A low rank coal low temperature drying system and method

Abstract

The present application relates to a low-rank lump coal low-temperature drying system and method, and belongs to the technical field of coal drying, which solves at least one of the problems of short residence time of low-rank lump coal to be dried in flue gas and low drying efficiency in the prior art. The present application adds porous particle drying medium into the fluidized bed, simultaneously utilizes the effect of magnetic field on the fluidized bed, uses fluidizing air to make the medium composed of porous particles in a bubble-free fluidized state, increases the energy storage effect of the drying medium, saves the heat cost, and avoids the adverse effects of the existence of bubbles on the drying of coal. In addition, the coal successively passes through multiple drying chambers during the drying process, and the coal in each drying chamber fully contacts with the corresponding drying bed layer, thereby improving the heat and mass transfer efficiency and the drying efficiency.

Description

Technical Field

[0001] This invention relates to the field of coal drying technology, and in particular to a low-temperature drying system and method for low-rank lump coal. Background Technology

[0002] Low-rank coal contains a high moisture content, typically above 30%. During coal combustion, some heat is used to evaporate this moisture, which reduces the coal's calorific value and combustion efficiency. Drying low-rank coal can significantly reduce its moisture content, improve combustion efficiency, and decrease pollutant emissions. Furthermore, low-rank coal drying promotes comprehensive coal utilization, providing broader application opportunities for other uses. Therefore, developing low-rank coal drying technology is of great significance, not only improving combustion efficiency, reducing transportation costs, and increasing coal stability, but also promoting comprehensive coal utilization and reducing environmental impact.

[0003] High-temperature fluidized bed drying of low-rank coal is a common technology, generally using a high-temperature gas flow as the fluidizing medium. However, when using a high-temperature gas flow as the fluidizing medium, the contact time between low-rank coal and the high-temperature gas flow is short and insufficient, resulting in poor mass and heat transfer performance, making it difficult to achieve rapid and uniform drying. Alternatively, existing fluidized bed dryers may have air bubbles in the bed, leading to poor mass or heat transfer performance. Summary of the Invention

[0004] In view of the above analysis, the present invention aims to provide a low-temperature drying apparatus and method for low-rank lump coal, in order to solve at least one of the problems in the prior art, such as insufficient contact between low-rank lump coal and airflow during the drying process, short residence time of the low-rank lump coal to be dried in flue gas, and low drying efficiency.

[0005] In a first aspect, the present invention provides a method for low-temperature drying of low-rank lump coal, comprising drying the low-rank lump coal using a magnetically stabilized multi-chamber fluidized bed, wherein the fluidizing medium comprises porous iron particles and flue gas, and the magnetic field strength of the magnetically stabilized multi-chamber fluidized bed is 7100-9200 A / m.

[0006] Furthermore, the porous iron particles come into contact with the flue gas, forming a bubble-free fluidized bed under the action of a magnetic field.

[0007] Furthermore, the porous iron particles have a particle size of 70–130 μm and a true density of 7.5–7.9 g / cm³. 3 It has a porosity of 15%–30% and a bulk density of 1.6–2.0 g / cm³. 3 .

[0008] Furthermore, the flue gas temperature is 110-150℃, and the oxygen volume content is <5%.

[0009] Furthermore, the low-rank lump coal includes at least one of long-flame coal and lignite, and preferably, the particle size of the low-rank lump coal is 10-30 mm.

[0010] Furthermore, the drying method includes the following steps:

[0011] (1) Crush and screen the low-rank lump coal;

[0012] (2) Flue gas is introduced into a fluidized bed containing porous iron particles, and a bubble-free fluidized bed state is formed under the action of a magnetic field.

[0013] (3) The screened low-rank lump coal is added to the fluidized bed in step (2) for drying;

[0014] (4) The gas discharged from the fluidized bed is treated with dust removal, and the separated gas is mixed with the flue gas and fed into the fluidized bed for reuse.

[0015] (5) The dried low-rank lump coal is demediumed to obtain dried low-rank lump coal and porous iron particles respectively.

[0016] (6) The porous iron particles obtained in step (5) are added to a fluidized bed for recycling.

[0017] Furthermore, in step (2), in the drying chamber near the discharge port, 1.3≤V 通入流化床中的烟气的气速 / V 多孔铁颗粒的临界流化气速 ≤1.9, and in the remaining drying chambers, 1<V 通入流化床中的烟气的气速 / V 多孔铁颗粒的临界流化气速 <1.3.

[0018] Secondly, the present invention provides a low-temperature drying system for low-rank lump coal, comprising a crushing device, a screening device, a coal storage device, a drying device, a first desliming device, a descaling device, and a second descaling device connected in sequence. The drying device is further connected to a flue gas generator and a dust removal and separation device. The drying device is a magnetically stabilized multi-chamber fluidized bed dryer filled with porous iron particles, and both the first and second descaling devices include magnetic separators.

[0019] Furthermore, the flue gas generating device is connected to the upper and lower ends of the magnetically stabilized multi-chamber fluidized bed dryer, respectively, so that the flue gas enters from both the upper and lower directions of the fluidized bed dryer.

