JPS6075527A - Treatment of dust generated in an ironworks - Google Patents

Abstract

PURPOSE:To reutilize dust contg. iron and caustic lime powder generated in an ironworks as materials for producing iron by treating them rationally depending on wet condition and chemical property of the dust at the collected stage. CONSTITUTION:Collected dust contg. iron and lime is classified to wet collected dust consisting primarily of fine powder and ore and lime powder consisting of coarse particle. The ore and lime powder are crushed in dry atmosphere with blown air to produce crushed product contg. >=65% particles having <=45mu particle size and <=5% water. On one hand, the wet collected dust is dehydrated to <=40% water content, or it is blended after dehydration with separately collected fine powder of low water content to adjust the water content of the blended product to <=40%. When it is further blended with above-described crushed caustic lime powder and spread on a drying floor, temp. is elevated by the heat of reaction and contained water is evaporated to reduce the water content to <=25%. The dried powder is blended with the above described crushed ore powder together with binder and kneaded to reduce the water content to <=10%, then granulated by rolling and utilized for the source of iron.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention is a method for removing lime powder and iron-containing dust generated in a steel factory.
Sorting is done according to the type of collection and particle size at the time of collection,
The present invention relates to a method for treating iron-making dust generated in a steel-making factory, in which these processed materials are blended and granulated, and granulated so that they can be reused in steel manufacturing.

[Prior art]

In general, many types of dust are generated in steel factories during the manufacturing process. There are many types of these generated dusts, such as ore powder, sintered powder, steelmaking powder, rolling scale, quicklime powder, and direct reduction furnace powder, and these are generated in a wide variety of ways depending on the steel manufacturing process.

These generated dusts are collected by dry or wet methods to prevent environmental pollution and some of them are recycled, and treatment methods have been proposed for some of them to be reused.

For example, as a method for drying wet iron-containing fine powder such as converter slag in wet-collected converter-type steel or rolling slurry collected from the rolling process, the present inventors have developed an energy-saving drying method using the sun. This patent application was filed as Japanese Patent Application No. 136431/1980, and an effective granulation method for these iron-containing fine powders was developed and Japanese Patent Application No. 136430/1982 was filed. In addition, Japanese Patent Publication No. 57-43622 discloses a method for producing pellets for M steel using oil-containing and iron-containing slurry generated in steel factories. However, these known methods for treating iron dust only provide a method for simply treating a single type of iron-containing dust or dust with similar properties;
A comprehensive dust treatment method that utilizes the recyclable dust generated in steel factories by skillfully combining them according to their properties has not yet been devised.

[Purpose of the invention]

The present invention rationally utilizes the wet state and chemical properties of iron-containing dust and quicklime powder generated in a steel factory, regardless of whether it is a blast furnace type steel factory or a direct reduction type steel factory. The purpose of this invention is to provide an energy-saving method for manufacturing pellets for iron making, which can be reused as an iron source by comprehensively processing the pellets at low cost, and which is excellent.

[Structure of the invention]

The present invention will be described in detail below.

In the steel manufacturing process, blast furnace gas ash and sintered powder.

Converter dust, electric furnace dust, rolling scale, ore powder,
In direct reduction iron making, reduced iron powder is generated, and in calcining lime for use as an auxiliary raw material, many types of dust such as quicklime powder are generated.

These dusts are collected by a collection of collection devices such as cyclones or venturis, and have various properties and particle sizes as illustrated in Table 1 depending on the means of collection or location of collection.

4- As is clear from Table 1, the particle size of the various types of dust generated in steel factories differs depending on the place where they are collected. For example, ore powder is treated in a blast furnace treatment process or directly reduced in a reduction equipment factory. Continuous casting scale is generated during the continuous casting process of molten steel. The sieve of the granulation bracket generated in the granulation process of ore powder or fine powder iron source contains powder, or the continuous casting scale, etc., contains a relatively large amount of coarse powder. Further, the water content of the generated powder containing a large amount of coarse powder is relatively low.

In addition, quicklime powder generated during the production or handling of quicklime, which is indispensable as a raw material for steel production along with iron ore in a steel factory, does not contain moisture and is relatively coarse-grained.

On the other hand, steelmaking dust or dust generated from reduction furnaces in reduced iron manufacturing plants have fine particles and are collected using a wet method, so they are collected at a moisture content of 10%, which is suitable for reuse. Dehydration to a low water content is extremely difficult and requires a large amount of energy cost.

