Particle group repose angle measuring device and particle group repose angle measuring method

Abstract

The present application discloses a method for measuring the angle of repose of a particle group, and belongs to the field of measuring equipment. In view of the problem in the prior art that "the angle of repose measured by different researchers has no repeatability and comparability", in the technical solution of the present application, the inner bed and the outer bed are both cylindrical, the inner bed is sleeved in the outer bed, and the outer wall of the inner bed and the inner wall of the outer bed are spaced apart; the cylindrical upper end of the inner bed is located in the outer bed, and the gap between the cylindrical lower end of the inner bed and the cylindrical lower end of the outer bed is closed; the lower section of the side wall of the outer bed has a closable discharge orifice; the air distribution and mixing device is located at the lower end of the inner bed and the outer bed; the air distribution and mixing device has an exhaust port and the exhaust port opens toward the lower end of the inner bed. The advantages of the present application are: simple equipment and low investment; the method is easy to standardize and has good repeatability; the angle of repose is given a unique and definite value, which makes it have good comparability and can promote the research and development of particle technology.

Description

Technical Field

[0001] The invention relates to a particle group repose angle measuring device and a particle group repose angle measuring method, belonging to the field of measuring equipment. Background Art

[0002] In the chemical and energy industries, people often have to deal with gas-solid heterogeneous reactions (reactions between gases and solids). Such reactions usually consist of five steps in series: external and internal diffusion of the reaction gas, intrinsic chemical reaction, internal and external diffusion of the product gas. In order to reduce the resistance of the internal diffusion step and speed up the macroscopic reaction rate, the solid is usually crushed or prepared into small particles. It can be said that the vast majority of gas-solid heterogeneous reactions are presented in the form of reactions between gas and particle groups. There is no doubt that the physical properties of the particle group have an important influence on the design and operation of the reactor (fixed bed, moving bed and fluidized bed). Therefore, how to accurately and reliably measure these physical parameters is a very critical issue.

[0003] Among the many physical properties of particle groups, one of the most basic parameters is the angle of repose, also known as the angle of repose. It is often used to quantitatively characterize the flow properties of particle groups: the smaller the angle of repose, the better the flowability of the particles. It is generally believed that when the angle of repose is less than 30°, the particle group has good flowability; when the angle of repose is between 30° and 45°, the particle group has a certain viscosity and the flowability becomes poor; when the angle of repose is between 45° and 55°, the particle group has a high viscosity and the flowability is very poor; when the angle of repose exceeds 55°, the particle group becomes almost non-flowable, but moves as a whole (behaving like a rigid body).

[0004] At present, many types of repose angles have been reported in the literature, mainly including the repose angle on the infinite plane ( Figure 1 a) Angle of repose on a finite plane ( Figure 1 b) Tilt / slide repose angle ( Figure 1 c) and the rotation / roll repose angle ( Figure 1 d) The angle of repose to be measured in the present invention is Figure 1The angle of repose on the finite plane shown in b. There are two commonly used methods for measuring the angle of repose. The first one is as shown in Chinese invention patent CN202020157231.4. First, pour the particles into the funnel, then place the funnel at a certain height directly above the finite plane, and then the particles flow out from the bottom of the funnel to form a cone pile on the plane. When the cone pile grows to the point where the top just touches the funnel outlet and the particles stop flowing out, the angle between the measured cone surface and the horizontal plane is regarded as the angle of repose of the particle group. The second one is as shown in utility model CN201820813133.4. First, pour the particles into the funnel, then place the funnel at the center of the finite plane, and then slowly raise the funnel to form a cone pile on the plane. The angle between the measured cone surface and the horizontal plane is regarded as the angle of repose of the particle group. The significant disadvantage of these two measurement methods is that the repeatability is poor, resulting in incomparability between the measurement results of different researchers. There is great randomness and uncertainty in both the accumulation state of the particle group in the funnel and the impact of the particle group flowing out of the funnel on the formed cone pile.

