JP2018177871A - A method for producing molded coal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a molded coal for surely and stably obtaining the molded coal having high strength, and for stably improving a production yield of the molded coal accordingly.SOLUTION: The method for producing the molded coal comprises: a pulverizing step for pulverizing a raw coal, a mixing step for mixing coal powder obtained by the pulverizing step with a binder, and a molding step for molding a mixed product obtained into a block shape, wherein the mixing step utilizes coal particles having an average circularity of less than 0.73 and the molding step utilizes a mixed material obtained by mixing the coal particles having an average circularity of less than 0.73 with the binder. Further, the mixing step consists of mixing the coal particles having a mesh size of 0.3 mm in the mixed material so as to be 25% or less in terms of mass% with respect to a whole coal particles.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing molded coal blended as a coke raw material for coke oven charging.

  As well known, in the process of producing coke used in blast furnace operation, there is a technique of blending pre-formed coal as a coal raw material to be introduced into the coke oven. As a manufacturing method of such a shaped coal, it is common to grind | pulverize raw material coal, knead | mix by a kneader with a binder, and to manufacture by shape | molding by a molding machine. That is, pulverized coal obtained by pulverizing raw material coal, for example, pulverized coal in which about 3% of coal particles of 3 mm under occupy about 90% of all coal particles, is charged into a kneader, and kneaded with a binder such as tar It is general to form the obtained kneaded material into a lump of about 20 to 70 cc per piece by a twin roll molding machine or the like. In the initial stage after the start of kneading by the kneader, fine powder coal particles are aggregated via the binder to form coal particle aggregates (simulated particles) of a certain size, and the shearing action in the kneader is continued Thus, while the pseudo particles are separated, uniform mixing with the binder proceeds (kneading progresses).

  If the strength of the formed coal produced as described above is low, when the formed coal is charged into the coke oven and coked, the formed coal is destroyed at the time of handling of the formed coal or at the time of charging into the coke oven, The strength of coke coked by the furnace also tends to decrease. Also, if the strength of the formed coal is low and broken as described above when handling the formed coal or inserting it into the coke oven, the mass fraction of coke obtained (mass coke of a certain size or larger is obtained. Yield is also reduced. Furthermore, if a large amount of pulverized coal produced by the destruction of the formed coal is charged into the coke oven, a thick carbon layer is formed on the inner wall surface of the carbonization chamber of the coke oven, which adversely affects the coke oven operation. It also happens. Therefore, in the process of producing a coal briquette, it is strongly desired to obtain a coal briquette having high strength.

  Conventionally, as a technique for producing a high strength molded coal, for example, methods described in Patent Document 1 or Patent Document 2 have been proposed.

  According to the proposal of Patent Document 1, 5 to 10 parts by mass of a binder is added in a kneading step before molding using pulverized coal pulverized so that coal particles of 1.5 mm or less become 90% by mass or more. It is characterized by knead | mixing until the coal powder particle of 2 mm or more becomes 6 mass% or less. And in patent document 1, while adjusting the particle size of pulverized coal before kneading | mixing as mentioned above, it is supposed that high intensity | strength molded coal will be obtained by adjusting the kneading degree which makes the particle size after kneading | mixing an index There is.

  In the method of Patent Document 2, a binder is added to heated pulverized coal, and the mixture is kneaded, and then pressure-formed to produce molded coal, the binder is added to the pulverized coal heated to 135 ° C. to 170 ° C. and kneaded. Then, in the method of press-molding to produce a shaped coal, the particle size distribution of the pulverized coal and the binder after kneading is set to 600 μm or more: 35 mass% to 50 mass% and 75 μm or less: 5 mass% to 15 mass%. It is characterized by And in patent document 2, it is supposed that high-strength molded coal is obtained by adjusting the particle size distribution after kneading | mixing of pulverized coal and a binder as mentioned above.

  However, according to experiments by the present inventors, adjustment of the particle size of pulverized coal before kneading as shown in Patent Document 1, adjustment of the degree of kneading using the particle size after kneading as an index only, or Patent Document 2 It has been found that it is difficult to obtain a high strength molded carbon reliably and stably only by adjusting the particle size distribution after kneading as shown.

