In contrast to centrifuges, cyclone separators (used for solids-gas, solids-liquid, and gas-liquid separation tasks) are mechanically simple; comparatively inexpensive to buy, install, and run; compact compared to non-centrifugal (gravity) separators; and require little maintenance. Cyclone separators are used to recover the powders generated by spray drying. A high-velocity stream of powder and air is fed tangentially into the apex of a cylindrical vessel. This causes a swirling motion within the storm, resulting in the establishment of centrifugal forces. Because the powder particles are denser, they are thrown to the cyclone's wall, where they collide, lose kinetic energy, and descend to the bottom of the vessel, where they are collected and removed. At a different take-off point, the air is removed. Cyclones are low-maintenance items due to their simple design and lack of moving components.
1.1. Types of separation
· Gas-solids separation: In the dairy industry, cyclone separators are used for gas-solids separation, primarily to separate product fines from the air exiting spray dryers and fluidized bed dryers, in order to increase yield and reduce air pollution. This is the most frequent use of cyclones.
· Gas-liquid separation, primarily for in-line deaeration of milk (essential for maintaining the efficiency of downstream centrifugal separators) and separation of concentrate leaving an effect of a multiple-effect evaporator from the water vapour (steam) evaporated from the product in the effect. Clean separation stops bubbles of steam from being kept in the concentrate (ultimately diluting the concentrate when they condense on cooling) and carryover of concentrate into the steam side of the next effect or into the condenser in the latter application.
· Solids-liquid separation, which can be used to separate solids from waste sources. Hydro cyclones are solids-liquid cyclone dividers.
2.Principles of design and operation of cyclone separator
The cyclone is a vertical body with a conical bottom portion and a cylindrical top portion. The solids-air mixture enters the cylinder obliquely at the top. The flow of air around the curved wall of the cyclone converts the mixture's linear motion to rotational motion; the cyclone wall provides the centripetal force needed to make the air spin.
When the air begins to rotate, the fine particles, which are free to move relative to the air, move towards the wall because no centripetal force is applied to maintain them in orbits around the cyclone's axis. When they strike the wall, they are separated from the air and fall to the cyclone's bottom. The centrifugal effect is thus caused by the cyclone's form, the manner in which the mixture to be separated enters the cyclone, and the velocity of the mixture. (Which is generated by a fan in the case of dryer air, or by a pump, or by a pressure difference).
The separation of the particles in the manner described above is not instantaneous; the way the air flows through the cyclone achieves a suitably lengthy residence time. The air flows in a spiral route down the cyclone's cylindrical and conical parts, then inward towards the cyclone's axis, and ultimately upward into a coaxial tube from which it exits at the top.
The centrifugal effect is thus caused by the cyclone's form, the way the mixture to be separated enters the cyclone, and the velocity of the mixture. (which is generated by a fan in the case of dryer air, or by a pump, or by a pressure difference).
The air flows in a spiral route down the cyclone's cylindrical and conical parts, then inward towards the cyclone's axis, and ultimately upward into a coaxial tube from which it exits at the top.
The operation theory is founded on a vortex motion in which the centrifugal force acts on each particle, causing them to move away from the cyclone axis and towards the inner cyclone wall. The movement in the radial direction, on the other hand, is the product of two opposing forces: centrifugal force acting to move the particle to the wall and drag force acting to carry the particle into the axis. Separation occurs because centrifugal force is prevalent.
At the same velocity, powder and air enter the cyclone obliquely. Powder and air spin in a spiral down to the cyclone's base, separating the powder from the cyclone wall. Powder falls to the bottom of the cyclone via a locking device.
The centrifugal force experienced by each atom is depicted in the following equation:
C = mV^2/r
Where C denotes rotational force.
m = molecule mass
V is the perpendicular air velocity.
r= the radial distance from any given location to the wall.
3.Arrangement and efficiency
Cyclones can be used singly or in groups to create multi-cyclone systems. The efficiency of separation with a cyclone machine varies depending on the product, cyclone design, and particle size to be removed, but losses vary from 0.5 to 3 percent on average. The cyclone is typically used for material sorting between 5 and 200. The efficiency of the cyclone reduces as particle size decreases. A correctly designed cyclone will remove 99% of solids larger than 30 microns, 98% of material larger than 20 microns, 90% of material larger than 10 microns, and only 50% of material smaller than 5 microns.
The greater the particle mass, the greater the effectiveness. The shorter the distance the particle must travel, the better the efficiency, and the closest the particle is to the wall, the better the efficiency, because the velocity is greatest, and the radial distance is shortest. However, because particles must travel to the cyclone wall, an adequate air residence time should be considered when designing a cyclone.