FIELD OF INVENTION
The present invention relates to a weighing system for the coal charged into coke oven battery. More particularly, the invention relates to the development of a weighing system for estimating the weight of coal charged into coke oven battery, based on the number of integral and/or fractional rotation of a feeder means thereby improving the overall performance of the coke oven battery.
The present invention also relates to a method for estimating weight of the coal charged into an coke oven battery.
BACKGROUND AND PRIOR ART
In conventional coke oven, a few cases there are platform weighing system but it is difficult to maintain due to hazardous environment. In most of the cases there is no weighing system. The operator does it by estimation only.
Such conventional manually estimated system suffers from drawbacks / disadvantages which are discussed hereunder:
A. These are always chances that the oven is not filled
properly and consequently through put of the oven is
less.
B. Sometimes the operator overfills the oven and does not
know how much the overfilling is. The oven heating
system assumes constant weight and because of extra
weight the quality may not be good.
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provided,
D. Because of very hot and dusty environment, operator
charges very quickly and can not estimate whether the
oven is full or not.
E. No provision for storing the information of coal
charged and accountability of coal.
US4580698 describes an automatically adjustable continuous feeder system where a gate type feeder is used. The document has taught an efficient control means to control the flow rate by proportioning opening / closing of gate valve. It deals with control of flow rate based on level {sensed by an ultrasonic sensor) of material in the bunker and the weight of the material being discharged.
Thus there is a need to provide for a weighing system for estimating the weight of coal charged into coke oven battery, based on the number of integral and/or fractional rotation of a feeder means thereby improving the overall performance of the coke oven battery.
The present inventors have found that efficacy and improvement in the estimation of the weight of coal charged in a coke oven battery can be achieved by estimating the charged coal weight based on sensing the integral and/or fractional rotation of a feeder means.
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OBJECTS OF INVENTION
Accordingly, one object of the present invention is to provide a weighing system to estimate the weight of the coal charged into the oven to ensure that the oven is filled as per requirement.
Another object of the present innovation is to keep an accountability of the coal charged into the oven and to provide Management Information Service for performance improvement of coke oven.
SUMMARY OF INVENTION
Thus, according to one aspect of the present invention
there is provided a system for weighing coal charged into
the oven in a charging car comprising multiple hoppers,
said system comprising:
plural counting means connected with feeder means of the motor;
plural current sensors adapted to sense the feeder motor current and being operatively connected to said counting means such that the counting means read number of rotations after the motor current exceeds a predetermined threshold ampere;
programmable controller means connected to the counting means so as to receive information/data/signal pulses from the counting means; and
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human machine interface terminal means indicating various process parameters for the operator
wherein the weight of the charged coal is estimated based on the number of integral rotation and fraction of rotation of the feeder means.
According to another aspect of the present invention there is provided a method for estimating weight of coal charges in a coke oven battery based on the number of integral rotation and fraction of rotation of the feeder means and providing management information service, said method steps comprising :
sensing the feeder motor current exceeding a predetermined threshold ampere thereafter counting number of rotations of the motor feeders means by means of counting means; and receiving and processing sensed information/data/signal pulses adopting a programmable controller means.
DETAILED DESCRIPTION OF PRESENT INVENTION
The system of the present invention comprises hardware and software. The following are the hardware components;
i) Four numbers of encoders mounted in the motor shaft feeding the screw feeder. One motor shaft and the encoder mounting are shown in Fig 1. Four numbers of encoders are used as there are four hoppers in a charging car.
ii) Four numbers of current sensors for sensing the current drawn by four screw feeder motors. The current sensor outputs are connected with the analog input of the PLC system.
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iii) One PLC system to process the output pulses of
the encoders. The encoder signal is processed in a
counter module of the PLC. iv) A display unit to indicate the weight of the coal
charged, v) A PC which acts as the human machine interface to
indicate various process parameters for the operator.
The software component consists of a program which does the following operation. For each motor when the motor current drawn is more than 20 Amps, the encoder reading is taken and the number of integral rotation and the fraction rotation of the encoder is counted. The weight of coal charged from this screw feeder is a function of the number of rotation.
Coal discharge in kg = 78.06 X No of Rotation + 0.0012
From the above as weight of coal charged from this screw feeder is a function of the number of rotation, then
Wc = F(R)
Where R = Rl + R2, Rl stands for integral part of the rotation and R2 stands for fractional part of the rotation. The value of R2 is less than 1
In each revolution of the encoder it gives 1024 pulses. Thus R = number of pulses / 1024.
