FIELD OF THE INVENTION:
The present invention relates to an automatic control system for controlling the damper position in suction line in sintering plant for advantageous control of suction of air at reduced specific electrical energy consumption by the exhauster drive motor and thereby increasing the productivity in sintering process. The present invention is particularly directed to favor desired automatic control of damper position, driven by damper motor receiving appropriate signal from the PLC based unit on relevant input process data without any required manual interference/control. This would favour utilizing full suction capacity with provision for the operator to receive continuous feedback on the suction condition and avoiding any unwanted tripping of the exhauster motor. Advantageously, the system of the invention would further favour storing of relevant information on exhauster current, damper opening, frequency of the supply line and suction. The automatic control system is adapted with analog and digital input-output modules, making the system simple yet accurate and having wide application in sintering plants of steel plants for desired control on suction to favor high productivity in sintering process.
BACKGROUND ART:
In sintering plants air is sucked from the sinter bed by exhausters. In the existing sinter plant, there are two exhausters driven by AC synchronous motor with capacity of 4 MW such as to create an under bed suction head of around 1500mm of water column. The suction line is provided with damper means installed inside each of two separate branched ducting connected to main suction pipe line below the sinter bed at one end and the exhausters installed at the other end of the branched duct lines, in order to control the suction volume to effect saving in specific energy consumption while maintaining desired suction head to favour higher productivity of the sintering plant. The exhauster drive motors are of 230 amps rating, the required power being supplied from 11 kV supply line. By opening the damper more, air will be sucked in at larger amount and the suction head generated will also be more, but at the cost of higher consumption of electrical energy. When the suction is increased operatively by opening the damper more in either of the duct branching, the load current in the exhauster motor increases. If the load current increases more than the limiting value, there will be tripping of the exhauster motor. The load current is also a function of the supply frequency. When frequency is high, the speed of the motor is also high and as a result suction also increases. This increases the load current of the exhauster motor.
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Whenever the tripping of the exhauster motor takes place due to over load current due to reasons as described above, there is an unavoidable delay/interruption of around 1 hour to restore the system and thereby causing loss of production and productivity.
On the other hand, when the damper in any of the duct branching is closed more compared to its earlier position, the load current of the exhauster motor is reduced and consequently also the amount of air sucked through sinter machine decreases and this in turn reduces the production rate in the sintering machine/plant.
In the conventional practice, it was observed that damper position is not clearly known to the operator as there is no proper feedback of damper opening/closing. Hence damper control was not proper or proportionate to the required rate of production in the sintering plant and thus inducing uneconomic and uncontrolled consumption of energy.
In conventional sintering plant, opening and closing of the damper is done manually to control the amount of air suction according to the requirement of the sintering process. In such manually operated systems, the operator continuously monitors the current drawn by the exhauster motors and whenever the load current approaches nearer to the limiting current, the operator closes the damper from the present position by pressing a push button till the current is brought much below the limiting value. To be on safer side, the operator keeps a margin between the working value of the current and the limiting value of the current. Thus there remains always a possibility of inducing to the said existing manual system an opportunity loss incurred by not utilizing the full capacity of the exhauster in an optimal way and thereby getting less suction effect and consequent decrease in productivity of the sintering plant. Thus in the conventional manual control, the operator continuously monitors the exhauster current and operates two push buttons, one for opening the damper and the other for closing the damper, operatively through a damper motor receiving the corresponding signal from said push button operation. Under this conventional control of damper the amount of suction with human interface, the specific electrical energy consumption is increased.
If the current approaches near to rated current of 230 Amps, the operator closes the damper immediately so as to reduce exhauster current and avoid possible tripping. In case the current is much below the limit of 230 Amps, the operator opens the dampers and suction is increased and thereby the exhauster current increases from its earlier value.
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Conventional manually operated clamper control system suffers from disadvantages and limitations, which include:
(a) The manual system of control is always operated on a safe margin between the
working load current and the limiting load current for the exhauster motor and as
such the full suction capacity is not economically or optimally utilized.
