阅读说明：本技术 烧结矿的制造方法 (Method for producing sintered ore ) 是由 广泽寿幸 竹原健太 山本哲也 于 2018-04-16 设计创作，主要内容包括：本发明涉及烧结矿的制造方法,该方法能够不引入新的设备就提高托盘上层部的凝结材料的比例,由此能够延长装入层上层部的高温保持时间从而实现装入层上层部的烧结矿的成品率提高。该烧结矿的制造方法利用烧结机将被造粒后的烧结原料烧结,烧结原料包含：含铁原料,包含相对于烧结原料的质量为5质量％以上的量的粒径10μm以下的铁矿石粉；凝结材料,含有50质量％以上的粒径1mm以下的焦炭粉,且相对于烧结原料的质量为3质量％以上7质量％以下的范围内的量；以及含CaO原料,至少上述含铁原料在烧结原料被造粒之前被搅拌,在将烧结原料的全部造粒期间设为0～100％的情况下,在50～95％的造粒期间将凝结材料的一部分或者全部混合来进行造粒。(the present invention relates to a method for producing sintered ore, which can increase the proportion of a coagulated material in an upper layer portion of a pallet without introducing new equipment, thereby increasing the high-temperature retention time of an upper layer portion of a loading layer and improving the yield of sintered ore in the upper layer portion of the loading layer. The method for producing sintered ore sinters granulated sintering material by a sintering machine, the sintering material including: an iron-containing raw material containing iron ore powder having a particle size of 10 [ mu ] m or less in an amount of 5 mass% or more relative to the mass of the sintering raw material; a coagulation material containing 50 mass% or more of coke powder having a particle size of 1mm or less, and in an amount within a range of 3 mass% or more and 7 mass% or less with respect to the mass of the sintering material; and a CaO-containing raw material, wherein at least the iron-containing raw material is stirred before the sintering raw material is granulated, and when the total granulation period of the sintering raw material is set to 0 to 100%, a part or all of the coagulated material is mixed and granulated during 50 to 95% of the granulation period.)

1. A method for producing sintered ore by sintering a granulated sintering material by a sintering machine, wherein,

The sintering raw material comprises:

an iron-containing raw material containing iron ore powder having a particle size of 10 [ mu ] m or less in an amount of 5 mass% or more relative to the mass of the sintering raw material;

A coagulation material containing 50 mass% or more of coke powder having a particle diameter of 1mm or less, and in an amount within a range of 3 mass% or more and 7 mass% or less with respect to the mass of the sintering material; and

The raw material containing the CaO is mixed with the raw material,

At least the iron-containing raw material is stirred before the sintering raw material is granulated,

When the total granulation period of the sintering raw material is set to 0-100%, a part or all of the coagulation material is mixed and granulated during 50-95% of the granulation period.

2. The method of manufacturing sintered ore according to claim 1, wherein,

In the case where a part of the coagulated material is mixed during the 50 to 95% granulation,

And measuring the particle size of the granulated sintering raw material, and if the particle size is smaller than a predetermined particle size, adding 50 to 95% of the coagulated material mixed during the granulation.

Technical Field

The present invention relates to a method for producing sintered ore, in which granulated sintering material is sintered by a sintering machine to produce sintered ore.

Background

The sintered ore can be manufactured by: an appropriate amount of a secondary raw material such as limestone, silica or serpentine, an impure raw material such as dust, oxide scale or return fines, and a coagulant such as coke powder are mixed with iron ore powder of various brands, and the resulting mixture is mixed with water and granulated, and the granulated raw material is sintered by a sintering machine. The sintering raw materials are agglomerated by moisture at the time of granulation to form pseudo particles. The quasi-granulated granulation raw material helps to ensure good air permeability of the charged layer charged into the pallet of the sintering machine, and the sintering reaction can be smoothly performed by using the quasi-granulated granulation raw material.

Fig. 1 is a diagram illustrating a yield distribution of sintered ore. Fig. 1(a) shows a heating curve of the upper, middle and lower parts of the loading layer, and fig. 1(b) is a schematic cross-sectional view showing a yield distribution of the sintered cake. The numerical values in the boxes of FIG. 1(b) represent the yield of each layer of the sintered cake.

