Title of Invention

THE MICROPROCESSOR BASED REDUNDANT RAPPER CONTROLLER FOR RAPPING SYSTEM OF AN ELECTROSTATIC PRECIPITATOR

Abstract Electrostatic precipitators are used for collecting dust particles from dust-laden gases. For example in a thermal power plant electrostatic precipitator is used for collecting fly ash from exhaust gas or flue gas from furnace. The collected dust particles are dislodged from electrode plates using tumbling hammer mechanism. The hammer mechanism is driven by rapping motors Rapper controller switches ON/OFF those rapping motors, when necessary. Rapper controller is designed using microprocessor and has stanaby configuration. Main controller is called MASTER and standby controller is called SLAVE. MASTER and SLAVE are interfaced to provide highly reliable rapper controller configuration. During failure of MASTER, SLAVE will continue to control rapper motors and hands-over control to MASTER when MASTER becomes healthy.
Full Text FIELD OF INVENTION
The invention relates to an improved rapper controller for rapping system. More
particularly, it is a microprocessor based redundant rapper controller for rapping
system of electrostatic precipitator,
BACKGROUND OF INVENTION
Electrostatic precipitator is one of the effective methods 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
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. It uses electrostatic forces for collection of duct particles
by applying very high voltage to produce electrostatic forces between positive
and negative electrodes. The dust particles between electrodes get ionized and
get collected in electrode plates, viz., discharge electrode and collection plate.
As shown in Fig - 3, a prior art ESP is divided into number of ESP-fields.
Depending on the dust load number of fields is decided for an ESP. An ESP -
field is a set of a discharge electrode and collection plate.
During continuous operation of an electrostatic precipitator, the dust from
collector plate and discharge electrodes must be periodically removed for further
conveying of the collected dust. The dust removal mechanism typically consists
of a mechanical rapper.
Rappers are electro-mechanical devices that are used to mechanically dislodge
collected particulate/materials within an rapper system for an ESP-field consists
of a rapper motor connected to hammer mechanism that mechanically strikes
shock pad ESP-filed electrode at shock pad with the hammer transmits
mechanicals. 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.
An electronic rapper controller, which operates rapping motor, determines the
sequence, intensity, and duration of rapping for an ESP-filed.
In the prior art, it is well known that conventional rapper controllers, for a
tumbling hammer type rapping system, control rapper motors by switching then
ON or OFF periodically, so as to allow ash build-up on plates during OFF time
and remove ash during On time. These periods are dictated by ESP's operating
parameters viz., rapper motor's location with respect to gas flow, overall dust
load into electrostatic precipitator and other user defined options. ON and OFF
times are critically set to avoid excessive rapping or under rapping, bot7h are
detrimental to ESP performance. Excessive rapping will lead to more re-
entrainment and under rapping will cause more sparking in ESP resulting in poor
performance of ESP.
It is known in tine prior art that electronic controllers control rapping motors,
which are driving hammer to remove ash/duct collected on plates. The electronic
controllers vary in its construction, either analog or digital. Irrespective of the
construction, ON time and OFF time of rapping motor remains basic parameters
for controlling.
In the prior art, it is well known that ON/OFF time i.e. time period, of a filed will
vary depending on the particular filed's position with respect to gas flow
direction. If the filed is nearer to ESP entry, then the frequency of rapping will be
more, as the dust collection in that filed will be more. The frequency of rapping
will reduce towards the end of ESP. The frequency of rapper operation, i.e., the
cycle of ON and OFF, is determined by three operating parameters viz.. Start-
time, Run-time and Repeat-time of a rapping motor. 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 timings are generally calculated
and set based on the dust load entering each filed of the ESP along the gas flow
direction and other user defined methods.