Japanese Patent Laid-Open No. 6-330049 Japanese Patent Application Publication No. 2007-23170

  The present invention has been made on the background of the above-mentioned circumstances, and it has been made to ensure that molded carbon having high strength is surely and stably obtained, and accordingly, the manufacturing yield of molded coal can be stably improved. It is an issue to provide a method for producing coal briquettes.

When the present inventors repeated various experiments and examinations in order to solve the above-mentioned problems, the following new findings were obtained.

  That is, according to the experiments of the present inventors, the degree of spheroidization of the coal particles at the stage of the raw material after the pulverization before the start of the kneading largely affects the strength of the molded coal after the kneading and molding. It has been newly found that if the spheroidization of the coal particles to be provided and kneaded is excessively progressed, the strength of the formed coal decreases sharply.

  And as a result of repeating experiment and examination further, the degree of spheroidization of coal in the stage before kneading is evaluated by the degree of circularity of particles, and if the degree of circularity is less than 0.73 on average, kneading and molding It has been found that sufficient strength can be secured as the post-cast coal strength, and the present invention has been achieved.

Specifically, the method for producing the coal according to the basic aspect (first aspect) of the present invention is
It has a grinding process of grinding a coal raw material, a kneading process of kneading the coal powder obtained by the grinding process with a binder, and a forming process of forming the obtained kneaded material into a block form.
In the kneading step, kneading is performed using coal particles having an average circularity of less than 0.73, and the kneaded material comprising the obtained coal particles and a binder is subjected to the next molding step. It is.

  In the method for producing molded coal according to such a basic aspect, by setting the average circularity of coal particles provided in the kneading step to less than 0.73, molded coal having high strength can be reliably and stably obtained. be able to. Here, the coal particles to be subjected to the kneading step mainly include agglomerated particles (fine particles) in which fine particles are aggregated, and separated particles after aggregation in which aggregated pseudo particles are separated, and some of the particles are aggregated from the beginning The average degree of circularity of the coal particles subjected to the above-mentioned kneading step may also mean the overall degree of circularity including all these particles. However, as described below, as for all the coal particles to be subjected to the kneading step, it is usually that the coal particles having a particle diameter within the range of 0.1 mm to 1.0 mm occupy 60% by mass or more of the whole coal particles. Therefore, the average value of the circularity of coal particles in the range of 0.1 mm to 1.0 mm is represented, and the average value of the circularity of coal particles in the range of 0.1 mm to 1.0 mm is the average It may be taken as the roundness.

Further, in the method of producing the coal according to the second aspect of the present invention, in the first aspect,
In the kneading step, coal particles having a size of 0.3 mm under of a sieve mesh in the kneaded material to be obtained are kneaded so as to be 25% or less by mass with respect to all the coal particles.

  Here, the mass ratio of coal particles having a sieve size of 0.3 mm under in the kneaded material is used as an index of the degree of kneading in the kneading step. And by kneading the coal particles of 0.3 mm under with a mesh size of 25% or less by mass% to all the coal particles, the kneading degree is also secured, and the strength of the formed coal is more surely It can be stably enhanced. That is, the regulation of the average circularity of coal particles subjected to the kneading step described in the first aspect and the regulation of the mass ratio of coal particles of 0.3 mm under of sieve mesh in the kneaded material are combined. And the strength of the formed coal can be enhanced more reliably and stably.

  Here, the whole particle of coal including the pseudo particle and the particle from which the pseudo particle separated during the kneading is simply referred to as the coal particle. Therefore, for example, “coal particles during kneading” refers to pseudo particles and coal particles (including fine particles which are not aggregated in part) mainly consisting of pseudo particles and their separated particles when aggregation of pulverized coal proceeds. means.

Furthermore, in the method of producing the coal according to the third aspect of the present invention, in the first or second aspect,
The coal powder to be subjected to the kneading step after the pulverizing step is characterized in that coal particles of 0.3 mm under of sieve mesh occupy 80% or more by mass% with respect to all the coal particles. It is.

