Low-order lump coal low-temperature drying system and method

Abstract

The invention relates to a low-temperature drying system and a low-temperature drying method for low-order lump coal, belongs to the technical field of coal drying, and solves at least one of the problems of short retention time of to-be-dried low-order lump coal in flue gas, low drying efficiency and the like in the prior art. The drying medium of the porous particles is added into the fluidized bed, the action of the magnetic field on the fluidized bed is utilized, the medium composed of the porous particles is in a bubble-free fluidized state through fluidizing air, the energy storage effect of the drying medium is improved, the heat cost is saved, and the adverse effect of bubbles on coal drying is avoided. Besides, the coal sequentially passes through the multiple drying chambers in the drying process, the coal in each drying chamber is in full contact with the corresponding drying bed layer, the heat transfer and mass transfer heat efficiency is improved, and the drying efficiency is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of coal drying, and in particular to a low-temperature drying system and method for low-grade lump coal. Background Art

[0002] Low-rank coal contains a high amount of moisture, usually more than 30%. Part of the heat is needed to evaporate the moisture during coal combustion. The presence of moisture will reduce the calorific value and combustion efficiency of coal. By drying low-rank coal, its moisture content can be significantly reduced, the combustion efficiency can be improved, and pollutant emissions can be reduced. In addition, low-rank coal drying can promote the comprehensive utilization of coal and provide a broader application space for other utilization methods. Therefore, the development of low-rank coal drying technology is of great significance. It can not only improve the combustion efficiency of coal, reduce transportation costs, and increase the stability of coal, but also promote the comprehensive utilization of coal and reduce the impact on the environment.

[0003] Low-rank coal high-temperature fluidized bed drying is a common low-rank coal drying technology, which generally uses high-temperature airflow as a fluidizing medium to dry the coal. However, when high-temperature airflow is used as a fluidizing medium, when low-rank coal contacts with the high-temperature airflow, there are problems such as short contact time and insufficient contact, poor mass transfer and heat transfer performance, and it is difficult to achieve a fast and uniform drying effect. Or in the existing fluidized bed drying, there are bubbles in the bed layer, and the mass transfer or heat transfer performance is poor. Summary of the invention

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

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

[0006] Furthermore, the porous iron particles are in contact with the flue gas, and a bubble-free fluidized bed state is formed under the action of a magnetic field.

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

[0008] Furthermore, the flue gas temperature is 110-150° C., and the oxygen volume content is less than 5%.

[0009] Furthermore, 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.

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

[0011] (1) Crushing and screening low-grade coal;

[0012] (2) passing the flue gas into a fluidized bed on which porous iron particles are deposited, and forming a bubble-free fluidized bed state under the action of a magnetic field;

[0013] (3) adding the screened low-grade lump coal to the fluidized bed in step (2) for drying;

[0014] (4) The gas discharged from the fluidized bed is subjected to dust removal treatment, and the separated gas is mixed with the flue gas and passed into the fluidized bed for repeated use;

[0015] (5) subjecting the dried low-rank lump coal to de-intermediation treatment to obtain dried low-rank lump coal and porous iron particles;

[0016] (6) Adding the porous iron particles obtained in step (5) into a fluidized bed for recycling.

[0017] Further, in step (2), 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, 1<V in other drying chambers 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] In the second aspect, the present invention provides a low-temperature drying system for low-grade lump coal, comprising a crushing device, a screening device, a coal storage device, a drying device, a first medium removal device, a gangue removal device and a second medium removal device connected in sequence, and the drying device is also respectively connected to a flue gas generating device and a dust removal and separation device; wherein the drying device is a magnetically stabilized multi-chamber fluidized bed dryer filled with porous iron particles, and the first medium removal device and the second medium removal device both include magnetic separators.

[0019] Furthermore, the smoke generating device is connected to the upper end and the lower end of the magnetically stabilized multi-chamber fluidized bed dryer respectively, so that the smoke enters the fluidized bed dryer from two directions, namely, the upper end and the lower end.