(b) The operator has to continuously monitor the exhauster current of each exhauster
motor and lack of proper attention and monitoring on part of the operator may lead
to on one hand less suction and fall in sinter production rate or on the other hand,
the exhauster motor may trip due to load current crossing the upper limit.
(c) There is no feedback information to the operator as to how much the damper is open
at any point of time. There is no provision for display or indication of the damper
opening percentage.
(d) There is no provision for storing the information/data related to exhauster current,
damper opening, frequency of the supply line and amount of suction used/suction
head.
There was therefore a persistent need in the sintering plants to develop an automatic system for damper control and thereby controlling the amount of suction created by operatively by the exhauster such that the specific energy consumption is reduced with enhanced control with reliability and without any human interference, avoiding any possible occurrence of tripping of the exhauster motor due to load current crossing upper limit, causing interruption/delay in production till the system is further restored for sinter production.
OBJECTS OF THE INVENTION:
The basic object of the present invention is directed to develop a system for automatic control for the damper opening or closing to favour optimal creation of suction under the sintering bed in plant by the exhauster based on the load current data of the exhauster motor such as to enhance productivity, reduce plant down time due to tripping and reduce the specific electrical energy consumption rate.
A further object of the present invention is directed to automatic control of damper position-opening or closing, in the suction line and the amount of suction by the exhauster by
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advantageous use of programmable controller based on operating exhauster motor load current data.
A still further object of the present invention is to acquire and analyze the process data for the sintering plant such as the exhauster motor current, frequency of the supply line, the percentage opening of the damper, the suction and machine speed of the sinter machine, to favor tuning of the automatic controller to optimize the process parameters.
A further object of the present invention is directed to automatic control of damper and the amount of suction for sintering plant providing means for displaying the parameter values at any time and generating information on performance improvement of the plant for management reporting, as necessary.
SUMMARY OF THE INVENTION:
The basic aspect of the present invention is therefore directed to the invention of a sinter machine suction system adapted for automatic control of damper position in suction line comprising:
sinter machine operatively connected to exhauster means to suck air from the sinter bed; damper means provided in the line of suction of exhauster to control the suction;
said damper means operatively connected to a damper motor for opening and closing of the damper means;
a programmable logic controller with logic of control of said damper motor to open and close said damper means such as to maximize suction and reduce specific electrical consumption of power.
A further aspect of the present invention directed to a sinter machine suction system adapted for automatic control of damper position in suction line comprising:
current sensors for sensing the current drawn by exhauster means; frequency sensor to sense the power line frequency;
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damper position sensors adapted to measure the angle of opening of the dampers;
input contacts for each damper motor control panel comprising a first input contact for damper motor forward movement (corresponding to opening of damper) and a second input contact for motor reverse movement ( corresponding to closing of damper);
a programmable controller for generating forward and reverse movement for opening and closing of damper motors based on the above inputs;
output contacts from the programmable controller for each damper motor, one for forward and the other for reverse; and
human-machine interface for indicating various parameters for automatic damper control.
A still further aspect of the present invention directed to a sinter machine suction system adapted for automatic control of damper position in suction line comprising a display unit adapted to indicate the frequency of supply and/or any other process parameter.
According to a further aspect of the present invention directed to a sinter machine suction system adapted for automatic control of damper position in suction line comprising:
two numbers of current sensors for sensing the current drawn by two exhauster motors; one frequency sensor to sense the power line frequency;
two numbers of damper position sensors adapted to measure the angle of opening of the dampers;
two numbers of input contacts for each damper motor control panel comprising a first input contact for damper motor forward movement (corresponding to opening of damper) and a second input contact fro motor reverse movement ( corresponding to closing of damper);
a programmable controller for generating forward and reverse movement for opening and closing of damper motors based on the above inputs;
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two numbers of output contacts from the programmable controller for each damper motor, one for forward and the other for reverse;
one display unit to indicate the frequency of supply and/or any other process parameter; and
human-machine interface for indicating various parameters for said automatised damper control.
