JP2020084258A - Method for producing carbonaceous material-containing particles and method for producing carbonaceous material-containing sintered ore - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing carbonaceous interior particles capable of suppressing the collapse of carbonaceous interior particles in a process of being transported to a sintering machine and charged into the sintering machine. SOLUTION: This is a method for producing carbonaceous material interior particles, in which a powdery iron-containing raw material, a lime-containing raw material, at least one of an organic binder and bentonite, and cement powder are mixed to obtain a mixed powder. , The mixed powder and the carbonaceous material are granulated to produce carbonaceous material interior particles in which an outer layer composed of the mixed powder is formed around the carbonaceous material core. [Selection diagram] Fig. 1

Description

The present invention relates to a manufacturing technology of a sinter used as a raw material for iron making in a blast furnace or the like, and specifically, a method for manufacturing carbonaceous material-containing particles containing carbonaceous material and sintering the carbonaceous material-containing particles. The present invention relates to a method for producing a carbonaceous material-containing sintered ore produced as a part of a raw material.

In the blast furnace ironmaking method, iron-containing raw materials such as sinter, iron ore and pellets are mainly used as an iron source. Here, the sintered ore is a kind of agglomerated ore and is manufactured by the following procedure. First, from iron-containing raw materials such as iron ore and dust with a particle size of 10 mm or less, lime-containing raw materials such as limestone, quick lime, and steelmaking slag, MgO-containing raw materials such as refined nickel slag, dolomite, and serpentine, and silica stones. An appropriate amount of water is added to a granulation raw material composed of a SiO ₂ -containing raw material and a coagulating material made of powdered coke or anthracite, and mixed and granulated using a drum mixer or the like to obtain pseudo particles. Next, the granulation raw material as pseudo particles is charged into a pallet of the sintering machine that moves in a circulating manner, and the coagulating material contained in the granulation raw material is burned to form a sintered cake. After that, the sinter cake is crushed, cooled, and sized, and those having a certain particle size or more are collected as product sinter.

Conventionally, a method of uniformly performing liquid phase sintering on the entire sintering bed has been the main method, but in recent years, as in the past, a portion mainly of liquid phase sintering and a portion of which liquid phase generation is suppressed are mixed in the sintering bed. A sintering method aiming at a non-uniform structure has been studied. The reason is that, in the portion having a high melting point and hardly melting, many fine pores remain after firing, the contact area with the reducing gas increases, and a sintered ore structure that is easily reduced can be formed.

As a method for producing such an agglomerated ore, in Patent Document 1, a wet pellet in which a carbonaceous material is coated with iron ore powder and a CaO-containing raw material is prepared as a conventional method, which has a high melting point and suppresses liquid phase formation. The method of sintering in a lower suction type sintering machine after being mixed with the sintering raw material mainly composed of liquid phase sintering is disclosed.

Patent No. 5790966

As disclosed in Patent Document 1, a carbonaceous material-containing sintered ore is prepared by mixing carbonaceous material-containing particles having a carbonaceous material core with ordinary granulated particles having no carbonaceous material nucleus to obtain a sintering raw material and firing. It is manufactured by sintering with a binder. However, when the carbonaceous material-containing particles are granulated by the granulator and collapsed in the process of being conveyed and charged to the sintering machine, the portion that suppresses the liquid phase generation is not generated and the sintering is easily reduced. It cannot form a mineral structure. The present invention has been made in view of the above problems, and an object thereof is to convey the carbonaceous material-containing particles to a sintering machine and suppress the collapse of the carbonaceous material-containing particles in the step of charging the sintering machine. It is to provide a manufacturing method.

The features of the present invention that can solve such problems are as follows.
(1) A powdery iron-containing raw material, a lime-containing raw material, at least one of an organic binder and bentonite, and a cement powder are mixed into a mixed powder, and the mixed powder and a carbonaceous material are granulated. Then, the method for producing the carbonaceous material-containing particles, wherein the carbonaceous material-containing particles in which the outer layer made of the mixed powder is formed around the carbonaceous material core are produced.
(2) The mixing ratio of at least one of the organic binder and the bentonite to the mixed powder is 0.1% by mass or more and 3% by mass or less, and the mixing ratio of the cement powder to the mixed powder is 4% by mass or more and 10% by mass. The method for producing carbonaceous material-containing particles according to (1), wherein at least one of the organic binder and bentonite is mixed with the cement powder as described below.
(3) Granulation of the carbon material-containing particles produced by the method for producing carbon material-containing particles according to (1) or (2), by mixing and granulating an iron-containing raw material, an auxiliary raw material, and a coagulating material. A method for producing a carbonaceous material-containing sintered ore, which is compounded into granular particles as a sintering raw material, and the sintering raw material is charged into a pallet of a sintering machine and sintered.