As mentioned above, in steel manufacturing, the present inventors classify powder and granules that differ in their generation location or collection method according to their particle size structure, moisture content, and properties, and collect similar materials,
By appropriately combining and processing these methods, we have conducted various studies on a method for comprehensively processing powder and granules generated in iron manufacturing and reusing them as an iron source, leading to the completion of the present invention.

That is, the present invention classifies iron-containing dust and lime dust collected in a steel factory into wet-collected dust mainly consisting of fine particles and collected powder containing many coarse particles. , perform primary dehydration using a filter press, etc. On the other hand, coarse powder with a relatively low water content and easy to dry contains 65% fine particles with a particle size of 45 μm or less in an air drying atmosphere.
The quicklime powder is mixed with the dehydrated fine powder particles, and if necessary, quicklime powder prepared separately is added and mixed. This is spread on a drying bed and powdered. The temperature of the mixed granular material is raised by the heat of reaction between the moisture content of the grains and the blended quicklime, and after this is successively cultivated and dried, it is mixed with the above-mentioned low-moisture dry pulverized powder such as ore powder and a binder such as cement. It is characterized by blending and tumbling granulation.

In steelmaking, ore powder particles are generated during pre-processing of raw material iron ore, such as particle size adjustment of iron ore charged into a blast furnace, sintering of fine ore, or sizing process of raw material ore during direct reduction of iron ore. In order to directly transfer to pellets for granulation, many relatively large particles must be crushed. Moreover, these generated powders containing relatively coarse particles commonly have a low moisture content when collected and have good drying properties when blown with hot or cold air.

The present invention classifies such low water content collection powder that contains relatively coarse particles and requires pulverization and is easy to dry into the first group, and processes it using a rotary mill or the like having a hot air or cold air blowing device. Grinding is performed using a grinding device while blowing air, and the size is 45 μm.
Pulverize so that the following particle size powder is 65% or more. 4
If the proportion of fine powder with a particle size of 5 μm or less is 65% or less, the granulation efficiency deteriorates in transfer granulation, and high-quality granules cannot be obtained.

Furthermore, in the pulverization described in item 2, the moisture content must be kept at 5% or less, and if the moisture content in the pulverized product exceeds 5%, the pulverization efficiency decreases. In the above-mentioned pulverization of the present invention, pulverization in a blown air stream is exemplified, but the invention is not limited to this, and it is also possible to dry the material in advance and pulverize the dried product.

In addition, in the present invention, quicklime collected during the production or treatment process of quicklime, which is an auxiliary raw material, is also classified into the first group described in -, but quicklime powder containing relatively coarse powder contains water. The pulverization process can be carried out without drying.

On the other hand, dust collection slurries such as converter slurry or iron ore reduction furnace slurry contain extremely high moisture content because they are collected in a mixed manner. It is divided into two groups. These fine particles in the second group with a high water content are dehydrated to a water content of 50% or less by a suitable dehydrating means such as a filter press. This dehydration is 10% when the dehydrated powder is mixed with separately collected low water content iron-containing fine powder and tilled and dried.
The water content may be higher than that, but when the above-mentioned low water content powder is not blended, the water content should be dehydrated to 40% or less. Present invention 9- Moisture content of fine powder tilled and dried in Ming is 40%
However, if it exceeds 40%, a leachate layer will be formed on the surface of the powder layer spread on the tilling and drying bed, and drying will be significantly inhibited. The water content in the above dehydration is 5
If it is 0% or more, the required amount of the low water content iron-containing fine powder that is blended for moisture adjustment before tilling and drying becomes large, and the powder collected in the factory will not be enough.

Quicklime powder of the first group is added to the dehydrated fine powder according to its moisture content, and this is mixed so as to obtain an appropriate distribution within the water-containing fine powder, and then tilled and dried for concrete laying, etc. It is spread out in layers on the floor.

The thickness of the spread layer in the tillage drying bed is not particularly limited, but can be selected appropriately depending on the tillage ability, water evaporation ability, etc., and the thickness is preferably 50 cm or less. You can get results.

The mixed fine powder spread on the till bed generates heat due to the following reaction between the blended quicklime and the water content, raising the temperature of the fine powder.

CaO+ H20=Ca(OH)2+1.50
00 kcal/mo1 The present inventors have found that when lime powder is added to dust collection slurry (30 to 50% moisture) in a chemical equivalent of the water content, the temperature rise of the layered product is around 40℃ throughout summer and winter. I was able to get a huge increase.

The layered spread powder grains whose temperature has increased due to the above reaction are plowed by a suitable plowing and stirring means such as a tiller, and by stirring and mixing, they are sufficiently reacted and the high-temperature grain surfaces whose temperature has been raised are plowed. While exposing to the atmosphere, drying is accelerated by supplementary heating by the sun or, if necessary, by hot air.

