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Niro
Falling Film Evaporators for the Dairy Industry
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2Falling Film Evaporatorsfor the Dairy Industry
In concentration of dairy products the Nironame is synonymous
with efficient fallingfilm evaporators, designed with special
careto meet a wide variety of specifications andduties of the final
products.
Having installed hundreds of units world-wide during the last
decade, Niro hasacquired substantial experience and know-how to
comply with customer requirements.
In the early 80-ies evaporator design mostlyaimed at producing
bulk dairy products byconcentrating milk and milk by-products
athighest energy efficiency and at lowest cost.Many of the
functional properties of theproducts were often neglected.
During the late 80-ies and 90-ies the industrycame to the
conclusion that the future lay inspecialised production to meet
customerspecifications.
Furthermore, it was accepted that not onlyenergy, but also
increased continuous runningtimes without decrease in product
quality,reduction of product losses, and CIP costswere essential
elements to obtain savings.
Niro took up the new challenge, knowing that many of the
fundamental properties of apowder depend on the heating system of
theevaporator.
Today, modern evaporators for the dairyindustry feature items
such as,
Adjustable and controllable direct contactheat treatment
units.
Shortest possible residence time. Special design to prevent
bacteriological
growth including thermophiles. Special design of liquid
distribution
systems to ensure correct tube coverage. Extended tube length.
Efficient design of separators.
Niro has developed leading technologies onbasis of the
Laguilharre concepts. The 21stcentury dairy evaporator can
produce
concentrates to a wide variety of specifica-tions and duties to
suit further processing inthe spray dryer or in other
processes.
This is achieved by stable operation duringlong uninterrupted
runs without excessivefouling or product losses and with
negligiblebacteriological growth.
All installations are designed to optimiseenergy consumption,
functional specifica-tions, and capacities as well as capital
costs.
Evaporators and ancillary equipment aremanufactured in
fabrication facilities all overthe world.
Installation, commissioning, and controlsystems are supervised
by our technical- andprocess engineers.
Applications
Baby Food
Buttermilk
Coconut Milk
Cream
Hydrolysed Whey
Hydrolysed Milk
Milk Permeate
Milk Protein
Mixed Milk Products
Skimmilk
Whey
Whey Permeate
Whey Protein
Wholemilk
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3Design Features
Niro dairy evaporators concentrate heat-sensitive products using
design concepts thatmake it possible to operate with low
tempe-rature differentials. The ability to utilise longtubes, and
hence more heating surface pertube, ensures optimum tube
coverage,reduced residence time, better thermalefficiency, long
production runs, and shortCIP times. The Niro evaporator is in a
fullywelded construction to meet sanitarystandards.
Pre-heating
Niro dairy evaporators are equipped withexternal straight-tube
pre-heaters to achieve,
Short residence time in controlled parallel flow.
Optimum de-aeration of the calandrias. Accessibility for easy
inspection of the
heating surface.
Recently, a new pre-heating system wasdeveloped eliminating
surfaces to whichthermophilic bacteria and their spores canadhere
in a temperature zone allowinggrowth.
Evaporators equipped with this systemoperate for 20 hours or
more withoutdevelopment of vegetative thermophiliccounts or
thermophilic spore counts.
Further decrease in counts depends on the heat treatment
requirements of the process to follow.
Heat Treatment
As a standard feature Niro dairy evaporatorsare equipped with
direct-contact heattreatment systems to meet the most
stringentproduct specifications from the customers.
Niro avoids using the common termpasteurisation. Experience
proves that many
functional powder properties obtained in anadjacent spray dryer
are influenced by thetemperature/time conditions in the
heattreatment system.
Niro aims at obtaining functional propertiesof the final powder
being the direct result ofthe applied heat treatment. The
wantedpowder properties must be defined alreadyduring the plant
design phase.
The bacteria killing results from the heattreatment required for
the desired functionalproperties and combined with the new
pre-heating system it is always superior tothe results obtainable
by any other system.
Niro prefers this approach rather than toapply a heat treatment
to obtain a certainpasteurisation/sterilisation without beingable
to choose the specific functionalproperties wanted.
Direct contact systems ensure minimumheating time to reach a
desired temperature.Holding tubes can be included in order toobtain
certain final product properties.
