JP2001059121A - Production of metallic iron-containing bulky material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a producing system for working a metallic iron-containing dust cake recovered from various processes, such as from a converter in a steelmaking process into a form to be easily formed while restraining the oxidation of the metallic iron. SOLUTION: This method for producing the metallic iron-containing bulky material comprises the following four processes: (1) An alkaline compound composed of oxides or hydroxides of alkali metals or alkaline earth metals is added to the metallic iron-containing dust cake having 10-30 wt.% moisture content to adjust the mixture to have pH 8-14. (2) The mixture is uniformly mixed so as not to develop coagulation. (3) The obtd. mixture is press-formed to develop a bulky material. (4) The bulky material is aged to develop the objective metallic iron-containing bulky material having <=8 wt.% moisture content.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a lump from a dust cake containing metallic iron and a system therefor, particularly from a dust cake containing metallic iron discharged from various processes, to a blast furnace or a converter. The present invention relates to a method for producing a lump for reuse as a main raw material for steel making such as an electric furnace and a system therefor.

[0002]

2. Description of the Related Art Iron-based dust discharged from various processes, particularly converter dust discharged from a converter used in a steelmaking process, is composed of iron fine particles (1 to 100 μm), and a part of the dust is oxidized. Iron oxide (FeO), most of which is present as metallic iron (Me, Fe). In general, this dust is collected and filtered in water by a wet dust collector, dehydrated to a predetermined moisture content (for example, 10 to 30% by weight) to form a cake, and collected in the form of a dust cake containing metallic iron. The collected dust cake is mainly reused as iron resources in the iron making process of sintering plants, etc.
And pressure molding is difficult. Therefore, conventionally, the iron content in the dust cake has been oxidized in the air, and the moisture content has been reduced to about 5% by weight by solar drying using the heat of oxidation, and the dust cake has been reused.

[0003] However, the heat generated by this oxidation is sometimes very high and the oxidation proceeds in a short time, which is very dangerous. In addition, when the dust cake collected as described above is dried in the sun, most of the dust cake is turned into powder, so that the working environment is deteriorated due to dust generation. Further, if the powder is used as it is, there is a problem of reduced yield and transportability due to scattering. Therefore, it is necessary to add water again, dry it, and make it into a pellet when reused. In addition, since metallic iron in the dust cake is oxidized by drying, it is necessary to use a large amount of energy to reduce it when reusing.
As described above, in the conventional method, not only can the metal iron-containing dust cake be directly molded, but also the process becomes complicated, heat is generated,
There are problems in the working environment such as generation of dust, and problems in economy.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention solves the above-mentioned problem by directly processing, forming, and forming a dust cake containing metallic iron discharged and recovered from various processes such as a converter in an iron making process. An object of the present invention is to construct an integrated process in which the iron metal in the cake can be dried without oxidizing as much as possible and processed into a lump, so that the subsequent handling is greatly improved.

[0005]

SUMMARY OF THE INVENTION The present invention makes the recovered dust cake containing metallic iron alkaline, suppresses the oxidation and heat generation of the contained metallic iron, and replaces the conventional drying by the heat of oxidation with metallic iron. It is characterized by drying using the heat of hydration of the alkali compound blended in the contained dust cake. Specifically, the present invention relates to a method for producing a metallic iron-containing lump, wherein (1) a metallic iron-containing dust cake having a water content of 10 to 30% by weight is added to an alkali metal or alkaline earth metal. (2) adding an alkali compound consisting of an oxide or hydroxide of the above to prepare a mixture having a pH of 8 to 14; (2) mixing the mixture uniformly so as not to cause aggregation; ) Pressing the resulting mixture to form a lump; (4) curing the lump to produce a metal iron-containing lump having a water content of 8% by weight or less; And a method having

