Biomass charcoal for stamp-charge type coke ovens, method for producing biomass charcoal for stamp-charge type coke ovens, and method for producing coke.

Abstract

The present invention provides biomass charcoal for stamp-charge type coke ovens, a method for producing biomass charcoal for stamp-charge type coke ovens, and a method for producing coke, which can suppress a decrease in the strength of the coal cake even when a portion of the coal used as raw material for the coal cake carbonized in a stamp-charge type coke oven is replaced with biomass charcoal. A method for producing biomass charcoal for a stamp-charge coke oven, which is mixed together with coal in coal cake that is charged into the stamp-charge coke oven and carbonized, comprising a carbonization step of carbonizing the biomass raw material so that the atomic ratio H / C is either 0.25 or less or 0.45 or more.

Description

Technical Field

[0001] The present invention relates to biomass charcoal for a stamp-charged coke oven, a method for producing the biomass charcoal for a stamp-charged coke oven, and a method for producing coke.

Background Art

[0002] In the production of pig iron using a blast furnace, coke produced by carbonizing coal in a coke oven is used for the purpose of reducing iron ore, as a heat source, and ensuring air permeability in the blast furnace.

[0003] In recent years, the need to reduce CO2 emissions has been increasing. In order to reduce CO2 emissions in a blast furnace, studies are underway to replace part of the coal, which is a raw material for coke used in the blast furnace, with a carbon-neutral raw material such as biomass.

[0004] The coal used for coke production adheres to each other and agglomerates by softening and melting upon heating. However, biomass charcoal does not soften and melt upon heating. When such biomass charcoal is used for coke production, there is a concern about a decrease in coke strength due to poor adhesion between the coal-derived part and the biomass charcoal-derived part of the produced coke. Therefore, in coke production, techniques for suppressing a decrease in coke strength caused by the use of biomass charcoal have been conventionally studied. Patent Document 1 discloses a method for producing coke in which a woody biomass having appropriate volatile content and particle size is blended with the blended coal that is a raw material for coke. In Patent Document 1, it is said that by doing so, defects due to peeling between the coal-derived part and the biomass charcoal-derived part of the produced coke can be suppressed, and a decrease in coke strength can be suppressed. In Patent Document 1, the blended coal is not rammed before carbonization. Therefore, the coke oven used for coke production in Patent Document 1 is a top-charged coke oven described later.

[0005] On the other hand, it is known that improving the bulk density of the coal charged into the coke oven is effective in producing high-strength coke. Stamp-charge coke ovens are known as coke ovens that produce coke using coal with improved bulk density. In a stamp-charge coke oven, coal is compacted by a stamping device and formed into a block shape that is slightly smaller in size than the carbonization chamber. Hereafter, the compacted coal mass will be called a coal cake. Subsequently, the coal cake is charged into the carbonization chamber from the side and carbonized to produce coke.

[0006] A typical coke oven is a top-charge type coke oven, where coal is charged into the carbonization chamber by gravity. In a top-charge type coke oven, the bulk density of the coal in the carbonization chamber is 700-800 kg-dry / m³. 3 That is the case.

[0007] In contrast, in a stamp-charge coke oven, as mentioned above, coal cake is produced by a stamping device. Therefore, the bulk density of the coal cake is higher than that of the coal in the carbonization chamber in a top-charge coke oven, at 1000 kg-dry / m³. 3 This is the extent of the problem. In this way, the bulk density of the coke raw materials can be increased before carbonization in a stamp-charge type coke oven. Therefore, even if biomass coal is used in coke production, defects caused by the separation of the coal-derived portion from the biomass coal-derived portion of the coke after production can be suppressed. Consequently, the concern about a decrease in coke strength due to the use of biomass coal in a stamp-charge type coke oven is smaller than in the case of a top-charge type coke oven. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2024 / 181565 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] In stamp-charge type coke ovens, the strength of the coal cake produced by stamping is crucial. This is because if the coal cake is not strong enough, operational problems may occur, such as the coal cake collapsing during charging into the carbonization chamber. Therefore, various studies have been conducted on the relationship between the properties of coal and the strength of the coal cake. However, sufficient research has not been done on the properties and production methods of biomass coal that can suppress the decrease in coal cake strength, and there is still room for improvement in this regard.

