ELECTROSTATIC PRECIPITATION AND
ELECTROSTATIC PRECIPITATOR
Submitted To:
Group Name:
Group Members:
Department of Chemical
ELECTROSTATIC PRECIPITATION AND
ELECTROSTATIC PRECIPITATOR
Submitted To:
Mr. A. N. Tabish
Fantastic Four
Group Members:
Iqra Sarfraz 08-BPK-66
Amna Iqbal 08-BPK-75
Sidra Hafeez 08-BPk -76
Jawaeria Altaf 08-BPK-77
Department of Chemical Engineering UET,
City Campus (KSK), Lahore
ELECTROSTATIC PRECIPITATION AND
ELECTROSTATIC PRECIPITATOR
Engineering UET,
City Campus (KSK), Lahore
ELECTROSTATIC PRECIPITATION [1]:
“ Electrostatic precipitation is defined as the use of an electrostatic field for
precipitating or removing charged solid or liquid particles from a gas stream in which the
particles are carried in suspension.”
Principles of Electrostatic Precipitation [1]:
Basic Principle states that particles in a precipitation system are charged,
transported, neutralized, and removed.
Process of Precipitation [3]:
Process may occur within a single zone or be distributed into two zones:
• Charging Zone (intended to charge the particles).
• Collecting Zone (designed to settle the particles).
Efficiency of the Process [2]:
Electrostatic precipitation as practiced can remove some 98-99% of airborne dusts
and smokes, and about the same percentages of mould spores, but against the smaller
bacterial cells they are rather less effective, in the range of 95-97%.
Description of Mechanism [4]:
When particles in a gas are exposed to gaseous ions they become electrically
charged, this charge makes them mobile under the influence of an electric field. They
then drift toward an oppositely charged or grounded collector plate where they have their
charge neutralized. This is illustrated by the figure. Depending on the size of the particle
and the amount of charge it collects from the ions, the particle drift velocity may be from
0.1 to over 1.0 ft/sec. Once the charge is neutralized at the collector plate, the solid
particles can be either shaken or washed off under the influence of gravity. Electrostatic
precipitation uses these principles to remove particles of liquids and solids from gas
streams. Thus, the electrostatic precipitator must have:
• A method for ionizing the carrier gas.
• Directed flow of the feed gas through the ionizing region.
• An electric field to cause particle drift to the collecting electrode.
The charge to the carrier gas is supplied
generated by a non-uniform electric field. A corona is the local electrical breakdown of a
gas into electrically charged gaseous ions due to the high voltage. It is made possible by
the non-uniformity of the field, w
points, but weakens with distance from these regions. If the same voltage were applied as
a uniform field between flat electrodes, no breakdown would occur, it would not be
localized. In this case
between the plates rather than a corona
The common techniques for generating a non
wire or a rod equipped with many very sharp points as the discharge electrode. The thin
wire gives a relatively weak corona from the few small sharp imperfections in the wire
On the other hand, the sharp points intentionally placed on the rod literally spray a corona
into the gas phase. A number of different electrodes sharps have been tested to increase
corona discharge from sharp edges and points. However, if the percent of
escaping precipitation is plotted against corona power input per unit of gas flow, all the
precipitation uses these principles to remove particles of liquids and solids from gas
, the electrostatic precipitator must have:
A method for ionizing the carrier gas.
Directed flow of the feed gas through the ionizing region.
An electric field to cause particle drift to the collecting electrode.
The charge to the carrier gas is supplied by a high voltage direct current
uniform electric field. A corona is the local electrical breakdown of a
gas into electrically charged gaseous ions due to the high voltage. It is made possible by
uniformity of the field, which is very strong in the vicinity of thin wires or sharp
points, but weakens with distance from these regions. If the same voltage were applied as
a uniform field between flat electrodes, no breakdown would occur, it would not be
localized. In this case continuous breakdown would occur and would cause sparks
between the plates rather than a corona
The common techniques for generating a non-uniform field are to use either a thin
wire or a rod equipped with many very sharp points as the discharge electrode. The thin
wire gives a relatively weak corona from the few small sharp imperfections in the wire
On the other hand, the sharp points intentionally placed on the rod literally spray a corona
into the gas phase. A number of different electrodes sharps have been tested to increase
corona discharge from sharp edges and points. However, if the percent of
escaping precipitation is plotted against corona power input per unit of gas flow, all the
precipitation uses these principles to remove particles of liquids and solids from gas
Directed flow of the feed gas through the ionizing region.
