DE1433293A1 - Continuous process of making steel from iron ore - Google Patents

Description

Dr. Hans-Heinridi Willrath _{6200 WIESBADEtf} fl *. υ r 1 * 5 * Dipl.-Ing. Hany Roever "^ *" 'Dr w / b

• Patent Attorneys _ '1 ^{Tefefott (061i81)} ^ " series

: MTOJgATENT I f- ^ T7 -ττ- γ-ν 1

Bankx DKSdKf Buk AG. Wiesbad «« | IS * - * ■ * - * " Γ \ Ί / ι QOOQ * 3

L'Air Liquide, Societe Anonyme pour 1'Etude et! 'Exploitation of the Procßdes Georges Claude, 75, <^ uai d'Orsay, Paris (7e)

Continuous process of making steel from iron ore

The invention relates to a continuous process for the direct production of molten steel in a controlled manner Composition of iron ore using a fixed furnace with an annular hearth. Procedure for Direct steel production from iron ore can generally be divided into two classes: the low-temperature processes, those below the melting point of the metal work, and the high-temperature processes that work above this melting temperature · The low-temperature processes have the advantage of providing inexpensive energy balancing since they are generally capable of making effective use of the reducing properties of the Carbon monoxide at temperatures in the range of about 600 ° to make up to 800 ° C. However, they are generally slow and therefore do not lead easily by themselves a company of high specific production dJi., a Operation in which the tonnage is on in the time unit ' produced «metal is large in relation to the size of the plant. They also often have the further disadvantage

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that a spongyβ metal is formed, which is generally used Use is unsuitable and requires subsequent melting at a high temperature. This will make the gate parts outweighed the initial low temperature operation.

On the other hand, the effectiveness of the high temperature process generally well improved if the JSrz is preheated and preferably also at least partially in a preliminary stage is pre-reduced.

The invention has set itself the task of a highly specific one To make production in a stationary furnace with a ring-shaped hearth feasible, which is also easy to do with a can be linked to continuous casting. Furthermore, the object of the invention is a reduction method, which is in the Is able to a. Gas ~ with the highest possible ratio of Carbon monoxide to carbon dioxide in appropriate amounts for the Operation of a preheating and prereduction furnace. in the ideally the gas should preferably be almost pure fifonoxide be.

Accordingly, the invention is practiced by

a) forms a bath of molten iron and contributes this continuously in a closed circuit revolves at a regulated speed,

b) continuously crushed iron ore in a first zone of this bath, preferably in a preheated and prereduced state, and a reducing agent is injected, ·;: · .. ■ -. · .-

c) heat to the iron bath in sufficient quantity to maintain its thermal equilibrium feeds and

d) withdrawing molten steel as new metal from a second zone of the bath.

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Preferably, the molten steel can continuously, for example, by tapping the furnace directly into a continuous casting mold can be withdrawn.

A particularly important requirement is that the thermal Maintains the balance of the bath. The bath can receive heat from various sources, e.g. as electricity depending on how it is available at a reasonable cost; but according to an important feature of the invention, if all or a portion of the heat comes from burning a fuel is obtained, this is burned with an oxidizing gas with 60 to 100 vol .- ^ oxygen. This high oxygen concentration has the advantage that the volume of the combustion gases is reduced, which results in a very favorable ratio of available heat to total heat output and consequently a high specific steel production result. It also offers the advantage of delivering combustion gases in which carbon monoxide is less through inert nitrogen is diluted. Such rich gases are highly effective in a preheat and prereduction furnace.

Usually they are used in excess amounts

,. .be requirement of the pre-reducing furnace generated and the excess / indicates an asset for the whole operation because of the excellent economic value of such near gases as fuel, and as a raw material for the production of chemicals such as, for example, hydrogen, ammonia and methanol.

In order to properly control the composition of the steel withdrawn from the bath, the method according to the invention comprises also the following features:

a) The bath mass is between about 5 and 30 times the mass per hour from the bath stripped metal,

b) the bath flow corresponds approximately between the 4 and Twenty times the river. of the withdrawn new metal

c) the speed of rotation of the bath is a maximum of 10 cm per second.