In the prior art, mechanisms also exist to change the rapper frequency by way of
scaling up or down in proportional to the plant-operating load. The dust load
entering the ESP is proportional to the plant-operating load.
In the prior art, mechanisms also exist to change the rapper frequency by way of
scaling up or down in proportional to the plant-operating load. The dust load
entering the ESP is proportional to the plant-operating load.
In the prior art, mechanisms also exists to control all rapper system in an ESP by
a single rapper controller. The controller is based generally on analog circuits,
digital timers or microprocessor based electronic system. In the event of failure
of controller, if it controls all rapper systems of an ESP, the entire rapping
operation will be halted. Allowing ash buildup on electrode plates beyond
reasonable time will make ESP inefficient.
Generally, for a larger size ESPs, only common rapper controller, which can
control all rapper motors of an esp, is preferred for various reasons. Specially,
such a common controller approach will reduce operator overheads and helps in
coordinated operation with central plant controller, etc.
Electrostatic precipitator (ESP) is an air pollution control device designed to
electrically charge and collect dust particulates generated from industrial process
such as those occurring in power plants, pulp and paper mills.
ESP uses electrostatic forces for collection of dust particles by applying very high
voltage to produce electrostatic forces between positive and negative electrodes.
In short, function of an ESP can be described as under:
Electrostatic force -> charging of dust particle -^ migration of charged particle
towards electrode —>¦ attaching in electrodes -> discharging the dust particulate
from electrode by using rappers -> collection of dust in hopper -^ transportation
for dispatch.
In industry on continuous operation of an ESP, a huge dust particles are
accumulated on both the faces of electrode plate. The dust from collected plate
are periodically dislodged for further conveying of the dust to electrode plate for
the efficient operation. The dust removals mechanism typically consist of
mechanical rapper.
Rappers are electro-mechanical devices that are used to mechanical dislodge
collected particulate within electrostatic precipitator or dust collector. In general,
a rapper system for an ESP filed consist of a rapper motor connected to hammer
mechanism that mechanically strikes shock pad of respective electrode to which
it is connected, striking the ESP field electrodes at shock pad with the hammer
transmit mechanical forces to these components to dislodge collected material.
There are two types of hammer generally used in an industry:
1. Lifting hammer type
2. Tumbling hammer type
Lifting hammer type
The rapper consists of a cylindrical hammer or plunger and solenoid coil. The
hammer rest on the rapper shaft or anvil. When a solenoid coil is energized with
a DC voltage the resulting electro-magnetic force overcomes the force of gravity
and lift the hammer vertically to a height that is determined by the amplitude
and length of time of energization. When the energization is terminated, the
electromagnetic field is removed and the hammer drops due to gravitational
force and strikes the anvil. The hammer then rests on the anvil until the next
energization.
The system obtains the performance characteristics of a first rapper and
calculates a rapper lift value. The system then obtains performance characteristic
data from two or more additional rappers and calculates rapper lift values for
each rappers. Finally the system compares the rapper lift value of each additional
rapper and adjust its performance characteristics so that substantially
approximates the performance characteristics of the first rapper.
US 20030010203 provides an improved method and system to control the
rapping process used to clean the internal collection plates and discharge
electrodes of electrostatic precipitators. The system obtains the performance
characteristics of a first rapper and calculates a rapper lift value. The system
then obtains performance characteristic data from two or more additional
rappers and calculates rapper lift values for each of the rappers. Finally, the
system compares the rapper lift value of each additional rapper and adjusts its
performance characteristics so that it substantially approximates the
performance characteristics of the first rapper.

