Coke manufacturing method

Abstract

Provided is a coke production method with which it is possible to suppress, with a simple procedure, coke strength deterioration due to the use of biomass, while said biomass is contained in blended coal serving as a coke raw material. In one aspect, the present invention provides a coke production method including a step for preparing blended coal containing coal and torrefied woody biomass, and a step for coking said blended coal, wherein: (1) the torrefied woody biomass has a volatile content of 25 mass% or less and has particle sizes such that the mass percentage of particles in the range of 0.10-mm plus sieve and 0.60-mm minus sieve is equal to or greater than 60 mass% according to sieving in conformity to the particle-size testing method defined in JIS M8801:2008; or (2) the torrefied woody biomass has a volatile content that is greater than 25 mass% and equal to or less than 40 mass% and has particle sizes such that the mass percentage of particles in the range of 0.10-mm plus sieve and 0.30-mm minus sieve is equal to or greater than 60 mass% according to said sieving.

Description

[Technical Field]

[0001] The present invention relates to a method for producing coke using a coal blend containing semi-carbonized woody biomass. [Background technology]

[0002] Due to growing interest in environmental issues, studies have been conducted on the production of coke using blended coal obtained by adding biomass, a renewable resource, to coal. Because biomass has low energy efficiency and poor handling in its original state, biomass with an increased carbon content through heat treatment, such as semi-carbonized biomass, has been provided, and the use of semi-carbonized biomass in coke production has also been studied.

[0003] Patent Document 1 describes a method for producing coke by heating and carbonizing raw coal, characterized in that woody waste that has been heat-treated in advance is charged into a coke oven together with the raw coal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-307683 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology described in Patent Document 1 aims to provide a coke production method that uses raw coal and woody waste that has been semi-carbonized in advance by heat treatment, allowing for the simultaneous processing of large amounts of woody waste without causing deterioration in the quality of the coke. Patent Document 1 describes that semi-carbonization is a process that reduces the volatile content of the woody waste to a certain extent, rather than completely carbonizing the woody waste. Patent Document 1 also exemplifies the properties of the woody waste used, citing a volatile content of 45 to 65% by mass as the woody waste after heat treatment. However, woody waste with such a high volatile content shrinks significantly during coking, which is likely to cause defects due to peeling between the coking portion derived from the raw coal and the woody waste, thereby reducing the strength of the coke. Patent Document 1 does not address means for reducing such disadvantages during coking.

[0006] An object of one aspect of the present invention is to solve the above-mentioned problems and to provide a coke production method that can incorporate biomass into a coal blend, which is a raw material for coke, while suppressing a decrease in coke strength caused by the use of the biomass in a simple procedure. [Means for solving the problem]

[0007] The gist of the present invention is as follows. [1] A method for producing coke, comprising: Preparing a blended coal containing coal and semi-carbonized woody biomass; coking the blended coal; Including, The semi-carbonized woody biomass is (1) The volatile content is 25% by mass or less, and when sieved in accordance with the particle size test method specified in JIS M8801:2008, the mass ratio of particles on a 0.10 mm sieve to particles on a 0.60 mm sieve is 60% by mass or more; or (2) A method for producing coke having a volatile content of more than 25% by mass and not more than 40% by mass, and a particle size in which the mass ratio of particles over a 0.10 mm sieve and under a 0.30 mm sieve is 60% by mass or more in the sieving. [2] A method for producing coke, comprising: Preparing a blended coal containing coal and semi-carbonized woody biomass; coking the blended coal; Including, The semi-carbonized woody biomass is (1) A volatile content of 25% by mass or less, and a particle size of 0.10 mm or more and 0.60 mm or less when sieved in accordance with the particle size test method specified in JIS M8801:2008, or (2) A method for producing coke having a volatile content of more than 25% by mass and not more than 40% by mass, and a particle size in the sieving that is above a 0.10 mm sieve and below a 0.30 mm sieve. [3] The volatile content of 25% by mass or less is 15.9% by mass or more and 23.7% by mass or less, 3. The method for producing coke according to item 2, wherein the volatile content of more than 25% by mass and not more than 40% by mass is 28.9% by mass or more and 38.2% by mass or less. [4] A method for producing coke, comprising: Preparing a blended coal containing coal and semi-carbonized woody biomass; coking the blended coal; Including, The semi-carbonized woody biomass has a volatile content of 40% by mass or less, and a particle size in which the mass ratio of particles passing through a 0.10 mm sieve to a 0.60 mm sieve is 60% by mass or more when sieved in accordance with the particle size testing method specified in JIS M8801:2008, the particle size of the semi-carbonized woody biomass is adjusted according to the amount of volatile matter of the semi-carbonized woody biomass based on a relational expression created in advance between a variable x that is the amount of volatile matter of the semi-carbonized woody biomass and a variable y that is the particle size of the semi-carbonized woody biomass; The relational expression is an expression in which the slope (Δy / Δx), which is the ratio of the increment Δy of the variable y to the increment Δx of the variable x, is negative. Coke manufacturing method. [5] 5. The method for producing coke according to any one of items 1 to 4, wherein the semi-carbonized woody biomass is a product of heat treatment of woody biomass at 200°C or higher and 500°C or lower. [Effects of the Invention]

[0008] According to one aspect of the present invention, a coke manufacturing method can be provided that can incorporate biomass into a coal blend, which is a raw material for coke, while suppressing a decrease in coke strength due to the use of the biomass in a simple procedure. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the relationship between the particle size of semi-carbonized woody biomass and the I-beam strength of the coke. [Figure 2] FIG. 2 is a diagram showing the relationship between the volatile matter (VM) of semi-carbonized woody biomass and the I-type strength of the coke for particle size category (a) of more than 0.10 mm and 0.30 mm or less according to Examples 1 to 6. [Figure 3] FIG. 3 is a diagram showing the relationship between the volatile matter (VM) of semi-carbonized woody biomass and the I-type strength of the coke for particle size category (b) of more than 0.30 mm and 0.60 mm or less according to Examples 7 to 9 and Comparative Examples 1 to 3. [Figure 4] FIG. 4 is a diagram showing the relationship between the volatile matter (VM) of semi-carbonized woody biomass and the I-type strength of the coke for particle size category (c) of more than 0.60 mm and 1.00 mm or less according to Comparative Examples 4 to 9. [Figure 5] FIG. 5 is a diagram showing the relationship between the volatile matter (VM) of semi-carbonized woody biomass and the I-type strength of the coke for particle size category (d) of more than 1.00 mm and 3.00 mm or less according to Comparative Examples 10 to 15. [Figure 6] FIG. 6 is a graph showing the degree of decrease in I-beam strength of coke due to the use of semi-carbonized woody biomass, expressed as an average value when the volatile matter (VM) is 25 mass % or less. [Figure 7] FIG. 7 is a graph showing the degree of decrease in I-type strength of coke due to the use of semi-carbonized woody biomass, expressed as an average value when the volatile matter (VM) exceeds 25 mass %. [Figure 8] FIG. 8 is a graph showing the relationship between particle size distribution and I-type strength in Examples 10 to 13 and Comparative Example 16. [Figure 9] FIG. 9 is a graph showing the relationship between particle size distribution and I-type strength in Examples 14 to 17 and Comparative Example 17. [Figure 10] FIG. 10 is a diagram in which the plot shown in FIG. 1 is re-plotted with the x-axis representing the amount of volatile matter and the y-axis representing the intermediate particle size. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, exemplary aspects of the present invention (sometimes referred to as the present embodiment in this disclosure) will be described, but the present invention is not limited to the following aspects.

