FIELD OF INVENTION
The present invention relates to a method to provide uniform flue gas distribution inside
the Electrostatic precipitator without deflection plates for equal ash distribution and
collection. This invention relates to the flow pattern of flue gas inside the Electrostatic
precipitator (ESP) casing which contains the collecting and emitting electrodes for the fine
collection of Ash particles (APH), which is then collected through ESP hoppers by rapping
mechanism. The flue gas flowing from Air-preheater to ESP chamber via ESP inlet ducts,
use the flow correction mechanism such as splitters at ESP inlet funnel and three no’s of
Gas distribution (GD) screens in the downstream direction. The small deflection plates are
fixed to the GD screen in order to correct the flow which is passing through the GD
screens in to the ESP chamber.
This invention relates to the different arrangement of geometry at ESP inlet funnel as well
as different sized holes inside the GD screen to enable uniform flue gas distribution inside
the ESP casing without the need for deflection plates.
The requirement of uniform flow is very much essential for the effective usage of
electrode collection area resulting in equal ash collections which in turn reduces the
emission meeting the guaranteed parameters.

BACKGROUND OF INVENTION
An Electrostatic Precipitator (ESP) is a component of a power plant that collects and
removes ash particles from a moving flue gas using the electrostatic principle. ESP’s are
highly efficient separation devices effectively uses the resistance of the dust particles,
collected using the charging mechanism between the collecting and emitting electrodes
facilitate for easier removal of fine particulate matter like coal dust which is then rapped
and collected through ESP hoppers.
The flue gas moving from Air pre-heater via ESP inlet ducts enters into the ESP chamber
through ESP inlet funnel. The presence of vertical and horizontal splitters inside the ESP
funnel distributes the flow equally in all the directions as the flow expands into the ESP
chamber through a divergent channel. The flow is equally distributed into each ESP with
the flow correction devices such as guide plates and guide vanes.
As the flow expands from ESP inlet, it come across three GD screens which distributes
the flow into the ESP chamber. The first and second screens (namely called as primary
and secondary screen) are placed near the entrance of the ESP chamber and the third
screen placed near the exit of the ESP inlet funnel. The uniformity in the flue gas
distribution inside the ESP is ensured by placing small sized flow correction devices such
as deflection plates which is fixed across the GD screen in large numbers. A considerable
number of man power is required to fix the deflection plates on GD screens.

The positions of several deflection plates which is fixed to the trailing primary and
secondary GD screens, are arrived by means of experimental testing of scaled physical
model in the laboratory setup. This correction of flow is demanded inside the ESP
chamber in order to have uniform flue gas distribution which in turn will increase the
efficiency of ESP. The flow correction is evaluated by the international standard of
‘The Institute of Clean Air Companies’ – Electrostatic Precipitator -7 (ICAC EP-7) which
demands 85 % and 99 % of the measured readings shall be less than 1.15 times and 1.4
times the average velocities respectively inside the individual ESP casing.
A non-uniform flow pattern will not only affect the performance of ESP, but also results in
more emission than the prescribed standard or the guaranteed parameter.
The other issues like erosion of plates, the unequal flue gas pattern from the upstream
direction and the inaccuracy in fixing the plates are some of the factors resulting in the
non-uniform flow. Also it is quite a tedious process in finding out the location of various
deflection plates in an experimental setup using a trial and error method.
To overcome the above mentioned issues, novel method was invented to provide uniform
flue gas distribution inside the ESP without the need for deflection plates. This was
carried out by modifying the duct geometry before ESP funnel and also by using different
sized holes on the gas distribution screens.

The ash or particulates are collected from coal burning power plants with the support of
dust filtration equipment’s like Multi-cyclones, ESP’s, bag filters & others. The collected
particulates are then stored in hoppers which is then periodically removed for further
collection. The proper collection of dust or ash particles depends on the uniform
distribution of flow in-between each electrodes across the ESP. This further depends on
the equal and uniform flue-gas distribution across the ESP. The non-uniform flow will not
only affect the performance of ESP but also results in unequal ash collection in ESP
hoppers.
There are other flow correction mechanism present in the existing cases such as splitters
and gas distribution screens. These splitters are varied in design for each ESP-duct
configuration. Presence of any upstream disturbances are also then propagated in same
manner to the ESP chamber through gas distribution screens, which leads to improper
flow distribution inside the ESP. The gas distribution screens at present has uniform sized
holes and acts as a passive suppressor of non-uniform flow, while the active deflection
plates are fixed to the gas distribution screens for flow correction. The location of
deflection plates are arrived by conducting a model study at laboratory setup, in such a
way to identify the upstream disturbances and suppress it. But in real site condition, the
disturbances are caused by other supporting components or by erosion of splitters and
deflection plates might result in non-uniform flow inside ESP chamber, leading to unequal

