Method for producing sintered ore

Abstract

The present invention comprises, in a sintering raw material, a pulverized product of a compression-molded product obtained through a pulverizing step (S112) in which a compression-molded product obtained by compressing and molding an aggregate of wood carbides is pulverized, and at least one of powdered coke and anthracite, and the apparent density of the compression-molded product is 0.6 g / cm3 or more.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing sintered ore used as a raw material for a blast furnace. Background Art

[0002] In order to reduce CO2 as a countermeasure against global warming, it is extremely important to change the conventional coal-derived binder to biomass carbon as a carbon-neutral carbon material. Regarding a method for manufacturing sintered ore using biomass carbon (biochar), the following technologies have been disclosed.

[0003] In the sintered ore manufacturing method described in Patent Document 1, a sintering raw material containing 0.1 to 9.0% by mass of biomass carbide containing less than 2.3% -dry of nitrogen and less than 1% -dry of sulfur, and the remaining part containing iron ore, coke, and other auxiliary raw materials is used, and sintered ore is manufactured by a downward suction type sintering machine. Thereby, NOx and SOx contained in the exhaust gas generated during the manufacture of sintered ore are reduced.

[0004] Patent Document 2 describes a method in which a raw material containing fine iron ore, a flux for composition adjustment, return ore, and a solid carbon material is used, and a concentration distribution of the solid carbon material is generated in the height direction of a pallet to manufacture sintered ore. In this sintered ore manufacturing method, in the sintering raw material containing fine iron ore, a flux for composition adjustment, and return ore, a solid carbide obtained by heat-treating oil palm kernel shell (PKS), i.e., oil palm kernel shell carbon (PKS carbon), is mixed, and one or more of coke and anthracite having a particle size smaller than that of the solid carbide are mixed. Thereby, during the manufacture of sintered ore, the amount of carbon dioxide discharged is suppressed, and the productivity of the sintering machine is increased.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-328044

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2013-237876 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] In Patent Document 1, as the biomass carbide, a solid component (residue) generated when biomass is thermally decomposed in an anaerobic or low-oxygen state is used. In addition, Patent Document 2 describes that as PKS carbon, any substance obtained by heat-treating PKS may be used. Specifically, PKS carbon manufactured by heat-treating dried PKS in an electric furnace at 700 °C for 1 hour is used.

[0011] Biomass carbide produced by heat treatment (dry distillation) of biomass is a porous material and thus has excellent combustibility (fast combustion rate). Therefore, it can increase the sintering rate when producing sintered ore. However, if the sintering rate increases excessively, it may instead reduce the yield and productivity of the sintered ore. Patent Document 2 (paragraph

[0044] ) also records that although PKS carbon has excellent combustibility through micropores, if the combustibility is not controlled, the yield will decrease. Here, the so-called combustibility refers to the reaction rate (combustion rate) when the carbon material burns in air. As an example, this combustion rate can be measured using a thermobalance as follows. Place a 10 mg carbon material sample (particle size 0.15 - 0.25 mm) in a thermobalance (manufactured by Rigaku Corporation / ThermoPlus Evo2 TG-DTA8120 / H-IR Smart Loader). After thoroughly purging the inside of the device with nitrogen, heat it at a heating rate of 100 °C / min in a state where nitrogen is flowing at 200 ml / min. After the sample temperature reaches the specified temperature (700 °C), immediately switch the flowing gas from nitrogen to air at 200 ml / min, measure the weight loss, and calculate the reaction rate dV / dt at each reaction rate from the data of the reaction time t (the elapsed time from switching the flowing gas from nitrogen to air) and the reaction rate V (V = [weight loss at each time - unburned material weight at the end of the measurement] / [initial weight of the sample - unburned material weight at the end of the measurement]). Calculate the average value up to V = 0 - 0.95, and thus calculate the combustion rate of each carbon material at the specified temperature.

[0012] An object of the present invention is to provide a method for manufacturing sintered ore that uses wood carbide, which is a biomass carbide (biochar), as a sintering raw material and can improve the yield and productivity.

[0013] Means for Solving the Problem

[0014] According to several aspects of the present invention, the following is provided.

[0015] [1] A method for manufacturing sintered ore, which includes, in the sintering raw material, a pulverized product of a compression molded product (charcoal compression molded pulverized product) obtained through a pulverization process, and at least one of pulverized coke and anthracite. In the pulverization process, a compression molded product (charcoal compression molded product) obtained by compressing and molding an aggregate of wood carbide is pulverized.

[0016] The apparent density of the above compression molded product is 0.6 g / cm 3 The above.

[0017] [2]The method for manufacturing sintered ore according to [1], wherein the crushed product of the above-mentioned compression molded product in the above-mentioned sintering raw materials and at least any one of the above-mentioned pulverized coke and anthracite are added in the latter half of the granulation process.

[0018] [3]The method for manufacturing sintered ore according to [1] or [2], wherein the crushed product of the above-mentioned compression molded product obtained through the above-mentioned crushing process is further subjected to a screening process of screening crushed products having a particle size within a specified particle size range as the above-mentioned sintering raw materials after the above-mentioned crushing process.

[0019] [4]The method for manufacturing sintered ore according to [3], wherein the above-mentioned specified particle size range is more than 0 mm and less than 10 mm.

[0020] [5]The method for manufacturing sintered ore according to [1] or [2], wherein the volatile component of the above-mentioned compression molded product is 20% by mass or less.

[0021] [6]The method for manufacturing sintered ore according to [1] or [2], wherein the above-mentioned compression molded product has the following processes as its manufacturing processes:

[0022] A carbonization process of carbonizing wood to produce the above-mentioned wood carbide; and

[0023] A compression process of manufacturing the above-mentioned compression molded product by compressing and molding an aggregate of the above-mentioned wood carbide using an adhesive,

[0024] The volatile component of the above-mentioned wood carbide is 15% by mass or less.

[0025] [7]The method for manufacturing sintered ore according to [3], wherein in the above-mentioned screening process, crushed products having a particle size greater than the upper limit value of the above-mentioned specified particle size range are further screened and reused as raw materials for the crushed products of the above-mentioned compression molded product in the above-mentioned crushing process.

[0026] [8]The method for manufacturing sintered ore according to [6], wherein the crushed product of the above-mentioned compression molded product obtained through the above-mentioned crushing process is, after the above-mentioned crushing process, subjected to a screening process of screening crushed products having a particle size within a specified particle size range as the above-mentioned sintering raw materials,

[0027] In the above-mentioned screening process, crushed products having a particle size smaller than the lower limit value of the above-mentioned specified particle size range are further screened and reused as raw materials for the above-mentioned compression molded product in the above-mentioned compression process.

[0028] According to the present invention, by pulverizing a compression molded article obtained by compression molding an aggregate of wood carbide and using the pulverized material as a part of the sintering raw material, the yield and productivity can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram showing an example of a sintering apparatus used in the stepwise charging and stepwise ignition sintering method.

[0030] Figure 2 It is a schematic diagram showing an example of a sintering apparatus used in the method for manufacturing sintered ore according to the first embodiment.

[0031] Figure 3 It is a diagram for explaining the first manufacturing method of the pulverized charcoal compression molded article.

[0032] Figure 4 It is a diagram for explaining the second manufacturing method of the pulverized charcoal compression molded article.

[0033] Figure 5 It is a diagram for explaining the third manufacturing method of the pulverized charcoal compression molded article.

[0034] Figure 6 It is a diagram for explaining the fourth manufacturing method of the pulverized charcoal compression molded article.

[0035] Figure 7 It is a diagram for explaining the fifth manufacturing method of the pulverized charcoal compression molded article.

[0036] Figure 8 It is a diagram for explaining the sixth manufacturing method of the pulverized charcoal compression molded article.

[0037] Figure 9 It is a diagram for explaining the details of the manufacturing process of the charcoal compression molded article in the fourth to sixth manufacturing methods of the pulverized charcoal compression molded article.

[0038] Figure 10 It is a diagram for explaining the seventh manufacturing method (a modified example of the sixth manufacturing method) of the pulverized charcoal compression molded article.

[0039] Figure 11 It is a schematic diagram showing an example of a sintering apparatus used in the method for manufacturing sintered ore according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention relates to a method for manufacturing sintered ore, which includes, in the sintering raw materials, a crushed product of a compression molded product obtained through a crushing process (hereinafter, for convenience, also simply referred to as a crushed charcoal compression molded product), and at least one of pulverized coke and anthracite (hereinafter, also referred to as pulverized coke or / and anthracite). In the crushing process, a compression molded product (hereinafter, for convenience, also simply referred to as a charcoal compression molded product) obtained by compressing and molding an aggregate of wood carbide is crushed, and the apparent density of the compression molded product is 0.6 g / cm 3 or more. The crushed product (crushed charcoal compression molded product) obtained by crushing a compression molded product (charcoal compression molded product) mainly made of wood carbide as biomass carbon (biochar) is used as a coagulant for the sintering raw materials together with pulverized coke or / and anthracite. Here, the terms used in this specification are defined as follows. "Wood" refers to the trunk or branches of a tree or the material made therefrom, and includes, for example, construction waste wood. "Wood carbide" refers to the carbide obtained by heat-treating (carbonizing) the above-mentioned "wood". "Aggregate of wood carbide" refers to an aggregate of only wood carbide particles or an aggregate of wood carbide particles joined with an adhesive, and the size and shape of the wood carbide particles are not limited. "Compressing and molding" means that compression is accompanied during molding, and includes not only compression molding, but also, for example, extrusion molding in which pressure is applied during extrusion. "Main raw material" refers to the raw material with the highest proportion (mass ratio) among all the solid raw materials in the solid raw material. "Crushing" means making the size smaller than the original compression molded product by applying energy to the compression molded product. It should be noted that the size after crushing is preferably set to a rough particle size suitable as a coagulant and less than 10 mm.

