FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
1 TITLE OF THE INVENTION :
DUST BURNER SYSTEM FOR INJECTING RECYCLED-DUST IN MELTER-GASIFIER WITH INCREASED DUST LOAD AND LONGER LIFE.
2 APPLICANT (S)
Name : JSW Steel Limited.
Nationality : An Indian Company.
Address : Jindal Mansion, 5-A, Dr. G. Deshmukh Marg, Mumbai - 400 026,
State of Maharastra, India.


3 PREAMBLE TO THE DESCRIPTION
COMPLETE

The following specification particularly describes the invention and the manner in which it is to be performed.


FIELD OF THE INVENTION
The present invention relates to a reliable dust burner system for improving operating efficiency and longer life of the Dust Burner in Corex, a smelting reduction iron making process. More particularly, the present invention is directed to a dust burner system adapted for higher dust load with higher oxygen flow rate for dust burning in a safe and reliable manner. Advantageously, the operating performances with improved design configuration ensure longer operating life of such dust burners. The constructional features of the modified dust burner according to the present invention enable increased dust load of the Burner from conventional 6000kg/hr to nearly 8000kg/hr with a corresponding increase in oxygen flow rate from 3500m3/hr to about 4500m3/hr, capability to withstand longer exposure to higher temperatures avoiding failure of tip surfaces or melting and resultant water leakage into the burner system, leading to lower downtime of plant and improved productivity in Corex with lower cost of operation for smelting reduction iron making in Corex process, thus favoring wide scale application in related industries.
BACKGROUND ART
It is well known in the existing art of iron and steel manufacturing, Corex relates to a technology for a smelting reduction iron making process. The Corex process is carried out using of two main reactors: (i) the reduction shaft and (ii) the melter-gasifier. The reducing gases generated in the melter-gasifier due to various reactions, are utilized advantageously to reduce the iron bearing materials in the reduction shaft. The gases before injecting into shaft is first cooled to 850°C and then cleaned using hot gas cyclone. The dusts separated from the gases are carried through Dust Recycling System (DRS) and clean gases are injected back into the melter-gasifier through dust burners to take part in reaction again at reasonably high temperatures, thus saving exhaust heat loss.
The dust collected in the cyclones is recycled back to the melter-gasifier through the dust burners, where the dust is burnt with additional oxygen injected through the burners. There are usually four such dust burners located around the circumference of the melter-gasifier above the charge bed. The dust burner conventionally consists of two shells; the inner shell is to carry the dust with nitrogen as a carrier gas. The narrow annular passage
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in the outer shell carries oxygen to burn the dust at the burner tip. Both the shells are provided with water-cooling jacket to contain temperature rise within limits. The water outlet of inner shell is the inlet to the outer shell.
The existing Dust burner systems in Corex process suffer from a number of limitations and disadvantages in terms of dust burning efficiency vis-a-vis Dust load capacity of the burners. It is experienced in the practical application of Corex process for smelting reduction iron making that an actual average Dust load is high enough ranging up to 8000 Kg/hr. Such excess dust could not be burnt in existing Dust Burner configuration which is unable to allow sufficient flow of oxygen to burn the excess dust, thus limiting the performance of the existing burners to a dust load up to about 6000kg/hr. Moreover, it is experienced in the art that due to high heat generation at the tip of Dust Burners caused due to insufficient cooling and higher actual dust load than designed, the Dust Burner face got burnt and punctured forming gap for water to enter Melter Gasifier. It has been further experienced that the dust used to erode the pin over time and loose the contact of diversion pipe and dust pipe. The conventional Dust Burner is found to ensure in the long run a maximum operating life of 4 months as against designed/expected life of 6 months. The above reasons thus lead to poor life of dust burners and thereby needing frequent repair/replacement of dust burners and incidental interruptions in smelting reduction operations in Corex, leading to loss of productivity.
There has therefore been a persistent need in the application of smelting reduction in Corex process for iron making, to develop an improved dust burner system capable of accommodating and burning higher Dust load in keeping with the Corex process requirements in reliable manner without the melting and burn through of the burner tip face and the resulting in forming gap for water to enter Melter Gasifier. The improved design configuration of such Dust Burner shall also favor higher oxygen flow rate commensurate with the Dust load/burning rate, the cooling arrangement of such improved burners also shall be adequate to contain temperature rise at burner tip area and eliminate chances of frequent failure of the burners and thus would lower down time of Dust Burners and enhance productivity.
