Particle size grading quantitative characterization method and efficient grading device for powder material with wide particle size range

Abstract

According to the particle size grading quantitative characterization method, particle size grading quantitative characterization is achieved, particle size distribution range characterization is added on the basis of the actually measured volume average diameter, and scientificity and reasonability of the material particle size requirement are improved; the high-efficiency grading device for the powder material with the wide particle size range is designed by taking steepness as a technical index, so that the particle size consistency of the powder material in the initiating explosive material preparation process is greatly improved, the performance reliability of a finished product agent is favorably improved, flying dust is not generated, manpower is thoroughly liberated, the labor intensity is reduced, and the production efficiency is improved. The harm of arm swelling, palm blistering and the like of workers in operation is avoided, and the occupational environment safety threat of the workers is relieved.

Description

Technical Field

[0001] The invention belongs to the technical field of pyrotechnic agent preparation, and relates to a particle size classification quantitative characterization method and a high-efficiency classification device for powder materials with a wide particle size range. Background Art

[0002] In the manufacture of explosives, in order to meet the performance requirements of the agent itself, it is often necessary to strictly control the particle size of pharmaceutical raw materials. For example, in the preparation of B / KNO3 agent, the average particle size of KNO3 is controlled to be below 10μm. The original particle size of KNO3 is about 130μm, and it is easy to absorb moisture and agglomerate. Therefore, KNO3 needs to be crushed and screened to make the average particle size of KNO3 after treatment below 10μm, and the more concentrated the particle size, the better.

[0003] In statistics, when comparing the concentration of multiple groups of data, the coefficient of variation is usually used for comparison (coefficient of variation = standard deviation / mean). Because the dimensional scale of each group of data may be different, the concentration of the data cannot be compared directly by comparing the standard deviation. Instead, the influence of the dimensional scale must be eliminated and the result of dividing the standard deviation by the mean is used for comparison.

[0004] The concentration of particle size distribution is a relative concept and has no standard. The particle size test results cannot provide the standard deviation of the particle size, only data such as D10 (10% boundary particle size), D50 (50% median particle size), D90 (90% boundary particle size), and average particle size. For raw materials with the same median particle size, "D90-D10" can be used to indicate the width of the particle size distribution range. However, the median particle size of each group of raw materials is usually different, so "D90-D10" cannot be directly compared, and the influence of particle size scale should be eliminated.

[0005] The traditional treatment method is to first use a jet mill to deagglomerate and grind KNO3, and then sieve the ground KNO3 powder. During screening, the particle size range is required to be narrow, and multiple adjustments and screenings are required, which is time-consuming and has a low yield.

[0006] Traditional screening methods include oscillating screening and forced screening. In oscillating screening, the screen is extremely fine because it is necessary to obtain finer KNO3. However, after a period of screening, the fine powder will clog the screen, making it impossible to continue screening. Therefore, the screening efficiency is extremely low, about 500g / h.

[0007] When forced screening, a certain external force is applied to the material during screening. During screening, some agglomerated materials may be dispersed through screening, and particles with a particle size slightly larger than the sieve holes may be forced to be screened and become undersize.

[0008] Therefore, it is necessary to determine a quantitative characterization method for particle size classification and an efficient classification device for powder materials with a wide particle size range to achieve quantitative particle size concentration distribution and rapid crushing and classification of materials with a wide particle size range. Summary of the invention

[0009] The technical problem solved by the present invention is to overcome the deficiencies of the prior art and to propose a particle size classification quantitative characterization method and a high-efficiency classification device for powder materials with a wide particle size range.

[0010] The solution of the present invention is:

[0011] A quantitative characterization method for particle size classification, using steepness S = D 50 / (D 90 -D 10 ), characterizes the concentration of the particle size distribution curve. The greater the steepness, the more concentrated the particle size distribution and the steeper the particle size distribution curve. D10 is the 10% boundary particle size, D50 is the 50% median particle size, and D90 is the 90% boundary particle size.

[0012] Preferably, it includes an automatic feeding mechanism, an automatic crushing mechanism, an automatic grading mechanism, and a collection system;

[0013] Automatic feeding mechanism: the powder raw materials to be processed are added into the automatic crushing mechanism by vibration;

[0014] Automatic crushing mechanism: Use supersonic airflow to collide, shear and rub the raw materials, and finally crush the raw materials. The crushed raw materials reach the automatic grading mechanism with the rising airflow;

[0015] Automatic grading mechanism: Classify fine materials that meet the steepness requirements to the collection system;

[0016] Collection system: used to hold the collected materials.

