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Welcome to our presentation on Liquid Mixing
Course Title: Pharmaceutical EngineeringCourse Code: PHR-320
Represented By……….
Rupom Mitra Kazi Nadim Hossain Md. Anin Nayeem
Liquid mixing Definition
Classification Importance
1.Miscible liquid2.Partially miscible liquid
3.Immiscible liquid
Mechanism1. Bulk Transport
2. Turbulent Mixing
3. Laminar Mixing
4. Molecular Diffusion
a
d
az
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-Motor
Shaft
Lid
Outlet
ImpellerBaffle
Jacket
Inlet
Mixing Vessels
Mixing vessels
Mixing Devices
oPropellersa. Top View
b. Side View
Fig: Propeller type of mixing devices. A 3 bladed design
Turbines30-50% of diameter of vesselSpeed 50-200 rev/min
UsesUsed in very viscous ranges up to 700 P.sCan handle slurries with 60% of solids
AdvantagesSuitable for Emulsification
Different types of turbines
Flow pattern during mixing
3 types1. Tangential or circular flow:
Direction: tangent to the impeller shaft
2. Radial flow: Direction: Vertical to the impeller shaft
3. Axial flow: Direction: Parallel to impeller shaft
Vortex formationCause:1. Shaft mounted vertically in the centre of the tank2. Turbines arranged perpendicular to shaft3. High impeller speed4. Unbaffled tank
DisadvantagesLow mixingAir bubbles contaminationOxidation of compounds
Prevention of vortex1. Avoid symmetry
Off centreInclinedSide entry
2. Baffeld containers3. More impeller4. Cylindrical Tank (Dead spots)
Return Flow with Draft Tubes
• Draft tubes are placed to control the direction and velocity of the flow to the the impeller
• These are mounted around the propeller. In case of turbines ,drufts tubes are mounted immediately above the impeller
Uses:
Used in Manufacture of certain emulsions..Airjet mixers for mixing of liquids employ draft tubes.
Disadvantage: Draft tubes add to the fluid friction in the system that reduce the rate of flow.
Equipment For Liquid Mixing
1.Air jet mixer2.Jet mixer3.Flow mixer or line mixer or pipe
Airjet MixerPrinciple: when compressed air jets are passed from thr bottom of a vessel,air bubbles are formed in the liquid phase.The buoyancy of the bubbles lifts the liquids,which are confines to the central portion due to the presence of drat tubes The floatage of the bubbles lifts the liquids,which are confined to the central portion due to the presence of draft tubes.
Construction: Compresses air or suitable gas is allowed to pass at high pressure from the inlet provided at the bottom of the tank.This causes buoyancyof the bubbles which lifts the liquid from bottom to the top of the vessel
Use: liquids of low viscosity, non foaming, non reactive with gas are mixed by using airjet mixer.
Jet mixer
Principle: The liquids to be mixed are pumped separately into a jet mixer at different velocities. During mixing the slow moving liquid will be drawn at high velocity jet. This increasess the volume of the jet and decreases velocity,which causes to jet to expand.
Conruction:• It consist of a vessel and a mixing device known as jet • A typical jet mixing system has 12 jets arranged radically in a
cluster in the centre of the mixing tank.The cluster of jets is called an eddy jet mixer.
• Av individual eddy jetmixer has two concentric nozzles with a suction chamber between them.
• Advantage: The power required for pumping is often sufficient to complete.
Flow Mixer or Line Mixer or Pipe Mixer
• It may consist of a baffled pipe or an empty chamber • Liquids to be mixed are passed through the pipe or chamber• Mixing takes place through bulk transport in the direction of
flow• The power supplied to pump the liquid itself accomplishes
mixing.• For effective mixing controlling the feed rate is essential.• If the input rate is difficult to controland fluctuations in the
added proportions of the liquids are unavoidable,contious mixing equipment of tank type is preferable.
Uses: When large volume of liquids are to be mixed,flow mixers are used.
Recommended