Coking coal preparation method and coal preparation system thereof

Abstract

The invention discloses a coking coal preparation method and a coal preparation system thereof, and the method comprises the following steps: separately crushing a plurality of coals required for preparation to obtain a plurality of first-order crushed coals; sorting the plurality of first-order crushed coal materials according to multi-stage hardness, and premixing the plurality of first-order crushed coal materials with similar hardness according to a ratio to obtain a plurality of first-order premixed coal; respectively crushing the plurality of first-order premixed coals until the pulverized coal content reaches a preset proportion to obtain a plurality of second-order crushed coals; then carrying out multi-stage separation on the multiple second-order crushed coal materials according to particle sizes, and premixing the coal materials with the same-stage particle sizes to obtain multiple second-order premixed coal; then, the multiple second-order premixed coals are crushed to the final particle size requirement range, and multiple third-order crushed coals are obtained; and finally, the various three-order crushed coal materials are fully and uniformly mixed through a uniform mixing mechanism, and the final coking coal is obtained. The method is not influenced by the quality of a coal source, meets the configuration requirements of various combined coking coals, and ensures that the quality of the prepared coking coals is stable.

Description

Technical Field

[0001] The invention relates to the technical field of coking, in particular to a method and system for preparing coking coal. Background Art

[0002] Coking coal is a mixed coal used for coking. The types and proportions of coal used vary according to different needs. In addition, it needs to be crushed to a certain particle size and fully mixed to ensure the quality of the coking coal. Usually, multiple types of coal required are weighed and mixed according to the proportion, and then crushed together to a suitable particle size. In the process of crushing, the various coals are fully mixed. However, this preparation method has high requirements on the quality of the coal source and is only suitable for coking coal with good adhesion and more uniform coal quality. Otherwise, it is easy to have problems of over-crushing or insufficient crushing of local coal, which also makes it impossible to fully mix the internal coal materials. Especially in factories with large-scale coal blending needs, on the one hand, the demand for coal is large and the coal source is wide and diverse. On the other hand, the configuration combinations of coking coal are diverse and the needs are different. Conventional configuration methods are difficult to meet production needs and it is difficult to ensure the stable quality of the prepared coking coal. Summary of the invention

[0003] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a method and system for preparing coking coal, which are not affected by the quality of the coal source, meet the requirements of configuring various combinations of coking coal, and ensure the stable quality of the prepared coking coal.

[0004] Technical solution: To achieve the above-mentioned purpose, a method for preparing coking coal and a system for preparing coking coal are provided in the present invention. The method prepares coking coal through the system. The system comprises a primary pulverizing unit, a secondary pulverizing unit and a tertiary pulverizing unit, and further comprises a primary sorting and premixing mechanism, a secondary sorting and premixing mechanism and a mixing mechanism.

[0005] The specific steps include:

[0006] S1. Use a primary crushing unit to crush a variety of coals required for the preparation separately, and crush them under the same crushing conditions for the same time, which is expressed as the primary crushing time T, to obtain a variety of first-order crushed coal materials for storage;

[0007] S2. The first-stage sorting and premixing mechanism sorts the various first-stage crushed coal materials in step S1 according to multiple levels of hardness, and premixes the various first-stage crushed coal materials with similar hardness according to the preset proportions of the coals required for preparing coking coal to obtain various first-stage premixed coals;

[0008] S3, crushing the various first-order premixed coals in step S2 separately by a secondary crushing unit, and crushing each first-order premixed coal until the coal powder content reaches a preset proportion, thereby obtaining a plurality of second-order crushed coal materials;

[0009] S4, sorting the various second-order crushed coal materials in step S3 by particle size by a secondary sorting and premixing mechanism, premixing coal materials of the same particle size, and obtaining a plurality of second-order premixed coals;

[0010] S5, crushing the multiple second-order premixed coals in step S4 separately by a three-stage crushing unit, and crushing each second-order premixed coal to a required final particle size range to obtain multiple third-order crushed coal materials;

[0011] S6. The various third-stage crushed coal materials in step S5 are fully mixed by a mixing mechanism to obtain final coking coal.