[0010] The technology disclosed in Patent Document 1 investigates the properties of woody biomass blended with coal when producing high-strength coke in a top-charge coke oven. Therefore, Patent Document 1 does not disclose anything about the properties of biomass charcoal that can suppress the reduction in strength of coal cake, nor does it disclose any method for producing biomass charcoal.

[0011] The present invention has been made to solve the above-mentioned problems, and aims to provide biomass charcoal for stamp-charge type coke ovens, a method for producing biomass charcoal for stamp-charge type coke ovens, and a method for producing coke, which can suppress a decrease in the strength of the coal cake even when a portion of the coal, which is the raw material for the coal cake carbonized in a stamp-charge type coke oven, is replaced with biomass charcoal. [Means for solving the problem]

[0012] The means to solve the above-mentioned problems are as follows: [1] A method for producing biomass charcoal for a stamp-charge coke oven, which is mixed together with coal in a coal cake that is charged into the stamp-charge coke oven and carbonized, comprising a carbonization step of carbonizing a biomass raw material so that the atomic ratio H / C, which is the ratio of hydrogen atoms to the number of carbon atoms, is either 0.25 or less or 0.45 or more. [2] The method for producing biomass charcoal for a stamp-charge type coke oven according to [1], wherein in the carbonization step, the biomass raw material is carbonized at a temperature of 300 to 400°C to make the atomic ratio H / C 0.45 or higher, or the biomass raw material is carbonized at a temperature of 600 to 1000°C to make the atomic ratio H / C 0.25 or lower. [3] A method for producing biomass charcoal for a stamp-charge type coke oven according to [1] or [2], comprising a grinding step to produce particles by grinding biomass charcoal for a stamp-charge type coke oven produced by carbonizing biomass raw materials in the carbonization step, wherein 70% by mass or more of the particles produced by grinding in the grinding step are particles with a diameter of 3 mm or less. [4] The biomass raw material to be carbonized in the carbonization step is seed husks, a method for producing biomass charcoal for a stamp charge type coke oven according to any one of [1] to [3]. [5] The method for producing biomass charcoal for a stamp charge coke oven according to [4], wherein the seed husk is at least one of palm husks, walnut husks, coconut husks, pistachio husks, and cashew nut husks. A method for producing coke, comprising: a stamping step of stamping a blended coal containing biomass coal for a stamp-charge type coke oven and coal, prepared by a method for producing biomass coal for a stamp-charge type coke oven described in any of [6] [1] to [5], to produce a coal cake; and a carbonization step of charging the coal cake produced in the stamping step into a stamp-charge type coke oven and carbonizing it to produce coke. [7] Biomass coal for stamp-charge coke ovens, which is mixed together with coal in coal cake that is carbonized in a stamp-charge coke oven, wherein the atomic ratio H / C, which is the ratio of hydrogen atoms to carbon atoms, is either 0.25 or less or 0.45 or more. [8] Biomass charcoal for stamp charge type coke oven as described in [7], wherein the mass percentage of particles with a diameter of 3 mm or less is 70% by mass or more. [Effects of the Invention]

[0013] According to the present invention, even if a portion of the coal used as a raw material for coal cake is replaced with biomass coal when manufacturing stamp-charge coke, a decrease in the strength of the coal cake can be suppressed. Furthermore, since a portion of the coal used as a raw material for coal cake is replaced with biomass coal when manufacturing coke, it can contribute to reducing CO2 emissions. [Brief explanation of the drawing]

[0014] [Figure 1] This is a flowchart illustrating the method for producing biomass charcoal for a stamp-charge type coke oven and the method for producing coke according to this embodiment. [Figure 2] This figure shows the types of biomass raw materials and the relationship between the atomic ratio and the strength ratio of coal cake. [Figure 3] This figure shows the relationship between the types of biomass raw materials, the atomic ratio, and the expansion rate when the compressive load is removed. [Modes for carrying out the invention]

[0015] The following describes embodiments of the present invention (hereinafter referred to as "these embodiments"). Note that the following description illustrates an example of these embodiments, and the present invention is not limited to these embodiments.

