FIELD OF THE INVENTION
The invention relates to a control system of electrostatic precipitator used for
air pollution control. More particularly, the invention relates to an electronic
apparatus for integrated control and monitoring of Ash level, Hopper Heater
and Rapper operation of Electrostatic Precipitator. The invention further relates
synchronized operation of Electrostatic Precipitator using the said parameters
for efficiently managing and maintaining Electrostatic precipitator.
BACKGROUND OF THE INVENTION
Electrostatic precipitation is one of the most effective processes to control air
pollution generated by industrial emissions. This technique, which has proved
to be highly effective in controlling air pollution, is used for removal of
undesirable matter from a gas stream by electrostatic precipitation.
Electrostatic precipitator (hereafter referred to as ESP) is an air pollution
control device designed to electrically charge and collect particulates generated
from industrial processes such as those occurring in power plants, cement
plants, pulp and paper mills and utilities. Electrostatic dust removing basic
working principle is that: when the dust laden gas flow through the high-
voltage static electric field inside ESP, dust is charged due to collisions with
positive and negative ion, under the action of the electric field the charged dust
particle moves to opposite charged electrode plates, viz., discharge electrode
and collection plate, and eventually gets adsorbed, thus achieving dust-
collecting effect. ESP is divided into a plurality of fields depending on the dust
load. During continuous operation of an electrostatic precipitator, the dust
from the collector plates and the discharge electrodes must be periodically
removed for further conveying of the collected dust. Dust collected on the
electrodes is removed periodically with mechanical hammers controlled by

rapping motors. The rapping mechanism is critical to ESP efficiency and so is
controlled automatically by a dedicated controlled or by the ESP Power supply
controller itself.
In the ESP, the rapping mechanism typically operated through tumbling
hammer mechanism, where in drive operates the hammer to dislodge ash
build-up on electrode surfaces. The Hopper at the bottom of ESP receives the
dislodged ash. The rapper drive is operated periodically and the periodicity
depends on the field position of rapper. The first field rapper operated more
frequently than down-stream field rappers and so on.
In the ESP, the removed dust from electrodes is collected at the Hopper, which
is located at the bottom of ESP. The hopper is generally in pyramidal or conical
shape and is sized to store the collected ash for a specific period so that the
ash evacuation can occur intermittently. Electronic probes (Ash Level
Indicators) are available to sense and indicate the present storage condition.
Such Ash Level Indicators (ALI) are so positioned in Hopper typically at two
locations such as LOW and HIGH positions to indicate the ash filling. LOW
position is placed at the bottom and HIGH is placed at top of hopper.
Generally, such ALI systems will indicate its output in the form of switch such
that one position of switch to indicate ash-filled-up and one position to indicate
no-ash-filled-up. The respective user system will read such switch position and
ascertain the status. For a typical ESP of 8-field and 4-Pass, there will be 64
Hoppers and therefore 128 ALI systems. Mechanism exists in the prior art to
sense ash presence in Hopper and suitably indicate in the form of switch.
In the ESP, Hoppers are filled with ash after rapping process. The filled-up ash
is evacuated from Hoppers through various means like ash-handling-system.
For maintaining smooth evacuation of ash, the Hopper temperature shall be

kept close to ESP inside temperature to maintain fluidity. Hopper Heaters are
employed for this purpose. They are so arranged in Hopper walls such that all
sides are uniformly heated for better efficiency. The systems are available are to
uniformly heat Hopper walls for a set temperature and suitably inform the user
of the running status in the form of switch.
Also, An individual standalone control systems cater to control and monitor the
Rapper System, Hopper Heater and Ash Level Indicator Monitoring. The
operator will monitor ash filled condition and suitably operate ash evacuation
system manually. The operator does not have any control over the rapping
process irrespective of ash filled-up condition in Hopper. There is no
mechanism exist to monitor all Hopper Heater status, all ALI status and
Rapper operation from a single point. In the prior art, no mechanism exist to
synchronize the operation of Rapper, ALI system and Hopper Heater status to
efficiently operate ESP for improved performance and availability, that may be,
shutting of Rapper process and charging of a field in case of Hopper Full
condition.
The European Patent application EP 1788208 discloses a method of monitoring
ash buildup in a particulate filter of an emission abatement assembly, the
method comprising the steps of: regenerating the particulate filter to remove
soot accumulated therein, generating a control signal subsequent to the
regenerating step, and determining a level of ash accumulation in the
particulate filter in response to generation of the control signal, and
The Chinese Patent application CN 202734909 U discloses the utility model
discloses a fluidized ash material level detector, which comprises a working gas
source, an air filtering pressure reducer, a gas flowmeter, a three-way joint, a
nozzle and a pressure transmitter, wherein the working gas source, the air
filtering pressure reducer, the gas flowmeter, the three-way joint and the