As shown in FIG. 1(a), the temperature of the upper layer of the loading layer is less likely to rise than that of the lower layer of the loading layer, and the holding time in a high temperature region exceeding 1200 ℃ is also shortened. Thus, the high-temperature holding time is shortened in the upper layer portion of the charge layer, the combustion melting reaction (sintering reaction) is insufficient, and the strength of the sintered cake is lowered. As shown in fig. 1(b), the yield of the sintered ore in the upper layer of the loading layer is lowered due to the strength reduction of the sintered cake, which causes the productivity of the sintered ore to be lowered.

In order to cope with such a decrease in the yield of the sintered ore in the upper layer portion of the charged layer, patent document 1 discloses that the yield of the sintered ore in the upper layer portion of the charged layer can be improved by using a gaseous fuel having a faster burning rate than coke. According to patent document 1, since the temperature of the upper portion of the loading layer can be increased in a short time by using the gas fuel, not only the upper portion of the loading layer where the cold strength of the sintered ore is liable to be lowered due to insufficient heat but also the strength of the sintered ore is increased in a wide portion including the middle portion of the loading layer, and the yield of the sintered ore is improved.

Non-patent document 1 discloses a technique for loading a charcoal material into an upper layer portion of a pallet using a device capable of loading coke powder into the upper layer portion of the pallet. Non-patent document 1 discloses a technique in which 0.2% of a carbon material is loaded into an upper portion of a tray, thereby increasing the maximum temperature of the upper portion of the loaded layer and extending the high-temperature retention time of the upper portion.

Patent document 1: international publication No. 2007/052776

Non-patent document 1: shi gan et al 5 noted "application result of upper part charging technique of carbon material in sintering machine added in ancient and Sichuan", CAMP-ISIJ, VOL.14(2001) -956

In the implementation of the technique disclosed in patent document 1, it is necessary to prepare a gaseous fuel in addition to a condensed material, and a blowing device for the gaseous fuel is required in the upper part of the sintering machine. Therefore, additional equipment investment is required and the cost of gas fuel is also incurred, so the production cost of the sintered ore increases. In the implementation of the technique disclosed in non-patent document 1, an apparatus for loading the carbon material into the upper layer portion of the tray is required, and therefore additional equipment investment is required.

Disclosure of Invention

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a method for producing sintered ore, which can increase the proportion of a agglomerated material to be loaded into an upper layer portion of a loading layer without introducing new equipment, thereby increasing the high-temperature retention time of the upper layer portion of the loading layer, and thus can improve the yield of the sintered ore in the upper layer portion of the loading layer.

The features of the present invention for solving such problems are as follows.

(1) A method for producing a sintered ore by sintering a granulated sintering material by a sintering machine, wherein the sintering material comprises: an iron-containing raw material containing iron ore powder having a particle size of 10 μm or less in an amount of 5 mass% or more relative to the mass of the sintering raw material; a coagulation material containing 50 mass% or more of coke powder having a particle size of 1mm or less, and in an amount within a range of 3 mass% or more and 7 mass% or less with respect to the mass of the sintering material; and a CaO-containing raw material, wherein at least the iron-containing raw material is stirred before the sintering raw material is granulated, and when the total granulation period of the sintering raw material is 0 to 100%, a part or all of the condensed material is mixed and granulated during 50 to 95% of the granulation period.

(2) The method for producing a sintered ore according to (1), wherein the particle size of the granulated sintering material is measured when a part of the agglomerated material is mixed during the 50 to 95% granulation period, and the agglomerated material mixed during the 50 to 95% granulation period is increased when the particle size is smaller than a predetermined particle size.

By carrying out the method for producing a sintered ore of the present invention, the proportion of the agglomerated material charged into the upper layer portion of the charged layer can be increased without introducing new equipment. This prolongs the high-temperature holding time of the upper layer portion of the charged layer, thereby increasing the strength of the sintered cake and improving the yield of the sintered ore in the upper layer portion of the charged layer.

Drawings

Fig. 1 is a diagram illustrating a yield distribution of sintered ore.