The relation between the coal charged and number of rotation is shown in Fig 3.
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The hardware components are described as below:
Programmable Controller System:
PLC system consists of Central Processing Unit (CPU), Analog input module, Counter module, Analog output module, Digital display unit etc. The part no. of the modules / software installed is as given in Table-1:

Table-1: Items in the Programmable Controller system
SI. No Item Specification Quantity
1.0 PLC system
1.1 CPU 192 KB programming memory and 2 MB
Flash EPROM 01
1.2 Power supply For CPU and other I/O modules 01
1.3 Analog Input module with front connector 8 Channel, 0 to +10 V DC 01
1.4 Analog Output Module with front connector 8 channel, 0 to +_10 V DC 01
1.5 Counter Module 4 channel 01
1.6 Communication processor For PLC and PC 01
1.7 Text Display unit 02
1.8 Interfacing unit for text display 02
1.9 Cable for text display 60 m
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2.0 Regulated DC power supply 24 V, 10 A 01
3.0 Programming terminal: PC P-IV 01
Input output modules are described below; Analog Input module:
One analog input module having the following specification
has been used for this purpose.
Number of channels per module: 8
Input range: 0 to + 10 V DC
Conversion time: Around 27 msec
The system uses Analog Input module TSX AEY 800 of
Schneider make. However, any other Analog Input module
having equivalent specification will also serve the
purpose.
Analog Output module:
One analog output module having the following specification
has been used for this purpose.
Number of channels per module: 8
Output range: 0 to + 10 V DC
Conversion time: Around 5 msec
The system uses having Analog Input module TSX ASY 800 of
Schneider make. However, any other Analog output module
having equivalent specification will also serve the
purpose.
Counter Module:
One counter module has been used to count the number of pulses obtained from encoder. This module is having four channels. Module cycle time is 10 msec. The counters can count pulses up to 40 kHz frequency approximately. The
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incremental encoder having direct and quadrature output can be directly connected with the counter module. The system uses Counter module TSX CTY 4A of Schneider make. However, any other counter module having equivalent specification will also serve the purpose.
Programming terminal:
A laptop Pentium-IV PC has been used as a programming
terminal for the programmable controller as well as human machine interface terminal. This PC is located in the control room.
Technical Specification of Current Sensor:
Current : 50 A : 1 A
Transformer
Current range : 0-1A
Output : 0-10 V DC isolated output correspond to
0-1 A current
Accuracy : +_ 0.25 %
Power supply : 230 V AC
Mounting : DIN rail mounting
Encoders:
There are four encoders mounted in the four numbers of screw feeder shaft through flexible coupling. The encoders are Heidenhain make having 1024 pulses per revolution. The encoders provide direct and quadrature pulses to sense the direction of rotation. The encoder operates on 24 V DC
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power supply. The encoder output is directly connected with counter module.
The system thus provides;
A method for weighing of coal charged into the oven based
on the number of rotation of the screw feeder.
Provides management information service.
The details of the innovation, its objects and advantages are explained in great detail in relation to non limiting exemplary embodiments of the weighing system through screw feeder in relation to the accompanying figures wherein;
BRIEF DESCRIPTION OF ACCOMPANYING FIGURES
Fig 1 shows the principle of screw feeder based weighing system.
Fig 2 shows Input and Output of the PLC.
Fig 3 shows relation between number of rotation of screw feeder and weight of coal discharge.
DETAILED DESCRIPTION OF ACCOMPANYING FIGURES
Reference is first invited to Fig 1 where the principle of the weighing system has been explained. There is a hopper (6) where coal is stored. The coal is charged into the oven through a screw feeder AB (5). There is a screw feeder motor (1) which rotates the screw through a gear (4) to reduce the speed of rotation. An encoder (E3) is connected with the motor shaft through a gear ratio (2). As the screw
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rotates, coal is discharged into the oven. The weight " of
the coal charged is directly proportional to the number of
rotation and fractional number of rotation of the screw
feeder.
Fig 2 shows the input and output of the PLC system. A display unit is connected with the analog output of the PLC through an analog isolation. The display unit is four digits.
Fig 3 shows the relation between the number of rotation of the screw feeder and the weight of the coal charged.
