KR20210072991A - Recycling method of FeNi air cooled slag - Google Patents

Abstract

The present invention relates to a method for recycling FeNi air-cooled slag, and specifically, to a method for recycling FeNi air-cooled slag, including the steps of: pulverizing FeNi air-cooled slag to a particle size 25 mm or less to obtain FeNi air-cooled slag particles; and separating FeNi air-cooled slag particle into high strength unit particles having particle diameter of 5-25 mm and weak strength unit particles having particle diameter of less than 5 mm.

Description

FeNi odd slag recycling method {Recycling method of FeNi air cooled slag}

The present invention relates to a FeNi lump slag recycling method.

A ferronickel smelter was established in Korea in 2008, stably supplying raw materials for stainless steel production. The ferronickel slag generated at this time is about 2 million tons per year, and the amount of generation is huge, and it is discharged by slag and slag (slow cooling method). The generation rate is usually 80% for slag and 20% for slag. to be.

The slag in the form of granules is generated by spraying and quenching the molten slag through high-pressure watering. It means the slag of the generated mass (塊狀).

FeNi slag is used as aggregate for concrete, etc. about 1.3 to 1.5 million tons, and recycling measures have been established to some extent as in Patent Application No. 2017-0178526.

On the other hand, since FeNi lump slag is generated as a rock mass as shown below, it is easy to use as a civil engineering material that comes into contact with the soil, such as a filling material or a raw material for civil engineering. However, the wear rate standard for using FeNi bulk slag for raw materials is 50% or less (abrasion rate measurement method: KS F 2508, abrasion test of coarse aggregates by Los Angeles testing machine), but the wear rate of FeNi bulk slag is 70% There is a problem that the Ni content in FeNi slag is 0.04 to 0.06%, which can exceed 0.05%, which is the standard for soil contamination content, so it is difficult to actually try recycling FeNi slag for civil engineering. .

The present invention is to provide a method for recycling FeNi lump slag that has been difficult to utilize in the prior art.

In one aspect of the present invention, the present invention comprises the steps of obtaining FeNi lumped slag particles by pulverizing the FeNi lumped slag to a particle diameter of 25mm or less; and separating particles having a particle diameter of 5 to 25 mm among the FeNi lump slag particles into shoulder-diameter particles and particles having a particle diameter of less than 5 mm into weak particles.

According to the present invention, it is possible to recycle unused FeNi bulk slag, and in particular, by using it as an aggregate and admixture for concrete, it is easy to secure economic feasibility compared to the existing one, and concrete secondary products, ready-mixed concrete, solidifying materials, etc. can be manufactured.

Figure 1 (a) schematically shows a process in which the FeNi lump slag is generated, and Figure 1 (b) shows the appearance of the surface layer, the middle layer and the lower layer of the FeNi lump slag produced by the same process as in Figure 1 (a).
Figure 2 shows the results of XRD analysis of the surface layer, the middle layer and the lower layer of Figure 1 (b).
3 shows the results of analyzing the content of some of the surface layer component and the lower layer component of FIG. 1(b), and _{impurities other than MgO and SiO 2} are not described.
4 schematically shows a method for recycling FeNi bulk slag of the present invention.
5 shows the results of comparison of compressive strength when the particles of the weak part of the present invention are used as an admixture.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiment of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

We analyzed the cause of the decrease in strength when FeNi slag is used for civil engineering.

As shown in Figure 1 (a), when the water spraying proceeds to the surface layer portion of the molten slag of 500 ℃ or higher, the surface layer portion is rapidly cooled, and the middle/lower layer portion that is still in a molten state is cooled gradually. Since the molten slag is attached (constrained) to the bottom surface, the surface layer portion that is quenched first by watering is hardened, and the middle/lower layer molten slag begins to harden while being pulled up toward the hardened surface layer portion. At this time, as shown in Fig. 1(b), the middle/lower layers generate a tensile stress (pulling force from both sides) between the bottom surface and the surface layer, and by this tensile stress, the middle/lower layers have a weak tissue (porous material). , fibrous) is generated, which causes a decrease in strength.

As described above, since the physical properties of the FeNi bulk slag vary depending on the surface layer, the middle layer, and the lower layer, the crystal phases of the surface layer, the middle layer and the lower layer were analyzed, and the results are shown in Table 1.

division MgO·SiO ₂
(Enstatite, pyroxene, Hardness 5) 2MgO·SiO ₂
(Forsterite, olivine, Hardness 7) surface layer 67.5 32.5 middle class 69.5 30.6 substratum 75.3 24.7

As shown in Table 1, the main crystalline components of FeNi lumped slag _{are composed of MgO·SiO 2} and 2MgO·SiO ₂ . In the case of the surface layer, 2MgO·SiO ₂ is contained relatively the most, whereas the lower layer contains 2MgO·SiO 2 becomes the content of SiO ₂ than MgO · SiO ₂ increases, the hardness is contained a large amount is relatively weak components.