[0041] Hereinafter, the present invention and its preferred embodiments will be described in detail with reference to the drawings. It should be noted that in this specification and the drawings, for components having substantially the same function, the same or similar names and / or the same or similar symbols are used, and thus repeated descriptions are omitted. In addition, for the convenience of description, hereinafter, the coagulant derived from wood (wood carbide without the compression molding process described later and the charcoal compression molded product with the compression molding process) is sometimes referred to as "the first carbon material for sintering", the coagulant not derived from wood (pulverized coke and anthracite described later) is referred to as "the second carbon material for sintering", and the two are distinguished.

[0042] 《First Embodiment》

[0043] The following describes an embodiment of the present invention. First, a method for manufacturing sintered ore will be described, and then, a compression molded product (charcoal compression molded product) obtained by compressing and molding wood carbide as a main raw material, and a pulverized product (charcoal compression molded pulverized product) obtained by pulverizing the same will be described.

[0044] (Method for manufacturing sintered ore)

[0045] Figure 1 It is a schematic diagram of a sintering apparatus 100 used in a one-stage charging and one-stage ignition sintering method using a Dwight-Lloyd (DL) type sintering machine. The sintering apparatus 100 includes a raw material tank group 1, a mixing and granulating device 2 (rotary drum mixer), and a DL type sintering machine 3.

[0046] For the raw materials of sintered ore (sintering raw materials), it is suitable to use iron raw materials such as iron ore (powder), iron-containing miscellaneous raw materials such as scale / ironmaking dust, MgO-containing auxiliary raw materials such as peridotite or serpentine, CaO-containing auxiliary raw materials such as limestone, return ore, and solid fuel that becomes the heat source for causing sintering reaction (coagulation), i.e., coagulant. As the coagulant, for example, sintering carbon materials (powder coke, anthracite, etc.) can be cited. As Figure 1 shown, each sintering raw material is stored in each raw material tank (11 to 1 X ) of the raw material tank group 1, cut out and mixed in a specified ratio. The mixed raw materials (mixed raw materials) are put into the mixing and granulating device 2 (rotary drum mixer) for mixing and granulating treatment to produce pseudo-particles. The granulated mixed raw materials (hereinafter, the granulated mixed raw materials after granulation treatment are also referred to as mixed raw material granulated products) are charged from the mixed raw material buffer hopper 21 onto a trolley (not shown) covered with bottom ore to form a raw material filling layer 10.

[0047] The raw material filling layer 10 continuously moves in the trolley forward direction 5 by the movement of the trolley. When the raw material filling layer 10 moves under the ignition furnace 4, the coagulant on the surface of the raw material filling layer 10 is ignited by the ignition furnace 4, and the sintering of the raw material filling layer 10 starts. After ignition, a wind box (not shown) is provided on the lower side of the trolley moving in the trolley forward direction 5, and air is sucked from below the trolley. Oxygen is supplied into the raw material filling layer 10 through this downward suction 6, and the combustion of the coagulant in the raw material filling layer 10 (combustion zone 10A) advances from the upper part to the lower part, and the raw material filling layer 10 is sequentially sintered by the combustion heat of the coagulant. The sintered cake 11 is discharged at the downstream end in the trolley forward direction 5 of the DL type sintering machine 3, and sized by crushing, screening, etc. The sintered ore with a particle size that can be charged into the blast furnace becomes the raw material for blast furnace ironmaking, and the other sintered ore is reused as return ore.

[0048] When loading the granulated mixture raw material onto a trolley, a loading device equipped with a segregation mechanism is used. Generally, the inclined flat chute type loading device 20 shown in Figure 1 is used. The inclined flat chute type loading device 20 includes: a mixture raw material buffer hopper 21 for accumulating the granulated mixture raw material, and an inclined flat chute 22 installed to incline downward in a direction opposite to the trolley advancing direction 5. By loading the granulated mixture raw material in the mixture raw material buffer hopper 21 onto the trolley using the inclined flat chute 22, an inclined surface 10x is formed on the upstream side of the raw material filling layer 10. Through the rolling classification action of the granulated mixture raw material in this inclined surface 10x, particle size segregation is caused in the layer thickness (layer height) direction of the raw material filling layer 10. Specifically, the smaller particles are more likely to be loaded onto the upper side of the raw material filling layer 10, and the larger particles are more likely to be loaded onto the lower side of the raw material filling layer 10.

[0049] Here, the granulation treatment of the above-mentioned mixture raw material aims to ensure the air permeability of the raw material filling layer. Generally, as described in the 3rd Edition of the Iron and Steel Handbook II Ironmaking - Steelmaking P84 ( Figure 2 .4) [October 15, 1979], it is pointed out that: for the main object of the granulation treatment, the fine powder raw material with a particle size below 0.25 mm forms pseudo-particles by attaching particles with a particle size of 1.00 mm or more as core particles around it, but the intermediate particle size particles with a particle size above 0.25 mm and below 1.00 mm are difficult to granulate and are not easily formed into pseudo-particles. Therefore, even in the case of performing granulation treatment, by adjusting the particle size of the added binder and using the above-mentioned inclined flat chute type loading device 20 for loading, the distribution of the binder in the height direction of the raw material filling layer can be adjusted.

[0050] For the binder when manufacturing sintered ore, the above-mentioned second sintering carbon material (powder coke or / and anthracite) is usually used. Powder coke is a substance obtained by crushing coke with a particle size unsuitable for blast furnace use (usually with a particle size of 40 mm or less) generated during the manufacturing process of blast furnace coke (lump coke) produced by heating coal in an anaerobic or low-oxygen atmosphere to a particle size suitable for sintering use. Compared with blast furnace lump coke, the coke for sintering is called powder coke. Anthracite is one of the classifications of coal (lignite, bituminous coal, anthracite), and it is the coal with the most advanced carbonization. Coal with a fuel ratio (fixed carbon / volatile component (mass ratio)) of 4 or more, simply speaking, with a volatile component of 10% or less and a carbon content of 90 mass% or more (anhydrous / ash-free basis) is classified as anthracite. Both anthracite and powder coke are used after being crushed to a particle size suitable for sintering use (roughly with a particle size below 10 mm and an average particle size of about 2 mm).

[0051] Next, for the method of manufacturing sintered ore of this embodiment, useFigure 2 will be described. In the method for manufacturing sintered ore according to the present embodiment, as a binder, a pulverized product (charcoal compression molded pulverized product) of a charcoal compression molded product obtained by compressing and molding an aggregate of wood carbide and pulverized coke or / and anthracite are used.

[0052] Figure 2 is a schematic diagram showing an example of the sintering equipment 101 used in the method for manufacturing sintered ore according to the present embodiment. The sintering equipment 101 is different from the above-described sintering equipment 100 only in that the charcoal compression molded pulverized product is added to the sintering raw materials stored in the raw material tank group 1. Hereinafter, only the differences from the sintering equipment 100 will be described, and repeated descriptions will be omitted. As Figure 2 shown, the sintering equipment 101 has a raw material tank group 1a, and in each raw material tank (11 to 1 X 、1 y ) such as the raw material tank 11, the raw material tank 12, and the raw material tank 1 y , pulverized coke A1, anthracite A2, and charcoal compression molded pulverized product A3 are stored respectively. The stored pulverized coke A1, anthracite A2, and charcoal compression molded pulverized product A3 are cut out in a predetermined amount (when the mixing ratio is 0% by mass, cutting out is not performed) based on the mixing ratio together with other sintering raw materials, and become the mixed raw materials. It should be noted that the present invention is not limited to the above configuration, and as long as the mixed raw materials in which the sintering raw materials containing the charcoal compression molded pulverized product A3 and the pulverized coke A1 or / and anthracite A2 are mixed based on the mixing ratio can be charged into the DL type sintering machine 3. For example, although not shown in the figure, two or more of the pulverized coke A1, anthracite A2, and charcoal compression molded pulverized product A3 may be mixed in advance in a homogeneous manner based on the mixing ratio, and the mixture may be stored in one raw material tank and cut out in a predetermined amount for mixing.

[0053] As described above, when manufacturing sintered ore, charcoal compressed briquettes and a second carbon material for sintering (pulverized coke or / and anthracite) are used as the binding material. Here, in the mass ratio [% by mass] of the fixed carbon component, when the total binding material is set to 100% by mass, the charcoal compressed briquettes are preferably 50% by mass or less. If the blending ratio of the charcoal compressed briquettes exceeds 50% by mass, the sintering speed becomes fast due to the excellent combustibility of the charcoal compressed briquettes, so the temperature in the raw material filling layer does not rise sufficiently, and thus the yield may decrease. It should be noted that by blending the charcoal compressed briquettes, for example, even in a small amount as the binding material (as long as the blending ratio of the charcoal compressed briquettes exceeds 0% by mass), it is possible to contribute to the reduction of CO2. The blending ratio of the charcoal compressed briquettes and the second carbon material for sintering (pulverized coke or / and anthracite) is also preferably adjusted so that the fixed carbon amount (industrial analysis value) becomes equal in the case of using only the second carbon material for sintering and the case of using the charcoal compressed briquettes and the second carbon material for sintering. This is because: since the ash content and volatile components of the second carbon material for sintering and the charcoal compressed briquettes are different, by setting the fixed carbon amount to be constant, the thermal effects during the combustion of the carbon materials can be made almost equivalent.