[0016] The inventors conducted diligent research to solve the above-mentioned problems and obtained the following findings. Specifically, the biomass charcoal for stamp-charge type coke ovens according to this embodiment (hereinafter referred to as biomass charcoal) exhibits different expansion rates when the compressive force is removed depending on the degree of carbonization, and in a specific carbonization state, the expansion rate when the compressive force is removed becomes extremely large. When biomass charcoal in such a specific carbonization state is blended with coal, which is the main raw material for coal cake carbonized in a stamp-charge type coke oven, and molded under compressive force, the biomass charcoal expands significantly as the compressive force is removed. As a result, density variations occur inside the coal cake after removal, and the strength of the coal cake is significantly reduced. Therefore, the inventors manufactured biomass charcoal in carbonization states other than the specific carbonization state that should be avoided when used as a raw material for coal cake. They found that by blending this with coal, which is the main raw material for coal cake, the adverse effects of biomass charcoal on the strength of the coal cake, i.e., the reduction in the strength of the coal cake, can be suppressed. Furthermore, they found that using seed husk charcoal as biomass charcoal can further suppress the reduction in the strength of the coal cake. This is because the expansion rate of seed husk charcoal is smaller compared to that of biomass charcoal.

[0017] FIG. 1 is a flowchart for explaining a method for producing biomass charcoal for a stamp charging type coke oven according to the present embodiment and a method for producing coke. In the flowchart shown in FIG. 1, first, a biomass raw material is carbonized and blended with a coal cake that is dry-distilled in a stamp charging type coke oven (not shown) to produce biomass charcoal to be blended (step S1, carbonization step). Here, the stamp charging type coke oven refers to a coke oven that charges a coal cake having a size slightly smaller than that of the carbonization chamber into the carbonization chamber and dry-distills it to produce coke. Coke produced in a stamp charging type coke oven may be referred to as stamp charging type coke (hereinafter simply referred to as coke). The coal cake is produced by compressing and molding the blended coal into a block shape having a size slightly smaller than that of the carbonization chamber by a stamping device arranged on the side of the carbonization chamber. The blended coal of the present embodiment is a blended coal containing coal and biomass charcoal, and the blending ratio of biomass charcoal is preferably about 10% by mass (hereinafter referred to as “%”) or less.

[0018] (Biomass raw material) The biomass raw material refers to an organic industrial resource derived from animals and plants. That is, the biomass raw material means products produced in industrial fields such as agriculture, forestry, animal husbandry, and fisheries, and waste generated in the production process of the products that can be used as industrial resources.

[0019] Among the biomass raw materials produced in the above-described industrial fields, biomass raw materials derived from agriculture and forestry are suitable as coke raw materials, that is, raw materials for stamp charging type coke. This is because biomass raw materials derived from agriculture and forestry have less ash content, and their quality, production volume, and circulation volume are stable compared to biomass raw materials produced in other industrial fields.

[0020] Examples of biomass raw materials derived from agriculture include residues from the production of plants used for food and fuel, and it is economically preferable to use these as raw materials for biomass charcoal. Specifically, examples of biomass raw materials derived from agriculture include rice husks, wheat straw, rice straw, sugarcane bagasse, PKS, EFB, palm trunks, walnut shells, coconut shells, pistachio shells, and cashew nut shells. PKS is palm kernel shell, EFB is palm kernel cluster, and palm trunk is the woody part of the palm kernel.

[0021] Among biomass raw materials derived from agriculture, the part classified as seed hull (hereinafter referred to as seed hull) is particularly preferred. Specifically, it is particularly preferable to use seed hulls such as PKS, walnut shells, coconut shells, and pistachio shells as biomass raw materials. This is because these seed hulls generally have a small expansion rate when the compressive load is removed.

[0022] Examples of biomass raw materials derived from forestry include woody biomass consisting of wood from coniferous trees such as cedar, pine, and cypress, and broad-leaved trees such as zelkova, birch, and eucalyptus. The part of the wood is not limited. In addition, thinned wood and construction waste can also be used as biomass raw materials derived from forestry, and it is economically preferable to use these as raw materials for biomass charcoal.