Fig. 2 is a schematic view showing an example of a sintered ore production apparatus that can be implemented by the sintered ore production method of the present embodiment.

Fig. 3 is a diagram showing a model used in the Discrete Element Method (DEM).

Fig. 4 is a diagram showing a state of loading onto a tray simulated by using a Discrete Element Method (DEM).

Fig. 5 is a coordinate diagram showing a result of calculating the pseudo particle diameter of each layer of the tray and the ratio of the condensed material existing in each layer from a simulation result by the Discrete Element Method (DEM).

Fig. 6 is a diagram showing the results of a pallet loading experiment for a sintering machine.

Fig. 7 is a coordinate diagram showing the relationship between the adjusted average particle size of the quasiparticles granulated by the granulation test and JPU of the loaded layer formed of the quasiparticles.

Detailed Description

The present invention will be described below with reference to embodiments thereof. Fig. 2 is a schematic diagram showing an example of a sintered ore production apparatus 10 that can be implemented by the sintered ore production method according to the present embodiment. The iron-containing raw material 14 stored in the storage tank 12 and the CaO-containing raw material 18 containing limestone, quicklime, and the like stored in the storage tank 16 are discharged as mixed raw materials 22 by predetermined amounts, respectively.

The iron-containing raw material 14 used in the present embodiment includes: iron ore powder having a particle size of 10 μm or less, iron ores of various brands, dust generated in iron works, and return ores having a particle size of 5mm or less screened out in a sintered ore production process. The iron-containing raw material 14 contains iron ore powder having a particle size of 10 μm or less in an amount of 5 mass% or more based on the mass of the sintering raw material. The content of iron ore powder having a particle size of 10 μm or less can be measured by using a laser diffraction/scattering particle size analyzer. In addition to the iron-containing raw material 14 and the CaO-containing raw material 18 being mixed in the mixed raw material 22, an MgO-containing raw material including dolomite, refined nickel slag, and the like may be mixed in the mixed raw material 22 as an arbitrary blending raw material.

The mixed feedstock 22 is conveyed by the conveyor 20 to a high speed stirring device 24. The high-speed stirring device 24 includes a stirring blade 26 that rotates at a high speed and a container 28 that rotates in an inclined state. The mixed material 22 conveyed to the high-speed stirring device 24 is put into the container 28, and is stirred by the rotation of the container 28 and the rotation of the stirring blade 26. Although the high-speed stirring device 24 of the present embodiment is described as an example including the container 28 that rotates in an inclined state, the container 28 may rotate without being inclined, and the same stirring effect can be obtained even when the container is not inclined.

The mixed raw material 22 stirred by the high-speed stirring device 24 is conveyed to the drum mixer 34 by the conveyor 30. The mixed raw material 22 conveyed to the drum mixer 34 is put into the drum mixer 34, and an appropriate amount of water 32 is added thereto to perform granulation. In the drum mixer 34, the coagulated material 36 is mixed for granulation in the latter half of the granulation period. The latter half of the granulation period is a granulation period that is 50 to 95% of the latter half of the granulation period when all the granulation periods are set to 0 to 100%. When the total granulation period is set to 0 to 100%, the coagulation material 36 is more preferably mixed until 70 to 95%.

In the drum mixer 34, the sintering material moves toward the discharge port of the drum mixer 34 as the granulation time elapses. Therefore, the position of the sintering material in the drum mixer 34 can be specified while 50 to 95% of the granulation period is being performed, and the setting material 36 can be mixed at the specified position. When the moving speed of the sintering material in the drum mixer 34 is assumed to be constant, the coagulating material 36 may be mixed at a position of 50 to 95% when the length from the inlet to the outlet of the drum mixer 34 is 0 to 100%. This can produce the quasi-particles 38 in which the coagulant 36 is externally attached. The granulation by the drum mixer 34 is performed for 300 to 400 seconds, for example. In the present embodiment, the raw material of the pseudo particles 38 with the coagulation material 36 externally attached is defined as a sintering raw material.

