The Leader i n M ix ing Techno logy

Impeller Technology

The key to an efficient mixing sys-tem is the impeller. For eachapplication there is an idealimpeller. Lightnin, with over 70years experience in fluid mixing,are uniquely placed to offer effec-tive solutions for all applicationareas.

Lightnin’s commitment toresearch and development hashelped to create a unique, mod-ern, spectrum of impellers, whichmeet the needs of processesaccurately and efficiently.Lightnin’s mixers range from fractional kW through to the

world’s largest unit at over2500kW. The use of Lightninimpellers has generated lowercapital and operating costs for many thousands of our customers world wide.

Research and DevelopmentThe Key to Successful Impeller Design

The LIGHTNIN Laser laboratoryLightnin operates the world's mostadvanced mixing laboratory. Usingthe four laser beams of a LaserDoppler Velocimeter (LDV) fluidmotion as pumping capacity and -direction at any point of a vessel

are converted into digital information vital to impeller designand optimisation.

Lightnin A6000 impeller operating in the laser laboratory

Finite Element AnalysisLightnin complement researchinto fluid dynamics and impellerdesign by employing advancedcomputational techniques in theform of (Finite Element Analysis -FEA). FEA is used principally intwo areas:

■ Modal Analysis. The naturalfrequencies of the mixer andits mounting structure can bepredicted, thus ensuring thatpotential costly vibration problems are eliminated at thedesign stage.

■ Optimising agitator design.FEA calculates mechanicaland structural integrity, withoutunnecessary overdesign, thusensuring customers receive themost cost effective mixingsolutions for their particularprocess.

Computational Fluid MixingThese accurate data from the LDVare combined with the power of"Computational-Fluid-Dynamics"-Programms (CFD) in order to predict the mixing dynamics inlarge tanks with unusual geometryor specific process require-ments.This powerful capabilityreduces substantially pilot- or fullscale trials.

CFM plots graphically display full scale mixer performance

Finite element analysis of high efficiencyimpeller blade

Impeller type: A310 - A510

Low viscosity and flow-controlled applications

The A310 - A510 series provides acombination of performance char-acteristics and high flow efficiencynot available from other types ofaxial flow impellers

The A310 - A510 can produce thesame flow and process results at alower power than other axial flowimpellers thus reducing operatingand capital costs.

Impeller type: C100 - C110Draft-tube circulators.

Designed specifically for depend-able draft tube service, the C100 - C110 has a true airfoilshape and provides high flow, evenin unstable process conditions,whilst minimising power require-ments. A specific family of impellers(unique to Lightnin) based upon theC100 - C110 design is available foruse in draft tubes.

Processes include alumina, gold,uranium and potash.

Impeller type: A200Low/medium viscosity, flow-controlled applications.

The traditional impeller for largervolume applications. Largelysuperceded by the A510, it still hasa specific role in applications wherea degree of fluid shear is beneficialto the overall process result.

Impeller Type: A340

Gas/ liquid applications with up-pumping characteristics

The A340 with up-pumping axialflow is the most recent developmentfor gas/liquid applications.

The A340 can be used for coalescing and non-coalescing systems and allows better

■ mass transfer

■ heat transfer

■ shorter mixing times

Un ique Impe l l e r Range fo r accura te ,

Impeller type: A6000Low viscosity flow-controlledapplications for hostile environments.

The A6000 is a composite con-struction impeller. It uses a highgrade vinyl ester resin system withstrength and corrosion resistancebeing key features.

Where exotic metals such as titanium, zirconium, hastelloy, etc.are required, the A6000 can be acost effective alternative. Due to theoptimum airfoil profile produced byimpact moulding production techniques, the A6000 is 25% moreefficient than the A510.

Impeller type: A315Axial flow impeller for gas/liquid applications

The A315 is capable of dispersinggas and controlling flow patterns atsignificantly higher gas rates thanother axial flow impellers.Compared to conventional Rushtontype radial flow turbines, the A315can provide up to 30% greater masstransfer at equal torque and powerconsumption.Good axial flow patterns from theA315 give good solids suspensionand significantly reduce powerrequirements.

Impeller type: A312Axial flow impeller for sideentry applications

The A312 is designed for the arduous requirements of pulp andpaper applications.

It is also used in other side entryapplications such as oil storage andFGD (Flue Gas Desulphurisation). Itis an axial flow impeller with a minimal radial flow component,unlike other conventional side entrymixer impellers.

Impeller type: R400Two bladed anchor for higherviscosity applications.

The R400 is a contoured two blad-ed anchor. It has applications inblending and particularly, heat trans-fer, where the viscosities range from10000 to 100000 centipoise.

Impeller type: R100 - R130High shear mixing and gas-liquid applications.

The R100 rushton turbine is the traditional impeller for gas - liquidmass transfer controlled systems. Itis also used where higher shear isneeded.

The R130 shown above has similarcharacteristics to the R100 but gives:■ A higher power input in the

gassed condition (reduced ‘K’ factor effect)

■ Lower power in the ungassedcondition

Impeller type: R500 (SAW Tooth)High shear, typically used fordifficult to disperse pigments.