KR 20020051015 provides a rapping control unit of pulse-jet filter system, which
can prevent dust from being adhered on adjacent filter cartridge by changing
rapping interval and time. CONSTITUTION: The system comprises a
programmable logic controller (2), a solenoid valve (4) and a signal transferring
part (6). Compressed air is ejected to filter bag of a pulse-jet bag filter. The
rapping interval and time is controlled by PLC and ejection is actuated by the
solenoid valve (4). The rapping sequence is expressed as follows : (k+1)
multiplied by n minus k, where k is positive numbers as 1,2,3 expressing
example numbers and n are every other raw numbers.
There is no mechanism exists in the prior art, which gives a standby system to
backup the operating rapper controller in the event of failure.
OBJECTS OF INVENTION
The primary object of the invention is to provide a highly reliable, redundant
rapper controller, which can control all rapper motors of an ESP. It will be able to
store user data on frequency of rapping for all motors, provide user interface and
work in coordination with central controller for ESP.
This invention specifically deals with development of a rapper controller with
redundancy feature. The rapper controller is designed using microprocessor and
peripheral ICs. It can control and monitor upto 24 rapper motors operating in an
ESP. The redundant rapper controller contains MASTER and SLOAVE modules. At
rapper controller startup, MASTER module will operate in main mode and SLAVE
module will take-over controlling rapper motors from the point where MASTER
has left. Rapper motors can be operated in MUNUAL mode or AUTO mode
operation requires a set of pre-determined times to be stored in EPROM.
SUMMARY OF INVENTION
Accordingly, there is provided an improved Rapper Controller for electrostatic
precipitator used for removing dust particles from electrodes of an ESP field
comprising; at least one MASTER module and one SLAVE module wherein the
operation of the MASTER and SLAVE modules are controlled by a microprocessor
and the controls like input scanning, output commanding, communication
interface, user interface signals are controlled by the peripherals Integrated
Circuits (ICs) and wherein the rapper start time, runtime and repeat time are set
depending upon the position with respect to gas flow direction and overall dust
load into electrostatic precipitator; the MASTER and SLAVE modules are
synchronized through a communication channel and a real time clock (RTC); the
MASTER and SLAVE modules have two independent communication channels;
the MASTER module and SLAVE module being operated in ACTIVE mode and in
STAND-BY mode respectively during start up and normal operation; the
communication exchange is initiated by a MASTER controller and responded by a
SLAVE controller, in case the MASTER controller fails to control the rappers due
to operational failure or software malfunction, the SLAVE controller will continue
to control the rappers and shall be active from the point where the MASTER
controller became inactive, till the MASTER controller becomes operative.
The instant specification deals with such a tumbling hammer type rapper in the
ESP field. In this tumbling hammer type rapper, one cam is mounted on rapper
shaft for each electrode plate during one rotation of shaft, the cam will be
tumbled when it starts rotate from top to downward movement and the hammer
will strike the shock pad of each electroplate due to gravity. A series of cams are
mounted having disposed in various angle with respect to shaft axis so that
during one rotation of shaft a numbers of cam can strike the numbers of
electroplate in one compartment.
The instant specification discloses a teaching for improved rapper controller for
ESP which contains two modules, master and slave, each module can control
motor of rapper start time, run time i.e. motor switch ON and OFF.
Each module is designed with micro-processor and peripheral circuits and
forming electronic cards. The hardware components of MASTER module and
SLAVE module are identical. But, the software is different. By changing the
software alone, the hardware can be made either MASTER or SLAVE module.
During startup, the MASTER module will be in ACTIVE mode and SLAVE module
will be in STAND-BY mode. MASTER module, which is in ACTIVE mode only, is
authorized to command the rapper motors; and SLAVE module, which is in
STAND-BY mode, will only follow MASTER module commands. In ACTIVE mode,
the MASTER module will operate the rapping motors either in AUTO or MANUAL
mode depending on the selection by the user. More specifically, the ACTIVE
mode module only can process inputs and outputs. In STAND-BY mode, the
SU\VE module will be receiving command information through a dedicated
communication channel (4) regularly and suitably operates its output channels as
per the command received from the MASTER i.e., it is not authorized to process
inputs and outputs but only follow the commands from the ACTIVE module.
Therefore, the output channels ([5],[7] of both the ACTIVE and STAND-BY
modules will be operating the same rapper motors at any point of time and will
reflect the MASTER command signal. Since, both the MASTER and SLAVE
module's output channels are physically connected (OR-ed) to rapping motors, if
any of the commands is ON the rapping motor will be ON.
Also, at startup, the real time clock (RTC) in the MASTER and SLAVE are time
synchronized either by the MASTER or the central ESP controller. If time is
synchronized, both the modules will generate identical commands and output
channel will control the same rapping motors. Since, they are operating in
ACTIVE or STAND-BY mode, they will be acting according to the mode as
explained above.
During operation, if the MASTER fails to commend the output channels due to
any fault in its hardware or software, it looses its ACTIVE mode and
subsequently the SLAVE will gain the ACTIVE mode status. Once the slave
becomes Active, it will start processing all inputs and outputs as per ACTIVE
mode. Since RTC is synchronized and all the user settings are already passed on
to the SLAVE by the MASTER through the communication channel during normal
operation, the command signal to output channel by the SLAVE will be no
different from the command signal generated by the MASTER if it were ACTIVE
and healthy.

