JP2015199999A - Manufacturing method of sinter ore - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of sinter ore capable of improving sinterability or molded article quality during recycling in a sintering process of a steel slag.SOLUTION: There is provided a manufacturing method of sinter ore including a compression molding process of compression molding a steel slag having the iron content of 15 mass% or more, the POcontent of less than 5.5 mass%, the SiOcontent of 20 mass% or less to prepare a molded article having volume of over 0.0063 cmand less than 2.3 cmand a granulation process of mixing and granulating an iron-containing raw material, an auxiliary material, a return ore, a dust and a carbonaceous material and a process for firing with a downward suction type sintering machine after mixing granular obtained in the granulation process.

Description

  The present invention relates to a method for producing sintered ore.

  In the iron making process, various by-products such as slag, dust and sludge are generated. Many of these by-products are reused as iron sources within the steelworks, and are used outside the steelworks as roadbed materials and cement materials. In addition, by-products having properties that are difficult to reuse are often simply landfilled. However, from the viewpoint of environmental protection in recent years, by-products such as landfill processing are also required to be recycled and reused as much as possible.

On the other hand, with the global increase in steel production, the depletion of high-quality resources is progressing. Impurities contained in iron ore, which is the iron source, specifically the inclusion of SiO ₂ and Al ₂ O ₃ components The amount is increasing year by year. When the by-products are reused in the steelworks system, it is desirable to use a material that does not increase these components that are the source of slag. Moreover, it can be said that a by-product method that enables reuse of by-products with particularly high SiO ₂ and Al ₂ O ₃ components outside the steelworks system is desirable.

Of the by-products, almost all of the blast furnace slag is reused outside the steelworks as roadbed material and cement raw material, whereas many steelmaking slags are difficult to reuse. Is not as advanced as blast furnace slag.
For example, among the steelmaking slag, desulfurization slag generated in the hot metal preliminary treatment step is mainly composed of iron and lime. For this reason, it is considered effective to reuse the desulfurized slag by replacing it with a part of iron ore and limestone which are sintering raw materials in the sintering process.

  In the sintering process, powdered iron ore raw materials containing iron (also referred to as “fine ore”), auxiliary materials containing lime, carbon materials containing carbon, etc. are piled up in the yard for each brand. . These stacked raw materials are transported to a raw material tank and cut out from the raw material tank in accordance with a pre-planned mixing ratio so that the components and the like are uniform. The cut out raw material is kneaded and granulated with water in a drum mixer, and is supplied to the sintering machine as a mixed raw material composed of an aggregate of various raw materials (hereinafter sometimes referred to as “pseudo particles”). . The pseudo particles to be granulated have a particle size distribution of about 0.25 to 10 mm, and the average particle size is about 3 to 5 mm.

The blended raw material is charged into a sintering machine pallet to form a sintered raw material packed layer (or simply referred to as “filled layer”). And by igniting the surface of the said packed bed with an ignition furnace, the combustion of the carbonaceous material contained in the pseudo particle which exists in the packed bed surface is started, and a sintering reaction starts.
The packed bed is sucked from below the pallet while moving from the supply side to the discharge side. Thereby, air flows in from the upper part of the packed bed, and the introduced air passes through the packed bed toward the lower part. As a result, the combustion part of the carbon material forms a high-temperature combustion zone, and the combustion zone moves from the upper part to the lower part of the packed bed. Along with the movement of the combustion zone, the surrounding pseudo particles are heated by the heat generated in the combustion zone, causing melting and assimilation reactions and sintering.
This melting and assimilation reaction starts from the formation of a calcium ferrite-based initial melt (melting point: about 1210 ° C.) at the interface between iron and lime, and the surrounding pseudo particles dissolve and proceed. The packed bed that has finally undergone the melting and assimilation reaction forms a sintered cake. The formed sintered cake is discharged from the discharge portion of the sintering machine.

