It is interesting to note, however, that wash water addition and frother dose did not affect collection rate constant. This supports the hypothesis that events occurring in the froth zone are not influencing the pulp zone.
Collection zone rate constant and froth zone recoveryin mechanical flotationenvironment
1175
Percent solids, impeller speed and collector dose seemed to play an important role in the pulp zone, i. e. the three of them are related to mass transfer rates from the pulp zone to the froth zone. They appeared to have indirect influence on froth behaviour, to the extent that froth stability was altered. Finally, in all the measurements conducted, froth zone recovery was observed to be very similar in magnitude for both minerals species analysed. This finding suggests that R e is non-selective for attached particles, i. e. drop-back rates are equivalent for both minerals (this does not include entrainment).
ACKNOWLEDGMENT The authors wish to thank Dr. N. W. Johnson and Mrs. Kylie Ward for the valuable support provided during the course of this study. The help and support of all people at the Copper Concentrator, Mount Isa Mines Limited, is gratefully acknowledged. The authors would also like to acknowledge the financial support of the sponsors of the AMIRA (Australian Mineral Industry Research Association)-P9L project, of which this work forms part. REFERENCES ,
2.
.
4.
.
.
7.
.
9.
10. 11. 12. 13. 14.
Feteris, S.M., Frew, J.A. and Jowett, A., Modelling The Effect Of Froth Depth In Flotation. International Journal of Mineral Processing, 1987. 20: p. 121-135. Laplante, A.R., Toguri, J.M. and Smith, H.W., The Effect of Air Flow on the Kinetics of Flotation Part 1: The Transfer of Material from the Slurry to the Froth. International Journal of Mineral Processing, 1983:11 p. p203-219. Falutsu, M. and Dobby, G.S., Froth Performance In Commercial Sized Flotation Columns. Minerals Engineering, 1992.5(10-12): p. 1207-1223. Amelunxen, R.L., Llerena, R., Dunstan, P. and Huls, B., Chapter 16, Mechanics Of Column Flotation Operation. in Column Flotation' 88. 1988. Littleton, Colorado, USA: Society Of Mining Engineers, Inc., AIME. Heiskanen, K., Kallioinen, J. and Leus, V., The Role Of Frothbed In Controlling Apatite Flotation Performance. in Beneficiation Of Phosphate: Theory and Practice. 1993. Littleton, Colorado, USA: Soc. Min. Met. Explor. Vera, M. A., The Determination Of The Collection Zone Rate Constant and Froth Zone Recovery By Column Flotation, M. Eng.Sc. Thesis, Julius Kruttschnitt Mineral Research Centre, Department Of Mining and Metallurgical Engineering. 1995, The University Of Queensland: Brisbane. p. 259. Woodburn, E.T., Austin, L.G. and Stockton, J.B., A Froth Based Flotation Kinetic Model.
Chemical Engineering Research and Design, Transactions of The Institution of Chemical Engineers, Part A, 1994. 72(March): p. 211-226. Vera, M.A., Franzidis, J.P. and Manlapig, E.V., The JKMRC High Bubble Surface Area Flux Flotation Cell. Minerals Engineering, 1999. 12 (5): p. 477-484 Engelbrecht, J.A. and Woodburn, E.T., The Effect Of Froth Height, Aeration Rate and Gas Precipitation On Flotation. Journal Of The South African Institute Of Mining and Metallurgy, 1975. 76: p. 125-132. Gomez, C.O., Uribe-Salas, A. and Finch, J.A., Gas Holdup Measurement In Flotation Columns Using Electrical Conductivity. Canadian Metallurgical Quarterly, 1991.30(4): p. 201-205. Finch, J.A. and Dobby, G.S., Column Flotation. First ed. 1990: Pergamon Press. 180. Moudgil, B.M., Correlation Between Froth Viscosity and Flotation Efficiency. Minerals & Metallurgical Processing, 1993 (May 1993): p. 100-101. Freund, J. and Dobias, B., Technical Note: Characterisation of Adsorption Layers on Fluorite Particles with Gamma Flotation. Minerals Engineering, 1992. 5(7): p. p851-854. Savassi, O.N., Alexander, D.J., Johnson, N.W., Franzidis, J.-P. and Manlapig, E.V., Measurement of Froth Recovery of Attached Particles in Industrial Flotation Cells. in Sixth Mill Operators' Conference. 1997. Madang--Papua New Guinea.
1176
M.A. Vera et al.
