Separation and extraction device and method for ferromagnetic tiny metal evidence

Abstract

The invention belongs to the technical field of fire explosive evidence extraction and identification, and particularly relates to a ferromagnetic tiny metal evidence separation and extraction device and method.The ferromagnetic tiny metal evidence separation and extraction device comprises a box body, a feeding port is formed in the top of the box body, one end of a magnetic roller is located below the feeding port, and a non-magnetic substance collection box and a magnetic substance collection box are arranged at the bottom of the inner side of the box body; the non-magnetic material collecting box is located below the feeding port, and the magnetic material collecting box is located below the magnetic roller away from the side of the feeding port. The magnetic roller comprises an outer roller, a center roller and an inner roller are sequentially arranged on the inner side of the outer roller, the outer roller is rotationally connected to the inner wall of the box body and connected with a motor, and a spiral scraper is arranged on the outer side of the outer roller; the center roller is fixedly connected to the inner roller, and the inner roller is fixedly connected to the inner wall of the box body. No central roller is arranged at the tail part of the outer roller far away from the feeding hole; and N / S levels are alternately arranged on the circumference of the center roller. According to the invention, rapid separation and extraction of tiny ferromagnetic metal material evidences such as electric welding slag, lighter windshields, ground fault splashing molten beads and the like can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of extraction and identification of physical evidence in fire and explosion, and particularly relates to a separation and extraction device and method for ferromagnetic tiny metal physical evidence. Background Art

[0002] Fire and explosion cases often cause huge casualties and property losses, and have extremely bad social impacts, seriously endangering national stability and social harmony. In the on-site inspection work of fire and explosion cases, the discovery and extraction of on-site physical evidence are very important and also a very laborious task. Due to the effects of fire and explosion at the scene, surrounding buildings are often damaged and collapsed, and various physical evidences are scattered in different areas of the fire and explosion scene, mixed with surrounding environmental items, resulting in the need for a large number of firefighters and relevant staff to clean, identify and screen. In the fire and explosion scene, various physical evidences are very small and widely distributed, especially in the rubble piles, bushes, green belts, and lawns, making it very difficult to discover and extract. Traditional methods for extracting tiny metal physical evidence mainly combine manual and expert identification. These two methods are extremely laborious, prone to omission and loss of physical evidence, and heavily rely on the expert skills of on-site inspectors. Especially for ferromagnetic tiny metal physical evidence, there is currently no good way to separate it, causing a lot of inconvenience.

[0003] Currently, the removal of iron from materials generally uses physical methods to separate impurity iron using magnetic separation equipment. For larger ferromagnetic impurities, such as those above 100 g, ordinary iron removers and magnetic separation drums can effectively separate them. However, for tiny ferromagnetic substances, especially those with a particle size less than 40 mesh, the separation difficulty is relatively large. As the particle size of ferromagnetic substances in materials becomes finer, electrostatic wrapping and magnetic wrapping will be very serious. Conventional iron removers or magnetic separation drums cannot effectively break these wrapping forces and cannot effectively separate ferromagnetic impurities in the materials. When separating ferromagnetic impurities in 60-mesh materials using a permanent magnetic drum, the separation efficiency is less than 30%, and the separated materials still contain a large amount of iron impurities, and the separated iron impurities also contain a large amount of materials.

[0004] When traditional iron removal equipment separates fine materials, it can be divided into two categories in terms of methods: dry method and wet method. The wet method generally uses equipment such as drum magnetic separators, high-gradient vertical ring magnetic separators, and drum internal magnetic separators. The dry method generally uses equipment such as permanent magnet drums, magnetic rods, and dry separators. The magnetic separation equipment of the wet method has a relatively mature process at present. However, traditional wet equipment has a large floor area, consumes a large amount of water, and the number of magnetic field reversals of a single device is small. In cases where very high requirements need to be met, a large number of devices are required, resulting in large investment. Taking the drum magnetic separator as an example, currently, the drum magnetic separator for separating magnetic materials is the mainstream device. Generally, the pole angle is between 118° and 142°, the number of material flips is between 3 and 6 times, and a single device cannot complete the task of material recovery and purification. Multiple devices need to cooperate to complete it. At least three devices are required for a single process line, and most use five devices to complete a process flow. Dry equipment generally uses permanent magnet drum-type equipment. Permanent magnet drum-type equipment also has problems such as insufficient number of flips, inability to open magnetic and electrostatic packages, low recovery rate, and serious entrainment. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a separation and extraction device and method for ferromagnetic micro metal physical evidence. Based on the special properties of micro ferromagnetic metals, the intermittent imparting and separation of magnetization force are applied to sort the micro ferromagnetic metal physical evidence in the physical evidence collected at the fire and explosion scene, realizing the rapid separation and extraction of micro ferromagnetic metal physical evidence such as electric welding slag, lighter windshields, and grounding fault splashed molten beads and the residues at the fire and explosion scene.