[0012] Furthermore, in step S2, by comparing the particle size changes of the raw coal ore before the primary crushing and the first-stage crushed coal material after the primary crushing, the hardness grade of the coal required for various preparations is evaluated, and the hardness grade H of the coal required for each preparation is expressed as:

[0013]

[0014] Where f is the particle size after primary crushing, and F is the particle size before primary crushing.

[0015] Furthermore, the particle size F before the primary crushing and the particle size f after the primary crushing are obtained: first, the coal at the feed port and the discharge port of the primary crushing unit are respectively recorded by the visual module to obtain two image videos corresponding to the state of the coal before and after the primary crushing, and then two frames of images separated by the primary crushing time T in the two image videos are extracted as a group of comparison objects, and the average values ​​of the coal particle sizes in the two comparison objects are obtained by image processing technology as the values ​​of f and F respectively.

[0016] Furthermore, in step S2, the sorting and premixing process of the first-order premixed coal is as follows: First, a plurality of first-order crushed coal materials are arranged in the numerical order of the corresponding hardness grade H to obtain a sequence A = {H1, H2...H n}, n∈N + And N ≥ 2; then starting from the end value of any end of the sequence, the sequence A is segmented in sequence with a preset numerical range width, and separated one by one to obtain multiple sub-sequences. After each sub-sequence is separated, the next segmentation starts from the end value of the remaining part of the sequence A close to the separation point; finally, the corresponding multiple first-order crushed coal materials in each sub-sequence are premixed to form a first-order premixed coal.

[0017] Furthermore, in step S2, the proportioning and premixing process of the first-order premixed coal is completed by the proportioning weighing system and the transfer scheduling system; first, after the coking coal preparation task is generated, the coal picking route is planned according to the required coal type, and the transportation devices are dispatched to the corresponding multiple coal picking points respectively, and then the specified amount of coal is weighed from the first-order crushing coal storage bin of the corresponding coal type through the weighing hopper of the coal picking point, and the loading of the relative transportation device is completed, and finally the feeding route is planned according to the hardness grade H of the loading, so that the transportation devices loaded with similar hardness grades go to the same premixing point for unloading, and the mixed storage is used as the secondary crushing feed.

[0018] Furthermore, in step S3, during the secondary crushing process, a fixed weight sample is weighed at regular intervals, coal powder with a particle size of less than 1 mm is screened out as a reference sample, the ratio of the reference sample weight to the total sample weight is weighed and calculated, and the crushing is stopped when the ratio reaches a preset proportion, wherein the preset proportion is less than the proportion of coal powder content in the final coking coal.

[0019] Furthermore, in step S4, coarse and fine grade sorting is completed by at least two layers of mesh screens, and the mesh apertures decrease from top to bottom, wherein the apertures of the two lowest layers of mesh screens are respectively set according to the two end values ​​of the final particle size requirement range.

[0020] Furthermore, in step S4, the total amount of coal passing through multiple bottom-level mesh screens is the total amount of coal powder, and the total amount of coal remaining on the bottom-level mesh screen is the total amount of second-order premixed grid coal; if the total amount of coal powder meets the coal powder ratio in the final coking coal, the second-order premixed grid coal does not need to undergo tertiary crushing and is directly mixed with other third-order crushed coal; if the total amount of coal powder is far lower than the required minimum value corresponding to the coal powder ratio in the final coking coal, the tertiary crushing parameters of the second-order premixed grid coal are adjusted according to the difference between the total amount of coal powder and the required minimum value, and when the total amount of coal powder reaches the required minimum value, the tertiary crushing of the second-order premixed grid coal is stopped.