Correspondence on papers published in Minerals Engineering is invited, preferably by e-mail to [email protected], or by Fax to +44-(0)1326-318352
Pergamon
0892--6875(99)00103-X
All rights reserved 0892-6875/99/$- see frontmatter
SIMULTANEOUS DETERMINATION OF COLLECTION ZONE RATE CONSTANT AND FROTH ZONE RECOVERY IN A MECHANICAL FLOTATION ENVIRONMENT
M.A. VERA, J.P. FRANZIDIS and E.V. MANLAPIG Julius Kruttschnitt Mineral Research Centre, The University of Queensland, Brisbane, Australia E-mail: M.Vera@ mailbox.uq.edu.au
(Received 6 July 1998; accepted 24 April 1999)
ABSTRACT
This paper presents the results of an investigation in which the new JKMRC Flotation Cell was used to determine the collection zone rate constant and froth zone recovery of a copper rougher ore simultaneously. The determination of these two parameters has been based on the straight line relationship that exists between the overall flotation rate constant and the froth depth [1]. Experimental work was conducted using a copper rougher ore with a P8o of 200 tzm. Operating variables such as airflow rate, impeller speed, feed percent solids, collector and frother dose, and wash water flow rate were investigated. Analysis for copper and iron minerals (chalcopyrite and pyrite, respectively) was carried out. The results indicate that the collection zone rate constant of both copper and iron minerals increased with increasing air flow. Froth zone recovery, on the other hand, decreased as air flow was increased, possibly as a result of increased detachment of particles from bubbles in the froth. Increasing the impeller speed also increased collection zone rate constant and decreased the froth zone recovery of both minerals. Experiments at different wash water flow rates have showed that events occurring in the froth zone do not affect the kinetics of the pulp zone. Moreover, and interestingly, the froth recovery of attached particles (wash water reduced entrainment to a minimum) was non-selective. The froth recovery curves for chalcopyrite and pyrite followed each other very closely in every instance studied. The work has proved that it is possible to measure both the collection zone rate constant and froth zone recovery simultaneously and continuously in a mechanical flotation environment. The results obtained to date are interesting and the work is continuing. © 1999 Published by Elsevier Science Ltd. All rights reserved.
Keywords Sulphide ores; flotation froths; flotation kinetics; froth flotation
1163
1164
M.A. Vera et al. INTRODUCTION
The process of flotation can be divided into two sections: recovery from the collection zone, and recovery from the cleaning (froth) zone. The role of the froth zone in determining flotation performance has been explicitly recognised by many investigators [ 1-6]. Despite this recognition, until recently, flotation modelling has been mainly accomplished by treating the flotation cell as a single rheological system (pulp-based model) or entirely empirically. However, Woodburn et al. [7], acknowledging that the performance factor needed for optimal design is best evaluated on the basis of a kinetic model, proposed a froth-based flotation kinetic modelling approach. The main idea behind this work was to model the kinetics in terms of the froth structure associated parameters. Although all the froth-based model parameters of the work of Woodburn et al. [7] seem to have a physical significance, they were estimated on the basis of very rough assumptions. It goes without saying that the froth structure and all the possible mechanisms occurring in the froth phase are important. Equally important is controlled experimentation on froth, which is very difficult. Model developments on the basis of froth structure might become unreliable when a number o f parameters is just guessed. Consequently, the present study has been conducted looking at the froth through a single parameter, froth zone recovery (Rf). This performance efficiency parameter is defined independently of any mixing regime as the mass rate of particles reporting to the concentrate via true flotation divided by the net mass rate of attached particles at the pulp froth interface. Rf is a number which lumps together the different effects of all possible mechanisms taking place in the froth phase. This paper presents the results of work in which the new JKMRC laboratory flotation cell [8] has been used to study the effects of operating variables, such as wash water flow rate, air flow rate, froth depth, impeller speed, percent solids, and collector and frother doses, on the flotation of copper ore. In particular, the effects of these variables on the collection zone rate constant k~ and froth zone recovery factor R e have been investigated separately, using the technique proposed by Feteris et al. [1], as well as Laplante et al. [2]. It is hoped that splitting the response into that of the pulp zone and froth zone separately will provide a much better understanding of the flotation process and the quantification of froth contribution to it.
BACKGROUND Figure 1 shows a diagram of the two phase flotation model. The collection zone and froth zone are clearly depicted. In this paper, the methodology described by Feteris et al. [1] has been used to quantify froth zone performance. Two important assumptions are involved in this methodology: (1) that the transfer of particles from the body of pulp to the pulp/froth interface depends only on events occurring in the pulp zone, and (2) that the transfer of particles from the froth to the concentrate depends only on events occurring in the froth zone. Sample collection at different froth depths provides the procedure for simultaneous determination of froth zone recovery and collection zone rate constant. The froth zone recovery efficiency equation is presented in equation 1, in which froth zone performance is defined as the total rate of transfer from the pulp to the concentrate divided by the rate of transfer from the pulp to the froth phase. Rf = k / k~
(1)
k, the overall flotation rate constant, is calculated from the overall recovery by considering the system as a perfect mixer: k = R / {~ (1 - R)} where R is experimental overall recovery and z is mean residence time.
(2)
Collection zone rate constant and froth zone recovery in mechanical flotation environment
1165
Concentrate
Froth
k
::ll:l:::l:lllll;llll;:lll:l::li:li::l:lllzl::ll:ll;:l;t:llllli:l
!:.-.:i!i!iiiigiiiigigigiii~!~i~i!iig~!!i!!!!iii~i!iiiiiiii~iiiiig~i!g!!ii!!~ i!i~i!~iiiiiiiiiiiiiiiiiiiiiiii~i!!!!!!i!iiiiiiiiiiii~iiiiiiiiii
k/k
Feed v
Pulp
Fig.1 Two-phase model description of flotation after [1]. The flotation rate constant at zero froth depth is the collection rate of the pulp zone (1%), which is independent of the froth depth. Thus, at zero froth depth, R~ by definition is equal to 100%. At all froth depths greater than zero, froth zone recovery will be less than or equal to 100%. Equation 1 may be developed further by incorporating a relationship between flotation rate constant (k) and froth depth (FD). The existence of a linear relationship with negative slope between flotation rate constant and froth depth has been reported by several researchers [ 1, 2, 9]. Such a relationship is plotted in Figure 2. Note that Figure 2 shows flotation rate constant as a function of froth depth for Run 4 (see Tables 1 and 2 below). Figure 2 depicts two repeatability tests for Run 4, which clearly suggest the same trend. These experimental results once more confirm the linear relationship between flotation rate constant and froth depth. Hence, the relationship can be expressed as follows: k = a - b (FD)
<3)
Now, when froth depth is zero, 1% may be determined by extrapolation as shown in Figure 2. Hence a = 1%. Next, let (FD)k= 0 be the intercept of the straight line (equation 3) with the X-axis, i. e. when k = 0 (this is equivalent to having a very deep froth, so that no material is transferred from the froth to the concentrate). Hence, b = kJ(FD)k=_ 0. Hence 1%= b * (FD)k=o. Substitution for a and b into equation 3 leads to: k = 1% { 1 - ( F D ) / ( F D ) k = o
}
(4)
which, when substituted into equation 1, yields: Rf = { 1 - (FD)/(FD)k=O }
(5)
This says that froth recovery per unit froth depth is constant. And, as indicated by Feteris et al. [1], for a given size range of mineral, the probability of drainage per unit froth depth is also constant.