After the SLAVE becoming ACTIVE and if the I^ASTER becomes healthy, the
SLAVE will hand-over ACTIVE status to the MASTER and will transfer all system
status to the MASTER. Subsequently, the RTC in both the MASTER and SLAVE
will be synchronized by the SLAVE and the SLAVE will go into STAND-BY mode.
BRIEF DESCRIPTION OF THE ACOMPANYING DRAWINGS
Now the invention is described in detail particularly with reference to the
drawings accompanying.
Fig. 1 - shows in block diagram, the rapper controller of the invention.
Fig. 2 - shows the microprocessor and the peripheral and circuits of the rapper
controller.
Fig. 3 - shows a typical Electrostatic Precipitator (EP)
Fig. 4 - shows an ESP during an industrial operation.
Fig. 5 - shows a lifting hammer in an ESP.
Fig. 6 - shows a tumbling type happer of the ESP.
DETAILED DESCRIPTION OF THE INVENTION
The redundant rapper controller controls upto 24 rapping motors using its output
channels and monitors all these motors whether they are ON or OFF using its
input channels. Each rapping motor can be switched - on either in MANUAL
mode or in AUTO mode. AUTO mode running requires the motor to have START
TIME, RUN TIME and REPEAT TIME. Start time determines, when a rapping
motor shall start for rapping. Run Time decides, how long rapping shall occur
and Repeat Time decides, at what frequency rapping card of module. These
timings are calculated according to position of rapping motor with respect to gas
flow direction and dust load in the gas flow. In MANUAL mode, rapping motor
can be switched ON and running continuously without time limit.
The redundant rapper controller has two modules, namely MASTER [1] and
SLAVE [2]. Each module is designed with micro - processor and peripheral
circuits and forming electronics cards. The hardware components of MASTER
module and SLAVE module are identical. But, the software is different. By
changing the software alone, the hardware can be made either MASTER or
SLAVE module.
During startup, the MASTER module will be in ACTIVE mode and SLAVE module
will be in STAND-BY mode. MASTER module, which is in ACTIVE mode only, is
only authorized to command rapper motors and SLAVE module, which is in
STAND-BY mode, will only follow MASTER module commands. In ACTIVE mode,
MASTER module will operate rapping motors either in AUTO or MANUAL mode
depending on the selection by the user. More specifically, ACTIVE mode module
only can process inputs and outputs. In STAND-BY mode, SLAVE module will be
receiving command information through dedicated communication channel [4]
regularly and suitably operates its output channels as per the command received
from MASTER i.e., it is not authorized to process inputs and outputs but only
follow the commands from ACTIVE module. Therefore, the output channels ([5],
[7] of both ACTIVE and STAND-BY modules will be operating the same rapper
motors at any point of time and will reflect MASTER command signal. Since, both
MASTER and SLAVE module's output channels are physically connected (OR-ed)
to rapping motors if any of the commands is ON, rapping motor will be ON.
Also, at startup, the real time clock (RTC) [26] in MASTER and SLAVE are time
synchronized either by MASTER or central ESP controller. IF time synchronized,
both the modules will generate identical commands and output channel will
control same rapping motors. Since, they are operating in ACTIVE or STAND-BY
mode, they will be acting according to the mode as explained above.
During operation, if the MASTER fails to command the output channels due to
any fault in its hardware or software, it looses its ACTIVE mode and
subsequently SLAVE will gain ACTIVE mode status. Once the salve becomes
ACTIVE, it will start processing all inputs and outputs as per ACTIVE mode. Since
RTC is synchronized and all the user settings are already passed on to SLAVE by
MASTER through the communication channel during normal operation, the
command signal to output channel by SLAVE will be no different from the
command signal generated by MASTER if it were ACTIVE and healthy.
After SLAVE becoming ACTIVE and if {RASTER becomes healthy, the SLAVE will
hand-over ACTIVE status to MASTER and will transfer all system status to
MASTER. Subsequently, the RTC In both MASTER and SLAVE will be
synchronized by SLAVE and SLAVE will go into SYAND-BY mode.
In fig. 1, the redundant rapper controller configuration is clearly represented. It
shows MASTER [1] and SLAVE [2] are interfaced each other by a communication
channel - 1 [4], which is meant for command and user information exchanger.
Another communication channel-2[3] makes then to communicate to central ESP
controller. MASTER [1] module is interface to its own output channel [5] and
input channel [6] and SLAVE module is interfaced to its own output channel [7]
and input channel [8]. The output channels of both through cable link [14] and
cable link [15] so that if any of the outputs is high the rapper motor [13] will be
on [11] and there by running rapping system of an ESP-field. When both
MASTER and SLAVE outputs are low, rapper motor [13] will be OFF. Similarly,
