RU2403289C2 - Method for separating metallic iron from oxide - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: invention refers to separation of metallic iron from fine iron containing metallic iron reduced from iron oxide, and residual iron oxides. Invention provides conversion of fine porous low-density iron to high-density agglomerates with increased content of metallic iron, which are capable for being used as charge for steel making. For that purpose, fine porous iron is supplied to flame of oxygen fuel burner having combustion intensity providing complete melting of fine porous iron, and producing power P at least equal to P=kmin (kW), where kmin is at least 1500 kWs/kg and (kg/s) is mass flow of introduced fine porous iron, with separation of metal bearing fine porous iron into metallic and oxide parts. Then two phases are separated into molten slag and molten iron in the appropriate oven or furnace and molten iron is converted to high-density agglomerates. ^ EFFECT: method of separation of metallic iron from oxide is proposed. ^ 11 cl, 3 dwg

Description

FIELD OF THE INVENTION

The present invention relates generally to a method for separating metallic iron from a finely divided oxide containing metallic iron recovered from iron oxide and residual iron oxides, in particular finely divided pyrophoric material, the so-called finely dispersed sponge iron, which is formed during direct reduction of iron.

State of the art

The main iron raw material for the manufacture of steel is molten iron from a blast furnace, from which steel is obtained in conventional oxygen converters. The main alternative to molten iron is the so-called direct reduction iron obtained by solid-phase reduction of iron ore. In recent years, great progress has been made in the manufacture of direct reduction iron. Direct reduction iron enters the steel production workshop (internal or external) either in the form of so-called sponge iron, into which direct reduction iron is converted immediately after reduction, or in the form of briquettes, for example, hot briquetted iron.

Spongy iron has a porous structure, which is formed as a result of the removal of oxygen from the original ore. Thus, sponge iron is a low-density product with a large internal metal surface, which makes it prone to self-ignition, which can begin when a small amount of moisture enters. During the oxidation of metallic iron by moisture, hydrogen is formed, which makes storage and transportation of sponge iron, in particular, sea transportation, very dangerous due to the threat of explosion and exothermic reactions. Therefore, special measures must be taken to transport sponge iron to external users. An alternative is hot briquetted iron, obtained by unloading hot direct reduced iron from a reducing atmosphere furnace and pressing at a discharge temperature to obtain a non-pyrophoric high-density product.

A by-product of the direct iron reduction process is finely divided sponge iron. In the process of direct reduction of iron, depending on the type of process and whether sponge iron is briquetted, different amounts of finely divided sponge iron are formed as a by-product. This finely dispersed sponge iron with a metallic iron content in the range of 5 to 90% creates a problem. Fine material is divided into several quality categories, and fine material with a relatively high metal content can be sold on the open market for use as a raw material for steel production, but at a price reduced due to its size, and with the same transportation and storage problems, as with regular sized sponge iron. Fine material with a low content of metallic iron is often stored unprocessed in large heaps. This, of course, creates a danger to the environment, and pressure from government bodies is growing. In addition, such a loss of metal-containing material is uneconomical.

A well-known solution to the transportation problem is the cold briquetting of finely divided material. However, it is associated with additional costs for a separate briquette installation, it usually requires a binder that further reduces the content of metallic iron and increases costs, and, in addition, finely dispersed material is formed in the briquetting process itself.

So, finely dispersed sponge iron usually has the following properties:

- too small a size, making it unsuitable for conventional processing and methods of loading into a steel furnace;

- often lower metallization (metallic iron content) compared with conventional direct reduction iron, leading to an increase in energy requirements in the steelmaking process and, as a result, to an increase in cost and lower productivity;

- The same or greater tendency to self-ignition compared to a spongy iron of normal size.

Due to these negative properties of finely dispersed sponge iron, it is either sold at a low price not for loading into a steelmaking furnace, but, for example, as an iron-containing additive in the production of sinter in a blast furnace, or, as already mentioned, is simply dumped into heaps due to its low value.

