KR20040020471A - Method for manufacturing pellet with by-products of stainless steel plant - Google Patents

Abstract

PURPOSE: A pallet manufacturing method is provided which prevents degradation or disintegration of green compact by changing initial hydration conditions according to CaO content of byproduct generated in the stainless steel manufacturing process and completely hydrating CaO non-hydrated in the water spraying pellet molding process. CONSTITUTION: In a method for manufacturing byproduct generated in the stainless steel manufacturing process into green compact, the method comprises the steps of mixing 100 weight parts of stainless steel electric furnace dust with 3 to 15 weight parts of water; mixing 100 weight parts of stainless steel refining furnace dust with 8 to 20 weight parts of water; aging the electric furnace dust mixed with water and the refining furnace dust mixed with water; mixing a binder with the aging treated dusts; molding the mixture into pellet as spraying water onto the mixture; and hardening and drying the pellet, wherein the refining furnace dust is substituted for some of refining furnace middle dust obtained by ball milling the mixture after mixing refining furnace dust with 8 to 20 weight parts of water, wherein the aging treated dust is mixed with 10 to 60 wt.% of scale and one or more oxides, and wherein the dried pellet contains a moisture content of 8% or less.

Description

Method for manufacturing pellet with by-products of stainless steel plant}

The present invention relates to a method for producing by-products generated in a stainless steel manufacturing process into a molded article, and more particularly to a method for inducing a hydration reaction according to the characteristics of the by-products and to produce pellets with low quality deviation.

Stainless steel is produced by melting molten iron and ferroalloy in an arc furnace using arc heat to make molten steel, and refining the molten steel in a refining furnace. In such a stainless steel manufacturing process, various by-products are generated for each process. Electric furnaces generate electric dust. In the refining furnace, heavy dust is collected in a cyclone, and dust is collected in a dust collector by fine powder.

Such electric furnace dust and refining furnace (middle) dust contain a large amount of valuable metals such as Cr and Ni in addition to iron components. Therefore, these dusts are made into briquettes and melted in a small electric furnace to recover ferroalloy and recycle other components as civil raw materials.

Prior art related to the technology for producing by-products produced in the stainless steel manufacturing process to briquettes is Korean Laid-Open Patent Publication No. 2000-0013357 (aging device of quicklime-containing dust for briquette manufacturing). This technique relates to a aging apparatus for dust used in the manufacturing process of FIG. 1 for recycling by-products generated in the stainless manufacturing process. In this aging system, water is added without any distinction between electric furnace and refining furnace dust, followed by hydration treatment as in Equation 1 below, followed by aging.

Scheme 1

CaO + H 2 O → Ca (OH) 2 + 15.2 kcal / mol

The aged raw material is produced by briquetting by mixing a binder such as molasses.

By the way, it is difficult to control the moisture content in the process of molding the dust generated in the stainless manufacturing process into briquettes. As a result, differentiation and decay of briquettes occurs frequently due to the progress of hydration of unhydrated quicklime after molding.

The present invention can be different from the initial hydration conditions according to the CaO content of by-products generated in the stainless steel manufacturing process, and to fully hydrate the unhydrated CaO in the pellet molding process of spraying water to prevent the differentiation or collapse of the molded body To provide a manufacturing method, the object is.

1 is a process chart for manufacturing by-products generated in the conventional stainless steel manufacturing process by briquettes.

Figure 2 is a process chart for producing by-products generated in the stainless steel manufacturing process pellets according to the present invention

* Description of the symbols for the main parts of the drawings *

1 ..... Furnace dust hopper 2 ..... Refinery dust hopper

2-1 ... Furnace Heavy Dust Hopper 3 ..... Grinder

4 ..... Aging 6 ..... Aged Dust Storage Hopper

7 .... scale hopper 8 .... iron oxide hopper

9 .... Binder Hopper 11 ..... Mixer

12 .... Pelletizer 12-1 ... Water Sprayer

13 .... curing hopper 14 ..... dryer

Method for producing a pellet using by-products generated in the stainless manufacturing process of the present invention for achieving the above object,

Mixing 3 to 15 parts by weight of water with 100 parts by weight of dust by stainless steel electric,

Mixing 8 to 20 parts by weight of water with 100 parts by weight of dust and stainless steel,

Aging the dust and refining roast with electric water mixed,

Mixing at least one kind and a binder in the aged dust,

Molding into a pellet while spraying water on the mixture,

Curing and drying the pellets.