Regarding the method of recycling desulfurized slag as a sintering raw material, there are the following techniques.
A method is disclosed in which desulfurized slag is mixed with desiliconized slag and dehydrated, and both slags are crushed and magnetically sorted to effectively use them as sintering raw materials (Patent Document 1).
Further, there is disclosed a method for using recovered slag in which desiliconization / desulfurization slag is distributed as a feedstock to either a sintering machine or a blast furnace based on the SiO ₂ content (Patent Document 2). .

In addition, dust containing iron oxide and metallic iron, a hydraulic binder, and after adding water to a chloride-based raw material and mixing, then molding, hydrating and curing the molded product, The method to do is shown (patent document 3).
Furthermore, after desulfurization slag is submerged and cooled, it is dried and mixed with gypsum-containing desulfurization slag powder, and powder such as powder coke and dust is added, and moisture is added and granulated with a pan pelletizer. A method for granulating a powder using a powder is disclosed (Patent Document 4).

Japanese Patent Publication No. 63-54663 Japanese Patent No. 3617488 JP 2009-179854 A JP 2008-95167 A

However, in Patent Documents 1 and 2, since the desulfurization slag is combined with the desiliconization slag, the SiO ₂ content in the slag becomes high, and the SiO ₂ and Al ₂ O ₃ components are problematic. In recent years, it cannot be said that it is an effective processing method when considered from the viewpoint of selecting a reuse destination according to the slag component.
Further, in Patent Document 3, for adding cement as hydraulic binder, becomes bringing SiO ₂ or Al ₂ O ₃ component from the outside. Furthermore, chloride is known to increase the generation of dust in sintered exhaust gas, and it is desirable to avoid its use for environmental protection. In addition, curing is necessary to obtain the required strength, and it is necessary to secure a holding space and the like.
Furthermore, in the above-mentioned patent document 4, since the gypsum-containing desulfurized slag powder is blended as a binder with powders such as powdered coke and dust, the amount of desulfurized slag used is limited. That's not true.

  The objective of this invention is providing the sintered ore manufacturing method which can improve sinterability and product quality at the time of reuse in the sintering process of steelmaking slag.

The present inventors considered that a method of forming steelmaking slag in advance and reusing it as a sintering raw material after reuse in the sintering process of steelmaking slag was effective.
Various studies were conducted to find out a method that can maintain and improve the sinterability and product quality when reusing the molding method and the molded steelmaking slag in the sintering process.
As a result, it was found that the steelmaking slag can be made into a molding suitable for sintering recycling by compression molding so as to have a specific size, and this molding can be used as a sintering raw material.

The gist of the present invention is as follows.
(1) A steelmaking slag having an iron content of 15% by mass or more, a P ₂ O ₅ content of less than 5.5% by mass, and a SiO ₂ content of 20% by mass or less is compression molded to exceed a volume of 0.0063 cm ³ A compression molding step for forming a molded product of less than 2.3 cm ³ and a granulation step for mixing and granulating the iron-containing raw material, auxiliary raw material, return mineral, dust and carbonaceous material, A method for producing a sintered ore, comprising: mixing a molded product to be obtained and a granulated product obtained in the granulation step, followed by firing with a downward suction type sintering machine.
(2) The method for producing sinter according to (1), wherein the steelmaking slag is desulfurization slag.
(3) The compression molding step is compression-molded into a molded product having a volume equal to or greater than the volume calculated from the average diameter of the granulated product obtained in the granulation step and less than 2.3 cm ³ in volume. The sintered ore manufacturing method according to (1) or (2).

  ADVANTAGE OF THE INVENTION According to this invention, at the time of reuse in the sintering process of steelmaking slag, sinterability and product quality can be improved.

The figure which shows the relationship between a molding volume and a production rate.

Hereinafter, embodiments of the present invention will be described in detail.
(Steel slag)
In the blast furnace ironmaking process, massive iron ore or agglomerated minerals such as sintered ore pellets, which have been processed to have a grain size and strength suitable for blast furnace charging, are reduced in the blast furnace. , Discharged as pig iron from the blast furnace. Pig iron is also called hot metal because it is discharged in a molten state at a high temperature.
This pig iron contains impurities such as carbon, phosphorus, silicon, and sulfur, and component adjustment including removal of impurities is performed in a steelmaking process that is the next process of the blast furnace. In a general steelmaking process flow, after hot metal pretreatment for desulfurization and desiliconization is performed, decarburization and dephosphorization are performed in a converter.
Table 1 below shows an example of measuring chemical components of steelmaking slag.

