Method and apparatus for producing ultrafine coal, ultrafine coal and its use

Abstract

This invention relates to the field of ultrafine coal powder preparation technology, and discloses a method and apparatus for preparing ultrafine coal powder, ultrafine coal powder and its applications, comprising: feeding coal-containing raw materials with a particle size ≤3mm into an air jet mill, and using steam to perform steam grinding of the coal-containing raw materials to obtain coal powder, wherein the pressure of the steam is 0.5-1.2MPa, the temperature is 180-320℃, the gas velocity of the steam entering the grinding chamber of the air jet mill is 360-1200m / s, and the pressure inside the grinding chamber of the air jet mill is -2Kpa-0KPa; feeding the coal powder for sorting, and sending the coal powder that meets the particle size requirement into a bag filter for collection to obtain ultrafine coal powder, wherein the particle size D of the ultrafine coal powder is... 97 With a particle size ≤10μm and a sphericity of 0.5-1, this invention improves the single-machine processing capacity of pulverized coal, and the particle size of the ground pulverized coal can reach 0.1μm, thereby improving working efficiency and overall primary energy efficiency, saving energy and reducing emissions, and lowering production costs. It meets the requirements of particle size and ash content of raw materials in fields such as high-end carbon materials from coal and nano-hydrogen fuels, and expands the application scope of coal-based carbon materials in high-end industries.

Description

Technical Field

[0001] This invention relates to the field of ultrafine coal powder preparation technology, specifically to a method and apparatus for preparing ultrafine coal powder, ultrafine coal powder and its applications. Background Technology

[0002] Coal-based carbon materials are high-carbon materials produced primarily from coal. Examples include coal-based graphene, anode materials, anodic materials, carbon quantum dots, and porous carbon. These high-end coal-based carbon materials have specific requirements regarding coal particle size and ash content. Providing ultrafine and ultrapure raw coal is a prerequisite for the preparation of high-end carbon materials. Therefore, how to prepare ultrapure and ultrafine raw coal has become a research hotspot and challenge both domestically and internationally.

[0003] Meanwhile, when coal is used as fuel, achieving efficient and clean use of coal to make it a coal-based special fuel with high combustion efficiency and low pollutant emissions is a research hotspot for coal as a fuel in the near future. The preparation of ultrapure and ultrafine coal powder to achieve micro-nano level particle size not only achieves high surface activity and low ash and sulfur content, but also ensures complete combustion, high burnout rate, low bottom ash discharge, and significant energy-saving effect after entering the boiler, reducing sulfur dioxide, nitrogen oxides and soot emissions. Therefore, it is a major research trend under the current dual carbon background.

[0004] CN 103990539B discloses a method and apparatus for controlling airflow in an air classifier mill. The apparatus includes a constant pressure air supply device and a grinding chamber with side nozzles and a bottom nozzle. The side nozzles and the bottom nozzle have a common air inlet. This common air inlet is connected to the constant pressure device via at least two pipes, each equipped with a pipe valve. Each pipe has a different diameter, and the diameter of the larger pipe at the next higher level is 1.5-4 times the diameter of the smaller pipe at the next lower level. The gas flow rate flowing into the largest pipe or the sum of the gas flow rates flowing into all the pipes is the set flow rate of the air classifier mill. This technology mainly focuses on the detailed patent invention and protection of the internal structure design of the air classifier mill, but does not yet cover the entire process flow, especially regarding the carrier gas used in the airflow. Whether the carrier gas is steam, an inert gas, or air significantly affects the entire operation, particularly for flammable and explosive solids like pulverized coal. Pulverized coal undergoes pyrolysis between 320 and 800°C, producing tar and significantly increasing its viscosity. Using conventional inert gases would not present these problems. Moreover, for carrier gases such as inert gases or air, due to the limitations of air compressors, the current grinding capacity of a single unit is difficult to exceed 1t / h.

[0005] CN 105728156 B discloses a process for preparing ultrapure coal, applicable to the field of mineral separation technology. 50mm low-ash anthracite is crushed by a high-efficiency crusher and then fed into a three-product interference bed for separation, yielding coarse clean coal, middlings, and gangue. The coarse clean coal is then classified by three cyclone screens and dewatered by a coal slime centrifuge to obtain coarse-grained ultrapure coal. The middlings are coarsely ground once and then fed into an arc screen for classification. The upper portion of the arc screen is fed into a spiral separator for tailings removal. The lighter product is then finely ground a second time and, together with the undersize from the three-product cyclone screen, overflow, centrifugal liquid from the coal slime centrifuge, and the undersize from the arc screen, is fed into a flotation device for flotation to obtain fine-grained ultrapure coal. This invention patent's technology is primarily designed for particles with diameters in the millimeter range; however, it cannot handle particles with diameters in the micrometer range. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of existing technologies, such as the risk of flammability and explosion of the working gas in air jet mills for crushing coal powder and the difficulty in achieving micro- and nano-sized coal powder particles after crushing. This invention provides a method and apparatus for preparing ultrafine coal powder, ultrafine coal powder and its applications. This invention avoids spontaneous combustion and explosion during the coal powder grinding process and enables the coal powder particle size to reach the nano-level.