[0054] (Charcoal compressed briquettes and their pulverized products)

[0055] Next, the apparent density and volatile components of the charcoal compressed briquettes and their pulverized products (charcoal compressed briquette pulverized products) will be described. In the present invention, by using the charcoal compressed briquettes in a part of the binding material to manufacture sintered ore, the yield and productivity of the sintered ore can be improved compared with the case of using wood carbide or its pulverized product in its original state to manufacture sintered ore. The apparent density of the charcoal compressed briquettes is preferably 0.6 g / cm 3 or more, more preferably 0.7 g / cm 3 or more. By setting the apparent density of the charcoal compressed briquettes to 0.6 g / cm 3 or more, the combustion speed can be inhibited from becoming too fast, so the yield and productivity can be improved compared with the case of using wood carbide. In addition, since the charging density of the blended raw materials increases, the production amount of the sintered ore increases. In addition, the apparent density of the charcoal compressed briquettes is preferably 1.3 g / cm 3 or less. This is because: if it exceeds 1.3 g / cm 3 , it is difficult to obtain the effect of improving combustibility.

[0056] The apparent density can be measured by the bead volume displacement method. The bead volume displacement method is the measurement method adopted by Micromeritics, and it is a volume displacement method using beads with high fluidity, namely DryFlо (suspected fluid), for the sample to be measured. Specifically, first, measure the volume X of only the beads placed in the sample chamber. Then, measure the volume Z of the beads in the layer where the sample to be measured is placed in the sample chamber. Calculate the volume (apparent volume) Y of the pores and voids containing the sample to be measured from the difference between the two volumes (Z - X). The apparent density [g / cm 3 becomes the value obtained by dividing the mass of the sample to be measured by the apparent volume Y.

[0057] The charcoal compression molded product preferably uses those with a volatile content of 20 mass% or less. The volatile content can be measured according to the provisions of JIS M8812:2006. The reasons for setting the volatile content of the charcoal compression molded product to 20 mass% or less are explained as follows. Conventional coal-based coagulants (the second sintering carbon material = pulverized coke or / and anthracite) were managed so that the volatile content became a specified value (for example, 10 mass%) or less. The reason is that unburned components (tar components) derived from the volatile content flow into the exhaust gas, which becomes the cause of malfunctions in machines such as exhaust gas electrostatic precipitators and exhaust gas blowers. On the other hand, even if the charcoal compression molded product has the same volatile content as the coal-based coagulant, the unburned components (tar components) flowing into the exhaust gas are less than those of the coal-based coagulant. Therefore, the upper limit of the volatile content is set to 20 mass% or less, which is different from that of the coal-based coagulant.

[0058] Here, before and after the charcoal compression molded product is pulverized, the volatile content and the apparent density do not change. Therefore, it is also possible to measure the volatile content and the apparent density of the charcoal compression molded product and use their measured values as the volatile content and the apparent density of the pulverized charcoal compression molded product. In addition, it is also possible to measure the volatile content and the apparent density of the pulverized charcoal compression molded product and use their measured values as the volatile content and the apparent density of the charcoal compression molded product.

[0059] (Method for manufacturing pulverized charcoal compression molded product)

[0060] The method for manufacturing the pulverized charcoal compression molded product (the first to seventh manufacturing methods) used in the production of sintered ore is described below with reference to the accompanying drawings.

[0061] (The first manufacturing method)

[0062] For the first manufacturing method of the pulverized charcoal compression molded product, use Figure 3A description will be given. First, in the charcoal compressed product obtaining step (S111), a charcoal compressed product is prepared. The prepared charcoal compressed product is, for example, a formed product obtained by compressing and forming an aggregate of a plurality of pulverized wood carbides using a compression molding machine, an extrusion molding machine, or the like, and is a charcoal compressed product in the market with an apparent density of 0.6 g / cm 3 or more. As long as it is a charcoal compressed product with an apparent density of 0.6 g / cm 3 or more, its manufacturing method is not limited. For example, generally, wood carbide is manufactured by carbonizing pulverized wood, and a charcoal compressed product is manufactured using wood carbide as a raw material.

[0063] In the pulverizing step (S112), the charcoal compressed product prepared in the charcoal compressed product obtaining step (S111) is pulverized. As the pulverizer, as long as it can pulverize the charcoal compressed product, for example, a rod mill, a hammer crusher, a roll crusher, a super sandblaster, a jaw crusher, a pan mill, etc. can be used.

[0064] The particle size of the pulverized charcoal compressed product is not particularly limited, but for example, it is preferably set to be less than 10 mm (undersize of a sieve with a sieve hole of 10.0 mm) (that is, the particle size range (specified particle size range) of the pulverized charcoal compressed product is set to have a particle size exceeding 0 mm and less than 10 mm). In addition, the average particle size of the pulverized charcoal compressed product is preferably 5 mm or less. This is because: if the average particle size is too large (exceeding 5 mm), when manufacturing sintered ore, the pulverized charcoal compressed product accumulates in the lower part of the pallet car and sinters on the grate bars, causing equipment failure. Furthermore, the average particle size of the pulverized charcoal compressed product is preferably 1 mm or more. This is because: if the average particle size is too small (less than 1 mm), it causes deterioration of ventilation in the raw material filling layer and a decrease in productivity when manufacturing sintered ore. Here, in this specification, the "particle size" of the pulverized charcoal compressed product, etc. is a value measured using a sieve based on JIS Z8801-1:2019. Here, in this specification, the "average particle size" refers to the arithmetic mean particle size. The arithmetic mean particle size is an average value calculated by loading and summing the median values of each particle size range based on the particle size distribution when screening (grading) using sieves with different sieve holes (mesh sizes) with the mass fraction of each particle size range.

[0065] The average particle size of the pulverized charcoal compression molded product is obtained as follows. After drying the pulverized charcoal compression molded product at 105°C for more than 2 hours, the pulverized charcoal compression molded product is classified by sieving for 5 minutes each using 6 sieves with different meshes (mesh sizes), and the sample mass wi of each particle size classification i is measured. As shown in Table 1, the particle sizes (0.25mm, 0.5mm, 1.0mm, 2.8mm, 4.76mm, 10.0mm) that become the boundary values of the particle size classification are the meshes of the sieves used in the classification. For example, the particle size classification "0.5-1.0" means that it is on the sieve when sieving with a sieve with a mesh of 0.5mm, and it is under the sieve when sieving with a sieve with a mesh of 1.0mm. The same is true for the particle size classifications "10.0~4.76", "4.76~2.8", "2.8~1.0", "1.0~0.5", and "0.5~0.25". In addition, the particle size cutoff "-0.25" means the undersize when sieving is performed with a sieve having a mesh size of 0.25 mm.

[0066] [Table 1]

[0067]

[0068] The average particle size [mm] is an arithmetic mean particle size calculated by loading the representative value xi (≈median value) of the particle size fractions as the mass fraction (mass ratio) of each particle size fraction as shown in the following formula (i).

[0069] Average particle size = Σwixi / Σwi(i)

[0070] xi: representative value of particle size classification i

[0071] wi: mass of sample with particle size classification i

[0072] The charcoal compression molded pulverized material after pulverizing in the pulverizing step (S112) is transported to the raw material tank 1 where it is stored. y (Refer to Figure 2 , Figure 11 The charcoal compression molded pulverized material accumulated in the raw material tank is removed from the raw material tank 1 based on a predetermined mixing ratio as described in the above-mentioned method for producing sintered ore. y (Refer to Figure 2 , Figure 11 ) is appropriately cut out and used as a sintering raw material.

[0073] (Second Manufacturing Method)

[0074] The second method for producing charcoal compression molded pulverized material is to use Figure 4 For explanation. Figure 4As shown in [description of Figure 2], in the second manufacturing method, a sizing process (S123) is added to the processes of the first manufacturing method. It should be noted that the charcoal compression molding product obtaining stage (step S121) and the pulverization process (S122) of the second manufacturing method are the same as the charcoal compression molding product obtaining stage (S111) and the pulverization process (S112) of the first manufacturing method, respectively. Therefore, the repeated description of these processes is omitted. Hereinafter, the sizing process (S123) will be described.

[0075] The sizing process (S123) is an additional process implemented, for example, when the particle size or particle size distribution of the charcoal compression molded pulverized product manufactured in the pulverization process (S122) is not suitable for direct use as a coagulant for sintering raw materials. In the sizing process (S123), charcoal compression molded pulverized products having particle sizes within a specified particle size range are selected from the charcoal compression molded pulverized products obtained in the pulverization process (S122). Then, only the selected charcoal compression molded pulverized products are used as the coagulant. Therefore, the sizing process (S123) is also a selection process for selecting charcoal compression molded pulverized products suitable for the coagulant.

