The selection process control includes automatic control of process parameters such as flotation, reselection, and magnetic separation.
The flotation process control is controlled according to the optimum process conditions and given parameters required by the flotation process. Its purpose is to: a stable flotation, flotation process to achieve optimized to get qualified concentrate grade, increase the recovery of useful metals, reduce the consumption of raw materials such as flotation reagent and, ultimately, the best technical and economic indicators . To this end, it is necessary to control the main process parameters such as flotation amount, slurry pH value, flotation tank level, and flotation machine aeration amount. In addition, process parameters such as slurry concentration, slurry temperature, foam layer thickness, and chute water addition can also be used as control parameters.
Flotation process control in the 1960s began using a local single-loop - stability control; to the end of the 1960s, X-ray fluorescence analyzer has become the core equipment beneficiation plant automation; since the 1970s, big changes in mineral properties The concentrator uses a multivariate control method. In recent years, due to the electronic computer entering the flotation process control, the level of beneficiation automation has been greatly improved.
Automatic control such as re-election and magnetic separation is applied less, and most of them are combined with equipment to form stand-alone control. This chapter focuses on the flotation process control, explaining the re-election examples, supply and design reference.
I. Flotation slurry pH control
The pH value of the flotation pulp has a great influence on the flotation index. The mineral can only be fully floated or suppressed at a suitable pH value; the agent can only play a sufficient role below the suitable pH value. Therefore, the pH of the flotation slurry must be automatically controlled.
There are usually two ways to control pH:
(1) Constant adjustment to keep the pH constant. This is a method that is more commonly used in some domestic factories. The pulp pH automatic adjustment system shown in Fig. 1 is composed of PHGF-13 acidity transmitter, PHG-21A industrial acidity meter, electronic potentiometer, regulator, servo amplifier, actuator and the like. The regulating valve is an open type diverting valve, which can clean the sludge in the valve at any time and can always keep the lime milk unblocked. Another type of pH automatic adjustment system is shown in Figures 2 and 3. The system features a sampled time regulator in the conditioning system. The entire adjustment process is intermittently performed, thereby overcoming the overshoot and oscillation caused by the long delay time of the adjustment object; the lime milk concentration is automatically adjusted to keep the concentration of the lime water constant. The concentration measurement of lime milk was carried out by electro-mechanical method. The pH detection and control can also be used with the Model 8701 pH Detector with Microcomputer. It has pH detection and control functions, and has an electrode automatic cleaning device, which is more suitable for pH detection and control of pulp.
Figure 1 pH adjustment system block diagram
Figure 2 Flow chart of pH adjustment process [next]
Figure 3 pH adjustment block diagram
(2) Track the changes in ore properties and adjust the pH value in time to obtain better flotation indicators. For example, in the process of copper- nickel mixed flotation, the pH is adjusted to achieve the maximum possible recovery. The system uses a statistical "trying method" based tuning algorithm (EVOP) to find the best operating point. It uses a time-sharing computer control program to automatically change the given value of the pH with a predetermined statistical model, so that the flotation process enters a new stable operating state, and then analyzes the original, fine, and The grade of the tailings, and calculate the recovery rate, compare it with the previous recovery rate to determine the direction and value of the next pH set value to achieve the best recovery rate. This exploration process is continuous. of. Usually every 6 minutes.
When installing the pH control system, pay attention to the choice of the pH meter probe installation position. Do not install it too close to the place where the lime is added so that the lime milk has not been thoroughly mixed with the slurry for the probe; it is not too far apart, increasing the lag time of the adjustment object. The representativeness of the test point should be considered, which reflects the pH of the entire subject.
Second, flotation and dosing control
The amount of dosing in the flotation process directly affects the flotation index. It is still the main control for most non-ferrous metal flotation plants to control the flotation process. Regulating the dosing volume of flotation operations can capture more useful metals and inhibit unwanted minerals, which is an important way to ensure flotation indicators. On the other hand, the amount of the drug is easily controlled, and the method is simple, and thus the drug adjustment is used as the main control means. Here are two ways to control the amount of flotation. One is to use a microcomputer-based dosing machine to achieve regular dosing. One is to use a current-carrying analyzer (or a semi-in-line analyzer) to calculate the corresponding dosing amount by measuring the metal grade and to control it. At the same time, it can control the dose of 5~48 points, and the effect is remarkable, which can improve the recovery rate of metal and save a lot of medicine.