Further, the present invention includes a mixer, a press molding machine, and a curing yard, wherein the mixer has a water content of 10 to 10.
A mixture having a pH of 8 to 14 obtained by adding an alkali compound comprising an oxide or hydroxide of an alkali metal or an alkaline earth metal to a metal iron-containing dust cake of 30% by weight is uniformly mixed so as not to cause aggregation. Mixing, the press molding machine press-molds the mixture obtained from the mixer to form a lump, and the curing yard cures the lump, and the moisture content is 8% by weight. The present invention relates to a system for producing a metal-iron-containing lump characterized by producing the following metal-iron-containing lump.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the step (1) of the present invention, the water content is 10 to 10.
An alkali compound consisting of an oxide or hydroxide of an alkali metal or an alkaline earth metal is added to the metal iron-containing dust cake of 30% by weight to prepare a mixture having a pH of 8 to 14. The metallic iron-containing dust cake refers to a dust containing metallic iron containing a certain amount of water. Dust containing metallic iron may be discharged from various processes, but is mainly used because converter dust discharged from a converter used in a steelmaking process is easily available. The iron-based dust is generally fine metal iron particles having a particle size of about 1 μm to 100 μm, preferably about 5 μm to 50 μm, and has a property of being easily oxidized. The dust is collected and filtered by a dust collector or the like to adjust the water content, and is preferably collected and filtered in water by a wet dust collector, dehydrated to a certain moisture content, and collected in a cake form. The recovered dust cake is generally an amorphous mud (liquid) containing a water content of about 10 to 30% by weight. The present invention mainly uses a dust cake containing the metal iron particles thus recovered as a raw material.

[0008] The water content of the metallic iron-containing dust cake is:
It is 10 to 30% by weight, preferably 15 to 25% by weight, based on the total amount of the dust cake. Since the metal iron-containing dust cake collected as described above generally contains about 10 to 30% by weight of water, the collected metal iron-containing dust cake may be used as it is. The water content can be adjusted to the above-mentioned water content by appropriately adding water.

[0009] The alkali compound is used to make the metallic iron-containing dust cake alkaline, pH 8 to 14, preferably pH 10 to 10.
Add to 14 By adding the alkali compound in this way, the metallic iron in the dust cake can be passivated, and the air oxidation of the metallic iron can be prevented. The alkali compound is mixed with the metallic iron-containing dust cake to maintain the fluidity without causing aggregation,
Excellent in dust particle size reduction and sizing. Further, the alkali compound reacts with water and significantly generates heat of hydration in order to significantly promote drying of the metallic iron-containing dust cake in the step (4). Preferred alkali compounds are hygroscopic, suppress oxidative heat generation, serve as a reaction heat source for moisture drying, and excel in fine-graining and sizing. Calcium hydroxide is a lime-based compound, and preferably calcium hydroxide is anhydrous calcium hydroxide in terms of hygroscopicity. More preferably, it is a mixture of anhydrous calcium hydroxide and calcium oxide. Calcium oxide has the advantage that the drying time can be further reduced, but calcium oxide lumps are likely to remain.
In order to prevent this, it is preferable to use a mixture with calcium hydroxide.

The alkali compound is at least 3% by weight or more, preferably 4% by weight or more, based on the desired alkalinity of the metallic iron-containing dust cake, depending on the gram equivalent inherent to the alkali compound. When the content is 3% by weight or more, oxidation of metallic iron in the dust cake is suppressed even when the mixture is heated to 150 ° C. In order to generate heat of hydration significantly, the content is at least 4% by weight or more, preferably 5% by weight or more. If it is 5% by weight or more,
It is preferable because it can be dried in 48 hours. on the other hand,
If the amount of the alkali compound is more than 20% by weight, there arises a problem of economical efficiency and a problem that, for example, the caking property is reduced and molding tends to be difficult. Therefore, the alkali compound is added in an amount of 3 to 20% by weight, preferably 5 to 20% by weight, based on the dust cake containing metallic iron. Further, when used in a mixture of anhydrous calcium hydroxide and calcium oxide, anhydrous calcium hydroxide is generally 38 to 97% by weight, preferably 50 to 97% by weight, and calcium oxide is 62 to 3% by weight based on the total amount of the alkali compound. % By weight, preferably 50
It is preferably about 3% by weight. When the proportion of calcium oxide is up to 50% by weight, no calcium oxide remains, which is preferable. Conversely, when the proportion exceeds 62% by weight,
It is not preferable because the remaining calcium oxide becomes remarkable.