By carrying out the method for producing a carbonaceous material-containing sintered ore of the present invention, it is possible to produce carbonaceous material-containing particles having high resistance to drop impact in the transporting step and high crushing strength. In the charging step, the carbonaceous material-containing particles that collapse can be reduced. As a result, a carbonaceous material-containing sintered ore in which a portion in which liquid phase generation is suppressed is generated in the subsequent sintering step and a sintered ore structure that is easily reduced is formed can be manufactured at a high yield.

It is a schematic diagram which shows an example of the manufacturing process 10 of the carbonaceous material interior particle which can implement the manufacturing method of the carbonaceous material interior particle which concerns on this embodiment. 7 is a graph showing the relationship between the mixing time in the kneader 28 and the crushing strength distribution of the carbonaceous material-containing particles granulated by the granulator 38. 5 is a photograph showing mixed powder 30, coke particles 32 (including carbonaceous material-containing particles in the middle of growth) and carbonaceous material-containing particles 40 existing in the granulator 38. It is a schematic diagram which shows an example of the manufacturing process 100 of the carbon material interior sintered ore which can implement the manufacturing method of a carbon material interior sintered ore. It is a graph which shows the relationship between the mixing ratio of PVA and the drop strength of carbonaceous material interior particles. It is a graph which shows the relationship between a curing period and the crushing strength of carbonaceous material interior particles. 3 is a graph showing the relationship between the mixing ratio of cement powder and the crush strength of carbonaceous material-containing particles. It is a graph which shows the relationship between the mixing ratio of cement powder and the porosity of the carbonaceous material-containing sintered ore. It is a graph which shows RI of the sintered ore of an Example and a comparative example.

Hereinafter, the present invention will be described through embodiments of the present invention. FIG. 1 is a schematic view showing an example of a carbonaceous material-containing particle manufacturing process 10 by which the method for manufacturing carbonaceous material-containing particles according to the present embodiment can be implemented. The method for producing carbonaceous material-containing particles according to the present embodiment will be described with reference to FIG.

In the carbonaceous material-containing particle manufacturing process 10, first, the iron-containing raw material 12 stored in the storage tank 14, the lime-containing raw material 16 stored in the storage tank 18, and the organic binder 20 or bentonite stored in the storage tank 22. 21 and the cement powder 23 stored in the storage tank 24 are cut out from the respective storage tanks by a predetermined amount to the carrier 25. The iron-containing raw material 12, the lime-containing raw material 16, the organic binder 20, or the bentonite 21 and the cement powder 23 are conveyed by a conveyor 25 to a kneader 28 such as an intensive mixer. The iron-containing raw material 12, the lime-containing raw material 16, the organic binder 20 or the bentonite 21, and the cement powder 23 are mixed together with an appropriate amount of water 26 in the kneading machine 28 to form a mixed powder 30.

In the present embodiment, the iron-containing raw material 12 is an example of a powdery iron-containing raw material, and for example, iron ore powder having a particle size of 150 μm or less and a specific surface area of about 2000 cm ² /g, dust generated in an iron mill, Sludge, etc. As the lime-containing raw material 16, any one or more of quick lime, limestone and slaked lime may be used. However, from the viewpoint of granulating the mixed powder 30, it is preferable to use quicklime or slaked lime having a high granulation effect. Further, dolomite [CaMg(CO ₃ ) ₂ ] that increases the viscosity of the melt generated during sintering may be added to the lime-containing raw material 16. That is, the lime-containing raw material is a raw material containing any one or more of quick lime, slaked lime, limestone and dolomite. The organic binder 20 is a material having a function of acting on water to impart plasticity to the granulated material, and is, for example, polyvinyl alcohol (PVA) or starch. The bentonite 21 is also a material having a function of acting on water and imparting plasticity to the granulated material, like the organic binder. Since the bentonite 21 increases the slag content in the granulated material, it is preferable to use the organic binder 20 containing no slag content as compared with the bentonite, as the material that acts on water to impart plasticity to the granulated material. . The cement powder 23 is a hydraulic cement, and is, for example, Portland cement, mixed cement, blast furnace slag cement, or the like. Since the cement powder 23 also contains calcium oxide (CaO), when the cement powder 23 is added, the cutout amount of quicklime is reduced by the amount of calcium oxide contained in the cement powder 23. In the following embodiments, Portland cement shown in Table 1 below was used as the cement powder 23. Although there are differences in the long-term strength of several months depending on the type of cement, in the application of the present invention, it is sufficient that the cement has a strength of 4 weeks or less, and long-term strength of several months is not required. Therefore, in this embodiment, any type of cement can be used. In cold regions and the like, the use of alumina cement is more preferable because the strength is developed in a shorter time.