[0006] A separation and extraction device for ferromagnetic micro metal physical evidence includes a box body, a magnetic roller, a magnetic material collection box, and a non-magnetic material collection box. The top of the box body is provided with a feeding port. One end of the magnetic roller is connected to the inner wall of the box body, and the other end is located below the feeding port and connected to the motor. The inner bottom of the box body is provided with a non-magnetic material collection box and a magnetic material collection box. The non-magnetic material collection box is located below the feeding port, and the magnetic material collection box is located below the magnetic roller on the side far from the feeding port.

[0007] The magnetic roller includes an outer roller, a central roller, and an inner roller. The central roller and the inner roller are sequentially arranged inside the outer roller. The outer roller is rotatably connected to the inner wall of the box body and connected to the motor. A spiral scraper is arranged on the outer side of the outer roller. The central roller is fixedly connected to the inner roller, and the inner roller is fixedly connected to the inner wall of the box body. The tail of the outer roller far from the feeding port is not provided with a central roller. N / S poles are alternately arranged on the circumference of the central roller.

[0008] The outer roller is made of non-magnetic material, and the inner roller can be made of magnetic material or non-magnetic material.

[0009] The central roller is made of rare earth magnetic material.

[0010] The outer wall of the box body is provided with a hand-held handle.

[0011] A method for separating and extracting ferromagnetic micro metal physical evidence, the specific steps are as follows:

[0012] First, the physical evidence is packaged and labeled according to the collection area. Then, the packaged physical evidence enters the inside of the box through the feeding port in turn and contacts the magnetic roller. The motor drives the outer roller and the spiral scraper to rotate, while the central roller and the inner roller remain stationary. When the non-ferromagnetic physical evidence in the physical evidence contacts the magnetic roller, it falls into the non-magnetic object collection box due to gravity; the ferromagnetic micro metal physical evidence in the physical evidence is adsorbed on the outer roller. As the outer roller rotates, the N / S poles on the central roller alternate, causing the ferromagnetic micro metal physical evidence to move relative to the outer roller. At the same time, under the push of the spiral scraper, the ferromagnetic micro metal physical evidence moves on the outer roller and falls into the magnetic object collection box under the action of gravity when there is no magnetic field at the tail of the outer roller.

[0013] The beneficial effects of the present invention are:

[0014] The outer roller of the present invention is provided with a spiral scraper, and the N / S poles are alternately arranged on the circumference of the central roller. When the physical evidence falls from the feeding port, the ferromagnetic micro metal physical evidence is adsorbed on the outer roller due to the influence of the magnetic field of the central roller. During the rotation of the outer roller, the N / S poles on the central roller alternate, enabling the ferromagnetic micro metal physical evidence to move relative to the outer roller. At the same time, under the push of the spiral scraper, the ferromagnetic micro metal physical evidence moves on the outer roller, and thus falls into the magnetic object collection box under the action of gravity when there is no magnetic field at the tail of the outer roller. When the non-ferromagnetic physical evidence contacts the magnetic roller, the magnetic field of the central roller has no obvious effect on the non-ferromagnetic physical evidence, and the non-ferromagnetic physical evidence falls into the non-magnetic object collection box due to its own gravity; the present invention overcomes the problems of limited flipping times, magnetic force wrapping, and electrostatic wrapping of the magnetic separation device in the prior art, modifies the design idea of moving in the circumferential direction in the prior art to increasing the axial movement through the spiral scraper, and thus generates a variable magnetic field through the alternate arrangement of the N / S poles of the central roller to cause relative movement between the ferromagnetic micro metal physical evidence and the outer roller, and then completes the extraction work of ferromagnetic substances. Description of the Drawings

[0015] Figure 1 It is a top view of the separation and extraction device of the present invention;

[0016] Figure 2 It is a front view of the separation and extraction device of the present invention;

[0017] Figure 3 It is a diagram of the magnetic pole setting of the central roller of the separation and extraction device of the present invention;