1166
M.A. Vera et al.
In this p a p e r t h e a b o v e p r o c e d u r e is u s e d to d e t e r m i n e kc a n d Rf f r o m c o n t i n u o u s flotation tests w h i c h w e r e c o n d u c t e d u n d e r b u b b l e s u r f a c e a r e a flux levels e q u i v a l e n t to t h o s e o b t a i n e d in f u l l - s c a l e o p e r a t i o n .
3.5 ~Collection
z o n e rate c o n s t a n t k c
3.0
.-"~
"~~O.
2.0
-
o
0.5 [
oRUN 4--1=.1
0.0 [
~ R U ? rep. 2
0
3
~ ,
,
/ =x,~ r
6 9 Froth D e p t h (cm)
12
15
F i g . 2 F l o t a t i o n z o n e rate c o n s t a n t (k) as a f u n c t i o n o f f r o t h d e p t h (FD). TABLE RUN
PARAMETER
AFR
VARIED
(L/min)
1 Experimental
% SOLIDS
IMPELLER
WASH
COLLECTOR
FROTHER
SPEED
WATER
DOSE
DOSE
.........................................................................................................................
1
AFR
conditions
C ~ m ) . .............. L . . ~ . . . . ~
.................. .(S(..t)................. . ( ~ . . - . ~ . ~ L
25.5
20.0
1070
290
240
8
2
42.5
20.0
1070
290
240
8
3
44.7
20.0
1070
290
240
8
...... 4 * ................................................... 5 2 : o
5
% SOLIDS
................ ..2.0:0 ...................... 1 . 0 2 0 ................... 2..9.9 . ....................... 2 . 4 . 0 ............................ ..s................
52.0
11.0
1070
290
240
8
52.0
20.0
1070
290
240
8
7
52.0
23.0
1070
290
240
8
8
52.0
27.0
1070
290
240
8
6*
9
IMPELLER
52.0
20.0
800
290
240
8
10*
SPEED
52.0
20.0
I070
290
240
8
....... 1 . ! ................................................... 5 . 2 : 0 . ................ 2 0 : 0 . ..................... ! 4 ~
12"
WASH
....... 1.3. ................
52.0
20.0
1070
.W..A..~R ................ 52:0 ................ .2..0:,9. ..................... .1.070.
.................... 2.9.o. ....................... 2 4 . 0 ............................. ..s...............
290
240
8
................... 5 . ~ ....................... 2 4 0 ............................. 8 ..............
14#
COLLECTOR
52.0
20.0
1070
290
80
8
15 ~
DOSE
52.0
20.0
1070
290
160
8
52.0 52.0
20.0 20.0
1070 1070
290 290
240 320
8 8
16~ 17 ~ 18~
FROTHER
52.0
20.0
1070
290
240
0
19#
DOSE
52.0
20.0
1070
290,
240
4
52.0 52.0
20.0 20.0
1070 1070
290 290
240 240
8 16
20 # 21 #
* same test: included as runs for ease of comparison # Tests conducted six months later.
