A drying and crushing method for mixed-size high-moisture low-rank coal

Abstract

This invention discloses a drying and crushing method for mixed-size, high-moisture, low-rank coal, belonging to the field of low-rank coal drying. It solves the problem that existing low-rank coal drying processes, which strictly limit the feed particle size, make drying and crushing soft low-rank coal with mixed particle sizes difficult. The drying and crushing method includes: Step 1, adding mixed-size, high-moisture, low-rank coal to a preheating and crushing unit for processing; Step 2, using a primary separation device to perform gas-solid separation on the preheated and crushed low-rank coal; Step 3, a drying unit to dry the incoming low-rank coal; Step 4, using a secondary separation device to perform gas-solid separation on the dried low-rank coal; Step 5, the separated, dried, small-particle-size, high-temperature low-rank coal enters a settling device to exchange heat with fresh air, and the cooled small-particle-size low-rank coal is the final product, discharged from the system. This invention achieves the crushing and drying of mixed-size, high-moisture, low-rank coal.

Description

Technical Field

[0001] This invention relates to the field of low-rank coal drying technology, and in particular to a drying and crushing method for mixed-particle-size high-moisture low-rank coal. Background Technology

[0002] my country has abundant reserves of low-rank coal, accounting for more than 50% of its total coal reserves. However, the high moisture content severely limits the clean and efficient utilization of low-rank coal. Drying and dehydration are essential steps in the clean and efficient utilization of low-rank coal. Crushing low-rank coal particles before drying can enhance the heat and mass transfer process within the particles during drying, thereby improving the drying rate and energy utilization efficiency. However, the crushing process of soft low-rank coal with high moisture content is prone to mud formation, and large-scale crushing is difficult to achieve in current industrial technologies. Summary of the Invention

[0003] Based on the above analysis, the present invention aims to provide a drying and crushing method for mixed-size high-moisture low-rank coal, in order to solve the technical problem that the existing low-rank coal drying process strictly limits the feed particle size, making it difficult to dry and crush soft low-rank coal.

[0004] The objective of this invention is mainly achieved through the following technical solutions: This invention provides a method for drying and crushing mixed-size, high-moisture, low-rank coal, comprising the following steps: Step 1: Add the mixed high-moisture low-rank coal to the preheating and crushing unit for processing to obtain preheated and crushed low-rank coal; Step 2: Use a primary separation device to perform gas-solid separation on the preheated and crushed low-rank coal, and discharge the separated low-rank coal particles into the drying unit. Step 3: The drying unit dries the low-rank coal that enters it to obtain dried low-rank coal. Step 4: Use a two-stage separation device to perform gas-solid separation on the dried low-rank coal to obtain high-temperature low-rank coal with small particle size. Step 5: The small-particle-size, high-temperature, low-rank coal is discharged into the settling device and heat-treated by exchanging heat with fresh air. The cooled small-particle-size, low-rank coal is the final product and is discharged from the system.

[0005] Furthermore, in step 1, during the feeding process, air is simultaneously supplied to the preheating crushing unit and the drying unit using the air supply unit.

[0006] Furthermore, in step 1, during feeding, a thermal explosion device is simultaneously activated for preheating and crushing to obtain preheated and crushed low-rank coal.

[0007] Furthermore, in step 1, when the preheating crushing unit just starts working, the drying medium used is hot gas supplied by the gas supply unit, with a gas temperature of 120℃-130℃ and a flow rate of 1.2-1.4m / s.

[0008] Furthermore, in step 1, after the preheating crushing unit and the drying unit are operating stably, the drying medium in the preheating crushing unit is a mixture of low-temperature humid tail gas discharged from the secondary cyclone separator and hot air discharged from the settling device that has recovered the sensible heat of the dried material.

[0009] Furthermore, in step 1, the temperature of the mixed gas is 120℃-130℃, and the flow rate is 1.2-1.4m / s.

[0010] Furthermore, in step 1, the particle size of the preheated and crushed low-rank coal is less than or equal to 6 mm.

[0011] Furthermore, in step 3, the particle size of the dried low-rank coal is less than or equal to 3 mm.

[0012] Furthermore, the moisture content of the mixed-size high-moisture low-rank coal is 30%-50% by mass.

[0013] Furthermore, the particle size of the mixed high-moisture low-rank coal is 25mm-150mm.

[0014] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: (1) The drying and crushing method for mixed-size high-moisture low-rank coal proposed in this invention is based on the drying characteristics of high-moisture low-rank coal to crush low-rank coal particles, which can accelerate the drying rate and improve energy utilization efficiency.

[0015] (2) By controlling the temperature of the mixed gas at 120℃-130℃ and the gas flow rate at 1.2-1.4m / s, the present invention can ensure sufficient preheating and crushing of high-moisture low-rank coal, and avoid the particle size of the discharged material being greater than 6mm.

[0016] (3) The temperature of the high-temperature, low-speed hot gas provided by the gas supply unit of the present invention is 240℃-260℃ and the wind speed is 0.5m / s-0.8m / s. The purpose of strictly controlling the gas temperature and flow rate in the drying fluidized bed is to ensure that the particle size of the material discharged after drying is less than or equal to 3mm.