In the step (2) of the present invention, the mixture is uniformly mixed so as not to cause aggregation. For mixing,
Any mixer can be used as long as it can be mixed without causing aggregation. As a mixing method, for example, a method may be adopted in which a fixed amount of raw materials is put into a batch type container and stirred. However, in order to enable continuous processing, it is preferable to use a continuous mixer (pug mill). In general, a pug mill has a two-axis horizontal structure and a horizontal two-axis structure in which a plurality of blades are attached so as to form a part of a spiral shape. When the raw material is supplied to one end of the pug mill, the raw material is sent to the other end while being mixed by a propulsive force based on the twist of the mounting angle of the blade. In addition, the mixing is generally performed by sufficiently mixing to form a mixture in which the metallic iron dust particles and the alkali composition are uniformly mixed. However, if the metal iron-containing dust cake mixture of the present invention is excessively stirred, the mixture agglomerates and loses fluidity. When aggregates are formed, molding failure occurs such that the aggregates are pinched when the mixture is filled in the molding machine, or the mixture cannot be filled in the molding machine. Even if it can be molded, the weight uniformity between the molded lumps tends to be lost. Therefore, it is preferable to maintain the mixing intensity at a relatively low level and generate a fluid mixture without causing aggregation. For example, the residence time is about 5-20 minutes, preferably about 8-18 minutes,
About 2 to 55 rpm, preferably about 12 to 4 rpm
Spin at 8 rpm, 100-350 kg per minute,
Processing is preferably performed at a processing speed of 130 to 300 kg per minute. In the resulting mixture, on the surface of a granular material in which a plurality of metal iron-containing dust particles holding a certain moisture content are aggregated, a form in which an alkali compound such as anhydrous calcium hydroxide is attached is called `` pseudo particle '' The structure is shown.
The particle size of the pseudo particles is 0.3 to 3 mm, preferably 0.5 to 2 m.
m, more preferably 0.8 to 1.5 mm. The pseudo particles have the same water content as the raw material metal dust cake, for example, a water content of 10 to 30% by weight.
The mixture as a whole is lower, e.g.
Since it has a water content of% by weight, it is possible to advance molding advantageously.

In the step (3) of the present invention, the obtained mixture is subjected to pressure molding to form a lump. For the pressure molding, any molding method such as roll molding or extrusion molding may be used, but roll molding is preferred. Further, any molding machine such as a roll molding machine (briquetting machine) and a tableting machine (tablet machine) may be used as the molding machine, but a roll molding machine is preferably used. Here, the roll forming machine, for example, a pair of rolls provided with a number of hemispherical depressions on the roll surface,
When the raw material passes through the gap, the raw material is compressed and, at the same time, a lump is formed. The distance of the raw material insertion gap of the molding machine is generally 0 to 10 mm, preferably 2 to 8 mm, more preferably 4 to 6 mm.
The shape of the obtained lump is oval, flat oval, cylindrical, planar, or the like, depending on the shape of the hollow. Pressing is performed in units of linear pressure (weight applied per tangent to a pair of rolls) in 0.2 units.
To 15 t / cm, preferably 0.3 to 4 t / cm.
The resulting agglomerates generally have a diameter of 20-75 mm, preferably 25-60 mm, more preferably 30-50 mm, and 20-900 g, preferably 35-500 g per lump , More preferably 65 to 200
g. However, the lump is not limited in shape, size, and weight as long as it is easy to enter a device to be reused.

