Sintered ore production method

Abstract

The purpose of the present disclosure is to provide a method for producing a sintered ore, said method being capable of suppressing reductions in the product yield and production rate of a sintered ore. A method for producing a sintered ore according to the present disclosure includes: a granulation step for obtaining a granulated material including at least a sintering raw material, a setting material, and a return ore; and a sintering step for sintering the granulated material. A first carbonaceous material is added as the setting material before the latter half of the granulation step, a second carbonaceous material is added as the setting material in the latter half of the granulation step, the return ore is added from the latter half of the granulation step to the sintering step, the first carbonaceous material includes a highly combustible carbonaceous material having a combustion start temperature of 550°C or less, and the second carbonaceous material includes a low-combustible carbonaceous material having a combustion start temperature of more than 550° C.

Description

Sinter manufacturing method

[0001] The present disclosure relates to a method for producing sintered ore.

[0002] The main raw material in blast furnace ironmaking is sintered ore. Sintered ore is typically produced as follows: First, iron ore as raw material and carbonaceous material as a coagulant are mixed in a predetermined ratio and granulated. The granulated raw material mixture is then loaded from a hopper onto a pallet of a downward-suction Dwight Lloyd (DL) sintering machine to form a sintered layer. An ignition furnace (igniter) ignites the carbonaceous material in the sintered layer from the top (surface layer). Air is then sucked from below the continuously moving pallet, and the suction causes the combustion of the carbonaceous material in the sintered layer to progress from top to bottom. The sintered layer is then gradually sintered by the heat of combustion. The sintered cake (sinter cake) obtained by sintering is then sized to a predetermined particle size to become sintered ore, the raw material in blast furnace ironmaking.

[0003] By the way, in recent years, global environmental issues (emissions of CO ２ In light of this trend, there is a demand for the use of biomass charcoal as a carbon-neutral agglomerating agent instead of coal-based coke breeze and anthracite, and the following methods for producing sintered ore are known.

[0004] Patent Document 1 discloses a method for producing sintered ore using a raw material blended with fine iron ores, a composition-adjusting solder, return ore, and solid carbonaceous material, with a concentration distribution of the solid carbonaceous material along the height direction of the pallet, characterized in that the sintered raw material blended with fine iron ores, composition-adjusting solder, and return ore is blended with oil palm kernel shell charcoal, a solid carbide produced by heat-treating oil palm kernel shell, and one or more of coke and anthracite having a particle size smaller than that of the solid carbide. According to the sintered ore production method in Patent Document 1, the PKS charcoal obtained by carbonizing and dry-distilling oil palm kernel shell (PKS) as biomass can be used in a sintering machine as a carbonaceous material for steelmaking. Furthermore, according to the sintered ore manufacturing method of Patent Document 1, PKS coal is a carbon-neutral material, and is also low-volatile and has good combustibility. Therefore, when manufacturing sintered ore, it is possible to suppress the emission of carbon dioxide, a greenhouse gas, and also to significantly improve the combustibility in the lower part of the sintered layer, thereby increasing the productivity of the sintering machine.

[0005] Further, the following method for producing sintered ore is known in which return ore is added to improve the productivity of sintered ore.

[0006] Patent Document 2 discloses a method for producing sintered ore using a Dwight Lloyd sintering machine, characterized in that a mixture of sintering raw materials, to which return ore is added after granulation, is used as the entire amount of sintering raw material. According to the sintering ore production method of Patent Document 2, the productivity of sintered ore can be significantly improved by using the raw material to which return ore is added after granulation as the entire amount of sintering raw material and firing it. It also claims that the productivity of sintered ore can be improved when the raw material to which return ore is added after granulation is used as part of the sintering raw material.

[0007] Patent Document 3 discloses a method for producing sintered ore in which a mixture of granulated raw materials for sintering and then added with all or part of the return ore is used as a sintering blended raw material, characterized in that the ratio of the return ore added after granulation to the sintering blended raw material is 5 to 25 mass%. According to the sintering ore production method of Patent Document 2, in the sintering ore production method, after granulating the sintering raw material, return ore is added at a ratio of 5 to 25 mass% to the sintering blended raw material, and this mixture is fired, thereby significantly improving the productivity of sintered ore.

[0008] Patent Document 4 discloses a method for producing sintered ore using a Dwight Lloyd sintering machine, which includes the steps of adding moisture to a sinter raw material that does not contain return ore, granulating the sintered material to produce granules, adding return ore having a particle size of 1 mm or more in an amount of 80% by mass or more to the granules, and mixing the granules to produce a mixture, and using the mixture as a blended raw material. According to the method for producing sintered ore in Patent Document 4, it is possible to increase the productivity by adding return ore with an optimized particle size after granulating the sintered material that does not contain return ore.

[0009] JP 2013-237876 A JP 2007-284744 A JP 2009-097027 A JP 2015-193930 A

[0010] Highly combustible carbonaceous materials, such as biomass charcoal as disclosed in Patent Document 1, have excellent combustibility and can improve the sintering rate. However, when a highly combustible carbonaceous material is used, the sintering rate is high, so the high-temperature holding time required to advance the sintering reaction is shortened, which can result in a decrease in the product yield and productivity of the sintered ore.

[0011] Furthermore, as mentioned above, highly combustible carbonaceous materials have a high combustion rate, and therefore the descent speed of the combustion zone is fast in sintered beds containing highly combustible carbonaceous materials. On the other hand, the cooling of the sintered bed after combustion depends on the gas velocity flowing through the sintered bed, so it is difficult to see any difference depending on the type of carbonaceous material. Therefore, when highly combustible carbonaceous materials are used, the high-temperature zone including the combustion zone expands in the vertical direction, increasing the airflow resistance of the sintered bed, which can reduce the product yield and productivity of sintered ore.

[0012] Therefore, an object of the present disclosure is to provide a method for producing sintered ore that uses a highly combustible carbonaceous material as a coagulant, and that can suppress a decrease in the product yield and productivity of sintered ore.

[0013] The present disclosure achieves the above object by the following means.

[0014] <Aspect 1> A method for producing sintered ore, comprising: a granulation step of obtaining granules containing at least a sintering raw material, a coagulating agent, and return ore; and a sintering step of sintering the granules, wherein a first carbonaceous material is added as the coagulating agent by the latter half of the granulation step; a second carbonaceous material is added as the coagulating agent in the latter half of the granulation step; the return ore is added from the latter half of the granulation step to the sintering step; the first carbonaceous material comprises a high combustible carbonaceous material having a combustion start temperature of 550°C or less; and the second carbonaceous material comprises a low combustible carbonaceous material having a combustion start temperature of more than 550°C; a content of the high combustible carbonaceous material in the first carbonaceous material is higher than a content of the high combustible carbonaceous material in the second carbonaceous material; and a content of the low combustible carbonaceous material in the second carbonaceous material is higher than a content of the low combustible carbonaceous material in the first carbonaceous material. In the second embodiment, the return fines are added simultaneously with the second carbonaceous material as the coagulating agent in the latter half of the granulation step. In the second embodiment, the highly combustible carbonaceous material comprises a compressed wood charcoal.