[0017] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings, which are particularly pointed out. Attached Figure Description

[0018] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0019] Figure 1 This is a schematic flow diagram of the drying and crushing method for mixed-size high-moisture-content low-rank coal of the present invention; Figure 2 This is a schematic diagram of the structure of the drying and crushing system for high-moisture, low-rank coal of the present invention.

[0020] Figure label: 1-Feed hopper; 2-Preheating crushing fluidized bed; 3-First-stage cyclone separator; 4-Drying fluidized bed; 5-Second-stage cyclone separator; 6-Settling device; 7-Preheating feed inlet; 8-Microwave generator; 9-First gas inlet; 10-First gas outlet; 11-First discharge outlet; 12-Drying feed inlet; 13-Second gas inlet; 14-Second gas outlet; 15-Second discharge outlet; 16-First dovetail inlet; 17-Second dovetail outlet; 18-Discharge outlet; 19-First branch pipe; 20-Second branch pipe; 21-Third branch pipe; 22-Fourth branch pipe; 23-Fifth branch pipe. Detailed Implementation

[0021] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0022] On the one hand, the present invention provides a drying and crushing method for mixed-size, high-moisture, low-rank coal, such as... Figure 1 As shown, the drying and crushing method includes the following steps: Step 1: Add the mixed high-moisture low-rank coal into the preheating and crushing unit through the feed hopper 1, and at the same time supply air to the preheating and crushing unit and the drying unit using the air supply unit; turn on the thermal explosion generating device to preheat and crush, and obtain the preheated and crushed low-rank coal. In step 1 above, the water content of the mixed high-moisture low-rank coal is 20%-50%, and its particle size range is 20mm-150mm.

[0023] In step 1 above, while the thermal explosion generating device is started, the accelerated crushing component is activated. Multiple flexible steel chains on the rotating shaft begin to rotate with the rotating shaft. During the high-speed rotation of the flexible steel chains with the rotating shaft, the flexible steel chains continuously collide with large particles of low-rank coal, and the large particles of low-rank coal are crushed into small particles of low-rank coal.

[0024] In step 1 above, the gas supply unit is turned on, and the hot gas supplied by the gas supply unit enters the preheating and crushing fluidized bed 2 through the first branch pipe 19. At the same time, large particles in the mixed high-moisture low-rank coal fall to the thermal explosion zone at the bottom of the preheating and crushing fluidized bed 2. Under the action of microwaves from the thermal explosion generating device, the large particles of low-rank coal undergo thermal explosion and are crushed into small particles of low-rank coal. Meanwhile, due to the impact of the flexible rigid chain on the large particles of low-rank coal, the crushing of the large particles of low-rank coal into small particles of low-rank coal can also be accelerated. The small particles of low-rank coal in the thermal explosion zone enter the fluidized bed layer with the hot gas flow, and tumble and heat in the fluidized bed layer, finally obtaining the preheated and crushed low-rank coal particles.

[0025] In step 1 above, when the preheated crushing fluidized bed 2 first starts working, the drying medium used is hot gas supplied by the gas supply unit, with a gas temperature of 120℃-130℃ and a flow rate of 1.2-1.4 m / s. After the preheated crushing fluidized bed 2 and the drying fluidized bed 4 have stabilized, the drying medium used in the preheated crushing fluidized bed 2 is a mixture of low-temperature, humid tail gas discharged from the secondary cyclone separator 5 and gas discharged from the settling device 6 that has recovered the sensible heat of the dried material. The temperature of this mixture is 120℃-130℃, and the flow rate is 1.2-1.4 m / s.

[0026] Controlling the temperature of the mixed gas at 120℃-130℃ and the gas flow rate at 1.2-1.4m / s ensures sufficient preheating and crushing of high-moisture-content low-rank coal, preventing the discharged material from having a particle size greater than 6mm.

[0027] Step 2: Use a primary separation device to perform gas-solid separation on the preheated and crushed low-rank coal. The separated gas is discharged from the drying and crushing system, and the separated low-rank coal particles enter the drying unit. In step 2 above, the low-rank coal particles treated by the preheated crushing fluidized bed 2 are introduced into the primary cyclone separator 3 for gas-solid separation. The separated low-rank coal particles enter the drying fluidized bed 4, and the separated dry tail gas is discharged from the drying and crushing system.

[0028] Step 3: Use the drying unit to dry the low-rank coal particles that have entered the unit to obtain dried low-rank coal. In step 3 above, high-temperature, low-speed hot gas supplied by the gas supply unit enters the drying fluidized bed 4 through the second gas inlet 13 and rapidly dries the low-rank coal particles that enter it.

[0029] The high-temperature, low-speed hot gas provided by the above-mentioned gas supply unit has a temperature of 240℃-260℃ and a wind speed of 0.5m / s-0.8m / s. The purpose of strictly controlling the gas temperature and flow rate in the drying fluidized bed 4 is to ensure that the particle size of the material discharged after drying is less than or equal to 3mm.

