FIELD OF THE INVENTION
The present invention relates to a methodology to determine the optimal proportions of the burden material for blast furnaces to produce hot metal and slag of desired chemistries. More particularly, the invention relates to a process to determine in real-time the proportions, distribution and tracking of burden receipt in a blast furnace producing hot metal and slag with desired chemistries.
BACKGROUND OF THE INVENTION
Raw materials are fed into the blast furnace by means of a material feeding system in the stock house comprising of stock bins with weighing scales and an associated conveyor belt. The burdens or batches consisting of the raw materials (ore, pellets, sinter, coke, flux, etc.) are precisely weighed and transferred to the conveyor belt. They are charged in a proper sequence of the materials. The sequence consists of the combination of material lots arranged in the form of master and slave. The material placed in the first section of the sequence is called the ‘master’ while all other materials placed in the following sections are referred as ‘slave’ (Refer Fig: 3). They fill up the twin BLT hoppers at the furnace top alternatively with the metallic and coke.
Traditionally, the calculation of the proportions of the burden materials is done manually. This method is inefficient as it cannot optimize the amount of fluxes required to achieve the desired hot metal and slag composition. Moreover it is prone to human error and may not, all the time, incorporate the latest chemical laboratory analysis of the raw materials. To the contrary of prior art calculation of burden material receipt, it is important to note that the proportion of the metallic, fuel and the fluxes in the burden should be such that the hot metal and the slag must attain the desired chemistry.

the prior art process optimizes the flux amount using matrix operations iteratively to attain the target chemical composition of the slag. Calculated weights of individual materials are verified with the stock-house bins and the BLT hopper capacities. In case the calculated weight becomes more than the bins or hopper capacities, the determined burden recipe are declared as invalid. Validated recipe is first converted into the charging burden where the master-slave sections and the charging sequence are configured along with the material weights and then the burden is directly transferred to the program-logic controllers (PLC) of the stock-house. PLC, in turn, sets the bins load-capacities according to the charging burden. The conveyor belt collects the raw materials of specified amounts from the specified bins.
The conveyor belt transports the batches to the BLT hoppers mounted at the furnace top. The hoppers discharge the materials of various sizes into the furnace through a rotating chute. They fall on the surface of the previously charged burden and forms a heap shaped layer on it. The discharged materials tend to spread radially according to their size and density. The radial distribution of Metallic-to-coke ratio due to the spread is an important criterion in the blast furnace operation as it influences the gas direction and consequently the speed of kinetic reactions inside the furnace. A non-uniform distribution of burden results in channeling, slipping or hanging state of the burden movement resulting into uneven descent rates and higher thermal loads. The chute is rotated at different angles and distributes the raw materials in the form of concentric rings at desired radial distances. Despite the full operational control of the chute angle and its speed the operators are unable to achieve proper radial distribution of the metallic and coke layers as the heap formation and the layered thickness are as such not visible to them.
In the blast furnace operation the raw materials enriched with iron-oxides are charged into the furnace along with the layers of coke and fluxes. Coke, as a

fuel, burns at the raceway at the lower part of the furnace where hot blast of air is blown in. The burning coke liberates sufficient amount of heat energy and produce carbon-mono-oxide (CO) and carbon-di-oxide gases (CO2). CO gas is the prime reducing agent of the iron oxides which in contact with it reduces the oxides to the molten iron. The proportion of the iron ore and semi processed agglomerates (Sinter and Pellet), coke and the fluxes plays an important role in the process to attain the optimum productivity of the hot metal with the desired chemistry. Fluxes or additives play a major role to control the physical properties of the slag like viscosity and temperature to meet the desired final chemistry of both hot metal and the slag.
The burden of a blast furnace is a mixture of the metal-oxides (Iron-ore, sinter and pellet), fuel (coke) and the fluxes (limestone, dolomite, quartz etc) which is charged from the furnace-top in the form of rings. It is charged periodically when the previous burden descended sufficiently below the stock-line of the furnace-throat. The proportion of the mixture is made on the basis of the availability of the raw materials with their latest chemistry including the moisture and the ash content of the coke. It is an important factor in the blast furnace operation as it directly influences the hot metal and slag chemistry. It (The proportions) should be such that both the liquids should able to attain the desired chemistry.
The burden is charged into the furnace at the throat level. It is distributed by a
chute rotating at a low and uniform speed. As the burden falls from the chute tip
it follows the trajectory path and strikes below the surface of the previously
charged burden and forms the heap at the striking point. As the chute rotates the heap extends all around to form a torus shaped ring of raw materials. The cross-sectional profile of a heap depends upon the repose angle which is the characteristic of the material itself. Multiple rings of different materials form at the throat level where one often flows over the other depending upon space availability at that location and the charging sequence. The burden profile influences the gas movement inside the furnace specially in the upper part of the