[0015] According to the method for producing sintered ore of the present disclosure, in a method for producing sintered ore that uses a highly combustible carbonaceous material as a coagulant, it is possible to suppress a decrease in the product yield and productivity of sintered ore.

[0016] Fig. 1 is a schematic diagram showing steps of a method for producing sintered ore according to an embodiment. Fig. 2 is a schematic diagram for explaining a method for producing sintered ore according to an embodiment. Fig. 3 is a schematic diagram for explaining a method for producing sintered ore according to an embodiment.

[0017] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present disclosure. In addition, in the description of the drawings, the same elements are given the same reference numerals, and duplicated descriptions will be omitted.

[0018] In this specification, the particle size can be determined by sieving using a rotary shaker for a predetermined period of time. For example, a particle size of 5 mm or more but less than 50 mm refers to a particle size that is on the upper side when sieved through a 5 mm sieve and is on the lower side when sieved through a 50 mm sieve.

[0019] <<Method for producing sintered ore>> The method for producing sintered ore disclosed herein includes: a granulation step of obtaining granules containing at least a sintering raw material, a coagulating agent, and return ore; and a sintering step of sintering the granules, wherein a first carbonaceous material is added as the coagulating agent by the latter half of the granulation step; a second carbonaceous material is added as the coagulating agent in the latter half of the granulation step; the return ore is added from the latter half of the granulation step to the sintering step; the first carbonaceous material includes a high combustible carbonaceous material having a combustion start temperature of 550°C or less; and the second carbonaceous material includes a low combustible carbonaceous material having a combustion start temperature of more than 550°C; the content of the high combustible carbonaceous material in the first carbonaceous material is higher than the content of the high combustible carbonaceous material in the second carbonaceous material; and the content of the low combustible carbonaceous material in the second carbonaceous material is higher than the content of the low combustible carbonaceous material in the first carbonaceous material.

[0020] According to the method for producing sintered ore of the present disclosure, in a method for producing sintered ore that uses a highly combustible carbonaceous material as a coagulant, it is possible to suppress a decrease in the product yield and productivity of sintered ore.

[0021] By the latter half of the granulation process, a first carbonaceous material is added as a coagulating agent, and in the latter half of the granulation process, a second carbonaceous material is added as a coagulating agent, and the content of high combustible carbonaceous material in the first carbonaceous material is higher than the content of high combustible carbonaceous material in the second carbonaceous material, and the content of low combustible carbonaceous material in the second carbonaceous material is higher than the content of low combustible carbonaceous material in the first carbonaceous material.As a result, the high combustible carbonaceous material with a low combustion start temperature (i.e., a fast combustion rate) is encapsulated in the granulated material, and the low combustible carbonaceous material with a high combustion start temperature (i.e., a slow combustion rate) is exteriorly packaged in the granulated material.

[0022] Without being limited to theory, it is believed that by utilizing the difference in combustion characteristics between the highly combustible carbonaceous material and the low combustible carbonaceous material used as the agglomerating material, the combustion of the agglomerating material is advanced from the exterior low combustible carbonaceous material to the enclosed high combustible carbonaceous material, thereby not only improving the overall sintering speed but also ensuring high temperature retention time, thereby suppressing a decrease in the product yield and productivity of sintered ore.

[0023] In addition, since the low-combustibility carbonaceous material, which has a slow combustion rate, is wrapped in the blended raw material granules, it is thought that the reaction with the oxygen supplied to the raw material packed bed is promoted, and the heated atmosphere provides sufficient heat for combustion.

[0024] Furthermore, the addition of return ore from the latter half of the granulation process to the sintering process reduces the ratio of ungranulated powder and reduces the packing density of the sintered layer (increases the porosity), which is thought to suppress an increase in the airflow resistance of the sintered layer. More specifically, (i) because no return ore is added until the latter half of the granulation process, even if the amount of moisture added throughout the granulation process remains the same, the moisture concentration of the intermediate granules containing the sintering raw material and the first carbonaceous material increases until the latter half of the granulation process, promoting adhesion between particles and reducing the ratio of ungranulated powder. Furthermore, (ii) the addition of return ore in the latter half of the granulation process generates interparticle friction between the intermediate granules containing moisture, which increases the interparticle porosity after charging into the sintering machine and reduces the packing density of the sintered layer (increases the porosity). The above (i) and (ii) are thought to suppress an increase in the airflow resistance of the sintered layer. Furthermore, an increase in the flow rate of the gas and suppression of particle deformation are expected to improve the sintering rate and product yield.

[0025] On the other hand, if the content of highly combustible carbonaceous material in the first carbonaceous material is the same as or lower than the content of highly combustible carbonaceous material in the second carbonaceous material, and the content of low combustible carbonaceous material in the second carbonaceous material is the same as or lower than the content of low combustible carbonaceous material in the first carbonaceous material, the amount of low combustible carbonaceous material contained in the blended raw material granules will increase, and the oxygen and heat required for combustion of the low combustible carbonaceous material will be less likely to be supplied, which may result in a decrease in the product yield and production rate of sintered ore.

[0026] The manufacturing method of the present disclosure will be described below with reference to Figures 1, 2, and 3. Figures 1, 2, and 3 are schematic diagrams showing one embodiment of the manufacturing method of the present disclosure.

[0027] The manufacturing method according to the present disclosure includes at least a granulation step S2 and a sintering step S3, and may also include a raw material blending step S1, a cooling and pulverizing step S4, and a classification step S5, as necessary. The raw materials and semi-finished products that have undergone each step may be transported to the next step by a transport device such as a belt conveyor.

[0028] <Raw material blending step S1> The raw material blending step S1 is a step of blending raw materials used in the production of sintered ore. In the raw material blending step S1, as shown in Fig. 2, the raw materials for the sintered ore stored in each raw material tank 1 are supplied onto a belt conveyor and blended at a predetermined ratio (blending ratio). Next, the raw materials are transported to a granulator 2, and the blended raw materials may be mixed in the granulator 2. Alternatively, the raw materials blended at a predetermined ratio (blending ratio) may be supplied onto a belt conveyor, transported to the granulator 2, and the blended raw materials may be mixed in the granulator 2.

[0029] In the manufacturing method of the present disclosure, the carbonaceous material added as a coagulant by the latter half of the granulation step S2 is referred to as the "first carbonaceous material." The first carbonaceous material may be added, for example, in the raw material blending step S1, or may be added in the former half of the granulation step S2 described below. Note that "by the latter half of the granulation step S2" means up to the start of the latter half of the granulation step S2.

[0030] <Granulation step S2> The granulation step S2 is a step of granulating the blended raw materials by the granulator 2. When the granulator 2 is of a continuous type, the granulation step S2 starts when the granulated material is supplied to the granulator 2, specifically, when it passes through an upstream inlet of the granulator 2, and ends when the granulated material passes through a downstream outlet of the granulator 2. When the granulator 2 is of a batch type, the granulation step S2 starts when the operation of the granulator 2 is started, and ends when the operation of the granulator 2 is stopped.