[0030] It should be noted that in the drying fluidized bed 4, when the moisture in the low-rank coal is removed to a low level, its particle strength will be greatly reduced. At this time, the low-rank coal particles are easily crushed into smaller low-rank coal fine particles under the action of mechanical friction. The low-rank coal fine particles are carried out of the drying fluidized bed 4 with the airflow, while the large low-rank coal particles that are not completely dried remain in the drying fluidized bed 4 to continue drying until they are fully dried and crushed into low-rank coal fine particles.

[0031] Step 4: Use a two-stage separation device to perform gas-solid separation on the dried low-rank coal to obtain crushed and dried high-temperature low-rank coal; Step 5: After drying, the small-particle-size, high-temperature, low-rank coal enters the settling device 6 to exchange heat with fresh air. The cooled small-particle-size, low-rank coal is the final product and is discharged from the system.

[0032] In steps 4 and 5 above, the dried low-rank coal separated by the secondary cyclone separator 5 enters the settling device 6 through the second discharge port, and the separated gas enters the preheating crushing fluidized bed 2 through the fourth branch pipe 22; the ambient temperature air supplied by the gas supply unit enters the settling device 6 through the first dovetail inlet 16 and exchanges heat with the dried low-rank coal in the settling device 6 to recover sensible heat; the low-rank coal that has completed the heat exchange settles to the bottom of the equipment in the settling device 6 and is discharged from the drying and crushing system through the discharge port 18.

[0033] Compared with the prior art, the present invention preheats and crushes high-moisture low-rank coal of mixed particle size by using a preheated crushing fluidized bed 2, which can expand the feed particle size for drying low-rank coal.

[0034] It should be noted that in this invention, the 170°C low-temperature, humid tail gas discharged from the secondary cyclone separator 5 and the 50°C hot air discharged from the settling pipe, which has recovered the sensible heat of the dry material, are both introduced into the bottom of the preheating crushing unit and used as a fluidizing medium to heat the material. Fresh, high-temperature hot air supplied by the air supply unit directly enters the drying fluidized bed 4 for high-intensity, rapid drying of small-particle, low-rank coal. By recovering energy from the entire drying unit, the overall energy utilization efficiency of the system is improved.

[0035] On the other hand, the present invention also provides a drying and crushing system for mixed-size, high-moisture, low-rank coal, such as... Figure 2 As shown, the drying and crushing system is used to implement the above-mentioned drying and crushing method. The drying and crushing system includes a preheating and crushing unit, a drying unit, a separation unit, and an air supply unit. The separation unit includes a primary separation device and a secondary separation device. The preheating outlet at the top of the preheating and crushing unit is connected to the inlet of the primary separation device. The first outlet 11 of the primary separation device is connected to the drying inlet 12 of the drying unit. The drying outlet of the drying unit is connected to the inlet of the secondary separation device. The air supply unit is used to supply air to the preheating and crushing unit and the drying unit.

[0036] Specifically, a feed hopper 1 is located at the top of the preheating and crushing unit, where mixed high-moisture low-rank coal of different particle sizes is stored. When the drying and crushing system is working, the mixed high-moisture low-rank coal of different particle sizes is fed into the preheating and crushing unit from the feed hopper 1. A first gas inlet 9 is located at the bottom of the preheating and crushing unit. The low-temperature, high-speed airflow provided by the gas supply unit enters the preheating and crushing unit through the first gas inlet 9, carrying the crushed and heated small particles of high-moisture low-rank coal into the drying unit via a primary separation device. The high-temperature, low-speed airflow provided by the gas supply unit enters the drying unit through the second gas inlet 13, where the preheated and crushed low-rank coal particles are rapidly dried. After gas-solid separation by a secondary separation device, the dried low-rank coal particles enter a settling device to recover heat.

[0037] It should be noted that, since the water content of the mixed-size high-moisture low-rank coal of this invention is 20%-50%, this high water content limits its grinding process. However, existing fluidized bed drying systems for low-rank coal have strict limitations on particle size, thus severely restricting the efficient and rapid drying process of high-moisture low-rank coal. Compared with existing technologies, this invention utilizes a preheating and crushing unit to preheat and crush the mixed-size high-moisture low-rank coal, and a drying unit to rapidly dry the preheated low-rank coal. After separation by a separation unit, the dried and crushed low-rank coal is obtained. Furthermore, since the preheating and crushing unit simultaneously crushes and heats the material, it can reduce the particle size and make the particle size uniform in the mixed-size high-moisture low-rank coal; on the other hand, it can also heat the low-rank coal to a certain temperature, preparing it for rapid drying in the subsequent drying unit.

[0038] To achieve sufficient preheating and crushing of mixed-size high-moisture-content low-rank coal, such as Figure 1 As shown, the preheating and crushing unit of the present invention includes a preheating and crushing fluidized bed 2; a thermal explosion device is provided at the bottom of the preheating and crushing fluidized bed 2, which is used to cause thermal explosion of high-moisture low-rank coal in the preheating and crushing fluidized bed 2.