In the step (4) of the present invention, the obtained mass is cured to form a metal-iron-containing mass having a water content of 8% by weight or less. Curing is performed by stacking a large number of masses on, for example, a flat land or the like and leaving the piles to stand. When the mass is cured, the alkali compound contained in the mass reacts with water in the mass to generate heat of hydration. The mass is dried by this heat of hydration,
A metallic iron-containing mass having a water content of 8% by weight or less, preferably 5% by weight or less is produced. From the viewpoint of shortening the drying time, the piled mass may be arbitrarily blown to promote the emission of steam, or may be subjected to forced drying. Further, from the viewpoint of curing stability, the ambient temperature of the curing yard may be controlled to be maintained at a constant temperature, for example, 80 to 90 ° C. For example, an infrared heat source is placed at equal intervals in the curing yard to perform forced drying and temperature control.

Hereinafter, the method of the present invention will be described with reference to the drawings. A metal-containing dust cake is placed in a raw material hopper (1), and a crusher attached to the lower end of the hopper
(2) The particle size is 0.5 to 50 mm, preferably 2 to 30 mm.
Crush to mm. The raw materials conveyed by the belt conveyors (3a) and (3b) are crushed by a crusher (4) to have a particle size of 0.5 to 15 mm, preferably 1 to 10 mm. In addition, belt conveyor
(3a) and (3b) are for transporting the raw material and the like to the next step, and the present invention is not limited to the number. Next, an alkali compound is added to the sized raw material, and water is added if necessary for moisture adjustment,
Mix with a mixer (6). Preferably, a pug mill is used in the mixer (6), and the mixture is uniformly mixed without agglomeration to produce pseudo particles having a particle size of 0.3 to 3 mm, preferably 0.5 to 2 mm. The mixed mixture is fed to a belt conveyor
(7a) Carry by (7b), and shape | mold with a molding machine (8).
Preferably, a roll forming machine is used for the forming machine (8),
For example, it is pressurized at a linear pressure of 0.3 to 2 t / cm and has an outer diameter of 30 to 5
Mold to 0mm. The molded mass is transferred to a belt conveyor
At (9a) and (9b), they are transported to the curing yard (10). The lump is left in the curing yard and cured and dried. If necessary, the ambient temperature of the curing yard is controlled at 80 to 90 ° C. Thereafter, the cured iron-metal-containing lump is reused as a product, mainly as an iron resource in an iron making process of a sintering plant or the like.

[0015]

EXAMPLES Reference Example 1: Selection of alkali compound In order to select an alkali compound suitable for the present invention, characteristics of various alkali compounds and compounds generally used as industrial binders were evaluated. Table 1 shows the results. The metal-containing mass used in this experiment was produced as follows. 10,000 kg of a metallic iron-containing dust cake having a water content of 20% by weight obtained from converter dust is crushed by a crusher (2).
Fine particles of about 10 mm or less (average 2 mm) were obtained by using a crushing machine (manufactured by Keihan Corp., decay type RC1) and a crushing machine (4) (manufactured by Keihan Corp., decay type DC2). To this, an alkali compound or the like was added at 10% by weight based on the dust cake. This mixture was mixed with a mixer (6) to obtain a mixture having a particle size of 1.5 mm.
The mixer (6) used was a KP2 pug mill manufactured by Keihan Co., Ltd., having a total length of 5 m, a horizontal rotating biaxial shaft having a diameter of 300 mm and a mixing blade of 200 mm x 300 mm.
The residence time of the pug mill is 11 minutes and the rotation speed of the rotating body is 32 rp.
m and processed at a rate of 215 g / min. Next, the molding machine
(8) was press-formed at 0.7 t / cm using a KDR800 roll forming machine manufactured by Keihan Corporation. Lump (approximately 3
(5 mm) was obtained, and was cured and dried in the curing yard (10) for 48 hours. Heating was performed using the heat of hydration generated from the hydration reaction of alkali compounds and the like, and forced drying was not performed.
The ambient temperature at this time was about 25 ° C.

