Claims:We Claim:

1. An iron ore lump screening system for efficient screening out of the iron ore lump under size fraction (-10 mm) for desired generation of lump ore size 10-40 mm suitable for feeding into blast furnace for iron making comprising:

differential single deck screening arrangement based vibratory screen including selectively provided plurality of screen panels having varied aperture sizes providing for adjustable differential mesh -openings for desired single deck screen based iron ore lump screening such that fractions of -10mm particles are effectively screened out during traversal on said single deck screen free of jamming and pegging problems.

2. The iron ore lump screening system as claimed in claim 1 wherein said differential single deck screening arrangement based vibratory screen of selectively provided screen panels having varied apertures include :
Effective screening area in the range of 6020 mm x 2400 mm and total length is7320 mm and total width is 2950 mm and wherein
a first part screen panel with aperture size 14 mm x 14 mmwith screening area preferably about 1204 mm x 2400 mm ;
a second and third part screen panel with aperture size of 12 mm x 12 mmwith screening area preferably about 2408 mm x 2400 mm ;
a fourth part screen panel with aperture of 10 mmx 10 mm with screening area preferably about 1204 mm x 2400 mm ; and
a fifth part screen panel with aperture size 8 mm x 8 mmwith screening area preferably 1204 mm x 2400 mm.

3. The iron ore lump screening system as claimed in anyone of claims 1 or 2 wherein said differential single deck screening arrangement based vibratory screen comprises of

screening Area: 6020 mm x 2950 mm.
having total length of 6020 mm divided into five equal parts of length 1204 mm each, wherein the width of the each individual screen panel is fixed at 300 mm with

the first part of 1204 mm as a polyurethane screen panel with aperture size 14mm x 14mm ;
the second and third part covering 2408 mm as a polyurethane screen panel with aperture size 12 mm x 12 mm ;
the fourth part of 1204 mm as a polyurethane screen panel with aperture size 10 mm x 10 mm ; and
the fifth part of 1204 mm as a polyurethane screen with aperture size 8 mm x 8 mm.

4. The iron ore lump screening system as claimed in anyone of claims 1 to 3 which is comparatively more efficient with respect to double deck screening system irrespective of the desired actual feed loading on the screen relative to the rated feed capacity which is preferably maintained as not to exceed 80 % of the rated tonnage or below 80 % of rated tonnage.

5. The iron ore lump screening system as claimed in anyone of claims 1 to 4 which is adapted with following screening parameters:

6. The iron ore lump screening system as claimed in anyone of claims 1 to 5 wherein said differential screening aperture provides for high wear which provides for percolation of very fine particles (< 2mm) in the feed end during stratification and also achieves a higher degree of screening whereby the average value of -10 mm in the output lump ore gets decreased from double deck screening arrangement of 29% to 16% and increases screening rate from 500 tph to 700 tph.

Dated the 25th day of March, 2021
Anjan Sen
Of Anjan Sen & Associates
(Applicants’ Agent)
IN/PA-199

, Description: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 :
A SYSTEM FOR SCREENING IRON ORE LUMP INVOLVING DIFFERENTIAL SINGLE DECK SCREENING ARRANGEMENT BASED VIBRATORY SCREEN.



2 APPLICANT (S)

Name : STEEL AUTHORITY OF INDIA LIMITED.

Nationality : Indian.

Address : Research & Development Centre for Iron & Steel,
Doranda, Ranchi, Jharkhand, India. PIN-834002.






3 PREAMBLE TO THE DESCRIPTION

COMPLETE

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

FILED OF THE INVENTION
The present invention relates to a system for screening iron ore lump through conversion of Double Deck to Single Deck screen. More particularly, the present invention is directed to a system for screening iron ore lump involving differential single deck screening arrangement based vibratory screen to ensure efficient screening of lump in preferred size range for feeding in blast furnace, substantially reducing -10 mm particles in the output lump ore.

BACKGROUND OF THE INVENTION
The existing Screen in the Lump Ore yard at Raw Material Handling Plant (RMHP), Bokaro Steel Plant (BSL) was screening out the under size fraction (-10 mm). This is a double deck screening system. The screening system had been facing a lot of problems, specially the excessive jamming in the bottom deck. This situation becomes severe in the rainy season. The gap of the bottom deck is only 1.5 ft as shown in Figure-1. So, cleaning of the screen is very difficult. As a result the total screening efficiency was deteriorated day to day. In order to improve the screening efficiency, it was planned to convert the double deck screening system to single deck system by installing a differential aperture screen panels.