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OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide for an improved dust burner system directed to enhance efficiency of the dust burning in dust recycling systems (DR5) of the Corex process by improving Dust load capacity of such burners and also to provide means for accommodating higher oxygen flow rate to burn the enhanced dust quantity in a simple, safe and reliable manner, longer service life of dust burner and increased plant availability.
Another object of the present invention is directed to a Dust Burner system for the DRS in Corex adapted to higher dust load and oxygen flow rate as compared to conventional practice, wherein the burner tip is adapted such that the heat generated due to dust burning even at higher dust load, the burner face do not melt down or burn through and gets punctured forming gap for water to enter Melter Gasifier causing stoppage of burner operation.
A further object of the present invention is directed to a dust burner system for the DRS in Corex adapted to higher dust load and oxygen flow rate wherein the problem of erosion of the contact pin for joining of diversion pipe and dust pipe, hanging in the dust pipe of burner, is avoided to further facilitate the performance of the burner.
A still further object of the present invention is directed to a dust burner system for the DRS in Corex adapted to higher dust load and oxygen flow rate wherein the inner and outer shell configuration/dimension is selectively maintained such that the section of flow passage is adequate for supply of required quantity of oxygen for burning of higher dust load.
A still further object of the present invention is directed to a dust burner system for the DRS in Corex adapted to higher dust load and oxygen flow rate wherein water cooling arrangement of the burner tip is sufficient enough to contain the tip temperature within safe limit without failure of function.
A still further object of the present invention is directed to a dust burner system for the DRS in Corex adapted to higher dust load and oxygen flow rate wherein the improved
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design configuration enable the capacity of dust burner to be enhanced to a Dust load of 8000kg/hr and oxygen flow rate for dust burning in the range of 4500 m3/nr.
A still further object of the present invention is directed to a dust burner system for the DRS in Corex adapted to higher dust load and oxygen flow rate with improved configuration of high capacity dust burner ensuring longer operating life of the burners up to 6 months without loss of efficiency or failure/downtime and thus enhancing productivity of the smelter reduction process in Corex.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to a dust burner system to inject the recycled dust in Melter-Gasifier in smelting reduction iron making adapted for increased dust load and longer life comprising
inner shell adapted to carry the dust with a carrier gas and an outer shell carrying oxygen to burn the gas, both said shells provided with water cooling jackets with diversion pipe for water;
said water diversion pipe being maintained parallel;
oxygen gap there between the inner and outer shells and the tip of the said inner and outer shells adapted such as to favour increased oxygen flow up to 4500 m3/nr and high dust loads up to 8000 kg/hr.
another aspect of the present invention is directed to a dust burner system wherein the inner shell and an outer shell are obtained of selective desired dimensions to allow said flow of desired quantity of oxygen to favor accommodating said increased dust load and longer life of burner.
A still further aspect of the present invention directed to said Dust Burner system wherein
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said inner and outer shells are substantially cylindrical in shape arranged in concentric manner along longitudinal axis ;
each of said inner and outer shells of the burner having embedded water cooling jacket in the concentric shell walls selectively spaced apart;
said diversion pipeline adapted to favor water circulation for shell cooling such that the water outlet of inner shell is operatively connected as the inlet to the outer shell;
a co-axial dust pipe for carrying dust in gas medium for burning at the burner tip.
According to yet another aspect of the present invention directed to said Dust Burner system, wherein the water diversion pipe is made parallel by installing a plurality of spacers and preferably 4 number spacers of 15 mm length at front and rear end of outer circumference at 90 degree angular gap.
A still further aspect of the present invention directed to a Dust Burner system, wherein the overall length of the outer shell of the dust burner from Melter Gasifier connection has been maintained at 1470 mm, the overall length of the inner shell of the Dust Burner has been maintained at 2327 mm and the total length of the modified dust burner assembly has been maintained at 2645 mm.
