DE10344198B4 - Method and plant for increasing steelmaking productivity - Google Patents

Abstract

Process for increasing productivity in steelmaking, using two-vessel technology, in which pig iron (1), sponge iron (2) and scrap according to the electric arc furnace and / or oxygen inflation method in proportions of 100% RE to 100 % DRI are processed with a scrap portion as a coolant, when inserting two electric arc furnaces (6) with an electrode system (5) and blowing lances, characterized in that oxygen via a top lance (10) in an amount between 150- 400 Nm ³ / min in a 200 t vessel (3) is fed and that in addition by in the bottom of the furnace (6a) evenly distributed purging (8) depending on the process phase, but without interruption, inert gas (9) with circulating pressure increases in successive Spülsteinen (8) from below with 50-100 N Itr./min is introduced.

Description

The The invention relates to a method of increasing productivity in steelmaking using two-vessel technology, in which pig iron, sponge iron and scrap according to the electric arc furnace and / or oxygen inflation method in proportions from 100% RE to 100% DRI with a scrap content as coolant are processed.

Increased productivity has generally been achieved through the use of two-vessel and thin-strand technology ( DE 196 23 671 A1 ; DE 196 21 143 A1 ). However, this increase is only possible by a certain increase in investment costs. An improvement of the metallurgical process in the areas of charging, melting and refining is not possible. Thus, the conventional steelmaking process limits its own advancement of its productivity.

Out DE-Z, "Metallurgical Plant and Technology International, Vol. 24, No. 4, 2001, pages 72-87 the method mentioned above known. In doing so, too Pig iron and iron sponge and scrap after the electric arc furnace and oxygen inflation process processed. Cast iron and sponge iron be in selected proportions used. However, it does not describe which specific measures are to be taken to the starting point for a more flexible steel production in terms of Delivery times, different steel grades and qualities to create.

Of the Invention is based on the object of intensifying the refining process, thereby increasing the steel quantities and lowering the tapping times.

The stated object is achieved in that oxygen is supplied via a top lance in an amount between 150-400 Nm ³ / min in a 200 t vessel and that in addition by evenly distributed in the bottom of the furnace bottom purging depending on the process phase, but without interruption, introducing inert gas with circulating pressure increases in successive purging pits from below at 50-100 N Itr./min. This saves considerable time in both melting and blowing, and the amount of steel output per unit of time becomes considerable. elevated. At the same time, the manufacturing process becomes more flexible with respect to mass steels and high-grade steels, so that shorter delivery times can be achieved for different steel grades. The oxygen inflation is started at a bath depth of 1000 mm pig iron. This initiates a particularly intensive bath movement.

The Efficiency of the process can be increased by the Sponge iron (direct and dry reduced iron / DRI) hot with temperatures greater than 600 ° C charged becomes. As a result, the melting time on the same bubble time Voted.

A Improvement that also affects the process in terms of time savings, is that the blowing angle at the outlet of the top lance at 10 ° -40 ° to the vertical is set.

Further support of the bath movement forces results from the fact that 6000 Nm ³ / h of oxygen are blown in through door lances. The bath movement is supported, for example, by wall lances with 50-100 Nm ³ / min oxygen in the sense of a rotation of the molten bath below the focal spot.

A other measure, To start the bath movement is that at startup blowing on the pig iron with oxygen charging with sponge iron is started.

A Plant to the raised Production of steel products is based on two electric arc furnaces, optionally operated according to the oxygen inflation method of a steelworks converter be, with an electrode system and blow lances.

These System triggers the task posed by the fact that in the bottom of the lower furnace each Electric arc furnace evenly distributed Flushing stones installed and that the top lance consists of two individual lances. Thereby finds an intensified stirring of the Melting, a correspondingly faster reaction takes place through the effects of the individual lances over distributed a larger bath surface becomes.

