METHOD FOR PRODUCING METALLURGICAL COKE AND METHOD FOR EVALUATING THE THERMALIZATION PROPERTIES

Abstract

The purpose of the present invention is to produce coke having sufficient strength to withstand use in a blast furnace, while using a larger amount of biomass as a coke feedstock than in conventional technologies. Provided is a method for producing metallurgical coke by carbonizing a feedstock in a chamber-type coke oven to give metallurgical coke, wherein the feedstock contains 30 wt% or less, relative to the total feedstock, of isolated lignin satisfying specific conditions.

Description

[Technical Field]

[0001] The present invention relates to a method for producing metallurgical coke and a method for evaluating its thermoplasticity. [Background technology]

[0002] In the production of pig iron using a blast furnace, coke is used to reduce iron ore and ensure gas permeability inside the blast furnace. Coke used for this purpose is called metallurgical coke (hereinafter, simply referring to coke will refer to metallurgical coke). Coke is generally produced by carbonizing coal as a raw material in a coke oven.

[0003] More than half of the CO2 emitted from blast furnaces comes from the carbon in the coke. Therefore, if the coal used as a raw material for coke could be replaced with biomass, a carbon-neutral material, it could significantly contribute to reducing CO2 emissions from blast furnaces. Therefore, there is a need for technology to use biomass raw materials instead of coal as a raw material for coke.

[0004] However, as reported in Non-Patent Documents 1 and 2, when biomass is mixed with coal and charged into a coke oven, the fluidity of the coal during carbonization is significantly reduced, resulting in a decrease in the strength of the resulting coke. Therefore, it is difficult to use biomass as a coke raw material without special pretreatment. The reason why biomass reduces the fluidity of coal is not fully understood, but it is thought that the oxygen atoms contained in biomass in relatively large quantities reduce the melting point of coal during carbonization.

[0005] Therefore, in order to use biomass as a coke raw material without reducing the strength of the coke, the use of biomass with a low oxygen content has been investigated.

[0006] For example, Patent Documents 1 and 2 propose a method of producing coke by adding char obtained by pyrolysis of biomass to coal. Also, Non-Patent Document 2 focuses on the fact that lignin, one of the main components of woody biomass, has a lower oxygen content than other components, and considers using lignin extracted from woody biomass as a coke raw material. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-77086 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-214268 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-73239 [Non-patent literature]

[0008] [Non-Patent Document 1] Flue, 2014, Vol.116, No.15, p.175-182. [Non-patent document 2] Energies, 2017, Vol.10, No.11, 1850 [Non-patent document 3] Iron and Steel, 2015, Vol.101, No.8, pp.407-415 [Non-patent document 4] Fuel Association Journal, 1975, Vol.54, Vol.12, pp.983-993 Summary of the Invention [Problem to be solved by the invention]

[0009] As mentioned above, using biomass as a coke raw material can contribute to reducing CO2 emissions from blast furnaces.

[0010] However, in the techniques proposed in Patent Documents 1 and 2, the amount of biomass char added had to be 5 wt% or less of the total raw materials in order to prevent a decrease in coke strength. Also, Non-Patent Document 2 reports that when lignin is used as a raw material, voids are generated, resulting in a decrease in coke strength.

[0011] As described above, conventional techniques have not been able to use a large amount of biomass as a coke raw material while maintaining coke strength.

[0012] The present invention has been made to solve the above-mentioned problems, and aims to provide a method that can produce coke strong enough to withstand use in a blast furnace while using a larger amount of biomass as a coke raw material than conventional techniques. [Means for solving the problem]

[0013] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using isolated lignin that satisfies specific conditions.

[0014] The present invention was completed based on the above findings, and the gist of the present invention is as follows.

[0015] 1. A method for producing metallurgical coke by carbonizing raw materials in a chamber-type coke oven to produce metallurgical coke, A method for producing metallurgical coke, wherein the raw material contains 30 wt% or less of one or both of isolated lignin and an organic solvent extract from the isolated lignin, each having a permeation distance of 12 mm or more, based on the total weight of the raw material.

[0016] 2. A method for producing metallurgical coke by carbonizing raw materials in a chamber-type coke oven to produce metallurgical coke, A method for producing metallurgical coke, wherein the raw material contains 30 wt% or less of one or both of isolated lignin and an organic solvent extract from the isolated lignin, each having a weight average molecular weight of 3100 or less, based on the total weight of the raw material.

