Method for evaluating the compatibility of different coal species, method for predicting coke quality, method for producing coke, and method for obtaining coal solubility parameters.

Abstract

To provide a method for evaluating compatibility between coals that enables simple and accurate prediction of coke strength.SOLUTION: A method for evaluating the compatibility between two types of coals, wherein solubility parameters of the two types of coals are obtained, and compatibility between the two types of coals is evaluated based on the distance between the solubility parameters of the two types of coals.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a method for evaluating the compatibility of different coal species, a method for predicting the quality of coke, a method for producing coke, and a method for obtaining coal solubility parameters. [Background technology]

[0002] Coke is produced by crushing coal to a predetermined particle size and then heating it in a carbonization furnace under oxygen-free conditions. To ensure stable quality, a blend of several types of coal is used as the coal.

[0003] The coke produced in this manner functions as a reducing agent, carburizing source, and heat source for iron ore in the blast furnace. The porous structure of the coke ensures the permeability and liquid permeability of the blast furnace. Therefore, the coke needs to have sufficient strength to prevent collapse or pulverization during the transport and blast furnace loading processes.

[0004] Furthermore, the properties of the coal used as a raw material greatly influence the strength of coke.

[0005] Therefore, various methods are being considered to predict the strength of coke obtained by carbon distillation of the coal used in the blended coal, based on the physical properties of the coal used.

[0006] Conventional techniques include using the average maximum reflectance of coal vitrinite (hereinafter sometimes referred to as Ro) or the maximum fluidity (hereinafter sometimes referred to as MF) measured by the Gieseler plastometer method. It is empirically known that these physical properties of coal are related to the coke strength after carbonization. Therefore, attempts have been made to predict coke strength by creating a regression equation using Ro and MF for each coal brand selected as a raw material for coke, as well as accumulated operational data.

[0007] Furthermore, Patent Document 1 describes a method for determining the surface tension (hereinafter sometimes referred to as γ) of semi-coke obtained by heat-treating coal, and for evaluating the adhesion between coals based on the difference in surface tension (hereinafter sometimes referred to as Δγ). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2013 / 145677 [Non-patent literature]

[0009] [Non-Patent Document 1] Julio C. Zuaznabar-Gardona et al., Journal of Molecular Liquids 294 (2019) 111646 [Non-Patent Document 2] Takabayashi et al. Journal of the Japan Petroleum Institute, Vol. 85, No. 2, pp. 124-128 (2020) [Non-Patent Document 3] Hiroshi Yamamoto et al. Chemical Industry, Vol. 61, No. 4, pp. 310-317 (2010) [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] When attempting to predict coke strength using the aforementioned Ro or MF, it was known that the actual coke strength often deviated from the prediction.

[0011] Furthermore, attempts have been made to evaluate the adhesion between coal particles from surface tension using the method described in Patent Document 1, and to predict coke strength based on this adhesion. However, this method had the problem of being complicated to operate and taking a long time to measure.

[0012] The present invention has been made in view of such circumstances, and an object thereof is to provide a method for evaluating the compatibility between coals that enables simple and highly accurate prediction of coke strength. Another object is to provide a method for obtaining the solubility parameter of coal that can be used in the method for evaluating the compatibility between coals.

Means for Solving the Problems

[0013] The gist of the present invention for solving the above problems is as follows.

[0014] [1] A method for evaluating the compatibility between two coals, comprising: obtaining the solubility parameters of the two coals, and evaluating the compatibility between the two coals based on the distance between the solubility parameters of the two coals. A method for evaluating the compatibility between coals.

[0015] [2] The method for evaluating the compatibility between coals according to [1], wherein the solubility parameter is a Hansen solubility parameter.

[0016] [3] The method for evaluating the compatibility between coals according to any one of [1] to [2], wherein the two coals are coals that have been heat-treated before obtaining the solubility parameters.

[0017] [4] A method for predicting the quality of coke, comprising predicting the quality of coke based on the compatibility between coals evaluated by the method for evaluating the compatibility between coals according to any one of [1] to [3].

[0018] [5] A method for producing coke, comprising determining the blending of coals based on the compatibility between coals evaluated by the method for evaluating the compatibility between coals according to any one of [1] to [3].

[0019] [6] A method for producing coke, comprising determining the blending of coals based on the quality of coke predicted by the method for predicting the quality of coke according to [4].

[0020] [7] A method for obtaining the solubility parameter of coal, The aforementioned coal is molded to produce tablets, The aforementioned tablet is permeated with a solvent, and the permeation time is measured. Based on the aforementioned penetration time, the affinity between the coal and the solvent is determined. A method for obtaining coal solubility parameters, comprising deriving the solubility parameters based on the affinity.

[0021] [8] The method for obtaining the solubility parameter of coal according to [7], wherein the coal is coal that has been heat-treated before obtaining the solubility parameter.

[0022] [9] A method for producing coke as described in [5] above, The solubility parameter is the Hansen solubility parameter, In determining the aforementioned blend, for all combinations of two types of coal to be blended, The distance ΔHSP between the aforementioned Hansen solubility parameters is 12.3 (MPa). 0.5 less than A method for producing coke, comprising selecting the coal to be blended in such a manner.

