Controlling foam removal in a sewage treatment plant
•Fullyautomatedfoamdetectionandactivationoffoamremoval•Measuringthereflectionfactorofthewatersurfaceusingalevelmeter•Noriskoffoamingover
1. Background Amanufacturerofnaturalproductsmadefrombrewer'syeastoperatesasmallfacilitytotreatitsownwastewater.Thewastewaterissprayedintothemiddleofasettlingtankmeasuringapprox.6mindiameter.Duetotheyeastresidueinthewater,foamformsonthesurfaceofthewater.Theeddyforcesthefoamtotheedgeofthetankandthencomestogethertowardsthecentre.Ifthefoamisnotremoved,thereisariskofoverfoaming.
2. Measurement requirements
Theoperatorwaslookingforareliablewaytodetectfoambuild-upsothattheexistingscraperwiththefoamextractorwasonlyusedwhennecessary.Tothisend,ameasuringpointnearthecentreofthetankwasspecified:whenthefoamreachesthispoint,thescrapercomesintooperation.
3. KROHNE solution
Thismeasuringtaskcanbetackledusingameasuringdevicecapableofidentifyingthecompositionoftheproductsurface.Here,acontactlessOPTIWAVE7300radarlevelmeasuringdevicewithaDN80dropantennawasusedasatestdevice.Themeasuringdevicewasplacedonaradialtrackabovethetank,positionedabovethemeasuringpointdescribedbefore.Thereflectivityvalueand/orthestrengthofthereflectedsignalwasassignedtothesignaloutputandtheOPTIWAVEwasconnectedtotheexistingSPSthatcontrolsthescraper.
APPLICATION NOTE Water & Wastewater
Application 242 EN.indd 1 29.03.2010 11:05:56 Uhr
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4. Customer benefits
Thisunusualsolutionallowstheoperatortousethefoamremovalmechanismcompletelyautomaticallywhenneeded.TheOPTIWAVE7300radarlevelmeasuringdevicewasdesignedforliquidapplicationsandfeaturesintegratedmeasurementofthereflectionfactoroftheproductsurface.Thesurfaceofthewaterishighlyreflectivebutfoamreducesthereflection.Thisenablesthedevicetoreliablydetectthepresenceofwaterorfoam.Thecompletelyencloseddrop-shapedpolypropyleneantennaresistsdepositsanddoesnotcorrode;boththeantennaandthemeasuringdevicearemaintenance-free.
5. Product used
OPTIWAVE 7300 C• RadarLevelMeterforliquidapplications• 2-wireFMCW24...26GHzradar• Continuousnon-contactlevelmeasurement• Integratedreflectivitymeasurementoftheproductsurface• Alsoavailablewithstainlesssteelhornantenna
APPLICATION NOTE
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The OPTIWAVE 7300 measures the reflectivity of the product surface
When foam builds up under the measuring device, the foam removal mechanism is activated
Application 242 EN.indd 2 29.03.2010 11:06:00 Uhr