Collection zone rate constant and froth zone recovery in mechanical flotation environment
TABLE
2a Testwork
Run Feed Grade (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
Cu
Fe
4.10
9.18
4.06
8.42
4 . 1 1 9.42
4.07
3.80
4.07
4.23
3.98
4.23
4.07
4.07
4.07
3.85
9.00
9.07
9.00
9.23
9.09
9.23
9.00
9.00
9.00
8.87
on the new JKMRC
f l o t a t i o n cell: S u m m a r y
1167
table of results
FD
Conc.Grade
Overall
k,
Rf
(cm)
(%)
Recovery (%)
(!/rain)
(%)
G-Cu G-Fe
R - C u R-Fe
CPY
PY
CPY
1.5
22.90 33.70 56.76 39.81
0.30
0.16
94.94
91.65
5.0
22.80 33.50 54.00 35.49
80.12
72.20
7.0
23.10 33.50 49.19 29.25
72.17
61.08
1.5
1 2 . 6 0 22.30 65.22 69.14
94.00
92.69
1.36
0.49
PY
5.0
1 8 . 8 0 30.00 63.03 61.59
80.25
75.62
7.0
20.20 31.50 82.57 61.22
72.35
65.87
1.5
1 6 . 0 0 29.70 65.25 63.57
5.0
20.10 32.90 64.15 62.09
74.69
82.63
7.0
21.30 33.30 80.50 57.38
64.57
75.68
1.5
1 2 . 6 0 24.00 92.56 80.81
88.63
56.20
5.0
1 8 . 5 0 32.00 90.33 72.55
62.76
60.65
7.0
1 8 . 7 0 31.90 68.01 57.03
47.65
44.91
1.5
1 7 . 5 0 31.70 56.32 61.42
0.35 88.64
91.48
5.0
1 9 . 2 0 33.90 79.17 53.31
62.14
71.59
7.0
20.70 33.50 76.51 50.59
47.00
60.23
1.47
3.01
1.41
3.01
0.40
0.98
92.41 94.79
1.5
1 2 . 5 0 24.00 92.68 80.81
56.63
56.20
5.0
1 8 . 5 0 32,00 90.33 72.55
62.76
50.65
7.0
1 8 . 7 0 31,90 86.01 57.03
47.68
44.91
1.5
1 4 . 1 0 25,50 91.04 73.88
90.79
91.74
5.0
1 7 . 5 0 31.60 87.93 68.45
7.0
1 8 . 6 0 32.00 56.04 64.50
1.5
1 7 . 3 0 31,30 87.97 68.79
92.50
91.27
5.0
1 8 . 8 0 32.10 65.07 60.72
74.99
70.90
7.0
1 9 . 1 0 32.20 63.30 56.37
64.99
59.25
1.5
1 7 . 4 0 29,50 68.77 69.15
94.15
95.48
5.0
20.50 32.90 84.36 65.37
80.50
84.68
7.0
21.20 33,10 63.25 64.71
72.70
78.63
1.5
1 2 . 5 0 24,00 92.68 80.81
68.83
88.20
5.0
1 8 . 5 0 32,00 93.33 72.65
62.76
60.65
7.0
1 8 . 7 0 31.90 86.01 67.03
47.68
44.91
1.5
1 1 . 1 0 21,80 93.25 50.49
56.69
87.48
5.0
1 7 . 1 0 30,70 88.68 71.48
55.64
55.25
7.0
1 8 . 5 0 3t.60
37.90
41.59
1.5
1 2 . 6 0 24.00 92.56 80.81
88.63
56.20
5.0
1 8 . 5 0 32.00 90.33 72.55
62.76
60.65
7.0
1 8 . 7 0 31.90 56.01 67.03
47.56
44.91
2.24
0.98
0.62
59.31 72.45 57.03 1.62
1.40
3.01
3.27
0.49
0.47
0.98
0.97
65.10 64.81 3.01
3.05
0.98
61.43
1.5
1 7 . 2 0 31.60 92.61 78.97
1.00 85.63
63.28
5.0
1 9 . 3 0 33.20 87.28 64.74
52.10
44.25
7.0
20.00 33.70 82.22 56.72
32.94
21.95
M. A. Vera et
1168
al.
T A B L E 2b S u m m a r y table o f results (cont.) Run
Feed Grade
FD
..................... .(~.~ ............... ~).
14#
15#
16#
17#
18#
19#
20#
21#
Cu
Fe
5.22
9.89
5.27
5.64
3.23
3.63
3.38
3.34
3.67
10.30
11.10
9.93
10.30
9.87
9.73
10.20
Conc. Grade ................ (.~). ............
G-Cu
G-Fe
Overall
k=
.R.e~ve.~.(.~) . . . . . . . . . . . . . R-Cu
Rf
~!/.m'....). . . . . . . . . . . . . . . . . . . . . . . ~ ) .
...........
R-Fe
CPY
PY
CPY
PY
80.92 42.51
1.25
0.21
91.72
90.03
1.5
17.30 25.30
5.0
18.80
26.40
70.76
33.62
49.56
56.38
7.0
20.10
26.90
63.50
26.82
38.31
40.21
1.5
16.30 25.30
82.53
46.46
65.79
87.98
5.0
20.40 3t.20 78.35 43.54
63.01
69.49
7.0
21.00
31.90
33.70
43.92
1.5
15.40
26.00 90.87 63.80
91.25
93.46
5.0
19.60
30.50 87.35 54.44
76.03
68.23
7.0
20.60
31.80
82.61
59.15
59.33
1.5
11.80
27.40
89.14 57.65
93.73
93.14
5.0
13.60
29,40
87.08
52.38
79.09
77.12
7.0
14.70 30.80
86.19
50.01
70.72
67.97
81.38
83.55
5.0
20.50 34.30 65.31
32.32
37.95
45.16
7.0
21,20
34.90
45.90
19.67
t3.13
23.23
1.5
18.70 33.90
70.98
31.48
84.79
84.92
5.0
18.70
49.31
49.73
7.0
19.30 33.60
52.87
21.66
29.03
29.92
1.5
18.00
34.20
75.97
36.90
89.23
90.90
5.0
18.60 34.00
70.95
32.82
64.10
71.81
7.0
19.20
34.70
63.03
27.42
49.74
60.63
1.5
16.10 34.30
79.19
47.88
93.85
90.24
5.0
16.20
33.90
75.93
36.59
79.51
67.46
7.0
17.60
34.60
74.22
27.16
71.32
54.44
75.46
1.50
0.23
41.31 1.65
0.31
50.77
1.5
1.71
0.80
0.76
0.28
0.17
0.10
33.60 61.67 28.21
0.71
0.79
0.13
0.19
# Tests c o n d u c t e d six m o n t h s latex
EXPERIMENTAL The high S b Flotation Cell [8] developed at the J K M R C was used in the experiments. The new J K M R C cell was designed to mimic industrial flotation conditions, i. e. to achieve superficial gas velocities equivalent to those produced at the industrial level. This generates bubble surface area flux values similar to those which have been measured in full-scale flotation cells. The new J K M R C cell is a 16-1itre mechanical flotation cell, which is operated continuously. The cell is rectangular with a cross-sectional area of 600 cm 2, and fitted with a bottom driven impeller. Tailings discharge and pulp level control are achieved by means of a weir. An adjustable porous ceramic plate is used to ensure a well-defined froth zone and to eliminate (or at least minimise) entrainment via wash water addition through it. A i r hold-up determination, which is required for calculation of the kinetic rate constant, is by means o f a conductivity technique [10].