In the kneading machine 28, it is preferable that the respective raw materials are sufficiently mixed by the kneading machine 28 to uniformly disperse the respective raw materials. Thereby, the quality of the carbonaceous material-containing particles 40 can be stabilized. For example, if the quick lime is not sufficiently dispersed and quick-lime is mixed with the carbonaceous material interior particles in excess of the set quality, the outer layer around the carbonaceous material core will be melted in the subsequent sintering step, and the carbonaceous material interior burned. You may not be able to obtain mine. Further, when the organic binder 20 and the cement powder 23 are not sufficiently dispersed and the mixing amount of the organic binder 20 and the cement powder 23 mixed with the carbonaceous material interior particles is less than the set quality, it is sufficient to withstand handling such as transportation. The strength may not be obtained, and the yield may be reduced. Further, if the homogenization of the water 26 is insufficient, there is a possibility that the subsequent granulation by the granulator 38 may be hindered.

FIG. 2 is a graph showing the relationship between the mixing time in the kneading machine 28 and the crushing strength distribution of the carbonaceous material-containing particles granulated by the granulating machine 38. In FIG. 2, the horizontal axis is the crush strength (N/piece) of the carbonaceous material-containing particles after 4 weeks of cement curing, and the vertical axis is the frequency (pieces). The dotted line in FIG. 2 indicates that the carbonaceous material-containing particles are granulated using the granulator 38 without mixing the raw materials in the kneading machine 28, and then the cement material is crushed for 4 weeks and then the carbonaceous material-containing particles are crushed. The intensity distribution is shown. The broken line indicates that the mixed powder obtained by mixing the respective raw materials for 10 seconds by the kneading machine 28 is granulated into the carbonaceous material-containing particles by using the granulating machine 38, and thereafter the cement material is subjected to cement curing for 4 weeks. The distribution of crushing strength is shown. The solid line indicates that the mixed powder obtained by mixing the raw materials for 60 seconds with the kneading machine 28 is granulated into the carbonaceous material-containing particles using the granulating machine 38, and then the cement material is subjected to cement curing for 4 weeks. The distribution of crushing strength is shown. The mixing time when each raw material is continuously charged into the kneading machine 28 and kneading is continuously performed can be calculated by dividing the retention amount of each raw material inside the kneading machine 28 by the charging speed. ..

As shown in FIG. 2, when the mixing was not performed at all, the distribution width of the crushing strength was wide, and many carbonaceous material-containing particles having a relatively low strength were confirmed. When the mixing was performed for 10 seconds, the carbonaceous material-containing particles having a lower strength were reduced as compared with the case where the mixing was not performed at all. When mixing was carried out for 60 seconds, the low-strength carbonaceous material-containing particles were further decreased, the high-strength carbonaceous material-containing particles were increased, and the crushing strength distribution width was narrowed. The mixing power at this time was 330 W/kg. The mixing power was calculated from the power consumption of the mixer/the mass of the mixture. The mixing energy when the mixing was performed for 10 seconds was 3300 J/kg, and the mixing energy when the mixing was performed for 60 seconds was 19800 J/kg. From these results, it is possible to improve the strength quality of the carbonaceous material interior particles and to make the strength quality uniform by stabilizing the quality of the carbonaceous material interior particles by mixing and uniformly dispersing each raw material in the kneading machine 28. I know that I can do it. It should be noted that the mixing time for which the respective raw materials can be sufficiently mixed is determined by using the raw materials used for producing the carbonaceous material-containing sintered ore, the mixing time and the distribution of crushing strength as shown in FIG. 2 using a kneader and a granulator. It can be determined by checking the relationship.

Next, a predetermined amount of the mixed powder 30 mixed by the kneader 28 and the coke particles 32 stored in the storage tank 34 are cut out by the carrier 36 to be a granulation raw material. In the present embodiment, the mixed powder 30 and the coke particles 32 are so mixed that the mixing ratio of the coke particles 32 to the granulation raw material is 1% by mass or more and 5% by mass or less, more preferably 2% by mass or more and 4% by mass or less. It is cut out.

In the present embodiment, the coke particles 32 are an example of a carbonaceous material, and the carbonaceous material has an outer layer made of the mixed powder 30 formed around it and becomes a carbonaceous material core. Anthracite or the like may be used as the carbonaceous material. Since coke particles and anthracite have a low volatile content, the use of these reduces the gas generated from the carbonaceous material during sintering and suppresses the decrease in strength of the carbonaceous material-containing sintered ore produced using the carbonaceous material-containing particles. To be done. As a result, it is possible to suppress a decrease in the yield of the carbonaceous material-containing sintered ore.

