Preparation system, process and application of ultrafine powder

Abstract

The invention discloses a preparation system and process of superfine powder and application. The preparation system comprises a fluidized bed jet mill, a first bag-type dust collector, suction equipment, a buffer bin and an optional material modification device. The prepared superfine fly ash and rubber have a good crosslinking effect, the problem of stacking treatment of the fly ash is solved, and high-value utilization of the fly ash is achieved. And meanwhile, the limitation of the existing grinding technology on the treatment scale and the limitation of the existing grinding technology on the lower limit of the grinding particle size are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrafine powder preparation, and in particular to an ultrafine powder preparation system, process and application, which can be typically applied to the preparation of ultrafine powders such as fly ash and coal powder. Background Art

[0002] Fly ash is the main solid waste discharged from coal-fired power plants and one of the largest industrial waste residues in my country. At present, the comprehensive utilization rate of fly ash is low. Therefore, how to reasonably utilize these fly ash and increase its added value is a key concern in this field.

[0003] The traditional comprehensive utilization of fly ash is mainly used for backfilling, brick casting, soil modification, etc., or mixed with cement for calcination. There are problems such as low effective utilization rate and unclear economic benefits. With the development of fly ash deep processing technology, especially the breakthrough of ultrafine grinding technology, ultrafine fly ash can be used in many high value-added industries such as rubber, plastics and composite materials. In particular, when used as rubber filler, there are relatively strict requirements on the morphology of fly ash. Since fly ash is a product after high-temperature crystallization, fly ash belongs to glass crystal, which shows that it is relatively smooth. If ultrafine fly ash is obtained by classification, even if the possibility of ultrafine fly ash being obtained by classification is not considered, the ultrafine fly ash obtained by direct classification is directly used as rubber filler. Due to the poor cross-linking between fly ash and rubber, the life of the product is generally relatively short. Therefore, how to make ultrafine fly ash better obtain the cross-linking effect with rubber on the basis of meeting the requirements of ultrafine fly ash particle size and morphology is also a key point in the preparation of ultrafine fly ash.

[0004] However, in the existing ultrafine powder grinding technology, the gas of the traditional air flow mill must be pressurized by an air compressor. However, due to the development of air compressor technology, that is, the limitations of the air compressor's gas output and pressure, the processing capacity of a single device is difficult to exceed 1t / h. At the same time, since the air compressor needs to be driven by electricity, the energy utilization efficiency of primary energy used for grinding is only about 20%. However, by using steam directly for grinding, the processing capacity of a single device can be about 5t / h, and its primary energy utilization efficiency can reach about 90%.

[0005] CN 109046722 A discloses a method for preparing ultrafine coal powder, which first obtains ultrafine coal powder with a low content of coarse particles by combining graded crushing with ball milling and optimizing the control parameters of each step of the planetary ball mill. The patent mainly grinds the raw coal by a mechanical method. However, due to the grinding technology adopted by the invention patent, the purity of the product has a great problem, and the general particle size is difficult to reach below D50=5um, which limits the application and promotion of the technology in the field of high-end carbon materials.

[0006] CN 103990539B discloses a method for controlling the airflow of an airflow mill and an airflow device, which includes a constant pressure air supply device and a fluidized bed airflow mill with a side nozzle and a bottom nozzle, wherein the side nozzle and the bottom nozzle have a common air inlet, and the common air inlet is connected to the constant pressure device via at least two pipelines with pipeline valves respectively provided, each pipeline has a different diameter, and the diameter of the larger pipeline of the upper level is 1.5-4 times the diameter of the smaller pipeline of the lower level, and the gas flow rate flowing in through the largest pipeline or the sum of the gas flow rates flowing in through all the pipelines is the set flow rate of the airflow mill. The airflow mill avoids blowing large particle powder to the sorting wheel by gradually increasing the flow rate of the high-speed airflow. This patent mainly provides detailed patent invention and protection for the design of the internal structure of the air flow mill. It does not yet involve the entire process flow of the air flow mill, especially the carrier gas used for the air flow. There are serious differences in the entire operation process for the carrier gas, whether it is steam, inert gas or air. This is especially true for flammable and explosive solids such as coal powder. Coal powder will undergo thermal decomposition reaction between 300 and 800°C to produce tar, and the viscosity of the coal powder will increase significantly. If conventional inert gas is used, there will be no corresponding problems.

[0007] CN 101654342A discloses a method for preparing fine fly ash by comprehensively utilizing low-grade flue gas and a special device thereof. The method comprises the following steps: the flue gas generated by boiler combustion is used to pneumatically convey the high-temperature dry fly ash into a steam crusher powered by low-grade superheated steam, and the pulverization and classification are performed, and the pulverization and classification are performed, and the pulverization and classification are performed, and the pulverized fly ash is collected by a steam dust collector to obtain a fine fly ash product, and the waste steam is discharged through an induced draft fan for curing concrete products or thermal insulation wall materials. However, the fine fly ash after grinding and pulverization has agglomeration due to steam condensation, which affects subsequent modification and application. At the same time, the conveying of the fly ash in the patent adopts the pneumatic conveying of flue gas instead of mechanical conveying, and has the defects of poor conveying effect and instability.