In the present invention, the lime content added for raising the reaction temperature is further effectively used as a slag forming agent during steel refining.

The moisture content of the tilled and dried fine powder as described above is reduced to 25% or less, but if the moisture content is 25% or more, the blend of the pulverized fine powder of the first group may also cause the mixture to have a moisture content of 25% or less. It is not possible to make the water content suitable for granulation.The dry fine powder particles of the second group, which have been dried to a moisture content of 25% or less, are the same as the dry pulverized powder particles of the first group. However, in this formulation,
The low water content powder of the first group is blended according to the water content of the dry powder of the second group. For example, when the water content of the dry powder of the second group is high, the low water content ground powder of the first group is mixed. is increased so that the average water content of the mixture is 10% or less.

In this way, the water content is blended to be 10% or less, and the mixed fine powder is further added with a binder such as cement and mixed thoroughly, and then processed using a transfer granulation device such as a polling drum or a polling disc. The granules are transferred to the granulator and granulated. This granulated material is further cured to obtain the necessary strength. As mentioned above, the treatment of the iron dust generated in the steel factory of the present invention is carried out based on the comprehensive viewpoint of classifying the generated dust into the first group and the second group according to its particle size and moisture content. Then, after drying and pulverizing the low-humidity phase powder and effectively utilizing quicklime powder to the wet fine powder, each of these treated fine powders of Group 12- is appropriately blended according to their moisture content. The major feature is that the moisture content can be adjusted to be suitable for transfer granulation.

〔Example〕

Examples of the present invention will be further described below.

The collected powder and granules shown in Table 2 generated at a steel factory are divided into the first group and the second group according to their particle size composition, and the powder and granules belonging to the first group, which have a relatively large amount of coarse particles, are heated to a temperature of 7.
It was pulverized in a roller mill in a hot air stream at oo°C to obtain the fine powder shown in Table 3.

=13- On the other hand, the dust slurry and lime mud with high water content classified into the second group were dehydrated using a filter press.
The moisture content was set to 50%, and this was blended with the crushed quicklime powder of the first group, and further mixed with the electric furnace slurry with a low moisture content of the second group. The moisture content of this mixture was 32%.

This mixture was sufficiently stirred to evenly distribute the mixed quicklime, spread out in a layer of 39 cm thick on a concrete drying bed, and left to stand for 24 hours until the moisture in the fine powder and the mixed quicklime were mixed. The temperature of the fine powder was raised by sufficiently reacting with the powder. Then, the water was evaporated and dissipated under the sun while being tilled and agitated using a tiller. 1 tilling and stirring
Repeatedly at time intervals, after reducing the moisture content to 23%, the first group of dry ground fine powder ore powder and pellet undersieve powder were added to this to reduce the moisture content of the mixture to 8%.
Adjusted to.

Next, 8% cement was added as a binder to the above mixture, the moisture content was adjusted to 10%, and the mixture was granulated using a disk-type granulator, and cured for 3 days to obtain -15 = crushing strength of 60 kg/bellet, granules. Pi! It was possible to obtain grains of 5 to 10 grains with a yield of 95%.

This cured grain is suitable as a charge to a sintering machine or a direct reduction furnace, and can also be effectively used as a temperature regulating material for steel manufacturing.

〔Effect of the invention〕

As described above, the present invention is a useful method for recovering and processing iron-making dust that can most rationally and efficiently form valuable dust generated in iron-making factories into granular materials suitable for reuse with less energy. It is.

Patent applicant Nippon Steel Corporation (one idiot) agent
Masu Tebori (and 2 others) 16-

Claims (1)

[Claims] 1. The collected iron-containing dust and lime dust are divided into wet-collected dust mainly consisting of fine particles and ore powder and lime powder (with a large proportion of coarse particles), and the ore powder and lime powder are air-dried. The fine powder collected by the wet method is either dehydrated to have a moisture content of 40% or less, or is further captured separately after dehydration. The mixture is mixed with the collected low water content fine powder to make the moisture content 40% or less, mixed with the above-mentioned crushed quicklime, spread on a drying bed, and heated by the heat of reaction between the mixed lime and the water contained in the fine powder. The water content is reduced to 6% or less by cultivating and drying it to remove water contained in it.Then, this is mixed and kneaded with the crushed ore powder together with a binder to reduce the water content by 10%.
A method for treating ironmaking dust generated in a steelmaking factory, which is characterized by dampening the dust to less than % and granulating it by transfer.