DE1408625A1 - High temperature process for reducing ores to metals - Google Patents

Description

High temperature process for reducing ores

With this registration, the priorities of June 27th and August 24, 1960 from United States patent applications Serial Eos. 38 852 and 51 582.

The invention relates to the control of sulfur content in metals, especially in metals, the reduction of Ores are mined. The invention relates in particular to the manufacture of pig iron, but is not limited thereto. A special subject of the invention is the reduction the sulfur content of iron, which is produced directly from ores using carbonaceous fuels that contain sulfur. The invention is also based on

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general metal refining processes, such as the operation of cupola ■ furnaces, the smelting of ferrous metals and their ores etc. applicable.

In the manufacture of iron from its oxide ores in the blast furnace or in the manufacture or refining of iron and other metals from their oxides in the blast furnace, cupola furnace, Siemens-Martin furnace etc. as well as in all processes in which the material is in the presence of a solid, carbonaceous material, How coke is melted together with a calcareous or slag-forming flux, there are difficulties in the process Control of the sulfur content of the reduced metal. For example, when making pig iron in a blast furnace, it is common Limestone (mainly CaCO) as a slag-forming flux used. The flux can also contain other carbonates, such as magnesium carbonate, and often smaller amounts of other carbonates contain. In the high-temperature process, these carbonates decompose to oxides, and if so in the following Description When speaking of Oxydes, this is related also on the carbonates from which the oxides are formed.

The slag-forming material can also be introduced into the furnace as CaO, MgO, etc. (eg as quick lime or dolomite, etc.) or in the form of one or more constituents of a self-starting sinter. Such a sinter is usually a combination of calcium oxide, an oxidic ore of the metal to be produced and usually small amounts of carbon and other oxides such as SiOp, AlpO ₅ , etc.

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The solid carbonaceous material, usually metallurgical coke, functions to produce it the required heat to supply the fuel required, to reduce the ore and provide mechanical support for the stacked To form metal ore. This material frequently contains undesirably large amounts of sulfur. In addition, the Ores themselves and the fluxes contain undesirably high amounts of sulfur, which if no suitable measures are taken will get into the finished product.

The allowable amount of sulfur in most metals is extremely low. Most metallurgical processes aim to keep the sulfur content as low as practically possible to keep. Many blast furnaces that use coke as fuel produce pig iron with a sulfur content of 0.02 to 0.04 Ctew.-jS. There is the general rule that pig iron be kept at a sulfur content below about 0.05 Grew .- ^ got to. -

Sulfur has various undesirable effects in the process subsequent processing. In the case of pig iron, for example, which is to be processed further on malleable cast iron pieces, the prevents Sulfur provides the graphitization necessary for a successful heat treatment. The sulfur also increases the shrinkage when Qiessen and causes the cast products to settle in bleed. In pig iron, which is processed further and is to be passed between hot rollers, the sulfur leads to cracking and roughening

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the surface when rolling. In the case of iron, that too austenitic Steels are to be processed, the sulfur reduces the machinability of the steel product and increases the rate of corrosion of iron and steels when they are acidic Media come into contact. -

Some of these adverse effects of sulfur can be eliminated by adding alloy metals such as manganese or copper. However, these metals are quite expensive and it is therefore far cheaper to use a low-sulfur high iron. Sulfur can be removed by adding substances such as calcium carbide, calcium cyanamide or calcium oxide to the hot metal in the ladle. But even here you have to be careful that no significant amounts of acidic slag are present, otherwise the sulfur from the slag. migrates back into the metal · Treatment with such substances must take place at a temperature above; 1370 °, usually at about 1427 ° or above. At these temperatures the carbide or the cyanamide is more effective than the calcium oxide; however, the first-mentioned substances tend to carburize the metal. However, too high a carbon content in the metal is unfavorable because it is used for the production of steel, wrought iron or malleable cast iron. etc. must be removed again. Therefore, one usually has to use calcium oxide to desulfurize iron which is to be further processed.

Another difficulty _t £ ÜR the removal of sulfur from iron or steel resulting from the presence of SlIi-

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cium. At .high temperatures above 1570 ° and usually in the The sulfur from the pig iron is in the order of magnitude νοϊι 1427 ° expelled to a certain extent. At these temperatures, however, silicon oxide is also reduced to silicon, and this stays in the metal. Purely many purposes and products the silicon content must be kept low.

For all of these reasons, the pig iron manufacturers demand often a raw material, i.e. an ore and a coke, of very low sulfur content. In general it is required that the coke no more than about 1.0 weight percent and the ore no more than about 0.02% by weight of sulfur. Most in the United Types of coke available in the United States contain about 0.6-0.8% by weight & sulfur. A large part of the sulfur goes into the slag (a typical slag contains about 0.8 to 2.0% by weight of sulfur), but something remains in the hot metal. As a result of the strong affinity of the iron and the partially reduced iron (PeO) that are in the shaft for the sulphurous gases flowing through them, such as hydrogen sulphide, practically no sulfur is drawn out of the shaft with the gases. .

