PhDproposal
Hydrodynamicsofbubblecolumnsintheheterogeneousregime:mechanisms,scale-upandmodelling.
Duration:3years,starting2017.
Location:LEGI(http://www.legi.grenoble-inp.fr/)&LGP2(http://pagora.grenoble-inp.fr/recherche/)laboratoriesatGrenoble,France.IFPEN-Lyon(http://www.ifpenergiesnouvelles.com)atSolaize,France.
Candidateprofile:engineeringorphysicsbackgroundwithstrongformationinfluidmechanics.Interestinexperimentationmeasuringtechniquesandmodelling.ExperienceusingMatlabisrecommended.
Topic: Bubble column reactors arewidelyused in the chemical andbiological industry, as Fischer-Tropschreactors,α-olefinsoxidationreactorsandasaerobicfermenters(seefigure).Theytypicallyconsist inacylindricalvessel filledwith liquidat thebottomofwhichgas is injected.Despite theirwidespreaduseinindustry,themodellingofsuchdevicesremainsunsatisfactoryduetothelackofreliablephysicalmodeldescribingtheinteractionsbetweenphases.Sofar,theexploitationofthesesystems relies on semi-empirical approaches based on experiments at different scales to adjustparameterssuchasbubblesize,turbulentviscosity,etc.
Figure1:bubblecolumnatLEGI(400mmdiameter,left)andatIFPEN-Solaize(3000mm,right)
Thegoalistoimproveourunderstandingofthehydrodynamicsinsuchcolumnsusingcombinedmeasurementsofvariousparameterssuchasvoidfraction,bubblesizesandvelocities,carrierphasevelocity... Experimentswill be performed in columnsof different sizes, typically from I.D. 400mm(columnavailableatLEGI)uptoI.D.3000mm(columnavailableatIFPEN-Solaize),usingaqueousaswellasorganicliquidsinordertovarythecoalescenceefficiency.Measuringtechniquesareavailable(suchasopticalprobes,endoscopiccamera,Pavlovtube,hotfilmprobes...)butsomedevelopmentsmayberequired.Differentadvancesaretobeachieved:Ø Improve measurement techniques (Pavlov tube) and deploy new ones (optical probes) to
measurethevelocitiesofbothliquidandgasphases.Ø Acquireandprocesslongtimeseriestobettercharacterizeclustersandvoids,notablybyVoronoï
analysis,withtheobjectiveofquantifyingconcentrationgradients,velocitiesandsizesofthese
structures as a function of column size and gas flow rate injected. Conduct combinedconcentration-liquidvelocitymeasurementstocharacterizeclusterdynamics.
Ø Investigatetheroleofsuchmeso-scalestructuresonturbulencegenerationandproposeadaptedclosures.
Ø Analyse the competition between coalescence and clustering on the homogeneous-heterogeneoustransition.
Ø Testanddevelopnewmodelsinagreementwiththeresultsobtained.
Theresultingdatabasewillbeusedtoderivephysicalmodels,withaspecialfocusonmomentumexchangesbetweenphases, bubble sizedistributions, turbulencegeneration,with theobjective tocharacterisetheflowofthecarrierphase(maximumvelocity,turbulenceintensity,etc.)inindustrialcolumns. These datawill be exploited to improve an existing 1Dmodel and to test the predictivecapabilitiesof2D/3DnumericalsimulationscurrentlyunderdevelopmentatIFPEN.
Contacts:
AtLEGI:MartinObligado,[email protected],tel.:+(33)476825046;Alain
Cartellier,[email protected].:+(33)476825048.
AtLGP2:DavideBeneventi,[email protected],tel.:+(33)476826954.
AtIFPEN:AnnForret,[email protected],tel.:+(33)437702542.
Applicationsreceiveduntil10/07/2017.ForapplyingsendanacademicCVtoM.Obligadoand/orA.Cartellier.
