JP2012092389A - Recycling method of slug of torpedo car and pellet suited for blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recycling method of slug of a torpedo car capable of recycling the slug of the torpedo car, which has been difficult to recycle effectively in a conventional manner, as a pellet suited for a blast furnace having high strength and high quality even in winter season, without requiring great facility investment, and to provide the pellet suited for blast furnace.SOLUTION: The slug 1 of the torpedo car containing 5 mass% or more of metal Fe is crushed and mixed with an iron ore 2, and a powder coke 3, a cement binder 4 and other iron raw materials 5 are blended therein. The mixture is pelletized and hardened to reuse as the pellet suited for the blast furnace. Blending ratio of the slug 1 of the torpedo car in the pellet is 5-25 mass%. As other iron raw materials, iron-contained dust may be used. Due to oxidation heat of the metal Fe, temperature rise of 10-20°C is caused, hydration reaction of cement is accelerated, and crushing strength of 6 MPa or more is obtained.

Description

  The present invention relates to a method for recycling chaos slag generated in a steel factory and a pellet for a blast furnace using chaos slag as part of a raw material.

  In a steel factory, various slags such as slag, slag pretreatment slag, and converter slag are generated in the steelmaking process until continuous casting of pig iron taken from the blast furnace. Some of these slags are sold and reused as roadbed materials, but chaos slag has high basicity, expandability, and dust generation sources such as quiche graphite. Therefore, it cannot be used as roadbed material for roads, and can only be used for temporary materials. For this reason, effective recycling was difficult.

  In addition, as described in Patent Document 1, after slag generated in a steelmaking process is crushed, Portland cement clinker and lime and / or gypsum are added to those subjected to deironing treatment, and pulverized and mixed. It has been proposed to be used as a binder for facing pellets (briquettes). However, this method has a problem in that the steelmaking slag is rapidly cooled and vitrified to ensure hydraulic properties, which requires a large investment in equipment such as a granulation facility.

  Moreover, when the pellet for blast furnace described in Patent Document 1 is put into the blast furnace, free water and hydrated reaction crystal water inside the blast furnace are brought into the blast furnace. For this reason, there is a problem that the amount of charging to the blast furnace is limited and only about 3% of the iron raw material can be charged.

  Further, in order to reduce the blast furnace coke ratio, it is necessary to adjust the carbon content by adding reducing coke as a fuel source to the blast furnace pellets. Increasing the carbon content increases the porosity, making it impossible to secure the required strength for blast furnaces. To ensure the required strength for blast furnaces, the amount of binder must be increased, and the production cost and quality of pellets for blast furnaces are reduced. There was a problem of lowering.

  Furthermore, such blast furnace pellets ensure the strength by cement hydration reaction, but in winter when the outside air temperature decreases, the cement hydration reaction does not proceed sufficiently, so the required strength for blast furnace There was a problem that could not be secured.

JP 61-178448

  Accordingly, the object of the present invention is to solve the above-mentioned conventional problems, and to remove chaos slag that has been difficult to effectively recycle in the past, without requiring a large capital investment, and for blast furnaces with high productivity, strength and quality. The present invention is to provide a method for recycling a chaos slag that can be recycled as pellets and a pellet for blast furnace.

  The method for recycling chaos slag of the present invention made in order to solve the above-mentioned problem is a chaos slag containing metal Fe, iron ore, powder coke, cement binder, and other iron raw materials. The mixture is stirred and mixed so that the mixing ratio of the car slag becomes 5 to 25% by mass, granulated and cured, and reused as pellets for a blast furnace. In addition, it is preferable to use a kneading wheel slag containing 5 mass% or more of metal Fe. Moreover, iron-containing dust can be used as another iron raw material.

  Moreover, the blast furnace pellets of the present invention made to solve the above-mentioned problems are obtained by crushing and mixing kneaded car slag together with iron ore, blending powdered coke, cement-based binder and other iron raw materials, and granulating. The blast furnace pellets obtained in this manner are characterized in that the value of (mass% of metal Fe / mass% of total C) in the pellet is in the range of 0.04 to 0.21. The crushing strength is preferably 6 MPa or more.

