JP6155602B2 - Method for producing sintered ore - Google Patents

Description

  The present invention relates to a method for producing a sintered ore which is a main iron ore raw material used in a steel production process, and more particularly to a method for producing a highly productive sintered ore.

  In a method for producing sintered ore by a dweroid type sintering machine, which is a general production method of sintered ore, it is necessary to improve the firing rate and yield in order to increase productivity. In order to improve the firing rate, it is necessary to increase the heat generation rate due to combustion to advance the firing reaction.

  For this purpose, it is important to increase the amount of oxygen supplied to the sintering bed, and a method for improving the air permeability of the sintering bed and increasing the sintering speed has been proposed. For example, a method of blending an appropriate amount of small ore of 8 to 15 mm, slag, etc. (see Patent Document 1), a method of adding molasses to raw ores and sufficiently agglomerating (see Patent Document 2), etc. Has been proposed.

  In order to improve the yield, it is necessary to improve the uniformity of the quality of the sintered ore. Normally, in a dwytroid type sintering machine, the quality of the sintered ore varies in the depth direction of the sintering bed, so the “variation” is reduced, the sintering strength is increased, and the yield is improved. A method has been proposed.

  For example, a method in which ore having a high melting property is charged in the surface layer of the pallet and a low melting property ore is charged in the lower layer (refer to Patent Document 3), the passing air volume of the sintered layer is measured with an anemometer, and the width direction A method for making the air volume uniform (see Patent Document 4, for example) has been proposed.

  In addition, since the surface layer of the sintering bed has a shortage of heat and the yield is poor, the particle size of solid combustibles such as coke and anthracite that exist in the outermost layer depth part of the sintering raw material layer to improve it. A method of increasing the heating amount of the surface layer by adjusting the average blending amount by reducing the thickness is proposed.

  For example, while adjusting the particle size distribution so that the solid combustible having a particle size of 1 to 3 mm occupies 50% or more of the solid combustible existing in the depth portion from the outermost layer of the sintering raw material layer to 30 to 50 mm, The blending amount of the solid combustible material existing in the depth portion is 1.08 to 1.42 times the average blending amount of the solid combustible material existing in the deeper portion (= the solid combustible material concentration in the surface layer ÷ the remaining layer) A solid combustible material concentration (defined as “segregation index”) has been proposed (see Patent Document 5).

Japanese Patent Laid-Open No. 01-205038 JP 58-107428 A JP-A-62-130229 JP 61-250120 A JP 05-098358 A

Productivity of sintered ore produced is determined by crossed with yield and baking speed. Conventionally, attempts have been made to improve the yield, but generally the yield is low at 50 to 100 mm from the outermost layer of the sintered layer. This is because in the sintering machine, after the raw material layer exits the ignition furnace, normal temperature air is sucked from above and cooled, so the surface layer is the highest necessary for the ore to melt and undergo a sintering reaction. This is because, in addition to the low reached temperature, the time for maintaining the high temperature is short.

  In order to solve this problem, Patent Document 5 proposes a method for improving the yield by increasing the coke of the surface layer and increasing the solid combustible substance concentration to increase the heat generation amount. In the method proposed in Patent Document 5, the particle size is set such that the solid combustible having a particle diameter of 1 to 3 mm occupies 50% or more of the solid combustible existing in the depth portion of 30 to 50 mm from the outermost surface layer of the sintering raw material layer. The distribution is adjusted so that the segregation index of the solid combustible substance concentration is 1.08 to 1.42.

  When the segregation index is 1.08 or more, the yield is improved and the productivity is improved. However, if it exceeds 1.42, the sintering speed is lowered and the productivity improvement effect is lowered. Stipulates that the segregation index is 1.08 to 1.42. The solid combustible substance concentration was changed by changing the coke amount of the surface layer in the range of 4.05 to 5.11% by mass, and in the lower layer, changing the coke amount in the range of 3.60 to 4.05% by mass. Yes.