In the present embodiment, as the steelmaking slag, one having an iron content of 15% by mass or more, a P ₂ O ₅ content of less than 5.5% by mass, and an SiO ₂ content of 20% by mass or less is used. The above range is a range excluding dephosphorization slag and desulfurization slag in Table 1. Here, the removal of the dephosphorization slag is to avoid the circulation of P in the iron making process. Moreover, the removal of the degassing slag is to prevent an increase in the blast furnace slag ratio by recycling SiO ₂ . Of these, the use of desulfurized slag is preferable because it contains iron and lime as main components and can be easily reused by replacing part of iron ore and limestone which are sintering raw materials in the sintering process.
Desulfurization slag is a by-product generated in the desulfurization process whose main purpose is to remove sulfur in the steelmaking process. In the desulfurization process, a desulfurizing agent is introduced into a kneading vehicle (torpedo car), which is a container for conveying the hot metal discharged from the blast furnace to the steelmaking process, and an apparatus for desulfurization treatment, such as an impeller, is used. It is carried out in KR (Kanbara Reactor) which is a desulfurization device that reacts both mechanically by stirring.

Quick lime (CaO) is mainly used as the desulfurizing agent. The desulfurization reaction using CaO is shown in the following formula (1).
CaO + [S] = CaS + 1 / 2O ₂ ↑ (1)
Since CaO has a high melting point and the reaction efficiency of CaO alone is low, desulfurization aids such as NaCO ₃ , CaF ₂ , and CaC may be used in some cases.
The desulfurized slag after desulfurization is collected in a pan, and after being cooled with water in a pit, it is magnetically selected. Large blocks and medium blocks selected by magnetic separation have a high Fe content, so they are recycled in a converter, and the remaining fine-grained parts are sent to a sintering plant as desulfurized slag for sintering.

As described above, the desulfurization reaction in the desulfurization step has low reaction efficiency, and F-CaO contained in the slag after desulfurization is about 21% by mass. And most of the desulfurization agent supplied remains as unmelted CaO powder or Ca (OH) ₂ powder generated by hydration reaction of CaO.
For this reason, it can be said that desulfurization slag is a mixture which has as a main component the unmelted desulfurization agent and the hot metal ingot mixed at the time of collection | recovery.
As shown in Table 1 above, it can be confirmed that the desulfurized slag is mainly composed of a metallic iron component (M-Fe) derived from pig iron and a CaO component derived from a desulfurizing agent.

The desulfurization slag for sintering is stored in a yard and is usually kept at a moisture content of about 5% by mass to 12% by mass.
In the present embodiment, in compression molding of desulfurized slag, which will be described later, the moisture of the desulfurized slag does not need to be specially adjusted, and can be directly used for molding within the range of 5% by mass to 12% by mass.

The size of the desulfurized slag molded product obtained by compression molding must be determined in consideration of the properties of the desulfurized slag, the reactivity of the molded product itself, the reactivity with the surroundings during sintering, and the like.
(Reactivity of desulfurized slag molding itself)
First, regarding the reactivity of the desulfurized slag molded product itself, only the desulfurized slag molded product was held alone in an electric furnace, and the influence was observed. The electric furnace was in an air atmosphere, and was kept in an atmosphere of 1300 ° C. for 5 minutes in order to simulate the temperature history of the combustion zone in the sintering process.
The desulfurized slag molded product after holding the electric furnace, although a slight melting reaction was observed, the shape at the time of compression molding was maintained despite the configuration in which the iron component and the lime component were arranged close to each other. . From the above results, it was confirmed that the melt assimilation reaction of the desulfurized slag molding was slower than that of a normal sintered raw material. This is because the desulfurized slag contains not the iron oxide but the M-Fe component, and the formation of the calcium ferrite requires a two-step reaction in which it is once oxidized and then reacted with the CaO component. Inferred.