The R500 provides high shear rates.It is generally used in conjunctionwith a high flow impeller in appli-cations involving a combination ofblending and a need for physicalchange created by fluid shear.

Impeller type: A400Helical impeller for high viscosity applications.

Where very high viscosity (above100,000 centipoise) is involved, helical impellers can be used. A variety of options in terms of number of flights, pitch and helix are available to suit the specificrequirements of the duty.

The A400 also promotes surfacerenewal and heat transfer.

Impeller type: A320High flow impeller for higherviscosity applications.

The A320 is designed to operate inhigher viscosity fluids. The effective-ness of many high efficiency impellersystems which are designed tooperate in the turbulent flow regimeis impaired as the viscosity of thefluid increases and the ReynoldsNumber decreases. This is not thecase with the A320. The uniquedesign of the impeller reduces bothcapital and operating costs. Blendtimes are also reduced compared toother ‘open’ impellers used at lowReynolds numbers.

guaran teed resu l t s

Impeller SelectionMixing is the key to process design. Impeller selection is a key to mixerdesign.

How impellers convert energy into fluid motion is fundamental to theirability to provide a predictable process result.

All the energy (P) applied by any mixing impeller produces a pumpingeffect (Q) and a velocity head (H), so that

P a QH

A knowledge of how this balance of energy distribution can change withimpeller geometry is fundamental to mixer design. Lightnin has used itsextensive knowledge of impeller fluid mechanics to develop a family ofefficient, process specific, impellers.

Impeller ComparisonBasic formularNot all impellers perform at a similar level of efficiency even though they may super-ficially look to be similar in design. The performance capability of flow impellers can be compared by an evaluation of flowefficiency.

A knowledge of the flow numbers (Nq) andpower number (Np) of the impellers beingcompared is required.

Advanced technology provides predictable mixing

Nq = Q

ND3

Nre = ND2r

m

Np = Impeller power number

Nq = Impeller flow number

N = Impeller rotational speed (1/sec)

Nre = Impeller Reynolds Number

mmmm = Viscosity in Pas

P = Impeller power (W)

D = Impeller diameter (m)

Q = Impeller primary flow(m3/sec) (pumping capacity)

r = Fluid density (kg/m3)

The following basic equationscan then be applied:

Impeller spectrum indicates relative powerapportioned to Q and H for various impellertypes.

Np = P

N3D5r

Impeller Spectrum

A6000

A310 - A510

C100 - C110

A320

A312

A315

A200

R100

R500

kW

Flow(Q)

Pressure

Head (Shear)H

Comparison BasisBefore two impellers can be compared, a basis for the comparison must be established.

Whilst many combinations of parameters can be applied (e.g. power required at constant flow and speed, orconstant speed and diameter), the most applicable to the flow controlled operations of blending, solids sus-pension and heat transfer is constant diameter, D and constant flow, Q. Applying the basic mixing formulae inratio form gives the following comparison

Table 2 demonstrates that at constant impeller diameter to tank diameter ratio (D/T) and constant flow Q (i.e.constant process result), the Lightnin A510 mixer requires 51% less power and less than half the torque (andtherefore lower operating costs), than a mixer fitted with a pitched blade turbine.

Using the formulare intable 1, the performanceof different impellers canbe evaluated in relation toeach other. For example,table 2 compares theLightnin A510 with a 45°Pitched Blade Turbine.

Table 1 Table 2Parameter Ratio

Speed Nq (2)Nq (1)

Diameter 1.0

Flow 1.0

Power Np1 (Nq2)3

Np2 (Nq1)3

Flow/Power Np2 (Nq1)3

Np1 (Nq2)3

Torque Np1 (Nq2)2

Np2 (Nq1)2

Parameter Lightnin Pitched A310 blade A200

Np 0.30 1.27

Nq 0.56 0.79

Speed 1.00 0.71

Diameter 1.00 1.00

Flow 1.00 1.00

Power 1.00 1.51

Q/P 1.00 0.66

Torque 1.00 2.13

1.0

E

05

02

Bran+Luebbe GmbH · P.O.Box 13 60 · D-22803 Norderstedt · Phone (040) 522 02-0 · Fax (040) 522 02 444 · E-Mail info@bran-luebbe.de · Internet http://www.bran-luebbe.de

Our Organisation

QualityWe recognize that our customers demand a highquality product manufactured and serviced in a timelyand efficient manner. Working within the processindustry we are fully aware of the specific demandsfor quality standards and all our companies are ISO 9001 accredited.

GuaranteeAll our products are built to last and we provide warranty periods that are appropriate for the specificindustries where the equipment is located.

How to contact us

Your local contact

Worldwide SupportCombining Bran+Luebbe, Lightnin, Plenty and Premier Mill has lead to a worldwide network ofexpertise in process equipment for industrial mixingand metering. With our own companies and representatives you will always find experiencedsupport immediately available.

After Sales and ServiceOur dedicated direct service teams are readily avail-able to support your process equipment at all times.Genuine spares and service solutions can be obtainedfrom all our companies and ensure operating capacityof your valuable production equipment.

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