Principle, Construction, Working, Uses, Merits and Demerits of Sieve Shaker and Cyclone Separator

Sieve Shaker

Principle

Die sieve shakers work on the principle of vibration, agitation, or gyration. In order to effectively use sieve shakers for screening, data on particle size distribution, sieve load, sieve shaking method, particle shape and size, and ratio of sieve open area to total area must be considered. Sieving can be affected by powder properties like friability and cohesion. In sieving, the sample is either horizontally or vertically moved, depending on the technology. The particles and sieve are moved around during this movement. Depending on the size of the particles, a particle flows through the sieve mesh or stays on the mesh surface. The likelihood of a particle passing through the mesh openings depends on factors such as particle size, particle orientation, and the number of times the particle comes in contact with the mesh openings. So, the sieving is influenced by the sieving time and the sieve movement.

Construction

Sieve shakers consist of a base, a cradle for holding sieves, and an electrical power unit. Figure below illustrates the cradle, which is constructed from two vertical rods joined at the lower ends by a platform. There is a horizontal support that can pivot freely around the higher ends that are shock-mounted. Holding the top bar securely against the nest of sieves are sieve holders, retainer rings, and nuts on the vertical support rods. The sieves used are standard sieves with varying sieve numbers.

Working

Arrangement of sieves in a nest is done with the coarsest at the top. On the top sieve (Figure), a sample of the powder is placed (50 grams). For a certain period of time, this sieve set is shaken for 20 minutes with the mechanical shaker apparatus. Each sieve is weighed after it has been shaken.

Uses

• Materials of all kinds are tested for particle size using sieve shakers.
• The machine can handle a maximum of 150 m of coarse material.
• For wet sieve analysis, the material analyzed does not come into contact with the liquid except to be dispersed.

Merits

• It is easy to operate a sieve shaker.
• Samples are separated in a short time.
• Only particles with a diameter up to 50 mm can be used.
• Installation takes up less space.
• It is possible to accurately and reproducibly size particles.
• Compared with other methods, this instrument has a lower cost.

Demerits

• Compared to wet sieving, dry sieving is less accurate for materials finer than 100 mesh.
• The sieve analysis assumes all particles are round (spherical), but this is not always true.
• An elongated particle or a flat particle cannot be reliably analyzed using a sieve.
• Particles smaller than 50 mm should not be used.
• Errors can occur if the size is further reduced.
• If not properly handled and maintained, sieves can become clogged and distorted.

Cyclone Separator

Principle

Solids and fluids are separated by centrifugal force in cyclone separators. Separation of particles is influenced by particle density in addition to particle size. With cyclone separators, different types of particles can be separated based on fluid velocity. Moreover, fine particles are also capable of being carried by the fluid.

Construction

Cyclone separators are a bit more complex to design, but they are better at removing particles. Cyclones work similarly to centrifuges. Fig. shows a cylindrical vessel with a conical base called the barrel. On the upper section of the vessel are tangential intakes and fluid outflows, while on the bottom is a solid exit. In addition to their many shapes and sizes, cyclones have no moving parts. For example, cyclone separators with a diameter of 1 to 2 cm can be used to determine particle size, and cyclone separators with a diameter up to 5 m can be used after wet scrubbers, but the basic separation principle remains the same.

Working

Separating solids involves suspending them in a gas stream. As a result, tangentially introduced feeds are introduced at a high velocity, causing rotation within the vessel. The solids are thrown to the walls by centrifugal force and vortices. When the speed of air slows down, particles leave the solid outlet. Fluid (air) escapes from the top through the central outlet.

Uses

Solids are separated from gases using this device.
It can separate the coarse particles from the fine particles in dust.

Merits

• Granules of fine grade. Since centrifugal force is much stronger than gravity, the cyclone classification can produce particles as small as 0.074mm. Most fine particle classification is done using hydro-cyclones.
• The classification process is highly efficient. The grading efficiency of this equipment is significantly higher than equipment for grading materials with very fine particles.
• Processes volume at a large rate.
• The cost of investment is low
• During shutdown, the cyclone retains a small amount of slurry for only a short time, and it is easy to handle.
• An easy-to-maintain structure that is lightweight, flexible, and has no moving parts.
• The footprint is small. Hydro-cyclones cover about l/30 to l/50 of the surface area of spiral classifiers with the same capacity.

Demerits

• It consumes a lot of power. It consumes about 5 to 8 times more power than other grading equipment to operate the sand pump used for the cyclone, which is used in mining.
• Wears fast. A regular replacement of the wear parts around the feed and settling inlets is particularly important. Because of this, wear-resistant parts are often used, such as inner rubber and polyurethane, as these are easily replaceable.
• Due to feed quality, feed particle size, and feed pressure fluctuations, the cyclone's functioning indicators are more impacted.

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