151017961-Experiment-4-Electrostatic-Precipitator.docx -...

EXPERIMENT 4
ELECTROSTATIC PRECIPITATOR
1.0 OBJECTIVES:
To demonstrate the electrostatic precipitator working principle.
To evaluate the effect of input velocity against separation efficiency and effect of particle size
on separation efficiency.
2.0 INTRODUCTION:
Electrostatic precipitator is a device designed to reduce particulate emissions in the exhaust
gas stream of an industrial application. It can collect particles with diameter of 0.1pm to
10.0pm, with a high efficiency (99%). An electrostatic precipitator contains some main
components listed as follows:
- An insulated and lagged shell
- Collection plate or tubes
- Discharge electrodes
- Collection plate rappers/electrode vibrators
- Hoppers
- Electrical system
Precipitators function by charging the dust particles in the gas stream electrostatically with
discharge electrode. The discharge electrode is a small diameter metal wire, used to ionize
the gas. A strong electric freld will then be created. The charged particles are attracted to and
deposited on flat collection plates or tubular collection electrode with an opposite charge
relative to that of the discharge electrode. The strength of the electric field between the
discharge and collection electrodes is controlled by the electrical system consists of high
voltage component. When enough dust has accumulated, the rapper imparts a vibration to
the collectors to dislodge the collected dust, causing it to fall with the force of gravity to
hoppers below. Hoppers are used to temporarily store the dust. The dust is then removed by
a conveyor system for disposal or recycling.

There are various sizes, types and designs of electrostatic precipitators depending on the
specified dust characteristics and the gas volume to be treated. For large power plants, it
may actually have multiple precipitators.
Types of Precipitators
There are two main types of precipitators:
- High-Voltage, Single-Stage : ionization and collection steps are combined. They are
commonly referred to as Cottrell precipitators.
- Low-Voltage, Two-Single : the ionizing section is followed by collection plates.
The high-voltage, single-stage precipitator is widely used in minerals processing operations
while the low-voltage, two-stage precipitator is generally used for filtration in air-conditioning
systems.
The two major types of high-voltage precipitators currently used are:
Plate : this is the majority of electrostatic precipitators installed. The collection electrodes are
flat, parallel surfaces that are 8 to 12 in. apart. A series ofdischarge electrodes spaced along
the centerline of two adjacent plates. The particles will'be discharged when the contaminated