1. Microcomputer dosing machine
The microcomputer dosing machine controls the on-off time of the solenoid valve to achieve timing and quantitative dosing for a plurality of dosing points, such as 48 points, and displays relevant parameters of each dosing point on the CPT screen. This improves the dosing control, and the set values ​​can be modified in time according to the changes in the process parameters during the dosing process. There are WG-10, BBH-1, DGY, WGY-1, WGY-2 and other types of dosing machines in China.
For example, the BBH-1 type dosing machine is composed of a quantitative bottle device controlled by a solenoid valve, a TP-801B single board machine, a CRT display and a printer.
The solenoid valve and the metering bottle device are shown in Fig. 4, which is the actuator of the dosing machine, and the flotation agent solution is stored in the drug storage box at a certain height. The siphon connects the reservoir to the dosing bottle via a solenoid valve. When the solenoid de-energized, the discharge solenoid drop tube blockage drug, drug kits rely on fixed pressure reservoir liquid level, the agent through the siphon, the electromagnetic valve flows quantitative bottles until full. The volume of the vial of the vial is determined based on the amount of the medicament and the level of the medicament in the reservoir. When the solenoid valve is energized, the electromagnet is lifted, and the siphon tube at the upper end of the solenoid valve is blocked, and the medicament in the medicine storage tank cannot flow out. The outlet of the lower end of the solenoid valve is opened, and the medicament in the metering bottle flows into the discharge tube through the solenoid valve and enters the flotation tank.
Three PIO chips are connected by using three output terminals of PSO, PS5 and PS6 of TP-801 single board I/O decoder. When the PIO is output as mode O, the three PIOs have a total of 48 outputs and are connected to 48 solenoid valve drive circuits. When an output of the PIO is set to "1", the output is high (+3.6 volts), the solenoid of the solenoid is energized by the driver, and the electromagnet is lifted. When the output of a certain point of PIO is “0â€, the output is low level (0 volts), the solenoid valve coil is de-energized, the electromagnet falls to block the discharge tube, and the quantitative bottle starts to charge again. The block diagram is shown in Figure 5. [next]
Figure 4 Â Executive agency
1. valve body; 2. coil; 3. iron core; 4. glass ball; 5. quantitative bottle; 6. rubber stopper; 7. hard plastic tube;
8. Siphon; 9. Funnel; 10 overflow storage tank; 11. Medicine box; 12. Return pump
Figure 5 circuit block diagram
Figure 6 Â Controlled dosing flow chart according to the amount of ore
G. slurry flow meter; D. slurry concentration meter; PT. differential pressure transmitter; ST. square opener; FC. flow regulator [next]
The single board machine displays the relevant data of the dosing on the CRT screen. The dosing amount per minute per minute and the cumulative dosing amount in 8 hours are printed every 8 hours.
The dosing time of this method can reach 0.1 second, and the dosing precision can reach 0.1 ml.
2. Control the dosage according to the proportion of ore in the ore.
This is the simplest way to control, as shown in Figure 6. The computer converts the flow rate and concentration signal of the ore slurry into the dry ore volume of the ore, and calculates the required amount of the medicament according to the dry ratio and the predetermined ratio (dosage per ton of ore) as a given value of the flow regulator. The medicament is adjusted by the regulator, and the medicament is dispensed through the dispenser to the dosing point of each flotation cell group. With this control method, the concentration of the drug should be kept constant, otherwise the concentration compensation should be performed. The liquid level of the reservoir and the pressure of the reagent circulation circuit need to be kept constant.
The signal for the ore amount can also come directly 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.
3. Control the dosage according to the proportion of metal in the ore
Figure 7 Â According to the amount of controlled dose control
G. slurry flow meter; D. slurry concentration meter
Figure 8 Â Block diagram of the amount of drug controlled by the amount of ore metal
For a drug such as a collector , the added amount is not only related to the amount of ore, but also related to the metal grade required in the ore. 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.
4. Control 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 metal amount of the ore and the feed-feedback mode of the tailings grade. The control formula is:
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