The present subject matter described herein, relates to a process of removal of impurities of hot metal by oxygen in a Basic Oxygen Furnace (BOF) converter and, in particular, to a method and system for monitoring steelmaking process in the BOF to determine steel and slag analysis during blowing in the Dynamic BOF (DBM) at fixed interval which is typically ten seconds. More particularly, the present subject matter provides an on-line process monitoring system for carrying out monitoring method in the BOF plant.
BACKGROUND AND PRIOR ART AND PROBLEM IN PRIOR ART:
[002] Hot Metal from the blast furnaces has many impurities which arc detrimental to the final quality of Steel products. These impurities need to be removed to use it in various Steel products. One of the processes to remove these impurities is Basic Oxygen Steelmaking. It is done in a vessel, called Basic Oxygen Furnace (BOF). In this process, most of impurities like 'P', 'Si' & 'C arc removed by oxidizing these with pure oxygen. In the BOF, Oxygen with supersonic speed is injected into liquid hot metal in BOF converter. In this process, most of impurities get oxidized and float above the liquid metal as slag. Carbon forms CO gas and goes out of the metal. The metal at end of treatment in BOF is almost pure Fe. It is important that impurities are removed at desired level and correct temperature is achieved at the end of treatment. A lot of heal is generated by oxidation of these impurities. In order to control the heat, coolant, such as iron ore and scrap are added to achieve correct temperature at end of treatment. The BOF converter is made of steel shell in outer region. Inside of the BOF converter is relined with refractory which basic in nature. The oxides formed by oxidation of Si and Phosphorus, namely Si02 and P205 is acidic in nature and would corrode the lining of the BOF converter. Therefore, sufficient basic material, such as lime need to be added in the BOF so that overall slag is basic

and it doesn't corrode the BOF converter. Lime also helps in better removal of Phosphorus from the liquid metal.
[003] Conventional prior arts of BOF steel making mostly deal with measurement of carbon content of BOF converter (e.g. WO/1997/016571), lance design for BOF steelmaking (e.g. WO/2007/054957), addition of iron pellet and reduction in oxygen flow rate (e.g. US Patent 5897684) and BOF steelmaking (e.g. US Patent 4529442). Indian patent application No. 623/KOL/2010 talks about BOF Static Model (BSM) which predicts amount of fluxes and coolants to be added as well as oxygen to be blown in BOF converter during start of blow.
[004] Depending upon the application for which Steel is being produced, addition of Ferro alloys are done. To control steel making process throughout blow is important. Generally steel and slag chemistry is known during end of blow. During progress of blowing steel and slag chemistry is not known. Ilcncc difficulty in control so that repeatable process control could be achieved specifically end blow phosphorus. To achieve consistent end blow control, it is important that blow is properly controlled throughout the blow. But biggest bottle neck does not know steel and slag chemistry during blowing. Therefore, a method and a system are required which calculates steel and slag chemistry throughout the blow. Using the calculated steel and slag chemistry blow could be optimized for consistent output. Better control of chemistry and temperature will also help in optimization of the cost of steelmaking in the BOF.
OBJECTS OF THE INVENTION:
[005] The principal objective of the present invention is to predict steel and slag chemistry during blowing without disturbing the process.
[006] Another object of the present invention is to develop an on-line process monitoring system for BOF plant.
i
[007] Another object of the present invention is to provide consistent output by optimizing the blow, where the blow can be optimized by knowing the steel and slag chemistry.

[008] Yet another object of the present invention is to provide better control of chemistry and temperature which will help in optimization of the cost of steelmaking in the BOF. SUMMARY OF THE INVENTION:
[009] The present subject matter relates a method and system for determining steel and slag analysis for basic oxygen furnace (BOF). The BOF monitoring system works on first principle, i.e., Mass Balance, process knowhow, and past data which calculates steel and slag analysis throughout the blow at fixed time interval (typically ten seconds). The monitoring system takes converter number, grade, HM weight, temperature and analysis; scrap type and weight; lance number, retained steel/slag weight, oxygen volume blown till current time, blow duration till current time, lime added till current time, dolomite added till current time, ore added till current time, N2/Ar purged till current time, lance height, lance height set point, oxygen flow rate, oxygen flow rate set point, stack gas flow rate, temperature and analysis at hood, hood pressure, hood pressure set point, secondary ventury opening, tuyere wise flow rate and back pressure, tuyere wise flow rate set point, rate of ore addition, lance inlet temperature and lance outlet temperature as input. The monitoring system uses the input and provides the steel and slag analysis on real time basis.
[0010] In order to further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit scope of the present subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, a reference number identifies the figure in

which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods or structure in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0012] Fig. 1 illustrates BOF monitoring system for determining steel and slag chemistry during blowing process in the BOF, in accordance with an embodiment of the present subject matter.
[0013] Fig. 2 illustrates flow diagram of the processes in Dynamic BOF' model (DBM), in accordance with an embodiment of the present subject matter;
[0014] Fig. 3 illustrates flow diagram of stack gas Based dynamic BOF Model (DBM), in accordance with an embodiment of the present subject matter;
[0015] Fig. 4 illustrates comparison between predicted and actual CO values of the DBM model M80302, in accordance with an embodiment of the present subject matter;
[0016] Fig. 5 illustrates comparison between predicted and actual CO values of the DBM model M80297, in accordance with an embodiment of the present subject matter;
[0017] Fig. 6 illustrates comparison between predicted and actual CO values of
the DBM model M80341, in accordance with an embodiment of the present
subject matter;
[0018] Fig. 7 illustrates experimental measurement on steel chemistry change,
i.e., change of bath composition with blowing time for 300 ton BOF during
blowing process in the BOF, in accordance with an embodiment of the present
subject matter;
[0019] Fig. 8 illustrates experimental measurement on steel chemistry change,
i.e., carbon removal and temperature profile for heat SI845 during blowing
process of the BOF, in accordance with an embodiment of the present subject
matter;