[0007] To achieve the above objectives, the present invention provides a method for preparing ultrafine coal powder, the method comprising:

[0008] Coal raw materials with a particle size ≤3mm are fed into an air jet mill, and steam is used as the working gas to perform steam grinding on the coal raw materials to obtain coal powder. The pressure of the steam is 0.5-1.2MPa, the temperature is 180-320℃, the gas velocity of the steam entering the grinding chamber of the air jet mill is 360-1200m / s, and the pressure inside the grinding chamber of the air jet mill is -2KPa-0KPa.

[0009] The pulverized coal is screened and then fed into a bag filter to collect ultrafine pulverized coal. The sphericity of the ultrafine pulverized coal is 0.5-1, and the particle size D is... 97 ≤10um, preferably D 97 ≤5um.

[0010] The second aspect of this invention provides an apparatus for preparing ultrafine coal powder, the apparatus comprising: a feeding unit, a grinding unit, and a collecting unit connected in sequence;

[0011] The feeding unit is used to feed coal-containing raw materials into the grinding unit;

[0012] The grinding unit includes: an air jet mill with a grinding chamber that uses steam as the working gas, wherein the feed inlet of the air jet mill is connected to the feed unit for steam-powered grinding of coal-containing raw materials from the feed unit;

[0013] The steam inlet of the air jet mill is provided with an even number of circumferentially symmetrically distributed first nozzles at the bottom of the grinding chamber. Each first nozzle is connected to a steam feed line to deliver steam at a pressure of 0.5-1.2 MPa and a temperature of 180-320°C into the grinding chamber. The ratio of the distance D2 between two relative first nozzles to the inner diameter D1 of the grinding chamber is 1.2-1.5, preferably 1.3-1.4. The angle between each first nozzle and the horizontal plane is 0-15°. The extended axes of each first nozzle intersect to form an impact point. The feed inlet is located above each first nozzle, and the feed inlet ensures that the coal-containing raw material falls within a distance of D2 / 2 from the impact point.

[0014] A classifier with a first outlet is provided, which is connected to the grinding chamber so that coal powder of the correct particle size can be screened and sent into the collection unit.

[0015] The collection unit includes a bag filter with an outlet pipe and an induced draft fan installed on the outlet pipe. The material inlet of the bag filter is connected to a first outlet through a pipeline, so that coal powder that meets the particle size requirements after being screened by the classifier is sent into the bag filter for collection under the suction of the induced draft fan, resulting in a sphericity of 0.5-1 and a particle size D. 97 ≤10um, D is preferred 97 Ultrafine coal powder ≤5um.

[0016] The ultrafine coal powder produced by the method described in this invention.

[0017] The application of the ultrafine coal powder described in this invention in the fields of rubber, olefins, nano-hydrogen fuels, or coal-to-oil substitution.

[0018] Through the above technical solution, this invention uses steam as the accelerating working gas to crush coal powder particles, avoiding the spontaneous combustion and explosion phenomenon during the coal powder grinding process and the problem that the maximum coal powder processing capacity is limited by the air compressor. Furthermore, by rationally setting the angle and number of nozzles, the energy consumption of the oscillation waves generated by the nozzles is reduced, and the energy is concentrated in the crushing and dispersion process of coal powder particles. This allows the coal powder particles in the grinding chamber to be accelerated to a maximum of 1200 m / s, increasing the maximum single-machine processing capacity of coal powder. Moreover, the particle size of the ground coal powder can reach 0.1 μm, which greatly improves the working efficiency and the overall primary energy efficiency, saves energy and reduces emissions, and reduces production costs. This meets the particle size requirements of coal-based high-end carbon materials and expands the application scope of coal-based carbon materials in high-end industries.

[0019] Other features and advantages of the present invention will be described in detail in the following specific embodiments. Attached Figure Description

[0020] Figure 1This is a schematic diagram of the overall structure of an apparatus for preparing ultrafine coal powder according to a preferred embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the nozzle arrangement according to a preferred embodiment of the present invention.

[0022] Explanation of reference numerals in the attached figures

[0023] 1. Airflow mill; 11. Grinding chamber; 2. Second nozzle; 3. First nozzle; 31. Steam feed line; 4. Classifier; 41. First outlet; 5. Feeding hopper; 6. Anti-clogging mechanism; 7. Screw conveyor; 8. Bag filter; 81. Material inlet; 9. Exhaust fan; 10. Air outlet pipe. Detailed Implementation

[0024] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "left," and "right" generally refer to the upper, lower, left, and right as shown in the accompanying drawings; "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0027] This invention provides a method for preparing ultrafine coal powder, the method comprising:

[0028] Coal raw materials with a particle size ≤3mm are fed into an air jet mill, and steam is used as the working gas to perform steam grinding on the coal raw materials to obtain coal powder. The pressure of the steam is 0.5-1.2MPa, the temperature is 180-320℃, the gas velocity of the steam entering the grinding chamber of the air jet mill is 360-1200m / s, and the pressure inside the grinding chamber of the air jet mill is -2Kpa-0KPa.