[0008] As the finer the particles of ultrafine powder, the larger the specific surface area, the adsorption and interaction forces between particles also increase accordingly, making it very easy for them to agglomerate and "grow" into secondary particles (agglomerates) with larger particle sizes, which greatly affects the particle size index of ultrafine powder prepared by gas phase dynamic mill and the subsequent separation and transportation processes. In addition, when superheated steam is used as the power, high temperature is likely to affect the use effect of the modifier, while low temperature is likely to cause water vapor condensation and agglomeration. Summary of the invention

[0009] The purpose of the present invention is to provide a system, process and application of ultrafine powder preparation. The prepared ultrafine powder has good crushing effect and is convenient for subsequent treatment and application.

[0010] To achieve one aspect of the above-mentioned invention object, the preparation system provided by the present invention adopts the following technical scheme:

[0011] A system for preparing ultrafine powders, comprising a fluidized bed airflow pulverizer, a first bag dust collector, a feed pipe, a suction device and a buffer silo; wherein:

[0012] The fluidized bed air flow mill is provided with a classifying wheel at the top and a slag discharge port at the bottom, and at least two steam nozzles arranged opposite to each other are provided in the fluidized bed air flow mill to form a collision zone between the steam nozzles, and a feeder is also provided above the steam nozzles;

[0013] The feeder is used to input external powder into the collision zone so that the powder is crushed;

[0014] The classifying wheel is used to utilize centrifugal force to return large particles of the crushed powder to the fluidized bed airflow mill for further crushing, and to send out steam and ultrafine powder obtained by crushing;

[0015] The feed port of the first bag filter is connected to the classifying wheel to receive and separate the ultrafine powder and steam, wherein the separated steam is sent out and the separated ultrafine powder is gathered at the conical bottom of the first bag filter for external delivery;

[0016] The conical bottom is also provided with a hot dry gas delivery pipe and a hot dry gas inlet distribution plate connected to the hot dry gas delivery pipe and arranged along the side wall of the conical bottom, so as to introduce the first hot dry gas into the conical bottom; a first material conveying screw is provided at the bottom outlet of the conical bottom, which is used to convey the ultrafine powder in the conical bottom into the material conveying pipe;

[0017] The suction device is used to deliver the sucked second hot dry gas into the feed pipe;

[0018] One end of the feed pipe is connected to the outlet of the suction device and the outlet of the first feed screw, respectively, so as to transport the ultrafine powder from the first feed screw carried by the hot drying gas sucked by the suction device;

[0019] A second bag dust collector is provided on the top of the buffer silo, and a feed port of the second bag dust collector is connected to the other end of the feed pipe, for receiving the hot dry gas and ultrafine powder delivered by the feed pipe and separating them to remove air, and the remaining ultrafine powder after separation flows into the buffer silo below;

[0020] The preparation system may further optionally include a material modification device, which is used to modify the ultrafine powder from the buffer silo using a modifier.

[0021] In the present invention, the term "optionally including" means that the defined objects are optional but not essential.

[0022] To achieve another aspect of the above-mentioned invention object, the preparation method provided by the present invention adopts the following technical scheme:

[0023] A process for preparing ultrafine powder, using the above-mentioned preparation system to prepare ultrafine powder; wherein:

[0024] Superheated steam is introduced into the fluidized bed air flow mill through the steam nozzle to grind the powder input through the feeder. The crushed materials are separated by the classification wheel. The large particles of powder return to the fluidized bed air flow mill for further grinding. The obtained ultrafine powder and steam enter the first bag dust collector for separation.

[0025] The ultrafine powder separated by the first bag dust collector is replaced by the first hot dry gas to remove the entrained steam, and then sent into the feed pipe through the first feed screw, and enters the second bag dust collector arranged on the top of the buffer silo under the transportation of the second hot dry gas delivered by the suction device for separation. The ultrafine powder obtained by separation flows into the buffer silo below for delivery.

[0026] In order to achieve the above invention object, the present invention also provides the application of the ultrafine powder prepared by the above preparation process, wherein the ultrafine powder is used as a filler for rubber preparation, wherein the ultrafine powder is fly ash with a particle size of 1-10 microns, so that the ultrafine fly ash can better obtain the cross-linking effect with the rubber on the basis of meeting the requirements of the particle size and morphology of the ultrafine fly ash. Compared with conventional air grinding, the present invention uses superheated steam grinding to further open up the pores inside the fly ash and increase its cross-linking effect in rubber preparation.

[0027] Compared with the prior art, the present invention has the following technical effects:

[0028] The present invention uses superheated steam to perform ultrafine grinding of materials instead of inert gas or air in traditional technologies, so that on the basis of ensuring system efficiency, the optimal particle size of the product can be controlled below 5um, overcoming the bottleneck of a single device's processing capacity not exceeding 1t / h, so that a single device's processing capacity can reach about 5t / h.