[0011] This embodiment provides a method for producing coke, including the steps of preparing a coal blend containing coal and semi-carbonized woody biomass, and coking the coal blend. Using biomass in addition to coal as a raw material for coke is advantageous from the viewpoint of reducing the consumption of fossil resources through the effective use of renewable resources.

[0012] <Semi-carbonized wood biomass> In this disclosure, biomass refers to renewable, biologically derived organic resources, excluding fossil resources. Biomass generally originates from agriculture, forestry, livestock, fisheries, waste, etc. Woody biomass is biomass with lignified tissue. Woody biomass may be derived from broad-leaved trees, conifers, ginkgo, bamboo, etc. Woody biomass may have various origins and forms, such as logs, thinned wood, scraps, waste wood, sawdust, bark, branches, and leaves. Woody biomass may be chips, powder, pellets, etc. Examples of woody biomass pellets include wood pellets (white pellets), bark pellets, and whole tree pellets. Semi-carbonized woody biomass can typically be obtained by heat treatment of woody biomass, more specifically, by dry distillation (i.e., heating in an air-free state).

[0013] Woody biomass is easily available in large quantities and has a relatively uniform quality. Furthermore, woody biomass tends to have a lower content of non-carbonaceous inorganic matter, such as ash, than non-woody biomass, which can be advantageous in terms of energy efficiency and resistance to corrosion of equipment. From these perspectives, woody biomass is particularly suitable as a coke raw material.

[0014] Torrefied biomass is biomass in which the organic components in the biomass are decomposed by heat treatment, increasing the carbon ratio, but the biomass still contains organic components because it is not completely carbonized. Carbonizing biomass offers the following advantages: improved energy efficiency due to an increase in the amount of combustion per unit mass, improved pulverizability, improved transportability due to reduced porosity, and improved handleability due to hydrophobicity (e.g., it can be stored in existing outdoor facilities, similar to coal). In other words, torrefied biomass is useful as a coke feedstock due to its high energy efficiency, moderate shrinkage upon heating similar to coal, ease of pulverization, and hydrophobicity. However, completely carbonized biomass is generally not suitable as a coke feedstock due to its low energy efficiency.

[0015] In one aspect, torrefied biomass is distinguished from fully carbonized biomass by the lower heating temperature (more specifically, up to 500° C.) required to carbonize the biomass. In one aspect, torrefied biomass is distinguished from fully carbonized biomass by having a high volatile content (more specifically, 1% by weight or greater).

[0016] When coal is carbonized to coke, the coal softens and expands, causing adhesion of coal particles and shrinkage due to degassing, resulting in the re-solidification of coke. When producing coke using a coal blend containing coal and biomass, to prevent a significant decrease in coke strength compared to when only coal is used, it is desirable to suppress the generation of defects due to peeling between the coal-derived coke portion and the biomass-derived coke portion at the end of carbonization (also referred to as "peeling defects" in this disclosure). More specifically, it is desirable to use biomass with a relatively small shrinkage rate upon heating (hereinafter referred to as "thermal shrinkage rate"). The main components of biomass are carbon, hydrogen, and oxygen. While the thermal shrinkage rate of uncarbonized biomass tends to be significantly higher than that of ordinary coal, the thermal shrinkage rate of semi-carbonized biomass is reduced due to the reduction in volatile matter and easily pyrolyzable components, resulting in a lower thermal shrinkage rate than before carbonization. Biomass, which is a semi-carbonized material, can have a thermal contraction behavior similar to that of coal during coking, so it is less likely to produce peeling defects between the coal-derived coke portion and the biomass-derived coke portion during coking, and high-strength coke can be produced.

[0017] The fixed carbon ratio of semi-carbonized woody biomass is preferably 50% by mass or more, or 60% by mass or more, or 70% by mass or more, in terms of low thermal shrinkage and excellent energy efficiency, and is preferably 90% by mass or less, or 80% by mass or less, in terms of no excessive carbonization, excellent energy efficiency, and coking behavior similar to that of coal. The fixed carbon ratio is a value measured by proximate analysis, which will be described in more detail in the [Examples] section.

[0018] From the viewpoints of energy efficiency and handleability, the ash content of semi-carbonized woody biomass is preferably 10% by mass or less, or 5% by mass or less, or 4% by mass or less. A smaller ash content is preferable, but from the viewpoint of the availability of semi-carbonized woody biomass, in one embodiment, the ash content may be 0.5% by mass or more, or 1.0% by mass or more, or 2.0% by mass or more. The ash content is a value measured by proximate analysis, which will be described in more detail in the [Examples] section.

[0019] The carbon element ratio of semi-carbonized woody biomass is preferably 50% by mass or more, or 60% by mass or more, or 70% by mass or more, in terms of low thermal shrinkage and excellent energy efficiency, and is preferably 90% by mass or less, or 80% by mass or less, in terms of no excessive carbonization occurring, excellent energy efficiency, and a shrinkage behavior during coking similar to that of coal. In one embodiment, the hydrogen element ratio of the semi-carbonized woody biomass may be 1% by mass or more and 5% by mass or less. In one embodiment, the nitrogen element ratio of the semi-carbonized woody biomass may be 0.1% by mass or more and 2.0% by mass or less. In one embodiment, the oxygen element ratio of the semi-carbonized woody biomass may be 1% by mass or more and 20% by mass or less. In one embodiment, the total sulfur element ratio of the semi-carbonized woody biomass may be 0.01% by mass or more and 1.50% by mass or less. The above ratios of each element are values ​​measured by elemental analysis, which will be described in more detail in the section [Examples].

[0020] The moisture content of woody biomass before semi-carbonization may vary depending on the origin of the biomass. For example, woody biomass may be dried to adjust the moisture content to about 5% to 15% by mass. In one embodiment, the moisture content of semi-carbonized woody biomass may be 1% to 5% by mass, or 1% to 3% by mass. The moisture content is a value measured according to JIS M8820-2000.

[0021] The bulk density of the semi-carbonized woody biomass is 300 kg / m in one embodiment. 3 ~1000kg / m 3 The bulk density is a value measured in accordance with ISO 17828:2015.

[0022] In one embodiment, the calorific value of the semi-carbonized woody biomass may be 4000 kcal / kg to 6000 kcal / kg. The calorific value is a value measured in accordance with ISO 18125:2017.

