JPH11269565A - Agglomeration of alkali-containing dust - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep strength without disintegration even after curing in the air over a long term and also, without requiring a means for preventing water splashing by adding fine powder containing Fe and FeO and water to dust containing a large quantity of Na2 CO3 and mixing and agglomerating. SOLUTION: Wet dust in steelmaking is regulated to have <= about 20% moisture by wing a thickener 1 and a filter press to obtain iron containing fine powder having >=70 wt.% Fe and FeO. This iron-containing fine powder is added to alkali-containing dust having >=20% Na2 CO3 produced in an iron work, or the like, and supplied from a storing tank 4, and mixed in a kneader 3 by adding water. The quantity of this iron-containing fine powder to be added is preferably 20-80 wt.%, while water is added so as to be preferably 0.7-1.5 wt.% to Na2 CO3 . This kneaded material is charged into an extrusion forming machine 5 and the obtd. columnar agglomeration A is cured in the air for a prescribed time so as to be reused as a material having a high strength to crushing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a process for agglomerating by adding ferrous fines alkali-containing dust which contains Na ₂ CO ₃ generated by SeiTetsusho like 20% by weight or more.

[0002]

2. Description of the Related Art In an ironworks, a large amount of iron-containing fine dust and sludge are generated from each of the ironmaking, steelmaking, and rolling processes, and a wet or dry dust collector and other devices are installed to collect the dust and sludge. I have. Of this collected dust,
Recycling of dust and sludge containing a large amount of iron has hitherto been carried out for the purpose of recovering an iron source in a pig or steel making process. On the other hand, if the alkali-containing dust containing a small amount of iron is reused as powder as it is, a problem may occur in the process of transporting the powder. For example, as disclosed in JP-A-6-264126, molten iron is used. The agglomerated dust collected from the pre-treatment process (dust containing alkali) and the agglomerated dust collected from the decarburization furnace (iron-containing fine powder) are mixed together to form the hot metal pre-treatment process. A method for achieving reuse has been proposed.

[0003]

However, Japanese Patent Application Laid-Open No.
Means for agglomerating dust collected from the hot metal pretreatment process proposed in Japanese Patent No. -264126 is to add cement or a hydraulic binder such as granulated blast furnace fine powder or quicklime, alone or in combination, and to add water thereto. In addition, they are mixed and agglomerated and cured in the air for a predetermined period of time. However, if the agglomerated material is left in the air for a long period of time, the hydraulic binder loses moisture, causing collapse (winding). For this reason, there is a problem that a means for preventing the scattering of water is required. The present invention is an alkali-containing dust for producing an agglomerate of an alkali-containing dust capable of maintaining strength at a low cost without disintegrating even after long-term air curing without the need for a means for preventing the scattering of moisture. It is an object of the present invention to provide an agglomeration method.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and the means 1 includes N
a ₂ CO ₃ was agglomerated and mixed with the addition of ferrous fines and water containing alkali-containing dust Fe and FeO 70% by weight or more, containing more than 20 wt%, alkali-containing to atmospheric curing the該塊formed product This is a dust agglomeration method. Further, in the above means, the means 2 further comprises the Fe
And an iron-containing fine powder containing FeO and FeO in an amount of 20% by weight or more and 80% by weight or less. In the means 1 or 2, the weight ratio of water contained in the agglomerate to Na ₂ CO ₃ in the alkali-containing dust at the start of the air curing is 0.7 or more and 1.5 or less. Thus, the method for agglomerating alkali-containing dust by adding the water is described. Na ₂ C
Examples of the alkali-containing dust containing O _{3 in an amount} of 20% by weight or more include dust generated in pretreatment of hot metal generated in an ironworks and blast furnace 2
Secondary dust ash etc. can be used. In addition, as the iron-containing fine powder, converter wet dust collected as steelmaking wet dust, steelmaking / rolling sludge, and the like can be used. Further, as an apparatus for agglomerating a mixture of alkali-containing dust and iron-containing fine powder, known means,
For example, a dish-type granulator or an extruder may be used to agglomerate into a sphere or a column, but in order to suppress the agglomeration of the agglomerate during reuse, a sphere is preferable, and the size is about 5 mm to 50 mm. It is good, but it is preferably 15 mm to 40 mm for handling.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to FIG. In FIG. 1, reference numeral 2 denotes a filter press, which dewaters slurry steelmaking dust (converter wet dust) having the components and particle diameters shown in Table 1 received from the thickener 1 to a moisture content of 20% by weight. Reference numeral 3 denotes a double-arm kneader kneader, which is a steelmaking wet dust as iron-containing fine powder dehydrated by the filter press 2 and an alkali-containing dust discharged from the storage tank 4 as shown in Table 1. The dust generated from the water is collected by a dry dust collector). 5 is an extrusion molding machine,
The kneaded material kneaded by the double-arm kneader kneader 3 is referred to as a columnar agglomerate A.