pressure transmitter are connected with one another in sequence by
connecting pipes; a manual valve I is arranged on the connecting pipe between
the working gas source and the air filtering pressure reducer; a manual valve II
is arranged on the connecting pipe between the three-way joint and the
pressure transmitter; the other port of the three-way joint is connected with the
nozzle by a signal into a standard current signal. The fluidized ash level
detector disclosed by the utility model can immediately work online with high
resolution; and through analog quantity output, the fluidized state and
material level of the ashes in electric precipitation ash hopper of a thermal
power plant are detected, so that safety problems in the material conveying or
storing process are solved. However, no system provisions are available in the
teachings of the documents to further integrate with other systems
components.
The Patent application CN 201644232 U discloses at the bottom of a hopper
with a heating plate electrostatic precipitator, comprising a housing (1), at the
bottom of the housing (1) is provided with hopper (2), hopper (2) is Chu Chen
mouth (3) characterized in that: the hopper (2) Chu Chen mouth (3) wall at the
top of the bucket with a heating plate (4), the heating plate (4) with the bucket
wall of lamination. The document does not show on how to integrate all heater
status for overall efficient operation of ESP.
The Patent application WO 2007051239 Al discloses an electrostatic
precipitator having a precipitator current operatively passing between
electrodes, a method of controlling energisation of the electrostatic precipitator
to reduce arc generation and/or back corona between the electrodes,
comprising the steps of monitoring said current to detect arcing between the
electrodes; and controlling energisation of the electrostatic precipitator using a

high speed switching circuit with a response time that is substantially less
than the arc generation time constant.
The Patent application EP 0052435 A1 discloses a method for removing
particle3 from a particle-laden gas stream is an electrostatic precipitator
electrically charging the particles by passing the gas stream through an
ionization field and attracting the thus charged particles to a grounded
collecting electrode for collection, characterized in that, prior to collection of the
particles, from about 1 to about 200 parts, per million parts of gas, of an
additive which is morpholine, an effective derivative of morpholine or a mixture
thereof is distributed across the gas stream within the ionization field to
enhance the efficiency of particle removal. The documents does not disclose
any method and procedure on how Hopper Heater, ALI and Rapping system
can be used for efficiently operation of ESP.
Accordingly, in the prior art, ESPs operation generally lack an integrated and
synchronized operation of all Hopper Heaters, Ash Level Indicators and
Rapping System to efficiently operate and to increase the availability of ESP by
isolation and targeted action on upstream equipment whenever needed.
OBJECTS OF THE INVENTION
The object of the invention is to propose a control system to monitor Hopper
Heater status, Ash Level filled-up Status and control Rapping process through
a common hardware for efficient operation of ESP.
Another object of the invention is to device a method by synchronizing Ash
filled-up condition in Hopper, Hopper heater status and Rapper control
mechanism to suitably alert the Central Plant Computer on potential
catastrophic failure condition of ESP.

Yet another object of the invention to integrate the hardware controllers, where
more of such controllers to be used for a single ESP, through standard
communication means.
Yet another object of the invention is to eliminate all signal cables running
between Hopper Heaters, Ash Level indicators and Rapper Monitors and
respective control panels.
Yet another object is to provide a system for controlling Rapping system,
monitoring Hoper Heater status and Ash Level filled-up status in Hopper of
ESP.
Yet another object is to provide a system for communicating among peers and
to central computer in the form of Controller Area Network (CAN) and
IEEE802.15.4 Wireless interface.
Yet another object is to provide a system for synchronizing Hopper Heater
status, Ash level filled-up status and rapper process control and suitably alert
central computer for safety operation.
SUMMARY OF THE INVENTION
Accordingly, there is provided an control system capable of monitoring Hopper
Heater status, Ash Level filled-up status at Hopper and Rapper motor control
through a control system. The system has plurality units of electronic
controller. Each electronic controller has plurality of opto-isolated input
channels and plurality of 250V capable relay outputs together with suitable

