CBA112736
FIELD OF INVENTION.
The present invention relates to raw coal feeders used for feeding bulk solids to pulverizers envisaged in coal-fired boilers. More particularly, the invention relates to an apparatus for on-line computation and control of bulk-solids feeding to a combustion system.
BACKGROUND OF THE INVENTION.
Coal fired boilers are employed world wide by thermal power plants, sugar industries, and many other industries which require steam and /or power for its operation. The coal feeders vary the raw coal flow to the pulverizer in proportion to demand and compute the amount of coal fed to the pulverizer over a period of time. To maintain the weighing accuracy of these coal feeders on long-term basis, re-calibration is required to be done under the following conditions.
• when any of the components in weighing system is changed.
• when any of the components in speed measuring circuit is changed.
• at regular intervals of around six months to take care of weighing system
components wear and tear/change in characteristics.
The raw coal feeders deliver coal in proportion to the fuel demand generated from the combustion control system envisaged in a boiler. In the existing systems, the coni/ol functions such as weighing, sensing, computings comparing, varying speed etc., to meet the demand are performed using hardwired electronic modules. The function of calibration is achieved by tuning the potentiometers located in the electronic modules.
In the presently available hardwired electronic control, more than eight varieties of electronic modules (Electronic cards) are used to perform weight sensing, speed measuring, rate multiplying computation and logic control functions.
These modules are mounted in the card rack assemblies, one fixed inside remote power cabinet and other mounted in the feeder integral cabinet.
During calibration of feeders under the conditions described above, the potentiometers located in the electronic modules need to be adjusted to arrive at the calibration accuracy. Repeated potentiometers adjustments are required on trial basis, to achieve the accepted level of accuracy. Hence the calibration process takes more time. Also the outputs of the potentiometers drift after few months of continuous operation due to feeder vibration etc. The drift in potentiometer setting results in change of calibration accuracy and hence error in feed rate and ultimately leading to weighing inaccuracy.
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CBA112736
CBA112736
OBJECTS OF THE INVENTION
It is an object of the invention to provide an apparatus for on line computation and control of bulk-solids feeding to a combustion system having automatic calibration facility.
Another object of the invention is to provide an apparatus for on line computation and control of bulk-solids feeding to a combustion system having self diagnostic features to guide the operator for easy trouble shooting.
A further object of the invention is to provide an apparatus for on line computation and control of bulk-solids feeding to a combustion system having compatible interfaces for integration with other controllers of the combustion system.
A still further object of the invention is to provide an apparatus for on line computation and control of bulk-solids feeding to a combustion system having facility for operational flexibility and fast/easy maintenance.
Yet another object of the invention is to provide an apparatus for on line computation and control of bulk-solids feeding to a combustion system having user friendly man-machine interface.
SUMMARY OF THE INVENTION.
Accordingly, there is provided an apparatus for on-line computation and control of bulk-solids feeding to a combustion system having a plurality of system controllers ; said apparatus comprising: a bulk solids feeding device having a drive motor directly connected to a. tachogenerator, and a clutch means coupled to the drive motor ; a remote cabinet having a processor, and a man-machine interface ; a communication cable interconnecting the device and the remote cabinet, wherein the processor is operable to receive instructions on operating characteristics of the drive motor from the tachogenerator and demand signals form the system controllers , and in that the processor is configured to generate and transmit command signals which after processing by the remote cabinet being fed to the clutch means thereby controlling the operation of the device .
The innovative aspect of the invention is to integrate Programmable Logic Controllers to execute specific functions, such as logic, sequencing, timing, counting and arithmetic to control the coal feeding process. The application programs are stored in read-write part of the memory of the controller. The feeder operates as per the logic programmed in the PLC. The man-machine interface envisaged as part of the controller provides apt t guidance for easy operation/ calibration in a user-friendly format to the operating personnel.
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CBA112736
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING.
FIG. 1- is a schematic block diagram of the apparatus of the present invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWING.