[0020] Fig. 9 illustrates predicted steel chemistry during blowing process of the BOF where heat no Ml 5890, in accordance with an embodiment of the present subject matter;
[0021] Fig. 10 illustrates experimental measurement on slag chemistry change, i.e., change of slag composition with blowing time for 300 ton BOF during blowing process in the BOF, in accordance with an embodiment of the present subject matter;
[0022] Fig. 11 illustrates calculated slag chemistry during blowing process of the BOF where heat no Ml5890, in accordance with an embodiment of the present subject matter; and
[0023] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[0024] The subject matter disclosed herein relates to a method and system for real time or dynamic monitoring of Basic Oxygen Furnace (BOF) plant. The present monitoring system calculates/predicts steel and slag chemistry during blowing process of the BOF. Where controller of BOF process uses calculated steel and slag chemistry to optimally control of BOF process. It automatically controls the complete blow including control of bottom purging, flux additions, coolant additions as well as hood opening using Dynamic BOF Model. Further, the present subject matter relies on instrumentation that automatically senses the condition of the hot metal and liquid steel. The system senses, observes, and measures the various parameters, such as converter number, grade, HM weight, temperature and analysis; scrap type and weight; lance number, retained steel/slag weight, oxygen volume blown till current time, blow duration till current time, lime added till current time, dolomite added till current time, ore added till current

time, N2/Ar purged till current time, lance height, lance height set point, oxygen flow rate, oxygen flow rate set point, stack gas flow rate, temperature and analysis at hood, hood pressure, hood pressure set point, secondary ventury opening, tuyere wise flow rate and back pressure, tuyere wise flow rate set point, rate of ore addition, lance inlet temperature and lance outlet temperature for calculating the steel and slag chemistry in the blow of the BOF. The required parameters arc polled at second interval, specifically at 10 seconds, and all the parameters or data is stored in the data of the server and system. The system extracts the data from the storage and uses the data for further calculation of steel and slag chemistry.
[0025] As explained above, the conventionally there is no method to calculate the steel and slag chemistry in the steel making process during blowing process in BOF. Generally steel and slag chemistry is known during end of blow. During progress of blowing steel and slag chemistry is not known. Hence difficulty in control so that repeatable process control could.be achieved specifically end blow phosphorus. To achieve consistent end blow control, it is important that blow is properly controlled throughout the blow. But biggest bottle neck is that the steel and slag chemistry is not known during blowing. Using the calculated steel and slag chemistry during blow can be used to optimize for consistent output in the BOF. Better control of chemistry and temperature will also help in optimization of the cost of steelmaking in the BOF.
[0026] In one embodiment of the present subject matter, the method calculates the steel and slag chemistry during blow in BOF. The present method is implemented by a monitoring system at the server which extracts the data of the blow and stored data of the blow and calculates the steel and slag chemistry. Further, the present monitoring system calculates the steel and slag chemistry during blowing of Basic Oxygen Furnace (BOF) at every fixed, interval, specifically at every 10 seconds. The system is implemented on the BQF and makes the BOF Dynamic BOF model (DBM). Where the DBM works on the principle of mass balance, process know how, and past data. The system of the DBM requires the various

inputs for calculation. These inputs can be categorised in two sections, i.e., heat wise data and ten seconds data after blow start till blow end.
[0027] Heat wise data
1. Converter number
2. Grade
3. HM weight, temperature and analysis
4. Scrap type and weight
5. Lance number
6. Retained steel/slag weight
Ten seconds data after blow start till blow end
1. Oxygen volume blown till current time
2. Blow duration till current time
3. Lime added till current time
4. Dolomite added till current time
5. Ore added till current time
6. N2/Ar purged till current time
7. Lance height
8. Lance height set point
9. Oxygen flow rate
10. Oxygen flow rate set point
11. Stack gas flow rate, temperature and analysis at hood
12. Hood Pressure
13. Hood Pressure set point
14. Secondary Ventury Opening
15. Tuyere wise flow rate and back pressure
16. Tuyere wise flow rate set point
17. Rate of Ore addition
18. Lance inlet temperature
19. Lance outlet temperature

[0028] The monitoring system of the DBM receives the above inputs and docs the calculations and provides the output. Where the output is Steel analysis and Slag analysis.
[0029] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.
[0030] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
[0031] Fig. 1 illustrates schematic block diagram of BOF monitoring system 300 for calculation of steel and slag analysis, in accordance with an embodiment of the present subject matter. The present BOF monitoring system 300 includes one or more processor(s) 301, interface(s) 302, memory 303 coupled to the processor

