| An Electrostatic Precipitator (ESP), or Electrostatic | | | | gas-flow particles. |
| Air Cleaner is a particulate collection device that | | | | The ionised particles, following the negative electric |
| removes particles from a flowing gas (such as air) | | | | field created by the power supply, move to the |
| using the force of an induced electrostatic charge. | | | | grounded plates. Particles build up on the collection |
| Electrostatic precipitators are highly efficient | | | | plates and form a layer. The layer does not |
| filtration devices that minimally impede the flow of | | | | collapse, thanks to electrostatic pressure (given |
| gases through the device, and can easily remove | | | | from layer resistivity, electric field, and current |
| fine particulate matter such as dust and smoke | | | | flowing in the collected layer). |
| from the air stream. In contrast to wet scrubbers | | | | Precipitator performance is very sensitive due to |
| that apply energy directly to the flowing fluid | | | | two particulate properties: 1) Resistivity; and 2) |
| medium, an ESP applies energy only to the | | | | Particle size distribution. These properties can be |
| particulate matter being collected and therefore is | | | | determined economically and accurately in the |
| very efficient in its consumption of energy (in the | | | | laboratory. A widely taught concept to calculate |
| form of electricity). | | | | the collection efficiency is the Deutsch model, |
| The most basic precipitator contains a row of thin | | | | which assumes infinite remixing of the particles |
| vertical wires, and followed by a stack of large | | | | perpendicular to the gas stream. |
| flat metal plates oriented vertically, with the plates | | | | Resistivity can be determined as a function of |
| typically spaced about 1 cm to 18 cm apart, | | | | temperature in accordance with IEEE Standard |
| depending on the application. The air or gas | | | | 548. This test is conducted in an air environment |
| stream flows horizontally through the spaces | | | | containing a specified moisture concentration. The |
| between the wires, and then passes through the | | | | test is run as a function of ascending or |
| stack of plates. | | | | descending temperature or both. Data are |
| A negative voltage of several thousand volts is | | | | acquired using an average ash layer electric field |
| applied between wire and plate. If the applied | | | | of 4 kV/cm. Since relatively low applied voltage is |
| voltage is high enough an electric (corona) | | | | used and no sulfuric acid vapour is present in the |
| discharge ionises the gas around the electrodes. | | | | environment, the values obtained indicate the |
| Negative ions flow to the plates and charge the | | | | maximum ash resistivity. |