[0006]

[Table 1]

The present inventors have conducted various experiments and studies to maintain the strength of the agglomerate of the alkali-containing dust without adding a binder or the like. As a result, the agglomerate is present at least on the surface of the agglomerate. It has been found that by oxidizing Fe and FeO to Fe ₂ O ₃ , the structure becomes denser and the strength can be maintained. The Na ₂ CO ₃ contained in the alkali-containing dust forms an alkali hydrate when adsorbing moisture, thereby reducing the distance between particles constituting the agglomerate and improving the density. However, when moisture in the alkali hydrate escapes, efflorescence occurs and strength is reduced. Therefore, it is necessary to maintain a state in which the alkali-containing dust adsorbs a certain amount of moisture. Therefore,
By mixing the iron-containing fine powder containing Fe and FeO with the agglomerate, Fe and F in the iron-containing fine powder at the surface of the agglomerate are mixed.
eO is oxidized with air to form an oxide film on the surface of the agglomerate, thereby making the tissue denser and suppressing the release of internal moisture from the surface, and forming an inner layer of the alkali hydrate. It is possible to prevent efflorescence. To obtain this effect, the content of Fe and FeO must be 70% by weight or more. It is preferable that the compounding amount of the iron-containing fine powder in the alkali-containing dust is 20% by weight to 80% by weight.
That is, if the amount of the iron-containing fine powder is less than 20% by weight, the amount of the iron-containing fine powder present in the surface layer portion of the agglomerate is insufficient, and the amount of the oxide film formed is insufficient. This is because the formation of water is insufficient, and it is impossible to prevent the internal moisture from leaking from the surface, and efflorescence occurs. On the other hand, if the content of the iron-containing fine powder exceeds 80% by weight, the amount of alkali-containing dust is small and the strength is weak.

The amount of water added at the time of agglomeration may be such that alkali-containing dust and fine iron-containing powder can be agglomerated by the agglomeration equipment. It is preferable to add water so that the weight ratio of / Na ₂ CO ₃ is in the range of 0.7 to 1.5. That is, when the weight ratio of water / Na ₂ CO ₃ is less than 0.7, the amount of Na ₂ CO ₃ in the alkali-containing dust reacting with water to form an alkali hydrate during air curing is insufficient. And it is not possible to obtain sufficient strength.
If the weight ratio of a ₂ CO ₃ exceeds 1.5, curing for a long period of time is required, and the agglomerates are easily deformed and broken in the transportation process after the agglomeration.

[0009]

EXAMPLE An example of producing agglomerate A using the equipment shown in FIG. 1 will be described below with reference to Table 2. The strength in Table 2 indicates the crushing strength per piece (kg / piece).

[0010]

[Table 2]

Examples 1 to 3 in Table 2 satisfy all the claims of the present invention, and the agglomerate A has a large crushing strength and does not generate efflorescence. Comparative Example 1
Is an example in which the mixing ratio of the iron-containing fine powder (converter wet dust) is outside the upper limit of claim 2. Since the content of the alkali-containing dust is small, the effect of improving the strength due to the alkali-containing dust inside the agglomerate cannot be exerted, and crushing occurs. Strength decreased. Comparative Example 2
Is an example in which the mixing ratio of the iron-containing fine powder (converter wet dust) is out of the lower limit of claim 2, an oxide film due to Fe ₂ O ₃ on the surface cannot be sufficiently formed, and efflorescence of the alkali-containing dust hydrate Was not able to be suppressed, and the crushing strength was also low. Comparative Examples 3 to 5 are cases in which the ratio of water / Na ₂ CO ₃ at the start of atmospheric curing in the double-arm kneader kneader 3 is out of the range of claim 3. As in Comparative Example 3, when the weight ratio of water / Na ₂ CO ₃ at the start of the air curing of the agglomerate A is outside the lower limit of the third aspect, no agglomerate can be obtained. This is because if the raw material moisture is low, Na
_{This is because 2} CO ₃ absorbs moisture and the distance between the particles of Na ₂ CO ₃ and the iron-containing fine powder cannot be shortened to form an agglomerate. When the raw material has a large amount of water as in Comparative Example 4, the raw material is fluidized and cannot be agglomerated. Even if agglomeration can be achieved, the strength is not significantly improved unless molded with an appropriate amount of water as in Comparative Example 5.

[0012]

As described above, in the method for agglomerating alkali-containing dust according to claims 1 to 3, it has not been possible to agglomerate alkali-containing dust with simple equipment. External processing can be avoided by reusing dust generated from steelworks.

[Brief description of the drawings]

FIG. 1 is an apparatus flow diagram for promoting the present invention.

[Description of symbols] 1 Thickener 2 Filter press 3 Double-arm kneader kneader 4 Storage tank 5 Extruder

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kanji Watanabe 1 Nishinosu, Oita, Oita, Oita Prefecture Inside Nippon Steel Corporation Oita Works (72) Inventor Kenji Yaegashi 1 Nishinosu, Oita, Oita City, Oita New Japan Inside Oita Works of Iron Corporation

Claims (3)

[Claims] 1. A method for agglomerating an alkali-containing dust containing 20% by weight or more of Na ₂ CO ₃ , wherein iron-containing fine powder containing 70% by weight or more of Fe and FeO and water are added to the alkali-containing dust. A method for agglomerating alkali-containing dust, comprising mixing and agglomerating, and curing the agglomerated product in the air. 2. The method for agglomerating alkali-containing dust according to claim 1, wherein the amount of the iron-containing fine powder containing Fe and FeO to be added is 20% by weight or more and 80% by weight or less. 3. The method according to claim 1, wherein the moisture contained in the agglomerate at the start of the atmospheric curing is Na ₂ in the alkali-containing dust.
The method for agglomerating alkali-containing dust according to claim 1 or 2, wherein the water is added so that the weight ratio to CO ₃ is 0.7 or more and 1.5 or less.