301, modules 304, and data 309. The processor(s) 301, may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, logic circuitries, and/or any devices manipulate signals based on operational instructions. Among other capabilities, the processor(s) 301 is configured to fetch and execute computer-readable instructions stored in the memory 303. Further processor 301 is a hardware device which communicates with the other software and hardware and processes the data and provides the results.
[0032] The interface(s) 302 may include a variety of software and hardware interfaces, for example, interfaces for peripheral device(s), such as a keyboard, a mouse, an external memory, and display device. Further, the interfaces 302 may facilitate multiple communications within a wide variety of protocol types including, operating system to application communication, inter process communication, client server communication, etc.
[0033] The memory 303 can includes any computer-readable medium known in the art including, for example, volatile memory, such as static random access memory (SRAM) and dynamic random access memory (DRAM), and/or non-volatile memory, such as read only memory (ROM), erasable programmable ROM, flash memories, hard disks, optical disks,, and magnetic tapes.
[0034] Further modules 304 and data 309 may be coupled with the processor(s) 301. The modules 304, amongst other things, include routines, programs, objects, components, data structures, etc., which perform particular tasks or implement particular abstract data types. The modules 304 may also be implemented as, signal processors), state machine(s), logic circuitries, and/or any other device or component that manipulate signals based on operational instructions. In another aspect of the present subject matter, the modules 304 may be computer-readable instructions which, when executed by a processor/processing unit, perform any of the described functionalities. The machine-readable instructions may be stored on an electronic memory device, hard disk, optical disk or other machine-readable storage medium or non-transitory medium.

[0035] In an implementation, module(s) 304 include calculation module, steel analyzer 306, slag analyzer 307 and other module(s) 308. The other module(s) 308 may include programs or coded instructions that supplement applications or functions performed by the BOF monitoring system 300.
[0036] The data 309 includes calculation data 308, analysis data 310 and other data 311. The other data 311 amongst other things, may serve as a repository for storing data that is processed, received, or generated as a result of the execution of one or more modules in the module(s) 304. Although the data 309 is shown internal to the BOF monitoring system 300, it may be understood that the data 309 can reside in an external repository, such as server 312, which may be coupled to the BOF monitoring system 300 over network. The BOF monitoring system 300 may communicate with the external repository through the interface(s) 302 to obtain information from the data 309.
[0037] As explained above, the BOF monitoring system 300 calculates steel and slag chemistry in the blow of the BOF. In one implementation, the calculation module 305 receives the current data of the blow from the stored data and current node of data. Further, the calculation module 305 receives the data from start of the blow till end of the blow in the BOF. The calculation module 305 reads data, such as oxygen volume, weight of lime, dolqmite and iron ore added till the current time. The calculation module 305 calculates total weight of Fe, Carbon, Si and Phosphorus using mass balance and read data. Further, the calculation module 305 uses weight, temperature and analysis of, Hot Metal, scrap weight and its analysis, target chemistry and temperature in the calculation. Further, the calculated total weight of Carbon, Si and Phosphorus is assigned to remaining carbon, Si and Phosphorus in the node for further calculation and analysis. Also weight of Fe203 in the node set to weight of iron ore and weight of FcO set to zero. Further, weight of un-dissolved CaO is calculated from weight of lime and dolomite and assigned to node.
[0038] Similarly the calculation module 305 receives the data from the previous node calculated data. The calculation module 305 does all calculation on the

received data and assigns the calculated data to current node for further calculations. All calculations are explained in detail in the method/process explanation. All the steps are not repeated here for clarification.
[0039] After calculation of all the data, the calculation module 305 assigns the calculated data to the current node for slag and steel analysis. The steel analyzer 306 performs steel analysis based on the calculated data and data assigned to the current node. The steel analyzer 306 receives the calculated data and performs tha action based on the given equations.
RemainingCn = RemainingCn - COxidizedn
RemainingSin = RemainingSi n - SiOxidizedn
RemainingPn = RemainingPn - POxidizedn
[0040] As explained in the equations, remaining C, Si and P in the current node is calculated after subtracting oxidized weight of the elements in the current node. After dividing remaining weight of an element with steel weight, steel analysis in the node is known. Volume of CO generated in the node is also calculated using mass balance. It is divided by node length to calculate CO rate. Rate of CO calculated by DBM and CO rate measured from waste gas measurement was used to validate the model.
[0041] Further, the slag analyzer 307 receives the calculated and assigned data and performs tha action based on the given equations.
TotalSiOxidizedn = TotalSi - RemainingSi _n
TotalPOxidizedn = TotalP - RemainingPn
[0042] Total weight of Si02 and P205 is calculated from weight of oxidized Si
and P as written above using mass balance by the* slag analyzer 307. Further,
weight of un-dissolved CaO is calculated from weight of Lime and Dolo. Weight
of dissolved CaO in a given node is calculated as given below.
v n_CaO_Dissolved = kl0*v nodelength* vTotalCaO Undissolved

Where klO is dissolution constant for CaO and v_node_length is node length in
seconds. klO is calculated based on experience and past data.
[0043] Now, weight of slag Fe in the current node is known. Percentage of Slag
Fe, Si02, P2O5 and CaO is generally constant in present scenario. Hence by
dividing sum of Slag Fe, Si02, P2O5 and CaO weight with this percentage gives
slag weight. Percentage of Slag Fe, Si02, P205 and CaO is calculated
subsequently.
[0044] In other implementation, the BOF monitoring system 300 is communicatively coupled with the server 312 over the network. The network may be internet, Intranet, LAN, WAN, WLAN, wifi and any other mode of communication. The BOF Monitoring system: 300 may stores the data on the server 312 and receives the calculated analysis.from the server over the network. The BOF monitoring system 300 may be implemented on the local machine at the location of furnace. The server 312 may be any communicating device and any operating machine which can store and perform actions. The complete communication may be architecture of client server communication. The person skilled in the art is very well aware about the client server communication structure. Further, the BOF monitoring system. 300 may be present at the server 312 and provide all calculation and analysis over the client machine via network.
[0045] Fig. 2 illustrates a method for calculation of the steel and slag chemistry in the blow of the BOF, in accordance with an embodiment of the present subject matter. Present methodology is not only limited to. the described steps and combination of the steps. A person skilled in the art will understand the steps of the method and can modify the steps and achieve the end results.
[0046] The method may be described in the general context of computer executable instructions. Generally, computer executable instructions can include routines, programs, objects, components, data structures, procedures, modules, functions, etc., that perform particular functions or implement particular abstract data types. The method may also be practiced in a distributed computing environment where functions are performed by remote processing devices that arc