An electric field to cause particle drift to the collecting electrode.
by a high voltage direct current corona
uniform electric field. A corona is the local electrical breakdown of a
gas into electrically charged gaseous ions due to the high voltage. It is made possible by
hich is very strong in the vicinity of thin wires or sharp
points, but weakens with distance from these regions. If the same voltage were applied as
a uniform field between flat electrodes, no breakdown would occur, it would not be
continuous breakdown would occur and would cause sparks
uniform field are to use either a thin
wire or a rod equipped with many very sharp points as the discharge electrode. The thin
wire gives a relatively weak corona from the few small sharp imperfections in the wire.
On the other hand, the sharp points intentionally placed on the rod literally spray a corona
into the gas phase. A number of different electrodes sharps have been tested to increase
corona discharge from sharp edges and points. However, if the percent of particles
escaping precipitation is plotted against corona power input per unit of gas flow, all the
data fall on a single correlating line. Thus, corona power input determines collection
efficiency for electrostatic precipitators.
ELECTROSTATIC
“An electrostatic precipitator is a large, industrial emission
designed to trap and remove dust particles from the exhaust gas stream of an industrial
process. “
Electrostatic precipitators are used for the collection
These are defined as follows:
• Dust----solid particles from 0.1 to 100 µm in diameter.
• Mist----liquid droplets suspended in a gas.
• Fume----solid or liquid particles formed by condensation from a vapor.
Construction of a
The basic ESP comprises
outlet transitions, dust collection,
supports the internal equipment such as collection surfaces, discharge electrodes and
rapping devices.
data fall on a single correlating line. Thus, corona power input determines collection
efficiency for electrostatic precipitators.
LECTROSTATIC PRECIPITATORS [7]:
An electrostatic precipitator is a large, industrial emission
designed to trap and remove dust particles from the exhaust gas stream of an industrial
Electrostatic precipitators are used for the collection of dusts, mists, and fumes.
These are defined as follows:
solid particles from 0.1 to 100 µm in diameter.
liquid droplets suspended in a gas.
solid or liquid particles formed by condensation from a vapor.
Precipitator [8]:
The basic ESP comprises a casing with inlet transition, gas distribution devices
outlet transitions, dust collection, hoppers and support steel. The casing
supports the internal equipment such as collection surfaces, discharge electrodes and
data fall on a single correlating line. Thus, corona power input determines collection
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
of dusts, mists, and fumes.
solid or liquid particles formed by condensation from a vapor.
gas distribution devices,
The casing encloses and
supports the internal equipment such as collection surfaces, discharge electrodes and
The most common material of construction for the casing and internal equipment is
mild steel, stainless steel and PVC materials are also
Working of a Precipitator
Working of an ESP comprises of s
• 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
surfaces
• Particle Dislodging
hopper
• Particle Removal
Designs of Electrostatic Precipitators:
• Wire-in-Plates Designs
The plate type units
the gas (air).
The most common material of construction for the casing and internal equipment is
mild steel, stainless steel and PVC materials are also used in special applications
Precipitator [7]:
Working of an ESP comprises of six activities as follows:
Charging of particles
Transporting the charged particles to the collecting surfaces
Precipitation of the charged particles onto the collecting surfaces
Charge Dissipation - Neutralizing the charged particles on the collecting
Particle Dislodging - Removing the particles from the collecting surface to the
Removal - Conveying the particles from the hopper to a disposal point
Designs of Electrostatic Precipitators:
Plates Designs
The plate type units are the most common designs for dry dust removal from
The most common material of construction for the casing and internal equipment is
used in special applications.