[0029] In the present invention, the ultrafine powder separated by the first bag filter is replaced by hot dry gas introduced from the hot dry gas inlet under the action of the suction device to remove the entrained steam, thereby reducing agglomeration and facilitating subsequent modification treatment.

[0030] The present invention arranges three temperature measuring ports, upper, middle and lower, inside the fluidized bed, which can be used to assist in detecting the material holding amount inside the fluidized bed, ensure that the solid material and steam amount inside the fluidized bed are within a reasonable range, and ensure the stable operation and efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1A schematic diagram of an embodiment of a preparation system of the present invention;

[0032] Figure 2 for Figure 1 A schematic diagram of a fluidized bed airflow mill with a guide plate;

[0033] Marking Description:

[0034] 1- fluidized bed airflow mill; 2- first bag dust collector; 3- feed pipe; 4- suction equipment; 5- buffer silo; 6- material modification device; 7- raw material silo;

[0035] 11-classifying wheel; 12-slag discharge port; 13-steam nozzle; 14-feeder; 15-guide plate; 16-side wall of fluidized bed jet mill; 17-air supply port;

[0036] 21-conical bottom of the first bag filter; 22-hot dry gas delivery pipe; 23-hot dry gas inlet distribution plate; 24-first material conveying screw;

[0037] 51 - the second bag dust collector; 71 - the third bag dust collector; 72 - the raw material conveying screw located upstream; 73 - the raw material conveying screw located downstream. DETAILED DESCRIPTION

[0038] The technical solution of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0039] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0040] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0041] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0042] like Figure 1 As shown, the preparation system of the present invention includes a fluidized bed airflow pulverizer 1, a first bag filter 2, a feed pipe 3, a suction device 4 and a buffer silo 5.

[0043] The fluidized bed air flow mill 1 is well known in the art, and is provided with a classifying wheel 11 at the top and a slag discharge port 12 at the bottom. At least two steam nozzles 13 are arranged opposite to each other in the fluidized bed air flow mill to form a collision zone between the steam nozzles, and a feeder 14 is also provided above the steam nozzle. The feeder is used to input external powder to the collision zone to crush the powder; preferably, the feeder 14 is used to transport the powder to the intersection point on the center line of the steam nozzle where the supersonic superheated steam airflow ejected by the steam nozzle collides. The powder is crushed after colliding with the supersonic superheated steam airflow crushed by the steam nozzle, and at the same time, the powder is crushed after mutual shear collision driven by the supersonic airflow input through the nozzle. The classifying wheel 11 is used to use centrifugal force to return the large particles of the crushed powder to the fluidized bed air flow mill for further crushing, and to send out the steam and the ultrafine powder obtained by crushing. Its specific structure is well known in the art and will not be repeated here.

[0044] The feed port of the first bag filter 2 is connected to the classifying wheel 11 to receive and separate the ultrafine powder and steam, wherein the separated steam is sent out (through the induced draft fan, not shown in the figure), and the separated ultrafine powder is gathered at the conical bottom 21 of the first bag filter for external delivery;

[0045] The conical bottom 21 is also provided with a hot dry gas delivery pipe 22 and a hot dry gas inlet distribution plate 23 connected to the hot dry gas delivery pipe and arranged along the side wall of the conical bottom, so as to introduce the first hot dry gas into the conical bottom 21; a first material conveying screw 24 is provided at the bottom outlet of the conical bottom, which is used to convey the ultrafine powder in the conical bottom into the material conveying pipe 3;

[0046] The suction device 4 is used to deliver the sucked second hot drying gas into the feeding pipe 3, wherein the first hot drying gas and the second hot drying gas may come from the same or different gas sources, such as high-temperature flue gas, hot air and / or hot nitrogen, etc. The suction device is well known in the art, for example, it may be a Roots blower.

[0047] One end of the feed pipe 3 is respectively connected to the outlet of the suction device 4 and the outlet of the first feed screw 24 to transport the ultrafine powder from the first feed screw 24 carried by the hot dry gas sucked by the suction device 4; for example, the end of the feed pipe 4 connected to the first feed screw 24 and the suction device 4 is provided with two openings, one of which is upward for connecting to the first feed screw 24, and the other opening is horizontally arranged for connecting to the air outlet of the suction device 4.

[0048] A second bag filter 51 is provided on the top of the buffer silo 5, and the feed port of the second bag filter 51 is connected to the other end of the feed pipe 3, for receiving the hot dry gas and ultrafine powder delivered by the feed pipe 3 and separating them to remove the dry gas. The remaining ultrafine powder after separation flows into the buffer silo 5 below for delivery.

[0049] Optionally, the preparation system further includes a material modification device 6, that is, the material modification device 6 may or may not be provided; the material modification device 6 is used to modify the ultrafine powder from the buffer silo 5 using a modifier; specifically, the material modification device 6 may be connected to the outlet of the buffer silo 5 through a star valve to receive the ultrafine powder to be modified.