[0023]

[10] A method for producing coke as described in [5] above, The solubility parameter is the Hansen solubility parameter, In determining the aforementioned blend, for all combinations of two types of coal to be blended, If the absolute value ΔLogMF of the difference in the common logarithms of the maximum fluidity measured by the Gieseler plastometer is 0.67log / ddpm or less, The absolute value ΔRo of the difference in the average maximum reflectance of vitrinite is 0.05% or more, The distance ΔHSP between the aforementioned Hansen solubility parameters is 4.2 (MPa). 0.5 below A method for producing coke, comprising selecting the coal to be blended in such a manner. [Effects of the Invention]

[0024] According to the present invention, a method for evaluating the compatibility of different coals can be provided, and based on this, coke strength can be predicted simply and with high accuracy. Furthermore, a method for obtaining coal solubility parameters that can be used in the aforementioned method for evaluating the compatibility of different coals can be provided. [Brief explanation of the drawing]

[0025] [Figure 1] This figure shows the relationship between the density of carbonized, tablet-formed coke and its crushing strength. [Figure 2] This graph shows the relationship between ΔHSP and the collapsing strength of coke. [Figure 3] This graph plots the weighted average intensity against the intensity obtained from actual measurements, relative to ΔHSP. [Figure 4] This graph shows the relationship between the bulk density and crushing strength of coke. [Figure 5] This graph compares the predicted intensity obtained from the regression line in Figure 2 with the predicted intensity obtained from the regression equation of the multiple regression analysis. [Modes for carrying out the invention]

[0026] The following describes specific examples of embodiments of the present invention. Note that the following description is illustrative and illustrates embodiments of the present invention, and the present invention is not limited in any way to the following embodiments.

[0027] [Compatibility between coals] As mentioned earlier, coke is obtained by the dry distillation of coal. In this process, the coal softens and melts, and then the softened and melted coal re-solidifies with foaming. The property of coal to melt and blend together when it is softened and melted is called the miscibility of coal.

[0028] If the miscibility between coals is low, the softened and molten coals will not mix. Then, upon re-solidification, interfaces remain in the coke. At this point, cracks occur due to these interfaces, reducing the strength of the coke. Therefore, to achieve high-strength coke, it is necessary to select coal varieties with high miscibility and blend them as raw materials.

[0029] [Solubility parameters] Solubility parameters (hereinafter also referred to as SP) are indicators of surface state calculated from molecular structure and surface energy. Substances with similar solubility parameters tend to dissolve well together because they have similar surface states.

[0030] The inventors conceived of evaluating the compatibility of different coals using solubility parameters. By blending coals with similar solubility parameters, the coals dissolve more effectively during the softening and melting process in carbonization, resulting in higher-strength coke. In other words, by utilizing the solubility parameters of coals, it is possible to predict coke strength and determine the coal blending ratio necessary to obtain high-strength coke.

[0031] The method for representing the solubility parameter is not particularly limited, and any preferred index such as a point in a 4-dimensional Cartesian coordinate system, a point in a 3-dimensional Cartesian coordinate system, a point in a 2-dimensional Cartesian coordinate system, or a 1-dimensional numerical value may be used. However, increasing the number of dimensions of the solubility parameter allows for the reflection of more factors that determine the surface state in the softened and molten state of coal, and enables a more detailed comparison of the surface state. From this viewpoint, it is preferable that the solubility parameter be represented as a point in a multi-dimensional Cartesian coordinate system. Furthermore, having 3 dimensions for the solubility parameter allows for sufficient reflection of factors that determine the surface state, and enables coordinate geometric evaluation using the solubility sphere method described later. From this viewpoint, it is even more preferable that the solubility parameter be represented as a point in a 3-dimensional Cartesian coordinate system. Hereinafter, the 3-dimensional Cartesian coordinate system may simply be referred to as 3-dimensional space. Also, the solubility parameter represented as a point in the 3-dimensional space may be referred to as 3-dimensional SP.

[0032] Examples of solubility parameters include, but are not limited to, the Hildebrand solubility parameter, which is expressed as a one-dimensional numerical value, and the Hansen solubility parameter (hereinafter sometimes referred to as HSP), which is a three-dimensional SP. Here, the HSP is a solubility parameter expressed as a point in a three-dimensional space with the dispersion force term (δD), polarization term (δP), and hydrogen bonding term (δH) as axes. Hereafter, the three-dimensional space with δD, δP, and δH as axes may be referred to as the Hansen space.

[0033] Among 3D SPs, HSP has a more comprehensive database compared to other solubility parameters. By using this database, coal solubility parameters can be easily derived using many solvents, improving the accuracy of coal solubility parameters. Therefore, it is preferable that the solubility parameter be an HSP.

[0034] Other solubility parameters besides those mentioned above include those derived by applying a correction to at least one of the three terms of the HSP, based on the HSP. In this case, the corrected solubility parameter may be a 3D SP or a solubility parameter other than a 3D SP. A specific example of the correction is to separate δH into a donor term and an acceptor term. The solubility parameter derived by this correction is represented as a point in a 4D Cartesian coordinate system with δD, δP, the donor term and the acceptor term as axes.

[0035] The distance between solubility parameters is the absolute difference between two solubility parameters when the solubility parameters are represented as one-dimensional numerical values. When the solubility parameters are represented as points in a multidimensional orthogonal coordinate system, the distance is the distance between two points in that multidimensional orthogonal coordinate system.