  According to the method for producing a shaped coal of the present invention, a shaped coal having high strength can be reliably and stably obtained, and the yield of the shaped coal can be improved to reduce the cost.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows an example of the whole structure of the installation for enforcing the manufacturing method of the formed coal of this invention. It is a figure which shows the result of Experiment 1 which becomes the basis of this invention, and is a graph which shows the relationship between the kneading | mixing time in a kneading | mixing process, and the shaping | molding yield and fall yield of the molding coal after shaping | molding of kneaded material. The figure which shows the result of Experiment 2 which becomes the foundation of the present invention, and shows the relationship between the number of rotations of the kneading blade in the kneading process and the integrated yield (the molding yield x the drop yield) of the molding coal after molding the kneaded material. It is a graph. The figure which shows the result of Experiment 3 which becomes the foundation of the present invention, and the mass ratio which the coal particle of 0.3 mm under in a kneaded material occupies with respect to all the coal particles, the formation yield of the molding coal after kneading thing formation, It is a graph which shows a relation with falling yield. It is a figure which shows the result of the Example of this invention, and is a graph which shows the relationship between the average roundness of the coal particle after grinding | pulverization which is provided to kneading | mixing, and the falling yield of the molding coal after kneading | mixing thing shaping | molding.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Basically, the method for producing molded coal according to the present invention comprises: a pulverizing step of pulverizing a coal raw material; a kneading step of kneading the coal powder obtained by the pulverizing step with a binder; It is premised to have a molding process for molding.
An example of the equipment configuration for carrying out the method for producing a coal briquette having such steps is shown in FIG.

  In FIG. 1, the raw material coal is crushed by a crusher 10 such as an impeller breaker, and the crushed raw material coal is transported by an appropriate carrier 12 and, for example, to three raw material coal hoppers 14A, 14B, 14C. It is thrown in one by one. Raw material coal (pulverized coal) cut out from raw material hoppers 14A, 14B, 14C by cut-out machines 15A, 15B, 15C is fed to kneading machines 18A, 18B, 18C through weighing conveyors 16A, 16B, 16C. . In addition, tar (for example, road tar) is supplied from the tar tank 20 to each of the kneaders 18A, 18B and 18C as a binder for molding.

  In each of the kneaders 18A, 18B, and 18C, in the initial stage, the fine powder coal particles and the binder are mixed, and the fine powder coal particles are aggregated to form aggregates of a certain size (pseudoparticles) It will be in the state of Further, with the progress of the kneading, coal particles in a pseudo-particle state separate and are uniformly mixed with tar, and as a whole, it becomes a kneaded material in which coal particles and tar are uniformly mixed. Such a mixture of coal particles and a binder is introduced into forming machines 22A, 22B, 22C such as double roll forming machines, formed into a block of about 20 to 70 cc per piece, and discharged as formed coal. It is carried out by a conveyor 24 to a not-shown coal briquette yard, and then charged into a coke oven as appropriate.

  The kneader may be either a continuous system or a batch system, or may be either vertical or horizontal, and any number of kneading blades may be used, such as a single screw system or a twin screw system, but any kneader may be used. Also, it has been found that the degree of spheroidization of coal particles after kneading is almost the same as the degree of spheroidization of coal particles at the stage of charging into the kneader, ie after grinding and before the start of kneading. There is.

  On the other hand, according to experiments and studies by the present inventors, it was found that the degree of spheroidization of coal particles before kneading (after grinding) has an influence on the strength of molded coal. Specifically, the degree of spheroidization of coal particles after pulverization, which is subjected to kneading, is the cross-sectional shape of the coal particles (projection when the particles are projected onto a projection plane perpendicular to the parallel rays by parallel rays) It has been found that if the degree of circularity of the shape of the image) is increased to 0.73 or more on average, the strength of the formed carbon is rapidly reduced.