[0005] In the prior art, there is still no method that can make the repose angles measured by different researchers have good repeatability and comparability, which has an adverse effect on the design and operation of various reactors and storage containers. Summary of the invention

[0006] In view of the problems existing in the prior art, a particle group repose angle measurement device and a particle group repose angle measurement method are proposed.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is a particle group repose angle measuring device, comprising a particle group containing device and an air distribution mixing device, wherein the particle group containing device has holes for particles to flow out;

[0008] The particle group containing device comprises an inner bed and an outer bed; the inner bed and the outer bed are both cylindrical, the inner bed is sleeved in the outer bed, and the outer wall of the inner bed is spaced apart from the inner wall of the outer bed;

[0009] The cylindrical upper end of the inner bed is located inside the outer bed, and the gap between the cylindrical lower end of the inner bed and the cylindrical lower end of the outer bed is closed; the lower section of the side wall of the outer bed has a closable discharge opening;

[0010] The air distribution and mixing device is located at the lower ends of the inner bed and the outer bed; the air distribution and mixing device has an air outlet and the air outlet opens toward the lower end of the inner bed.

[0011] Optimized, the above-mentioned particle group repose angle measuring device, the air distribution and mixing device includes an air chamber, the air chamber has an internal cavity, the air chamber is installed under the inner bed, and the internal cavity of the air chamber is connected to the lower end opening of the inner bed.

[0012] Optimally, the above-mentioned particle group repose angle measuring device has an air distribution port at the upper end of the wind chamber, the air distribution port is connected to the internal cavity of the wind chamber, and a gas distribution plate is provided between the air distribution port and the lower end opening of the inner bed.

[0013] Optimized, in the above-mentioned particle group repose angle measuring device, the gas distribution plate is formed by sintering multiple layers of stainless steel mesh, and the mesh holes of the gas distribution plate are connected to the inner cavity of the inner bed and the wind chamber.

[0014] Optimized, the above-mentioned particle group repose angle measuring device has an opening at the lower end of the wind chamber and an air intake plate is attached to the lower end of the wind chamber; the air intake plate has an air intake hole, the air intake hole of the air intake plate is matched with the lower end opening of the wind chamber, and the air intake hole of the air intake plate is opposite to the lower end opening of the inner bed.

[0015] Optimally, in the above-mentioned particle group repose angle measuring device, the inner bed and the outer bed are coaxially arranged; the upper end of the inner bed is chamfered internally; and a soft plug is provided in the discharge opening of the outer bed.

[0016] Optimally, in the above-mentioned particle group repose angle measuring device, the aperture of the gas distribution plate is smaller than the particle size of the particle group to be measured.

[0017] The particle group repose angle measurement method based on the particle group repose angle measurement device comprises the following steps:

[0018] 1) Pour the particles to be tested into the outer bed, with the surface of the particles to be tested higher than the upper edge of the inner bed; introduce fluidizing gas through the air distribution mixing device to mix the particles evenly;

[0019] 2) Slowly reduce the gas velocity to zero, and slowly discharge the particles from the lower side of the outer bed. The remaining particles form a cone pile at the upper end of the inner bed, and measure the angle β between the cone surface and the horizontal plane;

[0020] 3) The system changes the gas velocity reduction rate α; repeat step 2), draw a curve of β decreasing with α, and read the minimum value of β as the repose angle of the particle group.

[0021] Optimized, the above-mentioned method for measuring the angle of repose of the particle group is as follows: in step 1), when the fluidizing gas is introduced through the air distribution mixing device, the superficial gas velocity in the outer bed is maintained at 3 to 6 times the minimum fluidization velocity of the particle group, and fluidization is performed for a period of time to allow the particle group to be evenly mixed.

[0022] The beneficial effects of this application are:

[0023] The equipment is simple and the investment is small; the method is easy to standardize and has good repeatability; the angle of repose is given a unique and definite value, making it highly comparable and promoting the research and development of particle technology.