OBJECTS OF THE INVENTION
The basic object of the present invention is directed to a system for screening iron ore lump involving single deck with differential aperture screening arrangement to improve its screening efficiency.

A further object of the present invention is directed to said system for screening iron ore lump involving single deck with differential aperture screening based vibratory screen employed to screen out the -10mm iron ore particle present in lump ore.

A still further object of the present invention is directed to said system for screening iron ore lump involving single deck with differential aperture screening directed to conversion of double deck screening system to a single deck differential screening system capable to improve the screening efficiency of existing screening system.

Another object of the present invention is directed to said system for screening iron ore lump involving single deck with differential aperture arrangement wherein average value of -10 mm in the output lump ore gets decreased from the present level of 29% to 16.2%.

Yet another object of the present invention is directed to said system for screening iron ore lump involving single deck with differential aperture arrangement capable to avoid the jamming and pegging problems in the screen as experienced in existing double deck system.

A still further object of the present invention is directed to said system for screening iron ore lump involving single deck with differential aperture wherein the cleaning & maintenance of the screen is easier as compared to the previous system.

SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to an iron ore lump screening system for efficient screening out of the iron ore lump under size fraction (-10 mm) for desired generation of lump ore size 10-40 mm suitable for feeding into blast furnace for iron making comprising:

differential single deck screening arrangement based vibratory screen including selectively provided plurality of screen panels having varied aperture sizes providing for adjustable differential mesh -openings for desired single deck screen based iron ore lump screening such that fractions of -10mm particles are effectively screened out during traversal on said single deck screen free of jamming and pegging problems.
A further aspect of the present invention is directed to said iron ore lump screening system wherein said differential single deck screening arrangement based vibratory screen of selectively provided screen panels having varied apertures include:
effective screening area in the range of 6020 mm x 2400 mm and total length is 7320 mm and total width is 2950 mm and wherein
a first part screen panel with aperture size 14 mm x 14 mm with screening area preferably about 1204 mm x 2400 mm ;
a second and third part screen panel with aperture size of 12 mm x 12 mm with screening area preferably about 2408 mm x 2400 mm ;
a fourth part screen panel with aperture of 10 mmx 10 mm with screening area preferably about 1204 mm x 2400 mm; and
a fifth part screen panel with aperture size 8 mm x 8 mm with screening area preferably 1204 mm x 2400 mm .

A still further aspect of the present invention is directed to said iron ore lump screening system wherein said differential single deck screening arrangement based vibratory screen comprises of

screening Area: 6020 mm x 2950 mm,
having total length of 6020 mm divided into five equal parts of length 1204 mm each, wherein the width of the each individual screen panel is fixed at 300 mm with
the first part of 1204 mm as a polyurethane screen panel with aperture size 14mm x 14mm;
the second and third part covering 2408 mm as a polyurethane screen panel with aperture size 12 mm x 12 mm;
the fourth part of 1204 mm as a polyurethane screen panel with aperture size 10 mm x 10 mm; and
the fifth part of 1204 mm as a polyurethane screen with aperture size 8 mm x 8 mm.

A still further aspect of the present invention is directed to said iron ore lump screening system which is comparatively more efficient with respect to double deck screening system irrespective of the desired actual feed loading on the screen relative to the rated feed capacity which is preferably maintained as not to exceed 80 % of the rated tonnage or below 80 % of rated tonnage.

A still further aspect of the present invention is directed to said iron ore lump screening system which is adapted with following screening parameters:

A still further aspect of the present invention is directed to said iron ore lump screening system wherein said differential screening aperture provides for high wear which provides for percolation of very fine particles (< 2mm) in the feed end during stratification and also achieves a higher degree of screening whereby the average value of -10 mm in the output lump ore gets decreased from double deck screening arrangement of 29% to 16% and increases screening rate from 500 tph to 700 tph.