[0020] Furthermore, the dust removal and separation device includes a first separation device and a second separation device, wherein the first separation device is connected to the drying device.

[0021] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0022] (1) This invention adds a porous particle drying medium to a fluidized bed and utilizes the effect of a magnetic field on the fluidized bed. Fluidizing air is used to keep the porous particle medium in a bubble-free fluidized state, increasing the energy storage capacity of the drying medium, saving heat costs, and avoiding the adverse effects of air bubbles on the dried coal. Furthermore, the coal passes through multiple drying chambers sequentially during the drying process, ensuring full contact between the coal and the corresponding drying bed in each chamber, thus improving heat and mass transfer efficiency and consequently increasing the drying efficiency.

[0023] (2) Existing dryers that only use airflow as the drying medium are only subjected to two forces during the falling process of coal during drying: their own gravity and the drag force of the rising airflow. If the drying time of coal in the equipment is to be increased, the flow rate of the rising airflow can only be increased, which requires a lot of energy. In the method of the present invention, a fluidized bed with a certain temperature and density formed by porous iron particles and flue gas is used as the drying medium. During the falling process of coal during drying, in addition to being subjected to its own gravity and the drag force of the upward airflow, it will also be subjected to the upward buoyancy of the bed. Compared with using only airflow as the drying medium, the fluidized bed formed by porous particles and airflow can reduce the falling speed of coal, thereby increasing the drying time of coal and improving the coal drying effect.

[0024] (3) Compared with solid particles and airflow as fluidized bed, the present invention uses porous iron particles as fluidizing medium. Since the porous iron particles have higher specific surface area, adsorption and mass and heat transfer efficiency, they can achieve better rapid and uniform drying effect on low-rank lump coal.

[0025] (4) The flue gas of the present invention is simultaneously introduced into the fluidized bed in the drying device from two directions. A portion of the flue gas enters from the bottom of the fluidized bed, while a portion of the flue gas is continuously introduced laterally from the top of the fluidized bed to ensure the safety of the drying process.

[0026] (5) The method of the present invention treats and recycles the flue gas generated after drying, reducing environmental pressure; and the fluidizing medium is also recycled. The method of the present invention is simple, has low production cost, and is conducive to large-scale production.

[0027] 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 details specifically pointed out in the description and drawings. Attached Figure Description

[0028] 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.

[0029] Figure 1 This is a schematic diagram of a low-temperature drying system for low-rank lump coal according to the present invention.

[0030] Figure label:

[0031] 1- Crushing device, 2- Screening device, 3- Coal storage device, 4- Feeding device, 5- Magnetic stabilized multi-chamber fluidized bed dryer, 6- Discharge device, 7- First descaling device, 8- Descaling device, 9- Second descaling device, 10- Storage device, 11- First induced draft fan, 12- Flue gas generator, 13- Mixing chamber, 14- Second induced draft fan, 15- First separation device, 16- Second separation device, 17- Third induced draft fan. Detailed Implementation

[0032] 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.

[0033] A specific embodiment of the present invention discloses a method for low-temperature drying of low-rank lump coal, comprising drying the low-rank lump coal using a magnetically stabilized multi-chamber fluidized bed, wherein the fluidizing medium comprises porous iron particles and flue gas, and the magnetic field strength of the magnetically stabilized multi-chamber fluidized bed is 7100–9200 A / m, for example, 7100 A / m, 7200 A / m, 7300 A / m, 7400 A / m, 750 A / m. 0A / m, 7600A / m, 7700A / m, 7800A / m, 7900A / m, 8000A / m, 8100A / m, 8200A / m, 8300A / m, 8 400A / m, 8500A / m, 8600A / m, 8700A / m, 8800A / m, 8900A / m, 9000A / m, 9100A / m, 9200A / m.

[0034] Compared with existing technologies, this invention, by adding a porous particle drying medium to a fluidized bed and utilizing the effect of a magnetic field on the fluidized bed, uses fluidizing air to keep the porous particle medium in a bubble-free fluidized state. This increases the energy storage capacity of the drying medium, saves heat costs, and avoids the adverse effects of air bubbles on the dried coal. Furthermore, as the coal passes through each drying chamber sequentially during the drying process, the coal in each chamber is in full contact with the corresponding drying bed layer, improving heat and mass transfer efficiency, and thus increasing the drying efficiency.

[0035] This invention selects a magnetic field strength of 7100–9200 A / m. Within this range, the bed fluidization effect is relatively stable, and the bed interior can be composed of microbubbles or even reach a bubble-free state, effectively avoiding the decrease in drying effect caused by bubble short-circuiting, and achieving the best drying effect at both ends. When the magnetic field strength is higher than 9200 A / m or lower than 7100 A / m, the bed expansion rate decreases, the bubble behavior in the bed becomes violent, bubble short-circuiting becomes severe, and the drying effect decreases.

[0036] This invention uses porous iron particles as a fluidizing medium. Due to the porous structure of the porous iron particles, they have high specific surface area, adsorption capacity, and mass and heat transfer efficiency, which can achieve rapid and uniform drying effect on low-rank lump coal.