Disclosure of invention

An object of the present invention is to propose a method for converting finely dispersed low-density sponge iron into non-pyrophoric high-density agglomerates with a high content of metallic iron and a size that makes it possible to use them as a charge material for the manufacture of steel, by separating, in a liquid state, metallic iron from a finely divided oxide containing metallic iron and iron oxide, and subsequent cooling of the liquid metallic iron to obtain high otnostitsja.

Thus, the method offers a solution to the problems associated with finely divided spongy iron, as described above.

The present invention is based on the fact that finely dispersed material containing metallic iron and iron oxide can be fed directly into the torch and melted in it, allowing separation.

According to a first aspect of the present invention, there is provided a method for separating metallic iron from an oxide, as set forth in claim 1.

Using this method, the metal part of a finely dispersed material containing metallic iron and iron oxide can be separated from the rest and restored in a form suitable for use as raw materials for the manufacture of steel in foundry, etc.

Brief Description of the Drawings

Using the drawings below, a preferred embodiment of the present invention is described.

Figure 1 presents a schematic drawing of the installation used to implement the method according to the present invention.

Figure 2 presents a section of the burner used to implement the method according to the present invention.

Figure 3 schematically shows a front view of the burner shown in figure 2.

The implementation of the invention

The following is a detailed description of the method according to the present invention. In the following description, the term "fine material" refers to the material supplied to the installation. By "finely divided material" is meant a material with particles having a diameter of less than about 10 mm, preferably less than 6 mm. This finely divided material is a by-product of the direct reduction of iron, the associated briquetting process, etc. In addition, according to a preferred embodiment of the present invention, the metal content of the finely divided material is at least 5%, more preferably at least 20%, most preferably at least 50% by weight.

By sponge iron of low density is meant a product having a porous structure with a large internal metal surface, which is the result of the removal of oxygen from the original ore. Also, high density iron agglomerates are a product in which the density of individual agglomerates is higher than about 7.

Figure 1 presents a General view of the installation, generally indicated by 10, for separating metallic iron from a finely divided oxide containing metallic iron and iron oxide. The installation is built around the burner 20 installed in the side wall of the furnace 30. The burner is the so-called oxygen-fuel burner, and thus the fuel is supplied to it through the first supply line 21, and oxygen through the second supply line 22. Here, oxygen is understood as gas with an O ₂ content above 21% and preferably so-called technical oxygen with an O ₂ content _of about 90-100%.

Finely dispersed material enters the burner through the third supply line 23. The third supply line 23 is connected to any feed device, generally indicated at 40.

According to the embodiment of the invention shown in FIG. 1, the furnace chamber 30 is a separate unit having a closing outlet 32 located adjacent to the lower part of the unit for discharging molten iron separated by this method, or, alternatively, an outlet 38, preferably a siphon type , for continuous release of liquid iron. The chamber has a separate outlet 39 for continuous or batch discharge of liquid slag.

An apparatus according to one embodiment of the invention also contains a water bath for cooling liquid iron to obtain high density agglomerates and a device 60 for unloading the product from the cooling bath. To obtain agglomerates of a suitable size and shape, a device 51 is provided for separating the liquid metal effluent into droplets of a suitable size, which device may be constructed according to known published methods.

The first embodiment of the burner 20, essentially known, will be described in detail below in connection with FIGS. 2 and 3, wherein FIG. 2 is a sectional view of the front of the burner and FIG. 3 is a front view. This burner is adapted for use with gas fuels such as propane, natural gas or butane, or with liquid fuels.

The burner 20 comprises a main part 24, to which the supply lines 21-23, shown in FIG. 1, are connected. Part 24 has a substantially circular cross section, as can be seen in FIG. 3, where the configuration of the supply lines 21-23 is shown in more detail. Fuel is supplied through a first supply line 21 formed by six equidistant pipes 21a-f located at a constant distance from the central axis of the main part 24. Oxygen is supplied along the annular outer part 22 and, thus, surrounds the fuel entering through the pipes 21a-f. Finally, the finely dispersed material enters through a pipe 23 located along the central axis of the burner.

