BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The present invention relates broadly to a sinter plant and, more particularly,
to a control system for uniform transverse temperature distribution across a sinter
plant to improve sinter quality and thereby improving productivity.
2. DESCRIPTION OF THE PRIOR ART
Sinter is a very important raw material for blast furnace. Sintering is a process
where raw materials like iron ore fines, coke breeze and even limestone,
dolomite etc. are agglomerated together. Raw materials are collected at different
bunkers and are allowed to fall in a conveyer in certain proportion. The raw
materials are passed through a drum called "Nodulising Drum", for proper mixing
of raw materials. Water is sprayed on dry raw-mix to form granules.
Subsequently sinter-mix granules are transported by conveyer to a bunker. From
this bunker wet sinter-mix is charged to sinter machine pallet through a drum
feeder. The flow of raw-mix passes through a furnace called ignition furnace
where its uppermost layer is first ignited. As coke present in raw-mix burns
through combustion, its components are fused and sinter is formed. The machine
speed is adjusted in such a manner that just at the discharging end, whole raw
material is converted into sinter and sintering process is completed.
The exhaust gas temperature in wind boxes just below the pallet is an index
for assessing progress of sintering. In most of the conventional sinter plants, the
exhaust gas temperature in wind boxes is measured with the help of
thermocouples installed just beneath the pallet. The temperatures of last three
wind boxes are very crucial, as they indicate the completion of sintering. The
burn through point (BTP) temperature is attained at the last wind box. BTP is the
maximum temperature at the last wind box. At BTP the combustion at
bottommost layer of raw-mix is in progress. The sharp decline in temperature
after BTP indicates that combustion is completed at all layers and all raw-mix
layers are fully sintered. The BTP control system monitors the last three wind box
temperature and controls the machine speed in such a manner that sintering is
just completed at the last wind box.
Known prior arts for a control system for temperature distribution across a
sinter plant to improve sinter quality include EP Pat. No. 1466718 dated 2004-10-
13 to Chung and Allanic; US Pat. application No. 2003222066 dated 2003-12-04
to Low and Ake; WO Pat. Application No.9511100 dated 1995-04-27 to Benda
and Parasco; JP Pat. No. 63241124 dated 1988-10-06 to Nakahara; GB Pat. No.
1131842 dated 1968-10-30 to Metallgesellschaft AG and GB Pat. No. 1046729
dated 1966-10-26 to Sawada.

In EP Pat. No. 1466718 there is provided a method and apparatus for forming
three dimensional objects by laser sintering that utilizes a broad area thermal
vision system such as an infrared camera that can measure multiple
temperatures across the target area and use that temperature data as feed back
to a control system that both adjusts a zoned radiant heater system and adjusts
scan speed and laser power to control temperatures across the target area.
A thermocouple control system for selective laser sintering part bed
temperature control has been delineated in US Pat. application No. 2003222066.
The said system comprises of thermocouple disposed within a part bed of the
sintering machine and a temperature transmitter in communication with the
thermocouple. As per their invention the control circuitry, in communication with
control logic, controls the part bed temperature.
WO Pat. Application No.9511100 discloses a temperature-controlled laser
sintering system. The power control circuit controls a modulator that modulates
the power of the laser beam so as to maintain the thermal radiation emission
(and thus the temperature at the sintering location) at a substantially constant
level.
To improve productivity of a sintering machine of an exhaust gas circulation
system without degrading cold strength, by controlling a temperature of
circulating gas by adjustment of steam pressure in an evaporation part of a waste
heat boiler through which an exhaust gas is passed, a method for controlling
temperature of circulating gas for sintering has been disclosed in JP Pat. No.
63241124.
GB Pat. No. 1131842 narrates improvements in or relating to sintering
machine. In this patent a control system for the speed of the conveyer of a
sintering machine has been disclosed. The location of the maximum of the
temperature curve along the conveyer is determined by feeding signals
representing the temperatures in suction-boxes.
Two sets of controlling variables, including the temperature and pressure of
the waste gases is monitored are monitored by automatic control systems as
delineated by GB Pat. No. 1131842.
After an exhaustive study on the relevant patent documents and on existing
conventional sinter plant it has been found that air filtration velocity is more by
the side of the pallet than at the middle. This is known as "Rim Zone" effect. This
differential air velocity causes non-uniform sintering across the pallet width
causing differential exhaust gases temperatures across the width of pallet. Due
to rim zone effect, sintering is not uniformly completed across pallet width. This
seriously affects the quality of sinter, which is a very important raw material for
blast furnace. Conventional way to avoid this non-uniform temperature
distribution is to slow down the sinter machine speed so that raw-mix gets

