JP2005240142A - METHOD FOR UTILIZING MgO-C BASED WASTE REFRACTORY - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for utilizing MgO-C based waste refractories applicable in an iron manufacturing stage even when they are powdery. <P>SOLUTION: Powdery scrap generated by the pulverization/particle size regulation in MgO-C based waste refractories is blended as an MgO source in a sintering raw material. In this case, the grain size of the powdery scrap is preferably controlled to ≤10 mm. Further, the blending quantity of the powdery scrap may be the total quantity of the MgC source or may be a part thereof. Thus, the powdery scrap of the MgO-C based waste refractories which have to be temporarily placed in an iron mill or have to be subjected to industrial waste treatment can be effectively utilized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of using an MgO—C waste refractory, and in particular, is a technology that effectively uses the MgO—C waste refractory in an ironworks where it is generated to help save resources.

  Waste refractories generated in steelworks are generally reused by recycling them as refractory raw materials, smelting or refining auxiliary raw materials (for example, ironmaking materials, etc.). However, such a utilization method is limited to a part of waste refractory waste because an impurity problem occurs in the reuse destination depending on the component composition of the waste refractory itself or the kind of slag mixed therein. Therefore, conventionally, it has been used in civil works such as landfills or temporarily placed in steelworks.

  In recent years, in the process of melting molten steel, an MgO—C refractory lined material is used as a reaction vessel (for example, various converters, ladles, RH degassing apparatuses, etc.). For this reason, waste refractory scraps are often derived from MgO-C refractories, and the technology used as a refractory raw material as described above (for example, see Patent Documents 1 and 2) or The technique (refer patent document 3) utilized as an auxiliary | assistant raw material (slag making material) in pot refining is also disclosed.

However, when using the waste of the MgO-C waste refractory as a refractory raw material or an auxiliary raw material in the iron making process, the conventional techniques described in Patent Documents 1 to 3 all require crushing / sizing of the waste. is there. In other words, after crushing and sizing MgO-C waste refractory, it is separated with a sieve of about 10 mm, and only the relatively coarse particles on the sieve are reused as refractory raw materials and auxiliary raw materials in the refining process. Yes. On the other hand, the powder under sieving generated at the time of crushing and sizing contains a large amount of impurities such as slag, and is therefore unsuitable for recycling to refractory raw materials. In addition, when used as an auxiliary material in the refining process, the powdery material is difficult to handle and use (for example, throwing into molten steel) and has not been used. Therefore, about the waste of the MgO-C waste refractory with a large amount of powder under the sieve, 500 to 2000 tons per year is not currently reused, and the treatment is an important issue in the steelworks.
Japanese Patent Laid-Open No. 6-219853 JP-A-8-259511 JP-A-5-339615

  In view of such circumstances, an object of the present invention is to provide a method of using an MgO—C waste refractory that can be applied in an iron making process even if it is in a powder form.

  In order to achieve the above-mentioned object, the inventor diligently studied the effective use destination of the MgO—C-based waste refractory, and realized the result in the present invention.

  That is, the present invention is a method for using a MgO-C waste refractory characterized by blending powdery waste generated by crushing / sizing MgO-C waste refractory as an MgO source of a sintering raw material. It is. In this case, it is preferable that the particle size of the powdery waste is 10 mm or less. Moreover, the compounding quantity of the said powdery waste may be either the whole quantity of the said MgO source, or a part.

  According to the present invention, 500 to 2000 tons of MgO—C waste refractory waste that has been conventionally difficult to process can be reused. As a result, not only the entire MgO-C waste refractory can be effectively used, but also the amount of serpentine, dolomite, etc., which are MgO sources for the production of sintered ore, and coke powder, which is fuel, can be reduced.

  Hereinafter, the best embodiment of the present invention will be described based on the background of the invention.

  When reusing MgO-C waste refractory, crushing and sizing is performed, but as described above, powder waste under the sieve (-10 mm) has impurities such as slag for recycling to refractory raw materials. However, in order to use it as a secondary material in the refining process, it is difficult to handle because of difficulties in handling. Then, the inventor examined the utilization place of a powdery waste, and came up with thinking that it utilized for the sintered ore production of the artificial ore which is one of the iron source raw materials charged into a blast furnace.

  This sintered ore is referred to as a raw material for mixing, and iron sources such as powdered iron ore, sulfated iron, iron sand, scale, blast furnace dust and converter dust, powdered limestone, dolomite, serpentine, This is because the raw material is a mixture of auxiliary materials such as return ore and coke powder as fuel, and dolomite and serpentine also play a role as MgO source. Normally, after adding and mixing an appropriate amount of moisture to this blended raw material, mixing and granulating, the mixture is packed in layers on a mobile pallet, air is circulated, the carbonaceous material is burned, and the blended raw material is melted. Manufactured by cooling.

