FIELD OF INVENTION
The present invention relates to a method to increase the flue gas residence time inside the Electrostatic Precipitator (ESP) chamber to enhance the total collection efficiency of ESP in a steam Power Plant. More particularly, the invention relates to the enhanced collection of coarse and fine ash particles from the flue gas flowing with dust particles inside the ESP chamber, with the support of collecting and emitting electrodes. The ash particles, which gets attached to the collecting plates due to corona generation is then collected via ESP hoppers by rapping mechanism. The flue gas flowing from Air-preheater outlet via ESP inlet ducts into the ESP chamber, utilize the flow correction devices such as vertical and horizontal splitters located at ESP inlet funnel. There are three no’s of Gas distribution screens located in the downstream direction where the small deflection plates are fixed to the GD screen, in order to correct the non-uniform flow which is passing across the ESP.
This invention relates to the different arrangement of collecting plates inside the ESP chamber with the presence of few guide plates and guide vanes at upstream direction to the collecting plates. These guide plates provides the brownanian but uniform motion for the flow of flue gas inside each ESP fields. The requirement of uniform flow with increased residence time is very much essential for the effective usage of electrode collection area resulting in more collection efficiency.

BACKGROUND OF INVENTION
An Electrostatic Precipitator (ESP) is a constituent of a steam power plant that collects and removes ash particles from a moving flue gas using the electrostatic principle. ESP’s are the most reliable and highly efficient separation device effectively uses the resistance of the dust particles, collected using the charging mechanism between the collecting and the emitting electrodes. This enable for easier removal of coarse and fine particulate matter like coal dust inside the ESP, which is then rapped, collected through the ESP hoppers.
The flue gas with dust particles flows from the boiler enters the Air-preheater and passes into the ESP chamber via ESP inlet duct system and ESP inlet funnel. The existence of vertical and horizontal splitters inside the ESP funnel distributes the flow equally in all the directions as the expansion of flows takes place into the ESP chamber through a divergent channel. Also the flow is equally distributed into each ESP with the flow correction devices such as guide plates and guide vanes which are located at ESP inlet ducting system.
As the expansion of flow takes place from the ESP inlet, it encounters three gas distribution screens which distribute the flow evenly into the ESP chamber. The first primary and second secondary screen are placed near the entrance of the ESP chamber and the third funnel screen is placed near the exit of the ESP inlet funnel.

The uniform nature of flue gas flow inside the ESP is ensured by fixing the flow correction devices such as upward and downward deflection plates and throttling plates which are then fixed across the GD screen in large numbers.
The location of each deflection plates which are fixed to the trailing primary and secondary GD screens, are determined experimentally by testing one-tenth scaled physical model in the laboratory setup. This flow correction is required inside the ESP chamber in order to have more uniform flue gas distribution which in turn will increase the efficiency of ESP.
The flow correction is assessed 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.
The flow correction devices are utilized for correcting the flow which enters the ESP, which involves proper design of splitters and fixing the GD screen deflection plates. The ESP performance is deteriorated over a period of time, when there is an erosion of these deflection plates and guide plates or guide vanes due to flue gas flowing at very high velocity. These correction plates are located outside the ESP chamber. This contributes to more non-uniform nature of the flue gas flowing

into the ESP leading to improper and less collection of ash particles thus decreasing the total collection efficiency of ESP.
The complex flow phenomena inside the ESP and also the non-uniform flue gas distribution pattern will affect the performance of ESP to a great extent, and results in more emission than the prescribed standard or the guaranteed parameter.
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) Erosion of guide plates and guide vanes at inlet ducting system due to high velocity
b) Separation of flow due to sharp bends in the inlet duct connecting to the ESP inlet and obstruction due to internal structures.
c) Negative and positive of orientation of inlet ducting system with respect to ESP inlet funnel
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 due over a period of time.
f) The density difference of the flue gas due to high temperature inside ESP, hot flow expands, while the cold flow confines to the bottom.

These factors contribute to the complex flow phenomenon inside the ESP which leads to the low collection efficiency of ESP.
The other concerns like erosion of deflection plates and guide vanes due to high velocity and the unequal flue gas pattern from the upstream direction and the inaccuracy in fixing the deflection plates and the guide vanes are some of the factors resulting in the non-uniform flow. All these factors contribute to the complex flow phenomenon inside the ESP which leads to the low collection efficiency of ESP.
To overcome the above mentioned issues, innovative method was devised to provide the uniform flue gas distribution as well as to increase the residence time of flue gas inside the ESP. This was carried out by modifying the geometry at the upstream direction to the collecting electrode and fixing the guide plates to arrive at optimum flow condition.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a method to increase the flue gas residence time inside the Electrostatic Precipitator (ESP) chamber to enhance the total collection efficiency of ESP in a steam Power Plant which is capable of increasing residence time of flue gas by providing additional geometrical plates.

Another object of the invention is to propose a method to increase the flue gas residence time inside the Electrostatic Precipitator (ESP) chamber to enhance the total collection efficiency of ESP in a steam Power Plant which is able to make effective usage of electrode collection area to increase collection efficiency.
A still another object of the invention is to propose a method to increase the flue gas residence time inside the Electrostatic Precipitator (ESP) chamber to enhance the total collection efficiency of ESP in a steam Power Plant which can provide uniform flue gas distribution inside ESP casing for proper ash distribution and collection.
A further object of the invention is to propose a method to increase the flue gas residence time inside the Electrostatic Precipitator (ESP) chamber to enhance the total collection efficiency of ESP in a steam Power Plant which is capable of reducing the emission of plant by properly utilizing the electrode collection area provided by means of uniform electric field strength for each collecting electrodes.
SUMMARY OF THE INVENTION
The principle objective of this invention is to substantially improve the collection of ash particles by providing additional geometrical plates inside ESP in front of flue gas path before each collecting electrodes.

In conventional ESP, the flue gas entering from Air-preheater outlet enters into ESP inlet funnel via ESP inlet duct system where the guide plates and guide vanes are present for equal flue gas distribution. The vertical and horizontal splitters are located in side ESP inlet funnel distributes the flow equally in all the directions as the flow expands in the downstream direction from duct inlet area A1 into the ESP chamber area A2 where A1 is lesser than A2. The arrangements of the vertical and horizontal splitters are varied for each project depends on the positive and negative orientation of inlet duct in the upstream direction with respect to the ESP inlet funnel.
The flue gas flows in non-uniform pattern inside ESP due to high temperature and other factors like separation near the bends, before facing vertical and horizontal splitters. Hence the flow is subjected to encounter additional gas distribution screens which are located after the vertical and horizontal splitters, before the flow enters into the ESP chamber. The flow pattern of flue gas obtained in the ESP casing still reveals the non-uniformity nature of the flow, which is then corrected by fixing the large number of deflection plates to the GD screen, the location which dictated by the experimental testing, until the flow is corrected to uniform flow meeting the ICAC standard.
This traditional process of correcting the flow inside ESP involves proper design of splitters and fixing the GD screen deflection plates. The ESP performance is

deteriorated over a period of time, when there is an erosion of these deflection plates and guide plates or guide vanes due to flue gas flowing at high velocity and these correction plates are located outside the ESP. This contributes to more non-uniform nature of the flue gas flowing into the ESP leading to improper and less collection of ash particles thus decreasing the total collection efficiency of ESP.
The present innovation provides a unique method of providing uniform flow as well as increasing the residence time of the flue gas inside ESP by providing guide plates and guide vanes inside ESP by suitable modifying the arrangement of the collecting electrodes.
The flue gas after entering the ESP chamber encounters a series of guide plates and guide vanes located in front of each collecting electrodes. The guide plates are acted like baffles increases the residence or retention time of flue gas inside the ESP and guide vanes are utilized to provide more uniform flow inside the ESP. This allows for equal distribution of flue gas as well as uniform electric field strength for each collecting electrodes leading to increase in the collection efficiency.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Figure 1 - Isometric view of arrangement of collecting plates inside the ESP.

Figure 2 - Top view and side view arrangement of collecting plates inside the ESP.
Figure 3 - Top view of collecting plates with triangular guide plates at both the end.
Figure 4 - Top view of collecting plates with guide vanes at both the end.
Figure 5 - Side view and Top view of collecting electrodes with both guide plates and the guide vanes at each end of the collecting electrode.
Figure 6 - Top view of particles simulation inside the ESP with residence time
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
The arrangement of collecting electrodes and the existence of guide plates and guide vanes at both upstream and downstream of the collecting electrodes plays an important role in the establishment of uniform flow in the downstream direction and increase in the retention time of the flue gas. The flue gas after encountering the ESP inlet funnel and the gas distribution screens enters into the ESP chamber.

The flue gas then faces the series of collecting and discharge electrodes inside the ESP which are arranged in parallel. The collecting plate with length ‘x1’ (1) and collecting plate with length ‘x2’ (2) are arranged in alternate direction per field throughout ESP chamber. This arrangement is to make utilize the full electrode collection area and to increase the path distance of the flue gas.
The retention time of flue gas got increased further by providing a guide plates and guide vanes at both upstream and downstream end of the each collecting electrodes (1 & 2). The triangular shaped guide plates are arranged at the leading edge (3) and trailing edge (4) of the each alternate collecting electrodes. These plates effectively helps in diverting the flow into the spacing between the two collecting electrodes (1 & 2) leading to increase in the residence time of the flue gas. The uniformity of the flue gas entering the electrode spacing is ensured by providing the pair of guide vanes at the leading edge (5) and at the trailing edge (6) between each alternate collecting electrodes (1 & 2). These guide vanes helps in ensuring the equal and uniform distribution of flue gas inside the electrode spacing. This arrangements also aids in the effective utilization of collecting plate area by providing more uniform electrical field strength helps in more particulate collection.
The particulate simulation (7) exhibit a linear trend where the retention time of the flue gas increases as the length of the ESP increases. The coarse particles got

collected in the first few fields while the fine particles got collected in the next few fields. The collection of fine particles need more residence time for proper collection towards the end of the ESP. This arrangement of collecting plates with the support of guide vanes and guide plates helps in ensuring the uniform flow with more retention time of the flue gas, contributes to more particulate collection thus increasing the overall collection efficiency of the ESP.

WE CLAIM
1. A method to increase the flue gas residence time inside the ESP chamber to enhance the total collection efficiency of ESP in a steam Power Plant, the said method comprising:
providing flow correction devices consisting of vertical and horizontal splitters at ESP inlet funnel to distribute the flow of flue gas equally in all direction; providing a plurality of Gas distribution screens in the downstream direction having small distribution plates fixed to the said gas distribution screen to correct the non-uniform flow of flue gas passing across the ESP and to distribute the flow evenly into the ESP chamber, wherein, a series of collecting and discharge electrodes (1, 2) inform of collecting plates are arranged in parallel inside the ESP chamber to utilize the full electrode collection area and to increase the path distance of the flue gas, when the collecting plates (1, 2) are arranged in alternate direction per field throughout the ESP chamber, wherein guide plates (3, 4) and guide vanes (5, 6) disposed in at both upstream and downstream end of each collecting electrodes (1, 2) whereby said guide plates are arranged at the leading edge (3) and trailing edge (4) of each alternate collecting electrodes (1, 2), and said guide vanes are arranged at the leading edge (5) and at the trailing edge (6) between each alternate collecting electrodes (1, 2) to increase the residence time of the flue

gas ensuring equal and uniform distribution of flue gas inside the electrode spacing, wherein the arrangement of collecting plates supported with guide plates (3, 4) and guide vanes (5, 6) ensures uniform flow with increased residence time of the flue gas contributing to more particulate collection increasing overall collection efficiency of ESP.
2. The method as claimed in claim 1, wherein the flue gas entering the ESP chamber encounters a series of guide plates (3, 4) and guide vanes (5, 6) configured in front of each collected electrodes.
3. The method as claimed in claim 1, wherein the guide plates are acted as baffles to increase the residence time of flue gas inside the ESP and guide vanes are disposed to provide more uniform flow inside the ESP.
4. The method as claimed in claim 1, wherein guide plates are of triangular shape.