Title of Invention

METHOD AND EQUIPMENT FOR DEFINING THE HEIGHT OF SMELTING BATH FOR FOLLOWING CHARGES OF IRON IN AN ELECTRICAL ARC FURANCE

Abstract A method and an apparatus for determining for determining the melting bath height (5a) of successive pig iron charges in an electric-arc furnace (1) when producing steel from pig iron, whereby the lower furnace (1a), provided with a brick lining (3), receives varying volumes of pig iron (2), and the furnace is operated by way of an oxygen top blowing lance (4) establishes the distance (6) between the lance head and the melting bath height (5a) depending on the process, thereby that the melting bath level (5) of the respective charge is established by tilting the electric-arc furnace (1) and after re-tilting into the operational position (21a) by optical measurement, or at least by estimating, the tilting angle (α)and that, resulting therefrom, the melting bath height, (5a) is determined and thereafter the distance (6) of the oxygen top blowing lance (4) to the melting bath level (5) is adjusted.
Full Text FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION (See Section 10, rule 13)
METHOD AND EQUIPMENT FOR DEFINING THE HEIGHT OF SMELTING BATH FOR FOLLOWING CHARGES OF IRON IN AN ELECTRICAL ARC FURANCE
ISPAT INDUSTRIES LTD. of GEETAPURAM, DOLVI - 402 107 TALUKA PEN, DISTRICT RAIGAD, MAHARASHTRA, India INDIAN Company
The following specification particularly describes the nature of the invention and the manner in which it is to be performed : -

Method and apparatus for determining the melting bath height of successive pig iron charges in an electric-arc furnace.
The invention relates to a method and an apparatus for determining the melting bath height of successive pig iron charges in an electric-arc furnace when producing steel from pig iron, whereby the lower furnace, provided with a brick lining, receives volumes of pig iron being varying from charge to charge depending on the process and/or wear, and the furnace is operated by way of an electrode-system, and in other time intervals at least with an oxygen top blowing lance and the pig iron quantities to be fed in charges are respectively measured.
As is known furnace vessels with brick linings are subject to wear, so that in the course of several hundred melts the volume of the shell of the lower furnace increases and the melting bath level is lowered. On the other hand the charge volume cannot be increased as desired because the changed volume cannot be determined exactly. The brick lining wear therewith has an influence on the adjustment of the distance of the oxygen top blowing lance. In general the bath level height is therefore measured.
A method for measuring the height of the bath level of a metal bath situated below a slag layer in a container is known (DE 38 22 705 C2). In this case the container consists of a converter. The method and the arrangement operate by way of a measuring probe, which has a thermal element below a protective cap.
The measuring probe is dipped in so as to come to below this slag layer and to measure the oxygen partial pressure there. The measured result therewith is intended therefore not for the distance of the oxygen top blowing lance to the melting bath level.
A method for determining the height of the melting bath level of an electric-arc furnace is furthermore known from the DE 198 36 844 Al. Here the height of the
2

melting bath level is determined by means of a numerical combination of length dimensions, which arc measured partially indirectly and partially directly outside of the high temperature region of the electric-arc furnace. In doing so the procedure is such that the height of the melting bath level is determined from the difference of the position value of the electrode-carrier arm located in the operating position and the length of the graphite electrode as well as the corrected length of its electric-arc furnace. The latter value can, however, only be estimated.
The invention has as object to proceed not from the electrode carrier arm of the electric-arc furnace but from the distance, depending on the process, between the lance head of the oxygen top blowing lance and the melting bath level so as to adjust the required distance between the exit of the oxygen beam and the melt or slag ahead of the refining process.
The stated object is solved in accordance with the invention thereby that the melting bath level of the respective charge is established by tilting the electric- arc furnace and after re-tilting into the operational position by optical measurement, or at least by estimating, the tilting angle and that, resulting therefrom, the melting bath height is determined and thereafter the distance of the oxygen top blowing lance to the melting bath level is adjusted. The advantage is a sufficiently exact distance measurement in dependence on the height of the melting bath level, resulting indeed by wear of the brick lining, to which a process dependent position of the oxygen top blowing lance exists, and consequently a more favourable refining process can take place. Basically the required distance can be calculated from the tilting angle and eventually further known dimensions of the electric-arc furnace.
An embodiment of the invention envisages that the brick lining thickness, remaining after several charges, is additionally measured by measuring the outer temperature at the furnace floor shell and is taken into consideration. Therewith there is provided a possibility of controlling the value initially found.
3