[0037] In one specific embodiment, the porous iron particles come into contact with the flue gas and form a bubble-free fluidized bed under the action of a magnetic field.

[0038] In one specific embodiment, the porous iron particles have a particle size of 70–130 μm, for example, particle sizes of 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, and 130 μm; and a true density of 7.5–7.9 g / cm³. 3 For example, a density of 7.5 g / cm³ 3 7.6g / cm 3 7.7g / cm 3 7.8g / cm 3 7.9g / cm 3 The porosity is 15%–30%, for example, porosities of 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%, with a bulk density of 1.6–2.0 g / cm³. 3 For example, a bulk density of 1.6 g / cm³ 3 1.70g / cm 3 1.80g / cm 3 1.9g / cm 3 2.0g / cm 3 .

[0039] It should be noted that the porous iron particles described in this invention are all commercially available raw materials. Through extensive experimentation, the inventors have discovered that using the porous iron particles defined above in this invention results in good drying efficiency for low-rank lump coal and increases the residence time of low-rank lump coal in the fluidized bed.

[0040] In one specific embodiment, the flue gas temperature is 110-150℃, for example, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, or 150℃; the oxygen volume content is <5%, for example, 4.9%, 4.5%, 4.0%, 3.5%, 3.0%, 2.5%, 2.0%, or 1.5%; and the flue gas density is 0.85-0.95 kg / m³. 3 For example, 0.85 kg / m 3 0.86kg / m 3 0.87kg / m 3 0.88kg / m 3 0.89kg / m 3 0.90kg / m 3 0.91kg / m 3 0.92kg / m 3 0.93kg / m 3 0.94kg / m 3 0.95kg / m 3 .

[0041] It should be noted that using flue gas at 110-150℃ can reduce heat loss during the fluidization process of the bed, improve thermal efficiency, and increase the drying speed.

[0042] In one specific embodiment, the low-rank lump coal includes at least one of long-flame coal and lignite. Preferably, the particle size of the low-rank lump coal is 10-30 mm, for example, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 22 mm, 24 mm, 26 mm, 28 mm, or 30 mm.

[0043] It should be noted that the low-rank lump coal of the present invention is not limited to the above-mentioned coal types, but may also be a mixture of multiple coal types. Those skilled in the art can easily determine suitable process conditions based on the moisture content of the raw coal and the description herein.

[0044] For example, when the coal to be dried has a particle size of 10-30 mm, a moisture content of 30-40%, and a density of 1.45-1.85 g / cm³. 3 When processing low-rank lump coal such as lignite, bituminous coal, or low-rank bituminous coal, use materials with a particle size distribution of 70-130 μm, a porosity of 15%-30%, and a true density of 7.5-7.9 g / cm³. 3 Porous iron particles with a temperature of 110℃~150℃ and a density of 0.85~0.95kg / m³ 3The fluidized bed formed by the flue gas serves as the drying medium. In a drying chamber near the discharge port, with a magnetic field strength of 7100–9200 A / m and a pressure of 1.3 ≤ V... 通入流化床中的烟气的气速 / V 多孔铁颗粒的临界流化气速 ≤1.9, and in the remaining drying chambers, 1<V 通入流化床中的烟气的气速 / V 多孔铁颗粒的临界流化气速 <1.3. This invention can achieve the most ideal drying effect.

[0045] In one specific embodiment, the drying method includes the following steps:

[0046] (1) Crush and screen the low-rank lump coal;

[0047] (2) Flue gas is introduced into a fluidized bed containing porous iron particles, and a bubble-free fluidized bed state is formed under the action of a magnetic field.

[0048] (3) The screened low-rank lump coal is added to the bubble-free fluidized bed in step (2) for drying;

[0049] (4) The high-temperature gas discharged from the fluidized bed is treated with dust removal, and the separated gas is mixed with the flue gas and fed into the fluidized bed for reuse.

[0050] (5) The dried low-rank lump coal is demediumed to obtain dried low-rank lump coal and porous iron particles respectively.

[0051] (6) The porous iron particles obtained in step (5) are added to a fluidized bed for recycling.

[0052] In one specific implementation, in step (2), 1.3≤V in the drying chamber near the discharge port 通入流化床中的烟气的气速 / V 多孔铁颗粒的临界流化气速 The density of the fluidized bed in this drying chamber is ≤1.9, which makes the bed density less than that of the low-rank lump coal to be dried. The low-rank lump coal to be dried sinks, which facilitates discharge and can further improve the drying effect.

[0053] In the remaining drying chambers, 1 < V 通入流化床中的烟气的气速 / V 多孔铁颗粒的临界流化气速 A gas velocity <1.3 ensures that the bed density of the fluidized bed in this drying chamber is greater than the density of the low-rank coal to be dried. The low-rank coal floats on top of the drying chamber, facilitating feeding and movement from one drying chamber to another. Through extensive experimentation, the inventors have discovered that a gas velocity within the above range can guarantee the formation of a uniform and stable bed, resulting in excellent mass and heat transfer efficiency.

[0054] The bed density in the magnetically stabilized multi-chamber fluidized bed dryer 5 can be easily calculated based on the required coal falling time and bed height.