[0021] Furthermore, in step S6, the mixing mechanism longitudinally spreads the composite coal obtained by mixing multiple types of third-order crushed coal materials through the horizontal wind field, and sorts the composite coal materials according to different densities along the air supply direction under the action of the wind field. The coal materials after passing through the horizontal wind field are evenly spread on the moving conveyor belt. The moving direction of the conveyor belt is consistent with the air supply direction. The time difference of falling coal particles of different densities is utilized to make coal particles of different densities scattered in the same area of ​​the conveyor belt in sequence to form overlapping and mixing. The conveyor belt then transports the overlapping and mixed coal materials to the stirring device for further mixing by stirring.

[0022] Furthermore, it includes a coal preparation area and a plurality of configuration areas, and a plurality of the configuration areas are connected to the coal preparation area through respective primary sorting and premixing mechanisms, and the primary sorting and premixing mechanism includes a transfer scheduling system;

[0023] The coal preparation area is provided with a first-level crushing machine group, and the first-level crushing machine group includes a plurality of first-level crushers corresponding to a plurality of coals required for preparation, and each of the first-level crushers corresponds to a hardness monitoring module and a first-order crushing coal storage bin, and the first-order crushing coal storage bin is provided with a storage management module, and the hardness monitoring module is communicatively connected with the storage management module, and the storage management module is communicatively connected with the transfer scheduling system, and is used for updating the hardness distribution of the coal in the storage bin in the height direction in real time according to the feeding and discharging conditions of the first-order crushing coal storage bin and the changes in the feeding hardness, and feeding back the hardness of the currently discharged coal to the conveying device receiving the material in real time through the transfer scheduling system;

[0024] Each of the configuration areas is provided with a secondary pulverizer group, a secondary sorting premixing mechanism, a tertiary pulverizer group and a mixing mechanism which are connected in sequence.

[0025] Beneficial effects: The method and system for preparing coking coal of the present invention can eliminate the differences caused by factors affecting the crushing resistance of coal materials, such as coal material hardness, adhesiveness, inert matter content, etc., due to different coal sources purchased in different batches of various types of coal through multi-stage crushing, sorting and mixing. On the one hand, it can make the acquisition of coal sources more extensive, and on the other hand, when preparing coal, the quality of the coal materials and the final coking coal will not be affected by the quality of the raw coal. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A block diagram of a method for preparing coking coal according to the present invention;

[0027] Figure 2 This is a schematic diagram of the overall structure of a coal preparation system according to an embodiment of the present invention;

[0028] Figure 3 A schematic diagram of a single-line structure of a coal preparation system according to an embodiment of the present invention;

[0029] Figure 4 The figure is a schematic diagram of the structural relationship of a primary pulverizing unit, a primary sorting and premixing mechanism and a secondary pulverizing unit in one embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings.

[0031] As attached Figure 1-4The method and system for preparing coking coal are used to prepare coking coal. The system comprises a primary pulverizer unit 1, a secondary pulverizer unit 2, and a tertiary pulverizer unit 3, and further comprises a primary sorting and premixing mechanism 4, a secondary sorting and premixing mechanism 5, and a mixing mechanism 6. In the coal preparation process, the coal source sequentially passes through the primary pulverizer unit 1, the primary sorting and premixing mechanism 4, the secondary pulverizer unit 2, the secondary sorting and premixing mechanism 5, the tertiary pulverizer unit 3, and the mixing mechanism 6.

[0032] This solution aims at the different coal sources purchased in different batches of various types of coal. There may be differences in factors affecting the coal's ability to resist crushing, such as coal hardness, adhesiveness, inert matter content, etc. Multi-stage crushing, sorting and then mixing are used to eliminate the impact of this difference on the final coking coal quality. In response to the coal preparation needs of different customers, the coal source will not be restricted by the designated allocation of the preparation process. The coal source call is more flexible, which makes the coal source procurement range larger, more conducive to the simultaneous preparation of various combinations of coking coal, more full utilization of coal sources, and significantly improved coal preparation efficiency.

