Nozzle atomization and Rotary atomization
GEA Niro supply spray cooling/spray congealing plants designed to achieve the specific product and process requirements.
SPRAY COOLING
Cooling is performed using low temperature air. The melt can be atomized or prilled by a rotary atomizer equipped with a specially designed wheel. Another option is to atomize the melt by pressure nozzles or 2-fluid nozzles. Spray cooling is used 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.
MELT PROPERTIES
As the spray of melt droplets comes in contacts with cool air, the melt is cooled until reaching solidification. 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 might also sub-cool below solidification temperature. Data explaining the physical properties of the melt and behaviour during solidification are important to determine the size of the cooling chamber, select the method of atomization, and decide whether cooling should be conducted in co-current or counter current gas flow. In certain situations, a second stage cooling may be required.
Typical products from Nozzle atomization and Rotary atomization
SPRAY COOLING PRODUCTS
Encapsulated materials:
|
Fats
Glycerides |
Hydrates
Inorganic/organic melts
Quaternary ammonium compounds |
Fatty acids
Waxes |
DESIGN SELECTION
Fluid bed coolers supplied with cooled ambient air are often used for the second stage cooling. A possible alternative for certain applications is a cooling conveying system. Design selection is based upon product characteristics as well as the required particle size.
Typical products from Nozzle atomization and Rotary atomization
OPTIMIZATION OF COOLING ENERGY AND PRODUCT QUALITY
Plants in warm climate may require dehumidifying and cooling of the ambient air supply to the spray cooler. 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 year, hence reducing operational costs.