[0055] Specifically, the bed density is related to the porosity, particle size, density of the porous iron particles, flue gas velocity, and flue gas density. For a bed formed from the same type of porous iron particles, the bed density is related to the flue gas density and velocity. Based on the velocity of the low-temperature flue gas and the inherent properties of the porous particles, the density of the fluidized bed can be determined.

[0056] For example, the specific calculation process is as follows:

[0057] As the coal particle size increases, the drag force per unit mass of coal decreases. When the coal particle size exceeds 10 mm, the effect of airflow drag on the coal is almost negligible compared to the coal's own weight. Therefore, for a mass of m... 煤 Coal in the drying bed can be approximated as being subject only to its own weight G and buoyancy F. 浮 The effect is that, assuming the acceleration of the coal falling in the drying bed is *a*, and the initial velocity of the coal is 0, according to Newton's second law:

[0058] GF 浮 =m 煤 a (1)

[0059] The gravitational force G acting on the coal is:

[0060] G = ρ 煤 gV 煤 (2)

[0061] V 煤 Let g be the volume of the coal, which can be obtained through testing. g is the acceleration due to gravity, typically taken as 9.8 m / s². 2 .

[0062] The buoyancy F of coal in the bed 浮 for:

[0063] F 浮 =ρ 床 gV 煤 (3)

[0064] Therefore, the acceleration 'a' of the coal falling in the bed is:

[0065]

[0066] Let the height of the drying bed be H. 床 The coal falls over time t:

[0067]

[0068] Based on the required coal residence time and bed height in practice, and using all the above formulas (1) to (5), the required dry bed density value ρbed can be obtained:

[0069]

[0070] Let the porosity between porous iron particles during natural packing be ε, and the open area of ​​a single pore in the fluidized bed air distribution plate be A. D The flue gas flow velocity is U 气 The apparent density of porous iron particles is ρ 铁粉 The critical fluidization gas velocity for porous iron particles is U. 临界 The average particle size of the porous iron particles is d 铁粉 The density of the flue gas is ρ 气 The viscosity of the flue gas is μ 气 All of the above parameters can be obtained through existing experimental testing methods. Bed density ρ 床 It can be calculated using the following existing formula:

[0071]

[0072] Where Y is the correction parameter:

[0073] Y = 1.72Ar -0.133 (U 气 -U 临界 ) 0.02388

[0074] Where Ar is the Archimedes number:

[0075]

[0076] After obtaining the required bed density from (6), the relevant properties of the required porous iron particles can be determined according to the above formula (7), and then the porous iron particles can be prepared.

[0077] In one specific implementation, in step (4), the dust removal process also yields coal powder, which is then added to the flue gas generator 12 for reuse.

[0078] It should be noted that in step (4), the gas discharged from the fluidized bed enters the first separation device 15 for gas-solid separation. The solid is pulverized coal with a temperature of 90-130℃ and a moisture content of 5-10%. The pulverized coal is then transported to the flue gas generator 12 for reuse. After the gas enters the second separation device 16 to remove coal dust, a portion of the resulting tail gas enters the magnetically stabilized multi-chamber fluidized bed 5 for reuse, while the remaining tail gas is discharged. The gas temperature can be freely set as needed, preferably 110-150℃.

[0079] Preferably, a portion of the exhaust gas is fed into a combustion furnace to control the combustible gas content in the airflow, ensuring safety during the recovery and reuse of this portion of the exhaust gas, while the remaining exhaust gas is discharged into the air. The amount of each portion of the exhaust gas can be determined by technicians through relevant experiments or calculations based on the required dryness of the lump coal being dried.

[0080] The method of this invention enables the recycling of exhaust gas, thereby reducing the amount of exhaust gas emitted and alleviating environmental pressure. The coal dust generated during the drying process can be reused, reducing resource waste and lowering the cost of producing flue gas at a suitable temperature.

[0081] Another specific embodiment of the present invention, such as Figure 1 As shown, a low-temperature drying system for low-rank lump coal is disclosed, comprising a crushing and screening device 2, a coal storage device 3, a drying device, a first desliming device 7, a descaling device 8, and a second desliming device 9 connected in sequence. The drying device is also connected to a flue gas generator 12 and a dust removal and separation device. The drying device is a magnetically stabilized multi-chamber fluidized bed dryer 5 filled with porous iron particles. The first desliming device 7 and the second desliming device 9 both include magnetic separators for separating porous iron particles.

[0082] It should be noted that all devices in the system of the present invention are existing devices, and the magnetically stabilized multi-chamber fluidized bed dryer 5 has at least five drying chambers.

[0083] In one specific embodiment, the flue gas generating device 12 is connected to the upper and lower ends of the magnetically stabilized multi-chamber fluidized bed dryer 5, respectively, so that the flue gas enters from both the upper and lower directions of the magnetically stabilized multi-chamber fluidized bed dryer 5.

[0084] In one specific embodiment, the dust removal and separation device includes a first separation device 15 and a second separation device 16, wherein the first separation device 15 is connected to the drying device.

