02 Feb PRINCIPLE OF HYDROCYCLONES OPERATION
Hydrocyclones can be considered as a filtration system different from the most common physical filtration systems, such as media filters (deep filtration at low velocity), disc filters or screen filters (superficial filtration).
Hydrocyclones, or also called cyclones, are equipment designed for the separation of solid particles in liquid mediums and have numerous applications in the mining, food and chemical industries and of course, in agriculture, where they are widely used as sand separators in mainly underground catchments (well water).
Its function is the physical separation of particles with a specific weight much higher than the fluid due to the effect of the centrifugal force generated by the geometry of the hydrocyclone. The hydrocyclone has a cylindrical section, followed by a conical section. It has a tangential feed, an outlet (vortex) for the diluted fluid (overflow) and an output (apex) for the concentrated fluid (underflow) at the bottom with a collector tank.
The particles tend to settle and descend due to the force of gravity, which overcomes the frictional forces caused by the water.
In sandy water, the Stokes formula can be applied to calculate the settling velocity of the particle. In this formula, the settling velocity of a particle is determined by the quotient of the difference in densities of the solid and the liquid divided by a constant times the viscosity of the liquid and multiplied by gravity and the particle radius squared.
If we apply this equation to the different sizes of the sands, the coarsest sands would be separated from the fines ones as they fall at a higher speed. In order to separate the finer elements, we would get very slow sedimentation velocities, so we would need large surfaces. In this case, we could only act on gravity by creating a new gravity field (densities, viscosities, sand diameters and water diameters will be considered constant).
In order to increase the “gravity field”, the geometry of the hydrocyclone makes the coarser particles (sand) rotate close to the wall due to the centrifugal acceleration caused by the hydrocyclone, and the “main vortex” descends to the end of the conical part, where the narrowing (apex) produces a “secondary vortex” that separates the larger particles, leaving the fines and water through the vortex and leaving the coarse particles (sand) accumulated in the tank.
Therefore, the hydrocyclone geometry produces the acceleration that separates the coarser particles from the fines and water without the need for large sedimentation tanks.
LAMA hydrocyclones are designed for the most efficient separation of sand particles and are manufactured in different sizes and arrangements depending on the working flow rates. They are an economical method for the separation of sand in catchments and are usually accompanied by another filtration method for the cutting of the fines coming out of the vortex depending on the subsequent application of use.
The calculation of the length of the vortex, the diameter of the cylindrical part, the angle and length of the cone are decisive for the system to be as efficient as possible in sand separation and to retain a high percentage of the sand.
This equipment has no moving parts, so maintenance should only be focused on emptying the accumulation tank on a regular basis. A very common mistake in the facilities is not to empty the deposit, compromising its efficiency. In LAMA we propose to add to the purchase of the hydrocyclones a cleaning kit, obtaining practically null maintenance tasks. Our kits are automatically in charge of emptying this purge tank, without the need of external supervision.