Cooled, clarified liquid concentrate is sprayed through a nozzle at the top of a drying tower. The tower is at least 75 ft. (23 m) tall. Air that has been heated to about 480°F (250°C) is blown downward through the mist to evaporate the water. The air is diverted out of the tower near the bottom, and it is filtered to remove fine particles, which can be recirculated back through the tower or reintroduced during the agglomeration step. The dry coffee powder collects in the bottom of the tower before being discharged for further processing. The resulting powder contains 2-4% moisture and consists of free-flowing, non-dusty particles.
Spray drying may be followed by a step to form the powder into coarser particles that will dissolve more completely in the consumer's cup. The agglomeration process basically involves rewetting the surfaces of the coffee powder particles and bringing the particles into contact, so that they will adhere to each other and form larger, more granular particles. This is accomplished by exposing the powder to steam or a fine mist, while tumbling it in the air.