JP5558119B2 - How to use granular iron - Google Patents

Description

  The present invention relates to a method for using granular iron, and more particularly, to a method for using granular iron in which granular iron with a particle size of 7 mm or less recovered from steelmaking slag is used as an iron source.

  Conventionally, in steelmaking slag treatment at steelworks, a solidification process for solidifying molten slag, a cooling process for cooling the solidified slag to about 100 ° C., a fine granulation process for crushing to a particle size suitable for magnetic beneficiation, and grains by magnetic beneficiation In addition to the separation process of iron and slag, the stabilization process of slag by yard aging, and the like, a recycling process using granular iron as a raw material for steelmaking in a converter is performed. Normally, granular iron used as a raw material for steelmaking is a particle having a particle size exceeding 7 mm. When particles having a particle size of 7 mm or less are put into high-temperature pig iron, they are flamed and scattered by intense ascending current due to high temperature. The converter could not be charged due to operational problems.

  So, in patent document 1, it sprays so that a granular iron may be set | placed on the surface slag of the ladle after the hot metal preliminary treatment, and before decarburization refining, or the molten iron in a kneading vehicle, and let granular iron be taken in into slag. Thus, a method has been proposed in which contact with hot metal causing a rapid reaction is avoided and iron is recovered in molten steel by decarburization refining.

JP 2009-144179 A

  However, in the technique described in Patent Document 1, it is necessary to work carefully by providing a charging chute near the surface of the slag so that the granular iron does not penetrate the slag layer. Since the thickness of the slag layer is thin and changes each time, there is a problem that it is necessary to suppress the amount of granular iron input.

  On the other hand, it is conceivable that granular iron having a particle size of 7 mm or less is made into a raw material having a size that can be charged into a converter by agglomeration means such as granulation. However, granular iron is not water-absorbing in order to be processed by commonly performed granulation, for example, rolling granulation with a pan-type granulator or briquette molding with a double roll molding machine. In addition to being difficult to agglomerate in nature, there is a problem that the particle size distribution is coarse, and if agglomeration by these means is attempted, fine grinding or the like is required as pretreatment.

  Therefore, the present invention can be agglomerated without performing fine grinding or the like as a pretreatment, and uses the same equipment as existing converter charging materials using scrap or granular iron having a particle size exceeding 7 mm. It is another object of the present invention to provide a method for using granular iron having a particle size of 7 mm or less, which can be charged into a converter in a sufficient amount.

  The present inventors have intensively studied to solve the above problems. As a result, a pretreatment such as fine pulverization is performed by mixing a predetermined amount of steelmaking dust with granular iron having a particle size of 7 mm or less that is difficult to agglomerate due to its lack of water absorption. It has been found that agglomeration can be performed without any problem, and that the obtained agglomerated material exhibits a high strength that can withstand the charging of the converter, and the present invention has been completed.

  That is, the said subject is achieved by the following (1)-(3).

  (1) Granular iron (A) having a particle size of 7 mm or less (A) 20 to 80% by mass, steelmaking dust (B) 80 to 20% by mass, ((A) + (B) = 100% by mass) After kneading and agglomerating, the obtained agglomerated material is charged into a converter.

  (2) 3 to 10% by mass of fly ash (C) is further added to the total of 100% by mass of the granular iron (A) and the steelmaking dust (B), A method for using the granular iron described in 1).

  (3) A plurality of drums each having a drum for storing material therein and a plurality of rotors that rotate while revolving within the drum and that can be variable-speeded, wherein the rotors are arranged in a direction perpendicular to the rotor rotation axis. The above-mentioned (1) or (1), wherein the granular iron and the steelmaking dust are kneaded using a mixer having rotating blades of the following, pseudo-granulated, and then agglomerated using a rolling machine. The utilization method of the granular iron as described in 2).

  According to the present invention, by adding steelmaking dust to the granular iron, fine particles and stickiness are imparted to the granular iron, and thus granulation is difficult without performing pulverization or the like as pretreatment. Agglomeration of granular iron is possible. In addition, the strength of the agglomerate is increased in the process of oxidizing the fine metal iron derived from the steelmaking dust contained in the agglomerate of granular iron, allowing the agglomerate to be charged into the converter, and the iron content contained in the steelmaking dust. Can be recovered and used.

It is a figure which shows the example of a state change at the time of adding and knead | mixing water to a solid particle. It is a figure which shows an example of the flow of collection | recovery utilization of the iron content contained in a granular iron.