If it could be achieved that the slag had a larger one "Absorbs amount of this sulfur, then less sulfur would remain in the iron. One purpose of the invention is to do this." to reach.

Attsser also could be the total amount of sulfur in the system be decreased if you use a smaller amount of coke to reduce of metal ore, especially if the

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Coke is the main contributor to the sulfur content. It has already been proposed to use a [Cell of the coke when operating the blast furnace by fuels containing hydrogen, especially to replace gaseous or liquid hydrocarbons, such as natural gas, petroleum distillates or heavy petroleum residues. One object of the invention is the use of hydrogen-containing fuels, namely from hydrogen as such or from hydrocarbons, i.e. petroleum products with a molar ratio of hydrogen to carbon of at least 0.65 »for operating blast furnaces in such a way., that the amount of sulfur that eventually gets into the metal is reduced. With the right choice of conditions this goal can be achieved even if the hydrogen-containing fuels themselves contain some sulfur. Man can even use sulphurous fuels whose sehulphur content is so high that the total amount of sulfur introduced into the system is increased, and yet one can win a metal with a lower content of sulfur. if solid carbonaceous material and liquid or gaseous hydrogen-containing fuels are used together, it is preferable to use another agent, e.g., an oxide of a metal from Group II of the Periodic Table (preferably Calcium oxide or calcium carbonate), as detailed below is explained.

The removal of sulfur from pig iron is usually expressed by the following reaction equations:

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¹ - '• metal ⁼ ^ slag (equilibrium)

² · ^PeS slag ^{+ Ga0} slag ^{= GaS} visual slag ^{+ Ee0 slag}

^{5 G +} ^ slag = ^{Pe + G0} '

The temperature range in which these reactions occur with significant Velocities run is about 1427 ° and above. Therefore, the desulphurisation of the iron in the blast furnace takes place from the rest downwards. The reaction equation (1) describes the Transition of the into the reaction zone in solution in liquid bis introduced iron sulfide into the liquid slag. The reaction equation (2) describes the implementation of PeS with'CaO in the slag with the formation of relatively stable CaS and PeO. The reaction equation (5} describes the reduction of the PeO in the slag with solid carbon with the formation of carbon monoxide.

It has been found that the equilibrium of the sulfur distribution between metal and slag is reached faster when the sulfur is in excess in the iron than when it is in excess in the slag. That means that, provided there is sufficient contact, the sulfur content in the slag is brought to a higher value as it corresponds to the equilibrium distribution of sulfur between slag and bison, provided that that the process is only carried out for a limited period of time will. -

• Another aim of the invention is therefore.

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to take advantage of lative reaction rates in such a way that there is a higher sulfur concentration in the slag is achieved when it corresponds to the equilibrium.

According to the invention, this is achieved by reducing the amount of coke normally used and replacing it with an amount of a hydrogen-containing fuel, together with a finely divided flux, which is equivalent in terms of calorific value and chemical reducing power. For thermal reasons, oxides, e.g. calcium oxide, are preferred over carbonates.So natural gas, which mainly consists of methane (OH,), or various fractions of petroleum hydrocarbons can be blown or injected into the blast furnace at the most favorable point in order to generate the added fuel and the flux (usually mostly oxides of metals from Group II of the Periodic Table, "especially CaO; but this may also contain MgO and small amounts of other oxides) in the moving, normally downward-moving mixture of coke, era and reduced metal In a blast furnace of the usual type for the production of pig iron, the most favorable point for the injection of the hydrogen-containing fuel with the finely divided flux is approximately at the level of the wind form. Here the temperature is usually above 1370 ° and is usually 1427 ⁰ or more .

According to the invention, the sulfur absorption capacity can the smoke when operating the blast furnace in a more effective way be exploited in such a way that in the end a part of the sulfur

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from the metal, e.g. the pig iron, goes into the sole smoke. "If the Grleiohgewiohts Distribution between the sulfur in the Slag are the Sqhwefel imBojusigen ^^^^ the manufacture of a pig iron would be satisfactory Soh sulfur content do not present a problem, even if, for example, one is offering a hydrocarbon fuel with a high sulfur content the Windformem would clog. With the usual technical. However, only about a third to half of the sulfur absorption capacity of the carbonate is used up.

According to the invention, the effective contact area is therefore between flux or slag-forming material and metal enlarges-fc in order to approach equilibrium by increasing mass transfer speeds. In theory, this could also be done by magnification the contact time or increase in temperature. However, increasing the contact time increases the capacity of the furnace decreases, and increasing the temperature increases the silicon content of pig iron, since it contains silicon * substances normally in the refractory linings and often also in the Ores themselves are included.