[0085] In one specific embodiment, both the first desliming device 7 and the second desliming device 9 are connected to the fluidized bed dryer.

[0086] It should be noted that the crushing equipment, screening equipment, dryers, and separation equipment used in this invention are all conventional equipment in the fields of mineral processing engineering or chemical engineering. Any equipment capable of achieving the functions of this invention can be used in this invention. Preferably, the crushing device 1 in this invention can use conventional crushing equipment in the field of mineral processing, such as a roller crusher, for two-stage crushing.

[0087] In one specific embodiment, the crushing device 1 crushes low-rank lump coal to a particle size of less than 30mm, which is beneficial to improving drying efficiency.

[0088] The flue gas generating device 12 described in this invention can be any flue gas source, such as waste flue gas generated during industrial production, and may also include a mixing device.

[0089] The magnetically stabilized multi-chamber fluidized bed 5 of the present invention is connected to a quantitative feeding device 4, such as a star feeder, an SG type feeder, etc. More preferably, it is also connected to a discharge device 6, which is preferably an airlock.

[0090] The first separation device 15 described in this invention can be any gas-solid separation equipment commonly used in industry, such as an inertial dust collector, a cyclone separator, etc.

[0091] The second separation device 16 described in this invention is used to remove dust from the gas separated by the first separation device 15, forming exhaust gas. The separated coal powder is combined with the coal powder separated by the first separation device 15 and sent to the flue gas generator 12. Preferably, the second separation device 16 includes a bag filter.

[0092] The first desliming device 7 and the second desliming device 9 described in this invention are used to separate porous iron particles.

[0093] The technical solution of the present invention will be further explained below with reference to specific embodiments.

[0094] Example 1

[0095] This embodiment describes a system for low-temperature drying of low-rank lump coal, such as... Figure 1 As shown, it includes a crushing device 1, a screening device 2, a coal storage device 3, a drying device, a first desliming device 7, a gangue removal device 8, a second desliming device 9, and a material storage device 10 connected in sequence. The drying device is also connected to a flue gas generator 12 and a dust removal and separation device.

[0096] The drying device is a magnetically stabilized multi-chamber fluidized bed 5 filled with porous iron particles. In this embodiment, the magnetically stabilized multi-chamber fluidized bed 5 has five drying chambers. The first desliming device 7 and the second desliming device 9 both include magnetic separators.

[0097] Specifically, in this embodiment, the crushing and screening device 2 consists of a crusher and a vibrating screen. The vibrating screen separates coal particles that are still larger than 30mm after crushing for secondary crushing. If necessary, dust removal equipment can also be used in this crushing system.

[0098] In a further preferred embodiment, the flue gas generating device 12 is connected to the upper and lower ends of the magnetically stabilized multi-chamber fluidized bed 5, respectively, so that the flue gas enters the magnetically stabilized multi-chamber fluidized bed 5 from both above and below. The magnetically stabilized multi-chamber fluidized bed 5 is also connected to a feeding device 4 and a discharging device 6, wherein the feeding device 4 is a star-shaped feeder and the discharging device 6 is an airlock.

[0099] The dust removal and separation device includes a first separation device 15 and a second separation device 16, wherein the first separation device 15 is connected to the drying device. The first separation device 15 is a cyclone separator, and the second separation device 16 is a bag filter. The bag filter is sequentially connected to a third induced draft fan 17, a first induced draft fan 11, and a mixing chamber 13, wherein the mixing chamber 13 is connected to the magnetically stabilized multi-chamber fluidized bed 5.

[0100] In addition, industrial waste gas enters the flue gas generating device 12 through the second induced draft fan 14.

[0101] The first desliming device 7 and the second desliming device 9 are both connected to the storage device 10, which is connected to the magnetically stabilized multi-chamber fluidized bed 5.

[0102] This application example is a small-scale laboratory drying system. The bed height in the fluidized bed dryer used is set to 2m. In this embodiment, the magnetically stabilized multi-chamber fluidized bed 5 is equipped with five drying chambers.

[0103] Example 2

[0104] A method for low-temperature drying of low-rank lump coal using the system described in Example 1 includes the following steps:

[0105] (1) The low-rank lump coal is crushed in the crushing device 1 and screened in the screening device 2 to obtain low-rank lump coal with a particle size of 10-30mm.

[0106] (2) The low-temperature flue gas generated from the flue gas generator 12 is introduced into the magnetically stable multi-chamber fluidized bed 5, which is filled with porous iron particles, and a bubble-free fluidized bed state is formed under the action of the magnetic field.

[0107] (3) The screened low-rank lump coal is fed into a bubble-free fluidized bed through the feeding device 4 for drying.

[0108] (4) The low-temperature gas discharged from the fluidized bed enters the first separation device 15 for separation. The separated coal powder is fed into the flue gas generator 12 for reuse. The separated gas continues to enter the second separation device 16 for separation. The separated gas enters the third induced draft fan 17 and enters the mixing chamber 13 through the first induced draft fan 11 to mix with the low-temperature flue gas. It is then fed into the magnetically stabilized multi-chamber fluidized bed 5 for reuse. The separated coal powder is fed into the flue gas generator 12 for reuse.

