What is the core principle of dense medium coal preparation?

A gravity coal preparation method uses heavy liquid or suspension with density greater than water and between coal and gangue as medium to realize separation. According to the different media used, it can be divided into two categories: heavy liquid coal preparation and heavy suspension coal preparation.

Heavy liquids refer to aqueous solutions of some inorganic salts and high-density organic solutions. Heavy suspension is a two-phase fluid with a certain density and suspension state, which is made up of weighting materials (high-density solid particles) and water. When raw coal enters the separator with this suspension, the coal with density less than the suspension floats, and the gangue (or middle coal) with density greater than the suspension sinks, thus realizing density separation.

Extended data

The basic principle of dense medium coal preparation is Archimedes principle, that is, the buoyancy of particles immersed in liquid is equal to the weight of the same volume of liquid discharged by particles. Therefore, if the particle density is greater than the suspended density (ρ), the particles will sink; When it is less than ρ, the particles float; When it is equal to ρ, the particle is in suspension.

When particles move in suspension, they will not only be affected by gravity and buoyancy, but also be resisted by suspended liquid. Particles that initially move at an accelerated speed relative to the suspension will eventually move at their final speed relative to the suspension. The larger the particles, the greater the relative velocity, the faster the separation speed and the higher the separation efficiency.

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