A further development of the invention is given thereby that the tilting angle is determined by aiming towards a marker provided at the newly lined lower- furnace. No great material expense is necessary for this manner of operation.
Further characteristics provide that a defined brick course of the brick lining emerging from the hot melt after tilting is selected as marker.
Such a marker can be observed by means of a thermal camera.
The simplest method for determining the tilting angle consists therein that the tilting angle is estimated by naked eye through an open slag door.
An apparatus for determining the melting bath level of successive pig iron charges proceeds from an electric-arc furnace during production of steel from pig iron as state of the art, whereby the lower-furnace, provided with a brick lining, receives volumes in pig iron varying from charge to charge depending on the process and/or depending on wear, and the furnace with an electrode system and is provided in other time intervals at least with a liftable or lowerable oxygen top blowing lance and a lifting guide and the oxygen top blowing lance is adjusted relative to a process dependent distance from the melting bath level.
This apparatus is designed such that at the tiltable electric-arc furnace during open slag door an optical joining line is formed between an optical member and a marker opposite to the open slag door about in a straight line. Thereby the advantages stated regarding the process are also achieved.
Furthermore it is provided that the marker consists of a predetermined, defined brick course of the brick lining.
Furthermore the optical member consists of a thermal camera (of a so-called thermic eye).
4

A further development provides that metallic measuring rods are inserted between the brick courses, which rods are joined by way of an earth connection to the furnace floor shell. Each individual measuring rod forms a measuring point for the optical joining line.
A further development consists therein that the measuring rods are joined to an electrical current guiding measuring device for producing a measuring signal.
An automated measurement with connection to the motor for adjustment of the distance of the oxygen top blowing lance relative to the melting bath level is created thereby that a measuring circuit, consisting of the thermal camera and the video camera, is created, with several measuring rods, and a temperature evaluation arrangement for several measuring positions at the furnace floor shell of the lower-furnace being formed,
Finally the thermal camera can consist of an infra-red camera.
In the drawing examples of embodiments of the invention are represented, by means of which the applied method is described and is explained hereafter in more detail.
It is shown in:
Figure 1 a cross-section of an electric-arc furnace in operational position,
substantially the lower-furnace, with an indicated tilting position of about 10°,
Figure 2A a partial section through the brick lining in the lower-furnace,
Figure 2B the view associated with Figure 2A,
Figure 3 A a view towards the brick lining with tilted furnace,
Figure 3B a partial section with the thermal profile associated with Figure 3A
and,
Figure 4 a diagram for the temperature development in the furnace floor shell
in dependence on the wear caused by the number of melts.
5

In an electric-arc furnace 1 (Figure 1) with a brick lined lower-furnace la, a device for determining the melting bath height 5a with a melting bath level 5 when producing steel from pig iron 2 is provided, whereby the lower-furnace la provided with a brick lining 3 receives from charge to charge in process and/or wear dependence varying volumes of pig iron 2 (different pig iron quantities 2a) and the electric-arc furnace 1 with an electrode system (not shown) and in other time intervals at least a liftable and lowerable oxygen top blowing lance 4 and a (not shown) lifting guide and the oxygen top blowing lance 4 at a distance 6 to the melting bath level 5 depending on the process.
For determining the tilting angle a, in which the melting bath level 5 (if slags are included, result the melting bath height 5a) at the brick lining 3 changes its position, then thereby the brick lining 3 is heated, so that different forms of markers occur. Thus, for example, the heated brick can show another glowing colour than the brick not touched by the slag or the melt. Thus at the tillable electric-arc furnace 1 with open slag door 12 at times an optical joining line 13 is found between an optical member 10 and a marker 8 located relative to the open slag door 12 about in straight line. The brick lining 3 consists of a wear lining 3a and a permanent lining 3b. The marker 8 can consist of a predetermined defined brick course 9 of the brick lining 3. The optical member 10 is, for example, formed by a thermal camera 10a, a video camera 10b or of an infra-red camera 10c.
As drawn, for an automated adjustment of the distance 6 to the oxygen top blowing lance 4 between the brick courses 9 of a brick lining 3 being opposite to the slag door 12, metallic measuring rods 14 are inserted between the brick courses 9, which rods form a connection by way of an earth connection 15 to the furnace floor shell lb.
The measuring rods 14 are joined to an electrical, current conducting measuring device 16, which produces measuring signals 17, which, on calculation, operate a motor to adapt the lifting adjustment to the distance 6 of the oxygen top blowing lance 4.
6