[0017] 3. A method for producing metallurgical coke, comprising carbonizing a raw material to produce metallurgical coke, measuring the permeation distance of one or both of the isolated lignin and the organic solvent extract from the isolated lignin; A method for producing metallurgical coke, comprising using, as part of the raw material, one or both of an isolated lignin and an organic solvent extract from the isolated lignin, the measured permeation distance of which is equal to or greater than a predetermined reference value.

[0018] 4. A method for producing metallurgical coke, comprising carbonizing a raw material to produce metallurgical coke, measuring the weight average molecular weight of one or both of the isolated lignin and the organic solvent extract from the isolated lignin; A method for producing metallurgical coke, comprising using, as part of the raw material, one or both of an isolated lignin and an organic solvent extract from the isolated lignin, the measured weight average molecular weight of which is equal to or less than a predetermined reference value.

[0019] 5. A method for evaluating thermoplastic properties, comprising measuring the permeation distance of the isolated lignin or an organic solvent extract from the isolated lignin to evaluate the thermoplastic properties of the isolated lignin or an organic solvent extract from the isolated lignin. [Effects of the Invention]

[0020] According to the present invention, it is possible to produce coke with strength sufficient for blast furnace use while using a larger amount of biomass as a coke raw material than in the prior art. That is, as mentioned above, in the prior art, it was necessary to limit the amount of biomass added to 5 wt% or less of the total raw materials in order to prevent a decrease in coke strength. In contrast, in the present invention, isolated lignin, which is a biomass-derived component, can be used in an amount of up to 30 wt% of the total raw materials. Furthermore, by using isolated lignin that satisfies specific conditions, the present invention makes it possible to produce coke with strength sufficient for blast furnace use, contrary to conventional knowledge, even when a large amount of isolated lignin is used. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is an image of a cross section of the coke obtained in Example No. 4, observed with a polarizing microscope. [Figure 2] 1 is an image of a cross section of the coke obtained in Comparative Example No. 8 observed with a polarizing microscope. DETAILED DESCRIPTION OF THE INVENTION

[0022] Next, a method for carrying out the present invention will be specifically described. Note that the following description shows an example of a preferred embodiment of the present invention, and the present invention is not limited to the following description in any way.

[0023] (First embodiment) First, a method for producing metallurgical coke according to a first embodiment of the present invention will be described. In the method for producing metallurgical coke according to this embodiment, metallurgical coke is produced by carbonizing raw materials in a chamber-type coke oven.

[0024] The chamber-hearth coke oven is not particularly limited, and any chamber-hearth coke oven of any structure can be used. In the present invention, a chamber-hearth coke oven used in conventional general coke production that does not use biomass raw materials can be used.

[0025] The carbonization is not particularly limited, and a general carbonization method using a chamber-type coke oven can be applied.

[0026] In this embodiment, one or both of isolated lignin and an organic solvent extract from the isolated lignin are used as part of the raw material. In this specification, both "isolated lignin" and "organic solvent extract from the isolated lignin" may be collectively referred to as "isolated lignin."

[0027] Penetration distance: 12mm or more In this embodiment, it is important that the permeation distance of the isolated lignin blended with the raw material is 12 mm or more. The reason for this will be explained below.

[0028] The present inventors investigated the relationship between the behavior of isolated lignin in raw materials during carbonization to produce coke and the strength of the resulting coke. As a result, they found that the behavior of isolated lignin during heating varies significantly depending on the type of isolated lignin used. That is, many isolated lignins have poor thermoplasticity during heating, and therefore, blending isolated lignin with a raw material reduces the strength of the coke. On the other hand, they found that some isolated lignins have excellent thermoplasticity during heating and actually improve the strength of the coke.

[0029] Further investigations revealed that the thermoplasticity and melting properties of isolated lignin can be quantitatively evaluated based on the permeation distance. If the permeation distance of the isolated lignin is less than 12 mm, the thermoplasticity and melting properties of the isolated lignin are insufficient, resulting in insufficient coke strength. Therefore, in this embodiment, isolated lignin having a permeation distance of 12 mm or more is used. From the viewpoint of further increasing coke strength, the permeation distance is preferably 13 mm or more, and more preferably 15 mm or more. On the other hand, from the viewpoint of coke strength, the longer the permeation distance, the better, so the upper limit of the permeation distance is not particularly limited. However, from the viewpoint of ease of obtaining and preparing isolated lignin, the permeation distance is preferably 40 mm or less.