[0039] Specifically, the preheated crushing fluidized bed 2 of the present invention comprises, from top to bottom, a first cylindrical section, a conical section, and a second cylindrical section connected in sequence; wherein, the first cylindrical section is connected to the second cylindrical section through the conical section, the outer diameter of the first cylindrical section is larger than the outer diameter of the second cylindrical section, the area within the first cylindrical section is the fluidized bed layer, and the area within the second cylindrical section is the thermal explosion zone, where large low-rank coal particles with a particle size greater than 6mm settle and are mainly crushed; the preheating feed inlet 7 of the preheated crushing fluidized bed 2 is located at the bottom of the first cylindrical section; multiple thermal explosion generating devices are provided on the outer wall of the second cylindrical section, and the high-moisture low-rank coal entering the preheated crushing fluidized bed 2 through the preheating feed inlet 7 is subjected to airflow, and the large particles settle from the conical section to the second cylindrical section. Due to the microwave effect of the thermal explosion generating devices, the large low-rank coal particles undergo thermal explosion and are instantly crushed into small low-rank coal particles, which immediately enter the fluidized bed layer under the action of airflow and are tumbled and heated.

[0040] Compared with the prior art, the present invention sets a thermal burst generation device at the bottom of the preheated crushing fluidized bed 2. The thermal burst generation device can crush large particles of high-moisture low-rank coal into small particles of low-rank coal with uniform particle size, thereby expanding the feed particle size range of the drying and crushing system.

[0041] It should be noted that the second columnar section is equipped with a circular air distribution plate, which is set horizontally. The area enclosed by the circular air distribution plate and the bottom surface of the second columnar section is an air chamber, and the first gas inlet is connected to the air chamber. Ventilation holes are evenly distributed on the circular air distribution plate, and an accelerated crushing component is provided at the center of the top of the circular air distribution plate. This accelerated crushing component is used to accelerate the crushing process of large particles of high-moisture low-rank coal.

[0042] Compared with the prior art, the present invention can buffer the mixed gas entering from the first gas inlet by setting up a wind chamber (a mixed gas formed by the low temperature and moisture exhaust gas discharged from the secondary cyclone separator 5 and the gas discharged from the settling device 6 that has recovered the sensible heat of the dried material, the temperature of the mixed gas is 120℃-130℃ and the flow rate is 1.2-1.4m / s). By setting up a circular air distribution plate, the mixed gas can be uniformly entered into the preheated crushing fluidized bed, ensuring uniform contact between the gas and the high moisture content low-rank coal.

[0043] To accelerate the crushing of large particles of high-moisture, low-rank coal, the accelerated crushing component of this invention includes a rotating shaft and multiple flexible chains; wherein, the rotating shaft is arranged vertically, one end of the rotating shaft is fixed to a circular air distribution plate, and one end of the multiple flexible chains is detachably connected to the rotating shaft.

[0044] It should be noted that the above-mentioned flexible chain is a flexible rigid chain, and the length of the flexible rigid chain is less than or equal to the radius of the horizontal section of the second columnar segment; the number of flexible steel chains is 3-7, and the flexible steel chains are evenly arranged in the vertical direction along the axis of rotation.

[0045] Compared with the prior art, the present invention uses a rotating shaft to drive multiple flexible rigid chains to rotate. During the rotation, the flexible rigid chains collide with large particles of high-moisture low-rank coal, turning the high-moisture low-rank coal into small particles, thus accelerating the crushing process of high-moisture low-rank coal.

[0046] It should be noted that by setting a first gas inlet 9 at the bottom of the preheated crushing fluidized bed 2, the hot air flow provided by the gas supply unit can promptly lift the small particles of low-rank coal formed by microwave action to the fluidized bed layer, avoiding the problem of local overheating of microwave-heated materials, thereby improving the safety of the drying and crushing system.

[0047] It should be noted that the thermal explosion generating device of the present invention includes a microwave generator 8, which uses microwaves generated by the microwave generator 8 to heat and crush low-rank coal with high moisture content.

[0048] In order to separate the low-rank coal that has been heated and crushed in the preheating and crushing unit, the primary separation device of the present invention includes a primary cyclone separator 3; the top of the primary cyclone separator 3 is provided with a first gas outlet 10, the first feed inlet is provided at the top of the primary cyclone separator 3; and the second discharge outlet 15 is provided at the bottom of the primary cyclone separator 3.

[0049] Specifically, the small low-rank coal particles heated and crushed by the preheated and crushed fluidized bed 2 are carried by the airflow into the first-stage cyclone separator 3 through the first feed port. Under the action of the cyclone separator, the small low-rank coal particles are discharged from the first discharge port 11 and enter the drying unit for rapid drying.

[0050] The secondary separation device of the present invention includes a secondary cyclone separator 5; a second gas outlet 14 is provided at the top of the secondary cyclone separator 5; a second feed inlet is provided at the top of the secondary cyclone separator 5; and a second discharge outlet is provided at the bottom of the secondary cyclone separator 5.

[0051] In order to fully dry the preheated low-rank coal, the drying unit of the present invention includes a drying fluidized bed 4; the drying inlet 12 is located at the bottom of the drying fluidized bed 4, and the drying outlet is located at the top of the drying fluidized bed 4.

