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 IMPROVING SINTER QUALITY WITH RESPECT TO THE REDUCTION DISINTEGRATION INDEX(RDI).
2 APPLICANT (S)
Name : JSW Steel Limited.
Nationality : An Indian Company.
Address : Jindal Mansion, 5-A, Dr. G. Deshmukh Marg, Mumbai State of Maharastra, India. - 400 026,
3 PREAMBLE TO THE DESCRIPTION
COMPLETE
The following specification be performed. particularly describes the invention and the manner in which it is to

FIELD OF THE INVENTION
The present invention relates to a method for improving the sinter quality with respect to lowering the Reduction Disintegration Index (RDI) to favour higher reducibility of sinter and resultant increase in productivity of Blast Furnace (BF). Advantageously, the method of the invention would enable covering pores and cracks/gaps on surfaces of sinter mass such that the flow and passage for reducing gases, mainly CO, to hematite phase at 450°C-600°C, is reduced or prevented and thereby delaying the hematite to magnetite conversion and disintegration of sinter in the upper shaft of the Blast furnace. The present invention is thus directed to a method of controlling sinter quality in terms of higher hot metal yield/productivity in BF operation by maintaining lower RDI of Sinter, justifying its wide industrial application in BF operations in steel plants.
BACKGROUND ART
It is well known in the field of making iron and steel, that the Blast Furnace (BF) conventionally uses sinter as the main source of iron bearing charge which is reduced to iron by chemical reduction through a series of reactions in a reducing atmosphere during BF operation. Sinter is basically a tailor made agglomerate material comprising iron bearing fines, coke breeze and fine fluxes produced in a sintering plant and fed through conveyor to the BF charging hopper. It has an irregular shape and size maintained between 5-40mm with a desirable mean particle size (MPS) of 20mm. The sinter has a tendency to disintegrate when exposed to Carbon monoxide (CO) in the temperature range of 450-600°C. This degree of disintegration tendency of the sinters is measured or indicated by "Reduction Disintegration Index" (RDI). During the reaction with the reducing gases, mainly CO, the hematite phase present in the sinters is converted/reduced to magnetite (Fe203.FeO), which is highly porous and stressed due to increase in volume (an increase of around 25% of initial volume) in the course of reduction reactions. The induced stress initiates cracks in the matrix, which propagates on further reduction. These phenomena cause the disintegration of the sinter mass and generates fines.
While RDI has been considered as the indicator of the tendency of degree of disintegration of the sinter mass, it may be noted that a higher value of RDI means higher amount of hot fine generation, resulting in poor permeability at the upper shaft of the BF and thus lowers BF productivity. Higher RDI is the result of various factors such as


sinter chemistry, mineralogy, pore structure and sinter plant operating conditions. All the above considerations and parameters make sinter making and maintaining lower RDI as a plant specific technology.
The ultimate objective of the BF operation is to maximize yield of hot metal out of the charge containing sinter as main iron bearing source. This is achieved through reduction process or removal of oxygen from the charge of sintered agglomerates. This phenomenon of removal of oxygen from sinter per unit time is termed as the reducibility of sinter. Thus higher reducibility of sinter results in an increase in productivity of BF operation. The reducibility of sinter is highly dependent upon the amount of magnetite (FeO.Fe203) and presence of non-ferrous impurities, particularly silica (Si02), in the sinter. Higher proportion of magnetite (FeO. Fe203) in sinter and the impurities reduces the reducibility of sinter. The existing conventional process of BF operation contain the sinter mass of high level of impurities >19% including Si02, and FeO in the range of about 9-10%, which lowers the reducibility of sinter at high temperature and thereby lowers the BF productivity.
There had been therefore, a persistent need to develop a method for improving the sinter quality in terms of its higher reducibility by reducing impurities and controlled conversion of hematite to magnetite in reducing gas atmosphere at desired temperature as indicated by the RDI of the present invention, such as to favor controlled generation of hot fines and maintain desired permeability of charge at upper shaft of the Blast Furnace and thereby increasing the plant specific productivity and yield of BF operation.
OBJECTS OF THE INVENTION
The basic object of the present invention is therefore directed to a method of improving sinter quality by a selective lowering of the value of Reduction Disintegration Index (RDI) of the sinter mass so that the Yield and Productivity of BF operation is improved.
Another object of the present invention is directed to a method of improving sinter quality based on providing selective value of RDI such as to favor controlled conversion of hematite to magnetite and desired generation of hot fines maintaining desired permeability of charge/sinter mass, at the upper shaft of BF to achieve the desired yield.