Hereinafter, the present invention will be described in detail.

According to the present invention, since the CaO content and particle size of by-products generated in the stainless steel manufacturing process are different, a hydration process suitable for the characteristics should be applied. It is completed by noting that it can be done.

Table 1 and Table 2 below show the chemical composition and particle size distribution of dusts generated during the stainless steel manufacturing process.

division CaO MgO SiO2 M-Fe T-Fe Al2O3 ZnO PbO CuO NiO Cr2O3 MnO Electric furnace 4.4 1.53 7.05 1.14 29.1 0.36 7.36 1.48 0.63 2.13 19.1 3.4 Refinery Furnace Dust 26.8 6.1 8.48 12.2 32.6 0.26 0.01 0.05 0.18 2.54 14.4 4.4 Refinement Roast 23.9 5.8 5.4 4.95 30.2 0.3 0.56 0.25 0.37 2.63 14.2 3.3

division Electric dust Refining furnace heavy dust Refinery Dust Pass through 710um 100 85 100 Passed 500 um 95 75 99 Pass 300 um 85 36 98 Pass through 250 um 76 30 97 Pass through 150 um 60 15 95 Pass through 75 um 31 3 62 Pass through 45 um 2 0.5 25

As shown in Table 1, since the electric furnace dust is less CaO component than the refinery dust, the double free-CaO content is also reduced. In addition, as shown in Table 2, it can be seen that the refining furnace heavy dust is thicker than the electric furnace dust and the refining furnace dust.

Therefore, in consideration of the powder characteristics of the dust, it can be seen that the independent progress of the hydration reaction according to the characteristics of these dusts can prevent the collapse and differentiation of the molded body after molding and reduce the quality deviation of the molded body.

This invention will be described with reference to FIG. 2.

2 mixes water with the dust charged in the electric dust hopper 1 and the refinery dust hopper 2-1. It is preferable to mix 3-15 weight part of water with respect to 100 weight part with respect to an electric furnace dust. Moreover, it is preferable to mix 8-20 weight part of water with respect to 100 weight part with refining furnace dust. If the amount of water added to the dust is less than the above range, the free-CaO in the dust may not be sufficiently hydrated, and there is a fear that collapse and differentiation may occur in the molded body (pellets). In addition, when the amount of added water is large, the amount of water is large and workability is poor in the pellet forming process, and the shape of the molded body is irregular, resulting in a decrease in strength of the pellets.

In the present invention, the refining furnace heavy dust can be used under the same conditions as the refining furnace dust. Except that the refining medium dust has a large particle size, there is no big difference between the refining dust and the component, so the amount of water mixed can be used in the same way. Therefore, the refinery furnace dust can be replaced with a part of the refinery dust. However, since the particle size is large, it may be pulverized after mixing the water. Since the grinding of heavy dust in the refining furnace does not differ from the refining dust, the replacement amount is not very important.

That is, water is mixed with the dust charged in the heavy dust hopper 2-2, and it grind | pulverizes in the grinder 3. Differentiation occurs in the aging process, which is a post-process, but when mixed with water and pulverized, the hydration reaction occurs well during the aging process.

Dust mixed with water is aged in the ripening machine (4). It is preferable to carry out aging about 2 hours or more. In the case of ripening less than 2 hours, the hydration reaction proceeds after the pellet manufacturing process or pellet manufacturing may occur pellet differentiation.

The aged dust is transferred to the storage hopper 6 and stored. Ripening is also carried out in the storage hopper. The dust of the storage hopper 6 and the binder of the binder hopper 9 are mixed in the mixer 11.

One kind of scale and iron oxide produced in the stainless steel manufacturing process can be mixed and mixed with the dust and the binder. Scale is generated as a by-product in the hot rolling process of stainless steel, and iron oxide is produced as a by-product during the pyrolysis of pickling liquid in the cold rolling process. Tables 3 and 4 show typical compositions and particle size ranges of scales and iron oxides.

division CaO MgO SiO2 M-Fe T-Fe NiO Cr2O3 TiO2 MnO scale 3.96 0.33 2.53 11.07 49.5 7.6 15.5 Tr 1.1 Iron oxide 0.71 tr 0.68 tr 52.2 4.9 9.8 tr 0.57

division scale Iron oxide Pass through 710um 100 100 Passed 500 um 99 90.8 Pass 300 um 98 82.8 Pass through 250 um 97 25.7 Pass through 150 um 74.5 3.91 Pass through 75 um 16.0 0.22 Pass through 45 um 2.9 0.04

As shown in Table 3, since the scale and iron oxide contain more valuable metal components than dust, the scale and iron oxide may be added as a mixed material to the dust pellet manufacturing process in terms of the treatment of by-products and the recovery of valuable metals. In addition, because the particles of the scale and iron oxide is small, it serves as a filler between the large particles of the dust during pellet production and serves to densify the pellets to increase the strength of the pellets.