[0109] (5) The dried low-rank lump coal is discharged from the discharge device 6 and sequentially enters the first desliming device 7 for desliming treatment, the deganging device 8 for deganging treatment, and the second desliming device 9 for desliming treatment.

[0110] The porous iron particles separated by the first desliming device 7 and the second desliming device 9 enter the storage device 10 and are then added to the magnetically stabilized multi-chamber fluidized bed 5 for reuse; after processing by the second desliming device 9, dry low-rank lump coal is obtained.

[0111] In this embodiment, the low-rank lump coal is lignite with a moisture content of 35.5%, a particle size of 10–30 mm, and a density of 1.57 g / cm³. 3 The porous iron particles have a particle size of 72 μm and a true density of 7.53 g / cm³. 3 The porosity is 15.70%, and the bulk density is 1.88 g / cm³. 3 .

[0112] The temperature of the low-temperature flue gas is 115℃, and the density of the flue gas is 0.92 kg / m³. 3 The oxygen volume content is <5%, the critical fluidization gas velocity of the porous iron particles is 1.80 cm / s, the flue gas velocity in the drying chamber near the discharge port is 3.06 cm / s, and the bed density is 1.46 g / cm³. 3 The flue gas velocity in the remaining drying chambers was 2.3 cm / s, and the bed density was 1.66 g / cm³. 3 In this embodiment, the magnetic field strength of the magnetically stabilized multi-chamber fluidized bed dryer is 7100 A / m.

[0113] Example 3

[0114] A method for low-temperature drying of low-rank lump coal using the system described in Example 1 includes the following steps:

[0115] (1) The low-rank lump coal is crushed in the crushing device 1 and screened in the screening device 2 to obtain low-rank lump coal with a particle size of 10-30mm.

[0116] (2) The flue gas generated from the flue gas generator 12 is introduced into a magnetically stable multi-chamber fluidized bed with porous iron particles, and a bubble-free fluidized bed state is formed under the action of the magnetic field.

[0117] (3) The screened low-rank lump coal is fed into a bubble-free fluidized bed through the feeding device 4 for drying.

[0118] (4) The high-temperature gas discharged from the fluidized bed enters the first separation device 15 for separation. The separated coal powder is fed into the flue gas generator 12 for reuse. The separated gas continues to enter the second separation device 16 for separation. The separated gas enters the third induced draft fan 17 and enters the mixing chamber 13 through the first induced draft fan 11 to mix with the flue gas. It is then fed into the magnetically stabilized multi-chamber fluidized bed 5 for reuse. The separated coal powder is fed into the flue gas generator 12 for reuse.

[0119] (5) The dried low-rank lump coal is discharged from the discharge device 6 and sequentially enters the first desliming device 7 for desliming treatment, the deganging device 8 for deganging treatment, and the second desliming device 9 for desliming treatment.

[0120] The porous iron particles separated by the first desliming device 7 and the second desliming device 9 enter the storage device 10 and are then added to the magnetically stabilized multi-chamber fluidized bed 5 for reuse; after processing by the second desliming device 9, dry low-rank lump coal is obtained.

[0121] In this embodiment, the low-rank lump coal is lignite with a moisture content of 33.4%, a particle size of 10–30 mm, and a density of 1.48 g / cm³. 3 The porous iron particles have a particle size of 98 μm and a true density of 7.74 g / cm³. 3 It has a porosity of 23% and a bulk density of 1.75 g / cm³. 3 .

[0122] The low-temperature flue gas has a temperature of 135℃ and a density of 0.88 kg / m³. 3 The oxygen volume content is <5%, the critical fluidization gas velocity of the porous iron particles is 2.10 cm / s, the flue gas velocity in the drying chamber near the discharge port is 3.57 cm / s, and the bed density is 1.38 g / cm³. 3 The flue gas velocity in the remaining drying chambers was 2.6 cm / s, and the bed density was 1.58 g / cm³. 3 In this embodiment, the magnetic field strength of the magnetically stabilized multi-chamber fluidized bed dryer is 9200 A / m.

[0123] Example 4

[0124] A method for low-temperature drying of low-rank lump coal using the system described in Example 1 includes the following steps:

[0125] (1) The low-rank lump coal is crushed in the crushing device 1 and screened in the screening device 2 to obtain low-rank lump coal with a particle size of 10-30mm.

[0126] (2) The low-temperature flue gas generated from the flue gas generator 12 is introduced into a magnetically stable multi-chamber fluidized bed with porous iron particles, and a bubble-free fluidized bed state is formed under the action of the magnetic field.

[0127] (3) The screened low-rank lump coal is fed into a bubble-free fluidized bed through the feeding device 4 for drying.

[0128] (4) The low-temperature gas discharged from the fluidized bed enters the first separation device 15 for separation. The separated coal powder is fed into the flue gas generator 12 for reuse. The separated gas continues to enter the second separation device 16 for separation. The separated gas enters the third induced draft fan 17 and enters the mixing chamber 13 through the first induced draft fan 11 to mix with the low-temperature flue gas. It is then fed into the magnetically stabilized multi-chamber fluidized bed 5 for reuse. The separated coal powder is fed into the flue gas generator 12 for reuse.