A still further object of the present invention is directed to a method of improving sinter quality based on selective RDI value, wherein the flow and passage of the reducing gases, mainly CO, is reduced or prevented to reduce the hematite phase at a temperature range of 450-600°C, and thereby delaying the hematite to magnetite conversion and also the disintegration of sinter mass and generation of fines at the upper shaft of furnace, such as to maintain desired permeability and reducibility favoring higher yield.
A still further object of the present invention directed to a method of improving sinter quality based on selective RDI value, wherein the control on rate of conversion of hematite to magnetite and the disintegration of sinter to generate hot fines at a desired volume is achieved in a simple and cost-effective manner to delay its disintegration at even higher temperature at 600-800°C, when the surfaces, pores and cracks of sinter are allowed to come in contact with reducing gases and generate hot fines of desired volume.
A still further object of the present invention directed to a method of improving sinter
quality based on selective RDI value, wherein the lower value of RDI of sinter
is selectively achieved reducing the existing level of 28% to about 17%, by a simple and cost-effective utilization of integrated steel plant (ISP) waster water to improve yield of BF.
A further object of the present invention is directed to a sinter Reduction Disintegration Index (RDI) controlling solution for beneficial utilization in controlling the Reduction Disintegration Index (RDI) of sinter mass for improving productivity and efficiency of blast furnace.
Another object of the present invention is directed to industrial beneficial utilization of waste water (hard water) a bi-product of ISP in controlling the Reduction Disintegration Index (RDI) of sinter mass for improving productivity and efficiency of the BF.
SUMMARY OF THE INVENTION


Thus according to the basic aspect of the present invention there is provided a method for improving sinter quality with respect to the Reduction Disintegration index (RDI) thereby favour higher reducibility of sinter and increased productivity of Blast Furnace (BF) comprising:
Subjecting the sinter of particle size in the range of 8mm to 50mm to treatment with a RDI lowering solution, named JSW solution by researchers at JSW Steel Ltd, whereby the surfaces, cracks and pores of the sinter are covered by said JSW solution which reduce or prevent the flow and passage of reducing gases to hematite phase during 450-600°C and delay the hematite to magnetite conversion and disintegration in the upper shaft of the furnace.
Another aspect of the present invention directed to a method for improving sinter quality wherein said JSW solution comprises waste water (hard water) comprising:
pH in the range of 7 to 8.5;
total hardness , ppm in the range of 800 to 1000;
Calcium hardness, ppm in the range of 150 to 200;
Chlorides, ppm in the range of 700 to 900;
Cyanide, ppm in the range of 1 to 2; and
Total Fe, ppm in the range of 1 to 6.
A still further aspect of the present invention directed to a method for improving sinter quality wherein said RDI lowering solution comprises waste water (hard water) comprise bi-product of ISP.


According to a further aspect of the method of the present invention for improving sinter
quality wherein said waste water (hard water) comprise bi-product of COREX Gas
cleaning system, Cold Rolling Mill (CRM) waste water and Effluent Treatment Plant
comprise a chemical constitution of :
i) COREX waste water having:
pH in the range of 8 to 8.5 preferably 8.3;
Total Hardness,ppm of 900 to 1000 preferably 920;
Calcium hardness ,ppm of 200 to 230 preferably 220;
Chlorides,ppm of 700 to 935 preferably 709;
Cynide,ppm of 0.19 to 2.0 preferably 2.0;
Total Fe,ppm of 1 to 2.5 preferably 2.23.
ii) CRM waste water having:
pH in the range of 2 to 6.5 preferably 4.0;
Total Hardness,ppm of 60 to 850 preferably 650;
Calcium hardness ,ppm of 40 to 150 preferably 100;
Chlorides,ppm of 40 to 700 preferably 600;
Cynide,ppm negligible;
Total Fe,ppm of 3 to 30 preferably 20. and iii) Effluent treated water having:
pH in the range of 8 to 8.8 preferably 8.5;
Total Hardness,ppm of 900 to 1000 preferably 950;
Calcium hardness, ppm of 100 to 220 preferably 150;
Chlorides,ppm of 800 to 1200 preferably 900;
Cynide,ppm of 0.19 to 2.0 preferably 1.0;
Total Fe,ppm of 0.2 to 2.0 preferably 1.2.