Collection zone rate constant and froth zone recovery in mechanical flotation environment
1169
The experimental set-up is shown in Figure 3. Slurry was made up in a 120-1itre sump provided with a pneumatic mixer for good particle suspension. A centrifugal pump was used to re-circulate the solids and assist with particle suspension. Slurry was withdrawn from the sump with a peristaltic pump (feed pump), at a point located at the base of the conic section of the sump. Collector was added on-line continuously. Air addition was carried out using an in-line mixer [8]. This device was placed between the feed pump and the inlet to the flotation cell (underneath the impeller). In this configuration bubble formation takes place independently of the impeller mechanism, which means that bubbles are originated outside of the flotation cell. Froth depth was varied by moving the lip of the cell up and down and adjusting the height of the ceramic porous plate. In this way, froth depth was varied without changing the pulp volume. This plate located on the top of the cell was also used as a wash water distributor, and wash water addition was quantified by a well calibrated pump. Likewise, launder water was accurately measured.
M~,'alle flamticacell lip 1< froth del~ <8(era) W a s h w pump 0~- 11/mln We~
I
-~iii:.iii:.i:.i:.ii::i::ii:.iii:i:iiiiii~
\
Pmmnmlc~
!
Ceramic porousplate 1Jmd~ waler pump 1-2 l/nin
Collector a/klti/m
I
~m
i~
~ivm hnpaer
750< I m ~ ( i ~ d
Sum~w~ol
Tin~
< 1400
I
disdm'~.~[_..___J
Feed inlet
b 0.3-1 ~
Slalicin-line
Pressulised l ~ - , ~ r a ~ , ~ , ~ , a n i ~ pump
IIo~ta"
gauge
Air irmmre
40- 50L/rain
Fig.3 Schematic diagram of the new JKMRC flotation cell rig. The flotation testwork was conducted at Mount Isa Mines Ltd. (Copper Concentrator) over two periods, six months apart. The sample used was copper rougher feed which was floated at chemical conditions similar to those in the actual industrial circuit. The test procedure consisted of making up the slurry in the 120 litre sump at the required solids percent. Then, frother was added (8 ppm MIBC). Collector addition was carried out continuously with a peristaltic
1170
M.A. Vera et
al.
pump (240 g/t). Slurry ready to be floated was fed into the JKMRC cell by the peristaltic pump (3.5 1/min). Sample collection was conducted when steady-state was reached (approx. 2 mean residence times, 8 min). It should be noted that, in this system, the total tailings stream is made up of the tailings overflow and purge streams (Figure 3). For each run conducted, concentrate and tailings were collected at three different froth depths (1.5, 5, and 7 cm). The experimental conditions used in this study are given in Table 1. The parameters varied were air flow rate (AFR), solids percent, impeller speed (IS), wash water flow rate (WW), collector dose, and frother dose. Numerous tests were conducted to determine the reproducibility of the experimental technique, which was found to be good (see Figure 2). All the samples were weighed (wet and dry), and assayed for copper and iron to provide complete mass balances. The copper and iron assays were converted into chalcopyrite and pyrite using the following conversion factors: % CPY (chalcopyrite) = % Cu / 0.34624 % Fecpv = % CPY * 0.30423 % Fepv = % FeTot~ -- % Fecpv % PY (pyrite) = (% Ferot,~ - % CPY * 0.30423) / 0.4655
RESULTS AND DISCUSSION The feed grade, concentrate grade, overall recovery, collection zone rate constant (1%) and froth zone recovery (Rf) determined experimentally for both copper and iron minerals are shown in Table 2. As can be seen, there was a very small fluctuation of copper and iron content in the feed (average 4.05% Cu and 9.04% Fe) during the first period of testwork. However, during the experimental work conducted six months later, there was a much greater fluctuation in the Cu and Fe grades. Table 2 shows that concentrate grade increased in all cases as froth depth increased. On the other hand, overall recovery decreased in all cases as froth depth increased. These results were as expected. It is interesting to note that in general very good recoveries were achieved even though the mean residence time in the cell was less than 5 minutes. Table 2 also shows the effect of operating conditions on 1% and Rf. Runs 1 through 4 were c a m e d out at different aeration rates with all other conditions kept constant. These results indicate that as air flow rate increased, k~ increased for both copper and iron minerals, with the effect on chalcopyrite being much greater than the effect on pyrite. Rf, however, underwent a different behaviour. It increased slightly up to a point where it decreased drastically as air flow rate increased. This may be the result of an increase in detachment in the froth as the air flow rate was increased. It is worth mentioning that air injection took place through a static in-line mixer (see Figure 3), which broke down air into small bubbles independently of the impeller mechanism. It is believed that this device is responsible for the Rf behaviour. This is because of the compromise between superficial gas velocity and bubble diameter. These two quantities (Jg and db) or the combination of them (bubble surface area flux, Sb) have an effect on the stability of the pulp-froth interface, which will affect froth zone recovery. Figure 4 illustrates these effects graphically at 5 cm froth depth 1.
