what is agitator

8/2/2019 What is Agitator

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What is Agitator: Mechanical device which generate fluid motion toget desired process result.

What is difference between agitation & mixing?Agitation induces motion, gives a specific flow pattern and provides

circulation;Mixing is the random distribution of two or more separate phases orsubstances.

Agitator Purpose

Blending: Mixing miscible liquids mutually soluble liquids

Application : Mixing of paint in water, ETP Industry: Dosing tank, flash mixer

Solid suspension: Mixing of insoluble solid material

Application: Coal slurries, catalyst–polymer systems, crystallization,Paper pulp, minning industry like for leaching,

Solid dissolution: Mixing of soluble solid material

Emulsification / Dispersion: Mixing of non miscible liquids or solid &liquidsHigh Shear & Intense agitation.One phase is broken in discrete particles which are completely coveredby the second phaseApplication: Emulsification: Oil & water,paint industry

Dispersion: Mixing of wax in chemicals, gel

Gas Dispersion: Incoming gas is intimately distributed though out inliquid for chemical reactionApplication :for absorption, oxidation, hydrogenation, chlorination, fermentation, andso on also used for carrying out biochemical processes such as aerobic fermentation,and wastewater treatment aerator

Agitator Design: Complex study,Vendor Design, No API, ISO Standard or any other, IS9522, EEUA

Agitator Classification

Based on Mounting: Top Entry – Center / Clamped, Side Entry, BottomEntry

Base on Flow Pattern: Axial Flow, Radial Flow, Cross Flow



General Top Entry Agitator Assembly

Impeller:

What is impeller? Heart of agitator,

Impeller Classification based on flow pattern:

Axial Flow Impeller blending, solids suspension, solids incorporation ordraw down, gas inducement,and heat transfer The blades can be at any angle between 10 and 90◦ from the horizontal,

but the most common blade angle is 45◦impeller rotation to direct theflow toward the bottomhead or down-pumping., Radial Flow used for low to medium viscosity fluids.they are most effective for gas–liquid and liquid–liquid dispersion, theyprovide higher shear and turbulence levels with lowerpumping. Radial flow impellers discharge fluid radially outward to thevesselwallImpeller, High Shear Impeller, and Cross Flow Impeller

Terminology used with impeller:

Power No. NP = P/ρN3D5A dimensionless no., it is used to calculate the power drawn by animpeller,Depends on liquid property density viscosity, shape & size of theimpeller, impeller operating speed.

NP = P/ρN3D5

The power consumed by a mixer can

be obtained by multiplying pumping, Q, and head, H, and is given byP = NpρN3D5gc

Reynolds numbers Re = ρND2 / µ



A dimensionless number ratio of inertia force and viscosity force. Itdefines the flow regime

Reynolds numbers > 10,000 turbulent flowReynolds numbers <10 laminar flow.

In between, there is transition range,

Relation Ship between powers no. & Reynolds No.

Pumping No. Pumping is the amount of material discharged by therotating impellerAs evidenced in this figure, NQ increases as Re increasesup to Re of 10 000 and becomes constant at higher ReFor example, pumping is dependent on number of blades and theblade width.

Axial Flow Impeller: Propeller, Hydrofoil, Axial turbine, Pith paddle

Hydrofoil for applications where axial flow is important and low shear isdesired / twisted blades / This blade shape results in a lower powernumber and higher flow per unit power than with a pitched blade turbine



Radial Flow Impeller: Radial turbine, Radial paddle, Disc Turbine, Curvedblade disc turbine, Curved blade turbineHigh Shear Impeller: Saw Tooth cutter, Stator Rotor TypeCross Flow Impeller: Mig Type & Inter mig type

Shaft: Purpose of shaftMixer shafts are required to transmit the power from the mixer drive to

the impeller(s). With the transmission of this power, the shaft must handlethe loads occurring including the transmission of torque, overhungmoment due to hydraulic forces, and thrust. The shaft must also bedesigned to be stiff enough to limit vibration and deflection to acceptablelevels.

SOLID SHAFTING: most common ease of constructionimpeller hubs require a key to transmit torque

hollow shaft will be stiffer, or rather will deflect less under the sameoverhung momentLess weight means less thrust transmitted to the drive bearings, and a

longer expected bearing life. Less weight also helps avoid critical speed,frequently a limiting factor in mixer design.Overhang Mounted type & simply supported type or intermediatesupportSolid & Hollow

Shaft Seal: Purpose & where to be used1) lip seal2) stuffing box3) mechanical seal : single / double / with system Plan 53A & 544) Vapor seal

Bearing

Lantern stool bearingSteady bearing

Motor & gearbox:

Coupling



Agitator Design, Data sheet, Specification, Inspection

Input Data: Purpose, Component to be mixed, Spgravity , ViscosityTank Details

Process Design: Selection of impeller type, Size & operating speedReynolds No, Pumping rate, Tank turn over rate, Scale

of agitation, Solid Suspension: Particle Settling velocity. Consumedpower calculation

Mechanical Design: Motor horse power calculation, Shaft design: BM, Torque, Equivalent BM, Critical speed of Assembly, Bearing: Lifecalculation.

Specification: EIL or Uhde

Inspection & Testing:



Offer Evaluation:

what is agitator

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