[0023] (Biomass raw material carbonization method) In step S1, biomass charcoal is produced by carbonizing the biomass raw material by heat treatment. The heat treatment of the biomass raw material is preferably carried out in an atmosphere in which the supply of oxygen to the biomass raw material is cut off. For example, it is preferable to carry out the heat treatment in a container in which the inflow of air into the container is inhibited and an inert gas flows. That is, it is preferable to heat treat the biomass raw material in a non-oxidizing atmosphere. The heating of the biomass raw material may be carried out by heating the container and transferring heat from the container.

[0024] The heat treatment temperature and time used to carbonize biomass raw materials should be adjusted appropriately according to the type of biomass raw material so that the atomic ratio H / C (the ratio of hydrogen atoms to carbon atoms) falls within a predetermined range. For example, the atomic ratio H / C of biomass charcoal can be determined by carbonizing biomass raw materials at different heat treatment temperatures and times. A table summarizing the atomic ratio H / C for each heat treatment temperature and time is then created. Such tables are prepared for each type of biomass raw material. By using the above tables, the heat treatment temperature and time required to produce biomass charcoal with the desired atomic ratio H / C can be determined. The atomic ratio H / C is an indicator of the degree of carbonization of biomass charcoal produced by heat treatment of biomass raw materials. A smaller atomic ratio H / C indicates a more advanced carbonization.

[0025] In this embodiment, the atomic ratio H / C of biomass charcoal is preferably 0.25 or less, or 0.45 or more (H / C ≤ 0.25, 0.45 ≤ H / C), regardless of the type of biomass raw material. There are no upper or lower limits for the atomic ratio H / C, but for example, if the atomic ratio H / C is greater than 1.10, that is, if such biomass charcoal is used as a coke raw material, the coke production yield may deteriorate. Also, if the atomic ratio H / C is less than 0.01, the production cost of biomass charcoal may increase. Therefore, it is more preferable that the atomic ratio H / C is between 0.01 and 0.25, or between 0.45 and 1.10 (0.01 ≤ H / C ≤ 0.25, 0.45 ≤ H / C ≤ 1.10).

[0026] (Properties of biomass charcoal based on atomic ratio H / C) Biomass charcoal with an atomic ratio H / C in the range of 0.45 to 1.10 has the characteristics that compared with biomass charcoal with an atomic ratio H / C smaller than this range, carbonization has not progressed significantly and it is prone to creep deformation. When this biomass charcoal is compressed and held in a compressed state, creep deformation occurs, and as the amount of creep deformation increases, the compression load decreases. As a result, the amount of elastic deformation decreases, and the expansion, that is, the expansion rate, corresponding to the amount of elastic deformation when the compression force is removed becomes small. Therefore, when this biomass charcoal is blended as a raw material for coal cakes, high-strength molded products can be manufactured. The above-mentioned creep deformation means that when a certain load is applied, it gradually deforms.

[0027] Biomass charcoal with an atomic ratio H / C in the range of 0.01 to 0.25 has the characteristics that compared with biomass charcoal with an atomic ratio H / C larger than this range, carbonization has progressed relatively and it has a large elastic constant. Since the elastic constant of this biomass charcoal is large, the expansion rate when the compression force is removed is small. Therefore, when this biomass charcoal is blended as a raw material for coal cakes, high-strength molded products can be manufactured.

[0028] In contrast, biomass charcoal with an atomic ratio H / C exceeding 0.25 and less than 0.45 (0.25 < H / C < 0.45) has progressed more in carbonization than biomass charcoal with an atomic ratio H / C in the range of 0.45 to 1.10, so it is less likely to cause creep deformation. On the other hand, since the carbonization of biomass charcoal with an atomic ratio H / C in the range of 0.01 to 0.25 has not progressed as much, its elastic constant is small. Therefore, the expansion rate when the compression force is removed becomes large, and when this biomass charcoal is blended as a raw material for coal cakes, density variations occur inside the coal cake after unloading, and the strength of the coal cake decreases significantly.