To save energy the direct contact system canbe supplied with one
or more direct contactregenerative systems using flash vapours
topre-heat the product before final heating.
Some of the advantages of the direct contactsystem are,
Shortest possible residence time for theheating phase.
Possibility to provide optimum temperature/time combinations for
specific product qualities.
Possibility to achieve low heat productspecifications at higher
temperature.
Temperature efficiency (better bacterial kill effect).
Better heat stability in case of high heat stable powder.
Better instant properties. Lower concentrate viscosity. Better
coffee test stability in instant whole
milk powders.
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43-effect TVRMonotherm evaporator
Liquid Distribution System
A static distribution ensures that all tubes in the calandrias
receive equal amounts of liquid at all times, resulting in optimum
tubewetting rates.
The system can accept wide variations inliquid flow and flash
vapour.
The distribution system is the important key to long
uninterrupted operation hours.
Separator Design
Efficient liquid vapour separation is achieved by controlled
vapour velocitiesthrough tangential flow vapour separators,designed
for maximum separation efficiencyat minimum pressure losses.
Two different standard designs can beselected,
Stand-alone separator with tangential in-and outlets, situated
next to the calandria.
Wrap-around separator, integrated in thelower part of the
calandria.
For smaller duties and TVR evaporators the stand-alone separator
is the preferredchoice, whereas for higher duties and
MVRevaporators the wrap-around separator is bestsuited due to the
compact design (see below).
Compact Design
The free-standing design, in combination with longer tubes and
wrap-around separa-tors, reduces floor space requirements
andbuilding costs.
This arrangement offers excellent opportuni-ties for
installation of new evaporators inexisting buildings or capacity
extensions ofexisting evaporators.
Steam
Holdin
g tubes
Produc
t inlet
Direct p
asteuriz
er
Flash regenerator
TVR
Ste
am
Concentrate out
Condensate
Cooling water
Air
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53-effect MVR/TVRevaporator
Product Residence Time
The combination of pre-heating systems,direct-contact heating,
and longer evaporatortubes reduces the number of product
passesrequired for a given concentration, whichagain reduces the
product residence time inthe evaporator.
Residence times as low as 6-10 minutes arenow quite common,
depending on capacityand turn-down requirements.
The aim has been to try to achieve plug flow conditions in the
evaporator to obtainthe following,
Minimum heat load on the product. High reactivity of the plant,
eliminating
the need of feed forward control. Very short mix phases at
start-up and
shut-down, eliminating the need of whitewater provisions.
Limited product losses to waste watertreatment.
Reduced CIP liquid consumption. Reduced CIP time.
Cleaning-in-Place (CIP)
Cleaning costs are further minimised bydedicated and fully
automated CIP systems.The systems are designed for low-cost
causticsoda and nitric acid as cleaning agents.
Thermal VapourRecompression (TVR)
In multiple effect TVR evaporators using high pressure steam,
the heating medium inthe first effect calandria is vapour from one
of the associated effects, compressed to ahigher temperature level
by means of a steamejector (TVR). The heating medium in
anysubsequent effect is the vapour generated inthe previous
calandria. Vapour from the finaleffect is condensed with incoming
product,and if necessary supplemented by coolingwater.
Steam
Holdin
g tub
es
Direct
paste
urizer
Flash regenerator
MVR
TVR
Steam
CondensateConcentrate out
Concentrate out
Cooling water
Air
Product inlet
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62-effect MVR/TVRMonotherm evaporator
Mechanical VapourRecompression (MVR)
In MVR evaporators the heating medium in the first effect is
vapour developed in thesame or in one of the associated
effectscompressed to a higher temperature by one or several high
pressure fans (MVR). Any excess vapour from the high heat section
iscondensed or may be utilised in an integratedhigh concentrator.
The condensate is cooledby the feed product and can be used for
thecondenser or any external pre-cooling duties.
Equipment Selection
The most important consideration whendesigning an evaporator is
to obtain theability to produce a quality product duringlong
uninterrupted running hours with aminimum of fouling and without
bacteriaincrease.