[0020] Furthermore, the dust removal and separation device includes a first separation device and a second separation device, and 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) The present invention adds a porous particle drying medium into the fluidized bed, and utilizes the effect of the magnetic field on the fluidized bed, and uses fluidized wind to make the medium composed of porous particles in a bubble-free fluidized state, thereby increasing the energy storage function of the drying medium, saving heat costs, and avoiding the adverse effects of bubbles on the drying of coal. In addition, the coal passes through multiple drying chambers in sequence during the drying process, and the coal in each drying chamber is in full contact with the corresponding drying bed layer, which improves the heat transfer and mass transfer efficiency, thereby improving the drying efficiency;

[0023] (2) In the existing dryers that only use airflow as the drying medium, the coal is only affected by its own gravity and the drag of the rising airflow during the falling process during drying. If the drying time of the 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 layer with a certain temperature and density formed by porous iron particles and flue gas airflow is used as the drying medium. In addition to being affected by its own gravity and the upward drag of the airflow during the falling process during drying, the coal will also be affected by the upward buoyancy of the bed layer. Compared with using only airflow as the drying medium, the fluidized bed layer formed by porous particles and airflow as the drying medium can reduce the falling speed of the coal, thereby increasing the drying time of the coal and improving the coal drying effect.

[0024] (3) Compared with the case where solid particles and airflow are used as the fluidized bed, the present invention uses porous iron particles as the fluidized medium. Since the porous structure of the porous iron particles has a higher specific surface area, adsorption and mass transfer efficiency, it can achieve a better rapid and uniform drying effect on low-grade lump coal;

[0025] (4) The flue gas of the present invention is introduced into the fluidized bed in the drying device from two directions at the same time, a part of the flue gas enters from the bottom of the fluidized bed, and a part of the flue gas is continuously introduced horizontally at the top of the fluidized bed layer, thereby ensuring the safety of the drying process;

[0026] (5) The method of the present invention processes the flue gas generated after drying and recycles it to reduce environmental pressure; and the fluidized 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 the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings are only for the purpose of illustrating specific embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

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

[0030] Reference numerals:

[0031] 1-crushing device, 2-screening device, 3-coal storage device, 4-feeding device, 5-magnetically stabilized multi-chamber fluidized bed dryer, 6-discharging device, 7-first medium removal device, 8-gangue removal device, 9-second medium removal device, 10-storage device, 11-first induced draft fan, 12-smoke generating device, 13-air mixing chamber, 14-second induced draft fan, 15-first separation device, 16-second separation device, 17-third induced draft fan. DETAILED DESCRIPTION

[0032] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings 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 used 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-grade lump coal, comprising drying the low-grade lump coal using a magnetically stabilized multi-chamber fluidized bed, wherein the fluidized medium comprises porous iron particles and flue gas, and the magnetic field strength of the magnetically stabilized multi-chamber fluidized bed is 7100 to 9200 A / m, for example, 7100 A / m, 7200 A / m, 7300 A / m, 7400 A / m, 750 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 the prior art, the present invention adds a porous particle drying medium into the fluidized bed, utilizes the effect of the magnetic field on the fluidized bed, and uses fluidized wind to make the medium composed of porous particles in a bubble-free fluidized state, thereby increasing the energy storage function of the drying medium, saving heat costs, and avoiding the adverse effects of bubbles on the drying of coal. In addition, the coal passes through each drying chamber in turn during the drying process, and the coal in each drying chamber is in full contact with the corresponding drying bed layer, which improves the heat transfer and mass transfer efficiency, thereby improving the drying efficiency.

[0035] The present invention selects a magnetic field strength of 7100-9200A / m. In this range, the bed fluidization effect is relatively stable, the bed is microbubbles or even bubble-free, effectively avoiding the decline in drying effect caused by bubble short circuit, and achieving the best drying effect at both ends. When the magnetic field strength is higher than 9200A / m or lower than 7100A / m, the bed expansion rate decreases, the bed bubble behavior is violent, the bubble short circuit is serious, and the drying effect decreases.