[0029] Generally, when the heat treatment time is constant, the higher the heat treatment temperature of the biomass raw material, the lower the atomic ratio (H / C). For example, if PKS is used as the biomass raw material and heat treatment is performed at 300-400°C, the atomic ratio (H / C) can be adjusted to a range of 0.45-1.10. Also, if PKS is used as the biomass raw material and heat treatment is performed at 600-1000°C, the atomic ratio (H / C) can be adjusted to a range of 0.01-0.25.

[0030] Whether to adjust the atomic ratio H / C of biomass coal to the range of 0.45 to 1.10 or the range of 0.01 to 0.25 should be determined by the needs of the plant that produces coke using a stamp-charge type coke oven. If the goal is to increase the production volume of coke oven gas, a by-product of coke production, it is preferable to use biomass raw materials with an atomic ratio H / C in the range of 0.45 to 1.10 that is relatively less carbonized as a raw material for coal cake. If the goal is to increase the coke production yield, it is preferable to use biomass raw materials with an atomic ratio H / C in the range of 0.01 to 0.25 that is relatively more carbonized as a raw material for coal cake.

[0031] The heat treatment of biomass raw materials can be carried out using conventionally known heating devices such as rotary kilns, fluidized bed furnaces, electric furnaces, screw furnaces, shaft furnaces, and carbonization furnaces. Furthermore, the atomic ratio H / C mentioned above is calculated by quantifying the carbon atoms and hydrogen atoms in the biomass coal and obtaining the results from these quantifications. The quantification of carbon atoms and hydrogen atoms in biomass coal can be carried out in accordance with the "Methods for Elemental Analysis of Coal and Coke" specified in JIS, JIS M 8813:2006.

[0032] Next, the biomass coal produced by carbonizing the biomass raw material is crushed to form biomass coal particles (Step S2, crushing process). This is because if extremely coarse particles are present in the raw material, the coal cake is more likely to collapse starting from those points. Therefore, it is preferable to crush the coal to a degree similar to that of coal crushed in a typical coke manufacturing process.

[0033] (Method for crushing biomass charcoal) The apparatus and methods for crushing biomass charcoal are not limited. For example, biomass charcoal may be crushed using crushing equipment such as a hammer crusher, ball mill, or cutter mill. When the atomic ratio H / C of the biomass charcoal is 0.45 to 1.10 or 0.01 to 0.25, it is preferable to crush it in the same way as in general coke production. That is, it is preferable to crush the biomass charcoal so that 70% or more of the total amount of crushed biomass charcoal has a particle size of 3 mm or less. Here, 70% or more of the amount of particle size of 3 mm or less means that when sieving is performed using a sieve with a mesh size of 3 mm, the mass ratio of the biomass charcoal below the sieve to the total amount of crushed biomass charcoal is 70% or more. Note that the order of carbonization and crushing of the biomass raw material does not matter and should be determined according to the heating equipment and crushing equipment.

[0034] Next, the crushed biomass coal and coal are mixed in a predetermined ratio (Step S3, mixing process). This produces the blended coal, which is the raw material for coal cake. Preferably, the proportion of biomass coal in the blended coal is 10% or less. This is to reduce the likelihood of defects occurring due to the separation of the coal-derived portion and the biomass coal-derived portion of the coke after production. In other words, it is to suppress the decrease in strength of stamp-charge type coke.

[0035] The coal, the main raw material for coke, is crushed using a hammer crusher or similar device so that at least 70% of the particles are 3 mm or smaller. In addition to coal and biomass coal, oil coke, pitch, other raw materials mainly composed of carbon, and charred products obtained by heating these other raw materials may be blended into the coal mixture.

[0036] The apparatus and method for mixing the aforementioned materials contained in the blended coal are not limited. The materials may be mixed using a mixer commonly used in coke plants. Alternatively, the materials may be placed on a conveyor belt, and the fluid flow generated as they move from one conveyor belt to another will mix them. In other words, as the materials flow from one conveyor belt to another, each material generates a different fluid flow from the others, thereby mixing the materials.