A still further aspect of the present invention directed to a sinter machine suction system adapted for automatic control of damper wherein the programmable controller has analog input module, analog output module, digital input module and digital output module.
A further aspect of the present invention directed to a sinter machine suction system adapted for automatic control of damper position in suction line wherein the programmable controller is adapted to generate forward and reverse action of the damper motor which opens and closes the damper.
The present invention and its objects and advantages are described and illustrated in greater details with reference to the accompanying figures.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES:
Figure 1: is the illustration of the location of dampers and exhausters with motors, in the suction line in the sintering plant.
Figure 2: is the illustration of the conventional manual control of damper position/operation on the basis of continuous monitoring of the respective value of load current exhauster motor on display.
Figure 3: is the illustration of the scheme of the automatic programmable logic control based automatic system of the damper control for opening or closing according to the present invention.
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Figure 4: illustrates the different variable inputs to and outputs from the programmable controller of the present invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING FIGURES:
The present invention is directed to the automatic system for damper control in the suction line of the sintering plant advantageously overcomes the limitations of the existing manual control system, using a programmable controller with analog and digital input-output modules comprising hardware and software devices/components. Said automatic control also prevents tripping of the exhauster motors due to actual operating load current exceeding the limiting current (230 Amps) favoring eliminating delay/ interruption in production until restoration of the system/process.
Dampers are provided in the suction line of the sintering plants in the steel plants, wherein the air is sucked from below the sinter bed at desired volumetric rate and thereby creating suction head of about 1500 mm of water column, in order to favor desired rate of sinter production and related process variables.
Attention is first invited to accompanying figure 1, wherein a schematic illustration has been presented to show the suction line orientation and the locations of the dampers two in number operatively connected to a damper motor operated to either open or close the damper position in either of the ducts shown, each of which controlling the suction generated by each exhauster independently. Air is sucked by exhauster and vacuum is created in the suction line. There are two suction lines which are merged into one below the sinter bed. The accompanying figure 2, illustrates the conventional method of manual controlling of the damper by operating two numbers push buttons, one for opening the damper and the other for closing the damper to favor higher or lower suction by the respective exhauster on the basis of continuous monitoring of the load current display of exhauster motor and maintain a safe margin from the maximum limit of current to avoid tripping. Such manual operation suffers from an opportunity loss incurred due to not using the full capacity of the exhausters or maintains optimum level of suction head, matching with sinter production rate/process requirement. If the current approaches to 230 Amps, he closes the damper immediately so as to reduce the operating exhauster current. In case
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current is much below 230 Amps, the operator opens the dampers and suction increases and there by exhauster current increases.
Attention is now invited to the accompanying figure 3 is the illustration of the automatic control system of the amount of suction in sintering plant (SP) by controlling the damper operation-opening and closing positions, involving Programmable Logic Controller (PLC) with analog and digital devices as input output modules, supporting software means to facilitate analyzing the variable data input and generate appropriate output signal to the damper (DM) operation motor for favored opening and closing of the damper to control desired amount of suction for increased production without interruption. The automatic system of the present invention consist of both hardware and software means for favored PLC based control of the damper wherein the variable data input is processed through a processor for necessary control on safe limits of load current of the exhauster (ER) motor i.e. a lower limit of 224 Amps and higher limit of 230 Amps such that the favored quantum of suction is maintained when the actual operating load current remain within this range and the damper motor remain non-functional, and the damper is automatically opened when the current falls below 224 Amps and it is closed when the current exceeds the 230 Amps limit, on receiving the appropriate signals to each of the damper motor. Moreover, the PLC based controller and said software aided processor means also favors avoiding tripping of the exhauster motor and saving consequent loss of production in sinter plant. The system also provides display means/indicators for the frequency of supply power which is also monitored for safe range of operation of the exhauster favoring desired amount of suction, the angular position of each damper, the actual operating load current of the exhauster(ER) motor etc to favor monitoring the status of the operating parameters.
