Ultrafine grinding mill stirring device

Abstract

A superfine grinding mill stirring device includes a main shaft and an upper blade group and a lower blade group fixed to the main shaft; the main shaft passes through the coarse grinding chamber and fine grinding chamber of the superfine grinding mill; the lower blade group is located in the coarse grinding chamber, and the upper blade group is located in the fine grinding chamber; the upper blade group is composed of several layers of upper blades with inclined angles; the lower blade group is composed of several layers of lower blades with inclined angles; the height-to-diameter ratio of the upper blades is smaller than that of the lower blades; the height-to-diameter ratio refers to the ratio of the height to the diameter of a single layer of blades. The stirring device of the present invention has many advantages, such as a simple structure, good adaptability, uniform distribution of the medium in the mill, and low energy consumption.

Description

Technical Field

[0001] The invention belongs to the technical field of crushing, grinding or pulverizing, and in particular relates to an ultrafine grinding machine stirring device. Background Art

[0002] With the gradual depletion of easily smelted ores, refractory ores have become the main source of mineral processing. Refractory ores are usually in the form of micron-scale fine particles due to the fine particle size of the target minerals. Grinding is necessary to achieve monomer dissociation. The traditional crushing and grinding process consumes very high power and steel balls, resulting in high grinding costs. Many mines producing refractory ores cannot operate due to economic reasons. The product fineness of existing ordinary mills is generally around 74 microns, and the product fineness of spiral stirred mills is generally around 37 microns, which makes it difficult to meet the requirements for monomer dissociation of refractory minerals. The Isa mill of Netzsch Company in Germany has achieved a product fineness of 2 microns, but the Isa mill is a horizontal high-speed stirred mill that uses disc stirring. It has high processing precision requirements, a complex structure, and a high cost, which restricts its application.

[0003] The stirring device of the existing mill mainly adopts the following two forms:

[0004] 1. Spiral stirring device.

[0005] Existing vertical stirred mills typically use a spiral as the stirring mechanism. The spiral drives the mineral and grinding media in a low-speed rotation within the cylinder, achieving grinding through friction between the mineral and the grinding media. Vertical mills operate at a relatively low speed, with the spiral's outer edge typically velocities ranging from 1 to 3 m / s. The resulting particle size is 0.037 to 0.074 mm, and after classification, the product can reach 0.037 mm. This stirring mechanism limits operation to low speeds, with the friction between the mineral and the media on the spiral surface creating a grinding action that pulverizes the mineral, achieving conventional fine grinding.

[0006] When it runs at high speed, it will become a screw conveyor, and its lifting capacity is much greater than the centrifugal force. Therefore, the centrifugal force used to produce mineral crushing accounts for a small proportion of the total power consumption, and the useless power consumption is too large. Therefore, if high-speed operation cannot be achieved, ultra-fine grinding cannot be achieved. Its common structure is shown in Figure 1 The main structure includes a motor 101, a reducer 102, a bearing 103, a discharge port 104, a ball adding port 105, a stirring system 106, a cylinder 107 and a feed port 108.

[0007] 2. Disc (leaf) type stirring device:

[0008] Patent CN113145239A proposes a multi-layer disc-type stirring device. The disc is fixed to the main shaft and is equipped with a replaceable lifting block with an upward inclined surface. The transmission system drives the disc to rotate at a high speed, forcing the medium balls and materials to perform multi-dimensional circular rotational motion in the cylinder. The mineral particles are effectively ground through friction and impact collision under the weight pressure and extrusion force of the grinding medium.

[0009] The disc is installed on the main shaft and has a disc structure. The disc surface has holes. The lifting block is installed on the disc. The upper surface is tilted upward with an angle of 0.5° to 45° to the horizontal. The linear speed of the outer end of the disc is 5 to 50m / s, which can achieve high-speed operation, reduce the lifting force, improve the grinding effect, and also improve the energy utilization efficiency, realizing ultra-fine grinding.

[0010] refer to Figure 2 Its main structure includes motor reducer 201, upper bearing 202, stirring main shaft 203, ore discharge port 204, fixed plate 205, shaft sleeve 206, upper blade 207, cylinder 208, lower blade 209, transmission assembly 2010, lower bearing 2011, support 2012, ball adding port 2013, partition 2014, shaft seal 15, ore inlet pipe 2016 and screen plate 2017, etc.