  In the conventional technology that segregates the solid combustible concentration to improve yield and increase productivity, even if the amount of coke in the surface layer is increased, if the segregation index exceeds 1.42, the air permeability deteriorates. Therefore, it was thought that the firing rate was lowered and the productivity was not improved. Therefore, the present invention aims to improve productivity over the prior art in a method for improving productivity by segregating the grain size of the sintered raw material, and a method for producing sintered ore that solves the problem. The purpose is to provide.

In general, the firing rate in sintering, since it is the size rather affect the aeration rate of the sintered layer, in order to increase the firing rate, it is important to increase the airflow rate. Here, the air flow rate is determined by the air flow resistance of the sintered layer.

  In FIG. 1, the cross section in the advancing direction of the sintering machine of a sintered layer is typically shown. In the ignition furnace 6, the upper layer of the sintered layer is ignited to start the sintering reaction, but as the pallet advances in the traveling direction 9 by sucking the air 7 from above by the exhaust blower 8 below the sintered layer. The sintering reaction proceeds.

  The sintered layer is roughly composed of a raw material layer 1, a reddish tropical zone 2, and a sintering completion zone 3 from the viewpoint of the progress of the sintering reaction. The sintered layer is roughly composed of a surface layer 4 and a lower layer 5 from the viewpoint of the position and the mixing ratio of coke.

  The airflow resistance of the sintered layer is the sum of the airflow resistance of the three layers, which is roughly classified from the viewpoint of the progress of the sintering reaction. The thickness of each layer changes with the progress of the sintering reaction after the raw material layer exits the ignition furnace 6.

  The thickness of the red tropics increases with the progress of the sintering reaction. The reason for this is that the heat contributing to the sintering reaction is transmitted from the surface layer to the lower layer by ventilation, and the combustion heat of coke existing in the lower layer is added, and the lower layer accumulates more heat than the surface layer. is there. And since the red tropics are high temperature and there are many melts, ventilation resistance is overwhelmingly large.

  Therefore, the present inventors consider that the thickness of the red tropics has a strong influence on the air flow rate in the sintered layer, so that the red tropics do not become thicker than necessary in the region where the air flow resistance in the sintered layer is high. Led to the idea that is important. That is, the present inventors, among the surface layer and the lower layer, if the average particle diameter of the lower layer raw material particles having a high airflow resistance is increased, the specific surface area is decreased and the lower layer temperature is not increased more than necessary. The idea was that the thickness of the red tropics could be reduced and the ventilation increased.

  The particle diameter of the raw material in the present invention refers to the raw material particle diameter obtained by granulating auxiliary raw materials such as ore, coke, and lime, and the average particle diameter is the average of the particles inserted into the upper and lower layers. The average particle size can be evaluated with an average particle size measuring device using a sieve.

  In addition, the inventors have conceived that a sintered ore with low airflow resistance can be obtained by placing particles with high airflow resistance in the upper layer and sintering particles with high airflow resistance at the initial stage of firing.

  Therefore, the present inventors conducted a test for sintering by gradually decreasing the average particle size of the lower layer based on the above idea. As a result, it has been found that when the average particle diameter is larger than 3.0 mm, which has been performed so far, the air flow rate in the lower layer is greatly increased and the firing rate is significantly increased.

  At this time, it was found that the yield decreases due to the decrease in temperature accompanying the increase in the average particle size of the lower layer, but the increase in the firing rate compensates for the decrease in yield and the productivity is improved over the prior art. .

  Furthermore, it has also been found that when the average particle diameter of the raw material particles added to the surface layer of 50 to 100 mm is 1.0 mm or less, the temperature of the surface layer can be increased and the yield is improved.

  As described above, the present inventors have increased the average particle size of the lower layer to be larger than the conventional average particle size, and in addition, if the average particle size of the surface layer is reduced, the firing rate is increased while increasing the yield, I found that productivity was improved.

  The present invention has been made based on the above findings, and the gist thereof is as follows.