[0033] In one embodiment, the coal preparation system includes a coal preparation area 10 and several configuration areas 20, and the multiple configuration areas 20 are respectively connected to the coal preparation area 10 through their own first-level sorting and premixing mechanisms 4, and the first-level sorting and premixing mechanisms 4 include a transfer scheduling system 41; that is, each configuration area 20 corresponds to a combination of coking coal, and the transfer scheduling system 41 of the configuration area 20 generates a transportation task according to the formula, wherein a corresponding number of transportation devices or transportation fleets are dispatched according to the number of required coal types, and according to the required ratio of various types of coal, under full load conditions, the number of transfers or the number of vehicles dispatched by the fleet is selected.

[0034] The coal preparation area 10 is provided with a first-level crushing machine group 1, and the first-level crushing machine group 1 includes a plurality of first-level crushers 11 corresponding to a plurality of coals required for preparation, each of the first-level crushers 11 corresponds to a hardness monitoring module 12 and a first-order crushed coal storage bin 13, and the first-order crushed coal storage bin 13 is provided with a storage management module 14, and the hardness monitoring module 12 is communicatively connected with the storage management module 14, and the storage management module 14 is communicatively connected with the transfer scheduling system, and is used for updating the hardness distribution of the coal in the storage bin in the height direction in real time according to the feeding and discharging conditions of the first-order crushed coal storage bin 13 and the change of the feeding hardness, and feeding back the hardness of the currently discharged coal to the conveying device that is receiving the material in real time through the transfer scheduling system; wherein, the hardness monitoring module 12 is used for estimating the hardness of the coal according to the degree of crushing of the coal source after the first-level crushing, generally speaking, the fluctuation difference in hardness of the coal of the same batch or the same coal source is small, and the coal of different coal sources may have obvious hardness differences. Based on this, in order to improve the efficiency of coal preparation, the first-level crushing unit is maintained in a state of continuous operation, and the purchased coal materials of the same type but different coal sources are all crushed by the same first-level crusher and stored in the same storage bin for call. After being crushed by the first-level crusher, the coal materials directly enter the storage bin after passing through a short section of the conveyor belt. This short section of the conveyor belt is convenient for monitoring the degree of crushing. The storage management module 14 receives the detection signal of the hardness monitoring module 12 in real time, monitors the stacking height of the coal materials in the storage bin, and records and saves the hardness grade distribution of the coal materials in the storage bin in the height direction. At the same time, the storage management module 14 also updates the hardness grade distribution of the coal materials in the storage bin in the height direction in real time through dynamic recording of the feed amount and the discharge amount, ensuring that the hardness grade of the coal materials being discharged from the bottom of the storage bin can always be accurately fed back to the conveying device that is receiving the materials, so that the conveying device can plan the end point of its transportation task according to the obtained hardness grade.

[0035] Each of the configuration areas 20 is provided with a secondary pulverizer group 2, a secondary sorting and premixing mechanism 5, a tertiary pulverizer group 3 and a mixing mechanism 6 connected in sequence. Among them, the secondary pulverizer group 2 includes multiple secondary pulverizers corresponding to multiple hardness grade ranges, and each secondary pulverizer uploads its own position coordinates to the transfer scheduling system as an optional destination of a transportation task. Coal materials with hardness grades within a relative hardness grade range are transported to the same secondary pulverizer for mixing. The secondary sorting and premixing mechanism 5 includes multiple layers of screens corresponding to the discharge ports of each secondary pulverizer. The tertiary pulverizer group 3 includes multiple tertiary pulverizers corresponding to different particle sizes. The coal materials on the same layer of screens at different discharge ports are transported to the same tertiary pulverizer through a conveyor belt. The discharges of multiple tertiary pulverizers are connected to the mixing mechanism 6 through a conveyor belt for final full mixing to complete the preparation of coking coal.

[0036] The specific coal preparation process includes the following steps:

[0037] S1. Use the primary crushing unit 1 to crush the various coals required for the preparation separately, and crush them under the same crushing conditions for the same time, which is expressed as the primary crushing time T, to obtain various first-order crushed coal materials for storage;

[0038] Among them, by comparing the particle size changes of the raw coal ore before the first-stage crushing and the first-stage crushed coal material after the first-stage crushing, the hardness grade of the coal required for various preparations is evaluated. The hardness grade H of the coal required for each preparation is expressed as:

[0039]

[0040] Where f is the particle size after primary crushing, and F is the particle size before primary crushing.