[0023] Semi-carbonization can be carried out by heating woody biomass in any form (e.g., chips, powder, pellets, etc.), more specifically, by dry distillation, i.e., heating in an air-free state. Heating devices include batch heaters such as electric furnaces and continuous heaters such as kilns. Heating can be carried out at atmospheric pressure, but is not limited to this. From the viewpoint of smoothly progressing carbonization of biomass, the heating temperature is preferably 200°C or higher, or 210°C or higher, or 220°C or higher, or 230°C or higher, or 240°C or higher, or 250°C or higher, or 260°C or higher, or 270°C or higher, or 280°C or higher, and from the viewpoint of avoiding excessive carbonization and achieving the desired semi-carbonized state, and from the viewpoint of easily adjusting the volatile content of semi-carbonized woody biomass to a desired range, the heating temperature is preferably 500°C or lower, or 400°C or lower, or 390°C or lower, or 380°C or lower, or 370°C or lower, or 360°C or lower, or 350°C or lower, or 340°C or lower, or 330°C or lower, or 320°C or lower, or 310°C or lower, or 300°C or lower. The heating time may be appropriately selected depending on the properties of the biomass used, the desired volatile content, etc., and may be, for example, 10 to 30 minutes. The torrefaction may be carried out in superheated steam. The chemical composition of the torrefied product may be adjusted by adjusting the heating rate during heating.

[0024] The resulting product (more specifically, the dry distillation product), or a kneaded product obtained by adding a binder such as starch to the product (more specifically, the dry distillation product) and then kneading it, can be formed into a desired shape and recovered as semi-carbonized woody biomass. The semi-carbonized woody biomass may be in the form of powder, pellets, or the like.

[0025] Examples of pellets of woody biomass before semi-carbonization or semi-carbonized woody biomass include cylindrical pellets having a diameter of 5 mm to 10 mm and a length of 5 mm to 50 mm.

[0026] Torrefaction can remove components such as moisture, various gases, and wood vinegar from woody biomass. Wood tar may be removed or may remain substantially unremoved. The removed components may include useful chemicals such as acids, alcohols, and phenols, and these substances may be used as industrial materials for various applications. In one aspect, the inclusion of wood tar in the torrefied product can be advantageous from the standpoint of energy efficiency.

[0027] [Particle size] In one embodiment, semi-carbonized woody biomass contains particles that are 0.10 mm or larger (i.e., greater than 0.10 mm) and 0.60 mm or smaller (i.e., 0.60 mm or smaller) when sieved in accordance with the particle size testing method specified in JIS M8801:2008, in a mass proportion of at least 60% by mass. The mass proportion is preferably 70% by mass or larger, or 80% by mass or larger, or 90% by mass or larger, or 100% by mass. In particular, when the mass proportion is 80% by mass or larger, there is a tendency for the coke strength to improve significantly as the mass proportion increases. In one embodiment, the semi-carbonized woody biomass contains particles that are 0.10 mm or larger (i.e., greater than 0.10 mm) and 0.30 mm or smaller (i.e., 0.30 mm or smaller) in the sieving described above in a mass proportion of at least 60 mass%, and the mass proportion is preferably 70 mass% or larger, or 80 mass% or larger, or 90 mass% or larger, or 100 mass%.

[0028] In one embodiment, the particle size of the particles accounting for 60% by mass or more of the total semi-carbonized woody biomass is, from the viewpoint of availability, 0.10 mm sieve size (i.e., greater than 0.10 mm), or 0.15 mm sieve size (i.e., greater than 0.15 mm), or 0.18 mm sieve size (i.e., greater than 0.18 mm), or 0.212 mm sieve size (i.e., greater than 0.212 mm). If the particle size of semi-carbonized woody biomass is large, once spalling defects occur during coking, they tend to grow into larger defects. Therefore, a relatively small particle size is advantageous in terms of coke strength, and in particular, the absence of particles with excessively large particle sizes is advantageous in terms of coke strength. From the above viewpoint, the particle size of particles accounting for 60% by mass or more of the total semi-carbonized woody biomass is, in one aspect, 0.60 mm or less (i.e., 0.60 mm or less), preferably 0.50 mm or less (i.e., 0.50 mm or less), or 0.425 mm or less (i.e., 0.425 mm or less), or 0.355 mm or less (i.e., 0.355 mm or less), or 0.30 mm or less (i.e., 0.30 mm or less). Specifically, the particle size is evaluated in accordance with "5. Particle Size Test Method" of JIS M8801:2008, using a sieve conforming to JIS Z8801:2019. In a preferred aspect, the particle size of particles accounting for 70% by mass or more, or 80% by mass or more, or 90% by mass or more, or 100% by mass of the total semi-carbonized woody biomass is within the above range.

[0029] In semi-carbonized woody biomass containing at least 60% by mass of particles over a 0.10 mm sieve and under a 0.60 mm sieve, the mass proportion of particles over a 0.60 mm sieve is 40% by mass or less. Since a small amount of coarse particles is advantageous in terms of coke strength, this mass proportion of particles over a 0.60 mm sieve is preferably 30% by mass or less, or 20% by mass or less, or 10% by mass or less, or 0% by mass.

[0030] In semi-carbonized woody biomass containing at least 60% by mass of particles over a 0.10 mm sieve and under a 0.30 mm sieve, the mass proportion of particles over a 0.30 mm sieve is 40% by mass or less. Since a small amount of coarse particles can be advantageous in terms of coke strength, this mass proportion of particles over a 0.30 mm sieve is preferably 30% by mass or less, or 20% by mass or less, or 10% by mass or less, or 0% by mass.

[0031] In a preferred embodiment, the semi-carbonized woody biomass containing at least 60% by mass of particles over a 0.10 mm sieve and under a 0.60 mm sieve has a mass fraction of particles over a 0.038 mm sieve of 1% by mass or less, a mass fraction of particles over a 2.80 mm sieve of 1% by mass or less, and an average diameter of particles over a 0.038 mm sieve and under a 2.80 mm sieve of 0.212 mm or more and 0.505 mm or less.

[0032] In a preferred embodiment, the semi-carbonized woody biomass containing at least 60% by mass of particles over a 0.10 mm sieve and under a 0.30 mm sieve has a mass ratio of particles over a 0.038 mm sieve of 1% by mass or less, a mass ratio of particles over a 2.80 mm sieve of 1% by mass or less, and an average diameter of particles over a 0.038 mm sieve and under a 2.80 mm sieve of 0.147 mm or more and 0.299 mm or less.

