Electrostatic precipitators – general information

Air Pollution Control by Filtering Dust Particles from Combustion Gases Resulting from Burning Solid Fuels

Gases resulting from the burning of solid fuel in a furnace contain many dust particles. When the chimney releases these gases into the atmosphere without filtering the dust particles, the atmosphere can become polluted. Therefore, in applications utilizing the combustion of fuels, special filters are used to remove dust particles from the exhaust gases as much as possible before they are released into the atmosphere. This way, we can control air pollution. An electrostatic precipitator performs this task for furnace systems. This device is installed in the path of the exhaust gases from the furnace to the chimney so that it can filter the gases before they enter the chimney.

Principle of Operation of Electrostatic Precipitators

The operation of an electrostatic precipitator is quite simple. The filter has two sets of electrodes - one positive and one negative. The negative electrodes are in the form of rods or wire meshes. The positive electrodes are plates. The positive plates and negative electrodes are arranged vertically in the precipitator alternating with each other. The negative electrodes are connected to the negative terminal of a high-voltage DC power source, while the positive plates are connected to the positive terminal of the DC power source. The positive terminal of the power source can be grounded to achieve a stronger negative voltage on the negative electrodes.

The distance between each negative electrode and the adjacent positive plate, and the applied DC voltage, are chosen so that the voltage gradient between each negative electrode and the adjacent positive plate becomes large enough to ionize the medium between them. The medium between the electrodes is air, and due to the high negativity of the electrodes, corona discharge may occur around the electrode rods or wire mesh. Air molecules in the field between the electrodes become ionized, so this space will have a large number of free electrons and ions.

The entire system is enclosed in a metal container, with an inlet for the exhaust gases on one side and an outlet for the filtered gases on the other. As soon as the exhaust gases enter the electrostatic precipitator, the dust particles contained in the gases collide with the free electrons available in the medium between the electrodes, and free electrons attach to the dust particles. As a result, the dust particles become negatively charged. These negatively charged particles are then attracted to the positive plates by electrostatic force.

Consequently, the charged dust particles move toward the positive plates and settle on them. Here, additional electrons from the dust particles are removed on the positive plates, and the particles fall due to gravity. The positive plates are called collecting plates. The exhaust gases, after passing through the electrostatic precipitator, become almost free of ash particles and are ultimately discharged into the atmosphere through the chimney. The electrostatic precipitator does not directly contribute to the production of electrical energy in a thermal power plant but helps maintain atmospheric cleanliness, which is very important for living organisms. Below the electrostatic precipitator, there are hoppers for collecting dust particles. To speed up dust removal from the collecting plates, water modules can be applied at the top.

Features and Applications of Electrostatic Precipitators

Advantages of Electrostatic Filters

• Continuous dust removal from significant amounts of flue gases;
• High filtration efficiency due to low gas mixture flow resistance;
• High efficiency - up to 99%;
• Filtration of gases at high temperatures.

Disadvantages of Electrostatic Filters

• Need for additional safety measures or more expensive solutions due to the risk of flammable gases igniting;
• High production costs;
• Large size of the filters;
• Sensitivity to environmental changes and exhaust gas characteristics - temperature, humidity, resistivity.

Applications of Electrostatic Filters

• Dust removal from coal-fired boilers;
• Dust removal from metallurgical processes, e.g., ore sintering;
• Dust removal and degreasing of raw gas in coke ovens;
• Dust removal from gases in cement plants;
• Dust removal from exhaust gases in coal-fired power plants.

High-Voltage Power Supply Service for Electrostatic Filters

DACPOL Service offers professional high-voltage power supply service for electrostatic precipitators, including startup, maintenance, and repair. With years of experience with the high-voltage power supply manufacturer NWL, we provide comprehensive service for NWL PowerPlus and other power supplies available on the market. More information can be found on our website in the SERVICE, REPAIRS section.
If you have any questions, please feel free to contact us directly!