[0036] The present invention adopts porous iron particles as fluidized medium. Since the porous structure of the porous iron particles has high specific surface area, adsorption and mass transfer and heat transfer efficiency, the low-order lump coal can be dried quickly and evenly.

[0037] In a specific embodiment, the porous iron particles are in contact with the flue gas to form a bubble-free fluidized bed state under the action of a magnetic field.

[0038] In a specific embodiment, the particle size of the porous iron particles is 70 to 130 μm, for example, the particle size is 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm; the true density is 7.5 to 7.9 g / cm 3 , for example, the density is 7.5g / cm 3 , 7.6g / cm 3 , 7.7g / cm 3 、7.8g / cm 3 、7.9g / cm 3 , the porosity is 15% to 30%, for example, the porosity is 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, and the bulk density is 1.6 to 2.0 g / cm 3 , for example, the bulk density is 1.6 g / cm 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 the present invention are all commercially available raw materials. The inventors have found through a large number of experiments that the porous iron particles defined in the present invention have good drying efficiency for low-grade lump coal and increase the residence time of low-grade lump coal in the fluidized bed.

[0040] In a specific embodiment, the flue gas temperature is 110-150°C, for example, the temperature is 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, the oxygen volume content is less than 5%, for example, the oxygen volume content is 4.9%, 4.5%, 4.0%, 3.5%, 3.0%, 2.5%, 2.0%, 1.5%, and the flue gas density is 0.85-0.95 kg / m 3 , for example, 0.85kg / 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 the use of flue gas at 110-150°C can reduce heat loss during the bed fluidization process, improve thermal efficiency, and increase the drying speed.

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

[0043] It should be noted that the low-grade 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 according to the moisture content in the raw coal and the description of this specification.

[0044] For example, when the coal to be dried has a particle size of 10 to 30 mm, a moisture content of 30 to 40%, and a density of 1.45 to 1.85 g / cm 3 When using low-rank lump coal such as lignite, bituminous coal or low-rank bituminous coal, the particle size distribution is 70-130μm, the porosity is 15%-30%, and the true density is 7.5-7.9g / cm 3 The porous iron particles are at a temperature of 110℃~150℃ and a density of 0.85~0.95kg / m 3The fluidized bed formed by the flue gas is the drying medium. In the drying chamber near the discharge port, the magnetic field strength is 7100-9200A / m and 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, 1<V in other drying chambers 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. The present invention can achieve the most ideal drying effect.

[0045] In a specific embodiment, the drying method comprises the following steps:

[0046] (1) Crushing and screening low-grade coal;

[0047] (2) passing the flue gas into a fluidized bed on which porous iron particles are deposited, and forming a bubble-free fluidized bed state under the action of a magnetic field;

[0048] (3) adding the screened low-grade lump coal into the bubble-free fluidized bed in step (2) for drying;

[0049] (4) The high-temperature gas discharged from the fluidized bed is subjected to dust removal treatment, and the separated gas is mixed with the flue gas and passed into the fluidized bed for repeated use;

[0050] (5) subjecting the dried low-rank lump coal to de-intermediation treatment to obtain dried low-rank lump coal and porous iron particles;

[0051] (6) Adding the porous iron particles obtained in step (5) into a fluidized bed for recycling.

[0052] In a specific embodiment, in step (2), the drying chamber near the discharge port has a temperature 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, so that the bed density of the fluidized bed in the drying chamber is less than the density of the low-grade lump coal to be dried; the low-grade lump coal to be dried sinks, which is convenient for discharge and can further improve the drying effect.

