污水廠中的攪拌器p

1、Mixing in WWTPMixing DutiesWhat is the job of the mixer in WWTP ?What is the reason mixing is needed ?Prevent settling of solids in a liquidKeep the bottom free from sedimentsKeep the solids in a homogeneous suspensionMixing Duty: SuspensionDrawdown of solids from surfacee.g. Particles lighter than

2、the liquidMixing of miscible liquids / Elimination of concentration differencesSpecified degree of homogeneitySpecified mixing timeMixing InflowBatch MixingMixing Duty: BlendingTransport of liquid & matterLiquid transport into and out of aerated zonesMixing Duty: CirculationMixing Duties in WWTPSand

3、 gritsControl level of suspensionKeep sludge in suspensionAllow sand to settleMechanical TreatmentEqualisation & Retention basinsKeep solids in SuspensionIntake pump station / Lifting stationKeep bottom cleanDraw-down of floating wasteIntake to WWTPMixing Duties in WWTPBiological TreatmentAnaerobic

4、zonesKeep activated sludge in suspensionMix inflowAnoxic zonesKeep activated sludge in suspensionMix inflowMixing Duties in WWTPBiological TreatmentAerated tanksKeep activated sludge in suspensionCirculate liquid over aerated zonesSBR (Sequence Batch Reactors)Mixers and aeration work alternatingKeep

5、 activated sludge in suspensionMix inflowMixing Duties in WWTPFlash mixingMixing chemicals into sludgeGiven homogeneity and timeChemical TreatmentFloc mixingSuspensionGently circulation to achieve flocculationMixing Duties in WWTPSludge Treatment / HandlingMixing / collecting tanksMixing inflowsKeep

6、 sludge homogeneousDigestersKeep sludge homogeneousThickening / Storage tanksKeep sludge homogeneousThe Products: Flygt Mixers“Banana blade” mixers“Compact” mixersCompact mixersCompact Stainless steel designSmall / medium size diametersDirect driven (multi-pole)Flexible installation on Guide barsEas

7、y accessible for inspection & serviceSuitable for all tank shapes and sizes4600 - series46104620463046404650466046704680Banana Blade MixersLarge diameter & slow speedGear drivenSuperior efficiency = Low power consumptionCorrosion resistant coatingGuide bars installationSuitable for larger tanks of a

8、ll shapes4410/4430 - series44104430Installation SystemsSingle Guidebar systemThe most commonly used. Allows very flexible positioning for almost any tank.The mixer can either be hanging on a chain or wire resting on a support beamLifting davits are available.Installation SystemsTripod Guidebar syste

9、mMainly for the banana blade mixers, where the torsion loads are greater. Can also be used for the 4600 series.Double Guidebar systemSpecially designed for the banana blade mixers.Installation SystemsCantilever systemCan be used for the 4610 and 4620 mixers. Are available up to 3 m length.Bottom mou

10、nting systemCan be used for the 4610 and 4620 mixers.Using Flygt Mixers in WWTPAnoxic zonesAerated tanksSludge Handling / StorageAnoxic ZonesNo aeration equipment in tankMixing is needed for:SuspensionMixing inflowsCommon tank shapesAnoxic Zones for BNRO2Return Activated SludgeInternal Re-circulatio

11、nWaste Activated SludgeInflowAnoxic zoneAerobic zoneSedimentationBNR - Biological Nitrogen RemovalAnoxic Zones - Selecting MixersTanks Size and ShapeVolume to mixLosses due to geometryKeep sludge in SuspensionMix inflowsMixing Requirements+=RequiredPerformance(Thrust N)?Customer PreferencesInvestmen

12、tLCCOperation & Maintenance+Anoxic Zones - Selecting MixersExample 1: Anoxic zone - Small rectangular tank10 m6 m3 mSR4410 Prop.=1.8m & 18 rpm Pcons=0.6 kWSR4630 Prop.=7 (w. Jetring) Pcons=1.3 kWA simplified LCC: Investment + Energy cost over 5 yearsAnoxic Zones - Selecting Mixers20 m10 m6 mSR4410 P

13、rop.=2.2m & 25 rpm Pcons=1.4 kWSR4650 Prop.=7 (w. Jetring) Pcons=4.8 kWA simplified LCC: Investment + Energy cost over 5 yearsExample 2: Anoxic zone - Large rectangular tankAerated TanksAeration equipment cover part or all of tank bottom.Mixing is needed for:SuspensioncirculationCommon tank shapesAe

14、rated TanksPartial bottom coverageSuspensionCirculation of liquid over aerated areasFull bottom coverage (SBR)Suspension when aeration is turned offMixers & Aeration never operate at the same timeAerated Tanks - Selecting MixersExample: Racetrack with bottom diffusers2 x SR4430 Prop.=2.5m & 35 rpm P

15、cons=6.9 kW (tot)2 x SR4660 Prop.=15 (w. Jetring) Pcons=18.9 kW (tot)Sizing is based on:Size & geometry of tankAeration Required velocityInvestment + Energy cost over 5 yearsAerated Tanks - Selecting MixersLarge tanksEnergy efficientLarge volume CirculationSmaller tanksWhen installation might be dif

16、ficultSludge Handling / StorageSludge with DS 1%up to 10-15%Mixing is needed for:Mixing inflowsPrevent stagnant areaskeep homogeneousCommon tank shapesSludge characteristicsHigh concentration High viscosityIncreased power consumptionHigh “yield stress”stagnant zones with too small mixersMixing SludgeToo small mixerstagnant zonesSludge Handling - Selecting MixersNot suitable for sludge mixingLarger investmentLower power consumptionBetter cooling of motor at high viscositysmaller investmentHigher power consumptionSuitable when risk of cloggingWithout JetringWith Jet