FORM 2THE PATENT ACT 1970(39 OF 1970)&The Patent Rules, 2003COMPLETE SPECIFICATION(See Section 10 and Rule 13)1 TITLE OF THE INVENTION :A METHOD FOR OPTIMIZING BURDEN DISTRIBUTION UNDER HIGH PELLET OPERATION IN BLAST FURNACE.2 APPLICANT (S)Name : JSW Steel Limited.Nationality : An Indian Company. Address : Jindal Mansion, 5-A, Dr. G. Deshmukh Marg ,Mumbai - 400 026, State of Maharastra, India.3 PREAMBLE TO THE DESCRIPTIONCOMPLETEThe following specification particularly descibes the invention and the manner in be performed.which it is to

FIELD OF THE INVENTION
The present invention relates to a method of distribution of burden comprising the iron ore and the coke charges in the blast furnace such as to improve productivity, reduce fuel consumption, extend campaign life and reduce cost of production in BF operation. Iron ore commonly used as pellet is the major share of burden and the pellet proportion in the burden ranges normally from 60 to 80% and in few instances, it has gone up to 90-100% and the invention is directed to control the problems in burden distribution resulting from the conventional high rolling characteristics of pellets. Importantly, the present method is directed to favoring less rolling of pellets towards the center and effective distribution of burden for improving the gas utilization. Also the method of burden distribution would help in significantly maintaining the optimum peripheral temperature of 400°C-500°C and avoiding alkali build up on the wall and also to ensure desired central gas flow temperature of 350°C-400°C. Burden distribution model according to the present invention is further directed to determine weight distribution, volumetric distribution, layer profile and layer thickness of both ore and coke batches across the furnace. Advantageous introduction of a 'pellet rolling factor' would help to improve the accuracy of the model prediction which in turn help significantly in improving the understanding of burden layer profile at varied pellet proportion in the charging mix. Furthermore, the invention is directed to determining the charging pattern under high pellet operation and consequently improve productivity of furnace coupled with substantial saving in fuel consumption. The present method of burden distribution and selective pellet profile with optimized charge under high pellet operation has wide industrial application to achieve higher operating efficiency in BF operations.
BACKGROUND ART
It is well known in the art of iron and steel making that the Blast Furnaces are used extensively worldwide for producing molten iron. The conversion process of iron ores to molten iron occur in a close chamber of the BF where large amount of heat is generated through a series of chemical reactions. The charge of iron ore and coke, commonly known as 'burden' is fed in to the BF chamber through a hopper from top and hot air is blown through the bottom of burden through tuyeres. Pre-heated air at about 1100°C aids combustion of coke and thereby generates large amount of reducing gas in the lower part of the furnace. The hot reducing gases ascend up against descending burden. The burden undergoes several physical and chemical changes during its descend due to the reactions