[0053] In the rest of the 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, so that the bed density of the fluidized bed in the drying chamber is greater than the density of the low-grade lump coal to be dried, and the low-grade lump coal to be dried floats on the drying chamber, which is conducive to feeding from one drying chamber to another. The inventors have found through a large number of experiments that the gas velocity within the above range can ensure the formation of a uniform and stable bed layer, so that the bed layer has good mass transfer and heat transfer efficiency.

[0054] The bed density in the magnetically stabilized multi-chamber fluidized bed dryer 5 can be simply 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 the bed formed by the same type of porous iron particles, the bed density is related to the flue gas density and flue gas velocity. The density of the fluidized bed can be determined based on the velocity of the low-temperature flue gas and the inherent properties of the porous particles.

[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 will become smaller and smaller. When the coal particle size exceeds 10 mm, the effect of airflow drag on the coal is almost negligible compared with the coal's own gravity. 煤 The coal in the drying bed can be regarded as being affected only by its own gravity G and buoyancy F. 浮 The effect of the falling coal in the drying bed is assumed to be a, and the initial velocity of the falling coal is 0. According to Newton's second law:

[0058] GF 浮 =m 煤 a (1)

[0059] The gravity G on coal is:

[0060] G=ρ 煤 V 煤 (2)

[0061] V 煤 is the volume of coal, which can be obtained by testing. g is the acceleration of gravity, which can generally be taken as 9.8m / s 2 .

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

[0063] F 浮 =ρ 床 V 煤 (3)

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

[0065]

[0066] Assume the height of the drying bed is H 床 , the coal falling time is t:

[0067]

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

[0069]

[0070] Assume that the interparticle void ratio of porous iron particles when they are naturally stacked is ε, and the opening area of ​​a single small hole in the air distribution plate of the fluidized bed is A. D , the flue gas velocity is U 气 , the apparent density of the porous iron particles is ρ 铁粉 , the critical fluidizing gas velocity of porous iron particles is U 临界 , the average particle size of the porous iron particles is d 铁粉 , the density of smoke is ρ 气 , the viscosity of the smoke is μ 气 The above parameters can be obtained through existing experimental test methods. Bed density ρ 床 It can be calculated by 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 Archimedean number:

[0075]

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

[0077] In a specific embodiment, in step (4), the dust removal treatment also produces coal powder, which is added to the flue gas generating device 12 for repeated use.

[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 coal powder, the temperature of the coal powder is 90-130°C, the moisture content is 5-10%, and the coal powder is transported to the flue gas generating device 12 for reuse. After the gas enters the second separation device 16 to remove the coal dust, a part of the tail gas formed enters the magnetically stabilized multi-chamber fluidized bed 5 for reuse, and the rest of the tail gas is discharged. The temperature of the gas can be freely set as needed, and the preferred gas temperature is 110-150°C.

[0079] Preferably, a portion of the exhaust gas is introduced into the combustion furnace to control the combustible gas content in the gas flow to ensure the safety of this portion of the exhaust gas when it is recycled, and the remaining exhaust gas is discharged into the air. The amount of each portion of the exhaust gas can be determined by the technicians through relevant experiments or calculations according to the required dryness of the dried lump coal.

[0080] The method of the present invention can recycle the tail gas, reduce the exhaust gas volume, and relieve environmental pressure. The coal powder produced during the drying process can be reused, which reduces resource waste and reduces the cost of generating flue gas at a suitable temperature.

[0081] Another specific embodiment of the present invention, as Figure 1 As shown, a low-temperature drying system for low-grade lump coal is disclosed, comprising a crushing and screening device 2, a coal storage device 3, a drying device, a first medium removal device 7, a gangue removal device 8 and a second medium removal device 9 which are connected in sequence, and the drying device is also respectively connected to a flue gas generating device 12 and a dust removal and separation device; wherein the drying device is a magnetically stabilized multi-chamber fluidized bed dryer 5 filled with porous iron particles, and the first medium removal device 7 and the second medium removal device 9 both include a magnetic separator for separating the 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 a specific embodiment, the smoke generating device 12 is connected to the upper end and the lower end of the magnetically stabilized multi-chamber fluidized bed dryer 5 respectively, so that the smoke enters the magnetically stabilized multi-chamber fluidized bed dryer 5 from two directions, namely, from the upper side and from the lower side.