The PLC based automatic control system for damper control to optimize the amount of suction in sintering plant according to the present invention consist of following hardware components:
i) Two numbers of current sensors for sensing the current drawn by two exhauster motors.
ii) One frequency sensor to sense the power line frequency;
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iii) Two numbers of damper position sensor which measures the angle of opening of the damper;
iv) Two numbers of input contacts from each damper motor control panel; one for damper motor forward movement (corresponds to opening of damper) and other for motor reverse movement (corresponds to closing of damper);
v) A programmable controller for generating forward and reverse signals for the two damper motors based on the above inputs;
vi) Two numbers of output contacts from the programmable controller for each damper motor, one for forward and other for reverse rotation;
vii) One display unit to indicate the frequency of supply or any other process parameter;
viii) One human machine interface to indicate various process parameters for the operator.
The configuration and functional aspects of the hardware components of the PLC based automatic system in a preferred embodiment of the present invention are as described below:
Programmable Controller (PLC) System:
PLC system consists of Central Processing Unit (CPU), Input & Output Modules, Digital display unit etc., the specification/ratings and quantity of such components used are given in the accompanying Table - 1:
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The input and output modules of the programmable controller for damper control system to optimize the air suction in sintering plant, are illustrated in the accompanying figure 4. The configuration/specification of the Input output modules of the said PLC based automatic control system in a preferred embodiment of the present invention for the damper movement to favor generating optimum air suction below the sintering bed so as to improve production, are as described below;
Analog Input module:
Three numbers of analog input modules have been used for this purpose. Each analog input module used for this purpose is having the following specification:
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Number of channels per module: 8
Input range : 0 to + 10 V DC
Conversion time : Around 27 msec
The system developed was having Analog Input module TSX AEY 800 of Schneider make.
However any other Analog Input module having equivalent specification will also serve the
purpose.
Digital Input Module:
Two numbers of digital input modules each of 16 channels has been used. Each digital input
module used for this purpose is having the following specification:
Number of channels per module: 16;
Rated Voltage: 24 V DC;
The system was having Digital Input module TSX DEY 16D2K of Schneider make. However
any other Digital Input module having equivalent specification will also serve the purpose.
Digital Output Module:
Two numbers of digital output modules each of 16 channels has been used. Each digital
output module used for this purpose is having the following specification:
Number of channels per module: 16
Rated Voltage : 24 V DC
The system developed is having Digital Input module TSX DSY 16T2K of Schneider make.
However, any other Digital output module having equivalent specification will also serve the
purpose.
Programming terminal:
A 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 near the programmable controller. The specification of the PC is as given in Table-2 below.
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Technical Specification of Current Sensor:Current Transformer : 1 A : 1 A Current range : 0-1 A. Output : 0-10 V DC isolated output correspond to 0-1 A current. Accuracy : ±0.25% Current indication : 4 digit current indicator for control room. Power supply to the transducer : 230 V AC Mounting : DIN rail mounting.Technical Specification of Frequency sensor:Frequency Variation : 45-55 Hz Output : 0-10 V DC isolated output correspond to 45-55 Hz frequency Frequency Indication : 4 digit frequency indicator for control room. Accuracy : ± 1 % Response time : 60 msec Power supply to the transducer : 230 V AC

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Technical Specification of damper position sensor:Angular variation : 0-90° Output : 0-10 V DC isolated output correspond to 0-90° angle variation Damper position Indication : 4 digit position indicator Accuracy : ±1% Response time : 20 msec Power supply to the transducer : 230 V AC Diameter of shaft of sensor : 6-10 mm

It is thus possible by way of the automatic control system for damper control of the present invention thus provides Automatic control of dampers in the suction line for controlling the exhauster motor current up to the full capacity of the exhauster motor such that the suction is maximum which is desired for maximizing the production, avoiding delay/interruption due to tripping of the exhauster motors.
