Methods for evaluating the compatibility of different coal species, methods for predicting coke quality, and methods for producing coke.

Abstract

This invention provides a method for evaluating the compatibility of different coals, enabling simple and highly accurate prediction of coke strength. [Solution] A method for evaluating the compatibility between two or more types of coal when two or more types of coal are blended, comprising: obtaining the solubility parameter of each of the two or more types of coal; calculating the centroid of the solubility parameter; and evaluating the compatibility based on the difference between the centroid and the solubility parameter.

Description

[Technical Field]

[0001] This invention relates to a method for evaluating the compatibility of different types of coal, a method for predicting the quality of coke, and a method for producing coke. [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 stabilize the quality of coke, a blend of two or more types of coal is used.

[0003] Furthermore, coke functions as a reducing agent, carburizing source, and heat source for iron ore within the blast furnace. In this process, the porous structure of coke ensures the permeability and liquid permeability of the blast furnace. Therefore, 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 of semi-coke obtained by heat-treating coal and evaluating the adhesion between coals based on the difference in surface tension. [Prior art documents]

Patent Document

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] When attempting to predict the coke strength using the Ro or MF of each coal blended as a raw material for coke, it has been known that the actual coke strength often deviates from the prediction.

[0010] In addition, attempts have also been made to evaluate the adhesiveness between coals from the surface tension by the method of Patent Document 1 and predict the coke strength based on the adhesiveness. However, this method has problems such as complex experimental operations and long measurement time.

[0011] 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.

Means for Solving the Problems

[0012] The gist of the present invention for solving the above problems is as follows.

[0013] 1. A method for evaluating the compatibility between two or more coals when the two or more coals are blended, comprising: obtaining the solubility parameter of each of the two or more coals, calculating the centroid of the solubility parameters, and evaluating the compatibility based on the difference between the centroid and the solubility parameters. A method for evaluating the compatibility between coals.

[0014] 2. The method for evaluating the compatibility between coals according to 1 above, wherein the solubility parameter is a Hansen solubility parameter.

[0015] 3. A method for evaluating the compatibility between coals according to 1 or 2, comprising heat-treating two or more of the coals from which the solubility parameters are obtained.

[0016] 4. A method for predicting coke quality, which predicts coke quality based on the compatibility between coals evaluated using the compatibility evaluation method between coals described in any of 1 to 3 above.

[0017] 5. A method for producing coke, comprising determining the coal blend based on the compatibility between coals evaluated using the coal compatibility evaluation method described in any of items 1 to 3 above. [Effects of the Invention]

[0018] 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. [Brief explanation of the drawing]

[0019] [Figure 1] This graph shows the relationship between ΔHSP and crushing strength. [Figure 2] This graph shows the relationship between Ro and crushing strength. [Figure 3] This graph shows the relationship between ΔHSP and the Drum exponent. [Modes for carrying out the invention]

[0020] The following describes specific examples of embodiments of the present invention. Note that the following description is illustrative of embodiments of the present invention, and the present invention is not limited in any way to the following embodiments.

[0021] [Compatibility between coals] As mentioned earlier, coke is obtained by carbonizing coal. In this process, the coal becomes soft and molten, and then re-solidifies with foaming. When a blend of two or more types of coal is carbonized, the degree to which the softened and molten coals melt together is called the miscibility between the coals.

[0022] In other words, if the miscibility between coals is poor, the coals that make up the blend will not easily dissolve into each other in the softened and molten state. When the softened and molten coal re-solidifies, interfaces remain between the coals that did not dissolve within the coke. At this time, the strength of the coke changes due to cracking caused by these interfaces. Therefore, in order to achieve high-strength coke, it is necessary to select two or more types of coal to be blended, taking into account the miscibility between the coals, and to determine an appropriate blending ratio.

[0023] [Solubility parameters] Solubility parameters (hereinafter also referred to as SP) are indicators of surface state that can be calculated from molecular structure and surface energy. Substances with similar solubility parameters tend to dissolve well together because they have similar surface states.