  According to the present invention, not only can the metal Fe that is particularly abundantly contained in the slag of the kneading car be effectively used as iron in the blast furnace, but also the pellet porosity is reduced using the metal Fe as a granulated nucleus, and the strength is improved be able to. Further, the metal Fe contained in the kneading wheel slag can raise the pellet temperature by oxidation heat generation during curing, promote the cement hydration reaction, and increase the pellet strength. Since these mechanisms can compensate for a decrease in strength due to an increase in carbon, the strength required for blast furnace use can be ensured even when the carbon content is increased from 15% to 20-25%. Therefore, the present invention has an advantage that chaos slag, which has conventionally been difficult to effectively recycle, can be recycled as blast furnace pellets with high productivity, strength and quality.

It is a block diagram explaining the process of this invention. It is a graph which shows the relationship between the mixing ratio of chaos slag and the total Fe in pellets. It is a graph which shows the relationship between the mixing ratio of chaos slag and the amount of alumina in pellets. It is a graph which shows the relationship between the mixing ratio of chaos slag and the temperature rise amount of pellets. It is a graph which shows the relationship between C content rate (total C) in a pellet, and the crushing strength of a pellet.

  Embodiments of the present invention will be described below. In addition, the chaos slag used in the present specification is not necessarily limited to 100% strict chaos slag (slag taken out from the chaos vehicle), and other steel making such as hot metal pretreatment slag, converter slag, etc. It may contain a small amount of slag. That is, in this specification, 60% by mass or more is a chaos slag in a narrow sense, and is called a chaos slag.

  FIG. 1 is a block diagram for explaining the process of the present invention. First, the slag 1 is mixed with the iron ore 2 on the yard using a heavy machine and further mixed while being crushed by a crusher. In some cases, chaos slag and iron ore are crushed and mixed without shovel mixing. The mixing ratio of the chaos slag 1 will be described later. The chaotic vehicle slag 1 contains a relatively large amount of metal Fe, and usually contains 5 mass% or more of metal Fe. Table 1 shows the component range of the chaotic slag 1, but it goes without saying that there is some variation depending on the steel type and operating conditions.

  As shown in Table 1, since the total C amount of the kneading vehicle slag 1 is around 5% by mass, it is necessary to further add C in order to obtain pellets for the blast furnace. For this reason, powder coke 3 is added. As a binder, a cement-based binder 4 is added as in the conventional case. Furthermore, other iron raw materials 5 may be added. A typical example of the other iron raw material 5 is dust containing iron recovered in the steelworks, but it is not limited to this. These are crushed and mixed, granulated by a known granulator such as a pelletizer, etc., cured and hardened by advancing the hydration reaction of the cement binder 4. Since the pellets for the blast furnace produced in such a process are put into the blast furnace as an iron raw material, it is necessary to ensure the strength necessary for using the blast furnace. Here, the crushing strength is 6 MPa or more.

Here, the characteristics required for blast furnace pellets are summarized as follows.
1. The strength required for blast furnace use (crushing strength of 6 MPa or more).
2. The total Fe in the pellet is 25% or more because it is fed as an iron raw material.
3. The total C as a reducing agent in the blast furnace is 15% or more, preferably 20% or more.
4). In order to suppress the generation amount of slag, the content of Al ₂ O _{3 in} the pellet is less than 5%.

