JP2005146332A - Material for modifying blast furnace slag and modifying method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material for modifying blast furnace slag, which improves the quality of the blast furnace slag after having been solidified by modifying molten blast furnace slag without operation impediments, and to provide a modifying method therefor. <P>SOLUTION: In the process of adding a modifying material to the molten blast furnace slag, and then cooling and solidifying it into the blast furnace slag, the modifying material is a mixture of coal ash and a substance containing iron oxides. Then, the modifying material inhibits the production of a sintered compact. The modifying method comprises adding 1 to 30 mass% modifying material to the molten blast furnace slag, and then annealing or water-granulating it into the blast furnace slag. Thereby, the blast furnace slag after having been cooled and solidified becomes dense, acquires increased specific gravity, has higher value added, and expands the field of the applications. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a reforming material and a reforming method for reforming a cooled and solidified blast furnace furnace.

Conventionally, a molten blast furnace slag discharged from a blast furnace has been subjected to a slow cooling process in which it is gradually cooled and solidified, or a molten blast furnace slag is rapidly cooled by water, and then granulated.
Although the former was used mainly as a roadbed material as a slow cooling rod, since it has many pores and a small specific gravity, a dense, high specific gravity and hard blast furnace slow cooling rod has been demanded.
In addition, the latter water granulation has been mainly used as a raw material for cement, but as a new application, a technique for building in hard water granulation as “sand substitute” has been desired. That is, there has been a demand for water granulation with less bubbles and high density. To solve these problems, coal ash (commonly called fly ash, mainly composed of SiO ₂ and Al ₂ O ₃ ), which is industrial waste discharged from thermal power plants, is added to the molten blast furnace slag. Attempts have also been made to modify and use blast furnace slow cooling or granulated blast furnace as an aggregate for artificial civil engineering.

As an example of this, as proposed in Patent Document 1 and Patent Document 2, coal ash alone (powder) was injected into the hot metal of the hot metal and floated on the hot metal while using the heat of the hot metal. There is a method of melting the coal ash into the molten blast furnace slag and making slow-cooled slag or water granulation.

JP 2001-151540 A JP 2001-151546 A

However, in the method proposed in Patent Documents 1 and 2 above, since coal ash is added to the molten blast furnace slag alone, the coal ash lump adheres to and grows on the refractory at the location where the ash is added, such as firewood and pan. The operation of the ash furnace is extremely hindered, and the adhering sintered deposit mainly composed of coal ash (hereinafter also referred to as “sintered body”) does not dissolve at all in the molten blast furnace soot. The soot reforming could not be continued. In addition, even if the operator adds the sintered body to which the operator has adhered, the lump-shaped sintered body that has been pushed down even after the blast furnace is cooled and solidified is mixed as a foreign substance in the blast furnace and exhibits a red or black color. In addition to being shunned from the above, quality problems such as pulverization of these massive sintered bodies in the blast furnace pulverization process and hindering the particle size adjustment have occurred.

The present invention has been made in order to solve the above-mentioned problems, and means 1 includes adding a modifier to the molten blast furnace slag and then cooling and solidifying it to form a blast furnace slag. It is a reformer of a blast furnace soot that is a mixed granular material with an iron oxide-containing material containing iron oxide.
Furthermore, the means 2 is characterized in that T. in the iron oxide-containing material with respect to the coal ash. The blast furnace soot reformer according to means 1, wherein the iron oxide-containing material is blended so that the amount of Fe is 5 to 50% by mass.
Means 3 is that the iron oxide-containing material is T.P. The reformer for blast furnace dredge according to means 1 or 2, which is any one of dust, sludge, metal refining waste, and minerals containing Fe of 30% by mass or more.
Means 4 is a blast furnace slag that is obtained by adding 1 to 30% by mass of the modifier according to any one of the means 1 to 3 with respect to the molten blast furnace slag, and then gradually cooling or granulating the blast furnace slag. This is a modification method.
Means 5 adds 1 to 30% by mass of the modifying material to the molten blast furnace at one place or a plurality of places, and the addition amount per one place of the addition is 10% by mass or less. It is a method for reforming a blast furnace soot described in means 4.

In addition, as the iron oxide-containing material, iron ore powder, steel refining dust (dust generated from hot metal pretreatment furnace, converter, electric furnace, etc.), blast furnace dust collection dust (containing iron oxide powder and carbon powder), There are rolled sludge, bauxite pulverized dust, red mud (a waste generated during alumina refining and containing 35-50% iron oxide), and the particle size is preferably 2 mm or less from the viewpoint of solubility. Of course, a mixture of these may be used.
As the component of the coal ash, mass% of the sum of SiO ₂ and Al ₂ O ₃ which is a main component is preferable not less than 65%. Because both SiO ₂ and Al ₂ O ₃ have the effect of melting in the blast furnace soot and lowering the melting point of the blast furnace so as to solidify at a lower temperature, degassing of nitrogen gas, sulfurous acid gas, etc. until solidification This is because the blast furnace becomes more dense and strong.