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These measures ensure that the concentration of ore and reducing agent dissolved in the bath remains low, for example in the range of only about 1 $, so that additional material dissolves quickly and reacts quickly in the bath, and furthermore that all reactions are upstream of the steel casting «Are finished. In order to accelerate these reactions further, a stirring gas can advantageously be blown into the molten bath. This can be done in such a way that the circulation of the bath is promoted. The bigger one. However, part of the kinetic energy necessary to maintain the bath's circular motion is preferably supplied by the solids and the superplasticizer introduced into the bath, in particular by the combustion products which are developed by combustion with immersion within the bath. In order to avoid excessive turbulence, a critical ratio between the volume of the gas rising from the bath surface and the surface area should not be exceeded, so the area of this surface should be at least 5m / m, gases emerging from this surface per second.

In addition, or instead of this, you can continue to use the bath Keep measures in the cycle

a) electromagnetic pumping

b) siphon effect supported by vacuum

c) a union of the suction lifter effect supported by vacuum with the air buoyancy effect, d «n by emulsifying the molten metal with a thread blown into fine threads from below Receives gas flow.

The latter method can also be used for the ivletallaazug from the bath at the pouring point and for the combined cleaning effects of the vacuum and de's are injected Gas on the metal, creating the vacuum when flushing out

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BATHROOM CRIGfMAL

Support unwanted dissolved gases and solid inclusions.

The invention is described in more detail with reference to the drawing.

Fig. 1 is a schematic horizontal section through • a ring hearth furnace which is suitable for carrying out the method according to the invention.

Figure 2 is a vertical section through the same furnace.

Fig. 3 is a horizontal section of a modified one Oven shape.

FIG. H is a developed vertical axis through the furnace of FIG. 3.

Fig. 5 is a vertical section through a suction cup, wb he in conjunction with the furnace in support of the circular motion of the metal bath is used.

Fig. 6 shows schematically a ring hearth furnace ^ the with equipped with an electromagnetic inductor for the same purpose.

Fig. 7 shows a modified furnace design with two parallel channels, which are alternately connected at the end, so that a closed circuit is formed.

Fig. 8 is a topical vertical view of a Preheating and reducing furnace connected to a ring hearth furnace shown in the Sohnitt.

• *

The furnace shown in FIG. 1 has an annular channel 2 _t, the bottom of which lies between the outer wall 6 and the inner wall 8. This channel is connected through an opening 12 to an attachment 10 in which the final metal composition can be set. Löoher 14 serve as sole stone outlets. The means used to achieve the circular motion of the molten metal are symbolically represented as suction lifters 23

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in Pig. 3 »4, and 5 shown.

The ring channel is covered by a gas-tight, arched ceiling 9, through which the injector devices 15 are inserted. These can consist of lances 16, 18 and 20 according to FIG. 1, which are used to blow in a reducing agent, iron ore and a heating agent. The injectors 20 for the heating means may preferably consist of submerged burners 20 "as schematically shown in Fig. Indicated k. Further gas nozzles 17 can be provided in the form of porous blocks at the bottom of the channel. These porous injectors can be used in particular for blowing a stirring gas and also oxygen into the bath in order to support the combustion of the heating oil as well as to serve as a refining agent to adjust the final carbon content of the steel before casting.

Furthermore, the channel can be provided with weirs 26, as shown in FIGS. 3 to 5, in order to prevent a to maintain a higher metal level and thus the circulation of the bath in cooperation with the pump system, e.g. the Siphon 23 closed. support. Dependent transverse walls 33a and b in Figure 4 serve to hold back the slag and form it separate gas closures along the circular path. They can also form part of a lifting device 29 and 33a in FIG. There they form part of the vacuum chamber 23, which through a pipe 31a / a vacuum source, not shown, is connected. The siphon can also be anywhere along the circular path, however, it is preferably arranged at the metal casting point, where it is additionally used to achieve continuous degassing of the metal can serve just before casting. Alloy components can also preferably be the metal in the siphon be added where the blown at 17 at the bottom of the siphon Purge gas in the sense of a dispersion. such constituents acts in the molten metal.

