Scrubber NATCO

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Development of scrubber internals

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  • Design av demistere for hytrykksanvendelsehytrykksanvendelse

    S j t k l i 2009Separasjonsteknologi 2009

    September 30 2009September 30, 2009Presenter: Dag Kvamsdal

  • Overview todays presentationOverview todays presentation

    Quick overview of demisters Quick overview of demisters Typical separation performance requirement of

    demisters Operational envelope for scrubbers today Operational envelope for scrubbers today Testing of demisters in laboratory What will affect the demister performance Status on CFD calculations Status on CFD calculations Natco Norway focus for new development of

    demisters and scrubber internals

  • Demisters in a process systemDemisters in a process system

    Primary Separators

    Gas scrubbers

    Contactor towers

  • Demisters used in scrubbers and separatorsE lExamples

    Vanepack

    Demisting cyclones

    Separators

    Demisting cyclonesDemisting cyclones

    ScrubberSingle stage scrubber

  • Two types of demisters discussedAxial flow cyclones and vane packs

    Vane packVane pack

    Suited for low-mid pressure application p essu e app ca oand low gas loading

    Axial flow cyclones

    Suited for high pressure demisting

  • Separation efficiency scrubberUsing Natco Norway correlationsg y

    e

    f

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    [

    %

    ]

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    Efficiency demister

    0 % 20 % 40 % 60 % 80 % 100 % 120 %

    Relative flow rate

    li id

    gasgasuk

    =

    e

    p

    e

    f

    f

    [

    %

    ]

    gasliquid

    S

    e

    Efficiency bulk separation vesselK-value [m/s]

  • Required separation efficencyExample; Achieve 0.1 gal/MMSCF

    Demister section

    Process conditions Year 2011Operating pressure [bara] 25 1

    Example case

    section99.73 %

    Operating pressure [bara] 25.1Operating temperature [C] 105Gas actual flow rate [Am/h] 25263Gas actual density [kg/m] 22.5Gas actual viscosity [cP] 0.01

    I l t ti

    y [ ]Hydrocarbon liquid flow rate [Am/h] 22.71Oil actual density [kg/m] 881Hydrocarbon surface tension [N/m] 0.021Oil actual viscosity [cP] 13.0200

    Inlet section and vessel combined88.97 %

    Water flow rate [Am/h] 0.0Water actual density [kg/m] 991.5Water actual viscosity [cP] 0.6Liquid fraction [vol%] 0.09 %

    Overall efficiency: 99.97 %

  • Efficiency limitations for scrubbersOperational envelope LCO 0.1 gal/MMSCF

    1.0%

    1.5%

    u

    m

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    0.5%Li

    q

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    u

    Increasing Pressure

    0.0%kvalue [m/s]

    < 0.1 gal/MMSCF

    k value[m/s]

  • Options for demister testingThe Natco axial flow cyclone has been tested at the following labs

    Ai t l b t N t L b t R l fl id l b tAir water laboratory

    Functional testing of a

    Natco Laboratory

    Testing of individual

    Real fluid laboratory

    For instance StatoilHydro K-full axial flow cyclone box

    demisters and demister sections

    lab.

    Real fluids, Full size test

    Test pressure 1-5 bargModel fluids and possibility to run gas densities of 60 kg/m3

    ,sections and up to 150 bar

    densities of 60 kg/m

  • Testing high pressure demistersReal world vs laboratory conditions

    1 10 100

    Real world Gas density [kg/m3]

    Real world S rface tension [kg/m3]1 10 100

    Surface tension [kg/m3]

    10-3 10-110-2 100 101

    ScrubbersDemisters Diameter [m]10-3 10-110-2 100 101

    Ai tAir water

    Natco Norway Laboratoryy y

  • Separation efficiency for a demisterDifferences from lab to real conditions axial flow cyclones

    99.0%

    99.5%

    100.0% Test data

    Test data from air water gives 100%

    97.0 %

    97.5%

    98.0%

    98.5%

    E

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    Realfluids

    Test data from air water gives 100% separation efficiency, nothing to learn!

