Description:

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 system for storage and controlled feeding of flux materials onto existing coal conveyor for mixing, grinding and injection into Blast furnace. In this system, Calcined Dolomite brought from raw material plant is stored in dolomite storage day bin and Dolomite from the storage bin is discharged by belt weigh feeder in a desired ratio onto the existing underground inclined coal conveyor carrying the coal. The discharge rate should be controlled in auto mode such that the ratio of coal and dolomite is varied from 4:1 to 12:1 as per requirement. The major benefits derived by the system is in Sinter having less MgO are (i) Higher cold strength of sinter (ii)Higher Fe content in sinter,(iii) Improve size fraction of sinter, (iv) Permeability of BF burden will improve because of Less basic slag formed in bosh zone. In blast furnace performance, the Productivity of BF will increase because Permeability of the furnace will increase. Coke burning will be faster. Higher Fe in Sinter will lead to more production. CDI rate can be improved by better permeability of the Blast Furnaces.

BACKGROUND OF THE INVENTION

Applicant’s Bhilai Steel Plant(BSP) blast furnaces operates with higher slag rate and high alumina in slag because of higher gangue content from iron bearing materials, coke ash etc. To take care of high alumina in slag with respect to slag fluidity and melting temperature, higher amount of MgO is being charged through sinter. Different types of slag are formed at different locations inside the blast furnace. Normally the bosh slag has a higher basicity compared to primary, tuyere and final slag. Very high basic slag has normally high melting point and its viscosity varies significantly in cohesive zone and thus permeability of the furnace gets deteriorated. Injection of some amount of flux through tuyeres helps in reduction in excessive basic bosh slag formation decreases bosh slag volume and keeping basicity of slag formed across the height of the furnace evenly and at proper level with good melting properties.

There has been thus a need to develop a system for controlled feeding of calcined dolomite at desired proportion with coal to maintain required basicity of slag to ensure satisfactory performance of blast furnace. The system of present invention thus targets to enhancing CDI rate with higher productivity and good quality of hot metal in BF. Additionally following benefits are envisaged with Low MgO content in Sinter are (i) Productivity of Sinter Machine will improve (ii) Cold Strength of Sinter will improve (iii) Thickness of Cohesive zone will reduce (iv) Total Pressure drop in BF will decrease (v) Improve Slag Fluidity (vi) Decrease in Si & S content of hot metal (vii)CDI rate will improve etc.

OBJECTS OF THE INVENTION
The basic object of the present invention is directed to provide a system for storage and controlled feeding of flux materials/calcined Dolomite onto existing coal conveyor for mixing, grinding and injection into Blast furnace.

A further object of the present invention is directed to provide a system for storage and controlled feeding of flux materials/calcined Dolomite onto existing coal conveyor wherein discharge rate of dolomite should be controlled in auto mode such that the ratio of coal and dolomite is varied from 4:1 to 12:1 as per requirement.

A still further aspect of the present invention is directed to said system favouring Low MgO content in Sinter whereby (i) Productivity of Sinter Machine will improve (ii) Cold Strength of Sinter will improve (iii) Thickness of Cohesive zone will reduce and consequently permeability and productivity of BF will improve.

A still further aspect of the present invention is directed to said system targeted to maintain desired basicity of slag and enhancing CDI rate with higher productivity and good quality of hot metal in BF.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a system for controlled feeding of flux materials onto existing coal conveyor favouring mixing, grinding and injection into blast furnace comprising:

a flux storage bin to store flux material;

said flux storage bin cooperatively disposed with respect to coal conveyor and having atleast a belt weight feeder installed thereunder to extract and feed flux material on to said coal conveyor;

means for monitoring the coal rate and coal conveyor capacity and coordinate controlled flux to coal feed ratio for desired mixing, grinding and injection of flux into the blast furnace to control slag formation and productivity.