[0030] One index for evaluating the thermoplastic properties of coke raw materials is the maximum fluidity (MF) measured by the Gieseler plastometer method specified in JIS M 8801 "Coal-Testing Methods." However, because the Gieseler plastometer method was designed to evaluate the properties of coals, it cannot be used to evaluate the thermoplastic properties of isolated lignin. For example, even if the Gieseler plastometer method is used to measure the maximum fluidity of isolated lignin alone, the measurement cannot be performed correctly because the properties of isolated lignin and coals are completely different. Furthermore, when the maximum fluidity is measured in a mixture of isolated lignin and coal, the maximum fluidity value is extremely low, almost zero, even if isolated lignin with a long permeation distance is used. From these measurement results, it would normally be predicted that the strength of coke made using isolated lignin as a raw material would be significantly low. However, as shown in this specification, the use of specific isolated lignin as a raw material actually improves the coke strength compared to that of coke made using coal alone.

[0031] As described above, the maximum fluidity, which is a commonly known index of thermoplasticity, cannot adequately evaluate the thermoplasticity of isolated lignin and its influence on coke strength. Therefore, the method of evaluating isolated lignin proposed in this invention based on the permeation distance and the weight-average molecular weight (described later) is a completely new method that is completely different from conventional methods and is extremely effective in selecting isolated lignin to be used as a coke raw material.

[0032] In this embodiment, the permeation distance of isolated lignin is defined as the permeation distance measured by the following procedure.

[0033] First, the isolated lignin to be measured is sieved through a 2 mm mesh sieve to separate it into oversized and undersized fractions. The isolated lignin remaining on the sieve is crushed using a pestle and mortar, and the sieving process is repeated until the entire amount of isolated lignin passes through the sieve. Next, 1.0 g of the crushed isolated lignin that passed through the sieve is loaded into a quartz container with an inner diameter of 20 mm and a height of 100 mm. Then, a 200 g weight is dropped five times from 20 mm above the loaded isolated lignin. Furthermore, glass beads (diameter: 2.0 mm, material: soda glass, specific gravity: 2.5) are loaded on top of the loaded isolated lignin to a layer thickness of 50 to 55 mm. The weight of the loaded glass beads is defined as G (g).

[0034] A quartz filter (diameter: 19 mm×thickness: 5 mm) and a weight (1.6 kg) are placed on the layer of glass beads in this order.

[0035] The quartz container filled with the isolated lignin is then heated in an electric furnace in a nitrogen atmosphere from room temperature to 550°C at a rate of 3°C / min. The heated isolated lignin melts, expands, and penetrates the layer of glass beads, then re-solidifies and bonds to some of the glass beads. After natural cooling in a nitrogen atmosphere, the glass beads that did not bond to the isolated lignin are removed from the quartz container, and the weight M (g) of the glass beads is measured.

[0036] From the measured weight of the glass beads, the permeation distance D (mm) is calculated using the following formula (1). Penetration distance D(mm)=H×(GM)…(1) where: H: Filling height per unit weight of glass beads in the quartz container (mm / g) G: Weight of packed glass beads (g) M: Weight of the isolated lignin and unbound glass beads (g)

[0037] The method for measuring the permeation distance was determined with reference to the methods described in Patent Document 3 and Non-Patent Document 3. However, Patent Document 3 and Non-Patent Document 3 only use this method to evaluate the thermoplasticity and melting properties of coal and caking additives, and do not disclose its application to isolated lignin.

[0038] A method for preparing isolated lignin that satisfies the above conditions will be described later.

[0039] Blend amount: 30wt% or less Isolated lignin that satisfies the above conditions has excellent thermoplasticity and melting properties, and therefore can be added to the raw materials in larger amounts than conventional techniques. However, if the blending amount exceeds 30 wt% of the total raw materials, it will result in a decrease in coke strength. Therefore, the blending amount of the isolated lignin to the total raw materials is set to 30 wt% or less. On the other hand, while there are no particular restrictions on the lower limit of the blending amount, from the viewpoint of reducing CO2 emissions, it is preferably more than 2 wt%, more preferably more than 5 wt%, even more preferably 6 wt% or more, and most preferably 10 wt% or more.

[0040] When both the isolated lignin and the organic solvent extract from the isolated lignin are used as raw materials, the total amount of the isolated lignin and the organic solvent extract from the isolated lignin in the raw material is set to 30 wt % or less.

[0041] The size of the isolated lignin is not particularly limited, and any size of isolated lignin can be used. Generally, the particle size of isolated lignin is finer than the particle size of coal used in coke production, and it can be used as is without undergoing a process such as pulverization. However, from the viewpoint of improving the uniform dispersion of the isolated lignin in the raw material and reducing the variation in coke strength, it is also preferable to pulverize the isolated lignin in advance to increase the proportion of fine particles.