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

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: Front view of the existing double deck screen.
Figure 2: Schematic representation of the innovative differential single deck screening system according to present invention.
Figure 3: Pictorial view of the innovative differential single deck screening system according to present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The present invention relates to single deck with differential aperture screening system to improve its screening efficiency. More particularly, the present invention is directed to conversion of double deck screening system to a single deck differential screening system. Actually this system is employed to screen out the -10mm iron ore particle present in lump ore. Advantageously, the process of the present invention is capable to improve the existing screening system.

Accompanying Figure 1 shows the Front view of the existing double deck screen. This system cannot effectively screen out and reduce the -10mm size fraction in lump ore output. Moreover, it suffers from jamming problem and difficulty in maintenance and cleaning.

In actual practice, lump ore size ranges between 10-40 mm and it is directly fed into blast furnace for iron making. Ore of size less than 10 mm is being utilized in sintering process. Iron ore after mining and beneficiation is dispatched to plant. Thereafter, the Raw Materials Handling Unit processes the iron ores. It is stacked and reclaimed here. Then it is screened to separate out the -10 mm fraction from the input. The scope of this work is limited to conversion of double deck screening system to a single deck screening system. This innovative work focused in single deck differential screening of iron ore. The basic objective of the present invention is directed to providing a system and process for enhancement of screening operation; so that maximum fraction of -10 mm particles get recovered from the input ore and thereby, quality of blast furnace feed becomes superior which in turn results in lower coke rate during iron making process.

Screening efficiency of a vibratory screen depends on several factors and parameters as summarized in Table 1.

Table 1: Screening Parameters of the existing screen

Table 1 shows the screening parameters of the existing screen. In this investigation only the double screen deck is modified to single deck replacing existing double deck screen by keeping other parameters unchanged. The innovative differential single deck screening system is shown in Figure 2.

By the optimization of the above factors and parameters a vibratory screen could be made more efficient. The ideality of the screen should be able to transmit all of the undersize material in the feed. In practice, however, not all of the undersize material passes through the screen and the fraction of the feed undersize that does pass through. The efficiency is determined primarily by the actual feed loading on the screen relative to the rated feed capacity. The efficiency of transmission decreases if the screen handles with feed in excess of 80% of the rated tonnage because the access of individual particles to the screen surface is hindered to a greater or lesser degree. The efficiency also decreases as the actual feed tonnage falls below 80% of rated capacity because particles tend to bounce on the lightly loaded screen and make fewer contacts with the screen surface. In the present investigation, only one parameter i.e. differential aperture PU panel has been focused and it has planned in such a manner to make the screen comparatively more efficient.

Accompanying Figure 2 shows the schematic representation of the innovative differential single deck screening system.

The modified screening system is highlighted as follows:
• Screening Area: 6020 mm x 2950 mm.
• As described in the figure, the total length i.e. 6020 mm is divided into five equal parts of length 1204 mm each.
• The width of the each individual screen panel is fixed i.e. 300 mm.
• In the first part (i.e. 1204 mm) polyurethane screen panel with aperture size 14mm x 14mm has been installed.
• In the second and third part (i.e. 2408 mm) polyurethane screen panel with aperture size 12 mm x 12 mm has been installed.
• In the fourth part (i.e. 1204 mm) polyurethane screen panel with aperture size 10 mm x 10 mm has been installed.
• In the fifth part (i.e. 1204 mm) polyurethane screen with aperture size 8 mm x 8 mm has been installed.

Usefulness of the Invention:
• An interesting result is obtained after the installation of the Differential Single Deck PU Panel. The average value of -10 mm in the output lump ore gets decreased from the present level of 29% to 16.2%. This may be due to comparatively higher degree of screening in the differential screening aperture system.
• The differential screening aperture addresses a high wear areas and it optimizes the given screening task as expected. The differential single deck screening system very fine particles (< 2 mm) gets easily percolated in the feed end during stratification.

Industrial Applicability:
The system and process of the present invention is capable to decrease the -10 mm particles in the lump ore. This system has the potential to increase screening rate from 500 tph to 700 tph of the lump ore screen as observed in various experimental trials done under the advancement. This is applicable in any industrial high capacity lump iron ore screen. Hence, this invention is suitable for wide industrial application with significant process improvement.