A still further aspect of said method for improving sinter quality wherein the compounds of the solution melts as the temperature exceeds 600-800°C, thereby exposing the surfaces, cracks and pores of the sinter at such temperature to thereafter the reducing gases become substantially active on sinter for desired higher reducibility of sinter and increased productivity.
According to another aspect of the method for improving sinter quality wherein the hardness of the RDI reducing solution is selectively controlled by addition of halides.
A further aspect of the method for improving sinter quality according to the present invention wherein the deposition of the JSW solution on the sinter including at cracks or pores of sinter is carried out through spraying of the said JSW solution over the sinter on conveyor before its dispatch to the blast furnace.
In the above method of the invention, the said Sinter JSW solution further comprising waste water (hard water) preferably bi-product of COREX Gas cleaning system, CRM wastes water and Effluent Treatment Plant.
A still further aspect Sinter RDI lowering solution wherein said waste water (hard water)
comprise bi-product of COREX Gas cleaning system, CRM waste water and Effluent
Treatment Plant having a chemical constitution of:
i) COREX waste water having:
pH in the range of 8 to 8.5 preferably 8.3;
Total Hardness,ppm of 900 to 1000 preferably 920;
Calcium hardness,ppm of 200 to 230 preferably 220;
Chlorides,ppm of 700 to 935 preferably 709;
Cynide,ppm of 0.19 to 2.0 preferably 2.0;


Total Fe,ppm of 1 to 2.5 preferably 2.23.
ii) CRM waste water having:
pH in the range of 2 to 6.5 preferably 4.0;
Total Hardness,ppm of 60 to 850 preferably 650;
Calcium hardness ,ppm of 40 to 150 preferably 100;
Chlorides,ppm of 40 to 700 preferably 600;
Cynide,ppm negligible;
Total Fe,ppm of 3 to 30 preferably 20. and iii) Effluent treated water having:
pH in the range of 8 to 8.8 preferably 8.5;
Total Hardness,ppm of 900 to 1000 preferably 950;
Calcium hardness, ppm of 100 to 220 preferably 150;
Chlorides,ppm of 800 to 1200 preferably 900;
Cynide,ppm of 0.19 to 2.0 preferably 1.0;
Total Fe,ppm of 0.2 to 2.0 preferably 1.2.
The present invention and its objects and advantages are described in greater details with reference to the accompanying non-limiting illustrative figures.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1(A): is the illustration of the schematic arrangement of sinter plant of the existing system of the sintering plant producing sinter with conventionally high RDI.
Figure 1(B): is the illustration of the arrangement of sinter plant of the present system of the sintering plant producing sinter with preferred low RDI value, according to the invention incorporating spraying of sinter JSW solution on the sinter bed on conveyor.