In the case of using the scale and the iron oxide according to the present invention, at least one of the scale and the iron oxide stored in the scale hopper 7 and the iron oxide hopper 8 is supplied to the mixer 11 and mixed with the dust and the binder.

Portland cement is a typical binder. The amount of the binder is preferably 8-20 parts by weight based on 100 parts by weight of the feedstock (dust or dust + iron oxide and scale). If it is less than 8% by weight, there is a problem that the strength expression value is low, and if it is more than 20% by weight, the addition of a binder more than necessary causes an increase in the basicity value, which is not preferable.

Iron oxide and scale are secondary raw materials produced in the stainless steel manufacturing process, and since the properties are not significantly different from dust, there is no significant effect on the recovery of ferroalloy from the molded body. Thus, part of the dust can be replaced with iron oxide and scale. Preferably, it is preferable to mix 10-60 weight% of iron oxide and 1 or more types of scales with respect to 100 weight part of all raw materials (electric furnace, refinery (dust) dust, iron oxide, and a scale). If the mixing amount is less than 10% by weight, the strength value of the pellets is low, and when the mixing amount is more than 60% by weight, it is difficult to dissolve the pellets, so high temperature is required for dissolution.

The raw materials mixed in the mixer 11 are supplied to the pelletizer 12 to produce pellets while spraying water. Free-CaO is sensitive to water and affects the rate of hydration depending on CaO activity. Therefore, in the conventional briquette manufacturing method, there is no method of hydrating unhydrated quicklime during briquetting. However, in the pelletizer, since water may be added together with the feedstock during the molding process, the pellets are manufactured one by one, so that the unhydrated free-CaO component absorbs water and hydrates at this time. Therefore, it is not necessary to strictly control the moisture content before molding compared to briquetting.

The pellet is cured in the curing hopper 13. During curing, a method of curing by passing steam (about 70 ° C. or more) from the bottom up may be used. Steam curing has the effect of improving the initial strength of the pellet, shortening the drying time to shorten the shipping time of the product. Natural curing is possible, not steam curing.

The cured pellets are dried in a dryer 14. Drying may be natural drying or heating to a constant temperature. It is preferable to make moisture of a pellet into 8% or less of drying. If the amount of water contained in the pellet exceeds 8%, there is a risk of explosion when the pellet is dissolved.

The present invention will be described in more detail with reference to the following Examples.

Example 1

In order to determine the change in strength after pellet production according to the initial moisture addition amount of the dust of the electric furnace and the refining furnace, the amount of water input at the time of initial hydration was changed to compare the change of the strength value of the pellet two days after the pellet production.

division Electric furnace Refining furnace heavy dust + refining dust (5: 5 blended) Scale + Iron Oxide (5: 5 Blended) Initial moisture addition amount of electric furnace Initial water addition amount of heavy dust in refinery dust + refinery furnace Compressive strength (kgf) Comparative Example 1 20 35 45 2 15 5 Comparative Example 2 20 35 45 25 15 16.7 Comparative Example 3 20 35 45 10 5 2.5 Comparative Example 4 20 35 45 10 25 17.5 Inventive Example 1 20 35 45 15 15 38.4 The binder amount is 13% by weight based on 100 parts by weight of the entire raw material.

As shown in Table 5, Comparative Examples 1 and 2 show a state in which the amount of water added required for hydration of the electric dust is insufficient or excessive. Comparative Examples 3 and 4 show a state in which the amount of water required for hydration of the dust in the refining furnace is insufficient and excessive. As such, the strength of the prepared pellets varies depending on the amount of water required for the hydration of the quicklime-containing dust. When the amount of added water was small, sufficient hydration did not proceed, and the pellets were differentiated and disintegrated due to hydration after pellet production. If the amount of moisture is excessive, the shape of the pellet is irregular, which causes the strength of the pellet to decrease.

On the contrary, in Inventive Example 1 in which the amount of water is properly mixed according to dust, it can be seen that the compressive strength is the best.