By reducing the amount of coke and replacing it with one hydrogen-containing fuel can reduce the sulfur content of the metal will be reduced, even if the hydrogen-containing Fuel has the same or a higher soulfur content than the coke. As already mentioned, the hydrogen content should be of fuel be substantial and at least one molar ratio from hydrogen to carbon in the fuel from

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Correspond to 0.65; but it can also be much higher, land man can even use pure hydrogen within the meaning of the invention ,-, At the,

which contained 1.0 5 $ sulfur, the slag was found to contain 1.51 wt .- $ and the metal 0.026 G-ew.-f £ sulfur, which corresponds to a ratio of about 50 tons Part of the coke through a hydrogen-containing fuel, which would be injected together with the hot blower wind at the tuyeres, these "values changed to 1.294ew" ^ ^ - sulfur in the slag and 0.020 wt .- ^ sulfur in the metal, ie · A ratio of 64.5 J 1 · This change was achieved without injecting a flux.

It is believed that the hydrogen-containing fuel injected at the tuyeres replaces some of the carbon dioxide normally present in this area at a temperature above 1427 ° C. This likely affects the rate at which equilibrium of equation (3) is reached. It may also change the balance itself. By reducing the carbon monoxide concentration, the equilibrium of reaction equation (3) is shifted to the right. In a kind of chain reaction, this leads to similar shifts in equilibrium in reaction equations (2) and (1), so that relatively more sulfur goes into the slag and sulfur-free iron is produced.

If no hydrogen or only very little hydrogen is blown in at the windshield, as is the case with conventional loading

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.drive vcm blast furnaces without injection of a hydrogen-containing one Fuel that is lall, then there is solid carbon (coke) in abundance, and the hot blower wind produces ample amounts of carbon monoxide. This will al-

Ie equilibria shifted to the left. .

By injecting finely divided! Flux, such as Galium oxide, limestone, dolomite or the like., On the wind forms In addition to the hydrogen-containing fuel, this effect of removing sulfur from the metal product can be significant increase.

"For example, if you use 680 kg of coke with a sulfur content of 1 #; per * iron, the coke gives 6.8 kg of sulfur introduced into the blast furnace. The coke is now being used up 4-54 kg per t of metal is reduced, the amount introduced with the coke decreases Amount of sulfur from 6.8 to 4.5 kg per t of product. Will now this 226 kg of coke through 150 kg of oil with a sulfur content of 2.5 Grew .- $ replaced (which corresponds to about the same calorific value) , so with this hydrocarbon fuel e-fcwa 3.6 kg of sulfur introduced into the furnace. By the total amount of fuel So in the latter case, 8.1 kg of sulfur are introduced into the system.

If one adds galcium oxide in such an amount that thereby E.g. the 3.6 kg of sulfur that are absorbed with the hydrogen-containing fuel were introduced, and leads if this galium oxide is at the height of the wind form, then it becomes the amount of sulfur passing into the metal in comparison

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with the working method in which only solid fuel is used is reduced by at least a third. This effect is in addition to the beneficial effect of the hydrogen-containing one Fuel on the shift in equilibrium. The finely divided flux takes the sulfur out of the injected Fuel in a very effective manner. To achieve this, the flux can come as either a finely divided powder with the blower wind (which can be enriched in oxygen, but does not need to be enriched) or with the gaseous hydrogen-containing fuel (e.g. natural gas or low-boiling Hydrocarbons) or as a slurry in heavier petroleum products are injected.

For further explanation of the invention, reference is made to the drawing Referring to Figure 1, the East and the Lower Rope of a blast furnace of the usual type with the according to the invention necessary modifications and Fig. 2 shows a system for injection of finely divided sole-forming material into the wind shape together with a hydrogen-containing fuel shows

According to Fig. 1 of the wind ring 11 of the furnace P ^f duroh the connecting line 15 is connected to the usual tuyeres · Each of these is characterized Windformezt modified such that it contains a nozzle 15. Through these nozzles, a slurry of flux in a liquid, water-containing fuel is injected. This fuel can be a hydrocarbon fuel oil, for example a petroleum distillate, or a sohwerea residue oil in liquid form. be. The fuel is fed through line 16 to the

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Valve. MV fed, where he was burnt with the slurry of delicately urgent. Lime, OaO, or the like. Is mixed in oil, which is produced in the misoher 17. The mixture of oil and slurry flows from the valve MV into the manifold 18 and from there to the various injection nozzles 15 If the fuel is gaseous, i.e. consists of hydrogen or light hydrocarbons, or if it is before it reaches the furnace, passes into the vapor state, it is through. Line 20 (Pig. 2) is fed to the Venturi tube 21, so that the finely divided technical flux (oxide of one or more metals of Group II of the Periodic Table, preferably lime:, OaO, or dolomite, etc.) flowing out of the filling funnel 25 duroh the suction effect of the vapor or gaseous fuel stream is injected into the stream. Otherwise this system is the same as the liquid fuel system shown in! Ig · 1.