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The suction cup can also be a very effective means of Control of the flow of metal from the furnace channel into its continuous casting station can be used as shown schematically at 36 in Fig.4 .Is shown. There the metal flows in a water-cooled mold 38 and is drawn off by feed rollers 40 as an endless bar. The vacuum lifting system can also be used to increase the effectiveness of a carbonaceous Increase reducing agent by reducing the partial pressure of carbon monoxide is lowered above the bath.

Fig. 6 shows one equipped with a magnetic yoke 44 to assist the circular motion of the molten metal Ring channel 2, this yoke has a primary winding 46, the is connected to an alternating current source, not shown. The metal bath forms a single-lane secondary circuit. This system also acts to stir the bath and can also be used as a heating system for the bath. May that Process according to the invention continuously with a boiled Metal bath works whose temperature is always above 14 00 ° or 15 00 ° C, electrical power is used for heating at a high energy level and is therefore much more powerful than oils for melting one cold loading would be ». Electric current can also The bath can be fed through graphite plates immersed in it.

7 shows an arrangement ₇ which has two rectangular channels 2a and 2b which are connected at their ends by suction lifters 23a and 23b to form a single closed circle.

Fig. 8 shows a preheating and prereduction furnace which is attached to the annular reducing furnace can be connected. The ore is produced along with any additional allowances that may be required of lime or limestone from a hopper 50 in4 Drying silo 52 countercurrently with a hot air stream introduced, which is introduced at the lower end through line / f54 will. This air is first exchanged with the heat

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hot gases exiting from the reducing furnace through chimney 30b heated in the heat exchanger 56.

The ore is then fed into a pre-reduction stage, in which the advantage of the dissociation reaction of the carbon monoxide into carbon black and carbon dioxide can be used. The maximum yield of this reaction occurs at a temperature of about 575 ⁰ C. The activity of this reaction increases with pressure, and an operating pressure of about 15 to 20 bar can be suitable. After the iron ore is soaked with the resulting carbon black, the reduction of the eries occurs very quickly when this carbonized ore is introduced into the hot metal bath.

The carbonization reaction can be carried out in a suitable pressure vessel, whereby gas with a high carbon monoxide content is inserted in the lower parts of the vessel through a pipe 62 connected to a chimney 30c of the ring hearth furnace is connected. This chimney is preferably connected to a section of the furnace in which reducing conditions prevail so that the escaping gas consists mainly of carbon monoxide ^ this is achieved through the hanging walls, 33..iss, Pig. 8th

Gas closures and 33a and 33b in Fig. 4 that ** «separate / form, such as 13 was mentioned in connection with FIG.

The carbonized ore withdrawn from the carburizing vessel 60 can be further preheated, especially if the raw material contains carbonates, since a complete dissociation of the carbonates can require a temperature of about 100.degree. In order to keep the ore free flowing, the final preheating stage can be carried out in a vessel 66 using a neutral gas such as nitrogen. The nitrogen, which need only be of low purity, is fed through a pipe 68 which is connected to a heat exchanger or regenerator 70. The latter is heated by hot gases emerging from the ring hearth furnace. The ore is finally through "■

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Breasts 18 delivered into the bathroom · You from the Gefifl 60 uad 61 outgoing aase can go through pipes 64, 72 and 73 dem upper drying siIo 52 are supplied.

Sin essential Merkaal of the method according to the invention is that the liquid metal instead of slag as Carrier for blown grass and solid substances and as an exchange medium for warmth, mass and vital force is needed. Molten iron conducts heat far better than slag and is also less viscous · Actually supposed to the amount of slag preferably not significantly above di Go beyond the minimum amount required to remove contaminants such as sulfur and phosphorus *

Another essential feature is the use of a submerged burner for the direct supply of heat and kinetic energy to the metal bath. This means a fundamental deviation from earlier processes, in which combustion reactions take place above the bath and heat must therefore be transferred to the molten metal through the smokes. Another advantage is that submerged high-efficiency burners emit combustion product β with considerable living force, which makes them powerful as a drive for the metal along the hearth. These burners offer another advantage in their ability to operate efficiently even when the ratio of oxidant to fuel differs greatly in one direction or another from the stoeohiometric ratio. They can therefore be used to close the bathroom . heat while an excess of reducing agents is fed to them at the same time