[0050] In one embodiment, Figure 2 As shown, the fluidized bed air flow mill 1 is further provided with a guide plate 15, which is an annular plate connected to the bottom wall of the classifying wheel 11, and the guide plate 15 extends downwardly in an inclined manner, and the lower end of the guide plate 15 is close to the side wall 16 of the fluidized bed air flow mill 1 relative to its upper end, and is used to guide the unqualified large particle powder separated by the classifying wheel 11 to a position close to the side wall 16 of the fluidized bed air flow mill and downward, so that it falls at a low speed to the collision zone at the bottom of the fluidized bed air flow mill, and avoids it from mixing with the particles after the collision at the upper part of the air flow mill and re-entering the classifying wheel 11 for classification treatment, resulting in low classification efficiency or even entrainment.

[0051] Preferably, the inclination angle α1 of the guide plate 15 relative to the longitudinal center line of the fluidized bed airflow pulverizer is 20°-40°, the outer diameter of the upper end of the guide plate 15 is consistent with the outer diameter of the classifying wheel 11, and on the plane where the lower end of the guide plate 15 is located, the relationship between the lower end outer diameter d1 of the guide plate 15 and the inner diameter D0 of the fluidized bed airflow pulverizer is: d1=(0.85-0.9)D0.

[0052] In some embodiments, the preparation system further comprises a raw material bin 7, a third bag dust collector 71 is provided on the top of the raw material bin 7; two raw material conveying screws (72, 73) arranged in series are installed at the bottom of the raw material bin 7 to convey the powder from the raw material bin to the feeder. Preferably, the two raw material conveying screws are arranged in parallel up and down.

[0053] It is understood in the art that, in the present invention, the feeder can be arranged in a variety of forms while ensuring smooth material input. In some embodiments, the feeder 14 is a chute, and an air supply port 17 is provided on the chute for supplying air flow to strengthen the fluidization of the powder; in some embodiments, the feeder can be a nozzle, and the nozzle includes a powder channel for conveying fluidized powder and a steam channel sleeved outside the powder channel and coaxially arranged with the powder channel.

[0054] Or in some embodiments, the downstream raw material conveying screw 73 of the two raw material conveying screws arranged in series is used as a feeder to be directly inserted into the fluidized bed, so that the material is conveyed to the inside of the air flow pulverizer by mechanical conveying; at the same time, an air supply port can be provided on the downstream feed screw to replenish the air flow to strengthen the conveying of the powder. By setting up two-stage screws, it is helpful to prevent steam from condensing in the upstream feed screw, so as to facilitate maintenance; in addition, the present invention adopts screw mechanical conveying, which has a relatively high conveying capacity and a good crushing effect compared with pure pneumatic conveying (dilute phase conveying).

[0055] When preparing ultrafine powders, Figure 1 As shown, superheated steam is introduced into the fluidized bed air flow pulverizer 1 through the steam nozzle 13 to pulverize the powder input through the feeder, and the pulverized material is separated by the classifying wheel 11, wherein the large particle powder returns to the fluidized bed air flow pulverizer for further pulverization, and the obtained ultrafine powder enters the first bag dust collector 2 together with the steam for separation; the ultrafine powder separated by the first bag dust collector 2 is replaced and removed with the first hot dry gas introduced by the hot dry gas inlet distribution plate 23 at the conical bottom 21 to remove the entrained steam, and the hot dry gas is discharged from the top of the first bag dust collector 2 together with the steam, and the ultrafine powder is sent to the feed pipe 3 through the first feed screw 24, and is driven by the second hot dry gas from the suction device 4 to the second bag dust collector 51 arranged on the top of the buffer silo 5 for separation, and the separated ultrafine powder flows into the buffer silo 5 below, and is finally sent to the material modification equipment 6 for modification.

[0056] The following is an example of using fly ash and superheated steam introduced to a power plant or generated by a self-provided steam generator to pneumatically grind the fly ash. Figure 1 The preparation process is further described as shown:

[0057] The fly ash from the power plant is pneumatically conveyed to the raw material bin 7. A third bag dust collector 71 is installed on the upper part of the raw material bin 7 to ensure that the pressure of the system is balanced when the raw materials are conveyed into the raw material bin. Two raw material conveying screws (the upstream raw material conveying screw 72 and the downstream raw material conveying screw 73) arranged in parallel are installed at the lower part of the raw material bin 7 to convey the fly ash. At the same time, a weighing sensor can also be installed at the bottom of the raw material bin 7 to measure the conveying amount and ensure that the raw material bin always maintains a certain material level to prevent material shortage and other phenomena.

[0058] The bottom of the raw material bin 7 can also be provided with an air supply port to ensure that the material at the bottom of the raw material bin is in a fluidized state to avoid material bridging and blocking the bin. At the same time, a pneumatic hammer or air cannon or other striking device can be installed at the bottom of the raw material bin to further avoid material blocking.