[0011] However, in production practice, it was found that in order to prevent the medium from settling, the upper surface angle of the lifting block of the disc-type stirring device was relatively large. However, because the mineral particles are generally much smaller than the medium particle size, the lifting force on the slurry and mineral particles is too large, causing the mineral particles to be directly flushed out of the mill with the slurry, forming a short circuit. At the same time, there is a problem of high grinding power consumption. Summary of the Invention

[0012] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide an ultrafine mill stirring device, so as to solve the problems of high energy consumption and poor grinding effect existing in the existing ultrafine mill spiral stirring, rod pin stirring and disc stirring structures.

[0013] In order to achieve the above object, the technical solution adopted by the present invention is:

[0014] An ultrafine grinding mill stirring device comprises a main shaft and an upper blade group and a lower blade group fixed on the main shaft;

[0015] The main shaft passes through the coarse grinding chamber and the fine grinding chamber of the ultrafine grinder; the lower blade group is located in the coarse grinding chamber, and the upper blade group is located in the fine grinding chamber;

[0016] The upper blade group is composed of several layers of upper blades with inclined angles; the lower blade group is composed of several layers of lower blades with inclined angles;

[0017] The height-to-diameter ratio of the upper blade is smaller than that of the lower blade; the height-to-diameter ratio refers to the ratio L / D of the height L to the diameter D of a single-layer blade.

[0018] In one embodiment, the coarse grinding chamber and the fine grinding chamber are separated by a partition plate, the main shaft passes through the partition plate, and a gap is formed between the two for the coarsely ground material to pass through.

[0019] In one embodiment, the upper blade group and / or the lower blade group have at least two blades in a single layer. The blades are fan-shaped with a certain angle, evenly distributed along the circumference, and fixed on the main shaft.

[0020] In one embodiment, the upper blade adopts a structure with a small aspect ratio and a large diameter, and the lower blade adopts a structure with a large aspect ratio and a small diameter.

[0021] In one embodiment, the aspect ratio of the lower blade is 1 to 1.5 times that of the upper blade.

[0022] In one embodiment, the aspect ratio of the upper blade ranges from 0.05 to 1.

[0023] In one embodiment, the lower blade diameter D1 is 0.5 to 1 times the upper blade diameter D2.

[0024] In one embodiment, the diameter D2 of the upper blade is 0.5 to 0.95 times the inner diameter of the ultrafine grinding mill cylinder.

[0025] In one embodiment, the pitch ratio H / D of the upper blade is 0.2 to 2, and the pitch ratio H / D of the lower blade is 0.5 to 1 times the pitch ratio of the upper blade.

[0026] In one embodiment, the linear velocity of the outer end of the upper blade is 5 to 50 m / s, and the linear velocity of the outer end of the lower blade is 0.5 to 1 times that of the upper blade.

[0027] Compared with existing technologies, the present invention offers the following advantages: The ultrafine grinding mill agitator utilizes multiple layers of blades with a defined angle. These blades not only lift the grinding media to prevent them from settling, but also enable them to rotate at high speeds, colliding with mineral particles and producing a grinding effect. This provides appropriate lifting and centrifugal forces, enabling the mill to achieve higher impeller linear speeds and grinding energy intensity, improving ultrafine grinding capacity. While meeting the required grinding fineness, this significantly reduces energy consumption, thereby significantly lowering the operating costs of ultrafine grinding technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the spiral stirring device described in the background technology.

[0029] Figure 2 It is a structural schematic diagram of the disc (blade) type stirring device described in the background technology.

[0030] Figure 3 It is a schematic diagram of the assembly structure of the stirring device and the ultrafine grinder of the present invention.

[0031] Figure 4 It is a schematic diagram of the main shaft and blade structure of the stirring device of the present invention.

[0032] Figure 5 It is a schematic diagram of the blade structure of the stirring device of the present invention.

[0033] Figure 6 It is a schematic diagram of fluid mechanics simulation of the spiral stirring device, the disc stirring device and the blade stirring device of the present invention. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0035] As mentioned above, most of the useful minerals in difficult-to-smelt ores exist in the form of micron-scale fine particles, and grinding is necessary to achieve monomer dissociation. Therefore, an ultrafine grinder that can achieve micron-level grinding is needed. In this ultrafine grinder, the stirring device is one of its core components. When the spiral stirring structure operates at high speed, it is similar to a conveyor, resulting in a large amount of useless power consumption and limited crushing effect. The disc (blade) type stirring structure can reduce the lifting force under high-speed operation conditions, but when the mineral particles are much smaller than the medium particle size, its lifting force cannot be ignored. In actual application, it is easy for the mineral particles to be directly flushed out of the mill with the slurry to form a short circuit. At the same time, its grinding power consumption remains at a high level.