[0041] In order to ensure the efficiency and continuity of primary crushing, the primary crusher is required to maintain a uniform feeding and discharging speed. By controlling the flow of inlet and outlet, it is ensured that the time for a unit volume of coal to pass through the primary crusher is exactly T. After coal sources with different characteristics are crushed under the same conditions, their degree of crushing before and after can truly reflect the coal's ability to resist crushing. Since it only experiences a relatively short crushing time, this ability to resist crushing is mainly reflected in the hardness level of the coal. Therefore, the hardness level can be reflected by the change in particle size before and after primary crushing, thereby quantifying the hardness level of different coal sources, facilitating recording and data transmission, and providing data support for subsequent primary sorting premixing.

[0042] The particle size F before the primary crushing and the particle size f after the primary crushing are obtained: first, the coal at the feed port and the discharge port of the primary crushing unit 1 are respectively recorded through the visual module to obtain two image videos corresponding to the state of the coal before and after the primary crushing, and then two frames of images separated by the primary crushing time T in the two image videos are extracted as a group of comparison objects, and the average values ​​of the coal particle sizes in the two comparison objects are obtained through image processing technology as the values ​​of f and F respectively.

[0043] S2. The first-stage sorting and premixing mechanism 4 sorts the various first-order crushed coal materials in step S1 according to the multiple hardness levels, and premixes the various first-order crushed coal materials with similar hardness according to the preset proportions of the coals required for preparing the coking coal, to obtain various first-order premixed coals;

[0044] The sorting and premixing process of first-order premixed coal is as follows: First, arrange various first-order crushed coal materials in the order of the numerical value of the corresponding hardness grade H to obtain a sequence A = {H1, H2...H n}, n∈N +And N ≥ 2; then starting from the end value of any end of the sequence, the sequence A is segmented in sequence with a preset numerical range width, and separated one by one to obtain multiple sub-sequences. After each sub-sequence is separated, the next segmentation starts from the end value of the remaining part of the sequence A close to the separation point; finally, the corresponding multiple first-order crushed coal materials in each sub-sequence are premixed to form a first-order premixed coal.

[0045] The proportioning and premixing process of the first-order premixed coal is completed by the proportioning weighing system and the transfer scheduling system; first, after the coking coal preparation task is generated, the coal picking route is planned according to the type of coal required for preparation, and the transportation devices are dispatched to the corresponding multiple coal picking points respectively. Then, the specified amount of coal is weighed from the first-order crushing coal storage bin of the corresponding coal type through the weighing hopper at the coal picking point, and the loading of the relative transportation device is completed. Finally, the feeding route is planned according to the hardness grade H of the loaded material, so that the transportation devices loaded with similar hardness grades go to the same premixing point for unloading, and the mixed storage is used as the secondary crushing feed.

[0046] Among them, since during loading, the storage management module will feed back the hardness level of the discharged coal to the conveying device that receives the material, each H value in the sequence A can represent a conveying device, and the H values ​​corresponding to two conveying devices loaded with the same kind of coal may also differ greatly, so they will be divided into different sub-series, and each sub-series represents a secondary crusher. Due to the different proportions of each type of coal, the coal with a larger proportion may need to be transported multiple times. Usually, after the first wave of multiple required coals are taken, the sequence A is constructed according to the hardness level fed back by the first batch of conveying devices, and divided into several sub-series to basically determine the number of secondary crushers that need to be activated. In subsequent transportation, by judging which existing sub-series the hardness value falls in, it is selected to which secondary crusher to be transported for premixing and crushing.

[0047] This way, other influencing factors can be avoided and coal materials of similar hardness can be crushed together based on the hardness grade alone.