Figure 2: is the illustration of graphical presentation of the result of the laboratory scale application of the sinter RDI reducing solution spraying for the RDI (-3.15mm)% sinter reduced substantially from about 28% without treatment to 13% after the solution treatment of the sinter.
Figure 3 :indicates the RDI (-0.5mm %) values before and after the treatment of sinter by JSW solution. Theoretically the values should decrease, which is clearly shown in the figure. Few deviations are due to experimental errors.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURE
As discussed above, the present invention is directed to a method of improving the sinter quality for enhancing the yield/productivity of the BF by maintaining lower RDI of sinter, for which high level of, usually 9-10% of pre-reduced magnetite (FeO.Fe203) is maintained in sinter. More importantly, the sinter is treated with a JSW solution, prepared from the ISP's waste water prior to sending to the BF. The strength of sinter is also improved by increasing the bond strength of sinter, which is influenced by the sintering parameters and impurities such as Si02, CaO, MgO and Al203, added and or present in sinter. Normally, (CaO+MgO+Si02+ Al203) is maintained >18%, Si02 in the range of about 5-6% and MgO>1.4%. The combination of Si02 and MgO levels are maintained by the use of limestone or dolomite/dunite/serpenite. Higher value of RDI means higher amount of hot fine generation in BF operation, resulting in poor permeability at the upper shaft of the BF and thus lowers its productivity. RDI is the result of various factors such as sinter chemistry, mineralogy, pore structure and sinter plant operating conditions. All the above considerations and parameters make sinter making and maintaining lower RDI as a plant specific technology to improve yield.
As already described, that the Blast Furnace (BF) conventionally uses sinter as the main source of iron bearing charge which is reduced to iron by chemical reduction through a series of reactions in a reducing atmosphere during BF operation. Sinter is basically a tailored agglomerate material of iron bearing fines, coke breeze and fine fluxes produced in a sintering plant and fed through conveyor to the BF charging hopper. It has an irregular shape and size maintained between 5-40mm with a desirable mean particle size


(MPS) of 20mm. The sinter has a tendency to disintegrate when exposed to Carbon monoxide (CO) in the temperature range of 450-600°C. This degree of disintegration tendency of the sinters is measured or indicated by "Reduction Disintegration Index" (RDI). During the reaction with the reducing gases, mainly CO, the hematite phase present in the sinters is converted/reduced to magnetite (Fe203.FeO), which is highly porous and stressed due to increase volume (around 25%) in the course of reduction reactions. The induced stress initiates cracks in the matrix, which propagates on further-reduction. This phenomenon causes the disintegration of the sinter mass and generates fines.
The present invention is directed to reducing or preventing the flow and passage of the reducing gases, more particularly the CO, to hematite phase during 450-600°C, thereby delaying the conversion process of hematite to magnetite and disintegration of the sinter mass in the upper shaft of the furnace. This was achieved by deposition of a RDI reducing solution prepared by using waste water (hard Water), a bi-product of COREX Gas Cleaning system, CRM waste water and Effluent Treatment Plant. The Chemical analysis of the waste hard water used to prepare the JSW solution is given in the following Table I.
TABLE I

Properties COREX waste water CRM waste water Effluent treated water
PH 8.3 4 8.5
Total Hardness,ppm 920 650 950
Calcium Hardness,ppm 220 100 150
Chlorides, ppm 709 600 900
Cyanide, ppm 2 negligible 1
Total Fe, ppm 2.3 20 1.2
The compounds of solution melts as the temperature exceeds 600-800°C, thereby exposing the surfaces, cracks and pores of the sinter mass again, and enabling the reducing gases be substantially active on sinter. The results obtained through the laboratory trials with the waste water of varied hardness and properties, maintained by addition of halides in selective proportions, are presented in the accompanying Table II.