(1) In a method for producing a sintered ore, a raw material layer is divided into a lower layer and a surface layer on a pallet of a Dwytroid-type sintered, and a sintered ore is produced.
(I) making the average particle diameter of the raw material of the lower layer larger than the average particle diameter of the raw material of the surface layer,
(Ii) the surface layer contains at least a layer to the surface below 50mm from the surface of the material layer,
(Iii) The average particle diameter of the surface layer material is 2.4 mm or less , and
( Iv ) The lower layer raw material has an average particle size of 3.0 mm or more,
( V ) The method for producing a sintered ore, wherein the solid combustible concentration of the raw material of the lower layer is 3.0 to 4.0% by mass.

( 2 ) The lower layer includes at least a layer existing below 150 mm below the surface of the raw material layer, and has an intermediate layer between the surface layer and the lower layer, and the average particle diameter of the raw material of the intermediate layer is greater than the average particle diameter of the surface layer, and method for producing sintered ore according to (1), characterized in that the smaller than the average particle diameter of the lower layer.

According to the present invention, in the production method for improving productivity by segregating the average particle size in the sintering raw material in the upper layer and the lower layer, by making the average particle size of the lower layer larger than the average particle size in the upper layer , Productivity can be increased more than in the prior art.

It is a figure which shows typically the cross section in the advancing direction of the sintering machine of a sintered layer. It is a figure which shows the outline of a Dwightroid type sintering machine. It is a figure which shows the relationship between the average particle diameter of surface layer and a lower layer, and productivity. It is a figure which shows the relationship between the average particle diameter of a surface layer and a lower layer, and a yield. It is a figure which shows the relationship between the average particle diameter of a surface layer and a lower layer, and a baking rate. It is a figure which shows the relationship between the average particle diameter of a lower layer, and productivity at the time of changing the thickness of a surface layer with 25 mm, 50 mm, and 100 mm. It is a figure which shows the relationship between the particle diameter of a lower layer, and productivity at the time of changing coke density | concentration with 3.0%, 3.5%, and 4.0%. It is a figure which shows the relationship between an average particle diameter and layer depth at the time of providing an intermediate | middle layer between a surface layer and a lower layer, and making an average particle diameter small in steps.

  The method for producing a sintered ore of the present invention (hereinafter sometimes referred to as “the method of the present invention”) uses a dweroid type sintering machine as shown in FIG. 2 to produce a sintered ore as follows. To do.

  The iron ore raw material, which is a raw material, is further mixed with coke and limestone by adding moisture, and granulated to produce a sintered ore raw material (also called a sintered raw material). The manufactured sintered raw material is charged into the circulating pallet 10 from the charging device 12 and spread to a thickness of 300 to 1000 mm. A raw material region spread below the pallet among the spread raw materials is defined as a lower layer 19.

On the other hand, a raw material region spread on the lower raw material is defined as a surface layer 18. As the pallet proceeds in the direction of travel 15, the sintering reaction proceeds. A solid combustible (such as coke or anthracite) existing in the upper part of the raw material layer is ignited in an ignition furnace 11 installed immediately after the surface layer addition device 13. The suction of air by the exhaust blower 8 causes the air to flow downward from the upper surface of the raw material layer, whereby the combustion position moves from the upper part to the lower combustible material.

  A part of the raw material is melted by the combustion heat of the combustible material, and then, by cooling, the raw material particles are sintered with each other to form a sintered ore, which is discharged from the ore discharge part 14. The discharged sinter is then crushed to a size of about 50 mm or less with a crusher, sieved, and adjusted to a particle size that is easy to use in the next step.

  In the method of the present invention, among the yield and the firing rate affecting the productivity, in particular, the sintering speed can be made faster than the conventional firing rate, and the productivity can be made higher than the conventional productivity. It is a manufacturing method of ore.

  The sintering raw material used in the method of the present invention is manufactured by two raw material systems, a raw material system for preparing a sintering raw material to be supplied to the surface layer and a raw material system for preparing a sintering raw material to be supplied to the lower layer, and is mounted on a pallet. Entered.

  In the method of the present invention, the sintering raw material layer is defined by being divided into two regions, a surface layer and a lower layer. The upper region of the raw material layer is the surface layer, and the lower region is the lower layer (except for the case where an intermediate layer described later is provided).