linked through a communications network. In a distributed computing environment, computer executable instructions may be located in both local and remote computer storage media, including memory storage devices.
[0047] At step 100, blow in the BOF starts and timer of 10 seconds observe the data and saves the data in the storage.
[0048] At step 101, BOF monitoring system starts to receive the data obtain at the block 100.
[0049] At step 151, the BOF monitoring system 300 (it can be interchangeably referred as dynamic Basic Oxygen Furnace Model (DBM)) check whether it is first call for the system or not. If it is first call for the system, the BOF monitoring system 300 moves to step 102 for further processing.
[0050] At step 102, the DBM reads batch data, i.e., weight, temperature and analysis of Hot Metal, scrap weight, target chemistry and temperature and master data, i.e., Limits of input parameters and analysis of scraps from the stored database. The DBM also reads oxygen volume, weight of lime, dolomite and iron ore added till the current time. At step 103, total weight of Fe, Carbon, Si and Phosphorus is calculated using mass balance and data read in the step 102. The calculation module 305 of the BOF monitoring system 300 uses weight, temperature and analysis of Hot Metal, scrap weight and its analysis, target chemistry and temperature in the calculation. In process step 103, total weight of Fe is taken as steel weight. Further, the calculated total weight of Carbon, Si and Phosphorus is assigned to remaining carbon, Si, and Phosphorus in the current node for further processing. Also weight of Fe203 in the node set to weight of iron ore and weight of FeO set to zero. Weight of un-dissolved CaO is calculated from weight of lime and dolomite and assigned to node variable (v_Total_CaO_Undissolved) at process step 104.
[0051] At step 151, if it is first call for the system, the BOF monitoring system 300 moves to step 105 for further processing. In process step 105, the processed data for current node is read. The DBM reads previous node data in process step

106. Total weight of Carbon, Si and Phosphorus, Fe203, FeO, Si02, CaO, P205, steel and slag weight from previous node is assigned to current node in process step 107. Further, iron added in current code is added to calculated weight of Fe203 for current node.
[0052] After the process step of 104 or 107, the DBM moves to process step 108 for calculation of stable slag Fe. The calculation module 305 calculates the weight of the stable slag Fe. Further, the stable slag Fe is calculated based on below mentioned equation.
Calculation of stable slag Fe weight
Stable_SlagFe_weight = MinSlagFeWeight + kl*Input_Si + k2*Oxidised Si n i
k3*lance_height + k4*Lance_flow_rate + k5*TBM_efficiency + k6* remaining
C_n Eq.l
Where Constant MinSlagFeWeight, kl, k2, k3, k4, k5 and k6 is assigned based on experience and past data of the BOF converter. These parameters need to be tuned when the DBM is being used in a BOF converter.
[0053] At process step 109, calculation of stable slag FeO (v_Stable_Slag_FeO_Wt) and Fe203 (v_Stable_Slag_ Fe203_Wt) weight is calculated using mass balance and distribution of Fe into FeO and Fe203 at fixed ratio (typically 70:30 ratio).
[0054] At process step 110, calculated weight of the FeO and Fe203 from the previous node is assigned to current node. Further, total weight of FeO and l:e203 from previous node (pn) is taken as calculated weight of FeO (v_pn Total FeO) and Fe203 (v_pn_Total_Fe203) in the nth node, i.e., current node.
[0055] At decision step 152, it is checked whether v_Stable_Slag FeO Wt is lower than v_pn_Total_FeO. If the v_Stable_Slag_FeO_Wt is lower than v_pn_Total_FeO, the v_pn_Total_FeO FeO would be reduced. Amount of FeO reduced is calculated at process step 111.
Calculation of reduced FeO weight
v_n_FeO_reduced = k7*( v_pn_Total_FeO - v_Stable_Slag FeOJWt).. Eq. 2

Where k7 is FeO reduction rate and is calculated based on past data of the BOF converter.
[0056] Oxygen generated through FeO reduction is calculated using mass balance in process step 112. Also oxygen generated through FeO reduction is added to total lance oxygen available in the node. Total calculated weight of FeO (v_pn_Total_FeO) is reduced by v nFeOreduced.
[0057] At decision step 152, if vStableSlag^FeO Wt is more than
v_pn_Total FeO, v_pn_Total_FeO would be generated using lance
oxygen. Amount of oxygen used for FeO generation is calcuated at process step at
113.
Calculation of used oxygen for FeO generation

[0058] Lance oxygen (Oxygenn) used for Fe oxidation is calculated as above with an upper limit (typical 20 % for FeO).
[0059] Further, weight of FeO generated is calculated using mass balance at process step 114. Total calculated weight of FeO (vjm_Total_FeO) is increased by weight of FeO generated. Lance oxygen is reduced by the amount used for 1'cO oxidation here.
[0060] At decision step 153, it is checked whether v_Stable_Slag_ Fe203 Wt is lower than v_pn_Total_Fe203. If the v Stable_Slag__ Fe203_Wt is lower than v_pn_Total_ Fe203, Fe203 would be reduced. Amount of Fe203 reduced is calculated at process step 115.