[0059] After the material is quantitatively conveyed horizontally by the two-stage feeding screw, it is further conveyed to the inside of the fluidized bed airflow pulverizer 1 through the chute (that is, the feeder 14 arranged obliquely downward). At the same time, in order to ensure the material conveying effect, an air supply port 17 is opened on the chute to allow a certain amount of air to be introduced to strengthen the material conveying, avoid the occurrence of agglomeration, and help the material to be conveyed to the inside of the fluidized bed airflow pulverizer at a certain speed.

[0060] Of course, the feeding screw located below can also be directly inserted into the fluidized bed air flow mill, so that the material is transported to the fluidized bed air flow mill by mechanical conveying; at the same time, a certain air supply port is opened on the feeding screw to enhance the fluidization of the material inside the feeding screw.

[0061] Alternatively, after the material is quantitatively horizontally conveyed by the two-stage feeding screw, it is further conveyed to the inside of the fluidized bed air flow pulverizer through a nozzle. The nozzle includes a powder channel for conveying fluidized powder and a steam channel that is sleeved outside the powder channel and coaxially arranged with the powder channel. That is, the powder channel sprays the raw material fly ash to be crushed into the fluidized bed air flow pulverizer through the carrier gas, and the steam channel sprays superheated steam into the fluidized bed air flow pulverizer. After the superheated steam and the raw material fly ash are mixed at the nozzle head, they enter the fluidized bed air flow pulverizer together to fluidize and collide with the medium to be ground.

[0062] The fly ash transported to the fluidized bed air flow mill 1 moves at high speed driven by the superheated steam accelerated by the laval nozzle (i.e., the steam nozzle 13), and collides and crushes each other. At the same time, due to the suction of the induced draft fan (not shown in the figure) provided in conjunction with the first bag filter 2, the fly ash that collides and crushes each other will move upward along the fluidized bed air flow mill; in the process of the superheated steam clamping the crushed fly ash and moving upward along the center line of the fluidized bed air flow mill, the speed of the finer particles moving upward is faster than that of the larger particles, so in the process of moving upward, the particles will undergo shear collision and friction on the crushed particles, so that the particles at the outlet of the fluidized bed air flow mill have a certain sphericity, which is conducive to being used as rubber fillers.

[0063] Due to the high-speed rotating classifying wheel 11 installed on the top of the fluidized bed air flow mill and the suction force of the subsequent induced draft fan, superheated steam mixed with the crushed ultrafine fly ash enters the classifying wheel 11. By controlling the rotation speed of the classifying wheel, the fly ash with larger particles will be thrown out of the classifying wheel due to its larger centrifugal force at the same rotation speed, and will flow back into the fluidized bed air flow mill to continue grinding, while the smaller particles (ultrafine powder) will be sandwiched by the superheated steam and enter the next link through the central pipe of the classifying wheel.

[0064] The process parameters of the superheated steam from the power plant or steam generator are: pressure 0.5-1.2MPa, such as 0.8 or 1.0MPa, temperature: 200-320℃, such as 240, 260, 280 or 300℃, and it is transported to the steam nozzle installed on the cylinder of the fluidized bed air flow mill. The number of nozzles is preferably an even number, such as 4, or 6, or 8, and is symmetrically distributed. The angle between each nozzle and the horizontal plane is 0-15°, preferably 6-12°, such as 9°. The nozzle can be a Laval nozzle, and the gas velocity of the outlet steam is generally designed to be 2-2.5 Mach numbers, preferably 2.1-2.2 Mach numbers, such as 2.15 Mach numbers.

[0065] The inlet side of the steam nozzle 13 is connected to the annular main pipe surrounding the cylinder of the fluidized bed air flow mill, and the annular main pipe is connected to the steam delivery pipe delivered from the power plant or the steam generator. A slag discharge port 12 is set at the bottom of the fluidized bed air flow mill to discharge the un-crushed solid materials in the mill after the equipment is shut down.

[0066] In a preferred embodiment, for better stable operation and efficiency of the system, the volume ratio of solid volume to gas volume in the fluidized bed jet mill is controlled at 1×10 -2 -1×10 -4 Between, for example, 1×10 -3 , 5×10 -3 or 8×10 -3, where the solid volume can be obtained by dividing the mass by the true density. It can be understood that when too much fly ash is introduced, the heat absorption of the fly ash leads to the appearance of condensed water, which in turn causes the system to shut down and the fly ash cannot obtain sufficient acceleration and cannot be crushed, or when the amount of fly ash introduced is too little, the fly ash cannot obtain sufficient collision, which greatly reduces the efficiency of the entire system.

[0067] In some embodiments, three temperature measuring ports (not shown in the figure) at the top, middle and bottom can be set inside the fluidized bed air flow pulverizer, which can be used to assist in detecting the material holding amount inside the fluidized bed air flow pulverizer. For example, according to the specific heat capacity of the solid material, if too much solid material passes through, the material will absorb heat, thereby causing the temperature inside the fluidized bed to decrease. If too little solid material passes through, the temperature inside the fluidized bed is basically the temperature of superheated steam. Therefore, temperature monitoring can indirectly monitor the material holding amount inside the fluidized bed air flow pulverizer, thereby ensuring that the solid material and steam amount inside the fluidized bed air flow pulverizer are within a reasonable range, thereby ensuring the stable operation and efficiency of the system.