That is, 2MgO · SiO ₂ (olivine, hardness 7) of MgO · SiO ₂ (pyroxene, hardness 5) compared because pictures of robustness will the strength of the surface layer is high, FIG. XRD analysis of the surface layer 2 it is also the more MgO.SiO ₂ It can be seen that the crystal peak intensity (height) is lowered.

In addition, as shown in FIG. 3 , it can be seen that _{the content difference of MgO and SiO 2} is different in the surface layer and the lower layer of the FeNi lump slag, and in the case of the lower layer, the MgO content is relatively low, and the SiO ₂ content is relatively high. point can be checked.

On the other hand, when SiO ₂ is mixed with cement, a pozzolan reaction (Ca(OH) ₂ in cement reacts with SiO ₂ and water to form CaO-SiO ₂ -H ₂ O (Calcium silicate)) may occur as shown below. Therefore, it can contribute to improving the strength of cement.

Therefore, the present invention is to provide a method for recycling by physically separating the shoulder and neck (high strength) and weak (low strength) portions of FeNi slag.

In detail, the present invention comprises the steps of pulverizing FeNi lump slag to a particle size of 25 mm or less to obtain FeNi lump slag particles; and separating particles having a particle diameter of 5 to 25 mm among the FeNi lump slag particles into shoulder-diameter particles and particles having a particle diameter of less than 5 mm into weak particles.

The crushing may be performed through at least one crush method selected from the group consisting of a cone crusher, an impact crusher, a roll crusher, and a jaw crusher, but the present invention is not limited thereto, and the present invention provides the crush method as described above. Using a 5mm screen, the FeNi lump slag pulverized by the slag can be used to separate the shoulder-diameter particles with a particle diameter of 5 to 25 mm and the weak-part particles with a particle diameter of less than 5 mm.

On the other hand, the dog-diameter particles, the that of the bar, the dog-diameter particles of 65 to 70% by weight of MgO · SiO ₂ crystal, 2MgO · SiO ₂ crystal of 30 to 35% by weight as described above, obtained from the surface of the FeNi lump ore slag may include

Furthermore, since the shoulder-neck particle has excellent surface dry density, water absorption and wear rate, it can be used as an aggregate of concrete or ready-mixed concrete. Therefore, the present invention may include the step of using the shoulder and neck particles as an aggregate of concrete or ready-mixed concrete.

On the other hand, the weakened particles FeNi the like a bar, said weakened particles as described above, obtained from the bottom of the lump ore slag contains MgO · SiO ₂ crystal 73 to 78 less than wt%, 2MgO · SiO ₂ crystal 22 to 27% by weight can do.

Furthermore, as described above, the weak particles may be used as an admixture of concrete or ready-mixed concrete, or a solidifying material because the _{SiO 2 component is contained more than the shoulder and neck particles as described above.} Accordingly, the present invention may include the step of using the weak portion particles as an admixture of concrete or ready-mixed concrete, or a solidifying material. At this time, the solidifying material may mean to be utilized as a marine solidifying material (Deep cement mixing, DCM), but is not limited thereto.

In addition, when the weak particles have a fineness of 3000 to 4,650 cm ² /g, it is possible to provide excellent compressive strength as an admixture. When the fineness is ^{less than 3000 cm 2} /g, compressive strength may be lowered ^{when used as an admixture, and when it exceeds 4,650 cm 2} /g, when used as an admixture for concrete, there may be a problem of lowering the fluidity of the concrete. . Accordingly, the present invention may further include the step of pulverizing the weak portion particles to a fineness of 3000 to 4,650 cm ^{2 /g.}

On the other hand, when the weak part particles are used as an admixture, desulfurization dust may be additionally mixed and used to enhance the pozzolan effect. _{At this time, the desulfurization dust may contain Ca(OH) 2} , CaSO ₄ or NaSO ₄ as a by-product generated in the process of removing SOx generated in a kiln of a ferronickel smelter, for example, Ca(OH) ₂ may contain 50% by weight or more.

As described above, the present invention can provide a method of recycling FeNi lumped slag by separating the shoulder and neck particles from the weak part particles by using the different composition of the components of the surface layer part and the lower layer part of the FeNi lump slag, and in FIG. A method of recycling FeNi lump slag of the present invention is briefly shown.

Hereinafter, the present invention will be described in more detail through specific examples. The following examples are merely examples to help the understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

(1) Particles in the shoulder area

FeNi lump slag generated in the ferronickel smelter was pulverized to a particle size of 25 mm or less than 20 mm using a cone crusher.

