Magnetic separator and permanent magnet

The magnetic separator uses the magnetic difference between minerals for sorting, plays the role of improving the grade of ore, purifying solid-liquid materials, and recycling waste. It is the most widely used and highly versatile machine in the industry. One.

Magnetic separators are widely used in mining, wood, kiln, chemical, food and other industries. For mining, the magnetic separator is suitable for wet or dry magnetic separation of manganese ore, magnetite, magnetite, roasted ore, ilmenite, hematite and other materials with a particle size below 50mm. , Non-metallic mines, building materials and other iron removal operations and waste disposal operations

Structure and working principle of magnetic separator

The magnetic separator (take wet permanent magnetic cylinder magnetic separator as an example) is mainly composed of 6 parts: cylinder, roller, brush roller, magnetic system, tank and transmission part. The cylinder is welded into a cylinder by 2-3mm stainless steel plate, and the end cover is cast aluminum or workpiece, which is connected to the cylinder with stainless steel screws. The motor drives the cylinder, magnet roller and brush roller to rotate through a speed reducer or a step-less speed regulating motor.

After the ore slurry flows into the tank through the ore feed box, the ore particles enter the ore feeding area of the tank in a loose state under the action of the water flow of the ore spray pipe. Under the action of the magnetic field, the magnetic ore particles are magnetically aggregated to form a “magnetism group” or “magnetism chain”. The “magnetism group” or “magnetism chain” is subjected to a magnetic force in the slurry and moves toward the magnetic pole and is adsorbed on the cylinder . Since the polarities of the magnetic poles are alternately arranged along the direction of rotation of the cylinder and are fixed during operation, the “magnet” or “flux” rotates with the cylinder, and the magnetic stirring phenomenon occurs due to the alternating magnetic poles and is mixed. The non-magnetic minerals such as gangue in the “magnetism” or “magnetism chain” fall off during the tumbling, and the “magnetism” or “magnetism chain” that is eventually attracted to the surface of the cylinder is the concentrate. The concentrate is transferred to the weakest part of the magnetic system edge with the cylinder, and it is discharged into the concentrate tank under the action of the flushing water sprayed from the unloading water pipe, and the non-magnetic or weak magnetic minerals are left in the slurry and discharged out of the tank with the slurry , That is tailings.

Pulley Magnetic Separators

Classification of magnetic separator

Magnetic separators have multiple classifications according to different characteristics and standards.

According to the strength of the magnetic field and the strength of the magnetic field, it can be divided into:

Weak magnetic field magnetic separator: the magnetic field strength of the working gap is (0.6 ~ 1.6) × 105A / m, used to select strong magnetic minerals;

Medium magnetic separator: the magnetic field strength of the working gap is (1.6 ~ 4.8) × 105A / m, used to select medium magnetic minerals;

Strong magnetic separator: The magnetic field strength of the working gap is (4.8 ~ 20.8) × 105A / m, which is used to select weak magnetic minerals.

According to the selection medium, it can be divided into:

Dry magnetic separator: Separation in the air, mainly used to separate large and coarse particles of strong magnetic ore and fine particles of weak magnetic ore. At present, it is also trying to sort fine ferromagnetic ore;

Wet magnetic separator: select points in water or magnetic liquid. It is mainly used to separate fine-grained strong magnetic ore and fine-grained weak magnetic ore.

In addition, it can be classified according to the way the magnetic ore particles are selected, the movement direction of the feed material, the method of discharging the selected products from the selected section, and the structural characteristics of the discharged magnetic products.

 

Magnetic circuit design and magnet of magnetic separator

 

The closed circuit through which magnetic flux is concentrated is called a magnetic circuit. The magnetic system of the magnetic separator needs to generate a certain intensity of magnetic field, and most of the magnetic flux in the magnetic field can be concentrated through the separation space. The height, width, radius and number of poles of the magnetic system, the magnetic potential difference between adjacent poles, the pole distance, the width of the pole face width and the pole gap width, the shape of the pole and pole face, and the pole face to the center of the arrangement The distance and so on have no small effect on the magnetic field characteristics.

The magnetic separator shown in the following figure is an example. The magnetic circuit part adopts a five-pole magnetic system. Each magnetic pole is formed by bonding a ferrite and a neodymium-iron-boron permanent magnet block. It is fixed to the magnetic guide plate with a screw through the center hole of the magnetic block On the upper side, the magnetic guide plate is fixed on the shaft of the cylinder through the bracket, the magnetic system is fixed, and the cylinder can rotate. The polarities of the magnetic poles are alternately arranged along the circumference, and the polarities are the same along the axial direction. Outside the magnetic system is a roller made of stainless steel non-magnetically conductive material. The non-magnetically conductive material is used to avoid that magnetic lines of force cannot enter the selected zone through the cylinder and form a magnetic short circuit with the cylinder. The part of the tank close to the magnetic system should also be made of non-magnetic materials, and the rest should be ordinary steel plates or hard plastic plates.

For the permanent magnet separator, the permanent magnet is the most important component, and the quality of the permanent magnet determines its performance characteristics. The permanent magnets of magnetic separators are generally made to a certain size (for example, length × width × height = 85 × 65 × 21 mm), so they are traditionally called permanent magnet blocks or magnetic blocks for short. The permanent magnet materials that can be used in the magnetic system of the magnetic separator include permanent magnet ferrite, aluminum nickel cobalt, iron chromium cobalt and manganese aluminum iron, samarium cobalt permanent magnet materials, and neodymium iron boron permanent magnet materials. At present, the mainstream permanent magnetic materials used in domestic magnetic separation equipment are mainly permanent ferrite (strontium ferrite, barium ferrite), followed by neodymium iron boron permanent magnetic materials.

In the design of the magnetic system, it is necessary to choose which permanent magnetic material to use according to the specific conditions of various aspects. The influencing factors can be summarized into the following aspects:

Magnetic field strength: A constant magnetic field must be generated in the designated work space. The strength of this magnetic field determines which permanent magnetic material is required. The magnetic properties of NdFeB permanent magnets are much higher than ferrites.

Requirements for the stability of the magnetic field, that is, the influence and adaptability of permanent magnetic materials on environmental temperature, humidity, vibration and shock

Mechanical properties, such as the toughness, flexibility and compressive strength of the magnet;

Price factor