KR100660658B1 - Method for accelerating separation of granular metallic iron from slag - Google Patents

Abstract

SUMMARY OF THE INVENTION An object of the present invention is to promote the separation of granular metal iron and slag as a by-product produced by reducing and melting raw material agglomerates containing iron oxide-containing materials and carbonaceous reducing agents, so that the slag is sufficiently separated and removed, and the metal having excellent quality of iron. It is to provide a method for obtaining iron.

The present invention is a method for producing granular metal iron by reducing and melting a raw material compact including an iron oxide-containing material and a carbonaceous reducing agent, and rapidly quenching a mixed solid product of granular metal iron produced by the reduction melting and slag as a by-product. It is a method for promoting separation of granular metal iron and slag with the main purpose of promoting the separation of the granular metal iron and slag as a by-product.

Description

Method for promoting separation of granular metal iron and slag {METHOD FOR ACCELERATING SEPARATION OF GRANULAR METALLIC IRON FROM SLAG}             

The present invention relates to a method for promoting the separation of the resulting granular metal iron and slag as by-products when metal iron is produced by reducing and melting a raw material compact including an iron oxide containing material and a carbonaceous reducing agent. More specifically, the mixed raw material of granular metal iron and slag as a by-product produced by supplying the raw material compact to a reduction smelter and reducing, melting, and agglomerating iron oxide in the mass is easily formed into granular metal iron and slag. It is about an improved method to separate easily.

Metallurgical iron with low iron quality (SiO ₂ , Al ₂ O ₃ , CaO, etc. contained as gangue component in iron ore used as raw materials, ash in carbonaceous materials, etc.) Supplying a large amount of slag of iron), not only adversely affects the operability of the electric furnace by increasing the amount of slag, but also lowers the iron yield due to the incorporation of iron into the slag, increases in the energy source unit, Many problems arise, such as a decrease in productivity. Therefore, there is a demand for metal iron having excellent iron quality with low content of slag as a raw material for molten iron. As a method for producing such high-quality metal iron, as described in US Pat. No. 3,443,931 or the like, as described in US Pat. Various methods are known for producing metal iron with excellent iron quality by mixing carbonaceous materials with powdered iron oxide and forming them in a compact or pellet form, and heating and reducing them on a rotary furnace to produce metal iron. It is.

For example, Japanese Patent Application Laid-Open No. 2000-144224 is a steelmaking method for reducing and melting raw material compacts containing iron oxide-containing materials such as iron ore or iron oxide and carbonaceous reducing agents such as coke to obtain high purity metal iron. And the like. As also disclosed in this publication, in the technique of reducing and melting raw material compacts to obtain granular metal iron by using a mobile hearth type reduction melting furnace, iron oxide in the compacts is maintained while the raw material compacts are kept in a solid state. It is then reduced, and the slag as a by-product and iron are melted and agglomerated, respectively. Subsequently, when the molten metal iron and molten slag are cooled (eg, first cooling to cool to about 1,100 to 900 ° C.), the molten metal iron and molten slag are solidified (“granular iron” and “slag”. Particles, respectively). After the cooling and solidification, the granular metal iron and slag particles are discharged to the outside of the furnace. On the other hand, after being discharged, the granular metal iron and slag particles are naturally cooled (second cooling). In addition, the granular metal iron and slag particles are selected by any sorting means, and only the granular metal iron is used as a dissolving raw material such as steelmaking furnace.

In the metal iron manufacturing method as described above, since the cooling solidifies the metal iron and the slag, the first cooling step of cooling to below the freezing point thereof, and the second cooling further reducing the temperature for subsequent conveyance or sorting of the metal iron. Are divided into stages.

Most of the first cooling step is carried out in the reduction melting furnace, but after the first cooling, the slag particles are often present in an unseparated state (referred to as "mixed solids") to which the granular iron is attached. In addition, in the second cooling step, which is naturally cooled outside the furnace, the metal iron and the slag are separated, but not enough. For this reason, only granular metal iron was not effectively separated by magnetic screening or a sieve, so that a considerable amount of slag could not be prevented from being mixed with the granular metal iron. For this reason, although the metal iron itself has high purity, the amount of generation of molten slag in the steelmaking furnace is increased by the slag component incorporated in a state where it is not completely separated, thereby affecting operability and product quality. For this reason, there is a demand for a technique capable of effectively screening slag as metal iron and by-products in a state before separation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to promote the separation of slag as a by-product and granular metal iron produced by reduction melting of a raw material compact including an iron oxide-containing material and a carbonaceous reducing agent. The present invention provides a method for obtaining metal iron of good quality in which slag is sufficiently separated and removed.