As already mentioned, the burner 20 is installed in the side wall of the furnace 30. According to a preferred embodiment of the present invention, the burner may be inclined, i.e. can be located at different angles to the horizontal and vertical. Different orientations can be used to obtain the desired characteristics of the combustion process.

The method for separating metallic iron from a finely divided oxide containing metallic iron and iron oxide is described in detail below.

Finely dispersed material is transferred from the feeder 40 to the burner 20 by any suitable means, such as an inert or reducing carrier gas. The speed with which the finely dispersed material enters the burner is determined by the particular application.

The operation of the oxygen-fuel burner 20 is controlled by the amount of fuel and oxygen supplied through the first and second supply lines 21 and 22, respectively. Feeding lines are connected to fuel and oxygen sources (not shown), as usual.

Fuel, such as oil or gas, enters the feed pipes 21a-f, see FIG. 3, while the oxygen “shell” enters through the annular feed zone 22. The oxygen-fuel mixture creates a torch 25 with properties such as length , temperature, etc., which are regulated by the feed rate of fuel and oxygen. The higher the oxygen content, the higher the temperature, which theoretically can reach a flame temperature of approximately 2000 ° C or more. Thus, finely dispersed material is injected into the central part of the flame.

As can be seen in figure 2, the finely dispersed material is injected into the torch 25, where it is completely melted, thus allowing to separate the metal-containing finely dispersed material into metal and oxide parts. The separation of metal and oxide into two bulk phases, as described below, is due to the tendency of the systems to lower their total surface energy and due to the difference in the density of the two phases.

The melting is regulated by several parameters, from which the temperature and speed of the torch 25, stoichiometry, i.e. the ratio of the oxidizing gas to the additional fuel, the oxygen content of the oxidizing gas, the oxygen and additional fuel supply rate, the rate of introduction of the finely divided material and its characteristics, the passage time of the finely dispersed material through the torch, and the characteristics and configuration of the burner, such as a slope.

The required minimum power for the burner is calculated by the formula

P = k _min · θ (kW),

where k _min is at least 1500 kW · s / kg and preferably k _min is equal to 2500 kW · s / kg, and

θ (kg / s) is the mass flow rate of the introduced fine material.

A sign of the operation of the burner is that the burning intensity of the torch of the burner, defined as the power of the burner divided by the area of the smallest circle surrounding the base of the torch, is at least 10 kW / cm ² , and preferably the specified combustion voltage is at least 20 kW / cm ² .

The molten droplets fall to the bottom of the furnace 30, where they are added to the liquid charge. As can be seen in FIG. 1, the charge is divided into an upper layer 34 and a lower layer 36. In the upper layer, the oxide part of the material entering the furnace is collected in the form of liquid slag, while the liquid metal part is collected in the lower layer 36. Thus , and the metal and oxide parts can be removed from the furnace 30 by separate effluents for subsequent separate processing. This post-treatment preferably includes granulating the metal part by cooling the droplets of iron in the water bath, resulting in high density chunks, with at least 90% of the high density chunks having a preferred size of 10-40 mm. Cooling is preferably carried out using equipment according to the embodiment of the present invention shown in FIG. 1, but one skilled in the art will appreciate that similar granulation can also be carried out using any other means, such as dry granulation.

The method allows to process slag leaving the process in a liquid state, for subsequent use, for example, as iron-containing raw materials, which can be improved or directly used as slag raw materials, as a slag forming agent, as a material for filling road pavement, and t .d., and the processing includes measures such as granulation, slow cooling or mixing of the slag, for example, with lime or limestone for the manufacture of a slag-forming product, etc.

In its basic form, the method according to the present invention does not contain any active agents for carrying out chemical conversion. Thus, the method mainly separates metallic iron from oxide in a finely divided material containing metallic iron and iron oxide. However, it is preferable to add carbon-containing material together with the finely dispersed material and / or to conduct melting at a sub-stoichiometry, resulting in the reduction of iron oxide contained in the finely dispersed material.

