New technology and new technology for iron ore electrification

The method of charging the ore particles refers to conduction, induction, corona, and contact friction.
(1) Conductive charged ore particles are in direct contact with charged electrodes. Due to the different electrical properties of the ore particles, the behavior exhibited by the contact with the charged electrodes is also significantly different. Figure 1 shows the behavior of a conductor (indicated by a black sphere) and a non-conductor (indicated by a white sphere) in contact with a charged electrode.

The negative electrode indicates high voltage and the positive electrode indicates ground. After the conductor ore particles are in contact with the charged electrode, the electrode immediately conducts the charge to the ore particles due to its good conductivity, and the ore particles obtain the same electric charge as the electrode symbol, thereby being repelled and attracted to the positive electrode, as shown in FIG. 1B. All the charges are passed away.
Non-conducting ore particles are only poorly conductive due to their own conductivity, and can only be polarized by electric field. The charge cannot be directly transmitted to the ore particles. After polarization, the center of positive and negative charges is shifted. Positive polarity is generated near one end of the electrode, and the other end is generated. Negative electricity, and this charge can not be transmitted away, and once it leaves the electric field, it will return to its original state.
In the 1950s, an experimental type electric separator was produced in the UK. The high-voltage power supply can be directly connected to the drum, so that the mineral can be directly conducted and charged on the drum and sorted.
(2) Inductively charged induction is obviously different from conduction and conduction. Inductive charging is that the ore is not in contact with the electrode and is charged by the induction method, as shown in Figure 2.

After the conductor ore is induced in the electric field, one end of the negative electrode is positively charged and the other end is negatively charged; the non-conducting ore particles are only polarized by the electric field, and the positive and negative charge centers are offset, and the expressed charge is bound charge. And can't be removed. According to the principle of positive and negative electric attraction, the conductor immediately attracts the negative electrode (with electrode). At this moment, both positive and negative electricity are removed by conduction, and then negative charges are transmitted from the negative electrode to be repelled, and finally the ore remains at the same time. Grounded on the pole. If the two electrodes are not parallel plates and the electrodes are sharp, the conductor will attract the tip electrode, and the non-conducting ore particles will remain in the original position. [next]
(3) charged in the corona electric field

The above-mentioned conduction and induction charging are all electrostatic fields, neither of which discharges, but the corona charging is different. It is carried out in a high-voltage corona electric field to generate corona discharge and electron flow. Corona charging plays a very important role in the development history of the whole electrification, which greatly improves the efficiency of electrification. The charging process is shown in Fig. 3. It can be seen from the figure that both the conductor and the non-conductor can obtain the electric charge in the electric field. The conductor ore particles have a large dielectric constant and a large amount of electric charge, but because of their good electrical conductivity, the charge adsorbed on the surface can flow freely on the surface, so that it can be quickly distributed on the surface of the ore particles, as shown in Fig. 3A. Once in contact with the grounding pole, it is instantaneously transmitted to the grounding pole and disappears, as shown in Figure 3B. Although the non-conducting ore particles also acquire electric charges, their conductivity is poor, and even if they enter B, they cannot transfer the adsorbed charges. The charge absorbed by the conductor ore is only 1/40 to 1/1000 second, and the non-conductor ore particles are transported at least 100 or more times longer than the conductor because the charge cannot be transmitted away. It is attracted to the grounding pole. This situation is reflected in the high-voltage electrification, which is advantageous for the separation of conductors and non-conductors.
(4) Charged electric field in composite electric field The so-called composite electric field refers to the electric field combined with the corona electric field and the electrostatic field. One is that the corona electrode is in front and the static electrode is behind; the other is the Carpco electrode in the United States. The corona pole is mixed with the static electrode, and FIG. 4 shows two electrode structures.

In the case of a in Fig. 4A, both the conductor and the non-conductor ore are charged first in the corona field, but as the ore moves forward, it is immediately subjected to the action of the static electrode, and after the conductor transfers the charge, it is subjected to the static electrode. Inductively charged and attracted to the direction of the static electrode; non-conductor is different, because the absorbed charge can not be transmitted away, subject to the repulsive force of the static electrode, the ore is pressed against the grounding pole (drum surface or plane pole), obviously both The motion trajectory is very different, so it is shown as b in Figure 4A.
The characteristics of the US Capu Electrode are to strengthen the role of the electrostatic field, which enhances the attraction of the static electrode to the conductor, and strengthens the repulsive force to the non-conductor, so that it is attracted to the drumhead. [next]
(5) Friction and electrification
Frictional charging is to charge the ore particles by contact, collision and friction. One is that the ore particles and the ore particles rub against each other to obtain different symbols of charge; the other is that the ore particles collide with a certain material (including rolling) to charge them. This method was invented earlier, but it was not really used for mineral processing . The root cause of frictional collisions with each other, from the study of scholars in various countries, has a very clear conclusion, that is, due to the transfer of electrons. The mineral particles with large dielectric constant have high hope energy, are easily polarized, and are easy to dry. The outer electrons are given; otherwise, the lower dielectric constant has a lower energy level, is difficult to polarize, and is easy to accept electrons. The ore particles given electrons are positively charged, and the ore particles receiving electrons are negatively charged. Figure 5 is a schematic diagram of the frictional charging of two kinds of ore particles. After the friction between the two ore particles, the energy of a ore is high, giving Electron, positively charged, b ore has low energy, electrons, and negative electricity. It must be pointed out that not all minerals can be frictionally charged, but both minerals are non-conducting minerals, and both There is a significant difference in dielectric constant in order to generate electron transfer and maintain charge; two non-conductor minerals with the same dielectric constant have difficulty in generating charge due to their same energy level, and cannot be sorted by frictional charging; conductor Collision and friction with the conductor particles can also generate electric charge, but it cannot be maintained. This is because the charge has been lost before sorting, so it cannot be sorted by this method.

R. Beach suggested that if the ore particles rub against each other, the surface charge density obtained by each grain must be greater than 26.6 × 10 ^-6 Coulomb / m ² , otherwise the charge is difficult to maintain, and can not be used for frictional electrification.
After the various minerals are in contact with each other, they are charged with different symbols.
Minerals are triboelectrically charged with different materials, which refers to the charge that is rubbed against the ore tank to produce different symbols.

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