LED indicators for each input and output. The requirement of electronic
controller for an application depends on the signals to be handled.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG 1: Schematic view of Integrated system for Ash Level, Heater Status and
Rapper drives controls
FIG: 2 Schematic view of interface between Ash Level High/Low, Heater On/Off
and Rapper Drive Control
FIG: 3 Communication network scheme using open standard communication
protocols
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Fig:l shows the schematic view of electronic controller of the invention. The
Central Processing unit [CPU] (1) is connected to other peripheral components
via internal signal bus. The CPU (1) is made up of RM48L952 processor with
built-in flash memory to contain data. The non-volatile Memory (2) provides
stored user data to CPU (1). All user settings are stored permanently in non
volatile memory (2). The control activity of the system is achieved through
output circuit (3) which has plurality of 250V relays to switch outputs.
Accumulation of high ASH build-up, pre-warning for catastrophic failure of
ESP due to ash-build-up in more than user specified numbers of hopper for a
user specified duration is controlled, Rapper Motors and general indicator
lamps are activated by the output circuit (3). Ash build-up levels, hopper

heater running status and Rapper ON and OFF are indicated the input circuit
(4). Monitoring and control activities, Rapper ON/OFF, Hopper Heater Status
and Ash build-up level, are distributed with more than one unit of the
electronic Controller, depending upon its application. The optionally heater
on/off condition shows the status of heater running to keep the ESP hopper at
a specified temperature to fluidize ash evacuation. The ash level selectively
High/Low shows the filled-up status of ash at low level and high level in ESP
hopper.
The rapper process is a method to activate rapping process of the ESP field,
which is user defined. Rapping process activation is performed by controlling
rapping drives related to real time limits. It is also provided with means to
capture user on/off commands through push-button switches and activate
respective drives accordingly. The system automatically monitors the Heater
status, Ash level status for a user defined or factory set time to indicate and
communicate for any possible system failure. The communication is carried out
without any human intervention and further used for any upstream system
trip. The upstream system may be a furnace which produces ash for ESP to
collect. In such cases, these Electronic Controllers are linked through
Communication interface circuits viz, Controller Area Network (CAN) interface
(5) and wireless IEEE802.15.4 protocol interface (6). CAN (5) communication
channel links all Electronic Controllers using user selectable Baud rates
ranging from 4.8Kbps to 50Kbps. The CAN Communication provides an open-
standard communication interface for Datalink layer interface for Multi-Master
bus control mechanism using CSMA/CA protocol. Also, the Electronic
Controllers can link to themselves through ZIGBEE wireless network. ZIGBEE
communication provides an standard communication interface operating in
wireless domain using MESH network topology. Based on the user settings,

Electronic Controllers is connected to Zigbee network and receives Network ID
from Co-ordinator. Binding of input and outputs of Electronic Controllers are
done upon start-up by setting suitable Controller Address in each Electronic
Controller. Each electronic Controller is provided with suitable unique
communication network ID. The data is managed between Electronic
Controllers such that the integrated operation of ESP is achieved. The user can
configure input circuits (4) to any input types viz, Hopper Heater Status, ALI
and RAPPER Status. Similarly, Output Circuits (5) can also be configured by
the user to any required output. Status of each input and output is shared to
Central Computer vide CAN communication frames.
Fig: 2 shows the scheme of how the system (11) is connected to field systems.
The command is sent to the Rapper drive (9) by the system (11) through its
output circuit (3) and the user command is read through input circuit (4). The
Ash level High (7) and Ash level Low (8) signals are interfaced through input
circuit (4) of the system (11). The potential free contacts are extended to the
system (11) by ash level high (7) and ash level low (8). Similarly, the hopper
heater status (12) is also sensed by the system (11) through the said potential
free contacts. After sensing, Electronic Controllers information is transferred
through the communication channels. Designated Electronic Controllers
activates the respective relay outputs to indicate ESP critical monitoring. Also,
the designated Electronic Controller will operate rapper Motors as required by
user.
Fig: 3 shows communication network of the system through which the systems
are interconnected and interfaced to central computer (15). The system (11)
connects to other nodes through both Controller Area network (13) and
Wireless IEEE802.15.4 (14) via its Controller Area Network (CAN) interface (5)
and Wireless IEEE802.15.4 protocol interface (6). The Electronic controller also

