FBL x parma impianti rivista

starting and running is extremely
short even for high final concentrations.
Also the response times to
changes made to the values of final
concentration are very quick.
Rotor moves inside the cylinder
spreading the product into a thin
film corresponding to the interspace
between paddles and wall (1÷5
mm). Peripheral speed is higher
than 10 m/sec, thus securing selfcleaning
of the exchange surface
and extended operation periods
with no need for frequent washings.
A continuous film of product can be
maintained by the high value of centrifugal
force set by the rotor (30 G).
The evaporator body can be either
mounted horizontally or vertically.
The horizontal position delivers a
more efficient maintenance of the
machine and an easier extraction of
the rotor.
The vertical position is more suitable
for use in multi-effect systems,
where the other plants are built with
vertical axle, in order to reduce overall
dimensions on the floor.
However it is important to note the
considerable height needed for rotor
extraction if it is installed inside the
factory.
A main advantage of the vertical
model: the axial simmetry conditions
are maintained even when
there is an anomalous flooding in
the jacket (faulty condensate exhau-
62
st) and any loss of axiality is avoided,
as opposed to what occurring
with the horizontal model (possible
contact between rotor and stator).
The reduced extent of the exchange
surface (20 2 max) sets limits to the
turbulent thin film evaporator. This
explains why, for high capacities, it
can be advantageously integrated
into multi-effect systems for use only
in the final step of the process, the
hardest one.
Also the cost of the machine, rather
high, recommends its coupling with
more economical evaporation stages.
4 – Applications
The application fields for this evaporator
system are many and different,
not only limited to the food sector
but also boasting a wide range of references
in the chemical industry.
To remain in the food products sector,
the turbulent thin film evaporator
is used fo the concentration of:
-Mediterranean fruit (apricots, peaches,
pears, apples, plums) purees
-coloured fruit (strawberries, raspberries)
purees
-tropical fruit (mango, banana, passion
fruit) purees
-infusions (liquorice)
-meat broths and extracts
-fish boiling broths
-vegetable purees
-tomato juice (usually used as fini-
sher in multi-effect/stage systems)
-baby foods
Several specimens of versatile
plants, multi-effect and/or multi-stage,
exist. For instance, some double
and triple effect evaporators incorporate
one or two forced circulation
effects with only the first finisher effect
working as turbulent thin film
evaporator. So the possibility is given
for a single effect operation
using just the turbulent thin film evaporator.
The last method is applied
to process tropical purees of fruit
(mango, passion fruit, etc.) or coloured
fruit, whereas the 2/3 effect operation
is intended for tomato juice
evaporation only.
Various limits are set for maximum
concentration, depending both on
the kind of product and the impact of
suspended solids occurring in the
product:
40÷50% of solids for fruit and vegetables
40÷60% for extracts and broths
60÷70% for mildly pulpy juices (citrus
fruits, pineapples)
70÷80% for clear juices (apple, grapes,
dates).
When particularly flavoured products
are evaporated, the system is
equipped with a recovery unit to collect
the flavor components through a
vacuum operating filling distillation
column.