An industrial electrostatic precipitator, also known as ESP, is a device used for filtration of flowing gas are extremely important parts of thermal power plants nowadays because of ever-increasing concern about environmental pollution. It uses a high-intensity electric field to ionize the dust particles in the air stream and then these particles are collected by electrodes and later these particles are removed. But there are certain factors that can affect the performance of electrostatic precipitator and if you know them you can manage them well.
Functioning of the industrial electrostatic precipitator
Fine particles of dust and smoke are removed with the help of electrostatic charge. While wet scrubbers apply direct energy to the flowing medium, an electrostatic precipitator applies energy only to the particles being collected. An ESP consists of collecting plates and discharge wires. The discharge wires are subjected to a high voltage, creating an electrical field with the collecting plates. The gas around the discharge wires thereby gets ionized to supply ions. The aerosol particles in the gas that flows between the discharge wires and collecting plates get ionized and are collected by the collecting plates thus producing purified gas. The particles accumulated at the collecting plates are then removed by a number of methods such as:
- Scrapping by brush
- Dislodging by rubbing the collecting plates
- Water wash
There are a number of factors that can affect the performance of an industrial electrostatic precipitator in terms of its dust collection efficiency
- Dust has electrical resistivity properties: Dust collection efficiency is expected to be high in the area where there is normal resistance. Most aerosols fall under the category of normal electrical resistivity. Particles belonging to the low resistivity group show a loss of charge as they reach the collecting plates, thereby reducing the dust collection efficiency to a great extent. As the electrical resistivity increases, the dust collection efficiency of the industrial electrostatic precipitator decreases. There is also the chance of partial discharge from the dust collected at the collecting plates, resulting in frequent flashovers. As a result, there is a reduction in the applied voltage an also in the discharge current. Further increase in the electrical resistivity of the dust particles increases the discharge current to an abnormal range, thereby reducing the applied voltage, a phenomenon called the back corona. A recent development, termed as the moving electrode electrostatic precipitator is apt for high resistivity dust collection.
- Dust particle size to be collected: The collection efficiency of an industrial electrostatic precipitator is also determined by the size of the dust particles in the aerosol. Theoretically speaking, the velocity at which a particle travels towards the collecting plate is nearly directly proportional to the diameter of the particle. Hence, during a dust collection operation on an aerosol containing a variety of particle sizes, the collection efficiency of the electrostatic precipitator will be high for particles that are larger and lower for the smaller sized particles. In order to obtain optimum dust collection efficiency for small particle aerosol, the industrial electrostatic precipitator must be of a size to increase the time taken for the gas to pass through the unit, as compared to large particle aerosols.
- Concentration of the aerosol: The collection efficiency is highly affected by the concentration of the particles in the gas that need to be collected. With an increase in the concentration of particles in the aerosol at the inlet of the precipitator, the treating time of the gas in the industrial electrostatic precipitator unit increases. Also, with high aerosol concentration at the inlet and concentration of finer particles is high; the creation of a cloud of charged particles between the collecting plates and the discharge wires is facilitated by reduction of the corona discharge from the discharge wires.
If industrial electrostatic precipitator is installed with careful planning, it can bring a lot of advantages to the plant in the long run along with the removal of wet and dry pollutants.
Contributed by https://vortexeng.co.nz/