[0029] The pulverized coal is screened, and the pulverized coal that meets the particle size requirement is fed into a bag filter to collect ultrafine pulverized coal. The sphericity of the ultrafine pulverized coal is 0.5-1, and the particle size D is... 97 ≤10um, D is preferred 97 ≤5um.

[0030] Using air or inert gas as the accelerating carrier gas, pulverized coal particles can be accelerated to a maximum speed of 680 m / s. However, currently, due to limitations in air compressor output and pressure, the maximum processing capacity of a single pulverized coal crusher is difficult to exceed 1 t / h. This invention uses steam as the accelerating carrier gas for pulverizing pulverized coal particles, avoiding spontaneous combustion and explosion during the grinding process and the limitation of processing capacity by the air compressor. Furthermore, using steam allows pulverized coal particles to be accelerated to a maximum speed of 1200 m / s, and the maximum single-machine processing capacity can reach 5 t / h, greatly improving work efficiency. The particle size of the ground pulverized coal can reach 0.1 μm, meeting the particle size requirements of high-end coal-based carbon materials and expanding the application range of coal-based carbon materials in high-end industries.

[0031] In this invention, the pressure inside the grinding chamber of the air jet mill is -1.2 kPa to 0.3 kPa.

[0032] According to a preferred embodiment of the present invention, the pressure of the water vapor is 0.7-1 MPa, the temperature is 260-300°C, and the gas velocity of the water vapor entering the grinding chamber of the air jet mill is 540-1100 m / s.

[0033] As is well known to those skilled in the art, coal undergoes a pyrolysis reaction between 320 and 800°C, producing tar that significantly increases the viscosity of coal powder. In this invention, the temperature and pressure of the steam are controlled below the pyrolysis temperature of the coal powder, but still meet the kinetic energy required for coal powder crushing, thereby achieving the purpose of crushing coal powder.

[0034] In this invention, the steam is superheated steam, preferably from low-grade superheated steam from a power plant boiler and / or superheated steam produced by a steam generator.

[0035] It should be noted that the energy transfer process in traditional air jet milling—from fuel thermal energy to steam potential and thermal energy to electrical energy to air potential energy to the kinetic energy of the jet stream to the kinetic energy of the material particles—is lengthy and prone to losses. This results in a primary energy utilization rate of only about 20% for grinding. Consequently, this processing method is energy-intensive and has low capacity, significantly limiting the application of air jet milling. In this invention, industrial waste heat and / or boiler heating generate superheated steam, which then becomes the kinetic energy of the jet stream, leading to the kinetic energy of the material particles. This achieves a primary energy utilization rate of approximately 90% for grinding, thus saving energy and reducing costs by improving energy efficiency.

[0036] In this invention, the coal-containing raw material includes at least one of raw coal, fly ash, or coal gangue.

[0037] According to a preferred embodiment of the present invention, when the density of the solid material in the grinding chamber is greater than 4 g / cm³ 3At that time, secondary air is introduced into the grinding chamber, reducing the density of the solid material inside the grinding chamber to 2 g / cm³. 3 -4g / cm 3 The aforementioned preferred method can adjust the airflow field within the grinding chamber, preventing material agglomeration and improving grinding quality.

[0038] In this invention, the secondary air is selected from at least one of water vapor, nitrogen, and carbon dioxide.

[0039] It should be noted that when the feed rate is large, it will cause the internal pressure of the grinding chamber 11 to fluctuate sharply, thus affecting the operation of the entire system. The secondary air of the present invention can also play a role in stabilizing the pressure, thereby improving the stability of the system operation and preventing it from stopping in case of an emergency.

[0040] According to a preferred embodiment of the present invention, the ultrafine coal powder is dissolved in a solvent, stirred for a period of time, and then a flocculant is added for agglomeration treatment. After filtration, ultrapure ultrafine coal powder is obtained, wherein the ash content Ad on a dry basis of the ultrapure ultrafine coal powder is ≤1%.

[0041] Existing technologies typically employ chemical methods for ash removal from pulverized coal, but this approach is subject to environmental restrictions. Only when the particle size is less than 10 μm will the organic and inorganic components of the coal be fully dissociated, with a dissociation degree generally not less than 96%. In this invention, coal is ground to obtain ultrafine pulverized coal with a particle size of less than 10 μm. Under this condition, the ultrafine pulverized coal of this invention can be deashed using physical methods, and the ash content of the deashed pulverized coal can reach less than 1%. This meets the technical requirements for raw material particle size and ash content in high-end coal-based carbon materials and hydrocarbon micro / nano fuels, thereby expanding the application scope and promotion in the field of high-end carbon materials. Furthermore, it avoids the environmental problems caused by the large amounts of strong acid and alkali waste liquid generated by traditional chemical methods.