The granulation raw material is conveyed by a conveyor 36 to a granulator 38 such as a disc pelletizer. The granulation raw material is tumbled together with an appropriate amount of water 26 in the granulator 38, the coke particles 32 become the carbon material core by the bridging force of water, etc., and the carbon material interior in which the outer layer made of the mixed powder 30 is formed around the coke particles 32. Particles 40 are produced.

FIG. 3 is a photograph showing the mixed powder 30, the coke particles 32 (including the carbonaceous material-containing particles being grown), and the carbonaceous material-containing particles 40 existing in the granulator 38. The carbonaceous material-containing particles 40 are manufactured according to the carbonaceous material-containing particle manufacturing process 10 shown in FIG. 1. However, if the strength of the carbonaceous material-containing particles 40 is low, the carbon material-containing particles 40 collapse in the process of being conveyed to the next step. To do. Therefore, in the method for producing carbonaceous material-containing particles according to the present embodiment, the organic binder is added to the iron-containing raw material 12 and the lime-containing raw material 16 in order to impart resistance to drop impact to the carbonaceous material-containing granulated particles immediately after granulation. 20 or bentonite 21 is mixed. As a result, the drop impact resistance of the mixed powder 30 formed as the outer layer around the coke particles 32 is enhanced, and the collapse of the carbonaceous material-containing particles 40 in the process of being conveyed to the next step can be suppressed. In the present embodiment, the produced carbonaceous material-containing particles are once stored in the yard, and after being cured for a certain period of time, transported to the sintering machine and loaded. This aims to add a buffer to the inventory of carbonaceous material interior particles to minimize the operational impact on the sintering machine and to further improve the strength of the carbonaceous material interior particles during a certain curing period. is there. Therefore, in the method for producing carbonaceous material-containing particles according to the present embodiment, cement powder 23 is mixed with the iron-containing raw material 12 and the lime-containing raw material 16 in order to improve the strength during the curing period. As a result, during the curing period in the yard, the cement and water in the carbonaceous material interior particles cause a hydration reaction, and the strength of the mixed powder 30 formed as an outer layer around the coke particles 32 is increased, and the mixed powder 30 is transferred to the sintering machine. It is possible to suppress the collapse of the carbonaceous material-containing particles 40 in the process of transporting and loading into the sintering machine.

FIG. 4 is a schematic view showing an example of a carbonaceous material-containing sintered ore manufacturing step 100 in which the method for producing a carbonaceous material-containing sintered ore can be carried out. In the carbon material-containing sintered ore manufacturing step 100, in parallel with the carbon material-containing particle manufacturing step 10 shown in FIG. 1, iron-containing raw materials such as iron ore and dust having a particle size of 10 mm or less, limestone, and quicklime. , A raw material 50 containing an auxiliary raw material including a CaO-containing raw material such as steelmaking slag and a coagulating material such as powder coke or anthracite having a particle diameter of less than 3 mm is granulated by a granulator 52 such as a drum mixer. Grained particles. The auxiliary raw materials may include MgO-containing raw materials such as refined nickel slag, dolomite, and serpentine, and SiO ₂ -containing raw materials such as silica stone.

Then, the carbonaceous material-containing particles 40 are blended with the granulated particles obtained by granulating the raw material 50 to obtain a sintering raw material. Among the sintering raw materials, the granulated particles obtained by granulating the raw material 50 become the main part of the liquid phase sintering, and the carbonaceous material-containing particles 40 become the part in which the liquid phase generation is suppressed. It is preferable to mix the carbon material-containing particles 40 with the granulated particles so that the mixing ratio of the carbon material-containing particles 40 to the sintering raw material is 10% by mass or more and 30% by mass or less. This improves the air permeability of the sintering raw material and improves the productivity of the carbonaceous material-containing sintered ore.

The sintering raw material containing the carbonaceous material-containing particles is carried into the surge hopper of the downward suction type sintering machine 60. The sintering raw material is charged from the surge hopper into an endless moving type pallet to form a charging layer. The charging layer is ignited by an ignition furnace installed above, and the upper gas is sucked downward from a wind box installed below, whereby the charging layer is sequentially burned and sintered. The charging layer is sintered by the combustion heat generated by the combustion to form a sintered cake. The sinter cake is crushed and sized in the effluent section, and an agglomerate having a particle size of 4 mm or more is recovered as a product-containing carbonaceous material-containing sinter. The carbonaceous material-containing sinter produced in this manner is used as an iron-making raw material for the blast furnace 70. In addition, the particle size in the present embodiment is a particle size screened using a sieve having a nominal mesh size according to JIS (Japanese Industrial Standard) Z 8801-1. For example, a particle size of 4 mm or more means It refers to a particle size which is sieved on a sieve using a sieve having a nominal opening of 4 mm according to JIS Z8801-1.