receives user commands through these communication ports and suitably
decodes the commands for further execution. The communication details
include the binding information for each input with respective output (which
input channel status of an Electronic controller, another Electronic controller
to switch-on RAPPER Motor etc.,) The system operates rapper drives with a
predefined times as set by user for removing ash deposited in ESP collecting
electrodes. It ensures that at any point of time not more than four drives are
operated in an ESP Pass to minimize re-entrainment of ash into flue gas
stream. The process control and monitoring parameters are consolidated in the
form of communication frames and transmitted to Centralized Control System
through CAN and Zigbee communication interface. It reads user commands
through physical keys located at drive ends, and wirelessly transports the
commands using Zigbee to the power panels for powering the drive. The
system, consisting of Hopper Heaters, Ash Filled-up status and Rapper Motor
drives of ESP for a co-ordinated control using plurality of Electronic Controllers
linked through CAN and Zigbee Communication Interfaces.
The invention described herein is merely exemplary in nature and are not
intended to limit the scope, applicability, or configuration of the subject matter
in any way. Also, it should be understood that various changes can be made in
the function and arrangement of elements without distorting the scope of
invention.

WE CLAIM:
1. A method of controlling the ESP operation comprising the steps:
- Providing monitoring means to monitor the operation of atleast the
rapper process, hopper heater and ash level indicator (ALI) switch;
- Synchronizing the monitored data of the said rapper process, hopper
heater and ash level indicator (ALI) switch;
- Controlling rapping process of an ESP field based on the synchronized
data mentioned above and the field position;
- Communicating with the central control room through wired and/or
wireless network thereby integrating the operation of the ESP and
indicating for the any possible malfunction of the ESP and to trigger
plant trip.

2. The method as claimed in claim 1, wherein the monitoring, synchronizing,
controlling and communication activities are carried out automatically
without any human intervention.
3. The method as claimed in claim 1, wherein the heater maintains specified
temperature of the hopper for fluidizing ash evacuation.
4. The method as claimed in claim 1, wherein the rapper process is activated
based on user defined time period and automatically ensures that at any
point of time not more than 4 drives are operated in an ESP PASS to
minimize re-entrainment of ash into flue gas stream. It also takes
commands through ON/OFF push switch.
5. A integrated control system for electrostatic precipitator(ESP), to
implement the method of claim 1, comprising an electronic controller
which comprises:

- a processing unit (1) with in-built flash memory connected to peripheral
components;
- an output circuit (5) comprising plurality of relays to switch output;
- an input circuit (4) configured selectively to hopper heater status, ALI
and rapper status.

- means to indicate status of each input and output;
- Controller Area Network (CAN) Communication Channel and Zigbee
Wireless Communication Channel
- wherein the said electronic controller is interfaced with a communication
network to manage data between the said systems and the
communication network to obtain an integrated operation.

6. The Electronic Controller as claimed in 5, where CAN Communication
means an open-standard communication interface for Datalink layer
interface for Multi-Master bus control mechanism using CSMA/CA
protocol. The system has provisions to select suitable buad rate for
communication speed.
7. The Electronic Controller as claimed in 5, where ZIGBEE communication
means an standard communication interface operating in wireless
domain using MESH network topology. Based on user settings, Electronic
Controllers gets attached to Zigbee network and receives Network ID from
Co-ordinator. Binding of Inputs and outputs among Electronic Controllers
are automatically done upon start-up by setting suitable Controller
Address in each Electronic Controller.
8. An integrated system as claimed in 5, the system reads user commands
through physical keys located at drive ends, and wirelessly transports the
commands using Zigbee to the power panels for powering the drive.
9. An integrated system as claimed in 5, it operates the entire system
consisting of Hopper Heaters, Ash Filled-up status and Rapper Motor
drives of ESP for a co-ordinated control using multiple nos of Electronic
Controllers linked through CAN and ZIgbee Communication Interfaces.

ABSTRACT

A method of controlling the ESP operation comprising the steps: Providing
monitoring means to monitor the operation of atleast the rapper process, hopper
heater and ash level indicator (ALI) switch; Synchronizing the monitored data of
the said rapper process, hopper heater and ash level indicator (ALI) switch;
Controlling rapping process of an ESP field based on the synchronized data
mentioned above and the field position; Communicating with the central control
room through wired and/or wireless network thereby integrating the operation of
the ESP and indicating for the any possible malfunction of the ESP and to trigger
plant trip.