[0068] The qualified products after classification by the grading wheel 11 enter the downstream first bag dust collector 2. The ultrafine powder separated by the first bag dust collector is replaced by the first hot dry gas to remove the entrained steam, and then sent to the feed pipe through the first feed screw. Under the conveyance of the second hot dry gas delivered by the suction equipment, it enters the second bag dust collector arranged on the top of the buffer silo for separation. Since the residual steam in the ultrafine powder product is removed, it can be ensured that the cooling moisture absorption and agglomeration phenomenon will not occur subsequently.

[0069] The ultrafine products conveyed by pneumatic conveying enter the buffer silo 5, on the top of which a second bag dust collector 51 is installed for gas-solid separation, and then are temporarily stored in the buffer silo. The material modification device 6 is connected to the bottom outlet of the intermediate buffer silo, for example, it is connected to the bottom outlet of the intermediate buffer silo through the star valve. The star valve is mainly used for quantitative material transportation to ensure that the modification of the ultrafine powder of the downstream equipment can be carried out in a certain proportion. General modifiers include sodium stearate, silane coupling agent or a composite modifier of the two, which can enter from other ports of the material modification device. The mass ratio of the modifier to the ultrafine material is 0.5-2.5:100, such as 1:100, 1.5:100 or 2:100. The reaction time of the ultrafine powder and the modifier in the reactor of the material modification device is generally controlled at 20-50min, such as about 30min or 40min. The specific time needs to be adjusted according to the total amount of the modifier and the ultrafine material to ensure that the ultrafine modification encapsulation rate reaches more than 95%. The modified product flows out from the discharge port at the bottom of the reactor by gravity and is packaged.

[0070] Furthermore, the material modification device 6 has a heating function, which can ensure that the temperature inside the reactor of the material modification device is heated and maintained at a certain temperature, and the heating range is 0-100°C. In addition, the reactor is equipped with a breathing valve and a modifier inlet, and the modifier is transported to the inside of the reactor in liquid form through a quantitative feeding screw; the reactor is a hollow structure with a stirring paddle inside, and the stirring paddle is moved at a constant speed by an external motor. In addition, in order to ensure that the material inside the reactor can be discharged from the reactor smoothly, a vent is connected to the top of the reactor. When the reactor material is discharged from the reactor, dry air above normal temperature and below 90°C is introduced into the reactor from time to time to ensure that the material in the reactor falls smoothly.

[0071] In the present invention, the lower part or conical bottom of the raw material bin 7, the buffer bin 5 and the bag filter can be installed with an air intake pipe and a beating device such as an air hammer or a nitrogen cannon. The air intake pipe is mainly used to ensure that the material at the bottom of the bin is in a fluidized state to prevent the occurrence of bridging phenomenon, while the beating device such as an air hammer or a nitrogen cannon is mainly used to eliminate the general bridging phenomenon by means of mechanical external force, which can promote the normal operation of the system.

[0072] In the present invention, after the dust collection in the first bag filter 2, the separated steam is sucked out by the induced draft fan and can be recycled. At the same time, in order to prevent the bag filter from having an unsatisfactory effect, a cyclone dust collector or bag filter can be further added after the first bag filter to ensure the dust removal effect and the discharged steam meets environmental protection requirements.

[0073] In the present invention, in order to prevent steam condensation, a steam input port is provided between the pipe between the outlet of the classifying wheel and the first bag filter, and a low alarm and a low-low alarm of the steam temperature are provided on the connecting pipe. When the temperature is lower than 105°C, emergency steam is introduced to ensure that the steam temperature in the pipe is above 120°C. In addition, steam tracing or electric tracing can be provided at the bottom of the first bag filter to ensure that the temperature at the outlet is above the critical temperature to avoid the appearance of condensed water.

[0074] In the present invention, the entire system should be well insulated externally, wherein the bag filter, fluidized bed air flow mill and the intermediate connecting pipe can be insulated externally by means of insulation cotton or the like, or by means of an external jacket, through which high-temperature steam passes, to ensure that no condensed water appears inside the filter. The entire system maintains a negative pressure system.

[0075] The present invention is further described below with reference to embodiments.

[0076] Particle size detection: The laser particle size method is used to monitor the particle size of the powder.

[0077] Example 1

[0078] Use Figure 1 The preparation system shown is for preparing ultrafine powders, wherein four steam nozzles are provided, which are arranged obliquely upward with an angle of 6° with the horizontal plane.

[0079] Superheated steam is introduced into the fluidized bed air flow mill through the steam nozzle to grind the powder input through the feeder. The ground materials are separated by the classification wheel. The large particles of powder return to the fluidized bed air flow mill for further grinding. The obtained ultrafine powder and steam enter the first bag dust collector for separation.