In This plant can produce from 2.5 to 3.0 mill. Jato hot strip can be achieved, which can adapt to any market situation, both geographically regarding the Raw material and energy resources as well as market related the steel grades with C-steels, IF, ULC, Low, Medium, High-C steels, multiphase (dual and Trip-) steel grades, Si steels with 1-3% Si and stainless steels how austenite and ferrite can be made.

This distribution is made such that each 4-20 purging stones are evenly distributed. This can cause a rotation of the molten bath be prepared with simultaneous flushing, whereby the flushing becomes more efficient.

In order to is another regulatory option given, the amount of oxygen locally, temporally and in the pressure course supply.

It is advantageous that 150 to 400 Nm ³ / min can be inserted through each single lance. Thereby, the oxygen can be promoted at operationally manageable pressures that correspond to the metallurgical effects.

Older steel production vessels can be upgraded, by at least one per vessel Electrode system, a top lance, a door lance and a wall lance are provided.

The high levels of oxygen can further supplied in such a way be that wall lance in a wall module of the top furnace is arranged and consists of an oxygen ultrasonic blowgun. The wall module is inserted between the cooling walls of the upper furnace.

For an intensification the metallurgical process with higher heat fluxes is further advantageous that the lining in the lower furnace outside by means of internally cooled copper boxes (staves) is bordered and that lying on the upper edge of the furnace copper boxes a coherent cooling and support ring form.

A Design then still is that the lining in the lower furnace is delivered in the manner of a converter lining. This creates a higher one Resilience of the lining.

In the drawing are embodiments of Invention, based on which also the method and individual Procedural steps are explained below.

It demonstrate:

1 the sectional view of a two-vessel plant with shared lances and electrode system,

2 an enlarged view of a single oven and

3 a plan view of the lower furnace with the upper furnace removed.

The process of increasing steelmaking productivity by shortening the delivery times for steel products, increasing the number of steel grades, and controlling the quality of bulk or high-grade steels is accomplished using two-vessel and continuous casting thin-strand Technologies and based on pig iron 1 , Sponge iron 2 and scrap, and is performed based on the electric arc furnace and / or oxygen inflation method. After casting off the steel on a thin-strand continuous casting plant, a rolled strip can be produced from the casting heat in an immediately connected rolling train.

The pig iron 1 is obtained from a blast furnace or other pig iron producing plant and the sponge iron 2 from a downstream direct reduction plant.

The melting takes place in two juxtaposed steel production vessels 3 with several blow lances 4 and at least one electrode system 5 , In principle, two independent steel production vessels could also be used 3 but less economical if the same equipment were duplicated. To the two steel production vessels 3 is a vacuum system with two boilers downstream. In addition, two ladle furnaces with two treatment stands each for secondary metallurgy follow. The steel produced is poured, for example, in two parallel thin-strand continuous casting plants and rolled in an immediately connected finishing train with at least six rolling stands from the casting heat (with appropriate temperature equalization). This produces steel products, such as hot strip or long goods.

The steel production vessels 3 are in 1 represented and consist of electric arc furnaces 6 , each one a sub-furnace 6a and an upper oven 6b (from ge cooled walls) have. In the lower furnace 6a are in the lining 7 distributed over the circumference each 4-20 purging stones 8th for the supply of inert gas 9 intended.

The top of the upper furnace 6b introduced top lance 10 is made of two single lances 10a and 10b formed, which can be acted upon individually or collectively. In addition to the top lance 10 is per single vessel 3a one electrode system each 5 , a single lance 10a . 10b , a door lance 10c , a wall lance 10d in a wall module 11 arranged and consists of an oxygen-ultrasonic lance 12 ,

The lances 4 and the electrode system 5 are on a lifting and bogie 13 fastened by a lifting movement 14 both the single lances 10a . 10b (Top-lance 10 ) and the electrode system 5 lifted and by one rotary motion 15 over the other electric arc furnace 6 pivoted and by a lifting movement 14 can be lowered again in operating position. The lifting movement 14 can also be independent for the top lance 10 respectively.