The apparatus comprises a bulk solids feeding device (8), a remote cabinet (1) and interconnecting cables. The remote cabinet (1) contains the various hardware pertaining to the programmable logic controllers (2) and man-machine interface (3). The main control hardware of the controllers, that is a processor, executes and control the process.
The CPU of the processor receives the instruction from a memory, the feedback (i.e. actual speed of the drive motor which drives the feeding conveyor) from a tacho-generator (not shown) directly connected to a drive motor (4). The CPU then receives demand signal from the controller of the combustion system. On receipt of the signal, the CPU generates and transmits command signal to an output device. The motor speed control module, mounted in the remote cabinet (1) processes the output signal from the output device and converts the same into an Voltage signal which is fed to a clutch means (5) coupled to the drive motor (4).
The man-machine interface (MMI) unit provided on the door of the remote cabinet (1) communicates with the controller through at least one plug in cables. The keys of the MMI are configured according to the operational requirement of the feeding device. A simple hand-held (6) programmer is available to develop, debug and monitor ladder logic programs. The hand-held programmer (HHP) also provides system configuration and data monitoring/changing capability for the controller.
Feeder integral cabinet (7) is mounted on the bulk solids feeding device (8). The integral cabinet (7) contains the signal conditioning modules, selector switch and indicating lamps. The signal transfer and the communication between the remote cabinet (1) and the integral cabinet (7) is performed via a communication cable (9).
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CBA112736
We Claim:
1. An apparatus for on-line computation and control of bulk-solids feeding a
combustion system having a plurality of system controllers (2); said apparatus
comprising:
- a bulk solids feeding1 device (8) having a drive motor (4) directly connected to a tachogenerator of the system, and a clutch means (5) coupled to the drive motor (4);
a remote cabinet (1) having a processor, and a man-machine interface (3); a communication cable (9) interconnecting the device (8) and the remote cabinet (1), wherein the processor is operable to receive instructions on operating characteristics of the drive motor (4) from the tachogenerator and demand signals form the system controllers (2), and in that the processor is configured to generate and transmit command signals which after processing by the remote cabinet (1) being fed to the clutch means (5) thereby controlling the operation of the device (8).
2. The apparatus as claimed in claim 1, wherein the bulk-solids feeding device(8) is
provided with a feeder integral cabinet (7) having signal conditioning modules
and a selector switch.
3. The apparatus as claimed in claim 1, wherein the remote cabinet (1) having
respective hardware relating to the plurality of system controllers (2).
4. The apparatus as claimed in claim 1, wherein the remote cabinet (1) is provided
with a man-machine interface (MMI) having at least one key adaptable to the
operationable requirement of the feeding device (8).
5. The apparatus as claimed in claim 1, comprising a hand-held programmer (HHP)
configured to enable a data monitoring and data changing operation.
6. The apparatus for on-line computation and control of bulk-solids feeding a
combustion system having a plurality of system controller:;, wherein controller (2)
is substantially herein described, and illustrated with reference to the
accompanying drawing.

Accordingly, there is provided an apparatus for on-line computation and control of bulk-solids feeding to a combustion system having a plurality of system controllers ; said apparatus comprising: a bulk solids feeding device having a drive motor directly connected to a. tachogenerator, and a clutch means coupled to the drive motor ; a remote cabinet having a processor, and a man-machine interface ; a communication cable interconnecting the device and the remote cabinet, wherein the processor is operable to receive instructions on operating characteristics of the drive motor from the tachogenerator and demand signals form the system controllers , and in that the processor is configured to generate and transmit command signals which after processing by the remote cabinet being fed to the clutch means thereby controlling the operation of the device .
The innovative aspect of the invention is to integrate Programmable Logic Controllers to execute specific functions, such as logic, sequencing, timing, counting and arithmetic to control the coal feeding process. The application programs are stored in read-write part of the memory of the controller. The feeder operates as per the logic programmed in the PLC. The man-machine interface envisaged as part of the controller provides apt . guidance for easy operation/ calibration in a user-friendly format to the operating personnel.