[0076] As the specified particle size range (the particle size range of the charcoal compression molded pulverized product used as a coagulant for sintering raw materials), it is preferably set to 0.25 mm or more and less than 4.76 mm, for example. To set it to this particle size range, sieves with a sieve aperture (mesh size) of 4.76 mm and 0.25 mm are used for selection. That is, the charcoal compression molded pulverized products that pass through the sieve with a sieve aperture of 4.76 mm and are retained on the sieve with a sieve aperture of 0.25 mm are selected and used as the coagulant for sintering raw materials. In addition, the charcoal compression molded pulverized products less than 0.25 mm or exceeding 4.76 mm, that is, the charcoal compression molded pulverized products that pass through the sieve with a sieve aperture of 0.25 mm or are retained on the sieve with a sieve aperture of 4.76 mm, are separately recovered (refer to the dotted line in Figure 4 )

[0077] In addition, in the sizing process (S123), as implemented in the following examples, charcoal compression molded pulverized products having a specified particle size distribution can also be selected from the charcoal compression molded pulverized products obtained in the pulverization process (S122). Here, the so-called "particle size distribution" refers to the distribution of the proportion of the amount of particles (mass%) in each particle size range, and the "specified particle size distribution" is appropriately specified based on actual operations. As a method for selecting charcoal compression molded pulverized products having a specified particle size distribution (the particle size distribution of the charcoal compression molded pulverized product used as a coagulant for sintering raw materials), sieves with three or more different sieve apertures (mesh sizes) are used to classify into four or more particle size ranges, and the charcoal compression molded pulverized products in each particle size range are mixed in a proportion to form a specified particle size distribution and used as the coagulant.

[0078] The charcoal compression-formed pulverized material having a particle size within a specified particle size range or the charcoal compression-formed pulverized material having a specified particle size distribution selected in the granulation process is conveyed to the raw material tank 1 y (Refer to Figure 2 , Figure 11 ) and accumulated, and used as a coagulant for the sintering raw material. In this way, the pulverized material of the compression-formed product obtained via the pulverization process is preferably further subjected to a selection process of selecting a pulverized material having a particle size within a specified particle size range as the sintering raw material after the pulverization process. In addition, the pulverized material of the compression-formed product obtained via the pulverization process may also be further subjected to a selection process of selecting a pulverized material having a specified particle size distribution as the sintering raw material after the pulverization process. By using the granulated charcoal compression-formed pulverized material, the productivity of the sintered ore can be maximized. In addition, for the charcoal compression-formed pulverized material that is not selected and recycled, the use after recycling is not limited.

[0079] (The third manufacturing method)

[0080] For the third manufacturing method of the charcoal compression-formed pulverized material, use Figure 5 is used for the explanation. As shown in Figure 5 , in the third manufacturing method, a classification process (S133) is added to the process of the first manufacturing method. It should be noted that the charcoal compression-formed product obtaining stage (S131) and the pulverization process (S132) of the third manufacturing method are the same as the charcoal compression-formed product obtaining stage (S111) and the pulverization process (S112) of the first manufacturing method, respectively. Therefore, the repeated description of these processes is omitted, and the following is an explanation of the classification process (S133).

[0081] The classification process (S133) is an additional process implemented in cases where the particle size or particle size distribution of the charcoal compression-formed pulverized material produced in the pulverization process (S132) is not suitable for direct use as a coagulant for the sintering raw material, etc. In addition, in the granulation process (S123) of the second manufacturing method, the use after recycling of the charcoal compression-formed pulverized material that is not selected and recycled is not limited. In contrast, in the classification process (S133) of the third manufacturing method, a part of it is reused as a raw material for manufacturing the charcoal compression-formed pulverized material. By carrying out the reuse, the particle size range of the charcoal compression-formed pulverized material can be set to a more suitable range as the coagulant.

[0082] In the classification step (S133), the charcoal compression molded and pulverized product produced in the pulverization step (S132) is classified into at least the following three ranges based on a specified particle size range (the particle size range of the charcoal compression molded and pulverized product used as the agglomerating material for the sintering raw material) or a specified particle size distribution (the particle size distribution of the charcoal compression molded and pulverized product used as the agglomerating material for the sintering raw material) (hereinafter, the specified particle size range or the specified particle size distribution is also referred to as the particle size standard). The first is the charcoal compression molded and pulverized product selected as having a particle size that meets the particle size standard (hereinafter, also referred to as the first particle size pulverized product), the second is the charcoal compression molded and pulverized product having a particle size exceeding the upper limit value of the particle size standard (hereinafter, also referred to as the second particle size pulverized product), and the third is the charcoal compression molded and pulverized product having a particle size smaller than the lower limit value of the particle size standard (hereinafter, also referred to as the third particle size pulverized product). Therefore, the classification step (S133) is also a selection step for selecting the charcoal compression molded and pulverized product (the first particle size pulverized product) suitable for the agglomerating material.

[0083] The classification in the classification step (S133) can be carried out using a plurality of sieves with different screen apertures (mesh sizes) in the same manner as the above-mentioned sizing step (S123). The first particle size pulverized product is transported to and accumulated in the raw material tank 1 y (see Figure 2 、 Figure 11 ) and used as the agglomerating material for the sintering raw material. The second particle size pulverized product is transported to the pulverization step (S132) (see the dashed line in Figure 5 ) and becomes the raw material for producing the charcoal compression molded and pulverized product. By passing through the pulverization step (S132), it is pulverized to a particle size that meets the particle size standard. The third particle size pulverized product is separately recovered (see the dotted line in Figure 5 ). In this way, in the selection step, it is preferable to further select the pulverized product having a particle size larger than the upper limit value of the specified particle size range and reuse it as the raw material for the pulverized product of the compression molded product in the pulverization step.

[0084] For example, when the particle size standard is a specified particle size range, and the specified particle size range is 0.25 mm or more and less than 4.76 mm, for the charcoal compression molded crushed product having a particle size equal to or larger than the upper limit value (4.76 mm) of the particle size standard, in the crushing step (S132), it can be crushed again together with the obtained charcoal compression molded product. Thus, a crushed product having a particle size less than the upper limit value (4.76 mm) can be obtained. On the other hand, for the charcoal compression molded crushed product having a particle size less than the lower limit value (0.25 mm) of the particle size standard, the use after recovery is not limited. For example, it can be reused for manufacturing the charcoal compression molded product prepared in the charcoal compression molded product obtaining stage (S131). In addition, for example, when the particle size standard is a specified particle size distribution, the lower limit value of the particle size classification with the smallest particle size in the particle amount ratio (mass%) exceeding 0 mass% becomes the lower limit value of the particle size standard, and the upper limit value of the particle size classification with the largest particle size in the particle amount ratio (mass%) exceeding 0 mass% becomes the upper limit value of the particle size standard. In this way, it is also preferable that the crushed product of the compression molded product obtained via the crushing step, after the crushing step, via a selection step of selecting the crushed product having a particle size included in the specified particle size range as a sintering raw material, in the selection step, further selecting the crushed product having a particle size less than the lower limit value of the specified particle size range, and reusing it as a raw material for the compression molded product in the compression step. In addition, the crushed product of the compression molded product obtained via the crushing step can also, after the crushing step, via a selection step of selecting the crushed product having a specified particle size distribution as a sintering raw material, in the selection step, further selecting the crushed product having a particle size less than the lower limit value of the specified particle size distribution, and reusing it as a raw material for the compression molded product in the compression step.

[0085] (The 4th to 6th manufacturing methods)

[0086] In the above-described 1st to 3rd manufacturing methods, a method of manufacturing a charcoal compression molded crushed product using the charcoal compression molded product obtained in the charcoal compression molded product obtaining stages (S111, S121, S131) is shown. However, for the 4th to 6th manufacturing methods described later, it is a method of manufacturing a charcoal compression molded product from wood and using the manufactured charcoal compression molded product to manufacture a charcoal compression molded crushed product. For the 4th to 6th manufacturing methods, use Figures 6 - 9 is described.

[0087] Figures 6 - 8 are respectively diagrams for explaining the 4th to 6th manufacturing methods, Figure 9 is for explaining Figures 6 - 8 (the details of the manufacturing process (S200) of the charcoal compression molded product shown in the 4th to 6th manufacturing methods). As Figures 6 - 8As shown in the figure, the fourth to sixth manufacturing methods are different only in that the charcoal compression molding stage (S111) in the first to third manufacturing methods is replaced by the manufacturing process (S200) of the charcoal compression molding. The other processes (crushing processes S212, S222, S232, sizing process S223, classification process S233) are the same as the processes (crushing processes S112, S122, S132, sizing process S123, classification process S133) of the first to third manufacturing methods, respectively. Therefore, the repeated description of these processes is omitted. Hereinafter, the manufacturing process (S200) of the charcoal compression molding will be described.

[0088] (Manufacturing process of charcoal compression molding)

[0089] Hereinafter, for Figures 6 - 8 the manufacturing process (S200) of the charcoal compression molding shown in the figure, Figure 9 it will be described.

[0090] In the wood acquisition stage (S201), the wood used as the raw material is acquired. The type of the wood used as the raw material is not limited, and various types of wood can be used alone or in combination. In addition, the size of the wood (in other words, the size of the wood carbide) is not particularly limited. However, in order to easily compress the aggregate of multiple wood carbides in the subsequent compression process (S203), it is preferable to set the size of the wood to 30 mm or less. In this way, before carbonizing the wood, the wood can be crushed in advance to set the size of the wood to the desired size.

[0091] In the carbonization process (S202), the wood is carbonized to produce wood carbide. As the device for carbonizing the wood, for example, an externally fired rotary kiln, an internally fired rotary kiln, a fluidized bed reactor, a moving bed reactor (shaft furnace), etc. can be used. By carbonizing the wood, the volatile components remaining in the wood carbide can be further reduced compared to the volatile components remaining in the wood. In the present embodiment, it is preferable to carbonize the wood so that the volatile components of the wood carbide become 15% by mass or less. That is, preferably, as its manufacturing process, the compression molding has a carbonization process of carbonizing the wood to produce wood carbide, and a compression process of compressing and molding the aggregate of wood carbides by using an adhesive to produce the compression molding, and the volatile components of the wood carbide are 15% by mass or less. In the subsequent compression process (S203), since it is possible to mix the wood carbide and the adhesive to produce the charcoal compression molding, the volatile components of the charcoal compression molding may increase due to the volatile components in the added adhesive.

