Hygienic design in spray drying by aez97357

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									            Hygienic design in spray drying
                    Dehumidification of the process air




Carla Buijsse, Numico Research

i.s.m.
Arjon Beulens, Process Development
Hans Bosman, Nutricia Cuijk

Symposium Nederlandse Werkgroep Drogen
15-11-2007
                          Outline

Introduction
Infant Milk Formula: Powder Production
Spray drying: thermodynamic relations
Fluid bed cooling
Dehumidification of processing air: Technical realisation
Conclusions
Introduction
                         Introduction

Numico : a specialised nutrition company
   Babyfood
   Clinical nutrition


Baby food
   Infant Milk Formula
   Weaning food




               Food safety is first concern !
                      Infant Milk Formula
Babyfood has highest quality demands (safety, health)
IMF: mainly spray dried powders (from emulsions), to be reconstituted
prior to consumption
In IMF-powders presence of E. Sakazakii is high risk to preterm infants
IMF production process: constant improvements with a strong focus on
safety and reduction of safety risks
Infant Milk Formula:
Powder production
                                     IMF Production
IMF powder production: spray drying of concentrated emulsions
In spray drying process: large quantities of ambient air are used
Ambiant air conditions are varying strongly (and abruptly)

                 x (gr/kg dry air)                                    Absolute humidity
                     16
                     14
                     12
                     10
                      8
                      6
                      4
                      2
                      0
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                Based on KNMI-data                                  O
                              Process air

Fluctuations in process air


Unstable process conditions                 Hygiene+quality risks:
                                            • fouling
                                            • human intervention
                                            • process interruptions
                                            • powder off spec


Focuspoint in risk reduction: Process air
             Process air: dehumidification

Focuspoint in risk reduction: Process air

Improving hygiene+product safety through stabilising the spray
drying process by dehumidification of the process air

Drying process air using a sorption dryer

Dehumidified air to be used for
   Spray drier
   Fluid bed (drying + cooling)
Spray drying:
thermodynamic relations
                          T.




                               X (g water/kg dry air)
      Thermodynamics of spray drying:
           Drying air properties

Concentrate
                            Air in
                       (Ti, xi, RH%)
                                       Mollier diagram
                                       for air properties
                          Air out
                       (To, xo, RH%)




              Powder
               (Aw)
                             Mollier diagram
Describes the properties of air
    Temperature (°C)
    Absolute humidity (g/kg dry air)
    Relative Humidity (%)
                                                T.
    Enthalpy h (heat content) – kJ/kg dry air
2 properties known     others can be derived
Used for calculations of the processing air
    Heating
    Drying
    Humidification
    ..
                                                     X (g water/kg dry air)
                                       Mollier diagram

Temp.
                                 Temperature - lines
                                 Absolute humidity - lines

                                 Relative humidity - curves

                                 Constant enthalpy - lines




        X (g water/kg dry air)
                       0.1   0.2      0.3

               Inlet air:
               T=180°C                                    1
               X=10 g/kg                                        Mollier diagram:
               RH=0.18%
                                                          2      spray drying
                                                          3

      Temp.

                                            Outlet air:
                                                          10
                                            T=95°C
                                            X=42 g/kg     20
                                            RH=7.7%

                                                          100
Ambient air:
T=20°C
X=10 g/kg
RH=70%




                                   X (g water/kg dry air)
               Thermodynamics of spray drying:
                     Sorption isotherms
           Concentrate
                                        Air in
                                    (Ti, xi, RH%)
                                                            Mollier diagram
                                                            for air properties
                                       Air out
                                    (To, xo, RH%)


                                    Aw powder ≅ RH outlet air/100
                                    (at equilibrium between outlet air and powder)

Sorption isotherm          Powder
for Aw-H2O relation         (Aw)


        Moisture content
                       Sorption isotherms
At equilibrium: Aw = RH% / 100
RH% of the outlet air determined by the Tout
Aw of powder determined by the RH% of the outlet air

The sorption isotherm gives the relation                               Sorption isotherm

between the water activity Aw and the                          7
                                                               6
moisture content of a powder (at equilibrium)




                                                moisture (%)
                                                               5
                                                               4
SI depends on product composition                              3
                                                               2
                                                               1
                                                               0
                                                                   0    0.2        0.4   0.6

                                                                              Aw



       Tout    RH% air       Aw powder          Moisture% powder
                           Powder stickiness
             Concentrate                    Air in
                                         (Ti, xi, RH%)
                                                                Mollier diagram
                                                                  for air properties
                                           Air out
                                         (To, xo, RH%)