Transporting the charged particles to the collecting surfaces
Precipitation of the charged particles onto the collecting surfaces
Neutralizing the charged particles on the collecting
Removing the particles from the collecting surface to the
Conveying the particles from the hopper to a disposal point
dry dust removal from
• Wire-in-Pipe Designs
Pipe designs are mainly used for the removal of liquid or sludge particles and
volatilized fumes.
Division of Precipitators
Electrostatic precipitators are divided into two broad classes, depending on whether
the ionizing and collecting functions are combined or separated, in the
the central wire ionizing electrode is also one of the electrodes establishing th
causes the particle drift. In
electrodes are of widely different diameters so that corona discharge and ionization occur
only in the vicinity of the small diameter portion of the centr
two-stage unit is used industrially with a negative corona and washing of the collector
plates is done to recover the particles.
Types of Electrostatic
There are two types of electrostat
1. Dry Electrostatic
The dry ESP is the most common
dry state, such as cement and ash.
Pipe Designs
Pipe designs are mainly used for the removal of liquid or sludge particles and
volatilized fumes.
Division of Precipitators [4]:
Electrostatic precipitators are divided into two broad classes, depending on whether
the ionizing and collecting functions are combined or separated, in the
the central wire ionizing electrode is also one of the electrodes establishing th
causes the particle drift. In two-stage unit the ionizing electrodes and the drift field
electrodes are of widely different diameters so that corona discharge and ionization occur
only in the vicinity of the small diameter portion of the central electrode. This type of
stage unit is used industrially with a negative corona and washing of the collector
plates is done to recover the particles.
f Electrostatic Precipitators:
There are two types of electrostatic precipitators, dry, and wet.
Dry Electrostatic precipitator [9]:
The dry ESP is the most common. It collects and removes the particulate matter in
dry state, such as cement and ash.
Pipe designs are mainly used for the removal of liquid or sludge particles and
Electrostatic precipitators are divided into two broad classes, depending on whether
the ionizing and collecting functions are combined or separated, in the single-stage unit
the central wire ionizing electrode is also one of the electrodes establishing the field that
the ionizing electrodes and the drift field
electrodes are of widely different diameters so that corona discharge and ionization occur
al electrode. This type of
stage unit is used industrially with a negative corona and washing of the collector
wet.
oves the particulate matter in a
Operation [9]:
A dry electrostatic precipitator is used for removing dust particulates from a
flowing gas stream and comprises of an upright cylindrical vessel, each of precipitator
stages have particulate charging electrodes and associated collector electrodes, arranged
in a controlled flow path. A dust hopper located beneath each stage; and dust chutes
extending from the hoppers to discharge outlets at the bottom of the vessel. The particles
will be drawn towards plates hanging on the side of the device, where they will collect.
Periodically, the plates will be struck by a hammer, or something like it, or vibrated,
causing the particles, now discharged, to fall off. They are then collected, and disposed of
accordingly.
Applications [10]:
Some of the usual applications of dry ESP are:
1. Removal of dirt from flue gases in steam plants.
2. Cleaning of air to remove fungi and bacteria in establishments producing
antibiotics and other drugs, and in operating rooms.
3. Cleaning of air in ventilation and air conditioning systems.
2. Wet Electrostatic Precipitator:
Wet precipitators are used to strip gasses of "wet" particles, such as resin, oil, paint,
tar, acid, or anything that can't be handled well dry.
Principle:
It operates on the principle of uni-polar particle charging in the corona discharge
and particle precipitation under the field of their own space charge.
Operation [11]:
In WESP, the dust is removed by
plates by water sprays
Some systems use very little water and produce
clarifier and solid concentrator.
the primary target for the WESP is the submicron particular focus on heavy metals and
soot.
Applications:
1. Incinerators for industrial
2. Incinerators for municipal waste.
3. Boilers, melting furnaces,
Precipitator Selection
In the selection process the engineer specifies the particular applications, the gas
flow, temperature, pressure, dust concentration,
altitude, and as much other pertinent data as are available to him. In some cases it is
recognized that data on dust chemistry, fore example, may not exist.
The efficiency of
the dust is removed by continuous or periodic irrigation of the collection
or a water film.