Furthermore a measuring circuit 18 with current source 18a is formed, consisting of the thermal camera 10a, video camera 10b, several measuring rods 14, a temperature evaluation arrangement 19 for several measuring positions 20 at the furnace floor shell lb of the lower-furnace la. When reducing the brick lining thickness 7 at the measuring positions 20, different temperatures T occur (compare Figure 4) whereby, for example, a thickness 7 of the brick lining 3 is reduced by 1200 mm. The temperature T correspondingly increases from To to Ti and for this provides comparative values for optically measured tilting angle a and therewith the calculation of the melting bath height 5a.
The method for determining the melting bath height 5a is explained in more detail with reference to the Figures 2A, 2B, 3A and 3B:
The melting bath level 5 of the respective charge is tilted by tilting the electric- arc furnace 1 when in the tilting position 21 back into the operational position 21a shown in Figure 1, whereby the melting bath level 5a exposes markers 8. Thereby an optical measurement for at least an estimate of the tilting angle a takes place from which the melting bath height 5a can be calculated and from this there results the adjustment of the distance 6 of the oxygen top blowing lance 4 relative to the melting bath level 5.
With progressive numbers of melts the values found (compare Figure 4) can be controlled by way of the remaining brick lining thickness 7 by measurement of the external temperature T at the measuring positions 20 at the furnace floor shell lb and can be taken into consideration.
The tilting angle a is determined by aiming towards a selected marker 8 at the newly lined lower furnace la. According to the Figures 2A, 2B, 3A and 3B such markers 8 are brick courses 9 of the brick lining 3 emerging from the melt, whilst still hot, or the mentioned metallic measuring rods 14.
7

The simplist method to determine the tilting angle consists in aiming towards the marker 8 by way of the naked eye 11 along the optical joining line 13.
In Figure 2A the brick courses 9 are indicated by 1 - n. According to Figure 2B the slag surface 22 is located between the first and second brick course 9 and the melting surface 23 between the second and third brick course 9 in the operational position 21 of the electro-arc furnace 1.
In the Figures 3A and 3B the tilting position 21 (lower furnace la drawn in Figure 1 in dotted lines) is assumed. Thereby the slag surface 22 can be located between the first and second bricks of the brick courses 9 and the melting surface 23 between the third and fourth bricks of the brick courses 9. The temperature development to be adjusted is shown by way of the thermal- profile 24.
8

Reference List
1 electric-arc furnace
la lower-furnace
lb furnace floor shell
2 pig iron
2a pig iron quantity
3 brick lining
3a wear lining
3b permanent lining
4 oxygen top blowing lance
5 melting bath level
5a melting bath height
a tilting angle
6 distance
7 brick lining thickness
T outer temperature
8 marker
9 brick course
10 optical member
10a thermal camera
10b video camera
10c infra-red camera
11 naked eye
12 open slag door
13 optical joining line
14 metallic measuring rod
15 earth connection
16 measuring device
17 measuring signal
18 measuring circuit
18a current source

We Claim:
1. Method for determining the melting bath height (5a) of successive pig iron charges in an electric-arc furnace (1) when producing steel from pig iron (2), whereby the lower furnace (la), provided with a brick lining (3), receives volumes of pig iron (2) varying from charge to charge depending on the process and/or wear, and the furnace (1) is operated by way of an electrode-system, and in other time intervals at least with an oxygen top blowing lance (4) and the pig iron quantities (2a) to be fed in charges are respectively measured, characterized in that the melting bath level (5) of the respective charge is established by tilting the electric-arc furnace (1) and after re-tilting into the operational position (21a) by optical measurement, or at least by estimating, the tilting angle (a) and that, resulting therefrom, the melting bath height (5a) is determined and thereafter the distance (6) of the oxygen top blowing lance (4) to the melting bath level (5) is adjusted.
2. Method according to claim 1, wherein the brick lining thickness (7) remaining after several charges is measured additionally by measuring the outer temperature (T) at the furnace floor surface (lb) and is taken into consideration.
3. Method according to claim 1, wherein the tilting angle (a) is determined by aiming towards a marker (8) present at a newly lined lower-furnace (la).
4. Method according to claim 3, wherein as marker (8) a brick course (9), which is still hot and emerges from the melt, of the brick lining (3) is selected.
5. Method according to one of the claims 3 or 4, wherein that the marker (8) is observed by a thermal camera (10a).