[0037] After mixing each material, it is preferable to adjust the moisture content of the blended coal. Moisture content adjustment can be achieved by drying the blended coal using a coal humidity control facility, or by spraying water onto the blended coal from a nozzle. For the purpose of maximizing the strength of the coal cake, the moisture content of the blended coal after mixing is preferably 9-12% of the total mass of the blended coal including moisture.

[0038] Following step S3, the blended coal is compressed and molded to produce a coal cake slightly smaller than the dimensions of the carbonization chamber (step S4, stamping process). The coal cake is produced by a conventionally known drop-weight impact type stamping device, which compacts the blended coal by dropping a weight onto it. The coal cake is then charged into the carbonization chamber by being pushed in from the side by a charging device. After that, the coal cake is carbonized at a temperature of approximately 900°C or higher to produce coke (step S5, carbonization process).

[0039] (Effects / Actions) When coal cake is loaded into the carbonization chamber, it is subjected to vibrations and shocks caused by its own weight and the operation of the loading device used to load the coal cake into the chamber. If the strength of the coal cake is low, the aforementioned vibrations and shocks may cause the coal cake to collapse, leading to operational problems. However, in this embodiment, the atomic ratio H / C of the biomass coal is 0.25 or less, or 0.45 or more. Therefore, after the compressive force used in the production of the coal cake is removed, expansion of the biomass coal is less likely to occur. As a result, according to this embodiment, even if a portion of the coal used as the raw material for the coal cake is replaced with biomass coal, a decrease in the strength of the coal cake can be suppressed. Furthermore, this makes it possible to prevent the collapse of the coal cake due to vibrations and shocks when loading the coal cake into the carbonization chamber, and the resulting operational problems. Moreover, if seed husks with a small expansion rate after the compressive force is removed are used as the raw material for the biomass coal, the decrease in the strength of the coal cake and the occurrence of operational problems due to the collapse of the coal cake can be further suppressed. Furthermore, in this embodiment, since a portion of the coal used as a raw material for coal cake is replaced with biomass coal to produce coke, it can contribute to reducing CO2 emissions. [Examples]

[0040] The following describes embodiments of the present invention. Coal cake was produced by adding carbonized biomass raw materials to coal similar to that used in actual operations, in the same manner as in this embodiment. A strength test was performed on the coal cake to evaluate the effect of biomass char on the coal cake strength. The coal used had a degree of coalification (Ro) of approximately 0.96 and was crushed so that the proportion of particles with a particle size of 3 mm or less was 70% by mass (hereinafter simply referred to as %). 100% coal was mixed with 5% biomass char in a mixer, and then the moisture content of the blended coal was adjusted to 10%. In all cases, the biomass char used was crushed so that the proportion of particles with a particle size of 3 mm or less was 65-75%.

[0041] Using the aforementioned coal blend, a coal cake was manufactured following the procedure below. First, approximately 200g of coal blend was placed in a metal mold with an inner diameter of 10cm and a height of 20cm. A 9kg rammer was dropped onto the surface of the coal blend from a height of 30cm 10 times, compacting the coal blend with the impact of the rammer. This was repeated a total of 10 times to produce a coal cake with a diameter of 10cm, a height of 20cm, and weighing approximately 2kg.

[0042] Subsequently, the coal cake was removed from the metal mold, and its strength was measured using the unconfined compressive strength specified in JIS A 1216:2020. The strength of coal cake produced using only coal was used as the standard strength. The strength ratio of coal cakes produced by blending coal with biomass coal to the standard strength was then calculated, and the strength of each coal cake was evaluated based on this strength ratio.

[0043] Table 1 summarizes the types of biomass raw materials used in each invention example and comparative example, the atomic ratio H / C of the biomass coal, and the strength ratio of the coal cake for each invention example and comparative example. Figure 2 shows the relationship between the type of biomass raw material, the atomic ratio H / C, and the strength ratio of the coal cake. If the strength ratio of the coal cake is 85% or higher, it can be considered that the effect of blending biomass coal with coal on the strength of the coal cake is small and that it can be used without operational problems. If the strength ratio of the coal cake is 90% or higher, it can be considered that the effect of blending biomass coal with coal on the strength of the coal cake, i.e., the reduction in strength of the coal cake, is almost negligible.

