JP2000248320A - Method for agglomerating dezincing material from zinc- containing iron-making dust - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase used rate of sintered ore into a blast furnace and to further promote the recycle of zinc-containing dust in the iron works by regulat ing free carbon content in raw material to specifized range. SOLUTION: The free carbon content in the raw material consisting essentially of the zinc-containing iron-making dust is regulated to in the range of 5-13%. Therein, the free carbon is the carbon having the form which can use as a reducing agent of iron oxide and zinc oxide in the dust. In the case of being the free carbon content at less than 5%, the improving effect of the dezincing ratio is low, and in the case of being this content at >=13%, CO concn. in the exhaust gas is raised and the exhaust gas is naturally ignited, and not only the operation is difficult, but also the massive ratio is lowered. Further, in the case the free carbon quantity having only the zinc-containing iron-making dust raw material does not satisfy the above regulating range, it can be adjusted that the carbon source arranged in the other way is added into the dust raw material to this shortage quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dezincification of zinc-containing dust generated in various processing steps in a steel mill such as secondary ash of a blast furnace, converter dust, and electric furnace dust by a sintering machine. About the method.

[0002]

2. Description of the Related Art Hitherto, as a method for dezincing zinc-containing iron dust, a reduction volatilization method using a kiln (Wurtz method) has been widely used. On the other hand, the present inventors have developed many dezincification and agglomeration methods using a sintering machine which are suitable for the location conditions in the steelworks premises and which can be processed more easily and at a lower cost.
For example, JP-A-7-157829 discloses an invention relating to a method of blending raw material dust, JP-A-7-90395 discloses an invention relating to raw material particle size, JP-A-7-188786 discloses an invention relating to ventilation gas composition and firing temperature, and JP-A-7-138661, JP-A-8-127
Japanese Patent Application Laid-Open No. 821 and Japanese Patent Application Laid-Open No. Hei 9-157564 are related to a method for stabilizing firing.

However, even in the method disclosed by the present inventors in the above publication, the dezincing rate (the ratio of the difference between the zinc concentration in the raw material and the concentration of zinc remaining in the treated agglomerate after treatment) is determined. For blast furnaces with a strict zinc input limit of about 50%, complete recycling of the agglomerate after treatment is considered a problem in this regard. Restrictions sometimes occurred. Therefore, the present inventors have made two optimizations of the wind speed at the time of ventilation in the sintering machine and the thickness condition of the packed bed as means for improving the dezincing rate in the dezincification and agglomeration method using this sintering machine. The technology was developed and its contents were disclosed in Japanese Patent Application Laid-Open No. Hei 10-330851.

[0004]

SUMMARY OF THE INVENTION The present invention aims to further improve the technology described in each of the above-mentioned publications, and regulates the amount of free carbon to be contained in a sintering raw material. To further reduce the amount of zinc remaining in the product agglomerate ore, thereby increasing the amount of product sinter used in the blast furnace and further promoting the recycling of zinc-containing dust in steelworks. With the goal.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional method, and its gist lies in the following means. (1) When the zinc-containing iron dust is used as a main raw material and agglomerates with a sintering machine, the content of free carbon in the raw material is adjusted to a range of 5% to less than 13%. Dezinc agglomeration method. (2) The method for dezincification of zinc-containing iron dust according to (1), wherein when the amount of free carbon is insufficient with only the zinc-containing iron dust raw material, a separate carbon source is added and adjusted.

Here, zinc-containing iron dust refers to dust generated during the iron making process, such as blast furnace secondary ash, converter fine dust, electric furnace dust, etc., and has a high zinc content, so that it remains as it is. Refers to dust whose use in recycling is restricted, and usually refers to dust containing 0.1% or more of zinc. Further, free carbon refers to carbon in a form capable of acting as a reducing agent for iron oxide and zinc oxide contained in dust, and thus excludes carbon fixed in limestone or the like as CO2.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of the present invention will be described with reference to FIG. In the figure, reference numeral 1 denotes a raw material tank in which zinc-containing iron dusts and a carbon agent for adjusting free carbon are stored. The respective raw materials discharged after the use ratio is adjusted based on the object of the present invention are mixed by the second mixer and then mixed.
Is baked into a cake with a sintering machine. This sinter cake is roughly crushed by the primary crusher 4 and then sieved by the sieve 5 to collect a lump product on the sieve.

The lump product can be recycled as it is as a raw material for a blast furnace or a cooling agent for a converter. On the other hand, the under sieve is further pulverized by the secondary crusher (6) to obtain a powdery product. This powdery product can also be used as a blowing agent for hot metal pretreatment. When a powdered product is not required, the powdered product can be circulated and used as a raw material as shown by a broken line in the figure.