[0129] (5) The dried low-rank lump coal is discharged from the discharge device 6 and sequentially enters the first desliming device 7 for desliming treatment, the deganging device 8 for deganging treatment, and the second desliming device 9 for desliming treatment.

[0130] The porous iron particles separated by the first desliming device 7 and the second desliming device 9 enter the storage device 10 and are then added to the magnetically stabilized multi-chamber fluidized bed 5 for reuse; after processing by the second desliming device 9, dry low-rank lump coal is obtained.

[0131] In this embodiment, the low-rank lump coal is lignite with a moisture content of 33.1%, a particle size of 10–30 mm, and a density of 1.47 g / cm³. 3 The porous iron particles have a particle size of 128 μm and a true density of 7.88 g / cm³. 3 The porosity is 29.7%, and the bulk density is 1.64 g / cm³. 3 .

[0132] The temperature of the low-temperature flue gas is 147℃, and the density of the flue gas is 0.86 kg / m³. 3 The oxygen volume content is <5%, the critical fluidization gas velocity of the porous iron particles is 2.50 cm / s, the gas velocity of the flue gas in the drying chamber near the discharge port is 4.25 cm / s, and the bed density is 1.32 g / cm³. 3 The flue gas velocity in the remaining drying chambers is 3 cm / s, and the bed density is 1.52 g / cm³. 3 In this embodiment, the magnetic field strength of the magnetically stabilized multi-chamber fluidized bed dryer is 8200 A / m.

[0133] Example 5

[0134] The drying method for low-rank lump coal in this embodiment is the same as in Embodiment 2, except that the low-rank lump coal is long-flame coal with a moisture content of 35.1% and a density of 1.55 g / cm³. 3 The smoke density is 0.92 kg / m³. 3 .

[0135] Comparative Example 1

[0136] The drying method for low-rank lump coal in this embodiment is the same as that in Embodiment 2, except that porous iron particles are replaced with solid iron particles.

[0137] Comparative Example 2

[0138] The drying method for low-rank lump coal in this embodiment is the same as in Embodiment 2, except that the low-rank lump coal to be dried is replaced with bituminous coal with a moisture content of 10% and a density of 1.21 g / cm³. 3 .

[0139] Comparative Example 3

[0140] The drying method for low-rank lump coal in this embodiment is the same as in Example 2, except that the porous iron particles have a particle size of 45 μm and a true density of 7.735 g / cm³. 3 It has a porosity of 7.5% and a bulk density of 3.15 g / cm³. 3 .

[0141] Comparative Example 4

[0142] The drying method for low-rank lump coal in this embodiment is the same as that in Embodiment 2, except that porous iron particles are not added.

[0143] Comparative Example 5

[0144] The drying method for low-rank lump coal in this embodiment is the same as that in embodiment 2, except that the magnetically stabilized multi-chamber fluidized bed dryer 5 is replaced with a fluidized bed dryer without a magnetic field.

[0145] Comparative Example 6

[0146] The drying method for low-rank lump coal in this embodiment is the same as that in Embodiment 2, except that the magnetic field strength of the magnetically stabilized multi-chamber fluidized bed dryer is 2400 A / m.

[0147] Comparative Example 7

[0148] The drying method for low-rank lump coal in this embodiment is the same as that in Embodiment 2. The difference is that the critical fluidization gas velocity of the porous iron particles is 2.10 cm / s, and the gas velocity of the flue gas in all magnetically stable multi-chamber fluidized beds 5 is 2.40 cm / s, that is, all drying chambers have a critical fluidization gas velocity of 1.14 times that of the porous iron particles.

[0149] Comparative Example 8

[0150] The drying method for low-rank lump coal in this embodiment is the same as that in Embodiment 2. The difference is that the critical fluidization gas velocity of the porous iron particles is 2.10 cm / s, and the gas velocity of the flue gas in all magnetically stable multi-chamber fluidized beds 5 is 3.74 cm / s, that is, the critical fluidization gas velocity of the porous iron particles in all drying chambers is 1.78 times that of the porous iron particles.

[0151] Experimental Example 1

[0152] Low-rank lump coal was dried using the methods of Examples 2-5 and Comparative Examples 1-7. The dewatering rate of the low-rank lump coal was measured as (moisture content before drying - moisture content after drying) / moisture content before drying × 100%, and the residence time of the low-rank lump coal in the fluidized bed was also measured, as shown in Table 1.

[0153] Table 1

[0154]

[0155] According to Table 1, (1) Examples 2 to 5 all involved drying coal to a certain extent, indicating that the conditions in this invention can achieve coal drying.

[0156] (2) In Comparative Example 1, due to the use of solid iron powder, the density of the bed formed in all drying chambers is much higher than that of the coal to be dried, which makes it impossible for the coal to sink through the drying bed in the drying chamber near the discharge port, and thus the product cannot be discharged.

[0157] (3) In Comparative Example 2, the coal moisture content is lower than that described in this invention, and its density is lower than that of the drying bed formed by porous iron particles and flue gas. As a result, the coal cannot sink through the drying bed in the drying chamber near the discharge port, and the product discharge cannot be achieved.

