(1) Application fields of magnetic separation
Magnetic separation is a beneficiation method that utilizes the magnetic difference between minerals in an inhomogeneous magnetic field to separate different minerals. Magnetic separation is simple and convenient without additional pollution. Magnetic separation is widely used in ferrous metal ore sorting, selection of non-ferrous ores and rare metals, heavy medium beneficiation is recovered and purified magnetic media, removal of non-metallic mineral containing iron impurities to iron minerals Exclusion and aspects such as garbage and sewage treatment.
Magnetic separation is the main method of processing iron ore. China's iron ore resources are abundant. At present, the proven reserves have reached 50 billion tons, ranking among the top in the world, but the poor ore accounts for about 90%, the rich ore only accounts for about 10%, and about 5% of the rich ore contains harmful impurities. It cannot be directly smelted, so more than 90% of iron ore needs beneficiation. This is generally the case in other countries of the world. After ore dressing, the iron ore has improved the grade, reduced the content of silica and harmful impurities, and is beneficial to the smelting process. According to China's practice, for every 1% increase in iron concentrate grade, the blast furnace utilization factor can be increased by 2% to 3%, coke consumption can be reduced by 1.5%, and limestone consumption can be reduced by 2%.
Many non-ferrous metals and rare metal minerals have different magnetic properties. When the final concentrate cannot be obtained by re-election and flotation, it can be sorted by magnetic separation in combination with other methods. For example, the black tungsten coarse concentrate obtained by re-selection contains a certain amount of cassiterite , and the characteristics of the wolframite are weak magnetic and the cassiterite is non-magnetic. mine.
When coal or heavy medium beneficiation is selected, the use of magnetite or ferrosilicon as a heavy medium, due to the heavy recycle as a suspension medium, requires heavy medium recovered by magnetic separation and purification.
Non-metallic raw materials generally contain harmful iron impurities, and magnetic separation is one of the important operations in non-metal dressing. For example, when the iron content in the kaolin is high, the whiteness, refractoriness and insulation of the kaolin are lowered, which seriously affects the quality of the product. Generally, iron impurities are removed by 1% to 2%, and whiteness can be increased by 2 to 4 units. The most effective method for removing iron from kaolin is the high gradient magnetic separation.
For the sorting of kyanite , red tourmaline , feldspar , quartz , nepheline and diorite , dry magnetic separation has long been used.
The ore that enters the ore dressing plant or the coal preparation plant often mixes the irons brought in during mining. In order to protect the crusher and other equipment, it is necessary to remove the iron by magnetic separation before the bulk material is broken.
With the improvement of human environmental awareness and the need for resource regeneration, magnetic separation is widely used in the recovery and separation of steel slag and scrap metal and sewage treatment. Medically, magnetic separation is also used to separate red blood cells in the blood.
(II) Development of magnetic separation
China was the first country to discover magnetic phenomena. In the past 10,000 BC, the compass was invented using the polarity of magnets. In the 17th and 18th centuries, people began their first attempts to remove iron from cassiterite and other rare metal concentrates with portable permanent magnets. The industry began to sort ore by magnetic separation at the end of the 19th century. In 1890, a wet-type magnetic separator was introduced in Sweden, which was the prototype of a modern magnetic separator. By 1955, almost all magnetic separators were electromagnetic.
After 1955, with the magnetic system and material research applications, permanent magnetic separator material began to use alnico, ferrite and later gradually applied, a weak magnetic field such that a magnetic separator to achieve a permanent, series, Large size. In recent years, high-performance rare earth permanent magnets have been developed. The magnetic separation equipment made of this kind of magnet has high surface magnetic field strength, large magnetic field gradient, wide separation size range and large processing capacity, which makes the weak magnetic field magnetic separator Sorting efficiency is higher.
At the end of the 19th century, in order to magnetically select weak magnetic minerals, the United States developed a closed-type electromagnetic strong magnetic field belt magnetic separator. Later, the former Soviet Union and other countries developed strong magnetic disk, pro- and drum-type magnetic separators. However, they have small sorting space, low processing capacity and high production cost. In the 1960s, the Jones-type strong magnetic separator was first introduced in the UK. It has a large processing capacity and is an important breakthrough in the magnetic field separator.
The high gradient magnetic separator is a magnetic separation process developed in the 1970s. It can effectively recover magnetic mineral particles with very weak magnetic properties and fine particle size. It is an iron oxide ore with low grade, fine grain size and weak magnetic properties. The sorting has opened up new avenues. In recent years, high gradient technology and superconducting technology have been combined to develop a high gradient superconducting magnetic separator.