Also in said Dust Burner system the tip face thickness of the said inner and outer shells are increased to a thickness of 32 mm, to avoid burn-through or melting of tip face and resultant leakage of water in the melter-gasifier.
A stifl further aspect of the present invention is directed to a Dust Burner system wherein the inside diameter of circumferential outer shell of the dust burner is selectively maintained at 145 mm and the out side diameter of the circumferential inner shell is selectively decreased from 139mm to 135mm to increase the radial oxygen gap from 3mm to 5mm to enhance the desired oxygen flow for higher dust load.
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According to yet another aspect of the present invention directed to a Dust Burner system, wherein the dust and diversion pipe are welded together to thereby eliminate problems of dust erosion of pin.
Another advantageous aspect directed to said Dust Burner system of the present invention, wherein the Dust Burner angle at face is maintained same as 10 degree for both the inner shell and outer shell, ensuring achieving uniform oxygen gap of 5 mm.
A still further aspect of the present invention is directed to a Dust Burner system, wherein said increased oxygen gap in combination with the water cooling jackets provided in each of the outer and the inner shell of the dust burner favor achieving surprisingly higher cooling effect of dust burner tip/face assembly and thus avoiding the chances of burn through or puncture of face causing water leakage.
A still further aspect of the present invention is directed to a Dust Burner system, wherein the outer shell face has been maintained at 145 mm circumferential inside diameter with 10 Degree angle from 20 mm (45 Degree) chamfering end.
The advantages and objectives of the present invention are described in greater details with reference to the following non limiting illustrative figures.
BRIEF DESCRIPTION OF THE ACCOMANYING FIGURES
Figure 1: is the schematic illustration of the longitudinal sectional elevation of the complete Dust Burner assembly in general.
Figure 2: is the schematic illustration of the sectional view of the burner tip showing the relative disposition of the inner and the outer shell of the Dust burner, their shape and dimensions in conventional configuration of the dust burner face assembly.
Figure 3: is the schematic illustration of the sectional view of the burner tip showing the relative disposition of the inner and the outer shell of the Dust burner, with modified design configuration to achieve desired improved dust burning properties according to the present invention.
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DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES
Reference is first invited to the accompanying Figure 1 that schematically illustrates an embodiment of the full Dust Burner in a longitudinal sectional view wherein the different components of such dust burner and there relative disposition has been shown.
The Dust Burner comprising two substantially longitudinal cylindrical concentric shells having a burner tip of selective geometry, wherein the inner shell is to carry the dust with nitrogen as a carrier gas. The gap/passage between the inner and the outer shell carries oxygen to burn the dust. Both the shells are provided with water-cooling jacket. The water flow of cooling jacket through shells is so maintained that the outlet of inner shell is the inlet to the outer shell. Such water circulation for sequential cooling of the shells are facilitated by the use of a Diversion pipe assembly. A contact pin is used for joining of diversion pipe and dust pipe, that usually hangs inside the dust pipe of burner. Four such dust burners are selectively disposed around the circumference of the melter-gasifier above the char bed. The typical configuration of such Dust Burners are having a tip configuration with burner face assembly defining the burning performance as well as Dust load capacity of such burner.
The improved design configuration conforms to VAI design standards such that the Overall length of outer shell of Modified Dust Burner from Melter-Gasifier connection has been maintained as per VAI design of 1470 mm, the Overall length of the inner shell of modified Dust Burner has been maintained as per VAI design of 2327 mm and the total length of the modified dust burner assembly has been maintained as per VAI Design of 2645 mm.
The conventional burner face assembly, as schematically illustrated in the accompanying Figure 2 as cross sectional view, is characterized by the outer shell face Design of Dust Burner having 145 mm inside diameter with 10° angle of sloped wall from 20 mm circumferential 45° chamfering end and the inner shell angle is 10° with a tip diameter of 139mm. These diametric dimensions provide for an annular passage of 3mm thickness in between the outside surface of inner shell and the inside surface of outer shell, through which oxygen is supplied to burn the dusts and the cross sectional area of this annular gap limits the volume flow rate of oxygen for dust burning and is converging near tip due to
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provision of said angle of sloped walls of shells. The face thickness for inner and outer shell is conventionally maintained at 15 mm. The above given configuration enable the dust burners to take maximum dust load of about 6000 kg/hr with oxygen flow of 3750 m3/nr, which is not adequate as compared to the actual requirement in Corex operation and thus needing modification of the burner configuration and also to avoid over heating and melting/puncture of the tip surface forming gap for water to flow into the melter-gasifier. Dust erosion of the contact pin for joining the dUSt pipe and the diversion pipe is also quite common in conventional application of burners causing another failure mode.