[0036] The present invention will be described below based on specific embodiments. In the following embodiments and examples, the case in which the solubility parameter is HSP will be mainly described as an example, but as mentioned above, the present invention is not limited to HSP and can be applied to any solubility parameter.

[0037] (First Embodiment) In the first embodiment of the present invention, the compatibility between two types of coal is evaluated.

[0038] [Method for evaluating the compatibility of different types of coal] According to the present invention, the compatibility between two types of coal can be evaluated by the following procedure. Procedure (1) Obtain the solubility parameters of the coal. At this time, the solubility parameters may be obtained separately for each of the two types of coal, or they may be obtained simultaneously. Step (2) The compatibility between the coals is evaluated based on the distance between the two solubility parameters obtained.

[0039] [Procedure (1): Procedure for obtaining coal solubility parameters] The procedure for obtaining the solubility parameter of coal according to the present invention is described below.

[0040] Procedure (1) includes, for example, the following operations: Procedure (A): Determine the affinity between coal and the reference material. Procedure (B): Derive the solubility parameter of the coal based on the affinity described above.

[0041] In particular, when the solubility parameter is a three-dimensional SP, the solubility sphere method described later can be suitably used in procedure (B).

[0042] [Procedure (A): Procedure for determining affinity] This procedure determines the affinity between coal and a reference material using a unified standard.

[0043] In this invention, a solvent is used as the reference substance. The type of solvent used is not limited, but a low-molecular-weight pure solvent is preferable, as a database of solubility parameters exists.

[0044] The solvents are preferably of multiple types, more preferably 10 or more types, and even more preferably 15 or more types. Selecting a larger number of solvents improves the accuracy of deriving the solubility parameters.

[0045] Furthermore, it is preferable to select the aforementioned multiple types of solvents so that they consist of solvents with various physical properties. For example, it is preferable to select a wide range of solvents, such as water and aqueous solutions that have hydrogen bonds, nonpolar organic solvents, and polar organic solvents. Examples of nonpolar organic solvents include hydrocarbon-based organic solvents. Examples of polar organic solvents include organic solvents having functional groups such as formyl groups, carbonyl groups, hydroxyl groups, or amino groups. This makes it possible to evaluate the affinity of coal with solvents that have different solubility parameters, thereby improving the accuracy of deriving the solubility parameter of coal. For example, when using HSP as the solubility parameter, the values ​​of δP and δH differ greatly from solvent to solvent, so these values ​​can be dispersed by selecting solvents with various physical properties.

[0046] More specifically, it is preferable to use multiple types of solvents selected to contain at least one of all of (a), (b), and (c) below. (a) water or aqueous solution (b) Nonpolar organic solvents (c) Polar organic solvents Furthermore, one or more mixed solvents may be used as the solvent, which are obtained by mixing two or more miscible solvents in any proportion. In this case, the values ​​of each term in the solubility parameter of the mixed solvent can be determined as a weighted average calculated from the values ​​of the corresponding terms in the solubility parameter of the mixed solvents and the mixing ratio. Since the solubility parameter of the mixed solvent can be adjusted by adjusting the mixing ratio, using a mixed solvent makes it easy to disperse the solubility parameter.

[0047] Furthermore, when using three-dimensional SP as the solubility parameter, it is preferable to select the solvent such that the three-dimensional SP of the solvent is appropriately dispersed in three-dimensional space. This allows for more precise derivation of the three-dimensional SP of coal using the solubility sphere method.

[0048] In particular, when using HSP as a solubility parameter, it is best to select solvents such that the δH of each solvent is evenly distributed within and around the expected numerical range for coal's δH. This is for the following reasons: First, since δH is a component derived from hydrogen bonding, in coal it is thought to be related to functional groups such as hydroxyl and carboxyl groups at the molecular ends. Furthermore, since these functional groups often undergo condensation and elimination due to changes in the carbon skeleton structure caused by carbonization, δH is considered to be a term that particularly influences the molecular structure of the sample being measured.

[0049] When determining the affinity between coal and the aforementioned solvent, it is difficult to determine the affinity based on whether or not the coal dissolves, as coal is black. Therefore, as a specific method for procedure (A), the infiltration time method or the dispersion method described later can be used. In addition, other methods include determining whether or not the solvent is wettable to coal using values ​​such as the wetting area or contact angle, and determining the affinity based on the wettability.

[0050] [Infusion Time Method] This method involves dropping a solvent onto a tablet formed from coal and determining the affinity between the coal and the solvent based on the length of time required for the solvent to penetrate. Advantages of this method include its simple experimental procedure and short time requirement. Furthermore, because the experimental procedure is simple, it does not require the experimenter to possess advanced skills, and anyone can perform accurate measurements. For example, when determining surface tension using the method described in Patent Document 1 and then evaluating the adhesion between coal particles to predict coke strength, the experimental procedure becomes complex. In particular, when measuring surface tension using the film flotation method, the operation of dropping coal particles onto the liquid surface must be performed accurately, resulting in a significant complexity of the experimental procedure and a long time due to the large number of steps. In contrast, the method of determining affinity using the penetration time method and evaluating the compatibility between coal particles is experimentally simple. Furthermore, using the penetration time method, the measurement time can sometimes be reduced to within 1-2 minutes, making it possible to shorten the measurement time compared to other methods for determining affinity. The specific procedure of this method is described below.