[0048] S3. The various first-order premixed coals in step S2 are crushed separately by the secondary crushing unit 2, and each first-order premixed coal is crushed until the coal powder content reaches a preset proportion, so as to obtain a variety of second-order crushed coal materials; since coal materials of different hardness grades will form a certain amount of coal powder in the crushing process, but the proportion of coal powder in the final coking coal needs to be properly controlled and should not be too high. If the coal powder content is too high at this stage, and then a part of the coal powder is removed to achieve the proportion standard, it will cause the total amount to be missing, which may lead to an imbalance in the ratio. Therefore, the crushing time is controlled by monitoring the coal powder amount of each secondary crusher, wherein the secondary crushers corresponding to different hardnesses adopt the same detection standard, that is, the same preset proportion of coal powder content is used as a reference. Since it is relatively more difficult to produce coal powder in coal materials with higher hardness, coal materials with higher hardness can obtain a longer crushing time, so that the particle size is as small as possible. The preset percentage value of the coal powder content is set based on the coal powder content m when the first-order premixed coal with lower hardness is basically crushed to a state that meets the final particle size requirements, and only a small part of the coal powder has a relatively larger particle size due to its strong adhesion, and ensures that the final total amount of coal powder M=xm of x secondary crushers is lower than the expected total amount of coal powder in the final coking coal.

[0049] In the process of secondary crushing, fixed weight samples are weighed at regular intervals, coal powder with a particle size of less than 1 mm is screened out as a reference sample, and the ratio of the reference sample weight to the total sample weight is weighed and calculated. The crushing is stopped when the ratio reaches a preset proportion, wherein the preset proportion is less than the proportion of coal powder content in the final coking coal.

[0050] S4, sorting the various second-order crushed coal materials in step S3 by particle size by the secondary sorting premixing mechanism 5, premixing coal materials of the same particle size, and obtaining various second-order premixed coals;

[0051] The coarse and fine grade sorting is completed by at least two layers of mesh screens, and the mesh apertures decrease from top to bottom, wherein the apertures of the two lowest layers of mesh screens are respectively set according to the two end values ​​of the final particle size requirement range.

[0052] The total amount of coal that passes through multiple bottom-level screens is the total amount of coal powder, and the total amount of coal that remains on the bottom-level screen is the total amount of second-order premixed grid coal; if the total amount of coal powder meets the proportion of coal powder in the final coking coal, the second-order premixed grid coal does not need to undergo three-stage crushing and is directly mixed with other three-stage crushed coal; if the total amount of coal powder is far lower than the required minimum value corresponding to the proportion of coal powder in the final coking coal, the three-stage crushing parameters of the second-order premixed grid coal are adjusted according to the difference between the total amount of coal powder and the required minimum value, and the three-stage crushing of the second-order premixed grid coal is stopped when the total amount of coal powder reaches the required minimum value. In this way, the coal powder content is strictly controlled, and space is reserved for the amount of coal powder produced by other three-stage crushers.

[0053] S5, crushing the multiple second-order premixed coals in step S4 separately by the three-stage crushing unit 3, and crushing each second-order premixed coal to the required final particle size range to obtain multiple third-order crushed coal materials;

[0054] S6, fully mix the multiple third-order crushed coal materials in step S5 through the mixing mechanism 6 to obtain the final coking coal. The mixing mechanism 6 longitudinally spreads the composite coal material obtained by mixing the multiple third-order crushed coal materials through the horizontal wind field, and sorts the composite coal material according to different densities along the air supply direction under the action of the wind field. The coal material after passing through the horizontal wind field is evenly spread on the moving conveyor belt, and the moving direction of the conveyor belt is consistent with the air supply direction. The time difference of the falling of coal particles of different densities is used to make the coal particles of different densities be scattered in the same area of ​​the conveyor belt in sequence to form overlapping and mixing. The conveyor belt then transports the overlapping and mixed coal material to the stirring device, and further mixes it by stirring.