[0009]

[Table 1]

The present inventors conducted experiments by selectively using converter dust and blast furnace secondary ash having the chemical components shown in Table 1 as raw materials, and varying the mixing ratio of both. When the converter dust is replaced with the blast furnace secondary ash, the amount of free carbon in the raw material after mixing ranges from 1% of the case of the converter dust only (no blast furnace secondary ash) to the case of the blast furnace secondary ash only ( (Without converter dust).

The compounded raw materials were fired using a circular table type sintering machine (effective sintering area: 1 m ² ) at a layer thickness of 300 mm and an upper ventilation flow rate of 0.2 Nm / sec. After the sintered sinter cake was roughly crushed, the sinter cake was sieved with a 5 mm sieve, and the ratio of on-screen (+5 mm) to the total amount of the sinter cake was determined as the agglomeration rate. In addition, the ratio of the zinc content analysis value in the screened product to the zinc content calculation value of the raw material after blending was determined as the dezincing rate.

In the results of this experiment, as shown in FIG. 2, the dezincing rate changed from 55% to 89%, but the dezincing rate was improved generally in proportion to the increase in the amount of free carbon. This is presumably because the reduced atmosphere during firing was strengthened by the increased carbon, and as a result, reduction and volatilization of zinc oxide in the raw material was promoted. However, it was found that the +5 mm agglomeration rate was reduced by the addition of excessive free carbon of 13% or more. Although the cause is not clear, excessive melting due to excessive heat input causes local ventilation inhibition,
As a result, it is considered that firing became unstable.

Therefore, based on this result, in the present invention,
The free carbon content in the raw material was regulated within the range of 5 to less than 13%. That is, when the amount of free carbon is less than 5%, the effect of improving the dezincing rate is small. On the other hand, when it exceeds 13%, although the dezincing rate can still be improved, the exhaust gas spontaneously ignites due to the increase in the CO concentration in the exhaust gas, making it difficult to operate, and as described later in Examples, Due to the reduced agglomeration rate, the operation range is not practical.

In the present invention, when the amount of free carbon does not satisfy the range regulated by the present invention with only the zinc-containing iron dust raw material, the insufficient amount is supplied from a raw material tank storing a carbon source provided separately. However, it may be added to the zinc-containing iron dust raw material to adjust the amount of free carbon. Further, in the present invention, the zinc-containing iron dust is used as a main raw material, but dust and iron ore generated in other processes such as sintered dust having a low carbon or zinc content may be used in combination. .

[0015]

EXAMPLE Using the converter dust, the blast furnace secondary ash and the sintering dust (environmental dust collected in a product processing system of a sintering machine) shown in Table 1 as raw materials, the mixing ratio was changed in various ways. In the case where the amount of carbon is insufficient, a circular table formula is used for an example in which coke breeze is added as a carbon agent to satisfy the free carbon amount within the scope of the present invention and a comparative example in which the free carbon amount is outside the scope of the present invention. Sintering machine (effective sintering area 1
m ² ), and the results are shown in Table 2.

[0016]

[Table 2]

Regarding the dezincification rate, the working numbers 3 to 7 of the present invention all showed 68% or more, and the working numbers 8 to 9 of the comparative examples showed good values of 81% and 88, respectively.
In Example Nos. 1 and 2 of Comparative Examples, 53% and 62% were both lower than the present invention. Regarding the agglomeration rate,
Example numbers 3 to 7 of the present invention example and example numbers 1 and 2 of the comparative example
Occupied 62% or more, and was generally good, but Comparative Example Nos. 8, 9 were 54, 51%, which was poor.

[0018]

As described above, the dezincing property can be improved by applying the present invention to the agglomeration treatment of zinc-containing dust by a sintering machine. As a result, the amount of product agglomerate ore used in the blast furnace can be increased, and the recycling of zinc-containing dust in the steelworks can be further promoted.

[Brief description of the drawings]

FIG. 1 is a diagram showing a flow of processes from raw materials to finished products when implementing the present invention.

FIG. 2 is a graph showing changes in agglomeration rate and dezincing rate due to changes in the amount of free carbon in the raw material after blending.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw material tank 2 Mixer 3 Sintering machine 4 Primary crusher 5 Sieve 6 Secondary crusher

Continuing from the front page (72) Inventor Michiaki Sakakibara 1 Kimitsu, Kimitsu City, Chiba Prefecture Nippon Steel Corporation Kimitsu Works Co., Ltd. Kimitsu Office F-term (reference) 4K001 AA10 BA14 CA33 GA10

Claims (2)

[Claims] 1. A method for agglomerating with a sintering machine using zinc-containing iron dust as a main raw material, wherein the free carbon content in the raw material is adjusted to a range of 5% to less than 13%. Of dezincification of zinc-containing iron dust. 2. The dezincing lump of zinc-containing iron dust according to claim 1, wherein when the amount of free carbon is insufficient only with the zinc-containing iron dust raw material, a separate carbon source is added and adjusted. Formation method.