with the hot ascending gases, reducing the ore to iron and finally resulting in melting and accumulation of hot metal in the hearth at the bottom bed of BF. The iron ore is charged in BF in agglomerated form either as sinter having irregular shape or as pellet having somewhat uniform spherical shape to provide better permeability of burden for hot gases/air inside the furnace. The distribution of burden inside the BF chamber influences the parameters like productivity, fuel consumption, campaign life and cost and plays a significant role in BF operation. The conventional process in BF operation used pellet as major burden, the proportion of pellet varying in the range of 60-80% and in some instances it may go as high as 90-100%. Due to the high rolling characteristics of the spherical shaped pellets, ideal burden profile is difficult to maintain using pellets as a major burden. This led to the situation of high fuel consumption, low productivity, reduced refractory lining life, loss of staves coolers, low furnace availability etc. Several auxiliary units including stock house and charging equipments for burden distribution support BF operation. The BF operations were studied in furnace with inner volume of 1250 m3. It is provided with a Mini Bell Less Top (BLT) charging system with a single hopper. The charging process requires layer by layer distribution, the ore and coke batch being charged separately into the furnace. Conventionally the charging of ore and coke is designated by 04- and C4- respectively and when both ore and coke batch, jointly known as a charge is designated by Ci 04-. The existing system of BF charging had been limited to a maximum of 7 charges per hour. As a consequence, coke batch was difficult to split into two parts to accommodate center coke feed, designated by Cc to ensure high central gas flow inside the furnace. Therefore, existing system was incapable to execute Cc Ci 04- type of charging, resulting in poor center gas flow and lack of control to ensure desired temperature range. Moreover, in the high pellet operation, the pellets having the tendency to rolling towards the center, compounded the problem of diminished central gas flow and lack of control of favorable center gas temperature. Moreover, the Iron ore available and used in India for iron making contain high amount of Alkali i.e. Sodium and Potassium Oxides, which may condense at lower temperatures near the top of the furnace and thereby having a tendency to sticking to the furnace wall causing unstable furnace operation. This phenomenon of wall built up by the alkaline deposits needed to be avoided. Also, the increased peripheral gas flow rate is eventually associated with increased rate of fuel consumption that also adversely affected the refractory lining life, cooling system, coal injection rate etc.
The existing system thus suffered from the limitations and disadvantages including a), difficulty in achieving desired burden profile due to high rolling tendency of pellets; b). high

pellet proportion in burden caused layer collapse and higher fuel consumption; high pellet burden pushing more coke towards the wall causing excessive heat load on the wall and peripheral temperature near the wall at higher elevation used to rise up to 600-700°C as against the desired range of 400-450°C, causing damage to the stave coolers; c). increased amount of center coke at Rl & R2 position caused dominant central gas flow but peripheral gas flow gradually decreased to 100-200°C, causing frequent disturbance/instability in BF operation catalyzed due to high alkali load in the furnace (Na20 + K20) ranging up to 3.5 to 4.5 kg/thm as against the ideal of less than 3.0 kg/thm; and d). high rolling of pellets towards center causing accumulation of increased amount of ore at the center and thereby diminishing rate of central gas flow temperature up to 100-120°C as against ideal temperature of 450-550°C.
There has been thus been a continuing problem in BF operation to strike a balance between the central gas flow and the peripheral gas flow rate in order to maintain smooth, stable, cost effective and uninterrupted BF operations with increased productivity and extended campaign life. This is particularly of immense significance when the BF is under operation with pellets as major burden, due to the high rolling tendency of spherical shaped pellets from the near-wall locations to the central locations, compounded with this is the problem of high pellet portion in the burden causing layer collapse and higher fuel consumption. Moreover, the conventional process of burden distribution led to high pellet burden, pushing more coke towards the wall causing excessive heat load of the wall and rise in peripheral temperature beyond the desired limit and thereby damaging the stave coolers. Also, the existing method of burden distribution suffered from the limitation of diminished central gas flow temperature at a level lower than desirable due to the accumulation of ore at center caused due to high rolling of the pellets from walls to center as the burden descends.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to optimize burden distribution in BF, comprising the ore/pellet and coke, which would be adapted to control the high rolling characteristics of iron oxide charged in the form of pellets, having tendency of rolling from walls to the central part of BF chamber, for improved performance particularly under high pellet operation.

A further object of the present invention is directed to achieve a balance between the central gas flow and the peripheral gas flow by way of selective burden loading such as to favor maintaining the desired temperature profile across the furnace diameter.
A still further object of the present invention is directed to obtain moderate peripheral gas flow at reduced fuel consumption, by providing method of burden distribution which would control the rolling characteristic of pellets from the wall position towards the central position of the BF chamber.
Yet another object of the present invention is directed to provide for burden distribution which would avoid the tendency of the alkali deposit on the furnace walls at lower temperature at the upper zone of the furnace and thereby reduce wall erosion and improve stability in furnace operation.
A still further object of the present invention is directed to controlling the high pellet burden operation in BF by selectively charging of the burden near the wall such that flattening of these layers near the walls are ensured with the objective of arresting the high rolling tendency of pellets from the walls to the center.
A still further object of the present invention is directed to control the peripheral gas flow temperature in desired limit of 400-500°C adopting a selective burden distribution and associated saving in fuel consumption and thereby saving the stave coolers from damage.
A still further object of the present invention is directed to a method of burden distribution to achieve control of the central gas flow maintained by controlling the proportion of coke charged at the central annular positions in order to ensure favored central gas temperature of 350-400°C.
According to yet another object of the present invention directed to obtain a method for burden distribution which would favour determining the weight distribution, volumetric distribution, layer profile, and layer thickness of both ore and coke batches across the furnace and further favour an advantageous introduction of a pellet rolling factor to improve the accuracy of model prediction in order to optimize charging pattern under high pellet operation, for varied pellet proportion in the charge mix.