All the Figures depicting experimental results have been plotted for the 5 cm froth depth case only, so as not to clutter the Figures with data points. Similar trends were observed at 1.5 and 7 cm froth depths.
Collection zone rate constant and froth zone recovery in mechanical
_~
4
. . . . . :
t ;
. . . .
I ;
. . . .
i :
. . . .
i :
. . . .
-t ~"
2.s
"6 0
i..............
-I
1
i .............
i ..............
-
::..............
!.............
.
.
.
0
Py,
.
i
.
.
kc (l/min)
.
.
t0
.
I
I'"'"
.
.
.
.
20
..........
.
I
.
.
i--, ........
-
i
.
30
.
.
e0
:.,o
" ............
.
1171
100
. . . .
Cpy,ke(l/min)Ii . . . . . . . . . . . . . . . ~
'
0
i : ......
- ............
1.5
flotation environment
.
.
40
..........
:
.
i
,o '
50
-
0
60
Air F l o w R a t e (I/min)
Fig.4
Collection zone rate constant and froth zone recovery versus air flow rate. (%Sol = 20, IS = 1070 RPM, W W F R = 290 cm3/min, Collector dose = 240 g/t, and Frother dose = 8 ppm).
Figure 5 depicts the effect of percent solids on 1% and Rf at 5 cm froth depth (Runs 5 through 8). Varying percent solids affected both k c and Rf. The former went through a maximum value at 20--23 % solids. This may be related to the bubble carrying process, which indicates an optimum bubble loading to transfer particles from pulp to the froth; curves like these have been reported for column flotation tests [11]. R r increased slightly with increase in solids, which is an indication of bubble overloading. This is observed for copper minerals. The behaviour of pyrite is unclear, although the R~ values are very similar to those obtained for chalcopyrite. It is believed that these findings are also related to the static in-line mixer. This is operated with feed slurry, which will affect the performance of the in-line mixer (bubble size distribution) as its density (percent solids) changes.
8
---
'l .....
..I 6
!5 e, •
O~
4 3
''
"~-
cpy,
Rf(%)
I>".P"~..............
.............
' 'a . . . . . . . | .........
,I
:.... ..::__: i o
! ....
i ..............
i ............
i.............. [
.............
:. . . . . . . . . . . . . .
.............
' ...........................................
I
. . . . .
............
! ....
~-'-:-"
--
- - - .~
.;~:_ ...........
; .............
cpy, ke O/min) I . . . i . . . . . . . . . . ~
~
100
........
-: -
:::.............
so
; ............
........... i ............
40
2O
............. - ............. .:............. : ~ ; . - . . - ; ~ , ~ , ~ ........ ~............ O
0
....
'
:
5
10
i ....
~'7
.....--
":.
. . . . . .
-
15
:
i,,,,i
20
B--4
-'El
....
25
~.
o 30
% Solids
Fig.5
Collection zone rate constant and froth zone recovery versus percent solids (AFR 52 L/min, IS = 1070 RPM, W W F R = 290 cm3/min, Collector dose = 240 g/t, and Frother dose = 8 ppm).
Table 2 also shows (Runs 9 through 11) that 1%increased and Rf decreased as the impeller speed increased. This operating condition is responsible for the degree of particle suspension, as well as the level of turbulence in the cell. k c increases because pulp-froth transfer is promoted as a consequence of more energy being available. R r decreases probably because of a higher level of instability in the lower regions of the
1172
M . A . Vera et al.
froth, caused by the increased turbulence in the upper regions of the pulp zone (at the higher rpm values, the pulp-froth interface became very mobile and wavy). This additional energy in the froth would increase particle detachment all across the froth and promote drainage. Figure 6 shows 1% and Rf as a function of impeller speed at 5 cm froth depth. Of particular interest is the similarity of the Rf values for chalcopyrite and pyrite at each impeller speed. This finding suggests drop-back for both minerals without any selectivity in their rates of drainage. 8
' '
'
I
.... I
.=
6
•a
s
qP
E
3
....
! '
'
'
I ' '
' '
~-c,,..,(~)! --x--
,
:
:
i
i
i ..........
! ..........
........
py, Rf(%)
................... t
1
l
:, ....... !
::..........
I
0
~,"
:
i
~
:
i,,, 200
1100
:
i,,,
..i
....
i
:::~;~
400
600
":'i
.........
6o
~,
~..... i !..........i..........i..........1 ,o :
i
:
.........
! .... ::;"-~
,,,
--,
.......... ! .......... i......... -t '°
!~':
:
Impeller
Fig.6
' ! . . . . . . . . .
Cpy, kcO/min) I ..... ~
-.--P.,.c(~,m,n)
,..,,,
! ' '
i ..........
i .......... i .......... t
'
'
...... ~ ......... i .......... .......... ; ......... t
I
p-I
' I
'
- '
,~:,
,i" . . . . . .
800
1000
Speed
~ ........ 1 .o
;,,
1200
1400
--
,t o 1600
(rpm)
Collection zone rate constant and froth zone recovery versus impeller speed. (AFR 52 L/min, %Sol = 20, WWFR = 290 cm3/min, Collector dose = 240 g/t, and Frother dose = 8 ppm).