[0051] (Crush) During the molding process, it is preferable to crush the coal. While crushing is optional, crushing allows for finer particle size distribution of the coal, resulting in a more uniform distribution of gaps when the tablets are molded. This allows for more accurate measurement of the penetration time.

[0052] (molding) Next, the coal is molded to produce tablets.

[0053] The particle size of the coal used in the molding process is not particularly limited. However, from the viewpoint of using coal with adjusted particle size, the particle size of the coal is preferably 150 μm or less, and more preferably 50 μm or less. A particle size of X μm or less means that all coal particles pass through a sieve with an opening of X μm, and a particle size of Y μm or more means that all coal particles remain on the sieve with an opening of Y μm.

[0054] Any molding method can be used, but a preferred molding method is to fill a mold with the coal and pressurize it to produce tablets. Examples of tablet shapes include cylindrical and rectangular shapes. Here, it is preferable that the shape has a flat surface for dropping. Furthermore, from the viewpoint of making the pressure applied during pressurization more uniform, a cylindrical shape is more preferable.

[0055] There are no particular restrictions on the molding conditions, but it is preferable that the molding pressure be 100 MPa or higher in order to make the density distribution more uniform and improve the accuracy of the measurement. For the same reason, it is preferable that the height of the tablet be 5 mm to 15 mm. Also for the same reason, it is preferable that the tablet be cylindrical and the diameter of the molded body be 10 mm to 20 mm. Furthermore, it is preferable that the mass of the tablet be 0.5 g to 2.0 g.

[0056] (Solvent osmosis) Next, the molded tablets are permeated with a solvent, and the permeation time is measured. This permeation can be performed by dropping the solvent onto the tablets. It is preferable that the amount of solvent dropped onto the tablets be 2 μL or more, as this increases the time required for permeation to be completed and allows for a more accurate determination of the affinity between coal and the solvent. On the other hand, it is preferable that the amount dropped onto the tablets be 10 μL or less to prevent variations in permeation time due to the effects of wetting and spreading.

[0057] The method for measuring the penetration time is not particularly limited, but the time it takes for the solvent to disappear from the surface of the tablet may be observed with the naked eye.

[0058] (Affinity determination) Finally, the affinity between coal and the solvent is determined based on the penetration time. Specifically, if the penetration time is below a certain threshold, the affinity is determined to be "good," and if the penetration time exceeds the threshold, the affinity is determined to be "bad." The threshold can be arbitrarily determined by the type of solvent added or the experimental results, but from the viewpoint of further improving the accuracy of deriving the solubility parameter, it is preferable to determine it based on the ratio of good judgments to the total number of solvents. Specifically, it is preferable to set the threshold so that the ratio is 25% or more, and more preferably 35% or more. Furthermore, it is preferable to set the threshold so that the ratio is 75% or less, and more preferably 65% ​​or less.

[0059] [Dispersion method] This method involves dropping a solvent onto coal, shaking the container containing the coal and solvent, and then determining the suspension state of the mixture after standing. The advantage of this method is its simplicity, as it only requires stirring the coal and solvent and allowing it to stand. From the perspective of operational complexity, it is a simpler measurement method than other methods for determining affinity. Furthermore, it has the advantage of not requiring the experimenter to possess advanced skills, allowing anyone to perform accurate measurements. The specific procedure of this method is described below.

[0060] First, it is preferable to crush the coal to improve its dispersibility in the solvent and thus improve measurement accuracy. The coal before the solvent is added should preferably have a particle size of 150 μm or less, more preferably 100 μm or less.

[0061] The aforementioned methods of dropping, shaking, and standing are not particularly limited and can be carried out by any method.

[0062] After standing, the state of the liquid in the container is checked, and those that maintain a suspension state are judged to have "good" affinity. Conversely, those in which the coal powder has completely settled or floated, the liquid portion has become clear, and the coal and solvent have separated are judged to have "poor" affinity. The method for checking the state of the liquid is not particularly limited, but it may be checked with the naked eye or by using measuring instruments. When using measuring instruments, for example, an absorbance meter or a turbidity meter may be used, and the judgment may be made from the change in measurement data over time.

[0063] [Procedure (B): Procedure for deriving coal solubility parameters] In this procedure, the solubility parameter of coal is derived based on the affinity obtained in procedure (A) above.

[0064] In the derivation process, the derivation method can be appropriately determined so that the distance to the solubility parameter of a reference substance with "good" affinity is small, and the distance to the solubility parameter of a reference substance with "poor" affinity is large.

[0065] The method for obtaining the solubility parameters of the reference substance is not particularly limited. Preferred methods include obtaining them by calculation from the molecular structure and obtaining them by referring to a database. However, many solubility parameters listed in databases are subject to various corrections to reflect the actual system, and even for a specific reference substance, the solubility parameters may differ depending on the source of reference. Therefore, using two or more databases simultaneously can cause errors in the solubility parameters of the coal being derived. Thus, when obtaining the solubility parameters of a reference substance by referring to a database, it is preferable to use the same database for the two types of coal whose compatibility is to be evaluated.

[0066] Furthermore, if the solubility parameter is a three-dimensional SP, the solubility sphere method can be suitably used in this procedure (B).

[0067] Generally, solubility parameters are calculated from molecular structure. However, since the molecular structure of coal is amorphous, it is impossible to directly determine the solubility parameters. Therefore, by using this solubility sphere method, it becomes possible to indirectly derive the 3D SP of coal through geometrical analysis.

