Introduction The sizing of cyclones for dense medium separation, like most other things in this industry, is a combination of art and science. The selection process within itself is not complex, but there are a number of factors which must be taken into consideration to ensure that the cyclone size which has in the best separation efficiency is selected. Main Categories The selection process can be divided into the following main categories i.e. Inputs This covers feed parameters, yield, and design parameters which result in a mass balance. Diameter The full range of cyclone diameters which apply to the input data are calculated. Constraints The outputs of the diameter process are then checked against the following constraints:
The categories can be graphically depicted as follows:
Each of the categories will now be considered in greater detail. Inputs
Feed The minimum information required is the following: Tons per hour solids (dry). Particle density of the feed. Top size of the feed being treated. In order to ensure the best possible cyclone selection a full feed particle size distribution is required, but is unfortunately not always available. Yield The yield is required to determine the cyclone mass balance. The best possible information can be derived if a feed washability is provided. This enables the yield to be accurately determined and the sinks density can be calculated. Once again, this information is not readily available for many processes due to, amongst other factors, the density of separation. The next test is for the yield to be supplied by the end user. This can be determined by a mass balance around a plant or the results of pilot scale test work. If this is not available, then an estimate will have to be made based upon similar operations / applications.
Diameters
The next step is to calculate the relevant parameters for all the cyclone diameters which can be used for all the application. Top size
Figure 1
The cyclone diameter must be incremented until one which can handle the top size is found. Cyclone Capacity
/ 3 m ( y t i c a p a c t o 50.0 g i p S 45.0
47.4
Standard Hi Capacity
40.0
37.3
36.3
35.0 32.3 30.0
24.7
25.0 19.3
20.0 15.0
13.1 9.6
10.0 5.0
28.6
27.6 21.1
14.8
10.0
7.4 3.5 4.6
0.0 250
360
420
510
610
660
710
800
Cyclone Diameter
Figure 2 Please note that both standard and high capacity spigots are available and the calculation should be done for both. If the available spigot capacity is less than the required spigot capacity, recalculate N based upon the maximum spigot capacity.
New Cyclone Diameter
Constraints The output from the previous category must now be checked against the constraints that apply to this application.
This is a graphical process to ensure that everything is taken into
% Finer
Comment
0-5 %
Acceptable
5-15 %
On the limit
>15 %
Reduce cyclone diameter
Spigot Requirements The total available spigot capacity must be plotted against the required spigot capacity from the mass balance. This will assist to determine which cyclone diameters can be used and whether a standard or high capacity spigot is required. Number of Cyclones Calculate the total feed volume based upon the number of cyclones required and using the capacity figures in Table 1. Plot the required volume on the same graph. Note, that if the cyclone is spigot controlled, the calculated volume will be much higher than that based upon the feed medium to ore ratio.
Selection All the information required to make the final selection is now available.
Materials of Construction
If multiple cyclones have to be used, for N=2, it is possible to ensure good distribution. If N>4, then it is better to consider modules with individual modules having N=2,3,4. Inlet Shape Where square and rectangular inlets are available, the following guidelines apply: Square inlets can be used where a large top size must be accommodated or a low differential is required. Rectangular inlets are used to ensure a high differential. This is especially helpful for high density separations (>3.2) as the circulating medium density can be reduced and the inventory of medium is reduced. Pulp Distribution Where N>1, a distributor is required. A two way distributor can be designed to ensure that equal solids and liquid distribution is achieved. For N>2, distribution becomes increasing complex. Note that no static distributor can remove a bias which already exists. Engineered ceramic tiles are the preferred lining for pulp distributors as they give good wear life and can easily be designed to fit any distributor. Example
Design Parameters Ore: medium ratio Operating head
: :
7.5:1 12 D
Mass balance Feed
Floats
Sinks
Solids (tph)
100
98.5
1.5
Volume solids (m³/h)
38.5
37.9
0.6
Medium (m³/h)
288.8
202.2
86.6
Total medium (m³/h)
327.3
240.1
87.2
Diameter Top size Dc = 250
Top size = 18 mm (Figure 1) > 25 mm
Increment Dc Dc = 360
Square top size = 25 mm
u l o V
l a t o T , s e n o l c y C f o o N
0
Summary of Results Dc
Inlet shape
N
Spigot capacity (m³/h)
360
Square
5
37
420
Square / Rect.
3
30
510
Square / Rect.
2
29.6
610
Square / Rect.
2
42.2
710
Rect.
1
28.6
Number of Cyclones
1000 395
100
10
546 345
358
322
m m ( e z i s p o T
Cyclone Diameter Both the 420 and 510 mm cyclones will be acceptable. In terms of distribution, 2 cyclones is better than 3, which would support the choice of the 510 mm cyclone. The breakaway size for the 510 mm cyclone is 1.7 mm and the bottom deck is 1.6 mm so performance will not be sacrificed. Constraints Top Size 60
50
Square Rectangular Feed topsize
48 43
42
40 34
30 25
20
10
0
18
18
24
33 30
30
25
/ 3 m (
y t i c a p a c t o g i p S
.
Spigot Requirements
100.0
Standard Hi Capacity Required 9.6
10.0
27.6
13.1 10.0
19.3 14.8
21.1
24.7
37.3 28.6
47.4 36.3
7.4 4.6 3.5
1.0
0.1 250
360
420
510
610
Cyclone Diameter
Not a constraint N = 2 and Dc = 510 mm
660
710
800
Conclusion The process / procedure given provides the designer / end user with a tool to enable him to properly evaluate and select the correct cyclone for a given application taking all the relevant factors into account. It all adds up!
Cyclone Model
Cyclone Diameter (mm)
C250-20-1
92
95
97
100
103
C420-20-1
420
88
94
100 C CYCLONES ( WITH BA RREL ) - C APACITIES ( M3/ H Slurr y ) 105
110
115
120
125
129 Feed Head ( as a functi on of Cyclo ne Di ameter ) 133
7D
8D
9D
137
141
C510-20-1 10D 11D
145
12D
149
13D
14D
15D
16D
17D
18D
19D
20D
510
137
146
155
163
171
179
186
193
213
219
225
231
200
207
C610-20-1 485
610 For Other Conditions Use Formula :
Sqr Root ( H1 / H2 ) = C1 / C2 208
223
236
249
305
261
273
284
295
500
515
529
542
-
-
660
246
263
279
294
308
322
335
348
383
394
405
415
360
372
C710-20-1
710
300
321
340
358
376
393
409
424
467
481
494
507
437
454
439
453
C800-20-1
800
321
343
364
384
470
402
420