  Since the sintering raw material particles supplied to the surface layer and the lower layer are granulated in different raw material systems and charged from different charging devices, the average particle diameter of the sintering raw material in the surface layer and the lower layer can be changed. . As the above charging device, for example, as shown in FIG. 2, a device (surface layer adding device 13) for supplying the raw material to the surface layer is arranged after the device (charging device 12) for charging the raw material to the lower layer. Use a multi-level charging device.

In the method of the present invention, the average particle size, solid combustibles to be used as the carbonaceous material of the fuel, limestone, lime, by kneading ore (including return ores) in the average diameter of the granulated instrumentation Nyuhara fee grains terminal is there.

  In addition, although the raw material charged into the sintering machine usually contains about 10 to 20% of return ore return, the above conditions can be met even if the amount of return ore is larger than the above amount. . However, if the method of the present invention is carried out, the yield is improved, so the amount of return ore is reduced.

  Using the dweroid-type sintering machine shown in FIG. 2, the average particle diameter of the surface layer and the lower layer was changed, the yield and the firing rate were measured, and the productivity was calculated. The results are shown below. In addition, the thickness of the whole raw material layer is 600 mm, and the surface layer thickness is 50 mm.

  3, 4, and 5, six conditions are set in the range of the average particle diameter of the surface layer in the range of 1.0 to 3.5 mm, and the average particle diameter of the lower layer is set to 1.0 to 5 in each condition. The result of having tested in the range of 0.0 mm is shown.

FIG. 3 shows the relationship between the average particle diameter of the surface layer and the lower layer and productivity ”(production amount [t] per day and per m ^{2 of} pallet). FIG. 4 shows the relationship between the average particle diameter of the surface layer and the lower layer and the yield ”(yield [mass%] of the entire sintered ore per day). FIG. 5 shows the relationship between the average particle diameter of the surface layer and the lower layer and the firing rate (the average firing rate of coal per day [mm / min]). In addition, in FIGS. 3-5, the same code | symbol means the same surface particle diameter.

Here, the productivity of sintered ore means the production amount [t] of sintered ore per unit time (1 day) is the effective area of the sintering machine (= sintering machine width × machine length) [m ² ]. It means what was divided. Yield is the ratio of sinter collected by sieving the sinter produced by a sintering machine with a crusher, that is, 5 mm or more recovered with respect to the total sinter mass The ratio of the mass of sintered ore.

The firing rate is a rate at which the combustion reaction surface in the sintered layer proceeds downward, and is obtained by dividing the layer thickness by the time to reach the BPT. The BTP, stands for Burn T h rough Point, is that the position where the flue gas of the sintering machine becomes maximum temperature.

  As shown in FIG. 4, the yield decreases as the average particle size of the lower layer increases. The reason for this is that the temperature is lowered by reducing the specific surface area of the particles in the lower layer.

  On the other hand, as shown in FIG. 5, even if the average particle diameter of the lower layer is increased to 1.5 to 3.0 mm, the firing rate is only slightly increased.

  On the other hand, in the method of the present invention, by setting the average particle diameter of the lower layer to 3.0 mm or more, the firing rate can be increased as shown in FIG. 5, and as shown in FIG. Compensating for the decrease, productivity can be improved over the prior art.

  The reason why the firing rate is significantly increased is that if the average particle size of the raw material of the lower layer is larger than 3.0 mm, the red tropics of the lower layer will not be thicker than necessary, and the lower layer ventilation resistance will decrease and the ventilation rate will increase. This is probably because of this. When the average particle diameter of the lower layer raw material is more than 5.0 mm, the lower layer raw material is not melted, the air flow is overwhelmingly large, and the firing rate is overwhelmingly increased.

  Further, as shown in FIG. 4, when the average particle diameter of the lower layer is 3.0 mm or more, the yield is hardly changed even when the average particle diameter of the surface layer is increased from 1.5 mm to 3.0 mm. On the other hand, if the average particle diameter of the lower layer is less than 3.0 mm, the degree of decrease in yield is alleviated, and if the average particle diameter of the surface layer is less than 1.0 mm, the degree of decrease in yield is further reduced. Is alleviated and yield is improved.