[0052] The drying unit of this invention uses a high-temperature, slow-speed hot airflow to perform high-intensity, rapid drying of the preheated material. When the moisture content of the low-rank coal particles in the drying fluidized bed 4 is reduced to a low level, the particle strength of the low-rank coal fine particles will be significantly reduced. Under the action of mechanical friction between particles, the low-rank coal particles are easily crushed into even smaller fine particles. The fine particles are carried out of the drying fluidized bed 4 by the airflow, ensuring the uniformity of the output particle size of the drying fluidized bed 4.

[0053] In order to supply gas smoothly to the preheated and broken fluidized bed 2 and the dry fluidized bed 4, the gas supply unit includes a first branch pipe 19 and a second branch pipe 20; the gas supply unit is connected to the first gas inlet 9 at the bottom of the preheated and broken fluidized bed 2 through the first branch pipe 19; the gas supply unit is connected to the second gas inlet 13 at the bottom of the dry fluidized bed 4 through the second branch pipe 20.

[0054] Compared with existing technologies, the gas supply unit is connected to the first gas inlet 9 at the bottom of the drying fluidized bed 4 through the second branch pipe 20, which can ensure that the fully dried low-rank coal fine particles in the drying unit are carried out in time, while the large particles that are not fully dried remain in the drying unit to continue drying. While preventing the low-rank coal fine particles from being over-dried and reducing the risk of system combustion and explosion, the drying energy of different particle sizes has been optimized, and the energy utilization efficiency of the drying and crushing system has been improved.

[0055] In order to recover the sensible heat of the dried sample and improve the thermal efficiency of the system, the drying and crushing system for high-moisture low-rank coal of the present invention also includes a settling device 6; the feed inlet (i.e., the first dovetail inlet 16) of the settling device 6 is connected to the second discharge outlet 15, and the bottom of the settling device 6 is provided with a discharge outlet 18, through which the dried low-rank coal is discharged from the drying and crushing system.

[0056] Compared with existing technologies, the present invention can recover the heat carried by the dried low-rank coal through a settling device, thereby improving the thermal efficiency of the system.

[0057] It should be noted that the gas supply unit of the present invention also includes a third branch pipe 21; the gas outlet of the settling device 6 (i.e., the second dovetail outlet 17) is connected to the gas inlet of the preheated crushing fluidized bed 2 through the third branch pipe 21.

[0058] The aforementioned settling device 6 includes a hollow dovetail-shaped settling structure, which comprises a first dovetail and a second dovetail, both of which are axially symmetrical. The first dovetail has a first opening at its tail, and the second dovetail has a second opening at its tail. The first dovetail inlet 16 is connected to the second outlet of the secondary cyclone separator 5. Additionally, a gas supply unit is connected to the first dovetail inlet 16 via a fifth branch pipe 23 to provide ambient temperature gas to the settling device 6 to recover the sensible heat of the material. The second dovetail outlet 17 is connected to the first air inlet of the preheated crushing fluidized bed 2 via a third branch pipe 21. It should also be noted that a discharge port 18 is provided at the bottom of the hollow dovetail-shaped structure, through which small particles of low-rank coal, dried and crushed by the drying and crushing system, are discharged from the entire drying and crushing system.

[0059] Compared to existing technologies, in this method, the airflow carrying dry low-rank coal particles enters through the first dovetail inlet 16 and exits through the second dovetail outlet 17. During this process, the airflow resistance gradually increases, and the airflow velocity gradually decreases. This design ensures that the low-rank coal particles in the airflow have sufficient time to settle. Furthermore, the high-temperature material discharged from the bottom of the secondary cyclone separator 5 enters the settling device 6, and ambient temperature air is introduced into the settling device 6 to recover the sensible heat carried by the dried material. This reduces the heat loss of the entire drying and crushing system and improves the overall thermal efficiency. Additionally, the low discharge temperature of the dry material eliminates the risk of spontaneous combustion of dried low-rank coal when stockpiled.

[0060] The gas supply unit of the present invention also includes a fourth branch pipe 22. The second outlet of the secondary cyclone separator 5 introduces the discharged gas into the preheating and crushing unit through the fourth branch pipe 22, and uses the gas to preheat the high-moisture low-rank coal therein.

[0061] Example 1 The drying and crushing method for mixed-size high-moisture-content low-rank coal in this embodiment includes the following steps: Step 1: The mixed high-moisture low-rank coal is fed into the preheating and crushing fluidized bed 2 through the feed hopper 1. At the same time, the gas supply unit supplies gas to the preheating and crushing fluidized bed 2 and the drying fluidized bed 4. Simultaneously, the thermal explosion generating device is turned on for preheating and crushing to obtain preheated and crushed low-rank coal. In step 1, the mixed particle size material enters the preheating and crushing fluidized bed 2. At the same time, the low temperature and high speed airflow provided by the gas supply unit enters the preheating and crushing fluidized bed 2 through the first gas inlet 9 at the bottom. The large particles of low-rank coal in the mixed particle size material fall downward to the thermal explosion zone, are heated under the action of microwaves and undergo thermal explosion, and are crushed into small particles of low-rank coal. The fine particles in the mixed particle size material tumble and are heated in the preheating and crushing fluidized bed 2.