At the point where the fuel is injected, lies the temperature in the furnace is over 1570 ° and is usually 1427 ° or more. The finely divided flux comes with the injected one Fuel when burned in close contact and takes so-sulfur out of it, if it contains' sulfur also comes with the droplets of iron and sinking downward Slag in contact, which on the liquid level of the

so the molten slag 25 and the molten iron 26 sink down.

A certain reduction in the sulfur content of the metal can be achieved by simply using

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a hydrogen containing fuel or hydrocarbon fuel works, or that the finely divided flux in in such a form and quantity that in the end an excess -ferring sulfur from the metal product into the slag takes place. Preferably, however, both measures are carried out at the same time taken so that by applying a massive amount of injected hydrogen fuel or hydrocarbon fuel and a massive amount of fine particles Calcium oxide, limestone, dolomite or the like. The sulfur content is reduced considerably at the lowest cost. When the injected; the hydrogen-containing fuel contains soh sulfur, at least as much finely divided flux is preferably injected at the same time that it covers the whole absorbs so-called sulfur imported in this way.

In addition, the invention enables a lower Amount of flux to apply (because the flux has more soh sulfur absorbs), or ores with a higher than normal soulfur content to use and / or coke and / or to use flux of higher than the normal sulfur content. On the other hand, the invention enables, even if the coke and the coal have a low sulfur content, the use of high sulfur hydrocarbons as a supplement Fuels, this is made possible by the simultaneous injection of the finely divided flux. All these various options have a very beneficial effect in special cases. The invention therefore enables the downgrading

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the relative sulfur content of the metal produced for a wide range of raw materials. The invention is also based on Spruce ferrous metals can be used, with solid carbonaceous and hydrogen-containing liquid or gaseous reducing agents • free can be used together at high temperatures as the main reducing agent.

The introduction of the hydrogen-containing fuel and the Finely divided flux can of course be done in several ways, and the flux can be continuous or intermittent be injected. The proportions of fuel and / or flux can also be changed if this is the only way to reduce the sulfur content of the metal produced is achieved »

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Claims (9)

Patent claims Patent claims 1. High-temperature process for the reduction of ores with the formation of metal and sole, whereby hot blower wind is passed through a zone in which the raw material is an ore, a solid carbonaceous fuel, the heat. supplies and at the same time acts as the main reducing agent, and a flux which contains an oxide of a metal different from the Eetall of the ore · contains, and wherein at least one of the raw material · contains sulfur in amounts which normally lead to the formation of a metal part product of undesirably high Sulfur content, characterized in that at the same time as the blower wind and approximately at the same point in the zone a material containing a hydrogen-containing fuel, which is capable of ultimately transferring sulfur from the reduced or partially reduced metal into the slag, is injected in such a way that it comes into contact with the reduced or partially reduced metal * - t6 - BADORIGiNAt 809809/0198 2. Procedure according to. Claim 1 for the production of pig iron and slag from iron ore, solid carbon containing fuel and fluxes containing calcium oxide, characterized in that that together with the G-blower wind a sufficient Use a hydrogen-containing fuel as a substitute one part of the solid carbonaceous fuel and a distributed! flux can be injected so that in the end, a transfer of sulfur from the iron to the slag and consequently a reduction in the sesame sulfur content of iron takes place. 3 · The method according to claim 2, characterized in that a finely divided flux is used, which is a finely divided Contains oxide of a metal of group II of the periodic table. 4 · .Method according to Claim 3> characterized in that the metal oxide used is calcium oxide. 5. The method according to claim 1 to 4V, characterized in that that as an aqueous fuel hydrogen or a Hydrocarbon oil is used, with which the Aoiverhartniö from water to carbon is at least 0/65. 6. Method according to claims 1 to 5, characterized in that that a fuel is used that also contains sulfur. - 17 -809809/0198 7 · Procedure according to. Claim 6, characterized in that A heavy petroleum residue containing at least 1% by weight of sulfur is injected as fuel. 8. The method according to claims 1 to 7, characterized in that the mixture of fuel and finely divided oxides of metals of group II of the periodic table is injected into the furnace at a point which is essentially at the melting temperature of the metal so that the metal oxides absorb the sulfur and ;;; thereby reduce the sulfur content of the metal product has a P art. - ■ 9. Terfahren according to claim 8, characterized in that the normal amount of sluice agent due to the transfer of relatively more sulfur into the slag the normally existing need is reduced. _ ₁₈ _
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