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

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

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

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

[0088] The smoke generating device 12 described in the present invention can be any smoke source, can be waste smoke generated in an industrial production process, and can also include an air 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 feeder, etc. More preferably, it is also connected to a discharge device 6, and the discharge device 6 is preferably an air lock.

[0090] The first separation device 15 described in the present invention can be any gas-solid separation equipment conventionally used in industry, for example, an inertial dust collector, a cyclone separator, and the like.

[0091] The second separation device 16 of the present invention is used to remove dust from the gas being separated by the first separation device 15 to form tail gas, and the separated coal powder is combined with the coal powder separated by the first separation device 15 and sent to the flue gas generating device 12. Preferably, the second separation device 16 includes a bag filter.

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

[0093] The technical solution of the present invention is further explained below in conjunction with specific embodiments.

[0094] Example 1

[0095] A system for low-temperature drying of low-grade lump coal in this embodiment, such as Figure 1 As shown, it comprises a crushing device 1, a screening device 2, a coal storage device 3, a drying device, a first medium removal device 7, a gangue removal device 8, a second medium removal device 9 and a storage device 10 connected in sequence, and the drying device is also connected to a smoke generating device 12 and a dust removal and separation device respectively;

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

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

[0098] In a further preferred embodiment, the smoke generating device 12 is respectively connected to the upper end and the lower end of the magnetically stabilized multi-chamber fluidized bed 5, so that the smoke enters from the upper and lower directions of the magnetically stabilized multi-chamber fluidized bed 5. 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 air lock.

[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 dust collector. The bag dust collector is sequentially connected to a third induced draft fan 17, a first induced draft fan 11, and an air mixing chamber 13, and the air mixing chamber 13 is connected to the magnetically stabilized multi-chamber fluidized bed 5.

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

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

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

[0103] Example 2

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

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

[0106] (2) The low-temperature flue gas generated by the flue gas generating device 12 is introduced into the magnetically stabilized multi-chamber fluidized bed 5 where porous iron particles are deposited, and a bubble-free fluidized bed state is formed under the action of the magnetic field;

[0107] (3) adding the screened low-grade lump coal into the 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, and the separated pulverized coal is input into the flue gas generating device 12 for reuse. The separated gas continues to enter the second separation device 16 for separation, and the separated gas enters the third induced draft fan 17, enters the air mixing chamber 13 through the first induced draft fan 11 to mix with the low-temperature flue gas, and then enters the magnetically stabilized multi-chamber fluidized bed 5 for reuse. The separated pulverized coal is input into the flue gas generating device 12 for reuse;

[0109] (5) The dried low-rank coal is discharged from the discharge device 6 and sequentially enters the first de-intermediation device 7 for de-intermediation treatment, the gangue removal device 8 for gangue removal treatment, and the second de-intermediation device 9 for de-intermediation treatment;

[0110] The porous iron particles separated by the first de-intermediation device 7 and the second de-intermediation device 9 enter the storage device 10 and are then added to the magnetically stabilized multi-chamber fluidized bed 5 for repeated use; after being processed by the second de-intermediation device 9, dry low-grade lump coal is obtained.

