JPH02149607A - Manufacture of iron powder from converter dust - Google Patents

Abstract

PURPOSE:To manufacture iron powder having high quality with simple treatment process by classifying and separating the granule of specific particle diameter from dust collected from a converter and dropping and selecting with the specific inclining angle after detaching stuck material by dry-type pulverizing. CONSTITUTION:The converter dust collected with dust collector, etc., is classified and the granule having 20 - 500mu particle diameter is separated and fine powder having much iron oxide content and coarse grain having much graphite and lime grain are separated. Successively, the separated granule having 20 - 500mu is pulverized and ground with the dry-type pulverizer and stuck material of graphite, slag, etc., on the coarse grain iron powder surface layer is detached. This pulverized and ground granule is supplied to the inclined face having 5 - 40 deg. inclining angle at slow speed and is dispersed and dropped to collect the iron powder at dropped ore side. By this method, the iron powder having >=about 94wt.% metallic iron is obtd. Further, in order to obtain the iron powder having higher quality, by treating the iron powder at the dropped ore side with 1 - 10 normal hydrochloric water solution, high quality iron powder having about 98wt.% metallic iron, is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing high-grade iron powder from dust from a steelmaking converter through simple processing steps.

[Prior Art] A large amount of dust is generated in a steelmaking converter in a steelworks.For example, a wet type! In dust treatment, the amount of dust generated can amount to about 1,000 tons per 180-ton converter. This dust contains about 60 to 70% metallic iron, and has a high iron quality, but it also contains graphite and CaO1Si.
It also contains a large amount of slag components such as ○2.

Conventionally, such converter dust has usually been used as part of the raw material for blast furnace sinter or pellets from the viewpoint of iron source recovery. Recently, attempts have been made to produce iron powder with higher added value from this converter dust.

Gold 1 iron powder has a variety of uses, such as powder metallurgy, welding rods, and cutting, and requires various properties.Currently, most of these industrially used iron powders are produced using the spray method or Manufactured by reduction method.

However, there are limits to the ability to manufacture high-grade iron powder at low cost because the manufacturing process is complicated and requires expensive raw materials, a large amount of energy, and other expensive auxiliary materials such as injection gas.

For this reason, it would be advantageous if high-grade iron powder could be produced from converter dust, which is a steelmaking byproduct.

Several methods for recovering iron powder from converter dust have been proposed in the past. For example, Japanese Patent Publication No. 5744724 discloses a method for recovering iron powder by wet pulverizing converter dust and then beneficiation using magnetic separation ability. A collection method is disclosed.

In addition, JP-A-59-1802 discloses that after pulverizing converter dust, it is magnetically sorted, the surface impurity layer of the obtained iron powder is treated with mineral acid of 0.3 to 0.9 N, and the powder is subjected to impact compression pulverization. A method for producing iron powder is disclosed.

[Problem to be solved by the invention] The methods proposed in the above-mentioned publications are considered to be advantageous methods for producing iron powder, but it is difficult to completely remove impurities such as graphite and slag components accompanying converter dust. There are limits to the separation. In particular, although magnetic separation is performed in both methods, fine particles of impurities mixed in the dust become entangled with the iron powder and become magnetized together with the iron powder, reducing the quality of the iron powder.

Furthermore, although wet pulverization is carried out in Japanese Patent Publication No. 57-44724, the surface of the metal iron powder is significantly oxidized during this wet pulverization to form an oxide scale layer, requiring a reduction treatment step or an oxidation treatment step. This complicates the manufacturing process, reduces the yield of iron powder, and inevitably increases costs.

The present invention is intended to produce high-grade, high-value iron powder from converter dust at a low cost by completely separating impurities such as graphite and slag components without performing a magnetic separation process or a wet pulverization process. be.

[Means for Solving the Problems] That is, the present invention includes (a) a first step of classifying collected converter dust to separate particles having a particle size of 20 to 500 μm, and (b) a step after classification. (c) a second step of crushing and grinding the granules using a dry pulverizer and peeling off adhesion such as graphite and slag on the surface layer of the granules; A third step is to collect iron powder from the fallen ore side, and separate and remove graphite and slag from the remaining ore side. Regarding the manufacturing method.

Furthermore, the present invention provides (a) converter dust 1 collected by a dust collector;
A first step of classifying ~ to separate granules with a particle size of 20 to 500μ, and (b) crushing the granules after classification using a dry pulverizer to remove graphite, slag, etc. on the surface layer of the granules. (c) The granules after grinding and grinding are dispersed and dropped on a slope with an inclination angle of 5 to 40 degrees, iron powder is collected on the falling ore side, and iron powder is collected on the residual ore side. Separate graphite and slag,
and (d) a fourth step of treating the iron powder on the falling ore side with an aqueous solution of 1 to 10 N hydrochloric acid. .