According to the present invention, the reformer can be easily added to the molten blast furnace slag without any operational trouble and can be smoothly dissolved in the molten blast furnace slag, so that the blast furnace slag after cooling and solidification becomes dense and the specific gravity increases. As a result, the added value of the blast furnace is increased and the use is expanded, and the effect brought to this field is extremely large.

Hereinafter, a blast furnace slag modifier and a reforming method thereof according to an embodiment of the present invention will be described in detail.
When the present inventors add coal ash alone to the molten blast furnace slag, as described above, the problem of adhesion of coal ash to the refractory material becomes obvious, and the cause of the coal ash in that form becoming insoluble in the molten blast furnace slag In order to investigate the above, an experiment was conducted in which coal ash was added alone to the molten blast furnace in a small crucible.
In this experiment, the blast furnace slag discharged from the blast furnace was melted in a small crucible, and coal ash having the components shown in Table 1 was added in an amount corresponding to 6% by mass of the molten blast furnace slag, and the state of melting was observed. did. As a result, the added coal ash did not readily melt in the molten blast furnace slag, but grew in a lump and adhered to the crucible wall or remained floating on the molten blast furnace slag.

In order to elucidate the mechanism of this phenomenon, the present inventors collected an undissolved portion (crucible adhering portion) of the added coal ash, and performed an optical microscope survey and an X-ray diffraction survey.
From the optical microscope investigation, this undissolved coal ash is in the form of “insulated brick” with a lot of pores. Further, from the X-ray diffraction investigation, (1) Mullite (3Al ₂ O ₃ · 2SiO ₂ : melting point 1934 ° C.) and (2) Cristobalite (SiO ₂ : melting point 1734 ° C.) were present. That is, it was found that when coal ash is added to the molten blast furnace slag, it is heated by the heat of the molten blast furnace slag and the extremely high melting point crystals of the above (1) and (2) are generated.

These high-melting-point crystals (solid) grow as a sintered body by using a melt in which coal ash is partly melted as a binder, grow as a sintered body, adhere to refractories, and form pores in the form of “insulating bricks” It became clear that the above-mentioned sintered body lump remained undissolved due to heat transfer rate control because of its massive shape. Since these sintered bodies contain a large amount of the above-mentioned crystals having a very high melting point, it has also been found that the sintered bodies themselves are no longer soluble in a molten blast furnace at about 1500 ° C.

Therefore, the present inventors have repeated experiments and studies on measures for preventing the high melting point crystals of the above (1) and (2) from being formed. As a result, it was discovered that when iron oxide was added to coal ash, the coal ash was smoothly dissolved in the blast furnace soot and the formation of the sintered body containing the above (1) and (2) was hardly recognized.
By adding iron oxide, it becomes a mixture of coal ash and iron oxide, and the components of this mixture become a ternary oxide of SiO ₂ —Al ₂ O ₃ —iron oxide. The effects of suppressing the formation of the high melting point crystals of the above (1) and (2) and the growth of those sintered bodies due to the SiO ₂ —Al ₂ O ₃ binary oxide formed upon addition It turned out to be due to. That is, the above-mentioned sintered body is contained in a blast furnace furnace that has been cooled and solidified after adding coal ash containing iron oxide (for example, sintered dust collecting dust containing components shown in Table 2 as an iron oxide-containing material) as a modifier. It was revealed by microscopic observation that the additive was not formed and the additive was uniformly dissolved in the molten blast furnace.
Further, it was confirmed that even when the modifying material was added after being formed into granules having a particle diameter of about 1 to 10 mm, it was dissolved in the molten blast furnace without any problem just like the powder.

In addition, the blast furnace slag cooled and solidified after the addition of the above-mentioned reformer becomes a dense slag with a high density and a high specific gravity with a very small number of bubbles compared to a conventional blast furnace slag without the addition of this reformer. It has been found that it is of high quality and can be used for new uses such as landscape materials.
Note that the above T.A. Fe is the Fe content excluding metallic Fe content, and is the total amount of Fe content in the form of iron oxide (FeO, Fe ₃ O ₄ , Fe ₂ O ₃ ).

Furthermore, in order to clarify the conditions that the present inventors should have in the modifier, which is a blended granule of coal ash and iron oxide, to express the effect of the iron oxide-containing material, Systematic experiments were repeated using the small crucible described above.

First, T.I. in the iron oxide-containing material to be blended with coal ash. An experiment for confirming the state of formation of the sintered body was performed using modifiers with various ratios of Fe content, and the results shown in FIG. 1 were obtained.
Incidentally, the coal ash used for the modifier at this time has the components and contents shown in Table 1 above, and further, as iron oxide, sintered dust collection dust having the components and contents shown in Table 2 above. Therefore, the temperature of the molten blast furnace to which this modifier was added was 1450 ° C. Further, the amount of the modifier added to the molten blast furnace slag was 10% by mass.