[0033] The above average diameter is preferably equal to or greater than the lower limit from the viewpoint of availability, and is preferably equal to or less than the upper limit from the viewpoint of obtaining good coke strength. The "average diameter of particles sieved over 0.038 mm and under 2.80 mm" in the present disclosure is determined in accordance with "5. Particle size test method" of JIS M8801:2008, using a sieve conforming to JIS Z8801:2019, by the following procedure. Specifically, semi-carbonized woody biomass is sieved, Particles on a 0.038 mm sieve and under a 0.10 mm sieve are considered to be particles of intermediate particle size (i.e., the intermediate value between 0.038 mm and 0.10 mm, hereinafter the same) 0.069 mm, Particles on the 0.10 mm sieve and under the 0.15 mm sieve are considered to be particles with an intermediate particle size of 0.125 mm. Particles on the 0.15mm sieve and under the 0.30mm sieve are considered to be particles with an intermediate particle size of 0.225mm. Particles on the 0.30 mm sieve and particles below the 0.60 mm sieve are considered to be particles with an intermediate particle size of 0.450 mm. Particles on the 0.60 mm sieve and below the 1.00 mm sieve are considered to be particles with an intermediate particle size of 0.80 mm. Particles on the 1.00 mm sieve and particles below the 1.40 mm sieve are considered to be particles with an intermediate particle size of 1.20 mm. Particles on the 1.40 mm sieve and under the 2.00 mm sieve are considered to be particles with an intermediate particle size of 1.70 mm. Particles over the 2.00 mm sieve and under the 2.80 mm sieve are considered to be particles with a medium particle size of 2.40 mm. Then, the average diameter is calculated according to the following formula. Average diameter (mm) = 0.069 x [mass fraction of particles with a mean particle size of 0.069 mm] + 0.125 x [mass fraction of particles with a mean particle size of 0.125 mm] + 0.225 x [mass fraction of particles with a mean particle size of 0.225 mm] + 0.450 x [mass fraction of particles with a mean particle size of 0.450 mm] + 0.80 x [mass fraction of particles with a mean particle size of 0.80 mm] + 1.20 x [mass fraction of particles with a mean particle size of 1.20 mm] + 1.70 x [mass fraction of particles with a mean particle size of 1.70 mm] + 2.40 x [mass fraction of particles with a mean particle size of 2.40 mm]

[0034] In one embodiment, the semi-carbonized woody biomass has a particle size of 0.10 mm oversieve (i.e., greater than 0.10 mm) and 0.60 mm undersieve (i.e., 0.60 mm or less) when sieved in accordance with the particle size testing method specified in JIS M8801:2008. Therefore, in one embodiment, the particle size of all particles of the semi-carbonized woody biomass is in the range of greater than 0.10 mm and 0.60 mm or less. In one embodiment, the particle size of the semi-carbonized woody biomass is, from the standpoint of availability, 0.10 mm oversieve (i.e., greater than 0.10 mm), or 0.15 mm oversieve (i.e., greater than 0.15 mm), or 0.18 mm oversieve (i.e., greater than 0.18 mm), or 0.212 mm oversieve (i.e., greater than 0.212 mm) (or 0.20 mm oversieve (i.e., greater than 0.20 mm)). When the particle size of semi-carbonized woody biomass is large, once spalling defects occur during coking, they tend to grow into larger defects. Therefore, a relatively small particle size is advantageous in terms of coke strength, and in particular, the absence of particles with excessively large particle sizes is advantageous in terms of coke strength. From the above viewpoint, in one aspect, the particle size is 0.60 mm or less (i.e., 0.60 mm or less), preferably 0.55 mm or less (i.e., 0.55 mm or less), or 0.50 mm or less (i.e., 0.50 mm or less), or 0.425 mm or less (i.e., 0.425 mm or less) (or 0.40 mm or less (i.e., 0.40 mm or less)), or 0.355 mm or less (i.e., 0.355 mm or less (or 0.35 mm or less (i.e., 0.35 mm or less), or 0.30 mm or less (i.e., 0.30 mm or less). Specifically, the particle size is evaluated in accordance with "5. Particle Size Test Method" of JIS M8801:2008, using a sieve conforming to JIS Z8801:2019.

[0035] The particle size may be adjusted to a desired range by pulverizing the semi-carbonized woody biomass (e.g., pellets) under controlled conditions. The pulverization may be carried out using, for example, a compression-type, shear-type, cutting-type, impact-type, and / or friction-type pulverizer. Examples of pulverizers include a hammer mill, a cutter mill, and a ball mill. The pulverization may be dry or wet, but is preferably dry. In a preferred embodiment, semi-carbonized woody biomass having a particle size of more than 0.10 mm and not more than 0.60 mm can be prepared by pulverizing pellets of semi-carbonized woody biomass using a hammer mill under conditions set according to the desired particle size. In one embodiment, the pulverized product may be further classified using a sieve. For example, the pulverized product may be classified using a 0.10 mm sieve and a 0.60 mm sieve conforming to JIS Z8801:2019 to recover particles that fit on the 0.10 mm sieve and under the 0.60 mm sieve, thereby obtaining semi-carbonized woody biomass having particle sizes that fit on the 0.10 mm sieve (greater than 0.10 mm) and under the 0.60 mm sieve (0.60 mm or less). The particles that fit on the 0.60 mm sieve removed by the classification may be subjected to the pulverization again.

[0036] As described above, a relatively small particle size of semi-carbonized woody biomass is advantageous in terms of coke strength. The inventors of the present invention have focused on the fact that even if semi-carbonized woody biomass has the same particle size, the shrinkage behavior during coking differs depending on the amount of volatile matter in the semi-carbonized woody biomass. They have therefore investigated a method for easily obtaining semi-carbonized woody biomass that is less likely to reduce coke strength. As a result, they have found that by adjusting the particle size of semi-carbonized woody biomass within a predetermined range depending on the amount of volatile matter, it is possible to effectively suppress peeling defects between the coal-derived coke portion and the biomass-derived coke portion during coking. Because the particle size can be easily controlled by adjusting the grinding conditions, etc., using semi-carbonized woody biomass whose particle size has been selected by such a method is advantageous in terms of easily producing coke with good coke strength using semi-carbonized woody biomass.

[0037] Specifically, for semi-carbonized woody biomass with a high volatile content, a small particle size is advantageous because the thermal shrinkage rate during coking is high. On the other hand, for semi-carbonized woody biomass with a low volatile content, the thermal shrinkage rate during coking is low, making it less likely to produce spalling defects, and therefore coke strength is less likely to decrease even if the particle size is relatively large. According to the inventors' studies, when the volatile content of semi-carbonized woody biomass is approximately 25% by mass or less, a certain degree of particle size reduction can effectively reduce spalling defects. However, when the volatile content exceeds approximately 25% by mass, further particle size reduction is required to reduce spalling defects. When the volatile content exceeds approximately 40% by mass, it tends to be difficult to reduce spalling defects even by particle size reduction. From this perspective, in one embodiment, semi-carbonized woody biomass with a volatile content of 40% by mass or less is used, and the target particle size of the semi-carbonized woody biomass is made different when the volatile content is more than 25% by mass and when it is 25% by mass or less, and the grinding conditions are appropriately designed to obtain this target particle size.