[0068] In the fusion sphere method, in procedure (B), first, an inscribed sphere is constructed in three-dimensional space that includes the points corresponding to the 3D SP of the reference material judged as "good" in the affinity determination in procedure (A), but does not include the points corresponding to the 3D SP of the reference material judged as "bad". Then, the coordinates of the center of the inscribed sphere are set as the 3D SP of the coal.

[0069] The method for constructing the inscribed sphere and the method for deriving the center coordinates are not particularly limited. Preferred methods include methods using manual calculations and methods using software.

[0070] The above describes procedure (1): the procedure for obtaining coal solubility parameters. However, there is no limit to the timing for obtaining solubility parameters when evaluating the compatibility of different coals. In other words, when evaluating compatibility multiple times, it is not always necessary to derive solubility parameters each time. If solubility parameters have been obtained in advance for one or both of the coals whose compatibility is being evaluated, these can be used to perform procedure (2) described below.

[0071] [Procedure (2): Procedure for evaluating the compatibility of different coal types] The following describes the procedure for evaluating the compatibility of different coals according to the present invention.

[0072] In this procedure, the compatibility between coals can be evaluated by calculating the distance between the coal solubility parameters obtained in the above procedure (1).

[0073] For example, the distance between the solubility parameters can be used as the value of the compatibility between the coals. In this case, the closer the distance, the higher the compatibility.

[0074] By evaluating the compatibility between different types of coal in this way, it becomes possible to accurately assess the fusion properties of coal in a softened and molten state. This, in turn, improves the accuracy of estimations for obtaining high-strength coke, optimizes coal blending guidelines, and leads to increased operational efficiency. Furthermore, it is expected to contribute to stable production through the selection of appropriate coal brands.

[0075] (Second embodiment) In a second embodiment of the present invention, the two types of coal are heat-treated before obtaining the solubility parameters by procedure (1) above. In other words, each of the two types of coal used in procedure (1) above is coal that has been heat-treated before obtaining the solubility parameters.

[0076] (Heat treatment) This step is optional. However, heat treatment of the coal can bring it closer to a softened and molten state, thereby improving the accuracy of compatibility evaluation. Therefore, it is preferable that the coal be heat-treated before obtaining the solubility parameters.

[0077] From the viewpoint of bringing the coal closer to a softened and molten state, the heat treatment is preferably carried out in an oxygen-free atmosphere. Also, for the same reason, the temperature of the heat treatment is preferably 350 to 800°C. Coal that has undergone the above heat treatment in an oxygen-free atmosphere and at a temperature of 350 to 800°C is called semi-coke. Furthermore, it is more preferable that the two types of coal are semi-coke before the solubility parameters are obtained.

[0078] The procedure following the heat treatment is the same as in the first embodiment.

[0079] (Third embodiment) In the coke quality prediction method according to the third embodiment of the present invention, the compatibility of coal is evaluated based on the coal compatibility evaluation method according to the present invention, and the coke quality is predicted based on the compatibility.

[0080] For example, if there are n pieces of coal to be used as a raw material for coke, the compatibility between two types of coal can be evaluated by comparing two combinations of the n pieces of coal. n The process is carried out in two ways. Note that the coal used for evaluating compatibility may be heat-treated coal. Then, a correction is made to the conventionally used coke strength prediction formula by adding a term that uses the compatibility evaluation result as a variable. Using the corrected prediction formula, the quality of coke can be predicted with high accuracy.

[0081] Another example involves sequentially determining the solubility parameters of incoming coal and comparing them to predict coke quality. This allows for early detection and addressing of variations in quality between batches.

[0082] (Fourth embodiment) The coke production method in the fourth embodiment of the present invention includes a step of determining the coal blend based on the compatibility between coals evaluated using the coal compatibility evaluation method according to the present invention. In other words, the coke production method in the fourth embodiment of the present invention is a coke production method in which the coal blend is determined based on the compatibility between two types of coal evaluated using the above-described coal compatibility evaluation method.

[0083] In the above process, by considering the results of the compatibility evaluation, it is possible to determine the coal blend that will yield high coke strength. The coal used for the compatibility evaluation may be heat-treated coal.

[0084] For example, the process involves establishing a rule such that the distance between the solubility parameters of two types of coal selected from among the candidate coal types is below a certain value (or less than a certain value), and then selecting coal according to the rule. This makes it possible to stably produce high-strength coke. The solubility parameter is HSP (unit: (MPa)) 0.5When using ), the distance between HSPs ΔHSP is preferably less than 12.3. In other words, in determining the blend, it is preferable to select the coals to be blended such that ΔHSP is less than 12.3 for all combinations of two types of coal to be blended. This further improves the strength of the adhesive interface between different types of coal, and as detailed in the examples, it is possible to produce coke with a higher strength than the weighted average strength of coke using single-type coal. ΔHSP is more preferably 7.0 or less, and even more preferably 4.2 or less. In addition, additional rules may be established to select coal in order to produce higher strength coke. For example, it is thought that the closer the physical properties of the blended coals are, the higher strength coke will be produced. Therefore, when selecting the coals, it is preferable to keep the absolute value ΔLogMF, the difference in the common logarithms of MF, below a certain value (or less than a certain value). However, from the viewpoint of balancing with other physical properties, it is also possible that higher strength coke can be obtained when the physical properties of the blended coals are far apart. Therefore, for example, the absolute value ΔRo of the difference in Ro may be set to be greater than or equal to a certain value. In particular, when determining the blend, it is preferable to select the coals to be blended such that all of the following conditions (1) to (3) are satisfied for all combinations of two types of coal to be blended. (1) ΔLogMF is 0.67log / ddpm or less (2) ΔRo is 0.05% or higher (3) ΔHSP is 4.2 or less This makes it possible to produce higher-strength coke, as detailed in the examples.