[0044] [Table 1]

[0045] As shown in Table 1 and Figure 2, the strength ratio of the coal cakes in Comparative Examples 1-4, which used biomass coal with an atomic ratio H / C between 0.25 and less than 0.45, was below 85%. Therefore, if the coal cakes of Comparative Examples 1-4 were used in actual operation, there is a possibility of operational problems such as the collapse of the coal cakes. In contrast, the strength ratio of the coal cakes in Invention Examples 1-9, which used biomass coal with an atomic ratio H / C between 0.45 and 0.25, was above 85%. Therefore, it was found that the coal cakes of Invention Examples 1-9 can be used without operational problems.

[0046] Furthermore, when comparing the strength ratios of coal cakes from biomass coal with similar atomic ratios (H / C), it was found that the strength ratio of coal cakes using seed hulls was higher than that of coal cakes using cedar wood. Specifically, as shown in Table 1 and Figure 2, the strength ratios of coal cakes in Invention Examples 5 and 7, which used seed hulls such as PKS and walnut shells as biomass raw materials, were higher than that of coal cakes in Invention Example 9, which used cedar wood as biomass raw material. From these results, it was found that using seed hulls as biomass raw materials can reduce concerns about the collapse of coal cakes.

[0047] Figure 3 shows the relationship between the type of biomass raw material, the atomic ratio (H / C), and the expansion rate when the compressive load is removed. The expansion rate was measured under the following conditions: Each biomass char was crushed and sieved to adjust the particle size to 44-74 μm. 0.85 g of the biomass char with this particle size adjustment was placed in a 16 mm diameter mold and compressed at a pressure of 100 MPa for 5 minutes. After that, the pressure applied to the biomass char was removed. The difference between the filling height of the biomass char in the mold before the pressure was removed and the filling height of the biomass char in the mold after the pressure was removed, i.e., the expansion width of the biomass char with the removal of the pressure, was determined. Then, the expansion width was divided by the filling height of the biomass char in the mold before the pressure was removed, and this was taken as the expansion rate of the biomass char.

[0048] As shown in Figure 3, the expansion rate of biomass coal with an atomic ratio (H / C) between 0.25 and less than 0.45 was higher than that of biomass coal with an atomic ratio (H / C) of 0.25 or less and 0.45 or more. In other words, biomass with an atomic ratio between 0.25 and less than 0.45 expands significantly upon unloading even after compression. Therefore, it was considered that if biomass coal with an atomic ratio (H / C) between 0.25 and less than 0.45 were used as a raw material for coal cake, density variations would occur inside the coal cake after unloading, resulting in a significant decrease in the strength of the coal cake. Consequently, it was found that biomass coal with an atomic ratio (H / C) of 0.25 or less and 0.45 or more is suitable as biomass coal for stamp-charge type coke ovens.

[0049] Furthermore, when comparing biomass charcoals with similar atomic ratios (H / C), as shown in Figure 3, the expansion rate of biomass charcoal made from PKS was lower than that of biomass charcoal made from the woody parts of cedar. This difference in expansion rates is thought to reflect the differences in the inherent properties of the biomass raw materials. In other words, by using biomass raw materials with inherently low elastic constants, such as PKS, it is possible to prepare biomass charcoal that has a low expansion rate when the compressive load is removed, making it easier to mold into a high-strength coal cake. [Explanation of Symbols]

[0050] S1 Carbonization process S2 Grinding process S3 Mixing process S4 Stamping Process S5 Carbonization process

Claims

1. A method for producing biomass charcoal for stamp-charge coke ovens, which is mixed together with coal in coal cake that is charged into a stamp-charge coke oven and carbonized, A method for producing biomass charcoal for a stamp-charge type coke oven, comprising a carbonization step in which biomass raw materials are carbonized such that the atomic ratio H / C, which is the ratio of hydrogen atoms to carbon atoms, is either 0.25 or less or 0.45 or more.