According to 2 is the lining 7 in the lower furnace 6a outside by means of internally cooled copper boxes 16 (so-called staves) additionally cooled. At the top 17 of the furnace 6a form the same or similar copper boxes 16 a cooling and support ring 18 for cooling and supporting the lining 7 ,

The lining 7 is in the style of a converter lining 19 (with sloping or vertical stones) delivered.

The following describes the parameters for the procedure used: Charging is done by inserting two electric arc furnaces 6 with an electrode system 5 , which are operated after the oxygen blowing of a steel factory converter, optionally, pig iron 1 (> 4% C,> 0.3% Si) and sponge iron 2 fed at least in a ratio 90:10, 50:50 to 100% DRI with a scrap content as a coolant and / or a sponge iron content. The times for the melt sequence are shortened over a selectable, chemically and physically possible amount of oxygen above 150 Nm ³ and below 400 Nm ³ per unit time. The oxygen density is specifically at 2-4 Nm ³ / t · min (400 Nm ³ / min in a 200 t vessel 3 ) and the bubble times are lowered to about 12-16 min.

Here, the selectable amount of oxygen through the top lance 10 in a 200 tonne vessel 3 be increased between 150-400 Nm ³ / min.

Charging the sponge iron 2 (Direct and dry reduced iron / DRI) can also be done with temperatures greater than 600 ° C.

It is beneficial to the bubble angle 20 ( 1 and 3 ) at the outlet of the top lance 10 to 10-40 ° to the vertical. The inflation 21 of O ₂ is depending on furnace profile 22 only at a bath depth 23 of 1000 mm pig iron 1 began.

In order to speed up the reactions and thereby gain time, can additionally through the wall-blow lances 10d be blown with 50-100 Nm ³ / min of oxygen.

Supportive here works that through the door blowgun 10c about 6000 Nm ³ / min of oxygen are blown.

At the start of oxygen blowing 21 on the pig iron 1 can also only be charged with sponge iron 2 to be started.

The inert gas 9 that through the purging stones 8th can be supplied with a high number of purging stones 8th , which are distributed over the ground, in circumferentially increasing pressure increases in successive purging stones 8th be introduced. This creates a rotation of the melt around a vertical central axis of the molten bath.

Furthermore, at a gas outlet 24 at the upper furnace 6b a gas analysis 25 made at the pressure and temperature values of the exhaust gas 26 be measured.

The values of gas analysis 25 , to pressure and temperature and composition of the exhaust gas 26 form the basis for a control loop 27 , The loop output signals volume, pressure and temperature (V, P, T) optimize the blowgun position or its orifice settings, the amount of oxygen to be supplied and the pressure in the oxygen. In addition to the height adjustment, the amount of oxygen and the oxygen pressure is the control loop output signal for the supply of inert gas 9 from the purging stones 8th (Quantity) used so that the gas composition consists largely of CO ₂ in the measuring point. This avoids post-combustion of CO. The process achieves an efficiency of approx. 98%.

The pressure conditions (rotation of the melt) in the 4-20 purging stones 8th wear to those in the 1 and 2 illustrated melt streams 28 under the slag layer 29 at. The inert gas 9 that through the purging stones 8th is 50-600 N Itr / min. The pressure on the top lance 10 is about 8-20 bar.

The heating times ( 2 ) in the electric arc furnace 6 with an input power of 80-130 MW is set to a Pfannenfolgezeit between 25-70 min. In the start-up phase is of a degree of filling of 40% of the pig iron 1 went out.

The tapping times (tap-to-tap times) result from the melting and blowing times of both steel production vessels 3 ,

The application of two steel production vessels 3 halves tapping times of 140-50 minutes.

According to 3 is the location of the purging stones 8th , from above with removed upper furnace 6b , visible, of which only a few are drawn. The wall modules 11 for the wall lances 10d are visible. In the center is the top lance 10 with 10 ° and 40 ° double cones, which determine the effective range of the focal spot. Besides, they are the location and direction of the door lances 10c visible, noticeable.

