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Home >> Electrostatic Precipitators >> What are they?

ESPs - What are they?        

Introduction

An electrostatic precipitator (abbreviated to "ESP" or "EP" or "precip"), is a particulate collection device that removes particles from a gas stream using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices that operate at a very low pressure drop, and can easily remove fine particulate matter such as dust and smoke from the air stream. In contrast to wet scrubbers and fabric filters, which apply energy directly to the flowing fluid medium, an ESP applies energy only to the particulate matter being collected and therefore is very efficient in its consumption of energy (in the form of electricity).

Basic process

A very high voltage (typically 40,000 to 110,000 Volts) is developed across an air gap between a discharge electrode (in blue opposite) and a flat metal collecting surface or plate (in red). The process gases (laden with dust) pass between these collecting surfaces and in so doing passes through the highly energised electric field.

The dust particles are then charged negatively by cascading electrons and gas molecules. The strong electrical field then drives the dust to the collecting plates where it's deposited.

(picture courtesy Wikipedia)

ESPbasic

Identifying different components

DryESP
Styles of Discharge Electrodes
DEs
CS1
CS2
Collecting Plates
Typically 4.5m - 15m long by 400mm - 800mm wide.

Factors affecting ESP performance

In performance of an ESP can be affected in one three general areas:

1. Mechanical

There are many mechanical issues which affect the performance on an ESP.  Firstly, the spacings between high voltage wires and (grounded) collecting plates is critical. An electrical field within an ESP will only create as much voltage as the closest clearance between high voltage and earth will allow.

Also poor or damaged mechanical rapping will cause decreases in collection efficiency and increased emissions.

2. Electrical

An electrostatic precipitator is a dynamic device that constantly changes during operation.  Unless your control system is closely following these changes you will not be achieving your maximum collection efficiency.

As microprocessors have increased in speed over the past 10 years, there have been many improvements in high speed control of ESPs.  One very simple way to gain a performance increase on an existing ESP is to upgrade the electrical system.

Process

3. Process

More than anything else, the process conditions will affect the performance of the ESP.  The resistivity of the dust evolved from the process is significant in dictating the performance of the ESP.  Also the resistivity is a function of the following parameters:

  • Gas temperature
  • Dust chemistry
  • Gas composition
  • Particulate sizing

As these parameters are all process related, changes in any of them will affect the performance of the ESP.


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