Calculation of Fe203
v n„ Fe203j-educed - k8*(v_pn_Total_ Fe203- v_Stable_Slag_ Fe203 JWt). Eq.5
Where k8 is Fe203 reduction rate and is calculated based on past data of the BOF converter.
[0061] Total calculated weight of Fe203 (vjpn_Total_Fe203) is reduced by v_nJFe203_reduced. Oxygen generated through Fe^Os reduction is calculated using mass balance at process step 116. Oxygen generated through Fc203 reduction is added to total lance oxygen available in the current node. [0062] At decision step 153, if v^Stable_Slag_Fe203_Wt is more than v_pn_Total_Fe203, Fe203 would be generated using lance oxygen. Amount of oxygen used for Fe203 generation is calcuated at process step 117. The calculation module caculates the amount of oxygen used for the Fe203.
Calculation for Fe203 using lance oxygen
, , c1 T: or,-i _ Cv Stable Slag Fc203 Wt-
v_oxygenJract_Slag_Fe203 - ^yjauu«G_ &_
v_pn_TotaLFe203)/v_Stable_Slag_Fe203_Wt: ... E<1-6
v n Oxygen Vol_SlagL_Fe203=v_oxygen_ftact_Sla&_Fe203*
- - - Eq. 7
vnoxygenvolume
Lance oxygen (vJu>xygen_volume) used for Fe oxidation is calculated as above with an upper limit (typical 10 % for Fe203).
[0063] Weight of Fe203 generated is calculated using mass balance at process step 118 Total calculated weight of Fe203 (v jn_Total_Fe203) is increased by weight of Fe203 generated. Lance oxygen is reduced by the amount used for Fe203 oxidation.

[0064] At process step 119, total available oxygen for C, Si, and P is calculated. The calculation module does this calculation and provide the calculated values.
[0065] Oxygen affinity has been defined which is proportional to heat of reaction, heat of solution, and weight percentage of the element in the node.
OxygenAfinityC = Heat_React_CO*Heat_Sol_C* v_pn_RemainingC .. Kq.8
OxygenAfinitySi = Heat_React_Si02,*Heat_Sol_Si* v_pn_Remaining Si Eq.9
OxygenAfinityP = Heat_React_P205* Heat_Sol_P* v_pn_Remaining P Kq.10
[0066] Further, oxygen affinity is calculated if concentration is more than certain lower limit. As shown in the fig. 2 at decision step 154, 155, and 156. In case of phosphorus, lower limit is theoretical phosphorus weight (vTheorPhos Wt) calculated in previous node. At process step 120, oxygen affinity for carbon is calculated. Oxygen affinity for silicon is calculated at process step 121. Oxygen affinity for phosphorus is calculated at process step 122. In process step 121, phosphorus reduction is also calculated.
[0067] In case remaining phosphorus (v_pn_Remaining_P) is less than theoretical phosphorus (v_Theor_Phos_Wt), P205 would be reduced and additional oxygen would be available for oxidation of carbon and Si.
vnPReduced =k9* (v_Theor_Phos_Wt-vjpn^RemainingP) *
v_pn_Remaining_P Eq. H
k9 is P205 reduction constant. It is decided based on experience and past data.
[0068] At the process step 123, calculation of oxygen available for elemental oxidation is done. The calculation module does the calculation of oxygen available for elemental.

Calculation of oxygen available for elemental oxidation.
TotalOxygenAfinity = OxygenAfmityC + OxygenAfinitySi + OxygenAfinityP Eq. 12
Oxygen Frac C = OxygenAfmityC / TotalOxygenAfinity Eq. 13
Oxygen Frac Si = OxygenAfinitySi / TotalOxygenAfinity Eq. 14
Oxygen_Frac_P= OxygenAfinityP / TotalOxygenAfinity Eq. 15
Fraction of total oxygen available to be used for oxidation of different elements is calculated using the above mentioned equations and calculation module.
[0069] At the process step 124, Weight of C, Si and P oxidized in the node is calculated using mass balance. Further, oxygen used for oxidation of C, Si and P is also calculated.
[0070] At process step 125, steel analysis is performed by the steel analyzer 306 based on the calculated data and data assigned to the current node. The steel analyzer receives the calculated data and performs tha action based on the given equations.
RemainingCji = RemainingCn - COxidizedn Eq. 16
RemainingSi n = RemainingSin - SiOxidizedn Eq. 17
RemainingPn = RemainingPn - POxidizedn Eq. 18
[0071] As explained in the equations, remaining C; Si and P in the node is calculated after subtracting oxidized weight of these elements in the node. After

dividing remaining weight of an element with steel weight, steel analysis in the node is known.
[0072] Volume of CO generated in the node is also calculated using mass balance. It is divided by node length to calculate CO rate. Rate of CO calculated by DBM and CO rate measured from waste gas measurement was used to validate the model.
[0073] At process step 126, slag analysis is performed based on the calculated data and data assigned to the current node. The slag analyzer receives the calculated data and performs tha action based on the given equations.
Total_SiOxidized_n = Total_Si - RemainingSin Eq. 19
Total_POxidized_n - Total_P - RemainingP_n Eq. 20
[0074] Total weight of Si02 and P205 is calculated from weight of oxidized Si and P as written above using mass balance by the slag analyzer. Further, weight of un-dissolved CaO is calculated from weight of Lime and Dolo. Weight of dissolved CaO in a given node is calculated as given below.
vji_CaO_Dissolved = kl0*v_nodejength* v_Total_CaO Undissolved Eq.21
Where klO is dissolution constant for CaO and vnodejength is node length in seconds. klO is calculated based on experience and past data.
[0075] The total weight of dissolved CaO (v_Total_CaO^ Dissolved) is increased by v_n_CaOJDissolved and weight of undissolved CaO is decreased by same amount.
[0076] Now, weight of slag Fe in the node is known. Percentage of Slag Fe, Si02, P205 and CaO is generally constant in present scenario. Hence by dividing sum of Slag Fe, Si02, P205 and CaO weight with this percentage gives slag weight. Percentage of Slag Fe, Si02, P205 and CaO is calculated subsequently.