Summary of the Invention

The present invention can solve the above problems as described below. That is, in the method for producing granular metal iron by reducing and melting raw material compacts containing an iron oxide-containing material and a carbonaceous reducing agent, a mixed solid product of granular metal iron produced by the reduction melting and slag as a by-product is quenched. A method for promoting separation of granular metal iron and slag with a main purpose of promoting the separation of the granular metal iron and slag as a by-product. In practicing the method of the present invention, it is advocated that the quenching is carried out using a refrigerant. It is also advocated that the quenching is carried out at a cooling rate of preferably at least 250 ° C./min, more preferably at least 350 ° C./min, at least in the range from the solidification temperature of the granular metal iron to 150 ° C. It is also a preferred embodiment to use water as the refrigerant in the present invention and to stop the quenching when the temperature of the metal iron reaches 150 ° C, to stay in the granular metal iron and to dry the attached moisture.

1 is a schematic explanatory diagram showing a circular moving hearth type reduction melting furnace to which the present invention is applied.

2 is a cross-sectional view taken along the line A-A in FIG.

FIG. 3 is an explanatory cross-sectional view illustrating the development of the moving furnace in FIG. 1.

4 is a schematic explanatory diagram showing cooling of a mixed solid by water spray.

5 is a schematic explanatory diagram showing cooling of the mixed solids by dipping.

6 is a schematic explanatory diagram showing cooling of a mixed solid with nitrogen gas.

7 is a schematic explanatory diagram showing cooling of a mixed solid with water.

The present inventors conducted extensive research to solve the problems of the prior art, and as a result, mixed solids of granular metal iron and slag as by-products produced by reducing and melting raw material agglomerates containing an iron oxide-containing material and a carbonaceous reducing agent In the case of quenching, it was found that the separation of the granular metal iron and slag as a by-product was significantly promoted, thus completing the present invention.

In the present invention, the raw material compact includes an iron oxide-containing material such as iron ore, iron oxide, or a partial reducing substance thereof, and a carbonaceous reducing agent such as coke or coal, and may include any additives or the like as necessary. In addition, the form of a raw material compact is not specifically limited, The molded object, such as pellet shape and briquette shape, can be illustrated. Moreover, also about the shaping | molding method of a raw material compact, arbitrary methods can be applied according to the shape of a compact. In addition, the mixing ratio of the iron oxide containing material and the carbonaceous reducing agent is not particularly limited, and may be selected in an appropriate mixing ratio according to the purpose. The size of the raw material compact is not particularly limited either.

Hereinafter, although granular metal iron is produced by reducing and melting such raw material compacts, the specific reduction melting method is not particularly limited, and it is preferable to use a known reducing melting furnace. In the present invention, the present invention will be described by illustrating a method of producing metal iron using a moving hearth type reduction melting furnace, but the present invention is not limited to the following description and illustrated examples. Hereinafter, with reference to the drawings showing a specific configuration will be described in detail.

1 to 3 are schematic explanatory diagrams showing an example of a moving hearth type reduction melting furnace developed by the present inventors to which the present invention is applied, showing that it is a domed structure having a donut-shaped rotating mobile phase, and FIG. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a schematic cross-sectional explanatory view showing in a rotational movement direction of the rotary hearth in FIG. 1 for clarity, and FIG. 2 is a furnace body which covers the said rotary hearth, and the rotary hearth 1 is comprised so that rotation drive at a suitable speed by the drive apparatus which is not shown in figure is possible.

However, the configuration of the moving hearth type reduction melting furnace to which the present invention is applied is not limited to the shape and structure as shown in Figs. 1 to 3, but includes a moving hearth as a component, for example, a straight image type. grate type) can be effectively used in mobile hearth type reduction melting furnace having a different structure.

The combustion burner 3 is arrange | positioned at the suitable place of the wall surface of the furnace 2, and the heat of combustion of the said combustion burner 3, and its radiant heat are transmitted to the raw material compact on the rotary hearth 1, and the said compacted material Heat reduction is performed. The illustrated furnace body 2 represents a preferred embodiment, in which the interior of the furnace body 2 has three partition walls K ₁ , K ₂ , K ₃ , in which the first zone Z ₁ and the second zone Z ₂ . Is divided into a third zone (Z ₃ ) and a fourth zone (Z ₄ ), and on the most upstream side of the rotational direction of the furnace body (2), the raw material supply means (4) is arranged in the opposite direction of the rotary hearth (1). , The discharging means 6 is provided on the most downstream side in the rotational direction (since it is actually provided on the vertical upstream side of the supply means 4).