  The relationship between the average circularity of the coal particles before kneading and the falling yield as an index of the strength of the formed carbon after crushing is shown in FIG. 5 as a result of an example described later. Here, the drop yield is, as will be described in detail later, the mass of all of the coal briquettes subjected to the drop test for 100 mm over of the coal briquettes, and the mass relative to all briquettes of the coal briquettes that were not broken to under 100 mm. It means a percentage and is therefore a value that is not easily broken by the drop test, ie the strength of the formed coal. If the falling yield is about 80% or more as a target value, it can be judged that the molded coal strength is high.

  From FIG. 5, it is shown that the falling yield as an index of the strength of the formed carbon tends to decrease as the average circularity increases from around 0.71, and in particular, when the average circularity becomes 0.73 or more, the falling rapidly It is clear that the yield drops and falls below the target of 80%. From such a relationship, in the present invention, the average degree of circularity of the coal particles to be subjected to the kneading is set to less than 0.73, in other words, the average degree of circularity of the coal particles is 0.73 in the crushing step before the kneading. It is decided to finish the grinding in less stages.

  In the above, the pulverization is finished when the average circularity is less than 0.73, but from FIG. 5, if the average circularity is less than 0.71, the falling yield is 90% or more, If high cast coal strength can be secured, and therefore grinding is terminated at a stage where the average circularity is less than 0.71, coal particles having an average circularity less than 0.71 are subjected to the next kneading step. It is possible to obtain a shaped coal having a high strength more reliably and stably.

Here, the above circularity can be calculated by image processing of a photographed image (two-dimensional image) of coal particles sampled immediately after the crusher 10, for example, and the area S of the particles in the two-dimensional image It is a value calculated by the following equation (1) from the relationship with the contour line length (perimeter length) L of the particle in the two-dimensional image.
Circularity R = 4πS / L ² (1)

In the experimental examples and examples of the present invention, the actual measurement of the average circularity was performed as follows.
That is, coal powder in a particle size range of 0.1 mm to 1.0 mm is to be measured, a two-dimensional image thereof is photographed, and the photographed image obtained is a particle shape measuring device (manufactured by Spectris, Ltd. Malvern Division, Image analysis was performed with Molofogi (registered trademark) G3-ID) to calculate the roundness R. Here, measurement was performed so that the number of measurement samples (the number of measurement particles) was 30,000 or more at each level, and the arithmetic average value was taken as the average circularity. In this measurement, the reason for using coal powder whose particle size is in the range of 0.1 mm to 1.0 mm is because particles of the particle size occupy 60% or more of the mass ratio of the target sample. .

  When the above circularity R is R = 1, this corresponds to the case where the shape of the two-dimensional image of the particle is a true circle, and therefore, in three dimensions, the particle is a nearly perfect sphere. Then, as the value of the circularity R becomes smaller than 1, the shape of the two-dimensional image of the particle deviates from a true circle, and the unevenness of the contour line becomes larger, that is, the unevenness of the particle surface becomes large in three dimensions. It means to become. Therefore, an average degree of circularity of less than 0.73 means that, on average, coal particles having a surface unevenness larger than a certain extent occupy a large number.

  As described above, if the coal particles used for kneading become close to spheres, the strength of the formed coal decreases after kneading and molding, in other words, the roundness of the coal particles used for kneading is a large value close to 1 The reason for the decrease in strength of the coal briquettes if this is not always clear, but is presumed as follows. That is, the contact area between the surface of the coal particles and the binder during kneading by the kneader decreases as the degree of circularity of the coal particles to be kneaded increases (closer to 1), and as a result, the strength after molding the kneaded material Is considered to be lower. At the same time, as the roundness of the coal particles is larger (closer to 1), during kneading, the friction of the coal particles on the kneading blade and the inner circumferential surface of the kneading machine and the friction between the coal particles decrease, so the same time Even if only kneading is performed, it is presumed that lowering of the degree of kneading also causes reduction in strength after molding of the kneaded material.

  Based on the above-mentioned findings, in the method for producing coal according to the present invention, in the crushing step, the grinding is finished at a stage where the average circularity of the coal powder particles is less than 0.73, and the average circularity is less than 0.73. The coal particles of the present invention are subjected to the kneading step together with the binder, and the kneaded material after kneading (kneaded product of coal particles having an average circularity of less than 0.73 and the binder) is And By doing so, it becomes possible to reliably and stably manufacture a shaped coal having high strength in the end.