[0077] At the process step 127, weight of theoretical phosphorus is calculated by the calculation module. Theoretical phosphorus to be used in calculation in next node is calculated using slag and steel weight and analysis as given below.
v_Theor_Phos_Wt = kll + kl2* vJtemainingC + kl3 * v_Total_P205
kl4*v_Total_CaO_Dissolved - kl5*v_Total_Slag_Fe _Wt Eq.22
kll, kl2, kl3, kl4 and kl5 are constants calculated from past data of the converter.
[0078] The obtained output for each element is noted for the current node and stored for future calculation.
[0079] Further, the DBM is linked with another model, i.e., Stack Gas Based Dynamic BOF model (SDBM) which runs after detection of critical point in the stack of gas pattern. It calculates the carbon oxidation rate and based on the flow of oxygen in the BOF.
[0080] At the process step 128, SDBM starts working and moves to step 200 of the Fig. 3.
[0081] At the step 200, calculation of C oxidation rate for each node is calculated. The carbon oxidation rate has been defined, which is ratio of CO rate and total oxygen (including oxygen from iron ore) available for reactions.
v_C_Oxidation_rate = (v_n_CO_rate_normalized* 10000*vnode length) / (60*(v_n_oxygen_volumejance + nvl(v_n_oxygen_from_FeOJFe2O3,0))) Eq.
23
[0082] At process step 201, calculation for peak carbon oxidation rate is
calculated after oxygen has blown at certain level (typically 70 %).
[0083] At process step 251, a check is performed to detect critical point for the C oxidation rate. If the critical pointed is detected, process moves to step 202 for further calculations. Where the critical point is defined as point during blowing when C oxidation rate drops below certain percentage (typically 70 %) of average

C oxidation rate during peak decarburization. After detection of critical point, percentage carbon in steel is predicted based on stack gas composition and flow rate at process step 202 using the below mentioned equation.
v_Remainingj:_perc = kl6*v_n CO_rate Eq. 24
vnCOrate is CO rate of stack gas in nth node and kl6 is constant calculated based on past data.
[0084] If critical point is not detected, SDBM stops and process moves to step 129 for writing output to database for current node.
[0085] The present method and system has been implemented successful in the industry which shows very good results. Validation of the DBM has been done for few months using online data as well as data available in literature.
[0086] Validation of the DBM and SDBM
[0087] Validation of some heats was done with rate of CO by comparing trends as illustrated in Figs [4-6],
[0088] In the fig. 4, BOF monitoring system is implemented for the Dynamic BOF model M80302. Further, calculated values of the BOF monitoring system is compared with the actual values. In the present comparison, CO is compared with the predicted value or calculated value by DBM with the actual CO. The calculated values are found very close to the actual or literature values.
[0089] In the fig. 5 BOF monitoring system is implemented for the Dynamic BOF model M80297. Further, calculated values of the BOF monitoring system is compared with the actual values. In the present comparison, CO is compared with the predicted value or calculated value by DBM with the actual CO. The calculated values are found very close to the actual or literature values.
[0090] In the fig. 6 BOF monitoring system is implemented for the Dynamic BOF model M80341. Further, calculated values of the BOF monitoring system is compared with the actual values. In the present comparison, CO is compared with

the predicted value or calculated value by DBM with the actual CO. The calculated values are found very close to the actual or literature values.
[0091] The above comparisons and validations are matching with actual trend in several heats. Further, the results were shown to person skilled in the art and persons working on the BOF like operators and they agreed that steel and slag trend predicted by DBM is matching with their process understanding.
[0092] For further validation of the DBM calculated results, measurement data available from literature as shown in Fig 7, 8 & 10 were compared with calculated data by DBM as shown in Fig 9 & 11. It has been found that the DBM model is matching well with experimental measurement. Further, the end point prediction of carbon and calculated values were compared for several thousands heats. All the results are well matching with the calculated values.
Advantages
[0093] Presently when the heats are more than 70 %, reblow is present. Further, reblow is not desired. It means many disadvantages in the form of material consumptions and production loss. Phosphorus in steel is generally not desired and efforts are put to reduce average value and its variation.
[0094] Further it is also desired to have minimum dissolved oxygen at blow end. More dissolved oxygen means dirty steel. Therefore, all good grade steel should be as clean steel as possible. Also high dissolved oxygen in steel means more alumina in tundish slag at caster. It means more aluminium consumption and difficult situation during casting.
[0095] After implementation of the DBM model in control mode, following benefits is expected:
1. Reblow would be reduced by fivefold for RH heats.
2. Variation in steel phosphorus, dissolved oxygen and alumina in tundish slag would be reduced by 25 % for all grades.