In Runs 12 and 13 the effect of wash water flow rate on 1% and Rf was investigated. Figure 7 shows that the kinetic process (pulp--froth transfer) was not affected by this variable, i. e. 1% remained unaltered for chalcopyrite and pyrite when wash water rate was increased from 290 to 600 cm3/min. This result is a validation of the first assumption of this methodology (see Background above), i. e. that only events or actions taking place in the pulp will affect iL On the other hand, Rf decreased as the water flow increased. This indicates that the drainage of weakly attached particles and a much better cleaning action in the froth was promoted as a result of increasing the wash water rate. (Note that wash water was added through the ceramic porous plate in all the experiments conducted. Consequently, reported results are believed to be mainly for attached particles, i. e. particles recovered by true flotation).
8
~
=
. . . .
,
. . . .
,
. . . .
7
Cpy, kc (llmin)
6
- ~ - ~,, ko (I,,,,) .........
5
i
i, ~ . . ~ . . . ]
; ........
.
~ .
i
i
i :
3
.........
' ...............
3=
o
2
..........
i. . . . . . . . . .
] ..........
~- -
1
.........
i ..........
" ........ l~-
o
0
.... 0
I . . . . . . . . 100
200
. . . .
I
. . . .
.
. .......... .
'
--o-
.
:. . . . . . . . . . .
.
.
.
I
: ..........
.
~ .........
flow
500
so
..
60
;o
i :
400
100
. . . .
C p y , R I (%)
"'-:~
i . . . . . . . . . . . .
water
. . . .
i..l --~*-" ~" Rf(~)
i ............................... :
300 Wash
'
...... i . . . . . . . . . . i-
~ ..........
.
. . . .
I .................
E
0
Fig.7
i
.................
o
~
~. . . . . . . . . .
: .........
l~ .........
: .........
I . . . . . . . . 600
700
,< t"D,
40
@,
20
""
0 800
rate (ml/mln)
Collection zone rate constant and froth zone recovery versus wash water flow rate. (AFR 52 L/min, IS = 1070 RPM, %Sol = 20, Collector dose = 240 g/t, and Frother dose = 8 ppm).
Collection zone rate constant and froth zone recovery in m e c h a n i c a l flotation e n v i r o n m e n t
1173
Runs 14 through 17 explored 1%and Rf at different collector concentrations. Table 2 shows that feed grade was not the same for each experiment, however an optimum collector dose does appear to exist, i. e. concentrate grade increased and then decreased. Overall recovery decreased as froth depth increased for each collector dose; at constant froth depth, it increased as collector dose increased, levelling off. By increasing collector concentration, kc for both chalcopyrite and pyrite increased, as did Rf for both minerals (Figure 8). A plausible explanation for this finding could be that viscosity increased in the froth zone owing to the large number of particles transported from the pulp to the froth [12]. Because of this, drainage rate (dropback) would be made difficult resulting in an increase of froth zone recovery.
~.
2
. . . . . . . .
= . . . . . . . .
I . . . . . . . .
~v
i ....
-.
...................
100
...
~,
tll i
0 u
........
1
;~o:
~
.......
~
...........
:
:
-o--Cpy,
:............
::........
Rf(%)l-I
>,--Py,
60
~="
I-t
b
._o _~
Cpy, 0.5
-
kc (l/min)
...
Py, kc (l/min)
| ...........
! ...........
~. . . . . . . . . . . . . . . . . . . . . .
-1
o ....
0
i ....
0
Fig.8
50
i ....
i ....
100
i ....
150
200
Collector
Dose
i . . . . . . . . 250
300
*~
=oi
o
350
(g/t)
Collection zone rate constant and froth zone recovery versus collector concentration. (AFR 52 L/min, IS = 1070 RPM, WWFR = 290 cm3/min, %Sol =20, and Frother dose = 8 ppm).
Figure 9 shows 1%and Rf as a function of frother concentration (Runs 18 through 21), at 5 cm froth depth. The results indicate that 1% was unchanged for both minerals as frother dose was varied. This finding suggests that frother did not contribute in any significant way to controlling bubble size distribution in the pulp zone (probably as a result of the external air injection by means of the in-line mixer). At the same time, Rf increased equally for both minerals as frother dose increased. These findings show that selectivity is achieved in the pulp zone, and again support the assumption that events in the pulp zone are unaffected by changes in the froth performance.
"11 60
1/ in) ~
~,
o=
~....................
_ "6 o
: : : : : : . . . . . . . . . : . . . . . . . . . . : . . . . . . . . . . :. . . . . . . . . . : . . . . . . . . . . : . . . . . . . . . . i. . . . . . . . . . : . . . . . . . . . ---'--'e-'~ --El: • ~ '
0.5 0 0
Fig.9
40
Py, kc ( l / m i n )
2
i .... l
4
l---i , ..........
6
8
10
Frother
Dose (ppm)
=r
12
!. ........
14
-~ 20
0 16
Collection zone rate constant and froth zone recovery versus frother concentration. (AFR 52 L/min, IS = 1070 RPM, WWFR = 290 cm3/min, Collector dose = 240 g/t, %Sol = 20).
1174
M.A. Vera et
al.
To sum up the findings of Figures 8 and 9, flotation requires the formation of a stable bubble-particle aggregate, which enables the particle to be carried over from the pulp to the froth. Two conditions are required to achieved this: (1) a good level of hydrophobicity (collector addition), and (2) an appropriate level of surface tension (frother dosage). The concept of the critical surface tension of wetting in the pulp has proved to be important for selective flotation [13]. This helps us understand that selectivity in the flotation process is taking place in the pulp, and that the froth zone is a hurdle to the efficient transport of particles to the concentrate as has been shown in this paper. Finally, one common observation of all the results obtained so far is that Rf appears to be non-selective for attached particles. This can be seen by simply correlating froth zone recovery values for pyrite and chalcopyrite. Figure 10 illustrates clearly that pyrite and chalcopyrite are related by a 45 ° straight-line, which is a good indication of the non-selective behaviour of attached particles throughout the froth zone. This finding has also been observed by Savassi et al. [14], who were not able to observe any significant upgrading of attached particles in the froth. This suggests that the froth zone only acts to reject the entrained particles, selectively, and not attached particles. This result merits further investigation.