[0042] Specifically, the isolated lignin preferably contains particles with a particle size of 3 mm or less at a ratio of 80 wt% or more, and more preferably contains particles with a particle size of 2 mm or less at a ratio of 80 wt% or more. Note that "a ratio of particles with a particle size of 3 mm or less at a ratio of 80 wt% or more" means that when the isolated lignin is passed through a sieve with 3 mm mesh and separated into oversized and undersized fractions, the weight ratio of the undersized fraction is 80 wt% or more of the total isolated lignin. Furthermore, "a ratio of particles with a particle size of 2 mm or less at a ratio of 80 wt% or more" means that when the isolated lignin is passed through a sieve with 2 mm mesh and separated into oversized and undersized fractions, the weight ratio of the undersized fraction is 80 wt% or more of the total isolated lignin.

[0043] On the other hand, the higher the proportion of fine particles, the better, so there is no particular upper limit. Therefore, the proportion of particles with a diameter of 3 mm or less contained in the isolated lignin should be 100 wt% or less. Similarly, the proportion of particles with a diameter of 2 mm or less should be 100 wt% or less.

[0044] The raw materials other than the isolated lignin are not particularly limited, and any raw material can be used. Typically, coal can be used as the raw material other than the isolated lignin. Any coal can be used as the coal without any particular limitation. Examples of the coal include raw coal commonly used in coke production, as well as non- or poorly caking anthracite, semi-anthracite, bituminous coal, subbituminous coal, and lignite. The raw materials can also be a mixture of one or more of coke breeze, oil coke, plastics, biomass other than the isolated lignin, and charcoal obtained by heat-treating biomass other than the isolated lignin. These raw materials can also be mixed with coal. However, since biomass other than plastics and isolated lignin (unheat-treated) contains a large amount of volatile matter, excessive incorporation can lead to a decrease in quality, such as an increase in porosity in the coke. Therefore, the total amount of biomass other than plastics and isolated lignin relative to the total raw materials is preferably 10 wt% or less, and more preferably 5 wt% or less. The lower limit of the total content of plastic and biomass may be 0%.

[0045] To further increase the strength of the coke, a binder may be added as part of the raw materials, such as one or more of coal tar pitch, tar, tar sludge, asphalt pitch, and solvent-refined coal.

[0046] (Second embodiment) Next, a method for producing metallurgical coke according to a second embodiment of the present invention will be described. Note that matters not specifically mentioned can be the same as those in the first embodiment.

[0047] Weight average molecular weight: 3100 or less In this embodiment, it is important that the weight average molecular weight of the isolated lignin to be blended with the raw material is not more than 3100. The reason for this will be explained below.

[0048] As described above, the inventors discovered that the thermoplastic properties of isolated lignin can be quantitatively evaluated based on the permeation distance. Further investigations revealed that the thermoplastic properties of isolated lignin are also correlated with the weight-average molecular weight of the isolated lignin. Specifically, the smaller the weight-average molecular weight of the isolated lignin, the better the thermoplastic properties, and therefore the stronger the coke.

[0049] On the other hand, if the weight-average molecular weight is greater than 3100, the thermoplasticity and melting properties of the isolated lignin become insufficient, resulting in insufficient coke strength. Therefore, in this embodiment, isolated lignin having a weight-average molecular weight of 3100 or less is used. From the viewpoint of further increasing coke strength, the weight-average molecular weight is preferably 3000 or less, more preferably 2900 or less, and even more preferably 2700 or less. On the other hand, from the viewpoint of coke strength, the lower the weight-average molecular weight, the better, so the lower limit of the weight-average molecular weight is not particularly limited. However, from the viewpoint of ease of obtaining and preparing isolated lignin, the weight-average molecular weight is preferably 1500 or more.

[0050] The weight-average molecular weight of the isolated lignin in the present invention is determined by gel permeation chromatography (GPC). More specifically, the weight-average molecular weight can be determined by the method described in the Examples.

[0051] A method for preparing isolated lignin that satisfies the above conditions will be described later.

[0052] In this embodiment, the amount of isolated lignin to be blended relative to the total amount of raw materials is set to 30 wt% or less. The reason for this is as explained in the first embodiment. The preferred amount of isolated lignin to be blended is also the same as in the first embodiment.

[0053] The isolated lignin may further have a permeation distance of 12 mm or more. In other words, in another embodiment of the present invention, one or both of the isolated lignin and the organic solvent extract from the isolated lignin may be used, which have a weight-average molecular weight of 3100 or less and a permeation distance of 12 mm or more.

[0054] (Third embodiment) Next, a method for producing metallurgical coke according to a third embodiment of the present invention will be described. Note that matters not specifically mentioned can be the same as those in the first embodiment.