[0096] Although implementations for the method and the system for size characterization of the plurality of green balls based by image acquisition system have been described in language specific to structural features and/or method, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/device/structure of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.
List of Symbols used in the specification
1. StableSlagFeweight: Stable weight of Fe in nth node
2. MinSlagFeWeight: Minimum slag Fe weight
3. Input Si: Weight of pure Si in nth node
4. OxidisedSin: Weight of oxidized Si in nth node
5. lanceheight: Height of oxygen lance from liquid steel surface
6. Lancefiowrate: Flow rate of oxygen
7. TBMefficiency: effectiveness of bottom purging
8. Remaining C_n: Remaining carbon in nth node
9. Remaining Sin: Remaining silicon in nth node
10. Remaining P_n: Remaining phosphorus in nth node
11. v_Stable_Slag_FeO_Wt: Stable weight of FeO in nth node
12. v_Stabie_Slag__Fe203_Wt; Stable weight of Fe203 in nth node
13. v_pn_Total_FeO: Total calculated weight of FeO
14. v_pn_Total_Fe203: Total calculated weight of Fe203
15. voxygenfractSlagFeO: Oxygen fraction available for Fe oxidation into FeO
16. v_oxygen_fract_Slag_Fe203: Oxygen fraction available for Fe oxidation into Fe203

17. OxygenAfinityC: Oxygen affinity for carbon
18. OxygenAfinitySi: Oxygen affinity for silicon
19. OxygenAfinityP: Oxygen affinity for phosphorus
20. Heat ReactCO: Heat of reaction for carbon oxidation into CO
21. HeatReact Si02: Heat of reaction for carbon oxidation into Si02
22. Heat_React_P205: Heat of reaction for carbon oxidation into P205
23. HeatSol C: Heat of solution of C into Fe
24. HeatSolSi: Heat of solution of Si into Fe
25. HeatSolP: Heat of solution of Si into Fe
26. v_Theor_Phos_Wt: Weight of theoretical phosphorus
27. v_pn_Remaining C : Weight of remaining carbon in previous node
28. v_pn_Remaining_Si: Weight of remaining silicon in previous node
29. v j>n_RemainingJP : Weight of remaining phosphorus in previous
node
30. Oxygen_Frac_C: Oxygen fraction for carbon
31. Oxygen_Frac_Si: Oxygen fraction for silicon
32. Oxygen_Frac_P: Oxygen fraction for phosphorus
33. COxidizedn: Weight of carbon oxidized in nth node
34. SiOxidizedn: Weight of carbon oxidized in nth node
3 5. POxidizedn: Weight of carbon oxidized in nth node
36. COGenerated_n: Volume of CO generated in nth node
37. Total_SiOxidized_n: Total Si oxidized till nth node
38. Total J>Oxidized_n: Total P oxidized till nth node
39. v n_CaO_Dissolved: Weight of CaO dissolved in nth node
40. v_Total_CaO_Undissolved: Weight of un dissolved CaO
41. v_Total_Slag_Fe_Wt: Total weight of slag Fe

42. v_Total_P205: Total weight of P205
43. v_Total_CaO_Dissolved: Total weight dissolved CaO
44. vnodelength: Length of node in seconds
45. v_C_Oxidation_rate: Carbon oxidation rate
46. vnoxygenvolumelance: Oxygen available from lance
47. vnoxygen from_FeO_Fe203: Oxygen available from reduction of FeO and Fe203
48. v_Remaining_C_perc: Remaning carbon percentage in steel
49. v_n_CO_rate_normalized; CO rate calculated by adding CO and C02 percentage in stack gas and multiplying with stack gas flow rate.
50. SlagWt: Slag weight

We claim:
1. A method to determine steel and slag analysis at fixed interval during
blowing in Basic Oxygen Furnace (BOF), the method comprises:
reading (102), by a processor (301), an input batch data, wherein the input batch data is weight, temperature and analysis of Hot Metal, scrap weight, target chemistry and temperature, parameters and analysis of scraps from the stored database, oxygen volume, weight of lime, dolomite and iron ore added till current time;
calculating (103), by the processor (301), weight of carbon, Si, and Phosphorus using mass balance and read data;
assigning (104, 107), by the processor (301), calculated weight of the carbon, Si, and phosphorus to current node for calculation;
calculating (108), by the processor (301), stable slag weight from the assigned calculated and the read input data;
calculating (109), by the processor (301), stable slag of Feo and Fe203 from the read input data using mass balance and distribution of FeO and Fe203 at fixed ratio;
comparing (152), by the prorcessor (301), weight the stable FeO and total calculated FeO;
upon determining total calculated weight of FeO is more than
weight of the stable slag FeO,
weight of FeO is reduced (111) by reduction process based on the past data of the BOF; and
calculating (112), by processor (301), oxygen generated during reduction of FeO using mass balance, wherein the weight of FeO is reduced by the reduced weight of the FeO;
upon determining total calculated weight of FeO is lower than the weight of the stable slag FeO,
weight of the FeO is generated by oxidation (113) using lance oxygen; and

calculating (114), by the processor (301), weight of the FeO generated using mass balance, wherein the calculated weight of FeO is increased by weight of FeO generated; comparing (153), by the processor (301), weight of stable slag Fe203 and total calculated weight of Fe203,
upon determining total calculated weight of Fe203 is more than the weight of the stable slag Fe203,
weight of Fe203 is reduced (115) by reduction process based on reduction rate and past data of the BOF; and
calculating (112), by processor (301), oxygen generated during reduction of Fe203 using mass balance, wherein the total weight of calculated weight of Fe203 is reduced by the reduced weight of the Fe203; and
upon determining total calculated weight of Fe203 is lower than the weight of the stable slag Fe203,
weight of the Fe203 is generated by oxidation (117) using
lance oxygen; and
calculating (118), by the processor (301), weight of the Fe203 generated using mass balance, wherein the total calculated weight of Fe203 is increased by weight of Fc203
generated;
calculating (123), by the.processor (301), oxygen available
for elemental oxidation;
calculating (124), by the processor (301), weight of the elementals oxidized using mass balance;
calculating (125), by the processor (301), steel analysis based on remaining weight of the elements; and
calculating (126), by the processor (301), slag analysis based on the oxidized weight of the Si an P.