The particle size of the coke particles 32 used in the method for producing carbonaceous material-containing particles according to the present embodiment is preferably 2 mm or more. By using coke particles having a particle size of 2 mm or more, it is possible to prevent the coke particles from disappearing in the step of sintering the sintering raw material containing the carbonaceous material-containing particles in a sintering machine. The particle size of the coke particles 32 is more preferably 3 mm or more. By using a carbonaceous material having a particle size of 3 mm or more, the disappearance of coke particles can be further suppressed.

On the other hand, when coke particles with a large particle size are used, the amount of combustion gas generated from coke during sintering increases, and cracks occur in the outer layer covering the coke particles in the carbonaceous material-containing sintered ore. When a crack is generated in the outer layer covering the coke particles, the strength of the carbonaceous material-containing sintered ore is greatly reduced, and as a result, the yield of the carbonaceous material-containing sintered ore is significantly reduced. Therefore, the particle size of the coke particles 32 is preferably 8 mm or less, and more preferably 6 mm or less.

Further, the particle diameter of the carbonaceous material-containing particles 40 produced is preferably 8 mm or more and 18 mm or less. As described above, the carbonaceous material-containing sinter having a particle diameter of 4 mm or more is recovered as a product sinter, and the sinter having a particle diameter of less than 4 mm is recycled (returned) as a sintering raw material. When the carbonaceous material-containing particles 40 are sintered by a sintering machine, the volume thereof becomes small due to evaporation of water or partial melting. Therefore, the particle diameter of the carbonaceous material-containing particles 40 is preferably 8 mm or more, and more preferably 10 mm or more, so that the carbonaceous material-containing particles 40 will not be returned to mine even if they are directly sintered.

On the other hand, when the thickness of the outer layer of the coke particles 32 formed on the carbonaceous material-containing particles 40 exceeds 5 mm, it becomes difficult to sinter all the outer layers of the carbonaceous material-containing particles 40 within a limited sintering time. Become. When a portion of insufficient sintering is present in the carbonaceous material-containing sintered ore, the strength of the carbonaceous material-containing sintered ore decreases and the yield of the carbonaceous material-containing sintered ore decreases. Therefore, the thickness of the outer layer of the carbonaceous material-containing particles 40 is preferably 5 mm or less. For example, the grain size of the carbonaceous material-containing particles when the particle diameter of the coke particles 32 is 8 mm and the thickness of the outer layer is 5 mm. The diameter is 18 mm. Therefore, the particle diameter of the carbonaceous material-containing particles 40 is preferably 18 mm or less.

In the method for producing carbonaceous material-containing particles according to the present embodiment, the organic binder 20 or the bentonite 21 and the cement powder 23 are mixed with the mixed powder, thereby increasing the strength of the carbonaceous material-containing particles 40 produced. ..

Next, the strength of the carbonaceous material-containing particles 40 will be described. From the time the carbonaceous material-containing particles 40 are manufactured to the time when the carbonaceous material-containing particles 40 are charged into the lower suction type sintering machine 60, the carbon material-containing particles 40 are transferred to a plurality of conveyors, stored in a yard, and cured for a certain period of time. Transferred to a sintering machine. For this reason, it is preferable that the carbonaceous material-containing particles 40 have a strength that can withstand the impact of connecting a plurality of transfer conveyors and the impact of loading the pallet of the downward suction sintering machine 60. First, carbonaceous material-containing particles having different drop strengths were manufactured on a trial basis, and the state of collapse of the carbonaceous material-containing particles after the transfer of the transfer conveyor was confirmed. As a result, even if the carbonaceous material interior particles are transported to the cement curing yard by making the drop strength of the carbonaceous material interior particles 5 times or more, the carbonaceous material interior particles after cement curing do not transfer the carbonaceous material interior particles to a plurality of transfer conveyors and downward suction type firing. It has been found that the binder 60 can withstand the impact of loading the pallet and can be directly fed to the downward suction type sintering machine 60. In the present embodiment, the drop strength is the number of drops required until the carbonaceous material-containing particles are dropped from a height of 45 cm and the particles collapse.

By using the organic binder 20 and the bentonite 21 that can impart plasticity to the granules, the drop strength of the carbonaceous material-containing particles immediately after granulation can be increased at an early stage. The organic binder 20 dissolves in water in the granulated product to improve the viscosity of water. The viscosity-improved water fills the voids in the granulated product, thereby imparting plasticity to the granulated product and improving the resistance to drop impact. Further, the bentonite 21 takes in water in the granulated product and swells it, and fills the voids in the granulated product, thereby imparting plasticity to the granulated product and improving resistance to a drop impact. Therefore, polyvinyl alcohol (PVA) powder, which is a kind of organic binder, is mixed with the mixed powder 30 of the outer layer formed around the carbonaceous material, and it is confirmed whether or not the drop strength of the carbonaceous material-containing particles can be made 5 times or more. In order to do so, carbonaceous material-containing particles were produced according to the carbonaceous material-containing particle producing step 10 shown in FIG.

