Fujian, a gold and silver mine is silver-based gold and silver mines, associated with a variety of non-ferrous metals copper, lead, zinc, silver grade of which 128.879 / t, gold grade of 0.729 / t, the value of the total value of silver More than 70%. The cyanide plant is designed by the traditional CCD method, namely, flotation concentrate cyanide, zinc powder replacement method to extract gold and silver, and other associated metals are comprehensively recovered by flotation method. Here, the cyanide process and cyanide raw material grinding are mainly introduced. Selection of process parameters such as degree and cyanide time.
First, the choice of cyanidation process
At present, the gold extraction methods commonly used at home and abroad include carbon slurry method (CIP and CIL) and zinc powder replacement method (CCD). The mechanism of the leaching process of the carbon slurry method and the zinc powder replacement method is completely the same. The difference is that the extraction method of the target mineral after leaching is different: the carbon slurry method extracts the leached gold and silver by the physical method of carbon adsorption, and the zinc powder replacement method is The leached gold and silver are extracted by the chemical method of zinc powder replacement; the equipment capacity and production cost of the carbon slurry method mainly depend on the amount of metal leaching and sucking (ie, the amount of gold loaded), and the zinc powder replacement method is The amount of minerals, regardless of the amount of metal, does not change much in the amount of precious liquid. Therefore, for materials with higher silver content, zinc powder replacement method should be used, and it is obviously uneconomical to use carbon slurry method to recover low-value silver.
The results of small-scale experiments and production process tests show that the leaching speed of gold is faster than that of silver. The suction speed of silver is faster than that of gold, but it is not as strong as gold; the resolution of silver is faster than that of gold; the rate of silver is faster than that of gold. But easy to fall off.
In view of the above analysis, for cyanide plants with high gold and silver grades and low concentrate content after re-election and flotation enrichment, it is suitable to use high cyanide concentration, high aeration leaching, zinc. Powder replacement method for gold extraction; for materials with finer grain size and lower gold and silver grades, it is suitable to use the whole mud cyanide carbon slurry method to extract gold.
Second, the choice of grinding fineness of cyanide raw materials
It is generally believed that the finer the particle size of the impregnated material, the higher the degree of dissociation of the gold monomer, which will facilitate the leaching of gold. However, it should be pointed out that the cyanide leaching of gold and silver is different from foam flotation. Flotation has the characteristics of selectively capturing the mineral of interest. Therefore, it is necessary to dissociate the target mineral by grinding to ensure that the surface of the target mineral has sufficient exposed surface to fully adhere the collector . The leaching rate of gold and silver can be dissolved by cyanide only by having exposed surfaces or cracks, and it is not necessary to be too finely ground. In addition, in the grinding classification process, especially in the classification equipment using the gravity principle, since the density of gold is much larger than other metal minerals and gangue, the dissociated gold in the graded particle size often enters the grit back to the grinding. Not only is it technically unreasonable, it is also economically uneconomical. Therefore, the fineness of the impregnated material should be scientifically controlled.
The results of the cyanide grinding fineness test for the ore sample are shown in Fig. 1.
According to the experimental research results, it is concluded that the grinding fineness has little effect on the leaching rate of gold, and has a slight influence on the leaching rate of silver, but the effect is not great, but with the increase of grinding fineness, the consumption of sodium cyanide gradually Increasingly, the sodium cyanide consumption is 13.6 kg/t concentrate under the condition that the grinding fineness is -0.043 mm or 60.O%; under the condition that the grinding fineness is -0.043 mm, accounting for 97.6%, The consumption of sodium cyanide is above 20kg/t concentrate. Therefore, considering the comprehensive consideration, the design index is selected as follows: the fineness of grinding is -0.043mm, accounting for 60.0%.
Third, the choice of cyanide time
At present, there is a more general view that the leaching time of the design should consider a certain amplification factor based on the test results. However, blindly extending the leaching time does not significantly increase the leaching rate of gold and silver, but instead causes the dissolution of harmful metal impurities and the consumption of cyanide.
The results of the leaching time test for the ore sample are shown in Fig. 2.
According to the test results, the leaching rate of gold and silver increased significantly with the leaching time, but the leaching rate increased slowly after the leaching time exceeded 40h. When the leaching time is 64h, the consumption of sodium cyanide is 1lkg/t concentrate; when the leaching time is 88h, the consumption of sodium cyanide is 21.5kg/t concentrate. The recommended leaching time is 66h. In combination with previous production practices, we have selected a leaching time of 80h. This time is longer than the general leaching time of gold, mainly because silver is the main object of recovery in the ore, and silver is more difficult to leaching than gold.