(Reactivity between desulfurized slag molding and powdered iron ore or limestone)
In the actual sintering process, when the sintered raw material packed layer is formed, other sintered raw materials exist around the desulfurized slag molded product, and the desulfurized slag molded product comes into contact with them. In order to simulate this state, the desulfurized slag molding was placed in a bed of powdered iron ore or limestone and held at 1300 ° C. for 10 minutes. The reason why the holding time was set to 10 minutes was that, in addition to the desulfurized slag molded product, it took into account that it took time to heat up due to the increase in the amount of the sample using powdered iron ore or limestone. is there.
The desulfurized slag molded product installed in the bed of powdered iron ore has undergone a melting reaction after holding the electric furnace, and about half of the desulfurized slag molded product is melted with the powdered iron ore present around it. It was assimilated. This is because the reaction between the CaO component present on the surface of the desulfurized slag molded product and the iron oxide content in the powdered iron ore existing around the desulfurized slag molded product proceeds rapidly, and the generated initial melt It is inferred that the M-Fe component in the desulfurized slag molding was dissolved.

On the other hand, the desulfurization slag molded product installed in the limestone bed did not proceed with the melting reaction after holding the electric furnace. As in the case where only the desulfurized slag molded product is held alone in the electric furnace, the reaction between the M-Fe component in the desulfurized slag molded product and limestone (CaO) requires an oxidation reaction, It is inferred that it became the rate-limiting factor of the reaction.
From the electric furnace holding test results shown above, the reaction characteristics in the sintering process of desulfurized slag moldings show behavior similar to lime-containing particles rather than iron-containing particles, that is, the surrounding iron ore in the combustion zone It is thought to react with stones.

(Compression molding process)
In the present embodiment, the desulfurized slag is compression molded into a molded product having a predetermined size.
Since the reaction proceeds by downward suction in the sintering process, it is advantageous from the viewpoint of the firing rate that the raw material has a larger particle size. However, the mixing ratio of the lime-containing particles in the entire sintered raw material is smaller than that of the iron-containing particles. For this reason, when the particle size of the desulfurized slag molding that exhibits similar behavior to the lime-containing particles is too large, the contact interface with the iron ore is reduced due to the decrease in the specific surface area, and the generation of the melt is hindered or biased. Eventually, the yield of the sintered product ore is expected to deteriorate.
Therefore, in producing a desulfurized slag molded product, there is an optimum size, and the appropriate particle size range is considered to be different from the molded product mainly composed of iron-containing particles.

Based on the above considerations, in this embodiment, it exceeds the volume 0.0063Cm ³ by compression molding the desulfurization slag and the molded article of less than 2.3 cm ^3.
By compression molding so as to be within the above range, it contributes to the improvement of the ventilation of the sintered raw material packed layer before the combustion zone passes during sintering. Further, during the passage through the combustion zone, the melt assimilation reaction proceeds promptly to generate a sufficient amount of melt, and it becomes possible to produce sintered ore without deteriorating the yield or strength of the sintered ore product.

Also, in the downward suction sintering process, the size of the particles filled in the sintering machine is an important factor that governs the firing rate and thus the productivity of the sintered ore. Fine particles clog the packed bed and deteriorate its air permeability, resulting in a decrease in the firing rate. On the other hand, coarse particles improve the air permeability and consequently increase the firing rate. Here, the average diameter of the pseudo particles granulated by a general granulation process is about 3 to 5 mm.
When the molded product is added to and mixed with the pseudo particles after granulation, the average diameter of the granulated product (pseudo particles) obtained in the granulation step described later is desirable, preferably from the viewpoint of securing the firing rate described above. It is preferable to perform compression molding so as to obtain the above size.