[0038] Semi-carbonized woody biomass according to one embodiment is (1) The volatile content is 25% by mass or less, and when sieved in accordance with the particle size test method specified in JIS M8801:2008, the mass ratio of particles on a 0.10 mm sieve to particles on a 0.60 mm sieve is 60% by mass or more; or (2) The volatile content is more than 25% by mass and not more than 40% by mass, and the particle size is such that the mass ratio of particles passing through a 0.10 mm sieve and under a 0.30 mm sieve is 60% by mass or more in the above sieving. Semi-carbonized woody biomass that satisfies the above condition (1) and semi-carbonized woody biomass that satisfies the above condition (2) may be used in combination.

[0039] Semi-carbonized woody biomass according to one embodiment is (1) A volatile matter content of 25% by mass or less and a particle size of 0.10 mm sieve (greater than 0.10 mm) and 0.60 mm sieve (0.60 mm or less), or (2) The volatile content is more than 25% by mass and not more than 40% by mass, and the particle size is above 0.10 mm sieve (more than 0.10 mm) and below 0.30 mm sieve (not more than 0.30 mm). Semi-carbonized woody biomass that satisfies the above condition (1) and semi-carbonized woody biomass that satisfies the above condition (2) may be used in combination.

[0040] When the volatile content of semi-carbonized woody biomass is 25% by mass or less, the thermal shrinkage rate of the semi-carbonized woody biomass can become close to that of coal to an extent that is useful for reducing peeling defects.

[0041] The volatile content of the semi-carbonized woody biomass is preferably 40% by mass or less, 38.2% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, 23.7% by mass or less, or 20% by mass or less, from the viewpoint of reducing shrinkage during coking and obtaining high coke strength. The volatile content of the semi-carbonized woody biomass is preferably 1% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, or 15.9% by mass or more, from the viewpoint of facilitating the design of carbonization conditions such that the carbonization of the woody biomass remains semi-carbonized. In one aspect, the volatile content of the semi-carbonized woody biomass may be more than 23.7% by mass and 38.2% by mass or less.

[0042] In one embodiment, when the volatile content of the semi-carbonized woody biomass is 25% by mass or less, the volatile content may be 15.9% by mass or more and 23.7% by mass or less. In one embodiment, when the volatile content of the semi-carbonized woody biomass is more than 25% by mass and not more than 40% by mass, the volatile content may be 28.9% by mass or more and 38.2% by mass or less.

[0043] The amount of volatile matter can be controlled by adjusting the heating conditions during semi-carbonization.

[0044] The amount of volatile matter in the present disclosure is a value calculated according to the following formula from the amount of mass loss Y (unit: g) and the amount of water Z (unit: g) that escapes from the system when sample X (unit: g) is placed in a crucible with a lid and heated at 900°C for 7 minutes without contacting the air. Volatile content (unit: mass%) = (YZ) / X x 100 The water content Z is a value measured in accordance with JIS M8820-2000.

[0045] In general, when woody biomass is heated, devolatilization occurs rapidly in the temperature range of around 300°C to around 500°C, and tends to saturate at temperatures higher than this. Since the heating conditions of 900°C for 7 minutes volatilize the volatiles in the sample almost completely, the amount of volatiles in woody biomass can be appropriately evaluated based on the change in mass before and after heating under these heating conditions.

[0046] <Coal and blended coal> The coal blend of this embodiment contains semi-carbonized woody biomass and coal. Although an embodiment in which the coal blend contains components other than semi-carbonized woody biomass and coal is not excluded as long as the effects of the present invention are not impaired, in a typical embodiment, the coal blend is composed only of semi-carbonized woody biomass and coal.

[0047] The coal contained in the coal blend may be one or more types of coal, or may be powdered coal. There are no particular limitations on the type of coal. Powdered coal refers to pulverized coal, and includes coal whose particle size has been further adjusted after pulverization, and agglomerated coal when agglomerated coal is mixed in. In this disclosure, agglomerated coal refers to coal with a spherical equivalent radius of less than 6 mm obtained by adding a caking filler to powdered coal (in one embodiment, powdered coal that falls under a 0.3 mm sieve) and compacting the mixture under pressure.

[0048] In one embodiment, the moisture content of the coal and the coal blend may be 5% by mass to 10% by mass, respectively. The moisture content of the coal and the coal blend may be reduced, for example, by a conventionally known coal dryer.

[0049] According to this embodiment, since a decrease in coke strength can be effectively suppressed while using biomass, the ratio of semi-carbonized woody biomass can be set to a relatively large amount, such as up to 5.0 mass% relative to 100 mass% of the blended coal. From the viewpoint of effectively obtaining the advantages of utilizing biomass, this ratio is preferably 1.0 mass% or more, or 1.5 mass% or more, or 2.0 mass% or more, and from the viewpoint of maintaining good coke strength, it is preferably 5.0 mass% or less, or 4.0 mass% or less, or 3.0 mass% or less.

[0050] <Process for preparing blended coal> The coke production method of this embodiment includes a step of preparing a coal blend containing coal and semi-carbonized woody biomass. The coal blend may be prepared by mixing coal and semi-carbonized woody biomass to produce a coal blend, or by obtaining a coal blend that is already known to contain coal and semi-carbonized woody biomass. In one aspect, the semi-carbonized woody biomass is a product of heat treatment of woody biomass at 200°C or higher and 500°C or lower. The heat treatment may be carbonization (i.e., heating in an air-free state). The heat treatment may be performed in superheated steam. In one aspect, the coke production method may include a step of producing semi-carbonized woody biomass. For example, the coke production method may include a step of heat treating woody biomass at 200°C or higher and 500°C or lower to produce semi-carbonized woody biomass.

[0051] <Process for turning blended coal into coke> The coke manufacturing method of this embodiment includes a step of coking the aforementioned coal blend. The coke oven may be any conventionally known coke oven. Since the shrinkage behavior of semi-carbonized woody biomass during coking is similar to that of coal, coke with good coke strength can be obtained by carbonizing the coal blend of this embodiment using an existing coke oven under existing coking conditions. The semi-carbonized woody biomass and coal may be mixed in advance and then charged into the coke oven. The carbonization conditions (temperature, time, etc.) for coking may be the same as when producing coke using only coal. In one embodiment, the carbonization temperature may be approximately 700°C to 1400°C.

[0052] [Additional Implementation] When the volatile content of semi-carbonized woody biomass is 25% by mass or less, a certain degree of particle size reduction effectively reduces peeling defects, but in one embodiment, the particle size may be further reduced. For example, semi-carbonized woody biomass with a volatile content slightly below 25% by mass may be further reduced in particle size. That is, in one embodiment, instead of setting different target particle sizes for semi-carbonized woody biomass when the volatile content exceeds 25% by mass and when it is 25% by mass or less, the target particle size for semi-carbonized woody biomass when it exceeds a volatile content slightly below 25% by mass and when it is equal to or less than that volatile content may be set differently.