According to another object of the present invention the same is directed to a method of optimizing burden distribution to ensure high productivity, uninterrupted operation of BF, lower fuel consumption, lower operation/production cost, improved quality of molten iron at BF output and extended campaign life.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a method for providing optimizing burden distribution under high pellet operation in blast furnace, comprising
a 'hump and dump' burden distribution of the charge of iron oxide as pellets and coke, wherein an initial hump of coke is formed at the center before charging the next dump thereby resisting rolling of pellets from walls towards the center;
forming of 'Coke terrace' comprising flattened layers in succession of ore and coke near wall adapted to minimize rolling of pellets towards centre and improves coke pushing effect and suppression of layer collapse and effective gas flow utilization.
A further aspect of the present invention is directed to a method for providing optimizing burden distribution under high pellet operation in blast furnace wherein said formation of coke terrace near wall is carried out such as to maintain optimum peripheral temperature in the range of 400-500°C, avoid alkali build up in the wall and avoid stave cooler failures.
A still further aspect of the present invention directed to a method for providing optimizing burden distribution under high pellet operation in blast furnace wherein 30-40 % of every coke base is charged at the center position to thereby ensure desired central gas flow temperature of 350-400° C.
According to yet another important aspect of the present invention directed to a method for providing optimizing burden distribution under high pellet operation in blast furnace wherein the furnace top is divided into eight concentric rings defining a central ring and an outer peripheral ring and above burden probes are provided at the top of the respective concentric rings to measure the temperature and composition of the upcoming gas at various sampling points and monitor the desired burden distribution control.

A still further aspect of the present invention directed to a method for providing optimizing burden distribution under high pellet operation in blast furnace wherein the same provides for estimation of the weight distribution, volumetric distribution, layer profile and layer thickness of both ore and coke batches across the furnace and optimizing the charging pattern under high pellet operation.
According to yet another aspect of the present invention directed to said method for optimizing burden distribution under high pellet operation in blast furnace wherein said burden profile controlling the pellet rolling towards the center and coke pushing effect towards the walls advantageously achieved a balance between the center and peripheral gas flow and temperatures, favoring eliminating layer collapse and thereby improved gas utilization by 3%;
A still further aspect of the present invention directed to a method for optimizing burden distribution under high pellet operation in blast furnace wherein the fuel consumption is reduced by 40kg/thm by increased gas utilization efficiency.
According to a further aspect of the present invention directed to a method for optimizing burden distribution under high pellet operation in blast furnace wherein the BF operation has been stabilized eliminating alkali deposit on wall, burden hanging and slipping, high heat load on bosh belly region and consequently improving the furnace availability by 4%;
A still further aspect of the present invention directed to a method for optimizing burden distribution under high pellet operation in blast furnace, wherein the optimization of the burden distribution under high pellet operation increased the productivity of the furnace by 20%.
The present invention its advantages and objects are described in further details with particular reference to the non-limiting exemplary illustrations.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: is an illustration of the concentric rings' positions marked Rl at center to R8 at the wall, provided at the top of the furnace to facilitate selective burden charging in BF operation;
Figure 2: is the illustration of the burden distribution control through center coke charging and flattening of ore/coke portion near wall in accordance with the present invention;
Figure 3: is the illustration of the Above Burden Profile (ABP) across the furnace diameter obtained under high pellet operation, according to the burden distribution method of the present invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES
As detailed hereinbefore, the present invention is directed to a method of burden distribution under high pellet operation and also to achieve optimized layer profile and thickness such that the desired balanced central and peripheral gas flows and corresponding temperature ranges are ensured at center and near walls. Such a burden distribution in accordance with the invention is directed to achieve higher productivity, lower fuel consumption, improve gas utilization efficiency, increased furnace availability with uninterrupted operation, avoiding alkaline deposit/built up on furnace wall at top , eliminating the layer collapse with high pellet burden, reducing stave cooler failure and thereby extending campaign life of furnace.
It is well known in the field of blast furnace operation that the conversion process of iron ores to molten iron occurs in a close chamber of the BF where large amount of heat is generated through a series of chemical reactions. The charge of iron ore and coke, commonly known as 'burden' is fed in to the BF chamber through a hopper from top and hot air is blown through the bottom of burden through tuyeres. Pre-heated air at about 1100°C aids combustion of coke and thereby generates large amount of reducing gas in the lower part of the furnace. The hot reducing gases ascend up against descending burden. The burden undergoes several physical and chemical changes during its descend due to the