[0036] To this end, the present invention provides an ultrafine grinding mill agitator. Its agitator blades are divided into two groups, upper and lower, with the upper and lower blades having different diameters and aspect ratios. The lower group uses blades with smaller diameters and larger aspect ratios to achieve low linear speeds and high lifting forces, thereby improving efficiency and preventing coarse particle settling. The upper group, on the other hand, uses blades with larger diameters and smaller aspect ratios to achieve high linear speeds and low lifting forces, thereby improving grinding efficiency and reducing wasted power consumption.

[0037] In the present invention, the aspect ratio is defined as the ratio L / D of the height L of a single layer of blades to its diameter D. The distance between each layer of blades is called the pitch, and the ratio of the pitch H to the blade diameter D is called the pitch ratio H / D.

[0038] For details, please refer to Figure 3The stirring device of the present invention is used in an ultrafine mill, specifically installed within the mill's barrel 7. It primarily comprises a main shaft 3 and a blade assembly secured thereto. In the present invention, the blade assembly is divided into an upper blade assembly and a lower blade assembly. Accordingly, the ultrafine mill chamber is divided into an upper fine grinding chamber 13 and a lower coarse grinding chamber 12.

[0039] The main shaft 3 passes through the coarse grinding chamber 12 and the fine grinding chamber 13 , and the lower blade group is located in the lower coarse grinding chamber 12 , while the upper blade group is located in the upper fine grinding chamber 13 .

[0040] For ease of description, the present invention names the blades of the upper blade group as upper blades 6, and the blades of the lower blade group as lower blades 8, that is, the upper blade group consists of several layers of upper blades 6 with inclined angles; the lower blade group consists of several layers of lower blades 8 with inclined angles.

[0041] The upper and lower blades of the present invention have different aspect ratios and outer diameters. The aspect ratio of the upper blade 6 is smaller than that of the lower blade 8, meaning the lower blade 8 has a smaller diameter and a larger aspect ratio, while the upper blade 6 has a larger diameter and a smaller aspect ratio.

[0042] In this invention, the main shaft 3 is connected to the motor reducer 1. The motor reducer 1 drives the main shaft 3 to rotate at high speed, forcing the media balls and material to perform multi-dimensional circular rotation within the cylinder. The mineral particles are effectively ground by the high-speed impact and collision of the grinding media. The entire stirring device is fixed to the upper and lower ends of the mill using bearings 2, which prevents vibration caused by high-speed rotation.

[0043] This structure allows the coarse particles in the feed, which has a wide particle size distribution, to be distributed in the lower coarse grinding chamber 12. The lower blade group's larger aspect ratio ensures sufficient lifting force, preventing settling of the grinding media and coarse mineral particles. The small diameter ensures effective coarse grinding while reducing power consumption. After being ground, the coarse particles enter the upper fine grinding chamber 13 along with the fine particles in the feed. The upper blade group's smaller aspect ratio reduces the lifting force, preventing mineral particles from being directly flushed out of the mill and causing short circuits. The large diameter provides sufficient grinding energy density, increasing the probability of impact collisions, thereby achieving ultrafine grinding of fine mineral particles, grinding the minerals to the micron level.

[0044] In one embodiment of the present invention, the coarse grinding chamber 12 and the fine grinding chamber 13 are separated by a partition plate. Obviously, the spindle 3 should pass through this partition plate, and the partition plate should have a gap or hole for the coarsely ground material to pass through. For example, the cross-sectional shape of this partition plate is the same as that of the ultrafine grinder's barrel 7, with its outer edge connected to the inner wall of the barrel 7. A gap for the coarsely ground material to pass through is formed between the outer wall of the spindle 3 and the inner wall of the central hole of the partition plate.

[0045] In one embodiment of the present invention, the upper blade group and / or the lower blade group, a single layer should have at least two blades. The blades of the present invention adopt a paddle-type structure with a certain inclination angle, that is, a single blade is a fan-shaped structure with a certain angle. On a certain layer, the blades are evenly distributed along the circumference and fixed on the main shaft 3.

[0046] In this embodiment, the blades with an inclined angle not only lift the grinding media to prevent them from settling, but also enable the grinding media to rotate at a high speed and collide with the mineral particles to produce a grinding effect.