[0024] The inventors conceived of evaluating the compatibility of coals using solubility parameters. The ease with which coals melt and dissolve during the softening and melting process in carbonization changes depending on whether the solubility parameters of the coals being blended are similar or not, and this affects the strength of the resulting coke. In other words, by utilizing the solubility parameters of coals, it is possible to predict the coke strength and determine the coal blend to obtain high-strength coke.

[0025] There are no particular limitations on the method of representing the solubility parameter; any preferred index can be adopted, 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. 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, enabling 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. 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.

[0026] 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.

[0027] 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, HSP is preferred as the solubility parameter.

[0028] 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.

[0029] The present invention will be described below based on specific embodiments. In the following embodiments and examples, the case where the solubility parameter is HSP will be described as an example, but as mentioned above, the present invention is not limited to HSP and can be applied to any solubility parameter.

[0030] [Method for evaluating the compatibility of different types of coal] First, a method for evaluating the compatibility of different coals according to one embodiment of the present invention will be described.

[0031] In this embodiment, the compatibility between two or more types of coal when they are blended together is evaluated. In other words, the object of evaluation in this embodiment is a blended coal mixture containing two or more types of coal. The number of types of coal blended together is not particularly limited, but three or more types are common, and it may be around 10 to 15 types. The blending ratio of the coals is also not particularly limited.

[0032] The compatibility between two or more types of coal can be evaluated by the following procedure. Procedure (1): Obtain the solubility parameters for two or more types of coal. The solubility parameters for each type of coal may be obtained separately or simultaneously. Step (2): Calculate the centroid of the coal solubility parameters obtained in Step (1). Step (3): The compatibility between coals is evaluated based on the difference between the centroid calculated in Step (2) and the coal solubility parameter obtained in Step (1).

[0033] [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.

[0034] 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 coal based on the affinity and the solubility parameter of the reference substance.

[0035] [Procedure (A): Procedure for determining affinity] This procedure determines the affinity between coal and a reference material using a unified standard.

[0036] In the present invention, a solvent can be 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 solvent solubility parameters exists.

[0037] 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 increases the accuracy of deriving the coal solubility parameters.

[0038] 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 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 of a solvent, 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.

[0039] More specifically, multiple types of solvents can be used, selected to include at least one selected from the group consisting of (a), (b), and (c) below. From the perspective of using solvents with various physical properties, it is preferable to select solvents that include 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 of the solvents.

[0040] Furthermore, when using three-dimensional SP as the solubility parameter of the solvent, 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 methods such as the solubility sphere method described later.

[0041] In particular, when using HSP as a solvent 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 coal being measured.

[0042] Generally, when determining the affinity between a substance and a solvent, the determination is made by whether or not the substance in question dissolves in the various solvents. However, when determining the affinity between coal and a solvent, it is difficult to determine the affinity based on whether or not coal dissolves, since coal is generally insoluble in various solvents. Therefore, the infiltration time method described later can be used as a specific method for procedure (A). In addition to the infiltration time method, methods can also be used to determine whether or not the solvent has wettability to coal using values ​​such as the wetting area or contact angle, and then determine the affinity based on that wettability.

[0043] [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 and evaluating the compatibility between coal particles using the penetration time method 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.

[0044] (Crush) When molding coal, it is preferable to crush the coal. Although crushing is optional, crushing makes the coal particles finer, resulting in a more uniform distribution of gaps when the tablets are molded. This allows for more accurate measurement of the penetration time.

[0045] (molding) Next, the coal is molded to produce tablets.

[0046] The particle size of the coal used for molding 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.

[0047] Any molding method can be used, but a preferred molding method involves filling a mold with coal and molding it under pressure to produce tablets. The tablet shape can be cylindrical or rectangular, for example. Here, the tablet shape is preferably one with a flat surface for dropping. Furthermore, a cylindrical shape is more preferable from the viewpoint of allowing for more uniform pressure application during molding.

[0048] 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.

[0049] (Solvent osmosis) Next, the molded tablets are permeated with the solvent and the permeation time is measured. The method for permeating the tablets with the solvent is not particularly limited, but it can be done by dropping the solvent onto the tablets. By increasing the amount of solvent dropped, the time required for permeation to be completed is extended, and the affinity between coal and the solvent can be accurately determined, so it is preferable to drop 2 μL or more of solvent. On the other hand, in order to prevent variations in permeation time due to the effects of wetting and spreading, it is preferable to drop 10 μL or less of solvent.