[0085] Another example is the process of selecting a substitute coal for a specific brand by choosing one with a similar solubility parameter range. This minimizes changes in coke quality due to a change in brand.

[0086] The bulk density of the coke produced is not particularly limited. However, if the bulk density is too low, the macroscopic strength may be low, so 0.82 g / cm³ is recommended. 3The above is preferable. On the other hand, when multiple regression analysis is performed on two types of blended coal, with ΔLogMF, ΔRo, and ΔHSP of the blended coal and the bulk density of the resulting coke as explanatory variables and coke strength as the dependent variable, there are cases where bulk density has a negative correlation with strength. That is, a high bulk density may conversely result in a low strength, so a bulk density of 0.92 g / cm³ is preferable. 3 The following is also acceptable.

[0087] (Fifth embodiment) A coke production method in the fifth embodiment of the present invention includes a step of determining the blend of coal grades based on the coke quality predicted by the coke quality prediction method according to the present invention.

[0088] (Sixth Embodiment) The sixth embodiment of the present invention provides a method for obtaining the solubility parameter of coal, which involves determining the affinity between coal and a solvent based on the infiltration time method and deriving the solubility parameter of the coal based on the affinity. The derivation is preferably performed by procedure (B).

[0089] (Seventh Embodiment) In the seventh embodiment of the present invention, the method for obtaining the solubility parameter of coal involves performing the heat treatment on the coal before determining the affinity between the coal and the solvent using the penetration time method. In other words, the coal used in the penetration time method is coal that has undergone the heat treatment before obtaining the solubility parameter.

[0090] The procedure following the heat treatment is the same as in the sixth embodiment. [Examples]

[0091] The application methods of the present invention will be described below based on an example of the following embodiment. However, the present invention is not limited to this embodiment.

[0092] [Obtaining HSP (Highly Severity Specification) for coal, etc.] First, the common logarithms (hereinafter sometimes referred to as LogMF) of Ro and MF for each coal listed in Table 1 were measured, and the values ​​listed in Table 1 were obtained. Ro was determined by the method in accordance with JIS M 8816. LogMF was determined by the method in accordance with JIS M 8801.

[0093] [Table 1]

[0094] Next, the HSP of each coal listed in Table 1 was determined using the dispersion method described above.

[0095] Coal of brand A listed in Table 1 was crushed to a size of 44 μm or less. 10 mg of the crushed coal was weighed out for each solvent to be added and placed in vials. Next, 5 mL of each solvent listed in Table 2 was added dropwise to each vial, and after thorough mixing, it was allowed to stand for 30 minutes. The state of the liquid in the container after standing was visually inspected, and those that maintained a suspension state were judged to have "good" affinity. Conversely, those in which the coal powder had completely settled or floated, the liquid portion had become clear, and the coal and solvent had separated were judged to have "poor" affinity. The HSPs listed in Table 2 for the solvents judged to have "good" affinity were represented as points in Hansen space, and the coordinates of the center of the inscribed sphere containing these points were taken as the HSP of that coal.

[0096] The same procedure was performed on coals other than brand A in Table 1 to obtain the HSP values ​​for the coals listed in Table 3.

[0097] [Table 2]

[0098] [Table 3]

[0099] Then, from the values ​​in Tables 1 and 3, three indices, ΔRo, ΔLogMF, and ΔHSP, were derived for the combinations listed in Table 4. ΔRo and ΔLogMF are the absolute values ​​of the difference between Ro and LogMF, respectively. ΔHSP is the HSP distance, and in this embodiment, it is used as a value indicating the compatibility between coals.

[0100] [Table 4]

[0101] Note that the HSP values ​​in Table 2 are based on the descriptions in Non-Patent Documents 1-3, and the units for each HSP item in Tables 2 and 3, and for ΔHSP in Table 4 are (MPa). 0.5 That's what I decided.

[0102] [Interface observation of coke] Next, the following experiment was conducted to evaluate the relationship between coal miscibility and coke quality.

[0103] Each type of coal listed in Table 1 was crushed to a particle size of 150 μm or less. Next, for each combination of levels 1 to 4 listed in Table 4, 0.5 mg of the crushed coal was sequentially filled into a cylindrical mold with a diameter of 13 mm. At this time, after filling the first type of coal, the surface was lightly smoothed with a pin before filling the second type of coal to smooth the interface. Then, press molding was performed with a load of 5 tons for 3 minutes to produce two-layered pellets.

[0104] To suppress the effects of expansion, the pellets were sufficiently restrained using wire. Next, the pellets were heated in a pure nitrogen atmosphere from room temperature to 900°C at a heating rate of 3°C / min, held for 10 minutes, and then allowed to cool naturally to obtain coke.