[0024] The technical solution of the present application proposes to obtain the accumulation state of the particle group before discharge by slowly reducing the gas velocity to zero, which can significantly reduce the influence of the wedge effect. It also proposes to obtain a cone pile for measuring the repose angle by discharge, which has good repeatability.

[0025] The method of the present application proposes to obtain the systematic evolution of the cone pile geometry by systematically changing the value of α, and select the minimum value from a series of measured values ​​of β as the angle of repose of the particle group to be measured, which can give the angle of repose a unique and definite numerical value, thereby making the measurement results of different researchers highly comparable. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The definitions of the four angles of repose and their measurement methods;

[0027] Figure 2 This is a schematic diagram of the structure of the particle group repose angle measurement device of the present application;

[0028] Figure 3 This is a schematic diagram of the accumulation state of particle groups after discharge;

[0029] Figure 4 is the particle size distribution curve of the particle group to be tested;

[0030] Figure 5 This is the variation curve of β as α decreases. DETAILED DESCRIPTION

[0031] The present application provides a particle group repose angle measuring device, wherein the middle opening of the air inlet plate 1 is used as a gas inlet, which is connected to the lower end of the wind chamber 2. The upper end of the wind chamber 2 is connected to the lower side of the gas distribution plate 3, which allows the gas to enter the inner bed 5 evenly to avoid channel flow and bias flow, and on the other hand, bears the weight of the particle group in the inner bed 5 to prevent the particle group from leaking into the wind chamber 2.

[0032] The upper side of the gas distribution plate 3 is connected to the lower end of the inner bed 5, and the lower end of the inner bed 5 is also connected to the lower end of the outer bed 6. A discharge hole is provided at the lower part of the outer bed 6 and is sealed by a soft plug 4. The outer bed 6 is sleeved outside the inner bed 5, and the height of the outer bed 6 is significantly greater than that of the inner bed 5.

[0033] Specifically, the inner bed 5 and the outer bed 6 are both cylindrical, the inner bed 5 is sleeved in the outer bed 6, and the outer wall of the inner bed 5 is spaced apart from the inner wall of the outer bed 6, and the inner bed 5 and the outer bed 6 are coaxially arranged. The cylindrical upper end of the inner bed 5 is located in the outer bed 6, the height of the outer bed 6 is significantly greater than that of the inner bed 5, the gap between the cylindrical lower end of the inner bed 5 and the cylindrical lower end of the outer bed 6 is closed, and the lower section of the side wall of the outer bed 6 has a closable discharge opening. The upper end of the inner bed 5 is chamfered, and the discharge opening of the outer bed 6 has a soft plug 4.

[0034] The air distribution and mixing device is located at the lower ends of the inner bed 5 and the outer bed 6, and has an exhaust port, and the exhaust port opens toward the lower end of the inner bed 5. The air distribution and mixing device includes an air chamber 2, and the air chamber 2 has an internal cavity. The air chamber 2 is installed below the inner bed 5, and the internal cavity of the air chamber 2 is connected to the lower end opening of the inner bed 5.

[0035] The upper end of the wind chamber 2 is provided with an air distribution port, which is communicated with the internal cavity of the wind chamber 2 , and a gas distribution plate 3 is provided between the air distribution port and the lower end opening of the inner bed 5 .

[0036] In this embodiment, the gas distribution plate 3 is formed by sintering multiple layers of stainless steel mesh, the mesh holes of the gas distribution plate 3 are connected to the inner bed 5 and the internal cavity of the wind chamber 2, and the aperture of the gas distribution plate 3 is smaller than the particle size of the particle group to be measured. The gas distribution plate 3 can make the gas enter the inner bed 5 evenly on the one hand, and prevent the material in the inner bed 5 from falling into the wind chamber 2 on the other hand.

