Title of Invention

AN APPARATUS FOR CONTROL OF COAL FEEDING DEVICE .

Abstract

The raw coal feeding device deliver coal in proportion to the fuel demand generated from the combustion control means envisaged in the boiler. The innovative aspect of this invention is to integrate advanced microprocessor / microcontroller based modules to execute the functions, such as logical, sequencing timing, counting, computation, closed loop control, data archiving and communication related to control the coal feeding process. The application program is stored in the read-write part of the memory of the microprocessor / microcontroller. The feeding device is operated in accordance an application program residing in the microprocessor / microcontroller. The man-machine interface provides apt guidance to the operating personnel for easy operation / calibration in a user-friendly manner. Accordingly, there is provided an improved apparatus for on-line computation and control of a raw coal feeding device in a coal fired boiler system, the system comprising a plurality of integrated control means including a combustion control means; atleast one belt-conveyor carrying coal regulatable by a drive means having an AC-induction motor and a clutch; and atleast one calibration probe, the apparatus comprising a remote control panel; a local control panel mounted on the raw coal feeding device, and connected via screened cable to the remote control panel; a man-machine interface operably connected being mounted on the door of the remote control panel; and configured to remotely operate the raw coal feeding device, wherein the combustion control means transmits a signal representative of the fuel demand by the boiler system, the local control panel having atleast one signal conditioning module for receiving the signals and transferring the conditioned signals to the remote control panel, and wherein the remote control panel comprising a plurality of card racks having atleast one microcontroller module operable to compute on-line data and control the drive means of the coal feeding device so as to feed raw coal in registration with the fuel demand communicated by the boiler system.