[0105] After carbonization, the coke retains the interface between the two types of coal that were combined. Therefore, the coke was cut, and the interface visible on the cut surface was observed using an optical microscope. Based on the observation results, the state of bubbles near the interface was evaluated. Table 5 shows the evaluation results for foaming near the interface.

[0106] [Table 5]

[0107] Coal type D is included in all combination levels 1 to 4, but it is a coal that tends to foam after carbonization. If the compatibility in the above combination is poor, the formation of homogeneous bubbles in coal type D is hindered by the influence of the interface, which is thought to result in poor uniformity of bubbles near the interface or an increase in the amount of bubbles. Coke with poor bubble conditions near the interface is thought to be prone to cracking at the interface and to have reduced strength.

[0108] If each of the indicators listed in Table 4 is appropriate as an indicator for predicting coke strength, then it is considered that the value at level 4 (good) is clearly lower than the values ​​at levels 1-3 (poor) in the evaluation results. This relationship could not be confirmed with the conventional indicator ΔRo. When ΔLogMF was used, the ΔLogMF values ​​for level 3 (poor) and level 4 (good) were close, making it difficult to distinguish between good and bad, and thus the above relationship could not be confirmed. On the other hand, when using ΔHSP according to the present invention, it was possible to confirm the existence of the above relationship, and the difference in compatibility could be accurately evaluated. In other words, it is considered that the compatibility evaluation method according to the present invention makes it possible to accurately predict the strength prior to the production of the coke.

[0109] [Strength Test 1] Next, we compared the strength of coke produced by carbonizing coal using combinations 2 and 5 from Table 4.

[0110] Three types of coal constituting the above combination were prepared and adjusted so that the particle size was greater than 74 μm and less than or equal to 1 mm. For coal type D, double the amount was prepared and divided equally for each combination. The coals were blended in a mass ratio of 1:1 according to the above combinations and thoroughly mixed. Using the powdered coals of each blend, 20 cylindrical coal tablets, approximately 10 mm in diameter and 10 mm in height, were produced at a pressure of 100 MPa. Fifteen of these tablets were subjected to carbonization in a heating furnace with controllable atmosphere and flow rate. The carbonization was carried out using nitrogen as the atmospheric gas, with a gas flow rate of 100 N mL / min, raising the temperature from room temperature to 900 °C at 3 °C / min, holding it for 10 minutes, and then allowing it to cool naturally to room temperature while continuing to flow nitrogen at the same flow rate. To prevent the tablets from merging due to expansion during carbonization, they were placed at a certain distance from each other in the furnace.

[0111] For each piece of coke produced by the carbonization process, the mass, diameter, and height were measured and the density (bulk density) was calculated. Ten pieces of coke were randomly selected, and their crushing strength was measured by a uniaxial compression test. The direction of the compressive load was the diametrical direction of the coke cylinder, and the compression speed was 1 mm / min.

[0112] The measurement results are shown in Figure 1. In the graph in Figure 1, the X marks and circles correspond to the measurement results of coke using coal blends 2 and 5, respectively, and the dashed and solid lines are linear approximations of the measurement points.

[0113] Factors influencing coke strength include not only the compatibility of coals but also the density of the coke. In fact, as shown in Figure 1, each coke made from two types of coal blends showed higher strength with increasing density. Therefore, by comparing cokes with the same density, the effect of density can be eliminated, and the influence of coal compatibility on strength can be evaluated. In Figure 1, the same coke density (e.g., 0.8 g / cm³) is used. 3 When comparing the levels, it was found that level 5 had a higher intensity than level 2.

[0114] As shown in Table 4, even when attempting to predict coke strength using the conventional index ΔRo, it was difficult to predict that Level 5 would exhibit higher strength. However, by using ΔHSP according to the present invention, it can be predicted that Level 5 has better compatibility between coals and can obtain high-strength coke.

[0115] [Strength Test 2] For each coal of Brands G to K, Ro and LogMF were measured by the methods described above, and HSP was obtained by the methods described above. The results are shown in Table 6. Also, three types of indices ΔRo, ΔLogMF, and ΔHSP in the combinations described in Table 7 were derived. The unit of each term of HSP in Table 6 and ΔHSP in Table 7 is (MPa) 0.5 was used.

[0116]

Table 6

[0117]

Table 7

[0118] Next, the coals were blended according to the combinations described in Table 7, and a strength test of the coked coke was conducted.

[0119] Five coals constituting the above combinations were prepared and adjusted to a particle size of 3 mm or less. According to the combinations 6 to 12 in Table 7, the coals were blended at a mass ratio of 1:1 and thoroughly mixed. Each blended coal in powder form was subjected to carbonization in a carbonization furnace with a diameter of 100 mm. The obtained coke was crushed to about 3 mm. The bulk density of the crushed coke was measured by a method conforming to JIS K 2151. Also, the crushing strength of the crushed coke was measured by a wooden hardness tester. In order to suppress the variation in the results to such an extent that the tendency of the results does not change, the measurement of the crushing strength was performed 50 times, and the average was taken as the crushing strength of the coke.

[0120] Figure 2 shows the relationship between ΔHSP and the coke collapse strength. The dashed line is a linear regression line. It was shown that the strength increases as ΔHSP decreases. Furthermore, using the regression line shown in Figure 2, collapse strength can be predicted based on ΔHSP.