[0031] In the manufacturing method of the present disclosure, the carbonaceous material added as a coagulating agent in the latter half of the granulation step S2 is referred to as a “second carbonaceous material.” In addition, in the manufacturing method of the present disclosure, return fines are added from the latter half of the granulation step to the sintering step.

[0032] In the manufacturing method of the present disclosure, the first carbonaceous material is added as a coagulating agent by the latter half of the granulation step S2. Here, the first carbonaceous material may be added all at once or in multiple batches by the latter half of the granulation step S2. Furthermore, when the first carbonaceous material is added in multiple batches, the composition of the first carbonaceous material added in one batch may be the same as or different from the composition of the first carbonaceous material added in another batch.

[0033] Similarly, in the manufacturing method of the present disclosure, a second carbonaceous material is added as a coagulating agent in the latter half of the granulation step S2. The second carbonaceous material may be added all at once or in multiple batches in the latter half of the granulation step S2. When the second carbonaceous material is added in multiple batches, the composition of the second carbonaceous material added in one batch may be the same as or different from the composition of the second carbonaceous material added in another batch.

[0034] The first carbonaceous material includes a highly combustible carbonaceous material, and the second carbonaceous material includes a low combustible carbonaceous material. In the present disclosure, since the content of the highly combustible carbonaceous material in the first carbonaceous material is higher than the content of the highly combustible carbonaceous material in the second carbonaceous material, a large amount of the highly combustible carbonaceous material is added by the latter half of the granulation step S2. Furthermore, since the content of the low combustible carbonaceous material in the second carbonaceous material is higher than the content of the low combustible carbonaceous material in the first carbonaceous material, a large amount of the low combustible carbonaceous material is added in the latter half of the granulation step S2. The first carbonaceous material and the second carbonaceous material will be described in detail in the section "<Agglomeration Agent>" below.

[0035] One aspect of the granulation step S2 of the manufacturing method of the present disclosure will be described. In the granulation step S2, for example, the first carbonaceous material is added to the sintering raw material all at once or in portions until the latter half of the granulation step S2. As a result, intermediate granules containing the sintering raw material and the first carbonaceous material are obtained from the start of the granulation step S2 until the latter half of the granulation step S2. Next, in the latter half of the granulation step S2, for example, after a predetermined time has elapsed since the start of the granulation step S2, the second carbonaceous material is added to the intermediate granules all at once or in portions. Then, from the latter half of the granulation step until the sintering step, for example, after a predetermined time has elapsed since the start of the granulation step S2, return fines are added.

[0036] Another aspect of the granulation step S2 of the manufacturing method of the present disclosure will now be described. For example, in the above-described raw material blending step S1, a first carbonaceous material is added to the sintering raw material, and the mixture is mixed to obtain a mixed raw material containing the sintering raw material and the first carbonaceous material. The mixed raw material is supplied to the granulator 2, and the granulation step S2 is initiated. In the latter half of the granulation step S2, specifically, for example, after a predetermined time has elapsed since the start of the granulation step S2, a second carbonaceous material is added as a coagulating agent to the granulator 2, and further granulation is performed. Then, from the latter half of the granulation step S2 until the sintering step, for example, after a predetermined time has elapsed since the start of the granulation step S2 and before the sintering step S3, return ore is added.

[0037] Each of the above-mentioned predetermined times is not particularly limited, and may be 50% or more, 60% or more, 70% or more, or 80% or more of the total granulation time (the time from the start to the end of the granulation step S2), and may be 99% or less, 98% or less, or 97% or less. For example, when the total granulation time is 480 seconds, the above-mentioned predetermined times may be 240 seconds or more, 228 seconds or more, 336 seconds or more, or 384 seconds or more, and may be 475 seconds or less, 470 seconds or less, or 466 seconds or less. Furthermore, each of the above-mentioned predetermined times is preferably set to a time within a range of 80% or more and 97% or less of the total time of the granulation step S2 (total granulation time (the time from the start to the end of the granulation step S2)). That is, after the start of the granulation step S2, the second carbonaceous material is preferably added between the time when 80% of the total granulation time has elapsed and the time when 97% of the total granulation time has elapsed. Furthermore, it is preferable that return ore is added simultaneously with the addition of the second carbonaceous material, or after the addition of the second carbonaceous material and before the sintering step S3. When the return ore is added after the addition of the second carbonaceous material and before the sintering step S3, it is preferable that the return ore is added immediately after the mixer outlet. This is because the return ore and the granulated material are mixed before reaching the sintering machine. In this case, the predetermined time for adding the return ore may be within a range of 100% to 105% of the total time of the granulation step S2. By setting the predetermined time for adding the second carbonaceous material within the above range, it is possible to obtain a blended raw material granulated product with better sinter productivity.

[0038] In the granulation step, a continuous granulator, for example, a constant-speed piston-flow type granulator, can be used. For example, when a constant-speed piston-flow type granulator is used, the raw materials and the like are transported at a constant speed within the granulator 2, so that the position where the second carbonaceous material is added can correspond to the time until the second carbonaceous material is added (the time from the start of the granulation step S2 until the second carbonaceous material is added). Specifically, the position where the second carbonaceous material is added may be a position that is 50% or more, 60% or more, 70% or more, or 80% or more of the total length of the granulator 2 (total length when a plurality of granulators 2 are connected in series) away from the upstream inlet side, or may be a position that is 98% or less, 97% or less, or 96% or less of the total length of the granulator 2 (total length of the granulator 2 when a plurality of granulators 2 are connected in series) away from the upstream inlet side.

[0039] 2, the second carbonaceous material may be supplied from a hopper 6 for later addition in a mixer and transported from the downstream outlet of the granulator 2 to a predetermined position inside the granulator 2 by a transport conveyor. Then, the second carbonaceous material may be added at the predetermined position inside the granulator 2, granulated together with the sintering raw material and the first carbonaceous material, and discharged from the downstream outlet of the granulator 2.

[0040] In the granulation step, a batch-type granulator, for example, a cylindrical batch-type drum mixer, can also be used. When a batch-type granulator is used, for example, moisture may be added to the sintering raw material, and the first carbonaceous material may be added by the latter half of the granulation step S2 to obtain intermediate granules containing the sintering raw material and the first carbonaceous material by granulation, and then the second carbonaceous material may be added to the intermediate granules in the latter half of the granulation step S2 (for example, after the above-mentioned predetermined time has elapsed) to obtain granules containing the sintering raw material, the first carbonaceous material, and the second carbonaceous material by further granulation, or moisture may be added to the sintering raw material and the first carbonaceous material to obtain intermediate granules containing the sintering raw material and the first carbonaceous material by granulation, and then the second carbonaceous material may be added to the intermediate granules in the latter half of the granulation step S2 to obtain granules containing the sintering raw material, the first carbonaceous material, and the second carbonaceous material by further granulation.

[0041] (Addition of return ore) In the present disclosure, the return ore is added from the latter half of the granulation step S2 to the sintering step. The return ore may be added at a timing different from that of the second carbonaceous material, or may be added simultaneously with the second carbonaceous material.