[0092] As described above, in order to set the volatile content of the charcoal compressed compact to 20% by mass or less, it is only necessary to reduce the volatile content of the wood carbide by the amount of increase in the volatile content caused by the addition of the binder. Since the amount of increase in the volatile content caused by the addition of the binder can be estimated to be 5% by mass, in order to set the volatile content of the charcoal compressed compact to 20% by mass or less, it is sufficient to set the volatile content of the wood carbide to 15% by mass or less.

[0093] Regarding the carbonization conditions of the wood, they include the carbonization temperature and the carbonization time, but it is only necessary to set the carbonization conditions such that the volatile content of the wood carbide becomes 15% by mass or less. For example, if the wood chips of cedar are carbonized at 800 °C for 1 hour, the volatile content of the wood carbide can be reduced to 4.8% by mass. Here, in terms of adjusting the volatile content of the wood carbide, it is preferable to appropriately set the carbonization temperature or / and the carbonization time.

[0094] In the compression step (S203), a charcoal compressed compact is manufactured by compressing the aggregate of the wood carbide produced in the carbonization step (S202). It is only necessary to compress the aggregate of the wood carbide to manufacture a charcoal compressed compact with an apparent density of 0.6 g / cm 3 or more, and the compression conditions, the forming method, the type of binder, the amount used, and the amount of water used can be appropriately determined. In addition, as described above, the apparent density of the charcoal compressed compact is more preferably 0.7 g / cm 3 or more, and further preferably 1.3 g / cm 3 or less.

[0095] When manufacturing the charcoal compressed compact, not only a compression molding machine but also an extrusion molding machine can be used. For example, a roll type (ring die type, flat die type), screw type extrusion molding machine can be used. As the forming method using a compression molding machine, a roll pressing method using a roll rotary compression molding machine, a tablet pressing method using a twin screw compression molding machine, etc. can also be adopted. The charcoal compressed compact can be formed into any shape (for example, granules (cylindrical shape), briquettes (pillow shape)).

[0096] In addition, when compressing an aggregate of wood carbide, it is preferable to use an adhesive or use water together with an adhesive. As the adhesive, for example, corn starch (starch), bentonite, coal tar, biomass tar, petroleum pitch, or cement can be used. When the wood carbide is set to 100% by mass, the amount of the added adhesive is preferably added at a blending ratio of 1% to 10% by mass (excluded from the total). The more the adhesive, the higher the strength, and thus the operation becomes better. On the other hand, if the blending ratio of the adhesive exceeds 10% by mass with respect to the wood carbide, the cost increases. In addition, for some adhesives (such as corn starch), in order to manufacture a firm molded product, it is also preferable to add additives such as alkalis and acids. After kneading the wood carbide with the adhesive and water, by supplying the kneaded product to a compression molding machine or an extrusion molding machine, a charcoal compression molded product can be manufactured. In addition, the wood carbide can be further pulverized (for example, the average particle size is pulverized to 1 mm or less) before kneading. Furthermore, a device (such as an extruder) that can also pulverize the wood carbide during kneading can be used.

[0097] The charcoal compression molded product manufactured in the compression step (S203) is transported to the pulverization steps (S112, S122, S132) as shown in Figure 9 and Figures 6 - 8 . By using an adhesive to manufacture the charcoal compression molded product in the compression step (S203), in the downstream steps, that is, the pulverization steps (S112, S122, S132), it is possible to suppress the charcoal compression molded product from being excessively pulverized. Then, when the charcoal compression molded product is pulverized, it is easy to obtain a charcoal compression molded pulverized product having a desired particle size due to the binding force of the adhesive.

[0098] (The seventh manufacturing method)

[0099] The seventh manufacturing method for the charcoal compression molded pulverized product will be described using Figure 10 . As shown in Figure 10As shown in , the seventh manufacturing method is a modified example of the sixth manufacturing method. In the seventh manufacturing method, it is different from the sixth manufacturing method only in the following point: the charcoal compression-formed crushed material (third-sized crushed material) smaller than the lower limit value of the particle size standard recovered in the classification step (S133) is transported to the compression step (S203) of the manufacturing process (S200) of the charcoal compression-formed product as indicated by the dashed line. The third-sized crushed material is returned to the above compression step (S203) and reused as a raw material for manufacturing the charcoal compression-formed product. By adding a binder or the like to the third-sized crushed material with a small particle size and the wood carbide transported through the carbonization step S202 and compressing and forming them, a charcoal compression-formed product that meets the particle size standard can be manufactured.

[0100] According to this embodiment, the charcoal compression-formed crushed material obtained by crushing the charcoal compression-formed product is used as a part of the coagulant. Since the wood carbide obtained by only carbonizing the wood is a porous body, it has excessive combustibility. If this wood carbide is directly used as a coagulant to manufacture sintered ore, as shown in the examples described later, the yield and productivity of the sintered ore will decrease. On the other hand, the compression-formed product (charcoal compression-formed product) obtained by compressing the aggregate of wood carbide can reduce the number and / or volume of pores present in the wood carbide due to compression, so excessive combustibility can be suppressed. Moreover, by suppressing excessive combustibility, as shown in the examples described later, a decrease in the yield and productivity of the sintered ore can be suppressed and increased. In addition, compared with the wood carbide, the charcoal compression-formed product has a greater strength and bulk density, so pulverization can be suppressed and a large amount of carbide can be transported at one time.

[0101] 《Second Embodiment》

[0102] Other embodiments of the present invention will be described below. In this embodiment, at least any one of the charcoal compression-formed crushed material, pulverized coke, and anthracite (pulverized coke and / or anthracite) in the sintering raw material is added in the latter half of the granulation process. Here, the so-called "latter half of the granulation process" refers to the latter time domain when the "total granulation time" described later is divided into the front and the back. Figure 11It is a schematic diagram showing an example of the sintering equipment 102 used in the method for manufacturing sintered ore according to the present embodiment. The sintering equipment 102 is different from the above-mentioned sintering equipments 100 and 101 in that the total amount of only the binder in the sintering raw materials is added (post-added) in the latter half of the granulation process. Hereinafter, only the differences from the sintering equipments 100 and 101 will be described, and repeated descriptions will be omitted. It should be noted that the method for manufacturing the charcoal compression molded and pulverized product used as the binder in the sintering raw materials in the second embodiment is the same as the method for manufacturing the charcoal compression molded and pulverized product in the first embodiment (the above-mentioned first to seventh manufacturing methods), so repeated descriptions will be omitted.

[0103] As Figure 11 shown in, the sintering equipment 102 has a raw material tank group 1c for accumulating sintering raw materials other than the binder, a raw material tank group 1d for accumulating the binder, and a mixer 7 for mixing the binder. In the raw material tanks 11, 12, and 1 y of the raw material tank group 1d, pulverized coke A1, anthracite A2, and charcoal compression molded and pulverized product A3 are respectively accumulated. After the pulverized coke A1, anthracite A2, and charcoal compression molded and pulverized product A3 accumulated in the raw material tanks 11, 12, and 1 y of the raw material tank group 1d are cut out in a prescribed amount based on the mixing ratio and mixed, they are mixed by the mixer 7 to become a homogenized mixture (hereinafter, also referred to as a binder mixture).

[0104] The addition of the binder in the latter half of the granulation process (post-addition of the binder) is carried out as follows. First, the sintering raw materials other than the binder are cut out from the respective raw material tanks (13 to 1 X ) of the raw material tank group 1c based on a prescribed mixing ratio and first put into the granulator for mixing. After mixing the sintering raw materials other than the binder, further humidification is carried out and granulation is started (hereinafter, the substance obtained by granulating the sintering raw materials other than the binder is referred to as a pre-granulated product). After starting granulation and after a certain period of time (during the granulation process), the above-mentioned binder mixture is put into the granulator to manufacture a compound raw material granulated product. By adding the binder mixture at an appropriate timing later, the binder is externally coated on the pre-granulated product (that is, it is not included in the pre-granulated product) and adheres to the surface layer of the pre-granulated product or exists as unattached independent particles. It is preferable to add only the binder (charcoal compression molded and pulverized product and pulverized coke and / or anthracite) in the latter half of the granulation process (the time domain in the latter half of the total granulation time in the granulation process).

[0105] Specifically, as Figure 11As shown in [Fig. 0], a cylindrical hybrid granulation device 2 in the form of piston flow that faces the downstream side and has a central axis inclined downward is used, and it is set to a state where a small conveyor is inserted from the downstream outlet into a specified position inside the hybrid granulation device 2. If sintering raw materials other than the binder (hereinafter also referred to as pre-addition sintering raw materials) are introduced from the upstream inlet, the introduced pre-addition sintering raw materials are mixed and then water is added, and they move toward the downstream side while granulating. The added binder mixture is loaded from the downstream outlet of the hybrid granulation device 2 into the conveyor and conveyed into the upstream side inside. The conveyed binder mixture is added to the pre-granulated material that moves while granulating from the upstream side inside the granulator at a specified position. Then, all the sintering raw materials (pre-granulated material and binder mixture) are granulated and discharged as compound raw material granules from the downstream outlet. It should be noted that it is not limited to the above configuration, as long as the binder (pulverized coke A1, anthracite A2, and charcoal compression molded and pulverized product A3) mixed in a specified mixing ratio is added at a specified timing during the granulation process.