furnace. With the change of the profile it is possible to direct the gas flow inward (central) or outward (peripheral).
The burden, once distributed at the throat level gradually sinks into the furnace shaft till it reaches the Belly region where it softens and melts to liquid metal. During this entire movement the stratification of the layers of coke and metalloids is preserved though the layers themselves shrink or swell depending upon the furnace slope and radius at that plane. Typically a burden takes 5 -6 hours to reach the bottom of the furnace.
Pulverized coal is injected into the furnace at its lower region with the hot blast air. It is required to attain the thermal stability of the furnace and is considered as a partial replacement of the expensive top-charged coke. . The trend of replacing coke by more quantity of pulverized coal is rising now-a-days as it is cheaper. The quantity of the coal injected at a particular time depends upon the quantity of the coke in the burden that has descended to the lower region (Belly Region).
Accordingly, to prior art, the furnace operators change the patterns of the
burden distribution mainly on the basis of the variation observed in pressure
drops, wall and top gas temperatures, top gas chemical analysis, hot metal and
slag chemistry and other furnace parameters. However, the burden becomes
untraceable once it descends below the stock-line in the throat region. The
information of the physical and chemical composition of the burdens is lost
herewith. Normally a burden takes 5 – 6 hours to reach the bottom (Tuyere Level) of the furnace. Tuyere is a refractory insulated nozzle through which the hot blast air along with pulverized coal, steam and a certain percentage of pure oxygen is injected into the furnace. They are mounted at a regular space all around the periphery at the lower part of the furnace. Underneath this level the hearth of the furnace is located where the hot metal and the slag are collected. Operators adjust the coal injection rate in order to maintain the thermal balance

of the furnace. The rate of injection is based on the coke quantity of the burden that arrives the lower part of the furnace.
Accordingly, prior art lack an automated and technically valid process to evaluate the coal injection the rate. Thus, the adjustment of rate of injection according to prior art is based on the operators’ experience on operational practices, and personal experienced of the operators.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a process to determine in real-time the proportions, distribution and tracking of burden receipt in a blast furnace producing hot metal and slag with desired chemistries.
Another object of the invention is to propose a process to determine in real-time the proportions, distribution and tracking of burden receipt in a blast furnace producing hot metal and slag with desired chemistries, in which the determined burden recipe creates a stock-house matrix to automatically set bin-weighting capacities in the stock-house.
A still another object of the invention is to propose a process to determine in real¬time the proportions, distribution and tracking of burden receipt in a blast furnace producing hot metal and slag with desired chemistries, which enables generation of a surface profile of the last-charged burden to allow the operators to maintain identical profile during offline distribution.
A further object of the invention is to propose a process to determine in real-time the proportions, distribution and tracking of burden receipt in a blast furnace producing hot metal and slag with desired chemistries, which enables tracking the burden descending movement with its physical and chemical attributes.

SUMMARY OF THE INVENTION
According to the invention, there is provided a process to determine in real-time the proportions, distribution and tracking of burden receipt in a blast furnace producing hot metal and slag with desired chemistries. In a process of development of the prior art, the present inventors noted that the burden is charged in a sequence of metallic and coke layers where each is distributed in the form of a ring at the furnace throat (top). The distributing pattern is another important factor in the blast furnace operation as it indirectly guides the gas flow and consequently influences the thermal load and the kinetic reactions of the blast furnace process. A proper distribution enhances the participation of the reducing gas in the kinetic reactions.
Once the burden descends below the stock-line it becomes invisible and untraceable. In order to maintain the thermal balance of the furnace it is important to balance the coke quantity which is charged at the top, with the pulverized coal (PCI) quantity which is injected near the bottom. The adjustment of the coal injection depends upon the coke-quantity in the burden which has arrived the lower part of the furnace, precisely in the bosh region. Since no burdens are traceable below the stock-line the adjustment of the coal-injection rate is made more heuristically and intuitively rather scientifically.
In one aspect of the invention, the process determines the optimal proportions of the burden materials, which is converted to a stock house matrix where each proportion is converted to individual weights in tons.
In a second aspect of the invention, using the physical dimensions of the throat and the chute, the operating parameters like chute angular speed (rpm), bulk material flow rate and the physical principles of falling body trajectory, the process simulates the burden profile at every burden charge and display it to the operator. It shows the radial distribution of metallic-to-coke ratio. Operators if