[0042] The return fines may be added all at once or in multiple divided portions from the latter half of the granulation step to the sintering step.

[0043] The return ore may be added by, for example, the following method. When a constant-speed piston-flow type granulator is used as the granulator 2, as shown in FIG. 2, the return ore is supplied from a bypass return ore hopper 7 downstream of the granulator, and is transported from the downstream outlet of the granulator 2 to a predetermined position inside the granulator 2 by a transport conveyor. The position to which the return ore is transported may be the same as or different from the position to which the second carbonaceous material is transported, as described above, and may be on the downstream outlet side of the granulator 2 relative to the position to which the second carbonaceous material is transported. Alternatively, as shown in FIG. 3, the return ore and the second carbonaceous material may be transported to a predetermined position by the same transport conveyor. Next, the return ore may be added at a predetermined position inside the granulator 2 and granulated together with the sintering raw material, the first carbonaceous material, and the second carbonaceous material, and the blended raw material granules may be discharged from the outlet of the granulator 2.

[0044] <Sintering Step S3> The sintering step S3 is a step of sintering the blended raw material granules, more specifically, a step of sintering the blended raw material granules to produce a sintered cake (sinter cake). The blended raw material granules are supplied, for example, from a belt conveyor to a surge hopper 3, and then supplied from the surge hopper 3 onto a pallet of a sintering machine 4 (e.g., a Dwight Lloyd (DL) type sintering machine), whereupon a raw material packed bed can be formed on the pallet. The raw material packed bed can be ignited in an ignition furnace and fired by the combustion heat of the sintering material in the raw material packed bed. The sintered cake obtained by sintering is, for example, discharged from the sintering machine, roughly crushed by a crusher (primary crushing), and sent to the cooling and crushing step S4.

[0045] <Cooling and crushing step S4> The cooling and crushing step S4 is a step of cooling and crushing the coarsely crushed sintered ore. The sintered ore is cooled by a cooling device to a temperature at which it can be transported by a belt conveyor. The sintered ore is then crushed by a crusher (secondary crushing) and sent to the classification step S5.

[0046] <Classification Step S5> The classification step S5 is a step of sizing the pulverized sintered ore for blast furnace use. The pulverized sintered ore is sized by, for example, combing using a product comb 5. The sizing process selects sintered ore of a particle size suitable for blast furnace charging (product sintered ore). The particle size of sintered ore suitable for blast furnace charging may be, for example, 5 mm or more and less than 50 mm. The particle size of sintered ore can be determined by sieving for 5 minutes using a rotary shaker. Note that if the particle size of the sintered ore exceeds the particle size suitable for blast furnace charging (for example, exceeds 50 mm), the sintered ore is pulverized to a particle size suitable for blast furnace charging or less (for example, 50 mm or less), and then sizing is performed again. The product sintered ore selected by the classification step S5 is transported to the blast furnace transport line L1, and the remaining sintered ore is transported via the return ore transport line L2.

[0047] The blast furnace transfer line L1 is a line that transfers the sintered ore to the blast furnace facility. The blast furnace transfer line L1 may be equipped with a transfer device such as a conveyor. The sintered ore having a particle size within a predetermined range can be transferred to the blast furnace facility and used as a raw material for blast furnace iron production.

[0048] The return ore conveying line L2 is a line that returns fine sintered ore that is not suitable as a blast furnace feedstock to the bypass return ore hopper 7. Sintered ore having a particle size smaller than that of the product sintered ore is conveyed by the return ore conveying line L2 to the bypass return ore hopper 7. The conveyed sintered ore is added as return ore from the latter half of the granulation step S2 to the sintering step S3.

[0049] <<Method for Producing Sintered Ore: Components>> The granulated material, sintering raw material, and coagulating agent employed in the production method of the present disclosure, as well as the sintered ore produced by the method of the present disclosure, will be described below.

[0050] <Granulated Material> The granulated material contains at least the sintering raw material, the coagulating agent, and the return fine, and may contain auxiliary raw materials and the like as necessary.

[0051] <Shape of Granules> In the manufacturing method of the present disclosure, the first carbonaceous material added by the latter half of the granulation process is likely to be encapsulated in the granules, while the second carbonaceous material added in the latter half of the granulation process is likely to be wrapped around the granules. Here, as described above, the content of high combustible carbonaceous material in the first carbonaceous material is higher than the content of high combustible carbonaceous material in the second carbonaceous material, and the content of low combustible carbonaceous material in the second carbonaceous material is higher than the content of low combustible carbonaceous material in the first carbonaceous material. Therefore, at the center of the granules, the first carbonaceous material may be present in greater amounts than the second carbonaceous material, and the high combustible carbonaceous material may be present in greater amounts than the low combustible carbonaceous material. Furthermore, at the outer side of the center of the granules, the second carbonaceous material may be present in greater amounts than the first carbonaceous material, and the low combustible carbonaceous material may be present in greater amounts than the high combustible carbonaceous material.

[0052] From the viewpoint of sinterability and air permeability, the particle size of the granulated product may be, for example, 2 mm or more and 15 mm or less, and the lower limit of the particle size may be 2 mm or more and the upper limit of the particle size may be 15 mm or less, or 10 mm or less. Here, the particle size of the granulated product can be determined by sieving the wet granulated product with a Rotap shaker for 10 seconds.

[0053] (Sintering raw material) The sintering raw material is not particularly limited, and may be an iron-containing raw material. The iron-containing raw material may be, for example, iron ore (fine ore), iron manufacturing dust (iron manufacturing dust, steel manufacturing dust, scale, etc.), etc. One type of sintering raw material may be used alone, or two or more types may be used in combination. In particular, the iron ore (fine ore) may be iron ore of a single brand (origin), or multiple types of iron ore of different brands (origins) may be used in combination.

[0054] The particle size of the sintering raw material may be, for example, 0.01 mm or more and 15 mm or less. The particle size of the sintering raw material can be determined, for example, by sieving the raw material with a rotor shaker for 5 minutes.

[0055] <Aggregating Agent> The aggregating agent is not particularly limited, but any agent that serves as a heat source during the sintering process can be appropriately used. In the manufacturing method of the present disclosure, at least a carbonaceous material is used as the aggregating agent.

[0056] (First carbonaceous material) The first carbonaceous material includes a highly combustible carbonaceous material having a combustion initiation temperature of 550° C. or less. In the manufacturing method of the present disclosure, the carbonaceous material as a coagulation material added by the latter half of the granulation step as described above is referred to as the “first carbonaceous material.”

[0057] Examples of highly combustible carbonaceous materials include biomass charcoal and non-biomass charcoal. Specific examples include oil palm kernel shell charcoal (combustion initiation temperature: 450°C) and compressed wood charcoal (combustion initiation temperature: 300°C). A single highly combustible carbonaceous material may be used alone, or two or more may be used in combination. The content of the highly combustible carbonaceous material in the granules may be 0.5% by mass or more but not more than 2.0% by mass, or 0.2% by mass or more but not more than 4.0% by mass, based on 100% by mass of the entire granules. The lower limit of the content may be 0.2% by mass or more or 0.5% by mass or more, and the upper limit of the content may be 4.0% by mass or less or 2.0% by mass or less. When two or more highly combustible carbonaceous materials are used in combination, the "content of the highly combustible carbonaceous material" refers to the sum of the respective contents.