                                         Aw powder ≅ RHoutlet air /100
                                         (at equilibrium between outlet air and powder)

                           Powder
Sorption isotherm
 for Aw-H2O relation
                            (Aw)
                                               Stickyness curve
                                                 Tst = f (Aw, H2O%)

        Moisture content            Sticky properties
                      Powder stickiness
 Sticky powder will give much fouling on walls and roof
 Sticky powder particles form lumps on fluid bed
 Powder stickiness depends on:
     Moisture% of powder
     Powder temperature (Tout-Tp ≅ 15°)




Tout ↔ RH% air ↔ Aw powder ↔ H2O% powder
                                                    powder stickyness
                                     T powder
                                                    Stickiness curve
                        Sticky temperature                                      Sorption + stickiness curve

           120                                                        120                                  7

           100                                                        100                                  6                Tst
                                     sticky
                                                                                                           5




                                                                                                               m oisture%
Tst (°C)




           80                                                         80
                                                                                                                            SI




                                                           Tst (°C)
                                                                                                           4
           60                                                         60
                                                                                                           3
           40                                                         40                                   2
           20         non-sticky                                      20                                   1
             0                                                          0                                  0
                 0        0.2        0.4      0.6                           0       0.2        0.4   0.6

                                Aw                                                        Aw




                     Sticky properties determine maximum allowed Aw, H2O%, RHout, Tout
          0.1   0.2   0.3



                                 1

                                                     Process control
                                 2

                                 3                          A     B     C
Temp.
                                       Xin (g/kg)           12    2      2
                                       Tin (°C)             180   180   205
                                 10
                                       Tout (°C)            98    98    98
                                 20
                                       Xout (g/kg)          45    35    45

                                 100   RHout (%)            7.3   5.7   7.3
                                       Evap.cap. (g/kg)     33    33    43
                                       Stickiness                 ↓     =
                                       Burning risk               ↓     ↑
                                       Capacity                   =     ↑

        X (g water/kg dry air)
     Spray drying: process control and hygiene

Unstable drying conditions may lead to powder stickiness
Powder stickiness may lead to fouling and hygiene/food safety risks
    Process interruptions
    Human intervention
    Product off spec
A stable process will reduce risks


      A constant low moisture content of the
      dehumidified drying air allows a better control of
      powder stickiness and fouling, resulting in
      reduced hygiene risks
Fluid bed cooling
                      Fluid bed: drying + cooling
 Concentrate
                        Dryer Air in


 Dryer
                        Dryer Air out



Fluidbed

                                                Powder
Mix FB Air in
                Dry FB Air in    Cooling FB
                                     Air in
                          Fluid Bed

In Fluid Bed (3rd section): cooling down of powder
Conventional: cooling and dehumidification by using icewater in a
heat exchanger
Risk: wet areas of condensation water which may come in contact
with powder     hygiene risk
Risk can be eliminated by using (externally) dehumidified air




   Absorption drying can dehumidify the cooling air
       without the drawback of “wet surfaces”
Dehumidification of processing air:
Technical realisation (sorption drier)
                             Technical realisation




                                                Spray
          Regeneration air                      Dryer

              Absorption                                Fluid Bed

                 unit

Ambient air                  Dehumidified air
                                                                    Powder
                       Principle of sorption driers




Source: Munters Droogsystemen
                                                              Baby Food



                   Principle of sorption drier: rotor
                                            Process air (1) is blown through
                                            the rotor. The rotor adsorbs the
                                            water and the air leaves the
                                            rotor as dry air (2)
           1                        2
                                            In a separate area the heated
                                            reactivation air (3) takes the
       4                                    moisture from the rotor and the
                                        3   wet air (4) is blown away;

                                            The rotor revolves by the
                                5           driving-motor (6-8 rev/hour)




Source: Munters Droogsystemen
Conclusions
           Benefits: Hygiene improvements

More stable process conditions, resulting in:
    Less manual interference resulting in lower contamination risks
    Hygiene improvement due to less off spec powder
    Less rejections for microbiological reasons
Reduction in amount of calamities
    Less lumps on fluidbed
    Less blockage of cyclones
Microbiological improvement
    No air-intake inside building itself
    Realise overpressure in building
Benefits: Improved process and product stability

Less fouling in spray drier
Longer running times
Less CIP-time
Increased capacity
Less off spec powder
Decreased variation in moisture content product
                        Conclusions


Improved hygiene, quality and food safety
Improved product and process stability through better controlled
drying conditions




        High, higher, highest quality babyfood!
Thanks for your attention!

       Questions?
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