The drum mixer 34 is an example of a granulating device for granulating the pellets 38, and the drum mixer 34 and the pan granulator may be used in combination instead of the drum mixer 34. For example, when the drum mixer 34 and the pan granulator are used in combination, granulation may be performed by the drum mixer 34 for 50 to 95% of the total granulation time, granulation may be performed by the pan granulator for the remaining 5 to 50% of the granulation time, and the coagulant 36 may be added when granulation is performed by the pan granulator.

the quasi-particles 38 are conveyed to the sintering machine 50 by the conveyor 40, and are charged into the pallet of the sintering machine 50. The pseudo particles 38 charged into the pallet form a charged layer, and the charged layer is sintered by a sintering machine 50, crushed, cooled, and sieved to produce sintered ore. The sintering machine 50 used in the present embodiment is, for example, a strand sintering machine.

In the method for producing sintered ore according to the present embodiment, the agglomerate 36 containing 50 mass% or more of coke powder having a particle size of 1mm or less is mixed in a range of 3 mass% or more and 7 mass% or less with respect to the mass of the sintering material. This can increase the proportion of the agglomerated material 36 charged into the upper layer portion of the pallet of the sintering machine 50, and can increase the yield of the sintered ore and the strength of the sintered ore in the upper layer portion of the charged layer. The content of the coke powder having a particle size of 1mm or less with respect to the total amount of the coagulated material was determined by screening the coke powder using a sieve having a mesh opening of 1mm based on JIS (Japanese Industrial standards) Z8801-1, measuring the mass of the screened coke powder, and dividing the measured value by the mass of the total amount of the coagulated material. The content of the coke powder having a particle size of 1mm or less is preferably 50 to 75 mass%, more preferably 65 to 75 mass%.

Next, the following description will be made on the discovery that the ratio of the agglomerated material 36 in the upper layer part of the pallet of the sintering machine 50 is increased by using the agglomerated material 36 containing 50 mass% or more of coke powder having a particle size of 1mm or less. The present inventors simulated the state of the pseudo particles 38 and the agglomerated material 36 charged into the pallet of the sintering machine 50 using a model in which a Discrete Element Method (Discrete Element Method) was applied to the charging section of the sintering machine 50. Fig. 3 is a diagram showing a model used in the Discrete Element Method (DEM). Fig. 3(a) shows a model 60 for calculating the force acting on individual particles, and fig. 3(b) shows models 62 and 64 for calculating the force acting between particles. As shown in fig. 3(b), the force between the particles is divided into a vertical component and a translational component, the vertical component is calculated by the model 62, and the translational component is calculated by the model 64.

by solving the equation of motion of each particle at each time using the model shown in fig. 3(a) and (b), the positions of the quasi-particles 38 and the coagulated material 36 charged into the pallet of the sintering machine were simulated. Fig. 4 is a diagram showing a state of loading onto a tray simulated by using a Discrete Element Method (DEM). Fig. 5 is a coordinate diagram showing a result of calculating the pseudo particle diameter of each layer of the tray and the ratio of the condensed material existing in each layer from a simulation result by the Discrete Element Method (DEM).

Fig. 5(a) is a coordinate diagram showing the average particle size of the quasiparticles in each of the upper, middle and lower layers of the tray relative to the average particle size of the quasiparticles as a whole, and fig. 5(b) is a coordinate diagram showing the proportion of the coagulated material present in the upper, middle and lower layers of the tray. In fig. 5 a and 5 b, the upper layer portion is a position where the layer thickness ratio (layer thickness/full layer thickness) of the tray is 0.17, the middle layer portion is a position where the layer thickness ratio (layer thickness/full layer thickness) is 0.50, and the lower layer portion is a position where the layer thickness ratio (layer thickness/full layer thickness) is 0.83. The mean particle size of the quasi-particles of the present embodiment is a harmonic arithmetic mean diameter and is a particle size defined by 1/(Σ Vi × di) (where Vi is the existence ratio of particles in the ith particle size range and di is a representative particle size of the ith particle size range).