[0158] (4) The porous iron particles used in Comparative Example 3 have a particle size lower than that specified in this invention, which makes it impossible for the bed to fluidize, form a dry bed, and thus make it impossible to dry the coal.

[0159] (5) Comparative Example 4 is an example that simulates existing hot air drying technology. Compared with Comparative Example 4, the residence time of coal in Example 2 is increased by about 4 times and the drying effect is improved by about 3 times. This shows that compared with existing hot air drying technology, the residence time of coal in the present invention is significantly increased and the drying effect is significantly improved.

[0160] (6) Compared with Example 2, Comparative Example 5 did not apply a magnetic field, and the short-circuiting behavior of bubbles in the bed was not suppressed, resulting in a significant reduction in drying effect.

[0161] (7) Compared with Example 2, the magnetic field strength of Comparative Example 6 is not within the specified range, resulting in poor suppression of bubble behavior in the bed and a significant reduction in drying effect.

[0162] (8) Compared with Example 2, Comparative Example 7 does not meet the requirement of 1.3cm / s≤V 通入流化床中的烟气的气速 / V 多孔铁颗粒的临界流化气速 The density of the bed formed in the drying chamber near the discharge port is much higher than that of the coal to be dried, which prevents the coal from sinking and being discharged through the discharge port.

[0163] (9) Compared with Example 2, Comparative Example 8 does not meet the requirement of 1cm / s < V 通入流化床中的烟气的气速 / V 多孔铁颗粒的临界流化气速 The density of the bed formed in the drying chamber is much lower than that of the coal to be dried because the coal sinks directly in the first drying chamber after being fed in, and cannot be dried in subsequent drying chambers. This results in the inability to complete the drying and discharge process.

[0164] 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 low-temperature drying of low-rank lump coal, characterized in that, The method includes using a magnetically stabilized multi-chamber fluidized bed to dry the low-rank lump coal, wherein the fluidizing medium includes porous iron particles and flue gas, and the magnetic field strength of the magnetically stabilized multi-chamber fluidized bed is 7100~9200 A / m; The method for low-temperature drying of low-rank lump coal specifically includes the following steps: (1) Crush and screen the low-rank lump coal; (2) Flue gas is introduced into a fluidized bed containing porous iron particles, and a bubble-free fluidized bed state is formed under the action of a magnetic field. (3) The screened low-rank lump coal is added to the fluidized bed in step (2) for drying; (4) The gas discharged from the fluidized bed is treated with dust removal, and the separated gas is mixed with the flue gas and then fed into the fluidized bed for reuse; (5) The dried low-rank lump coal is demediumed to obtain dried low-rank lump coal and porous iron particles respectively. (6) The porous iron particles obtained in step (5) are added to a fluidized bed for recycling.

2. The method for low-temperature drying of low-rank lump coal according to claim 1, characterized in that, The porous iron particles come into contact with the flue gas and form a bubble-free fluidized bed under the action of a magnetic field.

3. A method for low-temperature drying of low-rank lump coal according to claim 1 or 2, characterized in that, The porous iron particles have a particle size of 70~130μm and a true density of 7.5~7.9g / cm³. 3 It has a porosity of 15%~30% and a bulk density of 1.6~2.0 g / cm³. 3 .

4. A method for low-temperature drying of low-rank lump coal according to claim 1 or 2, characterized in that, The flue gas temperature is 110-150℃, and the oxygen volume content is <5%.

5. A method for low-temperature drying of low-rank lump coal according to claim 1 or 2, characterized in that, The low-rank lump coal mentioned includes at least one of long-flame coal and lignite.

6. The method for low-temperature drying of low-rank lump coal according to claim 5, characterized in that, The low-rank lump coal has a particle size of 10-30 mm.

7. The method for low-temperature drying of low-rank lump coal according to claim 1, characterized in that, In step (2), 1.3≤V in the drying chamber near the discharge port 通入流化床中的烟气的气速 / V 多孔铁颗粒的临界流化气速 ≤1.9, and in the remaining drying chambers, 1<V 通入流化床中的烟气的气速 / V 多孔铁颗粒的临界流化气速 <1.

3.

8. A low-temperature drying system based on the method for low-temperature drying of low-rank lump coal according to any one of claims 1-7, characterized in that, It includes a crushing device, a screening device, a coal storage device, a drying device, a first desliming device, a gangue removal device, and a second desliming device connected in sequence. The drying device is also connected to a flue gas generator and a dust removal and separation device. The drying device is a magnetically stabilized multi-chamber fluidized bed dryer filled with porous iron particles, and both the first and second desliming devices include magnetic separators.

9. The low-temperature drying system according to claim 8, characterized in that, The flue gas generating device is connected to the upper and lower ends of the magnetically stabilized multi-chamber fluidized bed dryer, so that the flue gas enters from the upper and lower directions of the fluidized bed dryer, respectively.

10. The temperature drying system according to claim 8, characterized in that, The dust removal and separation device includes a first separation device and a second separation device, wherein the first separation device is connected to the drying device.

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