[0017] Preferably, the automatic feeding mechanism comprises a hopper, a hopper cover, an L-shaped pipe and a motor;

[0018] The hopper is a conical structure and is installed on the platform. The hopper cover is used to cover the hopper. The small end opening of the hopper is connected to one end of an L-shaped pipe. The other end of the L-shaped pipe passes through the platform table and is connected to the material inlet of the automatic crushing mechanism. The motor output end contacts the outer wall of the L-shaped pipe.

[0019] Preferably, the automatic crushing mechanism comprises an air compressor, a first pipeline, a crushing chamber, a nozzle, and a compression chamber;

[0020] The lower end of the first pipeline is connected to the upper end of the crushing chamber, the upper end outlet of the first pipeline is connected to the automatic grading mechanism, and the side wall of the first pipeline is provided with a material inlet for connecting to the automatic feeding mechanism; the crushing chamber and the compression chamber are both columnar structures, and the crushing chamber and the compression chamber are not connected; the air compressor is connected to the compression chamber through a pipeline, and a gas flow regulating valve is arranged on the pipeline, and four nozzles are evenly distributed around the compression chamber, and the lower end of each nozzle is connected to the compression chamber, and the upper end is connected to the crushing chamber.

[0021] Preferably, the automatic grading mechanism comprises a second pipeline and a grading cylinder;

[0022] One end of the second pipeline is connected to the outlet of the automatic crushing mechanism, and the other end is connected to the classifying cylinder. A classifying impeller is arranged inside the classifying cylinder. The rotation frequency of the classifying impeller is adjusted by the classifying impeller stepless speed regulator so that the fine materials meeting the steepness requirements can be classified into the collection system.

[0023] Preferably, the grading cylinder is an integrally designed two-section structure, the upper portion is a hollow columnar structure, the lower portion is an inverted hollow conical structure, and the small end of the conical structure is the outlet end of the grading cylinder.

[0024] Preferably, the collecting system comprises a buckle and a collector; the collector is fixed to the outlet end of the grading cylinder by the buckle and is used for containing the collected materials.

[0025] Preferably, the collector can be removed by opening the buckle and the collected raw material fine powder can be poured out.

[0026] The beneficial effects of the present invention compared with the prior art are:

[0027] (1) The present invention proposes a quantitative characterization method for particle size classification: steepness S = D 50 / (D 90 -D 10 ), achieved the quantitative characterization of particle size classification, and increased the scientificity and rationality of material particle size requirements by adding particle size distribution range characterization on the basis of the measured volume average diameter;

[0028] (2) The present invention uses the steepness S = D 50 / (D 90 -D 10) as a technical indicator, a high-efficiency grading device for powder materials with a wide particle size range is designed, which greatly improves the consistency of powder material particle size in the process of pyrotechnics preparation, which is beneficial to the improvement of the performance reliability of finished medicines. The characterization method can be continuously extended to other applicable analytical indicators and industries, and has a good prospect. The device is equipped with an air flow control valve and a grading impeller stepless speed regulator, which can adjust the product particle size without stopping the machine, avoiding the problems of traditional crushing + screening, such as narrow particle size range requirements, multiple adjustments and screenings, long time consumption, and low yield. Human-machine isolation is achieved during the operation process, which solves the problems of high physical requirements, high labor intensity, and low labor efficiency of traditional grading methods; the operation process can reduce dust flying through system negative pressure control, which is beneficial to protecting occupational environmental health. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the device of the present invention;

[0030] Figure 2 This is a schematic diagram of the automatic crushing mechanism of the present invention;

[0031] Figure 3 This is the particle size distribution diagram of raw materials. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings.

[0033] The original particle size range of the raw materials of pyrotechnic agents is relatively wide, that is, the particle size span is large, generally ranging from microns to hundreds of microns. For example, the original particle size of a batch of tungsten powder ranges from 0.4μm to 205μm. Figure 1 shown.

[0034] In statistics, when comparing the concentration of multiple groups of data, the coefficient of variation is usually used for comparison (coefficient of variation = standard deviation / mean). Because the dimensional scale of each group of data may be different, the concentration of the data cannot be compared directly by comparing the standard deviation. Instead, the influence of the dimensional scale must be eliminated and the result of dividing the standard deviation by the mean is used for comparison.