[0037] The gas distribution plate 3 may also be in other forms, such as being formed by stacking multiple layers of non-woven fabric or using a polymer plate with fine through holes.

[0038] The lower end of the air chamber 2 has an opening and an air intake plate 1 is attached to the lower end of the air chamber 2. The air intake plate 1 has an air intake hole. The air intake hole of the air intake plate 1 is matched with the lower end opening of the air chamber 2, and the air intake hole of the air intake plate 1 is opposite to the lower end opening of the inner bed 5.

[0039] For a given particle, the particle group repose angle measurement method of this embodiment is as follows:

[0040] 1) Use a soft plug 4 to block the discharge opening at the bottom of the outer bed 6;

[0041] 2) Pour the particles to be tested into the outer bed 6 until the material surface is above the upper edge of the inner bed 5 by a certain distance;

[0042] 3) Fluidizing gas enters the wind chamber 2 through the air inlet plate 1, and then enters the inner bed 5 and the outer bed 6;

[0043] 4) maintaining the superficial gas velocity in the outer bed 6 at 3 to 6 times the minimum fluidization velocity of the particle group, and fluidizing for a period of time to make the particle group evenly mixed and eliminate the particle size difference classification;

[0044] 5) Slowly reduce the gas velocity to zero, and the rate of reduction of the gas velocity is represented by α;

[0045] VI) Pull out the soft plug 4, and the particle group slowly flows out of the outer bed 6 from the discharge orifice 4 until it stops flowing out, and obtain Figure 3 The particle group stacking state shown;

[0046] 7) Measure the height of the cone pile formed at the upper end of the inner bed 5, and calculate the angle β in combination with the outer diameter of the inner bed 5;

[0047] 8) The system changes the value of α and repeats steps 5) to 7);

[0048] IX) Draw the curve of β changing with α, such as Figure 5 As shown, the minimum value of β is read as the repose angle of the particle group to be measured.

[0049] For sand-I and sand-II, their particle size distribution is as follows Figure 4 As shown. Figure 5 As shown in Fig. 5a and Fig. 5b, as α decreases, β decreases first and then remains unchanged. The final constant value (also the minimum value) is selected as the repose angle of the particle group. When α is small, β is large because the bed collapses quickly. There is a certain wedge effect in the particle group obtained after the collapse, which increases the internal friction between the particles, and the particles can be piled up to form a sharper cone pile.

[0050] For an equal volume mixture of sand-I and sand-II, such as Figure 5 As shown in c, as α decreases, β first decreases, then gradually increases, and finally remains unchanged. The minimum value is selected as the repose angle of the particle group.

[0051] The reasons for this choice are as follows: 1. The initial decrease of β can be attributed to the occurrence of the wedge effect; 2. The subsequent gradual increase of β can be attributed to the occurrence and progression of particle size difference classification. As the gas velocity gradually decreases, large particles and small particles tend to be classified strongly, with large particles depositing at the bottom of the bed and small particles enriching at the top of the bed. When α>0.02m / s2, there is not enough time for this classification to occur, and the two types of particles in the resulting slump bed maintain a good mixture. When α<0.02m / s2, this classification begins to occur and becomes more and more significant as α decreases. 3. When α<0.002m / s2, this classification reaches its maximum and no longer changes further with the decrease of α, so β ​​remains unchanged. In short, when α<0.02m / s2, the measured β cannot represent the repose angle of the original particle group, but the repose angle corresponding to the finer components. In order to obtain the repose angle of the original particle group, α needs to be greater than 0.02m / s2. Within this range, the smaller the error bar, the better the measurement repeatability, so we selected the minimum value in the curve, where the error bar is the smallest.

[0052] Finally, for Sand-I or Sand-II, the large and small particles also tend to be classified during the process of reducing the gas velocity. However, due to the limited particle size distribution of the two sands themselves, even if the maximum degree of classification occurs, there will not be much deviation between the average particle size of the sand in the upper part of the bed and the average particle size of the sand in the whole bed, and there is no room for much change in the repose angle, so in Figure 5In 5a and 5b, except for the initial decrease due to the wedging effect, β hardly changes with the decrease of α.