[0050] The method for measuring penetration time is not particularly limited, but the time it takes for the solvent to disappear from the surface of the tablet can be observed with the naked eye.

[0051] (Affinity determination) Next, the affinity between the coal and the solvent is determined based on the measured penetration time. The method for expressing the determination of the affinity between the coal and the solvent is not limited. That is, the affinity may be determined in multiple stages (for example, two stages: good or bad), or it may be determined by determining a parameter that represents the affinity. To perform a more accurate evaluation, it is preferable to determine the affinity by determining a parameter that represents the affinity. As the parameter that represents the affinity, a value that can be directly obtained from the measured penetration time may be used, but it is more preferable to correct it using the evaporation time of the solvent, and more specifically, it is more preferable to use the value obtained by dividing the evaporation time of the solvent by the penetration time. This makes it possible to remove the effect of solvent evaporation from the measured penetration time. Specifically, the evaporation time of the solvent can be determined by dropping an amount of solvent equivalent to the amount dropped onto the coal-molded tablet onto a material where penetration does not occur, such as a Teflon plate, and measuring the time required for evaporation. The larger the value obtained by dividing the evaporation time of the solvent by the penetration time, the higher the affinity between the coal and the solvent is judged to be.

[0052] [Procedure (B): Procedure for deriving coal solubility parameters] In this procedure, the solubility parameter of coal is derived based on the affinity between coal and the reference substance, and the solubility parameter of the reference substance, which were determined in procedure (A). Generally, solubility parameters are calculated from the molecular structure. However, since the molecular structure of coal is amorphous, it is impossible to directly determine the solubility parameter. Therefore, the solubility parameter of coal can be derived by using the solubility parameter of the reference substance.

[0053] The method for obtaining the solubility parameters of a reference substance is not particularly limited. Preferred methods include calculating them from the molecular structure and obtaining them by referring to a database. However, the solubility parameters of reference substances listed in databases are often corrected in various ways 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 derived coal solubility parameters. Accordingly, when obtaining the solubility parameters of a particular coal by referring to a database, it is preferable to obtain the solubility parameters of all reference substances using the same database.

[0054] The solubility parameter of coal can be appropriately determined such that it is close to the solubility parameter of a reference substance with good affinity and farther from the solubility parameter of a reference substance with poor affinity. While the method for deriving the coal solubility parameter is not particularly limited, a suitable method is to use the centroid of the solubility parameter of the reference substance as the coal solubility parameter. Furthermore, when using a three-dimensional SP as the solubility parameter, the solubility sphere method can be suitably used.

[0055] First, we will explain a method that uses the centroid of the solubility parameter of the reference substance as the solubility parameter of coal. This method allows for precise measurement of the affinity between coal and the solvent, thereby enabling accurate determination of the coal solubility parameter. Here, the parameter representing the affinity between coal and the reference substance is used as a weight, and the weighted average of each term in the solubility parameter of the reference substance is calculated to determine the coal solubility parameter. For example, when using HSP as the solubility parameter, the centroid of the solubility parameter of the reference substance can be calculated from the following equations (1) to (4).

number

[0056] Next, the dissolution sphere method will be described. By using the dissolution sphere method, it becomes possible to indirectly derive the three-dimensional SP of coal through geometric analysis.

[0057] When using the dissolution sphere method, in the affinity determination of procedure (A), it is determined in two stages: good affinity or bad affinity. And in this procedure (B), first, an inscribed sphere that includes the points corresponding to the three-dimensional SP of the reference substance determined to have good affinity and does not include the points corresponding to the three-dimensional SP of the reference substance determined to have bad affinity is drawn in three-dimensional space. Then, the center coordinates of the inscribed sphere are taken as the three-dimensional SP of coal.

[0058] The method of drawing the inscribed sphere and the method of deriving the center coordinates of the inscribed sphere are not particularly limited. Preferred methods that can be used include a method using manual calculation and a method using software.