It is also important that the burners should operate in an oxidizing gas containing at least 60 pounds of oxygen with it a favorable ratio of available heat to total heat output is obtained the combustion of carbon with oxygen to carbon monoxide raw calculated 1 250 kcal / 4? CO formed is, so increases

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every nr CO, which leaves the furnace at about 1,600 ° C, has about 600 Kcal in heat balance with the bath. The difference of 650 Kcal is available for the ore reduction process. If, instead of using oxygen, a mixture of 50 % oxygen and 50 % nitrogen is used, the volume of the exhaust gases increases by 50 % and approximately 900 Kcal are continued, so that for the same amount of carbon burnt the available heat drops to 350 Kcal, that is, it is less than half the heat available in the case of pure oxygen.

The useful heat ratio can be increased to a certain extent by using a secondary combustion of carbon monoxide to dioxide. However, the overall economic equilibrium of the process is generally more favorable if a reducing equilibrium is maintained in the main part of the cycle and if the resulting gas, which contains more than 85 % carbon monoxide, is used outside the ring hearth furnace. This gas can be an excellent fuel for an MHD power plant, for example. It can also be used in a conversion cycle that supplies hydrogen for a fuel cell system or for the production of chemical products.

The preceding discussion has assumed that coal is used as both a fuel and a reducing agent. ί The method according to the invention can also work successfully with natural gas or other hydrocarbons. The fact that the iron ore is reduced at a relatively high temperature leads to very good utilization of the reducing power of the hydrogen contained in the hydrocarbons, since the equilibrium constant of HnO / Hp increases with temperature. On the other hand, carbon monoxide should preferably be used at relatively low temperatures, ie in the range of 600 ° to 800 ⁰ C. The best use of hydrocarbons is therefore achieved by first cracking them with the supply of carbon monoxide and hydrogen and then one

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a first fraction rich in carbon monoxide, which is fed to the prereduction furnace, and a second fraction rich in hydrogen separates, which is fed to the high-temperature reduction furnace.

As regards the physical aspect of the design of the reduction furnace, a dominant consideration is that the gas flow exiting through the bath surface

* 2

preferably not more than 1/5 * j second and m bath surface should be, as stated above. If one assumes, for example, that on the one hand the reduction of the ore leads to the formation of about 370 m * carbon monoxide per t of Elsen, while on the other hand the combustion of coal through the generation of the required heat of reduction leads to the formation of about 2 030 nr carbon monoxide per t iron, so that the total amount is about 2 4 uO or CO per t iron. One Mimmt in turn indicates that the plant for the production of 60 tons of steel is arranged in the hour or 1 ton per minute, then the corresponding · Tolumen evolved gas is 2400 »per Hinute or 40 tr per second amount, which is a Requires bath surface of 200 a. If one takes into account the loading depth, which can be, for example, 0.60 m, the bath volume will be approximately 120 nr, which corresponds to approximately 90 t of metal and is thus approximately fifteen times the amount of metal that is produced in the furnace per hour Aaraue is sucked off · The cycle ratio of the bath ·· and dl · speed of the bath circulation can easily be deduced if the width of the ring channel · · is taken into account «

The method according to the invention can itself be designed particularly well for complete automation « Through continuous automatic monitoring of the COg content of the exhaust gases in the final refining zone 10 of the FIf. 2, where some oxygen in the bath to adjust the final carbon « content of the steel is blown in just before casting, it is possible to automatically change the introductory ratio of irs and to regulate reducing agents and the supply of heat. These injections and also the supply of heat are preferably via a large proportion of the length of the bath. Another part of the gate

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1 * 33293

«• 12 *.

This method consists in that the dl · temperature is practically constant in any given part of the bath

From the economic point of view there is an advantage of Method according to the invention in its high specific Production. If one considers the above example iai dem dft « Bath volume of 120 he generating 69 i / ßxd odar

1 ^ 40 t / day corresponds to the specific production Jem ⁵ equals 12 t / day. This production is very cheap compared to the specific production of a typisoha *

Blast furnace, which i · w? Vateaagil · »

fortune lies.