  Here, in the pulverizing step, as the pulverization proceeds, the coal particles (the pseudo particles and the dispersed particles thereof) gradually become spheroidized and the average circularity increases (the value of the average circularity approaches 1), but the pulverization The degree of progress of the spheroidization (the degree to which the average circularity increases) differs depending on the type and structure of the machine. Therefore, in order to finish the grinding at a stage where the average circularity of the coal powder particles is less than 0.73 (preferably less than 0.71), as described above, the grinding experiment under a certain grinding condition is repeated in advance. Or, from the past results, the timing at which the average circularity is 0.73 or 0, 71 is predicted, and the grinding conditions may be adjusted so that the grinding is ended before the timing.

The type of crusher used in the crush process is not particularly limited, and a conventional crusher can be used. In short, as described above, the average circularity of coal particles after crush is less than 0.73. It may be crushed so as to be (preferably less than 0.71).
Further, the type of kneading machine used in the kneading step and the kneading conditions are not particularly limited, and kneading may be performed under appropriate conditions using a conventional general kneader.

  In the method of the present invention, basically, after commencing comminution, comminution may be finished before the roundness of coal reaches 0.73 (desirably 0.71), but sieving The stage after 0.3 mm under coal particles become 25% or less by mass% of all coal particles and before the average circularity becomes 0.73 (preferably 0.71) It is desirable to complete the grinding at

  Although the size or particle size distribution of the pulverized coal powder to be subjected to the kneading step is basically not limited, in general, coal particles of 0.3 mm under with a mesh size of 0.3% by mass relative to all coal particles Often use 80% or more, and in the case of the present invention as well, coal powder having a mesh size of 0.3 mm under represents 80% or more by mass relative to all coal particles is subjected to the kneading step Is preferred. In addition, it is needless to say that the powder after crushing in the crushing step may be sieved by an appropriate sieve, and the coal particle powder after sieving may be subjected to the kneading step.

  In the following, experiments 1 to 3 on which the present invention was made will be described.

  First, an experiment 1 as a basis for obtaining the knowledge that high-strength molded coal can be obtained by ending kneading at a stage where the average circularity of coal powder particles is less than 0.73 will be described.

[Experiment 1]
The effects of kneading time on molding yield and falling yield, and in turn the effect of average circularity of coal particles after kneading on molded coal strength, were investigated as follows using a batch-type vertical kneader .
Coal powder pulverized so that powder of under 3 mm occupies 80% by mass or more by a pulverizer is introduced into a batch type vertical kneader, and the rotational speed of the kneading blade is 120 rpm, and load tar is used as a binder. To 6% by mass ratio and kneading. At that time, the kneading time was variously changed within the range of 3 to 30 minutes. The kneaded product after kneading at each kneading time was molded by a molding machine, and the molding carbon obtained was examined for molding yield and dropping yield.

Here, the term "molding yield" means a yield at which massive molded coal having a desired size can be obtained for blending and charging as coal in a coke oven, and here, 10 mm of the coal after passing through a molding machine The mass ratio occupied by the above-mentioned coal briquettes is used as the molding yield. Specifically, the formed carbon after passing through the forming machine is classified by a sieve with a sieve of 10 mm, the amount of formed coal on the sieve is W1, and the total mass of the formed coal which has passed through the forming machine is W0.
Molding yield P1 = W1 / W0
Determined by

