Figure 9 Â Dosing amount of block diagram according to the amount of metal ore and tailings grade control
F 1 =A i1 x+B i1 Zn t +C i1 +D i1 E Â
(1)
F 2 =A i2 x+B i2 Zn t +C i2 +D i2 E
(2)
F 3 =A i3 x+B i3 Zn t +C i3 +D i3 E
(3)
Wherein F 1, F 2, F 3 - the amount of added copper sulfate, xanthate and frother per unit time;
X——the amount of metal in the ore ( zinc );
Zn t - the (zinc) grade in the tailings;
- a constant determined according to the type of ore; E——Additional correction factor for tailings grade:
E=E 1 +K
(4)
Where E 1 is the additional correction parameter for the tailings grade before 20 min;
K - the tailing grade correction factor, determined according to the given tailings grade and 40, 20 minutes ago and the current tailings grade, actually reflects the trend of tailings change, its value is 1,0, -1.
5. Control the dosage according to the recovery rate and concentrate grade
The useful mineral content in tailings can reflect the effect of flotation operation to a certain extent, but when the mineral properties change, it does not guarantee that the flotation process reaches a predetermined index. Therefore, it is necessary to further control the amount of the drug directly according to the recovery rate and the concentrate grade.
Figure 10 shows a block diagram of a control circuit collector lead-zinc flotation agent. It is based on the feed-feedback control method.
Figure 10 Â Lead-zinc mine flotation circuit collector control block diagram [next]
Carrier original X-ray analyzer, fine tailings grade of zinc Zn f, Zn c, Zn signal into a process computer, the computer first calculates a new grade ore recovery in accordance with the given values:
R ′ sP =[R SP +(ZN ƒ (n)-Zn ƒ (n-1).C )]
(5)
Where R SP is the predetermined recovery rate given;
Zn Æ’ (n), Zn Æ’ (n-1) - the nth and n-1th ore grades;
C——experience factor (C=6.666).
Then, the actual recovery rate R n is calculated from Zn f , Zn c , and Zn t . If R n ≥ , the additive addition amount Q n is calculated by the formula (5).
(6)
When R n <R ′ sp , the amount of the additive added is calculated by the formula (7).
Q n = {Q n-1 +Q n-1 [aKI(R sp +Zn f (n)-Zn f (n)-Zn f (n-1).C]}
(7)
Where Q n - the nth amount of collector added;
Q n-1 - the amount of collector added in the previous n-1th operation;
R SP - the predetermined recovery rate given;
R n , R m-1 - recovery of the nth and n-1th times;
aK——the gain parameter of the adjustment system (setting aK=0.01);
I——the coefficient of the adjustment system (setting l=3);
Zn sp - the given value of the Zn grade in the concentrate;
Zn C - the grade of Zn in the nth concentrate.
Adjustment limits are provided throughout the system. When the calculated added amount exceeds the limit value, the computer notifies the operator. In addition, a certain dead zone is usually specified near a given value to avoid oscillation of the regulation loop due to some ambiguous error.
Third, the flotation tank liquid level control
The flotation cell level is used to control the flotation index. During the flotation process, the upper grade of the concentrate foam is the highest, and the lower the grade, the lower the grade. Thus, when the level of the flotation tank increases, the amount of foam scraping increases, the recovery rate is high, but the concentrate grade decreases. The grade of tailings also declined. Therefore, the flotation index can be controlled by adjusting the level of the flotation tank. Figure 11 is a flow chart showing the use of flotation cell level to control the tailings grade. In the system, the feedback control is used to compare the tailings grade measured by the X-ray analyzer with the given tailings grade, and the difference is calculated according to the algorithm I to calculate the required tank level change, and control the tailings discharge. Valves to maintain liquid level stability and required tailings grade. Here, if the tailing grade parameter and the corresponding algorithm I are replaced by the concentrate grade, the system can also realize the concentrate grade control.
Figure 11 Using the flotation cell level to control the tailings grade block diagram [next]
The detection of the level of the flotation tank is mostly carried out by a float type liquid level gauge or a blown liquid level gauge. The surface of the buoy is coated with paint and placed in a cylinder to reduce the influence of fluctuations in the liquid level in the tank on the buoy. It is preferable to have a water spray cleaning device.
Fourth, centrifugal concentrator control
According to the nature of ore and slurry, it is reasonable to control the rotating speed of the centrifuge drum and the beneficiation cycle to obtain better beneficiation quality. In the automatic design of ore dressing, considering the variability of ore properties, PM550 programmable controller (PC) is used as the sequence control device of the centrifuge.
1. Centrifugal beneficiation and control principle
Figure 12 is a schematic view showing the structure of centrifuge beneficiation. According to different density and particle size, the sedimentation rate of the ore particles in the radial direction is different under the centrifugal force, so that the useful minerals are settled on the centrifuge chamber wall, and the useless minerals are discharged to separate the useful minerals from the useless minerals.
Figure 12 Schematic diagram of centrifuge beneficiation
F Vd — broken mine solenoid valve; F Vc — mine solenoid valve; F VF — mine solenoid valve
The radial settling velocity of the mineral under the action of centrifugal force is
Dr D 2 ( Ï s - Ï )
---=------------ ω 2 r
Dt 18 μ
(8)
Where r is the ore particle size moving distance;
D——the diameter of the ore;
Ï S - mineral density;
Ï - pulp density;
Ω——centrifuge drum angular velocity;
—— - viscosity of the ore flow.
In engineering, the drum angular velocity ω is determined by the speed of the drive motor. Therefore, in the case of a certain nature of the ore flow, the time for the ore to enter the sedimentation zone is
18μ r 2
t=--------------ln---
D 2 ω 2 (Ï s -Ï) r 1
(9)
As the slurry flows into the centrifuge, mineral particles deposit on the walls of the centrifuge chamber. If the ore feeding time is too long, the sedimentation layer will be too thick, which will deteriorate the ore dressing quality; if the ore feeding time is too short, the processing volume will be reduced, and the centrifuge efficiency cannot be exerted. Therefore, the centrifuge beneficiation is a process of periodically feeding the mine → breaking the mine → dividing the ore, rushing the mine, and re-feeding the ore. The process time is determined by the nature of the slurry and the drum speed of the centrifuge.
2. Control device selection
For a long time, each concentrator has used photoelectric disc or time relay to control the solenoid valves in each process of the centrifuge. When the nature of the ore flow changes frequently, these two methods have large disadvantages. Once the equipment is installed, it is difficult to change the control time; the adaptability and reliability are poor. [next]
Although the performance of the Z80 single-board machine program control device has been improved, the number of intermediate links has increased and the programming is complicated.
The development of PC technology provides a new and effective method for centrifuge control. The PM550 programmable controller is selected here.
3. Control programming
In order to balance the power supply to the ore pump, 16 roughing and 8 sweeping centrifuges were divided into 8 groups according to time, and 12 selected centrifuges were divided into 6 groups for control. The sweep control program is shown in Figure 13.
Figure 13 Centrifuge grouping control timing diagram
The working cycle of each (group) centrifuge is programmed according to the ladder diagram. Taking the first roughing centrifuge as an example, the program ladder diagram is shown in Fig. 14.
Figure 14 Centrifuge sequence program ladder diagram
In the program design, the solenoid valve malfunction diagnosis link is considered. I.e. each activation of the solenoid iron before the test operation state of the centrifuge, when the centrifuge is running, the solenoid valve is turned on delay; if the centrifuge is stopped, the solenoid valve is de-energized.
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