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

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

[0113] Example 3

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

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

[0116] (2) The smoke generated by the smoke generating device 12 is introduced into a magnetically stabilized multi-chamber fluidized bed in which porous iron particles are deposited, and a bubble-free fluidized bed state is formed under the action of a magnetic field;

[0117] (3) adding the screened low-grade lump coal into the 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, and the separated pulverized coal is input into the flue gas generating device 12 for reuse. The separated gas continues to enter the second separation device 16 for separation, and the separated gas enters the third induced draft fan 17, enters the air mixing chamber 13 through the first induced draft fan 11 to mix with the flue gas, and then enters the magnetically stabilized multi-chamber fluidized bed 5 for reuse. The separated pulverized coal is input into the flue gas generating device 12 for reuse;

[0119] (5) The dried low-rank coal is discharged from the discharge device 6 and sequentially enters the first de-intermediation device 7 for de-intermediation treatment, the gangue removal device 8 for gangue removal treatment, and the second de-intermediation device 9 for de-intermediation treatment;

[0120] The porous iron particles separated by the first de-intermediation device 7 and the second de-intermediation device 9 enter the storage device 10 and are then added to the magnetically stabilized multi-chamber fluidized bed 5 for repeated use; after being processed by the second de-intermediation device 9, dry low-grade lump coal is obtained.

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

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

[0123] Example 4

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

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

[0126] (2) The low-temperature flue gas generated by the flue gas generating device 12 is introduced into the magnetically stabilized multi-chamber fluidized bed in which the porous iron particles are deposited, and a bubble-free fluidized bed state is formed under the action of the magnetic field;

[0127] (3) adding the screened low-grade lump coal into the 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, and the separated pulverized coal is input into the flue gas generating device 12 for reuse. The separated gas continues to enter the second separation device 16 for separation, and the separated gas enters the third induced draft fan 17, enters the air mixing chamber 13 through the first induced draft fan 11 to mix with the low-temperature flue gas, and then enters the magnetically stabilized multi-chamber fluidized bed 5 for reuse. The separated pulverized coal is input into the flue gas generating device 12 for reuse;

[0129] (5) The dried low-rank coal is discharged from the discharge device 6 and sequentially enters the first de-intermediation device 7 for de-intermediation treatment, the gangue removal device 8 for gangue removal treatment, and the second de-intermediation device 9 for de-intermediation treatment;

[0130] The porous iron particles separated by the first de-intermediation device 7 and the second de-intermediation device 9 enter the storage device 10 and are then added to the magnetically stabilized multi-chamber fluidized bed 5 for repeated use; after being processed by the second de-intermediation device 9, dry low-grade lump coal is obtained.

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

[0132] The low-temperature flue gas temperature is 147°C and the flue gas density is 0.86 kg / m 3 , oxygen volume content <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 / cm 3 The flue gas velocity of the other drying chambers is 3 cm / s, and the bed density is 1.52 g / cm 3 , the magnetic field strength of the magnetically stabilized multi-chamber fluidized bed dryer in this embodiment is 8200 A / m.

[0133] Example 5

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

[0135] Comparative Example 1

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

[0137] Comparative Example 2

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

[0139] Comparative Example 3

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

[0141] Comparative Example 4

[0142] The method for drying low-grade 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 method for drying low-grade 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 by a fluidized bed dryer without a magnetic field.

[0145] Comparative Example 6

[0146] The method for drying low-grade 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 of low-grade lump coal in this embodiment is the same as that in Embodiment 2, except that the critical fluidizing gas velocity of the porous iron particles is 2.10 cm / s, and the flue gas velocity in all magnetically stabilized multi-chamber fluidized beds 5 is 2.40 cm / s, that is, all drying chambers have a critical fluidizing gas velocity of 1.14 times that of the porous iron particles.

[0149] Comparative Example 8

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

[0151] Test Example 1

[0152] The methods of Examples 2-5 and Comparative Examples 1-7 were used to dry the low-grade lump coal, and the water removal rate of the low-grade lump coal, i.e. (moisture content before drying - moisture content after drying) / moisture content before drying × 100%, and the residence time of the low-grade lump coal in the fluidized bed were tested, as shown in Table 1.

[0153] Table 1

[0154]

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

[0156] (2) In Comparative Example 1, due to the use of solid iron powder, the bed density formed in all drying chambers is much higher than the density of the coal to be dried, resulting in the coal being unable to sink through the drying bed in the drying chamber near the discharge port, and product discharge cannot be achieved.