Further, the falling yield means a yield which is capable of obtaining, among lumpy coals of a size which is desirable for blending and charging as coal in a coke oven, a coal which is smaller than the above-mentioned size and which is not broken by the falling test. Therefore, the drop yield corresponds to an index of average strength (molded body strength) for bulk molded coal of a size desired to be mixed and charged as coke in a coke oven, and the larger the drop yield, the more It means that charcoal intensity is large on average. As a specific drop yield measurement method, in the above-mentioned molding yield measurement, the formed coal (mass W1) on the sieve obtained by classifying the formed coal after passing through the forming machine with a sieve of 10 mm sieve, A drop test is conducted to free fall 10 times from a height of 2.5 m, and the coal which has been subjected to the drop test is again classified using a sieve with a sieve of 10 mm, the mass of the formed coal on the sieve is W2, and it passes through the molding machine The ratio to the total mass W0 of the formed coal was defined as the falling yield P2 of the following equation.
Falling yield P2 = W2 / W0

The results of the above-mentioned experiment 1 are shown in FIG. 2 with the kneading time on the horizontal axis and the molding yield and drop yield on the vertical axis.
As shown in FIG. 2, the molding yield and the falling yield tend to decrease as the kneading time increases, and in particular, the falling yield is from around the kneading time exceeding 10 minutes. There was a tendency for it to decline sharply.

  Also, the influence of the rotation speed of the kneading blade on the molding yield and the drop yield was investigated by the following Experiment 2.

[Experiment 2]
Pulverized coal powder which is crushed so that under 3 mm powder occupies 80% by mass or more is continuously fed to a continuous type horizontal twin-screw kneader, and Rhodtar as a binder and mass ratio to coal powder The mixture was kneaded while adding 7%. At this time, the rotation speed of the kneading blade was changed in the range of 30 to 48 rpm. The kneading time was adjusted to two levels (2.1 minutes, 3.2 minutes) by changing the weir height on the discharge side of the kneader to two steps and adjusting the residence time in the kneader to two steps.

The kneaded material after kneading at each kneading blade rotational speed and each kneading time was molded by a molding machine, and the molded coal obtained was examined for molding yield and falling yield, and the overall yield was evaluated by the following equation .
Overall yield = [casting yield] × [falling yield]

The results of the above-mentioned experiment 2 are shown in FIG. 3 with the rotation speed of the kneading blade on the horizontal axis and the total yield on the vertical axis.
As shown in FIG. 3, in any of the cases where the kneading time is 2.1 minutes and 3.2 minutes, the overall yield increases as the number of revolutions of the kneading blade increases from 30 rpm, and It was found that the total yield peaked at around 40 rpm, and the total yield decreased at a speed exceeding 40 rpm.
In the above experimental results, the overall yield is generally higher when the kneading time is 3.2 minutes than when the kneading time is 2.1 minutes, when compared at the same kneading time. This means that the kneading degree can be adjusted by adjusting the kneading time if the rotation speed of the kneading blade is kept constant.

  On the other hand, as already described, in the kneading step, the degree of progress of the kneading (kneading degree) is evaluated by the mass ratio occupied by coal particles of 0.3 mm under with a sieve of 0.3 mm in the kneaded material, The experiment 3 which became the basis which obtains the knowledge that it is desirable to finish kneading after the point where the coal particle of the sieve 0.3 mm under becomes 25% or less by mass% to all the coal particles is explained. .

[Experiment 3]
The influence of the size of the coal particles in the kneaded material after kneading on the molding yield and the falling yield was investigated as follows.
Coal powder pulverized so that 80% by mass of under 3 mm powder is occupied by a pulverizer is charged into a batch type vertical kneader, and Rhodtar as a binder is added 7% by mass ratio to coal powder Kneaded. The particle size of the coal particles in the kneaded material after kneading was measured, and the mass ratio of less than 0.3 mm coal particles to the total coal particles was calculated. In this experiment, by changing the kneading time and the rotation speed of the kneading blade variously, the mass ratio of less than 0.3 mm of coal particles to all coal particles was changed.
Furthermore, the kneaded material after kneading was molded by a molding machine, and the molding yield and drop yield were examined for the obtained coal.