sufficient time for sintering. However, this will result in lowering the productivity
level, which cannot be compromised.
Thus, it would be desirable to devise a sintering system, and more
particularly, more particularly, a control system for uniform transverse
temperature distribution across a sinter plant to improve sinter quality and
thereby improving productivity, that obviates the pitfalls of current sintering
schemes and provides an evenly sintered part.
3. SUMMARY AND OBJECTS OF THE INVENTION
Accordingly, the present invention is directed to propose a control system for
uniform transverse temperature distribution across a sinter plant to improve
sintered product quality and thereby improving productivity.
An object of the present invention is to provide a fully automated monitoring
unit for constant monitoring width-wise temperature profile of sinter bed in sinter
machine before discharging.
Another object of the present invention is to achieve uniform distribution of
transverse temperature profile of the sintering machine.
Another further object of the present invention is to provide differential
adjustment of bed height across pallet width through different sector gates
controlled by PLC system.
Yet another further object of the present invention is to develop a logic-based
system to calculate sector gate value position.
Still another object of the present invention is to provide an operator's friendly
Human Machine Interface (HMI) to facilitate the users with graphics, trends,
report etc analysing the progress of sintering process, BTP and machine speed.
Still another further object of the present invention is to provide a
communication driver in PLC platform using OPC (Object Linking & Embedding
for Process Control) for bi-directional data communication between PLC and the
built up model.
The various features of novelty that characterise the invention are pointed out
with particularity in the claims annexed to and forming a part of this disclosure.
For a better understanding of the invention, its operating advantages and specific
objects attained by its uses, reference is made to the accompanying drawings
and descriptive matter in which preferred embodiments of the invention are
illustrated.

To achieve these and other advantages and in accordance with the purpose
of the present invention, as embodied and broadly described, the control system
for uniform transverse heat pattern in sinter plant to control the sinter bed height
and consequently air filtration velocity across the pallet width thereby attaining
uniform transverse temperature pattern, the said control system includes:
a plurality of level of automation to automate the sintering process facilitating in
monitoring of width-wise temperature profile of sinter bed in sinter machine
before discharging;
a communication driver in a PLC platform;
three different sector gates controlled by the said PLC having a predetermined
bed height across pallet width, the said bed height being differentially adjusted
to achieve uniform transverse temperature profile whereby position of the said
three sector gates being varied by means of three electro-mechanical
actuators;
an interface to facilitate the users with graphics, trends, reports and controlling
parameters of the said sinter plant, the progress of sintering, BTP and machine
speed being effectively analyzed;
a plurality of object oriented logic-based rules for the said HMI to calculate a
desired sector gate opening / closing value position so as to attain uniform
transverse heat pattern;
a means for bi-directional data communication between the said PLC and the
said object oriented logic;
a plurality of particular OPC-based (Object Linking & Embedding for Process
Control) client logic-based rules for bi-directional data communication between
the said PLC and the said logic rules; and
a plurality of K-type thermocouples installed with tip exactly at the centre of each
of the three zones of the transverse cross sectional area of pallet in order to
monitor temperature across pallet, the mid point temperature of every zone
being an indicative of average temperature of respective zone measured for the
last three wind-boxes to monitor width-wise temperature variation as well as
BTP detection;
a means for temperature transmitter in communication with the said plurality of K-
type thermocouples incorporated into existing control circuitry in communication
with the said logic-based rules.
The control system for uniform transverse heat pattern in sinter plant to
control the sinter bed height and consequently air filtration velocity across the
pallet width thereby attaining uniform transverse temperature pattern wherein the
said control system facilitates a unique method of adjusting bed height of sinter-
mix in pallet in order to attain uniform temperature across the width.
The control system for uniform transverse heat pattern in sinter plant to
control the sinter bed height and consequently air filtration velocity across the
pallet width thereby attaining uniform transverse temperature pattern wherein