[0042] In this invention, the ratio of the flocculant dosage to the ultrafine coal powder is 0.2-2:100ml / g.

[0043] In this invention, the stirring speed is 500-4000 r / min and the stirring time is 0-30 min.

[0044] In this invention, the solvent is water and / or an organic solvent, preferably an alcohol, and more preferably ethanol.

[0045] According to a preferred embodiment of the present invention, the flocculant is an organic flocculant, preferably a non-polar oil, more preferably non-polar diesel oil and / or non-polar kerosene.

[0046] like Figure 1 , Figure 2As shown, the present invention provides an apparatus for preparing ultrafine coal powder, the apparatus comprising: a feeding unit, a grinding unit and a collecting unit connected in sequence;

[0047] The feeding unit is used to feed coal-containing raw materials into the grinding unit;

[0048] The grinding unit includes: an air jet mill 1 with a grinding chamber 11 that uses steam as the working gas, the feed inlet of the air jet mill 1 being connected to a feeding unit for steam-powered grinding of coal-containing raw materials from the feeding unit;

[0049] The steam inlet of the air jet mill 1 is provided with an even number of circumferentially symmetrically distributed first nozzles 3 at the bottom of the grinding chamber 11. Each first nozzle 3 is connected to a steam feed line 31, used to deliver steam at a pressure of 0.5-1.2 MPa and a temperature of 180-320℃ into the grinding chamber 11 through the first nozzle 3; the pressure inside the grinding chamber is -2 kPa to 0 kPa; the relationship between the distance D2 between two relative first nozzles 3 and the inner diameter D1 of the grinding chamber 11 is 1.2-1.5, preferably. The angle between each first nozzle 3 and the horizontal plane is 0-15°, and the extended axes of each first nozzle 3 intersect to form an impact point. The feed inlet is located above each first nozzle 3, and the feed inlet ensures that the coal-containing raw material falls within a distance of D2 / 2 from the impact point. Through the above settings, the gas velocity of the water vapor entering the grinding chamber 11 can be accelerated to 360-1200 m / s, and the material in the grinding chamber collides, shears, and rubs against each other at supersonic speed to achieve ultra-fine pulverization.

[0050] A classifier 4 with a first outlet 41 is provided, the classifier 4 being connected to the grinding chamber 11, so that coal powder of the correct particle size can be screened and sent into the collection unit.

[0051] The collection unit includes a bag filter 8 with an outlet pipe 10 and an induced draft fan 9 installed on the outlet pipe 10. The material inlet 81 of the bag filter 8 is connected to the first outlet 41 through a pipe, so that after the classifier 4 screens out coal powder that meets the particle size requirements, it is sent into the bag filter 8 for collection under the suction of the induced draft fan 9, resulting in a sphericity of 0.5-1 and a particle size D. 97 ≤10um, preferred particle size D 97 Ultrafine coal powder ≤5μm is ground, while coarse powder is returned to the grinding chamber for further pulverization.

[0052] It should be noted that, in order to further improve the dust removal effect, the bag filter 8 can be connected in series with at least one cyclone dust collector and / or bag filter, so that after the material in the grinding chamber is graded and filtered, the water vapor that meets the environmental protection requirements is discharged into the atmosphere through the induced draft fan 10.

[0053] This invention uses steam as the accelerating working gas for pulverizing coal particles. The angle and number of nozzles are rationally set to reduce the energy consumption of the oscillation waves generated by the nozzles, concentrating energy on the crushing and dispersion process of the coal particles. This allows the coal particles in the grinding chamber to be accelerated to a maximum speed of 1200 m / s, and enables a maximum single-machine processing capacity of 5 t / h, greatly improving work efficiency and overall primary energy efficiency, saving energy, reducing emissions, and lowering production costs. The particle size of the ground coal can reach 0.1 μm, meeting the particle size requirements of high-end coal-based carbon materials and expanding the application range of coal-based carbon materials in high-end industries.

[0054] According to a preferred embodiment of the present invention, the number of the first nozzles 3 is 2, 4, 6, 8, 10 or 12, more preferably 4, 6 or 8.

[0055] In this invention, when the finished product output of the grinding system is 1-5 kg / h, the distance D2 between the two first nozzles 3 is 200 mm-220 mm, preferably 205 mm-218 mm, and more preferably 216 mm; the inner diameter D1 of the grinding chamber 11 is 260-300 mm, preferably 275-285 mm, and more preferably 280 mm; the throat diameter of each first nozzle 3 is 1.5-5 mm, preferably 1.8-3.2 mm. Using the aforementioned parameters, when the grinding equipment is scaled up accordingly, since it is not limited by the air compressor, the maximum single-machine processing capacity of pulverized coal can reach 5 t / h, greatly improving work efficiency.