In order to produce pellets for blast furnaces that satisfy the above characteristics using the kneading car slag 1 as a raw material, it is first necessary to set the mixing ratio of the kneading car slag 1 within an appropriate range. FIG. 2 is a graph in which the horizontal axis represents the mixing ratio of chaos slag, and the vertical axis represents total Fe in the pellets. From this graph, it can be seen that, even if C in the pellet is 20%, the total mixing ratio of 25% or more is necessary to make the mixing ratio of the chaos slag 25% or less. FIG. 3 is a graph in which the horizontal axis indicates the mixing ratio of slagging slag and the vertical axis indicates the amount of alumina in the pellets. From this graph, it can be seen that in order to make the content of Al ₂ O _{3 in} the pellets less than 5%, it is necessary to set the blending ratio of the chaotic slag to 25% or less. On the other hand, if the mixing ratio is less than 5% in order to recycle the kneading car slag, the strength reduction due to the increase in the carbon content cannot be compensated for by the oxidation reaction heat of the metal Fe in the kneading car slag. Therefore, in the present invention, the mixing ratio of the chaotic slag in the pellets is set to 5 to 25% by mass.

Next, in order to increase the total amount of C in the pellets, it is necessary to add the powder coke 3. However, as described above, the powder coke 3 is a porous substance and causes a decrease in the pellet strength. Particularly in winter when the outside air temperature is low, the hydration reaction does not proceed sufficiently, which may result in insufficient strength. However, in the present invention, the hydration reaction temperature of the cement binder 4 is secured by utilizing the oxidation heat of the metal Fe contained in a large amount in the kneading wheel slag 1 to ensure the pellet strength. Since the hydration reaction is exothermic, the reaction is accelerated by increasing the reaction temperature. The oxidation reaction of metal Fe
MFe + 1 / 2O2 → FeO + 1132Kcal / kg-Fe (1) The reaction formula is shown. The inventors confirmed that about 70% of the reaction heat of the formula (1) corresponds to the temperature rise of the pellets from the drying experiment of the fine-grained iron source containing other metal Fe. Although the heat-up allowance changes depending on the reaction rate of metal Fe, the cement hydration reaction promotes the reaction at a rise of 20 to 30 deg, but does not change much above that.

  FIG. 4 is a graph in which the horizontal axis represents the mixing ratio of the kneading wheel slag, and the vertical axis represents the temperature rise of the pellets due to the heat of oxidation of metal Fe. According to the experimental results, the oxidation reaction rate of the metal Fe in the pellet is about 20, and when the reaction rate is 20%, the temperature rise range is 10 to 20 within the range of the mixing ratio of the chaotic slag 10 to 25%. It becomes ℃. As a result, the hydration reaction temperature of the cement binder 4 can be secured. In addition, it is preferable in terms of recycling the kneading vehicle slag that the calorific value due to the oxidation reaction of the metal Fe is a minimum to compensate for the decrease in the pellet strength due to the carbon increase.

  As described above, according to the present invention, by using the kneading wheel slag containing metal Fe, it is possible to increase the temperature field of the hydration reaction to promote the reaction, and to ensure the strength without increasing the amount of the binder. FIG. 5 is a graph in which the abscissa indicates the C content (total C) in the pellet and the ordinate indicates the crushing strength. When the upper straight line is a chaos slag compounding ratio of 13%, the lower straight line is This is a case where chaos slag was not blended. According to this graph, the crushing strength of the pellet when the C content in the pellet is 23% increases from 5.9 MPa to 7.1 MPa due to the mixing of the kneading wheel slag.

As for the relationship between the metal Fe and total C in the pellet, the strength increases as the amount of metal Fe increases, and the strength decreases as the total C increases as shown in FIG. When the mass% of metal Fe / mass% of total C is used as a relational index between metal Fe and total C, the effect of promoting the hydration reaction of the cement binder due to the rise in pellet temperature in the oxidation reaction in metal Fe is not 0.04 or more Is not sufficient, and if it is 0.021 or more, the reaction promoting effect due to temperature rise is saturated, so it is meaningless to increase it further. If carbon is simply raised, the strength will decrease by about 10%. If 0.08 or more is secured, the strength will be improved by about 10% compared to the conventional low-C product, so it can be used stably in the blast furnace. Necessary strength can be secured. Moreover, since the strength improvement effect is saturated at 0.17 or more, it can be said that 0.08 to 0.17 is a particularly desirable range. Metal Fe in the mixed car slag to be recycled needs a mass% of a certain amount or more, and if it is a mixed car slag containing 5% or more of metal Fe, restrictions on total Fe and Al ₂ O ₃ components in the pellets Therefore, it can be close to 0.08 which is the lower limit of the desirable range within 25% of the mixing condition of chaos slag.