In compression molding, it is preferable to use a double roll briquette machine. The linear pressure during molding is preferably in the range of 0.52 t / cm or more and 0.66 t / cm or less. If the linear pressure is less than the lower limit, the pressure is insufficient and the moldability may be poor. On the other hand, when the linear pressure exceeds the upper limit value, there is a possibility that so-called laminating occurs in which the pressure is too high, and the center portion of the molded product breaks. By setting the roll speed at the time of molding to about 350 cm / min, good molding efficiency can be obtained within the above linear pressure range.
In addition, even if a part or all of the molded product obtained by compression molding is, for example, crushed during the process to generate a powdered product, the molded product containing the powdered product is sieved, The effect of the present invention can be obtained by using only those within the range as raw materials.
When the desired size of the molded product is smaller than the cup shape of the briquette machine used for compression molding, first, in the compression molding process, the size is larger using a cup larger than the desired size. Mold the molding. Then, the obtained molded product is crushed, the crushed product is sieved, and classified so as to have the desired size.

(Granulation process)
Next, an iron containing raw material, an auxiliary raw material, a return mineral, dust, and a carbon material are mixed and granulated.
Specifically, an iron-containing raw material, a secondary raw material, return mineral, dust, and a carbonaceous material other than desulfurized slag are supplied to a drum mixer, mixed, and granulated to produce a granulated product. In addition, you may manufacture a granulated material by once mixing with a mixing mixer, and granulating with a drum mixer for granulation after that.

(Baking process)
And after mixing the molding of the desulfurization slag obtained by the said compression molding process, and the granulation obtained by the said granulation process, it bakes with a downward suction type sintering machine.
The blending amount of the desulfurized slag molded product is preferably in the range of more than 0% by mass and 6% by mass or less, particularly preferably in the range of 3% by mass or less, with respect to all raw materials. If the amount of the desulfurized slag molding exceeds the above range, SOx-based gas generated from the sulfur content in the desulfurized slag increases, and the exhaust gas treatment equipment such as desulfurized SOx and NOx, which is normally performed in the sintering process, increases. The load may increase.
Moreover, the desulfurization slag molding containing a CaO component will be used by replacing a part of limestone or quicklime. However, since the desulfurized slag molded product used in this embodiment has a larger particle size compared to the size of limestone, quicklime, etc., the desulfurized slag molded product has a blending amount exceeding the above range, and the replacement amount with limestone or quicklime. If the amount is increased too much, the sintering reaction becomes non-uniform and firing may be disturbed.

The sinter manufacturing method of this embodiment, steel slag, preferably using the desulfurization slag, the desulfurization slag exceeds the volume 0.0063Cm ^3, and compression molded into molded product of less than 2.3 cm ^3, which separately It is mixed with a granulated product obtained by granulation and used for sintering.
In this way, the desulfurized slag was compression molded to a size suitable for sintering in consideration of the properties of the desulfurized slag, the reactivity of the molded product itself, the reactivity with the surroundings during sintering, etc. By reusing such desulfurized slag moldings in the sintering process, the sinterability and product quality can be improved.
In the above embodiment, the desulfurization slag has been described. However, the desulfurization slag is not limited to the use of only the desulfurization slag. For example, only the decarburization slag may be used as long as the steelmaking slag is within the above range. And decarburized slag may be used in combination.

Next, the present invention will be described in more detail with reference to examples. In addition, this invention is not restrict | limited at all by these examples.
The effect of desulfurized slag molding on sinterability was confirmed by a sintering pot test that can simulate the sintering process on a laboratory scale.
(Sintering raw material)
As raw materials, desulfurized slag and general sintered raw materials such as fine ore, auxiliary raw materials, and carbon materials were used. Table 2 below shows the types of raw materials used and the blending conditions. Note that “other fine ores and miscellaneous ores” in Table 2 is a collection of raw materials having a relatively small blending amount, such as ore brands having a small blending ratio and lump ore under sieve powder.

For desulfurization slag, desulfurization slag for sintering recycling, which was collected from the sintering raw material yard of the steelworks, was used. Desulfurization slag for sintering recycling is a part of the desulfurization slag generated in the desulfurization process, classified by sieving or magnetic separation, and having a particle size suitable for sintering recycling, such as 15 mm or less or 10 mm or less. is there. Here, what collected the part 15 mm or less was used. The coarser portion is reused as an iron source for steelmaking.
The particle size distribution of the used desulfurized slag for sintering recycling is shown in Table 3 below.