  The reason for this is considered to be that when the average particle size of the surface layer is reduced, the yield of the surface layer is improved (not shown), and as a result, the overall yield is also increased. Although not shown, even if the average particle diameter of the surface layer is 1.0 mm or less, the productivity of the sintered ore is not improved.

  As shown in FIG. 5, when the average particle diameter of the lower layer is increased, the firing rate is increased. In particular, when the average particle size of the lower layer is 3.0 mm or more, the firing rate is rapidly increased. FIG. 3 shows productivity as a result of the yield shown in FIG. 4 and the firing rate shown in FIG. Productivity is determined by multiplying yield and firing rate.

  As can be seen from the figure, in the method of the present invention, in order to improve productivity as compared with the prior art, the average particle diameter of the surface layer is preferably 2.4 mm or less, and the average particle diameter of the lower layer is 3.0 mm or more. And

  The reason for this is considered to be that, as described above, the synergistic effect of the effect of improving the surface yield due to the increase in the amount of heat of the surface layer and the effect of increasing the amount of heat transferred to the lower layer due to the increase in the amount of heat of the surface layer is increased. In order to further improve the productivity, it is more preferable that the average particle diameter of the surface layer is 1 to 2.4 mm and the average particle diameter of the lower layer is 3.2 to 4.8 mm.

  Thus, in the method of the present invention, the average particle size of the lower layer is made larger than the average particle size in the prior art, thereby increasing the firing rate and increasing the productivity compared to the productivity in the prior art. Can do. Furthermore, in the method of the present invention, by reducing the average particle diameter of the surface layer, the yield can be significantly increased, and the productivity can be significantly increased compared to the productivity in the prior art.

  Next, the influence of the thickness of the surface layer will be described. FIG. 6 shows the relationship between the average particle diameter of the lower layer and productivity when the total layer thickness is 600 mm, the average particle diameter of the surface layer is 1.2 mm, and the thickness of the surface layer is changed to 25 mm, 50 mm, and 100 mm. Indicates.

Even when the surface layer thickness is as thin as 25 mm, if the average particle diameter of the lower layer is in the range of 1.5 to 3.0 mm, the productivity can be improved as compared with the prior art, but the improvement effect is small. Therefore, the surface layer thickness is preferably on 50mm or more. When the surface layer thickness is increased, the productivity is improved, but it is saturated at 50 mm, and even if it is 100 mm or more, the productivity is not improved. This is because, as the surface layer thickness is increased, the surface layer yield is improved, but the firing rate is decreased. Therefore, it is preferable that the thickness of the surface layer includes at least a layer from the surface of the raw material layer to 50 mm below the surface.

Furthermore, in the method of the present invention, the coke concentration was made lower than 4.0% by mass. Here, coke concentration, the mass of coke contained in the granulated particles is a value obtained by dividing the mass of the granulated particles. FIG. 7 shows the relationship between the particle size of the lower layer and the productivity when the coke concentration is changed to 3.0%, 3.5%, and 4.0%. As can be seen from FIG. 7 , productivity is further improved when the coke concentration is lowered to 3.5 mass%. This is because when the coke concentration is lowered, the maximum temperature reached by the particles is lowered, the ventilation resistance is lowered, and the ventilation amount is increased.

  Further, when the average particle size is increased, the productivity improvement effect when the coke concentration is lowered is increased. This is because the larger the average particle diameter, the smaller the specific surface area. Therefore, in order to melt and solidify the surfaces of the particles, the ratio of the area that must be dissolved as a whole layer can be reduced. This is because the required coke concentration can be reduced.

  Furthermore, when the coke concentration is lowered to 3.0% by mass, the maximum reached temperature is greatly reduced, the effect of decreasing the melt becomes stronger, the yield is deteriorated and the productivity is lowered. By reducing the particle size, it is possible to improve air permeability and increase productivity.

  Generally, when the granulated particles have different particle sizes, the coke concentration changes. However, when the granulation conditions are different, the coke concentration increases or decreases even if the particle sizes are the same. Therefore, instead of controlling the coke concentration by controlling the particle size, the sintering temperature is controlled by controlling the particle size.