[0055] In this embodiment, metallurgical coke is produced by carbonizing a raw material, and the permeation distance of one or both of the isolated lignin and the organic solvent extract from the isolated lignin is measured, and one or both of the isolated lignin and the organic solvent extract from the isolated lignin, which have the measured permeation distance equal to or greater than a predetermined reference value, are used as part of the raw material.

[0056] As described above, the thermoplasticity of isolated lignin can be quantitatively evaluated based on the permeation distance. Therefore, by measuring the permeation distance of isolated lignin and selecting and using isolated lignin having a permeation distance equal to or greater than a predetermined reference value, the strength of coke can be improved.

[0057] As described above, this embodiment is characterized by measuring the permeation distance of isolated lignin and selecting the isolated lignin to be used based on the measurement results. Therefore, the reference value used in selecting isolated lignin is not particularly limited and can be any value. The reference value may be predetermined depending on the required coke strength. For example, the reference value may be 12 mm, 13 mm or more, or 15 mm or more. Furthermore, the upper limit of the permeation distance is not particularly limited. However, from the viewpoint of ease of obtaining and preparing isolated lignin, it is preferable to use one or both of isolated lignin and an organic solvent extract from the isolated lignin having a permeation distance of 40 mm or less.

[0058] Similarly, in this embodiment, the amount of isolated lignin relative to the total raw material is not particularly limited, but is preferably 30 wt% or less. On the other hand, the lower limit of the amount is also not particularly limited, but from the viewpoint of reducing CO2 emissions, it is preferably more than 2 wt%, more preferably more than 5 wt%, even more preferably 6 wt% or more, and most preferably 10 wt% or more.

[0059] (Fourth embodiment) Next, a method for producing metallurgical coke according to a fourth embodiment of the present invention will be described. Note that matters not specifically mentioned can be the same as those in the second embodiment.

[0060] In this embodiment, as in the second embodiment, a metallurgical coke is produced by carbonizing a raw material. In this process, the weight-average molecular weights of one or both of the isolated lignin and the organic solvent extract from the isolated lignin are measured, and one or both of the isolated lignin and the organic solvent extract from the isolated lignin having the measured weight-average molecular weights equal to or less than a predetermined reference value are used as part of the raw material.

[0061] As described above, there is a correlation between the thermoplasticity and weight-average molecular weight of isolated lignin. Therefore, by measuring the weight-average molecular weight of isolated lignin and selecting and using isolated lignin having a weight-average molecular weight equal to or less than a predetermined reference value, the strength of coke can be improved.

[0062] As described above, this embodiment is characterized in that the weight-average molecular weight of isolated lignin is measured and the isolated lignin to be used is selected based on the measurement results. Therefore, the reference value used in selecting isolated lignin is not particularly limited and can be any value. The reference value may be predetermined depending on the required strength of the coke. For example, the reference value may be 3100 or less, 3000 or less, or 2900 or less. On the other hand, the lower limit of the weight-average molecular weight is not particularly limited, but is preferably 1500 or more.

[0063] Similarly, in this embodiment, the amount of isolated lignin relative to the total raw material is not particularly limited, but is preferably 30 wt% or less. On the other hand, the lower limit of the amount is also not particularly limited, but from the viewpoint of reducing CO2 emissions, it is preferably more than 2 wt%, more preferably more than 5 wt%, even more preferably 6 wt% or more, and most preferably 10 wt% or more.

[0064] (Fifth embodiment) A fifth embodiment of the present invention relates to a method for evaluating the thermoplastic properties of isolated lignin or an organic solvent extract thereof, in which the thermoplastic properties of the isolated lignin or the organic solvent extract thereof are evaluated by measuring the permeation distance of the isolated lignin or the organic solvent extract thereof.

[0065] In the third and fifth embodiments, the method for measuring the permeation distance is not particularly limited, but is preferably carried out in the following manner.

[0066] First, the isolated lignin to be measured is pulverized. The pulverized isolated lignin is preferably sieved as needed to adjust the particle size to a certain level or less. Next, the pulverized isolated lignin is filled into a measurement container. Any measurement container can be used, but a cylindrical container is preferably used. When a cylindrical container is used, the inner diameter of the container is preferably 10 mm or more. Furthermore, the inner diameter is preferably 50 mm or less. The material of the container is not particularly limited, but it is preferably made of quartz.

[0067] Next, pressure is applied from above the isolated lignin filled in the measurement container. The method of applying pressure is not particularly limited, but to ensure measurement reproducibility, pressure is applied under the same conditions for each measurement. For example, pressure may be applied by dropping a weight from above the isolated lignin filled in the measurement container.