  And the desulfurization slag for sintering recycling obtained by classification was adjusted in advance so that the water content was 11.0% by mass. The water content was adjusted by charging the classified desulfurized slag into a mixer and mixing and stirring for 1 minute while pouring water.

(Compression molding process)
Next, the desulfurized slag after moisture content adjustment was charged into a double roll briquette machine and compression molded. In the briquette machine used for compression molding, the roll size is 228 mm and the roll width is 76.2 mm (effective width 38 mm), the cup shape is almond shape, the cup size is about 1.7 cm ³ and about 3.0 cm ³ The roll of was used.
The compression molding conditions were a rotation speed of 5 rpm and a compression load of 4 to 5 tf (about 40 kN to about 50 kN). In addition, the roll speed at the time of the said rotation speed is 358 cm / min. The linear pressure (load / roll width) is 0.52 to 0.66 t / cm.
Then, a molded product compression molded with the above two types of cups and a molded product molded with the above two types of cups are crushed and sieved to a predetermined particle size, and the desulfurized slag molded product is organized by volume. The total size was adjusted to 6 levels and used (molded products 1 to 6).

(Granulation process)
Next, the raw materials excluding the desulfurized slag molded product are put into a drum mixer having a length of 600 mm and a diameter of 500 mm, and after rolling for 2 minutes, the raw materials are mixed so that the water content becomes 7.0% by mass. The mixture was granulated by rolling for 4 minutes at 25 rpm while pouring a predetermined amount of water into the mixer. This was made into the granulated material of an Example and a comparative example. Further, granulation was performed in the same manner as above except that the desulfurized slag powder was kept in a powder state and mixed with the raw material excluding the desulfurized slag molding. This was used as a granulated product of a conventional example. In the conventional example, the granulated product obtained here is a sintering raw material.
A part of the granulated product obtained in the granulation process was sampled. Then, the sample was dried at 105 ° C. until the water content became 0% by mass, and the dried sample was placed on a low-tap sieve shaker and sieved for 15 seconds without tapping, whereby the particle size distribution (below) , Called pseudo particle size distribution). The results are shown in Table 4 below.

The conventional example in Table 4 is a pseudo particle size distribution including desulfurized slag, which is obtained by blending and granulating desulfurized slag powder together with other raw materials. Moreover, an Example and a comparative example are the pseudo particle size distribution which made the pseudo particle by mix | blending and granulating the other raw material except a desulfurization slag molding.
When the load average diameter was calculated from the obtained pseudo particle size distribution, the load average diameter of the conventional example was 3.64 mm, and the load average diameter of the example and the comparative example was 3.78 mm. The average diameter of the general pseudo particles is about 3 mm to 5 mm, and it can be confirmed that the general pseudo particles are granulated under the raw material composition and granulation conditions in this test.

(Sintering pot test)
Based on the blending ratio shown in Table 2 above, a desulfurized slag molded product and a granulated product were blended, and a sintering pot test was performed using the obtained sintering raw material. In addition, desulfurization slag is a conventional example (unmolded powder), Comparative Example 1 (molded product 1), Example 1 (molded product 2), Example 2 (molded product 3), Example 3 (molded product 4), A combination of Comparative Example 2 (Molded product 5) and Comparative Example 3 (Molded product 6) was used.
In the sintering pot test, a sintering raw material is charged into a container having an arbitrary area and height, and the surface of the sintering raw material layer formed in the container is ignited and disposed at the lower part of the container. This test simulates the sintering process by sucking air from a wind box with a blower. By installing an orifice or the like between the wind box and the blower, the air volume or the negative pressure can be measured and controlled.