The pulverized FeNi lump slag was classified and collected into particle diameters of 5-20 mm and 5-25 mm, and the physical properties as aggregates for concrete were confirmed.

As physical properties as aggregates for concrete, the surface dry density, water absorption rate and wear rate were measured by the following methods.

[Measurement of surface dry density and absorption rate]

Surface dry density and water absorption were measured according to KS F 2503.

[Measurement of wear rate]

Wear rate measurement was performed according to KS F 2508.

Table 2 shows the results measured as described above.

division Surface dry density (g/cm ³ ) Absorption rate (%) Wear rate (%) Aggregate quality standards for concrete
(KS F 2527) 2.5 or higher 3 or less 40 or less natural gravel 2.65 1.2 22.5 FeNi weird slag 5-20mm 2.78 1.6 24.7 5~25mm 2.70 1.8 27.5

As shown in Table 2, it was confirmed that the 5-20 mm and 5-25 mm FeNi bulk slag stably satisfies the concrete aggregate quality standards.

(2) Fragile Particles

FIG an FeNi lump ore slag ground to a particle size less than 25mm or 20mm in the above (1) powder is 2,500cm ² / g class ^{(2,680cm 2 / g), 3,000cm} 2 / g class (3,110cm ² / g), and 3,500 cm ² / g class (3,650cm ² / g) were separated by the milling, in general, in use of cement (OPC; Ordinary Portland cement) for the comminuted material is a bonding material made of a cement admixture and mixed to serve as reference material The compressive strength performance was evaluated when the

In addition, in order to compare the compressive strength, instead of the FeNi bulky slag particles, fly-ash, a pozzolan material generally used in construction sites, was used.

Furthermore, the compressive strength when additionally used desulfurization dust generated in the FeNi production process was also compared, and the desulfurized dust used in this case used a material containing more than 50% by weight _{of Ca(OH) 2 .}

The mixing ratio of the prepared binder is summarized in Table 3 below.

OPC (wt%) Fly-ash (wt%) Weak Particles Desulfurization slag (wt%) 2500cm ² /g class 3000cm ² /g class 3500cm ² /g class Comparative Example 1 85 15 - - - - Comparative Example 2 85 - 15 - - - Comparative Example 3 80 - 15 - - 5 Example 1 85 - - 15 - - Example 2 80 - - 15 - 5 Example 3 85 - - - 15 - Example 4 80 - - - 15 5

A test specimen was prepared after mixing and curing by setting the weight ratio of the binder compounded as shown in Table 3, ISO standard sand, and water to 1:3:0.5, and the compressive strength of 7 days and 28 days of age was measured. evaluated, and the results are shown in FIG. 5 .

As a result, as shown in FIG. 5 , the compressive strength was evaluated to be lower than that of fly-ash, which is a conventional admixture ^{, at the powder level of 2500 cm 2 /g.} On the other hand, the powders of 3000cm ² /g grade and 3500cm ² /g grade showed higher strength than fly-ash, and in particular, it was confirmed that higher strength was expressed when mixed with desulfurization slag.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations are possible within the scope without departing from the technical spirit of the present invention described in the claims. It will be apparent to those of ordinary skill in the art.

Claims (8)

pulverizing FeNi lump slag to a particle size of 25 mm or less to obtain FeNi lump slag particles; and
A method for recycling FeNi lumped slag, comprising the step of separating particles having a particle diameter of 5 to 25mm among the FeNi lumped slag particles into shoulder-diameter particles and particles having a particle diameter of less than 5mm into weak-part particles.
According to claim 1,
The crushing will be performed through at least one crushing method selected from the group consisting of a cone crusher, an impact crusher, a roll crusher and a jaw crusher, FeNi bulky slag recycling method.
According to claim 1,
The shoulder and neck particles are MgO · SiO ₂ crystals 65 to 70% by weight, 2MgO ·SiO ₂ crystals 30 to 35% by weight, FeNi lump slag recycling method.
According to claim 1,
A method for recycling FeNi bulk slag, comprising the step of using the shoulder-neck particle as an aggregate of concrete or ready-mixed concrete.
According to claim 1,
The weakened particles MgO · SiO ₂ crystal is less than 73 to 78% by weight, comprising the 2MgO · SiO ₂ crystal 22 to 27 wt%, FeNi lump ore slag recycling.
According to claim 1,
A method for recycling FeNi bulk slag, comprising the step of using the weak part particles as an admixture of concrete or ready-mixed concrete, or a solidification material.
According to claim 1,
The FeNi bulk slag recycling method further comprising the step of pulverizing the weak particles to a fineness of 3000 to 4,650 cm ^{2 /g.}
8. The method of claim 7,
A method for recycling FeNi bulk slag, comprising the step of mixing the powdered weak part particles with desulfurization dust and using it as an admixture of concrete.

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