The carbonaceous material-containing particles were manufactured by the following procedure. First, iron ore powder having a particle size of 150 μm or less and a Blaine specific surface area of about 1500 cm ² /g, quick lime, and PVA powder having a particle size of 150 μm or less are mixed at a mass ratio of 95:4:1, A mixed powder was obtained by uniformly mixing with an intensive mixer. This mixed powder was mixed with coke particles having a particle size of 2 mm or more and 8 mm or less at a mass ratio of 98:2 to prepare a granulation raw material. This granulation raw material was tumbled by using a disc pelletizer to granulate the granulation raw material to produce carbonaceous material-containing particles in which an outer layer made of mixed powder was formed around the carbonaceous material. The water necessary for granulating the granulating raw material was supplied by spraying an appropriate amount into the intensive mixer and the disk pelletizer.

FIG. 5 is a graph showing the relationship between the mixing ratio of PVA and the drop strength of carbonaceous material-containing particles. In FIG. 5, the horizontal axis is the PVA mixing ratio (mass %), and the vertical axis is the 45 cm drop strength (times) of the carbonaceous material-containing particles. As shown in FIG. 5, when the mixing ratio of PVA was increased, the drop strength of the carbonaceous material-containing particles was improved. From FIG. 5, it can be seen that the PVA mixing ratio can be set to 0.1% by mass or more in order to achieve the target drop strength of the carbonaceous material-containing particles 5 times or more. On the other hand, even if the mixing ratio of PVA was higher than 2% by mass, the drop strength of the carbonaceous material-containing particles was not significantly improved, and a saturation tendency was observed. Furthermore, when the polyvinyl alcohol powder is mixed so that the mixing ratio of the polyvinyl alcohol powder to the mixed powder is 3% by mass or more, the polyvinyl alcohol powder is dissolved in the water brought in the iron ore powder and the water supplied at the time of granulation, and the viscosity is increased. And stable granulation became difficult. From these results, it is preferable to mix PVA so that the mixing ratio of PVA to the mixed powder is 0.1% by mass or more and 3% by mass or less, and the mixing ratio of PVA to the mixed powder is 0.1% by mass or more 2 It is more preferable to mix PVA so as to be not more than mass %. Further, bentonite may be used instead of PVA, which is an organic binder, or together with an organic binder. The improvement in strength due to the organic binder and bentonite is manifested by allowing the organic binder and bentonite to spread between the particles of the sintering raw material with a necessary minimum thickness. Therefore, regardless of these types, the same strength improving effect can be obtained by mixing the mixed powder at a mixing ratio of 0.1% by mass or more and 3% by mass or less.

In addition, the strength of the carbonaceous material-containing particles is also improved by mixing cement powder with the mixed raw material. Since cement powder is inexpensive, it is highly effective in suppressing manufacturing costs when it is used in a mass production process such as the production of sinter. First, in order to confirm the target strength, carbonaceous material interior particles with different crush strengths were manufactured on a trial basis, and the state of collapse of the carbonaceous material interior particles was confirmed after transfer conveyor transfer and pallet charging. .. As a result, by setting the crushing strength of the carbonaceous material interior particles to 49 N/piece or more, it does not collapse even if it is handled by a heavy machine or reclaimer, and the transfer of multiple conveyors and the pallet loading of the downward suction type sintering machine 60 are performed. It has been found that it can withstand the impact at the time of entry and can be directly sent to the downward suction type sintering machine 60. Therefore, in order to confirm whether or not the crushing strength of the carbonaceous material-containing particles can be increased to 49 N/piece or more by mixing the cement powder with the mixed powder 30 of the outer layer formed around the carbonaceous material, the charcoal shown in FIG. Carbon material-containing particles were manufactured according to the manufacturing step 10 of material-containing particles. In the present embodiment, the crush strength is the maximum strength measured by compressing the carbonaceous material-containing particles at a compression rate of 1 mm/min using a compression tester.

The carbonaceous material-containing particles were manufactured by the following procedure. First, iron ore powder having a particle size of 150 μm or less and a Blaine specific surface area of about 1500 cm ² /g, quicklime, and cement powder are mixed at a mass ratio of 95:1:4, and an intensive mixer is used. The mixture was uniformly mixed to obtain a mixed powder. This mixed powder was mixed with coke particles having a particle size of 2 mm or more and 8 mm or less at a mass ratio of 98:2 to prepare a granulation raw material. This granulation raw material was tumbled by using a disc pelletizer to granulate the granulation raw material to produce carbonaceous material-containing particles in which an outer layer made of mixed powder was formed around the carbonaceous material. The water necessary for granulating the granulating raw material was supplied by spraying an appropriate amount into the intensive mixer and the disk pelletizer.