[0018] Figure 4 It is a static magnetic field distribution diagram of the magnetic roller of the separation and extraction device of the present invention;

[0019] Figure 5Magnetic field distribution curve near the magnetic rod of the separation and extraction device of the present invention;

[0020] Figure 6 Magnetic field distribution nephogram at different positions of the magnetic rod of the separation and extraction device of the present invention;

[0021] In the attached drawings: 1. Box body; 2. Magnetic roller; 201. Outer roller; 202. Central roller; 203. Inner roller; 3. Magnetic substance collection box; 4. Non-magnetic substance collection box; 5. Feeding port; 6. Motor; 7. Spiral scraper. Specific embodiments

[0022] The present invention will be described in detail below with reference to the attached drawings.

[0023] The design principle of this application is as follows: For ferromagnetic tiny metal remnants at the fire and explosion site, they have strong magnetism, mainly due to their strong internal exchange field. The exchange energy of ferromagnetic substances is positive and relatively large, causing the magnetic moments of adjacent atoms to be parallelly oriented (corresponding to the stable state), forming many small regions - magnetic domains inside the substance. Each magnetic domain contains approximately 10 - 15 atoms. The magnetic moments of these atoms are arranged in the same direction, and there is a strong internal field called the "molecular field" inside the crystal. The "molecular field" is sufficient to automatically magnetize each magnetic domain to the saturation state. This self-generated magnetization intensity is called the spontaneous magnetization intensity. Due to its existence, ferromagnetic substances can be strongly magnetized in a weak magnetic field.

[0024] For non-magnetic metal remnants at the fire and explosion site, due to their obvious difference from the explosion residue impurities in the physical parameter of resistivity. Among them, the resistivity of metals (mainly copper) is below 1×10 -7 ohms, while the resistivity of non-metallic impurities is 1×10 -5Above that of Europe and America. Therefore, the electromagnetic field separation method can be used to separate the non-magnetic metal residues of explosive devices, and the effective fire evidence can be extracted by taking advantage of the different electrical conductivities of copper (aluminum) molten beads and non-metallic residues. The magnetic separation method is a technology that separates metals and non-metals based on the difference in the electrical conductivity of substances. When performing magnetic separation, two important physical laws, namely electromagnetic induction and Biot-Savart, are followed, that is, an alternating magnetic field that changes with time always gives rise to an alternating electric field; a magnetic field is induced in a current-carrying conductor. When non-magnetic metal particles pass through the changing magnetic field of the magnetic roller, an alternating magnetic field will be generated inside the particles, and an alternating magnetic field in the opposite direction will be generated around the particles. The magnetic field of the magnetic roller and the magnetic field induced inside the particles repel each other, and this repulsive force separates the required metal particles. During the magnetic separation process, in addition to the action of its own moment of inertia T, the magnetic force acting on the metal particles can be decomposed into a radial magnetic force Fr and a tangential magnetic force Ft. The resultant force of the magnetic force and gravity acting on the mixed material during the separation process is different, resulting in separation. The magnetic separation technology is mainly used to separate non-ferrous metals from metal and non-metal mixtures, and can also be used for the mutual separation of different non-ferrous metals.

[0025] In traditional magnetic separation equipment, the material generally moves in a circumferential direction. Taking a cylinder with a diameter of one meter as an example, considering the adsorption force of the magnetic field and the influence of the material entering and leaving the separation area, the number of magnetic poles is generally designed between 12 and 26 levels. Under the action of these magnetic poles, the material needs to complete the entire process of adsorption, flipping, and detachment. To increase the number of flips, the diameter needs to be increased. In the case of a small diameter, a different approach needs to be considered. Therefore, considering non-circumferential movement, the present invention is designed to move axially. If the material wants to move axially, there must be an axial driving force. Since spiral scrapers are designed on the outer roller of the magnetic roller to complete the axial driving; however, when magnetic impurities are adsorbed on the surface of the drum, under the adsorption action of the magnetic field, it is relatively stationary. To make the magnetic impurities move in a relative position, the present invention sets the central roller of the magnetic roller as an alternating N / S level, designs a changing magnetic field, and changes the magnetic poles to complete the relative movement of the magnetic impurities.