[0056] According to a preferred embodiment of the present invention, the angle between each of the first nozzles 3 and the horizontal plane is preferably 5-12°. Using the aforementioned angle has the advantage of significantly increasing product yield and improving product sphericity.

[0057] According to a preferred embodiment of the present invention, the feed inlet ensures that the coal-containing raw material falls within a distance D2 / 4 of the impact point. This preferred embodiment significantly increases the yield, efficiency, and quality of the ground product, avoiding the problem of short-circuiting of particle trajectories and affecting the efficiency of the entire grinding system due to the material being directly carried to the classifier by the airflow because it is not in the main airflow motion area.

[0058] According to a preferred embodiment of the present invention, the air jet mill 1 is provided with a secondary air mechanism to adjust the airflow field of the grinding chamber 11 and prevent the material inside the grinding chamber 11 from agglomerating. It should be noted that when the feed rate is large, it can cause drastic fluctuations in the internal pressure of the grinding chamber 11, thus affecting the operation of the entire system. The secondary air mechanism of the present invention can also play a role in stabilizing pressure, thereby improving the stability of the system operation and preventing shutdown in the event of an emergency.

[0059] According to a preferred embodiment of the present invention, the secondary air mechanism is located at a distance of ≥1 / 2, more preferably 2 / 3-3 / 4, along the height direction between the water vapor inlet and the first outlet 41.

[0060] According to a preferred embodiment of the present invention, the secondary air mechanism includes 4-6 circumferentially symmetrically distributed second nozzles 2 that are connected to the grinding chamber 11, and each second nozzle 2 is connected to a secondary air feed line with a valve. It should be noted that the arrangement of the nozzles in the secondary air mechanism is structurally similar to the arrangement of the steam inlet nozzles.

[0061] According to a preferred embodiment of the present invention, the angle between each of the second nozzles 2 and the horizontal plane is 0-15°, preferably 0-10°.

[0062] In this invention, the first nozzle and / or the second nozzle are Laval nozzles.

[0063] In this invention, gas-solid concentration sensors are installed at three positions (upper, middle, and lower) inside the grinding chamber 11 to detect the density of solid materials inside the grinding chamber.

[0064] In this invention, the bottom of the air jet mill is also provided with a slag discharge port communicating with the grinding chamber, which is used to discharge the un-crushed solid material in the grinding chamber after the machine is stopped.

[0065] In this invention, the feeding unit includes a screw conveyor 7 connected to the grinding chamber 11 through the feed inlet, a feeding bin 5 connected to the screw conveyor 7, and an anti-blocking mechanism 6 located between the feeding bin 5 and the screw conveyor 7 to prevent material blockage. The anti-blocking mechanism can ensure that the material in the feeding bin is continuously and stably transported to the grinding chamber via the screw conveyor.

[0066] It is understood that the present invention can also use concentric nozzles nested inside and outside to send materials and carrier gas into the grinding chamber. The relatively smaller nozzle is connected to the coal raw material feed pipeline, while the larger nozzle, which is concentrically set around the relatively smaller nozzle, is connected to the steam feed pipeline. This allows the steam and coal raw material to mix at the nozzle head and then enter the grinding chamber together for fluidized collision grinding.

[0067] In this invention, the anti-blocking mechanism 6 is a vibration device installed at the discharge port of the feeding hopper and / or an air pump for flushing the discharge port of the feeding hopper.

[0068] In this invention, the bag filter 8 is provided with a finished product outlet for discharging the ultrafine coal powder. The finished product outlet is connected to a purification unit. The purification unit includes a container connected to the finished product outlet. The container is provided with a stirring mechanism and a vacuum filtration mechanism. The container is connected to a solvent feed line and a flocculant feed line, so that the ultrafine coal powder is purified to form ultrapure ultrafine coal powder.

[0069] The present invention provides the ultrafine coal powder obtained by the method described herein.

[0070] The present invention relates to the application of ultrafine coal powder in the fields of rubber, olefins, and micro / nano hydrocarbon fuels or coal-to-oil substitution.

[0071] This invention employs existing technologies to ensure internal pressure in the logistics system and isolate it from external gases. For example, the finished product outlet of the bag filter in this invention uses a lock hopper mechanism from existing technologies. When ultrafine coal powder enters the lock hopper through the feed valve, the feed valve of the lock hopper is closed, and the discharge valve is opened to discharge the ultrafine coal powder. After the lock hopper is emptied, the discharge valve is closed, and then the feed valve is opened again. This process is repeated to ensure that the system operates normally under pressure. The water vapor logistics channel of this invention uses existing technologies for insulation to prevent water vapor condensation, which is not described in detail in this invention.

[0072] Various pipelines, valves, and other components that may be used in industry can be added to different parts of this invention as needed. This invention does not have any special requirements for this and will not be described in detail here.