FIG. 6 is a graph showing the relationship between the curing period and the crush strength of carbonaceous material-containing particles. In FIG. 6, the horizontal axis represents the curing period (Week), and the vertical axis represents the crushing strength (N/piece) of the carbonaceous material-containing particles. Further, in FIG. 6, the value in parentheses indicates the water content ratio (mass %) of the carbonaceous material-containing particles, the white circle plots indicate the measured values of the crush strength, and the black circle plots indicate the average value of the crush strength. As shown in FIG. 6, it was found that the curing period should be 3 weeks or more in order to achieve a crushing strength of 49 N/piece or more, which does not collapse even when handled by a heavy machine or a reclaimer after curing.

From this result, by mixing the cement powder so that the mixing ratio of the cement powder to the mixed powder is 4% by mass, the carbon material-containing particles having the crush strength of 49 N/piece or more are obtained. It was confirmed that it can be manufactured. On the other hand, when the cement powder was not mixed, the crush strength of the carbonaceous material-containing particles was 2.0 to 3.9 N/piece, and the crush strength of 49 N/piece or more could not be achieved.

Next, the mixing ratio of cement powder to the mixed raw materials will be described. The carbonaceous material-containing particles were manufactured by changing the mixing ratio of the cement powder to the mixed raw material to 0 to 6% by mass, and the crushing strength of each carbon material-containing particle was measured. In addition, when the mixing ratio of the cement powder was increased, the mixing ratio of the iron ore powder was reduced by that amount for adjustment. FIG. 7 shows the measurement results of the crushing strength of the carbonaceous material-containing particles.

FIG. 7 is a graph showing the relationship between the mixing ratio of cement powder and the crush strength of carbonaceous material-containing particles. In FIG. 7, the horizontal axis is the mixing ratio (mass %) of the cement powder to the mixed powder, and the vertical axis is the crush strength (N/piece) of the carbonaceous material-containing particles after 4 weeks. As shown in FIG. 7, the crushing strength of the carbonaceous material-containing particles is improved by increasing the mixing ratio of the cement powder to the mixed powder. As shown in FIG. 7, it is understood that the mixing ratio of the cement powder should be 4% by mass or more in order to obtain the crushing strength of 49 N/piece or more.

Next, a carbonaceous material-containing sintered ore is produced using a sintering raw material containing the carbonaceous material-containing particles produced by changing the blending ratio of cement powder to 0 to 12% by mass. A portion derived from the carbonaceous material-containing particles was extracted from the above. The porosity of the portion derived from the carbonaceous material-containing particles in the carbonaceous material-containing sintered ore was measured by the method specified in JIS R 1655:2003. FIG. 8 shows the measurement result of the porosity of the portion derived from the carbonaceous material-containing particles in each carbonaceous material-containing sintered ore.

FIG. 8 is a graph showing the relationship between the mixing ratio of cement powder and the porosity of the portion derived from carbonaceous material-containing particles in the carbonaceous material-containing sintered ore. In FIG. 8, the horizontal axis is the mixing ratio (mass %) of the cement powder to the mixed powder, and the vertical axis is the porosity (%) of the portion derived from the carbonaceous material-containing particles in the carbonaceous material-containing sintered ore. .. As shown in FIG. 8, when the mixing ratio of the cement powder to the mixed powder is increased, the porosity of the portion derived from the carbon material-containing particles in the carbon material-containing sintered ore decreases. The higher the porosity of the part derived from the carbonaceous material-containing particles in the carbonaceous material-containing sintered ore, is advantageous for the reduction reactivity in the blast furnace. Furthermore, if the mixing ratio of the cement powder is increased, the slag content in the blast furnace raw material increases, which is not preferable. Therefore, it is preferable that the mixing ratio of the cement powder is as low as possible. From these facts, the mixing ratio of the cement powder is preferably 10% by mass or less, and more preferably 6% by mass or less.

The crushing strength of the carbonaceous material-containing particles can be increased by increasing the mixing ratio of the cement powder to the mixed powder. However, if the mixing ratio of the cement powder is too high, the slag component of the carbonaceous material-containing particles increases. Further, if the mixing ratio of the cement powder is too high, the precipitate generated by the hydration reaction of the cement powder and water will block the pores in the carbonaceous material-containing particles, and the porosity of the carbonaceous material-containing particles will decrease. In order to suppress the increase of this slag component and ensure a porosity above a certain level, the mixing ratio of the cement powder to the mixed powder is preferably 4% by mass or more and 10% by mass or less, and 4% by mass or more and 6% by mass or less. The following is more preferable.