Some systems use very little water and produce sludge like residue others use a
clarifier and solid concentrator. Sometimes with pH adjustment and with flocculation aids
he primary target for the WESP is the submicron particular focus on heavy metals and
Incinerators for industrial waste.
Incinerators for municipal waste.
elting furnaces, desulfurizing systems.
Precipitator Selection [12]:
In the selection process the engineer specifies the particular applications, the gas
flow, temperature, pressure, dust concentration, efficiency required, residual permissible,
altitude, and as much other pertinent data as are available to him. In some cases it is
recognized that data on dust chemistry, fore example, may not exist.
The efficiency of electrostatic precipitators can be increased by:
or periodic irrigation of the collection
like residue others use a
ment and with flocculation aids
he primary target for the WESP is the submicron particular focus on heavy metals and
In the selection process the engineer specifies the particular applications, the gas
efficiency required, residual permissible,
altitude, and as much other pertinent data as are available to him. In some cases it is
recognized that data on dust chemistry, fore example, may not exist.
reased by:
• Larger collection surface areas and lower air flow rates give more time and
area for dust particle to collect.
• Increased speed of dust particles towards collection electrodes.
Advantages of Electrostatic Precipitation [5]:
1. High removal efficiency of fine particles/droplets.
2. Collection of either dry powder materials or wet fumes/mists.
3. Substances of a wide range of gas temperature up to approx 700 degree C.
4. Low operating costs, except at very high removal efficiencies.
Disadvantages of Electrostatic Precipitation [5]:
1. High capital costs.
2. Unable to collect gaseous pollutants.
3. Large space requirement.
4. Inflexibility of operating conditions.
Applications of Electrostatic Precipitation [6]:
The earliest applications were to the smelting and sulfuric acid industries and at
cement mills. Other important applications include removal of tar from coke-oven gases;
removal of acid fumes in petroleum refineries and chemical plants; recovery of such
industrially valuable materials as the oxides of tin and copper.
Expected Future Developments [13]:
The following trends and emphasis in electrostatic precipitator development are
forecast over the next few years.
1. Use of additives for gas conditioning to reduce the high resistivity problem.
2. Use of computer models for precipitator design and performance analysis.
3. Use of wet precipitators in controlling fine particles.
References:
1. Lawrence K Wang, and Norman C. Pereira, “Hand Book of Environmental
Engineering: Air and Noise Pollution Control”, Vol. 1, Ed. 1979, the Humana
Press Inc., pp. 103 and 104.
2. Lawrence K. Wang, Norman C. Pereira, Yung-Tse Hung, “Handbook of
Environmental Engineering: Air Pollution Control Engineering”, Vol. 1, Ed.
2004, the Humana Press Inc., pp. 154.
3. Mazen Abdel-Salam, “High Voltage Engineering: Theory and Practice”, Ed. 2,
Macrel Dekker Inc., pp. 645-646
4. Robert B. Long, “Separation Processes in Waste Minimization”, Ed. 1995,
Marcel Dekker Inc., pp. 278-280.
5. Lawrence K. Wang, Norman C. Pereira, Yung-Tse Hung, “Handbook of
Environmental Engineering: Air Pollution Control Engineering”, Vol. 1, Ed.
2004, the Humana Press Inc., pp.154.
6. http://www.britannica.com/EBchecked/topic/184043/electrostatic-precipitation
7. http://www.neundorfer.com/knowledge_base/electrostatic_precipitators.aspx
8. William L Heumaan, “Industrial Air Pollution Control Systems”, Ed. 1997,
Macrel Dekker Inc., pp. 472-474.
9. http://everything2.com/title/Electrostatic+Precipitator
10. http://www.ppcesp.com/ppcart.html
11. Walter R. Niessen, “Combustion and Incineration Processes”, Ed. 2002, pp.
575-576.
12. John. J. McKetta, “Unit Operations Handbook: Mechanical Separation and
Materials Handling”, Vol. 2, Library of Congress Cataloging-in-Publication
Data, pp. 339.
13. Lawrence K Wang, and Norman C. Pereira, “Hand Book of Environmental
Engineering: Air and Noise Pollution Control”, Vol.1, Ed.1979, the Humana
Press Inc., pp.141.