[0059] The above describes procedure (1): the procedure for obtaining coal solubility parameters. This procedure should be performed for each of two or more types of coal. Furthermore, there is no limit to the timing for obtaining coal solubility parameters when evaluating the compatibility of coals. In other words, when evaluating the compatibility of coals multiple times, it is not necessary to derive the coal solubility parameters each time. If solubility parameters have been obtained in advance for one or more types of coal included in the evaluation, these can be used to perform procedure (2) described below.

[0060] [Procedure (2): Procedure for calculating the centroid of the coal solubility parameter] Next, the centroid of the coal solubility parameter obtained by the above procedure (1) is determined. The centroid can be calculated using the proportion of coal used in the blend, for example, the weight ratio, as the weight. For example, when using HSP as the solubility parameter, the centroid of the coal solubility parameter can be calculated from the following equations (5) to (7).

number

[0061] [Procedure (3): Procedure for evaluating the compatibility of coals based on the difference between the center of gravity and the solubility parameter] Next, the compatibility between the coals is evaluated based on the difference between the centroid calculated in step (2) and the coal solubility parameter obtained in step (1).

[0062] When using HSP as the solubility parameter, the difference between the centroid of the coal solubility parameter and the solubility parameter of coal i is (δD cg -δD i sample δP cg -δP i sample δH cg -δH i sample It is represented as follows:

[0063] In this procedure, for example, the distance Δ between the centroid of the coal solubility parameter and the solubility parameter of coal i is calculated. i This should be calculated for all coal i (where i is an integer between 1 and the number of coals). Note that the distance between the centroid and the solubility parameter is the absolute difference between the two values ​​if the solubility parameter is represented as a one-dimensional numerical value. If the solubility parameter is represented as a point in a multidimensional Cartesian coordinate system, it is the distance between the two points in the multidimensional Cartesian coordinate system. When using HSP as the solubility parameter, Δ i This is calculated using the following formula (8).

number

[0064] While there are no particular limitations as an indicator of compatibility between coals, Δ i The maximum value of this can be used. This allows the influence of some coals on the overall compatibility, even if their solubility parameters are far apart, to be reflected as an indicator of compatibility between coals.

[0065] By evaluating the compatibility between coals in this way, the fusion properties of two or more types of coal in a softened and molten state can be accurately assessed. This, in turn, improves the estimation accuracy 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 types.

[0066] (Heat treatment) In a preferred embodiment of the present invention, two or more types of coal from which solubility parameters are obtained by procedure (1) may be heat-treated. In other words, each of the two or more types of coal used in procedure (1) may be coal that has been heat-treated before obtaining the coal solubility parameters.

[0067] Heat treatment can be performed as needed. However, heat treatment of coal can bring it closer to a softened and molten state, thereby improving the accuracy of evaluating the compatibility between different types of coal. Therefore, it is preferable to heat treat two or more types of coal from which solubility parameters are obtained.

[0068] From the viewpoint of bringing the coal closer to a softened and molten state, it is preferable to perform the heat treatment in an oxygen-free atmosphere. Also, for the same reason, it is preferable to set the heat treatment temperature to 350 to 800°C. Coal that has undergone heat treatment under the conditions of an oxygen-free atmosphere and a temperature of 350 to 800°C is called semi-coke. Furthermore, it is even more preferable that the two or more types of coal described above have been converted to semi-coke before obtaining the coal solubility parameters.

[0069] The procedure following the heat treatment can be the same as the compatibility evaluation method described above.

[0070] [Methods for predicting coke quality] In the coke quality prediction method according to this embodiment, the compatibility between coals is evaluated based on the above-described method for evaluating the compatibility between coals, and the coke quality is predicted based on the compatibility between the coals.

[0071] For example, by assuming a predetermined combination and blending ratio of coals as the blended coal, the compatibility between the coals in the blend can be evaluated, and the quality of the coke produced from the blend can be predicted based on the evaluation results. Specifically, the conventionally used coke strength prediction formula can be corrected by adding a term that uses the evaluation results from the above-mentioned coal compatibility evaluation method as a variable. Using the corrected prediction formula, the quality of coke can be predicted with high accuracy.

