In fact, there are three main factors affecting the dust removal effect of electrostatic precipitators: dust specific resistance, gas dust concentration and air flow speed. The dust removal efficiency of the electrostatic precipitator is described in detail below:
1 Dust removal efficiency: dust specific resistance
First, electrostatic precipitator dust removal efficiency - the specific resistance of dust
The dust with a specific resistance of 104 to 1011 Ω·cm has a good electrostatic dust removal effect. When the dust specific resistance is less than 104 Ω·cm, because the dust has good electrical conductivity, after reaching the dust collecting pole, the negative charge is released at a high speed, and it is very easy to induce a positive charge which is very similar to the dust collecting, because the same sex repels the dust. The composition moves along the outer surface of the plate, and the dust removal efficiency is also reduced.
When the dust specific resistance is greater than 1011 Ω·cm, the dust releases a negative negative charge, and a strong electric field strength is formed in the dust layer to ionize the air in the dust open space, presenting a re-corona appearance. The positive ions neutralize the negative ions during the movement of the negative electrode, and the dust removal efficiency is lowered.
The specific resistance is lower than 104 Ω·cm, which is called a low resistance type. This type of dust has a good electrical conductivity. When the charged dust particles reach the dust collecting pole, they will quickly release the negative electric charge, and at the same time, the electrostatic charge will obtain the positive electric charge with the same dust collecting.
If the repulsive force of the positive charge is greater than the adhesion of the dust, the accumulated dust particles will escape from the dust collection and return to the airflow. After the dust particles are hit by negative ions in the space, they take a negative charge from the head and move to the dust collecting pole. In this way, a lot of dust jumps along the surface of the plate and is finally carried out of the dust collector by the air flow. Electrostatic Precipitator disposal of metal dust, carbon black dust, graphite dust can see this phenomenon. A dust type specific resistance of 104 to 1011 Ω·cm is called a normal type. When this type of dust reaches the dust collecting pole, it will discharge the charge at a normal speed. Electrostatic precipitators for such dusts (such as boiler fly ash, cement dust, open hearth dust, limestone dust, etc.) usually achieve good results.
The dust specific resistance exceeds 1011~1012 Ω·cm, which is called high resistance type. After the high specific resistance dust reaches the dust collecting pole, the charge release is very slow, so that the dust collecting pole gradually accumulates a layer of negatively charged dust layer. Because of the same sex, the speed of the subsequent dust particles is slowed down. With the addition of the thickness of the dust layer, a large voltage drop ΔU is formed between the dust layer and the plate. Ways to overcome the impact of high specific resistance include: strengthening the rapping to keep the appearance of the plate clean; improving the power supply system, including the use of pulse power supply and an effective automatic control system; adding flue gas humidity, or adding SO3, NH3 to the flue gas and The Na2CO3 and the like increase the conductivity of the dust particles.
2 dust concentration in gas
The dust concentration is too high, the dust hinders the movement of the ions, and the corona current decreases. When it is severe, it is zero, corona is blocked, and the dust removal effect is drastically deteriorated.
There are two kinds of electric charges in the electrostatic precipitator, one is the charge of ions, and the other is the charge of charged dust particles. The movement speed of ions is also higher, about 60~100m/s, while the moving speed of charged dust particles is lower, usually below 60cm/s. Therefore, when the dust-containing gas passes through the electrostatic precipitator, the amount of charge carried per unit time is less than that when the air is cleaned, that is, the corona current at this time is small. If the dust concentration of the gas is very high, a large amount of fine dust particles are suspended in the electric field, which may cause the electrostatic precipitator to worry about a sharp drop in the halo current. In severe cases, it may approach zero. This condition is called corona blocking.
In order to avoid the occurrence of corona clogging, it is necessary to take certain measures when dealing with gases with high dust concentration, such as increasing the working voltage, selecting a corona pole with intense discharge, and adding pre-purification equipment. When the dust concentration of the gas is 30 g/m3, it is necessary to provide a pre-cleaning device.
3 air velocity
As the airflow speed increases, the dust removal efficiency decreases. The reason is that the wind speed increases, the time for the dust to stay in the dust collector is shortened, and the timing of charging decreases. At the same time, the secondary dust increase will increase as the wind speed increases.
The magnitude of the electric field wind speed has a great influence on the dust removal efficiency. When the wind speed is too large, it is easy to generate secondary dust, which reduces the dust removal efficiency. However, the wind speed is too low, the electrostatic precipitator is bulky, and the investment is also increased. According to previous experience, the electric field wind speed should not exceed 1.5~2.0m/s, and the dust collector with high dust removal efficiency should not exceed 1.0~1.5m/s.
In summary, this article has explained the relevant situation of the dust removal efficiency of electrostatic precipitators. I believe that everyone's understanding is getting deeper and deeper. I hope this article can have a relatively large reference value for readers.
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