observe abnormalities in the gas distribution simulate various charging patterns in this system and then physically charge the material as per the best simulated results.
Thus, the present invention adapts the simulation of the burden profile and the radial distribution of the metallic-to-coke ratio at the throat level.
In a third aspect of the invention, the stock level measurement by the radar is made on the basis of specific dimensions of the furnace, and hence deriving the descending rates of the burden. The results of the burden recipe and the stock house matrix simulates and displays the descending movement of the layers on real time basis. The operators, accordingly, adjust the coal injection by viewing the composition of the layers that arrive the belly region of the furnace.
The inventive process is designed in such a way that an sinter, pellet, coke and fluxes are determined through chemical balance of the hot-metal elements like Fe, Mn and P, and the slag compounds like Al2O3, MgO, CaO, SiO2. The invention considers the loss of oxides as flue-dust in the throat region and slag deposit in the bosh region of the furnace, and collects real-time data on the latest chemistry of the raw materials for application in the chemical balance equations.
The inventive process is enabled to simulate the radial distribution profile of the metallic and coke layers at the stock-line in the throat level, based on the trajectory laws of gravitational fall, the angle of repose of the heap formation and the coefficient of restitution of the throat wall where the discharged materials bounce back after hitting it. The trajectory path is determined from the mass flow rate, chute angle, angular velocity, co-efficient of friction of chute plate.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 Stock-House Arrangement of a blast furnace

Figure 2 Flowchart for the calculation of burden in a blast furnace
Figure 3 Graphic User Interface (GUI) of the Burden Calculator. The targets
are entered in the left column; the input like the availability of raw materials and fluxes in the middle column and the burden recipe as the results of the model is shown in the right column. The latest chemical analysis results that are fetched from the laboratory are shown in the GUI.
Figure 4 Stock house matrix editor from which Burden is automatically
created from the Burden Calculator. The quantities of the raw
materials and coke and fluxes in this charging are first validated
with the hopper and stock-house bins capacities and then
downloaded to Stock-House PLC which in turn set the bins weights according to the weights mentioned in the charged matrix.
Figure 5 The Burden distribution Profile and heap formation of each layer in
the burden at the stock level in the throat level, which also shows the radial distribution of metallic-to-coke ratio.
Figure 6 The Shaft Simulator showing the layers of burden as descend
through the shaft, the change in color indicating the change in burden chemical or physical composition
Figure 7 Architecture Diagram of the real time system of burden recipe
preparation, distribution and tracking in the blast furnace according to the invention
Figure 8(a) Division of a blast furnace upper part into multiple segments

Figure 8 (b) Trajectory profile and Point of Impact of the burden materials in the stockline level of the blast furnace
Figure 8 (c) Prediction of formation of Heap Shape in the throat of the blast furnace
DETAILED DESCRIPTION OF THE INVENTION
Burden Calculation
Assumption is that the Fe entering in to Blast Furnace = Fe coming out of the Blast Furnace +Fe loss in Flue Dust

and Ore (Kg/thm) respectively and %Sn, %P, %O are percentages of Sinter, Pellet and Ore in burden. %Fe(Sn), %Fe(P), %Fe(O) are percentage of Iron in Sinter, Pellet and Ore. Wloss is the weight of flue dust loss (kg). Total Fe (Kg/thm) in Burden is calculated by adding the above 3 equations and
equating it with WFe is weight of Fe in Kg/thm Kg of Fe in 1

ton of Hot Metal givens:

Where WCaO(M) is weight of CaO in metallic burden; % CaOSn, % CaOP, % CaOO are percentage of CaO in Sinter, Pellet and Ore. MSn, MP and MO are moisture associated with Sinter, Pellet and Ore.
Similarly, SiO2, MgO and Al2O3 are calculated and Basicity of slag (B2) is calculated as

Where, WSL is slag main loss i.e. weight of traces of oxides

Burden Distribution
1. Division of the Blast Furnace into small portions wherein the upper part of the
R blast furnace is approximated by a cylinder. The radius ( fur) as well as the
height are divided into equal distances and a quadratic raster where each of
the squares is the width of one ring.

