Spray Cooling of Products

During the spray cooling / spray congealing process a melt is formed into particles of sperical shape by spraying the melt into a cooling chamber.

 

SPRAY COOLING

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. Another option is to atomize the melt by pressure nozzles or 2-fluid nozzles. Spray cooling is utilized 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.

Nozzle and Rotary atomization
Nozzle atomization and Rotary atomization

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 could present an advantage.

Solidification Curve

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 is the best suited second stage cooler. Alternatively, the selection could fall on a pneumatic transport system with cooled conveying air.
Design selection is also based upon particle size requirements, from fine to coarse and extra coarse products.

Spray Cooled Products
Typical products from Nozzle atomization and Rotary atomization

OPTIMIZATION OF COOLING ENERGY AND PRODUCT QUALITY
Warm climate plant operation could 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 of the year. This reduces operational costs.

OPERATIONAL PLANTS
Over the years Niro has supplied a number of plants specially designed for spray cooling and / or congealing of various products. The majority of these plants designs meet individual requests and demands, which is our intention.

The online news service, Dairy Reporter has a brief description of GEA Niro A/S in which, they inform their readers about GEA Niro A/S' spray cooling capabilities.