As can be seen from FIG. 1, the iron oxide containing T.I. When the blending ratio of Fe is less than 5% by mass, the growth of the sintered body of the high melting point crystal generated from the SiO _{2 component} and the Al ₂ O ₃ component in the coal ash cannot be suppressed, There is a large proportion of coal ash that remains on the upper surface of the molten blast furnace slag without adhering or lump and remains as undissolved, which is undesirable in terms of operation or blast furnace slag quality. On the other hand, if the blending ratio exceeds 50% by mass, the above-described suppression of the growth of the sintered body by the iron oxide mixing can be obtained, but the effect is saturated, and rather slag discoloration and the like are caused by the excessive mixing of iron oxide.
Therefore, the T.O. The blending ratio of Fe is preferably 5 to 50% by mass.

Further, the T.I. The present inventors repeated experiments using various oxide-containing materials because there is a concern that if the amount of Fe is too small, it is necessary to add a large amount of modifier to the molten blast furnace furnace. As a result, the T.O. It has been found that Fe is preferably 30% by mass or more. If it is less than 30%, components other than iron oxide in the reforming material are mixed in a large amount in the molten blast furnace so that the temperature drop when the modifying material is added to the blast furnace becomes large, and the original coal ash is mainly used. The effect as a modifier as a component cannot be sufficiently obtained, which is not preferable.

Moreover, FIG. 2 is a figure which shows the relationship between the addition ratio of the modifier of this invention with respect to a molten blast furnace slag, and the absolute dry specific gravity measured value of the blast furnace slag after cooling solidification. If the modifier addition ratio is less than 1% by mass, the increase in specific gravity of the blast furnace after cooling and solidification is slight, but if it exceeds 1% by mass, the effect of the modifier is manifested and the specific gravity increases significantly. . However, when the addition ratio of the reforming material exceeds 30% by mass, the specific gravity of the blast furnace iron increases, but the temperature of the molten blast furnace iron is significantly lowered due to the sensible heat of the reforming material, which hinders operation. That is, although there is no generation of a refractory crystal, the tendency to adhere to the refractory of the molten blast furnace becomes strong due to the low temperature, and the load of refractory maintenance after operation increases. Therefore, the modifier addition ratio of the present invention relative to the molten blast furnace is 1 to 30% by mass.
In addition, the vertical axis | shaft of FIG. 2 measured the bulk specific gravity after drying a blast furnace slag, and the merit that water absorption is also correspondingly reduced, so that an absolute dry specific gravity becomes large.

When there is a large amount of modifier added, in order to increase the contact area between the molten blast furnace slag and the reformer rather than concentrated addition at one location, there are multiple locations where the modifier is added to the molten blast furnace slag. It is preferable from the viewpoint of preventing the adhesion to the refractory due to the local temperature drop and accelerating the dissolution of the added modifier. The addition amount at one place is preferably 10% by mass or less with respect to the blast furnace.

The addition of the modifying material to the molten blast furnace can be performed anywhere as long as the blast furnace is in a molten state from the outlet hole of the blast furnace to the cooling pit. For example, a large bowl from the tap hole to the skinmer (a device that separates the molten iron and the blast furnace), a nose cake after separation, or a ladle for recovering the granular iron in the molten blast furnace cake (also referred to as a floating bowl) In addition, in the case of gradually cooling, it may be added to the pit or the pit. It may be added to the ladle that transports the molten blast furnace. A plurality of these locations may be used. As an addition method, powder may be added from above or may be blown into slag in a powder state.
In the embodiment, sintered dust collection dust is used as the iron oxide-containing material, but any of dust, sludge, waste during metal refining, and mineral may be used.

Further, when 2 to 12% by mass of carbon is contained in the reforming material, iron oxide and carbon in the sintered dust collection dust react to be oxidized to CO gas or CO ₂ gas to generate heat. This contributes to heating at the location where the modifier is added, facilitates melting of the modifier, and also enjoys the secondary effect that the generated gas promotes the reaction by stirring the dissolution reaction interface. It is preferable because it can be done.
This finding was confirmed not only in a laboratory test using a small crucible but also in an actual furnace test.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG.
FIG. 3 shows that a modifier made of coal ash mixed with iron oxide-containing material is added to the flow path until the molten blast furnace slag discharged from the blast furnace reaches the discharge (dry) pit 9 or the granulation facility 8. This is an example of slow cooling or water granulation. A reformer was added at a position indicated by a black circle to the molten blast furnace slag flowing out together with the molten iron from the slag opening 2 provided at the lower part of the blast furnace 1. That is, the hot metal 3 after the hot metal P and the molten blast furnace steel S are separated by the large hot water 3 and the skinmer 4, the hot water pan 6 which is a container for collecting the molten metal in the molten blast furnace steel S, Either the water granulation / discharge rod 7 immediately before the discharge pit 9, the pit outlet 10 of the discharge rod 7, or any place in the discharge pit 9 was used as a modifier addition location according to the amount of modifier addition. The results are shown in Tables 4-6.

