Packed Bed Fermenters

Packed Bed Fermenters

Packed Bed FermenterUsed with immobilized or particulate biocatalystsReactor: consists of a tube (usually vertical), packed with catalyst particlesMedium can be fed either at the top or bottom of the column and forms a continuous liquid phase between particlesMass transfer between the liquid medium and solid catalyst is facilitated at high liquid flow rates through the bedThe catalyst is prevented from leaving the column by screens at the liquid exit The particles should be relatively incompressible and able to withstand their own weight in the column without deforming and occluding liquid flow

Features1 particulate enzymes2 tube3 feed at the top/bottom, continuous4 high flow rates5 supported by screen6 incompressible particles2IMMOBILIZED CELLS

(Karel et al, 1984)1 particulate enzymes2 tube3 feed at the top/bottom, continuous4 high flow rates5 supported by screen6 incompressible particles3Sketch

Recirculating medium must be clean and free of debris to avoid clogging the bedAeration is generally accomplished in a separate vessel Commonly used with biofilms especially in wastewater engineeringGenerally used where substrate inhibition governs the rate of reactionModifications have been tried with limited success: tapered beds-to reduce pressure drop across the length of the reactor, inclined bed, horizontal bed, rotary horizontal reactorsFeatures1 free from debris2 aeration in separate vessel3 used with biofilms4 substrate inhibition governs rate of reaction5 modifications4Operation

Packed bedPacked bed with external aeration columnPacked beds can either be run in the submerged mode (with or without aeration) or in the trickle flow mode.

Injecting air and using a higher liquid flow rate for a short period will normally dislodge excess biomass.5

(Catapano et al, 2009)(Meuwly et al, 2007)Additional:Wash out of immobilized cells how to recover/regenerateDimensions (lab scale and industrial scale)Scaling up

6

(Warnock et al, 2005)CONCENTRATION PROFILES

(Warnock et al, 2005)Configurations

(Warnock et al, 2005)CONVENTIONALINTERNAL SILICONE TUBING FOR DIRECT AERATIONRADIAL FLOW PBR IN CSTRBASKET-TyPE

OperationEven distribution of the flow over the entire cross-section to avoid chanellingAny misdistribution of the liquid flow will result in poor performanceFlow velocities in the channels can be high to eliminate external mass transfer limitation in the adjacent liquid filmPlugging can be avoided but at the cost of high pressure drop

Continuous packed bed reactor vs. batch reactorEasy, automatic control and operation

Reduction of labor costs

Stabilization of operating conditions

Easy quality control of productsAdvantagesDamage due to particle attrition is minimal compared with stirred reactors

Simple to construct and operate

Can support high cell densities in a compact volumeDisadvantagesIf air is sparged directly into the bed, bubble coalescence produces gas pockets and flow channeling or maldistribution

Unsuitable for processes which produce large quantities of carbon dioxide or other gases which can become trapped in the packing

Can suffer blockages and poor oxygen transfer

LIMITATIONS TO SCALE UPSIZESAlthough a large variety of PBR systems have been assessed successfully in the laboratory [], few pilot-scale and industrial installations have been described. Indeed, most of published data deals with PBRs of less than 5 l of packed-bed volume. Only a few systems have been scaled-up to above 5 l. The current maximal packed bed volume appears to be in the range of 1030 l.-Meuwly et al (2007)

LAB SCALEVOLUME 0.01-5LSCALED UPVOLUME: 10-30LLIMITATIONS TO SCALE-UPLimit on amount of Carrier materials: have to withstand its own weightLIMIT ON OPERATION TIME: Catalysts regeneration requires shutdownLIMIT ON DEPTH/HEIGHT: OCCURRENCE OF axial gradients in concentrations of nutrientsLIMIT ON DIAMETER: limited by the ability to uniformly distribute the flow over the entire cross-section to prevent nonhomogeneities and chanellingISSUE: Leaking out of the catalystAn additional separation step is required to separtate leaked catalysts and productsReferences:Bioprocess Engineering Principles by Pauline M. Doran Types of Bioreactors bioprocessing.weebly.comPacked Bed Bioreactor userpages.umbc.eduApplicationsEnergyEthanol (Singh et al, 2003; Goksungur and Zorlu, 2000; Cabrera et al 1982)Biodiesel (Kyeong and Yom, 2013; Yoshida et al, 2012)ChemicalsAcetic acid (Horiuchi et al, 2002; Leite et al, 2006)Hydrogen (Leite et al, 2006)

ApplicationsWastewater treatmentBiological COD removal from food wastewater (Kariminiaee-Hamedaani et al ,2003)Metal ion removal (Narasimhulu and Yadav, 2014; Vimala et al, 2011; Cloirec et al, 2003)BioprocessingVaccines (Spier and Whiteside, 1976; Rajendran et al, 2014)Enzyme (Pandey and Radhakrishnan, 1992)

ApplicationsBiomedical & tissue engineeringBioArtificial liver (BAL) (Allen and Bhatia 2002; Patzer 2001; Reviewed by Warnock et al 2005)

LATEST BALSPHEROID RESERVOIR OF PORCINE HEPATOCYTES SPHEROIDS(IMAGE FROM THE MAYO CLINIC)(STUDY BY GLORIOSO ET AL, 2015)

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