Superconducting technology is a very active research field in the contemporary era. China has been studying superconducting magnetic separators since the 1970s. This magnetic separator uses a superconducting material as a coil to operate at very low temperatures (near absolute zero). After the coil is connected to the current, a strong magnetic field of 1600 or more can be generated in a large sorting space, and the coil consumes almost no electric energy, and the magnetic field does not attenuate for a long time. At present, superconducting magnetic separation has gradually entered the industrial production from the laboratory, Germany Humboldt company DESCOS superconducting cartridge magnetic separator, British CCL CRYOFOS magnetic separator, the United States magnetic separator, Czech medium The type of reciprocating magnetic separator and the small medium type superconducting magnetic separator of the UK 10 have been applied in actual production.
Magnetic fluid sorting is a new subject in magnetic separation. Its sorting theory, preparation of magnetic fluid and sorting equipment are still in the process of improvement. Magnetic fluid separation is based on special fluids such as paramagnetic liquids, ferromagnetic suspensions and electrolyte solutions. The use of fluids in the combination of magnetic fields or magnetic fields and electric fields produces a "weighting" effect, A new sorting method that enables the separation of different minerals by the difference in magnetic properties and density or the difference in magnetic properties, electrical conductivity and density. Can be divided into magnetic fluid static sorting and magnetic fluid dynamic sorting. Whether the magnetic fluid separation process can be widely used in industrial applications depends on the preparation of inexpensive magnetic fluids, and water-based ferrofluids are expected to be effective and inexpensive magnetic fluids.
In addition to improving the performance of the magnetic separator to achieve magnetic separation, the magnetic phase can be added to the slurry to enhance the magnetic properties of the target mineral by selective adsorption of the target particles and magnetic particles. This is the carrier magnetic separation process. The magnetic separation carrier may be a large magnetic particle, or may be a fine particle magnetic species or an ion having a large magnetic moment such as ruthenium or osmium . The carrier magnetic separation technology can be used for the separation of fine particles after fine grinding of minerals and the removal of suspended particles in wastewater.
The use of comprehensive force field sorting has developed rapidly in recent years. Through the superposition of various force fields, the competitiveness of the sorting system can be improved, thereby improving the performance of the sorting equipment. There are mainly the following combinations of force fields: vibration force field and magnetic separation, centrifugal force field and magnetic separation, gravity and magnetic separation, flotation and magnetic separation.
Second, the principle of magnetic separation
(1) Magnetic basis
A magnetic field is a special state of matter and is displayed around a carrier conductor or pole. The physical quantities describing the magnitude and direction of the magnetic field are magnetic induction B and magnetic field strength H. In the International System of Units, the unit of magnetic induction B is Tesla, denoted as T, and the dimension is I-1MT-2. Sometimes use Gauss this unit, 1T = 10000 Gauss. The international unit of magnetic field strength H is ampere per meter [A/m) and the dimension is IL-1. The relationship between magnetic induction and magnetic field strength is as follows:
B=μH (4-5-1)
In the formula, μ is called the magnetic permeability of the substance.
When the magnetic medium is placed in a magnetic field, it is magnetized by the action of the magnetic field, thereby generating a magnetic moment in the medium. The magnetic moment per unit volume is called the magnetization, and the magnetization is a physical quantity that characterizes the degree of magnetization of the magnetic medium. In general, the magnetization M at a point in a magnetic medium is proportional to the magnetic induction at that point, expressed in the International System of Units as:
In the formula, k is called the volume susceptibility of the substance, and there is no dimension.
In a magnetic medium, the magnetic induction at any point in the magnetic field, in addition to the original magnetic field, should include the additional magnetic field generated by the magnetization of the magnetic medium. Therefore, in a magnetic field having a magnetic medium, the following relationship exists between the magnetic induction intensity B, the magnetic field strength H, and the magnetization M at any point:
B=μ(H+M) (4-5-3)
Comparing equations (4-5-1), (4-5-2), and (4-5-3)
Let μ = 1 + k, and let u be the relative magnetic permeability of the magnetic medium.
k is only related to the nature of the magnetic medium. It is the amount indicating how easily the substance is magnetized, and the larger the value of k, the easier it is to be magnetized. For most substances, k is a constant and k of a ferromagnetic substance is not a constant.
The ratio of the volume magnetic susceptibility of a substance to its own density, called the mass susceptibility of a substance, or the specific magnetic susceptibility (coefficient) of a substance.
(2) Basic conditions of magnetic separation
Magnetic separation is performed in a non-uniform magnetic field provided by the magnetic separation device. After being magnetically selected into the sorting space of the magnetic separation equipment, it is subjected to the interaction of magnetic force and mechanical force (including gravity, centrifugal force, fluid resistance, etc.), and moves along different paths, and the pulp is separately intercepted to obtain different The product is shown in Figure 4-5-1.
