In places where muddy waters exist in nature, hydrocyclones are used to separate the particles from each other by sedimentation. The sediment particles at the bottom form a darker precipitate than at the inlet, and the remaining water is purified from the coarse particles and separated. In the mining industry there is an artificial pool where this procedure takes place and it called “thickener”.

The flow rate of the water passing through the thickener is high enough to prevent the fine particles from settling and cause them to separate from the upstream, allowing the fine and coarse particles to be separated. Hydrocyclones have centrifugal forces that increase the sedimentation rate and facilitate separation. Hydrocyclones are equipment that work according to this principle.

The pressurized feed from the inlet of the hydrocyclone provides suspension return movement. The slurry entering the cyclone tends to leave the cyclone from the lower outlet (apex), forming a vortex on the inner surface of the cylindrical and conical walls. As a result, only part of the flow leaves the cyclone downstream (at its apex) and takes with it coarse particles or even all solids. The remaining liquid rises upwards and leaves the cyclone at the upper outlet, forming a secondary vortex surrounding the center of the hydrocyclone. A low-pressure zone forms at the center of the secondary vortex where all the bubbly or dissolved air in the mixture is collected.

Since the circular velocity of this vortex is higher, a greater centrifugal force is produced. In this way, a more effective separation occurs. In the secondary vortex, radially separated fines precipitate, then mix with the primary eddy and many exit the lower outlet of the hydrocyclone. Therefore, separation in the hydrocyclone occurs as a result of two separate phases, and the final extent of separation is largely determined by the acceleration of the inner vortex.

In addition, secondary currents and circulation zones are formed in the cyclone, as the liquid entering the cyclone creates an internal vortex by ascending and returning tangentially up to a certain point with a spiral motion along the wall. In addition to this complex flow structure, the parameters, geometry and operating principle affect the performance of the cyclone. Operating conditions include initial flow and particle size distribution at the inlet. Among them, the capacity of the cyclone is mainly determined by the inlet section, body length, outlet pipe diameter, flow rate, temperature, liquid density, pressure, diameter, chemical properties, etc. Particles multiplicity also complicates the analysis of the flow area and the determination of the cyclone efficiency. Even small changes in these parameters affect performance.

Therefore, in order for these parameters to work optimally with each other, their values need to be optimally adjusted. It can be said that the reason for the increase in hydrocyclones use especially in recent years is that it consists of fixed parts, does not require maintenance costs, is easy and cheap to manufacture and has high efficiency.

The advantages of cyclones used as pre-separator, main separator and sampler in different sectors are as shown below.

• No need for maintenance.
• It offers high collection efficiency. It ensures that the dimensions that are difficult to recover with many systems are included in the material again.
• No more cleaning required.
• Used for separation and collection of fine-grained materials with optimum pressure losses.
• It is produced to hold particles larger than 40 microns in industrial dust collection systems from 50 m3/h to 400 m3/h.
• The space it occupies in the system is less than other systems.