[0068] Next, a plurality of glass beads are packed on the packed isolated lignin to form a glass bead layer of a predetermined thickness. The glass beads are of the same size and material. The preferred diameter is 1.0 to 3.0 mm. The thickness of the glass bead layer is not particularly limited, but is preferably 40 mm to 70 mm.

[0069] Furthermore, a weight is placed on the glass bead layer to apply a load to the isolated lignin. The weight is preferably a weight that provides a load of 5 to 80 kPa depending on the inner diameter of the container. It is also preferable to place a plate-shaped member between the glass bead layer and the weight. By placing the weight via the plate-shaped member, the load can be more uniformly transmitted to the glass beads, improving measurement accuracy. The plate-shaped member is preferably made of quartz. From the viewpoint of facilitating the escape of gas generated during heating, the plate-shaped member is preferably porous. For example, a quartz filter can be used as a porous plate-shaped member. If the plate-shaped member is not porous, it is preferable to provide a gap between the inner wall of the measurement container and the plate-shaped member to facilitate the escape of gas.

[0070] The measurement vessel filled with the isolated lignin is then heated to a predetermined temperature. The heated isolated lignin melts, expands, and penetrates the layer of glass beads, then re-solidifies and adheres to some of the glass beads. The heating is preferably carried out in an inert atmosphere, more preferably in a nitrogen atmosphere. The heating temperature is not particularly limited, as long as it is 500°C or higher and does not affect the test results, but a temperature of 500°C to 600°C is preferred to properly evaluate the thermoplasticity and melting properties of the isolated lignin.

[0071] After cooling, the glass beads that did not adhere to the isolated lignin were removed from the quartz container, and the weight M (g) of the glass beads was measured. From the measured weight of the glass beads, the permeation distance D (mm) was calculated using the following formula (1). Penetration distance D(mm)=H×(GM)…(1) where: H: Filling height per unit weight of glass beads in the quartz container (mm / g) G: Weight of packed glass beads (g) M: Weight of the isolated lignin and unbound glass beads (g)

[0072] The permeation distance is preferably measured by the method described in the first embodiment.

[0073] (Method for preparing isolated lignin) Next, a method for preparing isolated lignin will be described. In the present invention, isolated lignin obtained by any method can be used without any particular limitation. For example, isolated lignin precipitated from black liquor, which is generated as a by-product of the cooking process in a chemical pulping method, can be used. Precipitation of isolated lignin from black liquor can be carried out, for example, by adding an acid such as carbonic acid or sulfuric acid to the black liquor.

[0074] The wood raw material used to produce isolated lignin is not particularly limited and any wood can be used. Both broad-leaved and soft-leaved trees can be used as the wood raw material.

[0075] For example, the isolated lignin may be isolated lignin (kraft lignin) obtained by kraft cooking of wood. The conditions for kraft cooking are not particularly limited, but the sulfidity of the kraft cooking liquor is preferably 5 to 75%, more preferably 15 to 45%. The effective alkali addition rate is preferably 5 to 30% by weight, more preferably 10 to 25% by weight, per bone-dry weight of wood. The cooking temperature is preferably 130 to 170°C. The cooking method may be either a continuous cooking method or a batch cooking method. When a continuous digester is used, a modified cooking method in which cooking liquor is added at multiple points can also be used, and the method is not particularly limited.

[0076] It is preferable to use a cooking aid during cooking. The cooking aid is preferably one or more selected from known cyclic keto compounds, such as benzoquinone, naphthoquinone, anthraquinone, anthrone, phenanthroquinone, and the quinone compounds substituted with alkyl groups, aldehyde groups, amino groups, fluorine groups, etc.; hydroquinone compounds such as anthrahydroquinone, which are reduced forms of the quinone compounds; and 9,10-diketohydroanthracene compounds, which are stable compounds obtained as intermediates in the Diels-Alder method for synthesizing anthraquinone. The cooking aid is preferably added at a rate of 0.001 to 1.0% by weight.

[0077] If the weight-average molecular weight or permeation distance of the isolated lignin does not meet the criteria, a portion of the isolated lignin may be extracted with an organic solvent. If the organic solvent extract meets the above criteria, the organic solvent extract can be used as a coke feedstock. Any organic solvent can be used as the organic solvent. Acetone is preferably used as the organic solvent.