A further aspect of the present invention is directed to said system comprising electrically operated monorail telpher and grab bucket of desired capacity to transfer dumped flux material from ground to said flux storage bin preferably of one day requirement storage capacity of 50 ton based on about 10Kg/THM injection rate;
said flux storage bin including a motorized rack & pinion gate installed at the bottom opening for isolation purpose during maintenance activity.

A still further aspect of the present invention is directed to said system comprising of belt weigh feeder under the said flux storage bin installed to extract flux material from said flux storage bin to feed to the existing coal conveyor provided to achieve the desired flux to coal ratio from 1:4 to 1:12 considering coal rate and existing coal conveyor capacity involving VFD drive in belt weigh feeder.

A still further aspect of the present invention is directed to said system comprising belt weigher installed in existing said coal conveyor to monitor the coal flow rate such that the flux extraction and feed rate is controlled based thereon to achieve desired flux to coal ratio.

A still further aspect of the present invention is directed to said system comprising Industrial controller means to set flux to coal ratio such that based on thus set ratio and input coal flow rate received from belt weigher, the controller is adapted to generate signal to the VFD drive of belt weigh feeder for the amount of flux to be extracted and fed to the coal conveyor.

A still further aspect of the present invention is directed to said system which is adapted such that said storage and controlled feeding of the flux material onto existing coal conveyor for mixing, grinding and injection into Blast Furnace to achieve the desired ratio within an accuracy of +/- 0.5%.

Another aspect of the present invention is directed to said system comprising :

said flux storage bin includes grid opening preferably of 100mm x 100mm with single opening having motorized R&P gate preferably also including provision for manual opening, said grid of the flux storage bin preferably having square openings with adequately provided flats and rods supported on beams, said grids arranged in removable sections with size of the out let preferably about 500mmx500mm and including poking holes for clearing the jam at outlet if required;

said belt weigher being automatic and electronic type installed in coal conveyor to give a feedback of coal quantity to controller which controls the discharge of calcined dolomite based on set ratio of coal : dolomite;

said belt weigh feeder having continuous flow characteristics including a VFD drive for AC motor to vary the flow rate and having load cells and bottom opening of 500x500mm, said weigh feeder having both remote and local control panel near to the weigh feeder, said remote panel having the provision through the controller to set the desired quantity as set point and the weigh feeder is adapted to maintain the same within an accuracy of +/-0.5%., said weigh feeder panel including the following displays: Feed rate indications in tons/hr, totalized display, Set point indicator, annunciations lamps and set point increase/decrease.

motorized R&P gate provided below said flux storage bin for opening and closing day bin opening for maintenance purpose;

electrical control panel comprising of weigh feeder panel and local control posts adapted to include following MCC in the panel : Telpher LT drive motor, Telpher hoisting drive motor, R&P gate drive motor and weigh feeder motor-VFD drive, the controller receiving input from belt weigh scale for input of coal quantity on coal conveyor and based on the set ratio of coal : dolomite, the weigh feeder sets the VFD drive for flow rate of calcined dolomite.

Yet another aspect of the present invention is directed to said system in operative connection to blast furnace enabling incorporation of low levels in the range of 2.2 % to 2.3% MgO content in sinter in blast furnace favouring (i) Higher cold strength of sinter (ii)Higher Fe content in sinter,(iii) Improve size fraction of sinter,(iv) Permeability of BF burden will improve because of Less basic slag formed in bosh zone.

A further aspect of the present invention is directed to a method for enhancing CDI rate and productivity and quality of hot metal produced in blast furnace involving step of controlled feeding of flux material onto existing coal conveyor for mixing, grinding and injection into blast furnace involving the system as described above.

A still further aspect of the present invention is directed to said method wherein the sinter used is provided with low MgO content in the range of 2.2% to 2.3%, said low MgO sinter used in the process favouring (i) Higher cold strength of sinter (ii)Higher Fe content in sinter,(iii) Improve size fraction of sinter,(iv) Permeability of BF burden will improve because of Less basic slag formed in bosh zone.