Fourth, the choice of other process parameters
(1) Leaching equipment
Under the premise of meeting the leaching time requirements, there are two options to choose from. Option 1: Select large equipment, the number of leaching tanks is small, easy to operate, manage and maintain; Option 2: Select small equipment, multiple equipments can be used in series, can be leached in sections to avoid the phenomenon of "slurry short circuit". Industrial test and production practice results show that the series of 4 tanks or more can avoid the slurry short circuit. The final choice of the cyanide plant The 8.0m×8.5m leaching tank 5 tank is used as the leaching equipment, and the leaching tank is used in series to leaching.
(2) Pulp pH
Lime is often used in the production to adjust the pH of the slurry. Lime as a protective base prevents the hydrolysis of cyanide and precipitates certain harmful impurities. Theoretically, the pulp pH=9 is the optimum value for gold leaching, and the pH value of the controlled pulp is usually in the range of 9 to 1 l. If the pH value is too high, the dissolution of some metal impurities will be accelerated, and the consumption of cyanide will be increased. In actual production, the pH should be controlled to be relatively stable, and the appropriate pH value should be determined according to actual production conditions.
(three) cyanide concentration
Generally, in the case where the gold grade of the infusion material is high, the leaching operation attempts to take a higher cyanide concentration to accelerate the dissolution of gold. At the same time, however, the amount of dissolution of other metals is correspondingly increased, which not only consumes a large amount of cyanide, but also consumes oxygen necessary for gold dissolution, resulting in a decrease in the rate of gold leaching. During the leaching process, cyanide should be added in multiple stages, and the cyanide concentration should always be maintained within the appropriate range. In addition, the concentration requirements of cyanide also vary with climate change. Generally, the cyanide concentration required in winter is slightly higher than that in summer.
The appropriate cyanide concentration should be determined by experiment, and the lower cyanide concentration should be selected as much as possible while ensuring the leaching effect.
(4) Oxygenation
Oxygen as an oxidant is as important as cyanide during cyanide leaching, and oxygenation is required. For impregnated materials with high mud content and high levels of harmful metal impurities, the oxygen consumption will be greatly increased, and attention should be paid to strengthening the supply of wind and mechanical agitation.
V. Conclusion
(1) For materials with high gold and silver content, zinc powder replacement method is generally adopted; for materials with lower gold and silver content, the whole mud cyanide carbon slurry method is generally adopted.
(2) The fineness of grinding is not as fine as possible. The economical and reasonable grinding fineness should be selected according to the comprehensive consideration of tests, production practices and technical and economic indicators.
(3) The choice of cyanide time should not be as long as possible. The appropriate leaching time should be determined through experiments and comprehensive consideration from the technical and economic perspectives.
(4) Cyanide leaching equipment should select large equipment as much as possible under the premise of satisfying at least 4 tanks. The pH value of the pulp and the concentration of cyanide should not be too high. Low pH and low cyanide concentration should be used as much as possible. The pH and cyanide concentration of each tank are always maintained within an appropriate range.
(5) In the cyanidation leaching process, 0 2 as an oxidant is as important as CN - , and it is necessary to perform oxygenation during the leaching process.
(6) In the selection of process technical parameters, it should pass the more sufficient test and argumentation, refer to the production practice, and consider the comprehensive technical and economic indicators to ensure the technical indicators of the cyanide leaching process are advanced and reasonable.
Deep
groove Ball Bearing
Deep groove Ball Bearings are with the
characteristics of simply designed structures; low friction coefficient and
high limit rotational speed. Their range of application is very wide. They can
mainly carry radial load and certain thrust load. When the radial internal
clearance increased, the bearings have the functions of angular contact ball
bearings that a larger thrust load can also be carried.
Structures
1.
Basic
type 60000
Applications of this type of bearing can be
found in situations where there are no special requirements for mounting and
sealing.
2.
With
one shield (-Z) on one side or two shields (-2Z) on both sides.
The shields are made of steel sheet. Adequate lubricating grease has
been put in the deep groove ball bearings with two shields during assembling
process and there is no need to clean the bearing or add lubricant as mounting.
It is noncontact seal, and compared with deep groove ball bearings with seals,
they have less friction and suitable for applications with high rotational
speed requirement.
3.
With
one seal(-RS)on one side or two seals(-2RS)on both sides
The
seals are made of rubber with steel sheet reinforcement. It is contact sealing
that could seal much better but have high friction and low limit rotation speed
if the seals contact with the outside of the inner ring; while it is
non-contact sealing that has the same limit rotation speed as the basic type. The
lubricant has been prefilled in the bearing with seals both sides, so there is
no need to clean and fill the lubricant as mounting.
