Cyclone It is a coal preparation equipment with simple structure, no moving parts and high separation efficiency. Because the cyclone has no moving parts, the separation process depends on the flexible coordination of its own structural parameters and external operating parameters to achieve the separation accuracy. This is a significant difference between cyclone coal removal method and other coal preparation methods.
Dense medium cyclone is a kind of separator which uses centrifugal force field which is tens or even hundreds of times stronger than gravity. Its separation process depends on the flexible coordination of its own structural parameters and external operation parameters to achieve the separation accuracy. This is the outstanding feature of cyclone coal preparation which is different from other coal preparation methods. The characteristics of heavy medium are as follows
1. The separation efficiency is high. The separation efficiency of dense medium cyclone is high among various gravity coal preparation methods.
2. The adjustment range of sorting density is wide. The separation density of dense medium coal preparation is generally 1300 kg / m3 ~ 2200 kg / m3, which is easy to adjust, and the error can be kept within ± 0.5%.
3. It has strong adaptability and wide separation particle size range. The particle size, quantity and quality of raw coal are allowed to fluctuate greatly in dense medium coal preparation.
4. The production process is easy to realize automation. The density, liquid level, viscosity and magnetic content of suspension used in dense medium coal preparation can be automatically controlled.
In the separation process of dense medium cyclone, the material and suspension are fed into the cyclone with a certain pressure along the tangent direction to form a strong vortex flow; the liquid flow starts from the feed inlet to form a downward external spiral flow along the inner wall of the cyclone; a rising inner spiral flow is formed near the cyclone axis; air is drawn in due to the negative pressure of the internal spiral flow The clean coal in the feed flows upward with the inner spiral and is discharged from the overflow port, while the gangue flows downward with the outer spiral and is discharged from the underflow port. The formation mechanism of air column is as follows: because the underflow pipe and overflow pipe are directly connected with the atmosphere, the two-phase flow into the cyclone moves with strong spiral vortex. When the tangent speed becomes white and reaches the critical speed, some resistance will be generated at each outlet of the cyclone to form the internal rotating flow field, causing axial negative pressure. Air enters the cyclone through the overflow pipe and underflow pipe Under the combined action of axial negative pressure drive and fluid convection transmission, it gradually develops into a through air column. When the particle density is greater than the density of the suspension, the resultant force of the particles at the radius of R in the suspension is positive, and the particles are thrown out of the spiral flow; otherwise, the particles are thrown into the internal spiral flow, so as to separate the particles with the density greater than the medium and the particles with the density less than the medium. In the cyclone, the centrifugal force is several to dozens of times larger than the gravity, so the separation speed is greatly accelerated and the separation effect is improved.
Analysis of wear mechanism
(1) Micro cutting wear the so-called micro cutting wear refers to the scratch of the inner surface caused by irregular particles in the working fluid of hydrocyclone. Micro cutting wear depends not only on the material and hardness of the cyclone, but also on the geometric shape, tangential velocity, radial velocity and axial velocity of the particles. Even if the hardness of the particles is less than that of the material of the hydrocyclone, it can also play the role of micro cutting wear on the inner wall of the cyclone;
(2) Surface fatigue wear surface fatigue wear refers to the stress produced by the alternating friction between particles and liquid on the inner wall of hydrocyclone, which produces great deformation and stress at the contact point, which makes the inner surface of hydrocyclone form wear and peel off the abrasive particles. The surface fatigue wear is a kind of wear form which gradually invades into the deep layer from the inner surface of hydrocyclone. Generally, it occurs at the defects in the inner wall of hydrocyclone, and then gradually expands under the repeated scouring;
(3) Corrosion wear is caused by the chemical or electrochemical reaction between the inner wall of hydrocyclone and the medium in the liquid. This kind of wear is called corrosive wear. Corrosion wear can be divided into three types: direct oxidation wear, cavitation wear caused by tiny bubbles in the liquid and medium wear due to the chemical properties of the medium itself.