The above and other objects and advantages of the present invention are described hereunder in greater details with reference to following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: line diagram showing the basic layout scheme of the invented system.
Figure 2: is the line diagram showing the general arrangement of the system according to present invention.
Figure 3: shows the schematic Flow sheet of co-injection of Pulverized coal and MgO involving the system of present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
The present invention is directed to provide a system for storage and controlled feeding of flux materials/calcined Dolomite onto existing coal conveyor for mixing, grinding and injection into Blast furnace, wherein discharge rate of dolomite can be controlled in auto mode such that the ratio of coal and dolomite is varied from 4:1 to 12:1 as per requirement of downstream application.

The system is designed such that Calcined Dolomite from Raw Material Plant (RMP) is transported to the proposed site by truck dumpers. The truck dumpers will unload the calcined dolomites on the ground inside the dumping shed of the proposed day bin building. Dolomite will then be stored into the Dolomite storage bin using monorail Telpher and grab bucket. Dolomite from the storage bin will be discharged by belt weigh feeder in a desired ratio onto the existing underground inclined coal conveyor carrying the coal. The discharge rate should be such that the ratio of coal and dolomite will vary from 4:1 to 12:1 as per requirement. The existing conveyor capacity is 60 TPH. At present, the existing underground coal bunker is provided with slide gate at outlet. The coal is feed to coal conveyor through manual opening of this slide gate. The existing coal conveyor is provided with belt weigher to record the coal conveying rate and accordingly dolomite feed rate is controlled to maintain the desired coal and dolomite ratio. The general arrangement of controlled calcined dolomite feeding is shown in Figure 1 showing the basic Scheme of the system. The general arrangement drawing of the system according to present invention is shown in accompanying Figure 2. The details of the various features of the installed system are described below:

Installed System:
Storage Bin: 01 No : The storage bin has a capacity of 70m3, which has been designed to cater to calcined dolomite requirement of BF#1 & 5 subject to maximum injection rate of coal : dolomite in the ratio of 4:1. The details of storage bin are shown in Figure 1 & 2. The material of construction is MS as per IS 2062 with UHMWPE with 9 million g/mol(min) liner plate. The liner plates are 20mm thick and method of fixing is CSK screwed with plug. The plate angle of day bin is 65 degree having grizzly bar provided at the top. The grid opening size is 100mm x 100mm with single opening having motorized R&P gate. Provision for manual opening is also there. The grid of the storage bin has square openings with adequately designed flats and rods supported on steel beams. The grids shall be arranged in removable sections. Size of the outlet is 500mmx500mm. The storage bin has poking holes for clearing the jam at outlet if required.

Belt Weigher: 1 No : The belt weigher is automatic and electronic type which is installed in coal conveyor to give a feedback of coal quantity to controller which controls the discharge of calcined dolomite based on set ratio of coal : dolomite.

Belt Weigh Feeder: 1 No: The rated capacity of belt weigh feeder is 15TPH having continuous flow characteristics. It has a VFD drive for AC motor to vary the flow rate. It has two number of load cells with accuracy of +/-0.5%. The bottom opening is of 500x500mm. This weigh feeder has both remote and local control panel near to the weigh feeder. Remote panel has the provision through the controller to set the desired quantity as set point and the weigh feeder is able to maintain the same within an accuracy of +/-0.5%. The weigh feeder panel has the following displays: Feed rate indications in tons/hr, totalized display, Set point indicator, annunciations lamps and set point increase/decrease.

Motorized Rack & Pinion Gate : 1 No : The location of motorized R&P gate is below storage bin for opening and closing bin opening for maintenance purpose. It has been provided with hand wheel to operate it manually. The body is MS/ISMC-150, gland plate 20mm thick, pin type guides of EN-8 for free movement of the slide plate. The drive is supported on a pair of totally enclosed self-aligning flanged type ball bearing. The installation is horizontal with opening size of 500mm x 500mm.

Monorail Telpher with Grab Bucket: 1 No : Grab bucket is 4 rope clam shell type with bucket volume of 1.5m3. The material of construction is wearing edger TISCRAL type and other portion tested quality MS plate. The operation is through pendent with push button. The grab width in open position is 2-2.5m. The monorail telpher has lifting capacity of 150% more than the grab bucket capacity. The lifting height is 12m and hoisting speed is 6m/min, travel speed 10m/min with 12m as travel length. The operation is through pendent with push button.