Full Text

FIELD OF INVENTION The present invention relates an improved apparatus for on line computation and control of a coal feeding device during its feeding raw coal to pulverizers in coal- tired boilers. BACKGROUND OF THE INVENTION Coal fired boilers are employed world wide by thermal power plants and many other industries which require steam and / or power for its operation. The coal from a bulk storage is fed to a pulverizer through a coal feeding device. The coal feeding device weigh the raw coal passing through a conveyor belt, adjust the quantum of coal fed to the pulverizer in proportion to demand of the system and compute the amount of coal fed to the pulverizer over a period of time. It is essential to maintain the weighing accuracy of the feeding device on a long-term basis. To achieve this, re-calibration of the coal feeding device is required to be done under the following conditions: • When any of the components in weighing system / speed measuring circuit is changed. • At regular intervals of around six months to take care of weighing system components wear and tear. In the presently available hardwired electronic (solid state) control, more than nine varieties of electronic modules (Electronic cards) are used to perform weight sensing, speed measuring, rate multiplying computation, belt speed and logic control functions. These modules are mounted in the card racks - one number, rack fixed inside remote power cabinet and another mounted in the feeder integral cabinet. During calibration of feeders under the conditions described above, the potentiometers located in the field mounted modules need to be adjusted to arrive at the calibration accuracy. Repeated adjustment of the potentiometers are required on trial basis, to achieve the accepted level of accuracy. Hence the calibration process takes more time (approximately one hour). Also the output of the potentiometers drift after few months of continuous operation due to feeder vibration etc., which ultimately affect the weighting accuracy. United States Patent no. 5,784,974 titled "System for improving fuel feed control of volumetric coal feeders" discloses a feeder system for measuring and controlling the massed feed rate of particulate fuel material, such as coal particles, made up of a group of volumetric feeders and a gravimetric feeder coupled to the group of volumetric feeders. The system controls the fuel feed rata of the volumetric feeders based upon data communicated from the gravimetric feeder. The reference in gist discloses a method of controlling a group of volumetric feeders with a gravimetric feeder coupled to it. The invented design pertains to an apparatus for controlling the feed rate of only an individual coal feeding device. United States Patent no. 4,582,026 titled "Feed-forward type automatic control system" describes an automatic anticipatory control system for controlling, by one common control quantity, a plurality of points of operation that can be changed over individually and arbitrarily between start and stop operations and between an automatic operation mode and a manual operation mode. In gist, the disclosure relates to an apparatus for controlling the feed rate of only one coal feeding device. Thus, the major disadvantages of the prior art constitute repeated adjustment of the potentiometers leading to delay and inaccuracy in measurement. OBJECTS OF THE INVENTION It is therefore, an object of the invention to provide an improved apparatus for controlling a coal feeding device in a steam generation system. Another object of the invention is to provide an improved apparatus for controlling a coal feeding device in a steam generation system having automatic calibration facility and does not require any manual settings or adjustments in the Electronic Hardware. A further object of the Invention is to provide an improved apparatus controlling a coal feeding device in a steam generation system which has self-diagnostic features to guide the operator for easy troubleshooting. A still further object of the invention is to provide an improved apparatus controlling a coal feeding device in a steam generation system which is capable of establishing compatible interfaces for integration with other controllers and control means of the generation system. Yet another object of the invention is to provide an improved apparatus for controlling a coal feeding device in a steam generation system which is capable of easy maintenance and user friendly. SUMMARY OF THE INVENTION The raw coal feeding device deliver coal in proportion to the fuel demand generated from the combustion control means envisaged in the boiler. The innovative aspect of this invention is to integrate advanced microprocessor / microcontroller based modules to execute the functions, such as logical, sequencing timing, counting, computation, closed loop control, data archiving and communication related to control the coal feeding process. The application program is stored in the read-write part of the memory of the microprocessor / microcontroller. The feeding device is operated in accordance an application program residing in the microprocessor / microcontroller. The man-machine interface provides apt guidance to the operating personnel for easy operation / calibration in a user-friendly manner. Accordingly, there is provided an improved apparatus for on-line computation and control of a raw coal feeding device in a coal fired boiler system, the system comprising a plurality of integrated control means including a combustion control means; atleast one belt-conveyor carrying coal regulatable by a drive means having an AC-induction motor and a clutch; and atleast one calibration probe, the apparatus comprising a remote control panel; a local control panel mounted on the raw coal feeding device, and connected via screened cable to the remote control panel; a man-machine interface operably connected being mounted on the door of the remote control panel; and configured to remotely operate the raw coal feeding device, wherein the combustion control means transmits a signal representative of the fuel demand by the boiler system, the local control panel having atleast one signal conditioning module for receiving the signals and transferring the conditioned signals to the remote control panel, and wherein the remote control panel comprising a plurality of card racks having atleast one microcontroller module operable to compute on-line data and control the drive means of the coal feeding device so as to feed raw coal in registration with the fuel demand communicated by the boiler system. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING Figure 1 - Shows a schematic diagram of the improved apparatus according to the present invention. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The improved apparatus comprises a Remote control panel, a Local Control Panel and associated interconnecting cables. As shown in Figure 1, the Remote control panei (1) consists of card racks (3) which comprise the microprocessor / microcontroller module, power supply and motor speed control module and other interface electronic modules. The card rack is wired with various system components. A Man-Machine Interface (2) is mounted on the door of the Remote Control Panel. The Local Control Panel (4) is mounted on the coal feeding device, and houses a signal conditioning module (5). Weighing modules (6) are used to weigh the coai passing through a fixed length of the conveyor belt. The coal feeding device has a drive means which consists of an AC induction motor (9), eddy current clutch (10) and gear reducers (11) to drive a conveyor belt. The interconnections between the Remote Control Panel (1) and the Local Control Panel (4) are made by special screened cable (8) to facilitate signal transfer. To perform calibration of the feeding device, two numbers of calibration probes (7) are hooked up to the signal conditioning module (5) whenever required. The calibration is done by attaching test weights to the coal feeding device. The improved apparatus maintains the feed rate accurately as per fuel demand signal from the combustion control means by regulating the current to the coil of the clutch means (10). The regulation of the current to the clutch coil controls the speed of the belt conveyor through gear reducers (11). In order to regulate the clutch coil current, the microprocessor / microcontroller estimates the required motor speed set point. To determine the actual federate, computation is carried out. The computation comprises