First, a sintering raw material was charged into a cylindrical container having a diameter of 300 mm and a height of 500 mm to form a raw material packed layer. Then, the surface of the raw material charging layer was ignited with a burner for 1 minute, and calcination was performed by sucking downward at a negative pressure of 9.8 kPa (1000 mmH ₂ O) from the lower part of the cylindrical container.
In addition, the thermocouple was inserted into the cylindrical container for every fixed layer height, and the combustion front descending speed (FFS: Flame Front Speed) was calculated from the temperature change measurement value. Further, a thermocouple was also arranged in the wind box, and the firing end time was defined as 3 minutes after the time when the exhaust gas temperature showed the maximum value.
The sintered cake obtained after the completion of firing was dropped 4 times from a height of 2 m, and then classified by a square sieve having a diameter of 5 mm, and the product yield was evaluated using the sieve as a product sintered ore. . The production rate was calculated from the firing end time and the product yield. Further, the product sintered ore after product yield evaluation was further classified with a sieve, and the rotational strength index TI was measured. The results are shown in Table 5 below.

As shown in Table 5, compared with the conventional example which used unshaped powder | flour as a raw material as it was, the result in which the production rate rose in Examples 1-3 using the moldings 2, 3, and 4 was obtained.
On the other hand, in Comparative Example 1 using the molded product 1, the production rate was lower than in the case of the unmolded powder which is a powdery product because the volume of the molded product was too small. Moreover, in Comparative Examples 2 and 3 using the molded products 5 and 6 having a large volume, the production rate was slightly lower than that of the unmolded powder as a powder. This is because, based on the result that the rotational strength index TI of the product and the product yield are reduced, the presence of a molded article having a large volume in the packed bed causes locally unstable portions of ventilation and firing. Presumed to have occurred.

FIG. 1 shows the result of arranging the molded product volume (logarithmic scale display) on the horizontal axis and the production rate on the vertical axis. The data points shown in FIG. 1 represent examples in which molded articles 1, 2, 3,... Are used from the left. Moreover, the horizontal broken line at the production rate of 34 t / d / m ² indicates the production rate of the conventional example (unmolded powder). The vertical broken line at the position of volume 0.0063 cm ³ indicates the volume when the sphere is approximated in the weighted average diameter 2.29 mm of the used desulfurized slag.
As shown in Table 3 above, desulfurized slag has a wide particle size distribution, but the weight average diameter of the green powder used in the conventional example is 2.29 mm. The volume of a sphere with a diameter of 2.29 mm is about 0.0063 cm ³ .
As shown in FIG. 1, the volume of the sphere at the weighted average diameter of the unmolded powder is located between Comparative Example 1 using the molded product 1 and Example 1 using the molded product 2. Further, the production rate of the conventional example using unmolded powder is located between the production rate of Comparative Example 1 using the molded product 1 and the production rate of Example 1 using the molded product 2. From this result, it can be seen that the desulfurized slag has a volume exceeding 0.0063 cm ³ , that is, the production rate is increased by molding the desulfurized slag to a volume larger than that obtained by spherical approximation from the weighted average diameter of the raw material to be molded .
Further, when the size of the molded product was 2.3 cm ³ or more, the production rate was reduced to the same or lower than that of the conventional example using unmolded powder. Thus, if the size of the molded product is too large, it is presumed that the firing becomes unstable.
Is the above molded product obtained by compression molding the desulfurization slag, size volume exceeds 0.0063Cm ^3, i.e., at least the volume calculated from the weighted average particle size of steelmaking slag itself used, 2.3 cm ³ less than The range is desirable from the viewpoint of maintaining the production rate.

Claims (3)

1. Steelmaking slag having an iron content of 15% by mass or more, a P ₂ O ₅ content of less than 5.5% by mass, and a SiO ₂ content of 20% by mass or less is compression molded to exceed a volume of 0.0063 cm ³ . A compression molding process for forming a molded product of less than 3 cm ³ ;
A granulation step of mixing and granulating iron-containing raw materials, auxiliary raw materials, return ore, dust and carbonaceous materials,
Have
A method for producing a sintered ore, comprising: mixing a molded product obtained in the compression molding step and a granulated product obtained in the granulation step, and then firing the mixture in a downward suction type sintering machine. .   The method for producing sintered ore according to claim 1, wherein the steelmaking slag is desulfurization slag. The compression-molding step is compression-molded into a molded product having a volume equal to or larger than a volume calculated from an average diameter of the granulated product obtained in the granulating step and less than 2.3 cm ³ in volume. The sintered ore manufacturing method according to claim 1 or 2.

Images