Spray-Cooled Products - (alternatively spray congealing).
SPRAY COOLING
Spray cooling (alternatively spray
congealing) is a process by which a melt is formed into particles of spherical
shape by spraying the melt into a cooling chamber. The cooling is performed by
air introduced at sufficient low temperature. The melt can be atomized or
prilled by a rotary atomizer equipped with a special designed wheel, or be
atomized by pressure nozzles or 2-fluid nozzles. Spray cooling has applications
in the chemical, food, and pharmaceutical industries. It is a convenient method
of transforming melted feed stocks into free-flowing particulates of controlled
particle size.
Importance of melt properties
When a spray of melt
droplets contacts a cool air environment, the melt cools first to the
solidification temperature. For a pure substance the congealing then takes
places at a constant temperature during release of the product's heat of
solidification.
Not all products have a clearly defined solidification
point. The phase change may take place over a range of temperature or the
product may go from a melt phase to solid amorphous form without the release of
all the heat of solidification, since a non-crystalline formation occurs. The
droplets may also sub-cool below the solidification temperature. Data on the
physical properties of the melt and behaviour during solidification are
important to size the cooling chamber, select the method of atomization, and
determine whether the cooling should be conducted in cocurrent or
countercurrent gas flow. An additional second stage cooling may also be found
advantageous.
PRODUCTS
- Encapsulated materials
- Fats
- Glycerides
- Hydrates
- Inorganic/organic melts
- Quaternary ammonium compounds
- Fatty acids
- Waxes
DESIGN SELECTION BASED UPON THE SOLIDIFICATION PROPERTIES OF THE
MELT
The most suitable second-stage cooler is a fluid bed supplied
with cooled ambient air. Alternatively, a pneumatic transport system with
cooled conveying air might be suitable.
UTILIZING CLOSED CYCLE
SPRAY COOLING ENABLES OPTIMIZATION OF COOLING ENERGY REQUIREMENTS AND PRODUCT
QUALITY
Plant operation in warm and humid climates will normally
require the ambient air supply to the spray cooler to be dehumidified and
cooled. To reduce the extra energy consumption involved, it is common practice
to recycle the process air, thereby minimizing the load on the
dehumidification/cooling unit.
The recycle system is designed to permit
a bleed of air from the system, enabling an intake of ambient air in cases,
where there is a degree of evaporation associated with the spray cooling. The
multi-way damper incorporated in the recycle system also allows the plant to
run in open cycle without the dehumidification/cooling unit in operation during
the colder and dryer seasons of the year. This reduces operational costs.
PARTICLES
Design selection is based upon particle size requirement, from
fine to coarse and extra coarse products.
PLANTS
Over the years we have supplied a number of plants specially designed for
spray cooling and / or congealing of various products. The majority of the
plants have been specially designed for individual needs of the clients.
It is our intention to meet the special demands and needs in this area
of processing .