As a result of simulation using the discrete element method, as shown in fig. 5(a), the quasiparticles having an average particle diameter smaller than the whole average are present in many cases in the upper layer portion of the tray, and the quasiparticles having an average particle diameter larger than the whole average are present in many cases in the lower layer portion of the tray. As shown in fig. 5(b), when the ratio of the average particle diameter of the coagulant to the average particle diameter of the quasiparticles is increased, the proportion of the coagulant present in the upper layer of the tray is decreased, and the proportion of the coagulant present in the lower layer of the tray is increased. On the other hand, if the ratio of the average particle size of the aggregate to the average particle size of the quasiparticles is smaller, the proportion of the aggregate existing in the upper layer of the tray becomes higher, and the proportion of the aggregate existing in the lower layer of the tray becomes lower.

as described above, the inventors have found that, as a result of simulation using the Discrete Element Method (DEM), the particle size of the coagulation material 36 can be reduced, thereby increasing the proportion of the coagulation material 36 to be loaded into the upper layer portion of the tray. In order to confirm this with the actual sintering machine 50, a loading experiment into a pallet of the sintering machine 50 was performed. In the loading experiment, a coagulated material in which the content of coke powder having a particle size of 1mm or less was adjusted to 30 mass% and a coagulated material in which the content of coke powder having a particle size of 1mm or less was adjusted to 55 mass% were prepared, and pseudo particles obtained by separately granulating each coagulated material by externally coating the mixed raw material were used. The quasiparticles were charged into the tray of the sintering machine 50, and the average particle diameter of the quasiparticles at the positions where the layer thickness ratio of the quasiparticles charged into the tray was 0.17, 0.50, and 0.83, and the proportion of the coagulated material contained in the quasiparticles were measured.

Fig. 6 is a diagram showing the results of a loading experiment into a pallet of a sintering machine. Fig. 6(a) is a coordinate diagram showing the average particle diameter of the quasi-particles at each position of the tray, and fig. 6(b) is a coordinate diagram showing the ratio of the coagulated material at each position of the tray. The "-1 mm ratio" in FIGS. 6(a) and 6(b) means the content of the coke powder having a particle size of 1mm or less with respect to the whole coke powder.

In fig. 6(a), the horizontal axis represents the arithmetic mean particle diameter (mm) of the quasi-particles, and the vertical axis represents the layer thickness ratio (-) of the sintering machine pallet. As shown in FIG. 6(a), even when the sintering material contains 30 mass% of the coke powder having a particle size of 1mm or less and 55 mass% of the coke powder having a particle size of 1mm or less, the pseudo particles having a smaller arithmetic mean particle size are mostly loaded into the upper layer of the pallet having a relatively large layer thickness, and the pseudo particles having a smaller arithmetic mean particle size are mostly loaded into the lower layer of the pallet having a relatively small layer thickness.

In fig. 6(b), the horizontal axis represents the ratio (-) of the condensed materials, and the vertical axis represents the layer thickness ratio (-) of the sintering machine pallet. The ratio of the condensed material ratio is a value calculated by [ the ratio of the condensed material (mass%) in each layer thickness ]/[ the ratio of the condensed material (mass%) ].

As shown in FIG. 6(b), in the sintering material containing 30 mass% of the coke powder having a particle size of 1mm or less, the ratio of the agglomerated material is smaller in the upper portion of the pallet and larger in the lower portion of the pallet. On the other hand, when the sintering material containing 55 mass% of the coke powder having a particle size of 1mm or less is used, the ratio of the agglomerated material in the upper portion of the tray increases, and the ratio of the agglomerated material in the lower portion decreases. As a result, in the sintered raw material containing 55 mass% of the coke powder having a particle size of 1mm or less, the ratio of the agglomerated materials was substantially the same between the upper portion and the lower portion of the pallet. From fig. 6(a) and 6(b), it can be confirmed that by using the coagulation material containing 55 mass% of the coke powder having a particle size of 1mm or less with respect to the mass of the coagulation material, the amount of the coagulation material charged into the upper layer portion of the pallet of the sintering machine 50 is increased as compared with the case of using the coagulation material containing 30 mass% of the coke powder having a particle size of 1mm or less with respect to the mass of the coagulation material, which is less than 50 mass%.