  In the method of the present invention, the segregation of the average particle diameter is not limited to two steps (two-step segregation) of the surface layer and the lower layer. An intermediate layer may be provided between the surface layer and the lower layer for multistage segregation.

  FIG. 8 shows the relationship between the average particle diameter and the layer depth when an intermediate layer is provided between the surface layer and the lower layer and the average particle diameter is gradually reduced. As described above, since the thickness of the surface layer is preferably 50 mm or more, the surface layer is 50 mm in FIG. In the two-stage segregation (thick broken line in the figure), the depth is more than 50 mm. When an intermediate layer is provided (thick solid line in the figure), the lower layer is a sintered raw material having an average particle diameter of 3.0 to 5.0 mm starting from at least 150 mm below the surface of the raw material layer. It is preferable. In FIG. 8, the starting point is 150 mm. Even when an intermediate layer is provided, the surface layer preferably has an average particle diameter of 1.0 to 2.4 mm (a dotted line in the figure indicates a preferable upper and lower limit of the upper layer).

  This is because as the intermediate layer becomes thicker, the effect of improving the firing rate due to the decrease in the average particle size of the lower layer is diminished, which adversely affects productivity. Therefore, the intermediate layer is preferably provided between 25 and 150 mm below the surface of the raw material layer, and more preferably provided between 50 and 120 mm. Such stage segregation can be achieved, for example, by providing a raw material system to be supplied to the surface layer, the middle layer, and the lower layer, and charging the pallet.

  If an intermediate layer is provided between the surface layer and the lower layer, and the average particle size of the intermediate layer is larger than the average particle size of the surface layer and smaller than the average particle size of the lower layer, in the two-stage segregation, immediately below the surface layer By increasing the average particle diameter in the layer (lower layer), it is possible to reduce the influence that the temperature difference increases and the yield decreases.

  Therefore, step segregation is preferred. In the stage segregation, in the droidoid sintering machine shown in FIG. 2, an intermediate layer charging device having the same structure as the surface layer adding device 13 is arranged between the charging device 12 and the surface layer adding device 13. This can be realized by charging a sintering raw material adjusted to an average particle size necessary for each layer.

  Further, in the surface layer and / or the lower layer, the average particle size may be varied within an appropriate range of the average particle size of the surface layer and an appropriate range of the average particle size of the lower layer. For example, the average particle diameter may be continuously varied as indicated by a thin solid line x shown in FIG.

  Next, examples of the present invention will be described. The conditions of the examples are one example of conditions adopted for confirming the feasibility and effects of the present invention, and the present invention is limited to this one example of conditions. Is not to be done. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Example)
A sintering test was performed in the following procedure.

  (1) Add 7% of moisture to the raw material cut out from the raw material hopper, granulate with a solid combustible substance concentration of 3.8%, and add the drum from the charging device 12 to the Dwytroid type sintering machine shown in FIG. The pallet 10 was charged through a feeder, and a lower packed layer was formed with a thickness of 600 mm. At that time, in the granulator, the particle diameter added to the raw material was changed, and the average particle diameter of the sintered raw material charged in the lower layer was changed in the range of 3.0 to 5.0 mm.

In another granulation system, the average particle diameter added to the raw material was changed in the range of 1.0 to 1.5 mm. The raw material granulated here was added to 50 mm of the surface layer by the surface layer addition device 13. Table 1 shows the average particle diameter of the raw material added to the surface layer and the average particle diameter of the raw material charged in the lower layer.

The raw material was charged into the Dwightroid type sintering machine shown in FIG. 2 in two stages with a two-stage charging apparatus to form a raw material layer. As shown in FIG. 2, air was sucked by the exhaust blower 8 from the lower part of the sintering machine, and the surface layer 18 of the raw material layer was ignited by the ignition furnace 6. At this time, the amount of suction air was adjusted so that the suction pressure of the exhaust blower 8 was 1000 mmAq, and this pressure was maintained until the sintering was completed.