[0058] In the manufacturing method of the present disclosure, from the viewpoint of utilizing biomass charcoal and productivity of sintered ore, the highly combustible carbonaceous material preferably includes wood charcoal, more preferably includes a compressed product of the wood charcoal, and even more preferably includes pulverized material of the compressed product of wood charcoal.

[0059] The terms used in this specification are defined as follows: "Wood" refers to the trunks and branches of trees, or materials made from these, including, for example, construction waste. "Wood charcoal" refers to a charcoal obtained by heat treatment (dry distillation) of the above-mentioned "wood." "Compression molded product" refers to a molded product that has been compression molded, and includes not only compression molding but also extrusion molding in which pressure is applied during extrusion. "Pulverized product" refers to a product that has been crushed using a crusher (for example, a rod mill, hammer crusher, roll crusher, super sander, jaw crusher, fret mill, etc.).

[0060] The wood carbonized material may contain water, alkali, acid, etc. from the viewpoint of granulation. Furthermore, the wood carbonized material may contain a binder, although this is not particularly limited. Examples of the binder that can be used include cornstarch (starch), bentonite, coal tar, biomass tar, petroleum pitch, and cement. By including a binder in the wood carbonized material, for example, excessive pulverization of the compression-molded product can be suppressed when the compression-molded product is pulverized.

[0061] The combustion initiation temperature of the highly combustible carbonaceous material is 550 ° C. or less, 540 ° C. or less, 530 ° C. or less, 520 ° C. or less, 510 ° C. or less, or 500 ° C. or less, or 250 ° C. or more, 300 ° C. or more, or 350 ° C. or more. The combustion initiation temperature is measured by placing 10 mg of a measurement sample in a differential thermal-thermogravimetric simultaneous measurement device (Rigaku Corporation / Thermo Plus Evo2 TG-DTA8120 / H-IR Smart Loader), heating at a temperature increase rate of 100 ° C. / min with air circulating at 200 mL / min, and measuring the weight loss of the measurement sample during heating. Specifically, the reaction rate dX / dt at each reaction time t is calculated from the data on the reaction time t and reaction rate X (X = weight loss at reaction time t / initial weight of sample) obtained by measurement, the reaction time t at which dX / dt exceeds 0.0005 is determined, the temperature at reaction time t is determined, and this temperature is taken as the combustion start temperature (however, weight loss that occurs due to the removal of moisture contained in the carbonaceous material at temperatures below 250°C is excluded).

[0062] The particle size of the highly combustible carbonaceous material may be, for example, 0.25 mm or more and 5.00 mm or less, and the lower limit of the particle size may be 0.25 mm or more, 0.50 mm or more, or 1.00 mm or more, and the upper limit of the particle size may be 5.00 mm or less, 4.50 mm or less, or 4.00 mm or less. The particle size of the first carbonaceous material can be determined by sieving for 5 minutes using a rotary shaker. Furthermore, the first carbonaceous material having a particle size of 2.8 mm or more is preferably contained in an amount of 20% by mass to 60% by mass relative to 100% by mass of the total amount of the first carbonaceous material.

[0063] The volatile content of the highly combustible carbonaceous material is not particularly limited, but may be 0% or more and 20% or less, and the upper limit of the volatile content may be 20% or less, 15% or less, or 10% or less, and the lower limit of the volatile content may be 0% or more, 1% or more, or 5% or more. Here, the volatile content can be measured in accordance with the provisions of JIS M8812:2004.

[0064] The content of the highly combustible carbonaceous material in the first carbonaceous material may be, for example, 60% by mass or more and 100% by mass or less, relative to 100% by mass of the total amount of the first carbonaceous material, and the lower limit of the content of the highly combustible carbonaceous material may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, and the upper limit of the content of the highly combustible carbonaceous material may be 100% by mass or less, 99% by mass or less, or 90% by mass or less. Furthermore, the content of the low combustible carbonaceous material described below in the first carbonaceous material may be 0% by mass or more and 40% by mass or less, relative to 100% by mass of the total amount of the first carbonaceous material, and the lower limit of the content of the low combustible carbonaceous material may be 0% by mass or more, 1% by mass or more, 10% by mass or more, or 20% by mass or more, and the upper limit of the content of the low combustible carbonaceous material may be 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less. Here, when the first carbonaceous material is added in multiple batches, the content of the high combustibility carbonaceous material, the content of the low combustibility carbonaceous material, and the total amount of the first carbonaceous material are based on the total amount of carbonaceous material as agglomeration material added up to the latter half of the granulation process.

[0065] The amount of the first carbonaceous material added may be 0.30% by mass or more and 1.80% by mass or less relative to 100% by mass (parts by mass) of the sintering raw material, and the lower limit of the amount added may be 0.30% by mass or more, 0.50% by mass or more, or 0.80% by mass or more, and the upper limit of the amount added may be 1.80% by mass or less, 1.50% by mass or less, or 1.20% by mass or less. Here, when the first carbonaceous material is added in multiple batches, the amount of the first carbonaceous material added is the total amount of carbonaceous material added as a coagulant up to the latter half of the granulation step.

[0066] (Second carbonaceous material) The second carbonaceous material includes a low-combustibility carbonaceous material having a combustion initiation temperature of more than 550° C. In the manufacturing method of the present disclosure, the carbonaceous material added as a coagulation agent in the latter half of the granulation step as described above is referred to as the “second carbonaceous material.”

[0067] Specific examples of low-combustibility carbonaceous materials include coke breeze (combustion initiation temperature 670°C) and anthracite (combustion initiation temperature 650°C). A single low-combustibility carbonaceous material may be used alone, or two or more low-combustibility carbonaceous materials may be used in combination. The content of the low-combustibility carbonaceous material in the granules may be 2.0% by mass or more and 4.0% by mass or more, or 1.5% by mass or more and 4.5% by mass or less, based on 100% by mass of the entire granules. The lower limit of the content may be 1.5% by mass or more, or 2.0% by mass or more, and the upper limit of the content may be 4.5% by mass or less, or 4.0% by mass or less. When two or more low-combustibility carbonaceous materials are used in combination, the "content of low-combustibility carbonaceous materials" refers to the sum of the respective contents.

[0068] The combustion initiation temperature of the low combustibility carbonaceous material is higher than 550° C., and may be higher than 560° C., higher than 570° C., higher than 580° C., higher than 590° C., or higher than 600° C., and may be not higher than 700° C., not higher than 650° C., or not higher than 600° C. For a method for determining the combustion initiation temperature, see the description of "(First carbonaceous material)" above.

