Selection process control (2)

The signal for the ore amount can also be directly taken from the output of the ore belt scale. As shown in Figure 7. In the absence of a computer, a conventional meter can be used instead of a computer.

(C) the ratio of the amount of metal ore to a control dosage collector such as an agent, not only the amount of drug added to the ore, but also to other metals selected from the ore requires about taste. Therefore, it is generally used to control the dosing amount according to the proportion of the metal amount of the ore. As shown in Figure 8. The dosing ratio (dosing amount per ton of metal) can be given manually or according to a certain relationship according to the original ore grade.

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(4) Controlling the dosage according to the amount of metal in the ore and the grade of tailings

The flotation process is more complicated. The two simple feedforward controls mentioned above cannot overcome the influence of other disturbances, and only the medicament can be roughly controlled. Therefore, it must be corrected by other parameters that reflect the effect of flotation. Among these parameters, the most commonly used is the tailings grade. FIG 9 is a block diagram of a control agent of lead zinc flotation employed. It controls the various dosages according to the amount of metal in the ore and the grade of the tailings before feeding. The control formula is:
F ₁ =A _i1 x+B _i1 Zn _t +C _i1 +D ₁₁ E (1)
F ₂ =A _i2 x+B _i2 Zn _t +C _i3 +D _i3 E (2)
F ₃ =A _i3 x+B _i3 Zn _t +C _i3 +D _i3 E (3)
Wherein F _1, F _2, the addition amount of copper sulfate, xanthate and frother F ₃ --- in the time unit;
x———the amount of metal in the ore (zinc);
Zn _t — the (zinc) grade in the tailings;
A _{i1 to i3} , B _{i1 to i3} , C _{i1 to i3} , D _{i1 to i3} — a constant determined according to the type of ore;
E————Additional correction factor for tailings grade;
E=E ₁ +K (4)
Where E ₁ ——— additional correction parameters for tailings grade before 20 min;
K———The correction coefficient of tailings grade, 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.[next]
(V) Controlling the dosage according to 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 the 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 control block diagram of a lead-zinc flotation circuit collector. It is based on a feedback control method.
Carrier original X-ray analyzer, fine tailings grade of zinc Zn _f, Zn _c, Zn _t signal into a process computer, the computer first calculates a new grade ore recovery in accordance with the given value of R _'sp:
R' _sp =[ R' _sp +(Zn _f (n)-Zn _f (n-1)•C) (5)
Where R _sp — the predetermined recovery rate given;
Zn _f (n), Zn _f (n-1)—the nth and n-1th ore grades;
C———experience coefficient (C=6.666)
Then, the actual recovery rate R _{n is} calculated from Zn _f , Zn _c , and Zn _t . The collector addition amount Q _n is calculated as R _n ≥ R' _sp .

Where Q _n ——— the amount of the nth collector added;
Q _n-1 ——— The amount of collector added before the first n-1;
R _sp ———the predetermined recovery rate given value;
R _n , R _n-1 — the recovery of the nth and n-1th times;
aK————Adjust the gain parameter of the system (setting aK=0.01);
I————the coefficient of the adjustment system (setting I=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. [next]
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.

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.

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