[0073] The present invention will be further illustrated below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0074] The following embodiments employ the following methods: Figures 1-2 The apparatus shown includes a feeding unit, a grinding unit, and a collecting unit connected in sequence.

[0075] The feeding unit feeds raw coal with a particle size ≤3mm into the grinding unit;

[0076] The grinding unit includes: an air jet mill 1 with a grinding chamber 11 that uses steam as the working gas; the steam inlet of the air jet mill is provided with an even number of first nozzles 3 circumferentially symmetrically distributed at the bottom of the grinding chamber; each first nozzle is connected to a steam feed line 31 for feeding low-grade superheated steam from the power plant into the grinding chamber through the first nozzle 3; the feed inlet of the air jet mill is located above the first nozzle; the extended axes of each first nozzle intersect to form an impact point.

[0077] The air jet mill is equipped with a secondary air mechanism, which includes 4-6 circumferentially symmetrically distributed second nozzles that are connected to the grinding chamber. Each second nozzle is connected to a secondary air feed line with a valve.

[0078] The grinding chamber is connected to the classifier 4. The collection unit includes a bag filter 8 with an exhaust pipe 10 and an induced draft fan 9 installed on the exhaust pipe. The material inlet 81 of the bag filter is connected to the first outlet 41 of the classifier through a pipeline to obtain ultrafine coal powder. The finished product outlet of the bag filter 8 is connected to a container. The container is equipped with a stirring mechanism and a vacuum filtration mechanism. The container is connected to a solvent feed pipeline and a flocculant feed pipeline, so that the ultrafine coal powder is purified to form ultrapure ultrafine coal powder.

[0079] The feeding unit includes a screw conveyor connected to the grinding chamber through the feed inlet, a feeding hopper 5 connected to the screw conveyor 7, and a nitrogen pump located between the feeding hopper 5 and the screw conveyor 7; a cyclone dust collector is installed on the material inlet 81 and the first outlet 41 of the bag filter.

[0080] Example 1

[0081] Adopting such Figure 1 The apparatus shown prepares ultrafine coal powder. The steam inlet of the air jet mill 1 is equipped with four circumferentially symmetrical first nozzles 3 evenly distributed at the bottom of the grinding chamber. The ratio of the distance D2 between two relative first nozzles 3 to the inner diameter D1 of the grinding chamber 11 is 1.34. The angle between each first nozzle 3 and the horizontal plane is 7°. The feed inlet allows the coal-containing raw material to fall at a distance of D2 / 6 from the impact point.

[0082] The secondary air mechanism is located at 2 / 3 of the distance along the height direction between the steam inlet and the first outlet 41; the secondary air mechanism includes four circumferentially symmetrically distributed second nozzles 2 that are connected to the grinding chamber 11, and each second nozzle 2 has an angle of 7° with the horizontal plane.

[0083] The steam pressure was 0.9 MPa, the temperature was 300℃, the steam velocity entering the air jet mill chamber was 846 m / s, and the pressure inside the air jet mill chamber was -1 kPa; the particle size D of the ultrafine coal powder obtained after grinding was... 97 Its value is 2µm, and its sphericity is 0.8;

[0084] Ultrafine coal powder was dissolved in water and stirred at 500 r / min for 20 min. Then, non-polar diesel oil was added for agglomeration treatment. The ratio of ultrafine coal powder to non-polar diesel oil was 100:1 g / ml. After filtration, ultrapure ultrafine coal powder was obtained. The ash content of the ultrapure ultrafine coal powder on a dry basis was measured to be 0.73%.

[0085] Example 2

[0086] Adopting such Figure 1The apparatus shown prepares ultrafine coal powder. The steam inlet of the air jet mill 1 is equipped with 6 circumferentially symmetrical first nozzles 3 evenly distributed at the bottom of the grinding chamber. The ratio of the distance D2 between two relative first nozzles 3 to the inner diameter D1 of the grinding chamber 11 is 1.24. The angle between each first nozzle 3 and the horizontal plane is 3°. The feed inlet allows the coal-containing raw material to fall at a distance of D2 / 4 from the impact point.

[0087] The secondary air mechanism is located at half the height distance between the steam inlet and the first outlet 41; the secondary air mechanism includes four circumferentially symmetrically distributed second nozzles 2 that are connected to the grinding chamber 11, and each second nozzle 2 has an angle of 7° with the horizontal plane.

[0088] The steam pressure was 0.7 MPa, the temperature was 260℃, the steam velocity entering the air jet mill chamber was 638 m / s, and the pressure inside the air jet mill chamber was -1 kPa; the particle size D of the ultrafine coal powder obtained after grinding was... 97 ≤2.8um, sphericity is 0.77;

[0089] Ultrafine coal powder was dissolved in water and stirred at 500 r / min for 20 min. Then, non-polar diesel oil was added for agglomeration treatment. The ratio of ultrafine coal powder to non-polar diesel oil was 100:1 g / ml. After filtration, ultrapure ultrafine coal powder was obtained. The ash content of the ultrapure ultrafine coal powder on a dry basis was measured to be 0.81%.