In operating this reduction melting furnace, the rotary hearth 1 is rotated at a predetermined speed, and the raw material compact is supplied from the supply means 4 to the appropriate thickness on the rotary hearth 1. The raw material mass supplied to the hearth 1 receives the heat of combustion and radiant heat by the combustion burner 3 during the process of movement in the first zone Z ₁ , and the carbonaceous material in the mass and the combustion thereof. By the produced carbon monoxide, the iron oxide in the compact is heated and reduced while being kept in a solid state. Subsequently, the metal iron produced by further heat reduction in the second zone Z ₂ and almost completely reduced is carburized by melting in a third zone Z ₃ by further heating under a reducing atmosphere. In the molten slag as a by-product and molten slag thus produced, molten slag is present on the molten iron due to the difference in specific gravity. These molten metal iron and molten slag are cooled to a solidification point or lower by any cooling means C in the fourth zone Z ₄ , respectively, and solidified, and are continuously discharged by discharge means 6 provided downstream thereof. . In addition, molten metal iron and molten slag are separated by the cooling and solidification, respectively, to form granular metal iron and slag particles, but the slag and metal iron are not separated, and the granular metal iron (mixed solids) with slag is also present. do. Thus, the granular iron, slag particles and mixed solids are discharged out of the furnace. In addition, the mixed solids and the like thus discharged (hereinafter, also referred to as "mixed solids and the like" means granular metal iron and slag particles also included) are in a relatively high temperature state (eg, solidification temperature to 900 ° C). )to be.

In the present invention, by quenching the mixed solids discharged at a relatively high temperature state, by using the difference between the shrinkage rate of the metal iron and the slag shrinkage rate constituting the mixed solids to promote the separation of the iron and slag, the slag component is almost It is separated into granular metal iron and slag particles (not composed of slag components such as SiO ₂ , Al ₂ O ₃ , and CaO, which are included as gangue components in iron ore used as raw materials or ash in carbonaceous materials, etc.). .

In the present invention, "quenching" means faster cooling than when the mixed solids are naturally cooled in the atmosphere. However, the rapid acceleration of the mixed solids, including the use of a coolant, to accelerate the separation of metal iron and slag is more effective. As it is increased, it is advocated. In the case of quenching at a rate of 250 ° C./min or more, the contact portion between the metal iron and the slag is caused by a sudden change in the shrinkage rate of the metal iron constituting the mixed solids and the shrinkage rate of the slag (that is, the difference in thermal expansion rate). It is preferable because warpage occurs in order to promote separation of iron and slag. More preferred cooling rate is at least 350 ° C / min. In addition, the cooling rate is preferably calculated by continuously measuring the temperature change of the mixed solids discharged to the outside of the furnace.

Although the quenching method itself is not specifically limited, It is preferable to quench using liquid and / or an inert gas as a refrigerant. In addition, the quench by liquid is faster than the quench by inert gas, and since the cooling rate is faster and a higher separation effect is acquired, it is advocated. The liquid used in this case is not limited, and also the presence or absence of additives in the liquid is not limited. It is preferable to use water from a viewpoint of economy, safety, and cooling efficiency. Moreover, it does not specifically limit also as an inert gas. It is preferable to use nitrogen gas from the viewpoint of economy and safety.

For example, in the case of quenching with water, the water may be sprayed onto the mixed solids while controlling the supply amount by any spraying means such as spraying to perform the desired cooling rate. For example, as illustrated in FIG. 4, the mixed solids and the like discharged from the moving hearth type furnace are mounted on the moving means 9 such as a belt conveyor through the supply pipe 8 and moved, and an arbitrary number in any section. It is preferable to spray water toward the mixed solid matter etc. from the spray means 11 provided. By the spraying, the mixed solids are quenched, and the separation of slag and iron is promoted by the difference in shrinkage rate, thereby obtaining granular iron and slag particles. Alternatively, the mixed solids may be quenched so as to achieve a desired cooling rate by storing water in the cooling tank and adjusting the water temperature by supplying and discharging water. For example, as illustrated in FIG. 5, mixed solids and the like discharged from the moving hearth furnace 7 are introduced and immersed in a cooling tank 13 filled with water 12 through a supply means 8 such as a supply pipe. It is preferable to make it take from a cooling tank by arbitrary carrying out means, such as a conveyor, after making it quench to predetermined temperature. The quenching method in which the mixed solids are immersed in water is preferable because the cooling rate is faster than the quenching method in which water is sprayed, and thus a large difference in shrinkage rate is obtained.