[0055] On the premise that the particle sizes of all coal materials except the coal powder content are at the same level, the difference in the influence of the wind field due to the density is used to make the coal materials of different densities relatively evenly distributed after falling. Generally speaking, the density of the same type of coal materials is not much different, which makes the different types of coal materials relatively evenly distributed. Finally, after a certain period of stirring, complete mixing is achieved. The final coking coal not only has uniform particle size, but also all types of coal materials are fully mixed, ensuring the stable quality of coal preparation.

[0056] The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the above principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing coking coal, characterized in that: Coking coal is prepared by a coal preparation system, wherein the coal preparation system comprises a primary pulverizer group (1), a secondary pulverizer group (2) and a tertiary pulverizer group (3), and further comprises a primary sorting and premixing mechanism (4), a secondary sorting and premixing mechanism (5) and a mixing mechanism (6); The specific steps include: S1. Using a primary crushing unit (1), multiple types of coal required for the preparation are crushed separately and all are crushed under the same crushing conditions for the same time, which is represented by the primary crushing time T, to obtain multiple types of first-stage crushed coal materials for storage and standby; S2. The first-stage sorting and premixing mechanism (4) sorts the various first-stage crushed coal materials in step S1 according to the multiple hardness levels, and premixes the various first-stage crushed coal materials with similar hardness according to the preset proportions of the coals required for preparing the coking coal, thereby obtaining various first-stage premixed coals; S3, using the secondary pulverizer (2) to crush the various first-order premixed coals in step S2 separately, and crushing each first-order premixed coal until the coal powder content reaches a preset proportion, thereby obtaining a plurality of second-order crushed coal materials; S4, sorting the various second-order crushed coal materials in step S3 according to the coarseness and fineness of the particles by means of a secondary sorting and premixing mechanism (5), premixing the coal materials of the same particle size, and obtaining various second-order premixed coals; S5, using a three-stage crushing unit (3) to crush the various second-order premixed coals in step S4 respectively, wherein each second-order premixed coal is crushed to a required final particle size range, thereby obtaining a plurality of third-order crushed coal materials; S6. The various third-stage crushed coal materials in step S5 are fully mixed by a mixing mechanism (6) to obtain final coking coal.

2. A method for preparing coking coal according to claim 1, characterized in that: In step S2, by comparing the particle size changes of the raw coal ore before the primary crushing and the first-stage crushed coal material after the primary crushing, the hardness grade of the coal required for various preparations is evaluated. The hardness grade H of the coal required for each preparation is expressed as: Where f is the particle size after primary crushing, and F is the particle size before primary crushing.

3. A method for preparing coking coal according to claim 2, characterized in that: The particle size F before the primary crushing and the particle size f after the primary crushing are obtained as follows: first, the coal at the feed port and the discharge port of the primary crushing unit (1) are image-recorded by a visual module to obtain two image videos corresponding to the state of the coal before and after the primary crushing; then, two frames of images separated by the primary crushing time T are extracted from the two image videos as a group of comparison objects; and the average values ​​of the coal particle sizes in the two comparison objects are obtained by image processing technology as the values ​​of f and F, respectively.

4. A method for preparing coking coal according to claim 3, characterized in that: In step S2, the sorting and premixing process of the first-order premixed coal is as follows: First, a plurality of first-order crushed coal materials are arranged in the numerical order of the corresponding hardness grade H to obtain a sequence A = {H1, H2...H n }, n∈N + And N ≥ 2; then starting from the end value of any end of the sequence, the sequence A is segmented in sequence with a preset numerical range width, and separated one by one to obtain multiple sub-sequences. After each sub-sequence is separated, the next segmentation starts from the end value of the remaining part of the sequence A close to the separation point; finally, the corresponding multiple first-order crushed coal materials in each sub-sequence are premixed to form a first-order premixed coal.