[0106] Preferably, the granulation time of the pre-addition sintering raw materials until the addition of the binder mixture is set to 75% to 96% relative to the total granulation time of the sintering raw materials, that is, the addition timing is set to a time within the range of 75% to 96% of the total granulation time of the sintering raw materials in the granulation process. In addition, it is more preferable to set the addition timing to a time within the range of 80% to 96% of the total granulation time of the sintering raw materials in the granulation process. For example, when the total granulation time is 240 seconds, the compound raw materials (pre-addition sintering raw materials) other than the binder mixture can be granulated for 225 seconds, and then the binder mixture can be added and granulated for 15 seconds. If the addition is earlier than 75% of the total granulation time, it is impossible to sufficiently prevent the binder from being encapsulated in the granules. In addition, if the addition is later than 96% of the total granulation time, the granulation treatment of the binder becomes insufficient. Here, the so-called "total granulation time" refers to the time for granulating the sintering raw materials and does not include the time for simple mixing (mixing time) from when the sintering raw materials are introduced into the granulator until water is added. The drum mixer mainly used as a granulation device in the sintered ore manufacturing equipment is an isokinetic piston flow type. Therefore, the addition position can be implemented by making the above granulation time correspond to the distance in the machine length direction of the drum mixer.

[0107] As described above, when the binder mixture is post-added, the binder mixture is externally coated on the granulated product of the sintering raw material, so that the reaction with oxygen in the atmosphere supplied to the raw material filling layer can be promoted. In addition, sufficient heat supply is received from the heated atmosphere to carry out combustion. As a result, the combustion rate of the binder is increased, and thus the productivity is further improved. If the binder is encapsulated by co-granulation, it is difficult to receive the supply of oxygen and heat required for combustion. In addition, by using a granulated product of a mixed raw material externally coated with a highly combustible charcoal compressed and crushed product and a second carbon material for sintering with low combustibility (pulverized coke or / and anthracite), the high-temperature holding time can be ensured, and the yield and productivity can be improved.

[0108] Example

[0109] The following describes the tests related to the present invention described above and each configuration applicable to the present invention.

[0110] 《Example 1》

[0111] In Example 1, wood carbides WC1 and WC2 were produced from wood. Further, compressed products (charcoal compressed products) CM1, CM3, and CM4 were produced from wood carbide WC1, and a compressed product (charcoal compressed product) CM2 was produced from wood carbide WC2. The apparent density and BET specific surface area of each were measured (refer to Table 2 described later).

[0112] (Method for producing wood carbides WC1 and WC2)

[0113] After the wood was crushed to a size of 30 mm or less, wood carbides WC1 and WC2 with different volatile components were produced by adjusting the temperature of dry distillation (thermal decomposition) of the crushed material using a rotary kiln. Specifically, the dry distillation temperature (highest temperature in the furnace) was set to 700 °C, and the dry distillation time was set to 1 hour.

[0114] (Method for producing compressed products CM1, CM2, CM3, and CM4)

[0115] Next, after crushing the wood carbide WC1 to a size of 5 mm or less, 0.4 L / kg - crushed material of water and a binder are added to the crushed material, and kneading is carried out while heating to 80 °C using a twin - screw extruder. By extruding the kneaded material using an extrusion molding machine with an annular die pattern, cylindrical (diameter 8 or 20 mm, length 10 mm to 30 mm) compression - molded articles (granules) CM1, CM3, and CM4 are manufactured. CM1, CM3, and CM4 are made into compression - molded articles with different apparent densities by changing the throughput and die conditions (die diameter and length, extrusion pressure, etc.). Similarly, after crushing the wood carbide WC2 to a size of 5 mm or less, 0.4 L / kg - crushed material of water and a binder are added to the crushed material and kneaded, and a cylindrical (diameter 20 mm, length 10 mm to 30 mm) compression - molded article (granule) CM2 is manufactured by extruding the kneaded material. As the binder when manufacturing the compression - molded articles CM1, CM2, CM3, and CM4, corn starch (addition amount: 8 mass%) is used. It should be noted that this addition amount represents the blending ratio (external number) when the wood carbide is set to 100 mass%.

[0116] (Determination)

[0117] For each of the above - mentioned wood carbides WC1, WC2 and compression - molded articles CM1, CM2, CM3, and CM4, proximate analysis and elemental analysis are carried out, and the apparent density and BET specific surface area are measured. In addition, for pulverized coke used in the production of sinter, proximate analysis and elemental analysis are also carried out, and the apparent density and BET specific surface area are measured.

[0118] (Proximate analysis and elemental analysis)

[0119] In proximate analysis, in accordance with the provisions of JIS M8812:2006, the contents [mass% - dry] of ash, volatile components, and fixed carbon are measured. In elemental analysis, in accordance with the provisions of JIS M8813:2004, the contents [mass% - dry] of carbon (C), hydrogen (H), nitrogen (N), and total sulfur (T(Total) - S) are measured.

[0120] (Method for measuring apparent density)

[0121] Using a commercially available density measuring device (manufactured by Micromeritics / GeoPyc1365), the apparent densities of wood carbide WC1, WC2, compression molded products CM1, CM2, CM3, CM4, and pulverized coke were measured respectively. For the measurement samples of wood carbide WC1 and WC2, they were adjusted by sieving to have a particle size in the range of 3 mm or more and less than 5 mm. For the measurement samples of compression molded products CM1, CM2, CM3, and CM4, for compression molded products CM3 and CM4, the molded products with the molded size (diameter of 8 mm, length of 10 mm to 30 mm) were used, and for compression molded products CM1 and CM2, the molded products with the molded size (diameter of 20 mm, length of 10 mm to 30 mm) were used. For the measurement sample of pulverized coke, pulverized coke having the following particle size distribution (Table 5 below) was used. In addition, all the measurement samples were previously dried (heated at 105 °C for 24 hours) using a dryer (manufactured by Yamato Scientific / inert gas furnace DN611I).

[0122] The apparent density was measured by the above-mentioned bead volume displacement method. The measurement sample was added to the layer of DryFlow (quasi-fluid), and after measuring the volume (apparent volume) of the pores and voids containing the measurement sample, the apparent density was calculated from the apparent volume and the mass of the measurement sample.

[0123] (Method for measuring BET specific surface area)

[0124] The BET specific surface areas of wood carbide WC1, WC2, compression molded products CM1, CM2, CM3, CM4, and pulverized coke were measured respectively by the gas adsorption method using N2 gas and the gas adsorption method using CO2 gas.

[0125] In the gas adsorption method using N2 gas, as a pretreatment, using a sample pretreatment device (manufactured by Micromeritics / VacPrep061), for wood carbide WC1, WC2, compression molded products CM1, CM2, CM3, CM4, and pulverized coke, while evacuating to vacuum, heating was carried out at 150 °C for 4 hours to prepare measurement samples with a particle size of 0.25 mm to 0.5 mm. Then, using a volumetric adsorption amount measuring device (manufactured by Micromeritics / TriStarII), by adsorbing N2 gas (adsorbed gas) at -196 °C (liquid nitrogen cooling) for the prepared measurement samples, the adsorption amount Q of N2 gas in the range of relative pressure (ratio of measurement pressure P to saturated vapor pressure P0, P / P0) of 0.02 to 0.1 (0.01 scale) was measured. Based on this adsorption amount Q, the BET specific surface area was calculated as described later.

[0126] In the gas adsorption method using CO2 gas, as a pretreatment, a sample pretreatment device (manufactured by Micromeritics / VacPrep061) was used. For wood carbides WC1, WC2, compression molded products CM1, CM2, CM3, CM4, and pulverized coke, while performing vacuum evacuation, heating was carried out at 150 °C for 4 hours to prepare measurement samples with a particle size of 0.25 mm to 0.5 mm. Then, a volumetric adsorption amount measurement device (manufactured by Micromeritics / TriStarII) was used to measure the adsorption amount Q of CO2 gas in the range of relative pressure (the ratio P / P0 of the measurement pressure P to the saturated vapor pressure P0) of 0.012 to 0.030 (0.002 scale) by adsorbing CO2 gas (adsorption gas) at 0 °C (ice water cooling) for the prepared measurement samples. Based on this adsorption amount Q, the BET specific surface area was calculated as described later.

[0127] The BET specific surface area S [m 2 / g] is calculated by the following formulas (1) and (2) according to JIS Z8830:2013.

[0128]

[0129] S = s × Q m × K A (2)

[0130] In the above formula (1), P is the measurement pressure [Pa], P0 is the saturated vapor pressure [Pa] of the adsorption gas (N2 gas or CO2 gas), and "P / P0" represents the relative pressure [-] of the adsorption gas. Q is the adsorption amount [mol / g] of the adsorption gas measured by the above gas adsorption method, and Q m is the monolayer adsorption amount [mol / g], and C is the BET parameter [-].

[0131] In the above formula (2), S is the BET specific surface area [m 2 / g], s is the molecular cross-sectional area [m 2 , Q m is the monolayer adsorption amount [mol / g], and K A is the Avogadro constant [mol -1 .

[0132] (Measurement results)

[0133] In Table 2 below, the measurement results of proximate analysis, ultimate analysis, apparent density, and BET specific surface area are shown for wood carbides WC1, WC2, compression molded products CM1, CM2, CM3, CM4, and pulverized coke, respectively.