more bed height corresponds to less air filtration velocity and less bed height
corresponds to more air filtration velocity.
The control system for uniform transverse heat pattern in sinter plant to
control the sinter bed height and consequently air filtration velocity across the
pallet width thereby attaining uniform transverse temperature pattern wherein
one of the said automated levels having a plurality of K-type thermocouples, a
means for temperature transmitter in communication with the said
thermocouples, a digital encoder, a plurality of actuators and a plurality of
isolators.
The control system for uniform transverse heat pattern in sinter plant to
control the sinter bed height and consequently air filtration velocity across the
pallet width thereby attaining uniform transverse temperature pattern wherein
one of the said automated levels having the said PLC, a plurality of input / output
cards and ethernet data highway.
The control system for uniform transverse heat pattern in sinter plant to
control the sinter bed height and consequently air filtration velocity across the
pallet width thereby attaining uniform transverse temperature pattern wherein the
Level - 2 of the said automation is connected to Level - 1 of the said automation
through the said high-speed ethernet data highway.
The control system for uniform transverse heat pattern in sinter plant to
control the sinter bed height and consequently air filtration velocity across the
pallet width thereby attaining uniform transverse temperature pattern wherein the
said logic-based rules reside in a PC-based system that in turn is a part of said
Level - 2 of the said automation system.
The control system for uniform transverse heat pattern in sinter plant to
control the sinter bed height and consequently air filtration velocity across the
pallet width thereby attaining uniform transverse temperature pattern wherein the
data acquisition system is implemented through PLC acting as the said Level - 1
of automation and a high level PC acting as the said Level - 2 of automation.
The control system for uniform transverse heat pattern in sinter plant to
control the sinter bed height and consequently air filtration velocity across the
pallet width thereby attaining uniform transverse temperature pattern wherein the
temperature data of the last three wind-boxes of the said sinter plant and
machine speed are analysed by the said logic-based rules in the said Level - 2
PC, and the valve position set points of the sinter plant downloaded to the said
PLC finally driving the actuator through a plurality of MCB panels.
A sinter plant having the control system for uniform transverse heat pattern in
order to control the sinter bed height and consequently air filtration velocity
across the pallet width thereby attaining uniform transverse temperature pattern.

4. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
A more complete understanding of the present embodiments and advantages
thereof may be acquired by referring to the following description taken in
conjunction with the accompanying drawings, in which like reference numbers
indicate like features, and wherein:
Fig. 1 shows a conventional sinter machine delineating the process of operation;
Fig. 2 is a schematic diagram illustrating the non-uniform width-wise sintered
product;
Fig. 3 is a schematic diagram illustrating an ideal case of uniform width-wise
sintered product;
Fig. 4 is the temperature distribution pattern at different wind box location
according to the present invention;
Fig. 5 illustrates the thermocouple installation in order to monitor temperature
across pallet according to the present invention;
Fig. 6 illustrates the system configuration according to the present invention;
Fig. 7 depicts a flow chart of the logic-based system to calculate sector gate
value position according to the present invention;
Fig. 8 illustrates a HMI screen indicating the exhaust gas temperature of the last
three wind boxes, machine speed etc. according to the present invention; and
Fig. 9 delineates a HMI screen-elucidating trend of three temperatures, viz., left,
center and right, of a particular wind box according to the present invention.
5. DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO
THE ACCOMPANYING DRAWINGS
The methodology adopted in the present invention is to control the sinter bed
height and consequently air filtration velocity across the pallet width to attain
uniform transverse temperature pattern as depicted in Fig. 3. This methodology
is based on the concept that more bed height corresponds to less air filtration
velocity and less bed height corresponds to more air filtration velocity. The
control system facilitates a unique method of adjusting bed height of sinter-mix in
pallet in order to attain uniform temperature across the width.

