1) Turbines
Turbines are mechanical devices used for mixing different types of fluids with different types of blades and impellers.
Principle
Turbines differ from the propellers. as they rotate rotor blades at a lower speed as compared to the propellers, and also the ratio of the vessel diameter and the impeller diameter is low. Turbines are used for mixing high viscosity liquids because of the greater shear forces produced by them as compared to the propellers. They are used especially for the preparation of emulsion. For preventing vortex formation, baffles are often used.
Construction
Turbines consist of a circular disc having short blades attached to It. Their diameter is 30-50% of the vessel diameter. They rotate at speed (lesser than the propellers). Different steam turbines have blades of different shapes, like straight, curved, pitched, or vertical.
Radial and tangential flow is produced by flat-bladed turbines; however, on increasing speed, the radial flow dominates. Axial flow is produced by pitched. bladed turbines. Rapid currents, high turbulence, and intense shear are Observed near the impeller. A diffuser ring (a stationary perforated or slotted ring surrounding the turbine) is used to further increase the shear forces stereo mixing produced by turbines.
The fluid passes through the perforations of the diffuser ring, thus reducing rotational impulse turbine swirling high and low pass filters
and vertexing.
Working
Turbines operate similar to a centrifugal pump working in a vessel against negligible back pressure. Mixing is accomplished by the wind turbines blades which constrain and discharge the liquid.
These streams cause mixing in their energy. On operating the turbine mixers at high rotational speeds, prominent radial, as well as tangential flow occurs along with the formation of vortex. This situation mixing stage demands installation of baffles into the vessels for a uniform mixing to occur.
Uses
Turbines have the following uses:
l) Due to high shear forces, they are effective for high viscous solutions, e syrups, glycerin, etc.
2) They are suitable for liquids of large volume and high viscosity.
merits
Turbines have the following merits:
1) They provide greater shearing forces than propellers. so the pumping lese, therefore, are suitable for emulsification.
2) They do not damage dispersed particles at economical speeds.
Demerits
Turbines have the following demerits:
1) Due to the absence of vertical flow, they are less suitable for suspension.
2) They are expensive to fabricate, and are restricted to a narrow range of speeds.
3) They are expensive.
2) Paddles
Paddles are mechanical devices used for mixing the liquid materials. They are similar to the plow type but the designs of paddles mounted on the shaft are different from that of plow mixers.
Principle
Paddles work on the principle of kneading action and they apply shearing forces for mixing liquids.
Construction
Paddles are flat blades attached to a vertical shaft rotating at a speed of 100rpm.
Simple flat paddles are used for mixing liquids of low viscosity. Big paddles (shaped to fit closely to the vessel surface) are used for mixing high viscosity liquids. Paddles of different sizes and shapes are used in pharmaceutical industries as per the product's nature and viscosity.
Working
Paddles are attached to a vertical shaft rotating at a speed of 100rpm. Simple flat paddles are used for mixing liquids of low viscosity. Big paddles (shaped to fit closely to the vessel surface) are used for mixing high viscosity liquids. Paddles Of different sizes and shapes are used in pharmaceutical industries as per kinetic energy the Product's nature and viscosity. They can also be used for kneading and for audio mixing mastering engineer pastes since the kneading action shows or allows phase changes from dry to paste when liquid is added. The type of paddles used and the speed of rotation together bring about mixing of liquids.
Uses
Paddles have the following uses:
1) They are used for manufacturing antacid suspensions, agar and pectin-related purgatives, and anti-diarrheic mixtures such as bismuth-kaolin.
2) They are used for drying and cooling bulk powders.
3) They can be used for cohesive materials.
4) They are used in pharmaceutical industries and biotechnology laboratories. 5) They are also used in food and chemical industries.
Merits
Paddles have the following merits:
l) They operate at low speed; thus, vortex formation does not occur.
2) They undergo good radial and rotational flow.
3) They are economic.
4) They are versatile.
5) They can be used as a continuous and batch process.
6) They are simple and can be easily handled.
7) They provide efficient mixing.
8) They do not result in segregation of materials.
9) They carry out the mixing process in a short duration.
10) They provide a high yield.
Demerits
Paddles have the following demerits:
l) They are not suitable for mixing suspensions, and require baffled tanks.
2) Their pumping capacity is small.
3) They require high power for operating efficiently.
Factors Affecting Mixing
A single factor alone is not involved in mixing. Nevertheless, the most significant consideration is flow Pelton wheels property of the components influenced by the following factors:
1) Surface Nature: Because of the entry of active ingredients into the pores of other elements, suitable mixing may not individual tracks occur due to the rough potential energy surface of the particular element.
2) Particle Density: This factor has less importance. Sudden halt of the mixing process or presence of small panicles with high density accelerates the process of demising because the material with high density travels downward and residue at the bottom.
3) Particle Size: Two powders which are of almost the same particle Size are easy to mix. Small particles go to the bottom by passing the gaps between the bigger particles and get parted due to the pass filter difference in particle size. Under the gravitational force effect, flow mixing engineer property rises with an increase in panicle size, but after a certain point flow property declines. Mixing is promoted by free-flowing powder having a mean particle size of less than
4) Particle Shape: For uniform mixing the ideal particle shape is spherical. The particles of irregular shape are not separated easily if power plants mixed together due to interlocking between the particles.
5) Particle Charge: Separation or aggregation occurs as some particles employ attractive forces which are generated electrical because of their electrostatic charges.
6) Material Proportion: By mixing two powders in an equal ratio by weight and volume, finest outcomes multitrack recordings can be obtained. Mixing occurs in the ascending order of the weights of two powders if their ratio varies to a greater extent reaction turbine.
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