The properties of each compound were evaluated with respect to hygroscopicity, heat resistance, heat of hydration, and passivation of iron. Hygroscopicity is
20 g of water was added to 100 g of each compound to evaluate whether fluidity (powder) was maintained. The evaluation was performed according to the following criteria. A: Absorbs water and completely maintains fluidity. ：: Absorbs water and has no problem in fluidity. ×: liquid or water cannot be completely absorbed. The heat resistance was evaluated by heating and maintaining the metal-iron-containing lump produced by the above-mentioned method in a thermostat at 107 ° C. for 2 hours, observing the appearance of the heated product with the naked eye, and evaluating the following criteria. A: No change in appearance. ：: The surface layer partially solidifies and hardens. Δ: Discoloration and shape change. X: Discoloration and burning. As described above, the heat of hydration was determined by charging 2 kg of a mixture of metallic iron-containing dust and each compound in an insulated container, and heating at room temperature (25 ° C.).
(° C.). The evaluation was performed according to the following criteria. ：: Heat generation of 30 ° C. or more as compared with normal temperature. ：: Heat generation of 10 to less than 30 ° C. as compared to normal temperature. Δ: Heat generation of less than 10 ° C. as compared with normal temperature. X: No heat is generated. The passivation of iron was performed by mixing each compound in a metal iron-containing dust cake at 10% by weight, measuring the pH based on the pH measurement method of JIS, and evaluating according to the following criteria. A: A mixture having a pH value of 10 or more. ：: A mixture having a pH value of 8 or more and less than 10. Δ: A mixture having a pH value of less than 8. ×: A mixture in which the aqueous solution is not ionized.

[Table 1] Table 1 Evaluation of properties of alkali compounds As can be seen from Table 1, preferred alkali compounds of the present invention are hygroscopic, have excellent heat resistance, generate good heat of hydration, and show good passivation of iron, especially alkali metals or It was found that among the alkaline compounds composed of alkaline earth metal oxides or hydroxides, they were anhydrous calcium hydroxide and calcium oxide. Cement shows the next best value, but the cement contains a large amount of sulfur and the like which are impurities in the iron making process, and the drying time in the curing process is long (3 days or more). Is not preferred.

Reference Example 2: Determination of the Alkali Compound Content The relationship between the alkali compound and the required drying time in the step (4) in order to measure the amount of the alkali compound required to significantly generate the heat of hydration is described. evaluated. The metal-containing mass used in this experiment was molded in the same manner as in Reference Example 1 except that calcium hydroxide was used as an alkali compound and the amount of calcium hydroxide was changed.
The mass was cured at an ambient temperature of 25 ° C., and the time required for the water content of the metal-iron-containing mass to reach 5% by weight was measured. Table 2 shows the results.

Table 2 Relationship between alkaline compound and drying time Amount of calcium hydroxide added (% by weight) Reaction temperature (° C) Required drying time (hour) 130 ° (measurable) 2 40 144 4 65 72 88 82 40 12 92 24 It can be seen from Table 2 that the reaction temperature increases as the mixing ratio of calcium hydroxide increases, the evaporation of water is accelerated, and the drying time is shortened. Therefore, in order to generate heat of hydration significantly, it is necessary to add at least 4% by weight or more, and preferably 6% by weight or more from the viewpoint of shortening the drying time.
From the viewpoint of moldability and drying time, it was found that the content was more preferably 8% by weight or more.