When an evaporator is directly connected to a spray dryer, other
considerations aresignificant as well, i.e.
powder functionality, correct flow rate and concentration to
the
dryer for different products, no intermediate holding time.
The features of the Niro evaporator make thispossible for both
MVR- and TVR designs.
The choice between MVR and TVR and thenumber of effects (surface
installed per ton ofwater evaporated) depends on various
factorswhich may vary from site to site,
Local prices of the different energy sources. Possibilities for
utilisation of condensate. Depreciation of the capital cost
involved
(incl. building). Cleaning costs incl. product losses.
Plants with low energy consumption require more surface, and
apart from longerresidence time for the product, more
surfacerequires higher investment, higher cleaningcost, and,
potentially, heavier product lossesand increased heat damage to the
concentrate.
The right choice for each individual projectmust be based on a
case study.
Steam
Holdin
g tubes
Direct p
asteur
izer
Flash regenerator
MVR
Plate h
eat
exhang
er (PHE
)
Steam
Concentrate
Condensate
Product inlet
Cooling waterAir
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7Condensate
Condensate quality is an important functionof the separator
performance and the productto be concentrated. Hot condensate can
beused as boiler feed water, CIP liquid, or forpre-heating the
drying air of an associatedspray dryer.
The condensate may also be additionallytreated in an RO polisher
as well aschemically to produce water of anexceptional quality.
This is particularlyimportant on locations with limited suppliesof
water or poor water quality.
Process Control andInstrumentation
Evaporators are suited for a completelyautomated control
procedure, meeting therequirements for safe, informative,
andflexible operation.
Our systems feature,
Automatic plant start-up, shut-down, andCIP cleaning
procedures.
Individual control level for each activator,e.g. motor,
valve.
Recipe system with access control and realtime trends.
Historical trends with hard copy print-out. Reporting on printer
or to file for spread
sheet use. Event/alarm logging. Dynamic on-screen sequence
description
in plain text. Standard tuning of control functions. Advanced
control system.
Thermophilic vegetative cell count/g of total solid.Normal
configuration.
1 hour 7 hours 14 hours 19 hours
Feed 1,600 10,100 800 1,800
After PHE 800 14,200 59,000 148,000
After preheat 1,100 275,000 3,000,000 3,000,000
After 1st effect 1,315 134,210 239,473 650,000
After 2nd effect 1,097 112,195 236,584 636,585
After 3rd effect 2,173 130,000 193,478 523,913
Concentrate 674 5,956 23,695 306,521
Powder 700 1,400 16,500 258,000
Thermophilic vegetative cell count/g of total solid. Skim
milk.Low thermophile configuration.
10 hours 12 hours 14 hours 16 hours 18 hours 20 hours
Feed 5,400 2,700 1,700 37,000 38,000 10,200
After PHE 8,500 2,400 1,600 6,100 13,200 13,200
After preheat 7,800 2,300 700 5,200 6,000 7,600
Before 1st effect 500 500 1,100 1,100 1,900 1,200
After 1st effect 789 1,500 289 289 2,500 4,474
After 2nd effect 1,400 2,214 380 1,007 714 714
Concentrate 1,300 2,000 2,826 740 1,956 1,220
Powder 1,250 2,350 1,200 1,200 1,100 1,200
Thermophilic aerobic spores count/g of total solid. Skim
milk.Heat treatment 90C / 30 seconds.Low thermophile
configuration.
10 hours 12 hours 14 hours 16 hours 18 hours 20 hours
Feed 800 400 300 900 500 1,000
After PHE 500 500 200 1,000 200 400
Before 1st effect 400 700 500 500 700 1,100
After 1st effect 421 315 526 158 289 240
Concentrate 217 174 652 347 521 196
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Niro France S.A.S 4 rue J.P. Timbaud B.P. 80 Montigny le
Bretonneux F 78185 St Quentin en Yvelines France Tel +33 1 30 14 61
10 Fax:+33 1 30 07 06 62 E-mail [email protected]
Niro A/S Gladsaxevej 305 PO Box 45 DK-2860 Soeborg Denmark Tel
+45 39 54 54 54 Fax +45 39 54 58 00E-mail: [email protected] Web-site:
www.niro.dk B
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Niro France S.A.S.