[0078] The extraction method is not particularly limited, but for example, the isolated lignin can be stirred in an organic solvent to extract a portion of the isolated lignin into the organic solvent. The organic solvent is then evaporated to obtain an organic solvent extract of the isolated lignin. If the molecular weight or permeation distance of the obtained organic solvent extract satisfies the criteria, it can be used as a coke feedstock. [Example]

[0079] Next, in order to confirm the effects of the present invention, the following tests were carried out.

[0080] Example 1 Ten types of isolated lignin with different permeation distances and weight-average molecular weights were used as raw materials to produce coke. The types of the 10 isolated lignins used are shown in Table 1. Nos. 1 to 8 are isolated lignins, and No. 9 is an extract obtained by extracting a portion of No. 6 isolated lignin with acetone. On the other hand, No. 10 is the residue from the extraction.

[0081] The permeation distance and weight-average molecular weight of each isolated lignin were measured by the following methods. The measurement results are shown in Table 1.

[0082] (penetration distance) The permeation distance of the isolated lignin was measured by the method described in the first embodiment.

[0083] (Weight average molecular weight) The weight-average molecular weight of the isolated lignin was measured by gel permeation chromatography (GPC) under the following conditions: Analytical equipment: High-performance liquid chromatograph LcSolution Multi-PDA (Shimadzu Corporation) Column: HM-55F custom-made column (Tosoh) ·Separated liquid: 0.5M NaOH ·Flow rate: 1.0mL / min Detector: UV detector (280nm)

[0084] The isolated lignin was used as part of the raw material to produce coke by the following procedure. The following tests were carried out under conditions simulating the carbonization conditions in a chamber-type coke oven.

[0085] First, each of the isolated lignins shown in Table 1 and coal were crushed to 0.5 mm (100%). The crushed isolated lignin and coal were mixed in a ratio of 80 wt% coal and 20 wt% isolated lignin, and then molded into a cylindrical shape. The molding was carried out by placing 1.0 g of the coal and isolated lignin mixture (dry) into a mold with a diameter of 12 mm and applying a compressive force of 2 tf. The coal used was coal A (see Table 2), which has a maximum fluidity MF of 29 ddpm and a reflectivity Ro of 1.23%.

[0086] The obtained molded product was heated to 1000°C at a heating rate of 3°C / min in a N2 gas flow to produce coke. Thereafter, the strength of the obtained cylindrical coke was measured. The indirect tensile strength described in Non-Patent Document 4 was measured as the coke strength. The measurement results are shown in Table 1.

[0087] For comparison, the results of coke production using only coal A without adding isolated lignin are also shown in Table 1 as No. 11.

[0088] The coke strength of No. 11, which was produced using only Coal A without adding isolated lignin, was 3.5 MPa. The indirect tensile strength of cylindrical coke cut into a cylindrical shape from ordinary coke varies widely, but averages about 5 MPa.

[0089] As can be seen from the results shown in Table 1, the inventive examples using isolated lignin satisfying the conditions of the present invention had significantly improved coke strength compared to No. 11, which did not use isolated lignin. In contrast, the comparative examples using isolated lignin that did not satisfy the conditions of the present invention had coke strength that was comparable to or inferior to No. 11, which did not use isolated lignin.

[0090] [Table 1]

[0091] Polarizing microscope images of the cross sections of the cokes obtained in Example No. 4 and Comparative Example No. 8 are shown in Figures 1 and 2. In Figures 1 and 2, the white areas represent coal, the gray areas represent isolated lignin, and the black areas represent voids. As shown in Figure 1, in the coke of Example No. 4, the isolated lignin flows between the coal particles to form bonds. In contrast, in the coke of Comparative Example No. 8, as shown in Figure 2, the coal particles and isolated lignin are surrounded by voids, and they are not bonded together. It is believed that these differences in the internal structure of the cokes result in differences in coke strength. As mentioned above, these structural differences are thought to be due to the differences in the thermoplasticity and melting properties of the isolated lignin used.

[0092] Example 2 Next, various carbonaceous materials and isolated lignin were combined to produce coke. Specifically, the raw materials used were mixtures of the carbonaceous materials shown in Table 2 and the isolated lignin used in Example 1. The blending amounts of the carbonaceous materials and the isolated lignin were as shown in Table 2.

[0093] The carbonaceous material and isolated lignin were molded into a cylindrical shape using the same procedure as in Example 1. The cylindrically molded raw material was then carbonized under the same conditions as in Example 1 to obtain a cylindrical coke. The coke strength (indirect tensile strength) of the obtained cylindrical coke was measured using the same method as in Example 1. The measurement results are shown in Table 2.