Example 1 10,000 kg of a metallic iron-containing dust cake having a water content of 20% by weight obtained from converter dust was crushed with a crusher (2) (made by Keihan Co., RC1) and a crusher (4) ( Made by Keihan,
About 10mm or less, average 2mm over DC2)
Of fine grains. To this, 10% by weight of anhydrous calcium hydroxide was added to the dust cake. This mixture was mixed with a mixer (6) to obtain a mixture having a particle size of 1.5 mm.
The mixer (6) used was a KP2 pug mill manufactured by Keihan Co., Ltd., having a total length of 5 m, a horizontal rotating biaxial shaft having a diameter of 300 mm and a mixing blade of 200 mm x 300 mm.
The residence time of the pug mill is 8 minutes, and the rotation speed of the rotating body is 48 rpm
And processed at a rate of 300 kg per minute. Next, the molding machine
(8) Roll forming was performed using a KDR800 roll forming machine manufactured by Keihan Co., Ltd.
A lump having a mass of 10 g and a diameter of about 35 mm was obtained. The obtained mass was cured and dried in the curing yard (10). Heating was performed using the heat of hydration generated from the hydration reaction of anhydrous calcium hydroxide, and the reaction temperature was 90 ° C. The ambient temperature at this time was about 25 ° C. After curing for 48 hours, a metallic iron-containing mass having a water content of 5% by weight was obtained.

Example 2 The same experiment as in Example 1 was carried out using a mixture of 70% by weight of anhydrous calcium hydroxide and 30% by weight of calcium oxide based on the total amount of the alkali compound. As a result, a metal-iron-containing lump having a water content of 5% by weight was obtained in the same manner as in Example 1 without remaining calcium oxide.

[0020]

According to the production method of the present invention, not only can the production process of the lump containing metallic iron be simplified and the working environment can be improved, but also the added value of the product can be improved. The reuse of the discharged iron-based dust can be performed in an efficient and economically advantageous manner.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus suitable for implementing the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Raw material hopper 2 Crusher 3a, 3b, 5, 7a, 7b, 9a, 9b Belt conveyor 4 Crusher 6 Mixer 8 Molding machine 10 Curing yard

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kimiaki Ezaki 2-4-1 Tenjin-cho, Takatsuki-shi, Osaka 203 Sunshine Tenjinyama 203 (72) Inventor Mitsutake Take 1-37-10 Minami-Oizumi, Nerima-ku, Tokyo (72) Inventor Hiroaki Akasaki 11-1-7 Jiyugaoka, Munakata-shi, Fukuoka (72) Inventor Nobuyuki Kudo 2-2-23-1 Furusobe-cho, Takatsuki-shi, Osaka F-term (reference) 4D004 AA21 BA05 CA03 CA04 CA14 CA15 CA22 CA35 CA42 CB13 CB16 CB31 CB45 CC03 CC11 DA02 DA03 DA06 DA09 DA10 4K001 AA10 BA14 CA26 CA28 CA31

Claims (2)

[Claims] 1. A method for producing a metal-iron-containing lump, comprising: (1) adding an alkali metal or alkaline earth metal oxide or water to a metal iron-containing dust cake having a water content of 10 to 30% by weight; A step of preparing a mixture having a pH of 8 to 14 by adding an alkali compound composed of an oxide; (2) a step of uniformly mixing the mixture so as not to cause aggregation; and (3) a resulting mixture. To form a lump; and (4) curing the lump to produce a lump containing metal iron having a water content of 8% by weight or less. And how. 2. A mixing machine, a press molding machine, and a curing yard, wherein the mixing machine is configured to add an alkali metal or alkaline earth metal to a metallic iron-containing dust cake having a water content of 10 to 30% by weight. A mixture having a pH of 8 to 14 to which an alkali compound composed of an oxide or a hydroxide is added is uniformly mixed so as not to cause aggregation, and the press molding machine adds the mixture obtained from the mixer. Press molding to form a lump,
The above-mentioned curing yard cures the above-mentioned lump, and produces the lump of iron-containing lump having a water content of 8% by weight or less, the system for producing the lump of lump containing metal.