Evaporator Presentation

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    Nestle Milkpak Ltd. SKP 2004

    M.Arshad

    Training onPowder Manufacturing

    Evap & Egron Department

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    Nestle Milkpak Ltd. SKP 2004

    M.Arshad

    Evaporator

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    M.Arshad

    Introduction

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    Contents:

    Milk evaporation statistics

    What is evaporation and why do it

    Characteristics of evaporation Evaporator types

    Falling film principle

    Falling Film Evaporator elements

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    Global Statistics on Milk (2004)

    World fresh milk

    production:

    577 Mio Ton Nestle share:

    12.1 Mio Ton

    Nestle

    2.1%

    Others

    97.9%

    Nestle

    Others

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    Statistics on Milk Processed withEvaporators (2004)

    Fresh milk processed atNestl: 12.1 Mio Ton

    Milk processed in

    Evaporators: 8.0 Mio Ton

    (66% of Nestl total milk)

    SCM9%

    Others

    6%

    UHT + steril

    7%

    Chocolate

    7%

    IceCream

    5%Milk powders

    50%

    Evap

    7%

    White refr.

    9%

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    What is Evaporation?

    Change from liquid phase to the vapour phase

    For example,Boiling water

    Heat

    Water

    Vapour

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    What is Condensation

    Change from vapour phase to the liquid phase

    For example,

    Condensing steam

    Heat

    Condensate

    Vapour

    ?

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    Evaporation by means of steam

    Heat transfer because of

    temperature difference

    Condensate

    Steam

    Milk

    Vapour

    Steam at

    Higher temperature

    Vapour at

    Lower temperature

    Surface to

    exchange heat(indirect)

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    So during evaporation:

    * Solids do not evaporate ,hence

    * Concentration of solids in liquid phase increases

    100 kg Milk, 12 % TS:

    12 kg solids88 kg water Evaporator

    76 kg vapour

    24 kg Milk, 50 % TS:

    12 kg solids12 kg water

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    Evaporation / ConcentrationMethods

    Evaporator(indirect) - liquid in - liquid out

    Spray Dryer(direct) - liquid in - solid out

    Roller Dryer(indirect) - liquid in - solid out

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    Why Evaporate/concentrate

    Volume ReductionFor example: to reduce transport volume of Milk from source to factory.

    PreservationFor example: Milk Powder: suspended bacteriological activity due to lack of

    water.

    ?

    ConvenienceFor example: - Evaporated Milk.

    - Instant Coffee/ Tea whitener

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    Evaporator Types

    The Old Vacuum Pan

    Recirculation Evaporators

    Climbing Film Evaporators

    Falling Film evaporators

    Plate Evaporators

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    Energy Use =

    1.25 KW/Kg H2O

    Energy Use =

    0.07 KW/Kg H2O

    SPRAYDRYER

    Fresh milk:

    1000 kg

    Energy Use

    = 4.2 KW/Kg H2O

    Energy Use

    = 4.2 KW/Kg H2O

    Evaporates

    3.1 kg of water

    Evaporates

    121 kg of water

    Evaporates

    747 kg of water

    Why are Evaporatorsthe preferredconcentration

    equipment(example IMP)

    time: 12-15 min Time: 1/4-1 min Time: 5-15 min

    12.5% 97.3%95%49.5%Evaporator Spray dryer Afterdryer

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    Evaporator Process ATSKP

    Std silo

    Condenser

    Pre-heating

    Thermo compressorPasteuriser

    DSI

    Back pressure

    Evaporation in

    1st Effect

    2nd Effect

    4

    th

    Effect-A&B3rd Effect-A&B

    Ex-Evap

    Homo tank

    Buffer tank(if need)

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    BRAN & LUEBBEMETERING SYSTEM

    Flowsheet of SKP evap.

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    Evaporator Process

    Standardized Silo Plan

    Batch card

    Quality

    MSA/DPSA

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    Evaporator Process

    CondenserSTD Milk Temp

    Cooling tower

    Preheating of milk

    Vapour condensation

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    Condenser

    Vapoursarecondensedby

    means of Cooling Water

    This creates a SUCTION EFFECT

    i.e. VACUUM

    In

    The BIG volume

    0ccupied by the

    VapoursIs suddenly

    reduced to

    To a very small

    volume of liquid

    Out

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    Condensate

    Condensate from Pasteurizer: -->Boiler House

    Condensate from 1st effect: -

    conductivity measurement, if OK

    --> to Boiler House

    Condensate from other effects andCondenser:

    --> Other uses

    Pure-Condensate

    Condensate-

    from Product

    Vapour

    Condenser

    Pasteurizer

    Condensate from Steam-recompressedvapours

    Steam

    Steam

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    Pre-Heaters

    Product IN

    Pre-Heater C

    Pre-Heater 1

    Pre-heat Product to ~70 C

    Thermal EconomyEnergy has already worked

    upstream Gentle heating

    Low T

    Heating media (vapours) at the rightT readily available

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    Evaporator Process

    Balance TankBalance tank is a feeding source of Evaporator in

    this we volume makeup

    Buffer milk & wet rework

    Th C

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    Thermo-Compressor

    Vapour Pump H P Driving Steam

    recompresses and mixes

    with the Sucked Vapour

    Simple, no moving parts

    Robust (not much to go wrong) Small Unit, for Large Volumes.

    To Next Effect-or

    To Condenser

    Vapour, mixed

    Compressed

    with Steam

    Driving Steam

    Sucked Vapours

    Heating Side

    Fed to

    of #1 Effect at

    higher T

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    Msteam

    Psteam

    Msuck

    Mdisch

    Psuck

    Pdisch

    1 2 3 4 5

    1) Head

    2) Steam Nozzle

    3) Converging Section

    4) Throat

    5) Diverging Section

    Thermocompressor Nozzle

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    Pasteuriser

    Pasteuriser

    Heats Product, from ~70 C to ~ 85 C Heating time is Critical

    long time = Coil

    short time =PHE

    = Straight Tube Running time > = 20h

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    DSI

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    DSIDirect Steam Injection

    Short Time Heat Treatment

    Heat Productfrom 85 C to say 108C

    Followed by Holding Tube

    -Holding time - 5 to 10 Sec

    -Variable holding time as needed

    -Watering effect ~ 4% for 20Ctemperature rise

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    Why Back Pressure?

    Product at high T >100 C

    Uniform flow

    To avoid boiling

    Ensures:

    Correct T is reached

    Correct holding time Prevents:

    Premature Flashing

    Back Pressure

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    Evaporator Process

    Evaporation in1st Effect

    Product Inlet Nozzle at ist effect

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    Product Inlet Nozzle at ist effect

    Flash-Vapour

    Calandria Top Cover

    Product Feed-Under Pressure

    And Diverter

    Flow through

    S.S. Nozzle

    d lThe Back pressure

    will depend on "l"

    and "d",

    calculated for a

    certain flowrate

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    Evaporator Process

    Evaporation in2nd Effect

    E P

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    Evaporator Process

    Evaporation in

    4th Effect-A&B

    E t P

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