8o
Y = 0.9964x
80
~
50
~
40
~
30 20 lO o
0
10
20
30
40
50
60
70
80
90
100
Froth Zone Recovery of Chalcopyrite (%)
Fig.10 Pyrite-Rf versus chalcopyrite-Rf, the non-selective graph.
CONCLUSIONS The new JKMRC high S b flotation cell has been used for the simultaneous determination of collection zone rate constant and froth zone recovery allowing the flotation process to be studied considering the two phases, viz. froth zone and pulp zone, independently. This determination was carried out continuously. As expected, collection zone rate constant showed a strong dependence on aeration rate, which once again proves the importance of this parameter on flotation. Froth zone recovery was found to be strongly affected by impeller speed, air flow rate, wash water addition, and frother dose. It is interesting to note, however, that wash water addition and frother dose did not affect collection rate constant. This supports the hypothesis that events occurring in the froth zone are not influencing the pulp zone.
Collection zone rate constant and froth zone recoveryin mechanical flotationenvironment
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Percent solids, impeller speed and collector dose seemed to play an important role in the pulp zone, i. e. the three of them are related to mass transfer rates from the pulp zone to the froth zone. They appeared to have indirect influence on froth behaviour, to the extent that froth stability was altered. Finally, in all the measurements conducted, froth zone recovery was observed to be very similar in magnitude for both minerals species analysed. This finding suggests that R e is non-selective for attached particles, i. e. drop-back rates are equivalent for both minerals (this does not include entrainment).
ACKNOWLEDGMENT The authors wish to thank Dr. N. W. Johnson and Mrs. Kylie Ward for the valuable support provided during the course of this study. The help and support of all people at the Copper Concentrator, Mount Isa Mines Limited, is gratefully acknowledged. The authors would also like to acknowledge the financial support of the sponsors of the AMIRA (Australian Mineral Industry Research Association)-P9L project, of which this work forms part. REFERENCES ,
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10. 11. 12. 13. 14.
Feteris, S.M., Frew, J.A. and Jowett, A., Modelling The Effect Of Froth Depth In Flotation. International Journal of Mineral Processing, 1987. 20: p. 121-135. Laplante, A.R., Toguri, J.M. and Smith, H.W., The Effect of Air Flow on the Kinetics of Flotation Part 1: The Transfer of Material from the Slurry to the Froth. International Journal of Mineral Processing, 1983:11 p. p203-219. Falutsu, M. and Dobby, G.S., Froth Performance In Commercial Sized Flotation Columns. Minerals Engineering, 1992.5(10-12): p. 1207-1223. Amelunxen, R.L., Llerena, R., Dunstan, P. and Huls, B., Chapter 16, Mechanics Of Column Flotation Operation. in Column Flotation' 88. 1988. Littleton, Colorado, USA: Society Of Mining Engineers, Inc., AIME. Heiskanen, K., Kallioinen, J. and Leus, V., The Role Of Frothbed In Controlling Apatite Flotation Performance. in Beneficiation Of Phosphate: Theory and Practice. 1993. Littleton, Colorado, USA: Soc. Min. Met. Explor. Vera, M. A., The Determination Of The Collection Zone Rate Constant and Froth Zone Recovery By Column Flotation, M. Eng.Sc. Thesis, Julius Kruttschnitt Mineral Research Centre, Department Of Mining and Metallurgical Engineering. 1995, The University Of Queensland: Brisbane. p. 259. Woodburn, E.T., Austin, L.G. and Stockton, J.B., A Froth Based Flotation Kinetic Model.
Chemical Engineering Research and Design, Transactions of The Institution of Chemical Engineers, Part A, 1994. 72(March): p. 211-226. Vera, M.A., Franzidis, J.P. and Manlapig, E.V., The JKMRC High Bubble Surface Area Flux Flotation Cell. Minerals Engineering, 1999. 12 (5): p. 477-484 Engelbrecht, J.A. and Woodburn, E.T., The Effect Of Froth Height, Aeration Rate and Gas Precipitation On Flotation. Journal Of The South African Institute Of Mining and Metallurgy, 1975. 76: p. 125-132. Gomez, C.O., Uribe-Salas, A. and Finch, J.A., Gas Holdup Measurement In Flotation Columns Using Electrical Conductivity. Canadian Metallurgical Quarterly, 1991.30(4): p. 201-205. Finch, J.A. and Dobby, G.S., Column Flotation. First ed. 1990: Pergamon Press. 180. Moudgil, B.M., Correlation Between Froth Viscosity and Flotation Efficiency. Minerals & Metallurgical Processing, 1993 (May 1993): p. 100-101. Freund, J. and Dobias, B., Technical Note: Characterisation of Adsorption Layers on Fluorite Particles with Gamma Flotation. Minerals Engineering, 1992. 5(7): p. p851-854. Savassi, O.N., Alexander, D.J., Johnson, N.W., Franzidis, J.-P. and Manlapig, E.V., Measurement of Froth Recovery of Attached Particles in Industrial Flotation Cells. in Sixth Mill Operators' Conference. 1997. Madang--Papua New Guinea.
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