The control system also limits the exhauster current within the limiting value in order to avoid tripping of the motor due to excess load. It also provides information about the damper position to the operator and management information on plant performance on demand.
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WE CLAIM:
1. A sinter machine suction system adapted for automatic control of damper position in
suction line comprising:
sinter machine operatively connected to exhauster means to suck air from the sinter bed; damper means provided in the line of suction of exhauster to control the suction;
said damper means operatively connected to a damper motor for opening and closing of the damper means;
a programmable logic controller with logic of control of said damper motor to open and close said damper means such as to maximize suction and reduce specific electrical consumption of power.
2. A sinter machine suction system adapted for automatic control of damper position in
suction line as claimed in claim 1 comprising:
current sensors for sensing the current drawn by exhauster means;
frequency sensor to sense the power line frequency;
damper position sensors adapted to measure the angle of opening of the dampers;
input contacts for each damper motor control panel comprising a first input contact for damper motor forward movement (corresponding to opening of damper) and a second input contact for motor reverse movement ( corresponding to closing of damper);
a programmable controller for generating forward and reverse movement for opening and closing of damper motors based on the above inputs;
output contacts from the programmable controller for each damper motor, one for forward
and the other for reverse;and
human-machine interface for indicating various parameters for automatic damper control.

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3. A sinter machine suction system adapted for automatic control of damper position in
suction line as claimed in anyone of claims 1 or 2 comprising a display unit adapted to
indicate the frequency of supply and/or any other process parameter.
4. A sinter machine suction system adapted for automatic control of damper position in
suction line as claimed in anyone of claims 1 to 3 comprising:
two numbers of current sensors for sensing the current drawn by two exhauster motors;
one frequency sensor to sense the power line frequency;
two numbers of damper position sensors adapted to measure the angle of opening of the dampers;
two numbers of input contacts for each damper motor control panel comprising a first input contact for damper motor forward movement (corresponding to opening of damper) and a second input contact fro motor reverse movement ( corresponding to closing of damper);
a programmable controller for generating forward and reverse movement for opening and closing of damper motors based on the above inputs;
two numbers of output contacts from the programmable controller for each damper motor, one for forward and the other for reverse;
one display unit to indicate the frequency of supply and/or any other process parameter;
and
human -machine interface for indicating various parameters for said automatic damper
control.
5. A sinter machine suction system adapted for automatised control of damper position in
suction line as claimed in anyone of claims 1 to 4 wherein the programmable controller has
analog input module, analog output module, digital input module and digital output module.
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6. A sinter machine suction system adapted for automatic control of damper position in
suction line as claimed in anyone of claims 1 to 5 wherein the programmable controller is
adapted to generate forward and reverse action of the damper motor which opens and
closes the damper.
7. A sinter machine suction system adapted for automatic control of damper position in
suction line substantially as herein described and illustrated with reference to the
accompanying figures.

An automatic control system for controlling the damper position in suction line in sintering plant/machine (SP) in steel plants for advantageous control on improvement in suction at reduced specific electrical energy consumption by the exhauster motor and thereby increasing the productivity in sintering process. The present invention is particularly directed to obtain the selective damper(DM) position, opening or closing, in said suction line of sinter plant using said automatic control system, such that maximum air is sucked through the suction line creating suction of around 1500 mm of water column; the said system favor avoiding tripping of the 4 MW synchronous AC motor for the exhauster(ER) and associated downtime till restoration operation of sintering plant(SP). The automatic control system uses programmable logic controller(PLC) with analog and digital input-output modules, sending appropriate signal to the respective damper motor, making the system simple yet accurate and having wide application in sintering plants of steel plants for desired control on suction to favor high productivity in sintering process.