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

[0158] (4) The particle size of the porous iron particles used in Comparative Example 3 is lower than the range specified in the present invention, resulting in the inability to fluidize the bed and form a drying bed, thereby failing to dry the coal.

[0159] (5) Comparative Example 4 is an embodiment that simulates the existing hot air drying technology. Compared with Comparative Example 4, the residence time of the 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 the existing hot air drying technology, the residence drying time of the coal in the present invention is significantly increased, and the drying effect is also significantly improved.

[0160] (6) Compared with Example 2, in Comparative Example 5, no magnetic field was applied, and the short-circuiting behavior of bubbles in the bed was not suppressed, resulting in a significant reduction in the drying effect.

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

[0162] (8) Compared with Example 2, Comparative Example 7 does not meet the requirement of 1.3 cm / 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 relationship between the speed of the drying chamber and the discharge port is ≤1.9cm / s, which results in the bed density formed in the drying chamber near the discharge port being much higher than the density of the coal to be dried, making it impossible for the coal to sink and be discharged through the discharge port.

[0163] (9) Compared with Example 2, Comparative Example 8 does not meet the requirement of 1 cm / 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 relationship between the speed of the drying chamber and the speed of the coal is less than 1.3cm / s, resulting in the bed density formed in the drying chamber being much lower than the density of the coal to be dried. As a result, the coal sinks directly in the first drying chamber after being fed in and cannot be dried in subsequent drying chambers, resulting in the inability to complete the complete drying and successful discharge process.

[0164] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for low-temperature drying of low-grade lump coal, characterized in that: The method comprises adopting a magnetically stabilized multi-chamber fluidized bed to dry the low-grade lump coal, wherein the fluidized medium comprises porous iron particles and flue gas, and the magnetic field strength of the magnetically stabilized multi-chamber fluidized bed is 7100-9200A / m.

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

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

4. A method for low-temperature drying of low-grade lump coal according to claim 1 or 2, characterized in that: The flue gas temperature is 110-150° C., and the oxygen volume content is less than 5%.

5. A method for low-temperature drying of low-grade lump coal according to claim 1 or 2, characterized in that: 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.

6. A method for low-temperature drying of low-grade lump coal according to any one of claims 1 to 5, characterized in that: The steps include: (1) Crushing and screening low-grade coal; (2) passing the flue gas into a fluidized bed on which porous iron particles are deposited, and forming a bubble-free fluidized bed state under the action of a magnetic field; (3) adding the screened low-grade lump coal to the fluidized bed in step (2) for drying; (4) The gas discharged from the fluidized bed is subjected to dust removal treatment, and the separated gas is mixed with the flue gas and passed into the fluidized bed for repeated use; (5) subjecting the dried low-rank lump coal to de-intermediation treatment to obtain dried low-rank lump coal and porous iron particles; (6) Adding the porous iron particles obtained in step (5) into a fluidized bed for recycling.

7. A low-temperature drying system for low-grade lump coal, characterized in that: It comprises a crushing device, a screening device, a coal storage device, a drying device, a first medium-removing device, a gangue-removing device and a second medium-removing device which are connected in sequence, and the drying device is also connected to a smoke generating device and a dust removal and separation device respectively; Wherein, the drying device is a magnetically stabilized multi-chamber fluidized bed dryer filled with porous iron particles, and the first medium removal device and the second medium removal device both include magnetic separators.

8. The method according to claim 7, 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, 1<V in other drying chambers 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.

9. A low-temperature drying system for low-grade lump coal according to claim 7, characterized in that: The smoke generating device is connected to the upper end and the lower end of the magnetically stabilized multi-chamber fluidized bed dryer respectively, so that the smoke enters the fluidized bed dryer from two directions, the upper end and the lower end.

10. A low-temperature drying system for low-grade lump coal according to claim 7, characterized in that: The dust removal and separation device comprises a first separation device and a second separation device, and the first separation device is connected to the drying device.

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