Reference is now invited to the accompanying Figure 3 that schematically illustrates the Dust Burner tip configuration according to the present invention in sectional view. It is clearly apparent that the improvements in design configurations is directed to eliminate the limitations and difficulties observed in the prior aft and enhancing the Dust load capacity and tip temperature enduring capacity of the dust burners restricting the occurrences of burnt through and water getting inside the melter-gasifier. The salient constructional features in the embodiment of the improved burner accordinq to the present invention is primarily focused on important aspects of (i) increasing the oxygen flow rate to burn excess dust increasing the dust load capacity of burners, (ii) burner tip face assembly configuration adequate to withstand higher temperatures avoiding melt through or puncture, (iii) enhancing cooling performance, and (iv) avoiding failure of connector pin between dust pipe and the diversion pipe assembly.
The improved configuration according to the dust burner embodiment illustrated in the accompanying Figure 3, provide for higher volume flow rate of oxygen required to burn excess dust load, by adjusting the diameters of inner and outer shells such that the flow area for oxygen is increased. To achieve this, the outer shell face Design of modified Dust Burner has been maintained as per VAI Design of 145 mrn circumferential inside diameter with 10 Degree angle from 20 mm (45 Degree) chamfering end, while the inner shell of modified Dust Burner having circumferential diameter decreased from 139 mm to 135 mm, increasing the gap for Oxygen flow from existing 3 ntm to 5 mm, enabling higher volume flow rate oxygen adequate to burn excess dust in the range of actual dust load of 8000 kg/hr in Corex operation.
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It is apparent that to enhance the temperature bearing properties avoiding burn through, the Tip face thickness of the inner shell of modified Dust Burner has been increased from 15 mm to 32 mm and same has been accommodated in the Overall length of inner shell by shortening the water gutter length. Moreover, outer shell face Design of modified Dust Burner has been maintained as per VAI Design of 145 mm circumferential inside diameter with 10 Degree angle from 20 mm (45 Degree) chamfering end. Also, the inner shell face angle of modified Dust Burner angle has been maintained as per VAI design of 10 degree. Thus the inner shell and outer shell of modified Dust Burner angle at face being same as 10 degree, uniform oxygen gap of 5 mm is achieved.
A further important improvement of the modified configuration of the dust burner is in terms of assembly of the inner and outer shell comprising the dust pipe and the water and oxygen carrying passages substantially parallel for effective fluid circulation and heat transport to thereby avoiding overheating and burn through of the burner tip face. To achieve this the water diversion pipe was made parallel by installing 4 number SS 304 spacers of 15 mm length both at front and rear end of outer circumference at 90 degree angular gap. The pin connecting dust pipe and diversion pipe is removed and the dust and diversion pipe are welded together. Thus the modified configuration eliminates the possibility of dust erosion of the pin connecting the diversion pipe with the dust pipe, and these are held in their relative positions in a secured manner by means of non-corrosive SS spacers, favoring easy and smooth flow/circulation of oxygen or water as coolant. This improved cooling by way of improved circulation coupled with increased area of volumetric flow of oxygen, as well as increased burner tip face thickness of 32 mm ensure safe operation of burner tip face assembly avoiding overheating and leakage of water due to burn through/puncture even at higher dust load of up to 8000kg/hr. It is further ensured in the modified and improved design of the dust burner face assembly that the Dust Burner configuration has been maintained as per VAI design such that the inner shell face inline with the outer shell face aligned at the end of 20 mm (45 Degree) chamfer end hence inner shell is 20 mm inside of outer shell face. Thus water first entering the water cooling jacket of the inner shell effectively control the temperature rise of the tip face of inner shell.