[0026] Specifically, as Figures 1 to 3 shown, a device for separating and extracting ferromagnetic micro-metal physical evidence includes a box body 1, a magnetic roller 2, a magnetic material collection box 3, and a non-magnetic material collection box 4. The top of the box body 1 is provided with a feeding port 5. One end of the magnetic roller 2 is connected to the inner wall of the box body, and the other end is located below the feeding port 5 and connected to a motor 6. The inner bottom of the box body 1 is provided with a non-magnetic material collection box 4 and a magnetic material collection box 3. The non-magnetic material collection box 4 is located below the feeding port 5, and the magnetic material collection box 3 is located below the magnetic roller 2 on the side far from the feeding port 5;

[0027] The magnetic roller 2 includes an outer roller 201, a central roller 202 and an inner roller 203. The central roller 202 and the inner roller 203 are sequentially arranged on the inner side of the outer roller 201. The outer roller 201 is rotatably connected to the inner wall of the box body 1 and connected to the motor 6. A spiral scraper 7 is arranged on the outer side of the outer roller 201. The central roller 202 is fixedly connected to the inner roller 203, and the inner roller 203 is fixedly connected to the inner wall of the box body 1. The central roller 202 is not provided at the tail of the outer roller 201 far from the feeding port 5. N / S poles are alternately arranged on the circumference of the central roller 202.

[0028] In this embodiment, the height, lead and quantity of the spiral scraper 7 can be adjusted according to the shape and size of the physical evidence. The motor 6 can adjust its operating speed as needed. By adjusting the speed, the separation effect of different materials can be improved. For example, for smaller particle size or more iron content, the speed should be appropriately increased.

[0029] The outer roller 201 is made of non-magnetic material. The material of the inner roller 203 can be magnetic material or non-magnetic material. In this implementation, the outer roller 201 is made of stainless steel, and the inner roller 203 is made of non-magnetic material. Through simulation analysis, the materials of the outer roller and the inner roller of the present invention are further determined. As Figure 5 shown, it is the magnetic field distribution nephogram at different positions of the magnetic roller. On the surface of the magnetic roller, as the distance from the center of the circle in the radial direction increases, the magnetic field distribution gradually decreases. On the surface of the magnetic roller, the magnetic field is stronger. This reminds us that the outer roller arranged on the surface of the magnetic roller needs to use a non-ferromagnetic material to avoid magnetization and affect the use of the equipment. At the center of the magnetic roller, the magnetic field is smaller, and a magnetic material can be used as the structural material of the inner roller 203. However, in order to improve the robustness of the equipment, the inner roller 203 uses non-magnetic material.

[0030] The material of the central roller 202 is rare earth magnetic material, which can realize the adsorption of ferromagnetic tiny metal physical evidence.

[0031] A handle is provided on the outer wall of the box body 1 for easy movement and handling.

[0032] A method for separating and extracting ferromagnetic tiny metal physical evidence is as follows:

[0033] First, the physical evidence is sub-packaged and labeled according to the collection area. Then, the sub-packaged physical evidence enters the interior of the box body 1 through the feeding port 5 in sequence and contacts the magnetic roller 2. The motor 6 drives the outer roller 201 and the spiral scraper 7 to rotate, while the central roller 202 and the inner roller 203 remain stationary. When the non-ferromagnetic physical evidence in the physical evidence contacts the magnetic roller 2, it falls into the non-magnetic object collection box 4 due to gravity; the ferromagnetic tiny metal physical evidence in the physical evidence is adsorbed on the outer roller 201. As the outer roller 201 rotates, the N / S levels on the central roller 202 alternate, causing the ferromagnetic tiny metal physical evidence to move relative to the outer roller 201. At the same time, under the push of the spiral scraper 7, the ferromagnetic tiny metal physical evidence moves on the outer roller 201 and falls into the magnetic object collection box 3 under the action of gravity when there is no magnetic field at the tail of the outer roller 201.

[0034] Through numerical simulation, the present invention verifies the acting force of the changing magnetic field on the central roller, as Figure 4 shown, which is the static magnetic field distribution diagram under the condition of a 12-lobe permanent magnet magnetic roller. It can be seen from the figure that the magnetic field forms a closed curve from the N pole to the S pole, and a magnetic field gradient is formed on the surface of the magnetic roller, which is suitable for forming a gradient magnetization force, so that the adsorbed ferromagnetic tiny metal physical evidence can be affected by forces in different directions on the surface of the magnetic roller and move along with the rotation of the magnetic roller surface.