  Then, the sintered ore was discharged | emitted in the discharge part 14. After the completion of sintering, the sintered ore was extracted and a strength test was performed. In the strength test, the sintered ore was dropped 4 times from a height of 2 m and crushed, and the mass ratio of 5.0 mm or more was measured. Further, productivity was calculated from the yield and firing rate obtained in the sintering test. The results are also shown in Table 1. In Test Nos. 1 to 4, the thickness of the surface layer was constant at 50 mm.

  Test number 1 is a comparative example which is a basic condition. On the other hand, in Test Nos. 2 to 4, when the average particle size of the surface layer was set to 2.0 to 2.4 mm and the average particle size of the lower layer was set to 3.1 mm, it was proved that the productivity was overwhelmingly increased.

  (2) Next, the thickness for changing the average particle diameter on the surface layer was changed in the range of 25 to 100 mm. At that time, test numbers 5 and 6 were compared by setting the average particle diameter of the surface layer to 2.0 mm and the average particle diameter of the lower layer to 3.1 mm. It was confirmed that when the thickness for changing the average particle diameter of the surface layer is 50 mm or more, the productivity is improved, but the productivity is not greatly improved even when the surface layer thickened thickness is 100 mm.

  Test numbers 7 to 11 show the results when the average particle size of the surface layer is 1.0 mm or 1.7 mm and the average particle size of the lower layer is selected in the range of 2.5 to 3.6 mm. It can be seen that by reducing the average particle size of the surface layer, the average particle size of the lower layer can be further increased, and the productivity is further improved as compared with Test No. 4.

8, a case where is segregated separately average particle diameter in two stages, the average particle diameter and the layer in the case where the average particle diameter stepwise reduced (segregation) of the intermediate layer is provided between the front layer and the lower layer A comparison of depth relationships is shown.

  The average particle diameter of the surface layer was 1.7 mm, and the average particle diameter of the lower layer was 3.0 mm. The average value of the overall average particle diameter is the same. In the stepwise segregation shown in FIG. 2, the stepwise segregation is performed by providing an intermediate layer charging device between the charging device 13 and the surface layer adding device 12 and adjusting the average particle size required for each layer. The raw material was charged and formed.

Test numbers 12 and 13 show the yield, firing rate, and productivity. When stepwise put segregation, it can be seen that the yield is increased, the productivity is improved.

  As described above, according to the present invention, in the manufacturing method for improving productivity by segregating the average particle size in the sintering raw material in the upper layer and the lower layer, the average particle size of the lower layer is made larger than the average particle size in the upper layer. By increasing the size, productivity can be further improved as compared with the conventional technique. Therefore, the present invention has high applicability in the steel industry.

DESCRIPTION OF SYMBOLS 1 Raw material layer 2 Red tropics 3 Sintering completion zone 4 Surface layer 5 Lower layer 6 Ignition furnace 7 Air 8 Exhaust blower 9 Pallet advancing direction 10 Pallet 11 Ignition furnace 12 Charger 13 Surface layer addition apparatus 14 Excavation part 15 Advancing direction 18 Surface layer 19 Lower layer

Claims (2)

On the pallet of Dwightroid-type sintered, the raw material layer is divided into a lower layer and a surface layer, and a sintered ore manufacturing method for manufacturing a sintered ore,
(I) making the average particle diameter of the raw material of the lower layer larger than the average particle diameter of the raw material of the surface layer,
(Ii) the outer layer comprises at least a layer to the surface below 50mm from the surface of the material layer,
(Iii) The average particle diameter of the surface layer material is 2.4 mm or less , and
( Iv ) The lower layer raw material has an average particle size of 3.0 mm or more,
( V ) The method for producing a sintered ore, wherein the solid combustible concentration of the raw material of the lower layer is 3.0 to 4.0% by mass. The lower layer includes a layer existing at least 150 mm below the surface of the raw material layer, and has an intermediate layer between the surface layer and the lower layer, and the average particle diameter of the raw material of the intermediate layer is determined by The method for producing a sintered ore according to claim 1 , wherein the average particle size is larger than the average particle size and smaller than the average particle size of the lower layer.

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