The investment costs are also far lower than those for, Dreh * ovens are required. In fact, the method according to the invention can be carried out in existing open hearth furnaces after having put a pear in the hearth of the hearth has built a suitable thickness »ua to« inen Bingkanal u * to form this pillar.

Since the process does not require coke, but can work with almost any fuel available and no a Agglomeration of the ore demands, the savings are of the kind that it is economically possible in many cases, on the preheating stage at least in the introduction period to refrain from operating a new insert. BIa Gaaaagaba the plant can advantageously replace the Koksofengaa egg »» take, because ea has a high economic waiting uoA can be obtained at a much lower cost than Kokaofengaa, as much lower investment costs and much less work are required for maintenance and operation

Finally, the continuous mode of operation of the process and its adaptability are particularly suitable for combining this process with continuous operation. The production speed can easily be adjusted at any time so that it corresponds to the requirements of the GIaSBa * drive, and the relatively large bath mass makes it possible to arbitrarily interrupt production for periods of? . 809902 / "Π SR9 öHSG ^ M- INSPECA« ■

Claims (10)

Claims (y. Continuous process for the direct production of molten steel of narrowly regulated composition from iron ore, characterized in that one a) forms a ring-shaped bath of molten iron and lets it circulate continuously in a closed circle at a controlled speed, ί b) continuously blows crushed iron ore and a reducing agent into a first bath zone, o) the bathroom in sufficient proportion to maintenance supplies heat to its thermal equilibrium, d) adjusting the final carbon content of the steel in a second bath zone by blowing in oxygen and e) withdraws a steel fraction as new metal. 2. The method according to claim 1, characterized in that at least one T _e il receives the bath zugefUhrtön ^ heat by combustion of a fuel with a 60 to 100 vol .- # oxygen-containing gas. 3 «Method according to claim 1, characterized in that a) the circulation speed of the bath at most 10 om / sec. amounts to b) the bath mass Aim approximately 5 to 30 times the mass of the new metal withdrawn from the bath per hour. ( * speaks, o) the bath flow is about A to 20 times the plus of the withdrawn new metal is and d) the horizontal bath surface is at least 5m / nr ^ gas escaping from the bath surface per second. . 4. The method according to claim 1, characterized in that one a stirring gas is blown into the molten bath. 809902/0669 • -U- U33293 5. Terfahren according to claim 1, characterized in that the bath is kept in circulation by at least one of the following measures a) Kinetic energy developed within the bath Combustion products b) electromagnetic forces c) Emulsification of a metal stream with a gas blown in from below d) siphon effect supported by vacuum e) Combination of the above measures c) and d). 6. embodiment of the method according to claim 1, dsduroh characterized in that the steel obtained directly from the reducing bath is continuously cast as a continuously cast product. 7. The method according to claim 1 and 6 with continuous degassing and continuous strand, characterized in that a Met allst rom from the bath, by means of vacuum assisted siphon effect and at the same time withdraws the metal flow under vacuum with an adjustable purge gas flow cleans and drives controllably " 8. The method of claim 1 with primary use of carbon as a reducing agent, characterized in that the ore is in contact with circulating carbon monoxide preheated to such temperature and pressure conditions that Carbon monoxide in elemental carbon and carbon dioxide dissociated. 9. The method according to claim 1, characterized in that partially reduced ore in contact with hot nitrogen, which in heat exchange with the exhaust gas of the beduction bath has been preheated, at a temperature above that at which the ore is preheated in the presence of a reducing Gases would become doughy. 10. Oien for. Implementation of the method according to claim 1, characterized through a gas-tight enclosure, a Bing- j. hearth within the enclosure, facilities for upright 809902/0669 maintaining a continuous closed cycle of molten metal bath in the stove, means of heat supply to the bath, injection devices for crushed ore and reducing agents in the bath and extraction devices for one Electricity from new metal from the bathroom * 809902/066 9