6. Method according to one of the claims 1 to 4, wherein the tilting angle (a) is estimated by way of a naked eye (11) through an open slag door (12).
7. Apparatus for determining the melting bath height (5a) of successive pig iron charges in an electric-arc furnace (1) when producing steel from pig iron (2), whereby the lower furnace (la), provided with a brick lining (3), receives volumes of pig iron (2) varying from charge to charge depending on the process and/or wear, and the electric-arc furnace (1) is operated by way of an electrode-system, and in other time intervals at least with a liftable and lowerable oxygen top blowing lance (4) and a lifting guide and the oxygen top blowing lance (4) is adjustable to a distance (6) depending on the process relative to the melting bath level (5), characterized in that at the tiltable electric-arc furnace (1) during open slag door (12) an optical joining line (13) is formed between an optical member (10) and a marker (8) opposite to the open slag door (12) about in straight line.
8. Apparatus according to claim 7, wherein the marker (8) consists of a predetermined, defined brick course (9) of the brick lining (3).
9. Apparatus according to claim 7, wherein the optical member (10) consists of a thermal camera (10a).
10. Apparatus according to one of the claims 7 to 9, wherein metallic measuring rods (14) are inserted between the brick course (9), which rods are joined by way of an earth connection (15) to the furnace floor shell (lb).
11. Apparatus according to claim 10, wherein the measuring rods (14) are connected to an electrical current conducting measuring device (16) for producing a measuring signal (16).

12. Apparatus according to one of the claims 7 to 11, wherein it includes a measuring circuit (18) consisting of the thermal camera (10a) or a video camera (10b), several measuring rods (14), a temperature evaluation arrangement (19) for several measuring positions (20) at the furnace floor shell (lb) of the lower-furnace (la).
13. Apparatus according to one of the claims 9 or 12, wherein the thermal camera (10a) consists of an infra-red camera (10c).
Dated this 28th day of October, 2004.

HIRAL CHANDJ&AKANT JOSHI AptfNTFOR ISPAT INDUSTRIES LTD.

Documents:

1163-mum-2004-abstract.doc

1163-mum-2004-abstract.pdf

1163-mum-2004-claims.doc

1163-mum-2004-claims.pdf

1163-mum-2004-correspondence(ipo).pdf

1163-mum-2004-correspondence.pdf

1163-mum-2004-description(cancelled).pdf

1163-mum-2004-description(granted).pdf

1163-mum-2004-description[granted].doc

1163-mum-2004-drawing(cancelled).pdf

1163-mum-2004-drawing.pdf

1163-mum-2004-form 1(cancelled).pdf

1163-mum-2004-form 1.pdf

1163-mum-2004-form 19.pdf

1163-mum-2004-form 2(granted).pdf

1163-mum-2004-form 2(title page).pdf

1163-mum-2004-form 2[granted].doc

1163-mum-2004-form 3.pdf

1163-mum-2004-form 5.pdf

1163-mum-2004-power of attorney.pdf

abstract1.jpg


Patent Number 213002
Indian Patent Application Number 1163/MUM/2004
PG Journal Number 13/2008
Publication Date 28-Mar-2008
Grant Date 19-Dec-2007
Date of Filing 28-Oct-2004
Name of Patentee ISPAT INDUSTRIES LTD.
Applicant Address GEETAPURAM, DOLVI - 402107 TALUKA PEN, DISTRICT RAIGAD
Inventors:
# Inventor's Name Inventor's Address
1 DR. ING.FRITZ-PETER PLESCHIUTSCHNIGG REISERWEG 69, D-47269 DUISBURG
PCT International Classification Number C21C 5/46
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 103 52 628.5-24 2003-11-11 Germany