a calculation of the federate by utilizing the speed factor and weight factor previously obtained during the calibration process. The actual feed rate is compared with the fuel demand feed rate to determine the motor speed set point. The man-Machine Interface (2) unit provided on the door of the Remote Control Panel (1) communicates the data to the microprocessor / microcontroller module mounted in the card rack (3) in the Remote Control Panel. Membrane type keyboard provided as part of Man-Machine Interface, is especially configured to meet the operational requirement of the feeding device. The Remote Control Panel (1) mounted microprocessor / microcontroller has provisions for automatic calibration of coal feeding device, thus eliminating time consuming, trial and error potentiometer method of calibration. The Man- Machine Interface is extremely user friendly including self-prompting instructions and messages. The face of the interface has a sealed membrane with a full- function keyboard. Further the interface also provides event recording, self test and diagnostic features for quick trouble shooting and reducing down time of the equipment. The microprocessor / microcontroller module further provides direct interface with Distributed Control System (DCS) through serial communication ports, configurable to RS232C or RS485. It also includes total password security for the protection of calibration constants and capacity reprogramming parameters. The microprocessor / microcontroller module can be located up to 750 m away from the coal feeding device. The apparatus can also be used to handle continuous bulk movement of minerals ores anrirhomirak fnnrlch iffc anA a uariof-u n( nfj-iar> m»f«■>;*(«• process. The actual feed rate is compared with the fuel demand feed rate to determine the motor speed set point. The microprocessor / microcontroller module is located in a modular type panel for better aesthetics. The apparatus is user friendly such that calibration / re-calibration can be done by data entry through a alpha-numeric display device (located in a panel, mounted away from the raw coal feeding device) and without potentiometers adjustment. WE CLAIM 1. An improved apparatus for on-line computation and control of a raw coal feeding device in a coal fired boiler system, the system comprising a plurality of integrated control means comprising a combustion control means; at least one belt-conveyor carrying coal regulatable by a drive means having an AC-induction motor (9) and a clutch (10); and atleast one calibration probe (7), the apparatus comprising a remote, control panel (1); a local control panel (4) mounted on the raw coal feeding device, and connected via screened cable (8) to the remote control panel (1); a man-machine interface (2) operably connected being mounted on the door of the remote control panel (1); and means configured to remotely operate the raw coal feeding device, wherein the combustion control means transmits a signal representative of the fuel demand by the boiler system, the local control panel (4) having at least one signal conditioning module (5) for receiving the signals and transferring the conditional signals to the remote control panel (1), and wherein the remote control panel (1) comprising a plurality of card racks (3} having atleast one microcontroller module operable to compute on-line data and control the drive means (9,10) of the coal feeding device so as to feed raw coal in registration with the fuel demand transmitted by the boiler system; characterised in that the local control panel (4) having atleast one signal conditioning module (5) for receiving signals and transferring the conditional signals to the remote control panel (1) comprising a plurality of card racks (3) having atleast one micro controller module operable by a machine interface (2) and control the drive means (9,10) of the coal feeding device through motor speed control module so as to feed raw coal in registration with the fuel demand transmitted by the boiler system. 2. The apparatus as claimed in claim 1, wherein, the feeding device is calibrated by two number of calibration probes (7) are hooked up to the signal conditioning module 5 by attaching test weights to the coal feeding device. 3. The apparatus as claimed in claim 1. wherein the card rack (3) comprising a power supply and motor speed control module, and atleast one interface electronic module. 4. The apparatus as claimed in claim 1, wherein the microcontroller module communicates with the man-machine interface (2) which in turn enables the remotely controlled means to operate the coal feeding device. 5. The apparatus as claimed in one of the preceding claims, wherein atleast one weighing module (6) is disposed adjacent to the conveyor belt for weighing the coal passing through a conveyor belt. 6. The apparatus as claimed in claim 1, wherein the computation of the feed rate data comprises calculation of the feed rate by utilizing the calibrated speed factor and weight factor. 7. The apparatus as claimed in claim 1, wherein the actual feed rate is compared with the fuel demand feed rate to determine the motor speed set point. 8. The apparatus as claimed in claim 1, wherein the remote control panel comprising microcontroller module is operable for automatic calibration of the coal feeding device. 9. The apparatus as claimed in any of the preceding claims, wherein the microcontroller module provides direct interface with the distributed control means of the system via atleast one serial communication port configurable to RS 232C or RS 485. 10. An improved apparatus for on line computation and control of a raw coal feeding device in a coal-fired boiler system as substantially herein described and illustrated with the accompanying drawing. The raw coal feeding device deliver coal in proportion to the fuel demand generated from the combustion control means envisaged in the boiler. The innovative aspect of this invention is to integrate advanced microprocessor / microcontroller based modules to execute the functions, such as logical, sequencing timing, counting, computation, closed loop control, data archiving and communication related to control the coal feeding process. The application program is stored in the read-write part of the memory of the microprocessor / microcontroller. The feeding device is operated in accordance an application program residing in the microprocessor / microcontroller. The man-machine interface provides apt guidance to the operating personnel for easy operation / calibration in a user-friendly manner. Accordingly, there is provided an improved apparatus for on-line computation and control of a raw coal feeding device in a coal fired boiler system, the system comprising a plurality of integrated control means including a combustion control means; atleast one belt-conveyor carrying coal regulatable by a drive means having an AC-induction motor and a clutch; and atleast one calibration probe, the apparatus comprising a remote control panel; a local control panel mounted on the raw coal feeding device, and connected via screened cable to the remote control panel; a man-machine interface operably connected being mounted on the door of the remote control panel; and configured to remotely operate the raw coal feeding device, wherein the combustion control means transmits a signal representative of the fuel demand by the boiler system, the local control panel having atleast one signal conditioning module for receiving the signals and transferring the conditioned signals to the remote control panel, and wherein the remote control panel comprising a plurality of card racks having atleast one microcontroller module operable to compute on-line data and control the drive means of the coal feeding device so as to feed raw coal in registration with the fuel demand communicated by the boiler system.

Documents:

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

602-KOL-2005-FORM-27.pdf

602-kol-2005-granted-abstract.pdf

602-kol-2005-granted-claims.pdf

602-kol-2005-granted-correspondence.pdf

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

602-kol-2005-granted-drawings.pdf

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

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

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

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

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

602-kol-2005-granted-gpa.pdf

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

602-kol-2005-granted-specification.pdf