5. A method for preparing coking coal according to claim 4, characterized in that: In step S2, the proportioning and premixing process of the first-order premixed coal is completed by the proportioning weighing system and the transfer scheduling system; first, after the coking coal preparation task is generated, the coal picking route is planned according to the type of coal required for preparation, and the transportation devices are dispatched to the corresponding multiple coal picking points respectively, and then the specified amount of coal is weighed from the first-order crushing coal storage bin of the corresponding coal type through the weighing hopper at the coal picking point, and the loading of the relative transportation device is completed, and finally the feeding route is planned according to the hardness grade H of the loading, so that the transportation devices loaded with similar hardness grades go to the same premixing point for unloading, and the mixed storage is used as the secondary crushing feed.

6. A method for preparing coking coal according to claim 5, characterized in that: In step S3, during the secondary crushing process, a fixed weight sample is weighed at regular intervals, coal powder with a particle size of less than 1 mm is screened out as a reference sample, the ratio of the reference sample weight to the total sample weight is weighed and calculated, and the crushing is stopped when the ratio reaches a preset proportion, wherein the preset proportion is less than the proportion of coal powder content in the final coking coal.

7. A method for preparing coking coal according to claim 6, characterized in that: In step S4, coarse and fine grade sorting is completed through at least two layers of mesh screens, and the mesh apertures decrease from top to bottom, wherein the apertures of the two lowest layers of mesh screens are set according to the two end values ​​of the final particle size requirement range.

8. A method for preparing coking coal according to claim 7, characterized in that: In step S4, the total amount of coal passing through the bottom mesh screens is the total amount of coal powder, and the total amount of coal remaining on the bottom mesh screen is the total amount of second-order premixed grid coal; if the total amount of coal powder meets the proportion of coal powder in the final coking coal, the second-order premixed grid coal does not need to undergo third-stage crushing and can be directly mixed with other third-stage crushed coal; If the total amount of coal powder is far lower than the required minimum value corresponding to the proportion of coal powder in the final coking coal, the tertiary crushing parameters of the second-order premixed coal are adjusted according to the difference between the total amount of coal powder and the required minimum value. When the total amount of coal powder reaches the required minimum value, the tertiary crushing of the second-order premixed coal is stopped.

9. A method for preparing coking coal according to claim 8, characterized in that: In step S6, the mixing mechanism (6) longitudinally spreads the composite coal material obtained by mixing multiple types of third-order crushed coal materials through the horizontal wind field, and sorts the composite coal material according to different densities along the air supply direction under the action of the wind field. The coal material after passing through the horizontal wind field is evenly spread on the moving conveyor belt. The moving direction of the conveyor belt is consistent with the air supply direction. The time difference of falling coal particles of different densities is utilized to make the coal particles of different densities be scattered in the same area of ​​the conveyor belt in sequence to form overlapping and mixing. The conveyor belt then transports the overlapping and mixed coal material to the stirring device for further mixing by stirring.

10. A coal preparation system for a coking coal preparation method according to any one of claims 1 to 9, characterized in that: It comprises a coal preparation area (10) and a plurality of configuration areas (20), wherein the plurality of configuration areas (20) are connected to the coal preparation area (10) through respective primary sorting and premixing mechanisms (4), and the primary sorting and premixing mechanisms (4) comprise a transfer scheduling system (41); The coal preparation area (10) is provided with a first-level crushing machine group (1), and the first-level crushing machine group (1) includes a plurality of first-level crushers (11) corresponding to a plurality of coals required for preparation, each of the first-level crushers (11) corresponds to a hardness monitoring module (12) and a first-order crushing coal storage bin (13), and the first-order crushing coal storage bin (13) is provided with a storage management module (14), the hardness monitoring module (12) is communicatively connected to the storage management module (14), and the storage management module (14) is communicatively connected to the transfer scheduling system (41), and is used for updating the hardness distribution of the coal in the storage bin in the height direction in real time according to the feeding and discharging conditions of the first-order crushing coal storage bin (13) and the change of the feeding hardness, and feeding back the hardness of the currently discharged coal to the conveying device that is receiving the material in real time through the transfer scheduling system (41); Each of the configuration areas (20) is provided with a secondary pulverizer group (2), a secondary sorting premixing mechanism (5), a tertiary pulverizer group (3) and a mixing mechanism (6) which are connected in sequence.

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