reactions with the hot ascending gases, reducing the ore to iron and finally resulting in melting and accumulation of hot metal in the hearth at the bottom bed of BF. The iron ore is conventionally charged in BF in agglomerated form either as sinter having irregular shape or as pellet having somewhat uniform spherical shape to provide better permeability of burden for hot gases/air inside the furnace. The distribution of burden inside the BF chamber influences the parameters like productivity, fuel consumption, campaign life and cost and plays a significant role in BF operation. The conventional process in BF operation use pellet as major burden, the proportion of pellet varying in the range of 60-80% and in some instances it may go as high as 90-100%.
The present invention deals with the problem arising due to the high rolling characteristics of the spherical shaped pellets, ideal burden profile is difficult to maintain using pellets as a major burden. This has lead to situations of high fuel consumption, low productivity, reduced refractory lining life, loss of staves coolers, low furnace availability etc. Several auxiliary units including stock house and charging equipments for burden distribution support BF operation. To ascertain the optimized burden profile for high pellet operation, the BF operations in existing furnace with inner volume of 1250 m3 were studied. It is usually provided with a Mini Bell Less Top (BLT) charging system with a single hopper. The charging process requires layer wise distribution, the ore and coke batch being charged separately into the furnace. Conventionally the charging of ore and coke is designated by 04- and Cl respectively and when both ore and coke batch, jointly known as a charge is designated by d Ol. The existing system of BF charging had been limited to a maximum of 7 charges per hour. As a consequence, coke batch was difficult to split into two parts to accommodate center coke feed, designated by Cc to ensure high central gas flow inside the furnace. Therefore, existing system was incapable to execute Cc Ci 04- type of charging, resulting in poor center gas flow and lack of control to ensure desired temperature range. Moreover, in the high pellet operation, the pellets having the tendency to rolling towards the center, compounded the problem of diminished central gas flow and lack of control of favorable center gas temperature.
Thus the existing charge feeding arrangement was modified for better control of charge/burden. Reference is first invited to the accompanying Figure 1 that illustrates ,for the purposes of the present invention, the manner of dividing of the furnace top into eight concentric rings, sequentially numbered Rl, R2, ... R8, from central position (Rl) to the peripheral wall position (R8) of the cylindrical shell wall of BF chamber. Also to measure and