[0080] The ultrafine powder separated by the first bag dust collector is replaced by the hot dry gas introduced from the hot dry gas inlet under the action of the suction device to remove the entrained steam, and then enters the second bag dust collector arranged on the top of the buffer silo through the first feeding screw and the suction device for separation. The separated ultrafine powder flows into the buffer silo below and is finally sent to the material modification equipment for modification.

[0081] Among them, the fly ash feed particle size is: 100-200um; the superheated steam operating pressure is 0.9Mpa, the temperature is 240℃, the steam volume is: 2.84T / h, and the ultrafine powder product output is 3.4T / h. Among them, the volume ratio of the solid volume to the gas volume in the fluidized bed airflow mill is 3.8×10 -3 .

[0082] After testing, the modified ultrafine powder has a D97 of 6.066 μm, and the moisture content of the ultrafine powder sample reaches 0.6%.

[0083] Example 2

[0084] The difference from Example 1 is that the fly ash feed particle size is 100-200um; the superheated steam operating pressure is 1.1Mpa, the temperature is 240℃, the steam volume is 2.84T / h, and the ultrafine powder product output is 3.4T / h; and the angle between the steam nozzle and the horizontal plane is 9°. The rest is the same as Example 1. The volume ratio of the solid volume to the gas volume in the fluidized bed airflow mill is 3.1×10 -3 .

[0085] After testing, the particle size of the modified ultrafine powder is D97=5.591μm, and the moisture content of the ultrafine powder sample reaches 0.6%.

[0086] Example 3

[0087] The difference from Example 1 is that the particle size of fly ash feed is 100-200um; the superheated steam operating pressure is 0.7Mpa, the temperature is 240℃, the steam volume is 2.84T / h, and the ultrafine powder product output is 3.4T / h; and the angle between the steam nozzle and the horizontal plane is 12°. The rest is the same as Example 1. The volume ratio of the solid volume to the gas volume in the fluidized bed airflow mill is 4.9×10 -3 .

[0088] After testing, the D97 of the modified ultrafine powder is 10.38 μm, and the moisture content of the ultrafine powder sample reaches 0.6%.

[0089] Example 4

[0090] The difference from Example 1 is that the fluidized bed airflow pulverizer is further provided with Figure 2 The rest is the same as in Example 1.

[0091] After testing, the ultrafine powder product output is 3.8T / h. After testing, the modified ultrafine powder has a D97 of 6.066μm and a moisture content of 0.6%.

[0092] Example 5

[0093] The difference from Example 2 is that the steam nozzle is arranged horizontally. The rest is the same as Example 2.

[0094] After testing, the ultrafine powder product output is 1.7T / h. After testing, the D97 of the modified ultrafine powder is 12.3μm, and the moisture content of the ultrafine powder sample reaches 0.6%.

[0095] Comparative Example 1

[0096] The difference from Example 1 is that the hot drying gas inlet provided at the conical bottom of the first bag filter is closed, and the material discharged from the first feeding screw is directly fed into the material modification device. The rest is the same as Example 1, and the moisture content of the sample is 3% after testing.

[0097] Application Examples

[0098] The ultrafine powder prepared in Example 1 is used in the preparation of rubber: 35 parts of the modified ultrafine fly ash are mixed with 65 parts of natural rubber, 35 parts of styrene-butadiene rubber, 1.3 parts of DPG, 6 parts of 4010NA and 2.5 parts of sulfur, and the rubber is obtained by plasticizing at a plasticizing temperature of 160°C, a plasticizing time of 30 min and a stirring speed of 120 rpm.

[0099] The rubber was subjected to relevant tests, and the test results were as follows: tensile strength 17MPa, elongation at break 382%, hardness 72 shore A, density 1.27g / mm 3, wear 184mm 3 .

[0100] It can be seen from the above embodiments / comparative examples that providing a guide plate in the fluidized bed air flow pulverizer can effectively improve the yield of the device; in addition, after removing the hot drying gas inlet, the suction equipment and the buffer silo, the system device is at risk of shutdown due to the condensation of water vapor, and the moisture content of the sample is significantly increased; in addition, since the nozzle is set at an angle, it is conducive to further refinement of the powder compared to the horizontal setting.