2. Charging burden Simulation, where a cycle is a series of materials, which are charged into the furnace and is repeated after the completion. The burden flows down continuously and once the scheduled stockline level is reached other material is dumped into the furnace. The present system takes into account that between two top hopper discharges of the same material, no time lag occurs. The volume of material to be charged and the chute angle and the chute rotations are known for every position.
3. Calculation of Impact Point

1. The Initial position of chute is taken as P0 (h1,x1) .
2. h1 is incremented by Δh = 0.5 cm and corresponding P1(h2,x2) is determined.
3. Then it is checked weather line (P0 ,P1) intersect with the following or not

- Center Line (C0,C1)
- Wall of the furnace (P1,S1)

- Current burden profile. (C0, P1)
using the condition of two intersecting line.
4. If intersects:
i) the point of intersection is determined.
ii) this becomes the point of impact, where the material will deposit.
5. Otherwise, P1 becomes P0 and steps are repeated from step 2 until the
point of impact is found.
4. Heap formation at Point of Impact based on Gaussian distribution function of the falling stream of burden materials.
5. Burden Descend Simulation
6. Ring wise calculation of Ore/Coke ratio based on the distribution pattern and the total weight of metallic and coke.
Shaft Simulation
1. Pictorial representation of the working volume of the furnace showing various segments of furnace.
2. Determination of the number of matrices available in furnace, based on the total working volume and volume of each burden. This is calculated from total burden weight.
3. Determination of movement of each burden inside the blast furnace based on descent rate of the burden and pictorial representation in the real time. The descent rate is calculated from the radar signals above the stockline level of the furnace.
4. Compression ratio of each burden is assumed depending upon its location

inside the blast furnace working volume. The compression ratio assumed in the present system are shown in following table:

5. Based on the latest chemistry of the raw materials and using mass balance; the weight of Fe present in each burden is calculated.
6. Details of each burden (i.e. coke rate, coal injection rate, O/C ratio, B2, sinter percent, hot metal rate, slag rate, burden weight, and burden volume) are calculated of each burden. These details are calculated corresponding to each burden downloading time, residence time, expected time to reach tuyere.
7. Estimation of slag chemistry at hearth and bosh regions.
8. Calculation of hourly fuel rate based on momentary calculations.

WE CLAIM
1. A process to determine in real-time the proportions, distribution and tracking of burden receipt in a blast furnace producing hot metal and slag with desired chemistries, comprising the steps of:
- preparing an optimal burden proportion of the burden materials consisting of proportions of ore, sinter, pellet, coke and fluxes determined through chemical balance of hot metal elements such as Fe, Mn and P including the slag compounds for example Al2O3, MgO, CaO, SiO2, the loss of oxides in the form of flue-dust in the throat region of the blast furnaces as well as the slag deposit in the bosh region being taken into account, wherein the real time chemistry of the raw materials collected from the data base is applied in the chemical balance equations;
- generating a charging matrix which transforms said optimum burden receipt (%) into weights (tons) and create the charging sequences of the burden in the stock-house;
- developing a surface profile of the burden once charged and distributed at the furnace throat level based on gravitational laws, momentum and trajectory;
- determining and displaying the movement of the burden after charging into the furnace in the form of descending layers; and
- computing the burden descent rate by extracting he useful signals from the blast furnace radar which continuously measuring the level of the burden surface at the throat level remotely from a home location.

2. The process as claimed in claim 1, wherein the burden profile is simulated at every burden charge to exhibit the radial distribution of metallic to-coke ratio for displaying to the operators to adjust the charging patterns based on any abnormalities in the gas distribution when noticed.
3. The process as claimed in claim 2, wherein the burden profile is simulated using the physical dimensions of the throat and the chute, the operating parameters such as chute angular speed, bulk material flow rate, and the physical principle of falling body trajectory.
4. The process as claimed in claim 1, wherein the stock level measurement by the radar is made on the basis of specific dimensions of the furnace which derives the descending rate of the burden on real time.
5. he process as claimed in any of the preceding claims, wherein the burden volume from the burden weights as indicated in the charging burden and the bulk density is first determined to simulate the burden movement inside the furnace.
6. The process as claimed in claim 5, wherein the simulation of the burden movement inside the furnace is further determined depending upon the furnace dimensions, slopes in shaft and bosh regions, descent rate and hot metal generation rate.
7. The process as claimed in claim 1, comprising determining layer-wise thickness of all the burdens as descending through the furnace shaft.
8. The process as claimed in any of the preceding claims, wherein the coal-injection rate is adjusted by the operator based on the real-time display of

burden-movement including the coke quantity in the burden reaching the lower region.
9. The process as claimed in claim 1, wherein the time for a burden to reach the furnace lower region is determined from the display.
10. The process as claimed in claim 1, wherein the hot metal and slag quality including their chemical composition as produced can determined for each individual burden.