the running status [12] of the rapping motor passed on to both MASTER input
channel [6] and SLAVE input channel (8) through a cable link [16] and cable link
[17] respectively. It is clear from this redundancy configuration that even if there
is may fault in any of the components either the MASTER stream or in SLAVE
stream, if any one stream is healthy, the rapper system will function as designed
without any break in service.
In fig. 2, the hardware architecture of both MASTER and SLAVE module is
represented. Both MASTER and SLAVE have identical hardware. The Central
Processing Unit (CPU) of the modules contains a microprocessor [18] and
required number of peripherals. The microprocessor has two communication
peripherals ([19] & [20], one channels-1 for communication between MASTER
and SLAVE [27] and another one for communication [28] to central ESP
controller. It also has Real Time Clock [26] for AUTO mode operation for any
rapper motor and it is time synchronized between MASTER and SLAVE. The
microprocessor controls i.e., makes ON or OFF [ll],rapping motors through
output channels ([5],[7]) through a peripheral IC [24] and the ON/OFF feedback
status [12] Is read by a peripheral IC [25] through input channels ([6], [8]). It
also contains memory ICs to store program [21], AUTO mode time base for
rappers [22] and variables [23].
As shown in figure - 4, there are number of compartments arranged in series
where in each compartment consist of a number of electrode plate and cathode
wires are mounted on a central shaft wherein an electrostatic force is applied
and ionized dust particles are deposited on faces of electrode plate.
Figures 5 & 6 show respectively a lifting type hammer and a tumbling hammer.
WE CLAIM
1. An improved Rapper Controller for electrostatic precipitator used for
removing dust particles from electrodes of an ESP field comprising:-
- at least one MASTER module and one SLAVE module wherein the
operation of the MASTER and SLAVE modules are controlled by a
microprocessor and the controls like input scanning, output
commanding, communication interface, user interface signals are
controlled by the peripherals Integrated Circuits (ICs) and wherein
the rapper start time, runtime and repeat time are set depending
upon the position with respect to gas flow direction and overall
dust load into electrostatic precipitator;
- the MASTER and SLAVE modules are synchronized through a
communication channel and a real time clock (RTC).
- The MASTER and SLAVE modules have two independent
communication channels;
- The MASTER module and SLAVE module being operated in ACTIVE
mode and in STAND-BY mode respectively during start up and
normal operation;
- the communication exchange is initiated by a MASTER controller
and responded by a SLAVE controller, in case the MASTER
controller fails to control the rappers due to operational failure or
software malfunction, the SLAVE controller will continue to control
the rappers and shall be active from the point where the MASTER
controller became inactive, till the MASTER controller becomes
operative.
2. The Rapper controller as claimed in claim 1, wherein the rapping motors
of the Electrostatic precipitator is used for collecting dust particles from
the dust laden gases, by means of the rappers operated by the motors.
3. The Rapper controller as claimed in claim 1, wherein one of said two
independent communication channels is for achieving redundancy and
other one is for distributed control through the centralized ESP controller.
4. The Rapper controller as claimed in claim 1, wherein the protocol interface
defines a formulation of the communication packets which are exchanged
between the MASTER and SLAVE controllers.
5. The Rapper controller as claimed in claim 1, wherein a plurality of
connectors connect the output and input of the MASTER and SLAVE
controllers to respective fields.
6. The rapper controller as claimed in claim 5, wherein the individual output
from the MASTER and SLAVE controllers are achieves through operation
of LOGICAL-OR at the fields and the feedback status of the fields being to
both the MASTER and SLAVE controllers.
7. The rapper controller as claimed in claim 1, wherein a synchronization is
caused to force the SLAVE to follow the MASTER'S real time by sending a
RTC value to the SLAVE through the communication channel as a packet.
8. The rapper controller as claimed in claim 1, wherein the MASTER and
SLAVE controller have identical control status when the RTC is
synchronized.
9. The rapper controller as claimed in claim 1, wherein an ACTIVE mode of
the MASTER or the SLAVE indicates a state of the Rapper controller which
is presently which is presently and actively controlling and monitoring the
rappers and a STAND-BY mode indicates a state, which follows the actions
of the ACTIVE mode Rapper controller.
10. A process of purif/ing the dust laden gas generated in industrial activities
by using the improved rapper controller as claimed in claim 1 to 9.
11. An improved Rapper Controller for Electrostatic precipitator as herein
described and illustrated with reference to the accompanying drawings.


