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TITLE: AN ADVANCED RAPPER OPERATING METHOD FOR ELECTROSTATIC
PRECIPITATOR.
FIELD OF INVENTION:
The invention relates to operation of rapper drive motors
deployed in electrostatic precipitators used for air pollution
control.
BACKGROUND AND PRIOR ART;
Electrostatic precipitation is one of the most effective ways to
control air pollution generated by industrial emissions. This
technique, which has proven highly effective in controlling air
pollution, has been used for the removal of undesirable
particulate matter from a gas stream by electrostatic
precipitation. Electrostatic precipitators thereafter referred to
as ESP) is an air pollution control device designed to
electrically change and collect particulates generated from
industrial processes such as those occurring in power plants,
cement plants, pulp and paper mills and utilities etc. The
electrically charged particles are attracted towards electrode
plates, viz., discharge electrode and collection plate. ESP is
divided into a plurality of fields depending on the dust load. A
field is a set of a discharge electrode and collection plate. A
field is considered healthy as long 35 it is charged with
sufficient voltage and current between its discharge
and collection plate. During continuous operation of an
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electrostatic precipitator, the dust from collector plates
electrodes must be periodically removed for further conveying of
the collected dust. The duet removal mechanism typically
consists of a mechanical rapper.
Rappers are electro-mechanical devices that are used to
mechanically dislodge collected particulate/materials within an
electrostatic precipitator or dust collector, In general, a
rapper consists of a rapper motor connected to hammer mechanism
that mechanically strikes shack pad of respective electrode to
Which it is connected. Striking the field electrode it shock pad
with the hammer transmits mechanical forces to dislodge collected
materials. This type of rapping system is called tumbling—hammer
type rapper. Once the particulate is dislodged from the plates,
it falls into collection hoppers at the bottom of the
precipitator. fir electronic rapper controller, which operate
rapping motor, determines the sequence, intensity, and duration
of rapping.
In the prior art, conventional rapper controllers for a tumbling
hammer type rapping system are Known, which control rapper
motors by switching them ON or DFF periodically, so as to allow
ash build—up on plates during OFF time and ash removal during ON
time. These periods are dictated by ESP's operating parameters
Viz., rapper motor's location with respect to gas flow, overall
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dust Load into electrostatic precipitator and other user defined
options. ON and OFF times are critically set to avoid excessive
capping or under rapping, both of which are detrimental to ESP
performance. Excessive rapping will lead to more re-entrainment
and under rapping will cause more sparking in ESP, both resulting
in poor performance of ESP. It is also known in the prior art
that electronic Controllers control rapping motors, which drive
hammers to remove ash/dust collected on plates. These electronic
controllers can be of analog or digital type. Irrespective of
pthe type at the controller, ON time and OFF time of rapping motor
remain basic parameters far controlling, ON/OFF time i.e. time
period, of a field will vary depending on the particular field's
location with respect to gas flout direction. If the field is
meaner to ESP entry, then the frequency of rapping will be more,
as the dust collection in that field will be more. The frequency
Of rapping will reduce towards the end of ESP. The frequency of
rapper Operation is determined by three operating parameters
viz., Start-time. Run—time and Repest-1 time. Start-time determines
the starting time of rapping motor, Run-time determines how long
a rapper shall run and Repeat—time determines the time gap
between two Start-times. These timings are generally known as
periods of rapping.
In the prior art, mechanisms exist to set the periods directly in
the rapper controller and/or from a master controller. These
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timings are calculated and set based on the dust load entering
each field of the ESP along the gas flow direction and others user-
defined methods. Mechanisms also exist to change the rapper
period which is proportional to the plant-operating load, as the
dust load enteing the ESP is proportional to the plant-operating
load. But no mechanism presently exists to adjust the periods of
rapping motqrs in an ESP automatically without human intervention
depending on the ESP—field conditions. The subject invention
seeks to overcame this drawback.
OBJECTS OF THE INVENTION;
The invention seeks to provide an improved method to monitor
various parameters of the ESP viz., current position of all
rappers with respect to gas flow, healthiness of the fields, and
overall dust load into ESP.
Another object of the invention is to minimise manual
interference in the operation of the rapper motors of ESP,
thereby reducing losses due to human error.
Yet another object is to achieve automatic and continuous
optimisation of rapper operation timings under varying operating
conditions.
DESCEIRPTION OF THE INVENT ION :
The timings of a rapper should change if there is 4ny change in
the healthiness of any ESP-field immediately preceding its own
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ESP-field (i.e. to which it is attached), For example, if first
ESP—field has failed, then second ESP-field will effectively
become first ESP-field with respect to gas flow direction.
pHealthiness of a field means that that particular field is
powered and functioning as expacted. Healthiness of a field is
achieved when the particular ESP-field is charged with sufficient
voltage and current between its discharge and collection
plates. Further, the overall dust load into ESP is directly
proportional to the plant-operating load. A plurality of such
monitored parameters are to be communicated to respective rapper
controller. The rapper controller shall then modify the period
of operation of rapper motor automatically without any human
intervention based on these
monitored parameters.
The rapper motor periods are pre-calculated based an ESP
operating parameters., viz., position of the respective field
with respect to gas flow, healthiness of the fields and overall
dust load into ESP. These periods are stared in memory of
microprocessor based rapper controller.
The rapper controller communicates with centralized controller
for ESP "for periodic updates of ESP operating parameters. If
there is any change in ESP-field healthiness status, rapper
controller will read new periods for all rapper motors from its
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memory. This process is done without any human intervantion.
The invention will now be described in detail with reference to
the accompanying drawings.
Brief description of Accompanying drawings :
FIG. 1 is a block diagram illustrating the processor schematics
of micro-processor based controller with pre-calculated rapper
periods stored in memory unit.
FIG. 2 is a flow diagram of rapper operating periods control
logic.
FIG. 3 is a block diagram illustrating the method according to
the invention.
This invention deals with an advanced rapper operating method,
which specifically deals with aperating rapping system of ESP for
a power plant or process plant. By continuously monitoring the
ESP operating parameters, the rapping time periods of a
particular rapper are continuously adjusted so that the rapping
system gives an optimum rapping. The parameters, which are
monitored continuously, are the position of the particular ESP-
field in which the rapper is connected, he a1thiness of the
particular ESP—field and overall dust load into ESP, On
monitoring these parameters continuously, the electronic rapper
controller can decide on whether any of the currently operating
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time periods are to bechanged or not. If the periods are to be
adjusted based can the monitored parameters, the electronic rapper-
controller will retrieve a suitable time period set from its
memory and update its current operating time period. The time
periods are pre-calculated based or ESP parameters, viz. position
of the respective field with respect to gas flow, healthiness of
the field and overall dust load into ESP and stored in memory.
This automatic monitoring of ESP parameters and updation of time
periods is done without any human intervention.
In the block diagram shown in Fig. 1, micro-protessor (l) is
connected to a plurality of memory units, which are integrated
circuits, through data and control bus. Memory (3) is used to
store the programme of rapper controller. Memory (5) stores
variables of program during execution. The micro-procassor is
also connected to the communication interface (2), which acts as
an interface between rapper controller and central computer of
ESP. The monitored data viz field position with respect to gas
flow, EBP—field healthiness and overall dust load into EBP are
communicated to rapper controller through this communication
interface. On receipt of such parameters, the rapper controller
modifies the current time periods with the new one from its
memory automatically so that the rapping system functions
optimally and effectively.
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communication with the central computer for ESP through its
communication interface (2). Using communication, the rapper
controller receives parameter information viz., ESP—field
position with respect to gas flow direction, healthiness of ESP—
field and dust load into ESP, from central computer 1171. Upon
checking the parameters, rapper controller decides what action to
take. It may either change the current time period or leave
without any change (18). This process continues as long as the
rapper controller is operating.