[0053] In one embodiment, the semi-carbonized woody biomass is (1) The volatile content is 15.9% by mass or more and 23.7% by mass or less, and when sieved in accordance with the particle size test method specified in JIS M8801:2008, the mass ratio of particles on a 0.10 mm sieve to particles on a 0.60 mm sieve is 60% by mass or more; or (2) The volatile content is more than 23.7% by mass and not more than 38.2% by mass, and the particle size in the above sieving is such that the mass ratio of particles on a 0.10 mm sieve and under a 0.30 mm sieve is 60% by mass or more. It is possible. Semi-carbonized woody biomass that satisfies the above condition (1) and semi-carbonized woody biomass that satisfies the above condition (2) may be used in combination.

[0054] In one embodiment, the semi-carbonized woody biomass is (1) A volatile content of 15.9% by mass or more and 23.7% by mass or less, and a particle size of 0.10 mm or more and 0.60 mm or less when sieved in accordance with the particle size test method specified in JIS M8801:2008, or (2) A volatile content of more than 23.7% by mass and not more than 38.2% by mass, and a particle size of 0.10 mm or more and 0.30 mm or less when sieved in accordance with the particle size test method specified in JIS M8801:2008; It is possible. Semi-carbonized woody biomass that satisfies the above condition (1) and semi-carbonized woody biomass that satisfies the above condition (2) may be used in combination.

[0055] In one embodiment, the particle size of the semi-carbonized woody biomass may be adjusted according to the amount of volatile matter in the semi-carbonized woody biomass. For example, the particle size of the semi-carbonized woody biomass may be adjusted according to the amount of volatile matter based on a previously created relational expression between a variable x, which is the amount of volatile matter in the semi-carbonized woody biomass, and a variable y, which is the particle size of the semi-carbonized woody biomass. The relational expression may be an expression in which the slope (Δy / Δx), which is the ratio of the increment Δx in the variable x to the increment Δy in the variable y, is negative. The slope may be an exponential function, a linear function, or another slope. In one embodiment, the particle size as the variable y may be the "average diameter of particles over a 0.038 mm sieve and under a 2.80 mm sieve" of the present disclosure. In this case, it is preferable that the mass fraction under the 0.038 mm sieve is 1% by mass or less, and the mass fraction over the 2.80 mm sieve is 1% by mass or less. In one aspect, the relational expression may be obtained by: (1) setting a desired target coke strength as a threshold value; (2) examining whether or not the coke strength is equal to or greater than the threshold value while changing the combination of volatile matter content and particle size for one arbitrarily selected type of semi-carbonized woody biomass; and (3) deriving the relational expression based on the combination of volatile matter content and particle size that gives a coke strength equal to or greater than the threshold value.

[0056] In one aspect, the semi-carbonized woody biomass has a volatile content of 40% by mass or less, and a particle size in which the mass ratio of particles on a 0.10 mm sieve to particles on a 0.60 mm sieve is 60% by mass or more when sieved in accordance with the particle size testing method specified in JIS M8801:2008, and The particle size of the semi-carbonized woody biomass is adjusted according to the amount of volatile matter of the semi-carbonized woody biomass based on a relational expression created in advance between a variable x that is the amount of volatile matter of the semi-carbonized woody biomass and a variable y that is the particle size of the semi-carbonized woody biomass, The relational expression may be an expression in which the slope (Δy / Δx), which is the ratio of the increment Δy of the variable y to the increment Δx of the variable x, is negative. [Example]

[0057] Hereinafter, exemplary embodiments of the present invention will be further described with reference to examples, but the present invention is not limited to these examples in any way.

[0058] <Preparation of semi-carbonized woody biomass and coal> [Preparation of semi-carbonized woody biomass 1-6] Commercially available semi-carbonized woody biomass pellets 1 with a volatile matter (VM) of 38.2% by mass were prepared. These pellets were placed in the area of ​​a double-sided furnace dry distillation vessel where the longitudinal boards had been removed (40 mm wide x 60 mm high x 136 mm long). The pellets were heated at normal pressure at the temperatures shown in Table 1 to obtain semi-carbonized woody biomass pellets 2 to 6 with the volatile matter contents shown in Table 1.

[0059] Specifically, thermocouples were placed in the center and outermost parts of the charcoal in the width direction of the double-sided furnace. The heating temperature was set to five levels: 265°C, 285°C, 300°C, 320°C, and 380°C. At each level, the heating rate was set to 2°C / min to a temperature 30°C higher than the heating temperature. When the furnace temperature approached each of the five levels, the average temperature at both the center and outermost temperature measuring points at a height of 30 mm (i.e., the middle position at a height of 60 mm) of the charcoal reached each of the five levels. The heating was stopped and maintained, and then the sample was cooled. This maintenance period lasted for one hour. After cooling, the samples were stored in a resealable bag.

[0060] The heating temperatures shown in Table 1 were determined by determining in advance using a thermobalance the relationship between the heating temperature and the mass loss of semi-carbonized woody biomass 1, and based on this relationship, so as to obtain semi-carbonized woody biomass 2 to 6 with the desired volatile content.

[0061] [Table 1]

[0062] Each of the semi-carbonized woody biomass samples 1 to 6 was pulverized using a hammer mill and sieved in accordance with "8. Particle size determination method" of JIS M8100:1992 using a sieve conforming to JIS Z8801:2019. As a result, samples were obtained in four particle size ranges conforming to "5. Particle size test method" of JIS M8801:2008: (a) over 0.10 mm and up to 0.30 mm, (b) over 0.30 mm and up to 0.60 mm, (c) over 0.60 mm and up to 1.00 mm, and (d) over 1.00 mm and up to 3.00 mm (sieve size 2.80 mm).

[0063] [coal] The coal used was caking coal with a volatile matter (VM) of 27.5% by mass and a 3 mm undersize fraction of 100% by mass.

[0064] [Volatile content] For semi-carbonized woody biomass and coal, 1 g of sample was placed in a crucible with a lid and heated at 900°C for 7 minutes without contact with air. The mass loss Y (unit: g) and the amount of water Z (unit: g) that escaped from the system were used to calculate the mass loss using the following formula. Volatile content (unit: mass%) = (YZ) / 1 (unit: g) x 100 Since the moisture content of each sample used was substantially 0% by mass, the calculation was performed assuming the moisture content Z to be 0 g.

[0065] [Proximate analysis and elemental analysis] Semi-carbonized woody biomass 1 and coal (coking coal) were subjected to proximate analysis in accordance with JIS M8812:2006 and elemental analysis in accordance with JIS M8813:2006. Note that because semi-carbonized woody biomass has a high volatile content, the values ​​for fixed oxygen in the proximate analysis and C and O in the elemental analysis are high. The results are shown in Table 2.

[0066] [Table 2]

[0067] [Gas analysis] Gas analysis was performed on semi-carbonized woody biomass 1 and coal (coking coal) using a gas chromatograph / thermal conductivity detector (GC / TCD). Because semi-carbonized woody biomass has a high oxygen content, it tends to generate large amounts of CO and CO2 and little hydrocarbon gas. However, there is no significant difference in the types of gases generated between semi-carbonized woody biomass and coal. The results are shown in Table 3.