[0072] Another example involves sequentially determining the solubility parameters of incoming coal, changing the combination of coals used in the blend, and evaluating the compatibility between coals when the incoming coal is used in a predetermined blending ratio to predict coke quality. This allows for the appropriate design of coal combinations and blending ratios that take into account variations in quality from lot to lot.

[0073] One specific aspect of coke quality that can be predicted is coke strength. Examples of coke strength include crushing strength and drum index. When comparing cokes under conditions where the weighted average value of Ro in the blended coals is nearly equal, a decrease in the mismatch between the blended coals tends to lead to a decrease in the drum index, while the crushing strength tends to improve. This is thought to be because crushing tests and drum tests evaluate different failure modes.

[0074] [Method of producing coke] The coke manufacturing method according to this embodiment is a method for manufacturing coke in which the blend of coals is determined based on the compatibility between coals evaluated using the above-described method for evaluating the compatibility between coals. In other words, the coke manufacturing method includes a step of determining the blend of coals based on the compatibility between coals evaluated using the above-described method for evaluating the compatibility between coals.

[0075] In the aforementioned process, by considering the evaluation results of the compatibility between coals, it is possible to determine a coal blend that will yield high coke strength, i.e., the combination of coal brands and / or their blending ratios. Then, coke can be produced using the blended coal obtained based on the determined coal blend as the raw material.

[0076] For example, the above process may involve determining two or more coal brands and their blending ratios from among the candidate coal brands for coke raw materials, establishing rules so that the index of compatibility between coals is below a certain value (or less than a certain value), and selecting coal in accordance with the said rules. If the rules are not met, the compatibility between coals can be repeatedly evaluated by changing one or both of the coal brands and blending ratios. This makes it possible to stably produce high-strength coke.

[0077] Another example is the process of selecting a substitute coal for a specific brand, such that the compatibility values ​​between the coals are similar. Specifically, the compatibility between coals can be evaluated using the method described above for candidate blends that use the specific brand and those that do not, and the compatibility index for each blend can be compared. Then, the blend with a compatibility index close to that of the blend using the specific brand can be determined as the coal blend after the brand change. This minimizes the change in coke quality due to the change in brand. [Examples]

[0078] 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.

[0079] The coals used were coals A to U listed in Table 1. The common logarithms of Ro and MF (hereinafter sometimes referred to as LogMF) for each coal 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.

[0080] [Table 1]

[0081] (Example 1) (Acquisition of HSP for coal) In Example 1, the affinity between coal and solvent was determined using the infiltration time method, and the HSP of each coal was determined using the affinity measurement results and the HSP of each solvent.

[0082] First, coal samples A through M listed in Table 1 were air-dried, crushed, and then classified into particles smaller than 212 μm. These were then carbonized at 500°C to produce semi-coke (heat treatment). The resulting semi-coke was crushed and classified again into particles smaller than 212 μm. The classified semi-coke was formed into cylindrical pellets with a diameter of 32 mm. Two μL of each solvent listed in Table 2 was dropped onto the pellets, and the penetration time for each solvent was measured. The HSP values ​​for each solvent listed in Table 2 were based on the description in HSPiP 5th Edition 5.4.08. Similarly, the solvents were dropped onto a Teflon plate, and the evaporation time was measured.

[0083] [Table 2]

[0084] The value obtained by dividing the evaporation time of each solvent by the infiltration time is a parameter m representing the affinity between coal and the solvent. k The following was determined. Next, the centroid of the HSP of each solvent was determined according to the above equations (1) to (4), and this was used as the HSP of each coal. The obtained HSPs of each coal are shown in Table 1.

[0085] (Evaluation of compatibility between different types of coal) First, the blending patterns I to V in Table 3 were determined. In these blending patterns, the weighted average value of Ro of each coal used in the blend (Ro of the blended coal) was kept approximately constant. The Ro of the blended coal is shown in Table 3. Furthermore, according to equations (5) to (7) above, the centroid of the HSP of the coal in each blending pattern was calculated, and Δ was calculated according to equation (8) above. i We sought Δ i The maximum value (ΔHSP) is shown in Table 3.