[0069] The particle size of the low combustible carbonaceous material may be, for example, 0.10 mm or more and 5.00 mm or less, and the lower limit of the particle size may be 0.10 mm or more, 0.20 mm or more, or 0.5 mm or more, and the upper limit of the particle size may be 5.00 mm or less, 3.00 mm or less, or 2.00 mm or less. For a method of determining the particle size of the second carbonaceous material, please refer to the description of "(First carbonaceous material)" above.

[0070] The volatile content of the low combustible carbonaceous material is not particularly limited, but may be 0% or more and 15% or less, and the upper limit of the volatile content may be 15% or less, 10% or less, or 5% or less, and the lower limit of the volatile content may be 0% or more, 1% or more, or 3% or more. Here, the volatile content can be measured in accordance with the provisions of JIS M8812:2004.

[0071] The content of the low combustible carbonaceous material in the second carbonaceous material may be, for example, 60% by mass or more and 100% by mass or less, relative to 100% by mass of the total amount of the second carbonaceous material, and the lower limit of the content of the low combustible carbonaceous material may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, and the upper limit of the content of the low combustible carbonaceous material may be 100% by mass or less, 99% by mass or less, or 90% by mass or less. Furthermore, the content of the high combustible carbonaceous material in the second carbonaceous material may be, for example, 0% by mass or more and 40% by mass or less, relative to 100% by mass of the total amount of the second carbonaceous material, and the lower limit of the content of the high combustible carbonaceous material may be 0% by mass or more, 1% by mass or more, 10% by mass or more, or 20% by mass or more, and the upper limit of the content of the high combustible carbonaceous material may be 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less. Here, when the second carbonaceous material is added in multiple batches, the content of the low combustible carbonaceous material, the content of the high combustible carbonaceous material, and the total amount of the second carbonaceous material are based on the total amount of carbonaceous material added as a coagulation material in the latter half of the granulation process.

[0072] The amount of the second carbonaceous material added may be, for example, 2.00% by mass or more and 5.00% by mass or less relative to 100% by mass (parts by mass) of the sintering raw material, and the lower limit of the amount added may be 2.00% by mass or more, 2.50% by mass or more, or 3.00% by mass or more, and the upper limit of the amount added may be 5.00% by mass or less, 4.50% by mass or less, or 4.00% by mass or less. Here, when the second carbonaceous material is added in multiple batches, the amount of the second carbonaceous material added is the total amount of the carbonaceous material added as a coagulant in the latter half of the granulation step.

[0073] (Other Components in the First Carbonaceous Material and the Second Carbonaceous Material) The first carbonaceous material and the second carbonaceous material may contain agglomeration materials other than the high combustibility carbonaceous material and the low combustibility carbonaceous material. For example, the total content of the high combustibility carbonaceous material and the low combustibility carbonaceous material in the first carbonaceous material may be, for example, 60% by mass or more and 100% by mass or less, relative to 100% by mass of the total amount of the first carbonaceous material. The lower limit of the total content may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, and the upper limit of the total content may be 100% by mass or less, 99% by mass or less, or 90% by mass or less. The same applies to the second carbonaceous material.

[0074] <Return ore> Examples of return ore include under-comb ore that has been subjected to a combing process before being fed into a cooler, under-comb ore that has been subjected to a combing process after cooling in the cooler, dust recovered from a dust collector, under-comb ore that has been sieved before being charged into a blast furnace, etc. All or a part of the return ore can be used as a raw material for the blended raw material granules.

[0075] The particle size of the return ore may be, for example, 1 mm or more and 5 mm or less, and the upper limit of the particle size may be 5 mm or less, 4 mm or less, or 3 mm or less, and the lower limit of the particle size may be 1 mm or more, or 2 mm or more. The particle size of the return ore can be determined by sieving a sample using a punch sieve that is vibrated back and forth.

[0076] From the viewpoint of productivity of sintered ore, the amount of return ore added may be, for example, 5% by mass or more and 25% by mass or less relative to 100% by mass (parts by mass) of the sinter raw material, the lower limit of the amount added may be 5% by mass or more, 10% by mass or more, or 15% by mass or more, and the upper limit of the amount added may be 25% by mass or less, 20% by mass or less, or 15% by mass or less.

[0077] <Auxiliary raw materials> Examples of auxiliary raw materials include CaO-containing auxiliary raw materials such as quicklime and limestone, and SiO-containing auxiliary raw materials such as silica stone. ２ Examples of the auxiliary materials include MgO-containing auxiliary materials, and MgO-containing auxiliary materials such as peridotite, dolomite, and magnesite. The auxiliary materials are appropriately selected for the sintering reaction and component adjustment. One type of auxiliary material may be used alone, or two or more types may be used in combination.

[0078] <Sintered Ore> Sintered ore can be used as a raw material for blast furnace iron making, for example.

[0079] From the viewpoint of charging into a blast furnace, the particle size of the sintered ore is preferably 5 mm or more and less than 50 mm, and may be 7.5 mm or more or 10 mm or more, or 40 mm or less, 30 mm or less, or 20 mm or less. The particle size of the sintered ore can be determined by sieving for 5 minutes using a rotary shaker.

[0080] The present disclosure will be described in more detail with reference to the following examples, but the scope of the present disclosure is not limited to these examples.

[0081] In the following tests, only coke breeze is used as the low combustibility carbonaceous material, but the desired effect can be obtained by using both anthracite and coke breeze, or by using only anthracite, as the low combustibility carbonaceous material. Furthermore, oil palm kernel shell carbonaceous material or compressed (ground) wood charcoal is used as the high combustibility carbonaceous material, but the present invention is not limited to these cases. For example, the desired effect can be obtained by using any one of the other high combustibility carbonaceous materials or a mixture of multiple high combustibility carbonaceous materials.

[0082] In the examples, verification was carried out using a method known as a sintering pot test. Specifically, the sintering pot test is a test in which a blended raw material containing a fuel coagulant, sintering raw materials, and return fines is charged into a container of a predetermined size, ignited from the top, and sucked downward to allow sintering to proceed. The sintering pot test equipment does not move the raw material packed bed using a pallet like a Dwight Lloyd (DL) sintering machine, but it is a test equipment that can simulate sintering using a DL sintering machine. As shown in Tables 4 and 5 below, nine levels of tests were conducted: Examples 1 to 4, Comparative Examples 1 to 4, and a Reference Example.

[0083] <Raw Materials> Table 1 shows the combustion initiation temperatures, proximate analysis, and elemental analysis results of the low combustibility carbonaceous materials and high combustibility carbonaceous materials used in the Examples, etc. Coke breeze as the low combustibility carbonaceous material, oil palm kernel shell charcoal as the high combustibility carbonaceous material, and a compressed molded product (pulverized product) of wood charcoal were prepared as shown in Table 1.

[0084] Oil palm kernel shell charcoal is a carbonized product obtained by carbonizing and dry distilling oil palm kernel shell, which is the residue left after crushing the fruit of the oil palm, a type of biomass, and squeezing out the oil (palm oil).

[0085] The low combustibility carbonaceous material as the coagulating agent is not limited to coke breeze, but may be anthracite, or may contain coke breeze and anthracite. In the embodiment, coke breeze was used.