[0062] In step 1, the particle size range of the mixed low-rank coal is 25mm-150mm, and its moisture content by mass is 30%-50%.

[0063] In step 1 above, while the thermal explosion generating device is turned on, the accelerated crushing component is also turned on. Multiple flexible rigid chains on the rotating shaft begin to rotate with the rotating shaft. During the rotation of the rotating shaft, the flexible rigid chains collide with large particles of low-rank coal, and the large particles of low-rank coal are crushed into small particles of low-rank coal.

[0064] It should be noted that when the preheated crushing fluidized bed 2 first starts working, the drying medium used is hot gas supplied by the gas supply unit, with a gas temperature of 120℃-130℃ and a gas flow rate of 1.4m / s. After the entire drying and crushing system has been operating stably, the drying medium in the preheated crushing fluidized bed 2 is a mixture of low-temperature humid tail gas at 170℃ discharged from the secondary cyclone separator 5 and hot air at 50℃ discharged from the settling device 6 that has recovered the sensible heat of the dried material. The temperature of this mixture is 120℃-130℃ and the flow rate is 1.2-1.4m / s.

[0065] In step 1 above, particles with a feed size greater than 6mm fall to the bottom area of ​​the preheated crushing fluidized bed 2 (i.e., the thermal explosion area). Under the action of the microwave generator 8, a thermal explosion occurs. After crushing, low-rank coal particles with a size less than 6mm immediately enter the fluidized bed layer with the hot airflow. Larger particles remain in the bottom area of ​​the fluidized bed and continue to be heated and crushed by microwaves. Low-rank coal particles with a size less than 6mm are tumbled up and down with the airflow. The airflow temperature decreases from 120℃-130℃ to 80℃, and the low-rank coal particles are heated to 70℃-75℃. The preheated low-rank coal particles enter the primary separation device with the airflow.

[0066] Step 2: Use a primary separation device to perform gas-solid separation on the preheated and crushed low-rank coal. The separated gas is discharged from the drying and crushing system, and the separated low-rank coal particles enter the drying unit. Specifically, the airflow in the preheated and crushed fluidized bed 2 carries low-rank coal particles into the first-stage cyclone separator 3 for gas-solid separation. The separated gas is discharged from the first gas outlet 10. The temperature of the preheated and crushed low-rank coal is 70-75℃ and the particle size is less than 6mm. It falls to the second discharge port 15 and enters the drying unit through the drying inlet.

[0067] Step 3: The drying unit dries the low-rank coal that enters it to obtain dried low-rank coal; The hot air temperature in the drying unit is 250℃ and the wind speed is 0.6m / s. It enters the drying unit through the second gas inlet 13. The low-rank coal tumbles in the high-temperature hot air flow from bottom to top, and the moisture is quickly removed.

[0068] It should be noted that in the drying fluidized bed 4, the strength of the dried low-rank coal particles decreases. Under the action of mechanical friction, large particles are easily crushed into finer particles with smaller particle sizes. Fine particles with a particle size of less than 3 mm are carried out with the airflow, while particles with a size of 3-6 mm remain in the fluidized bed to continue drying.

[0069] Step 4: Use a two-stage separation device to perform gas-solid separation on the dried low-rank coal, and use a settling device 6 to settle the obtained solids to obtain dried low-rank coal.

[0070] In the drying unit, the airflow carrying the fine particles of low-rank coal enters the secondary cyclone separator 5 for gas-solid separation. The separated gas is drawn out through the second gas outlet 14. The separated low-rank coal is discharged from the second discharge port and, together with the 30°C air, enters the settling device 6 through the first dovetail inlet for heat exchange and settling to recover the sensible heat carried by the dry material. It is then discharged from the system through the discharge port 18 of the settling device 6.

[0071] The 170°C humid hot air discharged from the gas outlet of the secondary cyclone separator 5 and the 50°C hot air discharged from the gas outlet of the settling pipe are guided to the gas inlet 9 of the preheating crushing system to serve as a fluidizing medium for heating the material.

[0072] The 170°C humid hot air discharged from the second gas outlet 14 of the secondary cyclone separator 5 and the 50°C hot air discharged from the second dovetail outlet 17 of the settling device 6 are guided to the first gas inlet 9 of the preheating crushing fluidized bed 2. At this time, the temperature of the mixed gas is 130°C, which can be used as a fluidizing medium to preheat the high moisture content low-rank coal of the mixed particle size.

[0073] It should be noted that the dry low-rank coal discharged from the settling device 6 is at room temperature, which can not only significantly reduce the heat loss of the system and improve the overall thermal efficiency of the system, but also effectively prevent the risk of spontaneous combustion caused by the storage of dry low-rank coal.