[0035] The concentration of particle size distribution is a relative concept and has no standard. The particle size test results cannot provide the standard deviation of the particle size, only data such as D10 (10% boundary particle size), D50 (50% median particle size), D90 (90% boundary particle size), and average particle size. For raw materials with the same median particle size, "D90-D10" can be used to indicate the width of the particle size distribution range. However, the median particle size of each group of raw materials is usually different, so "D90-D10" cannot be directly compared, and the influence of particle size scale should be eliminated. Therefore, the present invention proposes to use the steepness S=D 50 / (D 90 -D 10), characterizes the concentration of the particle size distribution curve. The larger the value, the more concentrated the particle size distribution is and the steeper the particle size distribution curve is. In the example, the steepness S of the original tungsten powder particle size is about 0.5.

[0036] The invention relates to a high-efficiency grading device for powder materials with a wide particle size range, comprising an automatic feeding mechanism, an automatic crushing mechanism, an automatic grading mechanism and a collecting system, so as to achieve high-efficiency grading of powder materials with a wide particle size range.

[0037] Based on the steepness S characterization method, through pneumatic control technology, the automatic feeding mechanism, automatic crushing mechanism, automatic grading mechanism, and automatic discharging mechanism are controlled to achieve efficient and accurate grading of powder materials in a wide particle size range within the particle size range of (5-120) μm. The grading accuracy can reach S≥0.8 at 20 μm; the grading accuracy can reach S≥0.7 at 50 μm; and the grading accuracy can reach S≥0.6 at 100 μm. After grading, the particle size distribution of the material is more concentrated.

[0038] like Figure 1 , 2 As shown, the automatic feeding mechanism includes a hopper 1, a hopper cover 2, an L-shaped pipe and a motor. The automatic crushing mechanism includes an air compressor, a pipe 7, a crushing chamber 8, a nozzle 9, and a compression chamber. The automatic grading mechanism includes a pipe 3 and a grading cylinder 4. The collection system includes a buckle 5 and a collector 6.

[0039] The hopper 1 is a conical structure, installed on the upper layer of the platform, and the hopper cover 2 is used to cover the hopper 1. The small end opening of the hopper 1 is connected to one end of the L-shaped pipe, and the other end of the L-shaped pipe passes through the platform table and is connected to the material inlet of the automatic crushing mechanism, and the motor output end contacts the outer wall of the L-shaped pipe. The lower end of the pipe 7 is connected to the upper end of the crushing chamber 8, and the upper end outlet of the pipe 7 is connected to the automatic grading mechanism. The side wall of the pipe 7 is provided with a material inlet for communicating with the automatic feeding mechanism; the crushing chamber 8 and the compression chamber are both columnar structures, and the crushing chamber 8 and the compression chamber are not connected; the air compressor is connected to the compression chamber through a pipeline, and a gas flow regulating valve is provided on the pipeline. Four nozzles 9 are evenly distributed around the compression chamber, and the lower end of each nozzle is connected to the compression chamber, and the upper end is connected to the crushing chamber 8. One end of the pipe 3 is connected to the outlet of the automatic crushing mechanism, and the other end is connected to the grading cylinder 4. A grading impeller is provided inside the grading cylinder 4. The rotation frequency of the grading impeller is adjusted by the grading impeller stepless speed regulator, so that the fine materials that meet the steepness requirements are graded to the collection system. The grading cylinder 4 is an integrated two-stage structure, with the upper part being a hollow columnar structure and the lower part being an inverted hollow conical structure. The small end of the conical structure is the outlet of the grading cylinder 4. The collector 6 is fixed to the outlet of the grading cylinder 4 by four buckles 5 to hold the collected materials. The collector 6 can be removed by opening the buckles 5 to pour out the collected raw material fine powder. The collection system is made of stainless steel.

[0040] The gas flow regulating valve is used to adjust the gas flow and cooperate with the stepless speed regulator of the grading impeller to make the crushed and graded materials meet the steepness requirements.

[0041] The device of the present invention is applied as follows:

[0042] Manually put the raw materials of the medicine into the hopper 1, and then cover the hopper cover 2. Start the program, the motor vibrates, and the raw materials are vibrated into the crushing chamber 8 through the pipeline 7.

[0043] Then the air compressor will compress the air through the nozzle 9 to form a supersonic airflow for the crushing chamber 8. The raw materials are accelerated by the supersonic airflow in the crushing chamber 8, and collide, shear, and rub against each other at the intersection. When the external force applied to the particles is greater than the allowable stress of the particles themselves, the purpose of crushing is achieved.

[0044] The crushed raw materials follow the rising airflow through the pipe 3 to the classification barrel 4. Under the high-speed rotation of the classification impeller, the coarse materials are thrown to the outer barrel wall because the centrifugal force they are subjected to is greater than the carrying force of the airflow. The fine materials are subjected to a smaller centrifugal force and pass through the classification wheel to the collector 6. Open the buckle 5, remove the collector 6, and pour out the collected raw material fine powder.