[0090] Example 3

[0091] Adopting such Figure 1 The apparatus shown prepares ultrafine coal powder. The steam inlet of the air jet mill 1 is equipped with 12 circumferentially symmetrical first nozzles 3 evenly distributed at the bottom of the grinding chamber. The ratio of the inner diameter D1 of the grinding chamber 11 to the distance D2 between two opposite first nozzles is 1.46. The angle between each first nozzle and the horizontal plane is 13°. The feed inlet allows the coal-containing raw material to fall at a distance of D2 / 2 from the impact point.

[0092] The secondary air mechanism is located at 3 / 4 of the distance along the height direction between the steam inlet and the first outlet 41; the secondary air mechanism includes 6 circumferentially symmetrically distributed second nozzles that are connected to the grinding chamber 11, and each second nozzle has an angle of 2° with the horizontal plane;

[0093] The steam pressure was 0.65 MPa, the temperature was 220℃, the steam velocity entering the air jet mill chamber was 578 m / s, and the pressure inside the air jet mill chamber was -1 kPa; the particle size D of the ultrafine coal powder obtained after grinding was... 97 ≤3.4µm, sphericity 0.79;

[0094] Ultrafine coal powder was dissolved in water and stirred at 500 r / min for 20 min. Then, non-polar diesel oil was added for agglomeration treatment. The ratio of ultrafine coal powder to non-polar diesel oil was 100:1 g / ml. After filtration, ultrapure ultrafine coal powder was obtained. The ash content of the ultrapure ultrafine coal powder on a dry basis was measured to be 0.8%.

[0095] Example 4

[0096] Unlike Example 1, the first nozzle 3 has an angle of 11° with the horizontal plane, resulting in an ultrafine coal powder particle size D after grinding. 97 ≤3.2µm, sphericity 0.63, and ash content of ultrapure ultrafine coal powder on a dry basis of 0.95%.

[0097] Example 5

[0098] Unlike Example 1, the number of first nozzles is two, and the particle size D of the ultrafine coal powder obtained after grinding is... 97 ≤4.8µm, sphericity 0.64, and ash content of ultrapure ultrafine coal powder on a dry basis of 0.98%.

[0099] Example 6

[0100] Unlike Example 1, the angle with the horizontal plane is 0°, and the particle size D of the ultrafine coal powder obtained after grinding is... 97 ≤5.3um, sphericity 0.5, and ash content of ultrapure ultrafine coal powder on a dry basis of 1.04%.

[0101] Example 7

[0102] Unlike Example 1, the feed inlet allows the coal-containing raw material to fall at a distance of D2 / 3 from the impact point, resulting in ultrafine coal powder with a particle size D after grinding. 97 It has a particle size of 4 μm, a sphericity of 0.7, and an ash content of 0.9% on a dry basis for ultrapure and ultrafine coal powder.

[0103] Comparative Example 1

[0104] Using existing air classifier mills, nitrogen is used as the working gas to grind raw coal with a particle size ≤3mm. The nitrogen gas velocity entering the grinding chamber of the air classifier mill is 260m / s. The resulting ultrafine coal powder has a particle size D. 97 The particle size was 11 μm and the sphericity was 0.3. After purification, the ash content of the ultrapure ultrafine coal powder on a dry basis was 3.2%.

[0105] The above comparison demonstrates that the ultrafine coal powder prepared by the method and apparatus of this invention has a smaller particle size distribution and higher sphericity, and can grind the raw coal until the fixed carbon and ash in the coal achieve physical separation. In this way, it can be de-ashed and demineralized through the physical ash removal process in this patent, which significantly overcomes the pollution problems of strong acids and strong alkalis involved in the existing chemical ash removal methods, and has significant environmental advantages.

[0106] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing ultrafine coal powder, characterized in that, The method is carried out in an apparatus for preparing ultrafine coal powder, which includes a feeding unit, a grinding unit and a collecting unit connected in sequence. The feeding unit is used to feed coal-containing raw materials into the grinding unit; The grinding unit includes: an air jet mill (1) with a grinding chamber (11) using steam as the working gas; the feed inlet of the air jet mill (1) is connected to a feeding unit for steam-powered grinding of coal-containing raw materials from the feeding unit; the air jet mill (1) is equipped with a secondary air mechanism for adjusting the airflow field of the grinding chamber (11) to prevent material agglomeration in the grinding chamber (11); the secondary air mechanism is located at a distance ≥1 / 2 along the height direction from the steam inlet to the first outlet (41); the secondary air mechanism includes 4-6 circumferentially symmetrically distributed second nozzles (2) connected to the grinding chamber (11), each second nozzle (2) connected to a secondary air feed line with a valve; the angle between each second nozzle (2) and the horizontal plane is 0-15°; The steam inlet of the air jet mill (1) is provided with an even number of circumferentially symmetrical first nozzles (3) evenly distributed at the bottom of the grinding chamber (11). The number of first nozzles (3) is 4, 6 or 8. Each first nozzle (3) is connected to a steam feed line (31) for feeding steam at a pressure of 0.7-1MPa and a temperature of 260-300℃ into the grinding chamber (11) through the first nozzle (3). The ratio of the inner diameter D1 of the grinding chamber (11) to the distance D2 between two opposite first nozzles (3) is 1.2-1.