Although not shown, in the case of quenching using an inert gas such as nitrogen gas, the inert gas may be injected directly into the mixed solid, or the mixed solid may be exposed under an inert gas atmosphere.

In addition, the quenching method is not limited to these, and can also be carried out by combining the quenching method as appropriate. For example, the mixed solids may be quenched by spraying water in a nitrogen gas atmosphere, or the mixed solids may be quenched under a nitrogen gas atmosphere after spraying water.

In addition, the higher the temperature of the mixed solids at the start of quenching, the greater the separation effect by quenching. Therefore, it is preferable to quench the mixed solids in the high temperature state immediately after being discharged to the outside of the furnace. On the other hand, since the temperature of the mixed solids at the time of discharge varies depending on whether or not the mixed solids are cooled in the furnace, the specific quenching start temperature is not particularly limited, but the mixed solids discharged to the outside of the furnace are usually in a solid state. Therefore, in the preferred quenching temperature range, it is preferable to quench at least a part of the metal iron solidification point (about 1,280 ° C) to 150 ° C. This is because even if the liquid is quenched at a temperature of less than 150 ° C., sufficient thermal impact may not be given to the mixed solids and sufficient separation effect may not be obtained.

In addition, the term “at least a portion” within this range means that it is not necessary to continue quenching over the entire temperature range. For example, when performed at a cooling rate of 250 ° C./min or more at at least a portion of the metal iron freezing point to 150 ° C., rapid cooling of some temperature sections within the temperature range to a cooling rate of 250 ° C./min or more results in a different temperature range. This means that it can be cooled, and does not mean that the quench should be continued in the range of the metal iron freezing point to 150 ℃. In addition, rapid cooling can be continued beyond the said range, and it does not mean that rapid cooling must be stopped at the time which reached 150 degreeC. For example, it is preferable to quench to a metal iron freezing point to 150 degreeC, and to continue quenching even at the temperature below 150 degreeC, and to stop quenching at the point which reaches desired temperature.

On the other hand, the effect of promoting the separation by quenching used in the present invention is to use the torsional breakage of the metal iron-slag interface due to the heat shock by quenching, as described above, the quenching time can be very short, for example, for several seconds Sufficient cooling can achieve the purpose. In particular, in the case of quenching using a refrigerant, the mixed solid is quenched at the moment when the mixed solid comes into contact with the refrigerant to obtain a separation promoting effect. For example, when the mixed solids are immersed in water, at the moment of contact with the water, the temperature of the mixed solids decreases rapidly, causing torsional breakage of the metal iron-slag interface to be separated. Of course, since the quenching of the mixed solids continues during the immersion, the difference in shrinkage rate of the metal iron-slag interface of the mixed solids remaining in the unseparated state is increased, so that a separation promoting effect is further obtained, and the metal iron-slag unseparation rate is obtained. Is lowered.

In addition, in the present invention, the water is used for the quenching, and when the temperature of the metal iron reaches 150 ° C, the quenching is stopped, followed by natural cooling. That is, after cooling the mixed solids and the like to 150 ℃ by using water, and then naturally cooling after stopping the quenching (stopping contact with water), it is attached to the metal iron by the natural properties of the metal iron itself Since the water can be evaporated, the metal iron can be dried without providing a drying means such as a dryer.

As described above, the method of the present invention has been described in the case where the mixed solids are quenched together with the granular iron and slag particles discharged from the melt reduction furnace, but any fractionation means ( Sieve or magnetic screening device, etc.) to separate the metal iron and slag, and selectively collect granular iron, slag particles, and mixed solids, respectively, to selectively collect mixed solids alone, or both mixed solids and granular metal irons. The method of the present invention can also be applied, and the method of the present invention can be applied depending on the presence or absence of granular metal iron and slag particles.