In addition, the molten blast furnace iron having the chemical composition shown in Table 3 was used.

Moreover, the thing of the component shown in Table 1 was used for the coal ash.
Sintered dust collection dust having the components shown in Table 2 was used as the iron oxide-containing material. Furthermore, what has a component shown in the margin of Table 4 as another iron oxide containing material was used.

Since Examples 1 to 9 in Tables 4 to 6 are within the range of the conditions of the present invention, the deposits on the refractory (addition, growth or temperature of undissolved sintered body) accompanying the addition of the modifier The modifier can be continuously added without causing any operational troubles due to the increase in the drop, causing the inner surface of the molten blast furnace or the inner surface of the ladle to adhere to the refractory. A blast furnace furnace with low specific gravity and high specific gravity was obtained.

On the other hand, in Comparative Examples 1 and 5, the T.O. Since the blending ratio of Fe deviated from the lower limit of the range of the present invention, coal ash was not melted smoothly into the molten blast furnace so that a sintered body of high melting point crystals was formed, and a modification effect by adding a modifier was obtained. None of them became blast furnaces with low specific gravity.
In Comparative Example 2, contrary to Comparative Example 1, T.I. The blending ratio of Fe is outside the upper limit of the scope of the present invention, and the effect of the modifier added above the upper limit cannot be obtained, and in addition, a waste modifier cost is required, and in the iron oxide-containing substance T.A. There were also concerns about quality, such as a change in the color tone of the blast furnace due to the excessive addition of Fe.
In Comparative Example 3, the amount of the reformer added to the molten blast furnace slag deviated from the lower limit of the range of the present invention, so that the reforming effect by the modifier was insufficient and the specific gravity of the blast furnace slag was small.

In contrast to Comparative Example 3, the amount of addition of the reforming material to the molten blast furnace slag deviates from the upper limit of the scope of the present invention, so that the sensible heat taken away by the modifying material increases. The temperature of the part where the modifier is added in the molten blast furnace drastically decreases locally, but the modifier melts, but the viscosity of the molten blast furnace bowl after the addition increases, and the inner surface refractory of the large bowl and the potato pan after the addition of the modifier The adhesion amount of the molten blast furnace slag to the steel increased, resulting in complicated operations such as removal of the adhered slag after treatment, resulting in operational problems.
In Comparative Example 6, T.I. Since the Fe content is as low as 22% by mass, T.I. Since components other than Fe are mixed in a large amount in the molten blast furnace soot, the temperature drop when adding a modifier increases, causing operational problems, and the effect as a modifier mainly composed of coal ash. Was not sufficiently obtained, and the specific gravity was small.

It is explanatory drawing which shows the relationship between the compounding ratio of the iron oxide with respect to coal ash, and a coal ash undissolved ratio. It is explanatory drawing which shows the relationship between the addition ratio of the modifier with respect to a molten blast furnace slag, and the absolute dry specific gravity of a blast furnace slag. It is explanatory drawing which shows the position which adds a modifier to a molten blast furnace slag in the reforming method of blast furnace slag concerning one Example of this invention.

Explanation of symbols

1: Blast furnace, 2: Outlet, 3: Oiso, 4: Skinmer, 5: Firewood, 6: Floating hot pot, 7: Granulation / release basin, 8: Granulation equipment, 9: Discharge pit, 10: Pit exit

Claims (5)

When the modifier is added to the molten blast furnace slag and then cooled and solidified to form a blast furnace slag, the modifier is a mixed powder of coal ash and iron oxide-containing material containing iron oxide. Reformer for blast furnace. T. in the iron oxide-containing material with respect to the coal ash. The blast furnace soot reforming material according to claim 1, wherein the iron oxide-containing material is blended so that the amount of Fe is 5 to 50% by mass. The iron oxide-containing material is T.I. The blast furnace slag reformer according to claim 1 or 2, which is any one of dust, sludge, metal refining waste, and minerals containing 30 mass% or more of Fe. A blast furnace characterized in that after adding 1 to 30% by mass of the reforming material according to any one of claims 1 to 3 to a molten blast furnace slag, it is gradually cooled or granulated into a blast furnace slag. A method for reforming straw. 1 to 30% by mass of the modifier is added to the molten blast furnace at one place or a plurality of places, and the addition amount per one place of the addition is 10% by mass or less. The method for reforming a blast furnace soot according to claim 4.

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