[0068] [Table 3]

[0069] <Coke production and evaluation> [Examples 1 to 6] To 95 parts by mass of coal, 5 parts by mass of each of semi-carbonized woody biomass 1 to 6 in particle size category (a) greater than 0.10 mm and equal to or less than 0.30 mm was added, to obtain seven types of blended coals with a semi-carbonized woody biomass ratio of 5% by mass. Each blended coal was placed in a carbonization vessel with a coal charging capacity of 40 mm wide x 60 mm long x 60 mm high, and the resulting mixture was heated to a bulk density of 0.8 [g / cm 3 The coal was charged at a rate of 116 g (coal charge), and the temperature was raised from room temperature to 1,000°C at a rate of 3°C / min to carbonize the blended coal, which was then cooled. The powder was removed from the carbonized sample, and only the lumps were recovered. The lumps were placed in an I-type drum (cylindrical size: diameter 132 mm x length 700 mm) and rotated at 20 rpm for 30 minutes, i.e., 600 revolutions, after which the mass fraction of the lumps on the 9.8 mm sieve was measured. This value was taken as the I-type strength.

[0070] [Examples 7 to 9, Comparative Examples 1 to 3] Coke was produced and evaluated in the same manner as in Example 1, except that semi-carbonized woody biomass 1 to 6 having a particle size class (b) of more than 0.30 mm and not more than 0.60 mm was used.

[0071] [Comparative Examples 4 to 9] Coke was produced and evaluated in the same manner as in Example 1, except that semi-carbonized woody biomass 1 to 6 having a particle size class (c) of more than 0.60 mm and not more than 1.00 mm was used.

[0072] [Comparative Examples 10 to 15] Coke was produced and evaluated in the same manner as in Example 1, except that semi-carbonized woody biomass 1 to 6 having a particle size class (d) of more than 1.00 mm and not more than 3.00 mm was used.

[0073] [Reference example 1] Coke was produced and evaluated in the same manner as in Example 1, except that the blended coal was replaced with coal alone.

[0074] Figure 1 shows the relationship between the particle size of torrefied woody biomass and the I-type strength of the coke. For convenience, each particle size category is plotted in Figure 1 using the intermediate particle size. That is, the particle size categories (a) greater than 0.10 mm and less than 0.30 mm, (b) greater than 0.30 mm and less than 0.60 mm, (c) greater than 0.60 mm and less than 1.00 mm, and (d) greater than 1.00 mm and less than 3.00 mm are plotted using 0.20 mm, 0.45 mm, 0.80 mm, and 2.00 mm, respectively.

[0075] Figures 2 to 5 are diagrams showing the relationship between the volatile matter (VM) of semi-carbonized woody biomass and the I-type strength of the coke for particle size category (a) greater than 0.10 mm and equal to or less than 0.30 mm in Examples 1 to 6 (Figure 2), particle size category (b) greater than 0.30 mm and equal to or less than 0.60 mm in Examples 7 to 9 and Comparative Examples 1 to 3 (Figure 3), particle size category (c) greater than 0.60 mm and equal to or less than 1.00 mm in Comparative Examples 4 to 9 (Figure 4), and particle size category (d) greater than 1.00 mm and equal to or less than 3.00 mm in Comparative Examples 10 to 15 (Figure 5).

[0076] Figures 6 and 7 show the degree of decrease in I-type strength of coke due to the use of semi-carbonized woody biomass, as an average value for a volatile matter (VM) of 25% by mass or less (Figure 6), and as an average value for a volatile matter (VM) of more than 25% by mass (Figure 7), with respect to the decrease in strength compared to when no biomass is used.

[0077] 1 to 5, Reference Example 1, in which only coal was carbonized, had an I-type strength of 87.44 (dotted line in Figures 1 to 5), and a decrease in I-type strength due to the use of semi-carbonized woody biomass was observed in all of the coal blends. However, the decrease in I-type strength was small in particle size category (a) greater than 0.10 mm and equal to or less than 0.30 mm (Examples 1 to 6) and particle size category (b) greater than 0.30 mm and equal to or less than 0.60 mm (Examples 7 to 9 and Comparative Examples 1 to 3). As shown in Figures 1, 2, 6, and 7, in Examples 1 to 6, in all coal blends in which the volatile content of semi-carbonized woody biomass was 38.2 mass% or less, no significant decrease in I-type strength due to the use of semi-carbonized woody biomass was observed, and the effect of the volatile content in semi-carbonized woody biomass on I-type strength was small. On the other hand, as shown in Figures 1, 3, 6 and 7, in Examples 7 to 9 and Comparative Examples 1 to 3, the degree of decrease in I-type strength due to the use of semi-carbonized woody biomass was significantly smaller in the group of blended coals (Examples 7 to 9) in which the volatile content of semi-carbonized woody biomass was 25 mass% or less, compared to the group of blended coals (Comparative Examples 1 to 3) in which the volatile content of semi-carbonized woody biomass was more than 25 mass%.

[0078] As shown in Figures 1 and 4 to 7, in particle size category (c) greater than 0.60 mm and less than 1.00 mm (Comparative Examples 4 to 9) and particle size category (d) greater than 1.00 mm and less than 3.00 mm (Comparative Examples 10 to 15), the I-type strength decreased significantly due to the use of semi-carbonized woody biomass, but no clear trend was observed depending on the amount of volatile matter.

[0079] The above results show that because the I-type strength of coke decreases significantly when the particle size of semi-carbonized woody biomass exceeds 0.60 mm, it is advantageous for the particle size of semi-carbonized woody biomass to be greater than 0.10 mm and less than 0.60 mm. It can also be seen that within the particle size range of greater than 0.30 mm and less than 0.60 mm, when the volatile content exceeds 25% by mass, the volatile content has a significant effect on the I-type strength, but when the volatile content is 25% by mass or less, the effect of the volatile content on the I-type strength is small. Furthermore, when the volatile content is 25% by mass or less, the I-type strength was good for both particle sizes greater than 0.10 mm and less than 0.30 mm and particle sizes greater than 0.30 mm and less than 0.60 mm, which means that good I-type strength can be obtained with a particle size of greater than 0.10 mm and less than 0.60 mm.

[0080] In other words, when producing coke using a blended coal obtained by adding semi-carbonized woody biomass to coal, it is thought that the decrease in coke strength caused by the use of semi-carbonized woody biomass can be minimized by selecting an appropriate particle size range depending on the volatile content of the semi-carbonized woody biomass.

[0081] [Examples 10 to 13, Comparative Example 16] The I-type strength of the coke was measured in the same manner as in Example 1, except that the semi-carbonized woody biomass used had a volatile content of 23.7% by mass and the particle size distribution shown in Table 4. The semi-carbonized woody biomass particles having the particle size distribution shown in Table 4 were produced by the following method. The semi-carbonized woody biomass was pulverized using a hammer mill and sieved using a sieve conforming to JIS M8100:1992 "8. Particle size determination method" and JIS Z8801:2019. As a result, samples were obtained in four particle size ranges (Comparative Example 16 and Example 10) of greater than 0.038 mm and less than 0.10 mm, greater than 0.10 mm and less than 0.15 mm, greater than 0.15 mm and less than 0.30 mm, and greater than 0.30 mm and less than 0.60 mm, as particle size ranges conforming to JIS M8801:2008 "5. Particle size test method."