In coke oven battery coal is charged into the oven through charging car. The charging car is having 4 hoppers where the coal is stored. During charging the coal is fed into the oven through a screw feeder. A schematic diagram of the screw feeder arrangement shown in Fig 1. The screw feeder is rotated by an AC motor of 18.5 kW, 1500 RPM, 400 V, 33 Amps rating. As the screw feeder rotates, coal is taken from hopper and charged into the oven. In Fig 1, coal is stored in a hopper (6) . The screw feeder is rotated by a motor (1) , through a gear assembly (4) . The screw (5) of length AB rotates as the motor rotates. Depending on the number of rotation, the amount of coal charged is varied.
In a charging car there are four hoppers and each hopper is connected with the screw feeder mechanism. The coal is charged into the oven through 4 openings in the top of the oven. Thus, the amount of coal charged is the summation of the weight of the coal charged trough each screw feeder.
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The integrated weighing system consists of four current sensors and four encoders. The encoder inputs (E31, E32, E33, E34) , current signal inputs (CSl, CS2, CS3 and CS4) and analog outputs (01) of the programmable controller (7) for weighing system are shown in Fig 2. The total weight of the coal charged is the sum of the four weights from four screw feeders.
The weight of the coal charged into the oven is calculated in the programmable controller and the calculated weight is displayed in the display unit located in the control room. The weight of the coal charged into a particular oven is also shown in the PC and the charged coal weight data is stored with respect to oven number and time.
The invention has been described in a preferred form only and many variations may be made in the invention which will still be comprised within its spirit. The invention is not limited to the details cited above. The components like sensors, encoders as herein described do not limit the scope of the present invention and can be replaced by its technical equivalence and yet the invention can be performed. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.
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WE CLAIM
1. A system for weighing coal charged into the oven in a
charging car comprising multiple hoppers, said system
comprising:
plural counting means connected with feeder means of the motor;
plural current sensors adapted to sense the feeder motor current and being operatively connected to said counting means such that the counting means read number of rotations after the motor current exceeds a predetermined threshold ampere;
programmable controller means connected to the counting means so as to receive information/data/signal pulses from the counting means; and
human machine interface terminal means indicating various process parameters for the operator
wherein the weight of the charged coal is estimated based on the number of integral rotation and fraction of rotation of the feeder means.
2. System as claimed in claim 1, wherein the counting
means comprises encoders.
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i)current transformer and ii)processing electronics adapted to generate 0-10 V Analog signal.
4. System as claimed in claims 1 to 3, wherein the
programmable controller means comprises
i) analog input module being operatively connected to the output of the current signal processing electronics;
ii) analog output module being adapted to provide analog isolation for display and
iii) processor module operatively connected to the analog input and analog output so as to process pulses received from the encoder.
5. System as claimed in claims 1 to 4 further comprises
of counter module adapted to count pulses obtained
from the encoder.
6. System as claimed in claim 5, wherein the counter
module is adapted to count pulses up to 4 0 kHz
frequency approximately.,
7. A method for estimating weight of coal charges in a
coke oven battery based on the number of integral
rotation and fraction of rotation of the feeder means
and providing management information service, said
method steps comprising :
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sensing the feeder motor current exceeding a predetermined threshold ampere thereafter counting number of rotations of the motor feeders means by means of counting means; and
receiving and processing sensed information/data/signal pulses adopting a programmable controller means.
8. Method as claimed in claim 7, wherein the threshold
ampere is at least 20 amps.
9. Method as claimed in claims 7 and 8, wherein the
programming controller comprises a program for reading
specific integral and fractional rotation of the
encoder.
10. A system and method for weighing coal charged into the
oven in a charging car as herein substantially
described and illustrated with reference to the
accompanying figures.

Dated this the 14th day of March 2007
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The present invention relates to a system for weighing coal charged into the oven in a charging car. The system comprises plural counting means (E31, E32, E33, E34) connected with feeder means (5) of the motor, plural current sensors (CS1, CS2, CS3 and CS4) to sense the feeder motor current such that the counting means (E31, E32/ E33, E34) read number of rotations after the motor current exceeds a predetermined threshold ampere, programmable controller means (7) connected to the counting means (E31, E32, E33/ E34) to receive information/data/signal pulses from the counting means (E31, E32, E33, E34) and human machine interface terminal means indicating various process parameters for the operator wherein the weight of the charged coal is estimated based on the number of integral rotation and fraction of rotation of the feeder means. The present invention also relates to a method for estimating weight of coal charges in a coke oven battery based on the number of integral rotation and fraction of rotation of the feeder means.