[Function] Converter dust that is carried away in the exhaust gas during converter steelmaking and collected has a physical difference in composition between coarse grains within a certain particle size range and fine or large grains other than that. The shape characteristics are also distributed in different states, and if particles with a specific range of sizes are selected, it is easy to perform secondary processing to achieve high iron quality that cannot be obtained with particles of other sizes. It was found that coarse iron powder was obtained.

Table 1 below shows the physical forms of each component of iron powder (coarse iron powder and ultrafine iron oxide powder), graphite, and lime present in converter dust.

Section-V-j1 As stated in Table 1, in the form of generation, coarse iron powder with a particle size in the range of 20 to 500 μl is present in converter dust, which is fine. It can be separated as a single substance because it has a large difference in size and shape from iron oxide powder, graphite, lime, etc. This coarse iron powder has acid 1-hyscale, graphite, and slag components attached to the surface of spherical coarse metal iron particles.

This is because steel droplets scattered from molten steel during steelmaking in a converter solidify in a spherical state due to their surface tension, and an oxide film is formed on the surface of the droplets while flying or in a dust collector, and the droplets are entrained in the exhaust gas. This is probably due to the phenomenon that substances other than steel, such as slag and graphite, adhere to the surface.

When the surface of this coarse iron powder is crushed using a dry crusher, the graphite and slag attached to the surface are peeled off from the surface of the spherical coarse metal iron particles as fine powder with a size of less than 44 μm. It turns out.

This metallic iron is greatly different in size and shape from the exfoliated graphite and slag, and in this respect it exists in a form that is easy to separate.

The method of the present invention utilizes the physical properties of converter dust as described above.

In the first step of the present invention, the converter dust collected by a dust collector or the like is classified to have a particle size of 20 to 500 μm! 0 particles are separated. Through this separation, it is possible to separate fine powder of less than 20μI, which has a low iron quality and a high content of iron oxide, from large grains, which have a particle size of more than 500μI and have a low iron quality and a large amount of graphite and lime particles, resulting in a high iron recovery yield. At the bottom,
Iron content, or coarse iron powder, can be collected from converter dust. In this classification process, the particle size of the converter dust is 20 to 50.
Any method can be used as long as it can classify particles with a size of 0 μl, but a wet classification method is suitable.

In the second step, the particle size separated in the first step is 20 to 5.
The granules with a diameter of 0.00 μm are crushed into raw ore using a dry crusher, and deposits such as graphite and slag on the surface layer of the coarse iron powder are peeled off.

A dry ball mill, a vibration mill, etc. can be used as a crusher for V. Use of a wet pulverizer is not preferred because the metal surface oxidizes during wet pulverization to form an oxide scale layer, reducing the yield of iron powder. There is no particular restriction on the degree of processing of the crushed raw ore, but if the crushed raw ore is insufficient, the exfoliation of graphite and slag will be insufficient, and the iron quality of the resulting metallic iron powder will decrease. If too much ore is applied, some of the metallic iron particles will be crushed and mixed with graphite and slag, reducing the yield of metallic iron powder, which is undesirable. Graphai 1 ~ The purity and yield of the resulting metallic iron powder can be improved by crushing only the slag, peeling it off, and grinding it so that the metallic iron coarse particles remain as their original spherical coarse particles. It is advantageous from above.

In the third step, by utilizing the large difference in shape between the metal iron particles and the exfoliated graphite and slag in the granules after the pulverized ore in the second step, the granules after the pulverized ore are moved up the slope. The iron powder is collected on the falling ore side,
Separate and remove the slag on the residual ore side.
(Hereinafter, this process will be referred to as slope falling), in other words, only spherical metal iron particles roll down the slope and the irregularly shaped graphite and slag remain on the slope.
Single metallic iron particles can be separated on the falling ore side. At this time, the inclination angle of the slope needs to be 5 to 40 degrees. If the inclination angle is 5°, it is unfavorable because the number of metal iron particles remaining on the slope increases significantly.
If it exceeds 0°, irregularly shaped graphite and slag will roll on the slope and fall, reducing the iron quality of the iron powder. It is desirable that the feeding speed of the granules after pulverized ore onto the slope be as slow as possible.- If a large amount of granules after pulverized ore are fed onto the slope at once, spherical metallic iron particles and irregularly shaped graphite It falls down the slope in a state where it is entangled with slag and slag,
Graphite and slag mixed into the falling ore side is undesirable because it causes harmful effects.However, it is desirable to appropriately remove graphite and slag remaining on the slope so that they do not become an obstacle to the falling of metallic iron particles.

Further, the material used for the surface of the slope is not particularly limited, but it is desirable that the surface roughness is such that it is possible to retain the speci?cally fine graphite and slag on the slope.

It is possible to obtain iron powder containing 94% or more of metallic iron from converter dust by simply going through the above-mentioned first step, which is the classification step, second step, which is the crushed raw ore step, and third step, which is the slope fall sorting step. can.