monitor the temperature and composition of the upcoming BF gas accurately, a device
Above Burden Probe (ABP) device is placed at different sampling points e.g.SI, S2, S3 S9
for the corresponding locations across the furnace diameter. High temperature at the sampling points such as at S4, S5, S6 signifies dominant central gas flow and increased temperature near wall, is sensed by SI and S9 signifying dominant peripheral gas flow. Moreover, iron ore procured and used from Indian mines having high alkali contents, generates fumes during the BF reaction containing Na20 and K20 that condense at lower temperature near top of the furnace and thereby having a tendency to stick to the wall causing unstable furnace operation. The burden comprising varied proportion of pellet is selectively charged, such that the resulting performance was monitored through said ABP at desired locations, accordingly the burden distribution pattern as well as layer profile and layer thickness for both ore/pellets and coke across the furnace under high pellet operation was optimized.
As disclosed herein the present invention is directed to a method of burden distribution pattern under high pellet operation in BF wherein a Hump and Dump technique has been applied to avoid undesirable excessive rolling of the pellets from the walls to the center of furnace. Reference is next invited to the accompanying Figure 2, wherein the present hump and dump method of charging burden has been illustrated.
It would be apparent from the said figure 2 that in the present burden distribution, initially a 'hump' of coke was formed at the center of furnace chamber, before charging the next 'dump' of coke or ore/pellets. Such hump formation at center which grows in height at central location (e.g. Rl, R2) on successive charges, resist the tendency of rolling of pellets from the wall position towards the center. Both ore and coke batches are next dumped near the wall at similar ring positions (e.g. R6, R7) by preferred orientation of chute of the hopper, in alternate sequence to ensure flattening of these layers near wall. Thus the formation of flatten ore and coke layers near the wall helped minimizing rolling of pellets and pushing effect on coke towards the wall and thus enabling center coke feed in effect. Moreover, the present method of burden distribution has helped in suppressing the layer collapse which otherwise occur under high pellet operation. This has improved the gas utilization by 3%. The formation of 'Coke Terrace' near the walls has helped significantly in maintaining peripheral temperature in the desired range of 400-500°C, avoiding alkali built up on the wall and also reducing the stave cooler failure. In order to control and maintain the desired center gas flow and temperature, 30-40% of the every coke layer was charged

at the center position i.e. at Rl, to ensure central gas flow temperature in the preferred range of 350-400°C.
Reference is now invited to the accompanying Figure 3 wherein the gas flow temperature profile across the furnace diameter, sensed by the corresponding ABP probes located at SI to S9, have been illustrated as an improvement over the conventional practice of burden distribution such that the optimized burden distribution following the Hump and Dump technique according to the present invention apparently eliminating the undesired dominant peripheral gas flow and high temperature ranging 600-700°C and the diminishing central gas flow under high pellet operation due to excessive pellet rolling, causing coke being pushed to the walls, were rectified and balanced such as to obtain desired temperature profile at center and wall, in more stable operation, e.g. 350-450°C at center and 400-500°C at the walls and thus avoiding the alkaline deposit or damages of the stave coolers.
It is thus possible by way of the present invention to obtain a desired burden distribution profile under high pellet operation, preferably with a distribution model providing estimates for the weight distribution, volumetric distribution, layer profile and layer thickness of both ore and coke batches across the furnace, such that a balance between the central and the peripheral gas flow can be achieved in BF operation. Further, to improve upon the accuracy of the model prediction for such burden distribution in high pellet BF operation, a pellet rolling factor has been introduced. This method has helped in understanding the burden layer profile at varied pellet proportion in the charge mix. It has also helped in optimizing the charging pattern under high pellet operation. The present invention is thus directed to selective method of burden distribution under high pellet operation and also to achieve optimized layer profile and thickness such that the desired balanced central and peripheral gas flows and corresponding temperature ranges are ensured at center and near walls of BF chamber and thereby achieve higher productivity, lower fuel consumption, improved gas utilization efficiency, increased furnace availability with uninterrupted operation, avoiding alkaline deposit/built up on furnace wall at top , eliminating the layer collapse with high pellet burden, reducing stave cooler failure and thereby extending campaign life of furnace. The burden distribution under the present invention would thus facilitate the BF process worthy of wide and cost- effective industrial application in iron and steel industries.