Electrical Panels : The Electrical panel comprises of weigh feeder panel and local control posts. The panels are made of CRCA sheet with front bearing and load bearing bottom plate of 2mm thickness Degree of protection is IP-42. The following MCC is provided in the panel : Telpher LT drive motor, Telpher hoisting drive motor, R&P gate drive motor and weigh feeder motor-VFD drive. The Industrial controller takes the input from belt weigh scale for input of coal quantity on coal conveyor. Based on the set ratio of coal : dolomite, the weigh feeder sets the VFD drive for flow rate of calcined dolomite.

The operational features of the above stated system are as follows:

i. One set of electrically operated monorail telpher and grab bucket with appropriate capacity installed to transfer dumped flux material from ground to storage bin.
ii. One number of square section storage bin of adequate capacity to store one day requirement of flux material considering 10kg/THM injection rate is installed in the proposed system. A motorized rack & pinion gate is also installed at the bottom opening of the storage bin for isolation purpose during maintenance activity.
iii. One number of belt weigh feeder under the storage bin installed which extracts flux material from bin to feed to the existing coal conveyor. The extraction and feeding rate of flux material so decided as to achieve the desired flux to coal ratio. The flux to coal ratio may vary from 1:4 to 1:12 considering coal rate and existing coal conveyor capacity. The variation in flux to coal ratio is achieved by using VFD drive in belt weigh feeder.
iv. One number of belt weigher is installed in existing coal conveyor to know the coal flow rate so that the flux extraction and feed rate is decided to achieve desired flux to coal ratio.
v. One number of industrial controller installed in the existing PLC room to input the flux to coal ratio. Based on the input ratio and coal flow rate received from belt weigher, the controller send the signal to the VFD drive of belt weigh feeder for the amount of flux to be extracted and fed to the coal conveyor.
vi. The entire system is configured for storage and controlled feeding of the flux material onto existing coal conveyor for mixing grinding and injection into Blast Furnace to achieve the desired ratio within an accuracy of +/- 0.5%.

Industrial Applicability:
The operation of the invention has already been successfully experimentally tested in commercial/plant scale at CDPP-1 of BF-1 & 5 at Applicant’s production facility. The outcome of the innovation as tested is appreciable and can be implemented to similar other plants.

Usefulness of the Invention:
The system for calcined dolomite injection has been installed and commissioned in Applicants manufacturing facility which has shown satisfactory results. The addition of calcined dolomite is being done in auto mode in coal : dolomite ratio of 4:1 to 12:1. The Flow sheet of co-injection of Pulverized coal and MgO bearing flux is shown in accompanying Figure 3 which depicts the benefits of using low MgO in sinter making.

The major benefits in Sinter having less MgO are (i) Higher cold strength of sinter (ii)Higher Fe content in sinter,(iii) Improve size fraction of sinter,(iv) Permeability of BF burden will improve because of Less basic slag formed in bosh zone. In blast furnace performance, the Productivity of BF will increase because Permeability of the furnace will increase. Coke burning will be faster. Higher Fe in Sinter will lead to more production. CDI rate can be improved by better permeability of the Blast Furnaces

Claims:We Claim:

1. A system for controlled feeding of flux materials onto existing coal conveyor favouring mixing, grinding and injection into blast furnace comprising:

a flux storage bin to store flux material;

said flux storage bin cooperatively disposed with respect to coal conveyor and having atleast a belt weigh feeder installed thereunder to extract and feed flux material on to said coal conveyor;

means for monitoring the coal rate and coal conveyor capacity and coordinate controlled flux to coal feed ratio for desired mixing, grinding and injection of flux into the blast furnace to control slag formation and productivity.