[0134] [Table 2]

[0135]

[0136] (Volatile components)

[0137] In the above Table 1, the volatile components of the compression molded articles CM1, CM3, and CM4 (11.4, 11.3, 10.0 mass%) are higher than those of the wood carbide WC1 (3.9 mass%). However, the difference in the volatile components is due to the volatile components of the binder (corn starch) used during the molding of the pulverized wood carbide WC1. In addition, the volatile components of the compression molded article CM2 (19.7 mass%) are higher than those of the wood carbide WC2 (14.5 mass%). However, the difference in the volatile components is due to the volatile components of the binder (corn starch) used during the molding of the pulverized wood carbide WC2.

[0138] (Apparent density and BET specific surface area)

[0139] The apparent densities of the compression molded articles CM1, CM3, and CM4 (0.82, 0.62, 0.55 g / cm 3 ) are significantly higher than that of the wood carbide WC1 (0.21 g / cm 3 ). It is considered that this is because the wood carbide WC1 is compressed by the extrusion molding performed during the manufacture of the compression molded articles CM1, CM3, and CM4, resulting in a decrease in the number of pores and a reduction in the size of the pores present in the wood carbide WC1. In addition, the BET specific surface areas of the compression molded articles CM1, CM3, and CM4 are lower than those of the wood carbide WC1, especially the reduction in the BET specific surface area obtained by the gas adsorption method (N2) is large.

[0140] Similarly, the apparent density of the compression molded article CM2 (0.90 g / cm 3 ) is significantly higher than that of the wood carbide WC2 (0.25 g / cm 3 ). It is considered that this is because the wood carbide WC2 is compressed by the extrusion molding performed during the manufacture of the compression molded article CM2, resulting in a decrease in the number of pores and a reduction in the size of the pores present in the wood carbide WC2. In addition, the BET specific surface area of the compression molded article CM2 is lower than that of the wood carbide WC2, especially the reduction in the BET specific surface area obtained by the gas adsorption method (N2) is large.

[0141] As described above, the reason why the reduction in the BET specific surface area obtained by the gas adsorption method (N2) is greater than that obtained by the gas adsorption method (O2) is considered to be as follows: In the gas adsorption method (N2), large pores (mesopores to macropores other than micropores) become the adsorption targets, so mainly large pores are reduced by the compression molding.

[0142] 《Example 2》

[0143] (Test level)

[0144] In Example 2, sintering tests (4 tests) were carried out using the wood carbides WC1 and WC2, compression molded products CM1, CM2, CM3, and CM4, and pulverized coke shown in Example 1 as coagulants, and the combustion rate, yield, and productivity were evaluated. It should be noted that in this example, a test example in which only pulverized coke was used in the second sintering carbon material was shown, but in the second sintering carbon material, only anthracite or a mixture of anthracite and pulverized coke can also be used, and the same test results were obtained in the test examples using only anthracite or a mixture.

[0145] (Sintering test)

[0146] The sintering test was verified using a method commonly known as the sintering pot test. The sintering pot test is the following test: A mixed raw material containing a coagulant is placed in a container (sintering pot) of a specified size, and sintering is carried out by igniting from above and sucking from below. The sintering pot test is a test that does not have the movement of the raw material filling layer using a trolley like the DL type sintering machine, but can simulate the sintering using the DL type sintering machine. First, the raw materials used in the test and the test method will be described in turn, and then the test results will be described.

[0147] (Sintering raw materials)

[0148] Table 3 shows the mixing ratio [mass%] of each sintering raw material (except for the coagulant) for the mixed raw materials used in the sintering test.

[0149] [Table 3]

[0150]

[0151] As shown in Table 3, the proportions of the new raw materials (iron ores A to F, limestone, quicklime, and serpentine) and the return ore were set to be constant in all test examples. Iron ores A to F are iron ores with different brands (origins). As auxiliary raw materials, limestone, quicklime, and serpentine (MgO source) were used. The new raw materials were set to 100 mass%, and the mixing ratio of the return ore was set to 15.0 mass% in terms of the number other than the return ore.

[0152] Table 4 shows the test conditions (type of coagulant, mixing ratio [mass%], etc.) related to the coagulant in the mixed raw materials used in the sintering test. As shown in the upper part of Table 4, as the coagulant, wood carbide WC1 and pulverized coke were used in Comparative Example 1, wood carbide WC2 and pulverized coke were used in Comparative Example 2, compressed product CM4 and pulverized coke were used in Comparative Example 3, compressed product CM1 and pulverized coke were used in Examples 1, 4 to 6, compressed product CM2 and pulverized coke were used in Example 2, and compressed product CM3 and pulverized coke were used in Example 3. It should be noted that in the following description, as shown in Table 4, the compressed products CM1, CM2, CM3, CM4 and the wood carbides WC1, WC2 are also referred to as the first carbon materials for sintering, and the pulverized coke is also referred to as the second carbon material for sintering.

[0153] The mixing ratios of the coagulants (the first carbon materials for sintering and the second carbon materials for sintering) in each test example (Examples 1 to 6 and Comparative Examples 1 to 3 above) are specified based on the fixed carbon amount of the mixing standard (when 4.5 mass% of pulverized coke is mixed in terms of external number relative to 100 mass% of the new raw material). Specifically, based on the fixed carbon component mass ratio of the first carbon materials for sintering and the second carbon materials for sintering ("mass ratio of fixed carbon component" in Table 4) and the fixed carbon of the first carbon materials for sintering and the second carbon materials for sintering ("fixed carbon" in the proximate analysis in the upper part of Table 2), the fixed carbon amount (carbon component) of all the coagulants (the first carbon materials for sintering and the second carbon materials for sintering) contained in the mixed raw materials is adjusted so as to be constant in all the test examples (the same as the fixed carbon amount of the mixing standard). The mixing ratios of each coagulant (the first carbon materials for sintering and the second carbon materials for sintering) relative to the new raw material are shown in "(※) Mixing ratio of coagulant relative to new raw material" in Table 4.

[0154] [Table 4]

[0155]

[0156] The first carbon materials for sintering shown in Table 4 are pulverized products (pulverized products of wood carbides WC1, WC2, and pulverized products of charcoal compressed products CM1, CM2, CM3, CM4) obtained by pulverizing the wood carbides WC1, WC2, compressed products CM1, CM2, CM3, CM4 manufactured in Example 1 using a Best Fine Breaker (manufactured by Ogawa Sampling Co., Ltd. / 5001-1A) and a pan mill (manufactured by Ogawa Sampling Co., Ltd. / roller diameter: 450 mm, pan diameter: 910 mm, pan rotation speed: 13 rpm).

[0157] The table numbers (Table 5, Table 6, or Table 7) shown in the column of "Particle Size of Binder Material" in Table 4 are tables representing the particle size distributions of the binder materials (the first carbon material for sintering and the second carbon material for sintering) used in each test. In addition, the particle size classification shown in Tables 5 to 7 is the same as that in Table 1 above, where the proportion of each particle size is expressed as a mass ratio [mass%]. It should be noted that the particle size classification of "+10.0" in Table 7 refers to the oversize when sieving with a sieve having a mesh size of 10.0 mm. All the binder materials (the first carbon material for sintering and the second carbon material for sintering) are sized using sieves according to JIS Z8801-1:2019 so as to have the particle size distributions shown in the respective columns of Table 4 (Table 5, Table 6, or Table 7), and then used as sintering raw materials. As shown in Table 4, in Example 4 and Example 5, the particle size distribution of the first carbon material for sintering (compressed molded product CM1) was changed, and the influence of the particle size distribution was also studied. Specifically, Example 4 and Example 5 are the cases where the particle sizes of 4.76 mm or more ("10.0 to 4.76") and less than 0.25 mm ("-0.25") in the particle size distribution of Table 5 are excluded (Table 6) and the case where some particle sizes of 10 mm or more ("+10.0") not present in the particle size distribution of Table 5 are included (Table 7), respectively. It should be noted that if the particle size distributions of Table 5 and Table 6 are expressed in terms of particle size ranges, they correspond to "less than 10 mm and more than 0 mm" and "less than 4.76 mm and more than 0.25 mm", respectively.

[0158] [Table 5]

[0159]

[0160] [Table 6]

[0161]

[0162] [Table 7]

[0163]

[0164] (Granulation method)

[0165] As the granulator, an intermittent drum mixer with a cylindrical shape having a diameter of 1 m and a length of 0.4 m was used. For each of the above tests (except Example 6), the coagulants (the first carbon material for sintering and the second carbon material for sintering) were put into the granulator during the granulation process. Specifically, the total amount of sintering raw materials (iron ores A to F, limestone, quicklime, serpentine, and return ore) except for the coagulants (the first carbon material for sintering and the second carbon material for sintering) was put into the drum mixer (rotation speed: 23 rpm) and mixed for 1 minute. Then, water was added (humidity adjustment) to the drum mixer so that the target moisture value became 7.5% by mass (outside number) with respect to the mass of all the sintering raw materials (including coagulants and return ore), and further mixed for 3 minutes and 30 seconds (granulation treatment), and the drum mixer was temporarily stopped. Here, the coagulants (a mixture of the first carbon material for sintering and the second carbon material for sintering) were put into the drum mixer (post-addition), and then further mixed for 30 seconds (granulation treatment). In addition, for the case where the compression molded product CM1 was used, a test was also conducted in which the coagulants (the first carbon material for sintering and the second carbon material for sintering) were put into the drum mixer simultaneously with the sintering raw materials (pre-addition / Example 6). That is, in Example 6, all the sintering raw materials including the coagulants were put into the drum mixer simultaneously.