2. A method for producing biomass charcoal for a stamp-charge type coke oven according to claim 1, wherein in the carbonization step, the biomass raw material is carbonized at a temperature of 300 to 400°C to make the atomic ratio H / C 0.45 or higher, or the biomass raw material is carbonized at a temperature of 600 to 1000°C to make the atomic ratio H / C 0.25 or lower.

3. The process includes a crushing step to produce particles by crushing the biomass char for stamp-charge type coke ovens, which is produced by carbonizing biomass raw materials in the aforementioned carbonization step. A method for producing biomass charcoal for a stamp charge type coke oven according to claim 1 or 2, wherein 70% by mass or more of the particles produced by crushing in the crushing step are particles with a diameter of 3 mm or less.

4. The method for producing biomass charcoal for a stamp-charge type coke oven according to claim 1 or 2, wherein the biomass raw material to be carbonized in the carbonization step is seed husks.

5. The method for producing biomass charcoal for a stamp charge type coke oven according to claim 3, wherein the biomass raw material to be carbonized in the carbonization step is seed husks.

6. The method for producing biomass charcoal for a stamp-charge type coke oven according to claim 4, wherein the seed husk is at least one of palm husks, walnut husks, coconut husks, pistachio husks, and cashew nut husks.

7. The method for producing biomass charcoal for a stamp-charge type coke oven according to claim 5, wherein the seed husk is at least one of palm husks, walnut husks, coconut husks, pistachio husks, and cashew nut husks.

8. A stamping step to produce a coal cake by stamping a blended coal containing biomass charcoal for a stamp-charge type coke oven prepared by the method for producing biomass charcoal for a stamp-charge type coke oven according to claim 1 or 2 and coal, A method for producing coke, comprising a carbonization step of producing coke by charging the coal cake produced in the stamping step into a stamp-charge type coke oven and carbonizing it.

9. A stamping step to produce a coal cake by stamping a blended coal containing biomass coal for a stamp-charge type coke oven prepared by the method for producing biomass coal for a stamp-charge type coke oven described in Claim 3 and coal, A method for producing coke, comprising a carbonization step of producing coke by charging the coal cake produced in the stamping step into a stamp-charge type coke oven and carbonizing it.

10. A stamping step to produce a coal cake by stamping a blended coal containing biomass coal for a stamp-charge type coke oven prepared by the method for producing biomass coal for a stamp-charge type coke oven described in Claim 4 and coal, A method for producing coke, comprising a carbonization step of producing coke by charging the coal cake produced in the stamping step into a stamp-charge type coke oven and carbonizing it.

11. A stamping step to produce a coal cake by stamping a blended coal containing biomass coal for a stamp-charge type coke oven prepared by the method for producing biomass coal for a stamp-charge type coke oven described in Claim 5 and coal, A method for producing coke, comprising a carbonization step of producing coke by charging the coal cake produced in the stamping step into a stamp-charge type coke oven and carbonizing it.

12. A stamping step to produce a coal cake by stamping a blended coal containing biomass coal for a stamp-charge type coke oven prepared by the method for producing biomass coal for a stamp-charge type coke oven described in Claim 6 and coal, A method for producing coke, comprising a carbonization step of producing coke by charging the coal cake produced in the stamping step into a stamp-charge type coke oven and carbonizing it.

13. A stamping step to produce a coal cake by stamping a blended coal containing biomass coal for a stamp-charge type coke oven prepared by the method for producing biomass coal for a stamp-charge type coke oven described in Claim 7 and coal, A method for producing coke, comprising a carbonization step of producing coke by charging the coal cake produced in the stamping step into a stamp-charge type coke oven and carbonizing it.

14. Biomass charcoal for stamp-charge coke ovens, which is mixed together with coal in coal cake that is carbonized in a stamp-charge coke oven, Biomass charcoal for stamp-charge type coke ovens, wherein the atomic ratio H / C (the ratio of hydrogen atoms to carbon atoms) is either 0.25 or less, or 0.45 or more.

15. Biomass charcoal for stamp-charge type coke ovens according to claim 14, wherein the mass percentage of particles with a diameter of 3 mm or less is 70% by mass or more.

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