[0047] refer to Figure 4 and Figure 5 In order to improve energy efficiency, in one embodiment of the present invention, the following preferred parameters are provided:

[0048] The aspect ratio of the lower blade 8 is 1 to 1.5 times that of the upper blade 6 . The aspect ratio of the upper blade 6 preferably ranges from 0.05 to 1.

[0049] The diameter D1 of the lower blade 8 is 0.5 to 1 times the diameter D2 of the upper blade 6 , and the diameter D2 of the upper blade 6 is 0.5 to 0.95 times the inner diameter of the ultrafine grinder barrel 7 .

[0050] The pitch ratio H / D (the distance between the blades divided by the outer diameter of the blades) of the upper blades 6 is 0.2 to 2, and the pitch ratio H / D of the lower blades 8 is 0.5 to 1 times the pitch ratio of the upper blades 6.

[0051] This achieves:

[0052] The outer end linear velocity of the upper blade 6 is 5 to 50 m / s, and the outer end linear velocity of the lower blade 8 is 0.5 to 1 times that of the upper blade 6. At this speed, the coarse particles in the slurry can be forced to pass through the high linear velocity area between the main shaft 3 and the cylinder 7, thereby improving the grinding efficiency and energy density.

[0053] The above parameters can be selected based on actual mineral characteristics experiments and can be used in combination.

[0054] In one embodiment of the present invention, the ultrafine grinder further comprises the following structure:

[0055] There is a feeding chamber 11 below the coarse grinding chamber 12, and the coarse grinding chamber 12 and the feeding chamber 11 are separated by a sieve plate 9. There is a grading chamber 14 above the fine grinding chamber 13, and a fixed plate 5 is arranged between the fine grinding chamber 13 and the grading chamber 14. The main shaft 3 passes through the fixed plate 5, and there is a gap between the outer edge of the fixed plate 5 and the cylinder of the ultrafine grinder for the material to pass through after fine grinding.

[0056] In this embodiment, the classification chamber 14 is a conical structure, and the upper portion thereof is the discharge port 4 .

[0057] The following combination Figure 3-Figure 5, the present invention is further described:

[0058] Reference Figure 3-Figure 5 As shown, the prepared slurry enters the feed chamber 11 from the feed pipe 10, passes through the screen plate 9, and enters the coarse grinding chamber 12. It is stirred by the lower paddle 8 for coarse grinding. Here, the paddle height L1 is large, the diameter D1 is small, and the aspect ratio (L1 / D1) is large. The coarse particles in the material are ground down and, along with the fine particles, pass through the gap between the main shaft 3 and the interlayer partition plate and enter the fine grinding chamber 13. Stirred by the upper paddle 6, they collide and grind with the fine balls in the fine grinding chamber for fine grinding. Here, the paddle height L2 is small, the diameter D1 is large, and the aspect ratio (L2 / D2) is small. After fine grinding, the material passes through the gap between the fixed plate 5 and the cylinder 7 and enters the grading chamber 14 for grading. The fine-grade material overflows from the top into the discharge port 4, while the coarse particles return to the fine grinding chamber 13.

[0059] refer to Figure 6 , through the fluid mechanics simulation of three different types of stirring devices, we can see:

[0060] In the spiral stirring device, the particles are mostly distributed in the upper part and less in the lower part, resulting in low grinding space utilization;

[0061] In the disc-type agitator, most particles are distributed in the lower part, with fewer particles distributed in the upper part, resulting in low grinding space utilization.

[0062] The paddle-type stirring device of the present invention has more uniform particle distribution and higher grinding space utilization rate.

[0063] Therefore, through the above measures, the present invention reduces manufacturing difficulty and equipment investment, achieves efficient grinding of minerals, and achieves product particle sizes of up to 1-2 microns, laying the foundation for further efficient processing of difficult-to-smelt minerals. The stirring device has many advantages, including a simple structure and good adaptability; uniform distribution of the media within the mill; and low energy consumption.