TABLE II

Sample NamesRDI ReducingSolution RDI(-3.5mm)% RDI(-0.5mm)%
After Treatment Without Treatment After Treatment Without Treatment
Solution 1 26 28.5 12.4 6.8
Solution 2 14.3 28.5 6.8 6.8
Solution 3 5.8 23.5 2.6 7
Solution 4 14 20.9 5.9 4
Solution 5 17.1 28.7 4.6 6
Solution 6 12.8 28.7 4.3 6
Solution 7 19 27 6 4.8
It is noted that the results of experiments in laboratory scale show:
• the RDI(-3.5mm)% reduced from 28% to 13% ,and
• the RDI(-0.5mm)% undergoes very small decrease.
The respective observed results are further presented graphically in figure 2 and figure 3 respectively.
Reference is now invited to accompanying Figure 1(A) that illustrates the conventional arrangement of sinter making and feeding to the BF bunker as a main source of iron bearing charge. The schematic diagram illustrates the different portions of a sinter plant and their functional relation. The mix of iron bearing hematite ore/fines along with proportionate additives for bonding and other impurities are fed from bunkers to the conveyor through mixer and feeder at a desired rate and sintering process is ignited by COREX gas. As the sinter bed proceed on the sinter car, hot air draft adequate to attain desired temperature for sintering is supplied through the under bed flow passages. The hot sinter lump is broken into pieces after it is discharged at the end of the conveyor belt by a sinter breaker and screened by a Hot Screen such as to return the fine particles back to the feed hopper. The lumps of desired size are then transferred to the blast furnace through a sinter cooler and cold screening to further separate out smaller sized particles and fines and only bigger lumps of size with MPS of 20mm are passed on to the BF by conveyor.


Reference is next invited to the Figure 1(B), that new system and method for improving RDI based sinter quality according to the present invention, by preferred spraying and deposition of JSW solution of varied hardness and other properties developed in-house using ISP's waste water comprising bi-product of COREX gas cleaning system, CRM waste water and Effluent treatment plant, on to the sinter bed on conveyor before feeding into the Blast Furnace. The deposition results in reducing or preventing the flow and passage of the reducing gases (mainly CO) to hematite phase during 450-600°C, thereby delaying the hematite to magnetite conversion and disintegration in the upper shaft of the furnace.
It is thus possible by way of this invention to reduce the RDI (-3.5mm) of sinter from 28% to 17% by the preferred treatment of the sinter mass with the JSW solution of the invention having varied degree of hardness, to ensure delayed disintegration of treated sinter mass, which favors in maintaining desired permeability, adequate to enhance the yield of the BF operation.


WE CLAIM:
1. A method for improving sinter quality with respect to the Reduction Disintegration
index (RDI) thereby favour higher reducibility of sinter and increased productivity of Blast
Furnace (BF) comprising:
"Subjecting the sinter of particle size in the range of 8mm to 50mm to treatment with a JSW solution whereby the surfaces, cracks and pores of the sinter are covered by the said solution which reduce or prevent the flow and passage of reducing gases to hematite phase during 450-600°C and delaying the hematite to magnetite conversion and disintegration in the upper shaft of the furnace".
2. A method for improving sinter quality as claimed in claim 1 wherein said JSW solution
comprises ISP waste water (hard water) comprising:
pH in the range of 7 to 8.5;
total hardness , ppm in the range of 800 to 1000;
Calcium hardness, ppm in the range of 150 to 200;
Chlorides, ppm in the range of 700 to 900;
Cyanide, ppm in the range of 1 to 2; and
Total Fe, ppm in the range of 1 to 6.
3. A method for improving sinter quality as claimed in anyone of claims 1 or 2 wherein
said JSW solution comprises ISP waste water (hard water) comprise bi-product of
COREX Gas cleaning system, CRM waste water and Effluent Treatment Plant.


4. A method for improving sinter quality as claimed in claim 3 wherein said waste water (hard water) comprise bi-product of COREX Gas cleaning system and Effluent Treatment Plant comprise a chemical constitution of:
i) COREX waste water having:
pH in the range of 8 to 8.5 preferably 8.3;
Total Hardness,ppm of 900 to 1000 preferably 920;
Calcium hardness ,ppm of 200 to 230 preferably 220;
Chlorides,ppm of 700 to 935 preferably 709;
Cynide,ppm of 0.19 to 2.0 preferably 2.0;
Total Fe,ppm of 1 to 2.5 preferably 2.23.
ii) CRM waste water having:
pH in the range of 2 to 6.5 preferably 4.0;
Total Hardness,ppm of 60 to 850 preferably 650;
Calcium hardness ,ppm of 40 to 150 preferably 100;
Chlorides,ppm of 40 to 700 preferably 600;
Cynide,ppm negligible;
Total Fe,ppm of 3 to 30 preferably 20. and
iii) Effluent treated water having:
pH in the range of 8 to 8.8 preferably 8.5;
Total Hardness,ppm of 900 to 1000 preferably 950;
Calcium hardness, ppm of 100 to 220 preferably 150;
Chlorides,ppm of 800 to 1200 preferably 900;
Cynide,ppm of 0.19 to 2.0 preferably 1.0;
Total Fe,ppm of 0.2 to 2.0 preferably 1.2.