  As described above, according to the present invention, chaos slag that has been difficult to recycle can be recycled as blast furnace pellets with high productivity, strength, and quality without requiring large capital investment. . Embodiments of the present invention will be shown below.

  In addition to kneaded car slag, iron ore, powdered coke, cement-based binder, other iron raw materials were mixed with dried iron dust and blast furnace primary ash, granulated and hardened to obtain pellets for blast furnace. Table 2 shows the blending ratio, pellet components, and pellet strength for producing blast furnace pellets. In addition, the pellet intensity | strength sets the pellet intensity | strength of the comparative example 2 which mix | blended 10 mass% of powder coke to 100, without mixing kneading vehicle slag. In Comparative Examples 1 to 4 in which the kneading vehicle slag is not blended, when the powder coke is blended and the total C content is increased, the pellet strength tends to decrease. In Comparative Example 5 and Comparative Example 6, chaotic slag is blended, but since the blending amount is very small, the oxidation heat of metal Fe does not act to the extent that promotes the hydration reaction of cement, and pellets No improvement in strength could be confirmed.

  In Examples 1 to 12, the blending amount of the chaotic vehicle slag was increased from 5% by mass to 25% by mass, and the pellet strength increased with the increase of the blending amount of the chaotic vehicle slag. In Example 1 in which 5% by mass or more of the kneading car slag was blended, the pellet strength was equivalent to that in Comparative Example 2 in which the kneading car slag was not blended, and it is considered that the oxidation heat of the metal Fe promoted the cement hydration reaction. Depending on the blending amount of the kneading wheel slag, the heat of oxidation of the metal Fe contributed to the promotion of the cement hydration reaction, and the pellet strength increased. However, increase in pellet strength could not be confirmed in Comparative Example 7 and Comparative Example 8 in which kneading vehicle slag was blended in excess of 25 mass%.

Focusing on the mass% of metal Fe / mass% of total C, in the case of less than 0.04, that is, in Comparative Examples 1 to 6, an increase in the strength of the pellet could not be confirmed. In Examples 1 to 12 of 0.04 or more, the pellet strength increased as the mass% of metal Fe / mass% of total C increased. However, when it exceeded 0.21, an increase in pellet strength could not be confirmed. On the other hand, if it exceeds 0.21, the total Fe becomes less than 25%, and in addition, Al ₂ O ₃ becomes 5% by mass or more, which is not desirable as a pellet for a blast furnace. If the pellet strength is increased by about 10% of the conventional product (Comparative Example 2), it can be stably used for blast furnaces. For this reason, it is desirable that the mass% of metal Fe / mass% of total C is 0.08 or more, and if it exceeds 0.17, the amount of change in the effect of improving the pellet strength is saturated. Is desirable.

1 Chaos slag 2 Iron ore 3 Coke powder 4 Cement binder 5 Other iron raw materials

Claims (5)

  After mixing and mixing kneading car slag containing metal Fe, iron ore, powder coke, cement-based binder, and other iron raw materials so that the mixing ratio of kneading car slag is 5 to 25% by mass, A method for recycling chaotic slag, which is granulated and cured and reused as pellets for blast furnaces.   The method for recycling chaotic vehicle slag according to claim 1, wherein chaotic vehicle slag containing 5 mass% or more of metal Fe is used.   The method for recycling chaos slag according to claim 1, wherein the other iron raw material is iron-containing dust.   Blast furnace pellets obtained by crushing and mixing kneaded car slag with iron ore, blending coke breeze, cement binder, and other iron raw materials, and granulating them. (Metal Fe / total C in the pellets) ) In the range of 0.04 to 0.21. Crushing strength is 6 MPa or more, Blast furnace pellets according to claim 4 characterized by things.

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