[0086]

[0087] <Raw Material Blend> Table 2 shows the blending ratio (mass %) of each sinter raw material for the raw material blend used in the test. The proportions of the new raw materials (sinter raw materials) (iron ore, limestone, quicklime, and olivine) and the return ore were constant in all test examples (Examples 1 to 4, Comparative Examples 1 to 4, and Reference Example). Here, iron ores A to E are iron ores of different brands (origins). As shown in Table 2, the blending ratio of the return ore was 15% by mass, with the new raw materials being 100% by mass (parts by mass).

[0088]

[0089] Table 3 shows the mixing ratio (mass%) of the agglomerating agent in the blended raw materials used in the tests. Coke breeze was used as the low combustibility carbonaceous material in all test examples (Examples 1 to 4, Comparative Examples 1 to 4, and Reference Example). Oil palm kernel shell charcoal and a compressed product of crushed wood charcoal were used as the high combustibility carbonaceous material.

[0090] In the test examples (Comparative Examples 1-2 and Reference Example) in which only low combustibility carbonaceous material (coke powder) was used as the agglomerating agent, the mixing ratio of the agglomerating agent was 4.5 mass% with the new raw material being 100 mass% (parts by mass).

[0091] In the test examples (Examples 1-4 and Comparative Examples 3-4) using oil palm kernel shell charcoal or compressed wood charcoal (high combustible carbonaceous material) as the first carbonaceous material and coke breeze (low combustible carbonaceous material) as the second carbonaceous material, the blending ratios of the coke breeze and the low combustible carbonaceous material to the new raw materials (middle row of Table 3) were adjusted based on the blending amount of the coke breeze (4.5% by mass) in Comparative Examples 1-2 and the Reference Example, and the mass ratios of the carbon contents of the first and second carbonaceous materials (top row of Table 3) and the fixed carbon contents (Table 1) so that the fixed carbon contents (carbon contents) of all the coke breeze and the low combustible carbonaceous material contained in the blended raw materials were constant in all tests (Examples 1-4, Comparative Examples 1-4, and the Reference Example). The bottom row of Table 3 shows the blending ratios of the low combustible carbonaceous material and the high combustible carbonaceous material to the total amount of coke breeze.

[0092]

[0093] Tables 4 and 5 show the test conditions for producing sintered ore. The blending amounts of carbonaceous materials shown in Tables 4 and 5 are the same as the mass ratios of carbon contents shown in the upper part of Table 3. As shown in Tables 4 and 5, the low combustible carbonaceous material (coke fines) used as the second carbonaceous material had an average particle size of 1.0 mm. In addition, the mass ratio of the high combustible carbonaceous material having a particle size of 2.8 mm or more used as the first carbonaceous material was 30 mass% relative to the total mass of the high combustible carbonaceous material.

[0094]

[0095]

[0096] <Granulation method> A cylindrical batch-type drum mixer (diameter 600 mm, length 800 mm, rotation speed 25 rpm) was used as the granulator. In the granulation process, the final target moisture value was 7.5 mass% based on 100 mass% (parts by mass) of the total mass of the new raw material, the first carbonaceous material, the second carbonaceous material, and the return mineral, in all test examples (Examples 1 to 4, Comparative Examples 1 to 4, and Reference Example). In the case of lump-sum granulation, in-mixer post-addition, and post-mixer post-addition, the start of the granulation process was the time when the granulator was started, and the end of the granulation process was the time when the granulator was finally stopped. The time during which the granulator was stopped during granulation, for example to add the second carbonaceous material, was not included in the time from the start to the end of the granulation process.

[0097] (Granulation method: In the case of lump-sum granulation) In the lump-sum granulation of the Reference Example and Comparative Examples 3 and 4, the sinter raw material, the coagulating agent, and the return fines were charged into a granulator and mixed for 4 minutes. Next, water was added (humidity adjustment) to achieve the target moisture value, and the mixture was mixed for 4 minutes to obtain a granulated mixture of the blended raw materials. In these examples, the time from the start to the end of the granulation process was 8 minutes.

[0098] (Granulation method: When low combustible carbonaceous material and return ore are added later (later addition in mixer)) In Examples 1 and 2, the sinter raw material and the first carbonaceous material were charged into a granulator and mixed for 4 minutes. Next, moisture was added (humidity adjustment) to achieve a target moisture value, and the mixture was mixed for 3 minutes and 45 seconds, and the granulator was stopped. Thereafter, the second carbonaceous material and return ore were charged into the granulator and mixed for 15 seconds, to obtain a blended raw material granule. In these examples, the time from the start to the end of the granulation process was 8 minutes.

[0099] In Comparative Example 1, the sintering raw material was charged into the granulator and mixed for 4 minutes. Next, moisture was added (humidity control) to achieve the target moisture value, and the mixture was mixed for 3 minutes and 45 seconds, after which the granulator was stopped. Thereafter, the second carbonaceous material and return ore were charged into the granulator and mixed for 15 seconds to obtain a blended raw material granule. In this example, the time from the start to the end of the granulation process was 8 minutes.

[0100] (Granulation method: low combustibility carbonaceous material added later, and return ore added after granulation (post-mixer addition)) In Examples 3 and 4, the sinter raw material and the first carbonaceous material were charged into a granulator and mixed for 4 minutes. Next, moisture was added (humidity adjustment) to achieve the target moisture value, and the mixture was mixed for 3 minutes and 45 seconds, after which the granulator was stopped. Thereafter, the second carbonaceous material was charged into the granulator and mixed for 15 seconds. Then, the pre-blended raw material granules were discharged from the granulator, and return ore was added on the floor and mixed with a scoop to obtain blended raw material granules. In these examples, the time from start to finish of the granulation process was 8 minutes.

[0101] In Comparative Example 2, the sintered raw material was loaded into the granulator and mixed for 4 minutes. Next, moisture was added (humidity control) to achieve the target moisture value, and the mixture was mixed for 3 minutes and 45 seconds, after which the granulator was stopped. The second carbonaceous material was then loaded into the granulator and mixed for 15 seconds. The pre-blended raw material granules were then discharged from the granulator, and return ore was added and mixed with a scoop on the floor, resulting in a blended raw material granule. In these examples, the time from start to finish of the granulation process was 8 minutes.

[0102] <Charging Method> The pot test apparatus used was a cylindrical pot with a diameter of 300 mm and a height of 500 mm. As shown below, segregation-enhanced charging using a segregation-enhanced charging apparatus (slit bar charging apparatus) was simulated according to the method using a slit bar classifier described in "Materials and Processes 24 (2011), p. 795 (Hara et al.)."

[0103] (Segregation strengthening charging) The compound raw material granules classified using a slit bar classifier were charged into a sintering pot. Specifically, the compound raw material granules were fed into the slit bar classifier, and the compound raw material granules that fell through the slit bars were collected in collection boxes arranged directly below the slit bars, four of which were lined up from upstream to downstream, and the compound raw material granules that slid on the slit bars were collected in another collection box.

[0104] First, the granulated compound raw material that had slid over the slit bars was dropped into the pot from the top, and then the granulated compound raw material that had fallen between the slit bars and been collected was dropped into the pot from the top, starting with the granulated compound raw material in the downstream collection box.