5. A method for improving sinter quality as claimed in anyone of claims 1 to 4 wherein the solution compounds melt as the temperature exceeds 600-800°C, thereby exposing the surfaces, cracks and pores of the sinter at such temperature to thereafter the reducing gases become substantially active on sinter for desired higher reducibility of sinter and increased productivity.
6. A method for improving sinter quality as claimed in anyone of claims 1 to 5 wherein the hardness of the JSW solution is selectively controlled by addition of halides.
7. A method for improving sinter quality as claimed in anyone of claims 1 to 6 wherein the deposition of the JSW solution on the sinter including at cracks or pores of sinter is carried out through spraying of the said JSW solution over the sinter on conveyor before its dispatch to the blast furnace.
8. JSW solution comprising ISP waste water (hard water) preferably bi-product of COREX Gas cleaning system, CRM waste water and Effluent Treatment Plant.
9. JSW solution as claimed in claim 8 wherein said waste water (hard water) comprise bi-product of COREX Gas cleaning system, CRM waste water and Effluent Treatment Plant having a chemical constitution of :
i) COREX waste water having:
pH in the range of 8 to 8.5 preferably 8.3;
Total Hardness,ppm of 900 to 1000 preferably 920;
Calcium hardness ,ppm of 200 to 230 preferably 220;
Chlorides,ppm of 700 to 935 preferably 709;
Cynide,ppm of 0.19 to 2.0 preferably 2.0;
Total Fe,ppm of 1 to 2.5 preferably 2.23.


ii) CRM waste water having:
pH in the range of 2 to 6.5 preferably 4.0;
Total Hardness,ppm of 60 to 850 preferably 650;
Calcium hardness ,ppm of 40 to 150 preferably 100;
Chlorides,ppm of 40 to 700 preferably 600;
Cynide,ppm negligible;
Total Fe,ppm of 3 to 30 preferably 20. and
iii) Effluent treated water having:
pH in the range of 8 to 8.8 preferably 8.5;
Total Hardness,ppm of 900 to 1000 preferably 950;
Calcium hardness, ppm of 100 to 220 preferably 150;
Chlorides,ppm of 800 to 1200 preferably 900;
Cynide,ppm of 0.19 to 2.0 preferably 1.0;
Total Fe,ppm of 0.2 to 2.0 preferably 1.2.
10. JSW solution and a method for improving sinter quality with respect to the Reduction Disintegration index (RDI) thereby favour higher reducibility of sinter of particle size in the range of 8mm to 50mm to increase productivity of Blast Furnace (BF) substantially as herein described and illustrated with reference to the accompanying examples and figures.


ABSTRACT
TITLE: A METHOD FOR IMPROVING SINTER QUALITY WITH RESPECT TO THE REDUCTION DISINTEGRATION INDEX(RDI).
A method for improving the sinter quality with respect to lowering the Reduction Disintegration Index (RDI) to favour higher reducibility of sinter of particle size in the range of 8mm to 50mm and resultant increase in productivity of Blast Furnace (BF). Advantageously, the method of the invention would enable covering pores and cracks/gaps on surfaces of sinter mass by spraying waste water (hard water) comprising bi-product of COREX Gas cleaning system and Effluent Treatment Plant, such that the flow and passage for reducing gases, mainly CO, to hematite phase at 450°C-600°C, is reduced or prevented and thereby delaying the hematite to magnetite conversion and disintegration of sinter in the upper shaft of the Blast furnace. The present invention is thus directed to a method of controlling sinter quality in terms of higher hot metal yield/productivity in BF operation by maintaining lower RDI of Sinter, reducing the existing level of 28% to about 17%, justifying its wide industrial application in BF operations in steel plants.