5. The angle between each first nozzle (3) and the horizontal plane is 5-12°. The extended axes of each first nozzle (3) intersect to form an impact point. The feed inlet is located above the first nozzle (3), and the feed inlet causes the coal-containing raw material to fall within a distance of D2 / 4 from the impact point. A classifier (4) with a first outlet (41) is provided, the classifier (4) being connected to the grinding chamber (11) so that coal powder of the appropriate particle size can be screened and fed into the collection unit. The collection unit includes a bag filter (8) with an exhaust pipe (10) and an induced draft fan (9) installed on the exhaust pipe (10). The material inlet (81) of the bag filter (8) is connected to the first outlet (41) through a pipe, so that after the classifier (4) screens out coal powder that meets the particle size requirements, it is sent into the bag filter (8) for collection under the suction of the induced draft fan (9), resulting in a sphericity of 0.5-1 and a particle size D. 97 ≤5um ultrafine coal powder; the bag filter (8) is provided with a finished product outlet for discharging the ultrafine coal powder, the finished product outlet is connected to a purification unit, the purification unit includes a container connected to the finished product outlet, the container is provided with a stirring mechanism and a vacuum filtration mechanism, the container is connected to a solvent feed pipeline and a flocculant feed pipeline, so that the ultrafine coal powder is purified to form ultrapure ultrafine coal powder; The method includes: Coal raw materials with a particle size ≤3mm are fed into an air jet mill. Steam is used as the working gas to perform steam grinding of the coal raw materials to obtain coal powder. The steam pressure is 0.7-1MPa, the temperature is 260-300℃, the steam velocity entering the grinding chamber of the air jet mill is 540-1100m / s, and the pressure inside the grinding chamber is -2KPa to 0KPa. Secondary air is introduced into the grinding chamber to maintain the density of the solid material inside the grinding chamber at 2g / cm³. 3 -4g / cm 3 ; The pulverized coal is screened and then fed into a bag filter to collect ultrafine pulverized coal. The sphericity of the ultrafine pulverized coal is 0.5-1, and the particle size D is... 97 ≤5um; The ultrafine coal powder is dissolved in a solvent, stirred for a period of time, and then a flocculant is added for agglomeration treatment. After filtration, ultrapure ultrafine coal powder is obtained, and the ash content Ad on a dry basis of the ultrapure ultrafine coal powder is ≤1%.

2. The method according to claim 1, wherein, The steam originates from low-grade superheated steam from the power plant and / or superheated steam generated by the steam generator; and / or The coal-containing raw material includes at least one of raw coal, fly ash, and coal gangue; and / or The secondary air is selected from at least one of water vapor, nitrogen, and carbon dioxide.

3. The method according to claim 1, wherein, The ratio of the flocculant dosage to the ultrafine coal powder is 0.2-2:100 ml / g; and / or The stirring speed is 500-4000 r / min, and the stirring time is 0-30 min.

4. The method according to claim 1, wherein, The solvent is water and / or an organic solvent; and / or The flocculant is an organic flocculant.

5. The method according to claim 4, wherein, The organic solvent is an alcohol; and / or The flocculant is a non-polar oil.

6. The method according to claim 5, wherein, The organic solvent is ethanol; and / or The flocculant is non-polar diesel oil and / or non-polar kerosene.

7. The method according to claim 1, wherein, The ratio of the inner diameter D1 of the grinding chamber (11) to the distance D2 between the two first nozzles (3) is 1.3-1.

4.

8. The method according to claim 1, wherein, The secondary air mechanism is located at a distance of 2 / 3 to 3 / 4 of the height from the steam inlet to the first outlet (41); Each of the second nozzles (2) has an angle of 0-10° with the horizontal plane.

9. The method according to claim 1, wherein, The feeding unit includes a screw conveyor (7) connected to the feed inlet, a feeding bin (5) connected to the screw conveyor (7), and an anti-blocking mechanism (6) located between the feeding bin (5) and the screw conveyor (7) to prevent material blockage. Cyclone dust collectors are installed on the material inlet (81) and the first outlet (41) of the bag filter.

10. The method according to claim 9, wherein, The anti-blocking mechanism (6) is a vibration device installed at the discharge port of the feeding hopper and / or an air pump for flushing the discharge port of the feeding hopper.

11. The ultrafine coal powder manufactured by the method according to any one of claims 1-10.

12. The application of the ultrafine coal powder of claim 11 in the manufacture of rubber, olefins, nano-hydrogen fuels or coal-to-oil substitutes.

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