On the other hand, if the content of the coke powder having a particle size of 1mm or less is increased, the granulation property of the mixed raw material 22 is lowered. Therefore, in the method for producing sintered ore according to the present embodiment, the iron-containing raw material 14 is made to contain iron ore powder having a particle size of 10 μm or less in an amount of 5 mass% or more based on the mass of the sintered raw material. Iron ore powder having a particle size of 10 μm or less is granulated with a raw material having a large particle size to form spaces between raw material particles, and the spaces are filled with the granulated material, thereby improving the strength of the granulated material. Therefore, by containing 5 mass% or more of iron ore powder having a particle size of 10 μm or less with respect to the mass of the sintering material, the granulation property of the mixed material 22 can be improved. However, iron ore powder having a particle size of 10 μm or less tends to aggregate and become aggregated particles during transportation because it has a large surface coefficient and retains a large amount of water. When the iron ore powder having a particle size of 10 μm or less is agglomerated and granulated, the space between the raw material particles cannot be filled, and the granulation property of the mixed raw material 22 cannot be improved.

Therefore, in the method for producing sintered ore of the present embodiment, the raw material 22 is stirred and mixed by using the high-speed stirring device 24. Since the iron ore powder having a particle size of 10 μm or less, which has been aggregated and granulated, is pulverized by the stirring, the decrease in the granulation property of the mixed raw material 22 due to the aggregation and granulation can be suppressed. The stirring by the high-speed stirring device 24 is performed for the purpose of pulverizing the iron ore powder having a particle size of 10 μm or less, which has been aggregated, and therefore, it is only necessary to stir at least the iron-containing raw material 14. The high-speed stirring device 24 preferably stirs the mixed material 22 under stirring conditions in which the peripheral speed of the stirring blade 26 is 8 to 12 m/sec, the rotation speed of the container 28 is 0.5 to 2.0 m/sec, and the treatment time is 60 to 120 sec, and more preferably stirs the mixed material 22 under stirring conditions in which the peripheral speed of the stirring blade 26 is 9 m/sec, the rotation speed of the container 28 is 1.0 m/sec, and the treatment time is 90 sec.

In order to confirm the granulation property of mixed raw material 22, a granulation test of mixed raw material 22 was performed. The conditions and results of the granulation test are shown in table 1 below. Fig. 7 is a coordinate diagram showing the relationship between the adjusted average particle size of the quasiparticles obtained by granulation in the granulation test and JPU of the loaded layer formed of the quasiparticles. JPU is an air permeability index JPU measured by sucking cold air downward through a loading layer formed by loading the quasi-particles into a tray. The air permeability index JPU is calculated by the following formula (1).

JPU＝V/[S×(h×ΔP)]···(1)

Wherein, in the formula (1), V is the air volume (Nm3/min), S is the cross-sectional area (m2) of the packed layer, h is the height (mm) of the packed layer, and Δ P is the pressure loss (mmH 2O). The air permeability JPU becomes larger when the air permeability of the incorporated layer is high, and becomes smaller when the air permeability is low.

[ Table 1]

In the case of evaluating the air permeability, it is preferable to use a harmonic mean particle size. The gorgon equation represented by the following formula (2) in which the harmonic mean particle diameter is used to predict the pressure loss of the packed bed. Since the pressure loss predicted by this equation indicates the air permeability of the loaded layer, the adjusted average particle size related to the air permeability is used for the evaluation of the particle size of the quasi-particles of the present embodiment.

[ number 1]

In the above formula (2), Δ P/L is a pressure loss per 1m (Pa/m), ε is a porosity (-), u is a flow velocity (m/s), μ is a gas viscosity (Pa · s), Dp is a harmonic mean particle diameter (m), and ρ is a gas density (kg/m 3).

In table 1, the "sintering material" indicates a mixing ratio of the iron-containing material containing 8 mass% of iron ore powder having a particle size of 10 μm or less and the agglomerated material. The "pre-mixing" described in the column of "mixing of the coagulated materials" means a case where the coagulated materials are mixed before granulation by the drum mixer 34, and the "post-mixing" means a case where the coagulated materials are mixed in the latter half of the granulation period in which granulation is performed with the particles aligned by the drum mixer 34 and the coagulated materials are externally attached. The latter half of the granulation period in this test is a granulation period in which the total granulation period is 50 to 95% when 0 to 100% is set.