[0064] In a specific experimental case of the present invention, gold concentrate from a mine in Gansu was processed, and its particle size D90 (particle size when the screening rate is 90% by mass) was measured by a BT9300HT laser particle size analyzer to be 85 μm. The detailed particle size composition is shown in the following table:

[0065]

[0066] Three L-400 vertical mills with identical specifications and structures were constructed, each equipped with a spiral agitator, a disc agitator, and the multi-paddle agitator of the present invention. The gold concentrate was subjected to open-circuit grinding for three hours under the same grinding media and filling ratio conditions for comparison. Fineness was measured using a BT9300HT laser particle size analyzer. Power consumption was calculated using the real-time power display on the frequency converter. The specific conditions were as follows:

[0067] Step 1, grinding: first add water to 3 tons of raw materials to make a slurry with a solid-liquid mass ratio of 1:1; Steps 2, 3, and 4 are 1.31m each. 3 (Dry ore volume 1t)

[0068] Step 2: Use spiral stirring ultrafine grinding machine L400-L, feed rate 0.3m 3 / h (0.23t / h), motor frequency 30Hz. During operation, the motor current was overloaded, so the speed could not be increased. Open circuit grinding was carried out for 3 hours, and samples were taken every 30 minutes for fineness analysis.

[0069] Step 3: Use the paddle-type stirring ultrafine grinding mill L400-J of the present invention, with a feed rate of 0.3m 3 / h (0.23t / h), motor frequency 30Hz, grinding and sampling conditions are the same as above.

[0070] Step 5: Use the paddle-type stirring ultrafine grinding mill L400-J of the present invention, with a feed rate of 0.3m 3 / h (0.23t / h), motor frequency 50Hz, open circuit grinding for 3 hours, sampling every 30 minutes for fineness analysis.

[0071] Step 5: Use the disc-type stirring ultrafine grinding machine L400-P with a feed rate of 0.3m 3 / h (0.23t / h), motor frequency 50Hz, grinding and sampling conditions are the same as above.

[0072] The comparison of the three devices is shown in the table below:

[0073]

[0074] Experimental results show that the multi-layer paddle-type stirring device of the present invention is much better than the existing spiral and disc-type stirring devices in grinding effect, and its unit power consumption is also greatly reduced under the same fineness.

Claims

1. An ultrafine grinding mill stirring device, characterized in that: It comprises a main shaft (3) and an upper blade group and a lower blade group fixed on the main shaft (3); The main shaft (3) passes through the coarse grinding chamber (12) and the fine grinding chamber (13) of the ultrafine grinder; the lower blade group is located in the coarse grinding chamber (12), and the upper blade group is located in the fine grinding chamber (13); The upper blade group is composed of several layers of upper blades (6) with inclined angles; the lower blade group is composed of several layers of lower blades (8) with inclined angles; the upper blades (6) and the lower blades (8) lift the grinding medium to prevent it from sedimentation, and on the other hand, enable the grinding medium to rotate at high speed and collide with the mineral particles to produce a grinding effect; The height-to-diameter ratio of the upper blade (6) is smaller than the height-to-diameter ratio of the lower blade (8); the height-to-diameter ratio refers to the ratio L / D of the height L to the diameter D of a single-layer blade; The upper blade (6) adopts a structural form with a small aspect ratio and a large diameter, and the lower blade (8) adopts a structural form with a large aspect ratio and a small diameter. The aspect ratio of the upper blade (6) ranges from 0.05 to 1, the aspect ratio of the lower blade (8) is 1 to 1.5 times the aspect ratio of the upper blade (6), and the diameter D1 of the lower blade (8) is 0.5 to 1 times the diameter D2 of the upper blade (6).

2. The ultrafine grinding mill stirring device according to claim 1, characterized in that: The coarse grinding chamber (12) and the fine grinding chamber (13) are separated by a layer partition plate, the main shaft (3) passes through the layer partition plate, and there is a gap between the two for the coarsely ground material to pass through.

3. The ultrafine grinding mill stirring device according to claim 1, characterized in that: The upper blade group and / or the lower blade group have at least two blades in a single layer. The blades are fan-shaped with a certain angle, evenly distributed along the circumference, and fixed on the main shaft (3).

4. The ultrafine grinding mill stirring device according to claim 1, characterized in that: The diameter D2 of the upper blade (6) is 0.5 to 0.95 times the inner diameter of the ultrafine grinding mill cylinder.

5. The ultrafine grinding mill stirring device according to claim 4, characterized in that: The pitch ratio H / D of the upper blade (6) is 0.2 to 2, and the pitch ratio H / D of the lower blade (8) is 0.5 to 1 times the pitch ratio of the upper blade (6).

6. The ultrafine grinding mill stirring device according to claim 1, characterized in that: The outer end linear speed of the upper blade (6) is 5 to 50 m / s, and the outer end linear speed of the lower blade (8) is 0.5 to 1 times that of the upper blade (6).

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