In addition, according to the method of the present invention, the metal iron and slag constituting the mixed solids are separated into granular metal iron and slag particles, respectively, and then granular metal iron and slag are removed by any sorting means (sieve or magnetic screening device, etc.). By selectively collecting the slag particles, it is possible to obtain a metal iron raw material having a very low content of slag components having an iron purity of about 95% or more, more preferably about 98% or more.

Hereinafter, the method of the present invention will be described based on examples, but the present invention is not limited only to the examples, and may be appropriately changed in accordance with the spirit and the following description.

The raw material compact including iron ore and coal is supplied to the mobile hearth type reduction melting furnace shown in FIGS. 1 to 3 and heated and reduced in a state of maintaining the solid state by the combustion heat and radiant heat generated by the combustion burner ( Furnace internal temperature: 1300 ° C.). In addition, a mixture of the metal iron produced by heating and melting in a reducing atmosphere and slag as a by-product is cooled to 1,000 ° C. in the furnace, and the granular metal iron, slag particles, and mixed solids solidified by the cooling are moved downstream in the roadbed direction. Ejected by means of ejection means mounted on the. The discharged mixed solids and the like were introduced into a cooling tank to which the refrigerant shown in Table 1 was supplied through a supply pipe to perform quenching. The case of using nitrogen as the refrigerant is shown in FIG. Nitrogen gas was always supplied to the cooling tank (flow rate: 10 Nm ³ / hr), and the mixed solids and the like were quenched while adjusting the flow rate of nitrogen gas such that the cooling rate was 250 ° C / min. In addition, the flow rate of nitrogen gas was adjusted by exhausting it from the exhaust pipe 14. When the temperature of the feed, such as metal iron, has decreased to room temperature, take the metal iron from the cooling tank as needed to determine the total amount of mixed solids (see "mass of mixed solids" and "unseparated slag" in Table 1). It was. In the case of nitrogen cooling, the thermocouple was inserted into the storage portion of the mixed solid accumulated in the cooling tank to measure the temperature. The case of using water as a refrigerant is shown in FIG. 7. Water was previously stored in the cooling tank, and the supplied mixed solids and the like were cooled. In addition, when the cooling rate by immersion was measured separately, the cooling rate was 350 degreeC / min. When the temperature of the feeds such as the mixed solids was reduced to room temperature, metal iron was taken from the cooling tank as needed to measure the total amount of the mixed solids. In addition, in the case of water cooling, the cooling rate by immersion was measured separately. A thermocouple was inserted into a storage part of the mixed solid heated to 1,000 ° C. in a heating furnace, and the cooling rate was measured by immersing it. The results are shown in Table 1.

As shown in Table 1, the slag could be separated and removed from the mixed solids using nitrogen or water as the refrigerant. In addition, since the case of using water as the refrigerant shows a lower unseparation rate than when nitrogen is used as the refrigerant, it can be seen that the quench means for immersion is a more preferable quench means.

Comparative example

Granular metal iron was prepared by mobile hearth type reduction melting under the same conditions as in the above examples. The mixed solids discharged were naturally cooled to room temperature in the air, but the unseparation rate (15%) was very high.

As described above, according to the method of the present invention, the metal iron and slag constituting the mixed solid discharged to the outside of the furnace can be easily separated. According to the present invention, a metal slag raw material having no slag and high iron purity can be obtained. Thus, by constructing a continuous system using this as a steelmaking raw material, molten steel of stable quality can be increased while reducing power units such as an electric furnace. It can manufacture with productivity.

Claims (5)

A method of producing granular metal iron by reducing and melting a raw material compact including an iron oxide-containing material and a carbonaceous reducing agent, wherein the mixed solid product of the granular metal iron produced by the reduction melting and slag as a by-product is quenched to A method for promoting separation of granular iron and slag, characterized by promoting the separation of the granular iron and slag as a by-product. The method of claim 1, Method for promoting separation of granular metal iron and slag carried out by a quench refrigerant. The method of claim 1, A method for facilitating separation of granular iron and slag, wherein the quenching is carried out at a cooling rate of at least 250 ° C / min at least in the range of solidification temperature to 150 ° C. The method of claim 3, wherein A method for promoting separation of granular metal iron and slag in which quenching is performed at a cooling rate of 350 ° C./min or more. The method according to any one of claims 1 to 4, A method for promoting separation of granular metal iron and slag, which uses water as a refrigerant and stops quenching when the temperature of the granular metal iron reaches 150 deg. C, stays in the granular metal iron and dries the attached moisture.

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