"none" in the column "stirring treatment" means that stirring was not performed by the high-speed stirring apparatus 24, and "presence" means that stirring was performed by the high-speed stirring apparatus 24. The numerical value listed in the column of "-1 mm coke powder" indicates the content of the coke powder having a particle size of 1mm or less with respect to the mass of the agglomerated material. The numerical value described in the "JPU" column is the value of the air permeability index JPU calculated from the above expression (1).

In fig. 7, the horizontal axis represents the harmonic mean particle diameter (mm) of the quasiparticles, and the vertical axis represents the air permeability index JPU. Comparative example 1 is a granulation test example using a coagulated material in which the content of coke powder having a particle size of 1mm or less is 40 mass%. The content of the coke powder having a particle size of 1mm or less, which is deteriorated in pelletizability, was small in the agglomerated material used in comparative example 1, and therefore the blending average particle size of the quasiparticle was 2.22mm, and the air permeability index JPU was large. However, since the amount of the agglomerated material in which the content of the coke powder having a particle size of 1mm or less is 40 mass% is used, the amount of the agglomerated material in the upper portion of the charged layer cannot be increased, and the yield of the charged layer cannot be improved.

Comparative example 2 is a granulation test example using a coagulated material in which the content of coke powder having a particle size of 1mm or less is 65 mass%. The content of the coke powder having a particle size of 1mm or less, which deteriorates the granulation property, in the agglomerated material used in comparative example 2 was higher than that in comparative example 1. Therefore, the harmonic mean particle size of the quasiparticles of comparative example 2 was 1.73mm, which was smaller than the harmonic mean particle size of the quasiparticles of comparative example 1. The adjusted average particle size of the quasi-particles of comparative example 2 becomes smaller, and the air permeability index JPU of comparative example 2 is smaller than that of comparative example 1, and the air permeability of the incorporated layer of comparative example 2 is lower than that of comparative example 1.

Comparative example 3 is a granulation test example in which a coagulated material having a content of coke powder of 1mm or less in particle size of 65 mass% was used and the coagulated material was mixed in the latter half of the granulation period. Although the content of the coke powder having a particle size of 1mm or less in the agglomerated material used in comparative example 3 was not changed from that of the agglomerated material used in comparative example 2, the adjusted average particle size of the pseudo particles of comparative example 3 was 1.92mm, which was larger than that of the pseudo particles of comparative example 2. The difference between comparative example 2 and comparative example 3 is whether or not the coagulated material was mixed in the latter half of the granulation period. From this result, it is considered that the harmonic mean particle size of the quasi-particles of comparative example 3 is larger than that of the quasi-particles of comparative example 2 by mixing the coagulation material in the latter half of the granulation period. The blend average particle size of the quasi-particles of comparative example 3 is large, and the air permeability index JPU of comparative example 3 is larger than that of comparative example 2, and the air permeability of the incorporated layer of comparative example 3 is improved as compared with that of comparative example 2.

Comparative example 4 is a granulation test example using a coagulation material in which the content of the coke powder having a particle size of 1mm or less is 65 mass%, and an iron-containing raw material stirred by the high-speed stirring device 24. Although the content of the coke powder having a particle size of 1mm or less in the agglomerated material used in comparative example 4 was not changed from that of the agglomerated material used in comparative example 2, the harmonic mean particle size of the pseudo particles of comparative example 4 was 2.10mm and was larger than that of the pseudo particles of comparative example 2. The difference between comparative example 4 and comparative example 2 is whether or not the iron-containing raw material is stirred by the high-speed stirring apparatus 24. From the results, it is considered that the conditioning average particle size of the pseudo particles of comparative example 4 is larger than that of comparative example 2 by stirring the iron-containing raw material with the high-speed stirring apparatus 24 and pulverizing the iron ore powder having the aggregated particle size of 10 μm or less. The adjusted average particle size of the quasi-particles of comparative example 4 was large, and the air permeability index JPU of comparative example 4 was larger than that of comparative example 2, and the air permeability of the incorporated layer of comparative example 4 was improved as compared with that of comparative example 2.