As described above, the strength of the carbonaceous material-containing particles can be improved early by using the organic binder. On the other hand, cement powder is inexpensive, but it requires curing for a predetermined period to increase its strength. In the method for manufacturing carbonaceous material-containing particles according to the present embodiment, an organic binder and cement powder are mixed with the mixed powder. By mixing the mixed powder with an organic binder, the falling strength of the carbonaceous material-containing particles can be enhanced at an early stage, and by mixing the cement powder, the strength of the carbonaceous material-containing particles can be further enhanced after a predetermined period of time. .. As a result, the carbonaceous material-containing particles that collapse in the step of charging the sintering raw material and then charging into the sintering machine are reduced, and the carbonaceous material-containing sintered ore can be produced with a high yield.

Further, it is preferable to mix the mixed powder with 0.1% by mass or more of the organic binder and 4% by mass or more of the cement powder. Thus, by mixing the mixed powder with the organic binder in an amount of 0.1% by mass or more, the drop strength becomes 5 times or more, and the carbonaceous material-containing particles can be transported to the cement curing yard with a high yield. Furthermore, since 4% by mass or more of cement powder is mixed in the mixed powder, it does not collapse after being cured in a cement curing yard even if handled by heavy equipment or a reclaimer, and the transfer of multiple conveyer conveyors thereafter is performed. And, the strength is such that the lower suction type sintering machine 60 can withstand the impact when the pallet is loaded. As a result, the carbonaceous material-containing particles that collapse in the step of charging the sintering machine can be further reduced, and the carbonaceous material-containing sintered ore can be produced with a higher yield.

Next, the result of confirming the reduction reactivity of the carbon material-containing sintered ore produced by sintering the sintering raw material containing the carbon material-containing particles will be described. FIG. 9 is a graph showing RI of the sintered ores of Examples and Comparative Examples. RI is an index showing the reducibility of sinter and is a value measured according to JIS M8713.

In the comparative example shown in FIG. 9, the PVA and the cement powder were not mixed, and it was simulated that the carbonaceous material-containing particles collapsed in the process of being conveyed and charged into the sintering machine, and the burning without the carbonaceous material-containing particles was simulated. The binder material was charged into a sintering machine at a charging rate of 650 t/h to produce a sintered ore. On the other hand, in the examples, it is assumed that the carbonaceous material-containing particles do not collapse in the process of mixing PVA and cement powder, and conveying and charging to the sintering machine. /Equivalent) (h) was added to the sintering machine at a charging rate of 650 t/h to produce a sintered ore.

As shown in FIG. 9, it was confirmed that the RI of the carbon material-containing sintered ore of the example was 3% higher than the RI of the sintered ore of the comparative example. From this result, by using the method for producing carbonaceous material-containing particles according to the present embodiment to produce high crushing strength carbonaceous material-containing particles, conveyed to a sintering machine, carbonaceous material-containing particles that collapse in the process of charging, It can be seen that by reducing the amount, it is possible to manufacture a carbon material-containing sintered ore with improved reducibility at a high yield.

10 Carbon Material Interior Particles Manufacturing Process 12 Iron-Containing Raw Material 14 Storage Tank 16 Lime-Containing Raw Material 18 Storage Tank 20 Organic Binder 21 Bentonite 22 Storage Tank 23 Cement Powder 24 Storage Tank 25 Transport Machine 26 Water 28 Kneader 30 Mixed Powder 32 Coke Particles 34 Storage Tank 36 Conveyor 38 Granulator 40 Carbon Material Interior Particles 50 Raw Material 52 Granulator 60 Lower Suction Sintering Machine 70 Blast Furnace 100 Carbon Material Interior Sinter Ore Manufacturing Process

Claims (3)

Powdery iron-containing raw material, lime-containing raw material, at least one of an organic binder and bentonite, and cement powder are mixed to form a mixed powder, and the mixed powder and carbonaceous material are granulated, A method for producing carbonaceous material-containing particles, comprising producing carbonaceous material-containing particles in which an outer layer made of the mixed powder is formed around a carbonaceous material core. The mixing ratio of at least one of the organic binder and the bentonite to the mixed powder is 0.1% by mass or more and 3% by mass or less, and the mixing ratio of the cement powder to the mixed powder is 4% by mass or more and 10% by mass or less. Thus, the method for producing carbonaceous material-containing particles according to claim 1, wherein at least one of the organic binder and bentonite is mixed with the cement powder. The carbon material-containing particles produced by the method for producing carbon material-containing particles according to claim 1 or 2, are mixed with an iron-containing raw material, an auxiliary raw material, and a coagulating material to form granulated particles. A method for producing a carbonaceous material-containing sintered ore, which is prepared by mixing as a sintering raw material, charging the sintering raw material into a pallet of a sintering machine, and sintering.