[0074] Example 2 The drying and crushing method for mixed-size high-moisture-content low-rank coal in this embodiment includes the following steps: Step 1: The mixed high-moisture low-rank coal is fed into the preheating and crushing fluidized bed 2 through the feed hopper 1. At the same time, the gas supply unit supplies gas to the preheating and crushing fluidized bed 2 and the drying fluidized bed 4. Simultaneously, the thermal explosion generating device is turned on for preheating and crushing to obtain preheated and crushed low-rank coal. In step 1, the mixed particle size material enters the preheating and crushing fluidized bed 2. At the same time, the low temperature and high speed airflow provided by the gas supply unit enters the preheating and crushing fluidized bed 2 through the first gas inlet 9 at the bottom. The large particles of low-rank coal in the mixed particle size material fall downward to the thermal explosion zone, are heated under the action of microwaves and undergo thermal explosion, and are crushed into small particles of low-rank coal. The fine particles in the mixed particle size material tumble and are heated in the preheating and crushing fluidized bed 2.

[0075] In step 1, the particle size range of the mixed-grade low-rank coal is 60mm-150mm, and its moisture content by mass is 40%-50%.

[0076] In step 1, the mixed low-rank coal material entering the preheated and crushed fluidized bed 2 comes into contact with 135°C hot air flowing upwards in the fluidized bed at a velocity of 1.4 m / s. Particles larger than 6 mm fall to the thermal explosion zone at the bottom of the fluidized bed, where they undergo thermal explosion under the action of the microwave generator 88. Large particles are crushed into smaller particles, while particles smaller than 6 mm enter the fluidized bed layer with the rising hot air and tumble up and down with it. Larger particles remain at the bottom of the equipment and continue to be heated and crushed under the action of microwaves.

[0077] At the same time as the thermal explosion generating device is activated, the accelerated crushing component is also activated. Multiple flexible steel chains on the rotating shaft begin to rotate with the shaft. During the rotation of the shaft, the flexible steel chains collide with large particles of low-rank coal, and the large particles of low-rank coal are crushed into small particles of low-rank coal.

[0078] Step 2: Use a primary separation device to perform gas-solid separation on the preheated and crushed low-rank coal. The separated gas is discharged from the drying and crushing system, and the separated low-rank coal particles enter the drying unit. Specifically, the airflow in the preheated and crushed fluidized bed 2 carries low-rank coal particles into the first-stage cyclone separator 3 for gas-solid separation. The separated gas is discharged from the first gas outlet 10. The temperature of the preheated and crushed low-rank coal is 80°C and the particle size is less than 6mm. It falls to the second discharge port 15 and enters the drying unit through the drying inlet.

[0079] Step 3: The drying unit dries the low-rank coal that enters it to obtain dried low-rank coal; The hot air temperature in the drying unit is 240℃ and the wind speed is 0.8m / s. It enters the drying unit through the second gas inlet 13 at the bottom and tumbles in the high-temperature hot air flow from bottom to top, where the moisture is quickly removed.

[0080] It should be noted that in the drying fluidized bed 4, the strength of the dried low-rank coal particles decreases, and under the action of mechanical friction, large particles are easily crushed into finer particles with smaller particle sizes. Fine particles with a particle size of less than 2 mm are rapidly dried by the rising airflow and then discharged from the fluidized bed; particles with a particle size of more than 2 mm remain in the fluidized bed to continue drying.

[0081] This invention optimizes the energy input of low-rank coal particles of different sizes in a fluidized bed by controlling the residence time of particles of different sizes based on thermal fracturing, thereby improving the energy utilization efficiency of the system.

[0082] Step 4: Use a two-stage separation device to perform gas-solid separation on the dried low-rank coal, and use a settling device 6 to settle the obtained solids to obtain dried low-rank coal.

[0083] In the drying unit, the airflow carries fine dry material into the secondary cyclone separator 5 for gas-solid separation. The gas is drawn out from the second gas outlet 14. The dried material in the secondary cyclone separator 5 is discharged from the second outlet and enters the settling device 6 together with the 30°C air through the first dovetail inlet 16 for heat exchange and settling. After recovering the sensible heat of the dry material, it is discharged from the system through the discharge port 18 of the settling device 6.

[0084] It should be noted that after the dry material in the settling device 6 exchanges heat with the air, the air is heated to 50°C and introduced into the preheated crushing fluidized bed 2 through the third branch pipe 21; the material is cooled to 55°C and discharged from the settling device 6 through the discharge port 18.

[0085] It should be noted that the 160°C humid hot air discharged from the second gas outlet 14 of the secondary cyclone separator 5 and the 50°C hot air discharged from the second dovetail outlet 17 of the settling device 6 are guided to the first gas inlet 9 of the preheating crushing fluidized bed 2. At this time, the temperature of the mixed gas is 135°C, which can be used as a fluidizing medium to preheat the high moisture content low-rank coal of the mixed particle size.