The invention example 1 is a granulation test example in which a coagulated material having a content of coke powder of 1mm or less of 65 mass% and an iron-containing raw material stirred by a high-speed stirring device 24 are used and the coagulated material is mixed in the latter half of the granulation period. In the invention example 1, the agglomerated material was mixed in the latter half of the granulation period, and the iron ore powder having a particle size of 10 μm or less, which had been agglomerated, was pulverized, so that the adjusted average particle size of the quasi-particles of the invention example 1 was 2.65mm, which was larger than the adjusted average particle size of the quasi-particles of the comparative examples 1 to 4. The blend average particle size of the quasi-particles of invention example 1 was larger than that of comparative examples 1 to 4, and the air permeability index JPU of invention example 1 was also larger than that of comparative examples 1 and 4, and the air permeability of the packed layer of invention example 1 was improved as compared with comparative examples 1 to 4.

In this way, it was confirmed that the iron-containing raw material containing 5 mass% or more of iron ore powder having a particle size of 10 μm or less was stirred by the high-speed stirring device 24, and the adjusted average particle size of the pseudo particles was increased, and the air permeability of the charged layer was improved. Further, it was confirmed that the coagulation material 36 was mixed in the latter half of the granulation period to increase the adjusted average particle diameter of the quasi-particles, thereby improving the air permeability of the packed layer. Further, by using these, it was confirmed that the blend average particle size of the quasiparticles can be made larger than that of comparative example 1 in which the content of the coke powder having a particle size of 1mm or less is 40 mass%, and the air permeability of the packed layer can be improved.

In the method for producing coke according to the present embodiment, the proportion of the agglomerated material charged into the upper layer portion of the pallet of the sintering machine 50 is increased by using the agglomerated material containing 50 mass% or more of the coke powder having a particle size of 1mm or less. Further, by using an iron-containing raw material containing 5 mass% or more of iron ore powder having a particle diameter of 10 μm or less, subjecting the iron-containing raw material to a stirring treatment by the high-speed stirring apparatus 24, and mixing the agglomerated material in the latter half of the granulation period, it is possible to eliminate the decrease in the granulation property caused by using the agglomerated material containing 50 mass% or more of coke powder having a particle diameter of 1mm or less. This makes it possible to increase the proportion of the agglomerated material loaded into the upper portion of the tray without introducing new equipment, and thus to prolong the high-temperature retention time of the upper portion of the loaded layer, and to improve the yield of the sintered ore in the upper portion of the loaded layer.

In the present embodiment, an example in which all of the coagulant 36 is mixed in the latter half of the granulation period is shown, but the present invention is not limited to this. The setting material mixed in the latter half of the granulation period may also be a part of the setting material mixed in the sintering raw material. The amount of the coagulant mixed in the latter half of the granulation period is preferably 50 mass% or more based on the mass of the coagulant mixed in the sintering material. By setting the amount of the coagulant mixed in the latter half of the granulation period to 50 mass% or more, the amount of the coagulant mixed in advance with the mixed raw material 22 is reduced, and hence the granulation property of the mixed raw material 22 is improved.

Further, in the case where a part of the agglomerated material is mixed in the latter half of the granulation period, the pseudo particle diameter after the granulation is measured, and in the case where the pseudo particle diameter is smaller than a predetermined threshold value, the amount of the agglomerated material mixed in the latter half of the granulation period may be increased from the production of the sintered ore in which the pseudo particle diameter is smaller than the threshold value in order to increase the pseudo particle diameter granulated after the particle diameter is measured. As shown in comparative example 3 in table 1, when the coagulant is mixed in the latter half of the granulation period, the harmonic mean particle size of the quasiparticles becomes large. As shown in fig. 7, the decrease in the particle size decreases the air permeability of the packed layer. The decrease in the air permeability of the charged layer leads to an increase in the sintering time, resulting in a decrease in the sintered ore productivity. Therefore, a threshold value of the pseudo particle diameter capable of maintaining the target sintered ore productivity is set in advance, and when the particle diameter is smaller than the threshold value, the amount of the agglomerated material mixed in the latter half of the granulation period is increased to increase the pseudo particle diameter. This can maintain the target sintered ore productivity.