ash collections. The factors contributing to the non-uniform nature of the flow inside the
ESP in spite of presence of flow correction devices are summarized as below.
a) Duct orientation with respect to ESP inlet funnel (Negative or Positive offset)
b) Non uniform flow due to high temperature, causing changes in the density.
c) Flow separation due to bends in the inlet duct connecting to the ESP inlet
d) Differences in the inlet velocity profile caused by the supporting components
forming a dead zones
e) Erosion of flow correction devices like splitters and deflection plates
The resulting flow of the above highlighted issues renders the flow, non-uniform in
nature leads to decreased performance of ESP and unequal ash collections.
To avoid such consequences caused due to uneven flow distribution, the flue-gas
distribution system is designed to provide uniform flow pattern of flue-gas inside the ESP
chamber for an equal collection of ash, without the need for GD screen deflection plates.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a method to provide uniform flue
gas distribution inside the Electrostatic precipitator without deflection plates for equal ash
distribution and collection which is capable of eliminating the need for laboratory setup
required for finding the location of the deflecting plates.

Another object of the invention to propose a method to provide uniform flue gas
distribution inside the Electrostatic precipitator without deflection plates for equal ash
distribution and collection which enables avoiding huge number of man power for fixing
large number of deflection plates to large sized GD screen.
A still another object of the invention to propose a method to provide uniform flue gas
distribution inside the Electrostatic precipitator without deflection plates for equal ash
distribution and collection which is able to eliminate periodic inspection and replacement
of deflector plates.
A further object of the invention to propose a method to provide uniform flue gas
distribution inside the Electrostatic precipitator without deflection plates for equal ash
distribution and collection which is capable of reducing emission of Plant by properly
utilizing the electrode collection area provided by means of uniform flue gas distribution.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 – shows isometric view of primary and secondary chamber
Figure 2 – shows elevation and Plan view of primary and secondary chamber
Figure 3- shows isometric view of standard horizontal and vertical splitters

Figure 4 - shows elevation and Plan view of standard horizontal and vertical splitters
Figure 5 - shows isometric view of gas distribution screens with diameters d1, d2 & d3
Figure 6 – shows side view of gas distribution screens with diameters d1, d2 & d3
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
At present, flue gas entering from APH enters into ESP inlet funnel through ESP inlet
duct. The vertical and horizontal splitters are fixed in ESP inlet funnel distribute the flow
in all the directions as the flow expands from duct inlet area A1 into area A2 in the
downstream direction where A1d2>d3. The flow gets
reoriented into a more uniform flow in the downstream direction before entering into the
ESP chamber. The necessity of fixing the deflection plates are eliminated in this design
which is required for flow corrections in earlier design. The flow equally spaced in all the
direction inside the ESP chamber subject to the proper usage of electrode collection area
which leads to increased precipitation and equal ash collections in all the ESP hoppers.

WE CLAIM
1. A method to provide uniform flue gas distribution inside the Electrostatic precipitator
without deflection plates for equal ash distribution and collection, the said method
comprising;
providing two chambers, one primary chamber and other secondary chamber at outlet
of inlet duct system, the said primary chamber being made convergent in nature to
act as a flow suppressor to reduce upstream flow disturbances and the said secondary
chamber having plurality of fixed vanes (2) to cause a change in the flow direction of
a flue gas delivered from Air pre Heater ducts;
connecting, outlet of the secondary chamber to an Electrostatic precipitator inlet
funnel having horizontal and vertical splitters (3) disposed in equal spaced intervals to
provide equal distribution of flow in all directions; wherein the upstream uniform flow
is equally expanded into the divergent funnel to achieve uniform flow at the exit of
the funnel when the flow in X-direction is also symmetrical in Y and Z direction,
wherein the hole size of gas distribution screen (5) disposed in the downstream
direction is modified with different diameters d1, d2 and d3 such that the ratio d1/d2
and d2/d3 = 2[Sqrt x (1/ πε)] where ε is the expansion ratio with ε=f(v), with v as
the inlet velocity and d1>d2>d3 resulting a controlled and uniform flow in the
downstream direction entering the ESP chamber making the flow equally spaced in all
the direction inside the said chamber leading to increased precipitation and equal ash
collection in all ESP hoppers, subject to the proper usage of electrode collection area.