[0086] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for drying and crushing mixed-size, high-moisture, low-rank coal, characterized in that, Includes the following steps: Step 1: Add the mixed high-moisture low-rank coal to the preheating and crushing unit and process it to obtain preheated and crushed low-rank coal; During feeding, the thermal explosion generator is activated simultaneously to obtain crushed low-rank coal; The preheating and crushing unit includes a preheating and crushing fluidized bed; the bottom of the preheating and crushing fluidized bed is equipped with a thermal explosion device, which is used to cause thermal explosion of high-moisture low-rank coal in the preheating and crushing fluidized bed. The preheated crushing fluidized bed comprises, from top to bottom, a first cylindrical section, a conical section, and a second cylindrical section connected in sequence. The first cylindrical section is connected to the second cylindrical section via the conical section. The outer diameter of the first cylindrical section is larger than that of the second cylindrical section. The area within the first cylindrical section is the fluidized bed layer, and the area within the second cylindrical section is the thermal explosion zone. Large low-rank coal particles with a diameter greater than 6 mm settle into the thermal explosion zone for crushing. The preheating feed inlet of the preheated crushing fluidized bed is located at the bottom of the first cylindrical section. Multiple thermal explosion generating devices are installed on the outer wall of the second cylindrical section. High-moisture low-rank coal entering the preheated crushing fluidized bed through the preheating feed inlet is subjected to airflow. Large particles settle from the conical section to the second cylindrical section. Due to the microwave effect of the thermal explosion generating devices, the large low-rank coal particles undergo thermal explosion and are crushed into smaller low-rank coal particles. The smaller low-rank coal particles enter the fluidized bed layer under the action of airflow and are tumbled and heated. The second columnar section is equipped with a circular air distribution plate, which is arranged horizontally. The area enclosed by the circular air distribution plate and the bottom surface of the second columnar section is an air chamber. The first gas inlet is connected to the air chamber. Ventilation holes are evenly distributed on the circular air distribution plate. An accelerated crushing component is provided at the center of the top of the circular air distribution plate. The accelerated crushing component is used to accelerate the crushing process of large particles of high-moisture low-rank coal. The thermal explosion generating device includes a microwave generator, which uses microwaves generated by the microwave generator to heat and crush low-rank coal with high moisture content. The accelerated crushing component includes a rotating shaft and multiple flexible chains; wherein, the rotating shaft is arranged vertically, one end of the rotating shaft is fixed to a circular air distribution plate, and one end of each of the multiple flexible chains is detachably connected to the rotating shaft; the flexible chains are flexible rigid chains; The particle size of the mixed high-moisture low-rank coal is 25mm-150mm; Step 2: Use a primary separation device to perform gas-solid separation on the preheated and crushed low-rank coal, and discharge the separated low-rank coal particles into the drying unit. Step 3: Use the drying unit to dry the low-rank coal that enters it to obtain dried low-rank coal; Step 4: Use a two-stage separation device to perform gas-solid separation on the dried low-rank coal to obtain high-temperature low-rank coal with small particle size. The secondary separation device includes a secondary cyclone separator; the top of the secondary cyclone separator is provided with a second gas outlet; Step 5: The small-particle-size, high-temperature, low-rank coal is discharged into the settling device and heat-exchanged with fresh air. The cooled small-particle-size, low-rank coal is the final product and is discharged from the system. The gas supply unit is used to supply gas to the preheating crushing unit and the drying unit; the gas supply unit includes a first branch pipe and a second branch pipe; the gas supply unit is connected to the first gas inlet at the bottom of the preheating crushing fluidized bed through its first branch pipe; the gas supply unit is connected to the second gas inlet at the bottom of the drying fluidized bed through its second branch pipe. The gas supply unit also includes a third branch pipe; the gas outlet of the settling device is connected to the gas inlet of the preheated crushing fluidized bed through the third branch pipe. The gas supply unit also includes a fourth branch pipe. The second outlet of the secondary cyclone separator introduces the discharged gas into the preheating and crushing unit through the fourth branch pipe, and uses the gas to preheat the high-moisture low-rank coal therein. In step 1, after the preheating crushing unit and the drying unit are working stably, the drying medium in the preheating crushing unit is a mixture of low-temperature humid tail gas discharged from the secondary cyclone separator and hot air discharged from the settling device that has recovered the sensible heat of the dried material.

2. The drying and crushing method for mixed-size high-moisture low-rank coal according to claim 1, characterized in that, In step 1, during the feeding process, air is simultaneously supplied to the preheating crushing unit and the drying unit using the air supply unit.

3. The drying and crushing method for mixed-size high-moisture low-rank coal according to claim 2, characterized in that, In step 1, when the preheating crushing unit starts working, the drying medium used is hot gas supplied by the gas supply unit, with a gas temperature of 120℃-130℃ and a gas flow rate of 1.2-1.4m / s.

4. The drying and crushing method for mixed-size high-moisture low-rank coal according to claim 3, characterized in that, In step 1, the temperature of the mixed gas is 120℃-130℃ and the flow rate is 1.2-1.4m / s.

5. The drying and crushing method for mixed-size high-moisture-content low-rank coal according to claim 4, characterized in that, In step 1, the particle size of the preheated and crushed low-rank coal is less than or equal to 6 mm.

6. The drying and crushing method for mixed-size high-moisture-content low-rank coal according to claim 1, characterized in that, In step 3, the particle size of the dried low-rank coal is less than or equal to 3 mm.

7. The drying and crushing method for mixed-size high-moisture-content low-rank coal according to any one of claims 1 to 6, characterized in that, The moisture content of the mixed-size high-moisture low-rank coal is 30%-50% by mass.

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