[0082] [Table 4]

[0083] As shown in Table 4 and Fig. 8, the I-type strength of the coke was the best when the mass fraction of particles greater than 0.10 mm and equal to or less than 0.60 mm was 100 mass%. Even when particles smaller than 0.10 mm were present, the I-type strength of the coke was good when the mass fraction of such particles was 40 mass% or less.

[0084] [Examples 14 to 17, Comparative Example 17] The I-type strength of the coke was measured in the same manner as in Example 10, except that the semi-carbonized woody biomass used had a volatile content of 23.7% by mass and the particle size distribution shown in Table 5. The particle size categories were four: more than 0.10 mm and not more than 0.15 mm, more than 0.15 mm and not more than 0.30 mm, more than 0.30 mm and not more than 0.60 mm, and more than 0.60 mm and not more than 1.00 mm (for Comparative Example 17 and Example 14), or two: more than 0.10 mm and not more than 0.60 mm, and more than 0.60 mm and not more than 1.00 mm (for Examples 15 to 17).

[0085] [Table 5]

[0086] As shown in Table 5 and Fig. 9, the I-type strength of the coke was the best when the mass fraction of particles greater than 0.10 mm and equal to or less than 0.60 mm was 100 mass%. Even when particles greater than 0.60 mm were present, the I-type strength of the coke was good when the mass fraction of such particles was 40 mass% or less.

[0087] [Examples 18 to 20] The I-type strength of the coke was measured using the same procedure as in Example 10, except that the semi-carbonized woody biomass used had a volatile content of 34.4% by mass and the particle size distribution shown in Table 6. The particle size categories were four: greater than 0.038 mm and not greater than 0.10 mm, greater than 0.10 mm and not greater than 0.15 mm, greater than 0.15 mm and not greater than 0.30 mm, and greater than 0.30 mm and not greater than 0.60 mm (for Examples 18 and 19), or three: greater than 0.038 mm and not greater than 0.10 mm, greater than 0.10 mm and not greater than 0.30 mm, and greater than 0.30 mm and not greater than 0.60 mm (for Example 20).

[0088] [Table 6]

[0089] As shown in Table 6, when the volatile content was over 25% by mass, the I-type strength of the coke was particularly good in Example 20, where the mass proportion of particles greater than 0.10 mm and less than 0.30 mm was 100% by mass.The I-type strength of the coke was also good even when particles less than 0.10 mm were present but the mass proportion of these particles was 40% by mass or less (Example 18), and when particles greater than 0.30 mm were present but the mass proportion of these particles was 40% by mass or less (Example 19).

[0090] [Derivation of the relational expression] Figure 10 is a diagram in which the plot shown in Figure 1 is re-plotted with the x-axis representing the amount of volatile matter and the y-axis representing the median particle size. The threshold value was set at 86.2 for an I-type strength when the amount of volatile matter was 38.2 mass% and the median particle size was 0.2 mm, and the samples were classified as OK samples (I-type strength of 86.2 or more) and NG samples (I-type strength less than 86.2). Among the OK samples, the one with the largest median particle size for each volatile matter amount was selected. Furthermore, among those with the same median particle size, the one with the largest amount of volatile matter was selected. In other words, ultimately, Volatile content 15.9% by mass, mean particle size 0.8 mm, Volatile content 23.7% by mass, medium particle size 0.45 mm Volatile content 38.2% by mass, medium particle size 0.2 mm was selected. By exponential approximation, the following relational expression (1) was obtained: R 2 was 0.9929. y=2.0435e -0.061x (1) (wherein x is the amount of volatile matter (mass%) and y is the median particle size (mm).) The above relational expression (1) has a negative slope (Δy / Δx), which is the ratio of the increment Δx of the variable x to the increment Δy of the variable y.

Claims

1. A method for producing coke, comprising: Preparing a blended coal containing coal and semi-carbonized woody biomass; coking the blended coal; Including, The particle size of the semi-carbonized woody biomass is adjusted so as to obtain different target particle sizes when the volatile content of the semi-carbonized woody biomass is more than 25% by mass and when it is 25% by mass or less. As a result, the semi-carbonized woody biomass: (1) A volatile content of 25% by mass or less, and a particle size in which the mass ratio of particles on a 0.10 mm sieve to particles on a 0.60 mm sieve is 60% by mass or more when sieved in accordance with the particle size test method specified in JIS M8801:2008, or (2) A method for producing coke having a volatile content of more than 25% by mass and not more than 40% by mass, and a particle size in which the mass ratio of particles over a 0.10 mm sieve and under a 0.30 mm sieve is 60% by mass or more in the sieving.

2. A method for producing coke, comprising: Preparing a blended coal containing coal and semi-carbonized woody biomass; coking the blended coal; Including, The particle size of the semi-carbonized woody biomass is adjusted so as to obtain different target particle sizes when the volatile content of the semi-carbonized woody biomass is more than 25% by mass and when it is 25% by mass or less. As a result, the semi-carbonized woody biomass: (1) A volatile content of 25% by mass or less, and a particle size of 0.10 mm or more and 0.60 mm or less when sieved in accordance with the particle size test method specified in JIS M8801:2008, or (2) A method for producing coke having a volatile content of more than 25% by mass and not more than 40% by mass, and a particle size in the sieving that is above a 0.10 mm sieve and below a 0.30 mm sieve.

3. The volatile content of 25% by mass or less is 15.9% by mass or more and 23.7% by mass or less, The method for producing coke according to claim 2, wherein the volatile content of more than 25 mass% and not more than 40 mass% is 28.9 mass% or more and 38.2 mass% or less.

4. A method for producing coke, comprising: Preparing a blended coal containing coal and semi-carbonized woody biomass; coking the blended coal; Including, The semi-carbonized woody biomass has a volatile content of 40% by mass or less, and a particle size in which the mass ratio of particles passing through a 0.10 mm sieve to a 0.60 mm sieve is 60% by mass or more when sieved in accordance with the particle size testing method specified in JIS M8801:2008, the particle size of the semi-carbonized woody biomass is adjusted according to the amount of volatile matter of the semi-carbonized woody biomass based on a relational expression created in advance between a variable x that is the amount of volatile matter of the semi-carbonized woody biomass and a variable y that is the particle size of the semi-carbonized woody biomass; the relational expression is derived by setting a target coke strength as a threshold value in advance and examining a combination of a volatile matter content and a particle size that can obtain the target coke strength; An equation in which the slope (Δy / Δx), which is the ratio of the increment Δy of the variable y to the increment Δx of the variable x, is negative. Coke manufacturing method.

5. The method for producing coke according to any one of claims 1 to 4, wherein the semi-carbonized woody biomass is a product of heat treatment of woody biomass at 200 ° C or higher and 500 ° C or lower.

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