In order to monitor temperature across pallet, the transverse cross sectional
area of pallet is logically divided into three zones. The mid point temperature of
every zone is an indicative of average temperature of respective zone. It is
measured by K-type thermocouples (1) installed with tip exactly at the centre of
each zone. Mid point temperature of every zone is measured for the last three
wind-boxes to monitor width-wise temperature variation as well as BTP detection.
Fig. 5 illustrates the thermocouple (1) installation in order to monitor temperature
across pallet, according to the present invention.
Charging of raw-mix from bunker to pallet can be regulated by sector gate.
The opening or closing of this sector gate defines the bed height. However, with
only one sector gate, bed height is uniform across the pallet width. As pallet is
logically divided in three zones, three sector gates are installed to facilitate bed
height variation across the pallet width. Position of these sector gates is varied by
means of three electro mechanical actuators. The data acquisition system is
implemented through Programmable Logic Controller (PLC) acting as Level - 1
automation (7) and a high level PC acting as Level - 2 (8). These have been
delineated in Fig. 6. The temperature data of the last three wind-boxes and
machine speed are analysed by a logic-based rules in Level - 2 PC (5). The
application of the said logic-based rules calculates the desired sector gate
opening / closing position to attain uniform transverse heat pattern. The valve
position set points are downloaded to PLC that finally drives the actuator through
MCB panels (3).
The present invention has been tested in Sinter Plant # 2 of Durgapur Steel
Plant (DSP). The total length between furnace and discharge end in Sinter Plant
# 2 of DSP is found to be approximately 66 m and width 3 m. the air required for
combustion of raw-mix is made available by creating a suction under the bed by
a high capacity exhauster. Air permeates through the sinter mix in sinter bed and
moves towards exhauster through series of wind-boxes along the length of sinter
machine just below the pallet. The air, thus, helps in agglomerating the raw-mix
layer by layer. There are 33 wind boxes connected to the wind main at Sinter
Plant # 2 of DSP. A temperature distribution pattern at different wind box location
according to the present invention is depicted in Fig. 4.
Fig. 6 illustrates the system configuration according to the present invention.
The Level - 0 of automation (6) system comprises of a means for temperature
transmission (2), a plurality of K-type thermocouples (1), a digital encoder, a
plurality of actuators and a plurality of isolators. Level - 1 of the said automation
(7) system consists of Schneider Electrics™ PLC, a plurality of input / output
cards and Ethernet data highway. The logic-based rules reside in a PC-based
system that in turn is a part of Level - 2 (8) of the said automation system. The
Level - 2 (8) is connected to Level - 1 (7) through the said high-speed Ethernet
data highway.

The logic-based rules are developed in modular form using high level object
oriented logics. The communication driver between the said PLC platform and
the said object oriented logics is developed using concepts of OPC (Object
Linking and Embedding for Process Control). The data logging and control rule-
based systems are developed on PLC using Schneider Electrics, PL7 Pro PLC
standard software. Operator's friendly Human Machine Interface (HMI) has been
developed to facilitate the users with graphics, trends, reports, etc. The logic-
based rules for HMI have been run in Schneider Electrics, Vijeo Look HMI.
The developed control system calculates the desired gate opening with
respect to actual sinter bed temperature profile. The gate position set-points are
downloaded to PLC that finally actuates the sector gates for adjusting the
material flow at centre and both sides of pallet to maintain uniform width-wise
temperature.
In the present invention, the three sector gate positions are derived from
mathematical correlation equations, logic-based rules and plant production
schedule. The mathematical correlation equations are used to calculate the
average deviation of different zonal temperatures. The average zone
temperature is calculated for a cycle of 03 minutes by the following equations (1),
(2) and (3).

where, T^ = average temperature on coke oven (co) side at Z*1 iteration;
Tmdx = average temperature on middle (md) at /h iteration;
TMx = average temperature on blast furnace (bf) side at Z*1 iteration; and
x = wind boxes.
N = No. of interations
The total average zonal temperature is derived by the following equations (4)
through (6).



where, TJ = number of wind-boxes for which trial is conducted;
x = wind boxes;
TAvgCO = average temperature on coke oven (co) side;
TAvgbf = average temperature on blast furnace (bf) side; and
TAvgmd= average temperature on middle (md).
The temperature deviations are calculated as follows:

The sector gate control signal is generated depending upon desired values of
difference as shown in equations (7) and (8). Based on ATcoand ATW, the
inventive control system generates signal to open or shut the sector gates for a
determined values of ASG^, ASGwand ASG^. A flow chart of the said logic-
based system to calculate sector gate value position according to the present
invention has been indicated in Fig. 7. The ASG^, ASGwand ASG^are defined
below:
ASG^, = determined values for sector gate opening of coke oven (co) side;
ASGW= determined values for sector gate opening of blast furnace (bf) side;
and
ASG^, = determined values for sector gate opening of middle (md).
Accompanying Fig. 8 illustrates a HMI screen indicating the exhaust gas
temperature of the said last three wind boxes, machine speed etc. according to
the present invention and Fig. 9 delineates a HMI screen elucidating trend of
three temperatures, viz., left, center and right, of a particular wind box according
to the present invention.
While the principles of this invention have been described in connection with
specific embodiment, it should be understood clearly that these descriptions are
made only by way of example and are not intended to limit the scope of the
invention.