With snap ring groove on
the outer ring (-N)
The snap ring can be used to locate the
bearing in the axial direction so that the mounting in the housing is
simplified.
Cage material
Deep groove ball bearings generally use
pressed steel cages or solid cages. Phenol resin cage is suitable for
application with high limit rotational
speed.
Permissible Tilt Angle
Deep
groove ball bearings permit tilting angle between the inner ring and outer
ring. The details are listed in the Table 1.
Tolerance and
Clearance
The tolerance of deep groove ball
bearings is P0 basically. P5, P6, P4 and P2 are available for different
application.
The
radial internal clearance of Deep Groove Ball Bearing is as Table 3.
Dynamic equivalent radial load
Pr=XFr+YFa
Fr-Radial load
(kN)
Fa-Axial load (kN)
X-Radial factor
Y-Axial factor
X and Y values see Table below.
Static
equivalent radial load
P0r=Fr[kN]
P0r=0.6Fr+0.5Fa[kN]
Table
1 Permissible Tilt Angle
|
Radial internal clearance
|
The
permissible angle
|
|
0Basic group
3Group 3
4Group 4
|
8′
12′
16′
|
Table 2 Values
of X and Y
|
Type
of bearing
|
Relative axial load
|
Single row
|
Double row
|
e
|
|
|
|
|
|
|
|
|
X
|
Y
|
X
|
Y
|
X
|
Y
|
X
|
Y
|
|
Deep groove ball bearing
|
0.172
0.345
0.689
1.03
1.38
2.07
3.45
5.17
6.89
|
0.172
0.345
0.689
1.03
1.38
2.07
3.45
5.17
6.89
|
1
|
0
|
0.56
|
2.3
|
1
|
0
|
0.56
|
2.3
1.99
1.71
1.55
1.45
1.31
1.15
1.04
1
|
0.19
0.22
0.26
0.28
0.3
0.34
0.38
0.42
0.44
|
Table 3 Radial internal
clearance of deep groove ball bearing
μm
|
Nominal bore diameter d
mm
|
C2
clearance
|
Standard
clearance
|
C3
clearance
|
C4
clearance
|
C5
clearance
|
|
Over
|
To
|
Min
|
Max
|
Min
|
Max
|
Min
|
Max
|
Min
|
Max
|
Min
|
Max
|
|
2.5
6
10
18
24
30
40
50
65
80
100
120
140
160
180
200
225
250
280
315
355
400
450
500
560
630
710
800
900
1000
1120
|
6
10
18
24
30
40
50
65
80
100
120
140
160
180
200
225
250
280
315
355
400
450
500
560
630
710
800
900
1000
1120
1250
|
0
0
0
0
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
3
3
3
3
10
10
20
20
20
20
20
20
|
7
7
9
10
11
11
11
15
15
18
20
23
23
25
30
35
40
45
55
60
70
80
90
100
110
130
140
160
170
180
190
|
2
2
3
5
5
6
6
8
10
12
15
18
18
20
25
25
30
35
40
45
55
60
70
80
90
110
120
140
150
160
170
|
13
13
18
20
20
20
23
28
30
36
41
48
53
61
71
85
95
105
115
125
145
170
190
210
230
260
290
320
350
380
410
|
8
8
11
13
13
15
18
23
25
30
36
41
46
53
63
75
85
90
100
110
130
150
170
190
210
240
270
300
330
360
390
|
23
23
25
28
28
33
36
43
51
58
66
81
91
102
117
140
160
170
190
210
240
270
300
330
360
400
450
500
550
600
650
|
-
14
18
26
23
28
30
38
46
53
61
71
81
91
107
125
145
155
175
195
225
250
280
310
340
380
430
480
530
580
630
|
-
29
33
36
41
46
51
61
71
84
97
114
130
147
163
195
225
245
270
300
340
380
420
470
520
570
630
700
770
850
920
|
-
20
25
28
30
40
45
55
65
75
90
105
120
135
150
175
205
225
245
275
315
350
390
440
490
540
600
670
740
820
890
|
37
45
48
53
64
73
90
105
120
140
160
180
200
230
265
300
340
370
410
460
510
570
630
690
760
840
940
1040
1150
1260
|
Deep Groove Ball Bearing
Steel Cage Ball Bearing,Brass Cage Ball Bearing,Steel Cage Deep Groove Ball Bearing,Brass Cage Deep Groove Ball Bearing
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