[0053] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A particle group repose angle measuring device, comprising a particle group containing device, the particle group containing device having holes for particles to flow out, characterized in that: It also includes an air distribution and mixing device; The particle group containing device comprises an inner bed (5) and an outer bed (6); the inner bed (5) and the outer bed (6) are both cylindrical, the inner bed (5) is sleeved in the outer bed (6), and the outer wall of the inner bed (5) and the inner wall of the outer bed (6) are spaced apart; The cylindrical upper end of the inner bed (5) is located inside the outer bed (6), and the gap between the cylindrical lower end of the inner bed (5) and the cylindrical lower end of the outer bed (6) is closed; the lower section of the side wall of the outer bed (6) has a closable discharge opening; The air distribution and mixing device is located at the lower ends of the inner bed (5) and the outer bed (6); the air distribution and mixing device has an air outlet and the air outlet opens toward the lower end of the inner bed (5).

2. The particle group repose angle measuring device according to claim 1, characterized in that: The air distribution and mixing device comprises an air chamber (2), the air chamber (2) having an internal cavity, the air chamber (2) being installed below the inner bed (5), and the internal cavity of the air chamber (2) being communicated with the lower end opening of the inner bed (5).

3. The particle group repose angle measuring device according to claim 2, characterized in that: The upper end of the wind chamber (2) is provided with an air distribution port, which is in communication with the internal cavity of the wind chamber (2), and a gas distribution plate (3) is provided between the air distribution port and the lower end opening of the inner bed (5).

4. The particle group repose angle measuring device according to claim 3, characterized in that: The gas distribution plate (3) is formed by sintering multiple layers of stainless steel mesh, and the mesh holes of the gas distribution plate (3) are connected to the inner bed (5) and the internal cavity of the wind chamber (2).

5. The particle group repose angle measuring device according to claim 3, characterized in that: The lower end of the wind chamber (2) has an opening and the lower end of the wind chamber (2) is attached to an air intake plate (1); the air intake plate (1) has an air intake hole, the air intake hole of the air intake plate (1) is arranged in coordination with the lower end opening of the wind chamber (2), and the air intake hole of the air intake plate (1) is directly opposite to the lower end opening of the inner bed (5).

6. The particle group repose angle measuring device according to claim 1, characterized in that: The inner bed (5) and the outer bed (6) are coaxially arranged; the upper end of the inner bed (5) is chamfered; and a soft plug (4) is provided in the discharge opening of the outer bed (6).

7. The particle group repose angle measuring device according to claim 3, characterized in that: The aperture of the gas distribution plate (3) is smaller than the particle size of the particle group to be measured.

8. A method for measuring the angle of repose of a particle group based on the device for measuring the angle of repose of a particle group according to any one of claims 1 to 6, characterized in that: The following steps are involved: 1) Pour the particles to be tested into the outer bed (6), with the material surface of the particles to be tested being higher than the upper edge of the inner bed (5); introduce fluidizing gas through the air distribution mixing device to mix the particles evenly; 2) Slowly reduce the gas velocity to zero, and slowly discharge the particles from the lower side of the outer bed (6). The remaining particles form a cone pile at the upper end of the inner bed (5), and measure the angle β between the cone surface and the horizontal plane; 3) The system changes the gas velocity reduction rate α; repeat step 2), draw a curve of β decreasing with α, and read the minimum value of β as the repose angle of the particle group.

9. The method for measuring the angle of repose of a particle group according to claim 8, characterized in that: In step 1), when the fluidizing gas is introduced through the air distribution and mixing device, the superficial gas velocity in the outer bed (6) is maintained at 3 to 6 times the minimum fluidization velocity of the particle group, and fluidization is performed for a period of time to allow the particle group to be evenly mixed.

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