[0166] (Sintering method)

[0167] The granulated compound raw materials (granulated compound raw material products) after the granulation treatment were charged into a sintering pot. The sintering pot used in this test was a cylindrical pot with a diameter of 300 mm and a height of 600 mm. After the granulated compound raw material products were charged, the surface of the raw material packed layer (the layer formed by charging the granulated compound raw material products) was ignited for 90 seconds (heat: 165 MJ / ton of compound raw materials) using an ignition device. In addition, the suction negative pressure during sintering was adjusted by the valve opening of the suction side of the blower so as to be constant at 15.0 kPa (1530 mmHg2O) based on the measured value under the pot.

[0168] Temperature measurement using a thermocouple was also carried out together with the pressure under the pot. During sintering, if the combustion zone reaches the lowermost part of the raw material packed layer, the exhaust gas temperature under the pot starts to rise, soon reaches a peak value, and then decreases due to the end of the combustion of the coagulants in the raw material packed layer. The downward suction using the blower was stopped 3 minutes after the moment when the exhaust gas temperature reached the peak value (highest temperature). It should be noted that the sintering time t s [min] (refer to the following formula (4)) was set as the time from the ignition start moment to the moment when the exhaust gas temperature reached the peak value. Using the above sintering pot test, for each test example, the combustion progress speed (FFS), the yield, and the productivity were calculated.

[0169] (Sintering progress speed)

[0170] The combustion progress speed (FFS (flame front descent speed); Flame Front Speed) [mm / min] is the value obtained by dividing the layer thickness of the raw material filling layer when filling the raw materials for sintering in the sintering pot (the thickness in the height direction of the sintering pot) by the time from the moment of ignition of the raw material filling layer to the moment when the combustion zone reaches the lowermost part of the raw material filling layer (referred to as the arrival moment). In this embodiment, as the arrival moment, the moment of reaching the point where the exhaust temperature shows the highest temperature (sintering end point, BTP; Burn Through Point) is set.

[0171] (Yield rate)

[0172] The yield rate refers to the mass ratio of the sintered ore products to the sintered lumps (excluding the bottom layer ore). In this embodiment, after dropping the sintered lumps obtained after sintering from a height of 2 m five times, the sintered ore with a particle size of +5 mm (more than 5 mm) excluding the bottom layer ore is recovered as the product and the mass is determined as the product mass. Then, the value obtained by dividing the product mass by the mass of the sintered lumps excluding the bottom layer ore is defined as the yield rate. Specifically, based on the following formula (3), the yield rate R [mass%] is calculated. Product mass M s is the mass of the sintered ore on the sieve after screening with a sieve having a mesh size of 5 mm (product mass). In addition, the mass M t is the mass of the sintered lumps excluding the bottom layer ore.

[0173]

[0174] (Productivity)

[0175] The productivity refers to the productivity of the sintered ore [t / d (day) / m 2 . In this embodiment, as shown in the following formula (4), the productivity Pr [t / d / m 2 is calculated by dividing the above-mentioned product mass Ms [t] by the effective firing area (bottom area of the pot) S [m 2 and the sintering time t s [min].

[0176]

[0177] (Test results)

[0178] Table 8 shows the test results (combustion progress speed (FFS), yield rate, and productivity) of the above-mentioned various sintering pot tests.

[0179] [Table 8]

[0180]

[0181] In this embodiment, as described above, the first carbon material for sintering (wood carbide WC1, WC2, compression molded products CM1, CM2, CM3, CM4) is crushed and sized. In all test examples except for Examples 4 and 5, the first carbon material for sintering and the second carbon material for sintering are set to have the same particle size distribution (refer to Table 4) for use. Since the apparent density of the first carbon material for sintering hardly changes before and after crushing, the apparent density before crushing in Table 2 is shown in the column of the apparent density in Table 8. As shown in Table 4 and Table 8 above, when using the compression molded product CM1 (crushed product) as the first carbon material for sintering to produce sinter (Example 1), compared with using the wood carbide WC1 (crushed product) as the first carbon material for sintering to produce sinter (Comparative Example 1), the combustion progress rate (FFS) is suppressed, and the yield and productivity are improved. In addition, when using the compression molded product CM2 (crushed product) as the first carbon material for sintering to produce sinter (Example 2), compared with using the wood carbide WC2 (crushed product) as the first carbon material for sintering to produce sinter (Comparative Example 2), the combustion progress rate (FFS) is suppressed, and the yield and productivity are improved.

[0182] When using the compression molded product CM1 (crushed product) with a particle size distribution different from that of Example 1 as the first carbon material for sintering to produce sinter (Examples 4 and 5), compared with using the wood carbide WC1 (crushed product) as the first carbon material for sintering to produce sinter (Comparative Example 1), the combustion progress rate (FFS) is also suppressed, and the yield and productivity are improved. In addition, different from Example 1, when using the compression molded product CM1 (crushed product) that has undergone normal granulation treatment (pre-addition) as the first carbon material for sintering to produce sinter (Example 6), compared with using the wood carbide WC1 (crushed product) as the first carbon material for sintering to produce sinter (Comparative Example 1), the combustion progress rate (FFS) is also suppressed, and the yield and productivity are improved.

[0183] When using the compression molded product CM3 (crushed product) with an apparent density of 0.62 g / cm 3 as the first carbon material for sintering to produce sinter (Example 3), compared with Example 1 (0.82 g / cm 3 ) and Example 2 (0.90 g / cm 3 ), the combustion progress rate (FFS) is somewhat increased, and the values of the yield and productivity are decreased. However, compared with using the wood carbide WC1 (crushed product) as the first carbon material for sintering to produce sinter (Comparative Example 1), the combustion progress rate (FFS) is suppressed, and the yield and productivity are improved. In addition, when using the compression molded product with an apparent density of 0.55 g / cm3 In the case of manufacturing sintered ore using the compressed molded product CM4 (crushed product) as the first carbon material for sintering (Comparative Example 3), although the combustion progress rate (FFS) was suppressed compared to Comparative Example 1, it was not sufficient compared to Example 1. Therefore, the yield and productivity did not increase much.

[0184] As described above, the preferred embodiments and examples of the present invention have been described in detail with reference to the accompanying drawings. However, the present invention is not limited to the above examples. For those having ordinary knowledge in the technical field to which the present invention pertains, various modification examples or correction examples can obviously be conceived within the scope of the technical idea described in the claims. Of course, they are also understood to belong to the technical scope of the present invention.

[0185] Explanation of symbols

[0186] 1, 1a, 1c, 1d: raw material tank group, 2: mixing granulation device, 3: DL type sintering machine, 4: ignition furnace, 5: trolley forward direction, 6: downward suction, 7: mixer, 10: raw material filling layer, 10A: combustion zone, 10x: inclined surface, 11: sintered block, 20: inclined flat chute type charging device, 21: compound raw material buffer hopper, 22: inclined flat chute, 100, 101, 102: sintering equipment, S111, S121, S131: charcoal compressed molded product obtaining stage, S112, S122, S132, S212, S222, S232: crushing process, S123, S223: sizing process (sorting process), S133, S233: classification process (sorting process), S200: manufacturing process of charcoal compressed molded product, S201: wood obtaining stage, S202: carbonization process, S203: compression process

Claims

1. A method for manufacturing sintered ore, which includes, in the sintering raw materials, a crushed product of a compression molded product obtained through a crushing process, and at least one of pulverized coke and anthracite. In the crushing process, the compression molded product obtained by compressing and molding an aggregate of wood carbide is crushed. The apparent density of the compression molded article is 0.6 g / cm 3 or more.

2. The method for manufacturing sintered ore according to claim 1, wherein, The crushed product of the compression molded product and at least one of the pulverized coke and anthracite in the sintering raw materials are added in the latter half of the granulation process.

3. The method for manufacturing sintered ore according to claim 1 or claim 2, wherein, The crushed product of the compression molded product obtained through the crushing process is further subjected to a selection process of selecting, as the sintering raw materials, the crushed products having particle sizes included in a specified particle size range after the crushing process.

4. The method for manufacturing sintered ore according to claim 3, wherein, The specified particle size range is more than 0 mm and less than 10 mm.

5. The method for manufacturing sintered ore according to claim 1 or claim 2, wherein, The volatile component of the compression molded product is 20% by mass or less.

6. The method for manufacturing sintered ore according to claim 1 or claim 2, wherein, As its manufacturing process, the compression molded product has the following processes: A carbonization process of carbonizing wood to manufacture the wood carbide; And A compression process of manufacturing the compression molded product by compressing and molding the aggregate of the wood carbide by using an adhesive. The volatile component of the wood carbide is 15% by mass or less.

7. The method for manufacturing sintered ore according to claim 3, wherein, in the selection process, the crushed products having particle sizes greater than the upper limit value of the specified particle size range are further selected and reused as raw materials for the crushed product of the compression molded product in the crushing process.

8. The method for manufacturing sintered ore according to claim 6, wherein, The crushed product of the compression molded product obtained through the crushing process is, after the crushing process, subjected to a selection process of selecting, as the sintering raw materials, the crushed products having particle sizes included in a specified particle size range. In the selection process, the crushed products having particle sizes smaller than the lower limit value of the specified particle size range are further selected and reused as raw materials for the compression molded product in the compression process.

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