  Embodiments of the present invention will be described below.

(A) Grained iron The grained iron used in the present invention has a particle size of 7 mm or less generated by crushing / classifying steelmaking slag. By the way, in general, a state change when water is added to a solid particle and kneaded is considered as shown in FIG. 1 from the relationship between a solid phase, a liquid phase, and a gas phase. In particular, since granulation is a non-fluid state in which water floats on the particle surface due to the kneading action, and adjacent particles are continuously connected via the liquid surface. Above all, it is explained that it occurs on the lower moisture side. However, the granular iron particles are extremely poor in water absorption, and are not dispersed and become dispersed with relatively low moisture without passing through a kneaded state, making it difficult to agglomerate by granulation. In order to solve such a problem, in the present invention, steelmaking dust is blended in order to produce a mild state in the granular iron.

  As described above, the particle size of the granular iron used in the present invention is not particularly limited as long as it is 7 mm or less. Preferably it is 3 mm or less.

  In addition, as for the granular iron which concerns on this invention, if the particle size is 7 mm or less, what passed the sieve with an opening of 7 mm should just be used. For example, if the particle size is 3 mm or less, a particle having passed through a sieve having an opening of 3 mm may be used.

  The compounding quantity of the granular iron at the time of kneading | mixing which concerns on this invention is 20-80 mass% with respect to the total amount of granular iron and steelmaking dust, Preferably it is 30-75 mass%. Within this range, agglomeration of granular iron becomes possible, and the strength of the agglomerate is increased by the action of fine metallic iron derived from steelmaking dust contained in the agglomerate of granular iron. Is possible. When the blending amount of the granular iron is less than 20% by mass, the adsorptive power to the magnet is reduced, and conveyance using magnetic force becomes difficult. On the other hand, when the blending amount of the granular iron exceeds 80% by mass, the fine particles constituting the agglomerated material are insufficient, and the agglomeration does not proceed sufficiently.

  In addition, the quantity of the granular iron in the agglomerate obtained by kneading | mixing and agglomerating granular iron and steelmaking dust is substantially equal to the said compounding quantity. For this reason, the amount of granular iron in the agglomerated material is preferably 20 to 80 mass%, more preferably 30 to 75 mass%, based on the total amount of granular iron and steelmaking dust.

(B) Steelmaking dust Steelmaking dust used in the present invention is a process in which pig iron discharged from a blast furnace is poured into a converter, oxygen is blown into pig iron, and decarburized. In particular, it is collected in a venturi, separated from water by a thickener and then dehydrated by a filter press, resulting in a cake having a moisture content of approximately 15 to 40% by mass. When this steelmaking dust is left undisturbed, fine metallic iron contained in the dust is oxidized and begins to harden while generating heat.In the present invention, the steelmaking dust containing metallic iron before the oxidation reaction is started or during the reaction. Is preferably used. Steelmaking dust with a low content of metallic iron often causes the particles to solidify and the particle size distribution to change in a coarse direction, which is not only poor in the granulation effect of granular iron, but also the oxidation reaction of metallic iron. Since the strength development due to is inferior, the performance may not be sufficient as a material for promoting granulation of granular iron. Therefore, in the present invention, it is preferable to use steelmaking dust containing at least 20% by mass of metallic iron. The steelmaking dust discharged from the converter usually contains 30% by mass or more, preferably 50% by mass or more of metallic iron, and can be used as it is in the present invention.

  The compounding amount of the steelmaking dust during kneading according to the present invention is 80 to 20% by mass, preferably 70 to 25% by mass, based on the total amount of the granular iron and the steelmaking dust. Within this range, the agglomeration of granular iron becomes possible, and the strength of the agglomerated material is increased by the action of fine metallic iron derived from steelmaking dust contained in the agglomerated material of granular iron. Converter charging becomes possible. When the blending amount of the steelmaking dust is less than 20% by mass, the fine particles constituting the agglomerated material are insufficient and the agglomeration does not proceed sufficiently. On the other hand, if the amount of steelmaking dust exceeds 80% by mass, the water content of the agglomerate immediately after production becomes high, so that the agglomerate is soft and easily broken.

  The amount of steelmaking dust in the agglomerated product obtained by kneading and agglomerating granular iron and steelmaking dust is substantially equal to the above blending amount. For this reason, the amount of steelmaking dust in the agglomerated material is preferably 80 to 20% by mass, more preferably 70 to 25% by mass, based on the total amount of the granular iron and the steelmaking dust.