[0045] The present invention proposes a quantitative characterization method for particle size classification: steepness S = D 50 / (D 90 -D 10 ), realizes the quantitative characterization of particle size classification, adds the characterization of particle size distribution range on the basis of the measured volume average diameter, and improves the scientificity and rationality of material particle size requirements; steepness S = D 50 / (D 90 -D 10 ) as a technical indicator, designing an efficient grading device for powder materials with a wide particle size range can greatly improve the consistency of powder material particle size in the process of pyrotechnic agent manufacturing, which is beneficial to improving the performance reliability of the finished agent. At the same time, it does not generate dust, completely liberates manpower, reduces labor intensity, avoids hazards such as swollen arms and blisters on the palms of workers during operation, and eliminates threats to employees' occupational environmental safety.

[0046] The undisclosed technologies in the present invention are common knowledge to those skilled in the art.

Claims

1. A particle size classification quantitative characterization method, characterized in that: Using steepness S = D 50 / (D 90 -D 10 ), characterizes the concentration of the particle size distribution curve. The greater the steepness, the more concentrated the particle size distribution and the steeper the particle size distribution curve. D10 is the 10% boundary particle size, D50 is the 50% median particle size, and D90 is the 90% boundary particle size.

2. An efficient grading device for powder materials with a wide particle size range based on the particle size grading quantitative characterization method of claim 1, characterized in that: It includes automatic feeding mechanism, automatic crushing mechanism, automatic grading mechanism and collection system; Automatic feeding mechanism: the powder raw materials to be processed are added into the automatic crushing mechanism by vibration; Automatic crushing mechanism: Use supersonic airflow to collide, shear and rub the raw materials, and finally crush the raw materials. The crushed raw materials reach the automatic grading mechanism with the rising airflow; Automatic grading mechanism: Classify fine materials that meet the steepness requirements to the collection system; Collection system: used to hold the collected materials.

3. The high-efficiency classifying device for powder materials with a wide particle size range according to claim 2, characterized in that: The automatic feeding mechanism includes a hopper, a hopper cover, an L-shaped pipe and a motor; The hopper is a conical structure and is installed on the platform. The hopper cover is used to cover the hopper. The small end opening of the hopper is connected to one end of an L-shaped pipe. The other end of the L-shaped pipe passes through the platform table and is connected to the material inlet of the automatic crushing mechanism. The motor output end contacts the outer wall of the L-shaped pipe.

4. The high-efficiency grading device for powder materials with a wide particle size range according to claim 2, characterized in that: The automatic crushing mechanism includes an air compressor, a first pipeline, a crushing chamber, a nozzle, and a compression chamber; The lower end of the first pipeline is connected to the upper end of the crushing chamber, the upper end outlet of the first pipeline is connected to the automatic grading mechanism, and the side wall of the first pipeline is provided with a material inlet for connecting to the automatic feeding mechanism; the crushing chamber and the compression chamber are both columnar structures, and the crushing chamber and the compression chamber are not connected; the air compressor is connected to the compression chamber through a pipeline, and a gas flow regulating valve is arranged on the pipeline, and four nozzles are evenly distributed around the compression chamber, and the lower end of each nozzle is connected to the compression chamber, and the upper end is connected to the crushing chamber.

5. The high-efficiency classifying device for powder materials with a wide particle size range according to claim 2, characterized in that: The automatic grading mechanism includes a second pipeline and a grading cylinder; One end of the second pipeline is connected to the outlet of the automatic crushing mechanism, and the other end is connected to the classifying cylinder. A classifying impeller is arranged inside the classifying cylinder. The rotation frequency of the classifying impeller is adjusted by the classifying impeller stepless speed regulator so that the fine materials meeting the steepness requirements can be classified into the collection system.

6. The high-efficiency grading device for powder materials with a wide particle size range according to claim 5, characterized in that: The grading cylinder is an integrated two-section structure, the upper part is a hollow columnar structure, the lower part is an inverted hollow cone structure, and the small end of the cone structure is the outlet end of the grading cylinder.

7. The high-efficiency classification device for powder materials with a wide particle size range according to claim 2, characterized in that: The collecting system includes a buckle and a collector; the collector is fixed to the outlet end of the grading cylinder by the buckle and is used for containing the collected materials.

8. The high-efficiency classifying device for powder materials with a wide particle size range according to claim 7, characterized in that: Open the buckle, remove the collector and pour out the collected raw material fine powder.

Images