[0121] To investigate the effect of blending, specifically the influence of the strength of the adhesive interface between different coal types, coke was produced from single-type coals and its strength was compared with that of coke produced from blended coals. If there is no effect from blending, the strength of coke produced from blended coals is considered to be the weighted average of the coke strengths derived from each single-type coal. First, coals G to K were carbonized using the same method as for levels 6 to 12 to obtain coke, and then strength tests were conducted to obtain the strength of coke produced from single-type coals. Figure 3 shows a graph plotting the weighted average strength for combinations 6 to 12 in Table 7 against ΔHSP. The solid line is a linear regression line approximated with respect to the measured values, and the dashed line is a linear regression line approximated with respect to the weighted average strength. The graph showed a tendency for coke strength to be higher than the weighted average strength for combinations with smaller ΔHSP. From the obtained regression lines, it is considered that coke with a strength higher than the weighted average strength can be produced when ΔHSP is less than 12.3. Furthermore, it is thought that the difference between the weighted average strength and the actual coke strength can be further increased by setting ΔHSP to 7.0 or less.

[0122] Next, Figure 4 shows the relationship between the bulk density and crushing strength of coke for combinations 6-12 in Table 7. Generally, higher bulk density leads to higher strength, but in Figure 4, the crushing strength is 0.9 g / cm³. 3 The trend shifted from increasing to decreasing at that point. Levels that showed low crushing strength despite high bulk density all had a large ΔHSP. Thus, when comparing blended coals of different brands, higher coke density does not necessarily equate to higher coke strength; however, the distance between solubility parameters can be used to predict coke strength even in such cases.

[0123] To further improve the accuracy of strength prediction, a multiple regression analysis was performed using ΔlogMF and ΔRo as explanatory variables in addition to ΔHSP, and coke collapse strength as the dependent variable. The following regression equation was obtained. The coefficient of determination was high at 0.91, indicating excellent prediction accuracy. I=a×ΔlogMF+b×ΔRo+c×ΔHSP+d Here, a=-0.66, b=1.2, c=-0.38, d=13.9, and I is the predicted value of the coke collapse strength. Figure 5 shows a comparison between the predicted strength (ΔHSP) obtained from the regression line in Figure 2 and the predicted strength (multiple regression) obtained from the regression equation of the multiple regression analysis. It was shown that the predicted strength obtained from the regression equation of the multiple regression analysis is a more accurate value.

[0124] Furthermore, the combinations 10-12 in Table 7, which are shown in Figures 2 and 3 to have particularly high compatibility and coke strength, all have a ΔlogMF of 0.67 log / ddpm or less, a ΔRo of 0.05% or more, and a ΔHSP of 4.2 (MPa). 0.5 The following is the result. Considering the regression equation of the multiple regression analysis and the above numerical ranges together, it can be seen that by keeping ΔlogMF, ΔRo, and ΔHSP within the above numerical ranges, higher-strength coke with a coke strength of 11.9 (MPa) or higher can be produced. Furthermore, when the bulk density of the obtained coke was added to the above explanatory variables and the multiple regression analysis was performed, it was confirmed that the correlation coefficient of bulk density was negative. Since all combinations 10 to 12 in Table 7 had a coke bulk density of 0.92 or less, a bulk density of 0.92 g / cm³ is considered. 3 It is thought that even higher-strength coke may be produced under the following conditions.

Claims

1. A method for evaluating the compatibility between two types of coal, The solubility parameters of the two types of coal mentioned above were obtained, A method for evaluating the compatibility between coals, comprising evaluating the compatibility between two types of coal based on the distance between the solubility parameters of the two types of coal.

2. The method for evaluating the compatibility of coals according to claim 1, wherein the solubility parameter is the Hansen solubility parameter.

3. The method for evaluating the compatibility between coals according to claim 1, wherein the two types of coal are coal that have undergone heat treatment before obtaining the solubility parameters.

4. The method for evaluating the compatibility between coals according to claim 2, wherein the two types of coal are coal that have undergone heat treatment before obtaining the solubility parameters.

5. A method for predicting coke quality, which predicts the quality of coke based on the compatibility between coals evaluated using the method for evaluating the compatibility between coals described in any one of claims 1 to 4.

6. A method for producing coke, comprising determining the coal blend based on the compatibility between coals evaluated using the method for evaluating the compatibility between coals described in any one of claims 1 to 4.

7. A method for producing coke, comprising determining the coal blend based on the coke quality predicted by the coke quality prediction method described in claim 5.

8. A method for producing coke according to claim 6, The solubility parameter is the Hansen solubility parameter, In determining the aforementioned blend, for all combinations of two types of coal to be blended, The distance ΔHSP between the aforementioned Hansen solubility parameters is 12.3 (MPa). ０．５ less than A method for producing coke, comprising selecting the coal to be blended in such a manner.

9. A method for producing coke according to claim 6, The solubility parameter is the Hansen solubility parameter, In determining the aforementioned blend, for all combinations of two types of coal to be blended, The absolute value ΔLogMF of the difference in the common logarithms of the maximum fluidity measured by the Gieseler plastometer is 0.67 log / ddpm or less. The absolute value ΔRo of the difference in the average maximum reflectance of vitrinite is 0.05% or more, and The distance ΔHSP between the aforementioned Hansen solubility parameters is 4.2 (MPa). ０．５ below A method for producing coke, comprising selecting the coal to be blended in such a manner.

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