[0094] As shown in Table 2, in the examples of the present invention in which isolated lignin satisfying the conditions of the present invention was added, coke strength was significantly improved regardless of the type of carbonaceous material used. In particular, even when using a carbonaceous material that shows no melting properties, such as biomass char, by adding isolated lignin satisfying the conditions of the present invention, coke with strength comparable to that of ordinary coke (5 MPa) was produced. This is thought to be because the isolated lignin softens and melts, forming bonds between the particles of the biomass char. In contrast, in the comparative example in which only biomass char was used as a raw material without the addition of isolated lignin, the coke did not form clumps after carbonization, and coke strength could not be measured.

[0095] [Table 2]

[0096] Example 3 Next, coke was produced by varying the blending amount of isolated lignin. Specifically, a mixture of Coal A shown in Table 2 and the isolated lignin used in Inventive Example No. 1 and Comparative Example No. 6 of Example 1 was used as the raw material. The blending amounts of the carbonaceous material and the isolated lignin were as shown in Table 3.

[0097] The coal A and isolated lignin were molded into a cylindrical shape using the same procedure as in Example 1. The cylindrically molded raw material was then carbonized under the same conditions as in Example 1 to obtain a cylindrical coke. The coke strength (indirect tensile strength) of the obtained cylindrical coke was measured using the same method as in Example 1. The measurement results are shown in Table 3.

[0098] As shown in Table 3, in the examples using isolated lignin No. 1, which satisfied the conditions of the present invention, coke strength improved when the amount of isolated lignin was 30 wt% or less. However, in the comparative examples using isolated lignin at amounts exceeding 30 wt%, the samples deformed during carbonization and lost their cylindrical shape, making it impossible to measure strength. On the other hand, in the comparative examples using isolated lignin No. 6, which did not satisfy the conditions of the present invention, no significant improvement in coke strength was observed, regardless of the amount of isolated lignin added.

[0099] [Table 3]

[0100] Example 4 Furthermore, a large-scale test was conducted using the same combination of coal and isolated lignin as in Example 3 as raw materials. Specifically, coal A and isolated lignin (No. 1 or No. 6) were crushed to 100% -3 mm. After crushing, coal A and isolated lignin were mixed in the different ratios shown in Table 3, and the resulting mixture (15 kg-dry) was poured into a stainless steel container and cooled to 750 kg-dry / m. 3 The mixture was then carbonized at 1050°C for 6 hours to produce coke.

[0101] To evaluate the strength of the coke obtained by the above procedure, a drum test specified in JIS K2151:2004 was conducted under the conditions of 150 revolutions and a particle size of 15 mm or more. The drum strength index (DI 150 / 15) was measured, and the measurement results are shown in Table 3.

[0102] In this example, as in Example 3, the drum strength index improved when the amount of isolated lignin added was 30 wt% or less. However, when the amount of isolated lignin added exceeded 30 wt%, the drum strength index actually decreased. This is thought to be because isolated lignin contains more volatile matter than coal. In other words, when the amount of isolated lignin added exceeded 30 wt%, the decrease in strength due to the volatile matter exceeded the strength-improving effect of isolated lignin.

Claims

1. A method for producing metallurgical coke, comprising carbonizing a raw material in a chamber-type coke oven to produce metallurgical coke, A method for producing metallurgical coke, wherein the raw material contains 30 wt% or less of one or both of isolated lignin and an organic solvent extract from the isolated lignin, each having a permeation distance of 12 mm or more, based on the total weight of the raw material.

2. A method for producing metallurgical coke, comprising carbonizing a raw material in a chamber-type coke oven to produce metallurgical coke, A method for producing metallurgical coke, wherein the raw material contains 30 wt% or less of one or both of isolated lignin and an organic solvent extract from the isolated lignin, each having a weight average molecular weight of 3,100 or less, based on the total weight of the raw material.

3. A method for producing metallurgical coke, comprising carbonizing a raw material to produce metallurgical coke, measuring the permeation distance of one or both of the isolated lignin and the organic solvent extract from the isolated lignin; A method for producing metallurgical coke, comprising using, as part of the raw material, one or both of an isolated lignin and an organic solvent extract from the isolated lignin, the measured permeation distance of which is equal to or greater than a predetermined reference value.

4. A method for producing metallurgical coke, comprising carbonizing a raw material to produce metallurgical coke, measuring the weight average molecular weight of one or both of the isolated lignin and the organic solvent extract from the isolated lignin; A method for producing metallurgical coke, comprising using, as part of the raw material, one or both of an isolated lignin and an organic solvent extract from the isolated lignin, the measured weight average molecular weight of which is equal to or less than a predetermined reference value.

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