[0105] <Sintering conditions> After charging the blended raw material granules, the surface of the packed bed of raw materials was ignited (initial ignition) for 1.0 minute using an ignition device (flame heating). The negative suction pressure during sintering was adjusted by adjusting the valve opening on the suction side of the blower so that the measured value below the pot was constant at 1,300 mmAq (12.7 kPa).

[0106] Below the pot, temperature was measured using a thermocouple along with pressure. During sintering, when the sintering zone reached the bottom of the raw material packed bed, the exhaust gas temperature below the pot began to rise, eventually reaching a peak temperature, and then decreasing due to the end of coke combustion. Three minutes after the exhaust gas temperature reached the peak temperature, the suction of the blower was stopped. The sintering time was defined as the time from the start of ignition to the time when the exhaust gas temperature reached the peak temperature. The sintering speed (BTS: Burn through speed) was calculated by dividing the raw material layer thickness by the sintering time.

[0107] <Product Yield> After sintering, the obtained sinter cake was dropped four times from a height of 2 m. Sintered ore with a particle size of +5 mm (over 5 mm), excluding bedding ore, was collected as the sintered product, and its mass was calculated to determine the sintered product yield. The sintered product mass divided by the sinter cake mass excluding bedding ore was defined as the product yield.

[0108] <Production rate> The production rate is calculated by multiplying the sintered product mass (product mass (tons)) by the sintering time (converted into days) and the firing area (pot bottom area (m ２ The production rate (t / (D·m)) was calculated by dividing by ２ ))=Amount of product (t) / {Baking time (D)・Pot bottom area (m ２ )...Equation (1)

[0109] In the cases where the second carbonaceous material and return ore were added in the latter half of the granulation step (Examples 1 and 2), the sintering rate was higher, the productivity was higher, and the product yield was better than in the methods for producing sintered ore in Comparative Examples 1 and 4. Similarly, in the cases where the second carbonaceous material was added in the latter half of the granulation step and the return ore was added after granulation from the latter half of the granulation step to the sintering step (Examples 3 and 4), the sintering rate was higher, the productivity was higher, and the product yield was better than in the methods for producing sintered ore in Comparative Examples 2 and 5.

[0110] <Further Study> Table 6 shows the production conditions for further study, specifically, the types and compositions of the high combustibility and low combustibility carbonaceous materials in the first and second carbonaceous materials, and the addition positions of the second carbonaceous material and return fines.

[0111]

[0112] In Example 1-1, first, the sintering raw material and the first carbonaceous material were charged into a granulator and mixed for 4 minutes. Next, moisture was added (humidity adjustment) to achieve the target moisture value, and the mixture was mixed for 2 minutes 24 seconds, after which the granulator was stopped. Thereafter, the second carbonaceous material and return ore were charged into the granulator and mixed for 1 minute 36 seconds, thereby obtaining a blended raw material granule. The time from the start to the end of the granulation process was 8 minutes.

[0113] In Example 1-2, the proportion of oil palm shell kernel carbon having a particle size of 2.8 mm or more contained in the first carbonaceous material was set to 50 mass %, and a blended raw material granulated product was obtained in the same manner as in Example 1.

[0114] For Example 1-3, the ratio of compressed wood carbonized material (crushed material) with a particle size of 2.8 mm or more contained in the first carbonaceous material was set to 50 mass%, and a blended raw material granulated product was obtained in the same manner as in Example 1.

[0115] For Examples 1-4, a blended raw material granulation product was obtained in the same manner as in Example 1 using a first carbonaceous material containing compressed molded wood charcoal (crushed material) (70% by mass) as a highly combustible carbonaceous material and powdered coke (30% by mass) as a low-combustible carbonaceous material, and a second carbonaceous material containing compressed molded wood charcoal (crushed material) (30% by mass) as a highly combustible carbonaceous material and powdered coke (70% by mass) as a low-combustible carbonaceous material.

[0116] For Comparative Example 1-1, a granulated blend of raw materials was obtained in the same manner as in Example 1 using a first carbonaceous material containing compressed molded wood charcoal (crushed material) (30% by mass) as a highly combustible carbonaceous material and powdered coke (70% by mass) as a low-combustible carbonaceous material, and a second carbonaceous material containing compressed molded wood charcoal (crushed material) (70% by mass) as a highly combustible carbonaceous material and powdered coke (30% by mass) as a low-combustible carbonaceous material.

[0117] Even when the second carbonaceous material and return ore were added 6 minutes 24 seconds (4 minutes + 2 minutes 24 seconds) after the start of the granulation process (Example 1-1), the sintering rate was high, the productivity was high, and the product yield was good, similar to Example 1. Furthermore, even when highly combustible carbonaceous materials with different particle sizes were used (Examples 1-2 and 1-3), the sintering rate was high, the productivity was high, and the product yield was good, similar to Examples 1 and 2.

[0118] When the content of high combustible carbonaceous material in the first carbonaceous material was higher than the content of high combustible carbonaceous material in the second carbonaceous material and the content of low combustible carbonaceous material in the second carbonaceous material was higher than the content of low combustible carbonaceous material in the first carbonaceous material, as in Example 1-4, the sintering speed was higher, the productivity was higher, and the product yield was better than when the content of high combustible carbonaceous material in the first carbonaceous material was lower than the content of high combustible carbonaceous material in the second carbonaceous material and the content of low combustible carbonaceous material in the second carbonaceous material was lower than the content of low combustible carbonaceous material in the first carbonaceous material, as in Comparative Example 1-2.

[0119] While preferred embodiments of the disclosed method for producing sintered ore have been described, modifications can be made without departing from the scope of the claims.

[0120] 1 Raw material tank 2 Granulator 3 Surge hopper 4 Sintering machine 5 Product comb 6 Hopper for post-addition in mixer 7 Bypass return fine hopper

Claims

1. A method for producing sintered ore, comprising: a granulation step of obtaining granules containing at least a sintering raw material, a coagulating agent, and return ore; and a sintering step of sintering the granules, wherein a first carbonaceous material is added as the coagulating agent by the latter half of the granulation step; a second carbonaceous material is added as the coagulating agent in the latter half of the granulation step; the return ore is added from the latter half of the granulation step to the sintering step; the first carbonaceous material comprises a high combustible carbonaceous material having a combustion start temperature of 550°C or less; and the second carbonaceous material comprises a low combustible carbonaceous material having a combustion start temperature of more than 550°C; the content of the high combustible carbonaceous material in the first carbonaceous material is higher than the content of the high combustible carbonaceous material in the second carbonaceous material; and the content of the low combustible carbonaceous material in the second carbonaceous material is higher than the content of the low combustible carbonaceous material in the first carbonaceous material.

2. The manufacturing method according to claim 1, wherein the return fines are added simultaneously with the second carbonaceous material as the coagulating agent in the latter half of the granulation step.

3. The manufacturing method according to claim 1 or 2, wherein the highly combustible carbonaceous material comprises a compressed wood charcoal.

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