Figure 3 shows how the over-all system is arranged, The rapper
controller (7) is connected to output card (9), which switches ON
or OFF a rapper motor (12) through a connecting cable. The motor
ON or OFF status is conveyed through a cable to rapper controller
by input card (10), The rapper controller (7) is connected to
central computer of ESP (8) for information on parameters of
interest. The central computer of ESP (8) collects information
on those parameters (11) and communicates them to rapper
controller continuously. After receipt of the information, the
rapper controller decides on changing the time period if
required.
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The invention thus provides an advanced rapper operating method
for electrostatic precipitators (ESP) comprising a rapper
controller which switches ON or OFF a rapper motor through an
output card, the ON or OFF status of motor being conveyed to
controllar by input card, the said rapper controller being
connected to control computer of ESP which collects information
an parameters of interest and communication to said rapper
controller continuously, the said rapper controller comprising, of
a microprocessor connected to a plurality of memories through
data control bus and also to communication interface
characterized in that the time period of the rapper motor is
continuously adjusted depending upon the changes in the said
parameters of interest automatically without any human
intervention.
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We Claim :
1. An advanced rapper operating method for electrostatic
precipitators (ESP) comprising of a rapper controller (7) which
switches ON or DFF a rapper motor (12) through an output card
(?) , the DM or OFF status of motor (l2) being conveyed to
controller (7) by input card (l0), the said rapper controller
being connected to central computer of ESP (8) which collects
information on parameters of interest (11) and communicates to
said rapper controller continuously, the said rapper controller
comprising of a micro-processor (1) connected to a plurality of
memories (3, 4, 5) through data control bus (8) and also to
communication interface (2) characterized in that the time period
of the rapper motor (12) is continuously adjusted, depending upon
the changes in the said parameters of interest, automatically
without any human intervention.
2, An advanced rapper operating method as claimed in Claim 1,
wherein memory (3) stares the programme of the rapper controller
(7), memory (4) stores the precalculated time periods with
indering, memory (5) stores the variables of programme during
execution and the micro-processor (l) can retrieve any stored
data during execution of the programme.
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3. An advanced rapper operatingly method as claimed in claims a
and 2, wherein said memory comprises an integrated circuit (10)
to store desired data permanently.
4. An advanced rapper operating method as claimed in Claim 1,
wherein the ESP is divided into a plurality of fields, each field
comprising of a set of a discharge electrode and collection
plats, the said method monitoring the healthiness of all the
fields continuously and adjusting the rapping period according to
the healthiness of one or several fields.
5. An advanced rapper operating method as claimed in Claims 1
and 2, wherein the said method retrieves the appropriate
precalculated time period for the rapper central motor (12) from
memory (4) depending upon the changes in the parameters of
interest and replace load default time period (l6) with the new
time period so retrieved.
6. An advanced rapper operating method as claimed in claims 1
and 5, wherein the parameters of interest includes field position
with respect to gas flow direction, healthiness of fields and
dust load into ESP .
7. An advanced rapper operating method as claimed in claim 6,
wherein healthiness of field is achieved when the particular ESP—
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field is charged with sufficient voltage and current between its
discharge and collection plates.
8. An advances rapper operating method as claimed in claim 5,
the pre—calculated time period is dependant an healthiness of
fields which in-turn affects field position with respect to gas
flow direction.
9. An advanced rapper operating method for electrostatic
pracipitator substantially as herein described and illustrated.
Dated this 20th day of February, 2006.


IB/mh

An advanced rapper operating method for electrostatic
precipitators (ESP) comprising of a rapper controller (7) which
switches ON or OFF a rapper motor (12) through an output card
(9), the ON or OFF status of motor (12) being conveyed to
controller (7) by input card (10), the said rapper controller
being connected to central computer of ESP (8) which collects
information on parameters of interest (11) and communicates to
said rapper controller continuously, the said rapper controller
comprising of a micro-processor (1) connected to a plurality of
memories (3, 4, 5) through data control bus (8) and also to
communication interface (2) characterized in that the time period
of the rapper motor (12) is continuously adjusted, depending upon
the changes in the said parameters of interest, automatically
without any human intervention.