  By the way, when applying powdered serpentine and / or dolomite powdery scraps of MgO-C waste refractory as a raw material for sintering, the MgO content is sufficient or mixing of C is not a problem. There are three issues that must be taken into consideration: whether it will cause trouble during blast furnace operation.

  There is no problem with the initial MgO content. This is because the target MgO concentration as the sintered ore is about 1 to 2% by mass, and the powdery scrap of the MgO—C waste refractory contains 75 to 90% by mass of MgO. However, depending on the type of the MgO—C waste refractory, there are some containing 20 mass% C at the maximum. As this C, a graphite-like (graphite-like) thing is blended, and its combustibility is inferior.

  However, even in the manufacturing process of sintered ore, the maximum temperature reaches 1350 ° C., and the time of exposure to high temperature is usually 20 minutes or more, and it is burned because it is in the form of powder of 1 mm or less. It was thought that the second problem of inclusion could be solved. Therefore, the powdered waste of MgO-C waste refractory was actually blended in the sintering raw material, a sintered ore was prototyped, and the residual C was investigated. As a result, it was confirmed that no residual C was found, so it was determined that such MgO—C waste refractories could be used as a substitute for the MgO source of sintered ore. Furthermore, the target MgO concentration of slag in normal blast furnace operation is 5 to 10% by mass. Can MgO-C refractory powdered waste be used as an MgO source to satisfy this target MgO concentration? I confirmed. FIG. 1 shows the MgO concentration of the blast furnace slag when the total amount of the MgO source of the sintering raw material is dolomite and when the total amount is powdered scrap of the MgO—C refractory. In either case, it was within the range of the target MgO concentration of blast furnace slag, and it was confirmed that substitution with the powdery waste was possible. That is, even if the powdery waste of MgO-C waste refractory is replaced with dolomite or serpentine or the like, it is considered that there is no particular problem in both the sintering operation and the blast furnace operation. Was completed.

  In this invention, although the upper limit particle size of the said powdery waste is not specifically limited, It is preferable to use a 10 mm or less thing. If it exceeds 10 mm, the particle size is too large, and the reaction rate and melting rate are slowed when reacting and melting with other raw materials, which is not preferable. In addition, it is not necessary to provide a lower limit, because no matter how fine it is, pseudo particles are formed in the mixing and granulating step of the blended raw materials.

Moreover, in this invention, the mixture of the said powdery waste is good also as the whole quantity corresponded to MgO content of the serpentine and dolomite to substitute, and a part may be sufficient as it. This is because any compounding does not adversely affect the sintering operation. However, since dolomite also plays a role as a source of CaO and serpentinite as a source of SiO _2, it is necessary to determine the alternative amount in consideration of the entire sinter component when determining the total amount of raw materials. Needless to say.

  As shown in Table 1, the main composition of the raw material composition for producing sintered ore is as follows: fine iron ore: 40,000 t, return ore: 15,000 t, limestone: 3,000 t, dolomite: 2,500 t, and those -10 mm MgO-C waste refractory waste; 100 t. Table 1 also shows a conventional blending example in which such MgO-C waste refractory waste is not blended. The composition of the refractory waste 100t of 10 mm or less is a value determined by the balance of MgO-C waste refractory waste generated at the steelworks. And the sintering operation was performed on normal conditions.

As a result, as shown in FIG. 1, the MgO-C waste refractory powdered waste 100t of the sintered ore and the MgO source mixed with the whole amount of dolomite, the MgO concentration in the blast furnace slag is It did not change. Also, no particularly problematic phenomenon occurred in either the sintering operation or the blast furnace operation. In other words, conventionally, it has become possible to effectively use powdery waste of MgO-C waste refractories that had to be temporarily placed in an ironworks or disposed of industrially. In addition, in the practice of the present invention, the amount of dolomite or serpentinite used as an MgO source in the production of sinter can be reduced as compared to the conventional, and not only resource saving is achieved, but also a reduction in sinter production cost is expected. it can.

It is the figure which compared the MgO density | concentration in the blast furnace slag in the case where a dolomite is used as a MgO source of a sintering raw material, and the powdery waste of a MgO-C type waste refractory is used.

Claims (3)

A method for using an MgO-C waste refractory, characterized in that powdered waste generated by crushing and sizing MgO-C waste refractory is blended as an MgO source of a sintering raw material. The method for using MgO-C waste refractory waste according to claim 1, wherein the powdery waste has a particle size of 10 mm or less. 3. The method of using MgO—C-based refractory waste according to claim 1, wherein the amount of the powdery waste is the total amount or a part of the MgO source.

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