This formula shows that the essence of magnetic separation is achieved by the different effects of magnetic and mechanical forces on different magnetic particles. The ore entering the magnetic separator will be divided into two or more products. In the actual sorting, the magnetic ore and non-magnetic ore cannot enter the corresponding magnetic products, non-magnetic products and medium mines completely, but are randomly selected. Sex. Therefore, the effect of the magnetic separation process can be expressed by the recovery rate, the grade, the ratio of the magnetic substance in the magnetic product to the magnetic substance in the ore, and the content of the magnetic substance in the magnetic product.
(3) Magnetic force
The magnetic field has a uniform magnetic field and a non-uniform magnetic field. The uniformity of the magnetic field can be expressed by the magnetic field gradient
Show, ie grad H or grad B
The magnetic force acting on the magnetic particles in the magnetic field of the magnetic separator can be determined by the potential energy obtained during magnetization, and the potential energy can be obtained by the following formula:
According to the laws of mechanics, the magnetic force acting on a particle can be expressed by the negative gradient of the potential energy of the particle, ie
When the particle size is not large, it can be assumed that the volume magnetic susceptibility of the particles is a constant within the volume occupied, and the volume occupied by the particles is also approximately constant.
The concept of specific magnetic force is commonly used in magnetic separation studies, which is the magnetic force acting on a unit mass of particles. The use of the concept of specific magnetic force eliminates the effect of the actual voids in the mineral particles on the magnetic calculation.
HgradH is called magnetic field force and its unit is A2/m3. It is numerically equivalent The specific magnetic force. The definition of the magnetic field force indicates that only one suitable magnetic field strength is insufficient when magnetically selecting, and this magnetic field must also have a certain magnetic field gradient. This is why the magnetic separation emphasized earlier is done in a non-uniform magnetic field.
The magnetic or specific magnetic formulas indicate that the magnetic force acting on the magnetically selective particles is determined by the magnetic properties of the particles and the magnetic field force HgradH of the magnetic separation device. Whether it is to increase the magnetic field force or increase the specific magnetic susceptibility of the particles, the magnetic force of the particles can be increased. Therefore, any of the magnetic formulas can be improved to achieve the purpose of magnetic sorting. In the formula derivation, it is assumed that the magnetic force HdraH within the volume occupied by the particles is approximately constant. This assumption is only true when the particle size is small, and this assumption causes a large error when the particle size is large. Therefore, the magnetic force applied to large particles is calculated by applying the integral method, but the particle shape is irregular, so the integral calculation is difficult to do. The empirical method can be used as a reference.
When the ferromagnetic ore particles are close to or close to the magnetic system, the magnetic permeability of the air gap between the magnetic poles is increased, causing a large distortion of the magnetic field, resulting in an increase in the magnetic field strength and the magnetic field gradient. The actual magnetic force of the ore particles is greater than the formula calculation. value. At this point, a correction factor is introduced into the formula that takes into account the ratio of the average diameter of the ore particles to the pole length of the magnetic system. The correction factor is shown in Table 4-5-1.
The necessary condition for the separation of magnetic ore particles from non-magnetic ore particles is that the magnetic force acting on the ore particles is greater than the combined force of the mechanical forces, but it is difficult to distinguish and calculate all mechanical forces. The mechanical force is mostly based on the type of magnetic separator. Estimated by experience.
Leisuwash specializing in manufacture Automatic Car Wash Machine, Touchless Car Wash , Automatic Touchless Car Wash, touchless car wash equipment, robot car wash, smart car wash system, leisuwash 360, leisuwash leibao 360, laserwash 360, leisuwash touchless car wash machine, leisu wash touchless car wash automatic, leisu wash 360 high pressure touchless car wash equipment, robo car wash, touch free car wash, leisuwash 360 touch free car wash, leisuwash 360 price, automatic car wash price, leisuwash in malaysia, no touch automatic car wash machine, leisuwash 360 mini, leisuwash SG fully automatic car wash equipment.
Leisuwash S90 touchless car wash machine high intelligent high quality, with car wash + car care + drying process totally, each car wash takes time 1 minute to 5 minutes which depends on the car wash mode.
Leisuwash S90 Car Wash Machine is an entry level car wash unit, but you won`t find any low grade components and no cost cutting on the expense of quality. Each Leisuwash S90 is built by Leisuwash employees in accordance with our usual quality standards, the low price is achieved by high standardization and the use of proven technology. The Leisuwash S90 is for clients that need a wash machine at a competitive price with higher ROI.
Automatic Car Wash Equipment,Leisuwash S90 Drying,Automatic Leisuwash S90 Drying Car Wash Machine,Leisuwash S90 Drying Car Wash Machine
Hangzhou Leisu Cleaning Equipment Co.,Ltd , https://www.sdleisuwashtouchless.com