  Also, among the steelmaking dusts, oxidation dust containing iron that has undergone an oxidation reaction completely has a low granulation acceleration effect, but its moisture content is lower than that of steelmaking dust, so correction of the particle size distribution of granular iron and agglomeration are not possible. It can mix | blend as a moisture adjustment material in the case of crystallization.

(C) Fly ash In this invention, in addition to steelmaking dust, in order to further improve the granulation property of granular iron, coal-derived fly ash can be further added. The fine particles of fly ash not only further promote the granulation properties of the granular iron, but the calcium oxide, silicon dioxide, aluminum oxide, etc. in the fly ash are combined with the fine metallic iron derived from steelmaking dust. Further, the strength (crushing strength) of the agglomerate of granular iron is further increased.

  The addition amount of the fly ash is preferably 3 to 10% by mass and more preferably 3.3 to 9% by mass with respect to 100% by mass in total of the granular iron and the steelmaking dust. If the addition amount is in the above range, a sufficient granulation promoting effect can be obtained, and the strength (crushing strength) of the agglomerate of granular iron can be further increased.

  Further, instead of fly ash or in addition to fly ash, preferably a cement of about 5 to 10% by mass is added to the total 100% by mass of the granular iron and the steelmaking dust to produce an agglomerated product, It is also possible to increase the strength of the agglomerated material. Furthermore, for example, when 10% by mass of fly ash is used, the strength of the agglomerate can be increased by replacing part of the fly ash with cement.

  The method for producing the agglomerated product according to the present invention is not particularly limited. For example, the agglomerated product is obtained by uniformly kneading the granular iron, steelmaking dust, and if necessary fly ash. Further, if necessary, water may be added. The agglomeration method is not particularly limited, and examples thereof include a method in which the above components are stirred and mixed using a hand mixer, a high-speed stirring granulation mixer, etc., and then rolled using a drum-type container. .

  The amount of water added in the case of agglomeration is, for example, the amount of water that is insufficient so that the finished moisture content of the agglomerated product is preferably 5 to 17% by mass.

  In the present invention, for example, a high-speed agitation type granulation mixer as disclosed in Japanese Patent No. 3703640 can be suitably used, which can granulate cake-shaped steelmaking dust. This high-speed agitation type granulation mixer includes a drum for storing material therein, and a plurality of rotors that rotate while revolving inside the drum and that can be variable-speed, and the rotor serves as a rotor rotation shaft. It is a mixer having a plurality of rotating blades arranged in a direction perpendicular to it.

  Such a granulating mixer forcibly mixes the steelmaking dust and the granular iron while finely crushing the dewatered cake-like steelmaking dust by the rotating blades provided in the rotor of the mixer. Therefore, almost uniform pseudo-granulated material can be produced in a short time, and further, by passing through a rolling machine, the pseudo-granulated material agglomerates while entraining the ungranulated mixture and coarse-grained iron, An agglomerated product with a smooth surface, low powder content and good yield can be obtained.

  As a more specific example of the granulation mixer, for example, Pelegaia (registered trademark) manufactured by Kitagawa Iron Works Co., Ltd. may be mentioned.

  As the rolling machine, any shape can be used as long as it functions as described above. For example, a drum type rolling machine that rotates a horizontally placed drum can be used.

  The content of the granulated product having a particle size of 10 mm or more in the agglomerate of granular iron obtained by the method as described above is preferably 41 to 100% by mass. Moreover, it is preferable that it is 5-20 mass%, and, as for the moisture content in the agglomerated material (water content immediately after agglomeration), it is more preferable that it is 7-17 mass%.

  The agglomerates of granular iron obtained by the above method can be charged into a converter using existing charging equipment used for scrap or granular iron having a particle size exceeding 7 mm. In addition, the agglomerated product can be further strengthened by curing for more than half a day. The agglomerated material charged into the converter has a small amount of fine particles, so it hardly causes problems such as flame and scattering, and it falls on the hot metal and melts to flow as shown in FIG. Thus, recovery and use of iron contained in the granular iron is achieved.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example.

(Examples 1-3, Comparative Examples 1-3)
For the agglomeration of granular iron having a particle size of 7 mm or less, a granulation test by rolling using a hand mixer and a drum-type container was performed in order to confirm the granulation acceleration effect of steelmaking dust. Grain iron and steelmaking dust having a particle size of 7 mm or less are measured in a 2 L metal container at the blending amount shown in Table 2 below, until stirring and mixing with a hand mixer are possible until granulation is possible. Water was added and granulation was performed. Then, it agglomerated by rolling in a drum type container. In addition, the particle size distribution of the used granular iron was shown in Table 1 below. The steelmaking dust contained 30% by mass of metallic iron with respect to the total mass of the steelmaking dust.