We CLAIM:
1. A method for providing optimization of burden distribution under high pellet
operation in blast furnace, comprising
a 'hump and dump' burden distribution of the charge of iron oxide as pellets and coke, wherein an initial hump of coke is formed at the center before charging the next dump thereby resisting rolling of pellets from walls towards the center;
forming of 'Coke terrace' comprising flattened layers in succession of oxide and coke near wall adapted to minimize rolling and coke pushing effect and suppression of layer collapse and effective gas flow utilization.
2. A method for providing optimizing burden distribution under high pellet operation in blast furnace as claimed in claim 1 wherein said formation of coke terrace near wall is carried out such as to maintain optimum peripheral temperature in the range of 400-500° C, avoid alkali build up in the wall and avoid stave cooler failures.
3. A method for providing optimizing burden distribution under high pellet operation in blast furnace as claimed in anyone of claims 1 or 2 wherein 30-40 % of every coke base is charged at the center position to thereby ensure desired central gas flow temperature of 350-400° C.
4. A method for providing optimizing burden distribution under high pellet operation in blast furnace as claimed in anyone of claims 1 to 3 wherein the furnace top is divided into eight concentric rings defining a central ring and an outer peripheral ring and above burden probes are provided at the top of the respective concentric rings to measure the temperature and composition of the upcoming gas at various sampling points and monitor the desired burden distribution control.
5. A method for providing optimization of burden distribution under high pellet operation in blast furnace as claimed in anyone of claims 1 to 4 wherein the same provides for estimation of the weight distribution, volumetric distribution, layer profile and layer thickness of both ore and coke batches across the furnace and optimizing the charging pattern under high pellet operation.

6. A method for optimizing burden distribution under high pellet operation in blast furnace as claimed in anyone of claims 1 to 5 wherein said burden profile controlling the pellet rolling towards the center and coke pushing effect towards the walls advantageously achieved a balance between the center and peripheral gas flow and temperatures, favoring eliminating layer collapse and thereby improved gas utilization by 3%;
7. A method for optimizing burden distribution under high pellet operation in blast furnace as claimed in anyone of claims 1 to 6 wherein the fuel consumption is reduced by 40kg/thm by increased gas utilization efficiency.
8. A method for optimizing burden distribution under high pellet operation in blast furnace as claimed in anyone of claims 1 to 7 wherein the BF operation has been stabilized eliminating alkali deposit on wall, burden hanging and slipping, high heat load on bosh belly region and consequently improving the furnace availability by 4%;
9. A method for optimizing burden distribution under high pellet operation in blast furnace as claimed in anyone of claims 1 to 8, wherein the optimization of the burden distribution under high pellet operation increased the productivity of the furnace by 20%.
10. A method for optimizing burden distribution under high pellet operation in blast furnace with controlled rolling of pellets and balanced central and peripheral gas flow ensuring stable operation and longer uninterrupted availability of furnace, substantially as hereindescribed with reference to the accompanying illustrative figures.

ABSTRACT
TITLE: A METHOD FOR OPTIMIZING BURDEN DISTRIBUTION UNDER HIGH PELLET OPERATION IN BLAST FURNACE.
A method for optimizing burden distribution comprising pellets and coke charged in the blast furnace such as to improve productivity, reduce fuel consumption, extended campaign life and reduces cost of production in BF operation. Pellets ranges in burden from 60% to up to 100%. High rolling characteristics of pellets is controlled by adopting a "Hump and Dump" distribution avoiding rolling of the pellets towards the center, by initially forming a 'hump' of coke at the center before charging the next 'dump'. Both coke and ore batches are dumped in concentric rings towards the outer shell wall to ensure flattening of these layers near wall favoring avoiding coke pushing effect to the wall. The optimized burden distribution helped in improving gas utilization by 3%, attaining optimum peripheral and central gas temperature, saving in fuel consumption, avoid alkali build up on wall at top and layer collapse and thus stabilizing the BF operation. The selective pellet profile with optimized charge under high pellet operation has wide industrial application to achieve higher operating efficiency in BF operations.
Figure 2.