The obtained iron powder can be used as it is as industrial iron powder for full use, but in order to obtain even higher grade iron powder, in the fourth step, the iron powder on the fallen ore side is heated to a concentration of 1 to 10 normal. Hydrochloric acid treatment can be performed with hydrochloric acid. As a result, the oxide scale layer existing on the surface of the iron powder can be eluted, and high-grade iron powder containing 98% of metallic iron can be obtained. In this case, in consideration of neutralization of the acid by a basic compound such as CaO mixed in, treatment with a strong acid having an acid concentration of 1N or more is necessary. Hydrochloric acid is used as the acid.

Acids with oxidizing power, such as sulfuric acid and nitric acid, are undesirable because they oxidize iron and make it passivate at high concentrations. Note that the oxide scale layer can be sufficiently eluted without using concentrated hydrochloric acid exceeding 10N.

As described above, the present invention does not require a magnetic separation process or a wet pulverization process, and the coarse iron powder present in the converter dust is converted into metal iron particles by dry crushing raw ore.
The slag component is exfoliated and separated, and the iron powder is separated from the converter dust by taking advantage of the large difference in shape: metallic iron particles are spherical, while graphite and slag components are relatively fine and amorphous. It is characterized by the fact that it can produce high value-added iron powder through a simple and economical process of classification, crushing, and slope fall sorting.

[Example] The method of the present invention will be further explained below with reference to Examples.

and 11. 5 kfI of converter dust collected by a dust collector was wet classified using a Taylor standard sieve in its generated form, and the particle size was 20 to 500.
Particles of μm size were separated. The obtained granules are 100 to 120
After drying by keeping at °C for 3 hours, the raw ore was dry-pulverized for about 3 minutes using a vibration mill. Furthermore, the granules after grinding and grinding were dispersed and dropped onto a slope with an inclination angle of 20° to separate fallen ore and mature ore. The surface roughness of the slope is 10μ.
A low-carbon cold-rolled steel plate was used for the ring.

The sampled converter dust, the dry classified product collected from the classification in the first step, and the iron powder obtained on the falling ore side during the slope fall sorting in the third step were analyzed, and the results shown in Table 2 were obtained. Ta.

As seen in the results in Table 2, even if the converter dust remains in the generated form layer, just by separating the particles of 20 to 500 μm, the metallic iron (M, Fe) becomes 81.5% by weight, and the slope It can be seen that the metal iron quality improves to 94.6% by weight by drop sorting.

Incidentally, slope drop sorting was performed using slopes with slope angles of 5° and 40° instead of the slope with slope angle of 20°, but similar results were obtained.

Furthermore, the granules obtained on the falling ore side of the slope drop sorting were leached in 5 N hydrochloric acid 1.51 with mechanical stirring for 3 minutes, and P
The residue was dried. The components of this dried granule are also listed in Table 2. As shown in Table 2, the granules were high-grade iron powder containing 98.3% by weight of metallic iron.

In addition, the results were the same when the treatment was performed using 1N and 10N hydrochloric acid instead of 5N hydrochloric acid.

A microscopic photograph of iron powder treated with 5N hydrochloric acid is shown in FIG. 1. As seen in FIG. 1, it can be seen that this iron powder has a true spherical shape.

In addition, Table 2 shows typical components of commercially available reduced iron powder for comparison, but it is clear that the iron powder produced by the method of the present invention is completely comparable in terms of components. 'llll.

[Effects of the Invention] As described above, according to the method of the present invention, spherical high-grade iron powder can be produced from converter dust 1 through simple and few steps of classification, crushing, and slope fall sorting, and Iron powder of even higher quality can be obtained by subjecting it to hydrochloric acid treatment in the fourth step depending on the intended use of the iron powder.

Therefore, it is possible to economically add high value to the steelmaking by-product, converter powder, as industrial iron powder suitable for cutting, welding rods, powder metallurgy, and the like.

[Brief explanation of the drawing]

FIG. 1 is a micrograph (magnification x 100) showing the particle structure of the iron powder obtained in the example.

Claims (2)

[Claims] (1) (a) The collected converter dust is classified and the particle size is 2.
A first step of separating granules of 0 to 500 μm; (b) a second step of pulverizing the separated granules using a dry pulverizer and peeling off deposits on the surface layer of the granules; (c) A third step in which the granules after grinding and grinding are dispersed and dropped down a slope with an inclination angle of 5 to 40°, iron powder is collected on the falling ore side, and graphite and slag are separated and removed on the residual ore side. A method for producing iron powder from converter dust, characterized in that: (2) (a) The collected converter dust is classified and the particle size is 2.
A first step of separating granules of 0 to 500 μm; (b) a second step of pulverizing the separated granules using a dry pulverizer and peeling off deposits on the surface layer of the granules; (c) A third step of distributing and dropping the granules after grinding and grinding on a slope with an inclination angle of 5 to 40 degrees, collecting iron powder on the falling ore side, and separating and removing graphite and slag on the residual ore side; (d) A method for producing iron powder from converter dust, comprising a fourth step of treating the iron powder on the side of the ore drop with an aqueous solution of 1 to 10 N hydrochloric acid.