  The moisture content was measured using an infrared moisture meter (manufactured by Kett Science Laboratory).

  The particle size distribution was determined by performing classification using each sieve sieve and measuring the mass of particles falling within the particle size range shown in Table 1 below.

  The agglomeration was evaluated by selecting a granulated product having a size of 10 mm or more while visually confirming the particle size. Then, the mass of the granulated product having a particle size of 10 mm or more is measured, and the ratio of the granulated product having a particle size of 10 mm or more is 0% by mass to 40% by mass, x is 41% by mass to 70% by mass. The thing which is (triangle | delta) and 71 mass%-100 mass% was made into (circle).

  The evaluation results for the obtained agglomerated material are shown in Table 2.

  From the results shown in Table 2, it can be seen that by adding steelmaking dust in an amount of 20% by mass or more, the granulation property of the granular iron is increased and agglomerated.

(Examples 4-5, Comparative Examples 4-5)
Fly ash was further added to the blends of Example 1 and Comparative Example 3 where the agglomeration evaluation was Δ and x, respectively, and agglomerated. The blending ratio was set as shown in Table 3 below, and the agglomeration was performed in the same manner as in Example 1.

  Similar to Table 2 above, the results of evaluation of moisture content and agglomeration are shown in Table 3 below. In addition, evaluation of agglomeration is that in which the ratio of the granulated product having a particle size of 10 mm or more is 0% by mass to 40% by mass, x is 41% by mass to 70% by mass, Δ is 71% by mass to 70% by mass. What was 100 mass% was set as (circle). In addition, for each sample, the crushing strength (the load when the particles are applied and the particles are collapsed) is measured, and the value is shown when the crushing strength of the agglomerate of Example 1 is set to 100. . The crushing strength was measured using a crushing strength meter ZP-500N (manufactured by Imada Co., Ltd.).

  As is apparent from the results in Table 3, it can be seen that by adding 3 to 10% by mass of fly ash in addition to steelmaking dust, the granulation property of the granular iron is further improved and the strength is also improved.

(Example 6)
To the granular iron having a particle size distribution shown in Table 1 having a particle size of 7 mm or less, the same amount of oxidized dust that has undergone the oxidation reaction was added as the granular iron, and the mixture was added with stirring with a hand mixer. Improvement was not seen and it became sandy. Therefore, steelmaking dust is further added in a composition of 20% by mass, and the results when evaluated are shown in Table 4 below. As is apparent from Table 4, it can be seen that agglomeration can be achieved by adding steelmaking dust.

(Example 7)
A high-speed stirring granulation mixer (trade name: Pelegaia (registered trademark) VZ-500, Kitagawa Iron Works Co., Ltd.) was added to the agglomerated product obtained in Example 6 above by adding 6% by mass of cement. Manufactured) and a drum-type rolling machine (made by Kitagawa Iron Works Co., Ltd.) having a diameter of 1,600 mm and a length of 36,000 mm were used to produce 20 t of agglomerated granular iron. After curing for 2 days, the agglomerated material was charged into the converter at 1 t / charge, but stable operation could be performed without raising the flame.

Claims (3)

20-80 mass% of granular iron (A) whose particle size generated by crushing and classification of steelmaking slag is 7 mm or less,
In the process of pouring iron from the blast furnace into the converter, blowing oxygen into the pig iron and decarburizing, steelmaking dust (B) 80-20% by mass discharged together with exhaust gas ,
(However, (A) + (B) = 100 mass%)
After kneading and agglomerating, the obtained agglomerated material is charged into a converter.   The fly ash (C) of 3-10 mass% is further added with respect to a total of 100 mass% of the granular iron (A) and the steelmaking dust (B). To use grain iron.   A plurality of rotating blades each including a drum for storing material therein and a plurality of rotors that rotate while revolving within the drum and that are capable of variable speed, wherein the rotor is disposed in a direction perpendicular to the rotor rotation axis; 3. The grain according to claim 1, wherein the granular iron and the steelmaking dust are kneaded using a mixer having a quasi-granulating and pseudo-granulated, and then agglomerated using a rolling machine. How to use iron.

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