[0086] [Table 3]

[0087] (Crushing strength) Coals A to M listed in Table 1 were air-dried, crushed, and then classified into particles smaller than 212 μm. The coals were then blended according to the above blending patterns. The blending ratios were based on the weight of the air-dried coals. The resulting blended coal was carbonized at 900°C to produce coke. The resulting coke was crushed to approximately 3 mm, and its crushing strength was measured using a Kiya hardness tester. Figure 1 shows the relationship between ΔHSP and crushing strength. Crushing strength and ΔHSP showed a high correlation. For comparison, Figure 2 shows the relationship between Ro and crushing strength. Since Ro was almost constant in each blending pattern, if strength could be predicted using Ro, the crushing strength should also be constant. However, the crushing strength showed different values ​​for each blending pattern. Thus, even when the prediction accuracy of coke strength is poor when using commonly used coal properties such as Ro, the prediction accuracy can be improved by considering the compatibility between coals evaluated by the method of the present invention.

[0088] (Example 2) (Acquisition of HSP, etc., for coal) In Example 2, the HSP of each coal was determined using the molten sphere method.

[0089] First, coals N through U listed in Table 1 were air-dried, crushed, and then classified into particles smaller than 212 μm. They were then carbonized at 500°C to produce semi-coke (heat treatment). The resulting semi-coke was crushed and classified again into particles smaller than 212 μm. Next, 0.5 g of each classified semi-coke was taken. Then, coals N through U were added to test containers containing 10 ml of each solvent listed in Table 2, and the coal was dispersed. After 30 minutes, the dispersion state of the coal (affinity between coal and solvent) was visually evaluated in two stages. Score 1: Coal is dispersed throughout the solvent. Score 0: More than 10% of the solvent is transparent from the top. The above evaluations were performed for each type of coal using all the solvents listed in Table 2.

[0090] Next, for each coal, the dispersion state score for each solvent and the solvent's HSP were input as a dataset into the HSPiP software (5th Edition 5.4.08) to calculate the coal's HSP (δH, δP, δD). Specifically, an inscribed sphere was constructed in 3D space that included points corresponding to the HSP of solvents judged to have good affinity (score 1) and excluded points corresponding to the HSP of solvents judged to have poor affinity (score 0). The coordinates of the center of this inscribed sphere were taken as the coal's HSP. The obtained HSPs for each coal are shown in Table 1.

[0091] (Evaluation of compatibility between different types of coal) First, the blending patterns I to III in Table 4 were determined. In these blending patterns, the weighted average value of Ro of each coal used in the blend (Ro of the blended coal) was kept approximately constant. The Ro of the blended coal is shown in Table 4. Furthermore, according to equations (5) to (7) above, the centroid of the HSP of the coal in each blending pattern was calculated, and Δ was calculated according to equation (8) above. i We sought Δ i The maximum value (ΔHSP) is shown in Table 4.

[0092] [Table 4]

[0093] (Drum test) From the coals listed in Table 1, coals N to U were crushed to 3 mm or less, and the coals were blended according to the blending patterns listed in Table 4. The resulting blended coal was carbonized at 1,000°C to produce coke. A drum test was performed on the obtained coke according to JIS K2151 to obtain the drum index. The relationship between ΔHSP and the drum index is shown in Figure 3. Since Ro is almost constant in each blending pattern, if the strength could be predicted using Ro, the drum index should also be constant. However, the drum index showed different values ​​for each blending pattern. Thus, even when the accuracy of predicting coke strength is poor when using commonly used coal properties such as Ro, the accuracy of prediction can be improved by considering the compatibility between coals evaluated by the method of the present invention.

Claims

1. A method for evaluating the compatibility between two or more types of coal when two or more types of coal are blended, The solubility parameters of each of the two or more types of coal mentioned above are obtained, The centroid of the aforementioned solubility parameter is calculated, A method for evaluating the compatibility between coals, wherein the compatibility is evaluated based on the difference between the center of gravity and the solubility parameter.

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 or 2, comprising heat-treating two or more of the coals from which the solubility parameters are obtained.

4. 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 claim 1 or 2.

5. 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 claim 1 or 2.

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