Electrostatic precipitators are used for collecting dust particles from dust-laden gases. For example in a thermal power plant electrostatic precipitator is used for collecting fly ash from exhaust gas or flue gas from furnace. The collected dust particles are dislodged from electrode plates using tumbling
hammer mechanism. The hammer mechanism is driven by rapping motors Rapper controller switches ON/OFF those rapping motors, when necessary. Rapper controller is designed using microprocessor and has stanaby configuration. Main controller is called MASTER and standby controller is called SLAVE. MASTER and SLAVE are interfaced to provide highly reliable rapper controller configuration. During failure of MASTER, SLAVE will continue to control rapper motors and hands-over control to MASTER when
MASTER becomes healthy.

Documents:

00987-kol-2005-abstract.pdf

00987-kol-2005-claims.pdf

00987-kol-2005-description complete.pdf

00987-kol-2005-drawings.pdf

00987-kol-2005-form 1.pdf

00987-kol-2005-form 2.pdf

00987-kol-2005-form 3.pdf

987-KOL-2005-FORM-27-1.pdf

987-KOL-2005-FORM-27.pdf

987-kol-2005-granted-abstract.pdf

987-kol-2005-granted-claims.pdf

987-kol-2005-granted-correspondence.pdf

987-kol-2005-granted-description (complete).pdf

987-kol-2005-granted-drawings.pdf

987-kol-2005-granted-examination report.pdf

987-kol-2005-granted-form 1.pdf

987-kol-2005-granted-form 18.pdf

987-kol-2005-granted-form 2.pdf

987-kol-2005-granted-form 3.pdf

987-kol-2005-granted-form 5.pdf

987-kol-2005-granted-gpa.pdf

987-kol-2005-granted-reply to examination report.pdf

987-kol-2005-granted-specification.pdf


Patent Number 237903
Indian Patent Application Number 987/KOL/2005
PG Journal Number 03/2010
Publication Date 15-Jan-2010
Grant Date 12-Jan-2010
Date of Filing 31-Oct-2005
Name of Patentee BHARAT HEAVY ELECTRICALS LIMITED
Applicant Address REGIONAL OPERATIONS DIVISION (ROD), PLOT NO: 9/1, DJ BLOCK., 3RD FLOOR, KARUNAMOYEE, SALT LAKE CITY, KOLKATA-700091, HAVING ITS REGISTERED OFFICE AT BHEL HOUSE, SIRI FORT, NEW DELHI
Inventors:
# Inventor's Name Inventor's Address
1 KADAPERI PANCHATSARAM MANIMALA BOILER AUXILLIARIES PLANT, BHEL, RANIPET-632 406, TAMILNADU
2 BALAKRISHNAN VENKATESHWAR BOILER AUXILLIARIES PLANT, BHEL, RANIPET-632 406, TAMILNADU
3 VELU SUBBAN SURESHKUMAR BOILER AUXILLIARIES PLANT, BHEL, RANIPET-632 406, TAMILNADU
4 SOMESHWAR TUKARAM GAIKWAD BOILER AUXILLIARIES PLANT, BHEL, RANIPET-632 406, TAMILNADU
5 GOURI SHANKAR NAIK BOILER AUXILLIARIES PLANT, BHEL, RANIPET-632 406, TAMILNADU
PCT International Classification Number B03C 3/76
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA