Spray Cooling

Spray Cooling - the process where a melt is formed into particles of spherical shape by spraying the melt into a cooling chamber through which ambient or cooled, low temperature air is passing

Spray cooling (alternatively spray congealing) is defined as a process by which a melt is formed into particles of spherical shape by spraying the melt into a cooling chamber through which ambient or cooled, low temperature air is passing. Rotary (wheel) atomizers and nozzles are used to spray the melt. Spray cooling finds applications in the chemical, food, and pharmaceutical industries. It is a most convenient method of transforming melted feedstock into free-flowing particulates of controlled particle size.

Read more about the spray cooling.

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 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 unit in operation during the colder and dryer seasons of the year. This reduces operational costs.

Spray cooling: Importance of melt properties
Products that form melts have a solidification curve. When a spray of melt droplets contacts a cool air environment, the melt cools to a solidification temperature. Congealing then takes place at a constant temperature during release of the product's heat of solidification. When no longer in a fluid state, the droplets further cool to give stable solid particulate forms.

Some products do not have a clearly defined solidification point. The phase change may take place over a range of temperatures or the product may go from a melt phase to solid amorphous form without the release of heat of solidification, since a non-crystalline formation occurs. The droplet may sub-cool below the solidification temperature before suddenly hardening. Data on the physical properties of the melt and behavior during solidification is important to size the cooling chamber, select the atomizer, and determine whether the cooling should be conducted in one or two stages.