2. The method as claimed in claim 1, wherein the method further comprises calculating (123), by the processor (301), oxygen used for oxidation of different elements.
3. The method as claimed in claim 1, wherein the steel analysis is calculated by subtracting the oxidized weight of the elements from the remaining weight of the elements and dividing the remaining weight after subtraction of an element with steel weight.
4. The method as claimed in claim 1, wherein the slag analysis is calculated by subtracting the remaining weight of Si and P from the total weight of the Si
and P.
5. The method as claimed in claim 1, wherein the slag analysis further comprises calculating weight of dissolved and un-dissolved weight of CaO from the weight of Lime and dolo.
6. The method as claimed in claim 1, wherein the method further comprises: calculating (127) weight of theoretical Phosphorus (P) using slag and steel weight
and analysis.
7. A method for calculating oxygen distribution for elemental oxidation in
BOF, the method comprises:
calculating (119), by the processor (301), total oxygen available for
elements oxidation;
calculating (120, 121, 122), by the processor (301), oxygen affinity for
C Si, and P,
if remaining carbon is more than minimum carbon value; if remaining Si is more than minimum Si value; and if remaining P is more than minimum P value.
8. A method for calculating carbon percentage in Stack Gas Based BOF
Model (SDMB), the method comprises:
calculating (200), by the processing (301), carbon oxidation rate based on ratios of CO rate and total oxygen available for reactions;
calculating (201), by the processing (301), peak carbon oxidation rate;

detecting (251), by the processor (301), critical point, if critical
point is detected,
determining (202) carbon percentage in steel based on stack
gas composition and flow rate.
9. The method as claimed in claim 8, wherein the critical point is a point during blowing when C oxidation rate drops below certain percentage specifically 70% of average C oxidation rate during peak decarburization.
10. A Basic Oxygen Furnace (BOF) monitoring system (300) determine steel and slag analysis at fixed interval during blowing in Basic Oxygen Furnace (BOF), the BOF monitoring system (300) comprises:
a processor (301) coupled with the memory (303);
a calculation module (305) coupled with the processor (301) to,
read (102) an input batch data, wherein the input batch data is weight, temperature and analysis of Hot Metal, scrap weight, target chemistry and temperature, parameters and analysis of scraps from the stored database, oxygen volume, weight of lime, dolomite and iron ore
added till current time;
calculate weight of carbon, Si, and Phosphorus using mass
balance and read data;
assign calculated weight of the carbon, Si, and phosphorus to
current node for calculation;
calculate stable slag weight from the assigned calculated and
the read input data;
calculate stable slag of Feo and Fe203 from the read input data using mass balance and distribution of FeO and Fe203 at fixed ratio; compare weight the stable FeO and total calculated FeO;
upon determining total calculated weight of FeO is more than weight of the stable slag FeO,
weight of FeO is reduced (111) by reduction process based on the past data of the BOF; and

calculate oxygen generated during reduction of FeO using mass balance, wherein the weight of FeO is reduced by the reduced weight of the FeO;
upon determining total calculated weight of FeO is lower than the weight of the stable slag FeO,
weight of the FeO is generated by oxidation (113) using lance oxygen; and
calculate weight of the FeO generated using mass balance, wherein the calculated weight of FeO is increased by weight of FeO generated; compare weight of stable slag Fe203 and total calculated weight
of Fe203,
upon determining total calculated weight of Fe203 is more than the weight of the stable slag Fe203,
weight of Fe203 is reduced (115) by reduction process based on reduction rate and past data of the BOF; and
calculate oxygen generated during reduction of Fe203 using mass balance, wherein the total weight of calculated weight of Fe203 is reduced by the reduced weight of the Fc203;
and
upon determining total calculated weight of Fe203 is lower than the weight of the stable slag Fe203,
weight of the Fe203 is generated by oxidation (117) using lance oxygen; and
calculate weight of the Fe203 generated using mass balance, wherein the total calculated weight of Fe203 is increased by weight of Fe203 generated;
calculate oxygen available for elemental oxidation; calculate weight of the elemental oxidized using mass
balance; a steel analyzer (306) coupled with the processor (301) to,

calculate steel analysis based on remaining weight of the elements; and a slag analyzer (307) coupled with the processor (301) to,
calculate slag analysis based on the oxidized weight of the

Si an P.
11. The BOF monitoring system (300) as claimed in claim 10, wherein the steel analyzer (306) calculates the steel analysis by subtracting the oxidized weight of the elements from the remaining weight of the elements and dividing the remaining weight after subtraction of an element with steel weight.
12. The BOF monitoring system (300) as claimed in claim 10, wherein the slag analyzer (307) calculates the slag analysis by subtracting the remaining weight of Si and P from the total weight of the Si and P.
13. The BOF monitoring system (300) as claimed in claim 10, wherein the slag analyzer (307) further calculates weight of dissolved and un-dissolved weight of CaO from the weight of Lime and dolo.
14. The BOF monitoring system (300) as claimed in claim 10, wherein the calculation module (305) calculates weight of theoretical Phosphorus (P) using slag and steel weight and analysis.