The results of the above-mentioned experiment 3 are shown in FIG. 4, where the mass ratio of coal particles less than 0.3 mm in the kneaded material is on the entire coal particles on the horizontal axis, and the molding yield and falling yield on the vertical axis. Shown in.
As shown in FIG. 4, when the mass ratio of coal particles smaller than 0.3 mm in the kneaded material exceeds about 25%, the molding yield and the falling yield tend to decrease, especially the falling yield There was a tendency for the ratio to drop sharply from around 25%. This is the case where the mass ratio of less than 0.3 mm of coal particles in the kneaded material exceeds 25% in the case where the degree of kneading is insufficient, and the aggregation of the coal particles introduced into the kneader proceeds sufficiently It is guessed that it is not.

  Accordingly, from the results of Experiment 3 as described above, it has been found that if the mass ratio of coal particles smaller than 0.3 mm in the kneaded material is 25% or less, it is possible to secure the molded coal strength. That is, if kneading is continued at least after the mass proportion of coal particles smaller than 0.3 mm becomes 25% or less after the start of kneading, the average circularity is less than 0.73 as described above ( Combined with the use of the coal particles of preferably less than 0.71) for kneading, it is possible to secure sufficient cast carbon strength.

  Examples carried out to verify the action and effect of the present invention are shown below.

  Using an impeller breaker as a pulverizer, raw material coal was pulverized so that the powder of under 3 mm occupied 80% by mass or more. In grinding, the degree of spheroidization (average roundness) was variously changed by adjusting the grinding time. The pulverized coal powder was kneaded using a continuous biaxial horizontal type kneader, while adding 7% by weight of load tar to the coal powder, while setting the rotation speed of the kneading blade to 40 rpm, for various times. . About the kneaded material obtained by kneading | mixing of each time, one part was made into the sample for the measurement of circularity, and the remainder was shape | molded by the double roll type | mold molding machine as a target size of 40-50 cc to a briquette.

The average circularity of pulverized coal particles subjected to kneading is measured by the method and apparatus described above for coal particles having a particle diameter in the range of 0.1 mm to 1.0 mm. The average degree of circularity was defined as an average value of 30,000 to 35,000 circularities).
Moreover, about the briquettes finally obtained, as a parameter | index of the strength, the drop test which already mentioned was done, and the drop yield was investigated.
The results are shown in FIG.

  From FIG. 5, it is shown that the falling yield as an indicator of the strength of the formed carbon tends to decrease as the average circularity of the crushed coal particles subjected to kneading increases from around 0.71, and in particular, the average circularity If it is 0.73 or more, it is clear that the drop yield falls rapidly and falls below the target of 80%. Furthermore, it is clear from FIG. 5 that if the average circularity is less than 0, 71, it is possible to secure a higher formed carbon strength, which is a drop yield of 90% or more.

  In any of the conditions plotted in FIG. 5, it was confirmed that the mass ratio of less than 0.3 mm of coal particles in the kneaded material is 25% or less in the total coal particles. That is, the results shown in FIG. 5 can be said that the degree of kneading is maintained under any conditions.

  The preferred embodiments, experiments, and examples of the present invention have been described above, but these embodiments, experiments, and examples are merely examples within the scope of the present invention, and from the scope of the present invention Additions, omissions, substitutions, and other modifications of the configuration are possible without departing from the scope of the invention. That is, the present invention is not limited by the above description, and is limited only by the appended claims, and it is needless to say that the present invention can be appropriately modified within the scope.

10 Grinding machines 18A, 18B, 18C Kneading machines 22A, 22B, 22C Molding machines

Claims (3)

It has a grinding process of grinding a coal raw material, a kneading process of kneading the coal powder obtained by the grinding process with a binder, and a forming process of forming the obtained kneaded material into a block form.
In the kneading step, kneading is performed using coal particles having an average circularity of less than 0.73, and the obtained kneaded product is subjected to the next molding step. In the method for producing the coal according to claim 1,
In the above-mentioned kneading step, coal particles of 0.3 mm under of sieve mesh in the kneaded material to be obtained are kneaded so as to be 25% or less by mass% with respect to all coal particles. . In the method of producing the coal according to any one of claims 1 and 2,
The coal powder to be subjected to the kneading step after the pulverizing step is characterized in that coal particles of 0.3 mm under of sieve mesh occupy 80% or more by mass% with respect to all the coal particles. How to make charcoal.

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