[0035] Figure 6 It is the magnetization force distribution vector diagram at different positions of the magnetic roller. It can be seen from the figure that at different positions on the surface of the magnetic roller, the magnetization forces received by the physical evidence separated from the explosion site are different, showing a pulsed change law of strong-weak, strong-weak, which provides the possibility for the ferromagnetic tiny metal physical evidence to move on the surface of the magnetic roller through external forces. The magnetization force on the surface of the magnetic roller 2 only exists within a certain range. Therefore, it is required that the outer roller 201 arranged on the surface of the magnetic roller 2 not only needs to be made of non-ferromagnetic materials, but also be as thin as possible, so that the magnetic roller 2 can have a strong adsorption effect on the physical evidence separated from the explosion site.

[0036] The separation and extraction device for ferromagnetic micro metal physical evidence of the present invention has a large number of flipping times and a moderate magnetic field intensity, and can solve magnetic wrapping and electrostatic wrapping. A spiral scraper 7 is provided on the outer roller of the present invention, and N / S poles are alternately arranged on the circumference of the central roller 202. When the ferromagnetic micro metal physical evidence falls from the feed inlet 5, the ferromagnetic micro metal physical evidence is adsorbed on the outer roller 201 due to the magnetic field influence of the central roller 202. During the rotation of the outer roller 201, the N / S poles on the central roller 202 alternate, enabling the ferromagnetic micro metal physical evidence to move relative to the outer roller 201. At the same time, under the push of the spiral scraper 7, the ferromagnetic micro metal physical evidence moves on the outer roller 201, and thus falls into the magnetic material collection box 3 under the action of gravity when there is no magnetic field at the tail of the outer roller 201, completing the extraction of ferromagnetic substances; after the non-magnetic physical evidence enters the feed inlet 5, the magnetic field of the central roller 202 has no obvious effect on the non-ferromagnetic physical evidence, and the non-ferromagnetic physical evidence falls into the non-magnetic material collection box 4 under the action of its own gravity.

Claims

1. A device for separating and extracting ferromagnetic tiny metal evidence, characterized in that: It includes a box body, a magnetic roller, a magnetic material collection box and a non-magnetic material collection box. The top of the box body is provided with a feed inlet. One end of the magnetic roller is connected to the inner wall of the box body, and the other end is located below the feed inlet and connected to the motor. A non-magnetic material collection box and a magnetic material collection box are provided at the bottom of the inner side of the box body. The non-magnetic material collection box is located below the feed inlet, and the magnetic material collection box is located below the magnetic roller away from the feed inlet. The magnetic roller includes an outer roller, a center roller and an inner roller. The center roller and the inner roller are arranged in sequence on the inner side of the outer roller. The outer roller is rotatably connected to the inner wall of the box and is connected to the motor. A spiral scraper is arranged on the outer side of the outer roller. The center roller is fixedly connected to the inner roller, and the inner roller is fixedly connected to the inner wall of the box. No center roller is arranged at the tail of the outer roller away from the feed port. N / S levels are alternately arranged on the circumference of the center roller.

2. The device for separating and extracting ferromagnetic minute metal evidence according to claim 1, characterized in that: The outer roller is made of non-magnetic material, and the inner roller can be made of either magnetic material or non-magnetic material.

3. The device for separating and extracting ferromagnetic minute metal evidence according to claim 1, characterized in that: The material of the center roller is rare earth magnetic material.

4. The device for separating and extracting ferromagnetic minute metal evidence according to claim 1, characterized in that: The outer wall of the box body is provided with a carrying handle.

5. A method for separating and extracting ferromagnetic minute metal evidence, according to the separation and extraction device of claim 1, characterized in that: The specific steps are as follows: First, the evidence is packaged and marked according to the collection area, and then the packaged evidence is passed through the feed port into the box in turn and contacts the magnetic roller. The motor drives the outer roller and the spiral scraper to rotate, while the center roller and the inner roller are fixed. When the non-ferromagnetic evidence in the evidence contacts the magnetic roller, it falls into the non-magnetic collection box due to gravity; the ferromagnetic tiny metal evidence in the evidence is adsorbed on the outer roller. As the outer roller rotates, the N / S level on the center roller alternates to make the ferromagnetic tiny metal evidence move relative to the outer roller. At the same time, the spiral scraper pushes the ferromagnetic tiny metal evidence on the outer roller and falls into the magnetic collection box due to gravity when there is no magnetic field at the tail of the outer roller.

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