We Claim:
1. A control system for uniform transverse heat pattern in sinter plant to control
the sinter bed height and consequently air filtration velocity across the pallet
width thereby attaining uniform transverse temperature pattern, the said control
system comprising:
a plurality of level of automation (6, 7, 8) to automate the sintering process
facilitating in monitoring of width-wise temperature profile of sinter bed in sinter
machine before discharging;
a communication driver in a PLC platform;
three different sector gates controlled by the said PLC having a predetermined
bed height across pallet width, the said bed height being differentially adjusted
to achieve uniform transverse temperature profile whereby position of the said
three sector gates being varied by means of three electro-mechanical
actuators;
an interface to facilitate the users with graphics, trends, reports and controlling
parameters of the said sinter plant, the progress of sintering, BTP and machine
speed being effectively analyzed;
a plurality of object oriented logic-based rules for the said HMI to calculate a
desired sector gate opening / closing value position so as to attain uniform
transverse heat pattern;
a means (4) for bi-directional data communication between the said PLC and the
said object oriented logic;
a plurality of particular OPC-based (Object Linking & Embedding for Process
Control) client logic-based rules for bi-directional data communication between
the said PLC and the said logic rules;
a plurality of K-type thermocouples (1) installed with tip exactly at the centre of
each of the three zones of the transverse cross sectional area of pallet in order
to monitor temperature across pallet, the mid point temperature of every zone
being an indicative of average temperature of respective zone measured for the
last three wind-boxes to monitor width-wise temperature variation as well as
BTP detection; and
a means for temperature transmission (2) in communication with the said plurality
of K-type thermocouples (1) incorporated into existing control circuitry in
communication with the said logic-based rules.
2. A control system as claimed in claim 1 wherein the said control system
facilitates a unique method of adjusting bed height of sinter-mix in pallet in order
to attain uniform temperature across the width.
3. A control system as claimed in the preceding claims wherein more bed height
corresponds to less air filtration velocity and less bed height corresponds to more
air filtration velocity.

4. A control system as claimed in the claim 4 wherein one of the said automated
levels having a plurality of K-type thermocouples (1), a means for temperature
transmission (2) in communication with the said thermocouples (1), a digital
encoder, a plurality of actuators and a plurality of isolators.
5. A control system as claimed in the claim 4 wherein one of the said automated
levels having the said PLC, a plurality of input / output cards and ethernet data
highway.
6. A control system as claimed in the preceding claims wherein the Level - 2 of
the said automation (8) is connected to Level - 1 of the said automation (7)
through the said high-speed ethernet data highway.
7. A control system as claimed in the claim 1 wherein the said logic-based rules
reside in a PC-based system that in turn is a part of said Level - 2 of the said
automation (8) system.
8. A control system as claimed in the preceding claims wherein the data
acquisition system is implemented through PLC acting as the said Level - 1 of
automation (7) and a high level PC (5) acting as the said Level - 2 of automation
(8).
9. A control system as claimed in the preceding claims wherein the temperature
data of the last three wind-boxes of the said sinter plant and machine speed are
analysed by the said logic-based rules in the said Level - 2 PC (5), and the valve
position set points of the sinter plant downloaded to the said PLC finally driving
the actuator through a plurality of MCB panels (3).
10. A sinter plant having the control system for uniform transverse heat pattern as claimed in claims 1 to 9 in order to control the sinter bed height and
consequently air filtration velocity across the pallet width thereby attaining
uniform transverse temperature pattern.

ABSTRACT

A CONTROL SYSTEM FOR UNIFORM TRANSVERSE HEAT PATTERN IN
SINTER PLANT
The present invention relates to a control system for uniform transverse
temperature distribution across a sinter plant to improve sinter quality and
thereby improving productivity, the said control system, according to the present
invention, for uniform transverse heat pattern in sinter plant to control the sinter
bed height and consequently air filtration velocity across the pallet width thereby
attaining uniform transverse temperature pattern.