The carbon-containing material can also be added either to the “hot residue” of liquid iron remaining in the furnace after unloading the metal part of the charge, or injected / loaded in an appropriate form separately into the process chamber. This reduction process increases the yield of iron from the overall process. It should be noted that, depending on the operating conditions and the properties of the finely dispersed material, the addition of carbon-containing material can also be used to increase the carbon content in a metal product, which increases its value.

Fine material may contain some carbon, sometimes up to about 4%. This carbon is usually found in the form of iron carbide (Fe ₃ C). Typically, the required amount of added carbon-containing material when applying the method according to the invention depends on the level of carbon in the finely divided material.

A preferred embodiment of the method according to the present invention is described herein. The specialist is clear that it may be amended within the framework defined by the attached claims. Also, although the fine material is described as substantially dry, according to an alternative embodiment of the present invention, the fine material forms part of a suspension, which may consist of fine sponge iron mixed with an organic liquid. In addition, a separate furnace unit is presented here. The method according to the present invention is equally applicable to other types of furnaces, such as electric arc furnaces, induction furnaces, baffle furnaces, electric furnaces, blast furnaces, cupola furnaces, rotary kilns, converters, etc.

Also in the described embodiment, the burner is located in the side wall of the furnace. However, it is understood that other relevant positions are possible, for example, in the upper part of the furnace. In this case, finely dispersed material can be injected, for example, between three torches of the burner.

The document presents a burner of a specific configuration. It is understood that a burner of any suitable configuration can be used, with a different number of pipes, etc.

Claims (11)

1. A method of converting finely dispersed sponge iron of low density into high density agglomerates with an increased content of metallic iron, suitable for use as a charge for the production of steel, which comprises supplying finely dispersed sponge iron to a torch of an oxygen-fuel burner having a combustion tension that ensures complete melting of finely dispersed sponge iron, and generating power P, at least equal to P = k _min · θ (kW), where k _min is at least 1500 kW · s / kg and θ ( kg / s) represents the mass flow rate of the introduced finely dispersed sponge iron, with the separation of the metal-containing finely dispersed sponge iron into metal and oxide parts, the separation of two phases into liquid slag and liquid iron in an appropriate furnace or chamber, and the conversion of liquid iron into high-density agglomerates. 2. The method according to claim 1, characterized in that it contains an additional stage of processing liquid slag for subsequent use. 3. The method according to claim 1 or 2, characterized in that the liquid iron is converted into high density agglomerates by separating the output liquid iron stream into droplets of a suitable size and subsequent cooling of these drops in a cooling medium. 4. The method according to claim 3, characterized in that at least 90% of the obtained pieces of high density have a size of from 10 to 40 mm 5. The method according to claim 1, characterized in that the finely dispersed sponge iron has a diameter of less than about 10 mm, and preferably less than 6 mm 6. The method according to claim 1, characterized in that finely dispersed sponge iron is a by-product of the direct reduction of iron. 7. The method according to claim 1, characterized in that the metal content in the finely dispersed spongy gland is at least 5%, more preferably at least 20% and most preferably at least 50 wt.%. 8. The method according to claim 1, characterized in that it does not include active agents for the implementation of chemical conversion. 9. The method according to claim 1, characterized in that together with finely dispersed sponge iron, carbon-containing material is added to increase the yield of iron and / or increase the carbon content in the metal product. 10. The method according to claim 1, characterized in that the burner generates a power P of at least equal to P = k _min · θ (kW), where k _min is at least 2500 kW · s / kg and θ (kg / s ) represents the mass flow rate of the injected finely dispersed sponge iron. 11. The method according to claim 1, characterized in that the flame burning intensity, defined as the burner power divided by the area of the smallest circle surrounding the base of the flame, is at least 10 kW / cm ² , preferably at least 20 kW / cm ² .

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