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It is thus possible by way of the present invention to achieve increased dust load up to 8000kg/hr from melter-gasifier for recycling in Corex operation for smelting reduction iron making and with effective water cooling provision and increased oxygen flow up to 4500 m3/nr can take high dust loads up to 8000 kg/hr, to enable complete burning of the higher dust load for desired recycling to melter-gasifier. Modified dust burner face assembly with higher face thickness and preferred orientation of dust burning plane of tip favor uniform wear out of the face favour achieving desired enhanced reliability of Dust Burners in a simple and economic manner such that the life of the dust burners has increased from existing 3 months to up to 9 months and thus favoring its wide and advantageous industrial application in dust recycling systems for Corex process.
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We Claim:
1. A dust burner system to inject the recycled dust in Melter-Gasifier in smelting
reduction iron making adapted for increased dust load and longer life comprising
inner shell adapted to carry the dust with a carrier gas and an outer shell carrying oxygen to burn the gas, both said shells provided with water cooling jackets with diversion pipe for water;
said water diversion pipe being maintained parallel;
oxygen gap therebetween the inner and outer shells and the tip of the said inner and outer shells adapted such as to favour increased oxygen flow up to 4500 m3/hr and high dust loads up to 8000 kg/hr.
2. A dust burner system as claimed in claim 1 wherein the inner shell and an outer shell are obtained of selective desired dimensions to allow said flow of desired quantity of oxygen to favor accommodating said increased dust load and longer life of burner.
3. A Dust Burner system as claimed in anyone of claims 1 or 2 wherein
said inner and outer shells are substantially cylindrical in shape arranged in concentric manner along longitudinal axis ;
each of said inner and outer shells of the burner having embedded water cooling jacket in the concentric shell walls selectively spaced apart;
said diversion pipeline adapted to favor water circulation for shell cooling such that the water outlet of inner shell is operatively connected as the inlet to the outer shell;
a co-axial dust pipe for carrying dust in gas medium for burning at the burner tip.
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4. A Dust Burner system as claimed in any one of claims 1 to 3, wherein the water diversion pipe is made parallel by installing a plurality of spacers and preferably 4 number spacers of 15 mm length at front and rear end of outer circumference at 90 degree angular gap.
5. A Dust Burner system as claimed in any one of claims 1 to 4, wherein the overall length of the outer shell of the dust burner from Melter Gasifier connection has been maintained at 1470 mm, the overall length of the inner shell of the Dust Burner has been maintained at 2327 mm and the total length of the modified dust burner assembly has been maintained at 2645 mm.
6. A Dust Burner system as claimed in any one of claims 1 to 5 wherein the tip face thickness of the said inner and outer shells are increased to a thickness of 32 mm,
7. A Dust Burner system as claimed in anyone of claims 1 to 6 wherein the inside
diameter of circumferential outer shell of the dust burner is selectively maintained at
145 mm and the out side diameter of the circumferential inner shell is selectively
decreased from 139mm to 135mm to increase the radial oxygen gap from 3mm to
5mm to enhance the desired oxygen flow for higher dust load.
8. A Dust Burner system as claimed in any one of claims 1 to 7, wherein the dust and diversion pipe are welded together to thereby eliminate problems of dust erosion of pin.
9. A Dust Burner system as claimed in any one of claims 1 to 8, wherein the Dust Burner angle at face is maintained same as 10 degree for both the inner shell and outer shell, ensuring achieving uniform oxygen gap of 5 mm.
10. A Dust Burner system as claimed in any one of claims 1 to 9, wherein said increased oxygen gap in combination with the water cooling jackets provided in each of the outer and the inner shell of the dust burner favor achieving surprisingly higher cooling effect of dust burner tip/face assembly and thus avoiding the chances of burn through or puncture of face causing water leakage.
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11. A Dust Burner system as claimed in any one of claims 1 to 10, wherein the outer
shell face has been maintained at 145 mm circumferential inside diameter with 10
Degree angle from 20 mm (45 Degree) chamfering end.
12. A Dust Burner system adapted to burn increased dust load with longer operating life
as herein described with reference to the accompanying non limiting illustrative
figures.
Dated this 30th day of January, 2009 Anjan Sen
Of Anjan Sen & Associates (Applicants Agent)
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