The slag door is on the side of the slag extractor 30 , On the opposite side is the tapping 31 , which is drawn as a vertical channel with closure from below, but can also be designed as Abstichschnauze a Schnauzenkippers.

1

pig-iron

2

sponge iron

3

two Steel production vessels

3a

Single vessel

4

Lance

5

Electrode system

6

Electric arc furnace

6a

lower furnace

6b

top furnace

7

lining

8th

sink

9

inert gas

10

Top-lance

10a

Single-lance

10b

Single-lance

10c

Door-lance

10d

Wall lance

11

wall module

12

Oxygen Ultrasonic-lance

13

lifting and bogie

14

stroke movement

15

rotary motion

16

copper box

17

upper edge

18

Cold and support ring

19

Converter lining

20

bubble angle

21

inflation of oxygen

22

oven profile

23

bath depth

24

gas vent

25

gas analysis

26

exhaust

27

loop

28

melt flow

29

slag layer

30

slag door

31

racking

Claims (11)

Method of increasing steelmaking productivity using two-vessel technology, in which pig iron ( 1 ), Sponge iron ( 2 ) and scrap are processed according to the electric arc furnace and / or oxygen inflation method in proportions of 100% RE to 100% DRI with a scrap portion as a coolant, with insertion of two electric arc furnaces ( 6 ) with an electrode system ( 5 ) and blowing lances, characterized in that oxygen via a top lance ( 10 ) in an amount between 150-400 Nm ³ / min in a 200 t vessel ( 3 ) and that in addition by in the bottom of the furnace ( 6a ) evenly distributed purging stones ( 8th ) depending on the process phase, but without interruption, inert gas ( 9 ) with circulating pressure increases in successive purging bricks ( 8th ) is introduced from below at 50-100 N Itr./min. Process according to claim 1, characterized in that the sponge iron ( 2 ) is charged hot with temperatures greater than 600 ° C. Process according to Claims 1 and 2, characterized in that the blowing angle ( 20 ) at the outlet of the top lance ( 10 ) is adjusted to 10 ° -40 ° to the vertical. Method according to one of claims 1 to 3, characterized in that by door blow lances ( 10c ) about 6000 Nm ³ / h of oxygen are blown. Method according to claim 4, characterized in that at the start of blowing ( 21 ) on the pig iron ( 1 ) with oxygen the charging with sponge iron ( 2 ) is started. Plant for increased production of steel products with two electric arc furnaces ( 6 ), which can be selected according to the oxygen-inflation method of a steel mill converter ( 3 ) with an electrode system ( 5 ) and blow lances ( 4 ), characterized in that in the bottom of the lower furnace ( 6a ) of each electric arc furnace ( 6 ) evenly distributed purging stones ( 8th ) and that the top lance ( 10 ) from two individual lances ( 10a ; 10b ) consists. Plant according to claim 6, characterized in that in each case 4-20 purging bricks ( 8th ) are evenly distributed. Plant according to claim 6, characterized in that per single vessel ( 3a ) at least one electrode system ( 5 ), a top lance ( 10 ), a door lance ( 10c ) and a wall lance ( 10d ) are provided. Plant according to claims 6 and 7, characterized in that the wall lance ( 10d ) in a wall module ( 11 ) of the furnace ( 6b ) and from an oxygen ultrasonic lance ( 12 ) consists. Installation according to one of claims 6 to 9, characterized in that the lining ( 7 ) in the lower furnace ( 6a ) outside by means of internally cooled copper boxes ( 16 ) and that on the upper edge ( 17 ) of the furnace ( 6a ) lying copper boxes ( 16 ) a coherent cooling and support ring ( 18 ) form. Installation according to one of claims 6 to 10, characterized in that the lining ( 7 ) in the lower furnace ( 6a ) in the manner of a converter lining ( 19 ) is delivered.