Example 2

The effects of the scale and the amount of iron oxide added on the strength of the pellets were investigated in the preparation of pellets using by-products. The initial water content of the added dust was the same as that of Inventive Example 1 of Example 1, and was compared by measuring the compressive strength (kgf) 2 days after the pellets were prepared.

division Electric furnace Refinery Furnace Dust Scale + iron oxide (5: 5 combination) Amount of binder Compressive strength (kgf) Comparative Example 5 40 60 0 13 12.9 Comparative Example 6 38 57 5 13 17.8 Inventive Example 2 36 54 10 13 33.5 Inventive Example 3 30 45 25 13 37.2 Inventive Example 4 15 25 60 13 35.4 Comparative Example 7 10 15 75 13 35.1

As shown in Table 6, as a result of testing the effect of the scale and the amount of iron oxide injected into the pellet production on the strength change of the pellet, when the scale and iron oxide was not added as in Comparative Example 5, the strength value is relatively low Indicated. This is because when the pellets are made of dust only, especially in the refining furnace heavy dust, the particles are thick, so that the pellets are not densified and contain a lot of pores, resulting in a decrease in strength. In addition, as in Comparative Example 6, the relative compressive strength value was low even when the scale and the iron oxide 5% by weight relative to the total weight of the input material 100%.

However, as inventive examples 2, 3 and 4, the relative compressive strength value increased when the scale and the amount of iron oxide input exceeded 10% by weight. This is because the scale of fewer particles and the iron oxide powder fill the pores of the particles of the larger dust than the dust in the refining furnace, and thus the pellets produced are more densified.

On the other hand, when the amount of scale and iron oxide exceeds 60% by weight as in Comparative Example 7, there is no problem in strength expression. However, since the main crystal phase of the scale and iron oxide is composed of Fe2O3 and Fe3O4, when these components are high, there is a problem in that the melting temperature must be increased during the melting operation to recover valuable metals.

Example 3

As in Example 1 and Example 2, the effect of binder addition amount on the strength of pellets during pellet preparation was investigated. In general, binders are added to improve the strength of the pellets in the manufacture of the pellets. At this time, the input amount shows a difference in the added amount and strength value of the binder according to the nature of the input material.

division Electric furnace Refinery furnace dust + electric dust (5: 5 blended) Scale + Iron Oxide (5: 5 Blended) Amount of binder Compressive strength value (kgf) Comparative Example 8 30 45 25 3 5.2 Comparative Example 9 20 35 45 5 7.4 Inventive Example 5 20 35 45 8 25.2 Inventive Example 6 20 35 45 20 40.6 Comparative Example 10 20 35 45 30 45.4

As shown in Table 7, the comparative example 8 had a low compressive strength value when the amount of binder added was 3 wt% based on 100 parts by weight of the raw material, and the scale and the amount of iron oxide in the raw material were increased as in Comparative Example 9. When the amount of the binder was 5% by weight, the strength value of the pellets was low. On the other hand, when the addition amount of the binder as 8-20% by weight as inventive examples 5 and 6, the initial strength value of the pellets showed a strength value that can handle the pellets.

On the other hand, when the amount of binder added is more than 20% by weight as in Comparative Example 10, there is a disadvantage in that the consumption of SiO2, which is an auxiliary material, is increased in order to lower the basicity when melting the pellet in the future due to an increase in the basicity (CaO / SiO2 ratio) of the pellet. .

The present invention can provide a method for reducing the quality deviation of the molded article when the molded article is to be manufactured using a raw material containing free-CaO such as dust among the process by-products generated during the production of stainless steel and improve the quality of the molded article Provide a way to do this.

Claims (4)

In the method for producing by-products generated in the stainless steel manufacturing process into a molded body, Mixing 3 to 15 parts by weight of water with 100 parts by weight of dust by stainless steel electric, Mixing 8 to 20 parts by weight of water with 100 parts by weight of dust with stainless scouring, Aging the dust and refining roast with electric water mixed, Mixing a binder with the aged dust, Molding into a pellet while spraying water on the mixture, A method of producing pellets using by-products generated in the stainless steel manufacturing process comprising curing and drying the pellets. The method of claim 1, wherein the refining furnace dust is mixed with 8 to 20 parts by weight of water and replaced with a portion of the pulverized refining furnace heavy dust. The method of claim 1, wherein the aged dust is mixed with 10 to 60% by weight of at least one of scale and iron oxide. The method of claim 1, wherein the drying is performed so that the water content of the pellet is less than 8%.