[0101] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A system for preparing ultrafine powder, characterized in that: The preparation system comprises a fluidized bed airflow pulverizer, a first bag dust collector, a feed pipe, a suction device and a buffer silo; wherein: The fluidized bed air flow mill is provided with a classifying wheel at the top and a slag discharge port at the bottom, and at least two steam nozzles arranged opposite to each other are provided in the fluidized bed air flow mill to form a collision zone between the steam nozzles, and a feeder is also provided above the steam nozzles; The feeder is used to input external powder into the collision zone so that the powder is crushed; The classifying wheel is used to utilize centrifugal force to return large particles of the crushed powder to the fluidized bed airflow mill for further crushing, and to send out steam and ultrafine powder obtained by crushing; The feed port of the first bag filter is connected to the classifying wheel to receive and separate the ultrafine powder and steam, wherein the separated steam is sent out and the separated ultrafine powder is gathered at the conical bottom of the first bag filter for external delivery; The conical bottom is also provided with a hot dry gas delivery pipe and a hot dry gas inlet distribution plate connected to the hot dry gas delivery pipe and arranged along the side wall of the conical bottom, so as to introduce the first hot dry gas into the conical bottom; a first material conveying screw is provided at the bottom outlet of the conical bottom, which is used to convey the ultrafine powder in the conical bottom into the material conveying pipe; The suction device is used to deliver the sucked second hot dry gas into the feed pipe; One end of the feed pipe is connected to the outlet of the suction device and the outlet of the first feed screw, respectively, so as to transport the ultrafine powder from the first feed screw carried by the hot drying gas sucked by the suction device; A second bag dust collector is provided on the top of the buffer silo, and the feed port of the second bag dust collector is connected to the other end of the feed pipe, and is used to receive the hot dry gas and ultrafine powder transported by the feed pipe and separate them to remove the dry gas, and the remaining ultrafine powder after separation flows into the buffer silo below; The preparation system may further optionally include a material modification device, which is used to modify the ultrafine powder from the buffer silo using a modifier.

2. The preparation system according to claim 1, characterized in that: The preparation system also includes a raw material bin, a third bag dust collector is provided on the top of the raw material bin; two raw material conveying screws arranged in series are installed at the bottom of the raw material bin to convey the powder from the raw material bin to the feeder.

3. The preparation system according to claim 2, characterized in that: The feeder is a slide pipe, and an air supply port is provided on the slide pipe for supplying air flow to strengthen the conveying of powder; Alternatively, the feeder is a nozzle, and the nozzle comprises a powder channel for conveying fluidized powder and a steam channel sleeved outside the powder channel and coaxially arranged with the powder channel; Alternatively, the downstream feed screw of the two raw material feed screws arranged in series is used as a feeder and directly inserted into the fluidized bed, so that the material is transported to the air flow mill by mechanical conveying; at the same time, an air supply port is provided on the downstream feed screw for supplying air flow to strengthen the transportation of powder; Preferably, the feeder is used to convey the powder to the intersection point on the center line of the steam nozzle where the supersonic superheated steam airflows ejected from the steam nozzle collide.

4. The preparation system according to any one of claims 1 to 3, characterized in that: Each steam nozzle is arranged horizontally or inclined upward, with an angle of 0-15° to the horizontal plane, preferably an angle of 6-12° to the horizontal plane.

5. The preparation system according to any one of claims 1 to 4, characterized in that: A guide plate is also provided in the fluidized bed air flow pulverizer. The guide plate is an annular plate connected to the bottom wall of the classifying wheel. The guide plate extends downwardly in an inclined manner, and the lower end of the guide plate is close to the inner wall of the fluidized bed air flow pulverizer relative to the upper end thereof, so as to guide the unqualified large particle powder separated by the classifying wheel to a position close to the inner wall of the fluidized bed air flow pulverizer and move downward.

6. A process for preparing ultrafine powder, characterized in that: Ultrafine powder is prepared using the preparation system described in any one of claims 1 to 5; wherein, Superheated steam is introduced into the fluidized bed air flow mill through the steam nozzle to grind the powder input through the feeder. The crushed materials are separated by the classification wheel. The large particles of powder return to the fluidized bed air flow mill for further grinding. The obtained ultrafine powder and steam enter the first bag dust collector for separation. The ultrafine powder separated by the first bag dust collector is replaced by the first hot dry gas to remove the entrained steam, and then sent into the feed pipe through the first feed screw, and enters the second bag dust collector arranged on the top of the buffer silo under the transportation of the second hot dry gas delivered by the suction device for separation. The ultrafine powder obtained by separation flows into the buffer silo below for delivery.

7. The preparation process according to claim 6, characterized in that: The volume ratio of the solid powder volume to the gas volume in the fluidized bed airflow pulverizer is controlled at 1×10 -2 -1×10 -4 Preferably, three temperature measuring ports, upper, middle and lower, are provided inside the fluidized bed airflow pulverizer to assist in detecting the amount of material held inside the fluidized bed airflow pulverizer.

8. The preparation process according to claim 6 or 7, characterized in that: The process parameters of the superheated steam are: pressure 0.5-1.2MPa, temperature: 200-320°C; The steam nozzle adopts a Laval nozzle, and the gas velocity of the steam ejected is 2-2.5 Mach number.

9. The preparation process according to any one of claims 6 to 8, characterized in that: When the material modification device is used for modification, the modifier used is sodium stearate, silane coupling agent or a composite modifier of the two, and the mass ratio of the modifier to the ultrafine material is 0.5-2.5:

100.

10. Use of the ultrafine powder prepared according to any one of claims 6 to 9, characterized in that: The ultrafine powder is used as a filler in rubber preparation, wherein the ultrafine powder is fly ash with a particle size of 1-10 microns.

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