    95.5%

    96.0%

    96.5%

    97.0%Modelfluids

    AirwaterModel fluids gives reduced efficiency and it is possible to evaluate the geometry

    50% 70% 90% 110%

    Flow[]

    g y

    Real fluids gives considerably lower efficiency

  • Flow mechanisms in a demisterAffecting the separation Affecting the separation

    Droplet break up

    Droplet transportation

    Wall interaction

    Collisions / Coalescence

  • CFD challenge for demister equipmentg q p

    Why cannot CFD replace testing all together Limited computer capacity allows sets an upper limitation of the length scales

    that can be resolved CFD can only resolve the length < 1000 nodes in 3 dimension total nodes 10003

    = 109

    Equipment

    The challenge of CFD; it is all about scales

    Equipment

    TurbulenceDroplets Length [m]

    10-6 10-410-5 10-3 10-2 10-1 10-0

    CFD resolvedCFD resolvedCFD resolvedCFD resolved

    g [ ]

  • CFD ability to capture the flow field

    RANS calculations

    Time averaged solution that in many ways do y ynot visualize the real

    flow pattern in the vanepack

    LES calculations

    Able to calculate the main flow structures and the general flow pattern qualitative

    correct

    Calculation 15 000 CPU h iCPU hours using 7 000 000 cells

  • Multiphase flowIncluding; droplet break up, coalescence and wall film model

  • Flow in a vanepack as filmed in the laboratoryp y

    G d it 60 k / 3Gas density 60 kg/m3

  • Flow in the vanepack slow motionFlow in the vanepack slow motion

    Gas density 60 kg/m3

  • Efficiency vane packAs tested in the Natco laboratory

    99 %

    100%

    Vane pack efficiency

    High efficiency for k < 0 1 m/s for all96%

    97%

    98%

    99%

    n

    c

    y

    High efficiency for k < 0.1 m/s for all gas densities up to 60 kg/m3

    Falls below 99% when k>0 15 m/s92%93%

    94%

    95%

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    Increasing density

    Falls below 99% when k>0.15 m/s90%

    91%

    Kvalue[m/s]

    Vane pack efficiency 96%98%

    100%

    Vane pack efficiency compared to axial flow

    cyclones90%

    92%

    94%

    i

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    f

    f

    i

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    i

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    c

    y Vanepack

    Cyclones

    The axial flow cyclones can handle considerably higher flow without loss

    of performance82 %

    84%

    86%

    88%

    S

    e

    p

    a

    r

    a

    t

    80%

    82%

    Kvalue[m/s]

  • Development of scrubber internalsDevelopment of scrubber internals

    Under development Under development New generation of axial flow cyclones

    Should achive 10 times or more better performance than the existing axial flow cyclonesI t t f t i li l ti ll hi h Important for one stage inline solutions as well as high pressure scrubbers

    New scrubber inlet section New scrubber inlet section Should give 99% or better efficiency for a k-value in the

    vessel of 0 25 m/svessel of 0.25 m/s.

  • Next generation axial flow cyclonesOperational envelope LCO 0.1 gal/MMSCF

    1.0%

    1.5%

    u

    m

    e

    f

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    t

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    0.5%

    L

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    Increasing Pressure

    0.0%kvalue[m/s]

    < 0.1 gal/MMSCF

  • Design of Gas ScrubbersInlet devices

    g

    Inlet Vane Diffuser Swirl InletInlet Cyclone Distributor Statoils SPINLET

  • Efficiency for new type inletEfficiency for new type inlet

    Key for further scrubber development is to manage to remove 99% or more of the droplet in

    the vessel before demister up to k 0 25the vessel before demister up to k ~ 0.25

    1.5 %

    2.0%

    n

    > 0.1 gal/MMSCF

    1.0%

    1.5%

    l

    u

    m

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    0.5%Li

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    Increasing Pressure

    0.0%kvalue[m/s]

    < 0.1 gal/MMSCF