2. The system as claimed in claim 1 comprising electrically operated monorail telpher and grab bucket of desired capacity to transfer dumped flux material from ground to said flux storage bin preferably of one day requirement storage capacity of 50 ton based on about 10Kg/THM injection rate;
said flux storage bin including a motorized rack & pinion gate installed at the bottom opening for isolation purpose during maintenance activity.

3. The system as claimed in anyone of claims 1 or 2 comprising of belt weigh feeder under the said flux storage bin installed to extract flux material from said flux storage bin to feed to the existing coal conveyor provided to achieve the desired flux to coal ratio from 1:4 to 1:12 considering coal rate and existing coal conveyor capacity involving VFD drive in belt weigh feeder.

4. The system as claimed in anyone of claims 1 to 3 comprising belt weigher installed in existing said coal conveyor to monitor the coal flow rate such that the flux extraction and feed rate is controlled based thereon to achieve desired flux to coal ratio.

5. The system as claimed in anyone of claims 1 to 4 comprising Industrial controller means to set flux to coal ratio such that based on thus set ratio and input coal flow rate received from belt weigher, the controller is adapted to generate signal to the VFD drive of belt weigh feeder for the amount of flux to be extracted and fed to the coal conveyor.

6. The system as claimed in anyone of claims 1 to 5 which is adapted such that said storage and controlled feeding of the flux material onto existing coal conveyor for mixing grinding and injection into Blast Furnace to achieve the desired ratio within an accuracy of +/- 0.5%.

7. The system as claimed in anyone of claims 1 to 6 comprising :

said flux storage bin includes grid opening preferably of 100mm x 100mm with single opening having motorized R&P gate preferably also including provision for manual opening, said grid of the flux storage bin hoppers preferably having square openings with adequately provided flats and rods supported on beams, said grids arranged in removable sections with size of the outlet preferably about 500mmx500mm and including poking holes for clearing the jam at outlet if required;

said belt weigher being automatic and electronic type installed in coal conveyor to give a feedback of coal quantity to controller which controls the discharge of calcined dolomite based on set ratio of coal : dolomite;

said belt weigh feeder having continuous flow characteristics including a VFD drive for AC motor to vary the flow rate and having load cells and bottom opening of 500x500mm, said weigh feeder having both remote and local control panel near to the weigh feeder, said remote panel having the provision through the controller to set the desired quantity as set point and the weigh feeder is adapted to maintain the same within an accuracy of +/-0.5%, said weigh feeder panel including the following displays: Feed rate indications in tons/hr, totalized display, Set point indicator, annunciations lamps and set point increase/decrease.

motorized R&P gate provided below said flux storage bin for opening and closing bin opening for maintenance purpose;

electrical control panel comprising of weigh feeder panel and local control posts adapted to include following MCC in the panel: Telpher LT drive motor, Telpher hoisting drive motor, R&P gate drive motor and weigh feeder motor-VFD drive, the weigh feeder controller receiving input from belt weigh scale for input of coal quantity on coal conveyor and based on the set ratio of coal : dolomite, the weigh feeder sets the VFD drive for flow rate of calcined dolomite.

8. The system as claimed in anyone of claims 1 to 7 in operative connection to blast furnace enabling incorporation of low levels in the range of 2.2% to 2.3% MgO content in sinter in blast furnace favouring (i) Higher cold strength of sinter (ii)Higher Fe content in sinter,(iii) Improve size fraction of sinter,(iv) Permeability of BF burden will improve because of Less basic slag formed in bosh zone.

9. A method for enhancing CDI rate and productivity and quality of hot metal produced in blast furnace involving step of controlled feeding of flux material onto existing coal conveyor for mixing, grinding and injection into blast furnace involving the system as claimed in anyone of claims 1 to 8.

10. The method as claimed in claim 9 wherein the sinter used is provided with low MgO content in the range of 2.2% to 2.3%, said low MgO sinter used in the process favouring (i) Higher cold strength of sinter (ii)Higher Fe content in sinter,(iii) Improve size fraction of sinter,(iv) Permeability of BF burden will improve because of Less basic slag formed in bosh zone.