ESP Knowledge

Industries Process Material Collected Potential Problems
Cement Plants Cement Kiln

Cement Raw Mill

Cement Cooler

Cement Powder

(Mixtures of Limestone,  Calcium, Iron, Silica, Alumina, Sulfate)

The temperature of exit gas increased and the dew point lowered result in increasing the dust resistivity.
Pulp & Paper Recovery Boilers Fly ash:Sodium sulfate (Na2SO4 )

Black Liquor

Low resistivity of dust encourages re-entrainment problems and spark occurrence.
Smelters Smelting


Dry dust from ore production

(Copper, Iron Oxides, Sulfur concentrate)

Waste gas contains high-acid dew point temperature which leading to sticky dusts and corrosion.

(Utility Boilers)

Burning fossil fuels(coal) Coal Fly Ash Low sulfur coals has high resistivity fly ash

High sulfur coals has low resistivity fly ash





Wood chips

Rice Husks

Biomass Fly Ash Unburned Carbon possibly to clogged GD or Hopper

High moisture of dust results in low resistivity

An electrostatic precipitator is a large, industrial emission-control unit. It is designed to trap and remove dust particles from the exhaust gas stream of an industrial process. Precipitators are used in these industries

  • Power/Electric
  • Cement
  • Chemicals
  • Metals
  • Paper

In many industrial plants, particulate matter created in the industrial process is carried as dust in the hot exhaust gases. These dust-laden gases pass through an electrostatic precipitator that collects most of the dust. Cleaned gas then passes out of the precipitator and through a stack to the atmosphere. Precipitators typically collect 99.9% or more of the dust from the gas stream.

Precipitators function by electrostatically charging the dust particles in the gas stream. The charged particles are then attracted to and deposited on plates or other collection devices. When enough dust has accumulated, the collectors are shaken to dislodge the dust, causing it to fall with the force of gravity to hoppers below. The dust is then removed by a conveyor system for disposal or recycling.

Electrostatic precipitation removes particles from the exhaust gas stream of an industrial process. Often the process involves combustion, but it can be any industrial process that would otherwise emit particles to the atmosphere. Six activities typically take place:

  • Ionization – Charging of particles
  • Migration – Transporting the charged particles to the collecting surfaces
  • Collection – Precipitation of the charged particles onto the collecting surfaces
  • Charge Dissipation – Neutralizing the charged particles on the collecting surfaces
  • Particle Dislodging – Removing the particles from the collecting surface to the hopper
  • Particle Removal – Conveying the particles from the hopper to a disposal point

The original parallel plate–weighted wire design (described above) has evolved as more efficient (and robust) discharge electrode designs were developed, today focusing on rigid (pipe-frame) discharge electrodes to which many sharpened spikes are attached (barbed wire), maximizing corona production. Transformer-rectifier systems apply voltages of 50 – 100 kV at relatively high current densities. Modern controls, such as an automatic voltage control, minimize electric sparking and prevent arcing (sparks are quenched within 1/2 cycle of the TR set), avoiding damage to the components. Automatic plate-rapping systems and hopper-evacuation systems remove the collected particulate matter while on line, theoretically allowing ESPs to stay in operation for years at a time.

Table : Design criteria for ESP

Characteristic Typical value
Operating voltage 10-100
Gas flow (m3/hr) <10,000 to > 2,000,000
Gas velocity (m/s) 0.3 to 3
Gas temperature (˚C) Up to 450˚C
Dust loading (g/m3) Up to 100
Collecting efficiency (%) 95 to 99.9
Pressure drop 50 to 300
Power consumption (kWhr/1000m3) 0.05 to 2
Particle size (μm) All, with a minimum collection efficiency at 0.5 to 2
Dust resistivity (Ω∙cm) 10e4 to 10e11 (preferred value)
Dust migration rate (cm/s) 2 to 30